US2160288A - Conversion of hydrocarbons - Google Patents

Description

y 1939- R. F. RUTHRUFF 2,160,238

CONVERSION OF HYDROCARBONS Filed Aug. 8, 1955 swan/zed f. P Gama/Ina INVENTOR fioberf Fkafhruff ATTORNEY Patented May 30, 1939 UNITED STATES CONVERSION OF HYDROCARBONS Robert F. Ruthrufl, Hammond, Ind., assignor to Standard Oil Company, Chicago, 111., a corporation of Indiana Application August 8,

' 9 Claims.

This invention relates in general to the thermal conversion of hydrocarbon fluids and particularly to a combination process in which a mixed stream of normally gaseous olefins and an oil of gas oil characteristics is converted, the clean gas oil recovered therefrom being separately converted under vapor phase conditions, with the tar from each conversion step being deasphalted by a liquefied normally gaseous hydrocarbon,

specifically propane, recovered as a conversion product from the mixed stream, the normally gaseous hydrocarbons from the vapor phase step being utilized as charge or as an additional charge of olefins for the mixed stream.-

The invention will be described in detail with reference to the accompanying drawing which is a diagrammatic plan of apparatus suitable for carrying out the process.

Referring to the drawing, oil from any suitable in source, such as virgin gas oil obtained from a topping plant, not shown, is forced through a line I by means of a pump 2 into a heating coil 3, which may comprise sections in the radiant and convection chambers of a furnace structure 4.

. Gaseous olefins obtained from any suitable source, such as from a separate cracking operation, as well as from one of the stages of the instant process, are forced through a line 5 by means of a pump 6 into an absorber tower 1. 31) Absorber oil is introduced, through a line 8 by means of a pump 9 into the absorber 1 wherein it contacts upwardly rising gas. Gases unabsorbed by the absorber oil, such as hydrogen and methane, are vented from the absorber tower I 35 through a line H andthe enriched absorber oil is passed through line 12 to stripper tower l3. Stripped absorber oil is returned from the stripper l3 through a line I 4 by means of a pump l5 to the absorber tower I to be further enriched. 40 Gases are conducted from the stripper l3 through a line I 6 to the inlet of the heating coil 3. The thus mixed gas oil and gasesare passed through the heating coil 3 wherein the mixed stream is heated to a temperature of from 925 to 1050" F1, 5 while being maintained under a pressure of from about 200 to'750 lbs. per sq. in., to accomplish the desired conversion and polymerization of the stocks constituting themixed stream.

' The thus heated stream, is conducted from the 50 convection section of the heating coil 3 through a line H, controlled by a pressure reduction valve l8, into an evaporator tower l9 maintained at a pressure of from about 50 to 200,1bs. per sq. in., preferably at about 60 lbs. per sq. in. I

55 Simultaneously with the heating of the mixed 1935, Serial N... 35,335

stream of oil and olefins in the heating coil 3, a reduced crude oil, obtained from a topping plant or from any other source, is forced through a line by means of apump 20a into a heating coil 2| having sections in the radiant and con- 5 vection chambers of a furnace 22. Reduced crude passing through the heating coil 2| is therein heated to a temperature of from about 850 to 925 F., preferably about 860 F., while being maintained under a pressure of from about 100 10 to 800 lbs. per sq. in., preferably at about 200 lbs. per sq. in. to accomplish viscosity breaking thereof. The thus heated oil leaving the convection section of the heating coil 2| is conducted through a line 23 controlled by a pressure reduction valve 15 24 to the evaporator l8 where it mixes with the heated stock entering the evaporator through the line H. Separate evaporators for each stream may be provided.

