US2663595A

US2663595A - Transportation of granular solids

Info

Publication number: US2663595A
Application number: US184547A
Authority: US
Inventors: David B Ardern
Original assignee: Houdry Process Corp
Current assignee: Houdry Process Corp
Priority date: 1950-09-13
Filing date: 1950-09-13
Publication date: 1953-12-22
Anticipated expiration: 1970-12-22

Description

AGENT COMPRESSOR H w R w 1 mm 5 a n5. m m M M W 1 m m m a s Dm m F g a I 4 1 A 06/ a L f 7 & Z w w; H w M N m T TJ j a R N i i 1 E M Ll 1 w G REM N 0 W 6, H 1 a z N 48 B m M D M A L Wm. M S M M v. m 0 M m M Q? a: m R T x 5 W Mg M M m Z Z m a WW M Wm M RC 5 R 5 P; s 6 M "M F A Dec. 22, 1953 Filed Sept. 15, 1950 rfrlllrli Dec. 22, 1953 D. B. ARDERN 2,663,595

TRANSPORTATION OF GRANULAR SOLIDS 2 Sheets-Sheet 2 Y T 5 5' Filed Sept. 13, 1950 INVENTOR David Bflrdern AGENT employed, it is desirable to space such vessels as closely as possible in order to simplify and reduce the cost of supporting the various vessels. Another effect that occurs under some conditions with gas lift pipes of relatively large diameter is a mushroom effect in which the emergent par ticles, instead of fountaining or spraying outwardly and settling in the disengaging zone, form a relatively dense cloud or mass of particles suspended above the lift. Obviously, collision of the particles emerging from the lift with those in the cloud leads to undesirable attrition.

In accordance with the present invention, the undesirable effects noted above are minimized and/ or overcome in systems of the type here involved, by passing a stream of lifting gas and of particles at substantial velocity upwardly along the lower part of the vertical extent of each of such a plurality of vertically elongated laterally confined lifting paths or conduits, said lift paths or conduits being arranged equidistantly from or around a common vertical axis, individually flowing each of said streams in the upper parts of said lift paths along median flow lines which diverge from said common axis while individually confining the flow of the portion of each of said streams nearest said common axis to a flow path parallel to said axis. Such flow can be achieved by using pipes or conduits which taper eccentrically outward from their common vertical axis. v

In one embodiment of the invention, the streams of particles and gas, including the portions flowing divergently outward from the common axis, are discharged from the upper end of the lift path or conduit into a common gas-solid disengaging zone or hopper having a considerably greater horizontal cross sectional area than that of the circle circumscribing the tops of said lift paths or conduits. In the disengaging zone or hopper, the various streams of particles and gas flow, fountain or spray divergently outward from the common axis'with the result that there is' little or no'collision between particles from adjacent lift paths and subsequent disengagement and free settling of the particles is simpler. Under these conditions, attrition caused by in-- tor-particle collision or friction is minimized.

'The invention is especially applicable to systemsinvolving the catalytic conversion of petroleum, and for the purpose of illustrating the invention, it will be described hereinafter in connection with a catalytic cracking system for the conversion of high boiling hydrocarbons to motor gasoline. Such a system is setforth in detail below in connection with the description of the drawings in which:

' Figure 1 is a schematic generalized elevation of a typical system in which the present invention may be used;

Figures 2 and 3 are enlarged views, partly in section, of the upper portions of the gas lift pipes and disengaging hopper. shown in Figure 1, Figure 2 being an elevation partially in section along the lines 2-2 in Figure 3, and Figure 3 being a top view of a section along the lines 3-3 in Figure 2; y

Figures 4 and 5 are enlarged views of an em bodiment of the present invention to be used as upper parts of the gas lifts shown in Figures 1, 2 and 3, Figure 4 being an elevation and Figure 5 being a top view;

Figures 6 and 7 are top viewsofmodifications of the embodiment of the invention shown in Figures 4 and 5. 1

