US2310377A - System for handling abrasive powder - Google Patents

Description

VFeb. 9, 1943. v VOORHEES 2,310,377

SYSTEM FOR HANDLING ABRASIVE POWDER Filed Oct. 3l, 1940 facture of highjquality motorfuel.

Powdered catalyst systems have been foundto be far superior tcflxed bed systems in'many rei severeoperatingcondition ventionlis'to provideasolution :for this'problem, f to provideafco'mme l puxnpj jfo r handlingI noivirderecl'cataly `from a low pressure'zone-to handlingfofipowderedlcatalyst; derstood thatcertain aspects ofmyinvention-are A sive powders( Patented Feb. 9, 1943 ration of Vander-'veer Voorhees;Y llomewooii'lll., asslgn'or to v Y' l Standard 0il Company, Chicao,

Applicut netonnet-194e; seim1 nassaui i i-eclaims- 46141964254 This inventionrelates'to avsy'stemforhandling abrasive vpowderand it pertains more particug larly to ther-handling 'of powderedcatalystlin f manu-fl" hydrocarbon 'conversion processes Afor the spects but a seriousproblem in powdered .catalyst systemsvislthatI of handling-,the abrasive powder'and'particularly introducing this powder pressure. Ordinary pumps or .b1owers cannot be used for this: purpose because when powdered surfaces quickly become eroded and worn away by the abrasive action ci'v the catalyst. A pressure screw'of gradually diminished pitch has from a zone'of low pressure to a zone of high,

beenproposed as a solution to this problem but the friction losses insuch ascrew are enormous and here again the erosion due to' contact of catalyst particles with movingl metal surfaces makes it necessary to replace metal'parts at very short intervals. Pumps of the. pressure screw type are also .subject t'o thedisadvantagethat they are mechanically very inefficient and they cause an. agglomeration of the catalyst which seriously impairs'its activity. An lobject of my?- invention is to provide a means for handling 3d ment of my catalysthandling means. Y

powdered catalyst i which -willvavoid the above diiculties.

Some appreciation has been foundiwhich'twill tand 1 `ip 'underthe" suffisamevlikewise applicable to. the handling of other abraof this problem may be ap-y parent when it is considered'fthatfina 20,000 f barrel per dayl catalytic cracking-plant'it maybenecessary to handle about`20,000 tons per dayk of powdered cata1yst. V This ypresents `a chemical engineering problemof considerablemagnitudef subunits pioyed as the'seal arounda reciprocating solid Vmetalpistombutin this case that portion of the f pistonl which actually comes in contact with pow v dered catalyst vis'not subjected to sliding friccatalyticcrackingsystem.

Inpracticing my invention I aerate the p ow'- x dered catalyst `to such an extentv that it may behandled as a fluid. I then compress this iiuid and transierthe compressed aerated powder from v a low pressure zone to a highp'ressure zone while however, in connection with vitsapplication toa v preventing the powderl from contacting any metal 1 surfaces which are exposed to sliding fric-4 tiong These'compressing and transferring oper- 1 ations are eiected in a reciprocating surge pump Which is provided with a molten metal seal. In

one embodiment 'of the invention there isa surging' jb`ackg and forth ci.' the molten metal itself in ajpump chamber, the molten vmetal acting as; a Qpiston-ffor; drawing aerated catalyst 'into the Vpl'lmp chamber, compressing the aerated mixture 'and then-discharging the aerated mixture to the j .zone `ofY high pressure. In another emb'odimentf t of the invention the molten metal is merely emtion. j The invention will be more clearly understood VEby 'reference to the accompanying drawing which 1:; to snmreferamyabout 3:1.

' forms a part oi.' this speciiication and'in which: Figure Lisa' diagrammatick flow sheet of a catalytic cracking system employing one embodi- Figure 2 is azmodica'tion orthecatalyst handling meanswherein the solid metal piston does not come into contact .Withthe vpowdered-cata j ly's'tu" '11i f l '1f While the invention isapplicable to' anyhyfidrocarbon conversion .process Vsuch as dehydrof genation; hydrogenation, aromatization; isomerization,- all'ylation, gas-reversion,freforming. iSdterminada-,nvm beheren; described asap, i' f plied-to 'theicatalytio cracking of heavy hydm .carbone-such 'as gas 'oils .for the productionofv highoctaneinumber motor fuel.-

