RU2781149C1 - Method for compressing the stripped gas (variants) - Google Patents

Abstract

FIELD: gas industry.

SUBSTANCE: invention relates to low-temperature gas processing and can be used at gas processing plants and liquefied natural gas plants. The method includes heating of the stripped gas obtained by separating hydrocarbons C_2+higher from the dried gas during its low-temperature condensation, expanding and rectification, dividing the heated flow of stripped gas into two parts and compressing them. After compression, the second part of the flow of the stripped gas is cooled and then combined with the first stream of the stripped gas pre-cooled after compression, after which the combined flow of the stripped gas is directed for further use. In the second variant of the method, the compression of the second part of the flow of the stripped gas is carried out in at least two stages, while a part of the first flow of the stripped gas the pre-cooled after compression is connected to the second part of the flow of the stripped gas coming out of the first stage of compression, after which the combined flow of the stripped gas is fed to the second stage of compression and after cooling is directed to further usage.

EFFECT: increase in the reliability of the compressor equipment and reduction of operating costs.

6 cl, 7 dwg

Description

The present invention relates to the technique and technology of low-temperature gas processing and can be used at gas processing plants and liquefied natural gas plants, where stripped gas is compressed.

A known method of gas compression (see Eurasian patent No. 4469, F25J 3/02, pub. 04/29/2004), according to which the residual (leaned) gas is heated in a heat exchanger, and then subjected to the first compression in the first compressor connected to the turbine, to obtain a compressed fraction which is subjected to a second compression in a second compressor fed by a gas turbine to obtain another compressed fraction which is then air-cooled in an air cooler to obtain a compressed and cooled residual gas fraction.

The disadvantage of the known method is the lack of cooling of the stripped gas after the first compression in the first compressor connected to the turbine, which leads to an uncontrolled increase in the temperature of the compressed gas in the event of an anti-surge line opening and reduces the reliability of the compressor equipment. Also, a disadvantage of the known method is the higher cost of the distillation column (demethanizer), since its design pressure is determined by the process mode with the compressor equipment inoperative, connected to the expander turbine, when the lack of operation of the compressor equipment needs to be compensated by a higher pressure in the demethanizer.

The closest in technical essence and the achieved result is a method for compressing the stripped gas (see RF patent for the invention No. 2626270, F25J 3/00, pub. 07/25/2017), including heating the stripped gas obtained by separating hydrocarbons С ₂₊ above from the dried gas during its low-temperature condensation, expansion and rectification, compression of the stripped gas and cooling of the stripped gas, at that, before compressing the stripped gas, a part of the heated stream of the stripped gas is taken and its parallel compression is carried out, after which the streams of the compressed stripped gas are combined and sent for cooling.

Common features of the known and proposed method are:

- heating of the stripped gas in a recuperative heat exchanger obtained by separating hydrocarbons С _{2+ above} from the dried gas during its low-temperature condensation, expansion and rectification;

- separation of the heated stream of stripped gas into two parts;

- compression of the first and second parts of the stripped gas stream;

- cooling of stripped gas.

The disadvantage of the known method is the impossibility of maintaining an acceptable temperature in the compressor equipment when opening the anti-surge line due to the lack of cooling of the first stream of offgas after compression until it is combined with the second part of the stream of offgas, which leads to an uncontrolled increase in the temperature of the compressed offgas and, as a result, a decrease in reliability of the compressor equipment.

The technical result of the proposed method is to increase the reliability of the compressor equipment and reduce operating costs.

The specified technical result is achieved due to the fact that in the method of compression of the stripped gas according to the first variant, including heating the stripped gas obtained by separating hydrocarbons С _{2+ above} from the dried gas during its low-temperature condensation, expansion and rectification, the division of the heated stream of stripped gas into two parts, compression of the first and second part of the strip gas stream, cooling of the strip gas, according to the invention, after compression, the second part of the strip gas stream is cooled and then combined with the first strip gas stream pre-cooled after compression, after which the combined strip gas stream is sent for further use .

