FR2463758A1 - Ethylene recovery from pyrolysis gas mixts. - by condensation and removal of methane - Google Patents

Abstract

Process and appts. are claimed for the sepn. of olefins from pressurised gas mixts. comprising H2, CH4 and olefins. The method comprises (a) cooling the feed mixt. (I) by sequential stages to condense the olefins and part of the CH4 and H2, (b) sepg. at each cooling stage, the condensate from the gaseous residue, (c) demethanising the condensate to obtain pure olefins, and a residual gas mixt. (II) of H2, CH4 and traces of ethylene, (d) cooling (II) to obtain further condensate and using the liquid as a spray in the lemethanising step, (e) introducing the remaining cooled (II) into a first vortex tube to cause expansion and formation of a hot gas stream (III) and a cold gas stream (IV), (f) using (IV) to c cool (II( from step (c), (g) mixing (III) and (IV) and passing the mixt. through a second vortex tube to form a second hot gas stream (V) and a second cold gas stream (VI), (h) subjecting (I) to countercurrent heat exchange with (V), using (VI) to cool first (II) from step (c) and then (I), and (i) collecting olefin product from (c) and venting (II), having a reduced ethylene content, from the process. The process is used for recoving ethylane in yields of 99% or more from naphtha pyrolysis effluents. The appts. is simple in design, contg. no structural elements with moving parts, reliable and adaptable to automatic operation, No additional energy sources are required and in fact total energy demand is reduced.

Description

 The present invention relates generally to the field of petrochemistry and is particularly concerned with a process for isolating the components of gaseous hydrocarbon mixtures and an installation for carrying out this process.

 The invention is advantageously usable for separating a gaseous methane-hydrogen mixture from olefins (ethylene, ethane, propylene, propane, addition of C4 fraction) in the processes for obtaining ethylene and propylene of high purity from hydrocarbon mixtures. gas containing mainly hydrogen, methane and olefins.

 In modern petrochemical processes, ethylene and propylene find particularly numerous applications, especially for obtaining a large number of plastics such as polyethylene, polypropylene, copolymers of ethylene and propylene, and so on.

The ethylene and propylene purity requirements are very stringent (for example, the ethylene methane content should not exceed 0.0005 to 0.001 mol%). It is obvious that to obtain an ethylene of such high purity by isolating components of gaseous hydrocarbon mixtures, it is the separation of methane from olefins which requires the greatest energy expenditure.

 At present, in industrially developed countries, the starting material in petrochemicals is essentially ethylene, which produces 35 to 40 million tons per year.

 Thus, the development of economical and highly efficient processes for isolating the components of gaseous hydrocarbon mixtures, and of installations for their implementation, poses an urgent problem.

 Many different processes and installations are known today for the isolation of components of gaseous hydrocarbon mixtures and, in particular, for the separation of the methane-hydrogen fraction from olefins.

 A process for separating olefins from methane and hydrogen from a gaseous mixture of hydrocarbon compounds, mainly containing hydrogen, methane and olefins, is known (see US Pat. No. 3,434,388). According to this method, the gaseous mixture is cooled by gradually lowering the temperature in a very large number of stages, in order to condense the majority of the gases, composed mainly of olefins and a part of the methane with a certain proportion of The condensate discharged at each cooling stage flows in a demethanizer, from the top of which a gaseous methane-hydrogen mixture is removed with a certain proportion of ethylene, and the lower part, the olefins, which are then subject to further division. The gaseous methane-hydrogen mixture with a certain proportion of ethylene undergoes cooling until a gas-liquid mixture is obtained which is divided into a gaseous part and a liquid part. The gaseous part of the methane-hydrogen mixture with a certain proportion of ethylene is removed, while the liquid part of this mixture is divided into two streams. One current is used as a watering agent in the demethanizer, and the other is evaporated under a low pressure. The cold obtained is used for said cooling of the gaseous methane-hydrogen mixture with a certain proportion of ethylene.

 This process is carried out on an installation comprising a separation unit of the olefins and a part of the methane with a certain proportion of hydrogen and a release assembly of the gaseous methane-hydrogen mixture with a certain proportion of ethylene. The olefin separation assembly consists of refrigerants connected in series with each other and providing staged cooling of the gas mixture to be separated, and separators which divide the gas-liquid mixtures which form into a gaseous and a liquid part. The release assembly of the gaseous methane-hydrogen mixture with a certain proportion of ethylene consists of a demethanizer, a tubular condenser, a separator and a throttling valve. The demethanizer is connected to the liquid parts of the separators of the olefin separation unit.

