US3233005A - Production of acetylene - Google Patents

Description

Feb. 1, 1966 c. E. SHANNAHAN ETAL 3,

PRODUCTION OF ACETYLENE Filed March 5, 1962 V PREPURIFICATION PYROLYSIS, n ABSORBER GAS GAS TURBINE 5| PLANT 53 C02 ABSORBER AIR s4 sTEAM 1 Y" D972 -6l 49 WATER 2 ACETYLENE I ABSORBER WASTE HEAT BOILER ACETYLENE STRIPPER 39 36 ACETYLENE L, 34 WAU ACETYLENE WASH WATER AMMONIA WATER DISTILLATION INVENTORS 44 CORNELIUS E.SHANNAHAN HAYS c. MAYo BY @474 we. 64 47 ,4. 0- M ATTORNEYS AGENT t include United States Patent 3,233,005 PRODUCTION OF ACETYLENE Cornelius E. Shannahan, Garden City, and Hays C. Mayo, Huntington, N.Y., assignors to Pullman Incorporated, a corporation ot Delaware Filed Mar. 5, 1962, Ser. No. 177,353 3 Claims. (Cl. 260-679) This invention relates to the recovery of acetylene produced by the pyrolysis of hydrocarbons. More specifical- 1y, it relates to improvements in such a recovery process by which energy requirements of the process are supplied efficiently from the process itself.

A principal commercial process for the preparation of acetylene involves the pyrolysis of low boiling hydrocarbon feed stocks, i.e., light hydrocarbons ranging from normally gaseous hydrocarbons through light naphthas. In the pyrolysis process, the hydrocarbon feed is maintained under closely controlled conditions of temperature, pressure and reaction time to provide a gas mixture containing a recoverable quantity of acetylene. As indicated, the process is applicable to the conversion or normally gaseous hydrocarbons as Well as normally liquid hydrocarbons. In the conversion of normally gaseous hydrocarbons the feed material is preheated and combined with a quantity of oxygen in an amount sutficient to oxidize a portion of the hydrocarbon feed. This oxidation reaction supplies the bulk of the heat necessary for the conversion of the hydrocarbons to desired products. For the conversion of normally liquid hydrocarbons to acetylene, a suitable combustion gas, such as hydrogen or mixtures of hydrogen with carbon oxides, and hydrocarbon is burned with oxygen under conditions conducive to complete oxidation of the combustion gas. The liquid hydrocarbon feed, preferably preheated, is injected into the hot combustion gases. reheating of the liquid hydrocarbon feed should be kept substantially below reaction temperatures in order to avoid premature reaction.

Pyrolytic conversion of hydrocarbons is an endothermic reaction and the distribution, of the pyrolysis reaction products is determined to a significant extent by the reaction temperature and the reaction time in addition to the feed composition. Pressure also influences product distribution. As a general rule, high temperatures combined with short reaction times favor the production of acetylene whereas lower temperatures and longer reaction times favor the production of ethylene. Conditions most favorable for the production of acetylene involve reaction temperatures between about 1500 C. and about 3000 C. with a reaction time between about 0.001 and about 0.01 second. Unfortunately, conditions must favorable for the production of acetylene also tend to favor the production of higher acetylenic compounds such as methyl acetylene, vinyl acetylene, diacetylene, etc, various other C -C hydrocarbons, hydrogen, carbon monoxide and carbon dioxide. The commercial use of acetylene as a chemical intermediate as, for example, in the preparation of chlorinated ethylenes, acetic acid, vinyl chloride, vinyl acetate, neoprene, chloroprene, and acrylonitrile, requires acetylene of extremely high purity, n eces sitating substantially complete removal of all of the foregoing materials from the pyrolysis eflluent.