In addition, the compression of the second part of the stripped gas stream is carried out in at least two stages using intermediate cooling between the stages.

In addition, the compression of the first part of the stripped gas stream is carried out in at least two stages.

In addition, between the compression stages of the first part of the stripped gas flow, it is cooled.

In addition, the expansion of the dried gas is carried out in at least two stages with intermediate separation between the stages.

Also, the specified technical result is achieved by the fact that in the method of compressing the stripped gas according to the second variant, including heating the stripped gas obtained by separating C _{2+ higher} hydrocarbons from the dried gas during its low-temperature condensation, expansion and rectification, dividing the heated stream of stripped gas into two parts , compression of the first and second part of the stripped gas stream, cooling of the stripped gas, according to the invention, compression of the second part of the stripped gas stream is carried out in at least two stages, while part of the pre-cooled after compression of the first stripped gas stream is connected to the second part of the stream stripped gas leaving the first compression stage, after which the combined stream of stripped gas is fed to the second compression stage and, after cooling, is sent for further use.

The cooling of the second part of the stripped gas stream after its compression and its subsequent combination with the first stream of stripped gas already pre-cooled after compression according to the first and second versions of the proposed method allows, due to separate cooling of the first and second parts of the stripped gas stream, to avoid an uncontrolled increase in the temperature of the compressed gas in the compressor room. equipment and thereby improve the reliability of its operation.

Compressing the second part of the stripped gas stream in two or more stages, using, if necessary, intermediate cooling between the stages, can reduce the specific compression load and increase the consumption of the second part of the stripped gas stream, as well as reduce compression costs.

Expanding the dry gas in two or more stages with intermediate separation between the stages allows to achieve, if necessary, a higher degree of gas compression, as well as to reduce the specific compression load and energy costs for compression.

Thus, the claimed set of features of the proposed method according to the first and second options makes it possible to increase the reliability of the compressor equipment, reduce the operating costs for compression, and also, due to the constant pressure in the demethanizer, regardless of the operation of the compressor equipment, makes it possible to reduce the mass of the demethanizer and, as a result, capital costs .

Figures 1-7 show possible options for a low-temperature gas processing unit, on which the proposed method is carried out, where in Fig. 1-6 shows the proposed method for compressing the stripped gas according to the first variant, and Fig. 7 - the proposed method according to the second variant.

The installation according to the first version of the proposed method includes (see Fig. 1) a pipeline for supplying dried gas to a recuperative heat exchanger 1 connected to a separator 2, the outlet of the upper stream from which is connected to a turbo-expander unit (hereinafter referred to as TDA) 3 and further to a demethanizer 4 , and the outlet of the lower product from the separator 2 is connected to the throttle 5 and further to the demethanizer 4.

The demethanizer 4 is provided in the upper part with an outlet for the stripped gas, and in the lower part with an outlet for the C ₂₊ fraction. Reboiler 6 is installed at the bottom of the demethanizer.

The outlet of the stripped gas from the demethanizer 4 is connected to the recuperative heat exchanger 7 and further to the recuperative heat exchanger 1.

The outlet of the stripped gas from the recuperative heat exchanger 1 is connected to the compressor part 8 of TDA 3 to supply the first part of the stripped gas stream for compression, and is also connected to the compressor 9 to supply the second part of the stripped gas stream to compression.

The outlet of the first part of the stream of stripped gas from the compressor part 8 TDA 3 is connected to the air cooler (hereinafter referred to as ABO) 10 and further to the pipeline 11 for gas removal for further use.

The outlet of the second part of the stripped gas stream from the compressor 9 is connected to the air cooler 12, then to the cooled first stripped gas stream leaving the air cooler 10, and then to the pipeline 11 for gas removal for further use.

The pipeline 11 is equipped with an additional off-gas outlet 13 connected in series with recuperative heat exchangers 1 and 7, throttle 14 and demethanizer 4.

