RU2801681C1 - Method for separation of target fractions from natural gas (embodiments) - Google Patents

Abstract

FIELD: gas industry.

SUBSTANCE: present invention relates to the processes of separation of target fractions from gas mixtures, in particular, it can be used to extract propane-butane and ethane fractions from natural gas, stable gas gasoline, acidic components, water, etc. In the method for separating target fractions from natural gas, gas treatment includes the following processes one after another: heating natural gas in a gas-gas heat exchanger and a heater, expanding heated natural gas in a turbine of a turbo-expander unit (TEU), cooling gas in a gas-gas heat exchanger, separation of target natural gas fractions from natural gas by absorption, or adsorption, or membrane separation, compression of the entire flow of treated gas in the TEU compressor part, and the gas temperature upstream of the TEU turbine is maintained at such a level that the gas pressure at the outlet of the TEU compressor part exceeds the pressure gas in front of the TEU turbine.

EFFECT: significant reduction in capital and operating costs in plants designed to extract target fractions.

60 cl, 8 dwg, 3 tbl

Description

Technical field

The invention relates to the gas industry, and in particular to the processes of separation of target fractions from gas mixtures, in particular, can be used to extract propane-butane and ethane fractions from natural gas, stable gas gasoline, acidic components, water, etc. Natural gases are understood as gases contained in the bowels of the Earth, as well as gases of the earth's atmosphere. The proposed technology can be used for air drying, flue gas treatment, etc.

Prior Art

From the prior art, a method for processing natural gas is known, disclosed in US patent 4,889,545, published on December 26, 1989, which provides for multi-stage low-temperature cooling of gas with condensation due to heat recovery in heat exchangers, single-stage separation of the released liquid, pressure relief on gas streams by throttling and expanding in the turbine of a turbo-expander unit (TDA), supplying all cold streams to a distillation column to obtain a methane gas fraction and a fraction containing mainly ethane, propane and heavy hydrocarbons, heating the methane gas fraction in heat exchangers and then compressing it in the compressor part of the TDA. Before being fed into the gas pipeline, the methane gas fraction is additionally compressed in a compressor. The disadvantage of this method is that the pressure of the methane gas fraction after the TDA compressor part is significantly lower than the gas pressure at the inlet to the installation, therefore, an additional compressor is required at the outlet of the installation, which significantly increases the capital costs for the construction of such an installation.

The closest analogue to the claimed invention in terms of the essential features are the method and installation for the separation of target fractions from natural gas, disclosed in patent RU 2749628, published on 06/16/2021, in which the gas is processed by successive processes of gas compression in the main compressor, cooling gas in an air cooler, separation of propane-butane and ethane fractions from gas in a low-temperature condensation unit, which includes the process of gas cooling in heat exchangers, separation of condensed condensate from gas, gas expansion in the turbine of the main turboexpander or in a throttle, processing of cooled gas and / or condensate separated from the gas in a distillation column, heating the gas in heat exchangers, and after compressing the gas in the main compressor, the compressed gas with a temperature of at least 100°C is sent to the turbine of the additional turboexpander.

The disadvantage of this method is that the gas pressure at the outlet of such an installation (in the described patent 75 atm.) Is significantly lower than the gas pressure after the inlet compressor (150 atm.), Therefore, to transport commercial gas over long distances through main gas pipelines at the outlet from the proposed installation, it is necessary to install an additional compressor station to compress commercial gas before it is fed into the gas pipeline. Often, the pressure in such gas pipelines exceeds 150 atm. The cost of such a compressor station is usually commensurate with the cost of a plant for extracting target fractions from natural gas.

Disclosure of invention

The technical problem to be solved by the claimed invention is to reduce capital costs for the construction of installations for extracting target fractions from gas mixtures, by excluding such installations from the equipment. expensive compressor stations.

The technical result achieved in the implementation of the claimed invention is a significant reduction in capital and operating costs in plants designed to extract target fractions.

Further, on the example of natural gas produced in gas or oil fields, the principle of operation of the proposed method (options) will be described.

Typically, installations for extracting target fractions from natural gas include compressor stations. In particular, output compressor stations are installed at the outlet of the target fraction extraction units, which serve to increase the commercial gas pressure to the level necessary to supply commercial natural gas to the main gas pipeline.

In the proposed method, due to a special scheme for the use of a turbo-expander unit, it is possible to ensure the operation of the installation for extracting target fractions from natural gas in such a way that the gas pressure at the outlet of the installation exceeds the gas pressure at the inlet to the installation. Thus, compressorless supply of commercial gas to the main gas pipeline is ensured. The reduction in capital costs is due to the fact that the cost of a turbo-expander unit (TDA) is several times less than the cost of a compressor unit of the same capacity.

According to the invention, the technical problem is solved, and the technical result is achieved due to the fact that in the first method for separating target fractions from natural gas, gas treatment includes the following processes one after another: heating natural gas in a gas-gas heat exchanger and heater, expanding heated natural gas in the turbine of a turbo-expander unit (TDA), gas cooling in a gas-gas heat exchanger, separation of target natural gas fractions from natural gas by absorption or adsorption or membrane separation, compression of the entire treated gas flow in the TDA compressor part, and the gas temperature in front of the TDA turbine is provided at such a level that the gas pressure at the outlet of the TDA compressor part exceeds the gas pressure in front of the TDA turbine.

In the second version of the method for separating target fractions from natural gas, gas treatment includes the following processes one after another: heating natural gas in a gas-gas heat exchanger and a heater, expansion of heated natural gas in a TDA, gas cooling in a gas-gas heat exchanger, partial gas condensation using the cold of the refrigerating machine and separating the target components condensed during cooling in the separator and / or distillation column, followed by compression of the entire gas flow in the compressor part of the TDA, and the gas temperature in front of the TDA turbine is provided at such a level that the gas pressure at the outlet of the compressor part of the TDA exceeded the gas pressure in front of the TDA turbine.