The upper part of the demethanizer communicates, through the intertubes space of the tubular condenser, with the separator. The gas portion of the separator is connected to an exhaust pipe. The liquid portion of the separator is connected directly to the upper part of the demethanizer and, through the throttle valve, to the condenser tubes. These are, in turn, connected to the drain piping.

 The disadvantage of this method of isolating the components of gaseous hydrocarbon mixtures and the installation for its implementation is that the cold in the clearance assembly of the gaseous methane-hydrogen mixture with a certain proportion of ethylene is obtained by using a part of the liquid composed of methane with a certain proportion of ethylene, which gives rise to a loss of ethylene. The temperatures reached by this process do not completely remove, by condensation, ethylene gas mixture methane-hydrogen evacuated, which also results in a loss of ethylene.

 Furthermore, in these processes and installations, the energy potential of the gaseous methane-hydrogen mixture with a certain proportion of ethylene, which is under pressure, is not used to obtain more cooling.

 There is also known a process for isolating the components of a gaseous hydrocarbon mixture, mainly containing hydrogen, methane and olefins, and an installation for its implementation (see the American magazine "Chemical Engineering Progresse" 1971, v.67, N02, pp.41-44), which overcomes to some extent the disadvantages of the method and the plant described above, whereby the gaseous mixture is cooled in a plurality of stages with lowering temperature, in order to condense the majority of the gas, composed mainly of olefins and a part of methane with a certain proportion of hydrogen. The condensate discharged at each cooling stage is introduced into a demethanizer, from the upper part of which a gaseous methane-hydrogen mixture is removed with a certain proportion of ethylene, and from the lower part, the olefins which are subjected to a subsequent division.

 The gaseous methane-hydrogen mixture with a certain proportion of ethylene is subjected to cold cooling obtained by boiling the ethylene. This gives rise to the öszlation of a gas-liquid mixture which is then divided into a gaseous part and a liquid part. The liquid part composed of methane and ethylene is used as a watering agent in the demethanizer. The gaseous part of the methane-hydrogen mixture with a certain proportion of ethylene is subjected to a subsequent cooling which gives rise to the formation of a gas-liquid mixture. The gas-liquid mixture obtained is divided into a gaseous part and a liquid part. The liquid part composed of methane with a certain proportion of ethylene is sent as a watering agent into the demethanizer. The gaseous portion of the methane-hydrogen mixture with a slight proportion of ethylene is expanded to a low pressure and discharged. The resulting cold is used for said cooling of the methane-hydrogen mixture with a certain proportion of ethylene.

 The process which has just been described is carried out on an installation comprising a separation unit of the olefins and a part of the methane with a certain proportion of hydrogen, and a set of evolution of the methane-hydrogen gas mixture with a certain proportion of ethylene.

The olefin separation assembly is composed of refrigerants connected in series with each other, which provide step cooling of the gaseous mixture to be divided, and separators which divide the gas-liquid mixtures which form into a gaseous part and a liquid part. The release assembly of the gaseous methane-hydrogen mixture with a proportion of ethylene consists of a demethanizer, a refrigerant which uses liquid ethylene as a coolant, a separator, a a tubular condenser, another separator and a throttling valve.

The demethanizer is connected to the liquid parts of the separators of the olefin separation unit. The upper part of the demethanizer communicates through the coolant with a separator.

The liquid part of the separator is connected to the upper part of the demethanizer. The gas portion of the separator communicates, through the intertube space of the tubular condenser, with the other separator.

The liquid part of this separator is connected to the upper part of the demethanizer, while its gas part communicates through the throttle valve with the tubes of said condenser. These are, in turn, connected to a drain pipe.

 Although this method provides for obtaining a complementary cold by expansion of the gaseous mixture methane-hydrogen evacuated, which is under pressure, this relaxation process does not allow to fully utilize its energy potential. The temperatures thus obtained are not low enough to completely remove, by condensation, the ethylene methane-hydrogen gas mixture evacuated, which gives rise to a loss of ethylene.

 In addition, the use of liquid ethylene to obtain the cold necessary to cool the gaseous mixture discharged from the demethanizer leads to additional energy expenditure.

