US1960908A - Art of cracking hydrocarbons - Google Patents

Description

May 29, 1934- E. w. ISOM ET AL 1,960,908

ART OF CRACKING HYDROCARBONS Filed June 12, 1929 d1 6 1 A/e/ 0/7 ATTORNEYS Patented May 29, 1934 UNITED STATES PATENT OFFICE ART OF CRACKING HYDROCARBONS tion of Maine Application June 12, 1929, Serial No. 370,281

2 Claims.

This invention relates to improvements in the manufacture of lower boiling hydrocarbon oils, such as gasoline, from higher boiling hydrocarbon oils, such as gas oil, crude oil and reduced crude oil.

The present invention provides an improved method of cracking higher boiling hydrocarbon oils in which high boiling oil is heated to a high cracking temperature, upwards of about 900 F.,

under superatmospheric pressure to produce a high yield of gasoline in a single passage as a stream of high velocity through a heating opera tion, in which the hot oil products from the heat ing operation are suddenly cooled by direct heat exchange with introduced cooler high boiling oil to arrest objectionable reaction prior to separation, following expansion, of vaporized components and residual components of these hot oil products, and in which the hot oil products from the heating operation prior to such cooling are passed in brief indirect heat exchanging relation with residual components separated from the cooled oil mixture to assist in cooling the hot oil products from the heating operation and to promote complete separation of low boiling components from the residual oil mixture.

According to the present invention, a flowing stream of high boiling oil is heated to a high cracking temperature under superatmospheric pressure, the total stream of hot oil products from the heating operation is passed under maintained superatmospheric pressure in indirect heat exchanging relation with a body of residual oil in a vapor separating receptacle, the pressure on the 115 stream of hot oil products from the heating operation is then reduced and they are released under reduced pressure within the vapor separating receptacle, a stream of cooler high boiling oil is introduced into the stream of hot oil products from the heating operation before these hot oil products are released within the vapor separating receptacle but after the heat exchange with the body of residual oil therein, vapors including vapors of the desired low boiling oil are taken off the heat exchange with the body of residual oil therein, and residual oil is discharged from the vapor separating receptacle. The vapors taken off from the vapor separating receptacle may be subjected to any suitable condensing or fractionating and condensing or other recovery operation.

The invention will be further described in connection with the accompanying drawing which 5 illustrates, diagrammatically and conventionally,

fromthe vapor separating receptacle but afterin elevation and partly in section and with parts broken away, one form of apparatus adapted for carrying out the invention.

In carrying out the invention in the apparatus illustrated, high boiling oil, gas 011 for example, is forced, as a stream, through the heating conduit l in the heating furnace 2, the heat exchange coil 3 and the pressure regulating and reducing valve 4, successively, into the vapor separating receptacle 5 by means of pump 6; the high boiling oil is heated to a high cracking temperature, 900950 F. for example, under superatmospheric pressure, 300-600 pounds per square inch as discharged from the heating conduit for example, maintained and regulated by means of valve 4, in the heating conduit 1; the pressure on the stream of hot oil products discharged from the heating conduit is reduced at the valve 4, to a pressure approximating atmospheric pressure but sufiicient to maintain flow through the rest of the apparatus for example; relatively cool high boiling oil, gas oil, crude oil or reduced crude oil, or a high boiling oil fraction produced in the operation-for example, is introduced into the stream of hot oil products passing from the heat exchange coil 3 to the vapor separating receptacle 5 through connection 7; vapors, including vaporized components of the hot oil products discharged from the heating conduit and any vaporized components of the introduced cooling oil, separate from residual oil in the vapor separating receptacle 5 and escape through connection 9, to recovery apparatus for the separation and condensation of the low boiling oil product, gasoline for example; and a body of this residual oil is 9 maintained in the lower end of vapor separating receptacle 5 normally submerging the heat exchange coil 3 from which residual oil is discharged through connection 10 as the operation proceeds. The cooling high boiling oil may be introduced into the stream of hot oil products discharged from the heating conduit either be fore or after the reduction of pressure thereon, although the latter scheme of operation is usually more advantageous, but this cooling high boiling oil is introduced into the hot oil products discharged from the heating conduit after they have passed through the heat exchange coil 3 and before they are released within the vapor separating receptacle 5. The rate of introduction of cooling high boiling oil may be regulated to make the temperature of the resulting oil mixture so low that further reaction of the hot oil products discharged from the heating conduit 1 is arrested, although high enough to involve cracking 119 of components of the introduced cooling oil, or