In the third version of the method for separating target fractions from natural gas, gas treatment includes the following processes one after another: gas heating in a gas-gas heat exchanger and a heater, expansion of the heated gas in the turbine of a turbo-expander unit (TDA), gas cooling in a gas-gas heat exchanger, compression of the entire gas flow in the TDA compressor part, separation of target natural gas fractions from natural gas by absorption or adsorption or membrane separation, and the gas temperature in front of the TDA turbine is provided at such a level that the gas pressure at the outlet of the TDA compressor part exceeds the gas pressure in front of the turbine TDA.

In the fourth version of the method for separating target fractions from natural gas, gas treatment includes the following processes one after another: heating natural gas in a gas-gas heat exchanger and a heater, expanding heated natural gas in a TDA turbine, cooling gas in a gas-gas heat exchanger, compressing the entire gas flow in the compressor part of the TDA, partial condensation of the gas using the cold of the refrigerating machine and the release of the target components condensed during cooling in the separator and / or distillation column, and the gas temperature in front of the TDA turbine is provided at such a level that the gas pressure at the outlet of the compressor part of the TDA exceeded the gas pressure in front of the TDA turbine.

In the fifth version of the method for separating target fractions from natural gas, gas treatment includes the following processes one after another: separating target natural gas fractions from natural gas by absorption or adsorption or membrane separation, heating the gas in a gas-gas heat exchanger and heater, expanding the heated gas in the TDA turbine, gas cooling at least in a gas-gas heat exchanger, compression of the entire gas flow in the TDA compressor part, and the gas temperature in front of the TDA turbine is provided at such a level that the gas pressure at the outlet of the TDA compressor part exceeds the gas pressure in front of the TDA turbine.

In the sixth version of the method for separating target fractions from natural gas, gas treatment includes the following processes one after another: partial gas condensation using the cold of a refrigeration machine and separation of target components condensed during cooling in a separator and/or distillation column, subsequent gas heating in gas-gas heat exchanger and heater, expanding the heated gas in the turbine of the turbo-expander unit (TDA), cooling the gas in the gas-gas heat exchanger, compressing the entire gas flow in the compressor part of the TDA, and the gas temperature in front of the TDA turbine is provided at such a level that the gas pressure is at at the outlet of the TDA compressor part, the gas pressure in front of the TDA turbine exceeded.

The implementation of one of the six proposed options depends on the inlet pressure of natural gas. The first two options are implemented if the inlet gas pressure is too high for the normal operation of the unit for extracting target natural gas fractions from natural gas, in this option, before gas is supplied to the unit, the gas pressure in the TDA turbine is reduced.

The third and fourth variants of the proposed method are implemented if the inlet gas pressure is insufficient for the normal operation of the unit for extracting target natural gas fractions from natural gas. In this variant, after compression in the compressor part of the TDA, the gas pressure rises to a level exceeding the pressure of the inlet gas.

The fifth and sixth variants of the proposed method are implemented when the inlet gas pressure is sufficient for the normal operation of the block for extracting target natural gas fractions from natural gas, but after the block it is necessary to increase the pressure of the commercial gas.

In all embodiments of the method, after gas compression in the TDA compressor part and/or after separation of target natural gas fractions from natural gas, the gas is additionally subjected to at least one additional treatment, including gas heating in additional gas-gas heat exchangers and/or additional heaters, expansion of the heated gas in the turbine of the additional turbo-expander unit (DTDA), gas cooling and gas compression in the compressor part of the DTDA.

In cases where it is necessary to achieve high efficiency of turbines and TDA and/or DTDA compressor parts, it is advisable that the TDA and/or DTDA turbine include at least two turbine impellers, and the TDA and/or DTDA compressor part at least two compressor impellers.

Before any turbine impeller, the gas can be additionally heated, which makes it possible to increase the extraction of mechanical energy from the turbine impeller. Before any compressor impeller, the gas can be additionally cooled, which allows increasing the degree of gas compression in the compressor impeller.

The unit for extracting target natural gas fractions from natural gas can be located at a distance from the compressor part of the TDA, in these cases, the gas is transferred between the unit for extracting target natural gas fractions from natural gas and the TDA through a gas pipeline. Also, the unit for extracting target natural gas fractions from natural gas can be located at a distance from the heat exchangers and/or heaters, in these cases, the gas is transferred between the unit for extracting target natural gas fractions from natural gas and heat exchangers and heaters through a gas pipeline.

To ensure the removal of maximum mechanical energy, the gas temperature in front of the TDA turbine is provided at a level above 200 ° C,

Heating of natural gas in heat exchangers and/or heaters can be carried out due to the heat generated during the combustion of natural gas in pure oxygen. In this case, when natural gas is burned in pure oxygen, flue gas with a high concentration of CO ₂ will be formed, which can be immediately injected back into the reservoir at the field.

Brief description of the figures of the drawings

The essence of the invention is illustrated by drawings, where:

figure 1 shows a diagram of the proposed method according to the first and second embodiments of the method;

figure 2 is a diagram of the proposed method according to the third and fourth embodiments of the method;

figure 3 is a diagram of the proposed method according to the fifth and sixth embodiment of the method;

figure 4 is a diagram of the proposed method, explaining p. 2, 12, 22, 32, 42, 52 of the claims;

figure 5 is a diagram of the proposed method, explaining the implementation of the method according to p.

figure 6 is a diagram of the proposed method, explaining the implementation of the method according to p.