 There is also known in petrochemistry another method for isolating the components of hydrocarbon gas mixtures, which overcomes to a certain extent the aforementioned drawbacks of the methods described above. According to this process, the mixture of gaseous hydrocarbons containing mainly hydrogen, methane and olefins is cooled in several stages to temperatures which make it possible to eliminate the olefins and a part of the methane with a certain proportion of hydrogen. in the form of liquid condensate. The liquid condensate that is formed at each of these cooling stages is separated from the rest of the gaseous mixture and subjected to demethanization. The gaseous mixture remaining in the last cooling stage and which is composed of hydrogen, methane and a certain proportion of ethylene is removed to extract the hydrogen. The gaseous mixture methane-hydrogen, with a certain proportion of ethylene, which is formed as a result of the demethanization of liquid condensates, is subjected to subsequent cooling. This gives rise to the formation of a liquid condensate composed of methane and ethylene, which is separated and used as a watering agent in the demethanizer. The remainder of the gaseous methane-hydrogen mixture with a proportion of ethylene is expanded with use of the Ranque effect, whereby a cold gaseous stream and a hot gaseous stream are obtained. The hot stream is sent into the heating network. The cold stream is used for said cooling of the gaseous methane-hydrogen mixture with a proportion of ethylene, after which it is also introduced into the heating network.

 The process which has just been described is carried out in an installation comprising a separation unit of the olefins and a part of the methane with a certain proportion of hydrogen, and a release assembly of the gaseous methane-hydrogen mixture with a certain proportion of ethylene.

The set of olefins and a part of the methane with a certain proportion of hydrogen is composed of tubular heat exchangers and refrigerants providing stage cooling of the gaseous mixture to be divided, as well as separators comprising parts gas and liquid processors for dividing the gas-liquid mixtures formed at each cooling stage into a gaseous stream and a liquid stream.

 The tubes of all the tubular exchangers are interconnected in series and their intertubes spaces communicate with each other through the refrigerants and the gas portions of the separators. The clearance assembly of the gaseous methane-hydrogen mixture with a certain proportion of ethylene comprises a demethanization apparatus to which the liquid parts of the separators of the olefin separation assembly are connected, a tubular condenser ensuring the cooling of the gaseous mixture. methane-hydrogen with a certain proportion of ethylene until a gas-liquid mixture is formed, a separator comprising a gas part and a liquid part and dividing the mixture into a gaseous stream and a liquid stream, and a vortex pipe for expanding the gas stream and having a nozzle inlet, a cold end and a hot end.

 The upper part of the demethanizer is connected to the nozzle inlet of the swirl pipe through the intertube space of the tubular condenser and the gas portion of the separator. The liquid part of the separator is connected to the upper part of the demethanizer.

The cold end of the vortex hose communicates with the tubular condenser tubes, which, in turn, open into a drain pipe. The hot end of the swirling pipe also opens into the drain pipe.

 The use of the Ranque effect to obtain the cold used for cooling the gaseous methane-hydrogen mixture with a certain proportion of ethylene makes it possible to better utilize its energy potential compared with the installations described previously. However, the hot gas stream discharged from the plant has a high energy which, in the method and installation for its implementation which have just been described, is not used to obtain cold. The temperatures reached by this process do not completely remove, by condensation, the ethylene gas mixture methane-hydrogen evacuated, which causes a loss of ethylene.

 It follows from the foregoing that none of the known processes described and the installations for their implementation make it possible to completely remove ethylene from the gaseous methane-hydrogen mixture, the ethylene extraction rate not exceeding 98%. .

 The present invention therefore aims at a process for isolating the components of a mixture of gaseous hydrocarbons and an installation for its implementation, which would be designed so that the process of separation of the gaseous methane-hydrogen mixture, with a certain proportion ethylene, and the dipositif for its implementation can minimize the loss of ethylene gr ce the full use of the energy potential of methane gas mixture-evacuated hydrogen.

