US2422790A - Method of coking oils - Google Patents

Description

June 24, 1947. LEE ETAL 2,422,790

METHOD OF CQKING OILS Filed Bed. 19, 1940 an! [5 15/717 .9 N041.

INVENTORY I TORNEY k Patented June 24, 1947 METHOD OF COKING OILS Russell Lee and Henry D. Noll, Wenonah, and

Vladimir A. Kalichevsky, Woodbury, N. 1., aaaignors to Socony-Vacuum Oil Company, Incorporated, New York, N. Y., a corporation of New York Application December 19, 1940, Serial No. 370,813

4 Claims. 1

This invention is concerned with methods for the coking of mineral 011 residues, which have for their object the reduction of a heavy mineral oil fraction to a clean overhead stock, substantially free from constituents having coke forming tendencies under cracking conditions, and a solid carbonaceous residue of the nature of coke.

For many reasons it frequently becomes desirable to separate heavier petroleum oils in such manner. The more usual reason is for the preparation 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. I

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 filter clay or coke and allowing it to distill to dryness thereon. In this method the 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. The first modification suffers 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 flash distilled to dryness, and then passing it to a vapor separating chamber wherein vapors are removed and a coke deposit is built up. Practically all commercially used processes are of this kind, and so operated as 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 success but as yet without any wide commercial acceptance. v

This invention has for a major object the provision of a flash vaporization coking method wherein the coking distillation is conducted in the presence of a concurrently introduced flowing stream of granular solid adsorbent material, the solid residue of distillation being formed in and on said absorbent material and being conveyed from the vapor separation vessel therewith.

A first object is the provision of a flash vaporization coking process wherein the coke, during the period of its formation is brought into contact with nuclei of absorbent material upon which it may deposit. A further object is the prevention of adherence of coke particles, during the adherent, semiplastic stage of their formation, from coming in contact with apparatus parts whereon they may solidify to a hard, highly adherent deposit.

All these and other objects hereinafter set forth may be accomplished by the basic concept of this invention which is that of first heating the oil to be coked, in a flowing stream, to a temperature suflicient to insure its distillation to dryness, and flowing it into a vapor separating zone in company with a flowing stream of granular solid absorbent material.

This invention may be understood by reference to the drawing attached hereto, the single figure of which shows, in diagram form, an apparatus set-up wherein the process may be practiced.

In this drawing I represents a heating furnace and 2 a vapor separator. Oil to be coked is passed by pump 3 through heating coils l and 5 and passes through pipe 6 to vaporizer 2. If desirable, back pressure may be held on the oil during heating by valve 1. Suflicient heat is put into the oil in the furnace to insure distillation to dryness in vaporizer 2. If desirable, steam or other carrying agency such as light gases may be introduced by means of pipes 8 or 9, or into the vaporizer, as. by pipe I0. A dry. ranular, solid absorbent material such as fullers earth may be introduced, as by mechanism ll, so that the stream of oil and the stream of absorbent particles are intermingled in the vaporizer, thus causing the oil to vaporize in contact with the absorbent. In many cases, the absorbent so introduced will be returning from a regeneration operation and will be hot. In other cases, it may be desirable to heat it before introduction, and proper furnaces of known type may be installed for this purpose if desired. In some cases, it may be desirable to reflux the top of the vaporizer, either for control of product type or for control of carryover, and for this purpose trays or other contact devices l2 may be installed, provided with reflux from pipe l3. As discussed later, in some cases it is desirable to introduce absorbent into the oil, either before heating, or after heatin and before flashing, and to this end there is provided a mixing tank H, where a slurry of oil and absorbent may be made up, from which pump l5 may force oil through pipes l8, IT, or Hi. If

desired, provision may be made for preheating this slurry before introduction. The absorbent material, carrying the coke deposited thereupon will fall to the bottom of the vaporizer 2, from which it may be removed either intermittently or continuously by some device such as the star wheel l9. Vapor may be removed from the vaporizer by pipe 20, and purging, when necessary may be accomplished by admitting steam through pipe III or through pipe 2|.

