US2607635A - Transportation of granular solids - Google Patents

Description

9, 1952 R. KOLLGAARD TRANSPORTATION OF GRANULAR SOLIDS Filed Sept. 13, 1950 3 n ven tor Rayner K'ollgaara' OISE/V6465 All-7' 639$ All? COMP/FESSOR (lgaub I Patented Aug. 19, 1952 ReynerKollgaard, Media, Pa., assignor to Houdry- Process. Corporation, Wilmington, Del., a corporation of Delaware Application September 13, 1950-, Serial No. 184,545 5 Claims. (01. 302.--L7) Thepresent invention relates to cyclic procmasses: or systems inwhich solid particles or granul'esv of contact material circulate through adownfl'ow 'path' 'wherein'they pass through a process zone and are contacted with fluid and are thereafter elevated through an 'upfl'ow path for return "through thedownflowpath. The present: invention is more particularlyconcerned with the upfl'ow path wherein theparticles-are elevated, conveyed or transported through "a ver ti'cally elongated" laterally confined lifting zone orco'nduitby a lifting fiuid'or gas! 7 V Such proces'scs'or s stems,iwhich areaparticulai'ly adapted to therequir'ementsof'thechemical and oil refiningindustries, have a wide range of. usefulness. Thus the granular contact material may bea porous; or fused solid" and may m priseor' consist of a catalyst/ or catalytically inert material; the latter being usedfor heat exchange, or for the adsorption or fractionation of gases. The granular contact material-"canbe advantageeusl'y in the form or relativelylarge particles or granules, such as molded" pellets, formed spheres and the like ranging in size from 0.05 toiliiinch in diameter, which, wholly or in part, gravitate through process zones as compact downwardly moving non-turbulent beds in a manner known to the art.

' It has been found adva'intzjaigeous to transport the granular contact material for recirculation throughthe-proce'ss zones'of such syst'e'msby a pneumatic or gas lift I which provides an upfiow patli rne's stemmay comprise a single downflow" path which there are several process zones at different heights, through which zones thecontact mater-ia'l' fl'ows consecutively so that the solid pa'rticles need be transportedby theigas lift only once in a complete cycle of operation, ontlie system-may-cOmp'rise aplurality of gas lifts-and/or downflow paths, each downfiow path containingasingle process-zone. An exemplary system 'of'the' formertype has been described in anarticle entitled Houdrifiow: New Design in Catalyticcrackingj appearing in: the Oil and Gas'Journah page 78; January 13, 19.49. 'In suchfsystems the-use of aig'a's lift for the elevation ofthe 'granular contact :material, 'insteadlbf i the mechanical elevators formerly employed; produces; many advantages :both as to control (if-(the processing vari'ables (operating conditions) and as to 'efiiciency of operation (including cost and m'aintenance=)' but, at the' same time; creates new'probleins. One of the chief problems in" the operation or gas lifts or: "the type referred-to hereinis that or achieving ennui taneously a high rate -of circulation of solidparticles and easy andrapid return of solid particles from the upfiow path to the downflow path, while maintaining a low rate of attrition or breakage of the solid particles during such return.

The methods and apparatus disclosed in'the prior art. for. effecting the necessary reversal of flow'of the particles from the upflow pathito the downflow path produce high attrition ofthe para ticles'and/or necessitate the use-of bulkyrandexpensive equipment. Thus, when'the lift is operatedat-high rates of circulation'and'. at desirably low concentrations; the particles passing therethrough are traveling at such high velocities as they emerge from: the. lift that a considerable distance'is required for the particles to change their upward movement to downward movement due to the decelerating effect of gravity. Gonsequently, the vessel or zone-surrounding the top of the lift: must-ihbe tall (such a vessel is commonly referred to as. the disengaging vessel, hopper. or" zone, since it. can" be and .frequentlyis used:- fordisengaging: lifting gas; from solid. particles). Because thervdisengaging vessel is necessarily at the. top of the gas" lift, which may: be from lilil'to 20.0 or more feet high, the: problems and expense of: supporting: and bracing itat such a: height are multiplied. as the. height of the-vesssel increases. Consequently, the reduced height of disengaging vessels made possible by theipres ent: invention; as described below,lresults:-in:-considerable savings in the cost of construction of the supporting structure.

