US2915459A - Art of circulating contact material - Google Patents

Description

Dec. 1, 1959 c. G. KIRKBRIDE El'AL 2,915,459

ART OF CIRCULATING CONTACT MATERIAL Filed Dec. 9, 1953 INVENTORS m; Mags,

ATTOR NE 1 United States Patent z;91s,4's9 ART OF CIRCULATINGEONTACT MATERIAL Ghalmer Kirkbride, Wallingford, and'Jack C.D art, Moylan, Pa., assignors toHoutlry'Process Corporation, Wilmington, Del.,"a corporation (if Delaware Application December. 9,. 1953,; Serial bio- 397,212

'5 Claims. ,,(Cl. 208-148) zones wherein the particles gravitate while .beingcontacted with non-solid. materials which, under controlled conditions-of-contact, are maintained in a gaseous state, and

comprising a pneumatic lift wherein the particles are elevated by meansof a gaseous lift medium.

This invention is especiallyapplicable to the chemical processingarts, such as petroleum refining, and .is primarily concerned with thosetreatments in which gaseous material is contacted with particulate solid material while the latteris continuouslycaused to flow or be conveyed through a contactzone whereindesiredchemical or physical changes in one or both of-the materials are to be. effected.

Althoughtheinvention iscapable of .quite general application .to -various types of gas-solids treatment, it is particularly suited to, and it will hereinafter be described inconnection with, the conversion of hydrocarbons in the presenceof solid .catalytic material in the form of granules, pellets, or beads of a size, form and composition known to theart. Forexample, the catalyst may be in the.form.of-spheroidal beads of silica-alumina gel having anaveragediameter in the order of. about 4 mm.

In systems of the type to which the presentinvention relates, and whichinvolve a-continuous movement of granular-contact .material by gravity flow over a considerable vertical distance through a. confined'downflow path, and bypneumatic transportation along a confined vertical upflow or'lift pathfor return to the upper end of the downflow path, the matter of disengaging the contact material fromthe lift gas presents several serious problems.

When the contact material is extremely friable, and relatively costly, as where prepared beads .of silicaalumina gel are employed it is generally necessary to disengage the contact material uponits discharge from the pneumatic'lift by complete gravitationaldeceleration and free fall within an enlarged vessel or disengager surrounding thedischarge end of the lift path, The disengager is generally .of such shape and size as to provide sufficient disengagingheightbetween the upper end of the lift pipe and thetop of the disengager vessel for the solid ,particles to decelerate and reverse their direction of movement without substantial impingement of the solidparticles against the top and upper side walls of the vessel.

Under present conditions of commercial operation catalyst circulation rates are generally well in excess of 100 tons/hi1, such as in the range of about 250-500 tons/hr and distances over which the catalyst is to be pneumatically elevated are well 'in excess of 1.00 feet, such as in the range of about 200-400 ft.

It is known that when solids are conveyedupwardly through alift'path of uniform flow area by means of '2 gaseous material there is an-acceleratedmovement'of solid particlesc-alongthe1-entire path1by reason .of'the gradual :expansion of the liftgas occurring as a result of thepressure drop through the liftpath.

When the solids are conveyed in a dilute or-sparse phase,'such asat concentrations of upto about 10 lbs./ cu. ft., the maximum attained velocity, which in the case of a lift path of uniform flow area is the discharge velocity, may be relatively high. Such isespecially the casesinzpneumaticlift systems of the type referred to herein, in which the maximum attained velocity .is generally considerably-in excess of 101'5:ft./sec. -In present commercial operations maximum attained velocities are commonly inthe range of 40-601 ft./ see.

A further factor in the matter of velocity increase as a result-0f gas expansion must be considered 'when the gaseouslift mediumundergoes some chemical or physical change while traversing the liftipath. Such is the case when there is a1substantial evolution of heatwithin the lift path or a 1 transfer of heat therein causing a substantial'rise inJgas'temperature, as where the gaseous'lift mediumcomprises reactants which'produce gaseous reaction products inthe presence of'the solid contact material, ortcomponents which vaporize or gasify upon contact with lilBZSOlidS.

