US2702207A - Multiple lift for elevating granular solids - Google Patents

Description

MULTIPLE LIFT FOR ELEVATING GRANULAR SOLIDS Filed May 16, 1951 2 Sheets-Sheet l Ill 7 I 24 I I 5 r l a:

.s/AWM 4 i 17L l 4 I -H T u 1 ,2: Y 9 E INVENTOR MW 1 Kaberf/lldfizrk I z j/ BY I I5 I m ATTORNEY 19.55 R. M. SHIRK MULTIPLE LIFT FOR ELEVATING GRANULAR SOLIDS 2 Sheets-Sheet 2 Filed May 16 1951 United States Patent MULTIPLELIFI FOR ELEVATING GRANULAR SOLIDS R ohert M. Shirk, Wilmington, Del., assignor to Houdry Process Corporation, Wilmington, Del., a corporation of Delaware Application May 16, 1951, Serial No. 226,680

9 Claims. (Cl. 30253) This invention relates in general to a method and apparatus for elevating granular solid material by means of a gaseous lift medium. In particular, the invention s directed to a multiple lift in which granular material is conveyed through separate confined lift paths from a common source of distribution to individual engagement zones surrounding the lift inlets, and therein engaged by lift gas in such quantity as to convey the material into and upwardly through the variouslift paths to the desired elevation, and in such manner as to 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 moving compact mass of 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. 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 and returned to the upper end of the downfiow path for recirculation through the contact or treating zones.

Typical'systems to which the present invention maybe applied are those discussed generally in an article entitled The T. C. C. catalytic cracking process for motor gasoline production by R. H. Newton, G. S. Dunham and T. P. Simpson, recorded in the Transactions of the American Institute of Chemical Engineers, volume 41, page 215, April 25, 1945, and in other articles therein cited; and an article entitled Houdrifiow: New design in catalytic cracking appearing at page 78 of the January 13, 1949, issue of the 0il and Gas Journal.

The solid material comprising the circulating medium may be a catalyst or other contact material in the form of relatively large aggregates or agglomerated masses, such as pellets, beads, or coarse granules of a particle size in the range of about 0.05-0.25 inch, or for example, of an average particle size in the order of fourteen mesh or larger. In the case of a system for effecting hydrocarbon conversions, the granular material is preferably a catalyst, and the gaseous lift medium may comprise flue gas, steam, or other inert gas, or may comprise gaseous hydrocarbons, air, etc.

For convenience of description and illustration, the.

present invention will hereinatfer be considered in connectionwith a catalytic cracking system for converting hydrocarbons in the presence of granular catalyst gravitating as a compact non-turbulent mass.

In connection with the elevation of the catalyst for recirculation, both mechanical lifts and. pneumatic lifts have heretofore been employed. Mechanical lifts, however, such as those employing continuously rotating bucket chains, have in many instances been found impractical for various reasons, such as high initial costs, limited conveying capacity, excessive wear of the moving parts because of the difficulty in maintaining proper lubrication at the extremely high temperatures employed, and the necessity for providing special devices to accommodate elongation of the bucket chain as a result of temperature change, which may be of considerable amount in lifts that are several hundred feet in height.

In pneumatic systems to which the present 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 to the maintenance of uniform catalyst flow through the lift system. The problem of maintaining uniform catalyst flow is especially acute inmultiple lift systems wherein catalyst is supplied directly to the various lift pipes from 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 at the lower end thereof which will create an adverse.

pressure differential between the inlet end of the faulty lift pipe and the inlet ends of adjacent lift pipes. In such case, lift gas introduced adjacent the inlet of the erratically performing lift pipe may by-pass through the compact mass of catalyst surrounding the lift inlet to the inlet of the adjacent lift pipe, thus adversely affecting its performance and the performance of the lift system as a whole. The problem becomes especially acute when the shortest available path for gas flow through the compact mass of catalyst from one lift inlet to an adjacent inlet does not provide sufficient resistance to the flow of gas therethrough to overcome the adverse pressure differential existing between the respective lift pipe inlets. Experience has shown that, for various reasons, minor fluctuations in catalyst flow within the several lift pipes are inevitable during normal operation of the lift system. When the inlet ends of the multiple lift pipes are not sufficiently segregated within the downfiowing mass of catalyst, gas migration from the region surrounding an erratically operating lift pipe to the inlet of one or more adjacent lift pipes having a substantially lower inlet pressure is inevitable. The effect of lift gas migration away from the faulty lift pipe is cumulative. If migration continues, it may cause a complete interruption of catalyst flow in the faulty lift pipe and may adversely affect the operation of the remaining lift pipes by increasing the velocity of catalyst flow therein beyond acceptable limits.

