US1902808A

US1902808A - Conversion of hydrocarbons

Info

Publication number: US1902808A
Application number: US374471A
Authority: US
Inventors: Edwin F Nelson
Original assignee: Universal Oil Products Co
Current assignee: Universal Oil Products Co
Priority date: 1929-06-28
Filing date: 1929-06-28
Publication date: 1933-03-21
Anticipated expiration: 1950-03-21

Description

March 21, 1933. E. F.`NELsoN CONVERSION OF HYDROCARBONS Filed June 28, 1929 gllflw i ,25W/@mw dma/Ve 190372/ f/ness" Patented Mar. 21, 1933 UNITED STATES PATENT OFFICE EDWIN F. NELSON, OF CHICAGO, ILLINOIS, ASSIGNOR TO 'UNIVERSAL OIL PRODUCTS COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION 0F SOUTH DAKOTA CONVERSION OF HYDRO CARBONS Application led `Tune 28,

This invention relates to an improvement in processes for the conversion of hydrocarbons into more valuable products.

More particularly, the invention relates to an improvement in the handling of cracked distillatcs produced by the thermo decomposif tion of hydrocarbon oil whereby more suitable products are obtainable from the cracking process.

In the operation of commercial cracking processes, the resulting liquid distillate withdrawn from the receiver is charged with dissolved uncondensible gas and light hydrocarbons which are highly volatile. In operation, suiiiciently converted vapors which do not condense below a certain point are removed from the usual dephlegmating or fractionating zones of the cracking process, and these vapors together with the uncondensible gas formed in the process are condensed. This distillate and uncondensible gas collects in a receiver, the gas being removed from the top thereof and the liquid distillate from the bottom. It is this distillate which is found to be charged with dissolved uncondensible gas and highly volatile light hydrocarbons.

According to one of the methods used at present, the non-condensible ga's removed from the receiver is passed through a gas separator. Thus, it is obvious that the use of a receiver with a gas separator permits the gas escaping from the receiver to carrywith it considerable condensible fractions. In the chemical treatment, pumping operations' and storage of distillates of this character, the dissolved non-condensible gas and very light distillate are lost by evaporation. With the escape of these constituents by evaporation a certain portion of the desirable relatively heavier constituents of the distillate are carried away as well, so that the resultant loss is not only of the undesirable wild constituents, but also of certain desirable light ends of gasoline which by the employment of my invention may be saved.

It is a primary object, therefore, of the present invention to stabilize both the noncondensible gas and condensed distillate so that the non-condensible gas may be stripped of substantially all of the condensible frac- 1929. Serial No. 374,471.

tions and thus be substantially dry, while the distillate will be stripped of substantially all of the non-condensible gas and Very light ends.

As a feature of the present invention, the stabilization of the gas and the distillate may take place under plant pressure, that is, the pressure within the stabilizer may be the same as the pressure on the cracking process which produced the distillate and non-condensible gas, or it may be reduced relative thereto.

In one specific embodiment of my invention, I employ a tower or other suitable means as a stabilizer element to stabilize the noncondensible fractions from the pressure distillate. The latter may be then chemically:

treated, transferred and stored with mininum loss of the desirable components thereo Other advantages and objects of the invention will be more apparent from the following description.

By reference to the single figure in the drawing, which is a diagrammatic side elevational view of apparatus in which the process may be carried out, the operation will be obvious to those skilled in the art.

Referring more in detail to the'drawing, raw oil may be supplied through line 1 by means of pump 2 and adephlegmator 3, where it is preheated by partially condensing the vapors entering the bottom thereof, as will be hereinafter described. A hot oil pump 4 taking suction from the bottom of dephlegmator 3 through line 5 delivers the preheated oil and reflux condensate to a heating coil 6 located in furnace 7 and heated by means of burner 8. This furnace may be of any design suitable for heating the oil in coil 6 to the desired temperature. The heated oil passes out through transfer line 10, in which is interposed valve 11, to eX- pansion chamber 12. Vapors separating from non-vaporous products in chamber 12 may pass out through vapor outlet line 14,

controlled by valve 13, discharging in the line 15, controlledby valve 16,y into condenser coil 17. Unvaporized residue may be withdrawn from the chamber 12 through line 9, controlled by valve 9.

The distillate and uncondensible gas pass out through Iline 18 through stabilizer 19, which may be of any suitable construction, whereby intimate contact of vapor liquid may be obtained in order to arrive at equilibrium conditions. lf stabilizer 19 requires heating, means such as a steam coil in the bottom thereof, as indicated at 20, may be rovided.

ne of the novel features of the present invention takes advantage of the fact that the uncondensible gas escaping through line 21 will, through reduction in pressure by means of valve 22, become greatly cooled, depending upon the differential pressure employed between the stabilizer 19 and the pressure prevailing in coil23. If necessary, all additional cooling element may be einployed, such as a coil 24 located at or near the top of stabilizer 19. If Vall of the expanded 'gas is not necessary to obtain the requisite cooling, then regulated portions thereof may be passed through coil 23 and the remainder diverted from the coil by means of by-pass line 35, controlled by valve A direct gradient will necessarily prevail between the point at which line 18 enters the stabilizer and the top of the tower. Likewise, a direct gradient will prevail from the leating means at the bottom of the tower to the point at which line 18 enters the stabilizer; or, in other words, a gradient will prevail more or less uniformly from the bottom of the stabilizer to the top.

