Process for operating a magnetically stabilized fluidized bed

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FIGURE 5

f POINT OF MINIMUM FLUIDIZATION,UMF

TRANSiTION TO THE

BUBBLNG STATE, UT

77 - 25 O MCRON CO8 SPHERES

H = 4.8 OERSTEDS

O O 2O 3O 4O 5O 60 7O

SUPERFICIAL VELOCITY, U, CM/S

FIGURE 6

77-25O MCRONS

UN STABLY

FLUIDZED BED

REGON

4O --

STABLY FLUDZED

REGON

O M () () 17 TA/ y s V M

APPLIED FELD, H, OERSTEDS

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FIGURE 7

o 24 um MONEL

O 2 13t 37am MONEL

O 270t|OOum Nion Al2O3 O 335it 85um Nion Al2O3

VOID FRACTION AT TRANSiTION VELOCITY (UT),

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bed to accommodate the increased fluid flow until the

PROCESS FOR OPERATING AMAGNETICALLY gas velocity exceeds the free falling velocity of the STABLZED FLUDZED BED particles which are then carried out of the apparatus, a condition otherwise known as entrainment.

CROSS REFERENCE TO RELATED Fluidized beds possess many desirable attributes, for APPLICATION example, in temperature control, heat transfer, catalytic This application is a continuation-in-part of U.S. ap reactions, and various chemical and physical reactions plication Ser. No. 610,071 filed Sept. 3, 1975 now aban such as oxidation, reduction, drying, polymerization, doned, which in turn is a continuation-in-part of U.S. coating, diffusion, filtering and the like. application Ser. No. 514.003, filed Oct. 11, 1974, now 10 Among the problems associated with fluidized beds, a abandoned. most basic one is that of bubble formation, frequently

FIELD OF THE INVENTION

resulting in slugging, channeling, spouting, attrition and pneumaic transport. This problem is most common in

This invention relates to a fluidized bed process. gas-fluidized systems. Bubbling causes both chemical More particularly, the present invention is concerned 15 and mechanical difficulties: for example, in gas-solids with a process for operating a magnetically stabilized reaction gas bubbles may bypass the particles altogether fluidized bed under conditions such that the flow of gas resulting in lowered contacting efficiency while chaotic used to fluidize solid particulate magnetizable and flui motion of the bed solids may set up detrimental me dizable particles and an applied magnetic field are con chanical stresses tending to deteriorate the vessel and its trolled to the extent that there is substantially no time 20 contents. Many procedures and systems have been pro varying fluctuation of pressure at a point taken in the posed to effect improvements, for example, by the use bed. Such a magnetically stabilized medium has the of baffles, gas distribution perforated plates, mechanical appearance of an expanded fixed bed; there is no gross vibration and mixing devices, the use of mixed particle solids circulation and very little or no gas bypassing. A sizes, gas plus liquid flow schemes, special flow control bed of the magnetically stabilized medium shares many 25 valves, etc.

qualities of the normal fluidized bed; pressure drop is For example, U.S. Pat. No. 3,169,835 to Huntley et al effectively equal to the weight of the bed divided by its disclose that mesh packing throughout the bed breaks cross sectional area, and independent of gas flow rate or up large gaseous bubbles and prevents coalescense of of particle size; the medium will flow, permitting con existing bubbles. However, baffle devices do not pre tinuous solids throughput. Beds of the magnetically 30 vent the initiation of bubble formation. stabilized media also share some of the qualities of a DESCRIPTION OF THE PRIOR ART fixed bed; countercurrent contacting can be readily attained; gas bypassing is small or absent, making it In recent years patents have issued which describe possible to achieve high conversions and attrition is means for suppressing bubble formation in a fluidized minimal or absent. 35 bed. For example, U.S. Pat. No. 3,304,249 to Katz dis The simultaneous possession of properties usually closes that a stabilized fluidized bed is obtained when a associated with the media of fixed and of fluid beds is bed containing solids having a moderate surface elec highlighted, for example, in the use of a magnetically troconductivity is fluidized by a gaseous medium hav stabilized medium to trap particulates. Like the medium ing a sufficiently high ionizapotential to provide a co of a fixed bed, it will trap the particulates; like the me rona discharge without arcing and subjecting a high dium of a fluid bed, it will not clog - the pressure drop voltage to a portion of the bed to cause a corona dis of a bed of the medium will increase only by as much as charge in the fluidized bed.

due to the weight of the trapped material. In another patent, U.S. Pat. No. 3,439,899 to

BACKGROUND OF THE INVENTION

Hershler, there is disclosed a process for producing a 45 fluidized bed free of bubbles bypassing a fluid upwardly

Many chemical and physical processes such as cata through a particulate solid fluidizable material which lytic cracking, hydrogenation, oxidation, reduction, includes a plurality of discrete magnet particles having drying, polymerization, coating, filtering and the like a coercive force exceeding 50 oersteds to impart an are carried out in fluidized beds. A fluidized bed, upward force to the solid particulate fluidizable mate briefly, consists of a mass of solid particulate fluidizable 50 rial and subjecting the fluidizable material to a magnetic material in which the individual particles are neutrally field varying with time in direction and intensity to leviated free of each other by fluid drag forces whereby impart individual motions to the magnet particles. A the mass or fluidized bed possesses the characteristics of similar process is disclosed in U.S. Patent No. 3,219,318 a liquid. Like a liquid, it will flow or pour freely, there to Hershler. Z. I. Nekrasov and V. V Chekin, in their is a hydrostatic head pressure, it seeks a constant level, 55 articles appearing in Izy. Akad Nauk. USSR, Otdel, it will permit the immersion of objects and will support Tekh, Nauk, Metallurgiya i Topliyo at 6, 25-29 (1961) relatively buoyant objects, and in many other properties and at 1, 56-59 (1962) disclose that the formation of it acts like a liquid. A fluidized bed is conventionally bubbles and slugs in a fluidized bed may be eliminated produced by effecting a flow of a fluid, usually gas, over a wide range of variation of flow rates by a later through a porous or perforated plate or membrane un 60 ally applied variable magnetic field due to the interac derlying the particulate mass, at a sufficient rate to tion of this field with fluidized ferromagnetic particles. support the individual particles against the force of U.S. Pat. No. 3,440,731 to Tuthill discloses a process gravity. Conditions at the minimim fluid flow required for stabilizing and suppressing bubble formation in a to produce the fluid-like, or fluidized condition, i.e., the fluidized bed, containing particulate solids having ferro incipient fluidization point are dependent on many pa 65 magnetic properties by subjecting the fluidized bed to a rameters including particle size, particle density, etc. magnetic field. While it is disclosed that either an alter Any increase in the fluid flow beyond the incipient nating current or a direct current electromagnet may be fluidization point causes an expansion of the fluidized used, the only example in the patent describes an alter

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nating current electromagnet, thus producing a mag bly fluidized bed results over a substantial range of gas netic field varying with time in direction and intensity. velocities. m Numerous publications by Ivanov and coworkers and The basis for the phenomenon is believed to relate to a publication by Sonoliker et al disclose the application the behavior of magnetic stress in the fluidized medium of a magnetic field produced from a direct current (non which is viewed as a homogeneous magnetized contin time varying) electromagnet to fluidize iron or iron uum. A local perturbation in voidage modifies the uni chromium particles such as used in ammonia synthesis form magnetic stress of the unperturbed bed creating or carbon monoxide conversion. These articles include: magnetic forces that tend to restore the medium to the Sonoliker et al, Indian Journal of Technology, 10, uniform state. A general expression for the magnetic 377-379 (1972); Ivanov et al Zhurnal Prikladnoi Khimi, 10 in stress tensor is provided in Ferrohydrodynamics, Entry 43, 2200-2204 (1970); Ivanov et al., Zhurnal Prikladnoi Vol.the4,“Encyclopaedic Dictionary of Physics,' Suppl. by R. E. Rosensweig, Edited by J. Thewlis,

Khimi, 45, 248-252 (1972); Ivanov et al, International Pergamon Press (1971).

Chemical Engineering, 15, 557-560 (1975) (also pub lished in Chemical Industry, 11, 856-858 (1975) and The 5 SUMMARY OF THE INVENTION Soviet Chemical Industry, 6, 713-715 (1974); Ivanov et al, Comptes rendus de l'Academie bulgare des Science, As one embodiment of the present invention there is Tome 25, No. 8, 1053-1056 (1972); and Ivanov et al disclosed particulate a process for fluidizing a bed containing solid magnetizable, fluidizable material and fluid

Comptes rendus de l'Academie bulgare des Science, Tome 23, No. 7, 787-790 (1970). In some of the published 20 izing fluid located within an external force field wherein work of Ivanov and coworkers a gradient applied mag at lest a portion of said bed containing said solid particu late magnetizable, fluidizable material and fluidizing netic field is used to generate body forces to hold fine fluid particles in place and thus permit higher flow rates than tially are subjected to a nontime varying and substan uniform applied magnetic field having a substan in conventional beds. For example, the work reported tial component along the direction of the external force in British Patent No. 1,148,513 and Ivanov et al., Kinet. 25 field such that said

Katel 11, No. 5, 1214-19 (1970) varied the direction of dizable material hassolid a particulate magnetizable, flui component of magnetization the field from transverse to axial in relation the flow.

In general, the published works of Sonoliker et al and wherein at least a portion of said bedforce along the direction of the external field and

Ivanov et al, teach that higher gas velocities can be used solid particulate magnetizable, fluidizable materialtheis containing in the presence of an applied magnetic field than in its 30 stably fluidized by the flow of fluidizing fluid opposing absence. For example, Ivanov et al state in Zhurnal said external force field at a superficial fluid velocity Pikkladnoi Khinii, 45,248-252 (1972) at page 251: "Lin ranging between:

ear gas velocities higher by 30-40% can be used under (a) more than the normal fluidization superficial fluid high pressure in the presence of a magnetic field than in velocity required to fluidize said bed in the absence of its absence, at the same degree of bed expansion without 35 said applied magnetic field; and, appreciable breakdown of the bed structure and with (b) less than the superficial gas velocity required to out transport of particles out of the bed." However, cause time-varying fluctuations of pressure difference Sonoliker et al and Ivanov et al provide no recognition through said stably fluidized bed portion over a finite of the existence of the stably fluidized non-bubbling bed time period during continuous fluidization in the pres and appear to erroneously interpret the transition from ence of said applied magnetic field. The normal mini the stably fluidized state to the unstably fluidized (bub mum fluidization superficial fluid velocity is the fluid bling) state as the transition from fixed to fluidized velocity observed when the pressure difference of the states. Furthermore, they did not teach the essential role fluid passing through the fluidized bed, as measured played by orientation and the significance of role played between the upper and lower surfaces of the bed, is first by uniformity of the applied magnetic field. In a uni 45 substantially the same as the bed weight per unit cross form applied magnetic field, the bed is free of any net sectional area.

magnetic force. The strength of the magnetic field and its minimal Workers at the Brookhaven Laboratories, H. Katz deviation from a colinear orientation to the external and J. T. Sears, Can, J. Chem. Eng. 47, 50-53 (1969) force field are maintained so as to prevent and/or sup described a process for the stabilization of a fluidized 50 press formation of bubbles in the fluidized media at a bed of dielectric particles by use of an electric field. given fluid flow rate and with a selected fluidized parti These workers discloses that glass bead and silica gel cles makeup.

particle beds were observed to behave as packed beds at Fluid throughput rates which are up to 10 or 20 or flow rates (and pressure drops) of fluidizing gas up to 15 more times the flow rate of the fluidized bed at incipient times the normal incipient fluidization rate. Katz and 55 fluidization in the absence of the applied magnetic field Sears also disclose in the cited article the use of an are achieved, concomitant with the substantial absence imposed axial magnetic field (alternating or unidirec of bubbles. The magnetically stabilized fluidized bed tional) to stabilize a bed of iron particles, but indicate has the appearance of an expanded fixed bed with no that the iron particles under the influence of a strong gross solids circulation and very little or no gas bypass magnetic field are in the form of a slug 1ng.

