US1681899A - Art of cracking hydrocarbons - Google Patents

Description

Coungusm Filed. March 20, 1923 Patented Aug. 21, 1923.

UNITEDVSTATES PATENT OFFICE.

FRANK A. HOWARD, F ELIZABETH, NEW JERSEY, ASSIGNOR 1'0 STANDARD OIILDE" VELOPMEN'J. COMPANY, A CORPORATION OF DELAWARE.

ART OF CRACKING LEYDROGARBONS. 1

Application filed March 20, 1923. Serial No. 626,264.

This invention relates to the art of pyrolytic conversion of hydrocarbons into products of lower boiling point, and will befully understood from the following description, taken in connection with the accompanylng drawing which represents semi-diagramatically one form of apparatus contemplated in the invention.

In the Patent No. 1,415,232 to Ellis, there is set forth a process in which an oil is brought up to decomposing temperature by passing through a heated zone and is then allowed to crack while passing at a slower rate through row by a connection 4 leading to an upper row of tubes 5. The number of rows provided may be as preferred, but for usual condit ons two rows with the tubes in staggered positions is desirable. Such arrangement qulte completely presents surfaces intercepting ra d1ant heat rays from the furnace chamber, while allowing the hotcombustion gases to freely pass up beyond. From the lower 0011, a pipe 6 leads to a vaporizing chamber or still 7 This may be of any desired form, for instance of water-tube boiler type, or a simple shell still. A tar draw-off pipe 8 is connected at the lowest part, and from the top of the still a vapor line or pipe 9 leads to a second coil B in the furnace chamber 1. This coil may be constructed along the same general lines as the first coil and be made up of a pluralitypf rows of tubes 10 according to the capacity desired, the spacing of the tubes being such as to allow a good exposure to the combustion gases on their way to the exit fiues F. From this upper coil a discharge pipe 11 leads to an enlarged passageway or drum 12, which may conveniently be placed in the top of the same furnace-setting and lagged or heat-insulated on top, so as to maintain the temperature desired. The drum may, however, be set in any other way desired, so long as 1t 1s prepared to maintainthe temperature of its contents without'substantial decline.

From the enlarged passageway or drum 12 a vapor line or pipe 13 leads, preferably with a sli ht downward gradient, to a suitable recti ying device 14, which may be a dephlegmat-or or fractionating tower as desired. A vapor line 15 from the top of the rectifier 14 connects, through a suitable cooled con denser 15, with a receiving drum 16, having valve-controlled drain-line 17 and gas-release 18 as usual. A pipe 19 with pump 20 connects the lower part of the receiving tank with the upper part of the rectifier, for a purpose to be referred to later, and a reflux-pipe 21, with a pump 22 where necessary, leads from the lower part of the rectifier back to the still 7 In carrying out my process, the oil to be cracked is fed into the system by pipe 2. Advantageously such oil may be a crude from which the light constituents have been removed. Passing through the lower coil A, the oil is discharged into the still 7, having been heated-sufliciently to allow substantial vaporization of the constituents desired. Such additional heat as is necessary to efi'ect the degree of vaporization wanted is provided by firing the still 7 in the usual manner. In

this still it is the aim to take off the constituents most suitable for cracking, these being forwarded in vapor form to the coil B. The distillation is thus carried to a low percentage pitch bottom, as heavy as can be handled, the bottoms or residue being drawn oif, continuously or intermittently as desired, through the tar line 8. In this way, oils of any practicable content of crackable constituents may be efficiently handled, irrespective of asphalt or coke-forming contents, such materials being separated from the crackable constituents and eliminated before the cracking stage, and by eliminating such materials serious coke troubles in the cracking operation are avoided. The .pressure in the still 7 may be as low as is consistent with a good delivery rate of vapors on through the coil B, and depending upon the stock operated upon may in general lie between 5 and 150 pounds per square inch. As indicated, the vapors proceed to the coil B and passing therethrough are raised to a temperature of 875975 F. The position of this coil B is such that it is shielded by the lower coil A, the coil A in fact being designed as a screen interposed between the coil B and the furnace, to protect coil B against the radiant heat of the furnace. The coil A handling the feed oil at an adequate velocity on its way to the still 7 absorbs the radiant heat, it being harmlessly directed to raising the temperature of and partly vaporizing the oil on its way to the still. The heat effective. on the coil 13 is thus limited to the mild and relatively uniform heat of the combustion gases.

