US2412879A

US2412879A - Chemical process

Info

Publication number: US2412879A
Application number: US395920A
Authority: US
Inventors: Herbert G M Fischer
Original assignee: Standard Oil Development Co
Current assignee: Standard Oil Development Co
Priority date: 1941-05-31
Filing date: 1941-05-31
Publication date: 1946-12-17
Anticipated expiration: 1963-12-17

Description

D 17, 1946 H. G, M. FISCHER 2, 12,819

CHEMICAL PROCESS Filed May 31, 1941 rzncrlolvn TING COL UM/Y MA TEE/Al.

coknvc DRU l COOL/NC JA (K HEAT/N6 COIL Patented Dec. 17, 1946 Herbert G. M.

Fischer, Westfield, N. J assignor to Standard Oil Development Company, a corporation of Delaware Application May 31, 1941,

Serial No. 395,920

7 Claims. 19655) The present invention relates to the art of treating hydrocarbon oils to obtain desired prodand more particularly it relates to the thermove constituents boiling up to about 700850 F.

In processing a crude petroleum oil, the modern refiner must deal with the crude material in a manner to provide maximum quantities of desired products, and from time to time the coinmercial demand for certain petroleum products may vary widely. For example, in the northern part of the United States during the winter refinery it is the practice to subject it to a When, however, the commercial demand is such that increased desirable, the reduced a thermal treatment quantities of gasoline are crude may be subjected to whereby a verted to vaporizable hydrocarbons and a solid coke.

The coking operation, as ordinarily practiced in a modern refinery, entails a. number of practical operating diificulties and disadvantages. Probably the most troublesome aspect of a coking operation is the removal of the coke from the coking zone. The coking operation is generally performed by heating the reduced crude to a temperature within the range of from 800-1000 F'., usually in a coil, and then discharging the to obtain the maxiheated oil into a chamber where the oil is maintained at the temperatures indicated and under atmospheric or superatmospheric pressure for a sufficient period of time to efiect the desired conversion. As the process of coking proceeds in the chamber, the coke formed in the process accumulates progressively until finally a time is reached when the coking operation with respect to a particular chamber must be discontinued in order to remove the coke. The decoking is a time-consuming and'laborious operation since'the coke forms a strong, tough mass which to completely' remove, as stated, involves a great deal of labor.

Usually after a coking chamber has been taken 0d the onstream operation, it is first permitted to cool, whereupon the operators remove the coke.

The coke removal in the ordinary intermittent coking process is an operation which consumes considerable time and labor and, consequently, any method which will eliminate a substantial portion of the time and cost necessary to decoke a chamber would effect a material advantage.

The main object of the present invention is to carry out the coking of heavy petroleum oils continuously by forming the coke in such a manner that it is" highly frangible, relatively soft, and adapted to be continuously removed from the coking zone.

A more specific object of my invention is to carry out a, coking operation in the presence of added cellulose linters, threads, sawdust, wood flour or other cellulosic material in divided form, under conditions such that the charcoal resulting from the added with the formed coke and greatly reduces the tensile strength of the latter so that it maybe easily removed from the coking zone.

" Other and further objects of my invention will appear from the ensuing more detailed description'of my present invention.

The present'invention will be best understood by reference to the accompanying drawing which shows diagrammatically a form and arrangement of apparatus elements in which my process may be carried into practical effect. I shall describe the process in terms of the coking of a specific reduced crude, but it is to be clearly understood that the specific example I have chosen is ptu'ely illustrative and does not constitute a limitation of'my invention.

Referring in detail to the drawing, a reduced East Texas crude petroleum oil having an A. P. I. gravity of 18 is introduced into the system through line I. Sawdust of theordin'ary' comcellulosic material intermixes,

it mercial grade is withdrawn from hopper l4 through star feeder i5 and conduit l1 and discharged into the oil in line i and thereafter a slurry of sawdust and oil is discharged by pump 3 into a coil 6; disposed in a suitable furnace setting 5. In coil 4 the oil is heated to a temperature of from about 800 F. to ll F., and during the heating operation the sawdust/is at least partially converted to charcoal. The heated oil is withdrawn from the coil through line 5 and discharged into the top of coking drum 25 as shown. In order to assist in the vaporization of the oil, steam at a temperature within the range of from about 825 F. to 1100 F. is discharged into the.

7 upper part of drum 25 through line 23. Instead of introducing the sawdust into the liquid oil in line I, the sawdust may be introduced into the vapors in line 9, employing for the mixing of the oil vapors into the sawdust any suitable device, such as an injection means. This may be accomplished by means of the by-pass 5i.

Valves

52 and 53 are arranged respectively in lines ii and 5! to control the flow of the finely divided solid either to the heating coil or to line 9. In either event the amount of sawdust mixed with the oil may be from 1% to 10% by weight of sawdust and 90% to 99% oil.

The oil, ordinarily containing sawdust and/or however introduced therein, as indicated into the top of coking drum 25. The oil passes downwardly through the drum 25 and during this passage it is converted to vaporizable hydrocarbons and non-vaporizable hydrocarbons. A heavy oil or tar is formed in drum 25 under the conditions stated, particularly in the upper section of the drum represented by A. The tarry material thereafter continues its downwardly progress through the drum and the conversion continues.

