US1940955A - Process and apparatus for refining mineral oils - Google Patents

Description

W. G. LAIRDy Dec. 26, 1933.

PROCESS AND APPARATUS FOR REFINING MINERAL OILS Filed April 4, 1927 MQQQQ Patented Dec. 26, 1933v -1- ,UNITED PTNT This Y rRooEssAND 'Arrnaaros Fon REFINING `v`ivnNEaAit oILsn w Y VWilbur efraim. New York, N. Y., assigner to' Heat Treating Qonrpany, NewYork, corporationjof Delaware Appucatan'iiapfil 4, 1927.

' 'ji 1o claims.' ',(ol. 19e-69) invention` relates to a process andjappa ratus ffor refining mineral oils. "more particularly to the art of converting crude or other mineral y oil products into gasoline like material.'

The present invention isA Van improvement on the well known tube and drum oil cracking systems in Which oil to be cracked is 'passed under heated coil `mounted in affurnacatheninto a large .drum or still where vthe oil remains for a considerable time in order to allow the cracking reaction to complete itself.

`Probably the most outstanding disadvantage met with in the use of such cracking *systems is the accumulation o f `carbon in the'drum and often inthe dephlegmator which is used to `ex-V tract theheavier products from ing the accumu I the vapors leav reaction chamber. This carbon orcoke lation must beremoved at very frequent intervals, which necessitatesfthe shut down of the app aratus with subsequent cooling before the Workmen can removethe hardened `carbon from the .drum With pick and shovel or before boring or other devices can be used to remove the same.

In the use of the usual systems andoperating methods the principal lossire'sulting from` the accumu lation of carbon is the time lost in coolving the apparatus so thatthe carbon can be removed and that `lostoin starting up the appa'.-

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ratus again. Time consumed V in these operations l cuts down the productionof the apparatus, While the operating cost increases. If it is assumed'for example that the cracking apparatus Vmust be shutdown for several days each month toremove carbon vthe .decrease inproduction will be from l0 tof25%,whicl1 if avoided would result inA a `substan costs co tially equal prent; because the operating ntinue just the same. Y v- Anotherv defect vin present apparatuses and mode of operating the same is that where carbon is continuously allowed to :accumulate in the cracking drum the available storage for' hot oil becomes less andiess so that they time allowed for the cracking reaction becomes shorter 'as-the. run continues. I f

In present systems also the cracking operation is allowed to extend into .the dephlegmator'which is commonly used to receive Vanors'frorn` the cracking orgreaction drum. Thisris particularly true after acertain amount of carbon; pitch and tar is allowed' to collect in the 4reaction drum. Cracking inthe dephl'egrnator naturally produces carbon.

etc., which-cakes on the metalsurfaces or is returned' to the-heating furnace with the reiiux c ondensatze and thereby promotes the acand which may be a mineral oil of any type such as an asphaltic or parain oils, ris introduced into rkto point out that the oil in the heat exchangers 4 N.v y., a

- seriaiNo. 180,'723

cumulation of carbon and coke in the furnace tubes". l j Wherefore the present invention hasl for its object: .f

The Aprovision of a process and apparatus wherein the Variousdisadvantages enumerated aboveare overcome: 1 -f v The provision of an apparatus adapted to carry out the novelprocess pointed out hereinafter;

The provision of an apparatus'adapted to opero ate continuously at high .temperatures and pres-v sures: n "The provision of an oil .cracking apparatus adapted to provide a constantstorage-capacity for the oil undergoing cracking; To provide a continuous process for the crack,- ingof mineral oils as distinguished from processes in which kit is necessary to shut down to remove carbon; f f N v H v`Tofprovide a cracking process in which a constant volume of oil may vbe maintainedinthe cracking zone; and. f f y lTo provide a process-for crackingmineral oils in which the cracking ofthe oil isv restricted to the reactionfzone and not'allowed togo on in l the dephlegmator.