If desired, the furnaces 4 and 22 may be com- 20 bined within a single setting, the setting being provided with separately fired radiant heating chambers and a common convection heating chamber receiving combustion gases from each of the separately'fired radiant heating chambers. 25 The heated oil within the evaporator I9 is separated into vaporizable and non-vaporiza'ble constituents, the vaporizable constituents passing overhead through a line 25 connected to a hubble tower 26 having suitable fractionating means therein, notshown. The vaporous constituents passing through the bubble tower 2B, are therein fractionated and the overhead vaporous fraction is conducted through a line 21 and condenser 28 to a distillate receiver 29. Dry gas, such as hydrogen and methane, isv removed from the distillate receiver 29 through a valved control line 30 and suitably disposed of. If desired partof the distillate, which comprises gasoline-like constituents, may be returned to thebubble tower ,26 as refluxing medium for the upwardly rising vapors. As shown, part of the distillate may be withdrawn through a line. 3i and forced by means of a pump 32 to the upper part of the bubble tower 25. Other refluxing medium may be used. 5 The remaining distillate, or all of the distillate if part thereof is not used as a refluxingmedium, maybe withdrawnfrom the distillate receiver 29 through a line 33 and forced by means of a pump 34 to a stabilizing tower 35, the stabilizing tower being provided with suitable bottom heating means and top cooling means, not shown. The stabilizer 35 is preferably maintainedgat a pressure of from about 250-350 lbs. per sq. ,in., stabilized gasoline being withdrawn from the bottom thereof through a line 36 and passed to storage. Propane and lighter hydrocarbons separated from the gasoline are withdrawn from the stabilizer 35 through a line 31 and passed through a condenser 38 to a receiver 39. Incondensible fuel gas, which comprises hydrogen and methane is separated from the condensibles in receiver 39 and is withdrawn through a line 40 to be utilized as fuel.-- Condensed constituents within the receiver 39 may in part be returned to the stabilizer 35 as refluxing medium therefor. As shown, part of the liquid from the receiver 39 may be forced through aline 4| by means of a pump 42 into the upper part of the stabilizing tower 35. The remaining liquid from the receiver 39, or all of it if part is not used as a refluxing medium, is withdrawn therefrom at about atmospheric temperature through a line 43 and forced by means of a pump 44 to an accumulator tank 45. The liquid collected in the accumulator tank 45 which comprises predominantly propane, is efliciently used in accordance with my process to accomplish deasphalting of the tar produced in the process, as. will be hereinafter explained.

The unvaporized oil or tar collected in the lower part of the evaporating tower I 9 may be withdrawn therefrom through a line 45 and forced through a cooler 41 by means of, a pump 48. The tar, in passing through the cooler 41, which may be cooled in any suitable manner, is cooled to a temperature of about 100 to 150 F., and is passed to a tar accumulator 49 and furthertreated, as will hereinafter be described.

The condensate collected in the lower part of the bubble tower 25, which is a clean gas ofl suitable for vapor phase cracking, may be withdrawn therefrom through a line 50 and forced by means of a pump 5! to a gas oil accumulator 52. The gas oil from the accumulator 52 is forced through a line 53 by means of a pump 54 through a heating coil 55, which may comprise sections in the radiant and convection chambers of a suitable furnace 55. The gas oil in passing through the heating coil 55 is heated to a temperature of from about 875 to 950 F. or as high as 1100 F. while being maintained under a pressure of from about 200 to 750 lbs. per sq. in. and undergoes vapor phase cracking therein. The vapors leaving the heating coil 55 are conducted through a line 51 controlled by a pressure reduction valve 58 into an evaporating tower 59 maintained at a pressure of from about 50 to 200 lbs. per sq. in., preferably of about 60 lbs. per sq. in. The tar resulting from the vapor phase cracking of the oil passing through the heating coil 55 is separatedin the evaporator 59 and is collected in the lower portion thereof. This tar may be withdrawn from the evaporator 59 ,through a line 89 and forced through a cooler 5| by means of a pump 82 to the tar accumulator 49, wherein it mixes with the cooled tar withdrawn from the evaporator l9, previously described. The tar, in passing through the cooler 5|, is cooled to a temperature of from about 100 to 150 F.

