US2762658A - Method and apparatus for elevating granular material - Google Patents

Description

Sept. 11, 1956 R. M. SHIRK METHOD AND APPARATUS FOR ELEVATING GRANULAR MATERIAL Filed Dec. 29, 1951 570E465 VESSEL f 047/14 V57 1 FROM ff/L/V 0677/5070? INVENTOR ATTORNEY AND APPARATUS F OR ELEVATING GRANULAR MATERIAL Robert -M.-Shirk,;Wilmington, Del., assignor to Houdry Process-Corporation,Wilmington, Del., a corporation of Delaware Application December 29, 1951, Serial No. 264,081

8 Claims. (Cl. '2--53) METHOD This invention relates in general to a method and apparatus for elevating granular solid material by means of a gaseous lift medium. Inparticular, the invention is directed to a multiple lift in which granular material is conveyed through separateconfined lift paths from a common source of distribution to individual engaging zones surrounding the lift inlets, and therein engaged by lift gas in such quantity as to convey the material into and upwardly through the various lift pathsto the desired elevation,.and in such manner asto maintain substantially uniform flow along the plurality of lift paths.

The invention is especially applicable to petroleum refining and other chemical processing systems wherein gaseous reactants are contacted with a downwardly mov-.

ing compact mass ofv granular material, such as catalyst, along a downfiow path comprising one or more treating or contact zones, the catalyst being separated from the gaseous reaction products near the lower end of the downflow path and passed downwardly to the introduction zone of a pneumatic lift. Within the introduction zone the granular material is engaged by a stream of lift gas and conveyed upwardly through the lift to a disengaging zone at the desired point of elevation. I Within the disengaging zone --the lift gas is separated from the granular material and is discharged from the lift system, while the granular material is collected andreturnedto the upper end of the downfiow path for recirculation through the contact or treating -zones.

Typical systems to which the present invention may beapplied are those discussed. generally in an article en titledf TheT. 'C. C. catalytic crackingprocess for motor gasoline production by'R. H. Newton, 6. S. Dunham, and 'I. ;P.Simpson, recorded in the Transactions of the American Institute ofChemical Engineers, volume .41, pageZlS, April 25, 1945, and in other articles therein cited;,andan article entitled Houdriflow: New designin.

catalytic cracking.appearing at page 78'of the January 13, 1949, issue of the Oil and Gas Journal.-

The-solid material comprising the circulating medium maybe; a catalystor other contact materialin the form of relatively large aggregates or agglomerated masses, such as pellets, beads, or coarse granules of a particle size in the rangef; about 0.05-0.25 inch, for example, pre-.

dominantlycomprising particles of an average size in the -order.of0.15 inch. In the case of a system for effect.-

comprise gaseous hydrocarbons, air, etc.

For-convenience-of description and illustrationthe present invention will hereinafter be considered in connection with a catalytic cracking system for converting hydro- ,i carbons in the presence of granular catalyst gravitating. as a a compact non-turbulent mass.

In connection with the elevationv of the, catalyst for re- I cirtnllation, both mechanical lifts and pneumatic lifts have heretoforebeen .employed Mechanical lifts such as those .employingcontinuously rotating: bucket chains,

Patented Sept. 11, 1956 however have inmany instances been found impractical for various reasons, such as high initialcosts, limited conveying capacity, excessive wear-of the moving parts 7 because of the difficulty in maintainingproperlubrication at the extremely high temperatures employed, and the necessity for providing special devices to accommodate elongation of the bucket chain as a result of tern perature change, which may be of considerable amount in lifts that are several hundredfeet in height.

Inzpneumatic systems, to which thelpresent invention relates, many of the difficulties encountered with mechanical lifts are avoided. Pneumatic systems, however, have their own characteristic problems, especially with respect, to the avoidance of excessive catalyst attrition and erosion of mechanical parts, and tothe maintenance of uniform 7 catalyst flow through the lift system.. The problem. of maintaining uniform catalyst flow is especially acute in multiple lift systems wherein catalyst is supplied directly to the various lift pipesirom a common bed .or source of distribution containing the inlets to the lift pipes.

