US2366057A - Process of coking hydrocarbon oil - Google Patents

Description

F. R. RUSSELL PROCESS OF COKING HYDROCARBON OIL Filed Feb. 18, 194i Patented Dec. 26, 1944 I Francis R. Russell, Elizabeth, N.J., assignor to StandardOil Development Company, a corpo ration of Delaware Application February 18, 1941, SerialNo. 379,399

Claims.

The present invention relates to a method of treating hydrocarbons and, more particularly, it relates to a method of coking heavy hydrocarbon oils, such as topped or reduced crude petroleumoils, to produce gas oil, gasoline and coke.

terials being unavoidably also produced.

A great deal of research has been directed toward developing processes for coking heavy hydrocarbon oils in a continuous manner. As is well-known at the present time in the oil industry heavy residual hydrocarbon oils arecoked 1 in intermittent processes; that is to say,.the oil is heated to coking temperatures, and discharged into a drum,.usually heat insulated, where it is permitted to remain at coking conditions for a suflicient period of time to effect the desired conversion These processes result in the formation of considerable quantities of hard adherent cokewhichclings tenaciously to the walls of the drum. In this type of process, two or more drums are employed, and while the coking operation is taking place in one drum, the other drum ordrums are cooled and thereafter work} men remove'the coke from the drum usually by operations employing handtools. operation is difllcult, laborious and time-com suming and, consequently, the oil industry has been continuously seeking means to develop a The decoking charged. in the. form of droplets into the top of an elongated coking drum where it is permitted to pass'througha hot section to volatilize and crack the volatilizable constituents of the charg- 5 ing stock, leaving a residue of tacky carbonacesome noncondensable or normally gaseous ma- I ,tion into a cold section where the hot tacky H particles of carbonaceous material are cooled ous material which passes out of the hot secand hardened so that when they finally impinge 10 on the walls of the drum they are non-adherent and free flowing and may be withdrawn by gravityfrom the bottom of the said drum.

The present invention may be best under.-

stood by reference to the accompanying draw mg in which I Fig. I shows schematically a coking drum in which myinvention may be carried into eifect,

and in which it will benoted that the coking l drum proper is frustro-conic'al in shape and su goperimposed upon a cold section of greater diameter than the coking section and carries a water jacket or other cooling means, and; c

Fig. II represents a modification thereof in which water or other liquid is used as a cooling w 5 medium in, the cooling section. T

Referring in detail to Fig. I, a heavy residual crude petroleum oil, such astopped crude having an A. P. I. gravity of say 18 and obtained by distilling oil? the constituents of an East process which would constitute a distinct advantage over past and present methods. The present invention relates to a methodof con-. tinuously coking all of the heavy petroleum oil under conditions such that the coke formed in the process is of the buckshot type, that is to Texas crude oil boiling up to say 825 E; was i c discharged into the system through line Lthence discharged into a pump 3, thence discharged into a line 4 and thence discharged into a coil Q 6 disposed in a furnace setting 1 where the crude oil was heated to a temperature of from about say, a free-flowing powder-like dry coke, which is non-adherent and which may be continuously withdrawn from, the drum and, in particular, which coke does not adhere to the drum and form thick layers which would necessitate irequent shutdowns to remove the same.

