US2625442A - Apparatus for elevating granular material - Google Patents

Description

Jan. 13, 1953 R. KOLLGAARD APPARATUS FOR ELEVATING GRANULAR MATERIAL Filed Jan. 17; 1951 INVENTOR erjYollgaard Keyn BY \ALMW M2 MA.

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d 3 a +1 4 I .7, i 2 a I q, w z llvl 4 w A m ATTORNEY Patented Jan. 13, 1953 APPARATUS FOR ELEVATING GRANULAR MATERIAL Reyner Kollgaard, Media, Pa., assignor to Houdry Process Corporation, Wilmington, DeL, a corporation of Delaware Application January 17, 1951, Serial No. 20 ,323

' 5 Claims. (01. 302-17) This invention relates to improvements in a system for elevating granular material. The invention is particularly applicable to petroleum refining and other chemical processing systems involving the transfer and circulation of contact material, such as catalyst, of discrete particle S 29.

'In connection with such systems, catalyst or other contact material in the form of granules, pellets, beads, etc, of comparatively large particle size, is continuously circulated through one or more reaction zones in a path having a downflow portion along which the granular material is passed by gravity flow, and an upflow portion along which the granular material is elevated from a lower level to a substantially higher level. In earlier systems requiring the elevation of such granular material, mechanical means, such as bucket elevators, were commonly employed for transporting the material to the required elevation for recirculating the material through its downnow path. More recently, however, such elevation of granular material has been effected by pneumatic means, employing for this purpose an elongated vertical lift pipe associated with an introduction chamber at its lower end, wherein granular material, such as catalyst, is engaged by a gaseous lift medium supplied in sufiicient quantity to convey the catalyst upwardly through the lift pipe, and a disengaging chamber at its upper end wherein the catalyst may be disengaged from the lift gas and returned to the downflow path. Pneumatic lift systems employing both a single lift pipe and multiple lift pipes are in commercial use. The multiple lift systems may comprise a series of individual lift pipes extending from the lower lift hopper or introduction chamber to the upper lift hopper or disengaging chamber, or they may comprise short multiple lift feeder pipes which extend from the introduction chamber upwardly into the lower end of a large single lift pipe.

The principal application of the present invention is in connection with the multiple lift sys tems comprising either multiple lift pipes or multiple lift feeder pipes discharging into a single lift pipe.

A typical hydrocarbon conversion system to which the present invention may be applied is that illustrated and described in an article entitled Houdriflow: New Design in Catalytic *Cracking, appearing on page '78 of the January .13, 1949, issue ofthefOil and Gas Journal.

A problem of primary importance, in the elevation of granular solids of a frangible nature, is

that of attrition as a result of impact and friction, and various means have heretofore been employed for the purpose of maintaining attrition losses at a minimum.

It has been demonstrated that granular solids may be smoothly introduced into lift pipes of comparatively small diameter, and may be efficiently transported through such small diameter pipes with desired low attrition losses when the granular solids are introduced into the lift pipe in such manner as to maintain suitable concentration of the moving particles in the lift pipe and linear velocities therein at which such particles will move upwardly in substantially straight-line flow. As the diameter of the lift pipe is extended to greater and greater size for the purpose of handling the required large quantitles of granular solid, the attainment of straight-line flow at the inlet to the lift and within the lower portion thereof becomes more difficult, because of the tendency of the particles to flow laterally in a random motion with resultant introduction of factors tending to cause attrition.

It has also been demonstrated that improved lifting of granular solid materials, free of the above-mentioned difficulties, can be achieved even in lift pipes of comparatively large diameter if such granular material is initially accelerated upwardly through one or more comparatively narrow feeder pipes discharging at their upper ends into the lower end of the main lift pipe. Such method of operation tends to minimize or to eliminate the possibility of deviation of the granular material from straight-line flow.

Whether a single lift pipe, having a plurality of feeder pipes at the lower end, or multiple separate lift pipes are employed, it is difficult to obtain desirable characteristics of flow throughout the lift path without maintaining uniform conditionsat the inlet ends of the multipleilift pipes or the multiple feeder pipes. Variations in pressure at one or more inlets to the lift as a result of erratic operation thereof, may cause preferen tial flow of lift gas to other inlets at which a lower pressure exists, thereby causing erratic operation of the lift.

