CA1135207A - Magnetically stabilized fluid bed process operated in the bubbling mode - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A fluidized bed process having reduced solids backmixing with improved heat and means transfer characteristics, which comprises subjecting a bed comprised of fluidizable, magnetizable solids to a substantially uniform magnetic field, and passing a gas upwardly through said bed at a superficial gasvelocity at least twice the superficial minimum fluidization gas velocity, in the absence of said magnetic field, to produce bubbling therein without significant entrainment of solids in the gas leaving the bed. In order to obtain such high gas velocities while maintaining the bed in the fluidized state without significant backmixing of solids in the bed And entrainment of solids in the gas leaving the bed, it is preferable to employ magnetic fields having a field strength greater then 50 oersteds and particles containing at least 50 volume % non-magnetizable material.

Description

1135~0 Field o~ e In~elltion Thls inven~ion relat~s ~o a ~luidi.zed bed process.
3 More particularly, t~e invention is co~cerned wi~h 4 hycro^arbon con~ersion processes wherein a fluidiæed bed contailllng magnetizable.particles is subjected to a magnetic ie3.d.
7 ~ o 8 - M~ny c~emical and physical reactions such as 9 cataly~ic craeking, hydrogenation, oxidation, reduction9 ~o dr~ing, ~iltering, etc., are carried out in 1uidized beds. ~' 11 A fluid~æed bed~ briefly, consists o~ a mass of ~ particu-12 late solid mai.erial in which th~ individual particles are i.n conCinuous motion relative to each other whereby the l4 maxs or ~luidized bed possesses tha characteristics of a liquid. Like a l:Lquid, it will flow or pour freely, 16 there is a-hydros~a~ic head pressure, it seeks a cons~ant .:~ -17 level~ î~ w-l.ll permit the immersion o~objects ~nd: will ~`
8 suppor~ relatjvely buoyant objects, and in many oth~ ~
19 propertles i~ acts like ~ liquid. A fluidized bed is ~ :
conventi.ollally produced by ef~ec~ing a flow of a fluid, 21 usually gas, ~hrough a porous or perforate pla~e or mem~rane 22 underlying the pa~ticulate mass~ at a suf~icien~ ratë to 23 suppor~ the indi~idual partic].es against the force of 24 gravi~y. The mini~lum air flow or pressure drop requi~ed to produce ~ne ~I.uid-lilce~ or fluidiæed~ condition ~s 26 ~now~ as the m~nimum ~luidization and is dependent on ~7 many parameters including particle siæe, particle density, 28 ~tc. ~ny increase In the ~luid flow beyond minimum ~luidizat~.$rl causes an e~pansi~n of the fluidized bed to `~
30 accon~odate the ~ncre~sed fluid ~low unti3. the fluid '~:

~l3,s2a 7 S

l velocity exceetls the ~ree ~alling velocity of the particles

2 whic.h are then carried out of the apparatus.

3 Fluidized beds possess many desirable a~tributes,

4 for example, in temperature control, heat transfer, cata-

5 lytic reactions, and various chemical and physical reactions ¦

6 s~ch as oxidation~ reduction, drying, polymerization,

7 coating, dif~usion, ~ .ering and the like. H.oweverg the

8 establishment and maintenance of a stable fluidized bed

9 by conventional procedures is a sensitive and difficult lO process possessing many drawbacks and disadvantages.
Among the problems associa~ed wi~h ~luidized 2 beds, a most basic one is that of bubble ~ormation, l3 frequently resulti.ng in sluggingJ channelingg spou~ing 14 and pneumatic ~ransport; this problem is ~ost common in l~ gas-~luidized systems. The prol~lem necessitates critical 16 10w con~rol and a~fects design factors such as minim~m 17 1uidization velocities~ pressure drops, particle sizes~
lB etc. Bubbling causes bo~h chemical and mecha~ical l9 diffic~llties: for example, in gas soLids reactions gas 20 bubbles may bypass ~he particles altogether resulting in 21 lowered con~acting efficiency.
22 Idea~ly, a 1uidized bed should be free o~
23 bubbles, homogeneous, main~ain particle suspensi.on and 24 manies~ noncr~tical flow velocity control for various 25 be~ heights and bed densities~ Many procedures and sys~em~
26 have been proposed to efect improvements, for example, 27 by the use of ba~flesg gas distribution perora~ed pla~es, 2~ mechan-lcal vibra~ion and mixi.ng devices, the use of m-i~ed 29 particle sizes~ gas plus liquid ~low schemes, special flow control valves~ etc.

.i2~)7 i M~re rec~?ntly it has been disclosed in a number 2 o publications that the apl)licatîon oI a magnetic Eield 3 to 1uidiæ~(1 beds will result in cer~ain impro~lements in 4 the opera~.ion of the fluid~ zed bed. For example, Belgian Pater.~t No. 834,384 describes the application o substan 6 ~ially uniform ields to suppress bubble formatic)n in a.
7 1uidized bed. .
8 U . S . Patent: No . 3, 440, 731 is also directed to 9 bubble suppresslon i.n a fluidized bed by tl~e application of a magnetic 1eld to the bed particles which are magne-ll tizable. Patentee avoid~ bubble formation by the use of 12 relatively non unifo?.^m fields ~nd relatively low fluidizlng 13 gas velocities.
l4 Numerous publications disclose the applica~ion of a magne~ie field produced from ~3 direct cur~ent (nontime- : :
16 varying) electromagnet to ~luidized i.ron or iron~chromi ?7 particles such as used in ammonia synthesis or carbon 18 monoxide conversion.
lq In general~ the published works teach that higher gas velocities can be used in ~:he presence of an applied 21 magnetic field than in its absence.
~2 The aforedescribed prior art f~ to recognize 23 that stlch ~righ fluidizing gas velocil~ies as are contern~
24 plated by this lnvention could be employed without signifi-cant solids backmixing in the bed ~nd entrainment of solids 26 in the gas leaving the :Elulclized bed. Such high flu:idizing 27 gas velocities without ~ignifican~ solids ~ackmi.xing and 28 entrainrnent wotlld appear ~o be una~ta~nable with the type 29 o 1uidi~ab 1 e particle systems stuc~ied L)y prior wor~ers in this ~ield since th~ higher field streng~hs re(luired to ~ 4 ~