Several recovery processes are known for producing acetylene of the necessary purity. Generally, these processes involve the use of one or more solvents which are circulated in one or more absorption-stripping systems. Some of the solvents which are most commonly used acetone, butyrolactone, dimethylformamide, methanol, liquid hydrocarbons and liquid ammonia. In one such recovery process which is preferred, the pyrolysis gas, after removal of carbon dioxide and water,

, 3,233,0s5 Patented Feb. 1, 1966 is contacted with heavy naphtha under conditions suitable to absorb hydrocarbons heavier than acetylene including higher acetylenic compounds. The resulting prepurified gas is then contacted with liquid anhydrous ammonia which selectively absorbs acetylene leaving a tail gas containing hydrogen, carbon monoxide and methane. The rich liquid ammonia is stripped prior to recycle to drive oil a pure acetylene product.

Regardless of the particular recovery process which is used, it is necessary first to compress the pyrolysis gas since it is ordinarily generated at substantially atmospheric pressure and at least a substantial superatrnospheric pressure is necessary for operation of the recover process. In the case of many recovery processes, the higher the pressure used, the more efiicient is the separation. Unfortunately, however, the costs of compressing the pyrolysis gas are always great and become greater with higher pressure. Thus, it may be uneconomical in some cases to take advantage of the increased efficiency possible with high pressure. Even where the recovery process is operated at a relatively low superatmospheric pressure, there is strong incentive for reduc ing energy costs of the process in general and of compression in particular.

Accordingly, one object of the present invention is to provide a method for recovering acetylene from a gas produced by the pyrolysis of hydrocarbons characterized by improved efiiciency and economy. Another object of the invention is to reduce compression costs associated with acetylene recovery processes. Still another object of the invention is to make ciiicient use of tail gases separated from pyrolysis gas in conjunction with the recovery of acetylene therefrom. Various other objects and advantages of the invention will be apparent from the following detailed discussion and description.

In accordance with the improved method of the invention, a gas turbine is used to drive the pyrolysis gas compressor. At least a portion of the tail gas separated in conjunction with the recovery of acetylene from the pyrolysis gas is supplied to the gas turbine as fuel whereby at least a substantial portion of the power requirement of the compressor is supplied from the tail gas of the recovery process. In a preferred method of operation, still further improvements in overall etiiciency are obtained by recovering heat from the gas turbine exhaust and supplying this heat at suitable points in the recovery process.

A standard gas turbine plant is used to drive the pyrolysis gas compressor. This plant includes an air compressor, a combustion chamber and a turbine. Atmospheric air is compressed in the air compressor of the gas turbine plant to a pressure of about 50 to about p.s.i.g. The compressed air flows to the combustion chamber of the gas turbine plant where it reacts with tail gas from the recovery process. The amount of compressed air used is about 400 to about 500 percent in excess of that required for stoichiometric complete combustion of the tail gas. As a result of the burning in the combustion chamber, average gas temperatures of about 1250 to about 1500 F. are obtained. The hot gases of the combustion chamber of the plant at high pressure together with secondary air to insure complete combustion are then expanded in the turbine of the plant generating shaft power which is transmitted mechanically to the pyrolysis gas compressor. Thus, the production of useful work by expension is used in the performance of work of pyrolysis gas compression. The exhaust gas from the turbine is at substantially atmospheric pressure and a temperature of about 700 F. to about 950 F. In accordance with the preferred method of operation, this exhaust gas is passed to a waste heat recovery boiler in which there are at least two coils for recovering heat from the exhaust gas prior to its discharge to the stack. In the first coil, a process fluid is circulated from a tower in the acetylene recovery process requiring reboiling heat at a temperature level above about 250 F. In the second coil in the waste heat boiler, stream is generated at relatively low pressures for use throughout the plant. The exhaust gas from the turbine gives up heat to the fluids flowing in the coils and then flows to the stack at a temperature of about 400 to about 500 F.