This object is achieved by a method of isolating the components of a mixture of gaseous hydrocarbons containing mainly hydrogen, methane and olefins, of the type consisting in cooling said gaseous mixture in several stages to temperatures for removing olefins and some of the methane with a proportion of hydrogen from said gas mixture in the form of liquid condensate, with separation of said mixture at each cooling stage for demethanization, separation the gaseous methane-hydrogen mixture with a certain proportion of ethylene, as a result of the demolding of the liquid condensate, to cool it even more with separation of the liquid condensate resulting from this cooling, which is used as a watering agent during the demethanization, to expand the remaining gaseous part of the methane-hydrogen mixture with some p proportion of ethylene using the Ranque effect, whereby a cold gaseous stream and a hot gaseous stream are obtained, the cold stream being used for said cooling of the gaseous methane-hydrogen mixture with a proportion of ethylene, characterized according to the invention, in that the cold gaseous coolant is mixed, after its use for cooling said methane-hydrogen gas mixture with a certain proportion of ethylene, with the hot gaseous stream, and is subjected to an expansion using the Ranque effect, whereby a cold gaseous stream is obtained, a hot gaseous stream is obtained, after which the hot stream is passed directly countercurrently from the gaseous hydrocarbon mixture to be split and the cold stream passed through. previously countercurrent to the gaseous Methane-hydrogen gas, with a certain proportion of ethylene, separated by demethanization
The aim is also achieved by virtue of the fact that the installation for isolating the components of a gaseous hydrocarbon mixture, of the type comprising a separation unit of the olefins of the gaseous mixture to be divided, composed of tubular heat exchangers and refrigerants providing stage cooling of said gaseous mixture, as well as separators having a gas portion and a liquid portion and for dividing the gas-liquid mixtures formed at each cooling stage, into a gaseous stream and a stream liquid, the tubes of all the tubular exchangers being connected in series with each other, while their intertubes spaces communicate with each other through the refrigerants and the gas portions of the separators, and a release assembly of the gaseous mixture methane-hydrogen with some proportion of ethylene, composed of a demethanizer to which are connected the liquid parts of separators of the olefin separation assembly, a tubular condenser for cooling the methane-hydrogen gas mixture with a proportion of ethylene, a separator for dividing the formed gas-liquid mixture into a gaseous stream, and a liquid stream having a gas portion and a liquid portion connected to the top of the demethanizer, and a vortex pipe for expanding said methane-hydrogen gas mixture with formation of a current a hot gas stream, said pipe having a nozzle inlet connected to the upper part of the demethanizer apparatus through the gas portion of the separator and the intertube space of the tubular condenser, a cold end communicating with the tubes; the tubular condenser and through which flows the current flowing from the latter, and a hot end, characterized, according to the invention, e that the release assembly of the gaseous methane-hydrogen mixture with a certain proportion of ethylene contains another vortex hose comprising a nozzle inlet connected directly to the hot end of the aforementioned vortex pipe, and at its cold end, by through the tubes of the tubular condenser to which it is connected, and a cold end and a hot end, this hot end being connected to the tubular exchanger tubes of the olefin separation assembly directly, and the end cold, through the tubes of the tubular condenser through which passes the cold current that flows.

 Such a solution makes it possible to take full advantage, for the production of cold, of the energy potential of the gas mixture methane-hydrogen evacuated, being under pressure. The temperatures thus achieved, of the order of -145 to -1500C, reduce to a minimum the losses of ethylene. The extraction rate of ethylene reaches 99% and more, without having to use any additional source of energy to obtain cold.

 The invention will be better understood and other objects, details and advantages thereof will appear better in the light of the following description of an embodiment given solely by way of non-limiting example with references to the single drawing annexed which represents a technological block diagram of the process according to the invention.

 The present process for isolating the components of a mixture of gaseous hydrocarbons, mainly containing hydrogen, methane and olefins, provides for the cooling of said mixture in several stages with successive lowering of the temperature to ensure the condensation of the most of the gas, consisting of components with the highest boiling points.

 In this process, the temperature at the last cooling stage is chosen so that the gas discharged to this stage has the lowest boiling point.

 The gaseous mixture to be divided is cooled in stages to temperatures to remove olefins and a portion of methane added with hydrogen in the form of liquid condensate. The liquid condensate that forms at each cooling stage is then separated from the rest of the gas mixture and subjected to demethanization. The gaseous mixture remaining after removal of the olefins, consisting essentially of hydrogen and methane with a certain proportion of olefins, is removed to extract hydrogen thereafter (this part of the process is not considered in the present invention). The gaseous methane-hydrogen mixture, with a certain proportion of ethylene, which is formed as a result of the demethanization of the liquid condensates, undergoes additional cooling. This gives rise to the formation of a liquid condensate composed of methane and ethylene, which is separated and used as a watering agent in demethanization.

The remaining gaseous portion of the methane-hydrogen mixture, with a proportion of ethylene, is expanded with use of the Ranque effect, whereby a cold gas stream and a hot gas stream are obtained.