~ mai~t.~in ~l1e ~ r~icLes i~ e be~ would result in agglomera-2 tlon of t~1eir highl~ magnetLzable iron particles.
3 According tu the a~orementiorled ~3e]gian Patent ~ No. 834,3g4, the use of a magne~iclally stabilized, flui-5 diz~d bed minimizes solids backm-Lxing and. eliminates gas ~,~
6 by-passing of the fluidiæed solids by preven~in~ gas 7 bubbLe forma~ion. The elimination of backmixing in 8 certain opera~ions such as cat cracking, reforming~
9 hydrofining, hydrocracking, drying, etc., is particularl~

10 ad~antageous since it prevents baclcmixing o~ feed and .~t~

11 products and thereby results in a greater selec~ivity in

12 conversion of feed to desirable products. Unfortunately~

13 the advantages associated with the elimination of back~

14 mixing are partially offse~ by the poorer hea~ and mass transfer due ~o the rel~tively stationa~y positioning o 6 the fluidized solid particle. Such a decrease in ~eat transfer could, in some cases, cause hot spots on the 18 catalyst par~icles and lead to deactivation of th~
19 catalyst, slde reactions; selectivity loss, etc~ In :~
addition, ~empera~ure control ma~ be more difficult in 21 certain reactions such as catalytic cracking, catalytic 2~ reforming~ hydrocrackingg hydrogenation, etc~, which are 23 highly exothermic or endothermic in natureO
24 ; In accordance with the present invention it has - 25 been unexpectedly ound that a magnetically stabilized 26 fluid bed may be advantageously operated wi~h high 27 ~luidizin~ gas velocities in the region l~here bubbling 28 occurs in the bed because the bubbling obtained is uniform 29 and the b~bblcs ~hemselves are small ~nd inely divided.
Furtker, the palticl~ mo~rement inc~uced is g~eat~y . ~ , li~ (3'7 1e:;tl~ictecl i.~ erl::ion alld i.s w.i.~lloul: gross vertical ci.rculal:.ion wllich ac(~olllpallies hubbli.ng in the non-maglletically s~ahi.li.secl ~I.ui.d beds in ~.lse~ heretoore. ~rhe restricted yross mo~ement of soli.cls and backmixincJ of yas and solids is not very significallt whell khe bed of the invent:ion is subjected to an applied ma~netie fi.el.d and ope.rated in the bubbling mode.
The clisadvantages associated with the formation of bubbles in the fluidized bed may he offset by the advantages of good heat and mass transfer and solids transport.
Summary of the ~nvention A process for carrying out a drying, separation, catalytic regeneration or chemieal eonversion proeess in a fluidized bed, eomprisi3lg:
(1) preparing a becl comprised of eomposite particles of magnetizable and non-magnetizable material which eontain at least 50 volume % non-magnetizable material, said particles being charaeterized as having eatalytie or mass transfer.
eharaeteristies;

(2) subjecting the bed to a magnetie field having a vertieal component at a strength such that the composite particles having a component of magnetization along the direction of gravity, said magnetization, m ranging between 10 and 400 gauss;
(3) passing a gaseous stream upwardly through the bed to fluidize said bed of particles at a superficial gas velocity whieh is:
(a) at least twice the minimum superficial gas velocity required to fluidize the bed in the absenee of the mag-netie field, and (b) at least an amount sufficient to continuously .
cause time-varying fluctuations of pressure difference through the bed over a finite period of time during continuous fluidization whieh is indicative of bubble formation;

' , . ..

.

5~

(4) control.li.llcJ arld/or monitori.ng the magnetic ielcl strenqth ancl superfic:ial gas velocity based on the relative particle .magnetization, particle size ancl shape particle size distribution of t:he particl.es in the bed such that the following conditions are met:
(a) agglomeration of the composite particles cloes not occur;
(h) bubbling of the hed occurs in a very gentle quiescen-t manner, the bubbles in the bed are small, finely divided and substantially uniform;
(c) the particle movement is restricted in directiQn such that there is no gross verticle circulation of the particles or solids backmixing; and (d) the entrainment of solids in the gas is less than abou-t 15 grains of solids per SCF in the gas leaving the top of the bed.
The fluidizable solids which are used in the process of this invention include a composite of matnetizable and non-magnetizable ma-terials. The magnetizable materials include ferromagnetic and ferri-magnetic substances including, but not limited to, magnetic Fe30~, i.ron oxide (Fe203), ferrites of the form MO.Fe203, wherei.n M is a metal or mixture of 6a -~` ~135;~7 metals such as Zn, Mn, Cu, etc.; ferromagnetic elements includ~
ing iron, nickel, cobalt and yadolinium, alloys of ~erro-magnetic elements, etc. Other magnetizable substances which are useful herein are known in the art, for example, U.S.
Patents 3,439,899 and 3,440,731 ancl Belgian Patent 834,384.
In addition to the aforedescribed magnetizable sub-stances, the composite particles will include 50-99, preferably 80 to 95, volume 3 of a non-magnetizable material. In general, the non-magneti2able material will include a vast number of conventional materials which are inert and/or known to catalyze the desired reaction or the desired mass transfer operation such as drying, separation, etc.
Examples of catalytic materials which may be combined with the maynetizable material of the invention include those catalysts conventionally employed in such processes as fiuid catalytic cracking, reforming, hydrogenation, hydrocracking, isomerization, alkylation, polymerization, oxidation, etc.
Examples o materials for mass transfer useful herein include drying and separation agents such as the well known molecular sieves, activatecl charcoals, solid metallic and organic complex~
ing agen~s and other materials, such as silica gel, which are capable of adsorbing or otherwise capturing selected components of a multi-component gas stream.
The fluid catalytic cracking catalyst which may be incorporated into the magnetizable, fluidizable ~ - 7 -"~""`` ~ 1.3S;~