THE DISCOVERY OF THE PRESENT BRIEF DESCRIPTION OF THE DRAWINGS INVENTION FIG. 1 is a schematic representation comparing the

It has been discovered that by fluidizing a bed con magnetically stabilized fluidized bed of the present in taining solid particulate magnetizable and fluidizable 65 vention with an ordinary unstabilized fluidized bed. material with a fluid such as a gas or liquid in the pres FIG. 2 is a graphical illustration of a three phase ence of an applied uniform, time-steady magnetic field diagram displaying (1) the solid unfluidized region, (2) oriented parallel with the direction of fluid flow, a sta the stabilized, fluidized region (the operating region or

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zone of the present invention) and (3) the bubbling The process of the instant invention enjoys benefits of fluidized region, as a function of applied magnetic field solids facilitated for transport and limited pressure drop intensity and stabilizing velocity . . of a fluidized bed along with absence-of-backmixing FIG. 3 graphically illustrates the expansion of the normally associated with fixed bed processes. magnetically stabilized fluidized bed in response to in When fluid is passed upward through a bed of closely creasing gas flow at a constant applied magnetic field sized granular solids, a pressure gradient is required to intensity. overcome friction. In order to increase the rate of flow, FIG. 4 graphically illustrates the three phase regions, a greater pressure gradient is required. When the pres i.e., (1) the solid, unfluidized region, (2) the stabilized sure difference (also known as differential pressure and fluidized region and (3) the bubbling fluidized region as 10 pressure drop A P) approaches the weight of the bed a function of applied magnetic field intensity. The ex over a unit cross-sectional area, the solids begin to perimental system in this Figure is the same as used in move. This motion of the solids is created at superficial FIG. 3. The bed depths in this experimental system may fluid velocities far below the terminal free-settling ve be read from FIG. 3. locities of the solid particles and constitutes the begin FIG. 5 graphically represents the pressure drop of 15 ning of fluidization. Thus, the normal minimum fluidiza 177-250 micron steel (C1018) spheres as a function of tion superficial fluid gaseous or liquid velocity is the superficial gas velocity at a uniform applied magnetic fluid velocity observed when the pressure difference of field of 48 oersteds. l the fluid passing through the fluidized bed, as measured FIG. 6 graphically represents a three phase diagram between upper and lower surfaces of the bed, is first resulting from the plotting of the minimum fluidization 20 substantially the same as the bed weight per unit cross velocity and the transition fluidization velocity as a sectional area. As is well known, superficial fluid veloc function of an applied uniform magnetic field. The ex ity is a measure of the linear fluid velocity that would perimental system is the same as used in FIG. 5. pass through an empty vessel and it is measured in feet FIG. 7 illustrates a correlation of transition modulus 25 per second, centimeters per second, etc. This point of N, with transition velocity voidage e, which supports normal minimum fluidization superficial fluid velocity the conclusion of dimensional reasoning that a unique in the absence of an applied magnetic field is the mini relationship exists between these two variables for mag mum fluidization superficial fluid velocity of the pro netically saturated, long beds. The supported nickel cess of the invention.

material has a density of 1.30 g/cm and a magnetization 30 For solid particulate magnetizable and fluidizable of 5000 oersteds at an applied field of 228 gauss materials, the point of initial or minimum fluidization is DETAILED DESCRIPTION OF THE not affected by the presence or absence of an applied INVENTION magnetic field. However, when the minimum superfic ial fluid velocity is exceeded in a bed which is not sub

As indicated previously, the present invention relates 35 jected to the influence of an applied magnetic field, the to a process for operating a stably fluidized bed over a porosity of the bed begins to increase and the individual substantial range of fluid velocities. Fluid throughput particles move under the influence of the passing fluids rates which are 2, 5, 10, 15 and 20 or more times the concommitant with the formation of bubbles as shown normal minimum fluidization superficial fluid velocity in the left hand sketch of FIG. 1 of the drawings. Such of the bed containing the fluidizable material can be a normally fluidized bed experiences gross solids circu accomplished by practice of the invention concommi lation, gas bypassing, bubble formation, slugging and tant with substantial absence of gross solids circulation, bed fluctuation. By comparison, with application of a very little or no gas bypassing and minimal or absence magnetic field in accordance with the practice of the of bed fluctuation. The fluidized bed is stabilized by present invention, the bed is stabilized, thereby reduc subjecting at least a portion of the fluidized bed com 45 ing or eliminating: gas bypassing, bubble formation at prising solid particulate magnetizable and fluidizable the region or zone of the uniform magnetic field, slug material and a fluidizing fluid to a nontine varying ging and bed fluctuation. Thus, a greater efficiency of (direct current) and substantially uniform applied mag fluid-solids contacting can be accomplished by operat netic field having a substantial component along the ing the process of the present invention. direction of the external force field (which will gener 50 As further illustration of the present invention, the ally be gravity) such that the solid particulate magnetiz phenomenon of normal fluidization can be visualized in able and fluidizable material has a component of mag terms of a simple experiment by the left hand sketch of netization along the direction of the external force field, FIG. 1 in which a bed of solid particles is supported on As it will be seen from the description of the invention a horizontal porous grid in a vertical tube. A fluidizing and reference to the drawings, the maximum superficial 55 fluid in the form of a gaseous medium or liquid is then fluid velocity that can be employed while still maintain forced to flow upwards through the grid, and so ing a stable, nonfluctuating bed is a function of the through the particle bed. This flow causes a pressure component of magnetization of the solid particulate difference (pressure drop) across the length of the bed, magnetizable and fluidizable material along the direc and when this pressure difference is sufficient to support tion of the external force field which is imparted by the the weight of the particles, the bed is “incipiently fluid applied magnetic field. It is to be recognized that factors ized' (the superficial fluid velocity required to attain such as particle size, particle composition and shape, incipient fluidization is the "normal minimum superfic particle density, length and shape of the bed, etc. each ial fluid velocity'). The fluidized bed thus formed has affect the maximum fluidization velocity that can be many properties of a liquid; objects float on the surface achieved at a given component of magnetization. The 65 and the addition or withdrawal of solid particles in variation and adjustment of these factors will be appar process equipment is also facilitated. As shown by the ent to those skilled in the artin practicing the process of left hand sketch in FIG. 1, a gas-fluidized bed in which the present invention. the gas velocity is greater than the incipient gas veloc

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ity, most of the excess gas passes through the bed as length is greater than 100 mm, the transition is indepen bubbles. dent of bed length and exceeds incipient fluidization By providing the solids of the bed with magnetizabil velocity by a factor of 2.3 at the applied field of 5000 ity and applying a uniform, time-steady magnetic field oersteds. At bed length less than 50 mm, the transition oriented parallel with the direction of gas flow as shown 5 speed increases steeply as depth decreases, e.g., 4.6 in the right hand sketch in FIG. 1, it has been found that times greater than the incipient velocity at about 20 mm a stabilized non-fluctuating and essentially bubble-free length. Additional experiments have shown that the fluidized bed results over a substantial range of superfic transition velocity of a stabilized bed is unaffected by ial gas velocities. As shown in the sketch in FIG. 1, the the crosssection dimensions of the containing vessel for magnetic field may be conveniently furnished by 10 tests in which the hydraulic diameter varied from 3 to wound coils carrying a modest direct electric current 28 centimeters.

and surrounding the fluidization vessel. When the transition velocity is determined by the Referring to FIG. 3 of the drawings, there is an illus method described above for a number of different ap tration of the response of magnetized solids to increase plied field intensities, the results obtained give the plot of superficial gas velocity for a constant intensity of 15 of FIG. 4 of the drawings (FIG. 2 which is similar to applied magnetic field. The solid particles are a closely FIG. 4 is discussed further with respect to the exam graded range of nickel-copper alloy (Monel). Measure ples). The experimental system used to provide the data ments of a particulate sample with a vibrating sample in FIG. 4 is the same as that used in FIG. 3 described magnetometer yield magnetization values of 372 gauss above. The bed depths may be read from FIG. 3. FIG. at 5000 oersteds applied field, 326 gauss at 3000 oer 20 3 defines three regions that classify the physical state of steds, 250 gauss at 1000 oersteds and 132 gauss at 200 the bed emulsion as "unfluidized, "stably fluidized, or oersteds. The material is ferromagnetically soft with a "unstably fluidized.' The boundary between 'stably and remanence of less than 5 gauss. With no gas flow the “unstably fluidized' represents the transition described bed length is that of the randomly dumped solids. The previously while the boundary between "unfluidized' bed comprises 2840 grams of the Monel (copper-nickel 25 and 'stably fluidized' states represent incipient fluidiza alloy) of 177-250 micron particle size and specific grav tion. As will be demonstrated in the Examples, the incipient fluidization is affected little or none by the ity of 8.45 in a vessel of 7.57 centimeter diameter with applied an applied magnetic field intensity of 5000 oersteds that magnetic field intensity. For example, bed pres is uniform over the test region to within 1 percent. With sure difference initially is linear with flow rate, then a flow of air admitted to the vessel, the bed length is 30 breaks at the point of incipient fluidization with pres unchanging up to the point of incipient fluidization. sure difference (pressure drop) about constant and Thereafter, the bed accommodates increasing flow by a closely equal to the bed weight per unit cross-sectional process of homogeneous expansion in which detectable area. The slope of the initial linear portion of the curve bubbles are not present in the bed and the bed of solids is independent of applied field and it is predictable from in gas emulsion is free of fluctuation, agitation or solids 35 the low velocity limit of the well known fixed bed circulation. In this stable, calm state, a visual inspection Ergun relationship. The invariance of the plateau pres of just the bed fails to reveal its fluid like nature. How sure level to the presence of the applied field verifies the ever, objects are readily immersed into the bed as into a force free nature of the uniform magnetic field. Since liquid and when released light objects float and dense the incipient fluidization point corresponds to the inter objects sink. A hollow plastic sphere of 3.72 centimeter section of the said two lines, it follows that incipient diameter weighting 1.94 grams (ping pong ball) when fluidization is independent of applied magnetic field initially rotated continues to spin for several seconds, intensity.

thus indicating the very low frictional support it experi With velocity considered as analog to temperature or ences when floating partly submerged in the bed emul agitation influence, and applied field as analog pressure, sion. As the superficial gas velocity (flow rate) is in 45 FIG. 2 and FIG. 4 resemble a thermodynamic phase creased further, a point is ultimately reached where diagram of a pure substance having a solid (unfluidized bubbling suddenly commences. When the flow rate of or fixed bed), liquid (stably fluidized) and vapor (unsta gas is slowly increased to the vicinity of the transition bly fluidized or boiling) regions. This two phase magne point, the bed surface in some instances bubbles over tized flow in effect constitutes an aggregate composi part or all of its area for a limited time, then returns to 50 tion of matter having unique thermodynamic and trans the motionless state; aparently the medium adjusts to a port properties.

new structure. A small incremental increase in through Uniformity of the emulsion can be inferred from pres put then produces steady bubbling and bed fluctuation. sure measurements using a capillary tube connected to a This flow rate is taken as the experimental transition manometer and inserted vertically into the bed. It is point. The uncertainty introduced into the reported 55 found that pressure increases linearly with depth imply values in this manner is on the order of 5% or less of the ing that voidage is uniform from one layer to the next superficial gas velocity. As shown by FIG. 3, this point throughout the bed.

of transition from the calmed or stabilized state of flow Orifice discharge tests confirm the ability to transfer to the state of bubbling and bed fluctuation occurs at solids out of the containing vessel. The flow rate of the substantially higher flow rates than for the unmagne 60 solids is characterized by a constant value of discharge tized bed. As shown in FIG. 3, no expansion occurs coefficient independent of applied field intensity or until the vicinity of U, the minimum throughput ve initial depth of the bed. Additional tests using bands of locity causing bubbling in the absence of the applied surface pigmented solids as a color tracer demonstrate magnetic field. Expansion continues as gas flow in tht solids move through the bed in ideal piston-like creases with no bubbling, bed fluctuation or solids mix 65 motion with no backmixing when a series of eight ing up to the point U, the transition speed. It was found evenly spaced orifices are simultaneously opened that the transition velocity increases as the bed length around a circumference of the vessel cylindrical wall a decreases. When this Monel containing expanded bed short distance above the support grid. The plug nature

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of the flow is participated in by all the bed particles, ented magnetic field. Another advantage of uniform including those adjacent to the wall. In this respect, the field is reduction of magnet power. Because the power bed emulsion behaves as an inviscid medium displaying requirements for a given means field are less with more slip at the wall. At a distance on the order of the vessel uniform magnetic fields, it is preferred that variation of diameter above the orifices the flow must deviate from the varying magnetic field to the mean field in the bed simple one-dimensional motion. be no more than 100%, more preferably less than 50%, It has been found that orientation of the applied mag and most preferably less than 10%.

netic field is critical in achieving stable flow with the Generally, it will be shown that the greater the uni preferred direction colinear or parallel with the direc formity of the applied field, the greater will be the ten tion of flow and hence vertical in these experiments. 10 dency to form a homogeneous bed medium and one Experimental tests using a uniform transverse orienta which yields the greatest value of transition velocity. tion of applied field reveal that fluidization is achieved This fact furnishes the primary reason for utilizing uni but bubbling is not prevented, the bubbling occurring at form fields. Certain specific adverse influences of nonu the same throughput rate as in the absence of the ap niform field distribution are illustrated in Examples 3, 6 plied magnetic field, that is at incipient fluidization. 15 8 below.

