US2260620A - Process of refining petroleum oil - Google Patents

Description

Oct. 28, 1941. w- T. HANCOCK PROCESS OF REFINING PETROLEUM OIL Filed April l, 1940 NW mw Patented Oct. 28, 194i lUNITED STATEST'PATENT OFFICE 2,260,620 PROCESS OF REFiNING PETROLEUM OIL William T. Hancock, Long Beach, Calif. Application April 1, 1940, serial No. 327,198

s Claims. (ci. 196-14'0 This invention has to do with the refining of petroleum oils, and has for its general object to provide a combined treating and cracking system whereby the cracking plant charging stock is employed in the treatment of pressure distillate produced by Such plant, all in a manner to enable impurities removed from the distillate to be converted to desirable and recoverable fractions in the cracking plant, and to effect final removal from the system of sulphur-containing and other compounds from which it is desired to free the distillate prior to treatment.

The pressure distillate treating system employed is the general type described in Patent No, 2,162,715 issued to me on Process for rening cracked petroleum distillate. According to this system, heated pressure distillate is subjected to polymerization by contacting it with fullers earth or other adsorptive clays, and the polymerized distillate then is mixed with heated higher boiling oil which has a solvent affinity for gum-forming and sulphur-containing impurities of the distillate. The gasoline content of the distillate then is vaporized from the solvent oil, leaving the impurities in the latter. One of` my primary objects is to enable ksuch solvent oil to be used as cracking plant charging stock according to a meth-od that will subject hydrocarbons removed from the pressure distillate to reconversion, and accomplish the removal in or beyond the cracking system of undesirable impurities, principally sulphur compounds, from the pressure distillate to be sent to the treating system. This feature also is dealt with in my copending application Ser. No. 306,347, filed November 27, 1939, on System for rening petroleum oils, which discloses a process in which the solvent oil is used as cracking stock.

In accordance with the present process, pressure distillate freed from xed or uncondensible sulphur gases, is subjected to polymerization, then admixed with a heated higher boiling solvent oil, such as fuel oil. The gasoline content of the distillate subsequently is vaporized from the solvent oil 'and then condensed. All or a portion of the solvent oil, containing impurities removed from the pressure distillate, is supplied as charging stock to a cracking plant of suitable type and operation, in which the charging stock undergoes conversion to produce gasoline-containing pressure distillate, and usually an unvaporized heavy residue which is removed from the system. In this manner, hydrocarbons removed from the pressure distillate bythe solvent oil in the treating stage, are subjected to reconversion and recovery as desirable fractions in the cracking plant, and undesirable or non-recoverable impurities are removed from the system in the cracking plant residue.

The principal impurity removed in the cracking plant is sulphur which may have been retained in various combined forms by the solvent oil, andwhich is converted by the cracking operation to fixed gases. These gases, in turn,A are removed in the usual manner as the cracking plant tail gases, and preferably also by subjecting the pressure distillate to a stabilizing Or like treatment for the nal isolation of acid gases that may remain in the distillate after its condensation in the cracking plant.

4 The invention also provides a system for twostage treatment of the distillate by first contacting it with adsorptive material and solvent oil as hereinabove explained, and then again subjecting the first treated distillateor its gasoline fraction to polymerization and adrnixture With higher boiling solvent oil. This last mentioned solvent oil has a higher boiling range than the gasoline content of the distillate being treated, but preferably lower than the boiling range of the solvent oil employed in the first stage treatment. Preferably, gas oil is used as the second stage solvent oil, and after separation from the gasoline fraction of the distillate, is sent to a gas oil cracking plant operating to produce pressure distillate and to remove impurities in the same general manner as the fuel oil cracking plant. 'Ihe pressure distillates produced in the two cracking plants may be combined and subjected totreatment for the removal of impurities, allin the manner generally explained and as will hereinafter more fully appear.

The invention will be more fully understood from the following description of a typical and illustrative system representing a preferred embodiment of the invention. The description refers to the accompanying drawing illustrating the system diagrammatically and in flow sheet form.

Referring to the drawing, the system maybe described starting with the polymerizing treatment given the pressure distillate from the crackingunits and after removal of sulphur-containing gases, all as will hereinafter appear. The distillate is taken from a suitable source, such as storage conventionally illustrated by the tank l0, through line II to be pumped through a heater l2 in which the oil is heated to proper polymerizing temperature in excess of 200 F.,

and ordinarily in the neighborhood of 350 F.