It has been observed that when granularmaterial is pneumatically elevated through a plurality of closely-spaced parallel confined lift paths by initially starting a flow of lift gas alone along the lower '-'portions of the confined lift paths, and then, ;at a higher level therein, lintroducing granular material laterally therein from a common bed surrounding the lift pipes, any substantial variation in pressure at the granular material inlets of one lift path as a result of erratic lift performance therein will be reflected in the op eration of the nearest adjacent lift paths. The reason for this is that there is a preferential flow of lift gas from the former to the latter by reason of the fact that the narrow moving mass of granular material does not provide sufficient resistance to a flow of gas from the inlet of higher pressure to adjacent inlets of lower pressure,

In accordance with the present invention, the possibility of preferential flow of lift gas from the solids inlet of one lift pipe of a multiple lift unit for granular catalyst, or other contact material, to the solids inlet of another lift pipe receiving catalyst from a common bed is significantly decreased by segregating the solids inlets within the catalyst bed without increasing the lateral spacing of the lift pipes. The extent of segregation is such that the path for gas migration through the catalyst bed from one solids inlet to a solids inlet of the nearest adjacent lift pipe offers so high a resistance to flow that under the pressure differential existing at the time of erratic I bed contained within the lower lift hopper. The

annular Well surrounding each lift pipe inlet terminates adjacent but below the lower ends of the catalyst inlet ports in the side of the lift pipes. The depth of the well is such as to contain a sufficient column of catalyst to cause a resistance to flow of lift gas upwardly through one column, laterally to the adjacent column, and downwardly through the latter. The resistance to flow through the above-described path is such that most gas will flow up the erratically operating lift pipe rather than to the adjacent lift pipes.

For a fuller understanding of the invention and the advantages thereof, reference may be had to the following description read in connection with the accompanying drawing forming a part of this application, which:

Fig. 1 is a schematic view in elevation showing the general arrangement of the processing vessels, pneumatic lift, and transfer lines of a typical hydrocarbon conversion system; 7

Fig. 2 is an enlarged longitudinal cross-sectional view of the lower lift hopper of Fig, 1; and

Fig. 3 is a modification of the lower lift hopper of Fig. 1 showing its application to a multiple lift system employin a plurality of separate lift pipes for conveying catalyst to the desired point of elevation.

Referring to Figure l of the drawin catalyst in the form of granules, pellets, beads, etc is supplied to the downfiow path of the hydrocarbon processing system from a lift hopper l I, to which the catalyst has previously been elevated by means of a pneumatic lift. Lift hopper ll includes a disengaging zone or chamber wherein the catalyst is separated from the lift gas, the latter being removed through gas outlet line {2. and the catalyst (-3 being continuously withdrawn from the lower endof the lifthopper. through aseal leg it and introduced into the upper end Qf-a processing vessel l5 comprising an upper reactor section (5 and a lower regenerator section I! of greater diameter than the reactor section.

Liquid hydrocarbon feed is supplied to the reactor section l6 of vessel [5 through inlet line 18. As will be understood to those familiar with the art, hydrocarbon vapors may accompany the liquid hydrocarbons as part of the charge. Section It includes a reaction chamber wherein the hydrocarbons are contacted with the catalyst introduced through seal leg [4 to carry out the desired hydrocarbon conversion. Process steam may be introduced into the reaction chamber through inlet line [9, and steam or any other suitable inert gas may be introduced at the upper end of vessel [5 through inlet line 20 for the purpose of providing a gas seal in the seal leg M. The catalyst, which has become spent by reason of a carbonaceous deposit formed thereon during the reaction, together with the gaseous products of reaction, pass downwardly by gravity flow from the reaction zone at the lower end of section 16 into a solids-vapor disengager section located at the upper end of the enlarged regenerator section if, wherein the gaseous reaction products are separated from the spent catalyst. The gaseous reaction products are withdrawn from the vessel :5 through vapor outlets 2 I. The separated spent catalyst gravitates downwardly through a purging section wherein it is contacted with a stripping gas, such as steam, introduced through inlet 22. The purge steam and the vaporizable material removed from the spent catalyst together with the separated gaseous material, pass out of the vessel I5 through the vapor outlets 2!. From the purging section, the spent catalyst gravitates through a suitable internal conduit arrangement into the regenerating zone of regenerator section H. Within the regenerating zone, the spent catalyst is subjected, in known manner, to successive stages of regeneration. In the upper stage, oxygen-containing gas introduced through inlet 23 passes countercurrently to the flow of catalyst. The gaseous products formed in the upper stage of regeneration are removed from vessel l5 through flue gas outlet 24. From the first stage of regeneration the catalyst gravitates downwardly to the second stage of regeneration, intermediate cooling by indirect heat exchange with a circulating medium being provided, if desired. Oxygen-containing gas is supplied to the lower stage of regeneration through inlet 25, and the gaseous products of regeneration are removed from the upper end of the second regenerating stage through flue gas outlet 26.

