Recovery method and recovery system for high-order energy of acid gas removal device

Abstract

The invention relates to the technical field of acid gas removal, in particular to an acid gas removal device high-order energy recovery method and system, the recovery method adopts a first pressure recovery device and a second pressure recovery device to convert the pressure energy of a high-pressure rich solution into the pressure energy of a low-pressure solution, and the high-order energy of the acid gas removal device is obtained by combining a formula I and a formula II. The high-pressure sulfur-rich methanol and the pressurized sulfur-containing methanol are subjected to pressure energy conversion to obtain low-pressure sulfur-rich methanol and high-pressure sulfur-containing methanol, and the high-pressure carbon-rich methanol and the pressurized semi-lean methanol are subjected to pressure energy conversion to obtain low-pressure carbon-rich methanol and high-pressure semi-lean methanol, so that high potential energy is fully utilized, and the recovery rate of the high potential energy is increased.

Description

Technical Field

[0001] The invention relates to the technical field of acid gas removal, and in particular to a method for recovering high-level energy of an acid gas removal device and a system for recovering high-level energy of an acid gas removal device. Background Art

[0002] The purification process of coal chemical industry and high-sulfur and high-carbon crude synthesis gas usually adopts the acid gas removal process with low energy consumption. This process uses low-temperature methanol as an absorbent to remove CO2 and H2S from crude synthesis gas at high pressure and low temperature, with high gas purification degree and good selectivity. The methanol solution after absorbing CO2 and H2S has the characteristics of high pressure, low temperature and high gas content. The carbon-rich and sulfur-rich methanol solution needs to be generated by reduced pressure flash evaporation, nitrogen stripping and thermal regeneration process to generate semi-lean liquid and lean liquid, and the semi-lean liquid and lean liquid are recycled back to the absorption tower. Therefore, the regenerated semi-lean liquid and lean liquid need to be pressurized to high pressure before entering the absorption tower. Therefore, the semi-lean liquid and lean liquid circulation pumps have a high head, a large motor power, and need to consume a lot of electricity; and the rich liquid leaving the absorption tower usually enters the desorption tower after being reduced to a lower pressure through a pressure reducing valve, which causes a large loss of rich liquid pressure energy.

[0003] The existing technology widely adopts that the high-pressure, low-temperature, sulfur-rich and carbon-rich methanol solution after absorbing CO2 and H2S is directly sent to the downstream system through decompression, resulting in a huge waste of this part of high-level energy.

[0004] CN203635032U adopts the method of hydraulic turbine to recover the high-level energy of energy flow in the low-temperature methanol washing process. This method adds a hydraulic turbine to the existing process pipeline that can convert the high-level pressure energy of the low-temperature and high-cavitation fluid into kinetic energy. The kinetic energy output by the hydraulic turbine and the kinetic energy provided by the external electric drive motor jointly drive the process pump, reducing high-level energy waste and reducing power consumption. However, this method occupies a large area and includes turbines, clutches, starting machines, high-pressure pumps, multiple complex mechanical seals, additional lubrication systems, backwashing systems, etc. The structure is complex and there are many rotating parts. At the same time, there are also problems such as a narrow operating range, a large impact from system fluctuations, and a low energy recovery rate. Summary of the invention

[0005] The purpose of the present invention is to overcome the problems of narrow operating range, great influence of system fluctuations, low energy recovery rate and large footprint of the recovery device in the existing acid gas removal device, and to provide a high-level energy recovery method and a recovery device for the acid gas removal device. The recovery method improves the utilization rate of the high-level energy by converting the pressure energy of the high-pressure rich liquid into the pressure energy of the low-pressure solution.

[0006] In order to achieve the above-mentioned object, the first aspect of the present invention provides a method for recovering high-level energy of an acid gas removal device, the method comprising: subjecting low-pressure sulfur-containing methanol and low-pressure semi-lean methanol from a reabsorption process to a first pressurization and a second pressurization, respectively, to obtain pressurized sulfur-containing methanol and pressurized semi-lean methanol;

[0007] The pressurized sulfur-containing methanol and the high-pressure sulfur-rich methanol from the H2S absorption process are subjected to pressure energy conversion in a first pressure recovery device to obtain high-pressure sulfur-containing methanol and low-pressure sulfur-rich methanol;