Also, the pipeline 11 is equipped with an anti-surge line (shown in dotted lines in Figures 1-7) for the possibility of supplying gas from the discharge of the compressor part 8 of the TDA 3 to its suction and maintaining the required gas pressure at the suction.

The outlet of the upper flow from the separator 2 can be equipped with an additional outlet 15 connected to the recuperative heat exchanger 7, throttle 16 and further to the demethanizer 4.

If necessary, the installation may contain several stages of compression of the second part of the stripped gas stream using intermediate cooling between the stages. In FIG. 2 shows a variant with two compression stages, where the first compression stage contains compressor 9 and ABO 12, and the second compression stage contains compressor 17 and ABO 18.

If necessary, the installation may contain several stages of compression of the first part of the stripped gas stream. In FIG. Figure 3 shows a variant with two stages of strip gas compression in two compressor parts 8 of TDA 3 (see Fig. 3).

If necessary, the unit can be equipped with an additional air cooler 22 installed between the compression stages of the first part of the stripped gas stream (see Fig. 4).

The plant can be equipped with at least two dry gas expansion stages with intermediate separation between the stages. In FIG. 5 shows an option where the first stage of expansion contains the compressor part 8 and TDA 3, and the second stage contains the compressor part 19 and TDA 20, between which an additional separator 21 is installed.

In FIG. 6 shows a variant with two stages of dry gas expansion using intermediate separation between stages and two stages of compression of the first strip gas stream using cooling between compression stages (see Fig. 6).

If there are several stages of dry gas expansion, TDA can be installed on different shafts (see Fig. 5) or on one shaft (not shown in Fig.).

The installation according to the second variant of the proposed method (see Fig. 7) is equipped with an outlet 23 of a part of the first stream of offgas after its compression in the compressor part 8 and cooling in the air cooler 10, which is connected to the second part of the stream of offgas after its compression in the compressor 9 before the compressor 17.

The plant is also equipped with all the necessary shut-off and control devices and pumping equipment (not shown in Fig.).

The method according to the first variant is carried out on the installation as follows (see Fig. 1-6).

The purified and dried gas enters the low-temperature processing unit into the recuperative heat exchanger 1 for its cooling and partial condensation due to heat exchange with the stripped gas stream. Partially condensed gas from the recuperative heat exchanger 1 is sent to the separator 2, in which the gas and low-temperature condensate are separated. Further, low-temperature condensate from separator 2 is throttled in throttle 5 and sent to demethanizer 4, and the gas is sent to TDA 3 and then to demethanizer 4.

If a high degree of extraction of hydrocarbons С2 _+higher (or _С3+higher ) is required, part of the gas from the separator 2, bypassing the TDA 3, can be sent via an additional outlet 15 to the recuperative heat exchanger 7 for cooling and condensation and then fed to the irrigation of the demethanizer 4.

In the demethanizer 4, the top product is stripped gas, and the bottom product is the C _2+higher (or _C3+higher ) hydrocarbon fraction, which is sent for further processing.

The stripped gas is sent to the recuperative heat exchanger 7, then to the recuperative heat exchanger 1, in which the stripped gas stream is heated, after which the heated stripped gas stream is divided into two streams.

The first part of the stripped gas flow is sent for compression to the compressor part 8 TDA 3. The power of the compressor part 8 TDA 3 is determined by the amount of energy generated by reducing the gas pressure in TDA 3. The stripped gas in the compressor part 8 TDA 3 is compressed (compressed) to the required pressure . The proportion of gas sent to the compressor part 8 of TDA 3 is determined based on the amount of energy generated by reducing the gas pressure in TDA 3, so that the pressure of the stripped gas after the compressor part 8 of TDA 3 corresponds to the required pressure.

