WO2024172697A1 - Method for separating target fractions from natural gas (embodiments) - Google Patents

Abstract

The invention relates to the gas industry, and more particularly to processes for separating target fractions from gas mixtures, and can be used, in particular, for extracting propane-butane and ethane fractions, stable natural gasoline, acidic components, water, etc. from natural gas. In the present method for separating target fractions from natural gas, the treatment of the gas includes the following consecutive steps: heating natural gas in a gas-gas heat exchanger and a heater, expanding the heated natural gas in a turbine of a turboexpander unit (TU), cooling the gas in the gas-gas heat exchanger, separating target fractions from the natural gas by absorption or by adsorption or by membrane separation, and compressing the entire flow of the treated gas in a compressor part of the TU, wherein the temperature of the gas upstream of the turbine of the TU is established such that the pressure of the gas at the outlet from the compressor part of the TU exceeds the pressure of the gas upstream of the turbine of the TU. The technical result of the claimed invention is a significant decrease in capital costs and running costs at plants intended for the extraction of target fractions.

Description

METHOD OF SEPARATION OF TARGET FRACTIONS FROM NATURAL GAS (OPTIONS)

Field of technology

The invention relates to the gas industry, namely to processes for separating target fractions from gas mixtures, in particular, it can be used to extract propane-butane and ethane fractions, stable natural gasoline, acidic components, water, etc. from natural gas. Natural gases are 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

A method for processing natural gas is known from the prior art, disclosed in US Patent 4,889,545, published on 26.12.1989, 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 flows by throttling and expanding it in the turbine of a turboexpander unit (TEU), feeding all cold flows into a rectification 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 section of the TDU. Before feeding 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 compressor part of the TDA is significantly lower than the gas pressure at the entrance to the unit, therefore, an additional compressor is required at the exit from the unit, which significantly increases the capital costs of building such a unit.

The closest analogue to the claimed invention in terms of the set of essential features is the method and installation for separating target fractions from natural gas, disclosed in patent RU 2749628, published on 16.06.2021, in which gas is processed by sequentially following processes of gas compression in the main compressor, gas cooling in an air cooling apparatus, separating propane-butane and ethane fractions from gas in a low-temperature condensation unit, including the process of gas cooling in heat exchangers, separating condensed condensate from gas, expanding gas in the turbine of the main turboexpander or in a throttle, processing cooled gas and/or condensate separated from gas in a distillation column, heating gas in heat exchangers, and after gas compression in the main In the compressor, compressed gas with a temperature of at least 100°C is sent to the turbine of an additional turboexpander.

The disadvantage of this method is that the gas pressure at the outlet of such a unit (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, an additional compressor station must be installed at the outlet of the proposed unit to compress the commercial gas before feeding it 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 the unit for separating target fractions from natural gas.

Disclosure of invention

The technical problem that the claimed invention is aimed at solving is the reduction of capital costs for the construction of installations for extracting target fractions from gas mixtures, by eliminating expensive compressor stations from the equipment of such installations.

The technical result achieved by implementing the claimed invention is a significant reduction in capital and operating costs for installations designed to extract target fractions.

Below, using the example of natural gas extracted from gas or oil fields, the operating principle of the proposed method (options) will be described.

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

In the proposed method, due to a special scheme for using a turbo-expander unit, it is possible to ensure the operation of the unit for extracting target fractions from natural gas in such a way that the gas pressure at the outlet of the unit exceeds the gas pressure at the inlet of the unit. Thus, a compressor-free supply of commercial gas to the main gas pipeline is ensured. The reduction in capital costs occurs due to the fact that the cost of a turbo-expander unit (TEU) 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 of separating target fractions from natural gas, gas processing includes the following successive processes: heating the natural gas in a gas-gas heat exchanger and a heater, expansion of the heated natural gas in the turbine of a turboexpander unit (TEU), cooling the gas in a gas-to-gas heat exchanger, separating target fractions of natural gas from the natural gas by means of absorption or adsorption or membrane separation, compressing the entire flow of processed gas in the compressor section of the TDU, wherein the temperature of the gas in front of the TDU turbine is provided at such a level that the gas pressure at the outlet of the compressor section of the TDU exceeds the gas pressure in front of the TDU turbine.

