Process for operating a magnetically stabilized fluidized bed

Abstract

A fluidized bed process is disclosed which comprises subjecting a bed comprised of solid particulate magnetizable, fluidizable material within an external force field wherein at least a portion of the bed containing said solid particulate magnetizable and fluidizable material and fluidizing fluid are subjected to a nontime varying and substantially uniform applied magnetic field having a substantial component along the direction of the external force field such that said solid particulate magnetizable and fluidizable material has a component of magnetization along the direction of the external force field and wherein at least a portion of said bed containing the solid particulate magnetizable and fluidizable material is fluidized by a flow of fluid opposing said external force field at a superficial fluid velocity ranging between:

(a) more than the normal minimum fluidization superficial fluid velocity required to fluidize said bed in the absence of said applied magnetic field; and,

(b) less than the superficial fluid velocity required to cause time-varying fluctuations of pressure difference through said stably fluidized bed portion during continuous fluidization in the presence of said applied magnetic field. The strength of the magnetic field and its deviation from a vertical orientation are maintained so as to prevent and/or suppress the formation of bubbles in the fluidized media at a given fluid flow rate and with a selected fluidized particles makeup.

fluid throughput rates which are up to 10 to 20 or more times the flow rate of the fluidized bed at incipient fluidization in the absence of the applied magnetic field are achieved, concomitant with the substantial absence of bubbles. The magnetically stabilized fluidized bed has the appearance of an expanded fixed bed with no gross solids circulation and very little or no gas bypassing.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. application Ser. No. 610,071 filed Sept. 3, 1975 now abandoned, which in turn is a continuation-in-part of U.S. application Ser. No. 514,003, filed Oct. 11, 1974, now abandoned.

FIELD OF THE INVENTION

This invention relates to a fluidized bed process. More particularly, the present invention is concerned with a process for operating a magnetically stabilized fluidized bed under conditions such that the flow of gas used to fluidize solid particulate magnetizable and fluidizable particles and an applied magnetic field are controlled to the extent that there is substantially no time-varying fluctuation of pressure at a point taken in the bed. Such a magnetically stabilized medium has the appearance of an expanded fixed bed; there is no gross solids circulation and very little or no gas bypassing. A bed of the magnetically stabilized medium shares many qualities of the normal fluidized bed; pressure drop is effectively equal to the weight of the bed divided by its cross sectional area, and independent of gas flow rate or of particle size; the medium will flow, permitting continuous solids throughput. Beds of the magnetically stabilized media also share some of the qualities of a fixed bed; countercurrent contacting can be readily attained; gas bypassing is small or absent, making it possible to achieve high conversions and attrition is minimal or absent.

The simultaneous possession of properties usually associated with the media of fixed and of fluid beds is highlighted, for example, in the use of a magnetically stabilized medium to trap particulates. Like the medium of a fixed bed, it will trap the particulates; like the medium of a fluid bed, it will not clog - the pressure drop of a bed of the medium will increase only by as much as due to the weight of the trapped material.

BACKGROUND OF THE INVENTION

Many chemical and physical processes such as catalytic cracking, hydrogenation, oxidation, reduction, drying, polymerization, coating, filtering and the like are carried out in fluidized beds. A fluidized bed, briefly, consists of a mass of solid particulate fluidizable material in which the individual particles are neutrally leviated free of each other by fluid drag forces whereby the mass or fluidized bed possesses the characteristics of a liquid. Like a liquid, it will flow or pour freely, there is a hydrostatic head pressure, it seeks a constant level, it will permit the immersion of objects and will support relatively buoyant objects, and in many other properties it acts like a liquid. A fluidized bed is conventionally produced by effectng a flow of a fluid, usually gas, through a porous or perforated plate or membrane underlying the particulate mass, at a sufficient rate to support the individual particles against the force of gravity. Conditions at the minimum fluid flow required to produce the fluid-like, or fluidized condition, i.e., the incipient fluidization point are dependent on many parameters including particle size, particle density, etc. Any increase in the fluid flow beyond the incipient fluidization point causes an expansion of the fluidized bed to accommodate the increased fluid flow until the gas velocity exceeds the free falling velocity of the particles which are then carried out of the apparatus, a condition otherwise known as entrainment.