Although the presentinvention is to be hereinafter particularly 'described and'illustrated in connection with those-systems Whereinthe lift gas comprises gaseous material formed by the. reaction-within the lift path of reactant materials .introduced therein, it is'to be understood thatthe invention --is susceptible of broad application to other'systems also-presenting a problem in respect to excessive discharge velocities, even'though such problem in the latter case is'lessacute.

In accordance Withthe present invention, acceleration of granular contact material being conveyed upwardly: through a confined lift path by a gaseous medium which is subject to substantial expansion during such conveyance is effectively controlled by providing a gradually increasing flow area progressively upward through said lift path.

. .In one embodimentof the invention, although by no means limited'thereto, the cross-sectional area of the con fined lift pathis increased in approximate proportion to the contemplated increase in gas volume.

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

Fig. l is a :diagrammatic view, in elevation, showing ra 'typical hydrocarbon processing system to which the invention may be applied; and

Fig. 2 is a diagrammatic view, in elevation, showing a modification of the system of Fig. 1.

tReferringnow-toFig. 1 of the'drawing, there is diagrammatically illustrated a system suitable for the catalytic' cracking-of hydrocarbon vapors. The system comprises "elongated upflow and downflow paths through which granular contact material, such as catalyst in the form of granules, beads or pellets,is continuously circulated. While circulating, the catalyst is contacted with gaseous reactants for the purpose of carrying outthe desired hydrocarbon reaction and for continuously effecting a-regeneration of the-'catalyst'a ft'erit has been discharged from the reaction zone.

Fresh .regenerated. catalyst is continuously supplied to a lift-engager'vessel 1, thesrateof flow thereto being such as to continuously maintain a mass of the catalyst within the .lift engager in the tenant a compactmovingbed.

Hydrocarbon vapors heated to ,a relatively-high temperature, rare introducedinto .thelower region-of the lift engager'l, at a location substantially'below the surface of the bed of catalyst contained therein, by means of vapor inlet nozzle 2 which extends centrally upward through the bottom of the lift engager vessel. The hydrocarbon vapors are supplied to the nozzle 2 through a valve con trolled feed line 80.

The hydrocarbon vapors, serving as the lift gas, engage the catalyst in the lower region of the compact moving bed and convey it into and upwardly through an elongated vertical lift pipe 3 whose lower end extends downwardly into the lift engager vessel in axial alignment with the hydrocarbon inlet nozzle 2. The lower inlet end of the lift pipe 3 is submerged within the compact moving bed of catalyst and is spaced from the discharge end of the nozzle 2 sufliciently to provide a smooth uninterrupted flow of catalyst into the mouth of the lift pipe.

The upper end of the lift pipe 3 extends axially into the bottom region of a lift disengager vessel 11 which is of considerably greater horizontal dimension than the lift pipe. The lift pipe 3 discharges the catalyst and the gaseous reaction products upwardly into the disengager 11 and, by reason of the substantial increase in flow areas between the lift pipe and the disengager, the velocity of the gaseous material decreases to a point where it is insufficient to support the particles of catalyst. Consequently, the discharged particles of catalyst become disengaged from the lift gas by gravitational deceleration and thereafter fall freely to the bottom region of the disengager 11 where they may accumulate in the form of a compact moving bed whose upper surface is maintained at a level below the upper end of the lift pipe 3.

The gaseous reaction products formed within the lift pipe 3, and subsequently separated from the catalyst particles within the disengager 11, are withdrawn from the upper region of the latter through outlet conduit 12. The gaseous reaction products, which in the present embodiment comprise cracked hydrocarbon vapors, are passed through outlet conduit 12 into a cyclone separator 13, wherein the cracked vapors are freed of any catalyst fines which may have been carried overhead out of the disengager 11 with the gaseous material.