In Figure l is shown a typical embodiment of the type of system with which the present invention is concerned. Since the invention is directed primarily to the upfiow portion of the system and since the operation and construction of the reactor and regenerator or kiln of the typical system shown in Figure l are adequately described in the aforementioned article appearing in the Oil and Gas Journal, detailed illustration and description of the latter have been omitted for the sake of brevity. It is to be understood that various arrangements of kiln and reactor may be employed in connection with the present invention, as for example arrangements shown in the Houdry Pioneer, vol 5, N0. 1, February 1950. vThe system shown in Figure l differs from those shown in the cited publications in that a multiple lift is used in the former, while the latter employ single lifts.

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

Catalyst particles are withdrawn from the regenerator and flow downwardly in a conduit as a compact non-turbulent column to a gas lift inlet chamber or particlle supply hopper Hi surrounding the bottom of a plurality of gas lifts, and are transported, lifted or elevated vertically upward as a plurality of continuous streams of solid particles by transporting or lifting gas introduced at a substantial pressure, such as from about 1 to 10 pounds per square inch gauge, to inlet chamber by conduits H and/or I2. The inlet chamber it can be of any design suitable for multiple lifts, such, for example, as that disclosed in the copending application of R. N. Shirk and C. Bruckner, Serial No. 124,874, filed November l, 1949. Alternatively, a plurality of separate inlet chambers (one for each lift) can be employed. The gas used in lifting may be one derived from or one used later in the system, such as flue gas or hydrocarbon charge stock, either in liquid or vapor phase, respectively; or may be one used only for lifting, such as air or steam.

The particles of contact material pass upwardy through a plurality of vertical cylindrical pipes or conduits indicated generally by Hi to a closed disengaging vessel, hopper or separator l4 surrounding the top of lifts i3, which vessel comprises a confined gas-solids disengaging zone common to all thelift paths. The disengaged lifting gas is thereafter removed from vessel It, as from the top thereof by conduit I5.

. Particles of catalyst disengaged from the lifting gas settle on the surface of a bed 22 in vessel i l, from which bed the particles flow through a conduit or seal leg 16, as a relatively compact non-turbulent column of particles to the reactor. It is to be understood that a particular type of separator, such as vessel 14, is-not a part of this invention and that; separators other than the asthm thatimmediatelysurrounding the topsof lift pathsonconduite I 3 such as from-"5 to"-25"tiines the area 1 of theeircle' circumscrihirrg' the topsof gas lifts'lSi so"-that* the particles spraying or fountaining outof the lift pipes do not irn'pin'ge against the walls. Also; whenfree setting of the particles emergingfrom-the gas "lifts-is em ployed as a means ofseparating=the particles= and lifting gas, the distance ofthetop*ofvessel I l above-that of lift pipes l3; which-terminate on a common'horizontal plane; shouldbegreat enough that there is little orno'impact-of the particles-against'the to of the'clisengaging-hopper. Thus, for example; a -distance of about-10 to 35feet canbe employed when'the-cata-lyst particles emerge with an average-velocity-of 30' feet'per second-from lifts of6 to-20inches'in diameter;

As can be seeninFigures-l-and-2; lift pathsor conduits l3 provide a multiplicity or plurality" of vertically elongated laterally confined-parallel lift paths or passageways grouped-or-arrangedequidistantly from-a comm-0n" vertical-axis; As shown in Figure 3, the centers of the lower-partsof-the lift pipes fall'ona'circle whose"center-lieson the aforesaid common vertical'axis'and-are 40 arranged or spaced symmetrically-aroundthe circle (i. e.-, equidistantly ar0und-the*"common vertical axis). Moreover, the center of'the-common disengaging zone orhopper; which is preferably circular in horizontal cross section as shown in the drawing, also lies on the vertical axis and therefore is concentric with respect to" the multiplicity of lift paths;

