CN1509262A - Method for recovering ethane by refrigeration cycle with a mixture of at least two refrigerants, gas obtained by this method, and operating equipment - Google Patents

Abstract

This invention relates to a method and apparatus for refrigerating a gas mixture for cryogenic separation of the components of a pressurized gas (1). The method includes a refrigeration cycle in which a fluid (13) is separated in a separator container (B2) into a less volatile portion (4) for generating refrigeration at a relatively high first temperature in an exchanger (E1), and a more volatile second portion (5) for generating refrigeration at a relatively low temperature in an exchanger (E2). The heated and expanded portions (4, 5) are mixed and compressed within a compressor (K1). The portion (26) obtained from the compressor (K1) is cooled, thereby providing portion (13).

Description

Process for recovery of ethane by refrigeration cycle with mixture of at least two refrigerants, gas obtained by such process, and operating equipment

technical field

According to a first aspect of the present invention, the invention relates generally to the gas industry, and more particularly to a method of operating a multi-component refrigeration cycle for the recovery of ethane contained in pressurized gases comprising methane and _C2 and higher hydrocarbons.

Background technique

The term "multicomponent refrigeration cycle" is to be understood as meaning a refrigeration cycle which utilizes a refrigerant mixture consisting of at least two refrigerants.

More specifically, according to a first aspect of the present invention, the present invention relates to the recovery of ethane contained in a pressurized gas comprising methane and _C2 and higher hydrocarbons, a method of operating a refrigeration cycle in which relatively less volatile The first refrigerant is compressed, cooled and expanded for later use in cooling the pressurized gas to be separated or the first separated product to a relatively high first temperature, and relatively more volatile A second refrigerant is compressed, cooled and expanded for later use in cooling at least a second separated product obtained from said pressurized gas to a second relatively low temperature.

This type of refrigeration method is well known to those skilled in the art and has been used for many years.

These refrigeration methods have disadvantages with regard to operating costs due to the energy consumption associated with the low thermodynamic efficiency of these refrigeration cycles.

This known method also has disadvantages with regard to operating costs due to difficult maintenance and frequent intervention work, for example on compression equipment, pumps or other measuring and control equipment.

These disadvantages are themselves prohibitively expensive, prolonging the amortization period of the capital investment for such equipment due to production interruptions.

Contents of the invention

In view of this, it is a first object of the present invention to provide a method which, in accordance with the general definition given in the preamble above, is essentially characterized in that said first and second refrigerant They are used as a mixture when they are compressed and cooled, and this mixture is then separated into a first part containing mainly relatively less volatile first refrigerant and a relatively more volatile second refrigerant A second part of the refrigerant in which the first refrigerant is used for cooling to a relatively high first temperature and in which the second refrigerant is used for cooling to Relatively low second temperature.

This method, thanks to its high thermodynamic efficiency, makes it possible to limit the operating costs of the plant, especially its energy consumption, and, moreover, with regard to maintenance, reduces the number of devices in the plant by combining two refrigeration circuits into one. Thus, maintenance operations are simplified, the time required to determine the cause of equipment failure is shortened, and any production interruptions are shortened compared with equipment using methods utilizing prior art methods.

According to the first aspect of the method of the present invention, the first fraction may be cooled and expanded in a first exchanger, thereby producing a first expanded fraction which is then, before being introduced into the low-pressure stage of the compressor, is heated.

According to the first aspect of the method of the invention, the second fraction may be cooled in the first exchanger, then expanded in the second exchanger, then heated in the second exchanger and mixed with the expanded first fraction.

According to the first aspect of the method of the present invention, the third portion may be withdrawn from the first portion after the first portion has been cooled in the first heat exchanger, and the third portion may be expanded and heated in the first exchanger to provide a An expanded and heated fourth section, which may be introduced into the intermediate pressure stage of the compressor.

According to the first aspect of the method of the invention, the gaseous fifth part can be drawn from the refrigerant compressed at medium pressure in the compressor (K1), slightly above the expanded and heated fourth part, and then cooled and expanded to the same pressure as the fourth part, and then mixed with the fourth part.

According to the second aspect of the method of the present invention, the first and second refrigerants may be used as a mixture with a third refrigerant.

According to the second aspect of the method of the present invention, said refrigerant may be methane, ethylene and propane.