In the second variant of the method for separating target fractions from natural gas, the gas processing includes the following successive processes: heating the natural gas in a gas-to-gas heat exchanger and a heater, expanding the heated natural gas in the TDA, cooling the gas in the gas-to-gas heat exchanger, partially condensing the gas using the cold of the refrigeration machine and separating the target components condensed during cooling in a separator and/or a rectification column, followed by compression of the entire gas flow in the compressor section of the TDA, wherein 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 section of the TDA exceeds the gas pressure in front of the TDA turbine.

In the third variant of the method for separating target fractions from natural gas, the gas processing includes the following successive processes: heating the gas in a gas-to-gas heat exchanger and a heater, expanding the heated gas in a turbine of a turbo-expander unit (TEU), cooling the gas in a gas-to-gas heat exchanger, compressing the entire gas flow in the compressor section of the TEU, separating target fractions of natural gas from natural gas by means of absorption or adsorption or membrane separation, wherein the gas temperature before the TEU turbine is provided at such a level that the gas pressure at the outlet of the compressor section of the TEU exceeds the gas pressure before the TEU turbine.

In the fourth variant of the method for separating target fractions from natural gas, the gas processing includes the following successive processes: heating the natural gas in a gas-to-gas heat exchanger and a heater, expanding the heated natural gas in the TDA turbine, cooling the gas in the gas-to-gas heat exchanger, compressing the entire gas flow in the compressor section of the TDA, partially condensing the gas using the cold of the refrigeration machine and separating the target components condensed during cooling in a separator and/or a rectification column, wherein 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 section of the TDA exceeds the gas pressure in front of the TDA turbine.

In the fifth variant of the method for separating target fractions from natural gas, gas processing includes the following successive processes: separating target fractions of natural gas from natural gas by absorption or adsorption or membrane separation, heating the gas in a gas-to-gas heat exchanger and a heater, expanding the heated gas in the TDA turbine, cooling the gas in at least the gas-to-gas heat exchanger, compressing the entire gas flow in the compressor section of the TDA, wherein 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 section of the TDA exceeds the gas pressure in front of the TDA turbine.

In the sixth variant of the method for separating target fractions from natural gas, the gas processing includes the following successive processes: partial condensation of the gas using the cold of the refrigeration machine and separation of the target components condensed during cooling in a separator and/or a rectification column, subsequent heating of the gas in a gas-to-gas heat exchanger and a heater, expansion of the heated gas in the turbine of a turboexpander unit (TDU), cooling of the gas in the gas-to-gas heat exchanger, compression of the entire gas flow in the compressor section of the TDU, wherein the gas temperature in front of the TDU turbine is provided at such a level that the gas pressure at the outlet of the compressor section of the TDU exceeds the gas pressure in front of the TDU turbine.

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

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

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

In all embodiments of the method, after compression of the gas in the compressor section of the TDA and/or after separation of the target fractions of natural gas from the natural gas, the gas is additionally subjected to at least one additional processing, including heating the gas in additional gas-gas heat exchangers and/or additional heaters, expansion of the heated gas in the turbine of the additional turbo-expander unit (ATEU), cooling the gas and compressing the gas in the compressor section of the ATEU. In cases where it is necessary to achieve high efficiency factors of turbines and compressor parts of the TDA and/or DTDA, it is advisable that the turbine of the TDA and/or DTDA include at least two turbine working wheels, and the compressor part of the TDA and/or DTDA include at least two compressor working wheels.

Before any turbine wheel, the gas can be additionally heated, which allows increasing the mechanical energy extraction from the turbine wheel. Before any compressor wheel, the gas can be additionally cooled, which allows increasing the degree of gas compression in the compressor wheel.

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

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

Heating of natural gas in heat exchangers and/or heaters can be carried out using heat generated during combustion of natural gas in pure oxygen. In this case, combustion of natural gas in pure oxygen will produce flue gas with a high concentration of CO2, which can be immediately pumped back into the formation at the field.