These experiments comprised an applied magnetic field A spatially uniform DC field having a superposed AC of 570-20 oersteds over a shortbed of 150-420 microns component behaves substantially as a DC field provided nickel-on alumina particles of specific gravity 1.3 with the DC field intensity is substantially greater than the bubbling occurring at 2.8 to 2.6 cm/s with and without amplitude of the AC field component. the field. Applying 520 oersteds field parallel with the 20 The solid particulate magnetizable and fluidizable flow deferred transition to the extraordinary value of 43 particles to be used in the practice of the present inven cm/s; the bed expanded by 68 percent of its initial tion are preferably particles having a low or zero coer length. civity. All ferromagnetic and ferrimagnetic substances, In putting the present invention into practice, the including but not limited to magnetic FeO, y -iron substantially uniform constant magnetic field is applied 25 oxide (Fe2O), ferrites of the form XO.FeO, wherein to at least a portion or a zone of the fluidized bed con X is a metal or mixture of metals such as Zn, Mn, Cu, taining magnetizable, fluidizable solid particles. The etc.; ferromagnetic elements including iron, nickel, co portion of the bed or series of beds to be stabilized may balt and gadolinium, alloys of ferromagnetic elements, be designed to suite the particular process to use the etc. may be used as the magnetizable and fluidizable process of the invention. For example, in some fluidiza 30 particulate solids. Other non-magnetic materials may be tion processes, it may be expedient to stabilize the up coated with and/or contain dispersed therein solids permost 10-40% or region or zone of the bed while having the quality of ferromagnetism. For example, purposely allowing the remaining region or zone of the composites of magnetizable and fluidizable solid partic bed to be unstable. Alternatively, the fluidization vessel ulates, for example in some catalytic processes may may be disposed of separate and discrete sections, at 35 contain from 2 to 40 volume percent and preferably 5 to least one of which is stabilized by the proces of the 20 volume percent and more preferably 10-15 volume present invention. In both of such instances, it is pre percent of the ferro- or ferrimagnetic material and the ferred that the region is stabilized by the applied mag balance of the composite will be comprised of nonmag netic field having a variation of its vertical component netic material. Often it will be desirable to use a ferro that does not exceed 25% of the average vertical com or ferrimagnetic composite with a nonmagnetic cata ponent over the region or zone of the bed to be stabi lytic material. The fluidized bed containing the compos lized, said region containing the particulate magnetiz ites may also include particulate solids which are non able and fluidizable material. Preferably, the magnetic magnetizable. In other processes it may be desirable to intensity will vary no more than 10% and more prefera use 100% ferro- or ferrimagnetic materials as the partic bly no more than 5% over the stabilized region. Often, 45 ulate solids.

it will be deemed desirable to design such regions or An important factor in selecting or preparing the zones to have only about a 5% or less variance. magnetizable and fluidizable particulate solids is the In many processes it will be desirable that the entire magnetization Mof the particle. The higher the magnet fluidized bed in a fluidization vessel be stabilized in ization M of the particle, the higher will be the transi accordance with the teachings of the present invention. 50 tion velocity UT up to which the bed may be operated In such cases, the widest range of stable behavior of the without bubbling and bed fluctuation, all other factors fluidized medium is obtained when the applied mag such as particle size and distribution being held con netic field is substantially uniform throughout the entire stant. The magnetization of the magnetizable and flui bed containing the magnetizable and fluidizable solid dizable particles in the medium will have a magnetiza particles. Thus, when the magnetic field is applied hav 55 tion M of at least 10 gauss. Generally for high fluid ing a substantial vertical component to stabilize the velocities, the particles will have a magnetization, as fluidized medium, the variation of the vertical compo being imparted by the applied magnetic field, of at least ment of the magnetic field to the mean field in the bed 50 gauss, preferably at least 100 gauss and more prefera must be no greater than 50%, and most preferably no bly at least about 150 gauss, e.g., 150-400 gauss. For greater than 10%. Often, such fluidization units will be those processes requiring very high fluid velocities, the designed to have a less than 5% variation over the magnetization of the magnetizable, fluidizable particles 88. may be up to about 1000 gauss or more, but preferably As demonstrated in Table IX, Example 7 below, it 150-450 gauss.

has been unexpectedly found that nontime varying ver The magnetization M of the particles, as is well tical fields are preferred and provide advantages over 65 known, is defined as B-H in the particle, where B is the time varying fields, that is direct current (DC) rather magnetic induction and H is the magnetic field, the than an alternating current (AC) is used to energize the fields being defined in standard published works in elec electromagnet positioned to provide the vertically ori tromagnetism, e.g., Electromagnetic Theory, J. A. Strat

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ton, McGraw-Hill (1941). The value of M may be mea 10% above the normal minimum fluidization superficial sured in a variety of ways, all of which give the same fluid velocity of the bed containing the solid particulate value M since M has an objective reality. magnetizable and fluidizable material in the absence of One means for determining magnetization M of the the applied magnetic field. In some instances it will be particles in a bed under the influence of a given applied desirable to operate the process at more than 2, 5, 10, 15 magnetic field is to measure their magnetic moment at and 20 or more, and quite often 2 to 10 times the normal that field in a vibrating sample magnetometer under minimum fluidization superficial fluid velocity required conditions of similar voidage, sample geometry and to fluidize the bed containing the solid particulate mag temperatures as exist in the process to be used. The netizable, fluidizable materials in the absence of the magnetometer gives a value of ot, the magnetic moment 10 applied magnetic field.

per gram from which magnetization M is obtained from As the transition superficial velocities are increased the formula: the component of magnetization of the solid particulate M = 4 irpor magnetizable and fluidizable material along the direc tion of the external force field will have to be increased where p is the density of the particles in the test sample, 15 difference so as to prevent time-varying fluctuations of pressure through the bed during continuous fluidiza or is the magnetic moment in emu/g and M is the mag netization of the particles in gauss at the applied mag tion. It will be recognized that particles of high magnet netic field tested. ization such as iron and steel can achieve a very high Thus, it can be seen from the above discussion that 20 component of magnetization M at relatively low ap the fluid velocity region of stable operation is poten plied magnetic fields. These particles, however, have tially expanded with increasing magnetization of the the limitation that at applied magnetic fields, e.g., above particles. The actual magnetization of the particles in 50 to 100 oersteds, the particles tend to aggregate and the fluidization vessel will be a function of the particles take the form of a slug. Consequently, the level of su themselves (the degree of magnetizability they inher 25 perficial fluidization velocity that can be achieved with ently possess) and the intensity of the applied magnetic such particles is limited while still maintaining a non field. fluctuating bed. The maximum useful levels for the As stated above the magnetizable particles should magnetization M of most particles must be limited to have a certain degree of magnetization M which is about 500 to 1000 gauss in order to achieve a reasonably imparted to the particles by the intensity of the applied 30 fluid-like bed medium without undue agglomeration of magnetic field. Obviously one would seek the lowest particles. It can be calculated that for iron spheres applied magnetic field possible because of cost. Com (which is approximately similar to particulates used by monly many of the composite particles will require at Sonoliker etal and Ivanov et al) in a bed subjected to an least 50 oersteds, more often more than 100 and prefera applied field of 50 oersteds the maximum magnetization bly less than 1000 oersteds to achieve the requisite mag 35 Mof bed particle is about 300 gauss. However, it will be netization M. The determination of the applied mag recognized that at points of contact of the particles, the netic field will take into account the type of particles magnetization can be far greater and hence the mag fluidized, i.e., their magnetization, particle size and dis netic forces of agglomeration are greater. tribution, the fluid velocity to be used, etc. The occurrence of bed fluctuation as referred to As stated earlier the magnetizable and fluidizable herein furnishes a means of determining the transition particles may be admixed with nonmagnetic materials. 40 superficial fluid velocity. For example, fluctuation of a For example, silica, alumina, metals, catalysts, coal, etc. fluidized bed can be determined by a variety of tech may be admixed with the magnetizable and fluidizable niques which measure the fluctuation of a bed property. particles and the advantages of the present invention still obtained. In the case of admixtures (as opposed to 45 Thus, bed length fluctuation can be ascertained by a composite materials containing the magnetizable parti beam, etc. Aplaced

Hall probe in said bed, by reflection of a light convenient means for detecting bed fluctu cles) it is preferred that the volume fraction of magne ation is by determining the pressure difference through tizable particles exceed 25 percent, more preferably the exceed 50 volume percent. Often the bed will be com and bed containing the solid particulate magnetizable fluidizable particles. For present purposes a time prised of 100 volume percent of the magnetizable and 50 varying fluctuation fluidizable particles (i.e., it will not contain admixtures stably fluidized bed of pressure difference through the portion will be taken as indicative of other materials). When the nonmagnetizable admix that the superficial fluid ture exceeds 75 volume percent, the particle mixtures tion of the bed to go intovelocity has caused that por the unstable region as shown may separate analogous to liquids of limited solubility. in FIG. 2 and 4, i.e., the region beyond U. Preferably, The particle size of the fluidizable and magnetizable particles will range from about 0.001 mm to 50 mm, 55 the superficial fluid velocity will be less than 98% and more preferably less than 85% of the superficial fluid more preferably from 0.05 to 1 mm. Often the particle velocity necessary to cause fluctuations of the stably size will range from about 0.05 to 0.5 mm, preferably fluidized bed-portion pressure-difference. A fluctuation from 0.1 to 0.4 mm and more preferably from 0.2 to 0.35 mm. The particle size range referred to herein is that in the pressure difference in the bed is indicative of determined by the mesh openings of a first sieve bubble formation, and it is the intent of the present through which particles pass and a second sieve on invention to operate a fluidized bed in the substantial which the particles are retained. absence of bubbles. It will be recognized, of course, that The superficial fluid velocity to be used in practicing a non-fluctuating fluidized bed in accordance with the the invention will be more than the normal minimum practice of the present invention may contain some fluidization superficial fluid velocity of the bed contain 65 localized bubbles which are dissipated by the effect of ing the solid particulate magnetizable and fluidizable the magnetic field to thereby cause bed stabilization. material in the absence of the applied magnetic field. Such bubbles may be due to the presence of distribution Preferably the superficial fluid velocity will be at least means for introducing or removing fluids or solids from

Page 13

the fluidization vessel, the presence of obstructions of mean-pressure difference through the bed during con the flow, momentary pulses in flow rate of the solids or tinuous fluidization.

fluid in the vessel etc. In any event, the superficial fluid It is to be understood that the value of 0.1% is not to velocity should be controlled or monitored such that it be construed as those attributed to fluctuations of pres is less than the superficial fluid velocity required to 5 sure difference readings due to the grid, distributor cause time-varying fluctuations of pressure difference means for introducing or removing fluids or solids from through the stably fluidized bed portion over a finite the fluidization vessel, etc.

period of time, e.g., 0.1 to 1, preferably 1 to 10 seconds, and more preferably 10 to 100 second intervals during THEORY OF THE INVENTION continuous fluidization. The term fluctuations of pres 10 While not wishing to be bound by any theory, the sure difference through the stably fluidized bedportion, following theoretical explanation is offered for the pur as referred to herein, is meant to be restricted to those pose of further illustration of the invention. fluctuations attributed to the fluidization process itself Hydrodynamic stability analysis has revealed that the as a result of the fluid, i.e., gaseous material causing the uniformly magnetized medium in a long bed undergoes fluidization, and not external sources of vibrations 15 transition from the stably fluidized state in which there which may cause minor fluctuations of pressure read is no bubbling to the unstable ings, e.g., motors, fans, pumps, or due to the grid in the under conditions specified bybubbling the state of motion following stability bed, etc.

In determining the pressure difference through the criterion which has been derived.

stably fluidized bed portion as defined herein, it is meant 20 to include those measurements taken in the uppermost < unstable region or zone of the stably fluidized bed, i.e., the up NN, permost 20%, preferably uppermost and more prefer <1 stable ably uppermost 40% region or zone that is stably fluid ized. Thus, in testing for fluctuations in pressure 25 The criterion for stability when met ensures that chance through the stably fluidized bed portion, one can deter disturbance of voidages in the medium will decay so mine these fluctuations, if any, by measurement of dif that uniformity of the medium is preserved. N and N, ferential pressure and its fluctuation between two pres are dimensionless groups having the following defini sure taps, one located above the top surface of the bed tions:

and a second one located 20%, or 40% below the top 30 surface of the stably fluidized bed portion. In those "... pU, cases where it is desired to obtain a stably fluidized bed N= - portion at the lowermost region of the entire fluidized and bed, the measurements would obviously be taken at this 47(4-36) portion of the bed, i.e., one pressure tap at the grid and 35 ,----(1 + ( - x. the other pressure tap 20%, or 40% above the grid.

Additionally, where the stably fluidized bed portion is centrally located, one can determine the differential (1 - 6) (x, -X)o, cost

pressure and its fluctuation, if any, between two pres sure taps, one located 10%, preferably and more prefer N represents a ratio of kinetic energy to magnetostatic ably about 1/6 and more preferably 20% of the total energy of the bed solid, p is particle density (g/cm), U bed length above the center of the entire fluidized bed the gas superficial velocity (cm/s), and M denotes solids and the other pressure tap located an equal distance magnetization (gauss). M is a function of applied field H below the center. . .. . " attaining a saturation value at high levels of applied The ratio of root means square (rms) to mean value of 4s field. N, the voidage modulus, depends on the voidage pressure difference through the bed as detected by a fraction u, the chord susceptibility X = M/H, the tan pressure probe furnishes a convenient means to measure gent susceptibility X = 6M/6H, the angley between the the presence of fluctuation within the bed. direction of flow and the direction of a wave distur Letting AP be noted as the difference between AP bance and the orientation of magnetic field relative to and AP, where AP is the instantaneous value of pressure so the disturbance wave as specified by the angle 0. difference through the bed and AP, is the time mean For disturbance waves oriented along the direction of value of pressure difference through the bed, then the flow cos y is unity and N, takes on its greatest value, all quantity AP defined as follows is the "rms' value of other parameters held constant. Concomitantly, N. pressure fluctuation takes on its least value at the point of transition, so for a particle having given density p and magnetization M,

the velocity of throughput U is then at a least value.

APrms -(+ i (AP)'dir. ) Thus, the axial orientation of disturbance waves is the most dangerous orientation.