mfcatalysispfferably if the l i is oilfcharging stockisintroduced'thmugh (Pfand passed through, |l or pipe stm f l2 iid-transfer line 'I3 in which thevaporivzed gas Y! Y beataDressureof'aboutfatmpsphecto pounds-01" m0195961' Squalef inch, preferably 5150111; r10pounds persquare inch, and ata tem- Peretureof about-875 to 11oo y preferably 5*1-*51925 t3950 'F- Powdered-catalyst from Cham'bel, I4 -isintroduced into transfer-'11nf lav type such as acid treated bentonite, an aluminasilica gel composition or a natural or synthetic zeolite in which the alkali ions have been leached by acid or replaced by aluminum. Other forms of siliceous and aluminiferous materials, natural or artificial, may be employed. No novelty is claimed in a catalyst per se since such catalysts are well known to the art and a further description of such catalyst is unnecessary.

The average particle size of the catalyst is preferably from about 10 to 80 microns.l When compacted such catalysts may have an apparent density of about .6 to .7--a cubic foot may weigh about 40 to 45 pounds. However, when this catalyst is slightly aerated it behaves as a fluid, the density of which depends upon the catalyst particle size and the linear velocity of the aerating fluid. At linear aerating fluid velocities of the order of about l foot per second or less the catalyst may have a density of about 25 pounds per cubic foot. With linear aerating vapor velocities of about l to 2 feet per second the catalyst may have a density of about 10 to l5 pounds per cubic foot. By varying the linear velocity of the aerating vapors the density of the fluid catalyst mass may thus be controlled and this fluid mass of powdered abrasive powdered catalyst material can be handled as a heavy gas or liquid. l

The hot hydrocarbon vapors carry the catalyst introduced from chamber i4 into reactor I5 wherein catalytic conversion occurs. This reactor is designed to give the desired time of contact with vapors and catalyst holding time. For catalytic cracking the contact time may be about 5 to 25 seconds. preferably about 10 seconds, and the catalyst holding time may range from a minute to l5 minutes or more. The vapor velocity in the reactor may be about l to 3 or morev feet per second.

When in balanced operation, reaction products carry the powdered catalyst out of the reactor at the same rate as powdered catalyst is introduced into the reactor. 'Ihe withdrawn reaction product-catalyst mixture is passed by line I6 into cyclone separator Il from which reaction products are passed by line I8 to a suitable fractionation system. It will be understood, of course, that a plurality of cyclone separators may be employed in series for obtaining more complete catalyst separation and that Cottrell precipitators or other suitable means may be employed for removing the last traces of catalysts from the hydrocarbon stream.

Catalyst from separator I1 is passed through star feeder I9 to receiver 20 of which the upper part functions as a stripping section and the lower part as a catalyst accumulator. `Inert aeratng and stripping gases may be introduced through line 2| and withdrawn through line 22, preferably leading to line I8 (by connection not shown). Additional stripping gas may be introduced at the upper part of chamber 20 so that aeration in the base vvof this chamber may be controlled to give the desired catalyst density which may be about 10 to 25 pounds per cubic foot.

It is now necessary to transfer this powdered catalyst from accumulator tank which is at relatively low pressure to a regenerator system which may be at about 10 to 50 pounds higher pressure. To further complicate the problem, the catalyst at this stage is at a temperature of about 800 to 900 F. Ordinary pumps are utterly useless for effecting this transfer to a zone of higher pressure and. as above stated, the screw pumps of gradually diminished pitch are highly inefficient and objectionable. A feature of my invention is the provision of a new improved type of pump for handling this hot powdered catalyst.

My pump comprises a chamber 23 which has at its top an inlet valve 24 communicating with collector 20 and an outlet valve 25 communieating with surge drum 28. Valves 24 and 25 are at the top of chamber 23 and the cross-sectional area of these valves takes up asl nearly as economically possible the upper area of chamber 23. Chamber 22 is heavily insulated and may be provided with a heating element 21 for maintaining the desired temperature therein. Extending through packing gland 28, which may be made of a graphite-asbestos composition or other suitable material, is a reciprocating piston 29 driven by connecting rod 30 from any suitable source of power (not shown). Between the piston and the walls of chamber 23 there is a seal 3| of molten metal which may be lead but which is preferably an alloy of lead with tin, bismuth, antimony, zinc or other metal known to the art for such use. Mercury might be used as the molten metal but it is undesirable because it has a relatively high vapor pressure at the temperatures in the pump. The liquid seal should be one that does not wet the catalyst or deleteriously affect it.