Brief description of drawing figures

The essence of the invention is explained by drawings, where: Fig. 1 shows a diagram of the proposed method according to the first and second embodiments of the method; Fig. 2 - a diagram of the proposed method according to the third and fourth embodiments of the method; Fig. 3 - a diagram of the proposed method according to the fifth and sixth embodiments of the method; Fig. 4 - a diagram of the proposed method, explaining paragraphs 2, 12, 22, 32, 42, 52 of the formula of the invention; Fig. 5 - a diagram of the proposed method, explaining the implementation of the method according to paragraphs 3, 4, 13, 14, 23, 24, 33, 34, 43, 44, 53, 54 of the formula of the invention. Fig. 6 is a diagram of the proposed method, explaining the implementation of the method according to paragraphs 5, 6, 15, 16, 25, 26, 35, 36, 45, 46, 55, 56 of the claims. Fig. 7 is a diagram of the gas processing unit in the unit for separating target fractions of natural gas from natural gas using the low-temperature condensation process, in the case of separating the SZ+ fraction (NGL). Fig. 8 is a diagram of the gas processing unit in the unit for separating target fractions of natural gas from natural gas using the low-temperature condensation process, in the case of separating water vapor from natural gas.

The following positions are indicated on the figures:

1 - input flow of natural gas,

2 - heat exchanger,

4 - heater,

6 - TDA turbine,

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

10 - compressor part of the TDA,

13 - TDA turbine with two working wheels,

14 - compressor part of the TDA with two wheels,

15 - the first turbine wheel of the TDA turbine,

16 - intermediate heater,

17 - the second working wheel of the TDA turbine,

18 - the first working wheel of the compressor part of the TDA,

19 - intercooler,

20 - the second working wheel of the compressor part of the TDA,

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 - refrigeration machine,

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 flows.

Variants of implementation of the invention

The operation of the proposed invention according to the first embodiment of the proposed method is illustrated using the example of an installation, the diagram of which is shown in Fig. 1. The input flow of natural gas 1 is heated in heat exchangers 2 and heaters 4 and expand in turbine 6 TDA. Then the gas is cooled, for example in heat exchanger 2, and processed in block 8 for separating target fractions from natural gas. After processing in block 8, the gas is compressed in compressor section 10 TDA, and the gas temperature before turbine 6 TDA is provided at such a level that the gas pressure at the outlet of compressor section 10 TDA exceeds the gas pressure before turbine section 6 TDA.

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

In absorbers, a gas mixture is separated into its component parts by dissolving one or more components of this mixture in a liquid called an absorbent. An absorber is usually a column with packing or plates, into the lower part of which gas is fed, and into the upper part - liquid; gas is removed from the absorber from the top, and liquid - from the bottom. In this case, the target fractions are absorbed by the liquid. In some cases, gas bubbles through the absorbent poured into the column in the absorber. Detailed information on the designs of various absorbers can be found in the book by Ramm V. M. Adsorption of gases. 2nd ed., revised. and add. Moscow, "Chemistry", 1976.

An adsorber is a device for absorbing dissolved or gaseous substances by the surface layer of a solid body, called an adsorbent (absorbent). An adsorber is usually a vertical or horizontal vessel filled with a solid adsorbent. Activated carbon, silica gels, zeolites, clayey 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, while during chemical adsorption, new chemical compounds are formed. One of the features of adsorbers is the need for continuous or periodic regeneration. Adsorbent regeneration is usually carried out by heating it and/or blowing gas. Detailed information on the designs of various adsorbers can be found in the book by N.V. Keltsev, Fundamentals of Adsorption Technology, Moscow, 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 original natural gas is divided into two flows - into target fractions penetrating through the membrane (permeate) and into purified natural gas (retentate). Two-stage processing of natural gas is often used, in which the permeate is processed in the second stage also using membranes. Membranes are made of various materials, such as polymers, nanoporous, zeolite or silica materials, etc. Detailed information 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, Moscow "Chemistry", 1991.

