US1711351A - Art of cracking hydrocarbons - Google Patents

Description

Aprl30, 1929. E. w. lsoM ART OF CRACKING HYDROCARBONS Filed July 21, 1927 ATTORNEY Patented Apr. 30, v1929. l i

1 UNITED STATES j, 1,711,351 PATENT OFFICE.

EDWARDW. ISOM, 0F' SCARSALE, NEW YORK, ASSIGNOR T0 STNCLAIR REFINNG COMPANY, OF NEW YORK, N. Y., Av CORPORATION 0F MAINE.

ART 0F CRACKING HYDROCARBONS.

` Application ined July 21,

This invention relates to improvements in the cracking of heavier and higher boiling hydrocarbon oils for the productionof lighter and-lower boiling hydrocarbon o ils. In particular,- the invention .relates to im. provements in such operations Where the lheavier or higher boiling oil is cracked Wlnle in the vapor phase.

' The invention is of special value and application in the production of gasolines or motor fuels having 'a relatively highv cr1t1cal compression or having yanti-knock properties When burned in the usual type'of internal combustion gasoline engine.

The products of operations in which relatively intense or relatively severe cracking conditions are maintained include, if` the conditions are appropriate, vconstituentsof special Value' as' components of motor fuels. lith many more refractory stocks, such as kerosene and light gas oil, themore advantageous range of cracking temperatures lies -aboye the critical temperatureof the stock so that the operation must be carried outsub'- stantiallyin the vapor phase if such rela'-4 tively intense or -relatively severe cracking conditions are maintained. With heavier yor higher. boiling and` less refractory stocks, suchas heavy gas oil, the more advantageous range' of cracking temperatures may not eX- ceed the critical temperature of the stock,

but even in such cases the pressures necessary to maintain any substantial part of the f stock in liquid. phase are usually extremely,

high. 4

This invention relates particularly to operations in Which the heavier and higher boiling oil is heated in the vapor phase to a high cracking temperature, that is tov a cracking vtemperature upwards of 900 F.

Small amounts of tarry'matter or carbo-v vnaceous matter formed during the cracking operation or very small amounts of very heavyconstituents ofthe stock may be carriad vinthe oil-'va or mixture as a fog or mist, but the pre ominatin'g proportion of the oil is in the vapor phase throughout the cracking operation'.y i

Such relatively intense or relatively severe crackingconditions result in the formation of a large roportion-of* unsaturated hydrocarbons. Vome of. these unsaturated hydrocarbons are objectionable as components of motor fuel, andare removed by .suitable treatment before `the 'cracked product is 1921'. serialy No; 207,476.

ready for use as motor fuel, but many of these unsaturated hydrocarbons are the very constituents which serve to give the cracked product its special value'as motor fuel, that is which give the gasoline or motor fuel so produced a relatively high critical compression or anti-knock properties. Many of these desirable unsaturated constituents are unstable at elevated temperature, even at temperatures not much above the ordinarilyk encountered atmospheric temperatures.

From the stand point of heat economy and ofjelimination of otherwise necessary operations and the'apparatus required to carry out such operations, it is desirable to frac vtionate directly the products of suchcracking operations to secure a gasoline or motor fuel fraction Which does not require further distillation orredisti'llation. In the production of gasolines or motor fuels intendedto contain vsuch desirable unsaturated constituents in largel amounts such further distillation or redistillation is doubly undesirable because 'it again subjects such constituents to elevated temperatures.

It has previously lbeen suggested to reintroduce into direct Contact with the vapors 'in the fractionating operation to which the vapor mixture from a cracking operation is subjected a portion of thel nal gasoline or motor fuel product for effecting or promoting accurate separation'of the gasoline or motor fuel product. 'This scheme of operation isof value so far as effecting or promoting direct fractionation is concerned, but Whenit is applied to 'the fractionation of the vapor mixture from vapor phase'cracking operations in which the oil vapors are subjected to high cracking temperatures it frequently results in severe and excessive losses, apparently due to thel instability of unsaturated constituents of the cracked product. When reintroduced into such fractionat-ing operations, such unsaturated constituentsare of necessity subjected to the elevated'temperatures prevailing in the frac- 'tionatingoperatiom and part of them mayeven be subjected to higher temperatures where the heavier components condensed in the fractionating operation are again heatvsuch losses, 'and which has' several further important advantages.

According tothe present invention, the heavierv or higher boiling hydrocarbon oil to be cracked is"heated in the vapor phase to a high cracking temperature and, before condensation of the vdesired lighter and lower boiling oil, the vapors from the vapor phase clacking operation are subjected to a fractionating operation where anl 'oil of which v al least a substantial portion is vaporized in the fractionating operation but which is substantially, free from unsaturated components produced in the vapor phase cracking operation or unstableat the temperatures prevailing in the fractionating operation or at higher temperatures is introduced into direct contact with the vapors pas a cooling and condensing agent. Advantageously, this oil introduced into the fractionating operation as acooling and condensing agent is of boiling range corresponding to that of the desired product, for example, in the production of gasoline it is advantageous to use a gasoline fraction as a cooling and condensing agent in thefractionating operation.