Vaporous constituents leaving the evaporator 59 are conducted through a line 53 to a bubble tower 84 provided with conventional fractionating means, not shown. The vaporous constituents passing through the bubble tower 54 are therein fractionated to form a clean cycle condensate of gas oil characteristics and an overhead vaporous fraction. The cycle condensate may be withdrawn from the bubble tower 54 through a line 85 and forced by means of a pump into the gas oil accumulator 52 previously described,

amazes wherein it is mixed with the gas oil from the bubble tower 26, the thus mixed oil constituting the charge oil for the heating coil. 55. vaporous constituents leaving the bubble tower 64 pass through a line 51 in which is interposed a pump 68, and are forced into a stabilizing tower 59, which may be provided with bottom heating means and top cooling means, not shown. It is to be understood that a condenser and distillate receiver may be interposed between the bubble tower 54 and the stabilizer 69, in a manner similar to and operated the same as the condenser The stabilizer, maintained 28 and receiver 39. at a pressure of from about 250 to 350 lbs. per sq. in., is operated to produce the desired endpoint gasoline whichiswithdrawn from the bottom thereof through a line I0. Uncondensed gases containing oleflns are conducted from the stabilizer 69 through a line H to the line 5, wherein they are mixed with the oleflns passing therethrough, the thus mixed gases being passed through the absorbers 'I and I3 to be concentrated, as previously described.

If desired, in lieu of the single bubble tower 25, two bubble towers may be provided, a heavy condensate being withdrawn from the first and passed to the gas oil accumulator 52 and a lighter condensate being withdrawn from the second and recycled to the inlet, or some intermediate point,

v of the heating'coil 3.

The tar collected in, the tar accumulator 49, which is made up of tar withdrawn'from the evaporators l9 and 59, may be withdrawn therefrom through a line I2 and forced by means of a pump I3 into a deasphalter 14 which may be at a pressure of from 200 to 250 lbs. per sq. in. In order to deasphalt the tar to recover asphalt and oil suitable for viscosity breaking with the reduced crude heated in the heating coil 2|, this invention provides for the utilization of the liquid in any desired manner for example, by fractional distillation. If desired a part of the propane may be withdrawn through a line controlled by a suitable valve and passed to storage to be used for other purposes. Propane introduced into the deasphalter I4, which is preferably in small quan- 1 titles at the beginning in order to dilute the tar, removes the oil from the tar and forms a propane-oil solution which rises to the upper portion of the deasphalter 14. The temperature of deasphalter I4 is suitably between 125 to 200 F., and usually within 100 F. below the critical temperature of the liquefied gas. Generally I prefer to use from about 2 to 8 units of propane for each unit of tar deasphalted. This propane-oil solution from the top of deasphalter I4 is conducted through a line I8 to a separator 19, provided with bottom heating means 8| and top cooling means 82, and is therein separated into propane and a recycle oil stock. The separated propane is returned through a line 83 and compressor, 84 to the propane accumulator 45. The heavy oil which collects in the lower part of the separator I9 may be withdrawn therefrom through a line 85 and forced by means of a pump 88 to a recycle 011 stock accumulator 81. The oil collected in the accumulator 81 may be withdrawn through a line 88 and mixed with the reduced crude passing through the line 20 prior to entering the heating coil 2|.

The asphalt separated from the tar and collected in the lower part of the deasphalter 14 may be passed through a line 89, controlled by a valve 90, into a separator 9| provided with bottom heating means 92 and top cooling means not shown, if necessary. Any propane retained by the asphalt is separated therefrom in the separator SI and is returned through line 93 and compressor 94 to the line 83 where it mixes with propane being returned to the propane accumulator 45. The asphalt collected in the lower part of the separator 9| is characterized by a melting point, usually above 100 F. and may be withdrawn through a line 95 and passed to suitable storage.