Fluidized beds possess many desirable attributes, for example, in temperature control, heat transfer, catalytic reactions, and various chemical and physical reactions such as oxidation, reduction, drying, polymerization, coating, diffusion, filtering and the like.

Among the problems associated with fluidized beds, a most basic one is that of bubble formation, frequently resulting in slugging, channeling, spouting, attrition and in DateLm, cm Velocity, U_T, cm/s Transition, L_T, W/A ΔP H, Oersteds cm/s U_MF, L_M cm/s Velocity, U_T, Transition, L_T, cm/s W/A __________________________________________________________________________ 0 13.5 15.0 13.5 15.0 0.91 16 14.8 15.0 25.8 15.5 0.89 32 14.6 15.0 36.1 15.8 0.94 48 15.6 15.0 49.2 16.8 1.00 64 15.0 15.0 68.3 18.0 1.02 72 15.0 15.0 68.3 -- 1.00 __________________________________________________________________________ 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 catalyst was previously magnetized in an applied field of 5000 oersteds. Due to its remanent magnetization the material had the texture of wet sand, noticeable when pouring or screening.

A quantity of 1280 grams was added to a fluidization vessel having inside diameter of 7.33 cm. The depth of solids over the fitted porous distributor was 17.8 cm.

In the absence of applied field as air flow was increased the bed of solids was observed to develop voidage layers of separation in the upper one-third of the bed at a superficial velocity of 10.3 cm/s. Pressure drop through the bed increased smoothly with increase of superficial velocity until at 38.3 cm/s a spout formed in the bed and the pressure drop decreased from about 6.4 cm. of dibutylphthalate (DBP) to 2.9 cm. The spout had formed along the length of the 6 mm O.D. by 4 mm I.D. glass tube used as the pressure probe that was inserted to a 9 cm. depth within the bed. Thus, these solids failed to fluidize properly in the absence of applied field.

When uniform, axially oriented magnetic field of 40 oersteds was applied the measured pressure drop increased smoothly with increase of air flow rate up to a superficial velocity of 42.7 cm/s. A futther increase of superficial velocity to 46.6 cm/s then caused a spout to form adjacent to the probe and measured pressure drop decreased by about 47%. Again the bed structure deteriorated and lead to bypassing of the gas stream.

Finally, with applied field of 80 oersteds and the probe tip located about 5 mm. above the support grid, the bed retained its structural integrity throughout a test sequence in which superficial velocity ranged up to 100.4 cm/s. Pressure drop initially increased linearly with superficial velocity, then plateaued at 25.6 cm. DBP. The break in the curve of pressure drop vs. superficial velocity defined a point of minimum fluidization of 40.0 cm/s. The bed length was constant at 17.8 cm. up to the point of minimum fluidization, then expanded to 24.0 cm. at the said maximum flow rate of 100.4 cm/s. The bed remained free of bubbles or agitation of all flow rates studied. The test was repeated and displayed the similar behavior with maximum superficial velocity reacing 115 cm/s.

Magnetic moment of this ammonia catalyst is given in Table XVIII. The moment of 0.03 emu/g at zero applied field pertains to a powder sample of the -20/+30 mesh material that had previously been subjected to 5000 oersteds applied field. The low moment indicates the sample particles were nearly randomly oriented since the remanent magnetization is large for an undisturbed sample, i.e., 18.4 emu/g after exposure to applied field intensity of 16,000 oersteds.

TABLE XVIII
______________________________________
MAGNETIC MOMENT OF AMMONIA CATALYST
Applied Field, H., re.
Magnetic Moment emμ/g
______________________________________
0              0.03
40             1.58
80             3.26
5,000          144
16,000         166
0              18.4
______________________________________

EXAMPLE 14

This example illustrates that fluctuations of gas pressure distinguish the bubbling state of magnetized, fluidized solids from the stably fluidized state. In the stably fluidized state fluctuations are not detected.

