US1767360A - Method and apparatus for cracking oil - Google Patents

Description

n J. s. HARRISON f 1,767,360

METHOD AND APPARATUS FOR CRACKING OIL Filed March 26, .1927

J HN s. HARP 15 ON Patented June 24, 1930.

UNITED STATES PATENT orrlcs JOHN STEWART HARRISON, OF CLEVELAND, OHIO, ASS IGNOR TO STANDARD OIL DE- .V'ELOPMENT COMPANY, A CORPORATION OF DELAWARE METHOD AND APPARATUS FOR CRACKING OIL Application filed Ital-ch 26, 1927. Serial No. 178,547.

This invention relates to improvements'i-n equipment and methods for handling cracked hydrocarbon oil between the zones of crack- 'ing and final fractionation. I 1

The invention will be fully understood from the following description read in connection with the accompanying drawing, in which the figure is a diagrammatic side elevation of a cracking plant comprising my improvements.

Referring to the drawing, reference numeral 1 denotes a cracking coil in a furnace setting 2, and discharging through a pipe 3 into the lower part of an enlarged thermally insulated reaction chamber or soaking drum 4. The cracking equipment itself is not a part of the present invention, and any approved type may be adopted.

The cracked product passes from near the top of the soaking drum 4 through a pipe 5 into a tar separator 6. A pressure release valve 7 is installed in the pipe 5. A drawoff line 8 is connected to the separator, 6 and leads to a tar cooler 9. Vapors pass' from the separator through a pipe 10 to a perforated header 11 which is immersed ina body of liquid oil in an accumulator 12. Oil

to be cracked is supplied to the accumulator through a pipe 13. This includes a heat exchange coil 14; arranged in the upper part of a fractionating column or bubble tower 15.

A pipe 17 conveys vapors from the accumulator 12 to the bubble tower, preferably entering just above the bottom plate 18 therein. The fractionated product passes from the tower through.a-pipe 19 to a condensing coil 20 and a'receiving drum 21. This latter has a vent pipe 22 in which a pressure control valve 23 is installed.

Condensate formed in the tower and adapted for recycling is withdrawnto the accumulator 12 through pipe 24. The c'om-= bined liquid contents of the accumulator are forced by pump 25 through a pipe 26'to the v inlet end of the cracking coil 1.

A pipe 27 connects the separator 6 and the accumulator 12. CA valve 28 controls flow through this pipe. 'Valves 13' and'26 respectively control'flow through the pipes 13 i0 and'26. A pressure control valve 10" may coil and drum being about 450 lbs; per square be installed in pipe 10. between the separator 6 and the accumulator 12.

The operation of the process willbe clear from the following example in which it is assumed that gas oil is to be cracked. The gas oil is pumped through pipe 13 into accumulator 12 until the lever therein standsabout as shown in the drawin The oil is then pumped from the accumu ator through pipe 26 into the cracking coil 1, which is suitably fired. During the cracking period the temperature of the oil at the outlet of the coil will be held at about 875 F, and in the drum at about 800 F., the pressure in the inch.

The valve 7 will be set to give a pressure drop to about 60 lbs. gauge in the tar separator 6. This pressure is maintained throughout the rest of the system by means of valve 23 on the receiving drum 21. In some cases it is desirable to maintain a higher pressure in the tar separator, for example. 150 lbs. per square inch, though this may vary with the characteristics desired in the 7 tar product. The valve 10 may be set to give the required pressure difl'erential between the tar separator and the bubble tower.

: "The temperature of the tar in theseparater 6 will be about 67 5 F., when working ,at 60'lbs. pressure, and the vapors emerge from the separator at about the same tem-v perature. They impart their. heat to the oil in the accumulator, which should be maintained at not less than 550 F., as otherwise gasoline may be absorbed and retained by the gas oil supplied to the accumulator. At this temperature and 60 lbs. pressure, some kerosene, and perhaps light gas oil, will'pas's over with the gasoline into the bubble tower. If it is desired to crack the kerosene and/or any heavier distillate fraction produced, this -may be separately collected and returned to the accumulator or direct to the cracking coil. The temperature in thetar separator and the quality of the tar may be controlled by allowing more or less of the oil in. the accumulator to flow into the separator through a pipe 27. w

"The present invention makes eflicient use 10 of the heating and distilling efiect of the hot cracked product. High pressure heat exchangers are not required nor is the operation of the-bubble tower disturbed by showering oil through it to obtain preheat, as has heretofore been proposed. Further the accumula- 1 tor acts as a stripping zone in which the heavier fractions of the cracked vapors coming from the tar separator are condensed thus relieving the bubble tower and allowing it to. work in a more satisfactory manner.

