US2009277A - Conversion of hydrocarbon gases - Google Patents

Description

July 23, 1935- R. F. RUTHRUFF CONVERSION OF HYDROGARBON GASES Filed Dec. 26, 1935 INVENTOR RODSTZFRdZ/Zfdff ATTORNEY marred July 23, 1935 PATENT OFFICE.

, 2,009,217 comasrorz or nrmtoolmnorz GASES Robert F. Ruthrlifl, Hammond, Ind., assignor to Standard Oil Company, Chicago, 111., a corpo ration of Indiana Application December '26, 1933, Serial No. 703,914

6 Claims.

a of gaseous olefins by combined high temperature cracking of saturated gases of the methane series together with distillable vapors of low grade liquid petroleum oils such as heavy reduced crude oil, residual tars from cracking, etc.

It is well known that gaseous hydrocarbons of the methane series can be cracked to olefins at elevated temperatures.

Many attempts have also been made to convert heavy liquid peroleum oils into gaseous olefins but in general such processes have been impractical commercially on account of difllculties with coke deposition. I have found that if the heavy oils be vaporized with or without some slight extent of cracking and these vapors be admixed with a relatively large proportion of saturated gases, the mixture can be cracked to gaseous olefins at elevated temperatures with satisfactory conversion and yield without difficulty from coke deposition.

Briefly my process consists of introducing hot gaseous products from the high temperature cracking step into a cooler-vaporizer wherein they are cooled by direct contact with heavy petroleum oil such as residual tar from oil cracking, reduced crude, etc. Gases and vapors from this step are further cooled and introduced into a iractionating and separating device wherein the oleflnic gas produced in the high temperature cracking step is separated from the light andmedium oils produced from the heavy oil by distillation and/or cracking in the cooler-vaporizer.

These light and medium oils are then re-vaporized and the vapors preheated by suitable means, the preheated vapors being admixed with the saturated hydrocarbon gases constitutingthe main feed to the system, the mixture being then cracked in a tubular-fumace at elevated temperatures. Suitable apparatus for carrying out my process is shown in the drawing attached hereto which forms part of this specification and wherein,

Fig. 1 represents a diagrammatic elevational view of the entire apparatus, and

Fig. 2 represents a diagrammatic elevational view of a part of the apparatus showing a modified-method for vaporizing oils and admixing oil vapors with feed gases for high temperature cracking.

tem through line l0.

These gases may consist predominatingly of ethane, propane or butane or some mixture thereof, but may also contain certain quantities of inert gases such as hydro-gen or methane. Furthermore, if these gases are recovered from oil refinery operations, they may 5 contain certain quantities of the corresponding olefins but ordinarily will not contain more than or of such olefins. Gases in line l0 enter heater II and are preheated in coil I2 to a temperature of about 500-1000 F. after which the. 10 preheated gas is admixed with preheated oil vapors introduced from line 13. The mixture of gases and oil vapors is then heated in the remaining coils of furnace H to a temperature-of 1250-1750" F..whereby said gases and vapors are 15 converted to a high yield of gaseous olefins. Pressures of 0-200 lbs. per square inch above atmospheric are maintained upon the materials in the coil in furnace l I. Depending on the chemical composition of the hydrocarbon gases and vapors charged to the furnace the theoretical yield of olefins will vary, but ordinarily operating yields approaching 75% of the theoretical or better may be obtained.

Hot cracked products leave the heater ll through line l4, and are ordinarily passed directly to a coolingstep. Under certain conditions soaking drum l5 may be used in order to increase the time for the cracking reactions, in which case valves l6 and I6 are opened and valve H in by-pass I8 is closed.

In either case, whether or not the reaction chamber I5 is used, hot cracked products pass through line l9 and. are introduced at a relatively low point into cooler-vaporizer 20 wherein they. are contacted with heavy liquid oils introduced through line 2| at a higher point in cooler-vaporizer 20. These heavy oils will ordinarily comprise heavy reduced crude oil or heavy tar resulting from oil cracking operations. Heavy cycle 40 stocks from cracking operations may also be used.