Two thousand nine hundred and seventy grams of 177-250 micron spherical particles of C1018 steel described in Example 12 were placed in a fluidization vessel having inside diameter of 7.32 centimeters. The vessel was fitted with a pressure tap in the sidewall at a point 4 centimeters above the porous support grid. The pressure tap contained a wire mesh screen that prevented particles from leaving the vessel. One side of a U-tube manometer containing water water was connected to the tap and the other end of the manometer kept open to the atmosphere as was the top of the fluidization vessel. Uniformly, axially oriented magnetic field of 48 oersteds intensity was applied to the solids using the pair of six inch bore electromagnets. Increasing rates of steady air flow were admitted to the vessel to obtain measurement of pressure drop ΔPo read as difference in height of water in the manometer legs. When the bed became stably fluidized, its length gradually expanded with gas flow. Observation was also made of pressure drop fluctuation ±ΔP', if any, and presence or absence of visible bubbling or motion in the fluidized medium. The fluctuations in pressure drop represent values detected over about a ten second interval. The observed values of pressure drop, pressure drop fluctuations, bed length and other parameters, are listed in Table XIX.

From the data in Table XIX it may be seen that the stably fluidized state is clearly distinguishable from the settled state (fixed bed state) as well as from the unstably fluidized state. Thus, only in the stably fluidized state is pressure drop invariant of flow rate, and bed length increasing with an increase of flow rate, while pressure fluctuations are absent. Comparative behavior of the states is summarized in Table XX.

It is noted that in fluidized states the constant value of average pressure drop indicates the solids in the vessel were supported entirely by fluid forces. Visual observation of initial bubbling and motion in the bed coincide with the first detectable fluctuation of pressure drop (pressure difference).

TABLE XIX
______________________________________
PRESSURE DROP, PRESSURE FLUCTUATIONS,
AND BED LENGTH CHANGE OF AIR FLUIDIZED C1018
STEEL SPHERES OF 177-250 MICRON DIAMETER IN 48
OESTER APPLIED FIELD
Bubbles
U    Δ P
± Δ P'
Δ L,
State of    or
cm/s cm H2 O
cm H2 O
cm   the solids  Motion
______________________________________
5.6  19.1     0        0    Settled     No
8.5  34.8     0        0    Settled     No
12.7 54.0     0        0    Settled     No
15.2 51.6     0        0.5  Stably Fluidized
No
19.8 55.8     0        1.3  Stably Fluidized
No
25.4 56.5     0        2.0  Stably Fluidized
No
31.7 56.6     0.05     2.7  Unstably Fluidized
Yes
40.9 51.0     3.0      3.5  Unstably Fluidized
Yes
56.5 53.0     3.0      3.5  Unstably Fluidized
Yes
______________________________________

TABLE XX
______________________________________
DISTINGUISHABLE STATES OF THE
PARTICULATE SOLIDS
Pressure drop
Bed Length
State of    increase     increase  Pressure
Solids      with flow    with flow Fluctuates
______________________________________
Settled     Yes          No        No
Stably Fluidized
No           Yes       No
Unstably Fluidized
No           Yes       Yes
______________________________________

As can be seen from the above examples and description of the invention, the present invention provides a means for conducting a fluidization process at a wide range of flow rates before the bubble transition point is reached. For example, as discussed above, it has been found that the larger the magnetization M of the fluidizable and magnetizable particles up to the point of agglomeration, the higher will be the transition velocity U_T up to which the stably fluidized bed may be operated without bubbling and time-varying fluctuation, all other variables being equal. It will be recognized that in practicing the invention, it is the intent to operate the process in the stable., non-fluctuation manner wherein the stably fluidized bed is bubble-free. Accordingly, the size of bubbles in the stabilized fluidized media, if they do exist, will be about no larger than the spacing between particles and consequently do not cause time-varying fluctuations of the pressure difference through the fluidized bed over a finite period of time, e.g., 10 seconds, preferably a 100 second time interval during continuous fluidization.

As earlier indicated, the fluidization process of the present invention is useful in many applications heretofore used in the fluidization art. Of particular importance are the petroleum processes such as hydrofining, hydrocracking, hydrodesulfurization, catalytic cracking and catalytic reforming. The Table XXI summarizes typical hydrocarbon conversion process conditions effective in the present invention.