The separated fine particles of catalyst are discharged from the bottom of cyclone separator 13 and from the system through conduit 15, and the cracked'hydrocarbon vapors are discharged from the top of the cyclone separator through valve-controlled conduit 14. The cracked vapors may be conveyed by conduit 14 to other portions of the system, such as a fractionating tower, not shown.

The disengaged particles of catalyst, bearing a deposit of carbonaceous material acquired while traveling upwardly through the reaction zone, that is, the lift pipe 3,

are continuously withdrawn from the compact moving bed maintained in the bottom of the disengager 11 through an elongated seal leg 30, and are conveyed as a compact moving stream by gravity flow to the upper end of a re generator or kiln 70 wherein the carbonaceous deposit is removed from the catalyst by combustion in the presence of oxygen-containing gas.

Kiln 70 may be of any conventional type suitable for the desired regeneration of the catalyst particles. In the embodiment illustrated the kiln comprises a cylindrical vessel having an internal tube sheet 71, provided with a plurality of short nipples 72, extending horizontally across the upper region of the vessel 70, thus forming between the tube-sheet and the upper end of the vessel a distributing chamber into which the catalyst is introduced through the seal leg 30.

The nipples 72 continuously discharge catalyst from the distributing chamber into the regeneration zone comprising the major central portion of the vessel 7. The streams of catalyst are deposited directly onto the surface of a compact moving bed of catalyst continuously maintained within the regeneration zone. The catalyst forms a continuous compact moving mass extending downwardly through the regeneration zone to and through the lowermost region of the vessel 70, from which region operation.

it is continuously withdrawn as a compact moving stream through outlet conduit or seal leg 43. I

At a low level within the vessel 70 oxygen-containing gas, such as air, is introduced through inlet conduit 73. The air is distributed throughout the cross-sectional area of the compact moving bed by means of distributing devices 74, which may be in the form of inverted channels known to the art. The oxygen-containing gas flows from the distributing devices 74 both upwardly and downwardly within the kiln 70. The portion flowing upwardly passes countercurrently through the main portion of the regenerator bed and is disengaged at the exposed top surface of the bed. The disengaging surface of the bed is at a level coinciding with the discharge level of the nipples 72. The disengaged gaseous material, or flue gas, is collected in the solids-free space between and around the nipples 72 and is discharged therefrom through flue gas outlet 75.

The oxygen-containing gas which flows downwardly from the distributing devices 74 passes through a secondary stage -of the regenerating zone in the bottom region of the bed, which zone may be provided with a series of cooling coils, as illustrated, the inlet to which is designated by the numeral 76. In the secondary stage of the regenerating zone the oxygen-containing gas flows concurrently with the catalyst and is disengaged therefrom at the bottom of the zone by means of disengaging devices 77, known to the art. The disengaging devices 77 may be similar to the gas distributing devices 74, the direction of gas flow therein not being material to their Flue gas disengaged from the catalyst by means of disengaging devices 77 is conveyed out of the bottom region of the vessel 70 through flue gas outlet 78.

The catalyst discharging from kiln 70 through seal leg 43 is conveyed as a compact moving stream into the upper region of the lift engager 1 and is deposited directly onto the surface of the compact moving mass of catalyst maintained therein. In order to preclude any undesirable migration of gas between the kiln 70 and the lift engager 1 seal gas may be continuously introduced into the seal leg 43 at a suitable location along its length, as through inlet 79.

Referring again to the gas lift portion of the unit, it will be apparent that, since lift pipe 3 is employed asv the reaction zone wherein the hydrocarbon cracking reaction is carried out in the presence of the hot catalyst being transported through the lift pipe, there will necessarily be a considerable evolution of gaseous material within the lift pipe as a consequence of the cracking reaction. The resultant expansion of the gaseous material within the lift pipe tends to effect a substantial increase in the velocity of the lift gas, with consequent acceleration of the catalyst particles moving upwardly along the lift path. Such acceleration is in addition to the acceleration normally to be expected as a result of the pressure drop inherent in the movement of the admixture of gaseous material and solids through the lift pipe.

