US2002530A - Recycling process for cracking oil - Google Patents

Description

7 May28, 1935.

F. H. EDSON RECYCLING PROCESS FOR CRACKING OIL Filed April 29, 1931 Patented May 28, 1935 PATENT OFFICE 2,002,530 RECYCLING PROCESS FOR CRACKING OIL Frank H. Edson, Westfield, N. J., assignor to Standard Oil Development Company, a corporation of Delaware Application April 29, 1931, Serial No. 533,607 2 Claims. (01. 196-48) This invention relates to improvements in the recycling of hydrocarbon oils during the cracking operation.

The invention will be fully understood from the following description taken in connection with the accompanying drawing in which the figure is a diagrammatic side elevational view partly in section illustrating an apparatus for carrying out the invention.

Referring particularly to the drawing, a charging stock is conducted through a feed line I and pump 2 through a preheating coil 3 located in a fractionating tower 4. The heated oil is delivered into an accumulator 5 from which it flows through line 6 to charging pump 1 which forces the oil under elevated pressure through cracking coil 8 and line 9 into a soaking drum it where it is digested at the desired pressure for a sufiicient length of time to facilitate cracking of the oil. The digested oil is delivered from the soaking drum through a valved line I I into a separator I 2 which is maintained under reduced pressure and in which the greater portion of the oil is vaporized. The heavier unvaporized products are removed from the separator through line l3 to a suitable place of disposal, not shown.

The vapors leaving separator l2 are conducted through a line M to a fractionating tower I5 which is integral with accumulator 5. The heavier fractions in the vapors condensing in the fractionating tower mix with the fresh charging stock in the accumulator and the lighter uncondensed fractions are conducted through a line IE to fractionating tower 4. The uncondensed vapors and a condensed lighter fraction are withdrawn from the fractionating tower through lines I! and I 8 respectively to a suitable place of disposal not shown. The relatively heavy fractions condensing in the fractionating tower are conducted from a reservoir H], which forms the lower section of the tower, through a line 20 and pump 2| to the inlet line 6 leading into pump 1. Line 20 preferably terminates in a suitable injector 22 which opens into the intake of the pump preferably as close as possible to the pump. The condensate is delivered to the injector under suitable pressure to give suflicient velocity to the column of combined oils in the pump suction so that the oil will closely follow the pump plunger, during its intake stroke, without substantial vaporization. Any condensate in reservoir I9 in excess of that required in the system may be withdrawn through line 23 to a suitable place of disposal, not shown. The temperature at the top of tower [5 may be controlled by the quantity of condensate admitted through line 24. If desired a constant pressure regulator (not shown) may be installed to control the discharge of pump 2!.

By way of example only, and without intention to limit the invention, the charging stock to be cracked can be a gas oil which may be heated to 700 F., more or less, in the cracking coil and under a pressure of 500 pounds per square inch, more or less. The thus treated oil is delivered into the separator l2 at a reduced pressure of, for example, pounds per square inch, more or less, whereby the greater portion of the oil is vaporized and partially fractionated in tower [5. The condensate, still under a pressure of 85 pounds per square inch, more or less, is delivered to the intake side of the pump 1. The condensed fractions in reservoir [9 are also under a pressure of approximately 85 pounds per square inch, more or less. The pressure of this condensate is built up by pump 2| sufiiciently so that when the condensate is injected into the intake of pump 1 it will flow at surficient velocity and in sufficient amounts to cause the combined oils on the intake side of the pump plunger to closely follow the plunger upon its suction stroke without substantial vaporization. The pressure built up by pump 2! upon-the condensate in line 20 may, for example, be pounds to pounds per square inch, more or less.

By the procedure described the condensate from reservoir I 9 is recycled directly to the cracking coil under pressure sufficiently high to maintain it in liquid form without first passing through the accumulator 5. As a result, revaporization of the condensate from reservoir l9 which would normally occur due to the higher temperatures prevailing in accumulator 5 is prevented as well as the necessity for refractionating the resulting vapors. It will be understood that a portion of the unvaporized oil from accumulator 5 can be introduced into line 20 leading to the injector nozzle, if desired. The unvaporized oil can be introduced into line 20 on the inlet side of pump 2|, if desired.

Various changes may be madev within the scope of the appended claims in which it is desired to claim all novelty inherent in the invention as broadly as the prior art permits.

I claim:

1. In a continuous recycling process for cracking hydrocarbon oil, the steps which comprise cracking the oil at elevated temperature and under elevated pressure, vaporizing a portion of the thus cracked oil under reduced pressure, partially fractionating the vapors to produce a first condensate, recycling the condensate through a pump to the cracking step, condensing fractions of the remaining vapors to produce a second condensate and a desired vapor, and recycling the second condensate under greater pressure than the pressure on the first condensate directly to the intake of the pump at a velocity directed in the direction of said first condensate entering the intake of said first pump and high enough to cause the combined oils in the intake side of the pump to closely follow the pump plunger upon its suction stroke without substantial vaporization.

2. Apparatus for cracking oil and recycling con densate which comprises a heating and cracking element connected with a separator, a'line for discharging unvaporized oil from the separator, a first fractionating tower in vapor connection with the separator, a line for removing vapors from said first fractionating tower to a second fractionating tower,'a first reflux line for removing a relatively heavy condensate from the first fractionation tower and delivering it to the heating and cracking element, a first pump in said first reflux line, a second reflux line for removing a light condensate from the second fractionating tower and delivering it into an injector in said first reflux line at the intake of said first pump, said injector directed along the line of flow of the heavy condensate in said first reflux line, and a second pump forcing the light condensate in said second reflux line into said 1 injector so that said light condensate issues from the injector at a velocity pressure toward the intake of said first pump greater than the velocity pressure of said heavy condensate and means for passing fresh oil into said first fractionating 20 tower.

FRANK H. EDSON.

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