At the lower end of vessel l5 the regenerated catalyst is withdrawn through seal leg 2'! and introduced into the upper end of lower lift hopper 28. A lift pipe 29 extends between the upper and lower lift hoppers, providing a passageway for the upward conveyance of catalyst therebetween. Lift gas introduced into lower lift hopper 28, as through inlet lines 30 and 31, engages the regenerated catalyst and conveys it into and upwardly throughthe lift pipe 29 to the upper lift hopper I I. A more detailed description and illustration of the processing portion of the hydrocareon conversion system is not given for the reason that the invention is directed primarily to improvements in the pneumatic lift, and particularly to the inlet end thereof.

3 A clearer illustration of the meansfor effecting engagement betweenthe lift gas and the catalyst and the upward'convey' e th reo t r u h the lift ipe maybe had by reference to Figure d,

which shows an enlarged cross-sectional elevation view of the lower lift hopper 28, the lower end portion of the lift pipe- 29, and the multiple feeder conduits, presently to be described, for introducing the catalyst into the lift pipe.

Referring to Figure 2, the lower end of the lift pipe 29 is attached, as by a flanged connection, to the upper end of a housing member which forms the lower lift hopper 28. A tube-sheet 32 extends across the upper end of the hopper 28, preferably secured between the connected ends of the lift pipe and the hopper. Tube-sheet 32 supports the upper ends of a series of relatively short feeder conduits 33 having a combined cross-sectional flow area as near to the cross-sectional flow area of the lift pipe 29 as is practicable. Any suitable number of feeder conduits, may be employed, and they are preferably arranged in a uniform distribution pattern across the area of the tube-sheet 32. A horizontal partition 34 extends across the lower region of the hopper 28, and is provided with a series of openings corresponding to and concentric with the feeder conduits 33. The openings are of substantially greater diameter than the diameter of the feeder conduits and are provided with cylindrical members 35 attached along their upper edges to the perimeter of the openings in partition 34. End plates 36 extend horizontally from the lower perimeter of cylindrical members 35 to the outer surface of the feeder conduits 33, thus closing the lower end of the annular space between the cylindrical members 35 and the feeder conduits 33 and forming individual annular wells 31 about each of the feeder conduits. The lower ends of the feeder conduits extend a substantial distance below the bottom of the wells 31 and are in open communication with the chamber 38 formed in the lower region of the lower lift hopper 28 below partition 34. Orifice plates 39 are set in each of the feeder conduits 33 adjacent the lower end. A circumferential row of ports 40 are provided in the side wall of each of the feeder conduits 33 at a level slightly above the end plates 36 to provide open communication between the wells 31 and th feeder conduits 33.

The catalyst introduced. into the upper end of lower lift hopper 28, through seal leg 21, forms therein a downwardly moving compact non-turbulent bed 4!, supported by the partition 34 and completely filling the wells 31. The downwardly moving catalyst passes into the wells 31 and thence into the feeder conduits 33 through the side ports 49, the latter preferably comprising an equi-spaced circumferential row of longitudinally extending slots. To facilitate the movement of catalyst downwardly in bed 4! and laterally through the slots 49 into the feeder conduits 33, a quantity of lift gas is introduced through inlet line 3| into the free space formed beneath the annular member 42 attached along the inner wall of housing 28. Such gas passes with the catalyst into the feeder conduits and thence into the main lift pipe to supplement the primary supply of lift gas and to serve as control gas for varying the rate of catalyst flow through the lift.