The oil for cooling and condensing the vapors in the ,fractionating' operation, however, may contain some higher boiling components, advantageously not more than about 20% of components boiling off at a temperat'ure above the end boiling point of the de-l sired product, at atmospheric pressure. Or,

. therein.

an oil containing some components corresponding Iin boiling range tothe desired product but also containing a substantial proportion of heavier-components may be introduced into thevapors in the fractionating operation as a cooling and condensing agent at the same time being fractionated ,Lighter and lower `boilin components-of the oil introduced into the ractionating op-"'A eration in accordance with this inventionj which are suitable,l as components ofthe de-- sired product may thusbe blended with Hthe vapors of the desired product produced in the cracking operat-ion. For example, straight run gasoline or gasoline from other cracking operations free from such unstable unsaturated constituents required' to be blended with the gasoline producedlin the vapor phase cracking operation may be yutilized as a cooling and condensing agent 'may thus ber stabilized,f

The vapors lfrom theffractionating the present invention, before condensation to form the desired lighter and lower boiling In this` way, vthe cracked .vapors are subjected to treatment whilefresh from the crackingv operation vand part of the heat carried away from the f cracking operation by they vapors, may be utilized for effecting or promoting the vrefiningv treatment,` any components blended with the vapors in the fractionatingl operation being at lthe sametime subjected to the same treatment.v The cracked product, or the com osite product,

' ciiemically and physically, as part: of the complete operation by direc-t fractionation and direct treatment. A marketable gasoline or motor fuel, for example, may' thus be 'produced directly without requiring furthertreatment or disi tillation or blending. Gasoline or'gasolinecontaining oil introduced into the fractionating operation as a cooling-and condensing agent, however, may be subjected to treatment before being so\ introduced into the fractionating.operation.

'The invention will be` further described in `connection 'with the accompanying drawing which illustrate, 1n a dlagrammatic and conl.ventional manner, in elevation and partly in section, one form of apparatus adapted for carryingout one type of operation inwhich the improvement of the present, in-

aov

vention is embodied, but -it isintended and will be understood that this further description and illustration are for the purpose' of exemplilication and that the invention is not limited thereto.

Referring'to the drawing, the apparatusA illustrated comprises a heating conduit 1 arranged inthe heating flue of a furnace 2, l

' a series' of digesting drums 4. arranged in a vcorresponding series of lues inthe heating v chamber 36, a scrubbing tower 6, areflux tower 8, a Afractionating tower 10,' a treating tower 420, a condenser 25, a separator and receiver 30. 4coolers 1.8, 19 and 15, pumps 16,

17 and 12, and appropriateconnections. The

.scrubbing tower 6, for thek separation of entrained t-arry dr carbonaceous constituents,

may be provided interiorly with iballes,

best in its upper part. yThe refluxltower 8 may be of any construction suitable for reluxing the vapors; for example, it maybe in ordinary balie tower. The fractionating tower 1() may be of any construction-suitable for accurate lfractionation of the vapors; for example, it. may be 1 an ordinary bubble tower. The treating tower 20 may be of any suitable construction adapted to hold a body of the refining agent, such as fullers earth or aftreated clay, andto provide for passage of the vaporstherethrough. These towers, particularly towers 6, 8 and 10, may with advantagabe thoroughly lagged or thermally `insulated. to 'prevent or reduce heat loss. The condenser-25 and the coolers18', 19 and may be of ordinary construction.' The separator and receiver 30 is advantageously provided with baies above thev point of.

,discharge of the connection from the condenser to promote a clean separation between condensate and gases and vapors'remaining uncondensed. The pump 1.7 should be adapted to handle oil at relatively high temperature.