In such systems, erratic performance within one of the lift pipes may produce pressure fluctuations of suflicient magnitude at the lower or inletend thereof to create anv adyersepressure differential between the inlet endof the faulty lift pipe and the inlet ends of adjacent lift pipes; In such case,.lift gas introduced adjacentthe inlet of :the erratically performing lift pipe may by-pass through;

the compact mass of catalyst surrounding the lift inlet to theinlet of theadjacent lift pipe, thus adversely affecting its. performance and the performance ofthe lift system as a whole. The problem becomes especially acute when the shortest available path for. the gas to flow through ,the compact mass of catalyst from one. lift inlet not -sufliciently segregated withinthe downflowingmass ofcatalyst, gas'migration from the region surrounding an. erratically operating lift pipe to. the inlet of. oneor moreadjacent lift pipes having a substantially. lower inlet pressure, is inevitable. Theeffect of lift gas migration awayfrom thefaul ty lift pipe is cumulative. If migra: tion continues, it maycause .a complete interruption of catalyst flow in the ,faulty; lift pipe andmayadversely affect the operation of the remaining liftpipes ,by increas: ing the velocity of catalyst flow therein beyond acceptable 7 limits. This may occurregardless .of whether the segregaprovided by separate engager vessels for each of the lift P pe In accordance with the present invention, uniformity,

of solidsflow through the several lift paths of a multiple pneumatic lift, having segregated inlets fully submerged. within separate confined downwardly-moving compact columns continuously supplied 4 with granular material tion is provided-withina common; engager vessel or is from a common source of distribution, is obtained by introducingthemajor portion of lift gas around and ad jacent tothe lower periphery of each lift path, ,introduc,

ing a minor portion of lift gasgat an intermediate level along the outerperipheryof each compact column and L at alocation spaced laterally outward from the major stream of lift-.gas, and varying the amount of the minor portion of lift gas inaccordance with changes in,pr essure occurring within each lift path.

Ina p ferredme hs o c y ng Q t inv t onn t S eam l s a c ar .d w dlyt ash c l s s an a ma er a ia d t ws am;9 1 lntin the min n r apf th .to a .1. .g is intro:

duced at a rate insuificient of itself to effect the elevation of the granular material through the lift path.

The method of the invention does not preclude the incidental introduction into the compact moving column of additional small amounts of sealing gas conveyed thereto with the granular material, provided the substantial major portion of the total gas entering each lift path is supplied, as aforesaid, adjacent its lower perimeter.

A fuller understanding of the invention may be had by reference to the following description and claims taken in connection with the accompanying drawing illu strating a typical system including a hydrocarbon conversion unit, hereinafter called a unitized reactor, comprising in a single vessel superimposed zones including a conversion zone wherein the conversion is effected in the presence of downwardly moving catalyst, and a regeneration zone wherein carbonaceous material formed on the catalyst during the conversion is removed by combustion in the presence of oxygen-containing gas. In the drawmg:

Fig. l is a schematic view in elevation showing the unitized reactor provided with a multiple lift comprising four lift pipes disposed between the unitized reactor and a conventional storage vessel; and

Fig. 2 is an enlarged fragmentary sectional view of one of the lift engagers shown in Fig. 1.

Since the invention is directed primarily to the operation of the multiple lift system, and since the design and operation of the hydrocarbon conversion unit is similar in major respects to that described in the aforementioned article appearing in the Oil and Gas Journal, illustration and description of the unitized reactor in great detail have been omitted for the sake of brevity.

Referring to Fig. 1 of the drawing, the unitized reactor vessel is indicated by the numeral 11. Granular catalyst in an amount sufficient to provide a surge for the system is contained within a surge chamber located in the upper end of the vessel 11. The catalyst is passed downwardly from the surge chamber through the entire vessel 11 as a compact moving mass, passing thereafter successively through: a conversion zone wherein the catalyst is contacted with gaseous hydrocarbons, or both gaseous and liquid hydrocarbons, under conditions suitable to effect the desired conversion; a disengaging zone wherein the gaseous products of conversion are disengaged from the catalyst and are separately discharged from the vessel; a regeneration Zone wherein the catalyst is contacted with oxygen-containing gas to remove by combustion the deposit of carbonaceous material formed thereon while passing through the conversion zone; and a disengaging zone wherein the gaseous products of regeneration, or flue gases, are discharged from the regenerated catalyst and are separately discharged from the vessel.

