US1960909A - Art of cracking hydrocarbons - Google Patents

Description

, May 29, 1934. E. w. ISOM ART OF CRACKING HYDROCARBONS Filed April 14, 1931 (bade/merfrarf/aoa #0 Tower Vapor Separaflng Recap fa c/e ATTORNEYS Patented May 29, 1934 UNETED STATES ART OF CRACKING HYDROCARBONS Edward W. Isom, Sear sdale, N. Y., assigncr to Sinclair Refining Company, New York, N. Y., a

corporation of Maine Application April 14,

4 Claims.

This invention relates toimprovements in the production of lower boiling oils, such as gasoline, from higher boiling oils, such as crude oil, topped crude oil, flux oil and the like. The invention relates particularly to improvements in operations, carried out for this purpose, to which a dirty higher boiling stock is supplied and in which a clean higher boiling stock separated from the dirty higher boiling stock in the operation is heated after separation from the dirty stock to a high cracking temperature and in which vaporized components of both stocks are together subjected to a refluxing operation for the separation of the desired product or products and the clean stock to be heated in the operation to a high cracking temperature.

According to the present invention, the refluxing operation in which the separation of the desired product or products from the clean stock to be heated to a high cracking temperature is effected is controlled by passing reflux condensate from this refluxing operation in heat exchange with the vapors therein after cooling this reflux condensate by heat exchange with the dirty stock supplied to the operation, the dirty stock being concurrently preheated by this heat exchange.

' direct or indirect or both. Important advantages with respect to heat economy and with respect to control of the operation, among others, are thus secured without involving any contact between or intermixture of the dirty stock or any part of it and the vapors or any part of them or any condensate separated therefrom inthe refluxing operation.

The invention will be further described in. connection with the accompanying drawing which illustrates, diagrammatically and conventionally, one form of apparatus adapted for carrying out the invention. It is intended and will be understood that this more detailed description of the invention is for the purpose of illustration. The invention can be carried out in other and different forms of apparatus.

The apparatus illustrated in the accompanying drawing comprises two heating conduits 1 and 2 arranged in separate heating furnaces 3 and 4 respectively, a vapor separating receptacle 5, a fractionating tower 6, a heat exchanger 7, a condenser 8 and receiver 9, a cooler 10, and pumps 11, 1'2 and 13. The heating furnaces 3 and 4 maybe of any preferred construction and 1931, Serial No. 529,978

arrangement. The vapor separating receptacle 5 may be externally unheated but thermally in-, sulated to minimize heat loss. The fractionatirig tower 6 may be of any preferred construction, conventional bubble tower construction for example. This tower also may be thermally insulated to minimize heat loss. Pump 12 may be of any preferred type of hot oil pump. Any of the conventional forms may be used for the other elements of the apparatus.

In carrying out the invention in the apparatus illustrated in the accompanying drawing, a stream of residual stock, supplied through'connection 14, is forced successively through the heat exchanger '7 and the heating conduit 1' into the vapor separating receptacle 5 by means oi pump 11 and in the heating conduit 1 is heated to a temperature, for example, approximating 650850 F., a stream of distillate stock supplied through connection 15 or connections 15 and 16 is forced through the heating conduit 2 into the vapor separating receptacle '5 by means of pump 12 andin the heating conduit 2 is heated to a temperature, for example, approximating 900- 1050" F., vapors are taken off from the vapor sep-' arating receptacle 5 through connection 17 and in the fractionating tower 6 are subjected to a refluxing operation, one or more lower boiling products being taken off through connections 18, or 18 and 19, reflux condensate being supplied from the fractionating tower'6 to the heating conduit 2 through connection 15, and the refluxing operation is controlled, although not necessarily exclusively so, by heat exchange between the vapors in the refluxing operation and. reflux condensate returned to the refluxing operation through connection 20 after passing through the heat exchanger '7 in which the reflux condensate passing therethrough is cooled by heat exchange with theresidual stock supplied through connection 14.

Although the severe cracking effected in carrying out the operation in the apparatus illustrated is eiiected entirely in the heating conduit 2, some cracking may be effected in the'heating conduit 1. However, in general it is advantageous to limit the temperature to which the dirty stock supplied to the heating conduit 1 is heated therein to a temperature below which no substantial cracking of components of this stock occurs.