From the foregoing it is apparent that I have provided a novel combination process in which a stream of concentrated olefins and oil is thermally converted to produce gasoline, the propane from such operation being utilized to deasphalt tar produced in the process. It will also be apparent that my process provides for recycling the uncondensed gases from the vapor phase cracking operation for further treatment and the recovery of oil constituents from the tar, which oil may also be subjected to a viscosity breaking operation with the fresh reduced crude charging stock. My process enables the production of higher yields of gasoline, greater reduction of coke formation, and reduction in ultimate gas produced than in conventional cracking operations.

Where the expression a saturated predominantly C3 fraction is used in the claims; it is intended to cover a hydrocarbon comprising mostly propane with some propylene and traces of other hydrocarbons, such as ethane, ethylene, butane, butylene.

While the preferred embodiment of my invention hasbeen described, I do not limit myself to the precise details, except as defined in the following claims.

I claim:

1. In a process wherein a stream of gas oil is passed into a first cracking zone and therein heated to elevated temperatures to eiIect conversion thereof to form tar in an evaporating zone, clean cracked gas oil in a fractionating zone and stabilized gasoline in a stabilizing zone. the improvement which comprises mixing olefinic gas with said stream of gas oil for passage through said first cracking zone, withdrawing unconverted gases from said stabilizing zone and separating therefrom a saturated predominantly propane fraction, passing tar from the evaporating zone to a deasphalting zone, introducing at least a part of said saturated predominantly propane fraction into said deasphalting zone to therein deasphalt the said tar, cracking in a second cracking zone and recycling said deasphalted tar to said evaporating zone, conducting said clean cracked gas oil to a third cracking zone operating at a higher temperature than said first cracking zone wherein gasoline, tar and highly unsaturated olefinic gas is produced, recycling said highly unsaturated olefinic gas to said first cracking zone and conducting tar derived from saidclean cracked gas oil to said deasphalting zone wherein it is combined with tar derived from said conversion first mentioned.

2. In a process wherein a stream of gas oil is passed through a heating zone and therein heated to elevated temperatures to effect conversion thereof to form tar in an evaporating zone, clean cracked gas oil in a fractionating zone and stabilized gasoline in a stabilizing zone, the improvement which comprises mixing olefinic gas with said stream of gas oil for passage through said heating zone, withdrawing unconverted gases from said stabilizing zone and separating therefrom a saturated predominantly propane fraction, passing tar from the evaporating zone to a deasphalting zone, introducing at least a part oi said saturated predominantly propane fraction into said deasphalting zone to therein deasphalt the tar, cracking and recycling said deasphalted tar to said evaporating zone, withdrawing said clean cracked gas oil from said fractionating zone and passing it through a separate heating zone wherein it is cracked substantially in the vapor phase, separating the thus cracked products into passed through a heating zone and therein heated to elevated temperatures to effect conversion thereof to form tar in an evaporating zone, clean cracked gas oil in a fractionating zone and stabilized gasoline in a stabilizing zone, the improvement which comprises mixing olefinic gas with said stream of gas oil for passage through said heating zone, withdrawing unconverted gases from said stabilizing zone and separating therefrom a saturated predominantly propane fraction, passing tar from the evaporating zone to a deasphalting zone, introducing at least a part of said saturated predominantly propane fraction into said deasphalting zone to therein deasphalt the tar, cracking and recycling said deasphalted tar to said evaporating zone, withdrawing said clean cracked gas oil from said fractionating zone and passing it through a separate heating zone wherein it is cracked substantially in the vapor phase, separating the thus cracked products into vapor phase tar in a second evaporating zone, a clean recycle gas oil in a second fractionating zone, and stabilized gasoline and olefinic gases in a second stabilizing zone, and pasting said separated olefinic gases from said stabilizing zone to the stream of gas oil first mentioned. 4. In a process wherein a stream of gas oil is passed through a heating zone and therein heated to elevated temperatures to effect conversion thereof to form tar in an evaporating zone, clean cracked gas oil in a fractionating zone and stabilized gasoline in a stabilizing zone, the improve ment which comprises mixing olefinic gas with said stream of gas oil for passage through said heating zone, withdrawing unconverted gases from said stabilizing zone and separating therefrom a saturated predominantly propane fraction, passing tar from the evaporating zone to a deasphalting zone, introducing at least a part of said saturated predominantly propane fraction into said deasphalting zone to therein deasphalt the tar, cracking and recycling said deasphalted tar to said evaporating zone, withdrawing clean cracked gas oil from said fractionating zone and passing it through a separate heating zone wherein it is cracked substantially in the vapor phase, separating the thus cracked products into vapor phase tar in a second evaporating zone, a clean recycle gas oil in a second fractionatingzone and a stabilized gasoline in a second stabilizing zone and passing said vapor phase tar to the deasphalting zone previously mentioned where it is combined and treated with the tar from the evaporating zone first mentioned.