Fig.7 is a diagram of a gas treatment unit in a unit for separating target natural gas fractions from natural gas using a low-temperature condensation process, in the case of separating the C3+ fraction (NGL).

8 is a diagram of a gas treatment unit in a unit for extracting target natural gas fractions from natural gas using a low-temperature condensation process in the case of extracting water vapor from natural gas.

The figures show the following positions:

1 - input flow of natural gas,

2 - heat exchanger,

4 - heater,

6 - TDA turbine,

8 - block for extracting target fractions of natural gas from natural gas,

10 - compressor part of TDA,

13 - TDA turbine with two impellers,

14 - TDA compressor part with two wheels,

15 - the first turbine wheel of the TDA turbine,

16 - intermediate heater,

17 - the second impeller of the TDA turbine,

18 - the first impeller of the TDA compressor part,

19 - intercooler,

20 - the second impeller of the TDA compressor part,

21 - additional heat exchanger,

22 - additional heater,

23 - turbine DTDA,

24 - compressor part of the additional DTDA,

25 - target fractions extracted from natural gas,

26, 27 - recuperative heat exchangers,

28 - refrigerator,

29 - separator,

30 - compressor,

31 - distillation column,

3, 5, 7, 9, 11, 12, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44 - installation threads.

Embodiments of the invention

The work of the invention according to the first embodiment of the proposed method is illustrated by the example of the installation, the scheme of which is shown in Fig.1. The input stream of natural gas 1 is heated in heat exchangers 2 and heaters 4 and expanded in the turbine 6 TDA. Next, the gas is cooled, for example, in a heat exchanger 2, and processed in a block 8 for extracting target fractions from natural gas. After processing in block 8, the gas is compressed in the compressor part 10 of the TDA, and the gas temperature in front of the turbine 6 of the TDA is provided at such a level that the gas pressure is at outlet of the compressor part 10 TDA exceeded the gas pressure in front of the turbine part 6 TDA.

In accordance with the first and second embodiments of the proposed method, absorbers and/or adsorbers and/or membrane separation are used in block 8 for extracting target fractions from natural gas.

In absorbers, a gas mixture is separated into its constituent parts by dissolving one or more components of this mixture in a liquid called an absorbent. The absorber is usually a column with a packing or plates, in the lower part of which gas is supplied, and in the upper part - liquid; gas is removed from the absorber at the top and liquid at the bottom. In this case, the target fractions are absorbed by the liquid. In some cases, in the absorber, the gas is bubbled through the absorbent filled into the column. Details of the designs of various absorbers can be found in the book Ramm V.M. Gas Adsorption. Ed. 2nd, revised. and additional M., "Chemistry", 1976.

An adsorber is an apparatus for absorbing dissolved or gaseous substances by the surface layer of a solid, called an adsorbent (absorber). Typically, an adsorber is a vertical or horizontal vessel filled with a solid adsorbent. Activated carbon, silica gels, zeolites, clay materials, etc. can be used as an adsorbent. Chemical and physical adsorption are known. During physical adsorption, the absorption of target fractions occurs without chemical reactions; during chemical adsorption, the formation of new chemical compounds occurs. One of the features of adsorbers is the need for continuous or periodic regeneration. The regeneration of the adsorbent is usually carried out by heating and/or purging with gas. Details of the designs of various adsorbers can be found in the book by N.V. Keltsev, Fundamentals of adsorption technology, M., 1984.

In the case of membrane separation, the separation of target fractions from natural gas is carried out in membranes that have the property of selective permeability of natural gas components, i.e., different fractions of natural gas penetrate through the membrane at different rates. When processing gas in a membrane module, the source natural gas is divided into two streams - into target fractions penetrating through the membrane (permeate) and into purified natural gas (retentate). A two-stage treatment of natural gas is often used, in which the permeate is treated in the second stage also by means of membranes. Membranes are made from various materials, for example, from polymers, from nanoporous, zeolite or silica materials, etc. Details on the designs of various membranes can be found in the book by Yu.I. Dytnersky, V.P. Brykov, G.G. Kagramanov, Membrane separation of gases, M. "Chemistry", 1991

In accordance with the second embodiment of the proposed method, in block 8 for extracting target fractions from natural gas, gas treatment is carried out using a low-temperature condensation process, in which the gas is cooled using heat exchangers and a refrigeration machine, and the target components condensed during cooling are isolated in a separator and/ or distillation column. As an example, Fig.7 shows a diagram of a possible configuration of such a block 8. In block 8, the gas is cooled in recuperative heat exchangers 26 and 27, then the cooled gas is additionally cooled in the evaporator of the refrigerator 28. The hydrocarbon condensate condensed during cooling of the gas is separated from the gas in the separator 29. Next, the separated condensate is heated in a recuperative heat exchanger 26 and sent to a distillation column 31. Target fractions 25 are taken from the bottom of the column 31, weathering gases are taken from the top of the column, which are compressed using a compressor 30 and gas is supplied before the separator 29.

As one of the possible applications of the proposed method, table 1 shows the parameters of the main streams for the installation shown in Fig.1 for the case of extracting a fraction consisting of hydrocarbon components heavier than propane (C3+, NGL) from associated gas. The input stream 1 of natural gas with a pressure of 8.0 MPa and a temperature of 30°C is heated in the heat exchanger 2 and heater 4 to a temperature of 287.9°C. Next, the heated gas expands in the turbine of the turbo-expander unit to a pressure of 5.0 MPa and is cooled in the heat exchanger 2 to a temperature of 35°C and is sent to the unit 8 for separating target natural gas fractions from natural gas. In which with the help of absorbers (the first implementation of the proposed method); or adsorbers and/or membranes (second embodiment of the proposed method); or using a low-temperature condensation process, in which the gas is cooled using heat exchangers and a refrigeration machine, and the target components condensed during cooling are isolated in a separator and/or distillation column (the third embodiment of the proposed method), the target fractions of 25 natural gas are separated from natural gas C3+ gas (NGL). Purified from target fractions, the gas from the outlet of block 8 with a pressure of 4.8 MPa is compressed in the compressor part of the TDA to a pressure of 10.0 MPa. In this example, 188.9 tons of target C3+ fractions are released from the inlet gas at a flow rate of 910.8 tons/day of natural gas. In this case, the gas pressure of the gas 11 at the outlet of the compressor part of the TDA exceeds the pressure of the gas 5 in front of the turbine part of the TDA.

