US2403608A

US2403608A - Method of coking oils

Info

Publication number: US2403608A
Application number: US370812A
Authority: US
Inventors: John W Payne; Henry D Noll; Vladimir A Kalichevsky
Original assignee: Socony Vacuum Oil Co Inc
Current assignee: ExxonMobil Oil Corp
Priority date: 1940-12-19
Filing date: 1940-12-19
Publication date: 1946-07-09
Anticipated expiration: 1963-07-09

Description

MY 99 l945 .J. w. PAYNE ETAL 2,403,503 y METHOD oF COKIN@ oILs I Filed nec. v19, 1940 INVENTORJ BY 2 A TORNEY Patented July 9, 1 946 John W. Payne, Woodbury,

Henry D. Noll,

Wenonah, and Vladimir A. Kalichevsky, Woodbury, N. J., assignors to Socony-Vacuum Oil Company, Incorporated, New York, N. Y., a corporation of New York Application December 19, 1940, Serial No. 370,812

3 Claims. 1

ration of a charging stock for cracking purposes,

in order that, by the prior removal of coke forming bodies, the charge may be more conveniently handled in the cracking process. This is particularly true of vapor phase catalytic processes, wherein the coke forming bodies deposit upon the catalytic material and rapidly decrease its usefulness.

' Coking methods in general fall into three types. In the older and obsolete method the whole of the oil to be coked was delivered into a still and coked therein by the application of heat through the still walls. A second method, widely proposed, but little used is that of flowing the oil, 'unheated or partially heated upon a bed of refractory or other spreading material, such as nlter clay or coke and allowing it to distill to dryness thereon. In this method *theV spreading material is heated either by being placed in a container surrounded by heating gases, or, with the spreading material working slowly down through the container, the coke is burned from it in a lower zone, and the hot gases therefrom pass through and heat the spreading material in the coking zone. from the severe penalties attendant upon trying to transfer heat in high quantities into a mass of spreading material of loW heat transmissive ability. The second suffers from admixture of gases of combustion with the distillates from coking. For these reasons, neither are widely used., The final and most widely used method is that of heating the oil in a flowing stream to such a temperature that it may be ash distilled to dryness, and then Passing it to a vapor separating chamber wherein vapors are removed and a coke deposit is built up.V Practically all commercially used processes are of this kind, and so operated Yas to build up a massive coke deposit in spite of the necessity for periodically removing the vaporizer from service to break up and remove the coke. Attempts have been made to achieve spray-coking variations of this to give granular instead of massive coke deposits, with some suc- The first modification suiers 1 cess but as yet without any wide commercial acceptance.

This invention has for its object the provision of an improved method of coking by the flashV vaporization method capable of avoiding entirely the difIiculties attendant upon the 'removal of massive coke deposits from the vaporizing chamber. It has as an additional object the provision of'a method wherein the deposit Within the chamber is caused to be a relatively free iiowing granular mass, not predominantly cokey in nature. It has as a further object the provision of a process wherein the coke, when passing through that adhesive, semi-plastic state characterizing a stage in its formation is kept from contact with the working parts of the equipment and prevented from adhering thereto to be later distilled to a hard highly adherent deposit.

All these and other objects llow from the basic concept of this process which is that of rst heating the oil in a owing stream to a temperature suiicient to insure its distillation to dryness and then introducing it into a bed of refractory erranu` lar material in a vaporizer. This invention may be understood by referencev tolthe drawing attached to this specification, in which Figure l 'shows a set-up of apparatus for the performance ofthe process as shown in diagram form, and Figure 2 shows certain alternative details. In Figure 1 of this drawing, I represents a coking chamber or vaporzer, 'and 2 a tubular heating furnace. Oil to be coked is introduced by pump 3 to pass through tubes 4 and 5 in furnace 2, wherein it is heated to a coking temperature and from there passes by pipe 6 to vaporizer I where it is introduced below the level of a granular packing or spreading material l. If desirable in order to avoid premature separation of vapors, or for any other purpose, back pressure may be held upon the heating coils 4 and 5 through the agency of valve 8. Steam, in regulated amounts, to assist in the vaporization, may be inserted either through pipe 9 or pipe I0.

While vaporizer I is shown only partially filled with packing material 1 it will be understood thatV any level of packing material found desirable may be carried, as later explained. In order to facilitate change of packing material 'during operations, the vaporizer is tted above with a charging bin or hopper` ll equipped with slide valves or other suitable closures I2 and I3 whereby accessrof air vto the vaporizer or escape of end of Vaporizer I. Alternatively, these hoppers maybe omitted, and another vaporizer such as i may be provided With alternate use of vaporizer and removal and charge of spreading'material in that one not used for vaporization. Vapors are led from@ vaporizer I through pipe II to the usual fractionatingvr equipment er to other use, as may be desired.