According to a third aspect of the method of the invention, the invention relates to a methane-enriched gas and an ethane-enriched product obtained by the method of the invention, and to a _C2 and Products of higher hydrocarbons.

According to a fourth aspect of the method of the present invention, the present invention relates to an apparatus for recovering ethane contained in a pressurized gas comprising methane and _C2 and higher hydrocarbons, in particular operating in a multi-component refrigeration cycle, said The apparatus uses a refrigeration cycle and comprises means for compressing, cooling and expanding a relatively small, volatile first refrigerant for cooling the pressurized gas to be separated or the first refrigerant by means of said first refrigerant. means for separating the product to a relatively high first temperature, and means for compressing, cooling and expanding a relatively volatile second refrigerant for cooling by means of said second refrigerant from said pressurized Apparatus for obtaining at least a second separated product of gas to a relatively low second temperature, characterized in that the first and second refrigerants are used as a mixture when they are compressed and cooled, and said apparatus comprises means for separating said mixture into a first portion substantially containing a relatively small amount of a first volatile refrigerant and a second portion substantially containing a relatively large amount of a volatile second refrigerant, said first refrigerant being The first portion is used for cooling to a relatively high first temperature and the second refrigerant is used in a second portion for cooling to a relatively low second temperature.

Description of drawings

The present invention and other objects, features, details and advantages of the present invention will be more clearly understood by reading the following description with reference to the accompanying drawings, which are given by way of example only and are not intended to limit the present invention, in:

Figure 1 is a functional block diagram of a device according to an embodiment of the prior art; and

Fig. 2 is a functional block diagram of an apparatus according to a preferred embodiment of the present invention.

Detailed ways

The following symbols can be read from these two figures: FC for flow controller, GT for gas turbine, LC for level controller, PC for pressure controller, SC for speed controller, TC for temperature controller.

For the sake of clarity and simplicity, the lines used in the apparatus shown in Figures 1 and 2 will be designated with the same reference numerals as the gas parts flowing therein.

Referring to Figure 1, the apparatus shown is intended for use in the treatment of dry cracked gases, in particular, on the one hand, for the separation of a fraction mainly consisting of substantially _C2 -free methane and higher hydrocarbons, and on the other hand, with for the _separation of fractions consisting primarily of ethane and other C2 and substantially methane-free higher hydrocarbons.

This device has 3 separate lines. The first line corresponds to the path followed by the gas to be purified, the second line corresponds to the cooling cycle of the refrigeration unit whose refrigerant is ethylene, and the third line corresponds to the refrigerant whose refrigerant is propane The cooling cycle of the refrigeration unit.

More precisely, in the first line, the cracked gas 1, which is obtained at 15 °C and 18 bar with a flow rate of 3903 kmol/h, is cooled in the exchanger E1 in order to obtain -17.52 °C and 17.8 bar The cooled gas 302 . The latter is further cooled in the second exchanger E2 in order to obtain a partially condensed cooled fluid 303, -30.00°C, 17.6 bar. Stream 1 consists of 0.1% carbon dioxide, 24.3% methane, 74.4% ethane and 1.2% propane.

Stream 303 is then introduced into vessel V1 where it is subjected to separation of its liquid and gaseous components:

- The stream 304 of the gaseous phase, which is obtained at a flow rate of 2219 kmol/h, is cooled to -60° C. in the exchanger E3 and partially condensed in order to obtain a stream 305 at 17.4 bar. Said stream 305 is fed into the upper part of the splitting distillation column T1;

- the liquid phase flow 306, which is obtained at a flow rate of 1684 kmol/h, driven by the pump P1 into a pipeline comprising a controlled valve 321 whose opening depends on the level controller in the container V1, In order to output a stream 307 at -29.8°C and 19.6 bar. Said stream is then introduced into the middle of the splitting distillation column T1.

Steam 308, -65.79°C, 17.2 bar with a flow rate of 1358 kmol/h is produced at the top of distillation column T1, which is cooled in exchanger E4 to obtain partially condensed stream 309, -90°C, 17.0 bar. Said fluid is then divided into a gaseous fraction 310 and a liquid fraction 311 in vessel V2, wherein the gaseous fraction 310 amounts to 971 kmol/h and consists of 0.1% carbon dioxide, 94.9% methane and 5.0% ethane, and the liquid fraction 311 amount is 387 kmol/h, composed of 0.4% carbon dioxide, 47.6% methane and 52.0% ethane, which is driven along line 312 by pump V2. The line 312 includes a controlled opening valve 322 whose opening depends on the flow in the line.