These and other objects will be apparentzfrom the following detailed description taken in'. connection with the accompanying drawing* in Whicru-L- Y. y g f 85 The figure is a diagrammatic elevational view partly in section of an apparatus-in'y accordance' with the invention Vandin whichV the Inovel `process may be carriedout. l i 'f VVReferring to the drawing the oil to .be cracked base crudejoil, distillate l or residuumgfshale oil, oils resulting` from the distillation of coal yor a mixture of any of these the apparatus vthrough v95 the'pipe 2 by any convenient means such asa pumpV (not'f shown). Thef'oil thus `vintroduced passes' downward through a series of heat interchangers 4, mounted on a dephlegmating and The detailsof construcdescribed in a Ypending application Serial No.. 125,893,y filed July'BQ, 1925'. For present/'purposes .it Will be suicient 105 passes in heat exchange but out of contact with vapors from a cracking chamber described later.-

vThe pipe 8` discharges 'into va tank `10 from which theV preheated oil passeslby a valved pipe v12 to a tubular'cracking furnacef14. `where the oil 110 is heated to or above the cracking temperature under pressure. This furnace heater may be of any of the conventional pipe still furnace types.

VThe highly heatedv oil leaves the heater 14 by a In order to make proper connections with inlet and outlet pipes the ends of the chamber 18 are provided with central stu'ng boxes 24. At the inlet end the pipe 16 connects through a T with a perforated distributor pipe 26 which extends through the stuffing box 24 and into the chamber 18 a considerable distance. At the oppositeend of the chamber a vapor outlet pipe 28, arranged as shown, to extendabove the liquid level in the chamber 18, passes through the stuiling box 24 at the outlet end of the chamber. Within the chamber is placed a number of metal balls 30, which, as thechamber rotates, Akeep the carbon formed and deposited in the cracking operation from accumulating on the walls.

From the rotatable reaction chamber 18 the vapors pass by the offtake 28 which is connected to a valved vapor pipe 32 discharging into a chamber 34 forming the base of the tower 6. This chamber may or may not be constructed integral'with the dephlegmating tower, but for convenience is shown so constructed. The vapors entering the compartment or chamber`34 are sists of an .open ended pipe Vextending through and above a partition plate 42 which forms the upper vpart of compartment 34. These vapors thenpass through a series of alternately placed bubble cap trays 44 and heatinterchangers 4, so

'thatthey alternately pass through condensate maintained-on the trays and in heat exchange with charging stock passing through the exchangers 4. During the passage of the vapors through these various condensing and rectifying stages intheftower 6 the condensate produced in the units 4 flows 'counter to the vapors back onto'the bubble cap tray next below, while the condensate on the trays passes by conventional 'overflow pipes'onto the next bubble tray below and from'the lowermost tray into the condensate trap'formed bythe pipe 40 on the partition 42 Between each bubble tray in the tower is placed ay dead plate 46 which causes vapors to pass through suitableopenings (not shown) into the heat exchangers 4, from which the vapors not condensed pass 'by other openings into the space below the bubble tray next above.

While the condensate collecting on the partition 42 has a temperature considerably above that of the end point of gasoline it nevertheless contains absorbed gasoline (2 to 4%) which may be stripped therefrom by bubbling a gas through the condensate. This is accomplished by means of a gas distributor 48 mounted above the partition 42, gas being supplied hot or cold as desired from any suitable source by the valved pipe 50. Stripped condensate is withdrawn by a pump 52 through a pipe 54 and introduced into the advancing charging stock in one of the exchangers 4 by a pipe 56. The invention is not limited to the particular point at which the reux condensate is mixed with Vthe charging stock, since such mixing may be made in any of the exchangers 4, the tanklO or line 12 as desired.` It is preferred to maintain a considerable'body of condensate on the partition 42 in order to secure effective stripping of the gasoline therefrom. This may advantageously be accomplished by controlling the speed and operation (starting and stopping) of the Vpump 52' by an automatic device controlled in turn by the level of the liquidV condensate in the chamber abovethe plate 42. n

