US1632967A - Process for producing light hydrocarbon liquids - Google Patents

Description

June 1927.

21 E. c. HERTHEL PROCESS FOR PRODUCING LIGHT HYDROCARBON LIQUIDS Filed April 4, 1925 you; huw@ #QQ MOOD lll ATToRNEY line constituents, by the Patented June 2l, 1927.

EUGENE C. HERTHEL, OF CHICAGO,

PANY, OF NEWpYOBK,

ILLINOIS, ASSIGNOR '10 SINCLAIR REFINING COH- a CORPORATION or MAINE.

PBOCESS FOR PRODUCING LIGHT HYDROCRBON LIQUIDS.

Application led April 4, 1925. Serial No. 20,641.

This invention relates to improvements in the productionnotelight hydrocarbon oils, and particularly light gasolines, or oils con-` taining increased proportions of hght gasoheavier hydrocarbon oils under pressure.

The straight-run gasolines produced in the distillation of petroleum oils, and gasolines produced by cracking processes such as pressure arily employed, usually contain an amount of very light easily vaporizing constituents somewhat less than is desired for certain purposes, such as for use as' motor fuel. Because of this deficiency of ordinary gasolines, it has been customary for refiners to blend with their straight-run or cracked gasolinas varying proportions of very light oils such as those recovered from natural gas and caslnghead gas and commonly known as natural gas gasoline, casinghead gasoline and natural gasoline. While these very light oils are available in the variousgas and oil fields, special methods of recovery are required for separating and recovering them from gas mixtures in which they occur, and enormous losses by vaporiza'tion are usually involved in handling such very light oilsl 'from production through the refinery. Not 0 only are evaporation losses high, but, due to the ,high vapor pressures and the infiammability of these very involved in handling them, with the consequence that initial recovery, shipment. and ll storage, and handling in blending, and rening, of these very lightl oils become expenslve.

Among the objects of this invention is the rovision of an improved method for produc- 40 ing such very light hydrocarbon oils, or such light oil constituents, in the refinery, which avoids the disadvantages incident to such light oils as hitherto. available in production,handling, storing and shipping. In one aspect, the present invention provides an improved method for the poduction in the refinery of such very lig t oil stocks which may be employed as required, for example, in blending operations as previously practiced. In another aspect, this invention provides an improved method for increasing the amount of very light and easily Vaporizin constituents in gasolines, or pressure distil ates, producedv 1n cracking operations. Such oils, having an increased content of distillation oi distillatiomtwith the methods customthe l light oils, danger is` verylight components, may also be employed for blending with other heavier oils, or the operation may be re lated, in accordance vvith this invention, or the direct production of a distillate having the desired characteristics, particularly as to the content of very light and easily vaporizing constituents.

According to the present invention, a heavy oil is subjected to pressure distillation, and the pressure distillation is regulated in an improved manner to obtain a" pressure distillate containing very light constituents in increased concentration.

In carrying out the present invention, a.. heavy but easily cracked oil, such as coke still as oil or gas oil of high wax content, is su jec'ted vto distillation under pressure with a mild -application of heat, and very light constituents are vconcentrated in the distillate by subjecting the vapors to a refluxing operation which is re ulated to permit only a limited amount o the vapors to pass ofi as distillate. If such easily cracking stocks are subjected to extreme cracking temperatures, anexcessive formation of gas and coke results, but with af-mild application of heat the amount of gas and coke formation may be restricted while a tendency to form very light constituents is developed. Also, according to the present invention, thev refluxing operation is regulated so that a much higher proportionot the vapors, and particularly of the heavy.4 components of the, ^vapors, is returned to the pressure distillation than is common in retluxing operations employed in conjunction with pressure distillation processes. This reuxing of the vapors may be eil'ected by external cooling ot the vapors, but it is more advantageously effected by the introduction of fresh oil'to be supplied to the pressure distillation into direct contact with the vappors, the reflux together with the admixed resh oil then being returned to the pressure still. If the increased refiuxing Aemployed in carrying out .the present invention tends to choke the pressure still because of the return in large amounts of intermediate light constituents, the pressure is somewhat increased.

Where the refluxing is effected by the direct introduction of fresh oil into the vapors from the pressure still, oil at ordinary temperature'is supplied to the refluxing operation at a-rate of from about u to u. 300% or more et the rate atv which is taken olf, and the refluxing operation is controlled b regulating the rate at which the fresh oil7 is supplied thereto. For example, the supply of fresh oil to the refluxing operation may be regulated in accordance with the temperature at which the vapors forming the distillate escape from the refluxing operation. With this large amount of cool fresh oil introduced into con-v tact with the vapors in the refluxing operation, a large proportion of the vapors are refluxed land the very light constituents produced inthe cracking operation are concentrated-in' the pressure distillate.

