US2406313A - Cracking and coking hydrocarbon oils - Google Patents

Description

Aug. 27,1946.

J. M. BAR RON CRACKING AND CCKING HYDRQCARBON OILS Filed Nov. 28, 1942 Jossr-i Mascu Bunch INVENTOR IIIIIIIIIIMIIIIII .n'lmm nmumm wvvvlvllv mmlm 1:00 ozFu:

HIS

Patented Aug. 27, 1946 2,406,313 CRACKING'AND COKING HYDROCARBON OILS Joseph 'Mason Barron, P

to The Texas Company, proration of Delaware Application'November 28, 1942, Serial No. 467,177

:2 Claims. 7 1 This invention relates to certain "improvements in the cracking and coking of hydrocarbon oils.

The invention i concerned with the coking of residual constituents from a pressure cracking operation and contemplates a combination cracking and coking process in which a condensate stock is subjected to acracking temperature in a heating zone and the heated eflluent therefrom subjected to countercurrent contact with a heavy or residual stock "in a reaction chamber wherein separation of vapors from liquid residue occurs and in which'theresidue is flashed to coke bymeans of its contained heat. v

The invention is based upon the discovery that by having the heated condensate stock and the In accordance with the invention a condensate stock is passed through a heating zone and delivered to the lower portion of arreaction chamber into the upper portion :of'which a, heavy oil or residual stock is introduced reaction chamber i 'maintained at ajhigh cracking temperature sufiicient that upon the flashing of the residue a conversion to coke will occur.

sure is lowered and the residue flashed to coke.

In'the prior art practice coking has been accomplished with the aid of considerable quanticipal difficulties encountered has been that occasioned by the priming of the coking drum. In this priming, potential coke-forming constituents are carried with the eflluent vapor-s from the coking drum and create coking difficulties in the vapor line and in the dephlegmatin'g or fractionatin'g portion of the system. In order to avoid this diificulty it has been necessary in the past to Operate with relatively low charging rates to the coking drum and to maintain relatively high outage gauges therein, the outage gauge being the height of the space in the drum above the coke level. In accordance with the present invention, since the material directed to the coking chamber is essentially a liquid, the quantity of vapors and gases evolved from the Withdrawn as a fuel ort Arthur, Tex.,.assig11or' New York, N. Y., a corcoking chamber is greatly reduced Witha consequent material diminution in priming tendencies. The practice of the invention thus makes possible the maintenance of high charging rates to the coking drum and high levels therein While avoiding priming, with the result that a maximum amount of coke i produced per coke drum cycle. 7

Additional advantages of the high temperature in the reaction chamber made possible by the countercurrent operation therein are the resultant higherconversion per pass on the material delivered to the reactionchamber and the improvement in the efliciency of the operation by reason of the fact that the reaction chamber vapors pass directly to the dephlegmating or fractiona'ting portion of the system at maximum temperatures.

highly aromatic character well adapted for fuel oil blending. This heavy condensate may be oil product of the process. However, due to the heat made available by the countercurrent contact in the reaction chamber it is advantageous to combine the heavy tarry condensate with the cracked'residue being delivered to the coking drum. The primary dephlegmation of the coke still vapors is carried on at "relatively high temperatures within the cracking temperature rangeand coking tendencies'may be reduced to a negligible quantity Within the dephlegmator by maintaining therein a constant circulation of the-condensate formed. This oil;- cu-lation together with the return of the primary condensate to the coking drum insures that this heavy material will be ooked in the coke drum and not in the dephlegmator, or that the condensate may be withdrawn as a liquid product in cases wherein it is desired to obtain such fuel product.

The dephlegmated coke still vapors from the primary dephlegmating operation are combined with the vapors separately Withdrawn from the reaction chamber and subjected to dephlegmation with charging stock such a topped or reduced crude and the resultant mixture of reflux condensate and unvaporized charging stock is dirooted to the upper portion of 'the reaction chamber. The uncondensed vaporsfare subjected to further fractionation to separate a higher -boiling reflux condensate from lower boiling prodvmtsand this reflux condensateis cycled through :pipe or ber'so as to bring due is withdrawn through a vapor line 23 to arated by a trapout a heating coil wherein it is subjected to a crack- 7 ing temperature and the heated efliuent i distion of an apparatus adapted for the practice of r the invention.

In the apparatus illustrated a is disposed in a oil to a cracking temperature. The heated ef-' fluent passes through a transferlin l2 to a reaction chamber l3 which'is vertically disposed and heat insulated. As illustrated, the transfer line extends action chamber andttermin'ates in section l4 through which the heated are discharged in an upward direction a baflle l5. In inch transfer line the element In may be composed of a six-inch pipe. The products passing from the coil It to the reaction chamber will consist largely of vapors and gases and. upon being discharged through the enlarged. pipe [4 against the baffie IS an eflicient diffusion of i the vapors and gases is accomplished. A black oil or residual stock is'introduced to an upper portion of the reaction chamber l3 through a line l6 which extends within the reaction chamber and terminates in a distributor or spray nozzle l1. The spray I1 is arranged to spray the liquid oil in a downward'direction through the chamthe liquid oil into intimate contact with the rising vapors. It is desirable to have an unobstructed space between the distributor l and spray nozzle l1, free from baflles or any other contact elements, since it is contemplated to maintain such elevated temperatures therein that injurious coking would take place if surfaces were presented upon whichcoke deposition could take place- At the top of the chamber a ring spray pip l8 may be disposed for spraying oil against the wall of the chamber so as to produce, a downflowing liquid film which products against is conducive to the prevention of coke deposits Q on the wall of the chamber. I

liquid residue; takes l3. The separated upper portion of Separation of vapors from place in the reactionchamber vapors are withdrawn from the the chamber through a vapor line l9. Liquid is prevented from accumulating in the chamber by the rapid withdrawal "of liquid residue therefrom. In practicea very slight amount of vapor *may be withdrawn with the liquid, an amount 7 merely sufficient to insure. that no liquid level is maintained in the reaction chamber. The resia line 20 and pressure reducing valve 2i to a coking drum 22 wherein it is converted to coke by means of itscontained heat.- In practice a plurality of coking drums are employed so that while one is on stream the other or others may be down for coke removal and cleaning andthus continuity in the complete process is maintained. The coking drums are suitably heat insulated. V t