The primary stream of lift gas is introduced into the chamber 38 at the bottom of lower lift hopper 28 through inlet line 30. Chamber 38 serves as a manifold for supplying the primary stream of lift gas to the lower end of each of the feeder conduits 33. The orifice plates 39 serve to maintain a constant and uniform feed of lift gas into each of the feeder conduits. The lift gas introduced through inlet line 30 constitutes the major 6 portion of the lift gas necessary to elevate the catalyst through the feeder conduits into the main lift pipe 29. I

By reason of the increased cross-sectional flow area of the main lift pipe 29, as compared to the combined flow areas of all of the feeder conduits 33, there is a substantial reduction in gas velocity, and incidentally in the acceleration .Iof the catalyst conveyed by the gas upon discharge into the main lift pipe 29. In order to obviate such velocity reduction and to maintain a more nearly uniform movement of catalyst into and upwardly through the lift pipe, additional lift gas is supplied through inlet line 43 to the lower region of the lift pipe, preferably below the'discharge level of the feeder conduits 33. Thelift gas introduced through inlet line 43 is supplied in sufficient quantity to atleast maintain the discharge velocity of the catalyst'as it passes from the feeder conduits 33 into the lift pipe 29. If desired, such additional lift gas may be supplied in sufficient quantity to provide a substantial acceleration of the catalyst after it discharges into the lift pipe.

Fig. 3 illustrates the applicability of the invention to a multiple lift comprising a plurality of separate lift pipes 29 extending upwardly from the lower lift hopper 28. Although not illustrated in the drawing, it is to be understood that all of the lift pipes 29 extending into the upper lift hopper II for disengagement of the catalyst and the lift gas.

The lower ends of lift pipes 23 pass through tube-sheet 32, catalyst bed 4!, and cylindrical well-forming members 35, similar to the feeder conduits 33 of Fig. 2. The lift pipes 29 are slotted in the same manner as feeder conduits 33, so that catalyst descending into the wells 31 may enter the lift pipes 29' through the slots 40'.

Obviously any 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 by means of a gaseous lift medium comprising a plurality of closely-spaced parallel lift pipes, a housing surrounding the lower portion of said lift pipes, said housing having a lower chamber in open communication with the lower ends of said lift pipes and an upper chamber adapted to contain a downwardly moving bed of said granular material surrounding said lift pipes, means in the lower region of said upper chamber forming individual elongated wells about said lift pipes adapted to receive granular material from said bed, said lift pipes having openings into the lower region of said wells, means for introducing lift gas into said upper chamber, and means for introducing lift gas into said lower chamber, whereby the latter lift gas passes upwardly into the lower ends of said lift pipes and engages at a higher level therein said granular material conveyed through said openings by said firstmentioned lift gas, and the combined streams of lift gas convey said granular material upwardly through said lift pipes.

2. Apparatus as defined in claim 1 including a single lift pipe encircling at its lower end the upper ends of said plurality of lift pipes and to receive the streams of granular material and lift gas discharged therefrom, and means for introducing lift gas into the lower region of said single 7 lift pipe below the level of discharge from said plurality of lift pipes.

3. Apparatus for elevating granular material by means of a gaseous lift medium comprising a plurality of closely-spaced parallel lift pipes, means for introducing a gaseous lift medium from a common source into the lower ends of said lift pipes, a chamber adapted to maintain a compact moving bed of said granular material above the lower ends of said lift pipes, means for passing said granular material in separate confined streams from said chamber into said lift pipes, said streams of granular material being introduced laterally into said lift pipes at a level spaced a substantial distance above their lower ends, and means for introducing a gaseous liit medium into said compact moving bed of granular material for conveyance with said separate confined streams of granular material into said lift pipes.

4. Apparatus as defined in claim 3 wherein said confined streams of granular material are of such length as to impose a substantial restriction to gas flow along the path extending from the granular material inlet of one lift pipe, oountercurrently through its confined feed stream of granular material to said moving bed, laterally through a portion of said bed to an adjacent confined feed stream, and concurrently through the latter to its associated lift pipe inlet.

5. Apparatus as defined in claim 3 including a relatively large-size lift pipe having its lower end encompassing the upper end portions of said plurality of lift pipes and forming a vertical extension thereof, closure means sealing the spaces between the lower end of said large-size lift pipe and said plurality of lift pipes, and means for introducing a gaseous lift medium into the lower end of said large-size lift pipe at a level substantially below the discharge level of said plurality of lift pipes.

REYNER KOLLGAARD.

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

UNITED STATES PATENTS Number Name Date 299,279 Sachs May 27, 1884 1,730,195 Davis OCt. l, 1929

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