In block 8, for the separation of target C3+ fractions from natural gas, in this particular example, it is advisable to use:

- as an absorbent, gasoline, kerosene, solar distillate, or fractions that are part of natural gas, in the case of using absorbers (the first version of the proposed method),

- as an adsorbent, aluminum oxide, zeolites, silica gel, etc., in the case of using adsorbers (the second variant of the proposed method),

- as membranes, hollow fiber gas separation membranes, polymeric membranes, etc., in the case of using membranes (the second variant of the proposed method),

- propane, freon, ammonia refrigerating machines as a refrigerating machine, in case of using refrigerating machines (the third variant of the proposed method),

Heat exchangers 2 can be installed both in series with heaters 4, as shown in Fig.1, and in parallel. Heat exchangers 2 can have different designs and are made in the form of shell-and-tube, twisted, plate, and other devices.

Heaters 4 are heat exchangers in which gas is heated by transferring heat from a hot heat carrier such as hot oil, steam, flue gases, hot gas, hot liquid, etc. In this case, the heaters 4 may consist of several heat exchangers with different heat carriers. Hardware-wise, the heaters 4 can be made both in one unit with the heat carrier heating furnace, or separately. The hot gas used as a heat carrier can be hot gases available in the plant, in particular, for example, hot gases formed after gas compression in the TDA compressor part (stream 11).

A turbo-expander unit (TDA) is understood as a machine in which either the turbine and the compressor part are mechanically connected, while the mechanical energy from the turbine is transferred to the compressor part, or the turbine and the compressor part are electrically connected, while the turbine is connected to an electric generator, and the compressor part is connected to electric motor (electrical energy from the electric generator is transferred to the electric motor). Sometimes it is advisable to transfer mechanical work from the turbine to the compressor part using multipliers and gearboxes. Each turbine and compressor part of the TDA can be made according to the radial, axial and radial-axial scheme. In turn, in the case of using a radial scheme, both centripetal and centrifugal impellers and guide vanes can be used. Since the content of mechanical and liquid impurities is unacceptable at the inlet of the turbine and the compressor part, therefore, devices (separators, filters) that process gas must be provided in the TDA before gas is supplied to the turbines and compressor parts.

Table 1 streams 1 3 5 7 9 eleven 12 25 Temperature C 30.0 237.7 287.9 35.0 40.0 102.3 251.9 40.0 Pressure MPA 8.0 7.9 7.9 5.0 4.8 10.0 5.0 4.8 Mass flow Tons/day 910.8 910.8 910.8 910.8 721.9 721.9 910.8 188.9 Mole composition _CO2 0.0174 0.0174 0.0174 0.0174 0.0189 0.0189 0.0174 0.0000 N ₂ 0.0210 0.0210 0.0210 0.0210 0.0229 0.0229 0.0210 0.0000 CH ₄ 0.8313 0.8313 0.8313 0.8313 0.9049 0.9049 0.8313 0.0000 C ₂ H ₆ 0.0481 0.0481 0.0481 0.0481 0.0524 0.0524 0.0481 0.0000 C ₃ H ₈ 0.0490 0.0490 0.0490 0.0490 0.0005 0.0005 0.0490 0.5970 _{IC4H10 _} 0.0101 0.0101 0.0101 0.0101 0.0001 0.0001 0.0101 0.1231 NC ₄ H ₁₀ 0.0135 0.0135 0.0135 0.0135 0.0001 0.0001 0.0135 0.1645 IC ₅ H ₁₂ 0.0035 0.0035 0.0035 0.0035 0.0000 0.0000 0.0035 0.0426 NC ₅ H ₁₂ 0.0030 0.0030 0.0030 0.0030 0.0000 0.0000 0.0030 0.0365 C ₆ H ₁₄ 0.0020 0.0020 0.0020 0.0020 0.0000 0.0000 0.0020 0.0249 C ₇ H ₁₆ 0.0007 0.0007 0.0007 0.0007 0.0000 0.0000 0.0007 0.0090 0.0002 0.0002 0.0002 0.0002 0.0000 0.0000 0.0002 0.0024

The work of the invention according to the third and fourth embodiments of the proposed method is illustrated by the example of the installation, the scheme of which is shown in Fig.2. The input stream of natural gas 1 is heated in heat exchangers 2 and heaters 4 and expanded in the turbine 6 TDA. Next, the gas is cooled, for example, in a heat exchanger 2, and compressed in the compressor part 10 of the TDA, the compressed gas is processed in the block 8 for separating target fractions from natural gas, and the gas temperature in front of the turbine 6 of the TDA is provided at such a level that the gas pressure at the outlet of the compressor part 10 TDA exceeded the gas pressure in front of the turbine part 6 TDA.

Gas cooling before the compressor part 10 of the TDA can also be carried out in an air cooler.