The vapors and gases remaining uncondensed in the tower 6 are conducted by a valved pipe 58 to a condenser 60 which may be cooled by ico water or by cold charging stock before it enters the exchangers on the tower 6. The condensate thus produced together with fixed or non-condensed gases pass by a valved pipe 62 to a trap 64 fromwhich the condensed product isV drawn by a valved pipe 66 and the gases by a pipe 68. The fixed gases may be scrubbed and sent to storage by a valved pipe '70 or a portion of lthem (scrubbed or not) may bemixed with the charging stock by means of a booster '72 and pipe 74 which connects with the charging line 2. Y

In the operation of the apparatus a body of oil is accumulated and maintained in the reaction drum 18 to a vlevel slightly above the axis so vthat the oil and vapors from the pipe still 14 are disiis tributed into such. body by the distributor pipe 26. This body of oil, from the Very nature of the process. consists of aA mixtureof hydrocarbons (including absorbed gasoline), polymers, etc.. tar, pitch, Vcoke and carbon. Because of the tendency of the tars and carbon to settle out of the mixture (even when the chamber 18 is rotated) provision is made for taking olf the cleaner material by a'valved draw ofl pipe '76 which passes centrally through the vapor oiftake 28 and discharges directly into the compartment 34. The heavier material including the carbon and'pitch in suspension is withdrawn by asimilar valved pipe 78 centrally placed in the opposite end of the' chamber 18, this pipe however being bent downward inside the chamber so as to draw oil from the bottom thereof.. Oil and carbon withdrawn by the pipe '78 areY discharged into a stripper or concentrating stillj80 where the lighter products are distilled therefrom by introducing a gas through a gas distributor 82 mounted in the bottom of this still. The distillation is carried out at the same pressure as that used in the cracking still 18 so that the vapors evolved may be delivered either by a valved pipe 84 (by means of an aspirator) into the transfer line 16 or by a valved pipe 86 into the vapor line 32.

Which pipe to use will largely depend on the temperature of the vapors leavingthe stripper 80 and/or the viscosity of the oil in the chamber 18 which should be maintained belowl the saturation point of the tarry matter therein. The

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- to the Aextent distillation in thejstill L'is preferably carried of leaving only 4oil 4of the fuel oil type' together "with r'the suspendedvcarbom tar, pitch, etc., this mixture being withdrawn through al valve pipe 88 Vinto avcooler 90 from which the cooled mixture is passed to a'thickener A92 kby a pipe '94. `The oil-carbon mixture enters atthe top andnear `the center of thethickener, which by proper operation produces la'rapid separation ofthe oil from the carbon,t heoil overflowing into a troughiQG Yfrom which it is drainedby'a valved pipe 98,while the carbonis discharged at the bottom through a pipe bythe aid of-'a steam Aorgas ljet from 1a pipe10`2'.` The oil delivered lby the `pipe 98,r may be reintroduced into Vthe feed line at any point'or may be'used in the chamber 18 to carry out more carbon, etc., but it is usually too heavy for these purposes and is preferably used as fuel oil.

The relatively clean oil delivered to the chamber 34 from the cracking vessel 18 mingles with the oil sprayedhfrom the distributork3`6 and the condensate produced thereby. This Ymixturecontains an appreciable amount of absorbed gasoto draw oil from Athe chamber 10. Gas from the booster '72 may alsobe used in the injector 111 'for forcing the oil through the heater. It is preferred to maintain a substantial body of oil labove the distributor in chamber 34, which may be done automatically in the manner referred to above in connection with the oil level'maintainedrabove the partition 42; n