The heavy oil and the tar formed in the region generally indicated by A are converted to a frangible coke in. the region generally indicated by B. This coke: contains the charcoal resulting vaporized at least in part charcoal in line 9,

is then discharged 2- removed from the coking zone.

carbons, together with light and heavy naphtha, and light and heavy gas ol. These fractions may be recovered in any known manner and usually a heavy fraction is recycled to the line I! for further treatment in the process. A light fraction may be taken off from the top of column 42 by line 43 and a heavy fraction by line 50.

In order to point out the advantages of my presentinvention I may direct attention to a run which I made on an East Texas reduced crude having an A. P. I. gravity of l3, under the conditions hereinbefore specified, in which I employed 2% by weight of sawdust and found that 8% by weight of a friable, porous coke, based on the original feed, was formed. This coke was of such form and condition that it could be easily removed from a coking drum. I made a similar run with the same feed stock but omitted the sawdust, and I found that I obtained 15% by weight of coke and that the said coke was dense and hard and was difficult to remove from a coking drum. Therefore, there are two advantages in my present process, as follows: First, the amount of coke produced from a given stock is less and this means, of course, that more vaporizable hydrocarbons are produced, which is a known desideratum; and, second, the coke which I produced was easily crushable and porous in the case where I employed sawdust, while the reverse was true when sawdust was omitted.

To review briefly, the present invention relates to a; continuous coking operation carried out in the presence of a friable cellulosic material, such as sawdust, the sawdust serving to form an adsorbent charcoal during the heating, which charcoal is intermixed with the formed coke and renders the latter readily disintegratable or crushable' sothat it may be substantially continuously A relatively small amount of sawdust present in the oil during coking is sufficient to accomplish the desired result. I have found, for instance, that 2% by weight-of sawdust based on the oil fed is sufficient to produce a soft coke. The sawdust which I may from the car-bomzation of the sawdust, and it is 45 add may be either green wood sawdust or dry which forms a weak link in the structure of the coke so that the same may be readily broken into lumps and thus readily removed from the coking drum. If desired, grinding or crushing means the lower portion of drum 25 to disintegrate and reduce the coke into readily removable lumps. Additional steam, say at a temperature of 825 F. to 1100 F., may be discharged into the drum through line 30 volatile constituents.

The coke is withdrawn from the drum through a star feeder 3! and conduit 32. Since the. coke issuing from the drum 25 is at an elevated temperature, it is desirable to force this charcoal duce its temperature. This cooling; meansv may consist of water, or any other cooling fluid which may be circulated in a jacket surrounding conduit 32, or which: may not coke. The cooled coke is then discharged into a receiving" bin is at a temperature such that it will not ignite upon exposure to the air. Ordinarily a safe temperature would beone below 300 F. to 325 F.

The vapors formed in the coking drum 25 are withdrawn overhead through line 41 and delivered to a fractionating column 12. Ordinarily the coking operation results in the production of 5-25% of gasoline and. normally gaseous hydro- Zii may be positioned in be sprayed directly on the which is frangible sawdust. From a commercial standpoint, as well as from a technical standpoint, sawdust is a very desirable material since it is relatively inexpensive, constitutingto a large extent a waste product from saw-mills, and the like. I may of course use divided cellulosic material, such as in the form of wood flour, wood chips, wood meal, cotton linters, cottonseed hulls, etc.

The operation previously described is carried in order to purge the coke of 55 out under normal atmospheric pressure, but it is to be understood that my process is broad enough to be carried out under superatmosp'heric pressure; for instance, pressures as high as 100- 500 lbs/square inch in the coking zone. The

the withdrawn .60 amount of steam, if used, may be from 5-10 mol 7 coke through a suitable. cooling means 35 to rethis quantity is fed into the drum 28 and 38' as indicated. A- tem- F. in coking drum 25 gives per cent and 25 through lines perature of about l100 excellent results.

Many modifications of my invention will be apparent to those who are familiar with this particular art.

What I c aim is: r

1. A continuous method of. producing coke and easily disintegrated, comprising the coil preheating of a heavy petroleum oil to cok ng temperature but without substantial coke formation, commingling a cellulosic material with the preheated oil, passing the commingled preheated oil and cellulosic material into 6 r a zone wherein coke is formed, continuously dis- 1% to 10% of cellulosic material with a reduced integrating the coke, adjacent a point of withcrude petroleum oil and heating the mixture to drawal from said zone, and continuously remova temperature within the range of from about ing coke therefrom. 800 F. to 1100 F., thereafter discharging the oil 2. A continuous method of producing coke and cellulosic material into a coking zone, perwhich is frangible and easily disintegrated, committing the oil and cellulosic material to remain tinuously disintegrating the admixed coke and 4 The process set fOl th in claim 3 in which the charcoal adlacent a point of withdrawal from said cellulosic material is sawdus Z n a n n y moving the admixed 5. The process set forth in claim 3 in which the coke and charcoal therefrom. cellulosic material is wood flour.

3. A continuous method for converting ther- 20 6. The method set forth in claim 3 in which the mally a relatively heavy petroleum oil residual coke and charcoal mass are ground and then into vaporizable hydrocarbons containing subrecovered from the coking Zone.

Stantial quantities of s and coke-fo ming 7. The process set forth in claim 3 in which the constituents, Whlch process is characterized by cellulosic material is sawdust and in which the the feature that the coke produced is frangible 25 amount of sawdust is 2% by Weight of the oil. and readily crushable, which comprises mixing HERBERT G. M. FISCHER.