In block 8, the separation of target fractions can be carried out both with the help of absorbers, adsorbers, membrane separation, and with the help of partial gas condensation using the cold of a refrigeration machine and the separation of target components condensed during cooling in a separator and / or distillation column,

As one of the possible applications of the proposed method, table 2 shows the parameters of the main flows for the installation shown in figure 2 for the case of extracting water vapor from associated gas (gas dehydration). The input stream 1 of natural gas with a pressure of 5.0 MPa and a temperature of 30°C is heated in the heat exchanger 2 and heater 4 to a temperature of 306.6°C. Further, the heated gas expands in the turbine of the turbo-expander unit to a pressure of 3.0 MPa and is cooled in heat exchanger 2 to a temperature of 35°C and compressed in the TDA compressor section to a pressure of 6.0 MPa. Compressed gas is sent to block 8 for separating target natural gas fractions from natural gas. In which with the help of absorbers; or adsorbers and/or membranes; or using a low-temperature condensation process, in which the gas is cooled using heat exchangers and a refrigeration machine, and the target components condensed during cooling are separated in the separator, water 25 is separated from natural gas. In this example, from the input gas with a flow rate of 730.5 tons / day of natural gas is released 800 kg/day of water. In this case, the gas pressure at the outlet of the compressor part 10 TDA exceeds the gas pressure in front of the turbine 6 TDA.

table 2 streams 1 25 32 33 34 35 36 37 Temperature C 30.0 40.0 253.8 306.6 263.0 35.0 96.8 40.0 Pressure MPA 5.0 6.0 5.0 4.9 3.0 2.9 6.0 6.0 Mass flow Tons/day 730.5 0.8 729.8 729.8 729.8 729.8 729.8 729.0 Mole composition _CO2 0.0016 0.00 0.0016 0.0016 0.0016 0.0016 0.0016 0.0016 N ₂ 0.0019 0.00 0.0019 0.0019 0.0019 0.0019 0.0019 0.0019 CH ₄ 0.9852 0.00 0.9852 0.9852 0.9852 0.9852 0.9852 0.9862 C ₂ H ₆ 0.0044 0.0 0.0044 0.0044 0.0044 0.0044 0.0044 0.0044 C ₃ H ₈ 0.0045 0.00 0.0045 0.0045 0.0045 0.0045 0.0045 0.0045 _{IC4H10 _} 0.0009 0.00 0.0009 0.0009 0.0009 0.0009 0.0009 0.0009 NC ₄ H ₁₀ 0.0004 0.00 0.0004 0.0004 0.0004 0.0004 0.0004 0.0004 _H2O 0.0010 1.00 0.0010 0.0010 0.0010 0.0010 0.0010 0.0000

In block 8, for the separation of water vapor from natural gas, in this particular example, it is advisable to use:

- as an absorbent ethylene glycol (EG), diethylene glycol (DEG), triethylene glycol (TEG), methanol (fourth version of the proposed method),

- as an adsorbent aluminum oxide, zeolites, silica gel, etc. (fifth version of the proposed method),

- as membranes, hollow fiber gas separation membranes, polymeric membranes, etc. (fifth version of the proposed method),

- as a refrigerating machine propane, freon, ammonia, etc. (the sixth version of the proposed method),

For the example under consideration, one of the possible diagrams of block 8 according to the sixth method is shown in Fig.8. Gas 7 is cooled in the recuperative heat exchanger 27 and the evaporator of the refrigeration machine to a temperature of -25°C, the condensed water is separated from the gas in the separator 29, the gas from the top of the separator is sent to the recuperative heat exchanger for heating.

The operation of the invention according to the fifth and sixth embodiments of the proposed method is illustrated by the example of the installation, the diagram of which is shown in Fig.3. The input stream of natural gas 1 is processed in the block 8 for separating target fractions from natural gas, heated in heat exchangers 2 and heaters 4 and expanded in the turbine 6 TDA. Next, the gas is cooled, for example, in a heat exchanger 2, and compressed in the TDA compressor part 10, and the gas temperature in front of the TDA turbine 6 is provided at such a level that the gas pressure at the outlet of the TDA compressor part 10 exceeds the gas pressure in front of the TDA turbine part 6.

Gas cooling before the compressor part 10 of the TDA can also be carried out in an air cooler.

As one of the possible applications of the proposed method, table 3 shows the parameters of the main streams for the installation shown in Fig.3 for the case of extraction of acid components H ₂ S and CO ₂ from associated gas. The inlet stream 1 of natural gas with a pressure of 6.0 MPa and a temperature of 30°C is sent to the unit 8 for separating acidic components H ₂ S and CO ₂ from natural gas, in which the stream of acidic components 38 is separated, and the gas purified from acidic components is heated in heat exchanger 2 and heater 4 to a temperature of 300°C. Further, the heated gas expands in the turbine of the turbo-expander unit to a pressure of 4.0 MPa and is cooled in heat exchanger 2 to a temperature of 50°C and compressed in the TDA compressor section to a pressure of 6.5 MPa.

Table 3 streams 1 38 39 40 41 42 43 44 Temperature C 30.0 49.3 30.0 246.5 300.0 268.3 50.0 94.8 Pressure MPA 6.0 6.0 6.0 6.0 5.9 4.0 4.0 6.5 Mass flow Tons/day 1000.0 47.3 952.7 952.7 952.7 952.7 952.7 952.7 Mole composition _CO2 0.0159 0.7792 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 N ₂ 0.0129 0.0000 0.0132 0.0132 0.0132 0.0132 0.0132 0.0132 CH ₄ 0.9032 0.0000 0.9221 0.9221 0.9221 0.9221 0.9221 0.9221 C ₂ H ₆ 0.0422 0.0000 0.0430 0.0430 0.0430 0.0430 0.0430 0.0430 C ₃ H ₈ 0.0123 0.0000 0.0126 0.0126 0.0126 0.0126 0.0126 0.0126 _{IC4H10 _} 0.0046 0.0000 0.0047 0.0047 0.0047 0.0047 0.0047 0.0047 NC ₄ H ₁₀ 0.0043 0.0000 0.0044 0.0044 0.0044 0.0044 0.0044 0.0044 H ₂ S 0.0045 0.2208 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

In block 8, acidic components are separated from natural gas using absorbers; or adsorbers and/or membranes; or using a low-temperature condensation process, in which the gas is cooled using heat exchangers and a refrigeration machine, and the target components condensed during cooling are separated in a separator and / or a distillation column, the acidic components H ₂ S and CO ₂ are separated from natural gas. In this case, the gas pressure at the outlet of the compressor part 10 TDA exceeds the gas pressure in front of the turbine 6 TDA.