With cos y set equal to unity the further influence of

Thus the ratio of rms fluctuation to the mean is given 60 field orientation may then be noted from the functional as AP/AP. As a practical matter, the averaging time form of N. Thus, field applied transversely to the direc T need only be taken as about 10 to 100 seconds dura tion of flow and hence corresponding to cos 6 of zero tion of continuous fluidization. Preferably, in the opera yields an infinite value of N. In that case there is no tion of the instant process the flow of the fluidizing fluid finite value of N which can satisfy the stability crite is not substantially more than about 98%, more prefera 65 rion, hence: transversely oriented field canot stabilize bly 95% and still more preferably 85% of the superficial the bed. The least value of N, all other parameters held fluid velocity required to cause a 0.1% ratio of root constant, obtains with cos 6 of unity. Hence, the pre means square fluctuation of pressure difference to ferred orientation of magnetic field is parallel with the

Page 14

flow direction, that is, vertically oriented. The stability particles, a bed fluidizing medium, preferably a gas, and criterion discussed above relates to a modelled bed of means for generating a magnetic field operably con unbounded extent. Observed throughputs for actual nected to said vessel in such a manner that the magnetic bounded beds range from "equal to' to "greater than' field permeates substantially the total volume of said the estimate of throughput provided by the said crite fluidized bed, is of a uniform nature, and is oriented rion. Hence it will be understood that the instant inven with a substantial vertical component to the flow of tion is not meant to be limited by the said criterion. fluid through said fluidized bed. Ideally the magnetic field should be uniform through It is also found that the stablized bed of the present out the bulk of the bed containing the matter. A uniform invention functions as an effective filter to remove con field exerts no net force on an isolated single particle or 10 taminant particulates from a gas stream. The efficiency a whole bed of particles. The stabilization of matter for collection of flyash in a 10 centimeter length stabi achieved in the instant invention is due to local gradient lized filter bed of 250-420 micton magnetite particles as field magnetic forces originating within the bulk matter measured by an Anderson impactor was found to be in response to inhomogeneities in bulk matter distribu tion that may occur. In practice, any actual applied field 15 99.9% and greater for particulates of 4 microns and larger, and 95% for particulates of 2.1 microns. An will possess nonuniformities. A sufficiently uniform applied field of 150 oersteds with superficial gas veloc state of the stabilized matter when stabilization exists ity of 60 cm/s was used. Due to the fluidized state of the may be insured by requiring systematic forces of mag bed, the pressure drop remains nearly constant in opera netic origin to be sufficiently small.

In seeking a universal description of the magnetic 20 fines.even tion upon collecting several weight percent of transition phenomenon in the bed of stationary solids, the bed maythebebedremoved

When is loaded with fines, the contents of from the applied magnetic analytical model study as well as dimensional reasoning field to remove the fines and the magnetizable and flui lead to the conclusion that for a long bed of magneti cally saturated solids fluidized by a gas of negligible dizable particles can be reused. The stably fluidized bed of the present invention is density the transition speed UT (cm/s), particle density p 25 useful in removing particulate matter from fuid streams, (gm/cm), magnetization M (gauss) and bed voidage ea including when the magnetic moment of the particulate are functionally related as follows: matter times the magnetic moment of the solid particu N = f(e) late fluidizable, magnetizable material is less than 50(e- 30 mu/gr). At these conditions the particulate matter is

Here N is a dimensionless magnetic modulus represent retained in the stably fluidized bed, while the fluid ing a ratio of kinetic energy to magnetostatic field en stream is substantially devoid of the particulate matter ergy having the following definition: which passes through the stably fluidized bed. This embodiment of the invention is especially useful in 35 treating gas streams resulting from coal gasification processes, coal combustion, removal of particulates

Date for media 163,274 and 335 p. Monel, and 53,270 from boiler flue gases, removal of dust from agricultural and 335 u supported nickel in which voidage varies processes, blast furnaces and ore smelting, in petroleum from 0.35 to 0.76 shown in the plot of FIG. 7 support processing, oil shale conversion, tar sand processing the above deduction and are approximately correlated and other processes. Particulate matter removal using by the simple expression f(e) = (3/2) eso that N = the stably fluidized bed of the present invention is more

Referring again to FIG. 7, there is described the particulatethan effective prior art processes for removal of fine matter down to sizes of less than 2 microns.

correlation of transition modulus N, with transition In a preferred embodiment of this aspect of the inven voidagee which supports the theoretical conclusion of 45 tion, the solid particulate fluidizable, magnetizable ma dimensional reasoning that a unique relationship exists terial along with the particulate matter filtered from the between these two variables for magnetically saturated, fluid stream are continuously removed from the scrub long beds. The supported nickel material has a density ber vessel in which it is contained and passed into a of 1.30 g/cm and magnetization at 5000 oersteds ap second vessel wherein said particulate matter is sepa plied magnetic field of 228 gauss. 50 rated from the solid particulate fluidizable, magnetiz USES OF THE MAGNETICALLY STABILIZED able material, for example by elutriating said particulate FLUIDIZED BED matter in the absence of an applied magnetic field. The particulate fluidizable, magnetizable material is then

The fluidization process of the present invention may returned be advantageously be used in various applications, in 55 tion of this to the scrubber vessel. In one mode of opera cluding but not limited to catalytic cracking, fluid hy cess takes place aspect of the invention, the scrubbing pro droforming, alkylation, partial oxidation, chlorination, tion of absorptionsimultaneously of pollutants with a chemical reac from a gaseous fluid dehydrogenation, desulfurization or reduction, gasifica stream. As an example, a gaseous stream containing tion of coal, fluid bed combustion of coal, retorting of SO and particulate matter convert the oil shale, etc. In any of the above processes, the advan 60 ence of carbon to elemental sulfur plus SO in the pres carbon dioxide tages of calm flow may be realized when the composi in said fluidized bed at conditions wherein the particu tion of matter of the instant invention is employed in the late matter as well as any sulfur and/or carbon is re said process.

In general, it has been discovered that the instant tained infollowing said bed while carbon dioxide passes through.

invention for preparing stabilized, fluidized matter can 65 theThe examples serve to more fully describe readily be carried out in a fluidizedbed reactor compris invention, as well as to setandforth manner of making using the abovedescribed the best modes contem ing a vessel for containing the bed, a bed made up of plated for carrying out various aspects of the invention. fluidizable particulate solids, said particulate solids in cluding a plurality of separate, discrete magnetizable It is understood that these examples in no way serve to

Page 15

limit the true scope of this invention, but rather are TABLE I-continued presented for illustrative purposes. Applied Field Transition Superficial Bed Depth, It will be understood that all proportions are in parts Oersteds Velocity, cm/s by weight, unless otherwise indicated. 680 51 37

EXAMPLE 1.

Tengrams of a ferromagnetic nickel-containing cata From Table I it is seen that increase of the magnetic lyst supplied commercially by Chemetron Corporation field increased the flow rate at which transition to the and known as Girdler G87RS was charged to an open bubbling state occurred. At the maximum applied field 10 employed topped rectangular fluidization chamber having inner was 19.6 times of 680 oersteds, the transition flow rate of air dimensions of 1 inch by 1 inches over the cross section, lized medium than greater through the magnetically stabi and a height of 6 inches above a porous bronze support netized, incipiently through the medium of the unmag fluidized bed.

grid. The catalyst had been crushed and sized by screen ing to the range 0.15 to 0.42 millimeters. The catalyst is 15 rateAtofflow rates intermediate to the incipient fluidization 40 wt.% nickel on a support with the nickel prereduced I, light 2.6 cm/s and the transitional rates given in Table objects, e.g., a cork stopper or a hollow celluloid and stabilized by the manufacturer. The dumped height ball floated when placed in such beds. These objects, of the solids was 22 millimeters.

Coaxially surrounding the bed was an electromagnet when submerged in a bed and then released, instantly comprising two field coils operating on direct current, 20 were buoyed to the bed top surface, proving the fluid ized condition of the bed in the absence of bubbling.

wired in series and producing field in a common direc Additionally, the ball, when spun, continued its rotation tion, both coils having an inner diameter of 6inches and for several seconds, demonstrating a low level of fric square cross section of wound conductor of 4 inches, tional torque associated with the fluidized matter in this with face-to-face separation of the coils of 1.5 inches. stabilized mode of aggregation.

The coils provided a uniform, axially oriented field of 25 As flow is increased through the stabilized matter, the 80 oersteds per ampere over a 6 inch length of test region. The field was probed with a Hall gaussmeter beds expand to a remarkable degree. Maximum expan and it was established that over the test region the field levels isthe sion of stabilized bed at the various applied field given in the last column of Table I. The bed was uniform within 5% of the mean value axially, and exhibited an expansion of up to 66% of its as-dumped within +1% over cross sections transverse to the flow 30 depth. Deep beds are less expensive than shallow beds. direction. The midplane of the coils was located 40 mm The instant invention comprises a new composition above the top of the bed support grid.

With no current supplied to the coil, hence at effec analog thermodynamic properties in theFIG. of matter exhibiting unique properties.

form 2 illustrates of a phase tively zero applied field, the bed of catalyst particles diagram. The ordinate U representing superficial exhibited incipient fluidization at a superficial velocity, 35 ity, cm/sec or agitating influence is the analog ofvelocther i.e. volumetric flow rate divided by empty column cross modynamic temperature T while the abscissa giving section of 2.6 cm/s. Before the superficial velocity was field intensities H is the analog of thermodynamic pres increased to 2.7 cm/s the bed bubbled continuously. sure P. For concreteness, data of Table I are employed Thus, the unmagnetized bed exhibits virtually no range to plot curve AB which represents values of superficial of operation while in the fluidized state in which bub velocity at the point of transition from the stable "liq bles are absent.

In the test described above, the point of incipient uid” state L to the bubbling "vapor” state V. Thus, AB is analogous to the boiling point curve of a true liquid fluidization was determined by measurement of pres and the hydrodynamic neutral stability criterion giving sure differential across the bed as determined by an oil NNyof unity is the analog of the Clausius-Clapeyron manometer connected to a pressure tap below the bed 45 relationship for thermodynamic phase change. Line AC support grid and the readings corrected for the grid represents the minimum fluidization speed and demar pressure differential determined without particles in the cates the region of fixed bed or solid analog region S chamber. In this manner, it was established that the from the liquid analog region L. Thus line AC is analo pressure differential multiplied by the bed cross-section gous to a melting point curve. The line from zero area and divided by the weight of the bed particles 50 through A towards D represents normal fluidization in equalled unity in consistent units, as it should, at incipi the absence of field with bubbling occurring virtually at ent fluidization, and that the pressure differential passed the point of fluidization A, there being no range of through a calculus maximum and then remained sub stable operation. Operation at any field intensity with stantially constant at increasing flow rates. downward flow insures attainment of the "solid' state S The magnetic field was applied to the bed and the 55 or fixed bed condition. Thus it is seen that region L flow rate of air increased from zero until the point represents a broad new regime within which the new where bubbling began, as determined by visual observa composition obtains and which offers a novel medium tion. Transition to the bubbling state occurred at a defi heretofore unavailable for the contacting of gases with nite value of flow that is reproducible for each value of solids and for other technological tasks. applied field intensity. A set of values determined in this 60 The new composition has a uniform bulk density and manner is given below as Table I. reference to column three of Table I illustrates that TABLE I unlike normal fluidized matter the bulk density may be

Applied Field Transition Superficial Bed Depth, continuously adjusted simply by varying the flow rate Oersteds Velocity, cm/s of the fluidizing gas.

O 2.6 23 65 Transport properties of the new composition are

unique as well. For example, heat conductivity is far 400 34 36 lower than for normal fluidized matter. At the transition 520 43 37 point the matter undergoes a change in the nature of a

Page 16

phase change becoming bubbling fluidized matter pos magnetic field of a ceramic permanent magnet having sessing dramatic increase in heat conductivity. Many the dimensions 2 X 1.x inch with the direction of other examples could be cited of distinctive properties magnetization through the inch dimension. The mag such as the rheological properties, electrical properties netic field of the magnet is given in Table III for various and so forth.

Later in Example 4 it is demonstrated that unlike positions along the perpendicular from the center of the normal fluidized matter but like a true liquid the matter magnet's 2 inch by 1 inch pole face. The variation of of region L shows limited solubility effects. magnetic field in the transverse direction across the bed is about 168% relative to the mean field.

EXAMPLE 2

In this example the direction of the magnetic field Position, s Magnetic Field, H was transverse to the direction of air flow. The field (in) Oersteds was provided by a pair of ceramic permanent magnet . O 420 plates having pole faces dimensions of 6 inches by 3 1 340 inches and each a thickness of inch. Spaced 1 inches 15 2 220 from face to face, these magnets produced a uniform 3

magnetic field of 570 - 20 oersteds over the test region.

The mid-plane of the magnetic plates was located 1 inch above the bed support grid. In the range of positions given, the gradient of field is The bed and bed solids were the same as in Example 20 nearly constant, producing a maximum body force in

The response of this bed to increasing air flow rate is the direction transverse to the flow of about 1.3 times given in Table II below. the force of gravity. This force ratio was computed

TABLE II

from the relationship (4 at pg)-MdH/ds with g = 980

TRANSVERSE ORIENTATION OF FIELD

cm/s, p = 1.3 g/cm, dH/ds in units of oersteds/cm, 25 assuming the value M = 168 gauss. .

Field Superficial Bed

Intensity, Flow Rate, Depth, Fluid. Bub The magnet's 2X.1-inch pole face was stationed in Oersteds cm/s ization bling juxtaposition with the outside of inch thick walls of 570 0. 22 No No the vessel, at various stations along the bed bulk. As the 570 0.6(a) 25 Yes No 570 1.2 26 Yes. No. 30 result, fluidization was prevented at all flow rates over 570 .8 28 Yes No 570 2.8(b) 29 Yes Yes the range 0 to 60 cm/s. The nonuniform applied mag The bed was levitated or fluidized as evidenced by the expansion of the bed but the netic field locked the particles against each other and bed medium failed to float a test cork. the container wall, preventing fluidization. The bed exhibited violent slugging with chaotic flow at flow rates in excess of 2.8 The utility of the magnetically stabilized composition

35 is expanded using admixtures of magnetizable solids

From Table II it may be seen that, in common with with nonmagnetizable particulates as shown in the next the case of Example 1 wherein the field was vertically example. In the instant invention there is minimum oriented, the magnetized bed expands a great deal in tendency for the particles to segregate due to magnetic response to increasing flow of the support gas, air. Had attraction of the applied field since the applied field is the field of 570 oersteds been applied in the axial direc specified as preferably uniform. As a result, mixtures tion, the results of Example 1 indicate by interpolation may be fluidized and stabilized, exhibiting the transition that transition to bubbling would not occur until flow behavior and bed expansion properties. Thus, such mix rate equalled 45.5 cm/s, a flow rate that is 16 times tures may be employed in stabilized bed processes in greater than the flow rate at which bubbling actually 45 addition to beds comprised of all magnetic particles. occurred.