In accordance with the invention, granular material, such as catalyst in the form of pellets or beads, gravitating in a cyclic procedure through an elongated vessel compnsing one or more contact zones is withdrawn from the lower end thereof and passed to a pneumatic lift comprising a plurality of confined lift paths extending upwardly about and adjacent to the periphery of the vessel. At the upper end of the lift the granular material is separated from the lift gas and returned by gravity flow to the granular material inlet at the upper end of the vessel. In passing from the lower end of the vessel to the lift, the granular material initially flows as a confined compact stream along a substantially vertical path to a distribution zone of increased flow area, from which the material is passed downwardly, and radially outwardly therein as a compact annular column about the lower end portion of the confined lift path.

Lift gas may be introduced to the introduction zone at one or more places therein, such as: axially below the lift pipe inlet in a risingtsolid, annular, or split stream; around and adjacent to the lower periphery of the lift pipe in a downwardly directed annular stream; above the surface of the compact annular column within the introduction zone; or around and laterally remote from the lower periphery of the lift pipe. By the expression lift gas is meant such gas as is introduced primarily and essentially for the purpose of engaging the catalyst and conveying it upwardly through the lift pipe. It is contemplated, however, that additional small amounts of gas introduced at some point along the catalyst path to the lift, such as at the top of the distributing zone,

essentially for sealing purposes may flow with the granular material and eventually mix with the lift gas.

By arranging the multiple lift paths in a row about the periphery of the vessel or vessels constituting the vertical downflow path, the granular material may be passed from the lower end of the downflow path to the lower end of the lift and from the upper end of the lift to the upper end of the downflow path along radial paths of substantially uniform length. The lift paths may be spaced or grouped in any suitable symmetrical pattern around the vessel. The feeder paths for conveying the granular material from the distributor to the various introduction zones of the lift system are of sufiicient length to preclude any substantial gas migration from the region surrounding one lift inlet upwardly through its associated feeder path, across the distributor bed to an adjacent feeder path, and downwardly therethrough to its associated lift inlet as the result of a pressure differential existing between the inlet ends of the respective lift paths. Thus, each of the multiple lift paths is arranged to operate as a separate lift, and the invention contemplates that suitable controls will be provided to regulate the fiow of lift gas to each of the individual engaging zones in accordance with the performance of its associated lift, such controls preferably being responsive to pressure fluctuations in the lifts.

A fuller understanding of the invention may be had by reference to the following description and claims taken in connection with the accompanying drawing illustrating a typical hydrocarbon conversion unit, hereinafter called a unitized reactor, comprising in a single vessel superimposed zones including a reaction 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 drawing:

Fig. 1 is a schematic view in elevation showing the unitized reactor provided with a multiple lift comprising a plurality of lift pipes symmetrically distributed about and adjacent to the vessel;

Fig. 2 is an enlarged fragmentary sectional view of the lower end of the lift system shown in Fig. 1;

Fig. 3 is a plan view of Fig. l; and

Fig. 4 is a horizontal section taken along the line 4-4 of 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 maior respects to that described in the aforementioned article appearing in the Oil and Gas Journal, detailed illustration and description of the unitized reactor have been omitted for the sake of brevity.

Referring to Fig. 1 of the drawing, granular catalyst is continuously withdrawn from the bottom of a surge hopper 11 and is passed by force of gravity downwardly through a seal leg 12 to the upper end of the unitized reactor vessel, generally indicated by the numeral 13. In passing through the unitized reactor 13 the catalyst gravitates downwardly as a compact moving mass, passing successively through a zone in which the catalyst is contacted with hvdrocarbons in liquid or vapor phase under conditions effective to produce the desired conversion, a zone in which the gaseous products of conversion are separated from the catalyst, which has become contaminated by a deposit of coke thereon, and a zone in which the carbonaceous deposit is removed from the catalyst, as by combustion with oxygen-containing gas.

The reactivated catalyst is passed downwardly from the bottom of the vessel 13 through a vertical conduit 14 into a catalyst distributing chamber 15 axially aligned with the vessel 13. The catalyst flows from the lower end of the conduit 14 directly onto a compact moving bed 16 maintained within the distributing chamber. The bed 16 is not required for surge purposes. but is of sufiicient capacity to provide a continuous uniform flow of catalyst to the various lift pipes.

