US2334583A - Process for converting heavy petroleum oil into vapors and coke - Google Patents

Description

Nov. 16, 1 943.

E. D. REEVES 2,334,583

PROCESS FOR CONVERTING HEAVY PETROLEUM OIL INTO VAPORS AND 'COKE Filed July 27, 1940 C o/v V52 7152 COLD Flt? INLET W2 MSW L Patented Nov. 16, 1943 PROCESS FOR CONVERTING HEAVY PETRO- LEUM OIL INTO VAPQRS AND COKE Edward I). Reeves, Cranford, 3., assi nor to Standard Oil Development Companyp'a' corpo;

ration of Delaware ApplicationJuly 27, 1940, Serial No. 347,833

20mm; wri s-70) tionof the long chain hydrocarbons present The present invention relates to improvements in the art of treating hydrocarbon. oils such as petroleum oil. Moreparticularly, this invention relates to the conversion of relatively high'boiling petroleum oils into hydrocarbon oils oflower boiling range, and in its preferred modification relates to the coking of a reduced petroleum crude oil or heavy residual oil in a continuous manner under closely controlledconditions.

My invention is fully described in the following specification and cIairns reference being had to the accompanying drawing" v I F In refining crude petroleum oil, the'usual practioe is to first heat the oil to cause the vapori'za tic-n of the lower boiling fractions suchas naphthas, kerosene" and gas oil fractions; and to remove these fractions from the crude stills to form what are known as virgin fractions which may be employed after refining in the industrial'arts' as such, or thereafter further chemically converted to produce additional products such as motor turned to the coking zone forreuse in thelattt'er the reduced crude to form gas oil; gasoline, and

a solid coke within the body of the'molten metal or'salt: In this operationfthe inoltenmetal or. salt becomes contaminated with coke particles,

and I remove these coked bodies from the molten metal orbathby clischargingsame into. a vessel where the molten bath issubjectedto-the "influence of air which causes the oxidationand combustion ofthe coke to'form CO,.C O2, and other gaseousproclucts of combustion; after which the purified molten metal or saltis reprocess. In operating my process, I discharge the hot regenerated metal or salt at regenerated temperatures into thereaction vessel, and in' this fuel, range oil, domestic heating oilsand the i like. The material remaining in the still after the naphthas, gas oil, and kerosene have been removed is commonly referred to as reduced crude. This material has such a high boiling point that it cannot be wholly vaporized at any reasonable temperature, and therefore the practice is to convert this reduced crude to hydrocarbons of lower boiling range, generally, by one of two processes, namely, either by a viscosity reducing treatment or by a coking operation. The viscosity reducing operation results in the formation of gasoline, gas oil, etc. and a tarry material 7 which latter is removed from the viscosity. reducing operation and is often further treated to produce petroleum asphalt or fuels such as bunker fuel. The coking operation, on the other resu ts not only in the production of gas oil, ga nc and naphthas, but also in the production of a solid coke. The latter operation is usually performed in a drum, and periodically the oneration must be discontinued due to the deposition of cons derable quantities of coke, which coke ust be removed manually. The coking operais a batch or intermittent process, Last in the case where only one drum is emyed as the coking vessel. 7

In any improved process for coking reduced crudes, I operate continuously in a one drum cckingsystem. I accomplish this end by feed.-

the reduced crude oil into the bottom'of an elongated body of molten metal or salts heated to a temperature sumciently high to cause disrup- .mannerI take advantage of the heat. contained in the hot regeneratedimetalpr salt tozsupply-a portion ofthe heatrwhich is lost in the reaction zone by virtue of the endothermic reaction therein taking place. In other Words, the hot regenerated molten material as withdrawn from-the regeneration vessel ordinarily is ata'temperature in excess of the temperature prevailing in the reaction zone, and I am thus enabled to add heat to the reaction zone at the relatively high level therein prevailing, which, of'course', is not readily accomplished, because it is dirficult to add heat to a body which is at a relatively high temperature suchas that prevailing in the reaction zone.

One object of my invention is to coke continu? ously a reduced crude in the presence of 'amolten metal ora molten salt. 7 v

' Another object of my invention is to coke a reduced crude continuously in a molten bath of lead. V 9

Since the coking operation in its essence is analogous to the cracking of a gas oil,--it is an! other object of my invention to employ a molten bath in the coking zone, which'molten' bath consists of inorganic salts known to have catalytic activity inthe cracking ofhydrocarbon oils.

Other andfurther objects of my invention will more fully andat large appear from the following detailed descriptions.

To theaccomplisliment of the foregoing and related ends, I' provide a process and a suitable apparatus consisting essentially of preheating a reduced crude to atemperature of 700* more or less, and then discharging the reduced crude intoa point at near the bottom of a molten bath of lead, whereupon the lead bath which is maintained at a temperature of say 1000" F. becomes. the depository, for liquidfractions and solidcoke resulting from the temperature conditions to which the oil is subjected, while the gaseous decomposition products of the original oil pass upwardly through the bath of lead and are withdrawn overhead as a vapor fraction. The amount of liquid oil remaining in the lead bath under cest operating conditions is very small, and the lead bath containing the solid coke and a small amount of unvaporized or unchanged oil is discharged into a burning zone or regeneration zone where the lead bath is freed from carbonaceous material of all kinds by subjection under proper conditions of heat to the influence of air.