The liquid portion conveyed in line 312 is then introduced into the last stage of distillation column T1.

The gaseous portion 310 from vessel V2, having a temperature of -90.0°C, flows through exchanger E6 to provide a heated portion 313 at -35.0°C, which then passes through heat exchanger E7 to pass through controlled A heated portion 326 is provided before opening valve 317 , the degree of opening of which depends on the pressure in line 326 . After the product leaves valve 317, it is collected in delivery line 320 at 20°C and exits the plant.

There are several trays in the lower part of the fractionation distillation column T1, which are connected in pairs by heating pipes, two of which are shown in the figure. These are lines 315,316 and 318,319. Each of these heating lines forms a transverse reboiler in the case of lines 315 , 316 and a bottom reboiler in the case of lines 318 , 319 .

The fluid flowing in the pipeline 315 has a flow rate of 3000 kmol/h and a temperature of -20.6°C, and is heated by heat exchange with the cracked gas 1 in the heat exchanger E1 to provide a heated fluid 316 of -16.61°C, and then It is introduced on a tray below the tray used to recover fluid 315 . The temperature of the fluid flowing in said lines 315, 316 is regulated by means of a controlled opening valve 323 placed in a branch of the lines 315, 316, which does not pass through the exchanger E1. The opening of the valve 323 is controlled by a temperature controller connected to the pipeline 302 .

Similarly, the fluid flowing in line 318, with a flow rate of 3341 kmol/h and a temperature of -16.15°C, located at the stage below the stage where heated fluid 316 is introduced, passes in heat exchanger E5 and is supplied by propane The constituent refrigerant is heated by heat exchange to provide heated fluid 319 at a temperature of -14.87°C. This fluid is introduced onto the tray below the tray for recovery fluid 318 . The temperature of the fluid flowing through said lines 318, 319 is regulated by means of controlled opening valves 324 arranged in branches for the refrigerant conveyed in lines 220, 221 which do not pass through Switch E5. The opening of the valve 324 is controlled by a temperature controller connected to the pipeline 319 .

Finally, the residual liquid obtained at the bottom of the distillation column T1, which is rich in _C2 and higher hydrocarbons, is recovered through line 314 at -14.87 °C, 17.4 bar, and a flow rate of 2932 kmol/h. The line 314 has a valve 325 whose opening is controlled by a level controller for the liquid at the bottom of the distillation column T1.

In the second line, which corresponds to the cooling cycle of the refrigeration unit whose refrigerant is ethylene, the liquid ethylene stream 100 with a flow rate of 2570 kmol/h at a temperature of -30°C and a pressure of 19.58 bar is recovered from the storage vessel V5 . The stream 100 is divided into:

(a) a first stream 117, having a flow rate of 1993 kmol/h, expanded to 6.79 bar, cooled to -63°C by passing it through valve 120 to provide stream 101, which is mixed with stream 104 to produce stream 102, It feeds into exchanger E3 with refrigerated ethylene. The opening of the valve 120 is controlled by the liquid level controller in the exchanger E3.

(b) A second stream 114 with a flow rate of 577 kmol/h, expanded to 18.58 bar and cooled to -80° C. in exchanger E6 to produce a heated stream 115 .

Stream 115 with a flow rate of 577 kmol/h is divided into:

(a) A first stream 116 with a flow rate of 417 kmol/h, expanded to 1.83 bar, cooled to -93°C by passing it through valve 121 to provide stream 106 which is fed to exchanger E4 with refrigerated ethylene. The opening of the valve 121 is controlled by the liquid level controller in the exchanger E4. Furthermore, said level controller is servo-controlled by another level controller contained in a separate vessel V2;

(b) A second stream with a flow rate of 160 kmol/h in a line with a valve 122 whose opening depends on the flow in line 105 to produce a stream 104 at -79°C at 6.79 bar. Said stream 104 is mixed with stream 101 to produce a stream 102 before it is introduced into exchanger E3.

Evaporation of the ethylene contained in exchanger E4 enables stream 8 to be withdrawn from the top of distillation column T1 for cooling. This results in a -93°C, 1.83 bar ethylene vapor stream 107, which is sent to the low-pressure stage of compressor K1 via suction vessel V3.