solids of the invention include the highly active zeolite-containing catalysts and the amorphous silica-alumina catalysts.
In general, the zeolite-type catalysts are exemplified by those catalysts wherein a crystalllne aluminosilicate is dispersed with a siliceous matxix. ~mong the well-recognized types of zeolites useful herein are the "Type A", "Type Y", "Type X", "Type ZSM'I, mordenite, faujasite, erionite, and the like. A further description of these zeolltes and their methods of preparation are given, for example/ in V.S. Patent Nos. 2,882,243, 2,882,244; 3,130,007; 3,410/80~ and 3,733,390;
3,827,968 and patents mentioned therein.
Because of their extremely high activity, these zeolite materials are encapsulated with a material possessing a subs~antially lower level of catalytic activity such as a siliceous matrix material which may be of the synthetic, semi-synthetic or natural type. The matrix matexials may include silica alumina, ~ilica~gel/ silica-magnesia, alumina and clays such as montmorillonite, kaolin, etc.
The zeolite which is preferably incorpora~ed into the matrix is usually exchanyed with various cations to reduce the alkali metal oxide con~en~ ~hereof. In general, the a7kali matal oxide content of the zeolite is reduced by ion exchange treatment with solutions of ammonium salt, or salts of metals in Groups II to VIII of the Periodic Table or the rare earth metals. Examples of suitable cations include hydrogen, ammonium, calcium, magnesium, zinc, nickel, molybdenum and the rare earths ~ - 8 _ such as cerium, lanthanum, pras~odyrnium, neodymium, and mixtures thereof. The catalyst will typically contain 2-25%
of the zeolite component and 75-~8% of the matrix component.
The zeolite will usually be exchanged with sufficient cations to reduce ~he sodium level of the zeolite to less than 5 wt.%, preferably less than 1 wt. ~. Other specific exAmples of these types of catalysts are found, for exampler in U.S. Patent Nos.
3,140,243; 3,140,251; 3,140t2S2 and 3,140,253.
When used in hydrotreating or hydrofining reactions the catalyst component will contain a suitable matrix component, such as those mentioned heretofore and one or more hydrogenating components comprising the transition metals, preferably selected from Groups VI and VIII of the Periodic Table. Examples of suitable hydrogenating metals which may be supported upon a suitable matrix include, among others, nickel, cobalt, molyb-denum, tungsten, platinum, and palladium, ruthenium, rhenium, iridium (including the oxides and sulfides thereof). Mixtures of any two or more of such hydrogenating components may also be employed. For example, catalysts containing (1) nickel or cobalt, or the combination thereof, in the form o metal, oxide, sulfide or any combination thereof, and (2) molybdenum or tungsten, or the combination thereof, in the form o metal, oxide, sulfide or any combination thereof are known hydrofining catalysts. The total amount of hydrogenating component supported on the matrix may range from 2 to 25 wt. %, ~calculated as metal) usually 5 to 20 w~. % based on the total _ g -~i `` .1~35;~

weight of the catalyst composition. A typlcal hydrofining catalyst includes 3 to 8 wt. % CoO and/or NiO and about 8 to 20 wt. % MoO3 and/or WO3 (calculated as metal oxide).
Examples of reforming catalysts which may be used in accordance with the invention are those catalysts comprising a porous solid support and one or more rnetals ~or compolmds thereof, e.g. oxides) such as platinumt iridium, rhenium, palladium, etc. The suppor~ material can be a natural or a synthetically produced inorganic oxide or combination of in-organic oxides.
Typical acidic inorganic oxide supports which can beused are the naturally occurring aluminum silicates, parti-cularly when acid treated to increase the activity, and the synthetically produced cracking supports, such as silica-alumina, silica-zirconia, silica-alumina-magnesia, and crystalline zeolitic alumino-silicates. Generally, however reforming processes are preferably conduct~d in the presence of catalysts having low cracking activity, i.e., catalysts of limited acidity. ~ence, preferred carriers are inorganic oxides such as magnesia and alumina. Other examples of suitable reforming catalysts are found in U.S. Patent Nos. 3,415/737;
3,496,096; 3,537,980; 3,487,009; 3,578,583; 3,507,780; and 3,617,520.
The aforedescribed magnetizable material may be directly incorporated with the non-magne~izable material in accordance with well known techniques. ~or example, one or more of the aforedescribed non-;~ - 10 -~.135~t7 1 magnet:i.za~l.e ma~erlals ma~ be impregnated with a 2 solubl~ precursor of a erromagnetic or errimagnetlc 3 substance which is subsequently reduced to render the . 4 ~ar~cles ferrDmagnet-ic. or ferrim3gne~ic. ~lternatively9 5 the ferromagnetic or ferrimagnetic material may be 6 incorporclted ~n~o ~he non-magnetizable component by 7 encapsulation of inely divided fer~omagneti.c or ferri-8 magnet:ic m3t:erial. ~lhe partlcular me~hoc~ oE prepariIlg 9 a fluidizable SOlLd r7oes not form a part of this 10 ~n~Tcntion~
11 The fluidiz~od bed containing ~he magrle~izable~
2 fluidiæable cornposite particles o the ln~ention ~ay 13 lnclude composites o~J: other solids which a~e not mag-14 neti~able. In ~ddltion to the ma~netizable~ luidi~c~ble ¦
composi~e particles of the il~vention9 the bed may contain 16 ~ome particles which are lûO% ~erro~ or` ferrimagnetic 17 materials r 18 Arl imporl:ant factor -in selecting or preparing 19 the magneti7.ab1e, fluidizable composite partlcles of 20 the In~ention is the magneti~ation M of the particle~
21 ~e hlgher l~he magnetiza~ion M of the particle, the 22 higher w~ e the superficial gas veloci~y at which 23 the bed m~y be operated ~ithout signiicant backmixing 24 of solids ln the bed and sigIIif~ cant ent~ainmenl~ of 25 solids in the gas leaving the bedg all other factors 26 such as partiele si.ze, part:icle density~ particle siæe 27 distribution, ~as ~Tiscosity, gas density9 etc. being ~ held constant~ The magrletization. of the magnet:iæable"
2~ 1uidizal~1e composi~e J?articles Qf:' ~.he invention in 30 ~;he l~ed wLl.:L have~ a ma~netlzatioR M OL at least 10 .- 11- !