The reactivated catalyst is passed downwardly from the bottom of the vessel 11 through a vertical conduit 12 into a catalyst distributing chamber 13 axially below the vessel 11. The catalyst flows from the lower end of the conduit 12 directly onto a compact moving bed within the distributing chamber of sufficient capacity to provide a continuous uniform flow of catalyst to the various lift pipes.

From the lower end of the distributing chamber 13, the catalyst is passed downwardly and laterally through a plurality of feeder conduits 14 to a corresponding plurality of lift engagers 15, grouped symmetrically below and to one side of the vessel 11, in each of which the catalyst flows downwardly as a compact moving column 16, as shown in Fig. 2. The feeder conduits 14 form with the distributor 13 and the vertical conduit 12 a continuous seal leg between the lower end of the vessel 11 and the lift engagers 15. A vertical lift pipe 17 extends upwardlyfrom a low point within each compact column of catalyst 16. The vertical height of the column 16 is determined by the discharge level of conduit 14, and its surface 18 is inclined downwardly from the end of conduit 14 at the angle of repose for the particular catalyst. The lift pipes 17 are grouped as close to the vessel 11 as is practicable. In the illustrated embodiment of the invention four lift pipes arranged in a rectangular group are employed. Only two of the group are visible in the elevational view of Fig. 1. It is contemplated, however, that any suitable number and arrangement of lift pipes may be provided. Lift gas, supplied to the engagers 15 through upper primary inlet conduits 19 and lower secondary inlet conduits 21, engages the catalyst in the lower region of the vessels 15 and conveys the same into and upwardly through the lift pipes 17.

At the top of the lift, the pipes 17 discharge upwardly into a common disengager vessel 22 wherein the catalyst is disengaged from the lift gas. The separated lift gas is discharged overhead from the vessel 22 through conventional fines removal devices, and the separated catalyst is discharged downwardly through conduit 23 to the surge chamber at the upper end of vessel 11.

Referring again to the inlet portion of the lift system, clearly illustrated in the enlarged fragmentary sectional view of Fig. 2, each lift engager 15 comprises a hollow cylindrical member 24 concentrically surrounding the lower end portion of the lift pipe 17, and closed at its upper and lower ends by end plates 25 and 26, respectively. The lower end plate 26 is provided with a valve-controlled drain conduit 27, through which the catalyst may be drained from each lift when the system is shut down. The feeder conduit 14 is connected to one side of cylindrical member 24 at a point spaced from its upper end, and a feeder conduit 28, forming the discharge outlet of a catalyst storage vessel 29, is connected to the opposite side of vessel 24 at a level above the discharge level of conduit 14. A cylindrical sleeve member 31 is concentrically positioned between the lift pipe 17 and the cylindrical member 24. The sleeve 31 extends upwardly beyond the upper end plate 25 of the cylindrical member 24. An end plate 32 seals the upper end of the annular passage 33 formed between the lift pipe 17 and the sleeve member 31.

Primary lift gas is introduced into the annular passage 33 through the conduit 19 connected to the upper end portion of the sleeve 31, the lift gas traveling downwardly through the annular passage 33 and discharging in an annular stream about the lower periphery of the lift pipe 17. The annular stream of primary lift gas engages the catalyst flowing inwardly below the lower end of the I sleeve and carries the same upwardly into the mouth of the lift pipe. The lower end of the sleeve 31 preferably terminates slightly below the lower end of the lift pipe 17 as shown. An adjustable sleeve extension, not shown, may be provided at the lower end of the sleeve 31, however, in order to make the sleeve position adjustable to a level above or below the end of the lift pipe. Lift gas is supplied to the inlet conduits 19 from a manifold 34 connected to a source of lift gas through conduit 35. Such lift gas constitutes the major portion of the total lift gas.