In accordance-with the embodiment of-the present invention shown in the drawing, the major and lower arts 13a ofthe gas'lifts havea constant circular horizontal cross sectional area while the upper and minor parts'of" the gas lifts lsb taper eccentrically outward. Theeccentric. taper can take various forms: FQrJeXampIe, the" top of the lift pipe or" conduit shown in'Figure 5""terminates in-acircle-16 whbsecenteris ec centric with respect to the center *of thelower'" part. Alternatively; the top; may havethe form. of two spaced semicircles 'l i joined bljflat'p'arallel 'i walls [8, as shown in Figure 6 br-may-havet'the"* form of an oval l9; asshownimFigure-fli' The packing glands 2 l, which provide means for-seal ing vessel l4 atthe locations where the lift pipes enter the vessel; are constructedto fit'anypar ti'cularshape of the upper parts-ofthe liftcon dliits.

In all the embodiments shown, thatportion of the periphery of the-top ofeach-"liftthat'is nearest the common axis is inthesame vertical linewith the-corresponding portion" of them riphery of the lower part 1 3a '(i; e., the portion of periphery of each' lift pipe nearest the com= mon= axis-is parallelto andspaceda constant:

distance from -said" axis "over the entirewertical 1 eirten't' of tlie f lift plbe); differently? the hori'zontal' cross 'seetioris of thetbp and bot 7 tom of the conduits IS' aie-tim'gent at thepoihtnearest the 'cominon vertfcal axis of 'tli'e plurality of lift conduits when the topwro's'ssec-tiomis pro jected vertica-lly dwhward motel 'i'fguresfi, 6 and 7-); Ana result of cbnstructioh; only the portion of the=streami0figas and of particleson. each Iift patIi)" remote fro' "the common axis of all paths fibws radially otitward while the stream fiowsgenerauy upward the upper part2 Of eacHlift patIra p The *gas' lifts shfown ih tl ie d'i'awingi are oper ated by introclhcinparticles ah'd lifting gas to the "bottom of each=lift--path "=from i chamber ID the amount and?velbeitf efl-seiifigaiS heiii? suffif ci'nt ta aceelerate the upward' rrrovem'ent of sa'idr' particles te at: suhsta-ntliatl veldciti as discussed. more fully below? -sti-'e'ani of "gas and of par ticles flowse upwardly at? substantialx'reliu zityv through thelowerpart of each'qiftpath; whiclr has 'a -constantl'circularflow area, until 'it reaches the upper part-of thfe 'liftfi patlf I37); Because: the portion of the-periphery: of each of the lift" paths -remote from' -the common vertical axis of all I thelift paths tapers outwardm each= of the streamsef gas and oif articles individiiallyflows alonga median flow -line which diverges from" said-common laxis d; ez tlie plaint of average dis tributio'n'a of the. particles? in ea'ch streamcontinu'ously moves awai from theicommon -axisas the stream travels upwardlyf The-streams will therefore di'schargefromthe tops of tl ie =l-ift"pathsi so that theyzdiverge'from the common axis and the centerol vessel .1 4;: As: a result;elift condiiits of siz'es' useful :ini commercialrsiz'essystems; such asfromabout di to 25 iinches emeiamaam the lower-part; canibe'spaced iaroimd amcircl' of rel a-tively small-z radiusr. such! asi. preferably front t ncounteringaihterfer ence caused? byrcollisiontof:theerelatively central I portions of the various streamszd In a specific:aspectathetpresent mvention can be: employed: to: aidriirracontrolling the"velocity of p the gas andhenceeof theparticlessin the upper part of Tea-ch: gas-lift :vwliiclfivelocity increases in lift pathshavingaaiconstanticrossisectional "area: such'tincreasezirrtvelocity is producedriby th'e expansion 10f thewgas iresulting fromkthe reduction in" gaseous" pressure-i that: occurs as-"s the: stream of gasmoves: :upwardlyswill be noted' that;- in the present inventicna th'e'zhoriz'ontalcross sectional area; of thecondui ezgcth e fiew area of the stream-oi gas 'and of particles) gradually increases or expands in 'th upper part ofaclf lift until it reaches'a' maxi -um at -the 'top; Theexpansiondn 'fiow area is produeed by spacing the flow path"boundaries most reniote from the coinmon vertical axis at' d istances w 'i-ch constantly .and continuously ilicrease in'relation to the prox-- imity to the tops of the-lift-patEs: while the flow path boundaries nearest "said common' axis are spacedat constant distarrce thereirem: Depend= ing upon the size relatibnship bet-ween the ad-- ditiona-l area provided byrthe expansion" of the horizontal cross sectional 'area of-the' upper part of each" lift' andfthe *cOnStanthbrizdntal cross sectional area of the"'lower"part offea'ch lift; the velocityofthestreammffgas*and of particles as a whole can increase to"a*sli g'ht extent; remain constantbrrsubstantially decrease throughout the" upper-part offeachflift: v V