The vertical distance that the particles of catalyst will be projected upon leaving the lift pipe is a function of the velocity of the lift gas at the moment of discharge from the lift pipe. It is obvious therefore that any substantial evolution of gaseous material, or any substantial expansion thereof, whi1e passing through the lift path may cause the discharge velocity to be so high as to require an excessive vertical distance within the vessel 11 for complete disengagement of the solid particles. The present invention provides an effective control upon such discharge velocity of the lift gas by means of a fully tapered lift pipe. In other words, lift pipe 3 is of gradually increasing cross-sectional flow area from its lower to its upper end, such gradual increase, if desired, being approximately proportional to the progressive increase in gas volume through the lift path.

The extent of taper necessary to effect the desired velocity control in the lift pipe 3 is so slight that it is difiicult to visually illustrate the same without substantial distortion of the proportions of the apparatus. vIt is to be understood, however, that lift pipe 3 is taperedthroughout its length, as will more fully appear hereinafter in connection with the data particularly exemplifying typical operations in accordance with the invention. The taper is represented in Fig. 2 of the drawing .by the designation D for the diameter .at thebottom of the lift and D for the diameter at the top, the legends D and D being placed outside the engager and the disengager, respectively, merely for convenience of illustration.

Although the apparatus of Fig. 1 has been particularly described in connection with the catalytic cracking of hydrocarbons in the presence of a continuously circulating body of granular catalyst, in which operation the desired conversion of hydrocarbons is carried out in the upfiow path of the system and the regeneration of spent catalyst is carried out in the downfiow path, it will be obvious to those skilled in the art that the system as illustrated is adaptable to various other processes involving the contact of gaseous material with circulating granular contact material without necessarily being limited in regard to the type of reaction carried out respectively in the upflow and downfiow paths.

Referring to Fig. 2 of the drawing there is illustrated a system which in many respects is similar to that illustrated in Fig. 1, but which comprises add-itionallya reaction vessel 90 superimposed-above the reaction vessel 70,

and having open communication therewith by means of 3 a vertical conduit or seal leg 91 through which the circulating catalyst is continuously conveyed in the form of a compact moving column. Portions of the apparatus which are duplicated in the illustration of Fig. '2 have reference numerals identical to those of their counterparts in the illustration of Fig. 1.

The system of Fig. 2 is adapted for use in various conversion operations. In cases where it is desired to merely initiate the hydrocarbon cracking reaction within the lift pipe, and to thereafter continue the reaction to a desired point of completion within a separate reaction zone, the vessel 90 may provide a second reaction .zone, and the vessel 70 may serve as aregenerator. With this arrangement the partially-reacted gaseous material disengaged from the catalyst within :the disengager '11 and discharged therefrom through conduit 12, may be conveyed by means of conduits 1'4 and '14a't0 the upper end of reactor 90. As in the system of Fig. '1, the disengaged gaseous material is passed from the disengager 11 directly to a cyclone separator 13 which removes from the gas stream the particles of fines carried over in the gas outlet stream of the disengager.

The disengaged catalyst withdrawn from the bottom of disengager 11 is conveyed into the upper end of reactor 90 through conduit 30.

The incompletely reacted hydrocarbon vapors introduced into reactor 90 through conduit 14a passdownwardly through a compact moving bed of catalyst maintained within the reactor, and the gaseous reaction products are withdrawn from the lower end of the vessel 90 through outlet conduit 92, the latter conduit communicating with other treating portions of the system, such as a fractionator, not shown. I

The flow of catalyst through the'system of Fig. 2, and the 'manner of engaging the catalyst with hydrocarbon vapors and conveying the catalystthroug'h 'the lift pipe is similar to that described 'in'connection with Fig. 1, and is therefore notrepeated. The system of Fig. 2, however, is equally suitable 'for an operation i'n which the lift pipe is not to be used as 'a reaction zone 'but is-employed merely for the purposeofelevatingthe catalyst from the lower end of the down'flow path 'to-the upper end thereof by means 'of a suitable inert gaseous lift medium.