The second part of the stripped gas flow enters the compressor 9 for compression. The amount of this flow is not less than 15% and not more than 85% of the total stripped gas flow and is determined by calculation depending on:

- power of TDA 3, determined by the required degree of extraction of hydrocarbons С _{2+ higher} (or С _3+higher ) (the higher the degree of extraction of hydrocarbons С _{2+ higher} (or С _3+higher ), the higher the power of TDA 3 and the greater the amount of stripped gas is sent to the compressor part 8 of TDA 3 and a smaller amount of stripped gas is sent to compressor 9 for compression);

- compressor compression ratio (absolute pressure after the compressor divided by absolute pressure before the compressor), determined by the required pressure of commercial stripped gas. Compressing the second part of the stripped gas stream is expedient when the compression ratio of the stripped gas compressor is from 1.2 to 4.

The second part of the stripped gas stream is compressed by the compressor 9 to the required pressure of the commercial stripped gas corresponding to the pressure of the first part of the stripped gas leaving the compressor part 8 of TDA 3. After the compressor 9, the second part of the stripped gas flow is cooled in the ACU 12 and combined with the already pre-cooled in the ACU 10 by the first portion of the compressed gas stream. Next, the combined stream of stripped gas through pipeline 11 is sent for further use.

If a high degree of extraction of hydrocarbons C _{2+ above} (or C _{3 + above} ) is required, a part of the stream of stripped gas through the outlet 13 can be sent for cooling to the recuperative heat exchangers 1, 7 and then through the throttle 14 be fed to the irrigation of the demethanizer 4, which allows you to remove part of the stripped gas gas for cooling and condensation, in order to then use the condensed stream as a demethanizer reflux to increase the recovery of target hydrocarbons.

If the compression of the second part of the stripped gas stream is impossible or impractical to be carried out in one stage, then the second part of the stripped gas stream is compressed in at least two stages using intermediate cooling between the stages (see Fig. 2). The compression of the lean gas in two or more stages depends on how much the temperature of the lean gas stream increases during its compression and whether it will be possible to pre-cool this stream when it is compressed in two or more stages.

If the compression of the first part of the stripped gas stream is impossible or impractical to be carried out in one stage, then the first part of the stripped gas stream is compressed in at least two stages (see Fig. 3). If necessary, after each stage of compression of the first part of the stripped gas stream, it is cooled (see Fig. 4).

If necessary (when it is technically impossible or impractical to use one stage), the dried gas is expanded in at least two stages with intermediate separation between the stages (see Fig. 5).

If necessary (when it is technically impossible or impractical to use one stage), the expansion of the dried gas in at least two stages and the compression of the first stripped gas stream in at least two stages can be carried out simultaneously using intermediate separation between the expansion stages and cooling between the compression stages. (see Fig. 6).

The method according to the second variant is carried out on the installation as follows (see Fig. 7).

The purified and dried gas enters the low-temperature processing unit into the recuperative heat exchanger 1 for its cooling and partial condensation due to heat exchange with the stripped gas stream. Partially condensed gas from the recuperative heat exchanger 1 is sent to the separator 2, in which the gas and low-temperature condensate are separated. Further, low-temperature condensate from separator 2 is throttled in throttle 5 and sent to demethanizer 4, and the gas is sent to TDA 3 and then to demethanizer 4.

If a high degree of extraction of hydrocarbons С2 _+higher (or _С3+higher ) is required, part of the gas from the separator 2, bypassing the TDA 3, can be sent via an additional outlet 15 to the recuperative heat exchanger 7 for cooling and condensation and then fed to the irrigation of the demethanizer 4.

In the demethanizer 4, the top product is stripped gas, and the bottom product is the C _2+higher (or _C3+higher ) hydrocarbon fraction, which is sent for further processing.

The stripped gas is sent to the recuperative heat exchanger 7, then to the recuperative heat exchanger 1, in which the stripped gas stream is heated, after which the heated stripped gas stream is divided into two streams.

The first part of the stripped gas flow is sent for compression to the compressor part 8 of the TDA 3, in which it is compressed (compressed) to the required pressure and then goes to the AVO 10 for cooling.