Leaving heater I2 the distillate is discharged through line I3 into clay tower I4 wherein the distillate is subjected to polymerization by flowing through and intimately contacting a body of adsorptive material I5, such as the clays heretofore mentioned, within the tower. It will be understood that the path of Contact between ie distillate and adsorptive material may be lengthened as desired by using a single clay column of considerable height, or a plurality of series-connected clay columns.

A suitable solvent oil having a boiling range substantially higher than that of the gasoline content of the distillate, is introduced to the system through line i5. The solvent oil used consists of a suitable cracking stock and where, as in the illustrated system, the invention is adapted to subsequent or second stage polymerization of the distillate followed by solvent cil treatment of the distillate, the solvent oil introduced through line IS preferably is of a type having a higher boiling range than the solvent oil used in the second stage treatment. Typically, raw fuel oil may be introduced through line i5 and discharged by pump il through a heater i8 wherein the oil is heated to a temperature of around 500 F. tov 575 F., and discharged through line I9 to a receiver 25 wherein the heated solvent oil is intimately comingled with the polymerized pressure distillate flowing from the clay tower I4 through line 2l. Ordinarily it is preferred to adrnix the two oils in approximately the proportions of from three to four parts of the solvent oil to one part of the pressure distillate. Instead of mixing the oils beyond the fuel oil heater as described, the polymeriaed distillate may be taken through line 22 to be mixed with the fuel oil in line l5, and the two oils then heated together to a temperature of from 350 F. to 475 F. or above.

The mixed oils are discharged through line 23 to a suitable vaporieing zone, for example the bottom chamber 24 of the dephlegmator 25, within which the gasoline content of the distillate vaporizes and separates from the solvent oil, leaving gum-forming and sulphur-containing compounds of the distillate remaining in the unvaporized solvent oil. The heat supplied to the pressure distillate by the solvent oil, or by passage of the mixed oils through heater i8, may and preferably will be sucient to cause vaporization and separation of the entire gasoline fraction from the solvent oil within dephlegmator 25. However, where the temperature of the mixed oils introduced to the dephlegmator may not be suilicient to vaporize all of the gasoline, additional heat may be supplied as by means of the steam coil 25 in the bottom of chamber 2d within which the unvaporiaed oil collects.

The solvent oil, containing impurities removed from the pressure distillate, may be taken directly from the base of dephlegmator 25 through line 27 to be discharged via line 28 t0 the fuel oil cracking plant, or provision may be made for recirculating a portion of the solvent oil from the dephlegmator to the heater I 8, thereby maintaining a greater rate of solvent oil iiow to be mixed with the pressure distillate than the rate at which the oil is being supplied to the system through line I5. As a typical recirculating system, the solvent oil may be discharged through line 21 into accumulator 2S, from an upper location in which a portion of the oil is taken through line 3% to be combined at the proportioning valve 3I with the fuel oil in line I5. The accumulator is of suiicient volume to permit gravitation of heavier bodies to the bottom, from which the remaining portion of the solvent oil is withdrawn through line 28 to be fed to the cracking unit.

Leaving the dephlegmator 25, through line 32, the gasoline vapors may suitably be subjected to condensation as by a condenser 33 from which the condensate is collected in receiver 311. The condensate then is forced by pump 35 through line 36 to heater 3? wherein the oil is heated to around 350 F. for second stage polymerization. The heated distillate flows through line 38 to clay tower 39 to be contacted with adsorptive material 40, as previously described with reference to clay tower I4, Back pressure suicient to keep the distillate in liquid phase while contacting the adsorptive material may be maintained by valve 4I in line 42, or by valve 43 in line 44 beyond the mixer 45. Similar back pressure may be maintained on the distillate flowing through clay tower I4, by valve 45 or valve While it is desirable that in both stages the distillate be maintained in liquid phase while contacting the clay, it is to be understood that the distillate and the solvent oil may .be mixed under any desired pressure which may or may not be such as to maintain the gasoline content of the distillate in liquid phase in advance of the vaporizing zone.

