Low-temperature methanol washing acid gas h2s cryogenic separation system

Abstract

The application discloses a low-temperature methanol washing acid gas H2S cryogenic separation system and belongs to the cryogenic separation technical field in the coal chemical industry. In the separation system, a raw material gas buffer tank receives low-temperature methanol washing acid gas as raw material gas, and then enters the pressurizing end of an expander set for pressurization after passing through a raw material gas compressor, a first water cooler and an inlet buffer tank. Then, after passing through a second water cooler for cooling, the raw material gas enters a raw material gas condensing channel of a main heat exchanger for cooling to saturated raw material gas. The saturated raw material gas is used as the feed of an H2S rectifying tower, is condensed and separated into CO2-rich gas and H2S liquid in the H2S rectifying tower, and the H2S liquid product is further purified by a reboiler, gasified by an H2S gasifier and finally high-purity H2S product gas is obtained. The application adopts a process combining low-temperature condensation and expansion refrigeration, rectifies and purifies H2S in methanol washing acid gas and obtains high-purity H2S gas with higher economic value.

Description

Technical Field

[0001] This invention belongs to the field of cryogenic separation technology in the coal chemical industry, specifically relating to a low-temperature methanol washing acidic gas H2S cryogenic separation system. Background Technology

[0002] In the coal chemical industry, crude syngas typically contains excess acidic gases such as CO2 and H2S. Currently, a low-temperature methanol washing process is commonly used, leveraging methanol's high solubility for acidic gases at low temperatures to remove them. However, due to the limitations of this process, the separated acidic gases have high CO2 content and low H2S concentration. Existing technology uses the Claus process to treat these acidic gases and obtain sulfur products; this process is relatively mature. However, the market demand for sulfur is relatively saturated, making the product obtained after treating the acidic gases using the Claus process less economically viable.

[0003] High-purity H2S can be used as a raw material for the production of products such as methionine, dimethyl sulfoxide, and thiourea. With the continuous development of the biochemical and pharmaceutical fields, the application of high-concentration H2S is becoming increasingly widespread, and the demand is also growing. H2S with a molar fraction of 99.5% or higher has significant economic benefits in the current market environment. Therefore, there is an urgent need to develop a cryogenic separation system capable of separating high-purity H2S to overcome the shortcomings of existing technologies in terms of economic efficiency and further reduce the emission of acidic H2S gases. Summary of the Invention

[0004] The purpose of this invention is to address the problems of low purity and insufficient economic benefits of H2S obtained by existing separation technologies, and to provide a cryogenic separation system for acidic gas H2S obtained by washing with methanol at low temperature.

[0005] The specific technical solution adopted in this invention is as follows:

[0006] This invention provides a cryogenic separation system for methanol washing of acidic gas (H2S), comprising a feed gas buffer tank, a feed gas compressor, a first water cooler, an inlet buffer tank, a booster turbine expander, a second water cooler, a main heat exchanger, an H2S distillation column, an H2S vaporizer, and a propylene refrigeration ice machine. The main heat exchanger includes a feed gas condensation channel, a CO2-rich high-pressure gas channel, and a CO2-rich low-pressure gas channel.

[0007] The feed gas buffer tank inlet is connected to the external low-temperature methanol wash acidic gas, receiving it as feed gas. The feed gas buffer tank outlet is connected to the feed gas compressor inlet via a pipeline. The feed gas compressor outlet is connected to the inlet of the first water cooler via a pipeline. The first water cooler outlet is connected to the inlet of the inlet buffer tank located at the front end of the booster turbine expander unit via a pipeline. The inlet buffer tank outlet is connected to the booster end inlet of the booster turbine expander unit via a pipeline. The booster end outlet is connected sequentially to the feed gas condensation channel inlets of the second water cooler and the main heat exchanger via pipelines.

[0008] The outlet of the feed gas condensation channel of the main heat exchanger is connected to the feed inlet of the H2S distillation column via a pipeline. A condenser for cooling H2S is installed at the top of the H2S distillation column, and a reboiler for purifying H2S is installed at the bottom. The condenser has a first cooling inlet, a second cooling inlet, a CO2-rich low-pressure gas outlet, a propylene refrigerant outlet, a CO2-rich cryogenic gas inlet, and a CO2-rich cryogenic gas outlet.