The uncondensible gas passing through coil 23 will, at reduced pressure, pass out through line 25. The stabilized condensate from the bottom of stabilizer 19 may pass out through line 26 and cooler 27 into receiving drum 28 from which the condensate may be withdrawn through valve 29. By controlling the temperature conditions at the top of dephlegmator 3 a. portion of the condensate may be withdrawn from receiver 28 and forced through line 30 and valve 31 by pump 32. Provision is made through valve 33 for releasing gas from receiver 2S. which gas, under normal conditions, will not be liberated at the top of stabilizer 19 through line 21, pressure on the system being controlled by valve 22; that is,

valves

11, 13 and 16 will be open. y n

In an alternate method of operation, by the employment. of the valves just mentioned, differential pressures may be einable one. since material pressure reduction through valve 22'in line 21 is desired to get and a proper cooling elect for the top of stabilizer 19. Since gas relief valve 33 on receiving drum 28 will not normally be in use, the liquid level in stabilizer 19 should be ascertained by means of a gauge glass 34 located on the bottom thereof.

It will be understood that, by means of the present invention, a practically complete stabilized distillate may be recovered from the bottom of stabilizer 19; with the fixed gas discharging from the top of the stabilizer containing practically no gasoline-like material. By the control of pressure reduction by means of valve 22, and by means of the cooling means 21 and heating means 20, the character of both the stabilized condensate and the uncondensible gas leaving stabilizer 19 may be varied within relatively wide limits.

As an example of the conditions prevailing in one operation employed in my invention, a 24 B. gravity Mid-continent reduced crude oilfinay be charged to the cracking unit. The temperature of the discharge of heating coil 6 may be approximately 910 F.; the temperature at the top of dephlegmator 3 may be approximately 525 F.; the temperature of the condensate and non-condensible gas entering stabilizer 19 through line 18 ma be approximately 95 F.; the temperature o the gas exiting from the top of stabilizer 19 may be about 75 F. Steam may be employed at the bottom of stabilizer 19 1n coil 20 so that the temperature of the stabilized condensate leaving through line 26 may be about 165 F. aiid by passage through, cooler 27 may be reduced to approximately 85 F.

Pressures prevailing in the system may be approximately 275 pounds to the square inch at the discharge of pump 4, while the stabilizer may be maintained under a ressure of approximately 190 pounds, the di erence between these two pressures being due to hydroy static head and friction drop. The pressure may be reduced by valve 22 to substantially atmospheric, or )ust enough above atmospheric to overcome friction in passing through the, remainder of the apparatus. This pressure reduction will bring about a corresponding temperature reduction of F., which under these specific conditions, will be sufficient to condense substantially all of the portions ascending in tower 19 when brought into contact with the cooling coil.

A yield of about %4 pressure distillate will be obtained having an initial boiling point of approximately 110 F. and an end point of about ,550 F., containing about 73% of 437 F. end point gasoline. The iiiicondensible gas in stabilizer 19 discharged from line 25 will contain, by the charcoal test, less than a gallon of coiideiisible gasoline per thousand cubic feet. In operation without the stabilizer` under the saine conditions, the fixed gas from the. receiving'drum 28 will show a gasoline content of approximately two gallons per thousand cubic feet. A material loss will also occur by reason ofthe fact that the distillate will have an initial boiling point of about 90 F. and will show a vapor loss in handling and treating of approximately 2%.

It is to be understood that the specic figures given in this illustrative run are not to be taken in any sense as a limitation of the invention. The figures are merely illustrative of one specific embodiment of the invention.

The invention in its broad concept contemlates, first the separation of the uncondensil le gas from the liquid distillate under superatmospheric pressure, the subsequent reduction in pressure on said uncondensible gas thus bringing about a corresponding decrease in temperature, which decrea in temperature is utilized as a cooling medium to strip condensible fractions from the gas during' rthe separating step.

I claim as my invention:

1. In a process of hydrocarbon'oil conversion wherein said oil is heated to cracking temperature and 4suiiciently converted va-- pors and non-condensible gas separated from insuiiciently converted vapors and residue, superatmospheric pressure is maintained on said oil and vapors, and said suiliciently converted vapors and non-condensible lgas are condensed and cooled', the improvement whichl comprises separating the uncondensible gas from the condensed distillate under superatmospheric pressure in a separating zone, removing said separated gas from the separating zone, reducing the pressure thereon to thereby reduce its temperature, and returning regulatedportions of said gas under reduced pressure to said se arating zone and passing same therethroug rect contact with the gas being separated therein to condense condensible "portions associated with said gas. c

2. Inv hydrocarbon oil pressure cracking processes vwherein the cracked vapors and gases are cooled under superatmospheric pressure to condense the vapors, the improvement which comprises ingoducing the condensed distillate and gas to a stabilizing zone maintained under the superatmospheric pressure of the cracking process, separating the gas from the distillate in said zone, Vremoving the separated gas under pressure from the sta-` bilizing zone and reducing the pressure thereon, and passing the expanded gas in indirect heat exchange relation with the gas being separated in said zone.

In testimony whereof I aix my signature. j

EDWIN F. NELSON.