From the lower end of the distributing chamber 15, the catalyst is passed downwardly and radially outwardly through a plurality of feeder conduits 17 to a corresponding plurality of lift engagers 18, grouped below and about the vessel 13, wherein the catalyst flows downwardly as an inlet 27 in the bottom of the engager vessel.

compact moving columns 19, as shown in Fig. 2. The feeder conduits 17 are of substantially uniform length, and form with the distributor bed 16 and the vertical conduit 14 a continuous seal leg between the lower end of the vessel 13 and the lift engagers 18. A vertical lift pipe 20 extends upwardly from a low point within each of the lift engagers 18, the lower end. of the lift pipe being submerged within the column of catalyst 19 contained therein. The lift pipes 20 are distributed about the periphery of the vessel 13, and are located as close thereto as is practicable. of the invention illustrated in the drawing, twelve lift pipes are employed, arranged in groups of three located at the ends of cross-diameters. It is contemplated, however, that any suitable number and distribution of lift pipes may be provided. At the top of the lift, each group of three lift pipes extends into a common disengager, the four disengagers being so placed that the conduits leading from the bottom thereof to the surge hopper 11 are of substantially uniform length. If preferred, however, a single large disengager, which may incorporate the surge facilities, or separate disengagers for each lift pipe may be employed.

Referring to the inlet portion of the lift system, clearly illustrated in the enlarged fragmentary sectional view of Fig. 2, each lift engager comprises a closed cylindrical vessel 21 concentrically surrounding the lower end of the lift pipe 20. The feeder conduit 17 is connected to the side of cylindrical vessel 21 so that granular material introduced therein and flowing downwardly as a compact mass may have an exposed surface in the upper region of the vessel 21. A cylindrical sleeve member 22 concentrically spaced between the lift pipe and the wall of vessel 21 extends upwardly beyond the upper end of the vessel. A flange connector 23 seals the upper end of the annular space 24 formed between the lift pipe 20 and the sleeve member 22.

Lift gas is introduced into the annnular space 24 through an inlet 25 at the upper end of the sleeve 22,

the lift gas traveling downwardly through the annular space 24 and discharging in an annular stream about the lower periphery of the lift pipe. The annular stream of lift gas engages the catalyst flowing inwardly below the lower end of the sleeve and carries the same into the mouth of the lift pipe. The lower end of the sleeve 22 may terminate at or slightly above or below the lower end of the lift pipe, as desired. The desired sleeve setting may be predetermined and the sleeve constructed accordingly, or an adjustable sleeve extension, not shown, may be provided at the lower end of the sleeve 22 in order to make the sleeve position adjustable. Lift gas is supplied to the inlet 25 from a manifold 26 in the form of an annular pipe connected to the corresponding gas inlets of the remaining lift engagers. Preferably the annular manifold 26 is concentrically positioned with respect to the axis of the vessel 13.

Additional lift gas is supplied to the lift engager thrclaulglir 27 is preferably in axial alignment with the lift pipe, and is arranged to discharge a stream of lift gas at a point below and spaced a substantial distance from the mouth of the lift pipe, so that such lift gas is introduced into the bed of material formed below the end of the lift and diffuses upwardly through a layer thereof toward the mouth of the lift pipe. It is contemplated that the major portion of the lift gas will be introduced through the inlet 25, and only a relatively minor amount, preferably not more than about 25% of the total lift gas, will be introduced through the inlet 27.

It is further contemplated that in some cases it may be desired to introduce substantially the major portion of the lift gas through the inlet 27, in which case the sleeve 22 may be removed and the catalyst entering the lift engager 18 through feeder conduit 17 may flow downwardly as an' annular stream in contact with the outer surface of the lift pipe. Additional lift gas may be introduced at or above the level of the lift inlet and remote therefrom so that such gas will flow downwardly or laterally concurrently with the catalyst to the lift inlet, thus facilitating its flow and supplementing the lift gas introduced at other points. For example, such additional lift gas may introduced through inlet 28 at the upper end of the lift engager 18. Lift gas introduced for either downward or lateral concurrent flow with the catalyst, however.