 The cold stream is used for said cooling of the gaseous methane-hydrogen mixture comprising a certain proportion of ethylene.

Then the cold stream is mixed with the hot stream and expanded with use of the Bank effect, resulting in the formation of a cold stream and a hot stream. The hot stream then flows directly below the cost of the gaseous mixture to be divided, the refrigerant flow having passed countercurrently the gaseous methane-hydrogen mixture comprising a certain proportion of ethylene, obtained as a result of demethanization.

 The plant for carrying out said process for isolating the components of a gaseous hydrocarbon mixture mainly containing hydrogen, methane and olefins, comprises an olefin separation assembly 1 and a release assembly 2 methane-hydrogen gas mixture with a certain proportion of ethylene. The assembly 1 for separating the olefins from the gaseous mixture to be divided contains a tubular heat exchanger 3 whose intertube space 4 communicates, by a pipe 5, with a source of the starting gas mixture (not represented), and by a pipe 6, with a condenser 7. The refrigerant 7 is in turn connected by a pipe 8 to a separator 9 having a liquid part 10 and a gas part 11. The liquid part 10 of the separator 9 is connected, by piping 12, to the demethanizer 13 forming part of the assembly 2 for the release of the gaseous methane-hydrogen mixture. The gas portion 11 of the separator 9 communicates via a pipe 14 with the intertube space 15 of a tubular heat exchanger 16. The intertube space 15 communicates via a pipe 17 with a condenser 18 which is in turn connected by a pipe 19, to a separator 20 having a liquid portion 21 and a gas portion 22. The liquid portion 21 of the separator 20 is connected by a pipe 23 to the demethanizer 13. The gas portion 22 of the separator 20 communicates by a pipe 24 with the intertubes space 25 with the intertube space 25 of a tubular exchanger 26.The intertube space 25 communicates via a pipe 27 with a refrigerant 28 which is in turn connected, by a pipe 29, to a separator 30 having a liquid portion 31 and a gas portion 32. The liquid portion 31 of the separator 30 is connected by a pipe 33 to the demethanizer 13. The gas portion 32 of the separator 30 is connected by a tuya 34 intertubes 37 of a tubular exchanger 38. The intertubo space 37 communicates via a pipe 39 with a separator 40 having a liquid portion 41. and a gas portion 2. The liquid portion 41 of the separator 40 is connected by a pipe 43 to the demethanizer 13 through the inter-tube space 37 of the tubular exchanger 38. The gas portion 42 of the separator 40 is connected to a pipe 44 intended to to evacuate from the installation the gaseous mixture composed essentially of hydrogen and methane with a certain proportion of olefins. The assembly 2 for the release of the methane-hydrogen mixture, with a certain proportion of ethylene, comprises the demethanizer 13 whose upper part 45 communicates, by a pipe 46, with the intertube space 47 of a tubular condenser 48. The intertube space 47 is preferably connected by a pipe 49 to a separator 50 having a liquid part 51 and a gas part 52. The liquid part 51 of the separator 50 communicates by a pipe 53 with the upper part 45 The gas portion 52 of the separator 50 is connected by a pipe 54 to the nozzle inlet 55 of a swirling pipe 56 having a cold end 57 and a hot end 58. cold 57 of the swirling pipe 56 is connected by a pipe 59 to the tubes 60 of the tubular condenser 48. The tubes 60 are connected by a pipe 61 to a pipe 62. The hot end 58 of the pipe tourbill Onnaize 56 is connected to the pipe 62 by a pipe 63. The pipe 62 is connected to the nozzle inlet 64 of another swirl pipe 65 having a cold end 66 and a hot end 67. The cold end 66 of the pipe Vortex 65 communicates via a pipe 68 with the tubes 69 of the tubular condenser 48. The tubes 69 communicate by a pipe 70 with the tubes 71 of the tubular exchangers 38, 26, 16 and 3, which are interconnected by a pipe 72. tubes 71 of the exchanger 3 open into a pipe 73 intended to evacuate the gaseous methane-hydrogen mixture from the installation. The hot end 67 of the swirling pipe 65 is connected by a pipe 74 to the tubes 71 of the exchanger 26. The lower part 75 of the demethanizer 13 opens into a pipe 76 intended to remove the olefins from the installation.

 We will now examine the technological scheme for the isolation of the components of a gaseous hydrocarbon mixture according to the present invention.