The residual stock supplied to the heating conduit 1 may be supplied thereto under a pressure just suflicient to force it therethrough into the vapor separating receptacle 5 orit may be supplied under a somewhat higher pressure and this margin of pressure released as the hot oil products from the heating conduit 1 are discharged into the vapor separating receptacle 5. Similarly, the distillate stock supplied to the heating conduit 2 may be supplied thereto under a pressure just sufficient to force it therethrough into the vapor separating receptacle 5 or it may be supplied under a higher pressure and this margin of pressure released as the hot oil products from the heating conduit 2 are discharged into the vapor separating receptacle 5. The vapor separating receptacle 5 may be operated under a pressure, for example, in the neighborhood of atmospheric pressure or under a higher pressure, 100-150 pounds per square inch for example. The discharge pressure from the heating conduit 1 may exceed that prevailing in the vapor sepa rating receptacle 5 by as much as 100-200 pounds per square inch for example, and the discharge pressure from the heating conduit 2 may exceed that prevailing in the vapor separating receptacle 5 by as much as 500-800 pounds per square inch for example. Valves 21 and 22 are provided for maintaining any desired differential between the discharge pressure from the heating conduit 1 and the pressure prevailing in the vapor separating receptacle 5, and valve 23 is provided for maintaining any desired differential between the discharge pressure from the heating conduit 2 and the pressure prevailing in the vapor separating receptacle 5. The two streams of hot oil products discharged from the heating conduits 1 and 2 may be introduced into the vapor separating receptacle 5 at separate points or the hot oil products discharged from the heating conduit 1 may be introduced into the hotter oil products discharged from the heating conduit 2 before the latter are introduced into the vapor separating receptacle 5 to assist in checking overcracking of components of the latter. Residual tar is discharged from the vapor separating receptacle 5 through connection 24.

The reflux condensate supplied to the heating conduit 2 through connection is a distillate stock, or clean stock, having been separated as vapors from unvaporized constituents in the vapor separating receptacle 5 and condensed in the fractionating tower 6. Additional quantities of similar distillate stocks, or clean stocks, such as gas oil character or kerosene character fractions may be supplied through connection 16. The residual stocks supplied through connection 14 embrace crude oil stocks, topped crude oil stocks, flux oil stocks, tars from pressure distillation cracking operations, and similar dirty stocks.

The heating furnace 3 as illustrated is ar ranged to provide countercurrent heat exchange between the heating gases and the stock passing through the heating conduit 1, the stock thus being heated to a temperature progressing gradually to the maximum attained. The heating furnace 4 as illustrated is arranged to provide concurrent heat exchange between the heating gases and the stock passing through the heating conduit 2, thus making it possible to bring the stockto a high temperature approximating the maximum attained more or less quickly and to maintain it at this temperature or at a temperature gradually increasing from this temperature to the maximum attained for a longer or shorter period of time in the heating conduit by controlling the rate of firing of the furnace with respect to the rate of circulation of the stock through the heating conduit.

The cooled reflux condensate used for controlling the refluxing operation carried out in the frac-tionating tower 6 returned through connection may comprise all or a part forced through the heat exchanger 7 by means of the pump 12, the valve 25 being closed and the other part being supplied to the heating conduit 2, or all of the reflux condensate may be forced through the heat exchanger '7 and part returned through connection 20 and part supplied to the heating conduit 2 through valves 26 and 25 respectively, valve 27 being closed, or part of the reflux condensate may be supplied to the heating conduit 2 without passing through heat exchanger 7 through valve 2'? and part of the reflux condensate forced through the heat exchanger '7, this latter part being again divided by means of valves 25 and 26.

The cooled reflux condensate returned through connection 20 for controlling the refluxing operation may be introduced into the fractionating tower 6 through connection 28, in direct heat exchange with the vapors in the refluxing operation, or it may be circulated through the cooling coil 29 in the upper end of the fractionating tower 6 in indirect heat exchange with the vapors in the refluxing operation, and then either introduced into the fractionating tower 6 through connection 28 or discharged into connection 15 through connection 30. It will be appreciated that valved connection 31 and valved connection 32 may be closed completely in such operations or that either or both of these connections may be opened as by-passes to an extent regulated to assist in controlling the refluxing operation. A single product, gasoline for example, may be taken off as vapors through connection 18 or one or more additional products, kerosene and light gas oil for example, may be taken oi as condensates through connection 19 or corresponding connections. Uncondensed vapors and gases are separated in the receiver 9, the condensed product, gasoline for example, being discharged through connection 33 and uncondensed vapors and gases through connection 34. Control of ios lit

the refluxing operation in the fractionating tower 6 may be supplemented by the return through heated to a temperature of 750 F. as discharged from the heating coil 1. The discharge pressure of coil 1 may be maintained at approximately 200 pounds per square inch. Condensate from the bottom of the fractionating tower 6, having a gravity of 28-32 Baum, advantageously may be heated to a temperature of 975980 F. as discharged from heating coil 2, while maintaining a discharge pressure of 700-750 pounds per square inch thereon. The pressure in the vapor separating receptacle advantageously may be reduced to 35-50 pounds per square inch. Condensate withdrawn from the bottom of fractionating tower 6 at a temperature of approximately 625 F. may be cooled to about 225 F. by heat exchange with the dirty stock in heat exchanger 7. Condensate cooled in this manner may be turned to the upper end of the fractionating towerin quantities regulated to maintain the tem- Baume gravity topped crude advantageously may be perature of the vapor mixture in the upper end of this tower at about 380 F.