A relatively low boiling charging stock, such as gas oil, is introduced to the system through line 48 and is discharged by pump 49, with or without distillate taken from the clay tower through line 58, to a heater 5I wherein the oil is heated to a temperature that may correspond substantially to the temperature at which the fuel oil is heated in heater I3, as previously described. Also, the gas oil is mixed with the polymerized distillate in substantially the same proportions as before. The mixed oils are discharged through line 44 into a vaporizing zone 52 in a second dephlegmator 53, from the base of which the unvaporized solvent oil passes through line 54 to an accumulator 55. Again, all the oil may be taken from the accumulator to be discharged by pump 56 through line 5l to the gas oil cracking unit, or a portion of the oil may be recirculated through line 58 and the proportioning valve 59 to the heater 5I. The vapors'leaving dephlegmator 53 through line Eil may be passed through clay tower 6I to remove any remaining gum-forming or color-producing constituents, and then discharged through line 82 to fractionating column E3 for the removal of higher boiling ends that are condensed and withdrawn through line Sd. The gasoline vapors pass through line S5 to condenser 66, and the product condensate is collected in a final receiver 61.

The solvent fuel oil withdrawn from accumulator 29 through line 28 is pumped to a fuel oil cracking unit, generally indicated at 68, and the gas oil being withdrawn from accumulator through line 51 similarly is pumped to the gas oil cracking unit generally indicated at 69. Both solvent oils in the accumulators are of course heated, ordinarily to temperatures above 375 F. and thus provide preheated charging stocks for the cracking units. It will be understood that these cracking unitsY 68 and 69 may be of any suitable type adapted to 'convert their respective chargingstocks to pressure distillate, and therefore that the illustrated cracking units should be regarded as typical and illustrative only. The fuel oil cracking unit is shown to comprise a still I0 in which the charging stock is subjected to cracking under the usual temperatures and pressures, for example 9309 F. at 500 lbs@ per sq. in., from which the cracked hydrocarbons are discharged through lline 1I to a reaction and separating chamber 12. Beyond valve 1Ia the pressure may be reduced to about 250 lbs. per sq. in. inthe reaction chamber. The unvaporized residue, which may contain impurities removed from the pressure distillate by the solvent oil still charging stock, as previously explained, is withdrawn from the separator and removed from the system through the valved line 13. Thevapors leaving the separator through line 14 are subjected to fractionation in one or more dephlegmators 15 to condense heavy ends removed through line 16, and the vapors are' passed through vline 11 to condenser 18 `from which the gasoline-containing pressure distillate collects in receiver 19.

The illustrated gas oil cracking unit 69 is similar to the described fuel oil cracking unit, and the jcorresponding parts have been given'the same reference numerals. In the gas oil cracking still, the charging stock may be subjected to cracking at somewhat higher temperatures and pressure, for example at around 950 F. and 600 lbs. per sq. in., with a pressure of around 400 lbs. per sq. in. maintained in the reaction chamber. While the gas oil introduced to the system through line 48 may be taken from any suitable source, I prefer to utilize for the purposes of this solvent oil, the heated gas oil produced in the cracking plants, together with any additional make-up required, such as gas oil from a straight l run plant (not shown) introduced through line 48a. Accordingly, the gas oil condensates from the bottoms of dephlegmators 15 are shown to be delivered through lines 9i and 92 (and an accumulator 93 if desired) to the gas oil heater inlet line 48.

Uncondensible vapors together with some sulphur-containing and other fixed gases are removed through the valved lines 8l and 82 and taken through line 83 for further treatment or disposition,` as may be desired. The pressure distillates from both receivers 19 may be further treated by any suitable method for removal of sulphur-containing gases, in order that the distillate as supplied to the treating system may be as free as possible of unnecessary contamination. To illustrate a typical method, the distillate from receiver 19 is withdrawn through lines 83a. and 84 and passed through line 85 to a heater 8G wherein the temperature of the distillate is raised suiiiciently, e. g. 300 F., to permit vaporization of light ends and sulphur containing gases in the usual type of-pressure distillate stabilizing plant. The latter is shown conventionally as comprising one or more dephlegmators or fractionating columns 81 to which the heated distillate is supplied from line 88, the vapors and gases being removed through line 89 to be disposed of, if desired, with the xed gases taken fromr the' cracking units through line 83. The stabilized pressure distillate is taken through lineY 90 to storage l0, thereafter to be given the combined'clay and solvent oil treatments for the removal of impurities.

