US2059734A - Art of coking hydrocarbons - Google Patents

Description

Nov. 3, 1933. w, w. JOHNSON ART OF COKING HYDROCARBONS Filed March 22, 1952 INVENTOR )fl//V//m I4( la/man QBY @www

ATTORNEYS Patented Nov. 3, 1936 UNI- TED STATES PATENT OFFICE 2,059,734 ART oF coKING nYDRocARBoNs William Walton Johnson, Houston, Tex., assignor f to Sinclair Refining Company, New York, N. Y.,

a corporation of Maine Application March 22, 1932, Serial No. 600,424

This invention relates to improvements in operations combining a cracking operation in which oil is heated to a high cracking temperature in vapor phase, a coking operation in which oil is` reduced `to coke by direct heat exchange with hot oil products from the cracking operation and a scrubbing operation in which oil to be reduced to coke is preheated by direct heat exchange with hot oil products from the cracking and coking operations. In one aspect, this invention relates to improvements in the combined operation described in Letters Patent Number 1,831,719, granted to SinclairRelning Company, November 10, 1931, on anl application of Harry L. Pelzer.

The invention has several important advantages including improvement of the quality of coke produced in vthe coking operation and improvement of the eiciency of the scrubbing operation. Where the entire stream of hot oil prod- 20' ucts discharged from the cracking operation is passed through the coking operation, as in the operation described in Letters Patent Number 1,831,719 for example, the Volume of gaseous material passing throughv the coking operation 25 tends to reduce the density of the coke produced and also tends ,to carry over into the scrubbing operation unnecessarily large amounts of entrained oily or tarry material. By reducing the volume of gaseous material passing through the 30 coking operation, a denser coke can be produced in the coking operation, and by, at the same time, utilizing the remaining volume of gaseous material to bring the oil to be reduced to coke to a higher temperature in the scrubbing operation, before it is supplied to the coking opera- 35 tion, the productive capacity of the combined operation can be maintained undiminished or even increased. Increase in density of the coke product also operates to increase the productive capacity, per cycle, of the apparatus used for carrying out the coking operation.

According to the present invention, the stream of hot oil products from the cracking operation is divided into two parts, one of these parts is 45 passed through the coking operation and then introduced into the scrubbing operation, the other of these parts is introduced directly into the scrubbing operation without passage through the coking operation, the oil to be reduced to coke is introduced into the scrubbing operation and the liquid oil mixture separated in the scrubbing operation is supplied to the coking operation. The total heat transfer effected in the coking operation and the scrubbing operation can thus be maintained undiminished, or even increased, but

a part of the burden is transferred from the coking operation to the scrubbing operation while a reduced Volume of gaseous material is passed through the coking operation. The invention will be further described in connection with the accompanying drawing, which illustrates diagrammatically and conventionally, in elevation and partly in section and with parts broken away, one form of apparatus adapted for carrying out the process of the invention.

The apparatus illustrated comprises a heaterl I, a coking receptacle 2, a scrubbing receptacle `3, a fractionating tower 4, a condenser 5, a receiver 6 and a heater feed pump 1.

Oil to be cracked is forced through the heater I by means of pump 1, the oil being supplied to the heater through connection 9 and the resulting hot oil products being discharged through connection Ill, and inthe heater is' heated to a high cracking temperature, upwards of 950-1050 F.,for, example. The stream of hot oil products discharged through connection I0 is divided into two parts, by means of valves II and I2. One part is passed through the coking receptacle 2 and then introducedinto the scrubbing receptacle 3 throughconnections I3, I4, I5 and I6. 'I'he other part is introduced directly into the scrubbing receptacle 3 through connection l1. The oil to be reduced to coke is supplied to the scrubbing receptacle 3 through connection I8,

and the liquid oil mixture separated in the scrubbing receptacle 3 is supplied to the coking receptacle 2 through connections I9 and 20 by means of pump 2|. The liquid oil mixture separated in the scrubbing receptacle 3` may be brought to a temperature of 725-825 F. for example in the scrubbing receptacle 3. That part of the hot oil products discharged from the heater I which is passed through the coking receptacle 2 is, with advantage, introduced into the cokingv receptacle at a temperature upwards of 950-1000 F., best at the maximum possible temperature. The coking receptacle illustrated may be one of a series of similar coking receptacles similarly connected between the manifolds I3a., .Ilia and I9a to' permit continuous functioning of the combined operation even though the operation of individual coking receptacles becomes intermittent to permit the discharge, from time to time, of charges of coke as they accumulate. The precise manner in which the cracking operation is carried out, and the form of apparatus in which it is carried out, are not important so long as the hot oil products of the cracking operation are discharged therefrom at temperatures upwards of 950-1050 F. The scrubbing operation may be carried out as described in Letters Patent Number 1,810,048, granted to Sinclair Refining Company, June 16, 1931, on an application of Eugene C. Herthel.