Returning now to the absorbent material it may be any material of a granular, refractory, absorbent character, such as fullers earth, baux- 111 Prepared clay materials, crushed firebrick, crushed coke of petroleum or coal origin, or similar material. It should be in a form presenting a fairly large surface/volume ratio, and-yet of such size as to be free flowing in bulk. For introduction to the vaporizer. as at H, a fullers earth of -60 mesh size is an exemplary material. Another convenient material is pelleted clayey material, such as, for example, clay catalytic material in the form of short cylindrical pellets 2 to 4 m. m. in diameter. For introduction in slurry form, smaller sizes may in some cases be more desirable.

The intimate mixing of the stream of absorbent and the stream of oil in the distillation spaces causes the distillation to take place in such manner that the residue is deposited in and upon the absorbent. A very considerable amount of coke may be taken up by such absorbents and still leave a material substantially dry and free flowing in character. For example, a clay material of the nature of fullers earth or the clay pellets referred to may take about 25 percent or more of its weight of coke without substantial change in its handling characteristics.

It is of course necessary that the proportioning of the absorbent and oil be such that insufllcient coke is deposited to reduce the absorbent to a coherent mass.

Another feature arises from the possibility of introduction of the absorbent in slurry form into the stream of oil before vaporization. Particularly when relatively fine absorbent, say 60-100 mesh, is introduced to the oil stream prior to heating, the absorbent particles so introduced act as incipient coke collection points and so render the flnal clean separation of coke and vapor more easy by exerting an early control upon the size and density of the coke particles being formed.

Additionally, when an absorbent containing oil is used as a reflux at the top of the vaporizer 2 it has been found that considerable improvement in the cleanliness of overhead distillate may be experienced, as well as a valuable freedom from 4 buildup of cokey deposits in the vapor line 20 and in the fractionating equipment.

As an example of the operation of this process, a 22 A. P. 1. Oklahoma City residuum may be flashed at 900 F., in the presence of about 14% by liquid volumes (oil-water) of steam to yield about 97.4% by volume of a gas oil overhead, about 2.0% by weight of gas, and leave behind about 3.5% by weight of coke. If fullers earth be used as the absorbent material and it is desired to contaminate it only to the extent of about 10% by weight, then about 120 pounds of fullers earth may be fed the vaporizer per barrel of oil, and the resulting coked absorbent will be fully as dry and free flowing as that charged.

The discharged cokey absorbent may be regenerated in any manner suitable for the removal of coke, as by burning in known apparatus and returned to the process. In case coke be used as the absorbent, the discharged material may be used as fuel in its entirety.

We claim:

1. A method for preparing charging stock for catalytic cracking which comprises heating petroleum charging stock to a temperature suflicient to cause distillation to dryness, introducing the stock so heated into a vertically elongated chamber near the top thereof for free fall therein, maintaining said chamber substantially free of combustion supporting gas and products of combustion, introducing a flowing stream of granular contact mass material into said chamber below and in the path of fall of the heated stock, the flowing stream of contact mass material receiving the flowing stream of charging stock within said chamber in such manner that the vaporization takes place with the deposition of coke substantially wholly upon said contact mass without substantial alteration of the flow characteristics 4 thereof, and separately removing vapors and coke carrying contact mass from the top and bottom respectively of said chamber.

2. A method as claimed in claim 1 further comprising admixing granular contact mass material with said charging stock before introduction of the latter into the vaporizing chamber.

3. A method as claimed in claim 1 further comprising admixing granular contact mass material with said charging stock before heating thereof.

4. A method for preparing charging stock for catalytic cracking of mineral oil, which comprises heating petroleum charging stock under pressure to a temperature of about 900 F. sumcient to cause distillation to dryness, introducing the stock so heated into a vertically elongated chamber near the top thereof for free fall therein and flashing said stock therein, maintaining said chamber substantially free of combustion supporting gas and products of combustion, introducing a flowing stream of granular contact mass material into said chamber below and in the Path of fall of the heated stock. the flowing stream of contact mass material receiving the flowing stream of charging stock within said chamber in such manner that vaporization takes place with the deposition of the coke, substantially wholly upon said contact mass without substantial alteration of the flow characteristics thereof, removing vapors from the top of said chamber and separately removing the coke carrying contact mass from the bottom of said chamber.

RUSSELL LEE.

HENRY D. NOLL.

VLADIMIR A. KALICHEVSKY. (References on following page) REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Bowie et a1.- Apr. 24, 1923 Herthel et a1 Aug. 19, 1930 De Florez Apr. 8, 1941 10 Seguy Oct. 20, 1931 Knowles June 18, 1929 Number Number

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