The starting gas mixture, mainly containing hydrogen, methane and olefins (ethylene, ethane, propylene, propane, addition of C4 fraction), which is under a pressure of 32 to 38 mN / m2 at a temperature of + 130C, enters through the pipe 5 in the intertube space 4 of the tubular heat exchanger 3 of the assembly 1 for separating olefins from the gaseous mixture to be divided. In the heat exchanger 3, said gaseous mixture is cooled by the products of its division (the gaseous methane-hydrogen mixture) to a temperature of -5 to -10 ° C. and is then channeled through the piping 6 into the refrigerant 7, using liquid propylene evaporating at -180 ° C. as the refrigerating agent. In the refrigerant 7, the said gaseous mixture is cooled to a temperature of -1 ° C. This gives rise to the condensation of most of the fraction
C4, propylene, propane and some of the ethane and ethylene. The gas-liquid mixture thus formed enters the pipe 8 into the separator 9, where it is divided into liquid condensate and a gas mixture residue. The liquid condensate flows from the liquid portion 10 of the separator 9, through the pipe 12, into the demethanizer 13, while the remaining gas mixture is directed from the gas portion 11 of this separator, through the piping 14, to undergo additional cooling in the intertube space 15 of the tubular exchanger 16 cooled by the products of the gas mixture division.In the exchanger 16, the gaseous mixture is cooled to a temperature of -200 to - 250C and is then channeled, through the pipe 17, into the refrigerant 18 cooled by liquid propylene evaporating at -370C. In the refrigerant 18, said gaseous mixture is cooled to a temperature of -100 to -350C. As a result, the C4 fraction, propylene, propane, most of the ethane and ethylene, part of the methane and hydrogen are completely condensed.

The gas-liquid mixture formed arrives through the pipe 19 in the separator 20, where it is divided into liquid condensate and a gas mixture residue.

The liquid condensate flows from the liquid portion 21 of the separator 20, through the pipe 23, into the demethanizer 13, while the remaining gaseous mixture is directed from the gas portion 22 of this separator, through the piping 24, to undergo additional cooling in the intertube space 25 of the tubular exchanger 26 cooled by the products of the gas mixture division. In the exchanger 26, the gaseous mixture is cooled to a temperature of 350 to -40 C and then passes, through the pipe 27, in the refrigerant 28 cooled by liquid ethylene evaporating at -560C. In refrigerant 28, the gaseous mixture is cooled to a temperature of -50 to -530C. At this stage most of the ethylene and ethane, as well as some of the methane and hydrogen, condense. The gas-liquid mixture formed is directed by the pipe 29 into the separator 30 where it is divided into liquid condensate and a remainder of gaseous mixture. The liquid condensate flows from the liquid part 31 of the separator 30 through the piping 33, in the demethanizer i3, while the remaining gaseous mixture is directed from the gas portion 32 of this separator, through the piping 34, into the refrigerant 35 cooled by liquid ethylene evaporating at -98 C. In the refrigerant 35, the gaseous mixture is cooled to a temperature of -920 to -95 ° C. and enters via the piping 36 into the intertube space 37 of the tubular exchanger 38 cooled by the products of the division of the gas mixture.In the heat exchanger 38, the gaseous mixture is cooled to the temperature of -1800C. At this stage, most of the ethylene, ethane, a large part of the methane and, in part, hydrogen are condensed. The gas-liquid mixture formed is directed by the pipe 39 into the separator 40 where it is divided into liquid condensate and a gaseous mixture residue composed of hydrogen and methane with a certain proportion of ethylene and ethane. The liquid condensate flows from the liquid portion 41 of the separator 40, through the pipe 43, into the demethanizer 13 through the intertube space 37 of the tubular exchanger 38. The remaining gas mixture from the part gas 42 of the separator 40 is removed from the installation by the pipe 44 to subsequently extract the hydrogen.

 In the demethanizer apparatus 13, the liquid condensates passing through the pipes 12, 23, 33 and 43 are released from a gaseous methane-hydrogen mixture comprising a certain proportion of ethylene and which is discharged. of the upper part 45 of the demethanizer 13 by the pipe 46. The olefins are discharged from the lower part 75 of the demethanizer apparatus via the pipe 76.

