US2037238A - Hydrocarbon oil conversion - Google Patents

Description

HYDROCARBON OIL CONVERSION Filed April 2'7, 1927 Patented Apr. 14, 1936 UNITED STATES HYDROCARBON OIL CONVERSION Lyman C. Huff, Chicago, Ill., assigner, by mesne assignments, to Universal Oil Products Company, Chicago, Ill., a corporation of Delaware Application April 27, 1927, Serial No. 186,844 3 claims. (o1. 19e-4s) y 'I'he present improvements relate more particularly to the treatment of hydrocarbon oil whereby it is subjected to conversion conditions of temperature and superatmospheric pressure to produce large yields of commercial products such as gasoline and the like. v

The invention is more particularly applicable with processes of thattype in which hydrocarbon oil is passed through a heating coil Where it receives heat sufcient to cause conversion, the heated oil being vthen subjected to reaction which causes vaporization, the vapors being removed and subjected to dephlegmation, and the nonvaporous residual products of reaction separately removed. The vaporous products of reaction are subjected to dephlegmation and fractionation by ,the use of a cooling medium which causes the heavier portions to condense as reux condensate, which reflux is ordinarily returned to the heating lcoil for reheating.

In processes of this general character, it has been found that the reflux condensate at times contains various percentages of lighter fractions which are refractory to cracking and which should be preferably removed or stripped from said reflux before same is returned kto the heating coil to be again raised to conversion temperature.

It is the object of the present invention to remove and strip these light fractions from the combined feed and/or reflux condensate passing from the dephlegmator to the heating coil of a cyclic process.

In the specific embodiment of the invention, this object is accomplished by subjecting said reiluX condensate or the combined feed to heat prior to being passed through the cracking coil by passing same through a heating zone from which it may be discharged into a vapor separator, from which latter the portions which vaporize comprising said light fractions, are removed, While the unvaporized liquid may be preferably directed to the cracking coil.

The pressure maintained on the heating zone and vaporizer may be the same or lower or higher than the pressure maintained on the cracking zone.

The single gure is a diagrammatic floW chart illustrating the apparatus in which the invention may be carried out. v

Referring more in detail to the drawing, I designates a heating coil which may be positioned in the furnace 2, which latter may be heated by the burners3. The heating coil may comprise connected lengths of tubing having a diameter of say two to six inches more or less. The

furnace may be of any conventional type, and the same is true of the burners 3. Oil is fed into the heating coil I, as will be hereinafter described, Which for convenience Will be hereinafter referred to as the cracking coil. While passing through said heating coil, it is raised to a suitable con- Version temperature under the desired superatmospheric pressure. The heated oil is discharged from the coil I through the transfer line il, in which may be interposed the valve 5, into reaction drum 6 Which may comprise a shell of any desired size. The reaction drum 6 mayor may not be externally or internally heated. 'I'he proper temperature and pressure to which the oil is subjected While passing through the coil I, Will depend on the type of oil being heated, and the types of product desired; the most eiicient temperature and pressure conditions will be Within the knowledge of those versed in this art. If the drum 6 is externally unheated, it may be preferably provided with the usual insulation, not shown. This chamber may also be provided with the clean-out manholes ,'I, and with the nonvaporous residue drawoff lines 8 in which may be interposed the valves 9.

The oil being introduced to the drum 6 separates into vaporous and non-vaporous residual products of reaction, the latter being drawn olf through said draWoff lines 8 While the former pass out through the vapor outlet line I0 in Which may be interposed thel valve II discharging into a dephlegmator I2, which may be of any conventional type and provided with the usual dephlegmating means. To assist in the fractionation of the vapors, a cooling medium Which may comprise charging stock distillate, or any other desired cooling medium, may be introduced through the line I3 in which may be interposed a valve I4. The vapors remaining uncondensed after passage through the dephlegmator I2 may be removed through the vapor line I5 in which may be interposed a valve I6, which vapors may be condensed while passing through a conventional typeof condenser I'I, the condensed distillate passing through the line I8 `in which may be interposed a valve I9, collecting as liquid distillate in the receiver 20. The latter may be provided with gas relief line 2I and liquid drawoff line 22 controlled respectively by valves 23 and 24. The charging stock to be treated in the process, may be charged from storage tanks (not shown) through the line 25 in which may be interposed the valve 26 and pump 21, into the top of the dephlegmator I 2 Where it combines With reux condensate formed in said dephlegmator and is also preheated.

Reflux condensate formed in dephlegmator I2 and cooled at the bottom thereof, may contain a proportion of light fractions, the characteristics of which correspond to those of the distillate collected in the receiver 20, and which, if passed through the cracking coil, might cause a decrease in the capacity of the cracking unit, as well as an increase in the cost and decrease of the erhciency of the cracking reaction.

As a feature of my invention, the liquid oil collected in the bottom of the dephlegmator I2 and which may comprise reflux condensate and unvaporized charging stock in a heated condition, is Withdrawn through line 28 nwhich may be interposed a hot oil pump 29 controlled by valves 30, which pump may be by-passed through the by-pass line 3l in which may be interposed the valve 32.

The hot oil is passed from line 28 through the pump or through the by-pass lineinto the line 33, from which it may be charged through a heating coil 34, which maybe heated in any suitable manner, such as by the burners 36 in the furnace 35, or the coil 34 may be positioned in the furnace 2 similar tothe cracking coil I. For convenience, and for the purpose of i-dentication, this coil 34 may be referred to as the stripping or reboiling coil. The oil passing through the reboiling coil 34 is heated to a temperature at which the undesired light fractions contained therein, will vaporize, this reboiled oil being discharged from the coil 34 through the transfer line 35 in which may be interposed the valve 36, discharging into a vapor separator tank 31- wherein said light fractions separate in the form of vapors from the reboiled oil.