Evaporation of the ethylene contained in exchanger E3 causes stream 4 from vessel V1 to be cooled. A stream 103 of ethylene vapor at -62.83°C and 6.79 bar is thus obtained, which is sent to the intermediate pressure stage of compressor K1 via suction vessel V4.

The compressed ethylene obtained at the outlet of K1 provides a 17.75°C, 20.6 bar, 2570 kmol/h stream 112 which is cooled and condensed by passing it subsequently through exchanger E8, producing a -7°C, 20.1 bar fraction 118 , then through exchanger E9, thus creating a -30°C, 19.6 bar section 119 before feeding into vessel V5 with liquid ethylene.

In the third circuit, which corresponds to the cooling cycle of the refrigeration unit in which the refrigerant is propane, a pressurized liquid propane stream 220 with a flow rate of 4340 kmol/h is withdrawn from the storage vessel V6 at 42° C. and 18 bar. The stream 220 is cooled by heat exchange in exchanger E5 with the liquid flowing in lines 18, 19, thereby providing a cooled stream 221 at 33.64°C, 17.5 bar. While passing through the cooling line, making it through the exchanger E5, the line with the valve 24 enables the energy exchange within E5 to be regulated.

The cold fluid 221 of 4340 kmol/h is then divided into two streams:

The first stream 200 at 4030 kmol/h is expanded through valve 226 to provide stream 201 at 3.46 bar, -10°C. The opening of valve 226 is controlled by a liquid level controller in exchanger E8. Stream 201 is fed to exchanger E8 with refrigerated propane;

A second stream 222 of 310 kmol/h, which is cooled in exchanger E7 in order to produce a stream 223 at -25°C.

Stream 223 is expanded by passing valve 229, the opening of which is controlled by the flow in the line, resulting in expanded stream 224 at 1.48 bar.

The propane stream 201 introduced into exchanger E8 is partially evaporated in order to produce a gaseous phase 203 of 1387 kmol/h and a liquid phase 204 of 2643 kmol/h. The stream 204 is split into two streams:

Stream 205 at 1700 kmol/h is expanded through valve 227, the opening of which depends on the liquid level maintained in exchanger E9, so as to provide a 1.48 bar fed to exchanger E9 with refrigerated propane, -33 Stream 206 at °C;

Stream 208 of 943 kmol/h is expanded through valve 228, the opening of which depends on the liquid level maintained in exchanger E2, so as to provide a 1.48 bar fed to exchanger E2 with refrigerated propane, -33 Stream 225 °C.

Streams 225 and 224 are combined to form stream 209 before being introduced into exchanger E2.

The propane evaporated in exchanger E2 causes stream 2 to be cooled and partially condensed. The thus obtained -33°C, 1.48 bar propane vapor stream 210 is mixed with gas stream 207 from exchanger E9 to form stream 211 which is sent first into suction vessel V7 and then into the low pressure stage of compressor K2.

The propane evaporated in exchanger E9 causes stream 118 to be cooled and partially condensed. The thus obtained -33°C, 1.48 bar propane vapor stream 207 is mixed with gas stream 210 from exchanger E9 to form stream 211 which is sent first into suction vessel V7 and then into the low pressure stage of compressor K2.

The propane evaporated in exchanger E8 causes stream 112 to be cooled and partially condensed. The thus obtained -10°C, 3.46 bar propane vapor stream 203 is first fed into the suction vessel V8 and then into the intermediate pressure stage of the compressor K2.

Compressor K2 provides 78.02°C, 18.6 bar hot compressed propane gas with a flow rate of 4340 kmol/h. This stream 217 is cooled in a first exchanger E10 to provide a cooled stream 218 at 52.36°C at 18.3 bar and then cooled in a second exchanger E11 to provide a liquid stream 219 at 42°C at 18.0 bar. The latter is then stored in container V6.

Referring now to Figure 2, the apparatus shown is intended for use in the treatment of dry cracked gases, in particular, on the one hand, for the separation of a fraction mainly consisting of substantially _C2 -free methane and higher hydrocarbons, and on the other hand, Used to separate fractions consisting primarily of ethane and other _C2 and substantially methane-free higher hydrocarbons.

This device has 2 separate lines. The first line corresponds to the path followed by the gas to be purified, the second line corresponds to the cooling cycle of the refrigeration unit whose refrigerant is a mixture of at least 3 different products, in particular, They are propane, ethylene and methane.