In the last-mentioned type or opefationjthecodduit 6 14 of Fig. 2 may convey the lift gas to a stack, not shown The conduit 14a may thenserve as the inlet line for feeding hydrocarbon charge stock into the upper "end of the reactor 90. In such operation, the conduit will be employed to introduce inert gaseous material such as steam, flue gas, etc., through nozzle 2 into the lift engager 1.

It will be understood that in the modification of Fig. 2 provision for seal gas, other than that shown at 79 in connection with seal leg 43, may be provided where necessary to prevent undesirable migration of gaseous material between adjacent zones of the system. For example, as described and illustrated in our copending Serial No. 58,532, of which the present application is a continuation-in-part, seal gas may be introduced into the I upper end of either or both of vessels and 70 to prevent undesirable flowojf gas through seal legs 30 and 91, respectively.

The lift pipe 3 of Fig. 2 is also tapered slightly to accommodate the expansion of the gaseous material within the lift pipe. As mentioned .in connection with Fig. 1, however, the taper is so slight as to be incapable of clear illustration in thetlrawing without substantial distortion of the proportions of the apparatus. While there may be a greater need for providing a tapered lift pipe in cases where the lift pipe Sis employed as a hydrocarbon lift, because of the considerable evolution of gas eous material resulting from the reaction occurring within the lift pipe, it will be understood that it may be desirable to control the discharge velocity of the lift gas even in those cases where a reaction does not take place within the lift pipe and where the expansionof gaseous material therein is attributed solely to the inherent pressure drop through the lift path during operation of the lift. In any cases, it will be apparent that the employment of a tapered lift pipe permits :the catalyst to berdisengaged from the gaseous lift "medium within a shorter vertical distance.

'The velocity control obtained by tapering the lift pipe provides a substantial degree of flexibility in the operation of the lift system, and by reason of the fact that it serves to maintain the disengaging height required for complete gravitational deceleration of the solids at a practicable value it permits substantial savings in cost of materials, fabrication and erection to be'efiected.

The following data exemplifies an operation,. in accordance with the invention, carried out in ftheapparatus of Fig. 1:,

Example I rate of approximately 460tons *perhour.

The catalyst enters the lift engager 1 at a temperature of 938 F. and passes into the lift disengager 11 at a temperature of 900 F. The hydrocarbon material admitted to the nozzle 2 by way of the pipe 80 is a gas oil fraction totally .in the vapor phase. These hydrocarbon vapors enter the chamber 1 at a temperature of 850 F., at a pressure of 20 lbs. per sq. inch gauge and at a constant rate in the amount of 5000 bbls. per day, steam amounting to 10% by weight of the charge material accompanying the latter into chamber 1 by way of the pipe 80 and conduit 2. The mixture of hydrocarbon vapors and steam elevates the catalyst through the'pipe 3. In the disengager 11, where a pressure of '5 lbs. per sq. 'inch gauge is maintained, the cracked vapors "and steam at a temperature of 900 F. are disengaged from the catalyst and pass from the system by way of the pipe 12, the cyclone separator 13, and the pipe 14. 7

Heat in the amount of 10,055,000 B.t.u.s per hour is removed from the catalyst during upward passage thereof through the upflow path and is absorbed in the elevating medium comprising the aforesaid hydrocarbon vapors and steam. Of the total amount of heat thus absorbed, 2,450,000 B.t.u.s'per hour are absorbed in the hydrocarbon vapors; 195,000 B.t.u.s per hour are absorbed in the steam; and 7,410,000 B.t.u.s per hour are absorbed in the hydrocarbon vapors to promote the endothermic cracking reaction.