At all higher rates of flow in excess of 2.8 cm/s the EXAMPLE 4 bed exhibited violent slugging with chaotic flow. At all Admixtures were prepared of the nickel impregnated flow rates of less than 2.8 cm/s the bed medium failed to float a test cork. catalyst having a particle size range determined by In accord with well-known principles of physics, a 50 screening of 0.18 to 0.25 mm with a zeolite cracking single magnetizable particle placed in a uniform mag catalyst having particle sizes less than 0.07 mm. The netic field experiences no net force. In order to experi admixture was placed into the fluidization vessel de ence a force, a magnetizable particle must be subjected scribed in Example 1 to a typical depth of 25 mm. The to a gradient of applied field magnitude. The instant field source of Example 1 was utilized to provide speci invention preferably employs uniform applied magnetic 55 fied levels of applied magnetic field. Flow rate and bed field. As the result, when voidage nonuniformity tends expansion at the transition from the stably fluidized to develop in the medium, the uniformity of the field is condition perturbed locally, and field gradients created that exert of the teststoare the bubbling condition were noted. Results given in Tables IV and V below.

corrective forces returning the medium to its initial state of uniformity. 60 TABLE IV

Gradient magnetic field in the horizontal direction Transition Velocity of Admixtures (cm/s) can prevent the medium from achieving the state of Applied Field (Oersteds) fluidization, as illustrated in Example 3. Wt, % Magnetics O 100 300 500 700 EXAMPLE 3 - EFFECT OF TRANSVERSE 100 2.5 7 2. 33 37

MAGNETIC FELD GRADIENTS 50 <0.2 . - 3 5 6 The 1 x : x 6 inch fluidization chamber with the O <0.2

G87RS bed particles of Example 1 was subjected to the

Page 17

TABLE V TABLE VI

Bed Expansion of Admixtures at Transition - Discharge Coefficient for Flow Through an Orifice *:. . (% of Initial Height) Opening from a Bed of Magnetically Stabilized Fluid m Applied Field (Oersteds) Solids Wt. % Magnetics O 100 300 500 700 5 Discharge Coefficient, C, Di

mensionless Applied Field

50 < 10 18 22 23 80 Oersteds 400 Oesteds O 22 - Discharge Time, s 9.5 15

O 12.6 o .5

Admixtures containing 25% by weight of magnetics 16.0

did not remain homogeneously mixed during fluidiza 19.0 15 www tion. Such a phenomenon, resembling limited miscibility 20.6 .14 in liquid-liquid mixtures, must be determined on an individual basis for any particular admixture of bed 15 The above example and Table show that the stabi particles. lized fluidized solids flow in the manner of a liquid and The utility of the magnetically stabilized composi hence are facilitated for transport between and within tions in applications such as ab or adsorptive separation processing vessels. No prior art worker has reported of vapor species, catalyst utilization and regeneration, any measurement or experiment demonstrating this particulate filtration and subsequent bed cleaning, reac behavior. Prior to the present invention this behavior tion of solids in moving beds and allied applications in: for the magnetically stabilized solids was unknown. which bed solids must be transported to and from the COMPARATIVE EXAMPLES bed depend on the fluidized solids behaving as a me dium capable of flowing in response to a pressure differ EXAMPLE 6 ential. The following example illustrates that the solids 25 U.S. Pat. No. 3,440,731 of Tuthill provides an exam in the instant invention are imbued with fluid-line prop ple teaching the use of an alternating magnetic field to erties to a degree that is extremely well suited for such stabilize a fluid bed. The Tuthill example in common transport. with the instant invention utilized an axial orientation of EXAMPLES 30 field colinear with the flow direction. However, the A tall, cylindrical, fluidization vessel of transparent instant invention is distinguishable from the Tuthill plastic having inner diameter d of 7.37 centimeters and netic fieldin inspecifying example order to a nontime varying uniform mag obtain the widest range of bed wall thickness of 0.44 centimeters was provided with a stabilization over a specified range of gas fluidization circular orifice having diameter, d of 0.83 centimeters, 35 flow rates as a function of applied magnetic field. The orifice center was located 7.5 centimeters above the top of the bed's porous support grid. Quantities of Thus Tuthill repeatedly teaches that the magnetic field exerts a force on the magnetizable particles. As -40/+60 mesh G87RS magnetizable solids were ad already mentioned it is well known that a uniform mag mitted to the bed for tests in which the initial bed depth netic

L varied from 8.0 to 14.2 centimeters above the center 40 withinfield said exerts no force on a magnetizable particle field. In no manner does Tuthill teach, show of the orifice. The superficial air speed in all tests was or suggest that constant at 15.6 cm/s. Surrounding the bed was the usefully changea fluidization.

uniform field which exerts no force can

It is the new entirely sur source of uniform, axially oriented magnetic field pro prising discovery of this invention that a new and useful vided within the bore of the two six inch I.D. electro fluidized composition of matter may be achieved by use magnets. The applied field in these tests was of equal intensity on both sides of the orifice. When the orifice 45 of a uniform magnetic field which exerts no force. In was suddenly opened by removing a plug, it was ob that thecontradiction direct to Tuthill it is a necessary condition magnetic field be sufficiently uniform to exert served that the bed contents issued as a well definedjet. little or no force in order to achieve said new fluidized In a separate test with no fluidizing air flow, and with no applied field it was established that the powders 50 composition of matter. Failure to use a uniform mag netic field will have the result that the field exerts a jammed the orifice at once, and would not pass through force on the fluidized matter, causing it to be nonuni of their own accord. form with undesirable effects. Table IV provides experimental results obtained for To demonstrate the improved performance attendant the discharge of the stablized fluidized solids through to an increased uniformity of field, the Tuthill apparatus the orifice. The time for the solids to discharge to a 55 was duplicated and comparative tests performed as level Lof 4.0 centimeters above the orifice center was described in the following example. determined using a stopwatch, and a discharge coeffici An electromagnetic coil having an inner diameter of ent C computed as ..., -. . . 2 in. and a square cross section of 12 in. was fabricated of 14 gage copper wire. When supplied with 60 cycle current of 1.25 amperes, 3.9 volts were measured across

the magnet's terminals. The magnet resistance was 0.76 ohms and thus the IR power dissipated by the magnet was 1.2 watts. A Hall probe positioned 9/16 inch above where T is the time interval and g = 980 cm/s, the 65 the top of the coil measured a field intensity of 34 gauss, acceleration due to gravity. It may be seen from the At the same position Tuthill reports a field intensity of table that the orifice coefficient was constant at 0.14 to 365 gauss, or about ten times the value found here. It is 0.15 independent of initial bed depth or applied mag well known that the field generated by a coil of a given netic field intensity over the range studied. conductor having a given geometry depends only on

Page 18

the power input. If it is taken as a fact from Tuthill's Table VII representing incremental increases in super example, that his magnet also dissipated 1.2 watts, cor ficial velocity associated with the application of the responding to 0.8 amperes of current and resistance of magnetic field.

1.9 ohm, his field should be smaller. It appears that the With the magnet positioned above the bed the field field intensity reported by Tuthill would require 10 5 nonuniformity was 165% as detailed in Tables VII and times the current or 100 times the power he reported. VIII. A comparitive test at the nonuniformity of 51% Most likely the Tuthill field intensity is overstated. corresponded to positioning the magnet at the level of Notwithstanding the above variance, a duplicate of the center point of the bed. An additional test at nonuni the Tuthill bed was prepared comprising one hundred formity of 11% utilized another magnet, one having a 6 and ninety-two grams of in. diameter carbon steel 10 inch bore and 4 inch length.

balls charged to an open-topped cylindrical glass fluid In all cases, the application of magnetic field caused a ization chamber having an inner diameter of 13 in. and deferral of slugging to a higher value of gas throughput. a height of 24 inches. At the lower end of the column In the tests described the bed contents were observed the diameter was tapered and fitted with a gas inlet of to recirculate prior to the onset of bed slugging. Gener reduced diameter. Near the bottom of the column and 15 ally this recirculation is undesirable in applications of supported by the tapered section were several layers of stabilized beds requiring a high degree of staging or woven stainless steel mesh having about in. openings. excellence of countercurrent contacting. It was sus The mesh layers were arranged with their grid axes in pected that the cause of recirculation was the low pres non-orthogonal alignment to serve as a combination sure drop of the support grid relative to the pressure support grid for the balls and as a distribution plate for 20 drop of the bed. A grid of 100 mesh screen described in the fluidizing medium. As such this apparatus dupli the example below was substituted for the inch mesh cated the apparatus of Tuthill. of the Tuthill bed and cured the problem.

TABLE VI

INFLUENCE OF A.C. FIELD SPATIAL UNIFORMITY ON SLUGGING

OF BED OF 1/8 N. CARSON STEEL SPHERES

Superficial Velocity, ft/s

Test Mean Field, Nonuniformit Slugging

Reference Gauss of Field, 9% Motion Velocity Increment 439-14 O w 10.5 0 4391-15 35 165(d) 12.0 1.5 4391-19 36 51 13.4 2.9 3459-51 35 1. 14.4 3.9 10 mm height.

Mean Field = (Maximum field in bed + Minimum field in bed)/2.

Nonuniformity of field = (Maximum field in bed - Minimum field in bed) x 100/Mean Field.

Corresponds to nonuniformity in example of Tuthill.

TABLE VIII

MAGNETIC FELD PARAMETERS

Magnetic Field, Oersteds

Distance of Magnet Non Test Magnet Center over Grid, Magnet Maximum Minimum Mean uniformity, Reference Identification Inches Current, Amperes in Bed in Bed in Bed % 439-14 O 0(a) 0(a) 0(a) O 4391-15 2 inch bore 4. 3 63(b) 6(d) 35 165 4391-19 2 inch bore 1. 1 45(c) 27(b), (d) 36 51 3459-51 6 inch bore 1. 58 37(c) 33(b), (d) 35 11

Ignores laboratory background field of about 0.5 gauss.

Bed top surface.

Bed center.

Bed bottom.

The height of the settled bed of balls extended for 2:

inches above the topmost layer of mesh. 50 Since Tuthill employed a magnetic source driven by The electromagnetic coil was supported coaxially an alternating current, the direction of field reversed with the fluidization column with the mid-plane of the with time. If the bed of particles possess an appreciable coil at a height of 43 in. above the top-most layer of remanence the reversal of field direction can cause the mesh. particles to rotate or agitate in attempting to track the A rotameter fed by a regulated source of compressed 55 field direction. The following example demonstrates the air was provided to measure the flow rate. adverse influence alternating magnetic field can exert The results of a series of tests that indicate the influ on stability of such fluidized solids. ence of field uniformity on bed stabilization is summa EXAMPLE 7 rized by Table VIII.

In the absence of an applied field the bed fluidized at 60 The fluidization chamber of the example given previ a superficial velocity of 8.7 ft/s as evidenced by motion ously was modified by removing the coarse grid and of balls at the bed surface. At 9.2 ft/s the bed contents adding a grid of 100 mesh screen capable of supporting exhibited circulatory motion, rising at the center and powders that are screened to -40/+60 mesh. A pack descending at the walls. At 10.5 ft/s the bed slugged to ing of inch plastic spheres was provided upstream of a height of 10 mm. With further increases of flow rate 65 the mesh to insure a uniform approach flow. The first the bed contents could be made to slug to any desired quadrant hysteresis loop for G87RS powder was deter height within the column. The value of 10.5 ft/s was mined using a vibrating sample magnetometer. The adopted as a reference velocity, with the last column of saturation moment was 13.8 e.m.u./g. at 3500 gauss and

Page 19

remanence was about 3 em.u./g. A 39 mm depth of the ing applied magnetic fields can be deleterious to the G87RS powder was placed on the grid and a series of stability of fluidized magnetized solid particulates. tests performed using direct and then alternating cur TABLE X rent to energize the 1 x 13 inches cross-section mag STABILITY OF FLUIDIZED SOLIDS TO ALTER net described in the previous example. The results of 5 NATING MAGNETIC FELD these tests are summarized in Table IX. Here the term Example 6 Example 7 "transition speed" is used with a special meaning in Bed Media Iron spheres Catalyst powder reference to the AC tests wherein although the term Particle size, denotes the observation of surface bubbling the bed is R., cm.