In operations in which an overhead product is taken off as vapors, as through connection 18, and an additional condensate product is taken oil, as through connection 19, the arrangement of apparatus illustrated is particularly advantageous in providing for control of the refluxing operation in the upper part of the fractionating tower by indirect heat exchange between the vapors and the refluxing medium in this region and providing for control of the refluxing operation in the lower part of the fractionating tower, below the point at which the additional condensate product is taken off, by means of direct heat exchange between the vapors and the refluxing medium in this region.

I claim:

1. In the production of lower boiling hydrocarbon oils from higher boiling hydrocarbon oils, the improvement which comprises forcing a residual siock in a confined stream through a heating zone and thence directly into a vapor sepa rating receptacle, heating said stream of residual stock in said heating zone to at least an incipient crackin temperature at which its lower boiling components will vaporize, forcing a distillate stock in a confined stream through a second heating zone and thence directly into said vapor separating receptacle, heating said stream of distillate stock to a high cracking temperature in said second heating zone, taking off vapors from said vapor separating receptacle and subjecting them to a refluxing operation, supplying reflux condensate from said refluxing operation to said second heating zone, controlling said refluxing operation while passing reflux condensate from said refluxing operation in countercurrent indirect heat exchange with said stream of residual stock on its way to said first mentioned heating zone, thereby cooling the former, and passing the thus cooled condensate in heat exchange with the vapors in the said refluxing operation.

2. In the production of lower boiling hydrocarbon oils from higher boiling hydrocarbon oils, the improvement which comprises forcing a residual stock in a confined stream through a heating zone and thence directly into a vapor separating receptacle, heating said stream of residual stock in said heating zone to an incipient cracking temperature at which its lower boiling components will vaporize but at which no substantial cracking of its components occurs, forcing a distillate stock in a confined stream through a second heating zone and thence directly into said vapor separating receptacle, heating said stream of distillate stock to a high cracking temperature in said second heating zone, taking ofi vapors from said vapor separating receptacle and subjecting them to a refluxing operation, supplying reflux condensate from said refluxing operation to said second heating zone, controlling said refluxing operation by passing reflux condensate from said refluxing operation in countercurrent indirect heat exchange with said stream of residual stock on its way to said first mentioned heating zone, thereby cooling the former, and passing the thus cooled condensate in heat exchange with the vapors in the said refluxing operation.

3. In the production of lower boiling hydrocarbon oils from higher boiling hydrocarbon oils, the improvement which comprises forcing a residual stock in a confined stream through a heating zone and thence directly into a vapor separating receptacle, heating said stream of residual stock in said heating zone to at least an incipient cracking temperature at which its lower boiling components will vaporize, forcing a distillate stock in a confined stream through a second heating zone and thence directly into said vapor separating receptacle, heating said stream of distillate stock to a high cracking temperature in said second heating zone, taking off vapors from said vapor separating receptacle and subjecting them to a refluxing operation, supplying reflux condensate from said refluxing operation to said second heating zone, controlling said refluxing operation by passing reflux condensate from said refluxing operation in countercurrent indirect heat exchange with said stream of residual stock on its way to said first mentioned heating zone, thereby cooling the former, and passing the thus cooled condensate in direct heat exchange with the vapors in the said refluxing operation.

4. In the production of lower boiling hydrocarbon oils from higher boiling hydrocarbon oils, the improvement which comprises forcing a residual stock in a confined stream through a heating zone and thence directly into a vapor separating receptacle, heating said stream of residual stock in said heating zone to at least an incipient cracking temperature at which its lower boiling components will vaporize, forcing a distillate stock in a confined stream through a second heating zone and thence directly into said vapor separating receptacle, heating said stream of distillate stock to a high cracking temperature in said second heating zone, taking oii vapors from said vapor separating receptacle and subjecting them to a refluxing operation, supplying reflux condensate from said refluxing-operation to said second heating zone, controlling said refluxing operation by passing reflux condensate from' said refluxing operation in countercurrent indirect heat exchange with said stream of residual stock on its way to its first mentioned heating zone, thereby cooling the former, and passing the thus cooled condensate in indirect heat exchange with the vapors in the said refluxing operation.

EDWARD W. ISOM.

Images