The spent catalyst leaves the disengager 11 at a temperature of 900 F., and, at this same temperature, enters the regenerator housing 70. Air in the amount of 20,000 lbs. per hour is admitted to the housing 70 by way of the pipe 73 at a temperature of 150 F. This air flows counter-currently to the catalyst gravitating through the housing 70, the resulting flue gases being discharged by way of the pipe 75 at a temperature of 900 F.

Heat in the amount of 22,100,000 B.t.u.s per hour is liberated from the catalyst during the regenerating operation. Of this total heat, 3,920,000 B.t.u.s per hour pass from the housing 70 along with the flue gases; 8,125,000 B.t.u.s pass from the regenerator with the heat exchange medium traversing the tubes 76; and 10,055,000 B.t.u.s per hour are absorbed by the catalyst for utilization as described above.

The regenerated catalyst leaves the housing 70 at a temperature of 930 F. and, at this same temperature, enters the lift engager 1.

As stated above, the pressure within the lift engager 1 is 20 lbs. per sq. inch gauge, whereas, within the disengager 11, the pressure is lbs. per sq. inch gauge. Accordingly, the predetermined pressure drop through pipe 3 is 15 lbs. per sq. inch. At the level of the discharge pipe 75, the pressure is 5 lbs. per sq. inch gauge and, at the level of the inlet pipe 73, the pressure is lbs. per sq. inch gauge.

The height of the lift pipe 3 is one hundred and fifty (150) feet. The pipe 3 has a frusto-conical configuration, the diameters (D, and D at the bottom and top being 21 inches and 27 inches, respectively.

As stated above, hydrocarbon vapors in the amount of 5000 bbls. per day, together with steam in the amount of 10% by weight of the charge material, are admitted to the nozzle 2 for upward passage through the pipe 3. The vertical height of the gap g is set to control the quantity of catalyst admitted to the lower end of the pipe 3, so that theconcentration of the ascending catalyst is approximately 11.3 lbs. per cu. ft. at the bottom of said pipe 3 and approximately 6.5 lbs. per cu. ft. at the top thereof, the average concentration being about 8.9 lbs. per cu. ft. As stated above, the pressure drop through the lift pipe 3 under such conditions is approximately lbs. per sq. inch.

Under the conditions set forth above the velocity of the ascending catalyst at the top and bottom of the lift pipe 3 is approximately 10 feet per second.

The following data exemplifies an operation, in accordance with the invention, carried out in the apparatus of Fig. 2:

Example II .mitted to the nozzle 2 by way of the pipe 80 is a gas oil fraction existing totally in the vapor phase. These hydrocarbon vapors enter the chamber 1 at a temperature of 600 -F., at a pressure of 14 lbs. per sq. inch gauge, and at a constant rate iii-the amount of 6,750 bbls. per day, together with steam in the amount of 5000 lbs. .per hour. The mixture of hydrocarbon vapors and steam elevates the catalyst through the pipe 3. In the disengager 11 where a pressure of 7.5 lbs. per sq. inch gauge is maintained, the partially cracked vapors and steam are disengaged from the catalyst at a temperature of 895 F. and arethereafter passed through the pipe 12, the cyclone separator 13 and the pipe 14.

The catalyst enters the disengager 11 at a temperature of 895 F. and, at this same temperature, is passed through conduit 30 into the reactor disposed in superposed relation above the regenerator 70. The spent catalyst leaves reactor 90 at a temperature of 865 F., traverses vertical pipe 91 and, at the temperature last noted, enters the regenerator 70.

The partially cracked vapors together with the steam enter the housing 90 by way of the pipes 14 and 14a and flow in concurrent relation with respect to the catalyst gravitating through said housing 90, the cracked vapors and steam being withdrawn from the housing 90, by way of a pipe 92.

