US1962595A - Art of cracking hydrocarbons - Google Patents

Description

.Ill

June 12, 1934. E ;l HERTHEL ART 0F CRACKING HYDRocARBoNs Filed April 4, 195o ATTORNEYS fw, 0m,

Patented June 12, 1934` UNITED STATES PATENT OFFICE Eugene C. Herthel, Flossmoor, Ill., assignor to Sinclair Refining Company, New York, N. Y., a

corporation of Maine Application April 4, 1930, Serial No. 441,552

Ll Claims. (Cl. 196-107) 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 and reduced crude oil, by `5V pressure cracking' operations.

The present invention provides an improved apparatus of special Value and application for carrying out pressure cracking operations in which high boiling oil is heated to a cracking l temperature under high pressure and in which the hot oil products from this heating operation are separated into a vaporzed fraction and an unvaporized fraction under lower pressure, or socalled pressure coil cracking operations.

The invention will be described in connection with the accompanying drawing which illustrates, diagrammatically and conventionally, in elevation and partly in section and with parts broken away, apparatus embodying the invention.

In carrying out pressure cracking operations in the apparatus illustrated, a stream of high-boiling oil, gas oil, for example, is forced, by means of the pump 1, thru the connection 2, thru the series connected vertical heating tubes 3 arranged 25 in the heating furnace 4, then thru the connection 5 including the pressure regulating and reducing valve 6 into the evaporator 7. The oil is heated to a cracking temperature under high pressure during passage thru the heating tubes, to a temperature of S75-975 F., under a pressure of G-600 pounds per square inch, as discharged therefrom, for example. Vapors are taken off from the evaporator under a lower pressure, under a pressure of 10-50 pounds per square inch, for example, and a lower temperature, 70D-800 F., for example, is maintained in the evaporator. In the evaporator 7, a vaporized fraction is separated from an unvaporized fraction. The vapors comprising the vaporized fraction are taken off thru ..40 the connection 8 and are subjected to a refluxing operation in the reflux condenser 9 from which the vapors remaining uncondensed escape thru the connection 10, or thru suitable fractionating apparatus interposed in the connection 10, to the condenser 11 arranged to discharge into thereceiver 12 from which a condensed distillate product, gasoline or a gasoline-containing distillate for example, is discharged thru the connection 13, luncondensed vapors and gases being discharged thru the connection 14. vA super atmospheric pressure, lower, however, than the pressure under which the hot oil products are discharged thru the connection 5, may be maintained in the evaporator 7 and the reflux condenser 9, and in any vfractionating apparatus interposedin the connection 10, by means of valves 15 and 16 in the connection 10, or by means of suitable valves arranged beyond the condenser or the receiver. The operation of the reflux condenser 9 is controlled by regulated introduction, thru connection 17 by'nieans or" the pump 18, of a direct reuxing medium. The reflux condensate mixture formed in the reiiux condenser 9 ows, thru the connection 19, either to the intake 20 of the pump 1 thru the connection 21, or to the storage receptacle 22 thru the connection 23, or to the evaporator 7 thru the connections 2l, 24, 25 and 26. Another stream of high boiling oil, gas oil or reduced crudeoil, for example, may also be introduced, thru the connection 27 by means of the pump 28, or thru the connections 41 and 27 by means of the pump 18, either directly into the evaporator 7 thru the connection 29, or into the transfer connection between the valve 6 and the evaporator 7 thru the connection 30. Residual oil or tar, the unvaporized fraction separated in the evaporator 7, is discharged therefrom thru the connection 31.

In the apparatus illustrated, the connection 5,

the evaporator 7, the connection 8, the reflux condenser 9, the connections 19, 21, 24, 25, 26 and 2, and the storage receptacle 22-are with advantage thoroughly lagged or thermally insulated. Y

The heating furnace 4, in the apparatus illustrated, -may, with advantage,be arranged and operated as described in my application filed February 8, 1930, Serial No. 426,901.

In carrying out pressure cracking operations in the apparatus illustrated, a temperature low enough to arrest the cracking reaction initiated in the heater is maintained in the evaporator. Control oi the temperature prevailing in the evaporator 7 may be had by one or more of several methods of regulation. Cooler high boiling oil may be introduced into the hot oil prod.- ucts discharged from the heater or into the evaporator with the hot oil products, thru the connections 30 or 29 as just described, for example. Relatively cool gas oil may be so utilized to effect this regulation, for example, or relatively cool reduced crude oil may be so utilized. Where reduced crude oil is so utilized, it may be reduced to a flux or tar in the evaporator 7,7the flux or tar being discharged thru the connection 3l and the vapors comprising the fraction vaporized from the reduced crude oil being discharged to the reflux condenser 9 together with the vaporized fraction separated from the hot oil products discharged from the heater'in the evaporator. The reflux condensate mixture, or part of it,

from the reflux condenser 9, may be supplied to the evaporator 7 to effect, or to assist in effecting, this temperature regulation, thru the connections 21, 24, 25 and 26 as just described, or thru the cooler 33 and the connections 41 and 27.