The unvaporized reflux condensate and charging stock, stripped of light fractions in the tank 31. may be withdrawn throughv the line 38 in which may be interposed a hot oil pump 39 and Valves 40 from which the oil may be charged through the line 4I into the cracking coil I hereinafter described. The pump 39. may be bypassed through the by-pass line 42 in which may be interposed a valve 43. To insure proper operation of the hot oil pump 39, the level of the. oil in the vapor separating tank 31 may be controlled by means of automatic control 44 which may be of any standard make. The vapors separating in the tank 31 may be withdrawn through the top thereof through vapor line 4.5 in which may be interposed the valve 46, said vapors being introduced into the dephlegmator I2 for further fractionation, or if desired, the vapors from tank 31 may be directed to separate dephlegmating, condensing and collecting means, (not shown) through the line 45 in which may be interposed the valve 46.

According to the results desired, and the characteristics of the oil treated, the reboiling coil 34 and the vapor separator tank 31 may be maintained under a pressure higher or lower than, or equal to, the pressure maintained on the cracking coil I. Any one skilled in the art, will be able to maintain the required pressures on the various parts of the apparatus shown, which pressure may be uniform throughout the cracking apparatus, or differential pressures may be used. The various valves and pumps shown, can be manipulated to regulate this pressure. If desired, an additional supply of charging stock may be fedv to the cracking coil I directly'to the inlet thereof through feed line 41 controlled by valve 48. Further, it may be desirable to introduce little or no charging stock to the dephlegmator I2, in which event, all of the charging stock may be charged through the line 41.

The oil may be heated while passing through the cracking coil I to temperatures ranging from 700 to 900 degrees F., more or less, under pressures of from three hundred to several hunded pounds more or less. The most eflicient temperatures and pressures under which the oil is maintained in the coil 34, will depend upon the characteristics of the oil passing therethrough. For instance, if the oil is cracked in cracking coil I under a temperature of say 850 degrees F., and a pressure of say 200 pounds more or less, pressure on the dephlegmating Zone I 2 may be reduced to say 50 pounds by means of valve II, and the reiiux condensate or combined feed from the dephlegmator may be charged by pump 39 through the coil 34, where it is heated under a pressure of say 300 pounds, to 875 degrees F., subsequent to which the pressure. may be reduced or released by means. of valve. 36 down to say 50 pounds in the vapor separating tank 3.1. It isto be. understood that theser figures are merely illustrative, and are not to be taken as limiting the invention. in any way, as the proper temperatures and pressures to be. used, will vary with the character of oil treated, and the results desired.

In summing up, itis to be noted that the reboiling coil 34 may take any other form, justas long as the reflux or combined feed receives sufficient. heat to cause the light fractions entrained therein to. vaporize. The` novel steps-of the present invention, are to be distinguished from a process in which the reflux is subjected to different cracking conditions of temperature and pressure. than the charging stock. In those processes, the reflux is subjected in cracking conditions whereby conversion is effected, While in the present. process the reflux is subjected to distillation or reboiling to effect a release and stripping of the light fractions in the form of vapors without cracking.

I claim as my invention:

1. In. cracking heavier and higher boiling hydrocarbon oils for. the production of lighter and lower boiling hydrocarbon oils, the improvement which comprises subjecting the vapors from the cracking operation to a refluxingjoperation, introducing raw oil into direct contact with the vapors in the refluxing operation, taking olf vapors including vapors of the desired lighter and lower boiling oils from the reiluxing operation, stripping any of the desired lighter and lower boiling oils from the reflux condensate and admixed raw oil by vaporization therefrom after discharge of the mixture from the refluxing operation and before return to the crackingoperation under a pressure approximately equal to that prevailing in the reiluxing operation, taking off vapors of` lighter and lower boiling oils stripped from the reflux condensate, and returning reux condensate together with admixed raw oil freed of such desired lighter and lower boiling oils to the crackingoperation.

2. In cracking heavier and higherv boiling hydrocarbon oils for the production of lighter and lower boiling hydro-carbon` oils, the improvementwhich comprises subjecting the vapors from the. cracking operation to a refluxing operation, taking off vaporsincluding vapors of the desired lighter and lower boiling oils from thev refluxing operation, reheating reiiuX condensate from the refluxing operation to a temperature higher than that at which it is discharged from the refluxing operation and discharging it into a separate vaporizing zone, maintained under a pressure approximately equal to that prevailing in the refluXing operation, taking off vapors of any of the desired lighter and lower boiling oils associated with the reux condensate from the separate vaporizing zone, and returning reflux condensate freed of Such desired lighter and lower boiling oils from the separate Vaporizing zone to the cracking operation.

3. In cracking heavier and higher boiling hydrocarbon oils for the production of lighter and lower boiling hydrocarbon oils, the improvement which comprises subjecting the vapors from the cracking operation to a refluxing operation, introducing raw oil into direct contact with the vapors in the reuxng operation, taking off vapors including vapors of the desired lighter and lower boiling oils from the refluxing operation, reheating reflux condensate and admixed raw oil from the refluxing operation to a temperature higher than that at which it is discharged from the refluxing operation and discharging it into a separate vaporizing zone maintained under a pressure approximately equal to that prevailing in the refluxing operation, taking off vapors of any of the desired lighter and lower boiling oils associated with the reiiux condensate from the separate vaporizing zone, and returning reflux condensate freed of such desired lighter and lower boiling oils from the separate vaporizing 15 zone to the cracking operation.

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