5. A process for the production of gasoline which comprises, passing a stream of virgin gas oil mixed with normally gaseous hydrocarbons consisting predominantly of olefins, through a heating zone and therein subjecting said stream to elevated temperatures and pressures to accomplish conversion thereof, conducting said heated stream to an evaporating zone maintained at a lower pressure than said heating zone wherein tar is separated from vaporizable constituents, fractionating said vaporizable constituents in a fractionating zone to form an overhead vapor fraction and a cleangas oil condensate, condensing said overhead vapor fraction and thereafter stabilizing same to form a stabilized gasoline and a saturated predominantly propane fraction, passing said clean gas oil condensate from the aforementioned fractionating zone through a separate heating zone wherein it is cracked in the vapor phase, conducting the thus heated oil to a second evaporating zone wherein tar is separated from the vaporized constituents, fractionating the vaporized constituents to form an overhead vapor fraction and a recycle condensate, stabilizing said overhead fraction to form a stabilized gasoline, and an uncondensed gas fraction rich in olefins, conducting said uncondensed gas fraction to said first mentioned heating zone, withdrawing ,tar from the aforementioned evaporating zones and passing it to a deasphalting zone, where it is separated by the selective solvent action of propane into recovered oil and asphalt, cracking said recovered oil and recycling: the cracked products thereof to the evaporating zone first mentioned. 6. In a process wherein a stream of gas oil is passed through a heating zone and therein heated to elevated temperatures to effect conversion thereof to form tar in an evaporating zone, clean cracked gas oil in a fractionating zone and stabilized gasoline in a stabilizing zone, the improvement which comprises mixing olefinic gas with said stream of gas oil for passage through said heating zone, passing tar from the evaporating zone to a deasphalting zone wherein the tar is separated into asphalt and recovered oil by the selective solvent action of propane, merging the recovered oil with a stream of heavy reduced crude oil, passing the merged oils through a separate heating zone wherein they are subjected to elevated temperatures to effect viscosity breaking thereof, discharging the heated heavy oil to the evaporating zone wherein it is mixed with the stream resulting from the conversion of the mixture of said heated gas oil and olefins, withdrawing clean cracked gas oil from said fractionating zone and separately cracking it in the vapor phase at a temperature above that of the heating zone first mentioned wherein a gas high in olefins is produced, and recycling said gas high in olefins to said gas oil stream first mentioned for passage through said gas oil heating zone.