' AnJadditiohal"difficulty is encountered incommercial-v applications of gaslifts which involve the transfer of very large amounts of contact Y material, such as from 100 to 400 tons an hour,

and. need a gas lift pipe that is relatively wide, such as from 10' to 24- inches or more; A. Jet action occurs at the discharge end of the lift '(i. e-., the stream of particles emerging from the lift does not immediately dissipate or fountain into thesurrounding relatively more extensive emergent particles, instead of fountalning or spraying outwardly and settling in the disengaging zone, form a relatively dense cloud or mass of particles suspended above the lift. Obviously, collision of the particles emerging from the lift with those in the cloud leads to undesirable attrition. I

In accordance with the present invention, the undesirable effects noted above are minimized and/or overcome in systems of the type here involved, by passing a stream of lifting gas and particles moving at substantial velocity upwardly along the lower part of the vertical extent of a vertically elongated laterally confined lifting zone or conduit, flowing only portions of said stream' radially outward, while passing said stream generally upward along the upper part of the lifting zone. Such flow can be achieved by using a lift or conduit having a plurality of vertically elongated radial projections spaced around the periphery of the conduit, which projections are in communication with the conduit and taper outwardly along their vertical extents to the top of the conduit. The stream of particles and gas, including the radially disposed portions, is discharged from the upper end of the lifting zone or conduit into a gas-solid'disengaging zone or hopper having a considerably greater horizontal cross sectional area than that at the top of the lifting zone or conduit. Under the described conditions of operation, the horizontal area circumscribi'n'g the top of the lifting zone or con dui t' is substantially greater'than the horizontal area at the top of the lifting zone or conduit through"which the stream of gas and particles flow." Asa consequence of this relationship, the stream of particles and gas is dispersed or spread over'a'greater area than its flow area before the stream enters'the disengaging zone with the result that'i'subsequent disengagement and free settling of the particles is simpler and attrition betweenthe particles tends to be reduced.

'The invention is especially applicable to systems involving 'the'catalytic conversion of petroleum, andfor the purpose of. illustrating the invention, it willbe described hereinafter in connection with a catalytic cracking system for the conversion of high :boiling' hydrocarbons to motor gasoline. Suchfa system is set forth in detail below in connection with the description of the drawings in whichp'i' I Figure. l'is a schematic generalized elevation of a typical system in which the present invention may be used. 1

:Figures 2 and 3 are enlarged views of an embodiment or the present invention to be used as the upper portion of a gas lift in the system shown, in Figure 1, Figure 2 being an elevation partially in section along the lines 2-2 in Figure 3,-and Figure 3 being a top view;

Figure'4 is the top view of a modification'of the embodiment of the invention shown in Figures 2 and3;1 1

Figures 5 and 6 are another embodiment of the present invention to be'used as the upper portion of ages lift in the system shown in Figure 1, Figure 5, being an elevation partially in section along the lines 5-5 in Figure 6 and F ure 6 beinga top view, I I

'In Figure 1 is shown, a typical embodiment of thetype of system with which the present invention is concerned. 7 Since the invention is directed primarily to the upilow portion of the system and since the. operation and construction of the reactoriand regenerator or kiln of the typical system shown in Figure 1 are adequately described in the afore-mentioned article appearing in the Oil and Gas Journa detailed illustration and description of the latter have been omitted for the sake of brevity. It is to be understood that various arrangements of kiln and reactor may be employed in connection with the present invention, as for example arrangements shown in the Houdry Pioneer, vol. 1, February 1950.

As indicated in part by the labelled portions of Figure 1, relatively large particles of solid cracking catalyst, such as particles of between about 1 to 15 and preferably about 2 to 8 millimeters in diameter, flow downwardly through a reactor or cracking zone as a downwardly moving compact non-turbulent bed and contact hydrocarbons with the resultant formation of cracked products (synthetic crude) and are transferred through a conduit or seal leg to a regenerator, kiln or regenerating zone in which the coke deposited on the articles of catalyst in the cracking zone is removed. Compositions effective as hydrocarbon cracking catalysts (typically natural or synthetic aluminosilicates) and the conditions in the reactor and kiln are well known to the art and need not be repeated here.