~13S;~(17 ~ gau~s, Generally ~or h-Lgh gas veloci.ties, the particl~s 2 wlll have a magnetiæa~ion5 as belng imparted by the 3 applied magnetic field, of at least SO gauss, prefer~
4 able at least 100 gauss and more preferably at least abou~ 150 gauss, e~g. 150 gauss to 400 gauss. For 6 those ~rocesse~ advantageously operated at very hi~h 7 gas ve~ocities9 the magnetization of the magnetizable~
8 fluidizable composite particles of the inven~ion may 9 be up to abou~ 1000 gauss or more.
The m~gnetlzation M of the partlcles, as is well ll known, is deined as B-H in the partlcle, where B is the 12 magnetic induction and H is the magnetic ~leld, the ields 13 being defined ln s~andard publ-Lshed works in electromagne~
4 tism~ e.g.~ Electroma~netic Theory, J. A. Stratton, McGraw Hill (1941). The value of M may be measured in a variety 16 c~f ways, all of which give the same value M since M has an 17 objective reality.
l~ One means for deterrnining magnetization M o~ th 19 particles in a bed under the influence of a given applie~l magnetic field is to measure their magnetic moment at that 21 field in a vibrating sample magnetometer under conditions 22 Of similar voidage, sample geometry and temperatures as 23 e~ist in the process to be used. The magnetometer gives 24 a val-te o~ ~ , the magnetic moment per gram from whlch magW
neti~ation M is obtained from the formula:
26 M = 4~p~
27 where p is the density of the particles in the ~est 28 sample, ~ is the m~gnetlc moment in emu/g and M is the 29 magneti~ation of the partlcles in gauss at the appliecl magnetic field te~ted.

- l? -l General].y, the magnetization M of a particle as 2 obtained rom a magnetometer when ~ given magne~izing field3 Ha is appli.ed will not provide a value which is the same as ~ tlle magne~izat:ion of the par~icle in response to the same intensity of magnetic ~ield in the fluidized bed to be used 6 in accordance ~Jith the teachings of the present inven~ion.
7 The purpose of the ollow-lng is t~ indicate a 8 m~thod for determining the magnetization Mp o a ~ypical 9 particle ;n a bed from those values obtained from a magnetom-eter. Generally, this will require a calculation since the 11 e~ective .~ield that a bed particle is subjected to depends 12 on the applied field, the bed geometry, the particle geome-13 try, the bed voidage and particle magnetization. A general 14 eY.pregsion ha.s been derivecl to relate these quantlties lS based on the classical ~pprox;mation oi the Lorentz cavity 16 that is employed in analogous physical problems such as the 17 polarizat3.on of dlelectric molecules.
18 ~la = He -1- Mp ldp ~ (l-~o) (db-1/3)J (1) 19 Ha is the applied magnetic f-ield as measured in the absence of the part:icles, He the magnetic ield within a particle, 21 Mp the particle magnetization, dp the particle demagneti-22 zati.on coefficient, ~O the vol.dage in the particle bed, and 23 db tlle becl dernagnetlzation coe~flcient. The term -1/3 is 2~ due to thc Illagnetizillg influence o a (vi~tual) sphere su.r~oundi.llg the bed partlcle.
26 The expressi.on above applies as well to a sample 27 of particles SUCIl as used :;n a magnetometer measurem~nt.
28 Xn t~at case db is tlle demagnetiæation coefficient ds corre-29 spon-.ling to sh~pe o the cavity ~.n the sample holder.
~agnetome-iter rlleasurement produces a graph of Mp vs.

~ 3 S ~ ~

1 Ha Using ihe above equcl~lon and kr1own values cf dp, ds, 2 ~, Mp and ~ a correspondin~ valuc of Iie May be computed, 3 When the value o~ He is small its value found in this 4 manncr i.5 determinec1 by a differerlce between large num~ers~
5 hence is subject to cumulative errcrs. Accordir1gly, a modi-6 fied approach is useEul ~s described ;n tlle follow;ng.
7 Thus Lt is useul to define a reference quantity 8 Hs representin~ the calculated field in a spherical cavity 9 at the location of the particle. It i5 imagined that the 10 magnetizatlon of st~rrouncling particles is unchanged when 11 the said particle is removed.
12 Hs = Ha ~ ~p ~ o) (db~ )] (2) 13 Combining the two expressions gives an alternate relation~
14 ship for Hs~ in which Ha is eliminated. ;~

15 Hs ~ He ~~ Mpdp

16 This expression is recognized to give Hs as the change of

17 field in passing from the inside of a particle to t~e out-

18 side of the particle.

19 Denoting Km as the follo~ing constant

20 ~ ~l c`o)(ds~l/3) (43

21 then rom (2) K~n equals the quanti~y Mp/(Ha-HS) i.e.

22 Km ~ ~ (5)

23 Thus, on the graph of Mp vs. Ha straight llnes of slope Km

24 intersecting the measured curve and the Ha axis rela~e

25 ~orresponding values of Mp and Hs. Accordingly, a graph

26 may be constructed o~ Mp vs. Hs. For example~ when the

27 sample is contained in a spherical cav-Lty ds -~ l/3, Km is

28 infinite, and Hg equals Ha. ~or a long sample such that

29 ds ~ O~ I~m ls negative and Ha is less than 1-19 l.e. the field

30 magnetizing a particle of the sample is g~eater than the 1 ~,t .~

~3L352~7 ~ .