[0009] The CO2-rich cryogenic gas inlet of the condenser is connected to the interior of the H2S distillation column. The CO2-rich cryogenic gas outlet of the condenser is connected to the CO2-rich high-pressure gas channel inlet of the main heat exchanger via a pipeline. The CO2-rich low-pressure gas outlet of the condenser is connected to the CO2-rich low-pressure gas channel of the main heat exchanger via a pipeline. The CO2-rich high-pressure gas channel outlet of the main heat exchanger is connected to the CO2-rich high-pressure gas inlet at the expansion end of the booster turbine expander unit via a pipeline. The CO2-rich low-pressure gas outlet at the expansion end is connected to the first cooling capacity inlet of the condenser via a pipeline, providing cooling capacity. The cooling capacity outlet of the propylene refrigeration ice machine is connected to the second cooling capacity inlet of the condenser via a pipeline, providing cooling capacity. The propylene refrigerant outlet of the condenser is connected to the cooling capacity inlet of the propylene refrigeration ice machine via a pipeline. The CO2-rich low-pressure gas channel outlet of the main heat exchanger is connected to an external CO2 collection device via a pipeline.

[0010] The H2S liquid outlet after reboiler purification is connected to the H2S vaporizer inlet via a pipeline, and the H2S vaporizer outlet is connected to an external H2S product gas collection device via a pipeline.

[0011] Preferably, the above-mentioned feed gas compressor is a reciprocating compressor. Both the main heat exchanger and the condenser are aluminum plate-fin heat exchangers. The reboiler is a coiled tube heat exchanger.

[0012] Preferably, both the H2S vaporizer and the reboiler use the circulating cooling water from the first and second water coolers as the heat source for the heat exchangers.

[0013] Preferably, a liquid level regulating valve is installed on the pipeline between the reboiler and the H2S vaporizer at the bottom of the H2S distillation column.

[0014] Preferably, a first temperature regulating valve is installed on the pipeline between the condenser at the top of the H2S distillation column and the propylene refrigeration ice machine.

[0015] Preferably, the inlet of the expansion end of the above-mentioned booster turbine expander is provided with an inlet guide vane for adjusting the pressure, and a second temperature regulating valve is provided as a bypass.

[0016] Preferably, a flow regulating valve for adjusting the H2S product gas flow rate is installed on the pipeline between the outlet of the H2S vaporizer and the external H2S product gas collection device. A pressure regulating valve for adjusting the CO2 pressure is installed on the pipeline between the outlet of the CO2-rich low-pressure gas channel of the main heat exchanger and the external CO2 collection device.

[0017] Preferably, the outlet pressure setting range of the above-mentioned raw material gas compressor is 1.0 to 1.2 MPaG.

[0018] Preferably, the temperature setting range of the raw gas at the outlet of the raw gas condensation channel in the main heat exchanger is -10 to -15°C.

[0019] Preferably, the expansion end outlet pressure of the above-mentioned booster turbine expander is set in the range of 0.4 to 0.6 MPaG.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] This invention employs a process combining low-temperature condensation and expansion refrigeration to purify H2S from methanol-washed acidic gases through distillation, yielding high-purity H2S gas with higher economic value. Using the separation system provided by this invention, the purity of the obtained H2S gas can reach 99.5% Vmol. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the cryogenic separation system for washing acidic gas H2S with methanol provided in this embodiment;

[0023] In the diagram: 1. Raw material gas buffer tank; 2. Raw material gas compressor; 3. First water cooler; 4. Inlet buffer tank; 5. Pressure boosting end; 6. Expansion end; 7. Second water cooler; 8. Main heat exchanger; 9. H2S distillation column; 10. Condenser; 11. Reboiler; 12. H2S vaporizer; 13. Propylene refrigeration ice machine; 14. Liquid level regulating valve; 15. Flow regulating valve; 16. First temperature regulating valve; 17. Second temperature regulating valve; 18. Pressure regulating valve. Detailed Implementation

[0024] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. Technical features in the various embodiments of the present invention can be combined accordingly without mutual conflict.

[0025] In the description of this invention, it should be understood that the terms "first" and "second" are used only for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" and "second" may explicitly or implicitly include at least one of those features.

[0026] In the description of this invention, it should be understood that when an element is considered to be "connected" to another element, it can be a direct connection to the other element or an indirect connection, i.e., there is an intermediate element. Conversely, when an element is said to be "directly" connected to another element, there is no intermediate element.