In the particular embodiment r I is primarily for the purpose of exercising a control on the catalyst flow rate, since it is known that even relatively minor amounts of gasflowing downwardly or laterally with the catalyst in the lift engager may provide a substantial control on the catalyst flow into and through the lift pipe. It is thus evident that each lift pipe may be controlled by regulating the flow of minor amounts of the vessel 13. The lift gas introduced through the various inlets may be caused to flow into the lift .engager by reason of the maime'nance of higher gas pressure at the source of lift gas supply higher than the pressure required in the lift engager, or the lift gas may be supplied from a low pressure source and be passed into the lift engager by means of a thermo-compressor. In the latter case,

the lift gas introduced to the lift engager will include a sub-' stantial portion of the gas employed in the thermocompressor.

The lift pipe extends upwardly a substantial distance above the upper end of the surge hopper 11 and projects within a disengager 31, a separate disengagerbeing provided in the illustrated embodiment for each group of three lift pipes 20. Within the disengager31, catalyst is disengaged in known manner from the lift gas, the latter being discharged from the disengager vessel; through an outlet 32. Disengaged catalyst settling to the bottom of the disengager 31 is conveyed therefrom through feeder conduits 33 extending downwardly and radially inwardly toward the common axis of the unit. Feeder conduits 33 are connected to the upper end of surge hopper 11 and discharges the disengaged catalyst onto the bed of catalyst maintained therein for surge purposes.

While the illustrated embodiment discloses individual catalyst disengagers for each group of three lift pipes, it is to be understooduhat the invention contemplates the provision of a single large disengager vessel of a diameter sufficient to receive the upper ends of all the lift pipes, or of individual disengagers for each of the lift pipes. In

the case of a single large disengager, the catalyst disengaged from the streams of lift gas will settle to the bottom of the disengager vessel and flow downwardly and inwardly to a central outlet at the axis of the unit. The disengaged catalyst may then be passed vertically downwardly through a single feeder conduit centrally connected to the bottom of the disengager.

The size and arrangement of-the lift apparatus and transfer conduits connected therewith are such that pressure fluctuations occurring at the lower end of any one lift by reason of catalyst accumulation therein, will not "be reflected at the inlets of one or more of the remaining lifts. By reason of the relatively long path of flow required for any gas attempting to migrate from the region surrounding one lift inlet to another lift inlet, a sufliclent resistance to gas flow is imposed to preclude a gas migration for all pressure fluctuations normally to be expected. Because of the substantial pressure drop through the mass of catalyst in the path extending from one 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.

In the illustrated embodiment of the invention it has been assumed that the primary lift gas, that is flue gas, has been supplied from a source maintained at a pressure below the pressure required in the lift engagers 18. In order to introduce the flue gas supplied from manifold 26 into the sleeve 22 of the lift engager at the desired elevated pressure, a jet compressor 34 is placed in the gas inlet line 25. The jet compressor is supplied with steam at a relatively high pressure through conduit 35 connected to a steam manifold 36. Flue gas from the manifold 26 is conveyed to the jet compressor through conduit 37.

Each of the gas conduits leading to the lift engagers is valve-controlled in ,conventional manner. If desired, however, an automatic control system may be provided to separately control selective valves in accordance wi pressure changes in the lift system, so that any erratic operation in one of the lifts, withconsequent fluctuations in pressure therein, may cause the automatic control system to regulate the supply of gas to the faulty lift in such manner as to correct the adverse condition therein.

It is to be understood, of course, that where the kiln of a unitized reactor is operated at sufficiently high pressure, flue gas may be withdrawn therefrom and passed directly to the lift engagers without the assistance of devices such as the jet compressors 34.

It is to be particularly understood that the invention is not limited to any specific number of lift pipes or to any specific arrangement thereof about the periphery of the unitized reactor. The invention is also not limited w|th respect to the manner of introducing lift gas into the lift engagers. The lift gas may be introduced at any one or any combination of points herein indicated as being suitable and desirable for the introduction of lift The invention is also not limited with respect to the manner of effecting disengagement of the catalyst from the lift gas at the upper ends of the lifts and of returning the disengaged catalyst to the downflow path through the unitized reactor. I

Obviously many modifications and variations of the invention as hereinbefore set forth maybe 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:

1. A multiple lift for elevating granular material from the lower end to the upper end of an elongated vessel including one or more superimposed contact chambers dividual lift engagers surrounding the lower ends of said lift pipes, a vertical granular material discharge conduit extending downwardly from the lower end of said vesse], a distributing chamber at the lower end of said vertical conduit, a plurality of feeder conduits extending downwardly and outwardly from the bottom of said "distributing chamber to the upper region of said lift engagers, means for introducing a gaseous lift medium into said lift engagers at one or more places therein to engage said granular material and convey the same into and upwardly through said lift pipes, means at the upper end of said plurality of lift pipes for disengaging said granular material from said gaseous medium, and means for conveying the disengaged granular material downwardlyand inwardly to the upper end of said vessel.