1 ~ield applied to the sampl.
2 Additiol1a'lly, for a process bed, a constant Kp 3 may be defined as follows: -P ~ o)(d~ )3 (6) It may al50 be seen from ~q. (2) that a line of 6 slope-ICp passing through a point Ha on the horizontal 7 axis o~ the graph of Mp vs. ~ls intersects the curve on 8 the graph at a value of Mp giving the pa~icl.e magnetiza-9 tlon in the bed. Thus, the particle magnetization Mp in a process bed has been related to the ~ield Ha applied to the 11 process bed.
12 The relationship of Eq. (l) is an approximatlon 13 more likely to be accurate for beds hav~ng high voidage 14 than ~or very densely packed samples.
'15 - It is to be understood that the term "~pplied 16 magnetic ield" used throughout the specification and claims ~17 refers to an empty vessel applied m~gnetic field.
18 Thus, it can be seen from the above discussion 19 that tbe fluidizing gas velocity region of operation in accordance with the invention is potentially expanded with 21- increasi.ng magnetization of the particles. The actual magne-22 tiæation of ~he particl.es in the fluidization vessel will be 23 a function of the parti.cles themselves ~the degree of magneti~
:
24 zabili~y they inherently possess) and the intensity of the applied magnetic ield. ' 26 As stated above the magnetizable particles should 27 have a certain degl^ee of magnetiza~ion M which is imparted 28 to the partic'les by the ;ntel1sity of the applied magnetic 29 field. Obv:iously, one would seelc the lo~est applied magnetic field poss1~le because'o~ cost. Con~only, many of the com--~. .

$~ ~ 5'~

l posite pal:t;cles wtdLl require at least 50 oersteds7 prefer~
2 ably at leasL 100 and preferab]y less than 1000 oersteds ~o 3 achîeve the requ;sil:e magne~ization M. The determination of 4 the applied magnetic field will take into account the type of particles fluidl~ed, i.e., their magnetization M, parti-6 cle size and distribution, the fluidizing gas velocity to 7 he used, etc.
8 As stated earlier, it i5 contemplated that in some 9 cases the magnetizable~ fluidizable composite particles o~
l the invention may be admixed with non-magnetic particles.
Il For example, silica7 alumina1 metals, catalysts, coal, etc.
12 may be admixed with the magnetizable, fl~lidizable composite 13 particles. In the case o admixtures (as opposed to only l4 composite m~terials containing the magnetiæable par~icles) it is preferred that the volume fraction of magne~:izable, 16 fluidi~able composite particles exceed 25 perc~nt, more pre~-17 erably exceed 50 volurne percent. Ln most cases, the bed 18 will be comprised of 100 volume percent of the magnetizable, 19 iluidizable composite particles (i.e. it ~ill not cont~in admixtures of other materials)~ When the non-magnetizable 21 admixt~re exceeds 75 volume percent, the particle mixtures 22 may separate analogous to liquids of limited solubility.
23 The particle size of the fluidizable, magnetizable 24 composite particles will range from about O.OOl mm to 50 mm, more pre~erably ~rom 0.05 to 1 mm. Often the particle size 26 will range from a~out 0.1 to .75 mm. The particle size ~7 range referred to herein is that determined by the mesh 2a openings o a first sieve through which the particles pass 29 and a second sieve on which the particles are retalned.
The process of the invention permits operation ~ith 1~

~ 3~35~ 7 1 hi~h fluid:Lzin~ gclS v~locitles in the re~ion where bubbling 2 occurs without si~niicant entraimnent of solicls in thc gas 3 leaving the becl. In accor(lance wi~h ~he invention, the flui-4 dizing gas veloci~ wi]l be passed upl~ard:Ly through the bed S at a superficial gas velocity at least twice, e.g. 2 to 1~
6 times and as ~llch as 25 t:Lmes~ and more, the minimum super-7 ficial gas velocity required to flrlidize the bed in che ab~
8 sence of a magnetic field. In order to fluidize the solids 9 of the inventîorl at such high gas velociti.es without signifi-cant entrainmen~ of solids in ~he gas leaving the bed, lt i9 11 preferable ~o employ magnetic ;Eields havirlg a fi.el-d strength 12 greater than 50 oers~t:eds, more preferably, greater than 150 13 oersteds, with the upper limit being determined on the basis 14 of the amount o field which would cause agglomeration of the particles or slug forma~ion.
16 The minimum superficial gas velocity to be emp~oyed 17 in order to produce bubbling in the bed is a function of the 18 component of magnetization of the magneti~able, fluidi.æable 19 composite particles along the direction of the external force field, i.e. gravity in the verticle direction, which is irn 21 parted by the applied magnetic ~ield. It is to be recognized 22 that factors such as particle si~e, particle com~ositioll, 23 particle density, length and shape of the bed, etc. each afect 24 the gas :Eluidization velocity to be employed to achieve the benefits o~ the inventiorl at a given component of magnet;za-26 tion. The vflriation and adjustment o these fac Lors will be 27 apparent to those skilled in the art in practlcing ~he process 28 of ~he present invention.
29 ks is generally Icnowrl, the minimllm superficial gas velocity requirecl ~o ~luidize the bed in th~ absence o~ a mag~

~7 -~3S~

1 ne~ic fiekl ;s tha~. sllperficial g~s velocicy required to 2 transorm the bed o~ Darticles at rest, i e. a fixed bed~ to 3 a bed in the fluidi~ed state i e. a fluidized bed, in the 4 absence of an app'1iec] magnetic field. In general, this minl-mum ~lu-idlzation superficial gas velocity is the gas velocity 6 obse~ved when the pressure difference of the gas passing 7 through the f'lui-lized bed~ as measured between upper and 8 lower surfaces of the bed, is irst substantially the same 9 as the bed weight per unit cross-sectional area. As is well lo known, superficial gas velocity is a measure of the linear 11 gas velocity that would pass through an empty vessel and it 1~ is measured in feet per second, centimeters ~er second~ etc.
13 As the superficial gas velocities are increased, 14 the component of magnetization of the magne~izable, fluidiz-able composite particles along the direction of the external 16 force field7 i.e. gravity in the ver~ical direction, wi'1l at 7 some point have LO be increased so as to prevent signif-lcant 18 entra~nment of solids in the gas leaving ~he bed (and possibly 19 to prevent unacceptable backmi~;ng of the solids in the bed) It will be recognized that particles of high magnetization 21 such as iron and steel can achieve a very high compon~nt of 22 magneti~atlon M at relatively low applied magnetic rields.
23 T~lese particles, however, 'nave the limitation that at applied 24 ~lagnetic ields, e.g., above 50 or lO0 oersteds, the particles tend ~o agg~eg~te ancl take the form of a slug. Consequently~
26 the level of supericial fluidization gas velocity that can 27 ~e achieved w-ith such particles is limited while still main-~8 tairling fllticlization of the sol:id part:icles in the bed withotlt 29 s1gnificant entrail-lment of solids in the gas leaving the bed.
30 The ma~imum useful levels for the magnetization M o~ most :