The feedstock suitable for conversion in accordance with the invention include all of the well-known feeds conventionally employed in hydrocarbon conversion processes. Usually, they will be petroleum derived, although other sources such as shale oil and coal are not to be excluded. Typical of such feeds are heavy and light virgin gas oils, coker gas oils, steam-cracked gas oils, middle distillates, steam-cracked naphthas, coker naphthas, cycle oils, deasphalted residua, etc.

GENERAL

Generally, the magnetization M of a particle as obtained from a magnetometer when a given magnetizing field H_a is applied will not provide a value which is the same as the magnetization of the particle in response to the same intensity of magnetic field in the fluidized bed to be used in accordance with the teachings of the present invention.

The purpose of the following is to indicate a method for determining the magnetization M_p of a typical particle in a bed from those values obtained from a magnetometer. Generally, this will require a calculation since the effective field that a bed particle is subjected to depends on the applied field, the bed geometry, the particle geometry, the bed voidage and particle magnetization. A general expression has been derived to relate these quantities based on the classical approximation of the Lorentz cavity that is employed in analogous physical problems such as the polarization of dielectric molecules.

H_a =H_e +M_p [d_p +(1-ε_o)(d_b -1/3)](1)

H_a is the applied magnetic field as measured in the absence of the particles, H_e the magnetic field within a particle, M_p the particle magnetization, d_p the particle demagnetization coefficient, ε_o the voidage in the particle bed, and d_b the bed demagnetization coefficient. The term -1/3 is due to the magnetizing influence of a (virtual) sphere surrounding the bed particle.

The expression above applies as well to a sample of particles such as used in a magnetometer measurement. In that case d_b is the demagnetization coefficient d_s corresponding to shape of the cavity in the sample holder.

Magnetometer measurement produces a graph of M_p vs. H_a. Using the above equation and known values of d_p, d_s, ε_o, M_p and H_a a corresponding value of H_e may be computed. When the value of H_e is small its value found in this manner is determined by a difference between large numbers, hence is subject to cumulative errors. Accordingly, a modified approach is useful as described in the following.

Thus it is useful to define a reference quantity H_s representing the calculated field in a spherical cavity at the location of the particle. It is imagined that the magnetization of surrounding particles is unchanged when the said particle is removed.

H_s =H_a -M_p [(1-ε_o)(d_b -1/3)](2)

Combining the two expression gives an alternate relationship for H_s, in which H_a is eliminated.

H_s =H_e +M_p d_p (3)

This expression is recognized to give H_s as the change of field in passing from the inside of a particle to the outside of the particle.

Denoting K_m as the following constant ##EQU6## then from (2) K_m equals the quantity Mp/(H_a -H_s) i.e.

K_m =M_p /(H_a -H_s) (5)

Thus, on the graph of M_p vs. H_a straight lines of slope K_m intersecting the measured curve and the H_a axis relate corresponding values of M_p and H_s. Accordingly a graph may be constructed of M_p vs. H_s. For example, when the sample is contained in a spherical cavity d_s =1/3, K_m is infinite, and H_s equals H_a. For a long sample such that d_s =0, K_m is negative and H_a is less than H_s i.e. the field magnetizing a particle of the sample is greater than the field applied to the sample.

Additionally, for a process bed, a constant K_p may be defined as follows: ##EQU7##

It may also be seen from Eq. (2) that a line of slope -K_p passing through a point H_a on the horizontal axis of the graph of M_p vs. H_s intersects the curve on the graph at a value of M_p giving the particle magnetization in the bed. Thus, the particle magnetization M_p in a process bed has been related to the field H_a applied to the process bed.

The relationship of Eq. (1) is an approximation more likely to be accurate for beds having high voidage than for very densely packed samples.

It is to be understood that the term "applied magnetic field" used throughout the specification and claims refers to an empty vessel applied magnetic field.

TABLE XXI
______________________________________
Reaction Conditions
Principal   Temper-           Feed   Hydrogen
Conversion  ature    Pressure Rate   Rate
Desired     °F.
psig     V/V/Hr.
scf/Bbl
______________________________________
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     0.1-20.0
0
Catalytic Reforming
800-1000  50-1000 0.1-20.0
500-10,000
______________________________________

It will be understood by those skilled in the art that various modifications of the present invention as described in the foregoing examples may be employed without departing from the scope of the invention. Many variations and modifications thereof will be apparent to those skilled in the art and can be made without departing from the spirit and scope of the invention herein described.