The secondary lift gas is supplied to inlet conduits 21 from a manifold 36 connected to a source of lift gas through conduit 37. The secondary lift gas discharges from inlet 21 into a catalyst-free annular passage 38 formed between the cylindrical member 24 and a secondary sleeve member 39 concentrically positioned be tween the member 24 and the primary sleeve member 31. The upper end of secondary sleeve member 39 is secured to the inner wall of member 24 above and adjacent to the inlet 21 by a ring 41, which also closes the upper end of passage 38. The lower end of sleeve 39 should be at or above the level of the lower end of sleeve 31. If above such level, the distance should not be so great as to introduce an adverse pressure drop from the periphery of.

the column ofcatalyst to the lift pipe inlet. Thus, the annular column of moving catalyst 16 is constricted as it passes downwardly between the member24 and the aromas.

secondary sleeve 39.:. The expansion. of the column. 16

after it passes the lower end of sleeve 39 causes an eX-.-

posed annular surface 42 of .the catalyst to be formed, the surface 42-forining the-lowermost boundary of passage 38.' Th'e' secondary lift gas,enters the. downwardly'moving annular column .16 uniformly ab out the outer periphery thereof at a single level; and travels concurrentlywith the catalyst a relatively short vertical distance to the level where it flows inwardly underthesleeve 31." Th'epressure drop from inlet 21 to the lift path is therefore relatively small, thus maintaining thepressure requirements in supply line 37 advantageously 10w. Such secondary lift gas introduced through inlet 21 should in no case' constitute more than a relatively minor portion'ofthe'total lift gas, preferably not more than.25%' or the total gas, and insuflicient in amount to alone effect the" elevation of the catalyst through the lift pipe.

Since even relatively minorarnounts oflift gas flowing concurrentlywith the catalyst toward the lift inlet J exert a strong controlling influence on the rate. of catalyst flow through the lift pipe, such secondary gas is, in accordance with the invention, used as a process control to regulate catalyst flow.

While the'illustra'ted embodiment of the invention'dis closes a single disengager for thegroup of four lift pipes,

it is to be understood that individual di-sengagers may be providedlforieach of theiliftipipesr The size andl-arrangement-of-the. lift apparatus and transfer conduits connected therewith are such that presgion surrounding-one lift inlet to another-lift inlet,- a sufficient resistance to gastflow -is imposedstopreclude a gas migration for all pressure fluctuations normally to be ex= pected. Because of .the'substantial pressure drop through the mass of catalyst in thepath' extending 'fromone'-" lift' inlet to another lift inlet, any erratically operating lift will have a substantial period of time in which to correct itself before the resultant pressure fluctuations at the bottom of the faulty lift may be reflected at the other lift inlets.

Each conduit 19 and 21 for introducing lift gas into the separate engagers 15 is provided with a control valve. Thus, conduit 19 has a valve 43 by which the flow of the primary or major portion of the lift gas into the passage 33 may be controlled. Since control of the catalyst rate of flow through the lift pipe is to be effected elsewhere, valve 43 may be manually set to deliver a desired quantity of primary lift gas.

Conduit 21 is provided with a pressure control valve 44 connected through line 45 to a conventional pressure controller 46. Pressure controller 46 is connected by line 47 to a pressure tap 48 in the side of the lift pipe 17 at a point relatively close to the engager, for example, about ten feet above the upper end of sleeve 31. By means of the controller 46, valve 44 may be operated in accordance with pressure conditions within the lift pipe at the level of the pressure tap 48. Since the pressure at tap 48 reflects the operation of the individual lift, the supply of gas to any erratically operating lift may be varied so as to correct the adverse condition. Undesirable accumulations or concentrations of catalyst within a lift pipe, which would tend to cause slugging or other erratic performance, may be overcome by temporarily decreasing the rate of catalyst flow into the mouth of the lift pipe. Such decrease in the rate of catalyst introduction into the lift pipe is readily effected by decreasing the rate of in troduction of lift gas through conduit 21. As soon as the erratically performing lift resumes its proper operation, the pressure within the lift at the level of the pressure tap 48 decreases, thereby causing the valve 44 to be actuated by controller 46 so as to increase the rate of gas introduction through inlet 21.