7. A process for the production of gasoline which comprises, passing a stream of virgin gas oil mixed with normally gaseous hydrocarbons consisting predominantly of olefins, through a heating zone and therein subjecting said stream to elevated temperatures and pressures to accomplish conversion thereof, conducting said heated stream to an evaporating zone maintained at a lower pressure than said heating zone wherein tar is separated from vaporizable constituents, fractionating said vaporizable constituents ina fractionating zone to form an overhead vapor fraction and a clean gas oil condensate, condensing said overhead vapor fraction and thereafter stabilizing same to form a stabilized gasoline and a saturated predominantly propane fraction, passing said clean gas oil condensate from the aforementioned fractionating zone through a separate heating zone wherein it is cracked in the vapor phase, conducting the thus heated oil to a second evaporating zone wherein tar is separated from the vaporized constituents, separately fractionating the vaporized constituents to form an overhead vapor fraction and a recycle condensate, separately stabilizing said overhead fraction to form a stabilized gasoline and an uncondensed gas fraction rich in olefins, conducting said uncondensed gas fraction to said first mentioned heating zone, withdrawing tar from the aforementioned evaporating zones and passing it to a deasphalting zone where it is separated by the selective solvent action of propane into recovered oil and asphalt, merging said recovered oil with a stream of heavy reduced crude oil, passing said merged oils through another separate heating zone wherein they are subjected to elevated temperatures to effect viscosity breaking thereof and thereafter passing said last mentioned heated oil to the evaporating zone first mentioned where it is mixed with said heated stream resulting from the conversion of the mixture of gas oil and olefins.

8. The process of converting heavy hydrocarbon oils and olefin gases to gasoline, which comprises combining a stream of olefin gases and virgin gas oil, passing the gases and gas oil through a heating zone wherein they are heated to a temperature between 925 and 1050 F., at a pressure between 200 and 750 pounds per square inch, discharging the heated gases and gas oil into an evaporating zone wherein vapors are separated from tar, conducting the vapors to a fractionating zone wherein gasoline vapors and unconverted gases are separated from a clean cracked gas oil fraction, separating stabilized gasoline from uncondensable gases and a predominantly propane fraction in a separating zone and a stabilizing zone, conducting the clean cracked gas oil fraction to a second heating zone where it is heated to a temperature between 950 and 1100 F. and a pressure between about 200 and 750 pounds per square inch, discharging the heated clean cracked gas oil into a second evaporating zone wherein tar is separated from the vapors, conducting the vapors to a second fractionating zone wherein a recycle gas oil fraction is separated, recycling the recycle gas oil fraction to the second heating zone, conducting the vapors to a second stabilizing zone wherein stabilized gasoline is separated and uncondensed gases rich in olefins are removed, combining these gases with the virgin gas oil in the first heating zone, conducting tar from both evaporating zones to a deasphalting zone wherein it is separated into a heavy recovered oil and asphalt by the selective solvent action of a liquefied gas predominantly propane, combining the heavy recovered oil with reduced crude oil in a third heating zone where the oil is subjected to viscosity breaking at a temperature of between 850 and 925 F. and a pressure of about 100 to 800pounds per square inch and discharging the heated oil from the third heating zone into the evaporating zone first mentioned.

9. In the process of converting heavy oils into motor fuels boiling within the gasoline boiling range, the improvement comprising subjecting a virgin gas oil to the action of normally gaseous olefin hydrocarbons in an elongated heating zone of restricted cross section to a temperature of between 925 and 1050" F., introducing said virgin gas oil and olefin polymerization products into a polymerization products evaporating zone wherein unevaporated residue are separated from gases, gasoline vapors and refractory cycle stock vapors which are withdrawn to a fractionating zone, separating said vapors and gases in said fractionating zone into a refractory cycle stock reflux and vapors substantially free from hydrocarbons boiling above the gasoline boiling range, condensing a desired gasoline fraction from said vapors, withdrawing said refractory cycle stock reflux to a high temperature conversion zone and subiecting it to' heating in an elongated restricted stream to a temperature between 950 and 1100 F. whereby additional gasoline and olefin gases are produced, returning said last mentioned olefin gases to said virgin gas oil first mentioned,

withdrawing unevaporated residue from said polymerization products evaporating zone, subjecting it to extraction with a liquefied normally gaseous hydrocarbon whereby undesirable carhon-forming asphaltic constituents are rejected from the system and potential gasoline producing heavy hydrocarbons are recovered, subjecting said recovered hydrocarbons to mild conversion by heating in a restricted stream to a temperature between 850 and 925 F. and introducing the products of said mild conversion into said polymerization products evaporating zone.

ROBERT F. RUTHZRUI'F.

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