[0027] As a preferred embodiment, this example provides a low-temperature methanol washing acidic gas H2S cryogenic separation system, the specific setup of which is as follows: Figure 1 As shown.

[0028] The separation system includes a raw gas buffer tank 1, a raw gas compressor 2, a first water cooler 3, an inlet buffer tank 4, a booster turbine expander unit, a second water cooler 7, a main heat exchanger 8, an H2S distillation column 9, an H2S vaporizer 12, and a propylene refrigeration ice machine 13.

[0029] The main heat exchanger 8 is equipped with a raw material gas condensation channel, a CO2-rich high-pressure gas channel, and a CO2-rich low-pressure gas channel. In this embodiment, both the main heat exchanger 8 and the condenser 10 are aluminum plate-fin heat exchangers.

[0030] The acidic gas from the low-temperature methanol wash is used as the initial feed gas for this separation system. Since the initial feed gas has a low pressure, it first needs to enter the feed gas buffer tank 1. Then, it enters the feed gas compressor 2 through a pipeline from the outlet of the feed gas buffer tank 1. In the feed gas compressor 2, it is compressed and pressurized, transforming the initial feed gas into a high-temperature, high-pressure feed gas. Because reciprocating compressors have the advantage of a wide range of inlet and outlet pressures, a reciprocating compressor is used in this embodiment. Furthermore, the outlet pressure range of the feed gas compressor 2 is set between 1.0 and 1.2 MPaG.

[0031] The outlet of the raw material gas compressor 2 is connected to the inlet of the first water cooler 3 via a pipeline. The aforementioned high-temperature, high-pressure raw material gas is cooled in the first water cooler 3, becoming ambient-temperature, high-pressure raw material gas. The outlet of the first water cooler 3 is connected to the inlet of the inlet buffer tank 4 via a pipeline. The inlet buffer tank 4 is located at the front end of the booster turbine expander unit. The booster turbine expander unit includes a booster end 5 and an expansion end 6. In this embodiment, the outlet pressure of the expansion end 6 of the booster turbine expander unit is set within the range of 0.4–0.6 MPaG. The inlet of the expansion end 6 of the booster turbine expander unit is equipped with an inlet guide vane for pressure regulation, and a second temperature regulating valve 17 is provided as a bypass.

[0032] The outlet of the inlet buffer tank 4 is connected to the inlet of the booster end 5 of the booster turbine expander unit via a pipeline. The ambient temperature and high pressure raw material gas enters the booster end 5 of the booster turbine expander unit for further pressurization.

[0033] The outlet of the booster 5 is connected to the inlet of the second water cooler 7 via a pipeline, where the further pressurized raw gas is cooled to room temperature. The outlet of the second water cooler 7 is connected to the inlet of the raw gas condensation channel in the main heat exchanger 8 via a pipeline. The raw gas cooled to room temperature enters the raw gas condensation channel of the main heat exchanger and is cooled to saturation.

[0034] The outlet of the feed gas condensation channel in the main heat exchanger 8 is connected to the feed inlet of the H2S distillation column 9 via a pipeline. In this embodiment, the condensation temperature range of the feed gas exiting the feed gas condensation channel in the main heat exchanger 8 is controlled to be -10 to -15°C. A condenser 10 for cooling H2S is installed at the top of the H2S distillation column 9, and a reboiler 11 for purifying H2S is installed at the bottom. The condenser 10 is equipped with a first cooling inlet, a second cooling inlet, a CO2-rich low-pressure gas outlet, a propylene refrigerant outlet, a CO2-rich low-temperature gas inlet, and a CO2-rich low-temperature gas outlet. In this embodiment, to reduce the space occupied by the reboiler and improve heat exchange efficiency, the reboiler 12 adopts a coiled tube heat exchanger.

[0035] The saturated feed gas is used as the feed for H2S distillation column 9, and is further cooled and the H2S in the saturated feed gas is collected by the condenser 10 at the top of the column. In the H2S distillation column, the feed gas is separated into CO2-rich low-temperature gas and H2S liquid.