S~

particles will normally be less than about 1000 gauss, pre-~erably less than 400 gauss, in order to achieve a reasonably fluid-like bed medium without undue agglomeration of particles.
For example, it can be calculated that iron spheres in a bed subjected to an applied field of 50 oersteds has a magneti-zation M of bed particle of about 300 gauss. However, it will be recognized that at points of contact of the particles, the magnetization can be far greater and hence the magnetic forces of agglomeration are greater.
In the preferred embodiment of the invention, the fluidized bed is subjected to a substantially uniform magnetic field. This means that the magnetic ~ield is applied to have a vertical component to stabilize the fluidized medium and the variation of the vertical component of the magnetic field to the mean magnetic field in the bed will be no greater than 50 and preferably no greater than 10~.
The degree of magnetic field to be applied to the fluidized solids in the reaction zone will, as indicated, depend on the magnetization of the fluidizable particles and the superficial velocity of the fluidizing gas. The type and amount of the solids will also obviously have an effect on the strength of the magnetic fiPld ~o be employed. The strength o~ the field produced by an electromagnet can be finely adjusted by adjusting the current supplied to the electro-magnet. SpeciEic methods of applying the magnetic ~ield are also described in U.S. Patents 3,440,731 and 3,439,899 and Belgian Patent 834,384.
In accordance with the invention, the fluidized bed process is operated to produce bubbling in the bed without .~ - 19 -- ~13X2~7 1 signlficant en~ra-lnment of solids -in the fluid leaving the 2 bed. The polnt of bubbling ancl thc amount o entrainment can 3 be contro]led by adjusting particle density~ particle size, ¢ particle slape~ fluidi7-lng gas velocity and viscosity, parti-cle magnetization, strength of the field applied to the flui-6 dized bed, etc 7 Bubbling can be visuall~ observed ln an open top or, 8 alternately, transparent wall reactor such as may be used in 9 experimental and atmospheric pressure operation. As is known, at the point of bubbling the height of ~he fluidized bed be-.
11 gins to fluctuate and becomes difficult to measure. Signifi-12 cantentrair~ent is a point where unacceptable quantlt~es of 13 solids are stripped from the fluidizing medium and are carried 14 ~rom the bed region. And, significant backmixing reers to the condition where the lifting forces o the fluidizlng med 16 ium flow result in a suiciently great upward welling o 7 solids at some points in the bed, together with a correspond~
18 ing downflow at other points so that reactants enterlng the ~ -19 bed and reaction products returned to the reactant inlet zone ? by the circulating solids are comixed to an undesirable and 21 unusable degree. All three of these conditions may be inferred 22 by indirect measurement techniques when the process of the 23 invention is used in typical chemical or hydrocarbon reactor 2~ systems. Such measurement means include, buc are not limited to, the determination of heat transfer rates for-the bubbling 26 conditiorl, and the modification, upon passage through the bed, 27 of pulse shapes when pulses of a tracer component are intro-2~ duced with the fluidiæing medium for the backmix~ng condition.
29 hs indicated~ bubbling in a ~luidlzed bed is a ~ell 3~ known and recognlzed phenomena re.;ulting in fluctuations of ~ ~ 5 2 ~

l the fluidized bed l-ei~ht~ Bubbling, therefore, can be de~er-2 mined by a variety of techniques which measure the fluctual:ion 3 of bed helght (length~. Thus bed height fluctuation can be '4 ascertained by a l~all probe placed in a fluidized bed, the us~
of a laser beam or by pressure taps into the fluidized bed.
6 A convenient means f-or detectlng bed height fluctuation is by 7 determining ~he pressure difference through the bed con~aining 8- the magnetizable, fluidiz'able composite particles. Fluctua-9 tions in bed height will produce fluctua-tions in the pressure d;fference through the bed, thus indicating that ~he superfi-ll cial fluidization gas velocity is su~ficiently hlgh to pro~
12 duce bubbling in the flwidized'bed. With reference to Figure l3 1, this means that ~lle bed is operating in the region beyond 14 VT. Thus,'fluc~uatlons in the pressure difference in the bed l~ is indicative'of'bubble formation, and it is the in~ent o the 16 present invention to operate fluidized bed to produce bubbling 17 therein as a resuLt of a sufficiently hLgh gas fluidization 18 velocity. In one embodiment, thereore, the superficial gas l9 velocity is con~ro'lled and/or moni~ored such that it is suf-~0 ~icient to cause time-varying fluctuations of pressure differ~
2l ence through t'ne bed over a finite perlod of time, e.g. 1, 2, 22 10, etc. seconds, during continuous fluidiz~tion.
23 The upper limlt on the superficial gas velocity em-24 ployed in the present invention is tha superficial fluidiz-ing gas velocity which produces unacceptable carryover or en-2G trainment of solids in the gas leaving'the fluidized bed. In 27 othe~r words, the super~icial gas velocity is controlled and/or 28 mc~nitored so th~t there is no sign-ificant entrainment of sol-29 ids i.n the gas 'leav;ng the fluidized bed, e.g. less than 15 grains/SCF, preferabl~ less than 1.5 grains/SCY, more pre:~er-5 ~ ~7 1 ably less than .5 grains/SCF, e.g. .02 to O.l grains/SCF
2 (standard cubic ~ee~ at 60F and l atmos. pressure).
3 Preferably, conditions in the fluidized bed zone are 4 maintained to continuously produce bubbling therein without 5 signi~icant entrainment of solids in the fluid leavirlg the 6 bed. The ~luidiYJed bed is preierably operated in the bubbling 7 mode on a continuous basis as opposed to the occasional or 8 periodic operation of a magneticalLy stabilized fluidized bed 9 in the bubbling mode. It is recogniæed, however, that in some instances it may be desirable during operation of the fluidiz-11 ed bed process to occasionally operate the bed under conditions 12 which will not produce bubbling. For example, when it is de-13 sired to initiate a reaction which requires an elevation of 14 temperature within the bed and mixing motions would cool the bed and thus quench the reaction before the temperature is 16 reached at wh;ch sel-sustaining exothermic conditions are 17 reached.
18 The feedstocks suitable for conversion in accordanc2 19 wlth the inven~ion include any of the well-known feeds con-~0 ventionally employed in hydrocarbon conversion processes.
21 Usuallys they will be petroleum derived, althou~h other sQur-22 ces such as shale oil and coal are no~ to be excluded. Typi-?3 cal o~ such feeds are heav~ and light virgin gas oils~ heavy 24 and light virgin naphthas, solvent extracted gas oils, coker gas oils, steam-cracked gas oils, middle dist-îllates, steam-2b cracked naphthas, coker naph~has, cycle oîls, deasphalted 27 residua, etc.
28 The application of a magnetic ~ieLd to the reactor, 29 c~talyst regenerator, separation zone, clryîng gone,etc. in accordance wîth the invention is not to be limited to any .
- ~.2 ~