The high degree of refluxing employed is,

'in one aspect, characteristic of the present invention.Y Where the refluxing operation is carried out with the direct introduction of cool freshoil into the vapors therein, the degree 'of refluxinfr employed may be 4measured by the ratio between the rate at which` fresh oil is so supplied and the rate at which distillate is taken olf. Another measure of the degree of refluxing employed is the degree of concentration of the very light constituents in the pressure distillate. For example, pressure distilliates are obtained in carrying out the present invention of which more than about 20% boils onf up to 221 F. and more than about 40% up to 284 F. These hydrocarbon pressure distillates having this high content of very light constituents are also characteristic of the present invention. i

Where cool fresh oil is supplied to the refluxing operation in direct Contact with the vapors therein, and then supplied to the pressure still with the refiux admixed therewith, oil is4 withdrawn from the still charge to maintain it approximately constant as the o eration continues. With the high degree o reuxing employed in carrying out the invention and with this high rate of supply of fresh oil, the percentage of distillate off on the total charge is relatively low, for example it may approximate 30% or somewhat more, and the withdrawal of oil from the charge thus makes prolonged lc eration possible, even with easily cracking c arging stocks, because the pitch concentration of the charge is maintained below saturation or is allowed to build up only at a slow rate.

Where the refluxing operation is effected by external cooling of the vapors therein, fresh oil, which may be preheated, ma be supplied to the still and oil withdrawn fyrom the still charge, the rate of supply of fresh oil and of withdrawal of oil from the charge being regulated tomaintain the pitch content of the charge below saturation, or fresh oil .may be supplied at a somewhat reduced rate and oil may be withdrawn from the still charge at a reduced rate, or not at all,

and the operation carried out in a batch orse1ni-cont1nuous manner. In such an operation, the distillate taken oil o n the total charge may approximate 40% or somewhat more.

The invention will be further described in connection with the accompanying drawings which illustrate in a diagrammatic and conventional manner an apparatus adapted for carrying out the process of the invention. The pressure still illustrated in the draw ings is of the general construction and operation described in United States Letters Patent No. 1,285,200 granted to the Sinclair Relining Company, November 19, 1918 on the application of Edward W. Isom. The pressure still system illustrated in the drawings is shown in elevation and partly in Section with parts broken away.

Referring to the drawings, the pressure still comprises a bulk supply tank 1 and heating tubes 2, the heating tubes being arranged in the heating flue of a furnace 3 and the bulk supply tank being arranged away from the furnace, a circulating pump 4, and circulating connections 5,

6 and 7 connecting successively the bulk supply tank, the circulating pump and the lower end of the heating tubes, and the upper end of the heating tubes and the bulk Supply tanlr. Arrangedjabove the bulk supply tank is a reflux tower 8 provided with baflles 9p The reflux tower, the bulk supply tank, and the various circulating connections may be suit ably lagged to prevent'heat loss.

line 12 is arranged vto conduct va ors from the vapor dome on the bulk supp y tank to the lower end of the reflux tower and a refiux return line 11 is arranged to discharge reflux and admixed fresh oil from the lower end of the reflux tower into the upper end of the circulating connection 5 on the suction side of the circulating pump. From the upperend of the reux tower vapors escape through the vapor line l0 to the condenser 13 which discharges into a receiver 14 provided with a distillate outletl and a gas outlet 16. The pressure in the still may be regulated by a `valve 17 arranged between the reflux tower and may be regulated by suitable valves arranged beyond the condenser. A sprayhead 18 is arranged in the upper end of the refiux tower to which fresh oil is supplied through connection 19 which is provided with control valve 20. A connection 2l is arranged for supplying cool oil to the bearings of the circulating pump 4 to cool and protect them. A connection 22 is provided for pumping out and charging the still, and a tar draw-olf connection 23 is arranged for withdrawing tar laden oil during the operation of the still. In the furnace 3, one or more blowers A2st are arranged to withdraw relatively cool heating gases from near the exit iue 25 of the furnace and to return them -for admixture with the hot gases fresh the condenser, or it' A vapor los from the firebox 26 before the admixed gases pass over the heating tubes2 arranged in the fnrnace. g

' The invention will be further illustrated by the following specific examples of oper,-y

Vand 29.7%. up to 600 F. and had a pourl test of 65. The temperature of the heating gases as they first contacted with the heatlng .tubes was maintained at about 1900 F. During the run the head. temperature at the top ofthe tower averaged about 423 F. and was controlled by the introduction through the tower of a gas oil character stock having a gravity of about 33.5 B. and boilingoff about 1.8% up to 450F. about,13.2% up to 500 F. and about 70% up to 600 F. 'and having apour test of about 5. The rate of supply of fresh oil to the-top ofV the tower averaged about 269% of the rate at which distillate was taken off. Initiallydistillate was taken oif at the rate of about 680 gals. per hour, and, before the concentration of pitch in the still charge reached saturation, the withdrawal of tar was begun, and the rate of distillateoif was decreased. Beginningin the sixth hour of operation, tar having an` average avity of about 28.3 B. was drawn for a ut 22% hours at an average rate of about 995 gals'. per hour and distillate wastaken off during this period at an average rate of about 450 gals. per hour. rlhe run lasted 29 hours and during this time about 395600 gals. of-feed oil were introduced and about 14,470 gals. of distillate were taken oif. The uncondensed gases escaping `from the receiver amounted to about 70.6 lbs. er hundred gals. of distillate. The disti late had a gravity of 58.0 B. and boiled off 22.4% up to 22181?, 78.6% up to 400 F., 87.8% up to 450o F. with an end point of 508 F.