[0036] The CO2-rich cryogenic gas inlet of condenser 10 is connected to the interior of H2S distillation column 9; the CO2-rich cryogenic gas outlet of condenser 10 is connected to the CO2-rich high-pressure gas channel inlet of main heat exchanger 8 via a pipeline, where the CO2-rich cryogenic gas enters and is superheated to obtain CO2-rich high-pressure gas. The CO2-rich low-pressure gas outlet of condenser 10 is connected to the CO2-rich low-pressure gas channel of main heat exchanger 8 via a pipeline. The CO2-rich high-pressure gas channel outlet of main heat exchanger 8 is connected to the CO2-rich high-pressure gas inlet of expansion end 6 of booster turbine expander unit via a pipeline, where the aforementioned CO2-rich high-pressure gas enters expansion end 6 for expansion and refrigeration, becoming CO2-rich low-pressure gas.

[0037] The CO2-rich low-pressure gas outlet of expansion end 6 is connected to the first cooling capacity inlet of condenser 10 via a pipeline. The CO2-rich low-pressure gas enters condenser 10, providing a portion of the cooling capacity. The remaining cooling capacity of condenser 10 is provided by propylene refrigeration machine 13. The second cooling capacity inlet of condenser 10 is connected to the cooling capacity outlet of propylene refrigeration machine 13 via a pipeline, and the propylene refrigerant outlet of condenser 10 is connected to the cooling capacity inlet of propylene refrigeration machine 13 via a pipeline, forming a propylene refrigeration cycle. A first temperature regulating valve 16 is installed on the pipeline between condenser 10 and propylene refrigeration machine 13.

[0038] After the aforementioned CO2-rich low-pressure gas provides cooling, it enters the CO2-rich low-pressure gas channel inlet of the main heat exchanger 8 from the CO2-rich low-pressure gas outlet of the condenser 10, where it is reheated to room temperature. The CO2-rich low-pressure gas channel outlet of the main heat exchanger 8 is connected to an external CO2 collection device via a pipeline, which is equipped with a pressure regulating valve 18 for adjusting the CO2 pressure. The CO2 gas product, reheated to room temperature, is sent outside the system boundary and can be returned to the low-temperature methanol washing process for further processing.

[0039] The H2S liquid product separated in the H2S distillation column enters the reboiler 11 at the bottom for further purification to obtain H2S liquid product that meets the purity requirements. The H2S liquid outlet of the reboiler 11 is connected to the inlet of the H2S vaporizer 12 via a pipeline, and a liquid level regulating valve 14 is installed on the pipeline between the reboiler 11 and the H2S vaporizer 12. After passing through the H2S vaporizer, the H2S liquid product is vaporized into H2S gaseous product.

[0040] In this embodiment, both the H2S vaporizer 12 and the reboiler 11 use the circulating cooling water from the first water cooler 3 and the second water cooler 7 as the heat source for the heat exchangers. The outlet of the H2S vaporizer 12 is connected to an external H2S product gas collection device via a pipeline to complete the subsequent H2S product gas bottling process. A flow regulating valve 15 for adjusting the H2S product gas flow rate is installed on the pipeline between the outlet of the H2S vaporizer 12 and the external H2S product gas collection device.

[0041] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all technical solutions obtained through equivalent substitution or transformation fall within the protection scope of the present invention.