It will be understood that the invention is not limited to operation upon the particular stock referred to, and that variations in temperature and pressure are permissible.

Numerous changes and alternative arrangements may be made within the scope of the appended claims in which it is my intention to claim all novelty inherent in the invention as broadly as the prior art permits.

I claim:

1. Apparatus for cracking petroleum oil and separating gasoline therefrom, comprising a cracking coil, a soaking drum in series therewith, a sole means for withdrawing cracked material from said soaking drum, means for reducing pressure thereon, a tar separator, means for conducting material withdrawn from said soaking drum under reduced pressure thereinto, means for withdrawing tar from said separator, means for withdrawing vapor from said se arator, an accumulator having a normal liquid level therein, means for discharging the vapor withdrawn from said separator into said accumulator at a point below the said normal liquid level, means for conducting vapors from said accumulator, means for supplying oil thereto, means for conducting oil therefrom into the said cracking coil and a valved pipe connecting the said tar separator with the said accumulator at a point below the normal liquid level in the accumulator adapted to permit the transfer of liquid from'the said accumulator into the said tar separator.

2. Process of cracking petroleum oil and separating a distillate therefrom containing the cracked gasoline, which comprises heating petroleum oil to a cracking temperature by conducting same in a confined stream througha heating zone, retaining the heated oil under pressure in a digestion zone, continuously withdrawing cracked hydro-carbon material from the digestion zone in a single stream, discharging the stream of cracked hydrocarbon material under reduced pressure and principally in the vapor phase into a separating zone, separating tar therefrom and bubbling the remnant substantially tar free hydrocarbon vapors through a body of oil in a stripping zone under conditions adapted to partially condense said vapors while permitting a fraction containing substantially all the gasoline originally present in the said cracked hydrocarbon material Withdrawn from the digestion zone to remain uncondensed, rectifying the last mentioned uncondensed vapors in a rectifying zone under conditions of partial condensation to produce a condensate and an overhead distillate containing substantially all the gasoline, continuously supplying feed oil to the stripping zone and continuously withdrawing oil therefrom and conducting the same through the heating zone in the confined stream first mentioned.

3. The process according to claim 2 in which the condensate obtained in the rectifying zone is returned to the stripping zone.

4. The process according to claim 2 in which the temperature in the separating zone and the quality of the tar are controlled by allowing oil to flow from the stripping zone to the separating zone in an amount necessary or said control.

5. Process of cracking1 petroleum oil and separating a distillate t erefrom containing the cracked gasoline, which comprises heating petroleum oil-to a cracking temperature by conducting same in a confined stream through a heating zone, retaining the heated oil under pressure in a digestion zone, continuously withdrawing cracked hydrocarbon material from the digestion zone in a single stream, discharging the stream of cracked hydrocarbon material under reduced pressure and principally in the vapor phase into a separating zone, separating tar therefrom and bubbling the remnant substantially tar free hydrocarbon vapors through a body of oil in a strippin zone under conditions adopted to partia ly condense said vapors while permitting a fraction containing substantially all the gasoline originally present in the said cracked hydrocarbon material withdrawn from the digestion zone to remain uncondensed, continuously supplying feed oil to the stripping zone, Withdrawing oil therefrom and conducting the same through the heating zone in the confined stream first mentioned and controlling the temperature in the separating zone and the quality of the tar by allowing oil to flow from the stripping zone to the separating zone in an amount necessary for said control.

6. Apparatus for cracking petroleum oil and separating a distillate therefrom containing the cracked gasoline, comprising a cracking coil, a soaking drum in series therewith, a sole means for withdrawing cracked material from said soaking'drum, means for reducing pressure thereon, a tar separator, means for conducting material withdrawn from said soaking drum under reduced pressure thereinto, means for withdrawing tar from said separator, means for withdrawing vapor from said separator, an accumulator having a normal liquid level therein, means for discharging the vapor withdrawn from said separator into said accumulator at a point below the said normal liquid level, means for supplying oil thereto, a rectifying column, means for conducting vapors rom the accumulator into the rectifying column, 5 cooling means in said column, means for conducting away vapors and means for conducting away condensate from the rectifying column.

7. Apparatus according to claim 6 in 10 which the last mentioned means are adapted for conducting the condensate from the rectifying column into the accumulator.

JOHN STEWART HARRISON.

Images