3 ~ ~ ~ 7 1 spcc~fi~ rnetho~l of: pro(]ucillg 1she rnagne~ic fi.eld. C~nventi~n 2 al permanent magnecs and/vr eLect:romagneLs can be ernployed 3 to prov~ e tile rnagnetic ~ield used in the practice of this invention. The positioning of the magnets will, of course, S vary with the solids used, degree o fluldization required 6 and the effects desired. -rn the preferred embodlment of 7 ~his inven~ion, a cylindrical electromagnetic~ or an a range-8 ment of toroidally shaped electroma~net which produces a 9 magnetic fleld which i.s equ:ivalent 1:o that of a cylindrlcal electromagnet~ is employed to surround at leas~ a portion of 11 the 1uidizecl bed as this provides those skilled in the art 12 with an excellent method of achieving nea-r un-lform magnetic 13 field and stability throughou~ the bed Such electromagnets 14 when powered by direc~ current with the use of a rheostat, solid state con~roller, saturable core transformer, etc are 16 particularly desirable for applying a magnetic field to the 17 bed part-LcleF, and to provide an excellent method of maintain~
18 ing the fluidization of the bed particles in response to 19 changing flow rates of the fluidizing medium.
The process conditions to be employed in the practice 21 of the present invention will, of course, vary wlth the par-22 ticular physical or conversi.on reaction desi.red.
23 The following table summari~es typical hydrocarbon 24 conversion process conditions effective in the present invention 3"S~2~7 . ~ I
tl~ O O O
p:; ~ o o t~
D O O O
O O O
~0 ~t r~l r-( O ~1 OU I I
O O O
O O O
~ u~ u~ u~

tn O ~ ~ O O O O
rl t~ ~
~1 p~`_ O O o O
~rl ~ ~ t,`J C`J
~ ~ l l l l ~ a ~ ~~ r-l O ~
C~ i~ O O O O
O
~rl tG ~U ¦ O O O
tU h i O O
l:Y; ~ ~l O O O O
tl~ t~ t,~lu ~ r-l tn u~ I I I
o ç:~ O O O O
ul O u~
P~ c~

~ O C~
~ O O O O
- ~ O Ul O ~1 ta ~ to ,~
O t~ O O O O
C~ O C:~

~, I

i~
O bO
~ri bO
~n i . rl h .r~ Ei a~
u o ~o ~o ta O
U 5~ ~0 ~rl C ~
r-l u~~rl U 10 U
t~ Q) ~ t~ .~ .,1 ~1~ rl h ~ 1 ~J t) >~
U O ~ ~1 h )J t~ ta ~rl 1-1 ~ ~ t~) t~
~: X ~
l trl ~ u~ ~ r`

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1 BRIEF DES~I~lPTJ.ON r~)F rrJlP, D~A~TIJ~T~S' _ _ __ _ _ _ _ _ _ _ _ 2 F~gu~e 1 is a graphical illustlation of a t:hree~
3 pllase diag~am displaying a bed concaining magn~tizable, fluid~
4 lzable solids subjected to vario-ls magnetic ~ield intensi~ies 5 and fluiclizin~ gas velocit~es and operated (1) in the region 6 where the solids are unfluidized, (2) the region where the 7 sollds are fluidiæed and stabilized to eliminate bubbling 8 and (3) the region wheL-e bubbling occurs ln the 1uidized bed ~ (the region of the invention).
Figure 2 is a graph showi~g the results in terms of 11 bed ~oid ~raotion vs. ~luidizing gas velocity for a fluidized 12 bed operated ~t various gas 1ùidizing gas velocities.
13 Referring to Figure 1 in greater detail, this figure 14 illustrates the operating regimes that can be achieved when a l5 magnetic ield is applied to a fluldized bed o ~erromagnetic 16 solids at various superficial 1uidiæing gas velocities. The 17 region indicated as ~1~ is the region where the 1uidi~ing gas 18 velocity U is not high enough to fluidize t~le solids, i.e. the 19 solids are in a settled mass anal~gous to a ~ixed bed.
The regio~ indicated as (2~ is a region above the 2l minimum supericial gas velocity U~ required to fluidi~e the 22 bed at applied field H where the bed is expanded and the solids 23 beh~v~ like ~ rluid but there is essentiall~ no bubblig or 2~ motion of the sclids. The region indic~ted as ~3) is a region 25 above the transition s~perficial gas velocity UT (minimum super~
~6 ficial gas velocit~ to cause bubbling mode operation) at applied 27 field H where the bed is ex~panded and th~ solids beh2ve like a 28 1uid buc bubbling o~ the bed occurs in a very gentle quiesoent 29 manner with no grcss movement of solids or bac~nixing o gas ~ and solids. ~egio~ (3) is ~he region o~ ~he inven~ion.