The vapors from the coking drum pass through a primary dephlegmating zone. As illustrated, a lower section 25 and an upper section 26 septray 21. The vapor line 23 communicates with v the vapors from the coking operation are ,sub- .jected to a separate dephlegmation. 1 A limited heating coil in furnace ll adapted to heat the,

practice with a threetower 24 is provided having a discharged from the within the lower portion of the -rean enlarged I the lower section 25 wherein phlegmating zone amount of cooling is supplied to the dephlegmating zone 25 so as not to unduly reduce the temperature and so as to obtain a condensate consisting of extremely high boiling constituents collected as a tarry condensate at the bottom of the dephlegmator. A portion of this heavy condensate is continuously withdrawn through a line 28 and directed by a pump 29 through a line 30 to the upperportion of the dephlegmating zone 25. The function of this circulation is not to accomplish any cooling but merely to establish and maintain a flow of liquid through the dewhich will prevent coking.

. Heavy dephlegmateor condensate is withdrawn from the'dephleg'mator 25 through a line 3| and system as a fuel oil product pump 32 through a line 33 to the coking drum 22 or to the transfer line 20, so as to combine the heavy tarry material with the mixture of vapors and liquid which is passed from the reaction chamber 13/00 the cokin drum 22.

,or is directed by a The dephlegmated coke still vapors pass upwardly from theprimary dephlegmating zone 25 to the dephlegmating zone combined with the vapors which are separately withdrawn from the reaction chamber l3 and which are introduced through the vapor line [9 anda pressure reducing valve 34. In the dephlegmating zone 26 the combined vapors are dephlegmated with charging stock, such as crude petroleum or topped or reduced crude, introduced by a pump 35 through line 36. The resultant mixture of reflux condensate and unvaporized charging stock is withdrawn from the tray 21 through a line 31 and directed by a pump 38 through the line It to the reaction chamber [3. Uncondensed vapors-pass ing zone 26 through a vapor line 39 to a fractionating tower 40. This tower is equipped with bubble trays or othersuitable vapor-liquid contact elements and is supplied with conventional cooling or refluxing means (not shown). The vapors are subjected to fractionation therein to separate a lighter product of desired boiling point from higher boiling reflux condensate. Thereflux condensate is withdrawn and directed by apump 42 and line 43 to the heating coil Ill. The overhead vapors pass to a condenser 44 thence to a distillate receiver or gas separator 45 or naphtha distillate is collected.

A convenient method of supplyingthe limited amount of cooling required in the dephlegmating zone 25 is to withdraw a smallportionof the reflux condensate from line 4| through a branch line 46 thence through a cooler 41, and direct the cooled condensate by a pump 48 and line 49 to the dephlegmating section 25 or conveniently to the line 30. The line 43 may be provided with a branch-line 56 by which a rel. atively small portion of the hot condensate may be directed to the ring spray 18 for supplying the downfiowin film to the reation chamber iii. If desired, this hot condensate spray may be eliminated and ,onlythe black oil, conducted through line l3, admitted to the upper portion of the reaction chamber, in which case the black oil is preferably introduced at the top ofthe chamber and sprayed in such a way that a portion thereof will be directed againstthe wall of the chamber to produce a downflowing film;

Inpracticing the invention typical operating conditions involve temperatures of 1015 F.- -1030. F..in the outlet of the heating coil, l9, tempera+ 26 wherein they are from the dephlegmate through a line 4| wherein the desired gasoline tures of 920 F.-925 F. in the bottom of the reaction chamber I 3 under a pressure of 350 p. s. i., coke drum temperatures of 850 F.855 F. under a pressure of 160 pounds, temperatures of 900 F.-910 F. in vapor line H), temperatures of 920 F.-925 F. in the efiiuent passing from the reaction chamber to the transfer line 20, a pres sure of 150 pounds in the tower 24 with temperatures of 790 F.-810 F. at the bottom of dephlegmating zone 25 and temperatures of 800 F.-810 F. in the trapout tray 21 and with a pressure of 135 pounds in the tower 40 with temperatures of 680 F.700 F. at the bottom of the tower.

It is not necessary to coking drum other than that of the enterin oil.

ing and consequent cokin the primary dephlegmator. The present invention has made it possible to reduce the outage gauge to 20 feet, that a low as 15-17 feet, that is with coke depths of 23-25 feet, with a consequent increase in fresh charge capacity of 30 %-50%.

While the practice of the invention does not preclude the passage of the is readily accom- 6 I claim:

ing streams, maintaining a temperature approximating 920-925 upper portion of the reaction chamber.

.2. The process according to claim 1 wherein the said heavy tarry condensate is combinedwith liquid residue being delivered to the coking zone for coking.

JOSEPH MASON BARRON.

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