In block 8, for the separation of acidic components of H ₂ S and CO ₂ from natural gas, in this particular example, it is advisable to use:

- as an absorbent amines, zeolites, alkalis, or other innovative absorbents (the seventh version of the proposed method),

- as an adsorbent, activated carbon, molecular sieves, Zn oxides or Cu oxides, zinc-copper absorber, synthetic sorbent for gas purification from hydrogen sulfide containing 35-95% manganese oxides, or other innovative adsorbents (the eighth variant of the proposed method),

- as membranes, an elastic membrane, polymeric membranes or other innovative membranes (the eighth variant of the proposed method),

- as a refrigeration machine, propane, freon, ammonia, mixed refrigerants, carbon dioxide, air or other innovative refrigeration machines (the ninth version of the proposed method),

For the example under consideration, one of the possible diagrams of block 8 according to the sixth variant of the method is shown in Fig.8. Gas 7 is cooled in the recuperative heat exchanger 27 and the evaporator of the refrigeration machine to a temperature of -20°C, the condensed water is separated from the gas in the separator 29, the gas from the top of the separator is sent to the recuperative heat exchanger for heating.

In cases where a significant increase in gas pressure at the outlet of the installation is required, Figure 4 shows an embodiment of the method according to clauses 2,12,22,32,42,52 of the claims, in which, after compressing the gas in the compressor part 10 of the TDA, the gas is additionally subjected to at least one additional processing, including heating the gas in additional gas-gas heat exchangers 21 and/or additional heaters 22, expanding the heated gas in the turbine 23 of an additional turbo-expander unit (DTDA), cooling the gas in the heat exchanger 21, compressing the gas in compressor part 24 DTDA. A similar, at least one-time additional gas treatment can be carried out after gas treatment in the unit for separating target natural gas fractions from natural gas.

Turbine TDA and/or DTDA may include at least two turbine impellers. Figure 5 shows the turbine TDA 13 with two impellers. The use of two or more turbine wheels is advisable at high degrees of gas expansion in the turbine; in this case, the use of several impellers makes it possible to increase the efficiency (efficiency) of gas expansion in the turbine. This allows you to take a lot of mechanical energy from the turbine.

The compressor part of the TDA and / or DTDA may include at least two compressor impellers. Figure 5 shows the compressor part of the TDA 14 with two compressor impellers. The use of two or more compressor wheels is advisable at high degrees of gas compression in the TDA compressor part, in this case, the use of several impellers makes it possible to increase the efficiency (efficiency) of gas compression in the TDA compressor part. This makes it possible to provide a higher degree of gas compression in the TDA compressor part.

Compressor and turbine impellers of TDA and/or DTDA can be split into several independent housings to reduce the size of the housings, and reduce the cost of TDA and DTDA.

To increase the extracted mechanical energy, the gas can be additionally heated in front of any turbine impeller, as shown in the diagram of Fig.6. In this scheme, after heating the gas in heat exchanger 2 and heater 4, the gas expands in the first impeller of the TDA turbine, then the gas is heated in an additional heater 16 and expanded in the second impeller of the TDA turbine.

To increase the compression ratio in the TDA compressor part, the gas can be additionally cooled before any compressor impeller, as shown in the diagram of Fig.6. In this scheme, after gas compression in the first compressor impeller, the gas is cooled, for example, in an air cooler 19, and expands in the second TDA compressor impeller

In the case of a significant distance of the TDA from the unit for extracting target natural gas fractions from natural gas, the transfer of gas between the unit for extracting target natural gas fractions from natural gas and the TDA can be carried out through a long gas pipeline. Similarly, the transfer of gas between the natural gas extraction unit and the heat exchangers and/or heaters can also be carried out by means of a long gas pipeline. In some cases, the length of this gas pipeline can reach several tens of kilometers.

To reduce capital costs, DTA and DTDA can be made in the same building.

The gas temperature in front of the TDA turbine, in some cases, is provided at a level above 200°C. As experimental tests of installations based on the proposed method show, currently existing turbo-expander units make it possible to provide gas pressure at the outlet of the TDA compressor section exceeding the gas pressure in front of the TDA turbine section, at a gas temperature level in front of the TDA turbine at a level above 200 ° C.

Heating of natural gas in heat exchangers and/or heaters can be carried out due to the heat generated during the combustion of natural gas in pure oxygen. In this case, the burner of the heater is supplied with pure oxygen obtained from the air separation plant and natural gas. When natural gas is burned in pure oxygen, the flue gases will contain mainly CO ₂ and water vapor. In this case, the flue gas, after pre-treatment, can be injected into the reservoir, or used for other needs (for example, to produce pure CO ₂ or to feed plants or bacteria, in the production of protein).