2. Apparatus as defined in claim 1 in which said vertical conduit extends downwardly into said distributing chamber, and including means for introducing additional gas into said distributing chamber above the discharge level of said vertical conduit.

3. Apparatus as defined in claim 1 in which said lift pipes are arranged in uniformly distributed groups, and said means for disengaging said granular material from said gaseous medium at the upper end of said lift pipes comprises a plurality of disengagers each individual to one of said groups of lift pipes, a surge hopper at the upper end of said vessel, a second plurality of feeder conduits for conveying said disengaged granular material downwardly and inwardly from the lower ends of said disengagers to said surge hopper, and a conduit for conveyingsaid materiall from said surge hopper into the upper end of said vesse 4. Apparatus as defined in claim 3 in which all said feeder conduits for conveying granular material from said distributing chamber to said lift engagers and from said disengagers to said surge hopper are disposed substan-v tially radially with respect to the axis of said vessel, and in which the members of each plurality of feeder conduits are of substantially equal length.

5. Apparatus as defined in claim 1 in which said means for introducing a gaseous lift medium into said lift engagers comprises spaced concentric sleeve members surrounding the lower ends of said lift pipes and being coextensive therewith to a point above the upper ends of said engagers, said sleeve members being connected at their upper ends to said lift pipes and forming therewith annular gas passages communicating with said engagers about the lower periphery of said lift pipes, a gas manigrease? fold concentrically positioned below said vessel and within the peripheral row of lift pipes, means for conveying lift gas from said gas manifold to said annular gas passages, a second gas manifold similarly positioned, and means for conveying lift gas from said second gas manifold into the lower region of said disengagers substantially below the lower ends of said lift pipes.

6. Apparatus as defined in claim 5 in which at least said second gas manifold is connected to a source of lift gas maintained at a pressure substantially higher than the pressure at the inlets to said lift pipes.

7. Apparatus as defined in claim 6 in which the firstmentioned gas manifold is connected to a source of lift gas maintained at a pressure lower than the pressure at the inlets to said lift pipes, and in which said means for conveying lift gas from said first-mentioned gas manifold to said annular passages includes jet compressors.

8. In a system for circulating granular contact material, having a confined downfiow portion including one or more contact chambers and an upflow portion through which said granular material is elevated by means of a gaseous lift medium, the combination of a distributing chamber below the lowermost of said contact chambers, means for withdrawing granular material uniformly from said lowermost contact chamber and passing the same as a compact gravitating mass into said distributing chamber, a plurality of lift engagers, means for passing individual compact moving streams of granular material from said distributing chamber into and downwardly within said lift engagers, individual upright lift pipes arranged around and adjacent to said downfiow portion of said system, said lift pipes extending from a low level within said lift engagers and within said compact moving streams to a level substantially above the uppermost of said contact chambers, means for introducing lift gas at one or more locations within said lift engagers to convey said granular material into and upwardly through said lift pipes, disengager means communicating with the upper ends of said lift pipes for separating said granular material from said lift gas, means for returning disengaged granular material from said disengaging means to the upper end of said downfiow portion, and means for preventing a flow of gas between said lift engagers and said lowermost contact chamber, under normal conditions of pressure differentia'l, while permitting uninterrupted fiow of granular material therebetween.

9. Apparatus as defined in claim 8 wherein said means for preventing gas flow between said lift engagers and said lowermost contact chamber comprises seal gas introduction means in said distributing chamber whereby seal gas may be introduced therein to maintain a pressure sufficient to prevent undesired flow of gas through said compact moving streams.

References Cited in the file of this patent UNITED STATES PATENTS 528,417 Duckham Oct. 30, 1894 1,390,974 Von Porat Sept. 13, 1921 1,549,285 Baker Aug. 11, 1925 1,846,069 Schaub Feb. 23, 1932 2,561,771 Ardern July 24, 1951 FOREIGN PATENTS 7,075 Netherlands Mar. 18, 1922 180,397 Great Britain May 11, 1922

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