In Figure l the piston is shown in its lowermost position having been moved downwardly to draw in a charge of aerated catalyst through open valve 24. As the piston is moved upwardly valve 24 is closed and the fluid-like aerated catalyst mixture is compressed until the pressure is sufficient to open valve 25. vContinued upward movement of piston 29 expels the compressed aerated catalyst mixture through valve 25 to surge drum 26. When the piston again moves downwardly, valve 25 closes and the cycle is repeated.

It should be noted that the distance from the packing gland to the top of the piston in its lowermost position is slightly greater than the effective length of the piston stroke. This is of importance because it prevents any catalyst particles which might adhere to the piston from reaching the point at which sliding friction occurs. The molten metal seal 3| is of so much greater density than the catalyst that it prevents any catalyst material from reaching the packing gland.

While a single catalyst pump is shown in Figure 1, it should be noted that duplicate or triplicate plunps would be used in actual operation in order to maintain smooth continuous operation. The speed at which the piston moves upwardly in each pump is regulated to give a substantially constant rate of4 catalyst charge to surge drum 28. The design of driving means to accomplish this end is a matter of engineering skill and will, therefore, not be described in further detail.

From surge drum 26 the aerated catalyst mixture is introduced by line 32 to regenerator 33 wherein carbonaceous material is burned from the catalyst by air introduced through line 34. The regeneration is preferably at a temperature of about 1000 to 1050" F., the regenerating gas contact time is preferably about l0 to 15 seconds and the catalyst holding time in the regenerator is preferably about l to l0 or 15 minutes. The pressure in the regenerator may vary throughout Y a considerable range but is preferably about to` 25 pclmds per square inch, and commonly about pounds above the operating pressure existinginseparator Il.

The regeneration gasfcatalystmixture is thenl passed `through line ll-fto cyclone separator 3B from which regeneration gases are vented through line l1. I-Iere again-it should be understood that catalyst from the-regeneration gases.

, Regenerated catalyst passes through's'tar'feeder V Il to accumulatorV chamber 38 which is provided with a 'stripping section andan aerating lsection a .number'of cyclone separators may be usedin t series orparalleland other .suitable means may be employed for recovering the last traces of in the same way that was described in connection I with chamber 2t. The aeratingv gas inthiscaseis'l preferably a ilue gas introduced through line 40'.'

and withdrawn through line 4 I g Regenerated catalyst is returned from accumulatortank 39 to catalyst feed chamber I4 by meansof-catalyst pump 42 whichtunctions in exactly the same manner as the catalyst pump between chamber 2li and surge drum 26.

" Where there is a tendency for catalyst particles to adhere to the piston surface or where the pump structure las hereinabove described is for any other reason undesirable, I may employ a catalyst pump of the type illustrated in Figure 2. Here the pump .chamber 43 is provided with a-lateral packing-gland 44-throughwhich piston 45 extends. Chamber 43 contains sufficient molten metal 46 so that when the piston reaches the end 1 oi' its. stroke inthe' chamber the molten metal will substantially iill the chamber. As the piston fis moved -tothe right-,the liquid molten metal level-falls fand thus drawsinto chamber 43 a charge of aerated powdered catalyst. 0n the restroke of 'the piston the liquid level ris'es which closes valve 4l and compresses the aerated mixture 'untily ls'uicierit pressure isv yreached to open valve 48 after Which continued rising of the .liquid level inv chamber 43 displaces the aerated catalyst to thezoneofhigher pressure.

C The reciprocation of piston 45 should be relatively slow in order to prevent turbulence in the moltenl metal. A kcomplete stroke oithe piston may require from 5 to' '60 seconds depending somewhat upon size and design ofthe pump. In order to" avoid turbulencel may employ vertical `baffles 49 ora honeycomb baille [structure to inzsure uniform vertical' surges of the molten metal and toavoid turbulence therein. It is,v of course,

. important to prevent any .of the molten `metal from being carried to the .high pressure zone with expelled catalyst material but this. willnot prestarted up. Y

While I have disclosed preferred embodiments oi' my invention it will be understood that the invention is not limited to the details hereinabove set forth and that many modications and equiva lent structures will be apparent to those skilled ,n inthe art from the above disclosure. The invention is primarily applicable tothe handling of powdered .catalysts in hydrocarbon conversion systems but broadly it `relates to the handling of abrasive powders and particularly to the transferring of abrasive powders from a low pressure zone to a high pressure zone.