The spent catalyst introduced through pipe 91 into the regenerator 70 at a temperature of 865 F. gravitates through the regenerator 70 and passes therefrom at a temperature of 1067" F. Thereafter, the regenerated catalyst gravitates through the inclined pipe 43, and, at this same temperature, enters the lift engager 1. Air in the amount of 42,000 lbs. per hour is admitted to the regenerator by way of the pipe 73 at a temperature of F. The air flows counter-currently to the catalyst gravitating through the housing 70, the resulting flue gases being discharged by way of the pipe 75 at a temperature of 865 F.

Heat in the amount of 22,050,000 B.t.u.s per hour is removed from the catalyst during upward passage thereof through the lift pipe 3 and is absorbed in the elevating medium comprising the aforesaid hydrocarbon vapors and steam. While the catalyst and said medium are engaged with each other in the housing 90, heat in the amount of 7,350,000 B.t.u.s per hour is removed from the catalyst and absorbed in the aforesaid medium. Thus a total of 29,400,000 B.t.u.s per hour is absorbed in the medium comprising the hydrocarbon vapors and steam.

Heat in the amount of 44,800,000 B.t.u.s per hour is liberated from the catalyst during the regenerating operation. Of this total heat, 7,400,000 B.t.u.s per hour pass from the housing 70 along with the flue gases and 8,000,000 B.t.u.s per hour pass from the regenerator with the heat exchange medium traversing the tubes 76. The remainder, namely, 29,400,000 B.t.u.s per hour is utilizable as described above.

As stated above, the pressure within the lift engager 1 is 14 lbs. per sq. inch gauge whereas, within the lift disengager 11, the pressure is 7.5 lbs. per sq. inch gauge. Accordingly, the predetermined pressure drop through pipe 3 is 6.5 lbs. per sq. inch.

In the reactor 90, the pressure at the level of the pipe 14 is 7.3 lbs. per sq. inch gauge whereas, at the level of the pipe 92, the pressure is 5.9 lbs. per sq. inch gauge.

In the regenerator 70, the pressure at the level of the pipe 75 is 6.8 lbs-per sq. inch gauge whereas, at the level of the pipe 73, the pressure is 9.5 lbs. per sq. inch gauge.

The height of the lift pipe 3 is one hundred and fifty (150) feet. The pipe 3 has frusto-conical configuration, the diameters (D and D at the bottom and top thereof being 16.4 inches and 27 inches, respectively.

As stated above, hydrocarbon vapors in the amount of 6,750 bbls. per day together with steam in the amount of 5,000 lbs. per hour are admitted to the nozzle 2 for upward passage through the lift pipe 3. The vertical height of the gap g is set to control the quantity of catalyst admitted to the lower end of the pipe 3, so that the concentration of the ascending catalyst is approximately 7.5 lbs. per cu. ft. at the bottom of said pipe 3 and approximately 2.6 lbs. per cu. ft. at the top thereof, the

average concentration being about lbs. per cu. ft. As stated above, the pressure drop through the lift pipe 3 under such conditions is approximately 6.5 lbs. per sq. inch.

Under the condition set forth above, the velocity of the ascending catalyst at the top and bottom of the lift pipe 3 is approximately 15 feet per second.

From the foregoing examples of typical operations in accordance with our invention it may be seen that effective control of the velocity of solids flow through a lift pipe, with consequent control of the height of rise of the stream emerging from the lift pipe, is readily obtained by the provision of a lift pipe whose cross-sectional flow area progressively increases from the bottom to the top.

The degree of taper required to maintain a relatively uniform velocity of solids movement upwardly through the lift pipe is dependent upon various factors, principally those which tend to effect any substantial increase in the volume of gas flowing through the lift, such as the expansion of gas as a result of pressure drop or of in crease in temperature of the gaseous lift medium during its flow through the lift pipe and the possible evolution of gaseous material as a consequence of a chemical reaction or conversion of the gaseous lift medium within the lift pipe. It is contemplated that physical and chemical changes occurring while the solids are being transported through the lift pipe by the gaseous lift medium will be taken into consideration in determining the proper pipe taper to be employed. In any case, the angle of taper, that is, the angle between the lift pipe axis and the sides of the lift pipe will be relatively slight, as indicated by the data set forth in connection with Examples I and II.