I claim:

1. The process of refining petroleum oils that includes, subjecting separate oil streams to cracking in separate cracking zones, subjecting the hydrocarbons from said cracking zones to fractionation and condensation to produce gasoline-containing pressure distillate, subjecting said distillate, while heated, to polymerization by contacting it with adsorptive material, passing through a heating zone! a stream of solvent oil having a boiling range substantially higher than that of the gasoline content of the pressure distillate, mixing the heated solvent oil with the polymerized pressure distillate, vaporizing and separating the gasoline from 'the unvaporized solvent Voil in a .vaporizing zone, condensing the vapors to produce a gasoline-containing condensate, passing unvaporized solvent oil from the vaporizing zone to one of said cracking zones as charging stock, heating said condensate and contacting it with adsorptive clay, then mixing said condensate with heated yoil having a higher boiling range than the gasoline content of the condensate, vaporizing and separating the vapors from the higher boiling oil, subjecting the separated vapors to condensation, and passing the unvaporized solvent oil to the other of said cracking zones as charging stock.

2. The process of rening petroleum oils that includes, subjecting relatively high boiling and low boiling oils to cracking in separate cracking zones, subjecting the hydrocarbons from said cracking zones to fractionation and condensation to produce gasoline-containing pressure distillate, subjecting said distillate, while heated, to polymerization by contacting it with adsorptive material, passing through a heating zone a stream of solvent'oil having a boiling range substantially higher than that of the gasoline content of the pressure distillate, mixing the heated solvent oil with the polymerized pressure distillate, vaporizing and separating the gasoline from the unvaporized solvent oil in a vaporizing zone, condensing the vapors to produce a gasoline-containing condensate,passing unvaporized solvent oil from the vaporizing zone to one of said cracking zones as the higher boiling charging stock, heating said condensate and contacting it with adsorptive clay, then mixing said condensate with heated oil having a higher boiling range than the gasoline content of the condensate but a lower boilingrange than the first mentioned solvent vization by contacting oil, vaporizing and separating the vapors from the higher boiling oil, subjecting the separated vapors to condensation, and passing the unvaporized solvent oil to the other of said cracking zones as thevlower boiling charging stock.

3. The process of reiining petroleum oils that includes, subjecting separate oil streams to 'cracking in separate cracking zones, subjecting the hydrocarbons from-said cracking zones to fractionation andv condensation to produce gasoline containing pressure distillate, heating said distillate to a temperature in excess of about 200 F. andv subjecting the heated distillate to polymerit with adsorptive material, passing through a heating zone a stream of solvent oil having a boiling range substantially higher than that ofthe gasoline content of the pressure distillate, mixing the heated solvent oil With the polymerized pressure distillate, vaporizing and separating the gasoline from the unvaporized solvent oil in a vaporizing zone, condensing the vapors to produce a gasoline-containing condensate, passing unvaporized solvent oil from the vaporizing zone to one of said cracking zones as charging stock, heating said condensate and contacting it with adsorptive clay, then mixing said condensate with heated oil having a higher boiling range than the gasoline contentl of the condensate, vaporizing and separating the vapors from the higher boiling oil, subjecting the separated vapors to condensation, and passing the unvaporized solvent oil to the other of said cracking zones as charging stock.

4. The process of refining petroleum oils that includes, subjecting separate oil streams to cracking in separate cracking zones, subjecting the hydrocarbons from said cracking zones to fractionation and condensation to produce gasolinecontaining pressure distillate, removing sulphurcontaining gases from the distillate, subjecting said distillate, while heated, to polymerization by contacting it with adsorptive material, passing through a heating zone a stream of solvent oil having a boiling range substantially higher than that of the gasoline content of the pressure distillate, mixing the heated solvent oil with the polymerized pressure distillate, vaporizing and separating the gasoline from the unvaporized solvent oil in a vaporizing zone, condensing the vapors to produce a gasoline-containing condensate, passing unvaporized solvent oil from the vaporizing zone to one of said cracking zones as charging stock, heating said condensate and contacting it with adsorptive clay, then mixing said condensate with heated solvent oil having a higher boiling range than the gasoline content oi the condensate, vaporizing and separating the vapors from said solvent oil, subjecting the separated vapors to condensation, and passing the unvaporized solvent oil to the other of said cracking zones as charging stock.