The gaseous methane-hydrogen mixture (with a certain proportion of ethylene) having a temperature of -95 to 1000C enters through the pipe 46 into the intertube space 47 of the tubular condenser 48 cooled by the products of the gas mixture division. condenser 48, the gaseous mixture is cooled to a temperature of 1350 to -1400C. As a result of the gas mixture methane-hydrogen (with a certain proportion of ethylene) are at this stage condensed essentially all the ethylene, partly methane and an insignificant part of the hydrogen. The gas-liquid mixture formed is channeled by the pipe 49 in the separator 50 where it is divided into liquid condensate and a methane-hydrogen gas mixture residue. The liquid condensate flows from the liquid portion 51 of the separator 50 through the pipe 53 into the demethanizer 13 where it is used as a watering agent. The remainder of the gaseous methane-hydrogen mixture in the gas portion 52 of the separator 50 passes through the piping 54 to enter the vortex tube 56 through its nozzle inlet 55 to expand therein. As a result of the expansion in the swirling pipe 56 with a pressure of 32 to 38 mN / m2 at a pressure of 15 to 18 mN / m2, said mixture is divided into two streams: one cold, at a temperature of -145 to -1500C, and Other hot, at a temperature of -1050 to -110 C. The cold current flows from the swirling pipe 56 by its cold end 57 and enters through the pipe 59 in the tubes 60 of the tubular condenser 48.

By circulating by these tubes against the current of the methanehydrogen gas mixture with a proportion of ethylene, the cold stream heats up to a temperature of 1050 to -110 C and leads through the pipe 61 in the pipe 62. The hot stream flows from the swirling pipe 56 at its hot end 58 and also enters the piping 62 through the pipe 63. In the piping 62, the cold and hot streams mix and arrive in the swirling pipe 65 through its inlet. As a result of the expansion in the vortex hose 65 from a pressure of 15 to 18 mN / m 2 at a pressure of 2.5 to 3.5 mN / m, the gaseous mixture is divided in two streams: one cold, at a temperature of -1450 to -1500C, and the other hot, at a temperature of -95 to -1000C. The cold stream flows from the swirling pipe 65 at its cold end 66 and is directed through the pipe 68 into the tubes 69 of the tubular condenser 48. Circulating through these tubes countercurrently to the gaseous methane-hydrogen mixture with a certain proportion ethylene, the cold stream heats up to a temperature of -1050 to -110 C and then passes through the pipe 70 to arrive in the tubes 71 of the tubular exchanger 38. While circulating through these tubes against the current of the a gaseous mixture to be divided, the cold stream heats to a temperature of -95 to -1000 ° C. and passes through the pipe 72 into the tubes 71 of the tubular exchanger 26. The hot stream flows from the swirling pipe 65 through its hot end 67 and arrives, through the piping 74, in the same tubes 71 of the tubular exchanger 26.The cold and hot currents are mixed therein and this methane-hydrogen mixture passes through the tubes 71 of the tubular exchangers 26, 16 and 3, against the current of the gaseous mixture to be divided. This results in heating the methane-hydrogen mixture to a temperature of -10 to -150C, after which it is removed from the installation by the pipework 73.

 For the present invention to be better understood, an example of concrete but non-limiting embodiment in accordance with the technological scheme just described, will now be described.

Example
The starting gaseous mixture is obtained from a boiling point between 62 and 1800 ° C., by pyrolysis at a temperature of 823 to 850 ° C., with the addition of steam at a rate of 50% by weight relative to gasoline. The pyrogas (gas resulting from pyrolysis) is cooled to a temperature of 20 ° C. to 30 ° C. and compressed from 1.2 to 1.3 mN / m 2 to a pressure of 30.degree. at 40 mN / m2, at the same time removing from the gas mixture the acidic gez. C4 + heavy hydrocarbons are also removed from the compressed gas mixture, and the remainder of the gaseous mixture is hydrogenated to remove the acetylenic compounds, and then dried and cooled to +15 C.

 The gaseous mixture thus obtained, composed of hydrogen, methane and olefins, is subjected to the treatment according to the technological scheme described above.

 The annexed table at the end of the text gives a summary of the materials constituting the currents transported by the corresponding pipes of the technological scheme.

 This table contains, by way of illustration, particular working parameters relating to an exemplary embodiment of the process for isolating the components of the gaseous hydrocarbon mixture according to the present invention, but it is quite obvious that the framework of the invention can not be limited to the indicated data.

 Of the particular embodiment of the present invention given above, it is evident that it is possible to achieve all the objectives of the invention within the scope defined by the claims below. However, it is also obvious that certain modifications could be made to the operation of the operations constituting the process for isolating the components of hydrocarbon gas mixtures and to the constructive provisions of the installation for its implementation, without it being necessary. depart from the spirit of the invention.