The second part of the stripped gas flow enters the compressor 9 for compression, in which it is compressed to the required pressure of the commercial stripped gas corresponding to the pressure of the first part of the stripped gas leaving the compressor part 8 of the TDA 3.

After cooling in AVO 10, the first part of the stripped gas stream is divided into two streams, one of which is sent to the recuperative heat exchanger 1, then to the recuperative heat exchanger 7 and then through the throttle 14 enters the upper part of the demethanizer 4, and the other stream is connected to the second one through the outlet 23 part of the stream of stripped gas leaving the compressor 9, after which the combined stream is sent for compression to the compressor 17, then cooled in the air cooler 12 and then through the pipeline 11 is sent for further use.

For examples, calculation schemes of the process of low-temperature gas processing were used with calculated data obtained using the HYSYS computer simulation program.

To determine the flow rate of stripped gas flows sent to the TDA compressor part and for compression into the compressor, the following initial data were used:

- gas parameters at the TDA inlet (temperature, pressure, flow rate, composition) were determined by measuring or calculating previous technological stages;

- the pressure at the TDA outlet was selected based on the required degree of gas stripping;

- the TDA power was calculated according to the gas parameters at the TDA inlet and outlet;

- the processing of gas and the condensate released from it in the demethanizer was modeled, based on the requirement for the degree of gas stripping and the requirements for liquid products of the gas processing unit;

- Waste gas cold recovery was simulated based on the results of the demethanizer simulation and the requirements for cooling the processed feed gas as a result of cold recovery;

- the required pressure at the outlet of the stripped gas compressors was calculated based on the requirements for commercial stripped gas and its possible pressure losses;

- the amount of gas compressed by the compressor associated with the TDA was calculated based on the calculated capacity of the TDA, the parameters of the stripped gas based on the results of calculating the cold recovery of the stripped gas, the required gas pressure after compression;

- the proportion of gas sent to the compressor part of the TDA was determined as the ratio of the amount of gas compressed by this compressor to the total amount of stripped gas. Example 1 (see Fig. 1).

Purified and dried gas with a temperature of 22°C and a pressure of 6.47 MPa g. (hereinafter, excess pressure is given everywhere) in the amount of 800750 kg/h was sent to the recuperative heat exchanger 1, in which the gas was cooled to a temperature of minus 31.5°C and partially condensed due to heat exchange with the stream of stripped gas. Partially condensed gas from the recuperative heat exchanger 1 was then sent to separator 2, in which low-temperature condensate was separated from the gas at a temperature of minus 31.5°C and a pressure of 6.42 MPa.

Low-temperature condensate from separator 2 in the amount of 27526.97 kg/h was throttled to a pressure of 4.3 MPa and then, with a temperature of minus 43.79°C, was sent to demethanizer 4.

Gas from separator 2 in the amount of 773223.03 kg/h entered TDA 3, in which, as a result of gas expansion, the temperature and pressure of the gas decreased. The power of TDA 3 was 20330.0 kW. Gas from TDA 3 with a temperature of minus 50.26°C and a pressure of 4.3 MPa was then sent to demethanizer 4.

From the top of the demethanizer 4, the stripped gas in the amount of 762620.77 kg/h with a temperature of minus 50.31°C and a pressure of 4.3 MPa was sent to the recuperative heat exchanger 7, then to the recuperative heat exchanger 1. After heating, the stripped gas with a temperature of 13.37°C C and a pressure of 4.18 MPa was divided into two parts.

The first part of the stream of stripped gas in the amount of 648227.7 kg/h was supplied to the suction of the compressor part 8 of TDA 3, where it was compressed to the required pressure of commercial stripped gas of 7.5 MPa. After that, the gas was cooled in ABO 10 to a temperature of 25°C.

The second part of the stripped gas stream in the amount of 114393.1 kg/h was sent for compression to the compressor 9. The power of the compressor 9 was 3587.6 kW, the compression ratio of the compressor was 1.8. The stripped gas was compressed to a pressure of 7.5 MPa, after which, at a temperature of 66.04°C, it entered ABO 12 for cooling to 25°C and then combined with the already cooled first part of the stripped gas stream. The combined stream of stripped gas in the amount of 762620.77 kg/h with a temperature of 25°C and a pressure of 7.5 MPa was then sent to a further destination.