In accordance with the second embodiment of the proposed method, in block 8 for separating target fractions from natural gas, gas processing 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 separated in a separator and/or a rectification 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 refrigeration machine 28. The hydrocarbon condensate condensed during the cooling of the gas is separated from the gas in the separator 29. Then the separated condensate is heated in the recuperative heat exchanger 26 and sent to the rectification column 31. From the bottom of the column 31, the target fractions 25 are collected, from the top of the column, the weathering gases are collected, which are compressed with the help of the compressor 30 and the gas is fed before the separator 29.

As one of the possible applications of the proposed method, Table 1 shows the parameters of the main flows for the unit shown in Fig. 1 for the case of extracting a fraction consisting of hydrocarbon components heavier than propane (SZ+, NGL) from associated gas. The input flow 1 of natural gas with a pressure of 8.0 MPa and a temperature of 30°C is heated in heat exchanger 2 and heater 4 to a temperature of 287.9°C. Then, the heated gas expands in the turbine of the turboexpander unit to a pressure of 5.0 MPa and is cooled in heat exchanger 2 to a temperature of 35°C and sent to block 8 for separating the target fractions of natural gas from natural gas. In which, using absorbers (the first embodiment of the proposed method); or adsorbers and/or membranes (the 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 separated in a separator and/or a rectification column (the third embodiment of the proposed method), the target fractions of 25 natural gas SZ+ (NGL) are separated from the natural gas. The gas purified from the target fractions 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 natural gas are separated from the inlet gas with a flow rate of 910.8 tons/day target fractions SZ+. In this case, the gas pressure of gas 11 at the outlet of the compressor part of the TDA exceeds the pressure of gas 5 before the turbine part of the TDA.

In block 8, to isolate the target fractions of SZ+ from natural gas, in this specific example, it is advisable to use:

- gasoline, kerosene, solar distillate, or fractions included in natural gas, as an absorbent, 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 version of the proposed method),

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

- as a refrigeration machine, propane, freon, ammonia refrigeration machines, in the case of using refrigeration machines (the third version 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 manufactured in the form of shell-and-tube, twisted, plate and other devices.

Heaters 4 are heat exchangers in which gas heating is performed by transferring heat from a hot heat carrier, such as, for example, hot oil, steam, flue gases, hot gas, hot liquid, etc. In this case, heaters 4 can consist of several heat exchangers with different heat carriers. In terms of hardware, heaters 4 can be implemented both in one block with a heat carrier heating furnace, and separately. Hot gases present in the plant can serve as a hot gas used as a heat carrier, in particular, for example, hot gases formed after gas compression in the compressor part of the TDA (stream 11).

A turboexpander unit (TDU) is a machine in which either the turbine and compressor part are mechanically connected, with the mechanical energy from the turbine being transferred to the compressor part, or the turbine and compressor part are electrically connected, with the turbine connected to an electric generator, and the compressor part is connected to an electric motor (electric 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 reducers. Each turbine and compressor part of the TDU can be made according to a radial, axial and radial-axial scheme. In turn, in the case of using a radial scheme, both centripetal and centrifugal working wheels and guide vanes. Since the turbine and compressor parts must not contain mechanical and liquid impurities at the inlet, the TDA must be equipped with devices (separators, filters) that process the gas before feeding the gas to the turbines and compressor parts.

Table 1

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

Cooling of gas before the compressor section of the 10 TDA can also be carried out in an air cooling apparatus.

In block 8, the separation of target fractions can be carried out using absorbers, adsorbers, membrane separation, or by partial condensation of gas using the cold of a refrigeration machine and separation target components condensed during cooling in a separator and/or rectification 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 Fig. 2 for the case of extracting water vapor from associated gas (gas drying). The input flow 1 of natural gas with a pressure of 5.0 MPa and a temperature of 30°C is heated in heat exchanger 2 and heater 4 to a temperature of 306.6°C. Then, the heated gas expands in the turbine of the turboexpander 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 compressor section of the TDA to a pressure of 6.0 MPa. The compressed gas is sent to block 8 for separating the target fractions of natural gas from natural gas. In which, 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, water is separated from natural gas 25. In this example, 800 kg/day of water is separated from the input gas with a flow rate of 730.5 tons/day of natural gas. In this case, the gas pressure at the outlet of the compressor section 10 TDA exceeds the gas pressure in front of the turbine 6 TDA.