In the scrubbing operation carried on in the apparatus illustrated, the hot oil products coming directly from the cracking operation, through connection l1, and the hot oil products lcoming from the cracking operation through the coking operation, through connection I6, are discharged into and beneath the surface of a liquid body of oil maintained in the lower end of the scrubbing receptacle 3. Oil to be reduced to coke is supplied to this liquid body through connection I8 by means of pump 22. All or part of this oil may be introduced directly into the liquid body through connection 23, or all or part of this oil may be introduced into the Ascrubbing receptacle at an intermediate point in the path of vapor travel therethrough through connection 24, or all or part of this oil may be introduced into the liquid body after passing through the reux-condenser heat-exchanger 25 through connections 26 and 21. The oil to be reduced to coke, or part of it, or another oil stock, gas oil for example, may be supplied to the scrubbing receptacle through the connection between the coking receptacle and the scrubbing receptacle, connection l5 in the apparatus illustrated, as described in an application of Harry L. Pelzer, led March 7, 1932, Serial Number 597,187. The operation of the'scrubbing receptacle 3 may be controlled by the direct introduction of a reuxing agent through connection 28, by means of pump 29, or by means of either or both of the reflux condensers 25 and 30, or by these means conjointly. The reuxing agent supplied through connection 28 may comprise, for example, an oil vaporizing substantially completely under the conditions prevailing in the scrubbing receptacle 3; for example, a gas oil may be supplied through connection 3| or condensate separated in the fractionating tower 4 may be supplied through connection 32. The vapor mixture escaping from the scrubbing receptacle 3 is discharged into the lower part of the fractionating tower 4 through connection 33.

The fractionating tower 4 is arranged to permit the separation of one or two intermediate fractions. If two fractions are separated in the fractionating tower 4, the higher boiling fraction is discharged through connection 34 and the lower boiling fraction through connection 35. Either or both of these fractions may be supplied to the heater or either or both of these fractions may be discharged. The fraction discharged from the fractionating tower 4 through connection 34 may be discharged, in whole or in part, through connection 36, or may be supplied, in whole or in part, to the pump 1 through connection 31. The fraction discharged from the fractionating tower 4 through connection 35, may be discharged, in whole or in part, through connection 38, or may be supplied, in whole .or in part, to the pump 1 through connection 31. Raw oil stock may be supplied to the pump 1 through connection 39. The stock supplied toI the heater l may comprise mixtures of either or both of the fractions discharged from the fractionating tower 4 through connections 34 and 35 with raw stock supplied through connection 39, or the stock supplied to the heater l may consist exclusively of raw stock supplied through connection 39.

The fractionating ltower 4 may be controlled by .the direct introduction of a reiiuxing agent through connection 40, by means of pump 4I, or by means of either or both of the reflux condensers 42 and 43, or by both of these means conjointly. The reiiuxing agent supplied through connection 40 may comprise an oil vaporizing substantially completely under the conditions prevailing in the fractionating tower 4; for example, an extraneous gasoline stock may be supplied through connection 44 as described in Letters Patent Number 1,711,351, granted to Sinclair Refining Company, April 30, 1929, on an application of Edward W. Isom, or a part of the condensate product may be supplied through connection 45.

The vapor mixture escaping from the fractionating tower 4 flows to the condenser 5 through connection 46. The condenser 5 is connected to the receiver 6 in which the condensate product is separated from uncondensed vapors and gases, the condensate product being discharged through connection 41 and uncondensed vapors and gases through connection 48. Connection 49 is providedvto permit discharge of any water accumulating in the receiver 6, for example as a consequence of the introduction of steam into the coking receptacle 2 through connection 50 or into the scrubbing receptacle 3 through connection 5I. Connection 52 is provided for steaming out the coking receptacle 2.

The stocks supplied through connection I8 may comprise, for example, crudes, topped crudes, flux oils, tars including tars produced in cracking operations, other residual oils and the like. The stocks supplied through connection 39, or connection 3|, may comprise, for example, gas oil character and kerosene character stocks to be cracked. Gasoline, to be cracked or re-cracked, may also be supplied through connection 39. The combined operation of the invention is particularly advantageous for the production of motor fuel gasoline of high anti-knock value. y

In carrying out the invention, as in the apparatus illustrated, part but only part of the hot oil products discharged from the cracking operation is introduced into the scrubbing operation after passage through the coking operation and the remaining part of the hot oil products discharged from the cracking operation is introduced directly intol the scrubbing operation without passing through the coking operation. In the scrubbing operation the hot oil products coming from the cracking operation directly and from the cracking operation through the coking operation are subjected to direct heat exchange with oil to be reduced to coke thereby preheating this oil. At the same time, this oil acts as a scrubbing medium for the separation of oily and tarry material from these introduced hot oil products. The resulting preheated oil mixture is supplied to the coking operation to be reduced to coke. Because of the direct introduction of a part of the hot oil products from the cracking' voperation directly into the scrubbing operation,

to the scrubbing operation. This enables a re- 75 duced volume of gaseous material, hot oil products from the cracking operation, to carry the burden of the coking operation. The consequent reduction in volume of gaseous material passing through the coke, as it forms and as it accumulates,A in the coking operation, enables the production of a denser coke product. 'I'he reduction in volume of gaseous material passing through the coking operation, and through the receptacle in which the coking operation is carried out, also assists in limiting entrainment of oily and tarry material in the Vapor mixture passing from the coking operation to the scrubbing operation, thus improving the efficiency of the scrubbing operation in the combined operation. It is essential, to secure the advantages oi the present invention, both with respect to minimizing entrainme-nt from the coking receptacle and with respect to balancing the heat requirements of the coking operation and the scrubbing operation in the combined operation, that that part of the hot oil products from the cracking operation introduced directly into the scrubbing operation be so introduced Without passage through any part of the receptacle in which the coking operation is carried out.

I claim:

In an operation combining a cracking operation in which oil is heated to a high cracking temperature in vapor phase, a coklng operation in which oil is reduced to coke by direct heat` exchange with hot oil products from the cracking operation and a `scrubbing operation in which oill to be reduced to coke is preheated by direct heat exchange with hot oil products from the cracking and coking operations, the improvement which comprises dividing the stream of hot oil products from the cracking operation into two parts, passing one part of that stream through the coking operation and then introducing it into the scrubbing operation and during the coking operation, introducing the other part of

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