Claims

1. In a process for fluidizing a bed containing solid particulate magnetizable, fluidizable material within an external force field, wherein at least a portion of the bed containing said solid particulate magnetizable, fluidizable material and a fluidizing fluid are subjected to a nontime varying and substantially uniform applied magnetic field having a substantial component along the direction of the external force field such that said solid particulate magnetizable, fluidizable material has a component of magnetization along the direction of the external force field, the improvement which comprises continuously stably fluidizing at least a portion of said bed containing the solid particulate magnetizable, fluidizable material by a flow of a fluid opposing said external force field at a superficial fluid velocity ranging between:

(a) more than the normal minimum fluidization superficial fluid velocity required to fluidize said bed in the absence of said applied magnetic field; and

(b) less than the superficial fluid velocity required to cause time-varying fluctuations of pressure difference through said stably fluidized bed portion over a finite period of time during continuous fluidization in the presence of said applied magnetic field.

2. The process of claim 1 wherein said external force field is gravity.

3. The process of claim 1 wherein fluid is gaseous.

4. The process of claim 1 wherein the bed additionally contains nonmagentizable particles.

5. The process of claim 1 wherein the solid particulate magnetizable, fluidizable material is a composite of magnetizable material and nonmagnetizable material.

6. The process of claim 5 wherein the bed additionally includes nonmagnetizable particles.

7. The process of claim 2 wherein the solid particulate magnetizable, fluidizable material includes nickel.

8. The process of claim 2 wherein said bed containing solid particulate magnetizable, fluidizable material includes a zeolite cracking catalyst.

9. The process of claim 1 wherein said applied magnetic field is oriented substantially colinear with the flow of a fluidizing fluid.

10. The process of claim 1 wherein the uppermost 10-40% region or zone of the bed is stabilized by the applied magnetic field.

11. The process of claim 1 wherein the flow of fluid is not substantially more than about 98% of the superficial fluid velocity required to cause of 0.1% ratio of root-mean square fluctuation of pressure difference to mean-pressure difference through the stably fluidized bed portion containing the solid particulate magnetizable, fluidizable material during continuous fluidization in the presence of said applied magnetic field.

12. The process of claim 1 wherein the flow of gas is more than 2 times the normal minimum fluidization superficial gas velocity of the bed containing the solid particulate magnetizable, fluidizable material in the absence of the applied magnetic field.

13. The process of claim 1 wherein the flow of gas is more than 5 times the normal minimum fluidization superficial gas velocity of the bed containing the solid particulate magnetizable, fluidizable material in the absence of the applied magnetic field.

14. The process of claim 1 wherein the flow of gas is more than 10 times the normal minimum fluidization superficial gas velocity of the bed containing the solid particulate magnetizable, fluidizable material in the absence of the applied magnetic field.

15. The process of claim 6 wherein the flow of gas is more than 15 times the normal minimum fluidization superficial gas velocity of the bed containing the solid particulate magnetizable, fluidizable materials in the absence of the applied magnetic field.

16. In a process for fluidizing a bed containing solid particulate magnetizable, fluidizable material located within an external force field, wherein said solid particulate magnetizable, fluidizable material is subjected to a nontime carying and substantially uniform applied magnetic field which is oriented substantially colinear with the flow of a fluidizing gas and has a substantial component along the direction of the external force field such that said solid particulate mganetizable, fluidizable material has a component of magnetization along the direction of the external force field greater than 10 gauss, the improvement which comprises stably fluidizing at least a portion of said bed containing the solid particulate magnetizable, fluidizable material by adjusting and maintaining the flow of a fluidizing gas opposing said external force field at a superficial gas velocity ranging between:

(a) at least about 10% greater than the normal minimum fluidization superficial gas velocity required to fluidize said bed in the absence of said applied magnetic field; and

(b) not substantially more than about 98% of the superficial gas velocity required to cause a 0.1% ratio of root-mean square fluctuation of pressure difference to mean-pressure difference through said stably fluidized bed portion during continuous fluidization in the presence of said applied magnetic field.