Remanent moment,

not truly fluidized (lifted). 10 o, e.m.u./g. 1.5 3.0 TABLE IX Field intensity,

NFLUENCE OF ALTERNATING AND DIRECT Frequency, f. Hz 60 60 CURRENT FIELD SOURCES ONSURFACE N(computed) 0.13 BUBBLING OF AMAGNETIC POWDER Prediction Stable Unstable HAVING REMANENCE Observation Stable Unstable

Peak Field) Transition Velocity, cm/s 15

O 13.0 3.0 Example 3 has already illustrated the very adverse

7.8 influence that an appreciable transverse gradient offield 90 20.5 9.3 may exert on the ability of a bed of magnetizable parti 20 22.4 10,0 20 cles to be fluidized. In the following example, it is dem

DC and AC sources both 20% non-uniform over the bed volume.

onstrated that when the applied field is vertically ori ented it is preferable in the interest of achieving the

From Table IX it may be seen that application of the widest possible stable range of the bed at the lowest consumption of electrical power to utilize the most direct current field increased the transition velocity of 25 uniform possible magnetic field. the bed of powders while application of the alternating current field decreased the transition speed relative to EXAMPLE 8 the value observed in the absence of field. Thus, alter Various configurations of magnets, magnet position nating field is undesirable in preparing the said stabi relative to the vessel and magnet current were set up to lized compositions of matter. 30

The instant invention is distinguishable from the Tu provide constant discrete levels of field nonuniformity at several values of mean field applied over the volume thill art in that time steady magnetic fields are preferred in the instant invention. of a bed of -40/+60 mesh G87RS solids having a Ideally in a fluidized bed an individual particle of the settled bed depth of 39 mm. The magnets were those bed may rotate with a minimum of frictional torque due 35 described in the previous examples. The bed was the 1 to the negligible contact with neighboring particles. By inch inner diameter glass column.

considering the angular displacement of a bed particle The operating conditions and test results are given in having remanent moment in response to the magnetic Table XI where it may be seen that mean field was set torque set up by a reversing field, with rotation resisted at 0, 40, ca 120, or 400 oersteds in any given test and, by particle inertia alone, a criterion may be obtained likesiwse, the variation of field over the volume of the indicating the range over which alternating field pro bed in any one test established as 136%, 17% or 4%. duces an appreciable rotation of the particle and hence Transition speed was established by noting for a bed presumably tends to upset the stability of the bed. The whose contents had previously been aerated in the ab criterion may be stated as sence of applied field, the flow rate at which steady 45 bubbling was observed at the top surface after magnetic >l unstable field had again been applied. The last column of Table

Cl stable XI lists the width of the stable range, measured in veloc where ity units, between the normal fluidization speed of the bed and the speed at which bubble transition occurs. At

SoH 50 the low mean field of 40 oersteds where the stable range 8trRf is very narrow, about 4 velocity units (cm/s), the preci sion of the data does not permit any conclusion regard

The criterion applies for field cycle times that are ing the influence of field nonuniformity on transition. However, at the mean field of about 120 oersteds it is smaller than the duration of bed operation. Thus, direct seen that the field with 4% variation stabilizes twice as current beds, which have the greatest stability, are not 55 described by the criterion. In the formula or , is rema broad a nonbubbling range as the nonuniform 17% and nent moment (e.m.u?/g), His applied field (oersteds), R 136% cases. The same striking behavior is exhibited in is equivalent spherical radius of the particle (cm) and f the tests at 400 oersteds mean field in which stability is frequency (Hz). Table X comparing conditions of over a range of width 29.1 cm/s was achieved at 4% Examples 6 and 7 illustrates that the criterion predicts 60 spatial variation in applied field while 17% variation correctly the outcome of these tests. Thus, the criterion reduced the stable range to only 17.8 cm/s. is suggested to delineate the combinations of particle In addition to the superior performance attendant to magnetic moment and size, and magnetic field intensity use of uniform field it is noted that power consumption and frequency which permit bed stabilization to be to operate an electromagnet source of field is vastly obtained in the face of alternating field. Stability in the 65 reduced. For example, referring to Table XI, for mean race of alternating applied field is favored by large field of 120 oersteds, the equivalent stable range is ob particle size, high frequency, and small remanence. As tained at 136% nonuniformity as at 17%, but the power can be seen from the above Example, the use of alternat consumption assuming the magnet's resistance was un

Page 20

changed, was larger by the square of the ratio of cur valve permitted opening the discharge ports simulta rent. This computes to (25/3) or 69.4 times the power neously.

consumption at 136% as at 17% nonuniformity of field. A portion of the normally black bed solids was tagged with a surface coating of blue pigment particles,

TABLE X

INFLUENCE OF AXIAL D.C. FIELD AXIAL UNIFORMITY ON TRANSITION

TOBUBBLING FORBED OF 40/+60 MESHG87RS

Magnet Current, Mean Field. Nonuniformity Superficial Velocity,cm/s

Test No.() Configuration Amperes Oersteds of Field, 26 Transition Stable Range 47:20 None 0.0 O 0. 3.2 0.0 SO:A. T/A 9.0 40 136 17.8 4.6 47:24 T/C 10 40 7 6.6 3.4 49:B RAC 0.5 40 4. 7.3 4. 50:C TA 25.0 11 136 2.3 8.1 47:25 T/C 3.0 120 17 21.9 8.7 49:D RMC .5 120 4. 30.8 17.6 50E T/C 10. 400 17 3.0 17.8 47:10 RMC 5.0 400 4. 42.3 29.1 T denotes 2 inch bore 1" x 1" cross-section toroidal electromagnet.

R denotes two 6 inch bore electromagnets at inch separation,

A denotes magnet center 4 inches above support grid.

C denotes magnet center coincident with center of bed.

'settled bed depth of 39 mm over 100 mesh grid.

Definitions are given in footnotes to Table VIII.

Throughout the foregoing the discussion has utilized the artifice of a fluidization chamber operated in the presence of a gravitational force field. It will be evident Ultramarine 59-4933 of Cyanamid Company, and that the new composition of matter can be generated as 25 placed in the bed in layers. In the settled bed the blue well in other force fields provided the flow of fluidizing colored layers varied from 0.80 to 1.0 centimeter in gas is in the direction opposing the external force field. thickness with the bottom of the lowest layer located Thus the force field may be due to centrifugal forces of 9.7 centimeters above the distributor and the remaining a rotating system, or for the electrical force on charged layers spaced 5.0 centimeters apart from each other matter in an electrostatic field, or to dielectrophoretic 30 with the uppermost layer forming the top of the bed. force of electrically polarized matter in an electrostatic The field source was a 20 centimeter bore by 100 field having a field gradient, or to forces caused by centimeter long electromagnet solenoid made up of 12 presence of a magnetic field gradient, or to Lorentz identical pancake modules each having thickness of 4.1 force due to passage of a current at an angle to a mag centimeters and face to face separation of 7.0 centime netic field, or due to any other force field or to combina 35 ters over the region occupied by the vessel. The applied tions of the foregoing. In each instance the end result is field was uniform to within 2% over the test volume, the achieving of a stable form of fluidized matter having and in the test applied field intensity was constant at 400 the thermodynamic analog properties, transport proper Oersteds.

ties and other properties inherent to the state of bulk With the field applied and the discharge ports closed, matter already described. a flow of air was admitted to the vessel. As minimum It is noted that while the instant invention has been fluidization speed was passed the bed expanded with defined in terms of novel composition of matter, the further increase of flow rate and the colored bands were process for obtaining said composition, as claimed be observed to rise with the bed. The flow rate was low, is also a part of the instant invention. Also the brought to a superficial velocity of 30.5 cm/s. The inter composition of matter disclosed above may be arranged 45 faces between the colored layers and the bed remained throughout the contents of a bed, or alternatively, if sharply defined.

desired, at points or regions within a bed. It will be The rotary valve was actuated to suddenly open the understant that the term point denotes a localized re eight discharge ports. The bed volume then suddenly gion which in all dimensions is large compared to the contracted due to reduction of air flow up the bed as a spacing between particles and is small compared to any 50 portion of the flow bypassed through the discharge dimensions of the bed. ports. Then a slower process of bed movement contin EXAMPLE 9 ued in which the solids descended and the colored lay ers were observed to move down the column as bed

Example 5 demonstrated that the solids in the mag solids discharged through the vessel sidewall openings. netically stabilized fluidized bed will flow and dis 55 With the bed solids about half discharged the rotary charge through an orifice in the vessel sidewall. The valve was rapidly closed, the full upward flow of air purpose of this example is to demonstrate further that resumed, and the bed observed to expand and accom movement of the solids may achieve piston displace modate the increased air throughout that once again ment with no relative motion between bed solids when was established. .. the bed discharges. 60 With the bed then quiescent instable batch operation, Twelve hundred and eighty five grams of 350 to 840 the colored layers could be examined at leisure. Inspec micron G87Rs catalyst was placed in a 7.5 centimeter tion of the layers illustrated they were free of distortion transparent plastic vessel fitted with a porous disk dis and that the bed was free of solids backmixing insofar as tributor. The dumped bed height was about 28.4 centi could be detected from the appearance at the bed side meters. Eight discharge ports were provided symmetri surface and the bed top. There as no adherence of solids cally spaced around the vessel sidewall, each having to the wall and it was concluded the solids descended diameter 0.64 centimeter with the center of each hole with uniform speed over the bed cross section. Suff 3.8 centimeter above the top of the distributor. A rotary ciently close to the discharge ports the flow, of course,

Page 21

cannot remain one dimensional in character but must TABLE XII flow sideways. MAGNETICFIELD FLUCTUATION MEASUREMENTS Inspection of the solids discharged from the ports IN FLUIDEZED MAGNETIZED MEDIUM revealed the amounts to be closely equal and distributed Hall Probe Measurements in piles at nearly equal distances from the discharge H mean Hrms/H mean ports. O % State of Bed The rotary valve again was opened and the solids 569

quiescent quiescent permitted to discharge fully. Motion picture photo 442 O quiescent graphs were recorded of the test and verified the above 400

quiescent quiescent description. O 350 O quiescent

light bubbling moderate bubbling

The purpose of this example is to illustrate by mea 119 1.8 heavy bubbling surement the absence of fluctuations of bed voidage in 60

heavy bubbling heavy bubbling the stably fluidized magnetized bed of the present in 15 'rms is defined as the root mean square of the fluctuation signal. vention and the presence of fluctuations when the bed 'Values listed as zero in fact were somewhat less than the noise level after correct bubbles. ing for measured noise, hence are neglected. The neglected values ranged from One hundred and sixty six grams of -20/+30 U.S. 0.004 to 0.013 percent.

sieve G-87RS catalyst were placed in a 5 centimeter

I.D. glass vessel fitted with a porous disk distributor. A 20 EXAMPLE 11 magnetic field of 569 oersted intensity was applied to the bed. Nitrogen at ambient temperature and pressure This example demonstrates the influence of particle was passed upward at a superficial velocity of 51.4 cm/s size and bed mass on transition velocity. yielding an expanding bed height of about 15 centime Monel The bed solids were various narrowly sieved sizes of ters. Miminum fluidization velocity previously was 25 ing specific (ferromagnetically soft copper-nickel alloy) hav found to be 23.5 cm/s as determined from the break gravity 8.45 and particle magnetization of point in a curve of measured values of pressure vs. flow 372 gauss at 5000 oersteds applied field. The transparent rate. plastic cylindrical fluidization vessel was 7.57 centime A Hall effect gaussmeter probe (Bell Z OB4-3218) ter inside diameter and fitted with a porous disk distrib was mounted above the vessel with its active element in 30 utor.20The fluidizing gas was air. The field source was the middle of the bed of solids. The probe is a flat ended the centimeter bore electromagnet described in Ex cylinder of 0.81 cm O.D. sensing the magnetic field ample 9. This electromagnet was water cooled through component normal to the flat end, i.e. the axial compo its hollow copper conductive windings. nent of field in the vessel. The probe was connected to Results of test in which length of the bed and super a Bell 620 gaussmeter, whose outut was amplified by a 35 ficial velocity of the air were determined at the transi Tektronix AF 501. A custom low-pass filter having tion point are tabulated in Table XIII for various amplitude response down 50% at 70 Hz to eliminate a 5 amounts the bed of solids in the vessel. At every test condition was observed to fluidize smoothly, the bed top

KHz gaussmeter oscillator signal then fed a Disa 55 D 35 RMS unit operated with a 100 second averaging bubbling surface was flat and finely structured, and transition to time, whose output was recorded on a Hewlett-Packard 5% or lessoccurred suddenly with a reproducibility of of the superficial velocity, 7004B X-Y recorder.

Table XXII presents the sequence of mean axial mag It may be seen that transition velocity increases with netic field intensities applied to the bed, the fluctuation increase of particle size and decreases with increase of bed length. The transition speed of long bed tends to be of the field expressed as a percentage of the mean and invariant of bed length.

the visually observed state of the bed. Fluctuations 45 The response and expansion of a bed having a con were absent within the precision of the measurement at stant mass of Monel solids is given at Table XIV. As mean field intensities of 350 oersted and greater, corre superficial sponding to a visually observed quiescent state of the the bed remains velocity increases from its initial zero value bed. The fluctuation level rises very sharply as the field restructuring unchanged in length save for a minor is decreased through the bubble point, and more gradu 50 of the bed top surface. At the point of ally thereafter. The zero measured values of Hrms/H minimum fluidization the bed begins to expand. Expan means in column 2 of Table XII indicate the complete sion is continuous as flow rate increases with the me absence of bubbles in the fluidized medium. dium remaining quiescent in the stably fluidized state until the point of transition to bubbling occurs. The 55 break in the curve of bed length versus flow rate fur nishes a definitive means of determining minimum fluid ization speed as an alternative to determining the break in the curve of pressure drop versus flow rate.