The reflux condensate mixture formed in the reflux condenser 9 includes higher boiling components of the vaporized fraction separated from the hot oil products discharged from the heater in the evaporator 7, any corresponding higher boiling components of the vaporized fraction separated from high boiling oil supplied to the evaporator '7 thru the connections 26, 29 and 30 or any of them, and any unvaporized fraction of the reuxing medium introduced into the reflux condenser 9 thru the connection 17.

The storage receptacle 22 is provided to afford a suiicient permissible margin for accumulation of this reflux condensate mixture to permit appropriate regulation of the operation, particularly with respect to the heater and the reflux condenser, independently of the rate at which this reflux condensate mixturevis formed. In connection with operations in which a high rate of oil circulation thru the heater is maintained, the provision of the storage receptacle 22 affords the further advantage of providing a bulk supply of hot oil absorbing any sudden temperature fluctuations making possible more consistently uniform operation of the heater.

rIhe present invention comprises certain particularly advantageous arrangements, referring to the apparatus illustrated for the purpose of exemplication, of the reflux condenser and the storage receptacle with respect to the evaporator and the pump for maintaining circulation thru the heater.

lIhe reflux condenser 9 is connected with the vapor space in the evaporator 7 thru the vapor connection 8 and to the intake 20 of the pump 1 thru the liquid connections 19 and 21. The storage receptacle 22 is connected to the connections 19 and 21 between the reflux condenser 9 and the intake 2() of the pump 1 thru the connection'23. The intake 20 of the pump 1 is also connected directly to the Vapor space in the evaporator 7 thru the connections 24, 25 and 26. During operation, after normal operating conditions have been reached, the provision of the direct connection between the pump intake and the vapor space in the evaporator promotes the maintenance of more consistently uniform pressure on the pump intake, prevents the development of objectionable pressure differentials between the evaporator, the reux condenser and the storage receptacle, and affords a free path for overflow of any excess reflux condensate mixture formed in the reflux condenser. In this arrangement, the storage receptacle is, with advantage, positioned so that the normal head of liquid therein is insufficient to effect discharge of. liquid oil thru the connections 24, 25 and 26 into the evaporator. The storage receptacle 22 is also, with advantage, vented to the reiiux condenser I9 thru the vapor connection 32 betweenrthe upper part of the storage receptacle, or the vapor space therein, and the reflux condenser. In carrying out pressure cracking operations in the apparatus illustrated, raw gas oil may be utilzed as a direct refluxing medium in the reflux condenser 9, this gas oil thus being preheated before being supplied toA the heater as a component of the reflux condensate mixture formed in the reflux condenser 9. The rate at which the refluxing medium, raw gas oil for example, is introduced into the reflux condenser 9 is advantageously regulated to maintain the temperature of the vapors escaping from the reflux condenser at some value predetermined with respect to the pressure prevailing inthe reflux condenser to produce the particular distillate desired, or the particular vapor mixture desired if the vapor mixture is subjected to further fractionation before condensation. In operations of the type just described, the amount of heat to be absorbed in the reflux condenser may, either periodically or continuously during the operation, be so great that the supply of raw oil at a rate necessary to effect such heat absorption would involve progressive accumulation of the resulting reflux condensate mixture within the system. To avoid this situation, the cooler 33 connected between the storage receptacle 22 and the pump 18 is provided to permit reintroduction of the reflux condensate mixture, after cooling, into the reflux condenser as a refluxing medium, alone or in conjunction with another refluxing medium such as raw gas oil. Without the provision of a storage receptacle, this scheme of operation tends to interfere with the regular supply of the reux condensate mixture at consistently uniform temperature to the heater; with the provision of a storage receptacle this tendency is eliminated.

In initiating operation oil may be circulated thru the heater to and from the evaporator by means of the pump l thru the valve 34 until normal operating conditions of temperature and pressure are reached, the valve 34 being closed during normal operation, or raw oil may be circulated but once thru the heater without recirculating unvaporized oil collecting in the evaporator thru the heater. The invention affords advantages with respect to both methods of initiating operation.

Referring to the first method of initiating operation just mentioned, with the valve 34 open and a reflux condensate mixture accumulating in the storage receptacle 22, a tendency toward liquid surging back and forth between the evaporator and the storage receptacle, thru the c v open connections between the two, sometimes develops. Since the liquid in the evaporator is normally relatively hotter than the liquid in the storage receptacle, such surging tends to cause the supply to the heater, by means of the pump 1, of an oil mixture the temperature of which may vary abruptly and over a substantial range. Such sudden changes in temperature of the oil supplied to the heater subject the heating tubes and the connections in the heater thru which the oil is circulated to severe stresses. This is avoided by providing the separate direct valved connection 35 between the intake 20 of the pump 1 and the storage receptacle 22, this connection communicating with the interior of the storage receptacle at a point remote from the point at which the connection 23 communicates with the interior of the storage receptacle. The valve 36 in the connection 35 is closed during normal operation. However, When the valve 36 is open while operation is being initiated, two different paths between the storage receptacle and the pump intake are provided, the result being to check any tendency toward liquid surging between the evaporator 7 and the storage receptacle 22.