More precisely, in the first line, the cracked gas 1, which is obtained at 15°C and 18 bar, with a flow rate of 3903 kmol/h, is cooled in exchanger E1 to -60°C, 17.7 bar, so Said exchanger is a flat plate exchanger in order to obtain cooled gas 303. The latter is sent to the upper part of the splitting distillation column T1. Stream 1 consists of 0.1% carbon dioxide, 24.3% methane, 74.4% ethane and 1.2% propane.

In the same manner as in the process described in Figure 1, steam 308 is produced at the top of distillation column T1 at a temperature of -66.21 °C, at a pressure of 17.0 bar and at a flow rate of 1342 kmol/h, which is cooled in exchanger E2 so that A locally condensed fluid 309 is provided. Streams 308 and 309 consist of 0.16% carbon dioxide, 81.8% methane and 18.0% ethane. Stream 309 is then separated into a gaseous portion 310 and a liquid portion 311 within vessel V2. Said liquid portion 311 is conveyed under the force of gravity in a line comprising a controlled opening valve 322, the opening of which depends on the liquid level of container V1.

Then, the liquid fraction 311 is introduced into the last stage of the distillation column T1.

The gas portion 310 from vessel V2 consisted of 0.1% carbon dioxide, 94.9% methane and 5.0% ethane. This part enters the heat exchanger E2 at -90°C in order to obtain a heated -70°C section 326, which then proceeds through the exchanger E1 and through the controlled valve 317 whose opening depends on the pressure. After leaving valve 317, the product is collected in delivery line 320 at 39°C and exits the plant.

In the lower part of the fractionation distillation column T1, there are several trays connected in pairs by heating lines, two of which are shown in the figure. These are lines 315,316 and 318,319. Each of these heating lines forms a transverse reboiler in the case of lines 315, 316 and a bottom reboiler in the case of lines 318, 319 of a distillation column.

The fluid flowing in line 315 with a flow rate of 1000 kmol/h and a temperature of -40.7°C is heated in heat exchanger E1 to provide a heated fluid 316 of -19.4°C, which is then introduced for recovery of fluid 315 on the tray below the tray. The temperature of the fluid flowing in said lines 315, 316 is regulated by means of controlled opening valves 323 placed in branches of lines 15, 16 which do not pass through exchanger E1. The opening of the valve 323 is controlled by a temperature controller connected to the line 316 downstream of the point where the fluid flowing in the line 316 mixes with the fluid flowing in the branch line with the valve 323 .

Similarly, the fluid flowing in line 318 with a flow rate of 3790 kmol/h and a temperature of -17.36°C is heated in heat exchanger E1 to provide a heated fluid 319 of -14.94°C. This fluid is introduced onto the tray below the tray for recovery fluid 318 . The temperature of the fluid flowing through said lines 318, 319 is regulated by means of controlled opening valves 324, said valves being arranged in branches of lines 315, 316 which do not pass through the exchanger E1. The opening of the valve 324 is controlled by a temperature controller connected to the line 316 downstream of the point where the fluid flowing in the line 319 mixes with the fluid flowing in the branch line with the valve 324 .

Finally, the residual liquid obtained at the bottom of distillation column T1, which is rich in C _and higher hydrocarbons, is recovered through line 314 having a valve 325 whose opening is determined by the valve used at the bottom of distillation column T1 Liquid level controller control. The liquid has a temperature of -14.94° C., a pressure of 17.4 bar and consists of 0.1% carbon dioxide, 1% methane and 97.4% ethane and 1.5% propane.

In the second circuit, which corresponds to the cooling cycle of the refrigeration unit whose refrigerant is a mixture of at least 3 products, a refrigeration mixture 13 consisting of 5% methane 12, 25% ethylene 3 and 70% propane 2, Its temperature is 42° C., its pressure is 27.79 bar, its flow rate is 3970 kmol/h, said refrigerant mixture is divided into a first part 4 in the container V2, which mainly contains the first part 4 of the less volatile first refrigerant 2, and The second part 5 mainly contains the more volatile second refrigerant 3 and the more volatile third refrigerant 12 .

Stream 5 constituting the gaseous phase of separation vessel V2, which consists of 9.8% methane, 36.3% ethylene and 53.9% propane, with a flow rate of 1469 kmol/h, is cooled and condensed in heat exchanger E1 to provide Stream 14 obtained at °C.