Claims

1. A low-temperature methanol washing acid gas H2S cryogenic separation system, characterized in that, It comprises a raw material gas buffer tank (1), a raw material gas compressor (2), a first water cooler (3), an inlet buffer tank (4), a turboexpander unit, a second water cooler (7), a main heat exchanger (8), an H2S rectification tower (9), an H2S gasifier (12) and a propylene refrigeration ice machine (13); the main heat exchanger (8) is internally provided with a raw material gas condensing channel, a CO2-rich high-pressure gas channel and a CO2-rich low-pressure gas channel; The raw material gas buffer tank (1) is connected with the outside low-temperature methanol washing acid gas at the inlet and receives the low-temperature methanol washing acid gas as raw material gas; the outlet of the raw material gas buffer tank (1) is connected with the inlet of the raw material gas compressor (2) through a pipeline; the outlet of the raw material gas compressor (2) is connected with the inlet of the first water cooler (3) through a pipeline; the outlet of the first water cooler (3) is connected with the inlet of the inlet buffer tank (4) arranged at the front end of the turboexpander unit through a pipeline; the outlet of the inlet buffer tank (4) is connected with the inlet of the turboexpander unit at the pressurizing end (5) through a pipeline; the outlet of the pressurizing end (5) is sequentially connected with the inlet of the second water cooler (7) and the raw material gas condensing channel of the main heat exchanger (8) through pipelines; The outlet of the raw material gas condensing channel is connected with the inlet of the H2S rectification tower (9) through a pipeline; the top of the H2S rectification tower (9) is provided with a condenser (10) for cooling H2S, and the bottom is provided with a reboiler (11) for purifying H2S; the condenser (10) is provided with a first cold quantity inlet, a second cold quantity inlet, a CO2-rich low-pressure gas outlet, a propylene refrigerant outlet, a CO2-rich low-temperature gas inlet and a CO2-rich low-temperature gas outlet; The CO2-rich low-temperature gas inlet of the condenser (10) is in communication with the inside of the H2S rectification tower (9); the CO2-rich low-temperature gas outlet of the condenser (10) is in communication with the CO2-rich high-pressure gas channel inlet of the main heat exchanger (8) through a pipeline; the CO2-rich low-pressure gas outlet of the condenser (10) is in communication with the CO2-rich low-pressure gas channel of the main heat exchanger (8) through a pipeline; the outlet of the CO2-rich high-pressure gas channel of the main heat exchanger (8) is connected with the CO2-rich high-pressure gas inlet of the expansion end (6) of the turboexpander unit through a pipeline; the CO2-rich low-pressure gas outlet of the expansion end (6) is connected with the first cold quantity inlet of the condenser (10) through a pipeline to provide cold quantity; the cold quantity outlet of the propylene refrigeration ice machine (13) is connected with the second cold quantity inlet of the condenser (10) through a pipeline to provide cold quantity; the propylene refrigerant outlet of the condenser (10) is connected with the cold quantity inlet of the propylene refrigeration ice machine (13) through a pipeline; the outlet of the CO2-rich low-pressure gas channel of the main heat exchanger (8) is connected with the CO2 collection device outside through a pipeline; The H2S liquid outlet after purification of the reboiler (11) is connected with the inlet of the H2S gasifier (12) through a pipeline, and the outlet of the H2S gasifier (12) is connected with the H2S product gas collection device outside through a pipeline.

2. The low temperature methanol wash acid gas H2S cryogenic separation system according to claim 1, characterized in that, The raw gas compressor (2) is a reciprocating compressor; the main heat exchanger (8) and the condenser (10) are both aluminum plate-fin heat exchangers; and the reboiler (11) is a coil heat exchanger.

3. The low temperature methanol wash acid gas H2S cryogenic separation system according to claim 1, characterized in that, The H2S gasifier (12) and the reboiler (11) both use the circulating cooling water of the first water cooler (3) and the second water cooler (7) as the heat source of the heat exchanger.

4. The low temperature methanol wash acid gas H2S cryogenic separation system according to claim 1, characterized in that, A liquid level regulating valve (14) is arranged on the pipeline between the reboiler (11) at the bottom of the H2S rectification tower (9) and the H2S gasifier (12).

5. The low temperature methanol wash acid gas H2S cryogenic separation system according to claim 1, characterized in that, A first temperature regulating valve (16) is arranged on the pipeline between the condenser (10) at the top of the H2S rectification tower (9) and the propylene refrigeration chiller (13).

6. The low temperature methanol wash acid gas H2S cryogenic separation system according to claim 1, characterized in that, An inlet guide vane for regulating pressure is arranged at the inlet of the expansion end (6) of the booster turbo expander set, and a second temperature regulating valve (17) is arranged in bypass.

7. The low temperature methanol wash acid gas H2S cryogenic separation system according to claim 1, characterized in that, A flow regulating valve (15) for regulating the flow of H2S product gas is arranged on the pipeline between the outlet of the H2S gasifier (12) and the H2S product gas collecting device, and a pressure regulating valve (18) for regulating the pressure of CO2 is arranged on the pipeline between the outlet of the CO2 low-pressure gas passage of the main heat exchanger (8) and the CO2 collecting device.

8. The low temperature methanol wash acid gas H2S cryogenic separation system according to claim 1, characterized in that, The outlet pressure of the raw gas compressor (2) is set to be in the range of 1.0-1.2 MPaG.

9. The low temperature methanol wash acid gas H2S cryogenic separation system according to claim 1, characterized in that, The temperature of the raw gas at the outlet of the raw gas condensing passage in the main heat exchanger (8) is set to be in the range of -10 to -15℃.

10. The low temperature methanol wash acid gas H2S cryogenic separation system according to claim 1, characterized in that, The outlet pressure of the expansion end (6) of the booster turbo expander set is set to be in the range of 0.4-0.6 MPaG.

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