17. The process of claim 16 wherein said external force field is gravity.

18. The process of claim 16 wherein the uniformity of said applied magnetic field is such that the ratio of the local intensity of the applied magnetic field to the mean field varies by not more than 25% over the region of the fluidized bed containing the particulate magnetizable, fluidizable material.

19. The process of claim 16 wherein the uniformity of said applied magnetic field is such that the ratio of the local intensity of the applied magnetic field to the mean field varies by no more than 10% over the region of the fluidized bed containing the particulate magnetizable, fluidizable material.

20. The process of claim 16 wherein the uniformity of said applied magnetic field is such that the ratio of the loca intensity of the applied magnetic field to the mean field varies by no more than 5% over the region of the fluidized bed containing the particulate magnetizable, fluidizable material.

21. The process of claim 16 wherein the solid particulate magnetizable, fluidizable, material is a composite of magnetizable material and nonmagnetizable material.

22. The process of claim 16 wherein the flow of gas is more than 5 times the normal minimum fluidization superficial gas velocity of the bed containing the solid particulate magnetizable, fluidizable material in the absence of the applied magnetic field and the applied magnetic field strength is greater than 50 oersteds.

23. The process of claim 16 wherein the flow of gas is moe tha 10 times the normal minimum fluidization superficial gas velocity of the bed containing the solid particulate containing magnetizable, fluidizable material in the absence of the applied magnetic field and the applied magnetic field strength is greater than 100 oersteds.

24. The process of claim 23 wherein the applied magnetic field strength is greater than 200 oersteds.

25. In a process for fluidizing a bed containing solid particulate magnetizable, fluidizable material within an external force field, wherein at least a portion of the bed containing said solid particulate magnetizable, fluidizable material and said fluidizing fluid are subjected to a nontime varying and substantially uniform applied magnetic field having a substantial component along the direction of the external force field such the said solid particulate magnetizable, fluidizable material has a component of magnetization along the direction of the external force field, the improvement which comprises stably fluidizing at least a portion of said bed containing the solid particulate magnetizable, fluidizable material by adjusting and maintaining the flow of fluid opposing said external force field at a superficial fluid velocity ranging between:

(a) more than the normal minimum fluidization superficial fluid velocity required to fluidize said bed in the absence of said applied magnetic field; and,

(b) less than the superficial fluid velocity required the cause time-varying fluctuations of pressure difference through said stably fluidized bed portion over a 0.1 to 1 second time interval during continuous fluidization in the presence of said applied magnetic field. PAR

26. The process of claim 25 wherein the uniformity of said applied magnetic field is such that the ratio of the local intensity of the applied magnetic field to the mean field varies by no more than 25% over the region of a portion of the fluidized bed containing the particulate magnetizable, fluidizable material.

27. The process of claim 25 wherein the uniformity of said applied magnetic field is such that the ratio of the local intensity of the applied magnetic field to the mean field varies by no more than 10% over the region of a portion of the fluidized bed containing the particulate magnetizable, fluidizable material.

28. The process of claim 25 wherein the uniformity of said applied magnetic field is such that the ratio of the local intensity of the applied magnetic field to the mean field varies by no more than 5% over the region of a portion of the fluidized bed containing the particulate magnetizable, fluidizable material.

29. A fluidized bed process, which comprises stably fluidizing at least a portion of a bed comprised of solid particulate magnetizable, fluidizable composite particles which contain 2-40 volume percent of ferro- or ferrimagnetic material located within an external force field containing said composite materials to a nontime varying and substantially uniform applied magnetic field having a substantial component along the direction of the external force field such that said composite particles have a component of magnetization m along the direction of the external force field of at least 100 gauss by passing a gas opposing said external force field at a superficial fluid velocity ranging between:

(a) more than the normal minimum fluidization superficial fluid velocity required to fluidize said bed in the absence of said applied magnetic field; and,

(b) less than the superficial fluid velocity required to cause time-varying fluctuations of pressure difference through said stably fluidized bed portion over a 0.1 to 1 second interval during continuous fluidization in the presence of said applied magnetic field.

30. The process of claim 29 wherein said fluidized bed is subjected to an applied magnetic field ranging between 150 to 400 oersteds oriented axially to the flow of gas in the stably fluidized bed zone.