~135;~
, . . ~., DESCRIPTION OF THE PREFERN~D EMBODIMENTS
. . ._ The following example further illustrates the present invention.
An open-topped cylindrical Plexiglass column having an inner diameter of 28 centimeters and a length of 55 centi-meters was charged with 3,148 grams of fluidizable particles consisting of Ni on alumina containing 23 wt. % magnetizable Ni and sold under the trade mark Girdler G87RS and having an average particle si2e of 270 microns. Coaxially surrounding the bed of particles was a toroidal electromagnetic coil having an inner diameter of 40 cm consisting of a stack of 10 flat coils each 2.54 cm high with an outer diameter of 60 cm. The -coils were spaced in a vertical direction by 2.8 cm with each coil consisting of 170 turns of flat copper ribbon and about 0.05 cm thickness. The coil was supplied with direct current to produce a uniform, axially oriented field of 420 oersteads over the entire test region.
Air at various velocities was passed upwardly through the bed for fluidization. The fraction of the bed which was void was measured at various fluidizing velocities by measur-ing the increase in bed height and calculating the void frac~
tion from the weight of catalyst, the known particle density, and the cross-sectional area of the bed. The results are shown in Figuxe 2.
When the bed was operating in the bubbling mode, it was observed that the bubbling was very uniform and the bubbles were smaller as compared to bubbles produced in t.he absence of the magnetic field. Further, the downflow of solids at the vessel wall which is normally observed in a bubbling bed in . r the absence of a magnetic field was minimal in the instant ~, - 26 -:l i)uhblin~ bed su~)~ct~(] to a rr,agneti( field, Xn the presenc~
2 of t'ne rnagne~ic field, the ~ubblin~ occurs without significant ~-3 backmixing and results in good heat transer characteristics.
4 Entrainment of be~ fines less than 5 m:;crons did not occur except at very higl~ fluidizing velocitles. In this example, 6 entrainment of bed ~ines (less than 5, microns) started when 7 the air velocity was about 10 times the minimum fluidization 8 velocity or the ~luid bed, and bubbling occurred in the bed 9 at about 3.5 times the minlmum fluidiæation velocity.
The applied magnetic field of 420 oersteds used in 11 this exam~le resul-~ed in a magnetiæation of the fluidizable, 12 magnetizable composite particles o~ about 100 gauss when the 13 bed was at or above the transi~ion velocity, UT.

Claims (16)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for carrying out a drying, separation, catalytic regeneration or chemical conversion process in a fluidized bed, comprising:
(1) preparing a bed comprised of composite particles of magnetizable and non-magnetizable material which contain at least 50 volume %
non-magnetizable material, said particles being characterized as having catalytic or mass transfer characteristics;
(2) subjecting the bed to a magnetic field having a vertical component at a strength such that the composite particles having a component of magnetization along the direction of gravity, said magnetization, m ranging between 10 and 400 gauss;
(3) passing a gaseous stream upwardly through the bed to fluidize said bed of particles at a superficial gas velocity which is:
(a) at least twice the minimum superficial gas velocity required to fluidize the bed in the absence of the magnetic field, and (b) at least an amount sufficient to continuously cause time-varying fluctuations of pressure difference through the bed over a finite period of time during continuous fluidization which is indicative of bubble formation;
(4) controlling and/or monitoring the magnetic field strength and superficial gas velocity based on the relative particle magnetization, particle size and shape particle size distribution of the particles in the bed such that the following conditions are met:
(a) agglomeration of the composite particles does not occur;

(b) bubbling of the bed occurs in a very gentle quiescent manner, the bubbles in the bed are small, finely divided and substantially uniform;
(c) the particle movement is restricted in direction such that there is no gross verticle circulation of the particles or solids backmixing; and (d) the entrainment of solids in the gas is less than about 15 grains of solids per SCF in the gas leaving the top of the bed.

2. The process of claim 1 wherein the composite particles contain 80-95 volume % of a non-magnetizable material.

3. The process of claim 1 wherein the composite particles contain a zeolitic crystalline aluminosilicate and a ferromagnetic material.

4. The process of claim 1 wherein the composite particles possess mass transfer characteristics and include agents suitable for drying or separation processes, said agents being selected from the group consisting of molecular sieves, activitated charcoals, solid metallic and organic complexing agents and silica gel.

5. The process of claim 1 wherein the composite particles possess catalytic characteristics and include agents selected from the group consisting of highly active zeolite-containing catalysts, amorphous silica-alumina catalysts, and supported hydrotreating or hydrofining catalyst containing transition metals selected from Groups VI and VIII of the Periodic Table.

6. The process of claim 1 wherein the bed additionally includes some particles which are 100% ferro- or ferrimagnetic.

7. The process of claim 1 wherein the bed is subjected to a substantially uniform magnetic field of at least 100 oersteds oriented axially to the flow of gas in the bed.

8. The process of claim 7 wherein the variation of the vertical component of the magnetic field to the mean magnetic field in the bed is no greater than 10%.

9. The process of claim 1, 7 or 8 wherein said composite particles have a magnetization of at least 150 gauss.

10. The process of claim 1 wherein the entrainment of solids in the gas is less than about 1.5 grains of solids per SCF in the gas leaving the top of the bed.

11. The process of claim 1 wherein the entrainment of solids in the gas is less than about 0.5 grains of solids per SCF in the gas leaving the top of the bed.

12. The process of claim 1 wherein a vaporized hydrocarbon feedstock is fed into said bed and a hydrocarbon conversion takes place in said bed.

13. The process of claim 12 wherein hydrogen gas is fed into said bed with said vaporized hydrocarbon feedstock.

14. The process of claims 12 and 13 wherein said bed is at temperatures ranging from 500-800 F, and said composite particles are active for the catalytic desulfurization of said feedstock.

15. The process of claims 12 or 13 wherein said bed is at temperatures ranging from 800-1100 F. and said composite particles are active for the catalytic reforming of said feedstock.

16. The process of claims 1 or 4 wherein selected components of a multi component gas stream are absorbed in said bed in a separation or drying process.