'I he useoi` a gas, particularly the non-condensed gasjfrom the nal condenser, with the feed oil is especially desirable whensuch-stock as gas oil is used for cracking, due Vto the fact that a lower vaporizing temperature is secured inthe heat interchangers 4 where heat of ycondensation of vapors `from the still may be directly transferred to heat of vaporization lof the charging oil. Where, however, itis desirable to maintain a strictly liquid phase ofthe lcharging oil'theA gas circuit may be omitted-` A Y 'In carrying out the process the operation is `rendered continuous by the use of the ball'mill type reactionvdrum 18V in" such a manner asto keep the carbon and coke, formed by cracking of the oil, in a fine stateof subdivision so that it may be removed with the oil withdrawn'by pipe 78. The balls 30 which ymay be made of iron or steel should be suiciently large and heavy tofunction properly in grinding up the carbon and coke produced in cracking and a sufficient number should be used to give intimate rolling contact with' each ,other andthe fulllength of the bottom of the drum. As the drum is rotated with the metal balls 30 arranged in the manner indicated the walls of the rdrum are kept Yfree from any coke deposit and therefore the full capacity of the chamber is always in use.

The rotation ofthe drum may be either continuous in one direction or oscillating'. The osn lcillating'motion may be progressive, th'atis; a rotation flrst in one direction'vthrough a definite angle' then in the otherv` direction through a lesser or greater angle so that eventually acomlejector type so n charging stock it'may thermostat may plete rotation is made rotated )at any reasonablefspeed but u'sually'a" Very slow rotationA is sufcient to maintain the carbon insuspension and prevent coking on the walls. Infact an intermittent rotation of lsay The drum may alsobeVv is rotated for one day each week the carbon ac'- 'y cumulation' can .be completely 'removed without the necessityV of vever shutting down exceptfor fother causesr such as inspection or repairs.- The `rafteof rotation vor the frequency of the periods .ofrrotation will of course vdepend to lsome extent on the temperatures and pressures used in the lcrackingv apparatus or'. with the relative amount of unvaporized oil in the system which lmay, Vif found --desirable be all withdrawn by pipo '78. l l

, If the'intermittent rotation of the drum 18 jis practised the Yvalve in pipe 76 may be closed duringl rotation rand that in pipe r'78 left open so that the carbon being removed from the balls 30 and walls of the chamber will be more rapid# Y ly washedout.y During such a period the valve in pipe 84 may be open inv order to increase'the amount and therefore the fluidity of the 'oil put through the drum 18. The connectionv between pipe Stand 16A is preferably of the aspirator or y that the flow of the fiu'idsin pipe 16 will draw vapors from the pipe 84. Such connections are common and therefore notl shown.

When continuous rotation of the reaction aus noV

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chamber is practised the intake end of the pipe 76 may be screened if it is found that -too much carbon is being withdrawn by thispipe dueto the agitation in chamber 18.:V

In order toavoid contamination and stoppage with carbon of the dephlegmating and rectifying'part of the apparatus'it is an objectof the` present invention to .restrict the cracking operation-to the pipe stillfurnace lfiandl the drum 18. 'Sincethe oil and vapors leaving Athevcracking chamber by pipes y'76 and 32 are considerably above the cracking temperature provision is made for their cooling by vtheuse of a relatively cool oil from 'the spray 3 6 and the vaporization producedy by the stripping operation'in the lower part of chamber 34., If a crude oil is being used asa gasoline hydrocarbons by being all passed'through "the distributor 3,6v in Vwhich event the valvev in 'pipe '12 would be be completely-topped' of 'A y 'no' e, i

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used to control the valve in pipe 38 so that the quantityof coolingr fluidwill be governed bythe outlet temperature. This will also tend to vgive a constant perfo rrnaricev,by4 the-rectifying tower andtherefore moreuniforrnproducts.