31. The process of claim 29 wherein said fluidizing gas has a superficial velocity in the range of 2 to 10 times the normal minimum superficial gas velocity required to fluidize the bed in the absence of an applied magnetic field.

32. The process of 29 wherein the magnetizable, fluidizable composite particles contain catalytic nonmagnetic material.

33. The process of claim 29 wherein the magnetizable, fluidizable composite particles contain a zeolitic crystalline aluminosilicate and a ferromagnetic material.

34. The process of claim 29 wherein the magnetizable, fluidizable composite particles contain 5 to 20 volume percent ferro- or ferrimagnetic material and the balance is nonmagnetic material.

35. A process for controllably transporting a flowable bed containing magnetizable particles within a vessel, said bed being expanded and levitated within said vessel by a fluid stream, wherein the superficial fluid velocity of said fluid stream ranges between:

(1) more than the normal fluidization superficial fluid velocity required to expand and levitate said bed in the absence of said applied magnetic field; and

(2) less than the superficial fluid velocity required to cause time-varying fluctuations of pressure difference through said expanded and levitated bed over a finite period of time during continuous operation in the presence of said applied magnetic field, said process comprising the steps:

(a) subjecting at least a portion of said bed to an applied magnetic field having a substantial component along the direction of a force field external to said bed; and

(b) controllably transporting said bed within said vessel in response to a pressure differential in said bed.

36. The process of claim 35 wherein said external force field is gravity. 37. The process of claim 35 wherein said fluid is gaseous. 38. The process of claim 35 wherein said bed additionally contains nonmagnetizable particles.

39. The process of claim 35 wherein said magnetizable particles are comprised of composite particles which include magnetizable and nonmagnetizable material.

40. The process of claim 39 wherein said composite particles include a zeolitic material.

41. The process of claims 35, 36, 37, 38, 39 or 40 wherein said applied magnetic field is nontime-varying and substantially uniform.

42. The process of claims 35, 36, 37, 38, 39 or 40 wherein said applied magnetic field is time-varying and substantially uniform and wherein said magnetizable particles have a zero or relatively low coercivity.

43. The process of claim 35 wherein the flow of fluid is not substantially more than about 98% of the superficial fluid velocity required to cause a 0.1% ratio of root-mean square fluctuation of pressure difference to mean-pressure difference through the expanded bed in the presence of said applied magnetic field.

44. The process of claim 35 wherein the uniformity of said applied magnetic field is such that the ratio of local intensity of the applied magnetic field to the mean field varies by not more than 25% over the region of the bed containing the magnetizable particles.

45. The process of the claim 35 wherein the uniformity of said applied magnetic field is such that the ratio of the local intensity of the applied magnetic field to the mean field varies by no more than 10% over the region of the bed containing magnetizable particles.

46. The process of claim 35 wherein the uniformity of said applied magnetic field is such that the ratio of the local intensity of the applied magnetic field to the mean field varies by no more than 5% over the region of the bed containing magnetizable particles.

47. The process of claim 35 wherein said bed medium is transported in a plug-flow manner.

48. The process of claim 35 wherein said bed medium is transported from one vessel to another vessel.

49. A process for controllably transporting a flowable bed containing magnetizable particles within a vessel, said bed being expanded and levitated within said vessel by a fluid stream, said process comprising the steps:

(a) subjecting at least a portion of said bed to an applied magnetic field having a substantial component along the direction of gravity of at least 10 gauss within said bed; and

(b) controllably transporting said bed in response to a pressure differential in said bed within said vessel, wherein the superficial fluid velocity of said fluid stream ranges between:

(1) at least about 10% greater than the normal fluidization superficial fluid velocity required to expand and levitate said bed in the absence of said applied magnetic field; and

(2) less than the superficial fluid velocity required to cause time-varying fluctuations of pressure difference through said expanded and levitated bed over a finite period of time during continuous operation in the

presence of said applied magnetic field.

50. The process of claim 49 wherein the flow of fluid is not substantially more than about 98% of the superficial fluid velocity required to cause a 0.1% ratio of root-mean square fluctuation of pressure difference to mean-pressure difference through the expanded bed in the presence of said applied magnetic field.