Any suitable compressor can be used for pressuring the pyrolysis gas. Generally, it is preferred to use centrifugal compressors for this purpose. In order to avoid or minimize polymer formation and deposition from the hea sensitive unsaturated hydrocarbons in the pyrolysis gas, the compression is preferably done in several stages with interstage cooling such that the pyrolysis gas never absorbs sufficient heat of compression to raise its temperature above about 220 F. The number-of stages of compression required to satisfy this limitation will depend upon the inlet temperature, the first-stage-suction and final-stage-discharge pressures of the compressor and the temperature of available coolant. The final discharge pressure of the pyrolysis gas compressor is selected on the basis of the particular recovery process used. On this basis, the final discharge pressure of the pyrolysis gas compressor is generally about 60 to about 200 p.s.i.g., and preferably about 170 to about 185 p.s.i.g.

The tail gas used as fuel in the gas turbine plant is any one or more of the substantially acetylene-free streams separated in the course of the recovery process. Its specific composition will vary in accordance with the particular recovery process used and the point or points in such process at which the tail gas is separated. In every case, it will contain a substantial proportion of hydrogen and carbon monoxide. In many cases, it will also contain methane and small amounts of carbon dioxide and gaseous hydrocarbons heavier than methane. In the case of the preferred recovery process described involving heavy naphtha and liquid anhydrous ammonia absorbents, it is preferred to use the gas which passes through both absorption operations and which, after water washing for removal of vaporized ammonia, contains principally hydrogen, methane and carbon monoxide. In prior art processes, this tail gas has been wasted by burning in a flare stack and an important advantage is obtained by using at least part of it in accordance with the invention as fuel in the gas turbine plant. This tail gas is produced in such amounts that even where a neighboring synthetic methanol plant can use a gas of this composition as feed, there will generally remain sufficient tail gas for use as fuel in a gas turbine plant to provide the entire power requirement of the pyrolysis gas compressor.

The tail gas which is fired in the combustion chamber of the gas turbine plant is supplied thereto at a pressure of about 130 to about 150 p.s.i.g., i.e., a pressure which is about 80 to about 120 p.s.i. greater than the air pressure. This differential pressure is necessary for proper control of the operation of the gas turbine plant. It is particularly advantageous to operate the acetylene recovery process at a sufficiently elevated superatmospheric pressure such that the tail gas separated in the course thereof can be used directly, i.e., without further compression to meet the pressure requirement stated above for the gas turbine plant. Greatest efficiency is obtained where the pressure of the recovery process and accordingly, the discharge pressure of the pyrolysis gas compressor are sufliciently high to meet the pressure requirement for the tail gas without special compression thereof, but not substantially higher than that pressure.

As mentioned, a large stoichiometric excess of oxygen is supplied to the combustion chamber of the gas turbine plant. As a result, the exhaust gas from the turbine of the plant contains a substantial proportion of uncombined oxygen, generally about 16 toabout 18 mol percent. En-

6],. hanced efficiency in the heat recovery from the exhaust gas is obtained by firing supplementary fuel in the waste heat boiler to be burned using the uncombined oxygen in the turbine exhaust. Where supplementary fuel is fired, it can be a tail gas from the acetylene recovery process including another portion of the same tail gas passed to the combustion chamber of the gas turbine plant or it can be an extraneous fuel such as natural gas or fuel oil. The amount of supplementary fuel which is fired is influenced by the amount of uncombined oxyge in the turbine exhaust gas and the amount and level of heat which must be supplied in the waste heat boiler.

The heat content of the exhaust gas can be used in the waste heat boiler solely for generating steam if desired. This steam can be used directly in the process, for example as a stripping gas, or indirectly in the process, for example in a heat exchanger to provide reboiling heat. This technique has the advantage of permitting separate control of heat exchangers in reboiling service. However, where reboiling heat is required in the process at a temperature level above about 250 B, it is often advantageous, especially where water supply is limited, to pass the process fluid to be reboiled into indirect heat exchange in the waste heat boiler With the exhaust gas. It is found that this method is much more highly efficient thermally than one where steam is generated in the waste heat boiler at a sufficiently high temperature and pressure such that the generated steam can be used in a separate heat exchanger to provide reboiling heat at a temperature level above about 250 F. The economic advantages of this technique increase with an increase in the temperature level of reboiling heat required.