Table 2

In block 8, for the separation of water vapor from natural gas, in this specific example, it is advisable to use: ethylene glycol (EG), diethylene glycol (DEG), triethylene glycol (TEG), methanol (the fourth variant of the proposed method) as an absorbent, - as an adsorbent, aluminum oxide, zeolites, silica gel, etc. (the fifth variant of the proposed method),

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

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

For the example under consideration, one of the possible block 8 schemes 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 directed to be heated in the recuperative heat exchanger.

The operation of the proposed 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 flow of natural gas 1 is processed in the unit 8 for separating target fractions from natural gas, heated in heat exchangers 2 and heaters 4 and expanded in the turbine 6 of the TDA. Then the gas is cooled, for example in the heat exchanger 2, and compressed in the compressor section 10 of the TDA, wherein 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 section 10 of the TDA exceeds the gas pressure in front of the turbine section 6 of the TDA.

Cooling of gas before the compressor section of the 10 TDA can also be carried out in an air cooling apparatus.

As one of the possible applications of the proposed method, Table 3 shows the parameters of the main flows for the installation shown in Fig. 3 for the case of extracting acidic components H2S and CO2 from associated gas. The input flow 1 of natural gas with a pressure of 6.0 MPa and a temperature of 30°C is directed to the unit 8 for extracting acidic components H2S and CO2 from natural gas, in which the flow 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. Then the heated gas expands in the turbine of the turboexpander unit to a pressure of 4.0 MPa and is cooled in heat exchanger 2 to a temperature of 50°C and is compressed in the compressor part of the TDA to a pressure of 6.5 MPa. Table 3

In block 8, the separation of acidic components from natural gas is carried out 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 rectification column; the separation of acidic components H2S and CO2 from natural gas occurs. In this case, the gas pressure at the outlet of the compressor section 10 TDA exceeds the gas pressure in front of the turbine 6 TDA.

In block 8, to separate the acidic components H2S and CO2 from natural gas, in this specific example, it is advisable to use:

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

- as an adsorbent, activated carbon, molecular sieves, Zn oxides or Cu oxides, zinc-copper absorbent, synthetic sorbent for cleaning gases from hydrogen sulfide with a content of 35-95% manganese oxides, or other innovative adsorbents (the eighth variant of the proposed method),

- as membranes, elastic membrane, polymer 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 variant of the proposed method), For the example under consideration, one of the possible block 8 schemes 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 directed to be heated in the recuperative heat exchanger.

In cases where a significant increase in the gas pressure at the outlet of the plant is required, Fig. 4 shows an embodiment of the method according to paragraph 2, 12, 22, 32, 42, 52 of the invention formula, in which after gas compression in the compressor section 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 the additional turboexpander unit (ATEU), cooling the gas in the heat exchanger 21, and compressing the gas in the compressor section 24 of the ATEU. Similar, at least one-time additional gas processing can also be carried out after gas processing in the unit for separating target fractions of natural gas from natural gas.

The TDA and/or DTDA turbine may include at least two turbine working wheels. Fig. 5 shows the TDA turbine 13 with two working wheels. The use of two or more turbine wheels is advisable at high gas expansion rates in the turbine, in which case the use of several working wheels allows increasing the efficiency (efficiency) of gas expansion in the turbine. This allows taking off more mechanical energy from the turbine.

The compressor section of the TDA and/or DTDA may include at least two compressor working wheels. Fig. 5 shows the compressor section of the TDA 14 with two compressor working wheels. The use of two or more compressor wheels is advisable at high gas compression ratios in the compressor section of the TDA, in which case the use of several working wheels allows increasing the efficiency (efficiency) of gas compression in the compressor section of the TDA. This allows for a higher gas compression ratio in the compressor section of the TDA.