-I claim: 1. A system for handling a powdered abrasive solid material which comprises a collecting chamber means for introducing a powdered abrasive solid material into said collecting chamber, means for aerating vthe solid material in said chamber whereby the powdered solid behaves as a fluid, a pump chamber, a valve connection from said collecting chamber to said pump chamber, a discharge chamber, a valve connection between said pump-chamber and said discharge chamber, a reciprocating piston in said pump chamber for drawing aerated powdered abrasive solid'material from the collecting chamber into the pump chamber and for discharging said material from the pump chamber to the discharge chamber and a molten metal seal in said pump chamber for predered solid into a compression zone, increasing the pressure on the aerated powder in said compression zone while preventing contact between powdered solid and metal surfaces which may be exposed to sliding friction, and dischargingthe compressed aerated powder into a high .pressure zone.

4. 'I'he method of claim 3 wherein contact between abrasive powder and metal surfaces subject to sliding friction is prevented by a molten metal seal.

`5. The method of claim 3 wherein the compression and :transfer of the aerated powdered sent a-serious problem in view of theyvery great l density ci' themetalupongwhich the catalyst floats. Any inert .layer ofcatalyst which may form on thesurface. of 'thefmolten 'metalis of i cour-se, immaterial butthe gas in which the catalyst is vaerated should not'v include oxygen since it is desirablev toavoid `oxidation' fof the molten v mtal. Theaerating gas introduced through line 2i 'is' thereforepreferably va light hydrocarbon gas andthe aerating gas vntroduc'edfthrough line t 40 isprefera'blyaue gas;k

It 'will be'unders'to'om'of course, that thev lpump shown. in Figure 2 willbe heavilyinsulated' and tnat'lii; mayalso .be Vprovided with suitable .heating means.-T -The heating means. are notso essen- 1 Vtial infthis.modiilt'zation.i however, because .the hot catalystwmch-isbeme" bumped andere keep the molten metal from solidifyingl .the system is shut downfor .any reason this molten metal abrasive solid is eiected by reciprocating surfaces of molten metal.

, 6. In a hydrocarbon conversion 4system employing powdered catalyst which must be transferred from a low pressure zone to a high pressure zone the method of eilecting such transfer which comprises aerating said catalyst so that it behaves as a fluid, compressing said iluid while maintaining catalyst particles out of contact with metal surfaces which are subject yto sliding friction and discharging said compressed aerated mixture to the high pressure zone While preventing catalyst particles from contacting said surfaces subject to sliding friction.

7. The method of claim 6 wherein contact between catalyst particles and metal surfaces subjected to sliding friction is prevented .by molten .metaL 8. A hydrocarbon conversion process which 3 may be withdrawn through line Il and. a fresh Acharge of molten metal may be introduced through this .same -line when .the `system is again comprises heating a hydrocarbon oil to reaction temperature at reaction pressure. introducing powdered catalyst into the hot oil stream. contacting the hot oil and catalyst to effect conversion of the hydrocarbon, separating powdered catalyst from the conversion products. aerating the separated catalyst so that it will behave as a fluid. compressing said aerated catalyst without permitting said catalyst to come in contact with metal surfaces subject to sliding friction, introducing said compressed aerated powdered catalyst into a regeneration zone, burning carbonaceous material from the catalyst with oxygen in said regeneration zone, separating catalyst from regenerated gases. aerating regenerated catalyst so that it behaves as a fluid, compressing said fluid without permitting the catalyst to come in contact with metal surfaces subject to sliding friction and returning said compressed aerated catalyst for further mixture with hydrocarbon oils.

9. The method of transferring aerated powdered abrasive solids having the characteristics of a uid from a low pressure zone to a zone of higher pressure which comprises admitting said aerated solids into an enclosed space intermediate between said low pressure and high pressure zones, closing the passage connecting said low pressure zone with said enclosed space, forcing upwardly into said enclosed space a plunger substantially occupying the volume of said space and sealed relative to the walls thereof by packing means to prevent the escape of said powdered solids, thereby forcing said powdered solids into said zone of higher pressure, and separating said powdered solids and said packing means by a layer of uid metal, the depth of which is at least equal to the length of stroke of said plunger.

VANDERVEER VOORHEEB.

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