Entering the drum 12 from the coil B, the vapors are passed along at a suitable rate, the inlet preferably being arranged at one end and the outlet at the opposite end, and the temperature being maintained in general at 825950 F., a yield of 15-30% of gasoline I may be directly obtained.

The pressure in the drum 12 does notneed to be high, only sufiicient to maintain a suitable throughput, and may be for instance from 15 up to 150 pounds per square inch.

From the drum 12, the vapors proceed to the rectifier 1 1 where the gasoline constituents are sorted out and forwarded to the condenser 15and receiving drug 16. To facilitate such rectification, condensate is, drawn off from the receiver 16 and is forced by the pump 20 into the upper part of the rectifier and passing down countercurrent to the vapor, washes and fractionates it. The heavy reflux from the bottom of the rectifier, also that draining down from the vapor line ,13 by reascn of its downward slope, is returned through a suitable trap 23 and pipe 21 to the still 7 for recycling. Where desired, instead of returning the heavy condensate from the vapor line 13 to the still as mentioned, it may instead be drawn off aside by a pipe 24.

Vhile I have described my invention by reference to certain specific details, it will be understood that this is for the purpose of making the invention clear, and is not limitative. And the invention is to be considered as limited only as defined in the following claims, in which it is my intention to claim all inherent novelty as broadly as the prior art permits.

What I claim is:

1. Apparatus of the character described, which comprises a furnace, a heating coil in said furnace located as a screen to absorb radiant heat. a distillation chamber into which said coil discharges, another heating coil in said furnace screened by the firstmentioned coil and receiving vapors from the distillation chamber, an enlarged passageway into which the last-mentioned coil discharges, means for maintaining the temperature in the enlarged passageway without substantial decline, a vaporline leading from said enlarged passageway and having adownward slope therefrom. a rectifier for the vapors, a vapor line from the top of said rectifier, a c ndenser on said vapor line, a

tankfor receiving condensate, means for returning condensate from said tank into the top of the rectifier, and means for returning refiux from the bottom of the rectifier to the distillation chamber.

2. Apparatus of the character described, which comprises a furnace, a heating coil in said furnace located as a screen to absorb radiant heat, a distillation chamber into which said coil discharges, another heating coil in said furnace screened by the first-mentioned coil and receiving vapors from the distillation chamber, an enlarged passageway into which the last-mentioned coil discharges, means for maintaining the temperature in the enlarged passageway without substantial decline, a vapor line leading from said enlarged passageway and having a downward slope therefrom, a rectifier for the vapors, a vapor line from the top of said rectifier, a condenser on said vapor line, and means for returning condensate into the top of the rectifier;

3. Apparatus of the character described,

which comprises a furnace, a heating coil in said furnace located as a screen to absorb radiant heat, a distillation chamber into the combination of aheating coil located as a screen to absorb radiant heat, a distillation chamber into which said coil discharges, another heating coil screened by the firsbmentioned coil and receiving vapors from the distillation chamber, an enlarged passageway into which the last-mentioned coil discharges, means for maintaining the temperature in .the enlarged passageway without substantial decline, and means for rectifying vapors from said enlarged passageway.

5. In apparatus of the character described, the combination of a heating coil located as a screen to absorb radiant heat, a distillation chamber into which said coil discharges, another heating coil screened by the first-mentioned coil and receiving vapors from the distillation chamber, an enlarged passageway into which the last-mentioned coil discharges, and means for maintaining the temperatiire in the enlarged passageway without substantial decline.

6. In apparatus of the character described, the combination of a heating coil located as a screen to absorb radiant heat, a distillation chamber into which said coil discharges, another heating coil screened solely by the firstmentioned coil. and a vapor line from the chaniher to the last-mentioned heating coil.

7. In apparatus of the character described,

the cmnhination of a furnace, a heating coil 5 arranged to receive radiant heat from the furnace. a cracking passageway shielded from radiant heat solely by said coil, means for separating asphaltic substances from the hydrocarbon material which has traversed the heating coil, and means for passing vapors from the separating means to the cracking passageway.

FRANK A. HOWARD.

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