5. The process of rening petroleum voils that includes, subjecting relatively high boiling and low boiling oils to cracking in separate cracking zones, subjecting the hydrocarbons from` said cracking zones to fractionation and condensation to produce gasoline-containing pressure distillate, removing sulphur-containing gases from the distillate, sub'eo ing said distillate, While heated, to polymerization by contacting it With adsorptive material, passing through a heating zone a stream of solvent oil having a boiling range substantially higher than that of the gasoline content of the pressure distillate, mixing the heated solvent oil With the polymerized pressure distillate, vaporizing and separating the gasoline from the unvaporized solvent oil in a vaporizing zone, condensing the vapors to produce a gasoline-containing condensate, passing unvaporized solvent oil from the vaporizing zone to one of said cracking zones as the higher boiling charging stock, heating said condensate and contacting it With adsorptive clay, then mixing said condensate With heated oil having a higher boiling range than the gasoline content of the condensate but a lower boiling range than the first mentioned solvent oil, I

vaporizing and separating the vapors from the higher boiling oil, subjecting the separated vapors to condensation, and passing the unvaporized solvent oil to the other of said 'cracking zones as the lower boiling charging stock.

The process of reiining petroleum oils that includes, subjecting relatively high boiling and low boiling oils to cracking in separate cracking zones, subjecting the hydrocarbons from said cracking zones to fractionation and condensation to produce gasoline-containing pressure distillate, contacting the distillate, while heated, with adsorptive material, then mixing the distillate with al higher boiling range heated solvent oil, vaporizing the gasoline content of the distillate from the solvent `oil and cooling the vapors to produce condensate, passing the separated solvent oil to one of said cracking zones as the higher boiling charging stock, heating and contacting said condensate with adsorptive material, then mixing the condensate With a heated solvent oil having a oiling range higher than thegasoline content of the condensate but lower than that of the first mentioned solvent oil, vaporizing the gasoline from the mixed oils, and passing the unvaporized solvent oil to the other of said cracking zones as the lower boiling charging stock.

'7. The process o f refining petroleum oil that includes, subjecting the oil to cracking in a cracking zone, subjecting the hydrocarbons from said cracking zone to fractionation to produce relatively heavy residuum, gasoline-containing pressure distillate, and uncondensed gases, subjecting the distillate, While heated, to polymerization by contacting it With adsorptive material, passing through a heating zone a stream of solvent oil having a boiling range substantially higher than that of the gasoline content of the pressure distillate, mixing the heated solvent oil With the polymerized pressure distillate, vaporizing and separating the gasoline from the unvaporized solvent oil in a vaporizing zone, thereby leaving gum-forming and sulphur-containing impurities of the distillate in said solvent oil, reciroulating a port-ion of the solvent oil from the vaporizing zone to again be mixed with the polymerized pressure distillate, and passing another portion of said solvent oil from the vaporizing zone to said cracking zone as preheated charging stock.

8. The process of rening petroleum oil that includes, subjecting the oil to cracking in a cracking zone, subjecting the hydrocarbons from said cracking zone to fractionation to produce relatively heavy residuum, gasoline-containing pressure distillate, and uncondensed gases, subjecting the distillate, While heated, to polymerization by contacting it with adsorptive material, passing through a heating zone a stream of solvent oil having a boiling range substantially higher than that of the gasoline content of the pressure distillate, mixing the heated solvent oil With the polymerized pressure distillate, vaporizing and separating the gasoline from the unvaporized solvent oil in a vaporizing zone, thereby leaving gum-forming and sulphur-containing impurities of the distillate in said solvent oil, passing the heated unvaporized solvent oil from the vaporizing zone into an enlarged accumulator zone, recrculating a portion of the solvent oil from said accumulator zone through said heating zone to again be mixed with the polymerized pressure distillate, and passing another portion of said solvent oilr from the accumulator zone to said cracking zone as preheated charging stock.

WILLIAM T. HANCOCK.

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