In general it is most advantageous to use oils having a refractory character which renders them unsuitable for cracking to light liquid products by conventional oil cracking processes, since these oils are especially adapted by their chemical constitution for cracking to gaseous olefins.

I may also use heavy sludge or other by-product oils resulting from the chemical treatment or solvent extraction of lubricating oils or other petroleum products, or any other heavy oil containing distillable portions which may be cracked at high temperatures to gaseous olefins.

The unvaporized residue of the heavy oil is withdrawn from cooler-vaporizer 2|] through offtake 22 and the amount of oil introduced through heavy oil inlet pipe 2I is ordinarily adjusted so that the residue is just sufliciently fluid for removal through offtake 22. I may, however, modify cooler-vaporizer 20 so that same may be operated at higher temperatures (i. e., with smaller amounts of heavy oil introduced at inlet 2I) so that the residual part of the heavy oil is reduced to solid coke which may periodically be removed from the chamber by any suitable means.

Gases and vapors are removed from cooler-vaporizer 20 through line 23 and pass through cooler 24 prior to introduction into separator 25. From separator 25 the final olefinic gas product is removed through line 26 and is pumped by compressor 21 to separator 21a wherein any light oils of gasoline boiling range (formed either in furnace II or vaporizer I5) are condensed and removed, while the olefinic gas is passed to storage or to apparatus wherein it is converted into useful and desired products such as motor fuel, lubricating oils, or chemical derivatives.

The light and medium oils driven oif from the heavy oil in cooler-vaporizer 20 and condensed in cooler 24 are removed from separator 25 at a low point. The total oils condensed in 25 may for example be removed through bottom ofitake 28 and pumped by pump 29 through line 30 to preheater or heat exchanger 3 I. Following heater 3| vapors (and unvaporized liquid, if any) pass to separator 32'wherein any unvaporized liquid is drawn through offtake 33 and vapors pass through line I3 to join saturated gases incracking heater II for conversion to olefinic gases. I may, however, withdraw somewhat lighter oil condensate from separator 25 utilizing trap-out tray 34 as point of withdrawal thereof, in which case this lighter condensate is passed through valve 36 in line 31 to pump 29 for introduction as described into the cracking furnace II. In this case reboiling coils 38 or other reboiling or stripping means (including a suitable inlet for introduction of steam) are provided in the lower part of separator 25 and a drawoff 39 is provided for the elimination of heavy residue or bottoms from separator 25. In order to improve the separation in chamber 25 cooling coils 40 may be positionedv in the upper partthereof. Bottom oil or oil from trap-out tray 34 (depending on the setting of valve M in line 42 and valve 43 in line 44) may be withdrawn from separator 25 and passed through cooler 45 by pump 46 and introduced through line 41 to an elevated point in chamber 25 in order to provide additional cooling and scrubbing. I ordinarily operate separator 25 under such conditions that light oils of gasoline boiling range formed in heater I I or vaporizer I5 pass out of separator 25 and are collected in separator 21a. I may, however, provide an additional trapout tray in the upper part of separator 25 and draw light oils from this tray, or may operate separator 25 so that such light oils are condensed and withdrawn, together with heavier oils, from, trap-out tray 34 being thereafter stripped out of said heavier oils (by stripping means not shown) before said heavier oils go to heater I I.

Fig. 2 represents a modification of my process.

in which a somewhat different method of vaporizing the light and medium oils prior to introducing into the cracking step is used. Correspondingly numbered parts of Fig. 2 are the same in function as those of Fig. 1 and all other parts of the system not shown in Fig. 2 function as previously describedwith reference to Fig. 1.

The medium oils in line 30, after being optional- .through preheating coil 1y preheated in preheater or heat exchanger II, are introduced at an elevated point of vaporizer 48. Heated gases from line In after passing H I2 of furnace II and being heated therein to a temperature of 500-1000 F. are introduced into a low point of vaporizer 48 through line 49, by which means essentially all of the middle oils are vaporized, va-

pors and gases returning through line 50 to the remaining heating coils of heater I I while any unvaporized liquids are withdrawn through ofitake 5|.