 All such modifications will not be considered to depart from the general design and scope of the invention as defined by the claims.

 The proposed method of isolating the gaseous hydrocarbon mixture controls and the installation for its implementation are extremely effective.

With this process, losses of ethylene during evacuation of the methane-hydrogen gas mixture from the plant are virtually zero. The extraction rate of ethylene reaches 99 and higher. Temperatures between -1450 and -150 C, ensuring such a high rate of ethylene extraction, are reached only through the full utilization of the energy potential of the gaseous mixture methane-hydrogen, which is under pressure. There is no need for any other source of cold. At the same time, total energy expenditures are reduced by 15 and more.

 The installation for the implementation of the method is extremely simple from the point of view of construction, due to the complete absence of constructive elements comprising moving parts. The installation is reliable in service and can be easily automated.

 Of course, the invention is not limited to the embodiment described and represents that has been given as an example. In particular, it comprises all the means constituting technical equivalents of the means described and their combinations, if they are executed according to its spirit and implemented in the context of the following claims.

Table - 17 -

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Claims (3)

 A process for isolating the components of a gaseous hydrocarbon mixture containing mainly hydrogen, methane and olefins, of the type consisting in cooling said gaseous mixture in several stages to temperatures ensuring the elimination of said gaseous mixture, olefins and a part of the methane with a certain proportion of hydrogen, in the form of liquid condensate, with separation of this condensate of said mixture at each cooling stage in order to subject it to demethanization, to separate the gaseous methane mixture. hydrogen, with a certain proportion of ethylene, formed as a result of the demethanization, to cool it even more with separation of the liquid condensate resulting from this cooling, which is used as watering agent for said demethanization, to submit to expansion the remaining gaseous part of the methane-hydrogen mixture, with a certain proportion of ethylene, using the e and Ranque, whereby a cold gas stream and a hot gas stream are obtained, the cold stream being used for said cooling of the methanehydrogen gas mixture comprising a proportion of ethylene, characterized by mixing the cold gas stream. after its use for cooling the methane-hydrogen gas mixture comprising a proportion of ethylene with the hot gas stream and expanding with the Ranque effect, whereby a cold gas stream is obtained and a hot gas stream, after which the hot stream is passed directly countercurrently from the gaseous mixture whose components are to be isolated, and the cold stream, after passing it counter-current from the gaseous methane-hydrogen mixture. comprising a certain proportion of ethylene and separated by demethanization.  2. Installation for carrying out the process according to claim 1, of the type comprising an assembly for separating the olefins from the gaseous mixture whose components are to be isolated, composed of tubular heat exchangers and refrigerants providing the stage cooling. gaseous mixture, as well as separators each having a gas portion and a liquid portion and for separating the components of the gas-liquid mixtures forming at each cooling stage into a gaseous stream and a liquid stream, the tubes of all the tubular exchangers being connected in series with one another, and their intertubes spaces communicating with each other through the refrigerants and the gas portions of the separators, and a release assembly of a gaseous methane-hydrogen mixture with a certain proportion of ethylene, composed a demethanizer apparatus to which the liquid parts of the separators of said assembly are connected separation of the olefins, a tubular condenser for cooling the methane-hydro gas mixture with a certain proportion of ethylene, a separator for separating the resulting gas-liquid mixture into a gaseous stream, and a liquid stream and having a gas portion and a liquid portion connected to the upper portion of the demethanizer, and a tourbiilonraire pipe for expanding said gaseous methane-hydrogen mixture with formation of a cold gas stream and a hot gas stream, said pipe having a nozzle inlet connected to the upper part of the demethanizer through the gas portion of the separator and the intertube space of the tubular condenser, a cold end communicating with the tubes of the tubular condenser through which the flowing current flows, and a hot end, characterized in that the clearance assembly of the gas mixture methan e-hydrogen comprising a proportion of ethylene contains a second vortex pipe having a nozzle inlet connected to the hot end of the first vortex pipe directly, and at its cold end, through the tubes of the tubular condenser with which it communicates as well as a cold end and a hot end, this hot end being connected to the tubes of the tubular exchangers of the olefin separation assembly directly, while this cold end is connected to said tubes by the tubes of the tubular condenser through which the cold current flowing.  3. Hydrogen, methane and olefins characterized in that they are obtained from a mixture of gaseous hydrocarbons by isolation according to the process of claim 1.