so low as to inhibit any cracking of any components of the resulting oil mixture; the temperature of the body of residual oil in the lower end 5 of the vapor separating receptacle 5 may be maintainedjn the range approximating 7008()0 F. or in a 'irange approximating GOO-700 F. for example. The heat exchange coil 3 is advantageously arranged so that the path of travel therethrough for the hot oil products discharged fromthe heating conduit is short to minimize the period of time over which these hot oil products are subjected to cooling by. this indirect heat exchange. In the apparatus illustrated, the cooling high boiling oil is introduced-through connection 7 in intimate mixture with the hot oil products discharged from the heating conduit. This cooling high boiling oil must be supplied through connection '7 at a temperature lower than that at which the hot oil products from the heating conduitenter connection 8, but it may be used, beforelbeing :so supplied through connection '7, as a cooling medium in heat recovery heat exchangerslandso preheated to temperatures as high as 600 F. or higher prior to introduction into the, hot oil products discharged from the heating conduit.

' In initiating operation in the apparatus illus trated, high boiling oil is circulated from the 30 vapor separating receptacle 5 through the heat.- ing conduit 1 back to the vapor separating receptacle 5 by means of pump 6 and connection 11, valve 12 in connection 11, however, being closed during normal operation. During normal opera- 35' tion, residual oil discharged from the vapor separating receptacle 5 through connection is discharged through cooler 13 and connection 14.

The vapors escaping from the upper end of the vapor separating receptacle 5 through connection 9 are discharged into the lower end of fractionating tower 15. This fractionating tower may, for example, be of conventional bubble tower construction. The vapors remaining uncondensed escape from the upper end of fractionating tower 15 through connection 16 to condenser 17 arranged to discharge into the receiver 1 8,ijioin which condensate is discharged through connection 19 and uncondensed vapors and gases through "connection 20. The operation of the fractionating tower may be controlled, or in part controlled, by the regulated introduction of a part of the condensate collected in receiver 18, or. some similar low boiling fraction, into the upper endof the tower through connection 21 by means of pump 22. The operation of the fractionating tower 15 may also be controlled, in part, by the regulated introduction of raw hig'hboiling oil into the tower at an intermediate point through connection 23 by means of pump 24; .The operation of the fractionating tower 15 may also be controlled by regulated circulation of relatively cool high boiling oil through the heat exchange coil 25 by means of pump 26. An intermediate fraction may be discharged as a condensate from the fractionating tower 15 at an intermediate point through connection 27. The apparatusillustrated is arranged to provide for return 'to the fractionating tower 15 of vapors entrained in such discharged condensate or separated therefrom by the maintenance of a somewhat lower pressure in the separator 28 than prevails in the fractionating tower 15 at the point irompwhic'h the condensate is discharged, from 7 separator 28 through connection 29. Any intermediate fraction. so discharged is discharged from -oil supplied to the heating conduit 1 by means or pump 6 may consist exclusively of a condensate fraction separated in the fractionating tower 15 or of raw oil supplied through connection 32, or it may comprise a mixture including such a condensate fraction and raw oil.

The cooling high boiling oil supplied through connection 7 may consist either of raw high boiling oil, such as crude oil or reduced crude oil, supplied through heat exchange coil 25 and connection 38, or of raw high boiling oil, such as gas oil or crude oil or reduced crude oil, supplied through connections 36, 3'7 and 3 9, or of a condensate fraction supplied from the lower end of fractionating towerv 15 through cooler 35 and connections 37 and 39, or of any mixture of such oils or oil fractions.