Catalyst particles are withdrawn from the regenerator and flow downwardly in a conduit as'a compact non-turbulent column to a gas lift inlet chamber, or particle supply hopper Ill surrounding the bottom of a gas'lift, and are transported or lifted vertically upward as a continuous stream of solid particles by a gas introduced at a substantial pressure, such as from about 1 to 10 pounds; per square inch gauge, to inlet chamber 10 by conduit ll and/or l2. The gas used in lifting may be one derived from or one used later in the system, such as flue gas ;or hydrocarbon charge stock, either in liquid or vapor phase, respectively; or maybe one used only for lifting, such as air'or steam. The particles of contact material pass upwardly through a vertical cylindrical passageway, path, pipe or conduit indicated generally by l3 which provides a vertically elongated lifting zone to a closed vessel, hopper or separator l4 surrounding the top of .lift-l3, which vessel comprises a confined gas-solidsdisengaging zone. The disengaged lifting gas is thereafter removed from vessel M, as from the top thereof by conduit I5. a V

Particles of catalyst disengaged from thelifting gas settle on the surfaceof a bed invessel M, from which bed the particles flow through a conduit or sea] leg as a relatively compact nonturbulent column of particles to-the reactor. It is to be understood that a particular type of separator, such as vessel I4, is not a part of this invention and that separators other than the one illustrated, which perform-the function of, separating the elevating gas and particlesof catalyst by variousgspecific methods, maybe employed. Indeed, the gas, after disengagement from the particles of catalyst at the top of the lift path may, if desired, be passed downwardly through the bed of catalyst in the separator (as, for example, where hydrocarbons are employedas the lifting medium and cracking, in additionlto-that occurring in the lift-is desired), the-lifting gas being finally disengaged from particles of catalyst at the bottom of thebed in vessel l4. At any event vessel l4 i$;. f considerably greater horizontal cross sectional area: than 3thatyof -the top'of lift'path or conduit ,l3 such asafrom 25 to 100, times the area of the circle circumscribing the top ofthe ear, li tr i o t tthe pard ame er-z.-

f a eonstant circular horizont aeomee :ticlesmnnay n r fountaihinaoutiotgthelm pipe :do: not; impin e; a ain t: the walls: Also.- .1 when free Settling particlesemereine .fxomth asalift; isnemnloyed; as; a means .otrseparatin he; nantioleszand gastthe distanceiofg the top of vessel: above-tha f: liftapine lizshould e. t en u h-that: th re. is; little 012-1 simpan :panticles aga nst thaytono the disena gin pen .ioizexample'.:.aed stance f-about t 3. 5.- fe.e -canlbecmployed when the catahi pa times-emerge with. naveraeev lo ity of:3i):t etpera econdfrom- QfZ12;lI-Q'=2Q; inches the top'of' conduit! 3b along its com lete vertical xt nt Additional, latera1;confinement is providedubyiside; walls, la; Radialprojections, or 1 hainbers communicate un tructedly alon their. complete, vertical, extent with the; inter m of. lifting zone r conduit I3, I Inthe. embodiment otjthe present, invention; shown. in; Figures 2.2m. 3,,the? lift .pipepro er e, conduit 131) exclusive, of, the .radiai rojections) has the same .diametenfinthe upperr portion lili s in th. e-. ow

pqrtion. 13d. and-the} radial prpjectionsare channels h are; rectilinear. i n,.horizon1ta1; cross sec.- .tionalarea. i v; p p

hetm id fication shdwn in- .E e e he nadialjprojections.or chambers are the; form oigrooves 2|, having "straight' lradial; sidewalls l9 and arcuate outermost boundaries-'22 that are concave inrespect;toith einterior of conduit [3b. As shownin Figure 4, conduit l3b has been modifled between adjacent chambers to fpI'OYide arouate surfaces that QQ iYBX tothe interiorof. the

conduit; 7 I

The same type of radial projections or chambers l6 aszin Figures '2.and 3 are -employed in the embodiment shown in Figures 5 and 6 but the upper-901312101 ofconduit I312 v exclusive of; chamhers l;6, has been modifiedjso that it tapers; i-n- Wdfdly by hail n .a,, f.r.usto conical sh p tapering inwardlytoward the-top of the lift.