In carrying out the invention in the apparatus illustrated, for the production of gasoline or motorl fuelI for example, oil is supplied vto the heating conduit 1 and there vaporized and heated to a high cracking temperature and the resulting vapors are then passed, by means of connection 3, to the digesting drums 4 through which they pass serially. The temperature of the vapors as they are discharged from the heating conduit 1 may approximate 1,000o F.- 1,200 F. and the temperature of the vapors as they are discharged from vthe last digesting-drum may approximate 9 50O F.1,200 F. Heat for maintaining the required temperature in thedigesting drums 4 may be supplied to the lues in the heating chamber 36 in anyvsuitable manner. From the last. digesting drum, thel loil vapor, with .any .entrained tarry or carbonaceous matter, passes to the scrubbingtower 6 through connection 5. Vapors `from this tower pass to the reflux tower 8 through connectlon 7 and vapors remaining uncondensed in the reflux tower8 pass to the fractionating tower 10 through connection 9. Vapors remaining uncondensed in the fractionating tower es- -cape through connection 13 either to the condenser 25 through connection 32 or to the treating tower 20 through connection 29 and thence to the condenser 25 through connection 33.y The condenser 25 discharges into v the separator and receiver through connection 34. Uncondensed vapors and gases are discharged from this separator and recciver through connection -and the condensate through connection 31. Raw stock is supplied to the upper end of reflux tower 8 by means of pump 16 through connection 28, or part of the raw stock mayfbe supplied' directly to the heating conduit 1 vthrough connections 27 and 26. A part of the oil mixture discharged from the lower end of reflux tower 8 through connection 21 is introduced into the upper end of the scrubbing tower 6 through connections 22 and 23 by means of pump 17 to effect the separation of tarry and carbonaceous matter thereinhthe ,oil so introduced being largely vaporized againto escape through connection 7. The remaining oil mixture' discharged through ,connection 21, or part of it, is returned to the heating conduit 1 through connections 22, 24 and 26 by means of pump 17. The tarry and carbonaceous matter separated in' the scrubbing tower usually remains'uid while charged through cooler 19. The condensate.

separated from the vapor mixture in the fractionating tower 10 is discharged through connection-14 and cooler 15. The cooling and condensingv agent for effecting or controlling the fractionating operation carried out in the fractionating tower 10 is supplied to the upper part of this tower through connection. 11 by means of pump 12. The temperature of the vapors escaping from the scrubbing tower 6 may be maintained in the neighborhood of 500O F.550 F., the temperature of the vapors escaping from the reflux tower 8 in the neighborhood of 350 F.- 45,0o F.,.and the temperature of the vapors escaping from the fractionating tower 10 in the neighborhood of 300 F'.-380 F. In the cracking operation, it is advantageous to use only suflicient pressure 'to force the oil or oil vapor through the apparatus; the pressure inV the digestinfr drums, for example, may A' ing tower 2() inwhich they are contacted, for l example, with a body of fullers earth or.

treatedl clay. Any oijl condensing orcollecting` in' this tower is discharged through connection 3-7 The vapors escaping from thel fractionating tower, however, may be discharged directly to the condenser 25.

In carrying out the present invention in the apparatus illustrated, for the production 'of gasoline or motor fuel, a gasoline from some external source, or a gasoline fraction,l

or a naphtha fraction containing-a substantial portion of gasoline, is introduced into the upper end oft-he fractionating tower '10 through connection 11 as required to effect the necessary condensation therein. The rate of supply of such gasoline or gasolinecontaining oil, for example, may be regulated to maintain the temperature of the escaping vapors` at an appropriate predetermined value. lThis gasoline or gasolinecontaining oil, for example, may be "a straight run gasoline, or a gasoline from some other cracking operation, such as a gasoline produced by pressure distillation in which the stock supplied'to the cracking operation is subjected to `relatively mild crackingv conditions,`or a mixture of such gasolines-` The gasoline Iso introduced, or

' vapor phase cracking operation.. Any heavier components of the gasoline or gasolinecontaining oil so introduced into the fractionating tower 10 are, in the same fractionating operation, separated from Vthe vvapors subsequent-lyy condensed to form the desired gasoline or motor fuel product. Similarly, 'naphtha fractions from the straight-running of crude petroleum or fractions of crude petroleum, or pressure Adistillates including gasoline produced by relatively mild cracking together with heavier components, may be suppliedto vthe upper .end of the frac-l tionating tower 10 through connection 11 as a cooling and condensing agent. The lighter components of such naphtha fractions or pressure distillates, suitable as components of the desired product, are then separated from the 'heavier components escaping with the vapors of the desired product producedin the vapor phase crackingl operation.

The vapors of the desired lighter and lower boiling product, gasoline lor motor fuel for example, may be condensed without further treatment. AThese vapors, including the vapors produced in the vapor phase cracking operation and vaporized components of the oil introduced into the vapors in the fractionating operation as a cooling and condensing agent, are however advantageously subjected to refining treatment with an absorbent earth or clay after they leave the fractionating operation and before they are condensed' to form the desired product. In this manner, the invention makes it possible to produce a finished gasoline or motorfuel in asingle operation, the opera# tion including any necessary. or desired blending as well as treatment of the composite lproduct combined in the operation .in a particularly advantageous way.

v I claim: w

l. In cracking hydrocarbon oils for they production of lighter and lower boiling oils,y

the improvement which comprises heating the oil in the vapor phase to a high cracking temperature and,before condensation of the desired lighter and lower boiling oil, subjecting the vapors from thecracking operation to a fractionating operation, and introducing into direct Contact with the vapors in the fractionating operation, as a cooling and condensing agent, an oil of boiling range corresponding to that of the desired lighter and lower boiling oil but substantially free from unsaturated components unstable at the temperatures prevailing in the fractionating operation.