From the bottom of the demethanizer 4, the flow of hydrocarbons C _{2+ above} in the amount of 41130.0 kg/h with a temperature of 30.38°C and a pressure of 4.35 MPa entered the reboiler 6, after which part of the flow in the amount of 21863.41 kg/h returned into demethanizer 4 for heating the lower part of the column, and the other part of the flow in the amount of 19266.59 kg/h with a temperature of 99°C and a pressure of 4.35 MPa was sent for further processing. The degree of extraction of hydrocarbons WITH _2+higher in this option was 36%.

Example 2 (see Fig. 2).

Purified and dried gas with a temperature of 22°C and a pressure of 6.47 MPa g. in the amount of 800750 kg/h entered the recuperative heat exchanger 1, in which it was cooled to a temperature of minus 31.5°C and partially condensed due to heat exchange with the stream of stripped gas. Partially condensed gas from the recuperative heat exchanger 1 was sent to separator 2, in which low-temperature condensate was separated from the gas at a temperature of minus 31.5°C and a pressure of 6.42 MPa.

Low-temperature condensate from separator 2 in the amount of 27526.97 kg/h was throttled to a pressure of 3.0 MPa and, with a temperature of minus 43.79°C, was sent to demethanizer 4.

The gas from the separator 2 in the amount of 773223.03 kg/h entered the TDA 3. The power of the TDA 3 was 11055.0 kW. As a result of gas expansion in TDA 3, the gas temperature and pressure decreased. Gas from TDA 3 with a temperature of minus 68.76°C and a pressure of 3.0 MPa was then sent to demethanizer 4.

From the top of the demethanizer 4, the stripped gas in the amount of 746015.16 kg/h with a temperature of minus 67°C and a pressure of 3.0 MPa was sent to recuperative heat exchangers 7 and 1 for heating, after which with a temperature of 8.24°C and a pressure of 2.88 MPa was divided into two parts.

The first part of the stream of stripped gas in the amount of 111902.3 kg/h was supplied to the suction of the compressor part 8 of TDA 3, where it was compressed to the required pressure of commercial stripped gas, which was 13.5 MPa. After that, the gas was cooled in ABO 10 to a temperature of 25°C.

The second part of the stripped gas stream in the amount of 634112.9 kg/h was sent for compression in two stages. The compressor power of each compression stage was 31322.5 kW. The stripped gas at the outlet of the second stage of compression with a pressure of 13.5 MPa and a temperature of 155.52°C entered AVO 18 for cooling to a temperature of 25°C, after which it was combined with the cooled first part of the stripped gas flow and then the combined flow in the amount of 746015, 16 kg / h with a temperature of 25 ° C and a pressure of 13.5 MPa was sent to a further destination.

From the lower part of the demethanizer 4, the flow of hydrocarbons С _{2+ above} in the amount of 156569.85 kg/h with a temperature of 73.24°C and a pressure of 3.05 MPa was sent to the reboiler 6, after which part of the flow in the amount of 98835 kg/h was returned to the demethanizer 4 for heating the lower part of the column, and the other part of the flow in the amount of 57734.83 kg/h with a temperature of 99°C and a pressure of 3.05 MPa was sent for further processing. The degree of extraction of hydrocarbons With _{2+ above} this option was 51.6%.

Example 3 (see Fig. 3-6).

Purified and dried gas with a temperature of 22°C and a pressure of 6.47 MPa g. in the amount of 800750 kg/h entered the recuperative heat exchanger 1, in which the gas was cooled to a temperature of minus 31.5°C and partially condensed due to heat exchange with the stream of stripped gas. Partially condensed gas from the recuperative heat exchanger 1 was sent to separator 2, in which low-temperature condensate was separated from the gas at a temperature of minus 31.5°C and a pressure of 6.42 MPa.