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

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

To increase the degree of compression in the compressor section of the TDA, the gas can be additionally cooled before any compressor wheel as shown in the diagram in Fig. 6. In this diagram, after the gas is compressed in the first compressor wheel, the gas is cooled, for example, in the air cooling apparatus 19, and expanded in the second compressor wheel of the TDA.

In case of a significant distance of the TDA from the unit for separating the target fractions of natural gas from natural gas, the gas transfer between the unit for separating the target fractions of natural gas from natural gas and the TDA can be carried out by means of a long gas pipeline. Similarly, the gas transfer between the unit for separating the target fractions of natural gas from natural gas 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, the DTA and DTDA can be implemented in one housing.

The gas temperature before the TDA turbine, in some cases, is provided at a level above 200°C. As shown by experimental tests of installations based on the proposed method, currently existing turboexpander units allow providing gas pressure at the outlet of the TDA compressor section exceeding the gas pressure before the TDA turbine section, with the gas temperature level before 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 combustion of natural gas in pure oxygen. In this case, pure oxygen obtained in the air separation plant and natural gas are fed to the heater burner. When natural gas is burned in pure oxygen, the flue gases will contain mainly CO2 and water vapor. In this case, the flue gas, after preliminary processing, can be pumped into the formation, or used for other needs (for example, for the production of pure CO2 or for nutrition of plants or bacteria, in the production of protein).