2.'.In cracking hydrocarbon oilsfor the production of lighter and lower boiling oils, i l

the improvement which comprises heating the oil inthe vapor phase to a highcracking -4 temperature and, before condensa-tion of the.

desired lighter and lower boiling oil, subjecting the vapors from the cracking operation to a fractionating operation, and'introducing into direct contact with the vapors in the fractionating operation, as a cooling and condensing agent, an oil of boiling range correspondingto'that of the desired lighter.`

and lower boiling oil'but substantially free from unsaturated components produceduin the'vapor phase cracking operation.,

In cracking hydrocarbon oils for the Iproduction of lighter and lower boiling oils,

the improvement which comprises heating' the oil 1n the vapor phase to a cracking tem@ perature upwards of 900 F. and, before condensation of the desired lighter and lower boiling oil, subjecting the vapors from the cracking operation to a fractionating operation, and introducing into direct contact with the' vapors in 'the fractionating operation, as a cooling and condensing agent,

yan oil not more than 20% of which boils .olf at a temperature above the end boiling point of the desired lighter andflower boil-Q mg oil,'at atmospheric pressure, and which is substantially free from unsaturated `coinponents unstable at the temperatures prevailing in the fractionating operation.

soA

4. In 'cracking hydrocarbon oils for the production of lighter and lower boiling oils, the improvement which comprises -heating the oil in the vapor phase to a cracking temperature upwards of 9009 F. and, before condensation of the desired lighter and lower boiling oil, subjecting the vapors from the cracking operation to 'a fractionating operation, and introducing into direct contact with-the vapors in the vfractionating operation, as a cooling and`condensing agent, anoil not more than 20% of which boils oifat a temperaturel above thev end boiling point of the desired lighter and Alowerlooiling oil,

at atmospheric pressure, and whichissub-l stantially free from unsaturated components l produced in the 'vapor operation. f

5l In cracking hydrocarbon oils for the phase cracking production of lighter and lower boiling oils,`

the improvement which comprises heating the oil inthe vapor 1ihase toa high cracking temperature and, before condensation vof the desired lighter and lower boiling oil, subjecting the vapors from the cracking operation to a fractionating operation, introducing into direct contact with thegvapors in the fractionating operation, as a coolingand condensing agent, an oil of which at; least a substantial portion is vaporized therein and escapes with the Vapors'from the fractionating operation but whichis substantis ally freefrom unsaturated components proing operation including such gasoline to a fractionating operation to condense complofractionating nents higherk boiling than the gasoline, introducing into direct contact -with the vapors in the fractionatingoperation, a's a -cooling and condensing agent, a gasoline fraction substantially free from lunsaturated co m ponents produced in the vapor phase cracking operation, and separately condensing the gasoline vapors, including vapors of the gasoline produced inthe cracking operation andvaporized components of the gasoline fraction introduced into the 'vapors in theV operation, escaping' from the fractionating operation. 'c

/ 7. In cracking hydrocarbon oils for the production of lighter and lower boiling oils, the improvement which comprises heating the oil in the vapor phase to a high cracking temperature and, before condensation of the desired lighter and lower boiling oil, subjecting the vapors from thecracking loperation to va ractionatingv operation, introducing into direct contact with the vapors in the fractionating operation, as a cooling and -condensing agent, an oil of which at least a substantial portion is vaporized therein and escapes with the vaporstherefrom but which is substantially free' from unsaturated components produced in the vapor phase crackin operation, subjecting the vapors from the ractionating'operation,

including vapors produced 'in thecracking operation and vaporized components of the oil vintroducedfinto the vapors 'in the frac-- tionating operation, to treatment with an absorbent earth, and thereafter condensing.

the remaining vapors to form the desired lighter and lower boiling oil.

' 8. In cracking higher boiling hydrocarbon oils for the production of gasoline, the improvement which comprisesheating the higher boiling oil in the vapor phase to a` cracking temperature upwards of 900 F. and, before condensing the gasoline so introduced, subjecting the vapors from lthe cracking operation including such gasoline to a xfractionating operation to condense colnponents higher boiling thanr the gasoline, introducing into direct contact with' the vapors in the ractionating operation, as a cooling and condensing agent, a lgasoline fraction substantially freefrom unsaturated components produced inthe vapor phase cracking operation, subjecting the vapors,

including vapors of the gasoline l produced in the cracking operation andl vaporized components ofthe gasoline fraction introduced into the vapors inthe `ractionating operation, escaping from the fractionati'ng operation to treatment with an yabsorbent earth' and thereafter condensing the remaining gasoline vapors.

In testimony whereof, I have subscribed my namel J EDWARD w.y IsoM.

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