Thus the particles maybe "smopthlyjdecelrated' in"'the upper gp'azzt' i'or eachfliftjsojthat i'theygdis' charge '-f1omthe topthereof ataveldcity "sl'ib stantially'less than the maximum velocity attained in the lift, such as from about 10 to 40 percent of said maximum velocity, which is realized generally at about the point when the particles enter the upper and tapered part or section. Deceleration is achieved smoothly and without slugging (formation of spaced relatively dense bodies or clouds of particles which move intermittently up the-lift) in accordance with the present invention. Such deceleration can be achieved by using relatively small angles of taper, such as from about 0.2 to 5 degrees (the angle of taper being measured as the inclination of the outside wall to the vertical axis of the lift conduit indicated by angle AinFigure 5) extending over relatively long upper sections, such as from about to feet. When, alternatively, relatively sharp angles of taper, such as from about 10 to 30 degrees, are employed, it is preferred that the taper extend over a relatively short portion of the lift path such as from about 2 to 5 feet. (The term lift path as used herein is applied to the path extending from the bottom to the top of conduits l3.) Somewhat smaller angles of taper and/or shorter distances over which they extend should be employed when it is desired to maintain the velocity of the stream of gas and of the particles constant or to decrease the rate at which they would otherwise accelerate so that the velocity increases only slightly.

- Although the drawing shows the tapered walls as being straight it is within the scope of the present invention to have it curved so that the outer periphery of the lift conduit is somewhat trumpet shaped. In general, it is preferred to construct the lift conduits so that the ratio of the horizontal cross sectional area of the top of the conduit to that of the bottom is between about 1.3 to 5, the. upper portion of this range, such as from about 1.5 to 3, being preferred when it is desired to decelerate the particles in the upper part of the lift.

Deceleration of the particles in the upper part of the lift paths isiespecially advantageous when the maximum velocity of the particles attains a value of over about'30'feet per'second. Any substantial increase inma 'mumvelocity above this value results-in a considerable increase in the height of the disengaging vessel.v By means;

higher maximum veincreasing the height of the present invention, locities can be used without of the disengaging vessel by ticles in the upper part of the lift path, thereby avoiding the expense resulting from tall disengaging vessels, as pointed out above.

In all of the embodiments shown, tial fraction of the-particles ward lateral component of velocity as from the tops of the to move particles from immediately above the a sub'stan=-- have a small out-r they emerge lift paths. This efiect tendsfill.

ofthe apparent bulk density of the particles (i. e., the density of the packed mass of particles). For present commercial catalyst having apparent bulk densities of from about 40 to pounds per cubic foot, average concentrations of about 1 to '7 pounds per cubic foot have proven particularly advantageous. Experience has shown that an advantageous range of particle velocities is about 20 to feet per second (based on the average velocity of the particles at complete acceleration), although lower velocities may be employed, generally in relatively short lifts, such as those of 50 feet or less.