Although the modifications" shown employ-a .stxaight line, the taperdmay follow a curve so that thelradial projections:are-somewhat trumpet shaped.

The gas lifts shown in the drawings are operated by moving upwardly through the lower portion of the lifting zone or conduit a stream of lifting gas and particles at a substantial velocity. This stream has a constant, continuous circular flow area until it reaches the upper portion of the 6. lections or chambersiprovide;additionalfiow'area for the. streamvas. awhole. Dependingfiunon. the .sizeiielationship.between the additional areajmtovid'edi by the. radial: projections ofthe conduit and; theiarea of the lift conduityproper (i.. e the circular; portion of. conduit. exclusive. of the radial projections), the velocity of the. stream of gas and particles as a whole canbeaccelerated,

maintained; constant or decelerated: to; 'any:,de-

sirediextent. 'llhus'when relatively smallang es ofitap nare. employed, (the-angle of tapenz-is measured as-the; inclination of; side wall;l to; the

Me cali axis of" theiliitficonduitl, suclnas from .0;2.;.t.o. fiveceerees; of taper.- extending-mover rela- ;tigel -long;uppe1: sections, such-as from, about 10. to- 30-fect. the. used, the .1velocity; may rem in constant or; fisfilQWed down. to. :a minor extent such; as rom; 5. to. 20:per.cen.t. relatively harnane es; 0f taperisuch as from :1;0;to 3 de 1tee extending over a relatively short, portion. of the lift path, such jasiromaabout 2: to':5,.' feet, the palitic-12s canwbe. a c ler ed more rap dly, suchas from 10 Qw percent. The-termylift p th', as used herein. is; applied to; the path; extendin from the bottom. to the to Qf; conduit [3.

in the; embodim t/shown in Fi ures: 5. and 6, thQ 'VeIOClI Y*Ofi'DQJIlliClES;i11 the upper: portion of the'lif-t pipe may. be. slightly decneased; rer main constant, or; increase depending" 111 0.11v the r61ationship;-of-; the cross. sectionali flow: area of the lift. pine below the radial pr0.Elections. and that 'of-the complete; flow area at; the top of th lif pip This; embodiment has the; additional; advantaga. gained: by radually: decreasing the central; flow areaof the Iiftpath as. the

str am imovesz upwardly in; the; upper: portion: 1 3b,

of? tendingt0, forcel oi" urge; axrelatively large portion of the. Particles; into thesradialiiprojecitions. This decrease in central flow-area hasrthe further advantage of decreasing the: diameter ,of; -the jet. issuing from the top of they lifting zone thercby diminishingthe. extent of jet action of; the stream, of particles, with. a. consequent decrease; in the. height: necessary'for: free settling ofttlia emergingstream. of particles. j

, It will be. noted that, in. all aofmthe embodi merits: shown, the particles. emerge from the end of: the-lifting zone J or. conduit, disposed over 1 a 'greateruarea than: the areathrough which they are flowing.v (i. -e., the circle circumscrihingthe outermost portion of the liftconduit is-considerably-greater than the area at the top of the; conduit available: for the flow of granular materialand: lifting-- medium) thereby effecting minished tendency of the particles to form 2.

mushroom or cloud and/or to be broken by impact with other particles. Moreover, by providing a plurality of radial streams, the average distance of lateral travel of particles out of the stream of lifting medium is diminished so that, averagely, the particles can begin to decelerate at earlier time or lower height than if they were concentrated in a single stream of relatively large cross sectional area.