I, The'coolers 13, 35 and 30, or such of these coolers as are utilized in carrying out the invention in apparatus such as that illustrated, may consist of heat exchangers in which oil tobe processed or undergoing processing in the operation of the present invention or in some other operation is used as a cooling medium, or some extraneous cooling medium, water for example, may be used as a cooling medium in these coolers. fl t) In the apparatus illustrated, the vapor separating receptacle 5, the iractionating tower 15, and connections '7, 8, 9, 33, 34. and 38 are with advantage thoroughly lagged or thermally insulated.

In the improved method of operation provided by the present invention, any tendency toward entrainment of low boiling, or intermediate boiling, components, entrained or dissolved, in the residual oil discharged from the vapor separating receptacle is reduced to a minimum, although this residual oil includes not only very high boiling components of the hot oil products discharged from the heating'operation but also any very high boiling components of the cooling high fig); boiling oil introduced into thesehot oil products discharged from the heating operation, by means of a heat exchange which assists in cooling, or in initiating the cooling, of the hot oil products discharged from the heating operation but which 1730 heat exchange, limited by the temperature differential between the twomediainvolved as well as by the brief periodor" heat exchange preceding immediate further cooling of the hot oil products by direct heat exchange with the introduced cooling oil, need not involve any objectionable further reaction of the hot oil productsdischarged from the heating operation. Any tendency toward deposition of carbon or pitch from thehot oil products discharged from the heating opera-. tion during this heat exchange, in the heat ex-v change coil 3 in the apparatus illustrated, is minimized in the improved operation of the present invention by maintaining pressure on these hot oil products through this heat exchange.

At the end of a run, the heating conduit 1 is pumped out and steamed out by means of connec tion 40. 7

We claim: 7

11 Inthe manufacture-of lowerboilinghydrocarbon oils from higher boiling hydrocarbon oils, the improvement which comprises heating a flowing stream of high boiling oil to'a high cracking temperature in excess of approximately900 F. under superatmospheric pressure and producing a high yield of gasoline. in a single passage through the heatiif 'g'j operation, passing the total stream of hot oil products from said heating operation under maintained superatmospheric pressure in indirect h'iitexchanging relation with a body of residual oil in a vapor separating recepta cle and thereby transferring a substantial quantity of heat from the "stream of hot oil products to the body of oil in the vapor separating receptacle and promoting a more complete separation of low boiling components from the residual oil mixture, thereafter materially reducing: the pressure on said stream 01 11013 0. products and releasing them under materially reduced pressure 'within said vapor separating receptacle, introducing a stream of cooler high boiling oil into said stream of hot oil products from said-heating operation before they are released within said vapor separating receptacle and aftersaid heat exchange with the body of r idual oil therein in sufficient quantity to arre {cracking of the hot oil products discharged om said heating operation, and taking off vaporsgi ncluding vapors of the desired low boiling oil from said vapor separating recarbon oils from higher boiling hydrocarbon oils,

the improvement which comprises heating a flowing stream of high boiling oil to a high cracking temperature in excess of approximately 900 F. under superatmospheric pressure and producing a high yield of gasoline in a single passage through the heating operation, passing the total stream of hot oil products from said heating operation under maintained superatmospheric pressure in indirect heat exchanging relation with a body of residual oil in a vapor separating receptacle and thereby vaporizing from said body of residual oil substantially all of the oil components boiling below about 600 F., thereafter reducing the pressure on said stream of hot oil products and releasing them under reduced pressure within said vapor separating receptacle, introducing a stream of cooler high boiling oil into said stream of hot oil products from said heating operation before they are released within said vapor separating receptacle and after said heat exchange with the body of residual oil therein, and taking off vapors including vapors of the desired low boiling oil from said vapor separating receptacle and discharging residual oil therefrom.

EDWARD W. ISOM. EUGENE C. HERTHEL.

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