[0008] The pressurized semi-lean methanol and the high-pressure carbon-rich methanol from the CO2 absorption process are subjected to pressure energy conversion in a second pressure recovery device to obtain high-pressure semi-lean methanol and low-pressure carbon-rich methanol;

[0009] Wherein, the low-pressure sulfur-containing methanol and the high-pressure sulfur-rich methanol satisfy Formula I: [ΔP (11-12) ×Q 11 ]≤[ΔP (16-14) ×Q 14 ]; The low-pressure semi-lean methanol and high-pressure carbon-rich methanol satisfy Formula II: [ΔP (25-26) ×Q 25 ]≤[ΔP (30-28) ×Q 28 ].

[0010] Preferably, the first pressure recovery device and the second pressure recovery device each independently include: a pressure reducing end and a pressure increasing end, and the high-pressure side impeller of the pressure reducing end and the low-pressure side impeller of the pressure increasing end are connected via a rotating shaft.

[0011] The second aspect of the present invention provides a high-level energy recovery system for an acid gas removal device, the recovery system comprising: an absorption tower, a medium-pressure flash tower, a reabsorption tower and a thermal regeneration tower connected in sequence;

[0012] The absorption tower comprises an H2S absorption section arranged at the bottom and a CO2 absorption section arranged at the top, and is used to sequentially absorb H2S and CO2 from the crude synthesis gas;

[0013] A first pressure recovery device is provided on the pipeline connecting the low-pressure sulfur-containing methanol outlet of the reabsorption tower and the H2S absorption section, which is used to convert the pressure energy of the pressurized sulfur-containing methanol obtained by passing the low-pressure sulfur-containing methanol through the first pressurizing component with the high-pressure sulfur-rich methanol to obtain high-pressure sulfur-containing methanol and low-pressure sulfur-rich methanol;

[0014] The low-pressure sulfur-rich methanol enters the lower part of the medium-pressure flash tower for the first flash evaporation, and the obtained flashed sulfur-rich methanol enters the first pressure reducing valve, and the obtained reduced-pressure sulfur-rich methanol enters the lower part of the reabsorption tower for the second flash evaporation to obtain the low-pressure sulfur-containing methanol; the high-pressure sulfur-containing methanol enters the heater, and the obtained high-temperature and high-pressure sulfur-containing methanol enters the thermal regeneration tower, and the obtained lean methanol returns and is reused in the CO2 absorption section;

[0015] A second pressure recovery device is provided on the pipeline connecting the low-pressure semi-lean methanol outlet of the reabsorption tower and the CO2 absorption section, which is used to convert the pressure energy of the low-pressure semi-lean methanol obtained by the second boosting component and the high-pressure carbon-rich methanol to obtain low-pressure carbon-rich methanol, and the high-pressure semi-lean methanol is returned and reused in the CO2 absorption section;

[0016] The low-pressure carbon-rich methanol enters the upper part of the medium-pressure flash tower for the third flash evaporation, and the obtained carbon-containing methanol after flash evaporation enters the second pressure reducing valve, and the obtained carbon-containing methanol after pressure reduction enters the upper part of the reabsorption tower for the fourth flash evaporation to obtain the semi-lean methanol;

[0017] Wherein, the first pressure recovery device and the second pressure recovery device each independently include: a pressure reducing end and a pressure increasing end, and the high-pressure side impeller of the pressure reducing end and the low-pressure side impeller of the pressure increasing end are connected through a rotating shaft.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] (1) The recovery method provided by the present invention uses a first pressure recovery device and a second pressure recovery device to convert the pressure energy of a high-pressure rich liquid into the pressure energy of a low-pressure solution, and combines Formula I and Formula II to convert the pressure energy of high-pressure sulfur-rich methanol and pressurized sulfur-containing methanol to obtain low-pressure sulfur-rich methanol and high-pressure sulfur-containing methanol, and to convert the pressure energy of high-pressure carbon-rich methanol and pressurized semi-lean methanol to obtain low-pressure carbon-rich methanol and high-pressure semi-lean methanol, thereby achieving full utilization of high-potential energy and improving the recovery rate of high-potential energy;

[0020] At the same time, the pressure recovery device not only has a wide operating range and is not affected by system fluctuations and abnormal operations, but also has the characteristics of simple structure, small footprint, and reduced total power consumption of the device;