For a better understanding of the invention, reference is bad to the accompanying drawing in which there is shown, in diagrammatic form, suitable apparatus for carrying out a preferred embodiment of the invention.

In the drawing, a pyrolysis gas is introduced in line 311 having the composition given in the table below. This pyrolysis gas is obtained by the partial combustion of natural gas with oxygen. Prior to entering the process in line 11, it is contacted with water and with oil to remove free carbon or soot and any polymeric hydrocarbons which may be present. The pyrolysis gas is compressed in a compressor 3'12 from a pressure of about 1.0 p.s.i.g. at a temperature of about 93 F. to a pressure of about 170 p.s.i.g. and a temperature of about F. This compression is done in a centrifugal machine and in six stages after each of which the gas is cooled to a temperature of about 100 F. in order to prevent overheating of the pyrolysis gas and attendant polymer deposition problems. During compression, the maximum temperature of the pyrolysis gas is about 220 F. The six stages of compression and the intercooling are not shown in detail in the drawing in the interest of simplicity.

The compressed pyrolysis gas in line 13 passes to a C0 removal system shown generally by absorber 14 in which tie gas is contacted countercurrently with a total of about 73,676 gallons per hour of dilute aqueous ammonia to re move C0 The dilute aqueous ammonia is circulated in a standard absorption-stripping system (stripper not shown) being introduced to absorber 14 through line 16 and withdrawn through line 1'7.

The pyrolysis gas recovered from CO absorber 14 in line I18 passes to a system for the removal of hydrocarbons heavier than acetylene shown generally as prepurification absorber 19 in which the gas is countercurrently contacted With a total of about 16,153 barrels per stream day (b.p.s.d.) of heavy naphtha. Prior to its introduction into absorber 19, the gas in line 10 is contacted with dilute caustic for additional CO removal and is dried and cooled to 10 F., by means not shown. The composition of the gas entering absorber 19 is given in the table below. The heavy naphtha (boiling range of about 300 to about 450 F.) is circulated in a standard absorption-stripping system (stripper not shown) entering absorber 19 through operation of absorber 19 at a temperature of about 8 F. and a pressure of about 154 p.s.i.g., the overhead gas in line 23 is substantially free of higher acetylenic compounds and of other hydrocarbons heavier than acetylene. The csomposition of this gas is given in the table below.

The prepuriiied gas in line 23, at about 7 F. and about 152.2 p.s.i.g., is then contacted countercurrently in acetylene absorber 24 with about 359 gallons per minute of liquid anhydrous ammonia. The lean liquid ammonia is introduced into absorber 24 at about 33 F. through line 26 and the rich liquid ammonia, containing substantially all of the acetylene from the pyrolysis gas in line 33, is withdrawn from absorber 24 at about -42 F. and is passed through line 27 to acetylene stripper 28.

Acetylene stripper 28 is maintained at top conditions of about 13 F. andabout 13 p.s.i.g. and bottom conditions of about 6 F. and about 21 p.s.i.g. Vaporous ainrnonia is introduced into the bottom of acetylene stripper 28 through line 29 at the rate of about 29,850 pounds per hour and passes countercurrently upwardly driving off the absorbed acetylene into the overhead in line 31. The lean ammonia from the bottom of stripper 28 is withdrawn through line 32 and is returned to acetylene absorber 24 through line 26, for reuse.

The vaporous acetylene-ammonia mixture in line 31, having the composition given in the table below, is passed to an acetylene water-wash column 33 where it is countercurrently contacted with about 188 gallons per minute of cold water introduced through line 34 to absorb the ammonia. Substantially pure acetylene product is recovered overhead of acetylene water washer 33 in line 36 at about 87 F. and about 9.0 p.s.i.g. This product is of suflieient purity for use as a chemical intermediate, as earlier described.