Claims (60)

1. A method for separating target fractions from natural gas, which includes successive processes of heating natural gas in a gas-gas heat exchanger and a heater, expanding heated natural gas in a turbine of a turbo-expander unit (TDA), cooling gas in a gas-gas heat exchanger, separating from natural gas of target fractions of natural gas by absorption, or adsorption, or membrane separation, compression of the entire flow of treated gas in the TDA compressor part, and the gas temperature in front of the TDA turbine is provided at such a level that the gas pressure at the outlet of the TDA compressor part exceeds the gas pressure in front of the TDA turbine. 2. The method according to claim 1, characterized in that after compressing the gas in the compressor part of the TDA and / or after separating the target fractions of natural gas from natural gas, the gas is additionally subjected to at least one additional treatment, including heating the gas in additional gas heat exchangers -gas and / or additional heaters, expansion of the heated gas in the turbine of the additional turbo-expander unit (DTDA), gas cooling and gas compression in the compressor part of the DTDA. 3. The method according to claim 1 or 2, characterized in that the TDA and/or DTDA turbine includes at least two turbine impellers. 4. The method according to claim 1 or 2, characterized in that the compressor part of the TDA and/or DTDA includes at least two compressor impellers. 5. The method according to claim 3, characterized in that the gas is additionally heated before each turbine impeller. 6. Method according to claim 4, characterized in that the gas is additionally cooled before each compressor impeller. 7. The method according to claim 1, characterized in that the transfer of gas between the unit for separating target natural gas fractions from natural gas and the TDA is carried out through a gas pipeline. 8. The method according to claim 1, characterized in that the transfer of gas between the unit for separating target natural gas fractions from natural gas and heat exchangers and heaters is carried out by means of a gas pipeline. 9. The method according to claim 1 or 2, characterized in that the gas temperature in front of the TDA turbine is provided at a level above 200 °C. 10. The method according to claim 1 or 2, characterized in that the heating of natural gas in heaters is carried out due to the heat generated during the combustion of natural gas in pure oxygen. 11. A method for separating target fractions from natural gas, which includes successive processes of heating natural gas in a gas-gas heat exchanger and a heater, expanding heated natural gas in a TDA, cooling gas in a gas-gas heat exchanger, partial gas condensation using cold refrigerating machine and separation of the target components condensed during cooling in the separator and / or distillation column, subsequent compression of the entire gas flow in the TDA compressor part, and the gas temperature in front of the TDA turbine is provided at such a level that the gas pressure at the outlet of the TDA compressor part exceeds gas pressure in front of the TDA turbine. 12. The method according to claim 11, characterized in that after compressing the gas in the compressor part of the TDA and / or after processing the gas in the unit for separating target natural gas fractions from natural gas, the gas is additionally subjected to at least one additional treatment, including gas heating in additional gas-gas heat exchangers and / or additional heaters, expansion of heated gas in the DTDA turbine, gas cooling and gas compression in the DTDA compressor part. 13. Method according to claim 11 or 12, characterized in that the TDA and/or DTDA turbine includes at least two turbine impellers. 14. The method according to claim 11 or 12, characterized in that the compressor part of the TDA and/or DTDA includes at least two compressor impellers. 15. The method according to claim 13, characterized in that the gas is additionally heated before each turbine impeller. 16. Method according to claim 14, characterized in that the gas is additionally cooled before each compressor impeller. 17. The method according to claim 11, characterized in that the gas is transferred between the unit for extracting target natural gas fractions from natural gas and the TDA by means of a gas pipeline. 18. The method according to claim 11, characterized in that the transfer of gas between the unit for separating target natural gas fractions from natural gas and heat exchangers and heaters is carried out by means of a gas pipeline. 19. The method according to claim 11, characterized in that the gas temperature in front of the TDA turbine is provided at a level above 200 ° C. 20. The method according to claim 11 or 12, characterized in that the heating of natural gas in heaters is carried out due to the heat generated during the combustion of natural gas in pure oxygen. 21. A method for separating target fractions from natural gas, which includes successive processes of heating gas in a gas-gas heat exchanger and a heater, expanding the heated gas in a turbine of a turbo-expander unit (TDA), cooling gas in a gas-gas heat exchanger, compressing the entire flow gas in the TDA compressor part, separation of target natural gas fractions from natural gas by absorption, or adsorption, or membrane separation, and the gas temperature in front of the TDA turbine is provided at such a level that the gas pressure at the outlet of the TDA compressor part exceeds the gas pressure in front of the TDA turbine . 22. The method according to p. in additional gas-gas heat exchangers and / or additional heaters, expansion of heated gas in the DTDA turbine, gas cooling and gas compression in the DTDA compressor part. 23. The method according to claim 21 or 22, characterized in that the TDA and/or DTDA turbine includes at least two turbine impellers. 24. The method according to claim 21 or 22, characterized in that the compressor part of the TDA and/or DTDA includes at least two compressor impellers. 25. The method according to claim 22, characterized in that the gas is additionally heated before each turbine impeller. 26. Method according to claim 23, characterized in that the gas is additionally cooled before each compressor impeller. 27. The method according to claim 21, characterized in that the gas is transferred between the unit for extracting target natural gas fractions from natural gas and the TDA by means of a gas pipeline. 28. The method according to claim 21, characterized in that the transfer of gas between the unit for separating target natural gas fractions from natural gas and heat exchangers and heaters is carried out through a gas pipeline. 29. The method according to claim 21 or 22, characterized in that the gas temperature in front of the TDA turbine is provided at a level above 200 ° C. 30. The method according to claim 1 or 2, characterized in that the heating of natural gas in heaters is carried out due to the heat generated during the combustion of natural gas in pure oxygen. 