In another such operation, the pressure',

still was initially charged with about 8000 gals. of the same initial chargingstock and was brought to an operating pressure of about 125 lbs. per sq.`1ri. The temperature of the heating gases as they first contacted with the heating tubes was maintained at about 1900 F. As distillate was taken off, fresh gas oil was supplied to the top of the reflux tower atan average rate of about 278% of the rate at which distillate is taken off. the towerhead tem erature bein maintained at an average o about 431 This gas oil had a gravity of about 34.1 B. and boiled off about 1.9% up to 450 F., about 15.2% up to 500 F. and about 70.9% up to 600 F. and had a 'pour test of 0. Until the withdrawal of'rtar was begun, distillate .was taken ofi at a ratel of about 606 gals. per hour.. Beginning in the sixth hour of operation, tar was withdrawn at a rate of about 1030. gals. per hour for 23 hours duringl which period distillate'V was `taken 0H at a rate `of about 487 gals. per hour. The run lasted 28%c hrs. during which time about 40930 gals. 4of gas oil were supplied to the tower, 14680 gals. of distillate being taken off. About 65.3 lbs. of-gas per hundred gals. of distillate were produced. The distillate .had a gravity of about 57.9 B. and boiled off 24.6% up to 221 F., 77.2% up .to400 F. and 98.3% up to 450 F. with an endpoint of 510 F.

In carrying out the present invention, the concentration of light constituents in the Adistillate may be increased by increasing the rate at which fresh oil is supplied to the redux tower. When the rate of supply of fresh oil to the reflux towerv is increased the rate at which distillate is taken off is reduced and the percentage of distillate on the total still charge is reduced, but up to a certain point the production of gasoline character and very llght hydrocarbon oil constituents is not decreased and may even be increased to a substantial degree. The furnace temperatures employed may be as low as 1500 F. or even lower, and for the purpose of maintaining such low furnace temperatures it is vadvantageous to recycle .a part of the relatively cool heating 'gases leaving the heating ue of the furnace and to admix themwith the hot products of combustion freshy from the re-box before they pass through the heating flue, passin the inixture of tempered gases through te heating iiue, so that a high temperature promoting eflicient lcombustionl may be maintained in the irebox proper while a relatively low temperature is maintained in the heating iue. With more easily cracked charging stocks, the rate of reduction of light` constituents is relative y high, but the process of the invention is also applicable to relatively less easily cracked charging stocks by increasing the rate of reiiuxin and concentrating the light constituents 1n the distillate taken oif. In such an operation, however, the rate at which distillate is taken on' may be'reduced due to the slower rate of production of the desired light constituents. By employing somewhat increased pressures, the rate of vaporization in the lpressure still can be reduced, reducing the rcliux tower, and are usefulin the treatment of lessv easily cracked charging stocks u in accordance With the invention.

I claim:

l; A method of cracking heavier hydrocarbon oils for the production of light hydrocarbon oils containing very light constitu ents in high concentration, which comprises distilling heavier oil under pressure at 'a cracking temperature, subjecting the vapors of the cracked oil to a rei'luXing operation, and introducing fresh oil into the'reiuxing operation in direct contact with the vapors therein at a rate greater than about 190% of the rate at which distillate is taken off.

2. A method-.of cracking heavier hydrocarbon oils for the production of light hydrocarbon oils containing very light constituents in high concentration, Which comprises distilling heavier oil lunder pressure at a cracking temperature, subjecting the vapors of the cracked oil to a reluxing operationand introducing fresh oil into the the vapors therein at a rate between about .190% and 300% of the rate at Which 'distillate is taken off.

3. A method of cracking heavier hydrocarbon 'oi-1s for the production of light hydrocarbon oils containing very light constituents in high concentration, which co1nprises distillingA a'charge ot heavier oil under pressure at a cracking temperature, subjecting the vapors to a refluxing operation, introducing into direct Contact With the vapors in the refiuxing operation fresh oil at a rate of more' than about 190% of the rate at which distillate is taken oit', Withdrawing 'oil from the charge, and regulating the rate of supply of fresi oil and the rate at which oil is Withdrawn from the charge so that the percentage of distillate taken off on thc total charge including the fresh oil supplied thereto does-not substantially exceed In testimony whereof I aiiix my signature.

EUGENE C. HERTHEL.

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