The present application is a continuation-in-part of our application Serial No. 58,532, filed on November 5, 1948, now abandoned, and is directed specifically to that portion of the former application directed to the matter of obtaining velocity control of the solids flow through the lift path by means of a gradually tapering lift pipe.

What is claimed is:

1. In a cyclic system for the conversion of hydrocarbons, wherein solid contact material is elevated along a confined lift path by means of a gaseous lift medium introduced at the lower end thereof at least partially in a gaseous state, and wherein the elevation of said contact material along said lift path is accompanied by such increase in the volume of said gaseous lift medium as would normally tend to effect a relatively great increase in the velocity thereof, with attendant undesirable increase in the velocity of said solid contact material, the method which comprises maintaining a substantially uniform velocity of said contact material along said lift path by gradually increasing the diameter of the lift path so that over a lift path distance of about feet the ratio of the diameter at the uppermost and lowermost ends of the lift path will be in the range of about 1.28 to 1 to about 1.68 to 1.

2. The method as defined in claim 1, wherein said fluid lift medium comprises hydrocarbon material to be converted.

3. The method as defined in claim 1, wherein said lift path is of gradually increasing circular cross section.

4. The method as defined in claim 1, wherein said increase in volume of said gaseous material within said lift path is substantially in excess of that normally to be expected as a consequence of the decrease in pressure upwardly along said lift path.

5. The method as defined in claim 1, wherein said fluid lift medium comprises hydrocarbon material, and wherein said increase in the volume of said gaseous lift medium is the result of a partial conversion of said hydrocarbon material while passing through said lift pipe.

References Cited in the file of this patent UNITED STATES PATENTS 788,741 Trump May 2, 1905 2,398,759 Angeli Apr. 23, 1946 2,407,700 Huff Sept. 17, 1946 2,548,286 Bergstrom Apr. 10, 1951 2,628,188 Kirkbride Feb. 10, 1953 2,684,873 Berg July 27, 1954 FOREIGN PATENTS 180,397 Great Britain May 11, 1922

Claims (1)

1. IN A CYCLIC SYSTEM FOR THE CONVERSION OF HYDROCARBONS, WHEREIN SOLID CONTACT MATERIAL IS ELEVATED ALONG A CONFINED LIFT PATH BY MEANS OF A GSEOUS LIFT MEDIUM INTRODUCED A THE LOWER END THEREOF AT LEAST PARTIALLY IN A GASEOUS STATE, AND WHEREIN THE ELEVATION OF SAID CONTACT MATERIAL ALONG SAID LIFT PATH IS ACCOMPANIED BY SUCH INCREASE IN THE VOLUME OF SAID GASEOUS LIFT MEDIUM AS WOULD NORMALLY TEND TO EFFECT A RELATIVELY GREAT INCREASE IN THE VELOCITY THEREOF, WITH ATTENDANT UNDESIRABLE INCREASE IN THE VELOCITY OF SAID SOLID CONTACT MATERIAL, THE METHOD WHICH COMPRISES MAINTAINING A SUBSTANTIALLY UNIFORM-VELOCITY OF SAID CONTACT MATERIAL ALONG SAID LIFT PATH BY GRADUALLY INCREASING THE DIAMETER OF THE LIFT PATH SO THAT OVER A LIFT PATH DISTANCE OF UPPERMOST AND LOWERMOST ENDS OF THE DIAMETER AT THE UPPERMOST AND LOWERMOST ENDS OF THE LIFT PATH WILL BE IN THE RANGE OF ABOUT 1.28 TO 1 TO ABOUT 1.68 TO 1.

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