Returning to acetylene absorber 24, the unabsorbed gases including vaporized ammonia, of the composition given in the table, are withdrawn therefrom in line 37 at a temperature of about -33 F. and a pressure of about 147.3 p.s.i.g. They pass to a tail gas water-wash column 38 in which they are countercurrently contacted with about 110 gallons per minute of cold water introduced through line 39 to absorb ammonia.

The ammonia-water solutionsfrom the two water-wash columns 33 and 38 are withdrawn in lines 41 and 42, respectively, combined in line 43 and passed to an ammoniawater distillation column 44 in which they are resolved into an overhead ammonia fraction (about 33,872 pounds per hour) in line 46 and a bottoms Water fraction (about 148,233 pounds per hour) in line 47. These fractions are returned for reuse as absorbents. The ammonia-water distillation column 44 is operated at a pressure of about 298 p.s.i.g. and temperatures of about 117 F. at the top and about 422 F. at the bottom.

Returning to tail gas water-Wash column 38, the substantially ammonia-free tail gas of the composition given in the table is recovered overhead in line 48 at about 66 F. and about 142.4 p.s.i.g. The portion of this tail gas not required as fuel is delivered from the process through line 49. The balance, or about 558,000 standard cubic feet per hour, is passed through line 51 to a combustion chamber 52 of a gas turbine plant indicated generally at 53. It is to be noted that at the operating pressures of the described recovery process the tail gas diverted to turbine fuel in line 51 requires no booster compression.

tmospheric air is introduced into the gas turbine plant 53 through line 54 at a rate of about 525,000 pounds per hour to about 605,000 pounds per hour and is compressed to a pressure of about 50 to about 70 p.s.i.g. in the air compressor 56 of the plant. The compressed air in conduit 57 and the tail gas from line 51 are combined and react in combustion chamber 52 producing a gas in conduit 58 at a temperature of about 1250 to about 1450 F. and a pressure of about 50 to about 70 p.s.i.g. This gas is expanded in the turbine 59 of the plant producing the shaft power necessary to drive pyrolysis gas compressor 12 and air compressor 56. The horsepower requirement of compressor 12 of 11,200 is thus supplied entirely during normal operation using only process tail gas as fuel. Although only a single pyrolysis gas compressor 12 and gas turbine plant 53 are shown, two or more can be used in parallel to provide flexibility. In the present example, two parallel compressors and turbines are actually used.

The exhaust gases from turbine 59 are recovered in conduit 61 at a temperature of about 905 to about 920 F. and a pressure of about 4 inches of water. In the preferred embodiment illustrated, the exhaust gases, having the composition given in the table, are directed to a waste heat boiler 62 where their heat is recovered in reboiling ammonia-water distillation column 44 and in generating 450 p.s.i.g. saturated steam.

The reboiling duty of ammonia-water distillation column 44 is large, namely about 58,000,000 B.t.u. per hour, and is supplied at the high temperature of about 422 F. This high-level heat is provided by passing about 700,000 pounds per hour of Water from the bottom of column 44 through line 63 by means of pump 64 to coil 66 in waste heat boiler 62. The resulting vaporized bottoms liquid is admitted to column 44 through line 67.

For purposes of generating steam in waste heat boiler 62, boiler feed water is introduced through line 68, preheated in coil 69 and passed through line 71 to steam drum 72. Preheated water is withdrawn from steam drum 72 through line 73, vaporized in coil 74, and returned to steam drum 72 through line 76. The net steam production of 35,000 pounds per hour is delivered through line 77 to points of use in the process. The total duty of coils 69 and 74 in producing this steam is million B.t.u. per hour.