Low-temperature condensate from separator 2 in the amount of 27526.97 kg/h was throttled to a pressure of 4.3 MPa and, with a temperature of minus 43.79°C, was sent to demethanizer 4.

Gas from separator 2 in the amount of 773223.03 kg/h was sent to TDA 3, in which, as a result of gas expansion, its temperature decreased to minus 40.88°C, and the pressure was 5.36 MPa. After TDA 3, the gas entered the separation in an additional separator 21 to separate low-temperature condensate from the gas, which was then combined with low-temperature condensate from separator 2 and sent to the lower part of demethanizer 4. Gas from additional separator 21 entered TDA 20, after which, with a temperature of minus 50.26°C and a pressure of 4.3 MPa, the gas was then sent to demethanizer 4. The power of each TDA was 57522.8 kW.

From the top of the demethanizer 4, the stripped gas in the amount of 762620.77 kg/h with a temperature of minus 50.31°C and a pressure of 4.3 MPa was sent to recuperative heat exchangers 7 and 1, after which the heated stream of stripped gas with a temperature of 13.37°C and pressure of 4.18 MPa was divided into two parts.

The first part of the stripped gas flow in the amount of 533834.5 kg/h entered the first stage of compression in the compressor part 8 of TDA 3, after which it was sent to AVO 22 at a pressure of 8.84 MPa for cooling to a temperature of 25°C and then entered the second stage compression into the compressor part 19 TDA 20 for compression to the required pressure of commercial stripped gas, which was 13.5 MPa. After that, the first part of the stream of stripped gas entered ABO 10 for cooling to a temperature of 25°C.

The second part of the stripped gas stream in the amount of 228786.2 kg/h was sent for compression to the compressor 9. The power of the compressor 9 was 49305.3 kW. The stripped gas was compressed to a pressure of 13.5 MPa, after which, at a temperature of 66.04°C, it entered AVO 12 for cooling to a temperature of 25°C and then combined with the first part of the stripped gas stream cooled in AVO 10. The combined stripped gas stream in the amount of 762620.77 kg/h with a temperature of 25°C and a pressure of 13.5 MPa was then sent to its destination.

From the bottom of the demethanizer 4, the flow of hydrocarbons C _{2+ above} in the amount of 41130.0 kg/h with a temperature of 30.38°C and a pressure of 4.35 MPa entered the reboiler 6, after which part of the flow in the amount of 21863.41 kg/h returned into demethanizer 4 for heating the lower part of the column, and the other part of the flow in the amount of 19266.59 kg/h with a temperature of 99°C and a pressure of 4.35 MPa was sent for further processing. The degree of extraction of hydrocarbons WITH _2+higher in this option was 36%. Example 4 (see Fig. 7).

Purified and dried gas with a temperature of 22°C and a pressure of 6.47 MPa in the amount of 800750 kg/h entered the recuperative heat exchanger 1, in which the gas was cooled to a temperature of minus 31.5°C and partially condensed due to heat exchange with the stream of stripped gas. Partially condensed gas from the recuperative heat exchanger 1 was sent to separator 2, in which low-temperature condensate was separated from the gas at a temperature of minus 31.5°C and a pressure of 6.42 MPa.

Low-temperature condensate from separator 2 in the amount of 27526.97 kg/h was throttled to a pressure of 4.3 MPa and, with a temperature of minus 43.79°C, was sent to demethanizer 4.

The gas from the separator 2 in the amount of 773223.03 kg/h entered the TDA 3. The power of the TDA 3 was 397916.0 kW. As a result of the expansion of the gas, the temperature and pressure of the gas decreased. Gas from TDA 3 with a temperature of minus 50.26°C and a pressure of 4.3 MPa was sent to demethanizer 4.