Claims

Invention formula 1. A method for separating target fractions from natural gas, which includes the following successive processes of heating the natural gas in a gas-to-gas heat exchanger and a heater, expanding the heated natural gas in a turbine of a turboexpander unit (TDU), cooling the gas in a gas-to-gas heat exchanger, separating the target fractions of natural gas from the natural gas by means of absorption, or adsorption, or membrane separation, compressing the entire flow of processed gas in the compressor section of the TDU, wherein the temperature of the gas in front of the TDU turbine is provided at such a level that the gas pressure at the outlet of the compressor section of the TDU exceeds the gas pressure in front of the TDU turbine. 2. The method according to claim 1, characterized in that after compression of the gas in the compressor section of the TDA and/or after separation of the target fractions of natural gas from the natural gas, the gas is additionally subjected to at least one additional processing, including heating the gas in additional gas-gas heat exchangers and/or additional heaters, expansion of the heated gas in the turbine of the additional turbo-expander unit (ATEU), cooling the gas and compressing the gas in the compressor section of the ATEU. 3. The method according to claim 1 or 2, characterized in that the TDA and/or DTDA turbine includes at least two turbine working wheels. 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 paragraph 3, characterized in that the gas is additionally heated before each turbine wheel. 6. The method according to paragraph 4, characterized in that the gas is additionally cooled before each compressor wheel. 7. The method according to item 1, characterized in that the transfer of gas between the unit for separating target fractions of natural gas from natural gas and the TDA is carried out by means of a gas pipeline. 8. The method according to paragraph 1, characterized in that the transfer of gas between the unit for separating target fractions of natural gas from natural gas and the heat exchangers and heaters is carried out by means of a gas pipeline. 9. The method according to paragraph 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 paragraph 1 or 2, characterized in that the heating of natural gas in the 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 the following successive processes of heating the natural gas in a gas-to-gas heat exchanger and a heater, expanding the heated natural gas in the TDA, cooling the gas in the gas-to-gas heat exchanger, partially condensing the gas using the cold of a refrigeration machine and separating the target components condensed during cooling in a separator and/or a rectification column, followed by compression of the entire gas flow in the compressor section of the TDA, wherein 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 section of the TDA exceeds the gas pressure in front of the TDA turbine. 12. The method according to claim 11, characterized in that after compression of the gas in the compressor section of the TDA and/or after processing the gas in the unit for separating target fractions of natural gas from natural gas, the gas is additionally subjected to at least one additional processing, including heating the gas in additional gas-to-gas heat exchangers and/or additional heaters, expanding the heated gas in the DTDA turbine, cooling the gas and compressing the gas in the compressor section of the DTDA. 13. The method according to claim 11 or 12, characterized in that the TDA and/or DTDA turbine includes at least two turbine working wheels. 14. The method according to item 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 item 13, characterized in that the gas is additionally heated before each turbine wheel. 16. The method according to item 14, characterized in that the gas is additionally cooled before each compressor wheel. 17. The method according to item 11, characterized in that the transfer of gas between the unit for separating target fractions of natural gas from natural gas and the TDA is carried out by means of a gas pipeline. 18. The method according to paragraph 11, characterized in that the transfer of gas between the unit for separating target fractions of natural gas from natural gas and the heat exchangers and heaters is carried out by means of a gas pipeline. 19. The method according to item 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 paragraph 11 or 12, characterized in that the heating of natural gas in the heaters is carried out using heat generated during the combustion of natural gas in pure oxygen. 21. A method for separating target fractions from natural gas, which includes the following successive processes of heating the gas in a gas-to-gas heat exchanger and a heater, expanding the heated gas in a turbine of a turboexpander unit (TDU), cooling the gas in a gas-to-gas heat exchanger, compressing the entire gas flow in the compressor section of the TDA, separating target fractions of natural gas from the natural gas by means of absorption, or adsorption, or membrane separation, wherein the temperature of the gas in front of the TDA turbine is provided at such a level that the gas pressure at the outlet of the compressor section of the TDA exceeds the gas pressure in front of the TDA turbine. 22. The method according to item 21, characterized in that after compression of the gas in the compressor section of the TDA and/or after processing the gas in the unit for separating target fractions of natural gas from natural gas, the gas is additionally subjected to at least one additional processing, including heating the gas in additional gas-to-gas heat exchangers and/or additional heaters, expanding the heated gas in the DTDA turbine, cooling the gas and compressing the gas in the compressor section of the DTDA. 23. The method according to item 21 or 22, characterized in that the TDA and/or DTDA turbine includes at least two turbine working wheels. 24. The method according to item 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 item 22, characterized in that the gas is additionally heated before each turbine wheel. 26. The method according to item 23, characterized in that the gas is additionally cooled before each compressor wheel. 27. The method according to item 21, characterized in that the transfer of gas between the unit for separating target fractions of natural gas from natural gas and the TDA is carried out by means of a gas pipeline. 28. The method according to item 21, characterized in that the transfer of gas between the unit for separating target fractions of natural gas from natural gas and the heat exchangers and heaters is carried out by means of a gas pipeline. 29. The method according to paragraph 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 paragraph 1 or 2, characterized in that the heating of natural gas in the heaters is carried out using heat generated during the combustion of natural gas in pure oxygen. 