51. The process of claim 49 wherein the uniformity of said applied magnetic field is such that the ratio of the local intensity of the applied magnetic field to the mean field varies by not more than 25% over the region of the bed containing the magnetizable particles.

52. The process of claim 49 wherein the uniformity of said applied magnetic field is such that the ratio of the local intensity of the applied magnetic field to the mean field varies by no more than 10% over the region of the bed containing magnetizable particles.

53. The process of claim 49 wherein the uniformity of said applied magnetic field is such that the ratio of the local intensity of the applied magnetic field varies by no more than 5% over the region of the bed containing magnetizable particles.

54. The process of claim 49 wherein said bed medium is transported in a plug-flow manner within said vessel. 55. The process of claim 54 wherein said bed medium is transported from one vessel to another vessel.

56. The process of claim 49 wherein said applied magnetic field is nontime-varying and substantially uniform.

57. The process of claim 49 wherein said applied magnetic field is time-varying and substantially uniform and wherein said magnetizable particles have a zero or relatively low coercivity.

58. The process of claim 49 wherein said fluid is gaseous.

59. The process of claim 49 wherein said bed additionally contains nonmagnetizable particles.

60. The process of claim 49 wherein said magnetizable particles are comprised of composite particles which include magnetizable and nonmagnetizable material.

61. The process of claim 60 wherein said composite particles include a zeolitic material.

62. The process of claims 35, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60 or 61 wherein an ab- or adsorptive separation is taking place in said bed.

63. A process of controllably transporting a flowable bed containing magnetizable composite particles within a vessel said particles contain 2-40 volume percent of ferro- or ferrimagnetic material and the balance nonmagnetic material, said bed being expanded and levitated within said vessel by a fluid stream, said process comprising the steps:

(a) subjecting at least a portion of said bed to a substantially uniform magnetic field having a substantial component along the direction of gravity said that said composite particles have a component of magnetization m along the direction of the external force field of at least 100 gauss; and

(b) controllably transporting said bed within said vessel in response to a pressure differential in said bed, wherein the superficial fluid velocity of said fluid stream ranges between:

(1) more than the normal minimum fluidization superficial fluid velocity required to expand and levitate said bed in the absence of said applied magnetic field; and

(2) less than the superficial fluid velocity required to cause time-varying fluctuations of pressure difference through said bed over a 0.1 to 1 second interval during continuous operation in the presence of said

applied magnetic field.

64. The process of claim 63 wherein said bed medium is transported in a plug-flow manner.

65. The process of claim 63 wherein said bed medium is transported from one vessel to another vessel.

66. The process of claim 63 wherein said applied magnetic field is nontime-varying.

67. The process of claim 63 wherein said applied magnetic field is time-varying and said magnetizable material has a zero or relatively low coercivity.

68. The process of claim 63 wherein said applied magnetic field ranges between 150 and 400 oersteds oriented axially to the flow of the fluid. 69. The process of claim 63 wherein said composite particle include a zeolitic crystalline aluminosilicate and a ferromagnetic material and an ab- or adsorptive separation is taking place in said bed. 70. The process of claim 69 wherein said fluid is liquid. 71. The process of claim 69 wherein said fluid is gaseous.

72. The process of claims 35, 49, or 63 wherein a catalytic cracking reaction is taking place in said bed.

73. The process of claims 35, 49 or 63 wherein a fluid hydroforming process is taking place in said bed.

74. The process of claims 35, 49 or 63 wherein an alkylation process is taking place in said bed.

75. The process of claims 35, 49 or 63 wherein a partial oxidation process is taking place in said bed.

76. The process of claims 35, 49 or 63 wherein a chlorination process is taking place in said bed.

77. The process of claims 35, 49 or 63 wherein a dehydrogenation process is taking place in said bed. 78. The process of claims 35, 49 or 63 wherein a desulfurization or reduction is taking place in said bed.

79. The process of claims 35, 49 or 63 wherein the gasification of coal is taking place in said bed.

80. The process of claims 35, 49 or 63 wherein the fluid bed combustion of coal is taking place in said bed. 81. The process of claims 35, 49 or 63 wherein the retorting of oil shale is taking place in said bed.