TABLE XIII

CORRESPONDING VALUES OF TRANSITION LENGTH

AND VELOCITY IN VARIABLE MASS BEDS OF MONEL

H - 5080 Oersteds

Particle Size, Microns

Nominal Mass, 149-177 177.250 250-297

Grams L7 cm Up cm/s Ircm Up cm/s L7 cm Up cm/s

400 - - 5.6 90 5.0 15

Page 22

TABLE XIII-continued

CORRESPONDING VALUES OF TRANSITION LENGTH

AND VELOCITY IN VARIABLE MASS BEDS OF MONEL

His 5080 Oersteds

Particle Size, Microns

Nominal Mass, 149-177 177-250 250-297

Grams LT cm U7 cm/s Icm UT cm/s L., cm UT cm/s

(Minimum bubbling speeds in absence of field increase with bed mass over the range given below:

D., Microns Velocity, cm/s

TABLE XIV

RESPONSE AND EXPANSION OF CONSTANT MASS

MONEL SOLIDS TO INCREASING

Superficial Velocity,

Bed Length

AIR FLOW RATE

U., cm/s L., cm Comments 20 TABLE XV O P idized MAGNETIC MOMENT OF 177-250 MICRON C1018 2 23, E. STEEL SPHERES(), () IN APPLIED FIELDS 18 20.8 Unfluidized Applied Magnetic Magnetic Moment Magnetization 22 20.8 Unfluidized Field, H, Oersted o, empl/g M, gauss' 28 20.8 Min. Fluidization O 0.026 2.6 34 21.5 Stably Fluidized 25 16 668 67 40 22.3 Stably Fluidized 32 128 127 51 24.4 Stably Fluidized 48 186 184 57 25.5 Stably Fluidized 64 2.45 242 61 26.0 Stably Fluidized 80 303 300 66 26.3 Transition Point O(4) 0.030 3.0 Mass of Monel 2840 grams. 30 'Sample mass of 0.3329 grams in cylindrical sample holder of about 3 mm I.D. Particle size 177-250 micron.

Applied field 5000 oersteds Saturation moment in 16,000 oersteds applied field of 212 empl/g or 20,970 gauss, Vessel I.D. 7.57 centimeteters. M = 4rpor with density p taken as 7.87 gram/cm. 'Reduced from 80 oersteds.

EXAMPLE 12

The remanent magnetization of 2.6 to 3.0 gauss is 35 small compared to the magnetization values at the ap

This example demonstrates that minimum fluidization plied field intensities, hence the material may be re velocity of a magnetizable particle bed is constant and garded as ferromagnetically soft in this working range. unaffected by the presence or intensity of an applied Table XVI lists values of pressure drop across the magnetic field and that a higher velocity of gas whole bed length versus superficial flow rate at various throughput is required to cause the stably fluidized bed 40 intensities of applied magnetic field. FIG. 5 presents the to undergo transition from the quiescent state to a state data plot for the field intensity of 48 oersteds. The of bubbling or slugging motion. breakpoint of the curve is taken as the point of minimum A cylindrical fluidization vessel of 7.49 centimeter fluidization. Values of minimum fluidization velocity inside diameter and 41 centimeter height over a micro Urobtained in this manner are tabulated in the second porous support grid is loaded with 3110 grams of C1018 45 column of Table XVII. There it may be seen that mini iron spheres supplied by Nuclear Metals Corporation. mum fluidization speed has a sensibly constant value The iron spheres are screened to the size range of 177 to independent of applied field intensity.

250 microns. The bed length with initially loaded solids From column three of Table XVII it is seen that bed is 15 centimeters. The magnetic field source is the pair length is constant and unchanging below the point of of 6 inch bore electromagnets, each having length of 450 minimum fluidization. The bed expands at flow rates inches and face to face separation of 1.5 inches. The greater than minimum fluidization velocity, reaching magnetic field is oriented colinear with the bed flow the length given in the fifth column of Table XVII at axis, with the center of the magnet pair of the center of the point of transition to the bubbling state. The transi gravity of the bed contents. The fluidizing gas is air. tion to bubbling or slugging occurs suddenly as deter A long straight glass tube of 6 mm O.D. and 4 mm 55 mined by visual observation. Steady surface bubbling

I.D. is inserted vertically into the bed to sense gas pres for a minimum duration of about 30 seconds is taken as sure in the bed. The tube tip is positioned one centime criterion for the transition, with the velocity at transi ter above the bed grid and a U-tube manometer con tion denoted U.T. Values of UT are tabulated in the nected to the other end of the tube. The bed is fluidized fourth column of Table XVII. At H of 64 and 72 oer in the bubbling regime in the absence of field, then 60 steds, transition was to slugging.

collapsed by stopping the gas flow before the beginning FIG. 6 presents the diagram that results from plotting of a test sequence. The magnetic field is applied in the Urand Urversus applied field. The magnetically stabi absence of flow, and pressure measured in response to lized state of fluidized solids is defined by the region increases in flow rate at the constant magnetic field between the curves of M and UT. This region pro setting. 65 vides a broad operating range in which the medium is Magnetometer measurement of the iron solids using fluidized yet quiescent and free of bubbles or solids the vibrating sample technique gives the values of mag backmixing. The bed medium in this region is facilitated netic moment listed in Table XV. for transport, e.g. into or out of the containing vessel.

Page 23

TABLE XVI lyst was previously magnetized in an applied field of

INFLUENCE OF FLOW RATE AND APPLIED FIELD 5000 oersteds. Due to its remanent magnetization the INTENSITY ON PRESSURE DROPFOR FLOW OF material had the texture of wet sand, noticeable when AIR THROUGH A BED OF IRON SPHERES(), (2) pouring or screening.

Flow Rate, U Applied Field Intensity,H, Oersteds 5 A quantity of 1280 grams was added to a fluidization cm/s O 16 32 48 64 72

vessel having inside diameter of 7.33 cm. The depth of 4.25 5 15 solids over the fitted porous distributor was 17.8 cm.

In the absence of applied field as air flow was in 12.3 creased the bed of solids was observed to develop void 16.7 1. O age layers of separation in the upper one-third of the

bed at a superficial velocity of 10.3 cm/s. Pressure drop 25.3 through the bed increased smoothly with increase of

superficial velocity until at 38.3 cm/s a spout formed in 42.2 the bed and the pressure drop decreased from about 6.4 49.2 15 cm. of dibutylphthalate (DBP) to 2.9 cm. The spout had

98.0 - : formed along the length of the 6 mm O.D. by 4mm I.D. 'Pressure units are centimeters of mercury, extrapolated to support grid surface glass tube used as the pressure probe that was inserted based on linear change with distance. to a 9 cm. depth within the bed. Thus, these solids failed 'C1018 steel 177-250 microns, to fluidize properly in the absence of applied field. 20 When uniform, axially oriented magnetic field of 40

The final column of Table XVII tabulates the plateau Oersteds was applied the measured pressure drop in value of pressure drop normalized by the ratio of bed creased smoothly with increase of air flow rate up to a mass W to bed cross section area A; this quantity theo Superficial velocity of 42.7 cm/s. A futher increase of retically equals unity when expressed in dimensionally superficial velocity to 46.6 cm/s then caused a spout to consistent units. The experimental values are in reason 25 form adjacent to the probe and measured pressure drop able agreement with the theoretical expectation and decreased by about 47%. Again the bed structure dete verify the existence of the fluidized state of the bed in riorated and lead to bypassing of the gas stream. both the stabilized and bubbling regimes, i.e. regions in Finally, with applied field of 80 oersteds and the which velocity U is less than and greater than U re probe tip located about 5 mm, above the support grid, spectively. 30 the bed retained its structural integrity throughout a test Sonoliker, R. L. et al., Indian Journal of Technology, sequence in which superficial velocity ranged up to 10, 377 (1972) reported observations of fluidized iron 100.4 cm/s. Pressure drop initially increased linearly powders subjected to an axially oriented applied mag with superficial velocity, then plateaued at 25.6 cm. netic field. In particular in Table I of Sonoliker et al., DBP. The break in the curve of pressure drop vs. super experimental results are given for the minimum fluidiza 35 ficial velocity defined a point of minimum fluidization tion velocity of iron particles, including results for par of 40.0 cm/s. The bed length was constant at 17.8 cm. ticles of 244 microns diameter, hence comparable to the up to the point of minimum fluidization, then expanded size range studied here. The values of minimum fluidiza to 24.0 cm. at the said maximum flow rate of 100.4 cm/s. tion velocity in Sonoliker et al increase exponentally The bed remained free of bubbles or agitation at all flow with applied field intensity. This is in marked contrast 40 rates studied. The test was repeated and displayed the to the sensibly constant value of minimum fluidization similar behavior with maximum superficial velocity velocity characterizing the instant invention and illus reacing 115 cm/s.

trated by values in column two of Table XVII below. It Magnetic moment of this ammonia catalyst is given in is possible that Sonoliker etal observed transition veloc Table XVIII. The moment of 0.03 emu/g at zero ap ity Ur and identified it as minimum fluidization speed 45 plied field pertains to a powder sample of the -20/+30 UF. Accordingly, Sonoliker et al might have passed mesh material that had previously been subjected to through the stabilized region in a transitory manner in 5000 oersteds applied field. The low moment indicates their experiments. In any event it is clear that Sonoliker the sample particles were nearly randomly oriented et al provide no teaching of the existence of a stably since the remanent magnetization is large for an undis fluidized region as instantly claimed. In view of the 50 turbed sample, i.e., 18.4 emu/g after exposure to applied report of Sonoliker et all the performance in the instant field intensity of 16,000 oersteds.

process and the properties of the medium thereby gen erated are totally unexpected and surprising.

TABLE XVII

BEHAVOR SUMMARIZED FOR THE MAGNETIZED BED

OF STEEL SPHERES (177-250 MICRONS)

Applied Field Minimum Fluidization Bed Length. At Transition Bed Length. At AP H, Oersteds Velocity, Up Lim, cm Velocity, U cm/s Transition, L cm W/A O 13.5 15,0 3.5 S.O 0.91

64 15,0 SO 68,3 18,0 1.02 72 S.O 15,0: 68.3 100 At applied field of 80 oersteds the bed medium entrains as a plug moving up the vessel column at a gas throughput less than transition,

EXAMPLE 13

Ammonia catalyst of 3 to 6 mm. particle size was crushed and sieved to U.S. mesh -20/-30. This cata

Page 24

TABLE XVIII TABLE XIX-continued

MAGNETIC MOMENT OF AMMONIA CATALYST PRESSURE DROP, PRESSURE FLUCTUATIONS, Applied Field, H., re. Magnetic Moment emu/g AND BED LENGTH CHANGE OF AIR FLUIDIZED CO18

STEELSPHERES OF 77-250 MICRON DIAMETER IN 48

O 0.03 OESTERAPPLIED FELD 40 58 Bubbles

5,000 144 U AP. - A P A L, State of Ot 16,000 166 cm/s cm HO cmHO cm the solids Motion O 18.4 40.9 51.0 3.0 3.5 Unstably Fluidized Yes

EXAMPLE 14

TABLE XX

This example illustrates that fluctuations of gas pres DISTINGUISHABLE STATES OF THE sure distinguish the bubbling state of magnetized, fluid PARTICULATESOLIDS ized solids from the stably fluidized state. In the stably 15 State Pressure drop Bed Length fluidized state fluctuations are not detected. of increase increase Pressure Solids with flow with flow Fluctuates

Two thousand nine hundred and seventy grams of Settled Yes No No 177-250 micron spherical particles of C1018 steel de Stably Fluidized No Yes No scribed in Example 12 were placed in a fluidization Unstably Fluidized No Yes Yes | vessel having inside diameter of 7.32 centimeters. The 20 vessel was fitted with a pressure tap in the sidewall at a point 4 centimeters above the porous support grid. The tionAsofcanthebeinvention, seen from the above examples and descrip pressure tap contained a wire mesh screen that pre means for conducting the present invention provides a a fluidization process at a wide vented particles from leaving the vessel. One side of a range of flow rates before the bubble transition point is U-tube manometer containing water water was con 25 reached. For example, as discussed above, it has been nected to the tap and the other end of the manometer found that the larger the magnetization M of the fluidiz kept open to the atmosphere as was the top of the fluid ization vessel. Uniformly, axially oriented magnetic able and magnetizable particles up to the point of ag field of 48 oersteds intensity was applied to the solids glomeration, the higher will be the transition velocity using the pair of six inch bore electromagnets. Increas without bubblingtheand

Urup to which stably fluidized bed may be operated ing rates of steady air flow were admitted to the vessel variables being equal. time-varying It will be fluctuation, all other recognized that in prac to obtain measurement of pressure drop APo read as difference in height of water in the manometer legs. ticing the invention, it is the intent to operate the pro cess in the stable, non-fluctuation manner wherein the

When the bed became stably fluidized, its length gradu stably fluidized bed is bubble-free. Accordingly, the size ally expanded with gas flow. Observation was also 35 of bubbles in the stabilized fluidized media, if they do made of pressure drop fluctuation tAP, if any, and presence or absence of visible bubbling or motion in the exist, will be about no larger than the spacing between fluidized medium. The fluctuations in pressure drop particles and consequently do not cause time-varying represent values detected over about a ten second inter fluctuations of the pressure difference through the fluid val. The observed values of pressure drop, pressure ized bed over a finite period of time, e.g., 10 seconds, drop fluctuations, bed length and other parameters, are preferably fluidization.

a 100 second time interval during continuous listed in Table XIX.

From the data in Table XIX it may be seen that the As earlier indicated, the fluidization process of the stably fluidized state is clearly distinguishable from the present invention is useful in many applications hereto settled state (fixed bed state) as well as from the unsta- 45 fore used in the fluidization art. Of particular impor bly fluidized state. Thus, only in the stably fluidized tance are the petroleum processes such as hydrofining, hydrocracking, hydrodesulfurization, catalytic crack state is pressure drop invariant of flow rate, and bed length increasing with an increase of flow rate, while ing and catalytic reforming. The Table XXI summarizes pressure fluctuations are absent. Comparative behavior typical hydrocarbon conversion process conditions of the states is summarized in Table XX. 50 effective in the present invention. It is noted that in the fluidized states the constant The feedstock suitable for conversion in accordance value of average pressure drop indicates the solids in the with the invention include all of the well-known feeds vessel were supported entirely by fluid forces. Visual conventionally employed in hydrocarbon conversion observation of initial bubbling and motion in the bed processes. Usually, they will be petroleum derived, coincide with the first detectable fluctuation of pressure 55 although other sources such as shale oil and coal are not drop (pressure difference). to be excluded. Typical of such feeds are heavy and TABLE XX light virgin gas oils, coker gas oils, steam-cracked gas PRESSURE DROP, PRESSURE FLUCTUATIONS, oils, middle distillates, steam-cracked naphthas, coker AND BE LENGTH CHANGE OF AIR FLUIDIZED C1018 naphthas, cycle oils, deasphalted residua, etc. STEEL SPHERES OF 177-250 MICRON DIAMETER IN 48 60

OESTERAPPLIED FELD GENERAL

Bubbles

U AP, - A P A L, State of or Generally, the magnetization M of a particle as ob cm/s cm HO cmHO cm the solids Motion tained from a magnetometer when a given magnetizing

Settled

Settled

field His applied will not provide a value which is the 12.7 54.0 O O Settled No 65 same as the magnetization of the particle in response to

Stably Fluidized

Stably Fluidized

the same intensity of magnetic field in the fluidized bed 25.4 56.5 O 2.0 Stably Fluidized No to be used in accordance with the teachings of the pres 31.7 56.6 0.05 2.7 Unstably Fluidized Yes ent invention.