The rotary crackingrchainber 18 may beused in aconsid'er-ably different manner 'to that 'described above by providing two such chambers so arranged that one may be cut out ofthe systern when the other is use. If this is vdone the stunng.' boxes yare preferably substituted vby langesand no grindingelements' will be placedY in the chamber inpirci-iit. When a reactionV chamber has been in circuit rfor some time and hasaccumulated considerable carbon it is cut out and another cut in by a proper valve system. The one out of use isunbolted from the connecting pipes and either rotated in place or rolled on rails, which may take the place ofthe rollers 20, to a cleaning` system into-which it is then connected. This system will comprise. a means similar to the one shown for rotating the drum 18 together with oil storage and a carbon lter or separator. After the druin to be cleaned of carbon is placed in the cleaning circuit a number of balls similar to the balls 3) are run into it and the drum rotated to pound. up and free the carbon and coke collected therein. During rotation a stream of oil o r water is run .from a storage tank through the drum to carry out the pulverized carbon and coke which is continuously separated from the oil in any convenient inanner such as by means of a thickener. The oil is used over and over for this purpose. The use of two cracking chambers with one always in circuit gives ample time for the one out of circuit to be cooled, cleaned and replaced while the other is collecting carbon, coke, etc. above operation it is understood that either vor both of the withdrawallines 767er '78 may be used as long as possible to withdraw oil and/or oil with carbon in suspension. The above described method of cleaning a reaction drum may of course be used where only one drum is available in the cracking unit. n

The eiiiciency of the process is greatly increased by the use of the stripping chambers orv stills 80, 34 and that above the partition 42,

` by which all gasoline hydrocarbons are removed ,per square inch isysuilicient. y -the yapparatus may be maintained under differfrom the oil either before it is reintroduced into the heating tubes or discharged as residuum.

Furthermore sincethe charging stock is to contain no gasoline hydrocarbons or is to be freed of such, a larger percentage will be cracked to gasoline in accordance withthe Vlaw of mass action. Upon vthe same principle the introduction of the non-condensed gases from the rsystem into the charging oil tends to prevent the formation of such gases during the cracking of the oil. Ii crude is vbeing topped as referred to above,

gas from pipe '74 may be introduced directly into the line l2 beyond the valve. For'the same reason that non-condensed gases are passed with the charging stock they are preferably heated.

and used in the chamber if vapors therefrom are putin the line `16. l

The cracking apparatus may be maintained under anydesirable pressure consistent with the proper safety factors for the-materials of construction, but ordinarily from 150 to 300 pounds Certain parts of ent .pressures than other lparts (such as a progressive reduction) by the proper manipulation of4 the valves in pipes 16, 32, 76, 58 and 62. The booster 72 may be used to create a subatmospheric pressure in the condenser 60 and the tower 6 if desired.

Under certain operating conditions it may be desirable to use a plurality of ball mill `cham-- bers in series in order to effect the desired cracking of the oil or to give additional cracking capacity.

In order to prevent corrosion and carbonization of the steel of which the apparatus (including the balls 30) is constructed, it may be tin, chromiumor aluminum. i e

In the I The various parts of the lapparatus which would be exposed toradiation losses'are preferably covered with insulation., Besides having a coat of insulation on the chamber 18, it is also preferably set in aV housing constructedor lined with insulating Vmaterials so as `tocut down the heat loss.v These various features are not shown in the drawing inorderto avoid complicating thefsa'me.

It is understood thatthe metal vbal1s30 may be substitutedbyelements having other shapes or rods, etc., without departing from the spirit and scope of the invention, the broad aspect being theemployment of such loose elements as will free the carbon from themselves and the Walls of the chamber'and/orjpulverize'the same therein. e Y

Various other features of..constructionY and operation may be resorted to Without departing yfrom the spirit and scope of the present invention, such for example as not returning any part of the residuurn from the cracking chamber to the heater, using a by-pass around the chainber 18 to the chamber 34v forza portion of the oil from the heater 14 or constructing the reaction chamber 18 with other than acircular cross section. lIt may be made polygonal for example. Y.

`Having thus described the preferred form of the invention, what is claimed as new is:

l. An apparatus for distilling Yoils comprising an unheated rotatable cracking still, a plurality of metal balls in saidstill, aicooling chamber, means for passing vapors from ,said still Vto said chamber, means for spraying oil into said chainber to cool said vapors, a fractionating tower, means for conducting vapors fromsaid chamber into said tower, means to rotate said still and means for heating oil from said chamber and for conducting the heated oil into said still.