My invention will be ,best understood by describing an operation following the apparatus set forth in the drawing, in which a combination of suitable apparatus elements are shown diagrammatically.

Referring in detail to the drawing, a reduced crude, say an East Texas crude having an A. P. I. gravity of about 18 is introduced into the systemthrough line at a'temperature of about 700'F., and thence discharged into the bottom 'of converter 4, which converter contains a bath oil is resident in the molten bath B varies according to the nature of the feed stock, but in most cases the reduced crude should remain in the molten bath for 1-15 seconds depending on the volume of the charging stock. In other words, the charging stock is resident in the molten bath for a relatively short period of time. The gas oil upon formation is vaporized and passes upwardly through the bath into the upper portion of converter 4 and is eventually withdrawn through a vapor line 5. All of the vapors in line 5 are not gas oil vapors, but contain as well fractions boiling within the gasoline range or lower fractions. In the case where a noncatalytic molten bath is employed, best operating conditions require that the amount of gasoline and dry gas be held to a minimum, since the gasoline will not have a high anti-knock value, and the dry gases represent, in most instances. a loss of material. The gas oil recovered from converter 4 may be catalytically cracked to produce a high grade motor fuel, in an apparatus which is not illustrated in the drawing. The molten bath in the converter 4 is a moving body which moves upwardly to a level A maintained substantially constant and then s withdrawn from the converter through ondu t 8 and discharged into the top of a tower Ill. This tower is preferably packed with ceramic material over which the molten metal flows downwardly. At the same time, an oxidizing gas, such as atmospheric air. is discharged into the tower Hi throu h line H where it emerges within the tower throu h a series of nozzles I2 and then passes upward against the downfiowing molten material containing coke and unvaporized oil. The air causes the oxidation of the carbon contained in thejlead or other molten material without causing oxidation of the said molten material.

The carbonaceous material therefore 7 heat exchanger 21 where it may be either heated or cooled to bring it to the proper temperature for use in chamber 4, whereupon it is withdrawn from the heat exchanger through line 25 and redischarged into line 18 leading into the converter 4, as previously stated. In the case where heat exchanger 2| acts to cool the molten material in line 20, the cooling medium may be cold oil discharged into the heat exchanger through line 27 in such a manner that it passes in countercurrent heat exchange relation with the hot molten lead or inorganic salt, whereupon the oil is heated to a temperature of 500 F.-'. 00 F. and

thencewithdrawn through line 28 for charging through line I into the converter 4.

It is to be noted that the direction of flow of molten material from converter 4 to regeneration vessel l0 may be the reverse of that shown in the drawing. In other words, the molten material .in converter 4 may flow therefrom through pipe i3 and then upwardly through IS and through regeneration tower l I. For some purposes the latter direction of flow is preferable, since the concurrent flow of air would have a tendency to reduce the energy requirements below that required to'force the molten bath in the circuit shown from the reaction vessel to the regeneration vessel. 7

Referring to the revivifying or purifying tower i0, it is pointed out that it may be desirable in certain instances to mix a hydrocarbon, such as a normally gaseous hydrocarbon, with the air in line I l in order to form an easy combustible mixture which will facilitate the burning or oxidation of the carbonaceous material contaminating the molten metal or salt, The tower it, like the converter 4, may operate under superatmospheric pressure, say a pressure of 30 lbs. per square inch gauge.

With respect to the contact material which may be used as the molten bath material B, it is pointed out that not only lead and sodium chloride may be used, but also non-oxidizable salts such as NaAlCh, and ZnClz.

It is also pointed out that my invention is not limited to coking of reduced crudes but includes also operations such as cracking of gas oil to form gasoline. In the case where a gas oil is cracked to form gasoline products, it is of course preferable to use a salt bath consisting of a salt which has catalytic activity, such as NaAlCh, in order to produce a gasoline of high anti-knock rating.

Many modifications of my invention will readily occur to those skilled in this particular art.

What I claim is:

1. A process for converting heavy petroleum oil into vapors and coke which comprises passing the oil through a body of molten solids within a cracking zone, maintaining said molten solids within. the cracking zone at a temperature above the active cracking temperature of said oil, maintaining said oil in contact with said molten solids within said cracking zone for a period suflicient to convert the same into vapors and coke, re-

moving the cracked vapors from the cracking zone, removing a mixture of molten. solids and coke from the cracking zone, passing said mix ture of coke and moltensolids through a body of solid ceramic material, burning the carbonaceous deposits from said molten solids during passage through said body of ceramic material, and

thereafter returning said molten solids to said cracking zone.

2. A process for converting heavy petroleum l0 oils into vapors and coke which comprises passing the oil to be converted through a body of molten material maintained within a, cracking zone,

keeping said molten material within said crack ing zone at a temperature above the cracking temperature of said oil, keeping said oil in contact with said molten material within said crackassasssi Y f 3,

ing zone for a period sufflcient to convert said oil into cracked vapors and coke, removing said cracked vapors from said cracking zone, removing a mixture of molten solids and 'coke from f the cracking zone, passing said last-named mixv ture through a body of solid ceramic material,

burning carbonaceous deposits from said molten material during passage through said body of ceramic material, heating said molten material during the burning of said carbonaceous deposits 'to a temperature materially above the temperature maintained in said cracking zone, and thereafter returning said molten material while at said last-named temperature to said cracking 15 zone. v v

EDWARD D. REEVES.

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