The heat content of the exhaust gas in conduit 61 is augmented in waste heat boiler 62 by firing supplementary fuel through line 78. Provision is made to fire fuel oil of a heating value of about 26 million B.t.u. per hour or fuel gas of a heating value of about 12 to about million B.t.u. per hour This supplementary burning is highly efficient by reason of the high temperature of the uncombined oxygen in the exhaust gas supplied from conduit 61. The temperature of the flue gas out the stack of waste heat boiler 62 is about 450 F.

TABLE Compositions of principal streams, pounds per hour Reference Numeral for 11 18 23 31 37 48 *61 Stream COMPONENT *Weight percent.

When the foregoing process isstarted up, process tail gas is not available as fuel in the gas turbine plant 53. Although any suitable start-up procedure can be used, it is preferred to use a small steam turbine (not shown) to start compressor 12, the steam for which is generated in waste heat boiler 62 using extraneous hydrocarbon as fuel, for example some of the hydrocarbon which is to be pyrolyzed to produce acetylene. After brief operation in this fashion, sufiicient tail gas is a available in line 51 to operate gas turbine plant 53.

A comparison between operating costs of the gas turbine and of a standard steam turbine applied in the above-described process shows that, in fuel consumption alone, the steam turbine system requires approximately one-third more fuel than the gas turbine system. Other operating costs necessary with the steam turbine system and not involved in the gas turbine system render the latter still more economically advantageous.

It will be understood that the drawing and specific description thereof involve only the principal items of equipment. Various standard items such as pumps, heat exchangers, control valves and the like are not shown in the interest of simplicity. The need for such standard items and the points in the process where they are used will be readily apparent to those skilled in the art from the foregoing.

It will also be understood that various changes in the operating conditions and of the specific arrangement of steps described can be made without departure from the scope of the invention. For example, it will be noted that in the stripping of the rich naphtha absorbent in line 22 from prepurification absorber 19, a tail gas will be produced constituted by the impurities absorbed from the pyrolysis gas in absorber 19 and the stripping gas. Since this tail gas is at a relatively low pressure, it is preferably not used as fuel for combustion chamber 52, although such use can be made of it in accordance with the invention. his particular tail gas can advantageously be used, however, as part or all of the supplementary fuel fired in waste heat boiler 62 through line 78. The specific example given is thus not to be construed as limiting but as merely illustrative.

Regardless of the particular solvent or solvents used for the recovery of acetylene, or of the particular operating conditions used with the solvent system in the recovery process, a tail gas will be separated at one or more points and this tail gas can be used with efliciency as fuel in a gas turbine plant to drive the pyrolysis gas compressor in accordance with the invention.

What is claimed is:

1. In a process for the production of acetylene in which a hydrocarbon is pyrolyzed to produce a pyrolysis gas containing acetylene, hydrogen and carbon monoxide, said pyrolysis gas is compressed to a pressure of about 60 to about 200 p.s.i.g., and acetylene and a tail gas containing hydrogen and carbon monoxide are separately recovered from said compressed pyrolysis gas, the improvement which comprises supplying air at a pressure of about 50 to about 70 p.s.i.g. to a combustion chamber of a gas turbine plant, supplying at least a portion of said tail gas at a pressure of about 130 to about 150 p.s.i.g. to said combustion chamber of said gas turbine plant, the proportions of thereactants supplied to said combustion chamber being sufficient to provide about 400 to about 500 percent air in excess of that required for stoichiometric complete combustion of the tail gas, supplying flue gas at a temperature of about 1250 to about 1500 F. and a pressure of about 50 to about 70 p.s.i.g.

from said combustion chamber :of-said'gas turbine plant to a turbine of said gas turbine plant, expanding said flue gas with the production of useful Work in said turbine and supplying at least a portion of the work of said pyrolysis gas compressing step from that produced in the aforesaid expansion step.