[0021] (2) The method provided by the present invention is to respectively pressurize the low-pressure sulfur-containing methanol and the low-pressure semi-lean methanol (providing a booster pump with a small lift) to supplement the insufficient pressure energy, satisfying Formula III and Formula IV, so that the pressure of the high-pressure rich liquid flowing out of the high-pressure side of the boosting end of the pressure recovery device meets the pressure required by the downstream operation. Therefore, the present technology has the advantage of high energy recovery rate;

[0022] (3) The method provided by the present invention further provides a bypass pressure reducing valve (e.g., the third pressure reducing valve and the fourth pressure reducing valve) and a booster pump (e.g., the third booster pump and the fourth booster pump) to ensure that the absorption liquid is repeatedly circulated between the absorption tower and the reabsorption tower / thermal regeneration tower without the operation of the pressure recovery device. Therefore, the improved recovery method of the present invention also has the advantage of not being affected by system fluctuations and abnormal operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic structural diagram of a high-level energy recovery system of an acid gas removal device provided by the present invention;

[0024] Figure 2 This is a schematic diagram of the structure of a high-level energy recovery system of an acid gas removal device provided in Comparative Example 1;

[0025] Figure 3 This is a schematic diagram of the structure of a high-level energy recovery system for an acid gas removal device provided in Example 2.

[0026] Description of Reference Numerals

[0027] 1. Absorption tower; 2-1. First pressure recovery device; 2-2. Second pressure recovery device; 3. Medium-pressure flash tower; 4. Reabsorption tower; 5. Thermal regeneration tower; 6. Heater; 7. Third booster pump; 8. First booster component; 9. Third pressure reducing valve; 10. Crude synthesis gas; 11. High-pressure sulfur-rich methanol; 12. Low-pressure sulfur-rich methanol; 13. First pressure reducing valve; 14. Low-pressure sulfur-containing methanol; 15. Sulfur-containing methanol after boosting; 16. High-pressure sulfur-containing methanol ; 18. Lean methanol; 19. High-temperature and high-pressure sulfur-containing methanol; 20. Sulfur-rich methanol after flash evaporation; 21. Sulfur-rich methanol after decompression; 22. Second booster component; 23. Fourth booster pump; 24. Fourth pressure reducing valve; 25. High-pressure carbon-rich methanol; 26. Low-pressure carbon-rich methanol; 27. Second pressure reducing valve; 28. Low-pressure semi-lean methanol; 29. ​​Semi-lean methanol after boosting; 30. High-pressure semi-lean methanol; 33. Carbon-containing methanol after flash evaporation; 34. Carbon-containing methanol after decompression;

[0028] 01-1, the first hydraulic turbine device; 01-2, the second hydraulic turbine device. DETAILED DESCRIPTION

[0029] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0030] In the present invention, unless otherwise specified, "first", "second", "third" and "fourth" do not indicate a sequence or limit to each material or step, but are only used to distinguish or indicate that they are not the same material or step. For example, "first", "second", "third" and "fourth" in "first pressure reducing valve", "second pressure reducing valve", "third pressure reducing valve" and "fourth pressure reducing valve" are only used to distinguish that they are not the same pressure reducing valve; similarly, "first" and "second" in "first pressure recovery device" and "second pressure recovery device" are only used to distinguish that they are not the same pressure recovery device.

[0031] A first aspect of the present invention provides a method for recovering high-level energy of an acid gas removal device, the method comprising: subjecting low-pressure sulfur-containing methanol and low-pressure semi-lean methanol from a reabsorption process to a first pressurization and a second pressurization, respectively, to obtain pressurized sulfur-containing methanol and pressurized semi-lean methanol;

[0032] The pressurized sulfur-containing methanol and the high-pressure sulfur-rich methanol from the H2S absorption process are subjected to pressure energy conversion in a first pressure recovery device to obtain high-pressure sulfur-containing methanol and low-pressure sulfur-rich methanol;

[0033] The pressurized semi-lean methanol and the high-pressure carbon-rich methanol from the CO2 absorption process are subjected to pressure energy conversion in a second pressure recovery device to obtain high-pressure semi-lean methanol and low-pressure carbon-rich methanol;

[0034] Wherein, the low-pressure sulfur-containing methanol and the high-pressure sulfur-rich methanol satisfy Formula I: [ΔP (11-12) ×Q 11 ]≤[ΔP (16-14) ×Q 14 ];; The low-pressure semi-lean methanol and high-pressure carbon-rich methanol satisfy Formula II: [ΔP (25-26) ×Q 25 ]≤[ΔP (30-28) ×Q 28 ].