31. A method for separating target fractions from natural gas, which includes the following successive processes of heating the natural gas in a gas-to-gas heat exchanger and a heater, expanding the heated natural gas in a TDA turbine, cooling the gas in a gas-to-gas heat exchanger, compressing the entire gas flow in the compressor section of the TDA, partially condensing the gas using the cold of a refrigeration machine and separating the target components condensed during cooling, in 18 separator and/or rectification column, wherein the gas temperature before the TDA turbine is provided at such a level that the gas pressure at the outlet of the TDA compressor section exceeds the gas pressure before the TDA turbine. 32. The method for separating target fractions from natural gas according to paragraph 31, characterized in that after compression of the gas in the compressor section of the TDA and/or after processing the gas in the unit for separating target fractions of natural gas from natural gas, the gas is additionally subjected to at least one additional processing, including heating the gas in additional gas-to-gas heat exchangers and/or additional heaters, expanding the heated gas in the DTDA turbine, cooling the gas and compressing the gas in the compressor section of the DTDA. 33. The method according to paragraph 31 or 32, characterized in that the TDA and/or DTDA turbine includes at least two turbine working wheels. 34. The method according to paragraph 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 paragraph 32, characterized in that the gas is additionally heated before each turbine wheel. 36. The method according to item 34, characterized in that the gas can be additionally cooled before each compressor wheel. 37. The method according to paragraph 31, characterized in that the transfer of gas between the unit for separating target fractions of natural gas from natural gas and the TDA is carried out by means of a gas pipeline. 38. The method according to paragraph 31, characterized in that the transfer of gas between the unit for separating target fractions of natural gas from natural gas and the heat exchangers and heaters is carried out by means of a gas pipeline. 39. The method according to paragraph 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 paragraph 31 or 32, characterized in that the heating of natural gas in the heaters is carried out using heat generated during the combustion of natural gas in pure oxygen. 41. A method for separating target fractions from natural gas, which includes the following successive processes of separating target fractions of natural gas from natural gas by means of absorption, or adsorption, or membrane separation, heating the gas in a gas-to-gas heat exchanger and a heater, expanding the heated gas in a TDA turbine, cooling the gas at least in the gas-to-gas heat exchanger, compressing the entire gas flow in the compressor section of the TDA, wherein the temperature of the gas in front of the TDA turbine is provided at such a level that the gas pressure at the outlet of the compressor section of the TDA exceeds the gas pressure in front of the TDA turbine. 19 42. The method according to item 41, characterized in that after compression of the gas in the compressor section of the TDA and/or after processing the gas in the unit for separating target fractions of natural gas from natural gas, the gas is additionally subjected to at least one additional processing, including heating the gas in additional gas-to-gas heat exchangers and/or additional heaters, expanding the heated gas in the DTDA turbine, cooling the gas and compressing the gas in the compressor section of the DTDA. 43. The method according to paragraph 41 or 42, characterized in that the TDA and/or DTDA turbine includes at least two turbine working wheels. 44. The method according to paragraph 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 item 42, characterized in that the gas is additionally heated before each turbine wheel. 46. The method according to paragraph 43, characterized in that the gas is additionally cooled before each compressor wheel. 47. The method according to paragraph 41, characterized in that the transfer of gas between the unit for separating target fractions of natural gas from natural gas and the TDA is carried out by means of a gas pipeline. 48. The method according to paragraph 41, characterized in that the transfer of gas between the unit for separating target fractions of natural gas from natural gas and the heat exchangers and heaters is carried out by means of a gas pipeline. 49. The method according to paragraph 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 paragraph 41 or 42, characterized in that the heating of natural gas in the heaters is carried out using heat generated during the combustion of natural gas in pure oxygen. 51. A method for separating target fractions from natural gas, which includes the following successive processes of partial condensation of gas using the cold of a refrigeration machine and separation of target components condensed during cooling in a separator and/or a rectification column, subsequent heating of the gas in a gas-to-gas heat exchanger and a heater, expansion of the heated gas in a turbine of a turboexpander unit (TDU), cooling of the gas in a gas-to-gas heat exchanger, compression of the entire gas flow in the compressor section of the TDU, wherein the temperature of the gas in front of the TDU turbine is provided at such a level that the gas pressure at the outlet of the compressor section of the TDU exceeds the gas pressure in front of the TDU turbine. 52. The method according to item 51, characterized in that after compression of the gas in the compressor part of the TDA and/or after processing the gas in the unit for extracting target products from natural gas 20 fractions of natural gas, the gas is additionally subjected to at least one additional processing, including heating the gas in additional gas-gas heat exchangers and/or additional heaters, expanding the heated gas in the DTDA turbine, cooling the gas and compressing the gas in the compressor section of the DTDA. 53. The method according to paragraph 51 or 52, characterized in that the TDA and/or DTDA turbine includes at least two turbine working wheels. 54. The method according to paragraph 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 paragraph 53, characterized in that the gas is additionally heated before each turbine wheel. 56. The method according to paragraph 54, characterized in that the gas is additionally cooled before each compressor wheel. 57. The method according to paragraph 51, characterized in that the transfer of gas between the unit for separating target fractions of natural gas from natural gas and the TDA is carried out by means of a gas pipeline. 58. The method according to paragraph 51, characterized in that the transfer of gas between the unit for separating target fractions of natural gas from natural gas and the heat exchangers and heaters is carried out by means of a gas pipeline. 59. The method according to paragraph 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 paragraph 51 or 52, characterized in that the heating of natural gas in the heaters is carried out using heat generated during the combustion of natural gas in pure oxygen. 21