The foregoing being a complete description of my invention, I claim:

1. The process of producing gaseous olefins, which comprises subjecting a flowing stream of paraflinic hydrocarbon gases to a high gas-cracking temperature to-convert a substantial portion of the gaseous paraffins present in said gases to gaseous olefins, contacting the hot cracked gaseous products with heavy hydrocarbon oil whereby a substantial proportion of said heavy oil is vaporized, separating gases and vapors from unvaporized heavy oil, condensing said vaporized oil and separating same from gaseous products, and returning-said condensed oil to the'high temperature cracking step.

2. The process of producing gaseous olefins, which comprises subjecting a flowing stream of paraffinic hydrocarbon gases to a high gas-cracking temperature to converta substantial portion of the gaseous paraffins present in said gases to gaseous olefins, contacting the hot cracked gaseous products with heavy cracked hydrocarbon oil whereby a substantial proportion of said heavy oil is vaporized, separating gases and vapors from unvaporized heavy oil, condensing said vaporized oil and separating same from gaseous products, and returning said condensed oil to the high temperature cracking step.

3. The process of producing gaseous olefins, which comprises subjecting a flowing stream of parafiinic hydrocarbon gases to a high gas-crack ing temperature to convert a substantial portion of the gaseous paraffins present in said gases to gaseous olefins, contacting the hot cracked gaseous products with heavy hydrocarbon oil whereby a substantial proportion of said heavy oil is vaporized, separating gases and vapors from unvaporized heavy oil, condensing said vaporized oil and separating same from gaseous products, revaporizing said condensed oil and admixing preheated gaseous charging stock with said vapors prior to the high temperature cracking step.

4. The process of producing gaseous olefins, which comprises subjecting a flowing stream of parafiinic hydrocarbon gases to a high gas-cracking temperature to convert a substantial portion of the gaseous parafiins present in said gases to gaseous olefins, contacting the hot cracked gaseous products with heavy hydrocarbon oil whereby a substantial proportion of said heavy oil is vaporized, separating gases and vapors from unvaporized heavy oil, condensing said vaporized oil and separating same from gaseous products, vaporizing said condensed oil by direct contact with preheated gaseous charging stock, and passing the mixture of oil vapors and gaseous charging stock to the high temperature cracking step.

5. The process of producing gaseous olefins which comprises passing a mixture of parafiinic gases through a heating zone wherein said mixture is heated to a high temperature effective to convert a substantial portion of said paraflinic gases to gaseous olefins, contacting the resultant highly heated gases with heavy hydrocarbon oil to eifect cooling of said gases and volatilization of at least a portion of said heavy hydrocarbon oil, withdrawing the gases and vapors from the contacting stage, therebyseparating them from residual constituents of said heavy hydrocarbon oil, cooling the gases and vapors to liquefy condensible constituents therefrom, separating the thereby condensed constituents from the gases, and returning at least a portion of said constituents to said heating zone to effect a conversion thereof to gaseous olefins in the presence of fresh paraflinic gases traversing said heating zone.

6. The process of producing gaseous v olefins which comprises passing a mixture of paramnic gases through a heating zone wherein said mixture is heated to a temperature of from about 1250 to about 1750 F. to convert a substantial portion of said paraflinic gases to gaseous oleflns, contacting the resultant highly heated gases with heavy hydrocarbon oil to effect cooling of said gases and volatilization of at least a. portion of said heavy hydrocarbon oil, withdrawing the gases and vapors from the contacting stage, thereby separating them from residual constituents of said heavy hydrocarbon oil, cooling the gases and vaporsto liquefy condensible constituents therefrom, separating the thereby condensed constituents from the gases, and returning at least a portion of said constituents to said heating zone to effect a conversion thereof to gaseous olefins in the presence of fresh parafllnic gases traversing said heating zone.

ROBERT F. RU'I'HRUFF.

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