Stream 14 is then cooled in exchanger E2 to provide stream 15 obtained at -90°C, 27.1 bar. Stream 15 is expanded through valve 16 to provide stream 17 at a pressure of 2.3 bar and a temperature of -96°C. The opening of valve 16 is regulated by a temperature controller in line 310 .

Stream 17 is heated in exchanger E2 and partially evaporated so that the refrigeration requirements of exchanger E2 are met to provide stream 18 at the outlet of the exchanger at a temperature of -67.9°C and a pressure of 2.2 bar.

Stream 4 constituting the liquid phase of separation vessel V2, consisting of 2.2% methane, 18.3% ethylene and 79.5% propane, with a flow rate of 2501 kmol/h, is cooled in heat exchanger E1 in order to provide Get stream 19 below. Then split stream 19 into two streams:

Stream 8 , with a flow rate of 1000 kmol/h, is expanded by valve 20 to 8.1 bar, thereby producing stream 21 . The latter is vaporized and heated in exchanger E1, thereby producing stream 9 at 38.5 °C, 7.8 bar;

Stream 22, which has a flow rate of 1501 kmol/h, is expanded by valve 23 to 2.2 bar and mixed with stream 18 to produce stream 6. The latter, at a temperature of -64.93°C and a pressure of 2.2 bar, consists of 6.0% methane, 27.2% ethylene and 66.8% propane, evaporated and heated in exchanger E1, thus providing Stream 7.

Stream 7 is sent to the low pressure stage of compressor K1 through suction vessel V3. Stream 11, which comes from compressor K1 with a flow rate of 2970 kmol/h corresponding to all stream 7 entering the low-pressure stage of the compressor, is introduced into water exchanger E11 at 8.0 bar, 113.75° C., in order to produce 42.0° C., 7.7 Bar's cold stream 25.

Stream 9 flows through suction vessel V4 and is then mixed with stream 25 to provide stream 10 at 3970 kmol/h, 41.01 °C, 7.7 bar. Stream 10 is then introduced into the intermediate pressure stage of compressor K1.

Stream 26 from the high pressure stage of compressor K1 with a flow rate of 3970 kmol/h at a temperature of 111.66°C and a pressure of 28.39 bar is cooled in water exchanger E10 to provide stream 27 at 54.36°C. Finally, stream 27 is cooled to 42.0° C. in water exchanger E12 to produce stream 13 .

The performance characteristics of the two treatments are given below with the aid of a comparison table.

Comparison of compressor power (kW)

(power based on 82% variable efficiency) Conventional method (Figure 1) According to the method of the present invention (Fig. 2) vinyl compressor 2124 propane compressor 7406 Refrigerant Mixing Compressor 8708 total 9530 8708

The method according to the invention enables a power saving of 9.4%.

Comparison of Refrigerated Water Exchangers normal method Method of the invention water exchanger Heat exchanged (kW) MTD(°C) Exchange area(m ² ) Heat exchanged (kW) MTD(°C) Exchange area(m ² ) E10 3239 22.1 293 5989 35.2 341 E11 16426 8.88 3700 4451 24.4 365 E12 8211 6.88 2388 total 19665 3993 18651 3094

Compared with the conventional method, the area of the refrigeration water exchanger according to the method of the present invention is 29% smaller, and the water consumption is 5.4% less.

Comparison of Cryogenic Exchangers normal method Method of the invention switch Heat exchanged (kW) MTD(°C) Exchange area(m ² ) Heat exchanged (kW) MTD(°C) Exchange area(m ² ) E1 2000 11.2 357 30100 7.27 8286 E2 5658 6.74 1679 2367 3.49 1356 E3 5514 15.7 702 E4 1397 11.4 245 E5 1258 53.2 47 E6 606 8.59 141 E7 570 12.4 595 E8 929 11.0 169 E9 7500 3.75 4000 total 25432 7935 32467 9642

Compared to the known method, the method according to the invention uses a total exchange area which is 21% larger, however, the cost of the exchanger according to the invention is lower.

Quantity comparison of equipment items normal method Method of the invention cryogenic exchanger 9 2 water exchanger 2 3 container 8 4 Distillation tower 1 1 compressor 2 1 Pump 2 0 total twenty four 11

The method of the invention has only 11 equipment items, whereas the known method has 24 equipment items.

Comparison of the number of control systems: normal method The method of the invention flow control 3 1 Level Control 7 2 temperature control 2 4 Pressure control 1 1 total 13 8

The method of the present invention has 8 control systems, while the conventional method has 13 control systems.