Referring to the second method of initiating operation just mentioned, the provision of the storage receptacle 22 permits the accumulation of the reux condensate mixture produced, without circulation of this reflux condensate mixture thru the heater, until the reflux condensate mixture so accumulated has reached a temperature high enough to insure the elimination of water therefrom. The circulation of the reflux condensate mixture thru the heater may then be started. Any difficulties involved in the presence of water in the oil or oil mixture circulating thru the heater are thus avoided.

The storage receptacle for the reflux condensate mixture in the apparatus of this invention, the storage receptacle 22 in the apparatus illustrated, should be large enough to accommodate a charge of oil corresponding, for example, to the amount required to maintain circulation thru the heater at the normal rate of circulation for the particular operation for 10-20 minutes, or longer. The storage receptacle may with advantage be large enough to accommodate a charge of oil corresponding to the amount required to maintain normal circulation thru the heater for a period of 60-120 minutes. The larger this charge of oil, the greater its effect in maintaining consistently uniform conditions within the apparatus.

At the end of a run, the valve 37 is closed as steam is introduced thru connection 38 under pressure sufficient to blow the contents of the heater into the evaporator '7, and the evaporator '7 is then pumped out thru connection 39. In initiating operation, an initial charge of oil may be supplied to the evaporator 7 thru the connection 39.

Control of the rate of circulation of oil thru the heater may be had by regulating the speed of the pump 1. Very precise control of the rate of circulation of the oil thru the heater is sometimes facilitated by the use of the bypass valve 40 across the pump discharge and the pump intake.

I claim:

1. In apparatus for cracking hydrocarbon oils, an evaporator, a reflux condenser, a connection between said reflux condenser and the vapor space of the evaporator, a heater connected to the evaporator, a pump connected to the heater for forcing oil through the heater into the evaporator, a connection for supplying reflux condensate from the reflux condenser to the pump intake, a direct connection between the pump intake and the vapor space in the evaporator, said connection terminating in the evaporator at a point above the normal liquid level in the evaporator and below the point of entrance to the reflux condenser of the first mentioned connection between the reflux condenser and Vthe vapor space of the evaporator, a storage receptacle for reflux condensate connected to the connection between the reflux condenser and the pump intake positioned so that the normal head of liquid therein is sufficient to effect discharge of liquid oil to the pump intake and insufcient to effect discharge of liquid oil through said direct connection between the pump intake and the vapor space in the evaporator, a connection for taking off vapors from the reflux condenser and a connection for discharging residual oil from the evaporator.

2. In apparatus for cracking hydrocarbon oils, an evaporator, a reflux condenser, a connection between said reflux condenser and the vapor space of the evaporator, a heater connected to the evaporator, a pump connected to the heater for forcing oil through the heater into the evaporator, a connection for supplying reflux condensate from the reflux condenser to the pump intake, a direct connection between the pump intake and the vapor space in the evaporator, said connection terminating in the evaporator at a point above the normal liquid level in the evaporator and below the point of entrance to the reilux condenser of the first mentioned connection between the reflux condenser and the vapor space of the evaporator, a heat insulated storage receptacle for reflux condensate connected to the connection between the reflux condenser and the pump intake, a connection for taking off vapors from the reflux condenser and a connection for discharging residual oil from the evaporator.

3. In apparatus for cracking hydrocarbon oils, an evaporator, a reflux condenser connected with the vapor space of the evaporator, a heater connected to the evaporator, a pump connected to the heater for forcing oil through the heater into the evaporator, a storage receptacle for reflux condensate, a vapor connection between the upper part of the storage receptacle and the reflux condenser, a connection for supplying reflux condensate from the reflux condenser to the pump intake and a connection between this connection and the storage receptacle, a separate direct valved connection between a point in the storage receptacle remote from the point of connection of the connection just previously mentioned and the pump intake, a valved connection between the evaporator from a point below the normal liquid level therein and the pump intake, a connection for taking oil vapors from the reflux condenser and a connection for discharging residual oil from the evaporator.

4. In apparatus for cracking hydrocarbon oils, an evaporator, a reflux condenser, a connection between said reflux condenser and the vapor space of the evaporator, a heater connected to the evaporator, a pump connected to the heater for forcing oil through the heater into the evaporator, a connection for supplying reflux condensate from the reflux condenser to the pump intake, a direct connection between the pump intake and the vapor space in the evaporator, said connection terminating in the evaporator at a point above the normal liquid level in the evaporator and below the point of entrance to the reflux condenser of the ilrst mentioned connection between the reflux condenser and the vapor space of the evaporator, a storage receptacle for reflux condensate connected to the connection between the reflux condenser and the pump intake, a connection for taking off vapors from the reilux condenser and a connection for discharging residual oil from the evaporator.

EUGENE C. HERIHEL.

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