, Although the invention has been described in connection with a system employing a common disengaging zone, it can also, as pointed out above, be usefully applied to systems employing individual disengaging zones or hoppers for each lift. By disposing each lift eccentrically in each individual disengaging zone or hopper (i. e., near one side thereof), the group of disengaging zones can be spaced advantageously within the minimum circumscribing area. Under these conditions, the stream of gas and of particles discharge into each disengaging zone so as to spray or fountain divergently outward from the wall of the disengaging zone nearest the common vertical axis of the group of lifts. Because of the close spacing of the individual disengaging zones permitted by such an arrangement, all of the disengaging vessels can be supported by a single unitary structure at relatively low cost compared to the cost of individually supporting these vessels.

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

I claim as my invention:

1. Apparatus for elevating granular material by fluid lifting medium comprising a plurality of vertically elongated conduits grouped about a common vertical axis and terminating in a common horizontal plane, said conduits defining passageways for streams of granular material and fluid lifting medium; and a disengaging chamber surrounding the tops of said conduits and providing a confined space for disengaging said -granular material and said lifting medium; the

decelerating the par' lift path in a manner such that the density of particles in thlS ZG giOILIlI lS considerably diminished with a resultingdiminution in any tendency of the particles to form a mushroomor cloud.

It is tobe understood tion is applicable-to a 'de range of velocity corrditions and particle concentration or density in the lifting zone. Various velocities and concentrations can be obtained by varying the amount and pressure of the lifting gas such as by controlling either the total orrelative amounts of lift gas introduced fective range or particle concentration for commercial operationfirivolving the size of particles 0.5 to 20 percent referred to above is about that the present inven-- by conduits H or l2. Anefupper portion of each of said conduits tapering eccentrically outward from said common axis.

2. Apparatus for elevating granular material by fluid lifting medium comprising a plurality of vertically elongated conduits grouped about a common vertical axis and terminating in a common horizontal plane, said conduits defining passageways for streams of granular material and fluid lifting medium; and a disengaging cham- 'ber surrounding the tops of said conduits and providing a confined space for disengaging said granular material and said lifting medium; the upper portion or each of said conduits tapering outward along that part of its periphery remote from said common axis while that part of its periphery nearest said axis extends vertically upward in parallel relation to said axis.

3. Apparatus for elevating granular material by fluid lifting medium comprising a plurality of vertically elongated conduits grouped about a common vertical axis and terminating in a common horizontal plane, said conduits defining passageways for streams of granular material and fiuid lifting medium; and a disengaging chamher surrounding the tops of said conduits and providing a confined space for disengaging said granular material and said lifting medium; the upper portion of each of said conduits being ar ranged to discharge said granular material and fluid along a median line of discharge which is divergent with respect to said vertical axis.

4. In apparatus for elevating granular material by means of a gaseous lift medium the combination of: a plurality of upright elongated lift conduits of uniform circular cross section over the substantial major portion of their length and having their upper end portions tapered to provide a gradual increase in flow area, the median lines of said tapered portions being slightly inclined to the axes of the portions of uniform circular cross section, and a common disengaging vessel containing the upper end portions of said lift conduits.

5. Apparatus as defined in claim 4 wherein each of said tapered portions of said lift conduits has one side forming a straight longitudinal extension of a side of its associated portion of uniform circular cross section.

6. Apparatus as defined in claim 5 wherein said tapered portions of said lift conduits are frustoconical sections.

7. Apparatus as; defined in claim 4 wherein the cross-sectional areas of said tapered portions of said lift conduits have major and minor axes of difierent size.

8. Apparatus as defined in claim 4 wherein said plurality of lift conduits are grouped about a common vertical axis, which vertical axis lies in. each of the separate planes containing the main axis and the tapered-section median line of each of said lift conduits.

9. Apparatus as defined in claim 4 wherein said lift conduits are parallel and each of said tapered portions has one side forming a straight longitudinal extension of a side of its associated portion of uniform circular cross section.

DAVID B. ARDERN.

References Cited in the file or this patent UNITED STATES PATENTS Number Name Date 328,991 Westlake Oct. 27, 1885 2,386,491 McOmie Oct. 7, 1945 2,487,961 Angell Nov. 15, 1949 FOREIGN PATENTS Number Country Date 180,397 Great Britain May 11, 1922