Therefore, the method of the present invention is advantageous when producing purified gas. When the method of the present invention is carried out, the objects of the present invention are achieved while enabling the separation of methane and other components with high sensitivity.

Thus, the results obtained by the present invention offer the main advantages of a great simplification and saving in the construction and technology of the equipment, as well as the simplification of the methods of operating these equipment and the improvement of the quality of the products obtained by these methods.

Claims (11)

1. one kind is used for reclaiming to be included in comprising methane and C ₂With the ethane in the gas under pressure (1) of higher hydrocarbon, operate a kind of method of refrigeration cycle, wherein less relatively volatile first refrigeration agent (2) is compressed, cooling and expansion, so that be used to cool off a described separated gas under pressure (1) or first product separation to, the first high relatively temperature of wanting later on, and wherein more relatively volatile second refrigeration agent (3) is compressed, cooling and expansion, so that be used at least the second product separation that cooling obtains from described gas under pressure (1) later on to the second low relatively temperature ^*1, ^*2 is characterized in that, described first and second refrigeration agents (2,3) when being compressed and cooling off, they are used as a kind of mixture, then, this mixture is separated into the first part (4) that mainly comprises less relatively volatile first refrigeration agent (2) and the second section (5) that comprises relative more volatile second refrigeration agent (3), first refrigeration agent is used with the form of described first part, be used to be cooled to the first high relatively temperature, described second refrigeration agent uses with the form of described second section, is used to be cooled to the second low relatively temperature.

2. in accordance with the method for claim 1, it is characterized in that first part (4) is cooled, expands in first interchanger (E1), thereby produce first expansible part (6), then, in the lower pressure stage that is introduced into compressor (K1) (7) before, in described first interchanger, be heated.

3. in accordance with the method for claim 2, it is characterized in that second section (5) is cooled in first interchanger (E1), in second interchanger (E2), expand then, in described second interchanger, be heated then, and and expansible first part (6) mixing.

4. according to claim 2 or 3 described methods, it is characterized in that, third part (8) is drawn out of from described first part (4) after first part (4) cools off in first heat exchanger (E1), and described third part (8) expands in described first interchanger (E1) and heats, so that the 4th part (9) of an expansible and heating is provided, it is introduced into the medium pressure grade (10) of compressor (K1).

5. in accordance with the method for claim 4, it is characterized in that, gasiform the 5th part (11) from compressor (K1) to be drawn out of in the compressed refrigeration agent of middle pressure, the 4th part (9) a little more than expansible and heating, be cooled then and expand into and the identical pressure of described the 4th part, partially mixed with the described the 4th then.

6. according to the described method of any one claim of front, it is characterized in that the mixture of described first and second refrigeration agents (2,3) conduct and the 3rd refrigeration agent (12) is used.

7. in accordance with the method for claim 6, it is characterized in that described refrigeration agent can be methane, ethene and propane.

8. the gas of an enrich methane that obtains by the described method of top any one claim.

9. the product of a kind of enrichment ethane that obtains by any one described method of claim 1-7.

10. one kind is passed through the enrichment C that any one described method of claim 1-7 obtains ₂Product with higher hydrocarbon.

11. an equipment is used for reclaiming to be included in comprising methane and C ₂And the ethane in the gas under pressure of higher hydrocarbon (1), described equipment comprises and is used for compressing, cooling and expansion phase are to the device of few volatile first refrigeration agent (2), be used for by means of the described separated gas under pressure (1) or the device of first product separation to, first a high relatively temperature wanted of described first refrigerant cools, and be used for compressing, cooling and expansion phase are to the device of many volatile second refrigeration agents (3), be used for by means of the device of described second refrigeration agent (3) cooling from least the second isolating product to one second a low relatively temperature of described gas under pressure (1) acquisition, it is characterized in that, first and second refrigeration agents (2,3) being used as a kind of mixture when they are compressed and cool off uses, and described equipment comprises the first part (4) and the device that mainly contains relative volatile second refrigeration agent (3) second section (5) how that is used for described mixture separation is become mainly to contain few relatively volatile first refrigeration agent (2), described first refrigeration agent is used with the form of described first part, be used to be cooled to the first high relatively temperature, described second refrigeration agent is used with the form of second section, is used to be cooled to the second low relatively temperature.