2. In a process for the production of acetylene in which a hydrocarbon is pyrolyzed to produce a pyrolysis gas containing acetylene, higher acetylenic compounds, hydrogen and carbon monoxide, said pyrolysis gas is compressed to a pressure of about 170 to about 185 p.s.i.g., said compressed gas is contacted with heavy naphtha under conditions suitable to absorb higher acetylenic compounds and to produce a prepurified gas containing acetylene, hydrogen and carbon monoxide, contacting said prepurified gas with liqiud ammonia under conditions suitable to absorb acetylene selectively and to leave a tail gas containing vaporized ammonia, hydrogen and carbon monoxide, washing said tail gas with water to absorb vaporized ammonia and to produce ammoniafree tail gas and an ammonia-water solution, and subjecting said ammonia-water solution to fractionation in a fractionation zone, the improvement which comprises supplying air at a pressure of about 50 to about p.s.i.g. to a combustion chamber of a gas turbine plant, supplying at least a portion of said ammonia-free tail gas recovered at a pressure of about to about p.s.i.g. to said combustion chamber of said gas turbine plant, the proportions of the reactants supplied to said combustion chamber being suflicient to provide about 400 to about 500 percent air in excess of that required for stoichiometric complete combustion of the tail gas supplied, supplying flue gas at a temperature of about 1250 to about 1500 F. and a pressure of about 50 to about 70 p.s.i.g. from said combustion chamber of said gas turbine plant to a turbine of said gas turbine plant, expanding said flue gas with the production of useful work in said turbine, supplying at least a portion of the work of said pyrolysis gas compressing step from that produced in the aforesaid expansion step, recovering exhaust gas at substantially atmospheric pressure and at a temperature of about 700 to about 950 F. from said turbine of said gas turbine plant and cooling said exhaust gas to a temperature of about 400 to about 500 F. by passing the same in indirect heat exchange with a boiling liquid at a temperature above about 250 F.

3. The improved process of claim 2 in which said boiling liquid is a bottoms fraction of said fractionation zone whereby reboiling vapors for said fractionation zone are generated by heat recovery from said exhaust gas.

References Cited by the Examiner UNITED STATES PATENTS 2,449,096 9/1948 Wheeler 208-162 2,758,979 8/1956 Guthrie 252-417 2,915,570 12/1959 Busch-Petersen et al.

252-419 X 3,026,969 3/1962 Braconier et al. 260-679 X 3,095,293 6/1963 Kuerston 260-679 X ALPHONSO D. SULLIVAN, Primary Examiner.

Claims (1)

1. IN A PROCESS FOR THE PRODUCTION OF ACETYLENE IN WHICH A HYDROCARBON IS PYROLYZED TO PRODUCE A PYROLYSIS GAS CONTAINING ACETYLENE, HYDROGEN AND CARBON MONOXIDE, SAID PYROLYSIS GAS IS COMPRESSED TO A PRESSURE OF ABOUT 60 TO ABOUT 200 P.S.I.G., AND ACETYLENE AND A TAIL GAS CONTAINING HYDROGEN AND CARBON MONOXIDE ARE SEPARATELY RECOVERED FROM SAID COMPRESSED PYROLYSIS GAS, THE IMPROVEMENT WHICH COMPRISES SUPPLYING AIR AT A PRESSURE OF ABOUT 50 TO ABOUT 70 P.S.I.G. TO A COMBUSTION CHAMBER OF A GAS TURBINE PLANT, SUPPLYING AT LEAST A PORTION OF SAID TAIL GAS AT A PRESSURE OF ABOUT 130 TO ABOUT 150 P.S.I.G. TO SAID COMBUSTION CHAMBER OF SAID GAS TURBINE PLANT, THE PROPORTIONS OF THE REACTANTS SUPPLIED TO SAID COMBUSTION CHAMBER BEING SUFFICIENT TO PROVIDE ABOUT 400 TO ABOUT 500 PERCENT AIR IN EXCESS OF THAT REQUIRED FOR STOICHIOMETRIC COMPLETE COMBUSTION OF THE TAIL GAS, SUP-

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