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2. The process of cracking oil ina heating coil and in a rotatable externally unheated reaction drum containing freely-moving; `loose abrading elements, which comprises passing oil through the heating Vcoil and directly into the drum, heating the oil to a ycracking temperature in said coil, rotating said drum to causethe loosening and grinding by said elements ofthe residue produced from cracking said oi1,. Vand withdrawing from said drum the products Vof the cracking reaction whilethe drum is4 in rotation. Y. .Y

3. The process of` cracking hydrocarbon loils for the production Aof .gasoline-like products, which comprises passing the oil in-a conned stream under superatmospheric pressure through carbon or coke and to remove any coke deposited Von the Walls thereof, withdrawing oil residue from said chamber, conducting oil vapors from said chamber into a dephlegmating zone and subjecting the vaporized oil constituents to de phlegmating conditions in said kdephlegmating zone, to separate the gasoline-like materials from higher boiling vapors. Y

4.In the process of cracking mineral oils for the production of` gasoline-like products therefrom, in which a body of oil is maintained under cracking conditions of temperature and pressure in an externally unheated rotatable cracking chamber containing a plurality of loose 'metallic abrading elements', the improvement which comprises rotating said chamber, causingsubstan-V tial vaporizationof the oil Vin said-chamber, conl ducting vapors from said chamber to a'fractional condensing Zone wherein a reflux condensate is produced suitable for cracking, heating reiiux condensate from said zone to cracking temperature, and passing the products resultingl from the Y heating of said reflux condensate while at a high temperature into said rotatable vcracking chamber. 1

5. In the process of cracking 'mineral oils for the production of lower boiling point products therefrom in `which a mixture of oil and gas is passed through a heating Zone in which the mix- `ture is heated to the cracking temperature of the l oil and the resulting products from said heating introduced into a body of oil maintained at a cracking temperature in an externally unheated y rotatable cracking still containing a plurality of relatively heavy abrading elements, the improvement which comprises rotating said still to prevent the formation of cokeon the still walls by abrading elements of greater specic gravity than the oil to be distilled, which comprises subjecting a body of oil in said chamber toa distilling temperature sufficient to vaporize substantial portions of the oil, passing thevapors evolved from the oil in said chamber into a cooling chamber, distributing oil to be distilled intofthe'vapors insaid coolrelatively cool fluid.

ing chamber whereby said oil is topped and said. vapors cooled, passing the resulting cooled vapors into a rectifying zone and passing the topped oil through a heating zone and into the body of oil undergoing distillation in said vaporizing chamber.

'7. The process ofcracking oil in a heating coil and in a rotatable externally unheated reaction drum containing freely-moving loose abrading elements which comprise passing voil through the lheating coil and Idirectly therefrom into the drum,l r

heating the oil to -a cracking temperature in the said coil, rotating said drumto cause the loosen-A ing and grinding of said elements of the residue produced in cracking said oil, withdrawing the vapors produced in the cracking operation from K I said drum during the rotationv thereof and conducting them into a fractionatingzone, and immediately Acoolingthe vapors withdrawn fromy said drum to a temperature below the cracking temperature by contacting them with a cooling Y fluid prior to their fractionation in said fractionating zone. Y

8. The process defined by claim 3v in which the vapors conducted from said chamberr into the dephlegmating Zone are brought into intimate contact with a relatively cooler oil whereby the temperature of the vapors is reduced below the cracking point thereof. p

9. The process defined' by claim 4 in which the vapors conducted vfrom said chamberto said fractional condensing zone'are cooled to a temperature below that at which further cracking takes .placeby contacting therewith a relatively cool fluid. s

, v10..Th'e process defined by claim 2 in which. products ofthe cracking reaction withdrawn `from said drum are immediately cooled belowv the crackingv temperature `by lmixing them with a WILBUR G. LAIRD.

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