From the top of the demethanizer 4, the stripped gas in the amount of 898705.91 kg/h with a temperature of minus 50.31°C and a pressure of 4.3 MPa was sent to recuperative heat exchangers 7 and 1, after which the heated stripped gas with a temperature of 13.37°C and pressure 4.18 MPa was divided into two parts.

The first part of the stream of stripped gas in the amount of 517395.51 kg/h entered the compressor part 8 TDA 3, where it was compressed to a pressure of 5.84 MPa, after which it was sent for cooling in ABO 10 to a temperature of 25°C.

The second part of the stream of stripped gas in the amount of 381310.4 kg/h was sent to the first stage of compression in the compressor 9. The power of the compressor 9 was 44793.8 kW.

After cooling in AVO 10, the first part of the stripped gas stream in the amount of 517395.51 kg/h was divided into two streams, one of which in the amount of 117222.5 kg/h was sent to the recuperative heat exchanger 1, then to the recuperative heat exchanger 7 and then through the throttle 14 in the upper part of the demethanizer 4, and another stream in the amount of 400173.01 kg/h through the outlet 23 was connected to the second part of the stripped gas stream.

After the first compression stage, the second part of the lean gas stream was combined with a part of the cooled first lean gas stream supplied through the outlet 23, after which the combined lean gas stream entered the second compression stage in the compressor 17. The power of the compressor 17 was 74804.3 kW. The stream of stripped gas compressed to a pressure of 7.5 MPa with a temperature of 66.04°C entered AVO 12 for cooling to 25°C and then in the amount of 781483.41 kg/h with a temperature of 25°C and a pressure of 7.5 MPa was sent along appointment.

From the bottom of the demethanizer 4, the flow of hydrocarbons C _{2+ above} in the amount of 41130.0 kg/h with a temperature of 30.38°C and a pressure of 4.35 MPa entered the reboiler 6, after which part of the flow in the amount of 21863.41 kg/h returned into demethanizer 4 for heating the lower part of the column, and the other part of the flow in the amount of 19266.59 kg/h with a temperature of 99°C and a pressure of 4.35 MPa was sent for further processing. The degree of extraction of hydrocarbons WITH _2+higher in this option was 36%.

Thus, as can be seen from the examples presented, the proposed method for compressing stripped gas makes it possible, in comparison with the prototype, to increase the reliability of compressor equipment and reduce operating costs for compression.

Claims (6)

1. A method for compressing a stripped gas, which includes heating the stripped gas obtained by separating hydrocarbons С _{2+ above} from the dried gas during its low-temperature condensation, expansion and rectification, dividing the heated stripped gas stream into two parts, compressing the first and second parts of the stripped gas stream, cooling of the stripped gas, characterized in that, after compression, the second part of the stream of stripped gas is cooled and then combined with the first stream of stripped gas pre-cooled after compression, after which the combined stream of stripped gas is sent for further use. 2. The method of compressing the stripped gas according to claim 1, characterized in that the compression of the second part of the stream of stripped gas is carried out in at least two stages using intermediate cooling between the stages. 3. The method of compressing the stripped gas according to claim 1, characterized in that the compression of the first part of the stream of stripped gas is carried out in at least two stages. 4. The method of compressing the stripped gas according to claim 3, characterized in that between the stages of compression of the first part of the stream of stripped gas, it is cooled. 5. The method of compressing the stripped gas according to claim 3, characterized in that the expansion of the dried gas is carried out in at least two stages with intermediate separation between the stages. 6. A method for compressing the stripped gas, which includes heating the stripped gas obtained by separating hydrocarbons С _{2+ above} from the dried gas during its low-temperature condensation, expansion and rectification, dividing the heated stripped gas stream into two parts, compressing the first and second parts of the stripped gas stream, cooling of the stripped gas, characterized in that the compression of the second part of the stream of stripped gas is carried out in at least two stages, while a part of the first stream of stripped gas pre-cooled after compression is combined with the second part of the stream of stripped gas exiting the first stage of compression, after which the combined the stream of stripped gas is fed to the second stage of compression and, after cooling, is sent for further use.

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