It is realized that prior to this invention others had devised methods for continuous cok-' ing, but these methods have not been entirely successful. Perhaps the most successful methods developed heretofore are those in which a powdered material suchas sawdust is sprayed with theoil into the top of an elongated cylindrical coking drum, with the result that the tacky residues; regardless of the volatilizable a process in which a heavy residual oil ispre heated to coking temperatures and .then dis 850 F.-l100 F., the oil being passed through the coil at a suflicient rate of speed to permit only a limited amount of cracking in the said coil, so, that no appreciable coke forms in the 40 cgil or spray nozzles to be described. This can *be accomplished by heating the oil while it fiows through tubes of relatively small internal diameter, say from 1 in. to 2 in., with 3 in. as the upper limit, the oil flowingthrough the: tubes 5 at a relativelyhigh velocity; The oil heated to the temperature range indicated was withdrawn from the coil through line B and discharged into the top of coking drum l2, the oil in the drum emerging from a spray or atomizing device l4 ISOof conventional design. It, will be noted that constituents of the charging stock, are absorbed the coking drum is slightly.frustro conicaI in shape in the section indicated by C and that it 1 is superimposed on a cold section D, which section has a greater internal diameter than the of its greatest diameter. However, section C may be substantially cylindrical. The cold section D carries a cooling jacket I6 adapted to contain cold water, that is to say, a liquid having a temperature of 20 F. or thereabouts, or any other cooling medium. At least a portion of the water may be vaporized and a great cooling effect is obtained by said vaporization. The lower portion or base of the drum I2 is in communication, by means of conduit 20, with a screw conveyor 22, and as will more fully appear hereinafter, the coke delivered to screw conveyor 22 is discharged by the said conveyor into a receiving bin 26 or other suitable receptacle. Any known means for conveying or feeding a solid material may be employed. The volatile constituents resulting from the coking operation are withdrawn overhead from drum I2 through In order to assist in the general coking operation and, in particular, to facilitate the volatilization of those constituents of the original charging stock which may be readily volatilized, superheated steam, say at a temperature of 1100 F., was discharged into the lower end of the hot section through line '32. This steam had the effect of preventing the diffusion of hot gases into the cold section and tended to cause a general upward current or sweep of 'volatilizable constituents. The linear velocity, however, of gases, that is to say, the total gases in the hot section upwardly, should not be greater than -ft./second, and preferably is of the order of 1-2 ft./second,.so that entrainment of oil droplets or tar or coke shall not take place but rather that the said oil particles or tar or coke particles may substantially all pass by gravity through the hot.section to the cold section of the said drum. Furthermore, the vapor velocity should be solow that serious turbulence causing impingement of the tacky droplets or and hardened and in this form they were disthat, due to the particular shape of the top section I2, there is little or no tendency for sticky lumps or particles of tarry material or coke to cling or adhere to the inner walls of the said section, since the walls of the latter recede outwardly. By provision of lip l2--a further security against liquid issuing from spray nozzle l4 contacting the walls of the drum is obtained. Were it not for the said lip eddy current or the like might cause some liquid to be blown against the walls of the drum.

In Fig. II reference characters similar. to those in Fig. I apply to similar parts.

It will be noted that in this modification, oil ispreheated and sprayed into hot section C as in the prior modification. The coke formed,

however, gravitates into a water sump [1 which may or may not be coated with a layer of oil l8. The water is at'ordinary atmospheric temperature or at least below about 212 F. and it acts to chill and harden the coke and render it non-adhesive.

Optionally, water from pipe 20 may be discharged into the space above the liquid I! or IR to subject the coke to a preliminary cooling. Thereafter, the coke passes downwardly through the oil and water l8 and I1 and is withdrawn through gate valve 3| and pipe 30 in the form of a coke and-water slurry. Preferably, valve 3| is operated responsive to float 33 through relay electrical circuit 32 or some equivalent motivating means, in order, if desired, to maintain water discharged through inlet l-5 into water ll at some predetermined level. Another method of maintaining the water I! at a substantially constant levelis to provide pipe 34 with a horizontal bend or portion positioned at about the desired vertical level of water ll, whereupon a coke slurry may be withdrawn continuously from the'discharge end of the pipe 34.

Any liquid, such as hydrocarbon oil, brine so lution, etc., may be used in place of water.

Many modifications of my invention will be apparent to those skilled in this art without departing from the spirit thereof.

What'Lclaim is: v

1. A continuous method for coking heavy residual hydrocarbon oils which comprises heating the said oils to coking temperatures, discharging the said preheated oil into the top of a coking zone, the said coking zone being frustroconical in shape and having its largest diameter at the bottom thereof, causing the oil to charged from the drum through line 20 into conveyor 22 and from there into bin 26. der to prevent the escape of vapors from the cokingzone, it is advisable to cause a gas, such as flue gas, CO2, steam, etc., to flow counter- .buckshot coke may be discharged from the In ordrum through a star conveyor or any other device a into a receiving bin.

Inthe preceding description; i, l will be noted flow substantially straight down aided by gravity through the coking zone in a path whose diameter is substantially less than that of the said coking zone and which path is substantially concentric with the coking zone where volatilizable constituents are formed and removed from the'coking zone leaving a residue of coke, causing the coke to pass through a cooling zone where it is dried and hardened, and continuously recovering a free-flowing non-adherent coke from the bottom of said coking zone.

2. A continuous method for coking reduced crude petroleum oil which comprises heating the oil to a temperature within the range of from about 850 F. to 1100 F. in a preheating zone, withdrawing the oil from the preheating zoneand discharging it into the top of a vertical frustroconical coking zone, which zone is of greater diameter at the lower end,

is in indirect heat-exchange relation with the 10 coke.

4. The process set forth in claim 2 in which the cooling medium is a liquid in direct contact with the coke to be cooled.

5. The process set forth in claim 2 in which extraneous superheated steam is employed in the coking section to aid the volatilization of the lighter hydrocarbons.

FRANCIS R. RUSSELL.

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