31. A method for separating target fractions from natural gas, which includes successive processes of heating natural gas in a gas-gas heat exchanger and a heater, expanding heated natural gas in a TDA turbine, cooling gas in a gas-gas heat exchanger, compressing the entire gas flow into compressor part of the TDA, partial condensation of gas using the cold of the refrigeration machine and the release of the target components condensed during cooling in the separator and / or distillation column, and the gas temperature in front of the TDA turbine is provided at such a level that the gas pressure at the outlet of the TDA compressor part exceeds gas pressure in front of the TDA turbine. 32. The method of separating target fractions from natural gas according to claim 31, characterized in that after gas compression in the TDA compressor part and / or after gas treatment in the unit for separating target natural gas fractions from natural gas, the gas is additionally subjected to at least one additional additional processing , which includes gas heating in additional gas-gas heat exchangers and / or additional heaters, expansion of the heated gas in the DTDA turbine, gas cooling and gas compression in the DTDA compressor part. 33. The method according to claim 31 or 32, characterized in that the TDA and/or DTDA turbine includes at least two turbine impellers. 34. The method according to claim 31 or 32, characterized in that the compressor part of the TDA and/or DTDA includes at least two compressor impellers. 35. The method according to claim 32, characterized in that the gas is additionally heated before each turbine impeller. 36. The method according to claim 34, characterized in that the gas can be additionally cooled before each compressor impeller. 37. The method according to claim 31, characterized in that the transfer of gas between the unit for separating target natural gas fractions from natural gas and the TDA is carried out through a gas pipeline. 38. The method according to claim 31, characterized in that the gas is transferred between the unit for extracting target natural gas fractions from natural gas and heat exchangers and heaters through a gas pipeline. 39. The method according to claim 31 or 32, characterized in that the gas temperature in front of the TDA turbine is provided at a level above 200 ° C. 40. The method according to claim 31 or 32, characterized in that the heating of natural gas in heaters is carried out due to the heat generated during the combustion of natural gas in pure oxygen. 41. A method for separating target fractions from natural gas, which includes successive processes for separating target fractions of natural gas from natural gas by absorption, or adsorption, or membrane separation, heating the gas in a gas-gas heat exchanger and heater, expanding the heated gas in TDA turbine, gas cooling at least in the gas-gas heat exchanger, compression of the entire gas flow in the TDA compressor part, and the gas temperature in front of the TDA turbine is provided at such a level that the gas pressure at the outlet of the TDA compressor part exceeds the gas pressure in front of the TDA turbine. 42. The method according to claim 41, characterized in that after compressing the gas in the compressor part of the TDA and / or after treating the gas in the unit for extracting target natural gas fractions from natural gas, the gas is additionally subjected to at least one additional treatment, including gas heating in additional gas-gas heat exchangers and / or additional heaters, expansion of heated gas in the DTDA turbine, gas cooling and gas compression in the DTDA compressor part. 43. The method according to claim 41 or 42, characterized in that the TDA and/or DTDA turbine includes at least two turbine impellers. 44. The method according to claim 41 or 42, characterized in that the compressor part of the TDA and/or DTDA includes at least two compressor impellers. 45. The method according to claim 42, characterized in that the gas is additionally heated before each turbine impeller. 46. The method according to claim 43, characterized in that the gas is additionally cooled before each compressor impeller. 47. The method according to claim 41, characterized in that the gas is transferred between the unit for extracting target natural gas fractions from natural gas and the TDA by means of a gas pipeline. 48. The method according to claim 41, characterized in that the transfer of gas between the unit for separating target natural gas fractions from natural gas and heat exchangers and heaters is carried out through a gas pipeline. 49. The method according to claim 41 or 42, characterized in that the gas temperature in front of the TDA turbine is provided at a level above 200 ° C. 50. The method according to claim 41 or 42, characterized in that the heating of natural gas in heaters is carried out due to the heat generated during the combustion of natural gas in pure oxygen. 51. A method for separating target fractions from natural gas, which includes successive processes of partial gas condensation using the cold of a refrigeration machine and separating target components condensed during cooling in a separator and / or distillation column, followed by heating the gas in a gas heat exchanger gas and heater, expanding the heated gas in the turbine of the turbo-expander unit (TDA), cooling the gas in the gas-gas heat exchanger, compressing the entire gas flow in the compressor part of the TDA, and the gas temperature in front of the TDA turbine is provided at such a level that the gas pressure at the outlet of the compressor room part of the TDA exceeded the gas pressure in front of the TDA turbine. 52. The method according to claim 51, characterized in that after compressing the gas in the compressor part of the TDA and / or after treating the gas in the unit for separating target natural gas fractions from natural gas, the gas is additionally subjected to at least one additional treatment, including gas heating in additional gas-gas heat exchangers and / or additional heaters, expansion of heated gas in the DTDA turbine, gas cooling and gas compression in the DTDA compressor part. 53. The method according to claim 51 or 52, characterized in that the TDA and/or DTDA turbine includes at least two turbine impellers. 54. The method according to claim 51 or 52, characterized in that the compressor part of the TDA and/or DTDA includes at least two compressor impellers. 55. The method according to claim 53, characterized in that the gas is additionally heated before each turbine impeller. 56. The method according to claim 54, characterized in that the gas is additionally cooled before each compressor impeller. 57. The method according to claim 51, characterized in that the gas is transferred between the unit for extracting target natural gas fractions from natural gas and the TDA by means of a gas pipeline. 58. The method according to claim 51, characterized in that the transfer of gas between the unit for separating target natural gas fractions from natural gas and heat exchangers and heaters is carried out through a gas pipeline. 59. The method according to claim 51 or 52, characterized in that the gas temperature in front of the TDA turbine is provided at a level above 200 ° C. 60. The method according to claim 51 or 52, characterized in that the heating of natural gas in heaters is carried out due to the heat generated during the combustion of natural gas in pure oxygen.