It is to be particularly understood that the invention. I

is not limited to any specific number of lift pipes or to any specific arrangement thereof.- The invention is also not limited with respect to the manner of introducing lift gas into the lift engagers.

Thelift gas may be 'introduced at any one or any combination of points herein indicated as being suitable and desirable for the introduction. of liftgas. Furthermore, while the illustrated embodinient of the invention shows the catalystbeing passed fromthe lower end of the unitized reactor as a single confined stream to an enlarged distributor, andthen from the distributor in separate confinedstreams to the'various lift engagers, it is to 'be'understood that thedistributor 13 may be eliminated; aIn such case, the catalyst may be passed directly from the'lower. end of the unitized reactor as separateconfin'ed streams to the engagers, thelength of such separate streamsbeing, of course, sufficient to pro: vide the necessary seal-leg requirements between the, unitized reactor. and the'lift. engagers, and the manner of withdrawal from the unitized reactor beingsuch as to distribute catalyst uniformly .into each of the confined streams.

Obviously many modifications and. variations. of the invention .as hereinbefore set. forth may be made without -departing, from the spirit and. scopethereof, and 'thereforetonly such limitations should be imposed as are indicated in the appended claims.

This applicationis a'continuation-inpart of my copending applicatiom Serial No. 226,688; filed May 16, 1951; now PatentNo. 2,702,207, Feb. 15;- 1955;

What is claimedis':

1. ha cyclic hydrocarbon conversion process wherein granular contact .materialigravitates as a compact:.mov-

ing-imass..-through:-a confined-downflow path including. a

contact zone and is then elevated by means of a gaseous lift medium through-a plurality. ofconfined lift paths and prises the steps of: passing said granular material from the lower end of said downfiow path to each or" a plurality of confined engaging zones individual to and enclosing the lower end portion of said confined lift paths and being in fixed, unrestricted open communication therewith; passing said granular material downwardly within each engaging zone as a confined compact annular column surrounding the enclosed portion of said confined lift path; introducing a constant and major portion of lift gas into said engaging zone as a confined stream discharging downwardly therein along and immediately adjacent to the lower perimeter of said confined lift path, thereby initially engaging said granular material as the latter flows downward and radially inward from the lower inner periphery of said annular column; introducing a variable and minor portion of lift gas about the outer periphery of said confined annular column and at a low level therealong; and controlling the amount of said minor portion of lift gas in accordance with pressure changes in the lower end of said lift path, the amount of said minor portion of lift gas being varied in inverse relation to said pressure changes, whereby the rate of flow of said granular material into said lift path is controlled solely by control of said minor portion of lift gas.

2. A method as defined in claim 1, in which said granular material, while flowing from said contact zone to said engaging zone, is passed through a distribution zone adapted to distribute said granular material uniformly to the plurality of engaging zones.

3. A method as defined in claim 1, wherein said minor portion of the total lift gas is introduced into the outer periphery of said moving column at a level adjacent to the level at which said major portion of the total lift gas is introduced.

4. In a hydrocarbon conversion system wherein a continuous circulation of granular contact material is effected by pneumatic elevation thereof through a grouped plurality of lift pipes, the combination of: a tubular sleeve concentrically surrounding the lower end portion of each lift pipeso as to provide therebetween an annular passage for lift gas, said annular passage being closed at its upper end; a tubular vessel concentrically enclosing and extending below said sleeve so as to provide an outer annular passage therebetween for granular material and an engaging zone beneath said lift pipe for accumulation of said granular material and engagement thereof with lift gas, said engaging zone being in fixed, unrestricted open communication with the lower ends of both said outer annular passage and said lift pipe; means for introducing lift gas in major amount into the upper end of said annular gas passage; means for introducing granular material into the upper end of said outer annular passage so as to flow downwardly as a compact unthrottled moving column around said sleeve and into the bottomregion of said vessel; means for introducing lift gas in minor and controllable amount into said outer annular passage-at a low level along the outer periphery thereof; and means for controlling the flow of said minor amount of lift gas in accordance with pressure change Within the lower end portion of said lift pipe.