An important advantage of the use of radial streams is that particles moving laterally out of the stream of particles and lifting medium (as defined by the top of the lift path) for subsequent settling do so with a minimum of collision with other particles. This effect is in considerable contrast to a lift path of equal continuous circular cross section when the particles at the center must travel a considerable lateral distance'before they can settle. The small lateral distance of travel with reduced collision provided by the present invention tends to reduce "attrition and to result in a more stable operation of the gas lift.

It is to be understood that the present invention is applicable to a wide range of velocity conditions and particle concentration or density in the lifting zone. Various velocities and concentrations can be obtained by varying the amount and pressure of the lifting gas such as by controlling-"either the total or relative amounts of lift gas introduced by conduit H or l2. An

effective range or particle concentration for commercial operation involving the size of particles referred to above is from about 0.5 to 20 percent of the apparent bulk density of theparticles (i. e., the density of the packed mass of particles) For present commercial catalysts having apparentbulk densities of from about 40 to 55 .poundsper cubic foot, average concentrations of about 1 to 7 pounds per cubic foot have proven particularly advantageous. Experience has shown that an advantageous range of particle velocities is about 30 to 100 feet per second (based on the'average velocity of the particles at complete acceleration), although lower velocities, such as down to about 10 feet per second, may be employed generally in relatively short lifts such'as those of 50 feet or less.

Obviously many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim as my invention:

1. Apparatus for elevating granular material through a vertical lift path by a fluid lifting vme dium comprising a disengaging chamber at the upper end of said lift path adapted to disengage said granular material from said lifting medium and a vertically elongated conduit defining said lift path and terminating in said chamber, the upper end portion of said conduit being gradually expanded radially along longitudinally elongated areas spaced uniformly around the periphery thereof, the expanded portions forming channels in communication with the central region of said conduit, said channels being of gradually increased cross-sectional flow area along their vertical extents to the top of said conduit.

2.;The apparatus of claim 1 characterized in that the upper portions of said conduit between said expanded portions taper gradually inward.

' upper end of said lift path adapted to disengage said granular material from said lifting medium and a vertically elongated conduit defining said lift path and terminating in said chamber, the upper portion of 'said conduit having a plurality of vertically elongated channels spaced around the periphery thereof, said channels being in communication with said conduit and rectilinear in horizontal cross section, said channels tapering outwardly along their vertical extents to the top of said conduit whereby the horizontal area circumscribing the top of said conduit is substantially greater than the horizontal area at the top of said conduit available for the flow of granular material and lifting medium therethrough." V

5. Apparatus for elevating granular material through a vertical lift path by a fluid lifting medium comprising a disengaging chamber at the upper end of said lift path adapted to disengage said granular material from said lifting medium and a vertically elongated conduit defining said lift path and terminating in said chamber, the upper portion of said conduit having a plurality of vertically elongated grooves spaced around the periphery thereof, said grooves being in communication with said conduit and V-shaped in horizontal cross section with arcuate outer boundaries, said grooves tapering outwardly along their vertical extents to the top of said conduit wherebythe horizontal area circumscribing the top of said conduit is substantially greater than the horizontal area at the top of said conduit available for the flow of granular material and lifting medium therethrough.

REYNER. KOLLGAARD.

REFERENCE S CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,840,857 Testrup Jan. 12, 1932 2,396,491 McOmie Oct. 9, 1945 FOREIGN PATENTS Number Country Date 180,397 Great Britain May 11, 1922 268,667 Great Britain Apr. 7, 1927

Claims (1)

1. APPARATUS FOR ELEVATING GRANULAR MATERIAL THROUGH A VERTICAL LIFT PATH BY A FLUID LIFTING MEDIUM COMPRISING A DISENGAGING CHAMBER AT THE UPPER END OF SAID LIFT PATH ADAPTED TO DISENGAGE SAID GRANULAR MATERIAL FROM SAID LIFTING MEDIUM AND A VERTICALLY ELONGATED CONDUIT DEFINING SAID LIFT PATH AND TERMINATION IN SAID CHAMBER, THE UPPER END PORTION OF SAID CONDUIT BEING GRADUALLY EXPANDED RADIALLY ALONG LONGITUDINALLY

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