In Figure l, the vapors may be separated from any absorbent they may have entrained by a separator I8 inserted in the vapor line, or by a similarly functioning structure placed in the OD Ofv chamber I. In many cases, it maybe desirable to heat the absorbent material before introduction to the chamber, and, in such cases, hopper I I or its equivalent may be provided with tubes IS through which heat transfer medium at suitable temperature may be passed. In many cases, the material entering hopper Il will come thereto from a regenerating furnace, and need not be cooled before introduction.

A possible alternative form for the bottom of chamber-I is shown in Figure 2, wherein theV chamber is `at least partially'lled, from the bottom upward, by a baffling structure, Vsuch as the interlacedangle irons 223, through whichthe absorbent may lovv continuously if desired. In such cases, and with continuous flow, it is usually de sirable to utilize'asteam inletA 2 I, whereby steam may be introduced to cool, or purge, or blanket the absorbent, which may then 'be discharged, continuously, if desired, to atmosphere through throatl `22.

Steam purging or cooling may also be practised in Yhopper'ld of Figure 1 by means of pipe 23.

The packing or spreading material may be any material of a'granular, refractory, nature, preferably fairly free flowing, such as fullers earth', bauxite, prepared clays, crushed rebrick, crushed pumice,crushed coke of petroleum or coal origin, or similar material. It should be in a form such that it presents a fairly large surface/volume ratio and should be of sufcient size to be free iioW-' ing and not too readily'suspended Vin the vapor stream; Fullers earth of 304604mesh size is an exemplarymaterial, as' 'is clayY type catalyst in cylindrical pellet irom'Zl/g vto 4 mm. in diameter.

'In operation, the spreading material becomes heated to the coking temperature upon the en' trance' of the heated oil stream'and the distilla a tion takesl place W'ithinand upon thesurface of the spreading material.' The resulting coke is thus deposited within vand upon the surface lof this material, and a very considerable deposit of coke, to the amount of 25% 0r more'by Weight passage from liquid phase to coke is so rapid, that there is little opportunity for the formation of any deposits other than those formed in the spreading material.

Asan exampleof the operation of this process, a charge of 17.8 A. P. I. gravity crude residue may be heatedto 900 F.- and flashed in the presence of about 14% by liquid volume of steam to distll. off 'as an overhead 4.6% of non-condensible gases and 85.2% of clean distillate free of material having coke forming tendencies, to leave 10.2 percent of coke, all percentages being by Weight. If this operation is so handled according to this invention that the coke is deposited Yupon fullers earth, and the amount deposited limited to v10% of coke by Weight of the fullers earth', an amount which will not appreciably change the flow characteristics of the earth, a Coking chamber 10 feet in diameter, holding 25 feet of earth, would be sufficient for about four hours operation of a still handling 1000 barrels per stream day. Discharge of the chamber would' require a very much shorter time, and higher amounts of coke can be deposited without Yserious alteration of flow characteristics.

l The discharged spreading material may be burnedv under suitable conditions for the removal of the coke, and returned to the operation. In case the spreading material itself be coke, the disn charged material may beused as fuel in other operations, as for example, boiler furnaces or the furnace of this still.

We claim:

1.'A method for preparing charging stock for catalytic cracking which comprises heatinga petroleum charging stock 'to a temperature suicint to cause distillation to coke, introducing said vstock into and passing it in counter-current flow through a zone of moving granular Contact mass material, maintaining said zone substantially free of combustion supporting gas, and collecting the overhead vdistillate substantially free of cokeiorming constituents so that lit may be used as a charging stock in catalytic cracking with greatly reduced catalyst contamination.

2. A method for preparing charging stock for catalytic cracking which comprises heating a petroleum charging stock to a ltemperature sucient to cause distillation to coke, introducing said stock into and passing lit in c'ountercurrent nowV through a Zone of moving granular contact mass material, continuously adding granular contact mass material to said Zone and withdrawing it therefrom at a rate proportioned to the Vrate'of introduction of charging stock such that the accu'- mulation of coke on the granular contact mass material is never sufcientto substantially change the ovv characteristics of said material, maintaining said zone substantially free of combustion supporting gas, and collecting the overhead distillate substantiatlly free of coke-forming constituents soV thatit may be used as a charging stock in catalytic cracking with greatlyV reduced catalyst contamination. Y Y

3. 'A method for preparing charging stock for catalytic cracking which comprises heating a petroleum charging stock to a temperature Vsui-licient to cause distillation to coke, introducing said stock into and passing it in counter-current flow through a 'zone of moving granular Contact mass material, continuously adding heated granular con-tact mass material to said Zone and continuously withdrawing granular contact massmaterial having coke deposited thereon from said Zone While maintaining said zone substantially free ofl combustion supporting gas, and collecting 'theA overhead distillate substantiallyA free of coke-f VLADIMIR A. KALICHEVSKY.