5. Apparatus according to claim 4 wherein said means for introducing a controlled minor amount of lift gas into said outer annular passage comprises a relativelyshort cylindrical member concentrically positioned at the bottom of said outer annular passage and adjacent to the wall of said vessel so as to provide a short annular passage therebetween, said short passage being closed at its upper end and in open communication with said vessel at its lower end; and a conduit including a control valve for introducing lift gas at the upper end of said short passage.

6. Apparatus according to claim 5 wherein said means for controlling the flow of said minor portion of lift gas comprises a pressure controller connected between said 8 control valve and a pressure tap in the side of said lift pipe.

7. In a process for elevating granular .material through an elongated confined lift path by means of a gaseous lift medium wherein said granular material is continuously introduced into a vertically-elongated annular engaging zone containing the lower end portion of said confined lift path and is passed first downwardly around said lift path as an annular elongated compact moving column, and then unrestrictedly inward beneath the lower end of said lift path, the method of introducing said lift gas into said engaging zone to engage and convey said granular material through said lift path which comprises the steps of introducing the substantial major portion of said lift gas into said annular column as a downwardly directed annular stream along the lower perimeter of said lift path, introducing a relatively minor portion of the total lift gas into said annular column along its outer periphery and at a level adjacent to the level of said inlet, and controlling the amount of said minor portion .of the lift gas in inverse relation to changes in pressure within the lower region of said confined lift path.

8. A process as in claim 7 in which said changes in pressure are determined near the lower end of said lift path.

References Cited in the file of this patent UNITED STATES PATENTS 2,561,409 Ardern July 24, 1951 2,561,771 Ardern July 24, 1951 2,625,442 Kollgaard a Ian. 13, 1953 2,640,731 Hill June 2, 1953 2,666,731 Bergstrom Jan. 19, 1954 2,674,496 Thayer Apr. 6, 1954 OTHER REFERENCES New Houdriflow Cracking Unit etc., Petroleum Processing, vol. 5, June 1950, pages 601 to 605.

Claims (1)

1. IN A CYCLIC HYDROCARBON CONVERSON PROCESS WHEREIN GRANULAR CONTACT MATERIAL GRAVITATES AS A COMPACT MOVING MASS THROUGH A CONFINED DOWNFLOW PATH INCLUDING A CONTACT ZONE AND IS THEN ELEVATED BY MEANS OF A GASEOUS LIFT MEDIUM THROUGH A PLURALITY OF CONFINED LIFT PATHS AND RETURNED TO SAID DOWNFLOW PATH, THE METHOD OF ELEVATING SAID GRANULAR MATERIAL THROUGH SAID LIFT PATHS WHICH COMPRISES THE STEPS OF: PASSING SAID GRANULAR MATERIAL FROM THE LOWER END OF SAID DOWNFLOW PATH TO EACH OF A PLURALITY OF CONFINED ENGAGING ZONES INDIVIDUAL TO AND ENCLOSING THE LOWER END PORTION OF SAID CONFINED LIFT PATHS AND BEING IN FIXED, UNRESTRICTED OPEN COMMUNICATION THEREWITH; PASSING SAID GRANULAR MATERIAL DOWNWARDLY WITHIN EACH ENGAGING ZONE AS A CONFINED COMPACT ANNULAR COLUMN SURROUNDING THE ENCLOSED PORTION OF SAID CONFINED LIFT PATH; INTRODUCING A CONSTANT AND MAJOR PORTION OF LIFT GAS INTO SAID ENGAGING ZONE AS A CONFINED STREAM DISCHARGING DOWNWARDLY THEREIN ALONG AND IMMEDIATELY ADJACENT TO THE LOWER PERIMETER OF SAID CONFINED LIFT PATH, THEREBY INITIALLY ENGAGING SAID GRANULAR MATERIAL AS THE LATTER FLOWS DOWNWARD AND RADIALLY INWARD FROM THE LOWER INNER PERIPHERY OF SAID ANNULAR COLUMN; INTRODUCING A VARIABLE

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