Page 25

The purpose of the following is to indicate a method Thus, on the graph of M. vs. He straight lines of slope for determining the magnetization M, of a typical parti K intersecting the measured curve and the H axis cle in a bed from those values obtained from a magne relate corresponding values of M, and H. Accordingly tometer. Generally, this will require a calculation since a graph may be constructed of M. vs. H. For example, the effective field that a bed particle is subjected to when the sample is contained in a spherical cavity d = depends on the applied field, the bed geometry, the , K is infinite, and H, equals H. For a long sample particle geometry, the bed voidage and particle magnet such that d = 0, K is negative and His less than H, i.e. ization. A general expression has been derived to relate the field magnetizing a particle of the sample is greater these quantities based on the classical approximation of than the field applied to the sample. the Lorentz cavity that is employed in analogous physi- 10 Additionally, for a process bed, a constant K may be cal problems such as the polarization of dielectric mole defined as follows:

cules.

H = H. + M, (d+ (1-6)(d.-) (1) K, = (6)

His the applied magnetic field as measured in the ab sence of the particles, H, the magnetic field within a It may also be seen from Eq. (2) that a line of slope particle, M, the particle magnetization, d, the particle -Kpassing through a point H, on the horizontal axis demagnetization coefficient, e, the voidage in the parti-. of the graph of M. vs. H. intersects the curve on the cle bed, and d the bed demagnetization coefficient. The 20 graph at a value of Mgiving the particle magnetization term - is due to the magnetizing influence of a (vir in the bed. Thus, the particle magnetization M, in a tual) sphere surrounding the bed particle. - process bed has been related to the field Happlied to The expression above applies as well to a sample of the process bed.

particles such as used in a magnetometer measurement. The relationship of Eq. (1) is an approximation more In that case dis the demagnetization coefficient d, cor- 25 likely to be accurate for beds having high voidage than responding to shape of the cavity in the sample holder. for very densely packed samples.

Magnetometer measurement produces a graph of M It is to be understood that the term "applied magnetic vs. H. Using the above equation and known values of field' used throughout the specification and claims d, d, e M, and H, a corresponding value of H. may be refers to an empty vessel applied magnetic field.

TABLE XXI

Reaction Conditions

Principal Conversion Temperature Pressure Feed Rate Hydrogen Rate

Desired F. psig V/V/Hr. scf/Bb1

Hydrofining 500-800 50-2000 0.1-10.0 500-10,000

Hydrocracking 450-850 200-2000 0.1-10.0 500-10,000

Catalytic Cracking 700-1000 0-50 0.1-200 O

Catalytic Reforming 800-1000 50-1000 0.1-20.0 500-10,000

computed. When the value of His small its value found It will be understood by those skilled in the art that in this manner is determined by a difference between 0 various modifications of the present invention as de scribed in the foregoing examples may be employed large numbers, hence is subject to cumulative errors.

Accordingly, a modified approach is useful as described without departing from the scope of the invention. in the following. Many variations and modifications thereof will be ap Thus it is useful to define a reference quantity H, parent to those skilled in the art and can be made with representing the calculated field in a spherical cavity at out departing from the spirit and scope of the invention herein described.

the location of the particle. It is imagined that the mag netization of surrounding particles is unchanged when What is claimed is:

the said particle is removed. 1. In a process for fluidizing a bed containing solid particulate magnetizable, fluidizable material within an (2) 50 external force field, wherein at least a portion of the bed containing said solid particulate magnetizable, fluidiza

Combining the two expression gives an alternate rela ble material and a fluidizing fluid are subjected to a tionship for H, in which His eliminated. nontime varying and substantially uniform applied mag netic field having a substantial component along the

H. = H + Ma, (3) 55 direction of the external force field such that said solid This expression is recognized to give Has the change of ponent particulate magnetizable, fluidizable material has a com field in passing from the inside of a particle to the out ternal force of magnetization along the direction of the ex

field, the improvement which comprises

Denoting K as the following constant continuously stably fluidizing at least a portion of said 60 bed containing the solid particulate magnetizable, flui dizable material by a flow of a fluid opposing said exter

nal force field at a superficial fluid velocity ranging

(a) more than the normal minimum fluidization super then from (2) Kequals the quantity Mp/(H-H) i.e. 65 ficial fluid velocity required to fluidize said bed in the absence of said applied magnetic field; and

K = M/(H-H) (5) (b) less than the superficial fluid velocity required to cause time-varying fluctuations of pressure differ

Page 26

ence through said stably fluidized bed portion over external force field at a superficial gas velocity ranging a finite period of time during continuous fluidiza between:

tion in the presence of said applied magnetic field. (a) at least about 10% greater than the normal mini 2. The process of claim 1 wherein said external force mum fluidization superficial gas velocity required field is gravity. 5 to fluidize said bed in the absence of said applied 3. The process of claim 1 wherein fluid is gaseous, magnetic field; and 4. The process of claim 1 wherein the bed addition (b) not substantially more than about 98% of the ally contains nonmagnetizable particles. superficial gas velocity required to cause a 0.1% 5. The process of claim 1 wherein the solid particu ratio of root-mean square fluctuation of pressure late magnetizable, fluidizable material is a composite of 10 difference to mean-pressure difference through magnetizable material and nonmagnetizable material. . said stably fluidized bed portion during continuous 6. The process of claim 5 wherein the bed addition fluidization in the presence of said applied mag ally includes nonmagnetizable particles. netic field.

7. The process of claim 2 wherein the solid particu 15 17. The process of claim 16 wherein said external late magnetizable, fluidizable material includes nickel. force field is gravity.

8. The process of claim 2 wherein said bed containing 18. The process of claim 16 wherein the uniformity of solid particulate magnetizable, fluidizable material in said applied magnetic field is such that the ratio of the cludes a zeolite cracking catalyst. local intensity of the applied magnetic field to the mean 9. The process of claim 1 wherein said applied mag 20 field varies by not more than 25% over the region of the netic field is oriented substantially colinear with the fluidized bed containing the particulate magnetizable, flow of a fluidizing fluid. fluidizable material.

10. The process of claim 1 wherein the uppermost 19. The process of claim 16 wherein the uniformity of 10-40% region or zone of the bed is stabilized by the said applied magnetic field is such that the ratio of the applied magnetic field. 25 local intensity of the applied magnetic field to the mean 11. The process of claim 1 wherein the flow of fluid field varies by no more than 10% over the region of the is not substantially more than about 98% of the superfic fluidized bed containing the particulate magnetizable, ial fluid velocity required to cause of 0.1% ratio of fluidizable material.

root-mean square fluctuation of pressure difference to 20. The process of claim 16 wherein the uniformity of mean-pressure difference through the stably fluidized 30 said applied magnetic field is such that the ratio of the bed portion containing the solid particulate magnetiz loca intensity of the applied magnetic field to the mean able, fluidizable material during continuous fluidization field varies by no more than 5% over the region of the in the presence of said applied magnetic field. fluidized bed containing the particulate magnetizable, 12. The process of claim 1 wherein the flow of gas is fluidizable material.

more than 2 times the normal minimum fluidization 35 21. The process of claim 16 wherein the solid particu superficial gas velocity of the bed containing the solid late magnetizable, fluidizable, material is a composite of particulate magnetizable, fluidizable material in the magnetizable material and nonmagnetizable material. absence of the applied magnetic field. 22. The process of claim 16 wherein the flow of gas is 13. The process of claim 1 wherein the flow of gas is more than 5 times the normal minimum fluidization more than 5 times the normal minimum fluidization superficial gas velocity of the bed containing the solid superficial gas velocity of the bed containing the solid particulate magnetizable, fluidizable material in the particulate magnetizable, fluidizable material in the absence of the applied magnetic field and the applied absence of the applied magnetic field. magnetic field strength is greater than 50 oersteds. 14. The process of claim 1 wherein the flow of gas is 23. The process of claim 16 wherein the flow of gas is more than 10 times the normal minimum fluidization 45 more tha 10 times the normal minimum fluidization superficial gas velocity of the bed containing the solid superficial gas velocity of the bed containing the solid particulate magnetizable, fluidizable material in the particulate containing magnetizable, fluidizable mate absence of the applied magnetic field. rial in the absence of the applied magnetic field and the 15. The process of claim 6 wherein the flow of gas is applied magnetic field strength is greater than 100 oer more than 15 times the normal minimum fluidization 50 steds.

superficial gas velocity of the bed containing the solid 24. The process of claim 23 wherein the applied mag particulate magnetizable, fluidizable materials in the netic field strength is greater than 200 oersteds. absence of the applied magnetic field. 25. In a process for fluidizing a bed containing solid 16. In a process for fluidizing a bed containing solid particulate magnetizable, fluidizable material within an particulate magnetizable, fluidizable material located 55 external force field, wherein at least a portion of the bed within an external force field, wherein said solid partic containing said solid particulate magnetizable, fluidiza ulate magnetizable, fluidizable material is subjected to a ble material and said fluidizing fluid are subjected to a nontime carying and substantially uniform applied mag nontime varying and substantially uniform applied mag netic field which is oriented substantially colinear with netic field having a substantial component along the the flow of a fluidizing gas and has a substantial compo 60 direction of the external force field such that said solid nent along the direction of the external force field such particulate magnetizable, fluidizable material has a com that said solid particulate magnetizable, fluidizable ma ponent of magnetization along the direction of the ex terial has a component of magnetization along the direc ternal force field, the improvement which comprises tion of the external force field greater than 10 gauss, the stably fluidizing at least a portion of said bed containing improvement which comprises stably fluidizing at least 65 the solid particulate magnetizable, fluidizable material a portion of said bed containing the solid particulate by adjusting and maintaining the flow of fluid opposing magnetizable, fluidizable material by adjusting and said external force field at a superficial fluid velocity maintaining the flow of a fluidizing gas opposing said ranging between:

Page 27

(a) more than the normal minimum fluidization super of the external force field such that said composite parti ficial fluid velocity required to fluidize said bed in cles have a component of magnetization M along the the absence of said applied magnetic field; and, direction of the external force field of at least 100 gauss (b) less than the superficial fluid velocity required the by passing a gas opposing said external force field at a cause time-varying fluctuations of pressure differ 5 superficial fluid velocity ranging between: ence through said stably fluidized bed portion over (a) more than the normal minimum fluidization super a 0.1 to 1 second time interval during continuous ficial fluid velocity required to fluidize said bed in fluidization in the presence of said applied mag the absence of said applied magnetic field; and, netic field. (b) less than the superficial fluid velocity required to 26. The process of claim 25 wherein the uniformity of 10 cause time-varying fluctuations of pressure differ said applied magnetic field is such that the ratio of the ence through said stably fluidized bed portion over local intensity of the applied magnetic field to the mean a 0.1 to 1 second interval during continuous fluid field varies by no more than 25% over the region of a ization in the presence of said applied magnetic portion of the fluidized bed containing the particulate field.

magnetizable, fluidizable material. 15 30. The process of claim 29 wherein said fluidized bed 27. The process of claim 25 wherein the uniformity of is subjected to an applied magnetic field ranging be said applied magnetic field is such that the ratio of the tween 150 to 400 oersteds oriented axially to the flow of local intensity of the applied magnetic field to the mean field varies by no more than 10% over the region of a gas31.in The the stably fluidized bed zone. process of claim 29 wherein said fluidizing portion of the fluidized bed containing the particulate 20 gas has a superficial velocity in the range of 2 to 10 magnetizable, fluidizable material.

28. The process of claim 25 wherein the uniformity of quired to fluidize the bed insuperficial times the normal minimum the gas velocity re absence of an applied said applied magnetic field is such that the ratio of the magnetic field.

local intensity of the applied magnetic field to the mean field varies by no more than 5% over the region of a 25 32. The process of claim 29 wherein the magnetiz portion of the fluidized bed containing the particulate able, fluidizable composite particles contain catalytic magnetizable, fluidizable material. nonmagnetic material.

29. A fluidized bed process, which comprises stably 33. The process of claim 29 wherein the magnetiz fluidizing at least a portion of a bed comprised of solid able, fluidizable composite particles contain a zeolitic particulate magnetizable, fluidizable composite parti 30 crystalline aluminosilicate and a ferromagnetic material. cles which contain 2-40 volume percent of ferro- or 34. The process of claim 29 wherein the magnetiz ferrimagnetic material located within an external force able, fluidizable composite particles contain 5 to 20 field containing said composite materials to a nontime volume percent ferro- or ferrimagnetic material and the varying and substantially uniform applied magnetic balance is nonmagnetic kmaterial. . . . . . field having a substantial component along the direction 35