[0035] The inventors of the present invention have found through research that in a high-pressure energy recovery method, a pressure recovery device is used to convert the pressure energy of a high-pressure rich liquid into the pressure energy of a low-pressure solution through the mechanical energy of the rotating shaft of the device. That is, in the same device, the high-pressure side impeller at the pressure reducing end and the low-pressure side impeller at the pressure boosting end are directly connected through a rotating shaft. The high-pressure rich liquid at the pressure reducing end drives the high-pressure side impeller at the pressure reducing end, and drives the low-pressure side impeller at the pressure boosting end to rotate through the rotating shaft, thereby increasing the pressure of the low-pressure solution at the pressure boosting end. The "pressure energy" on the high-pressure side of the pressure reducing end is converted into the "mechanical energy" of the rotating shaft and then into the "pressure energy" on the low-pressure side of the pressure boosting end. This not only reduces the total power consumption of the device, but also improves the high-pressure energy utilization rate of the device and reduces high-pressure energy waste.

[0036] At the same time, bypass pressure reducing valves (e.g., the third pressure reducing valve and the fourth pressure reducing valve) and boosting pumps (e.g., the third boosting pump and the fourth boosting pump) are also provided to ensure that the absorption liquid is repeatedly circulated between the absorption tower and the reabsorption tower and the thermal regeneration tower when the pressure recovery device cannot operate.

[0037] In the present invention, in order to maximize the use of the pressure energy of the high-pressure rich liquid, the energy matching condition is selected as follows: the pressure energy of the high-pressure rich liquid is less than the pressure energy of the low-pressure solution. Therefore, it is necessary to set up an additional small booster pump to supplement the energy gap. Preferably, the low-pressure sulfur-containing methanol and the high-pressure sulfur-rich methanol satisfy Formula III: [ΔP (11-12) ×Q 11 +ΔP (15-14) ×Q 14 ]=[ΔP (16-14) ×Q 14 ]; The low-pressure semi-lean methanol and high-pressure carbon-rich methanol satisfy Formula IV: [ΔP (25-26) ×Q 25 +ΔP (29-28) ×Q 28 ]=[ΔP (30-28) ×Q 28 ].

[0038] In the present invention, unless otherwise specified, ΔP (11-12) ×Q 11 Refers to the pressure energy of high-pressure sulfur-rich methanol; ΔP (16-14) ×Q 14 Refers to the pressure energy of low-pressure sulfur-containing methanol; ΔP (15-14) ×Q 14 Refers to the supplementary pressure energy of low-pressure sulfur-containing methanol; ΔP (25-26) ×Q 25 Refers to the pressure energy of high-pressure carbon-rich methanol; ΔP (30-28) ×Q 28 Refers to the pressure energy of low-pressure semi-lean methanol; ΔP (29-28) ×Q 28 It refers to the supplementary pressure energy of low-pressure semi-lean methanol.

[0039] In the present invention, there is a wide range of choices for the pressure recovery device, as long as the high pressure energy is converted into low pressure energy. Preferably, the first pressure recovery device and the second pressure recovery device each independently include: a pressure reducing end and a pressure increasing end, and the high pressure side impeller of the pressure reducing end and the low pressure side impeller of the pressure increasing end are connected by a rotating shaft. In the present invention, the pressure recovery device is shaft-free and has no additional lubrication system.

[0040] In a specific embodiment of the present invention, high-pressure sulfur-rich methanol enters the high-pressure side inlet of the first pressure recovery device at the pressure reducing end, and the pressurized sulfur-containing methanol enters the low-pressure side inlet of the boosting end of the first pressure recovery device; in the first pressure recovery device, the "pressure energy" of the high-pressure sulfur-rich methanol at the high-pressure side of the pressure reducing end is first converted into the "mechanical energy" of the rotating shaft, and then converted into the "pressure energy" of the pressurized sulfur-containing methanol at the low-pressure side of the boosting end. As a result, the pressure of the pressurized sulfur-containing methanol increases and is converted into high-pressure sulfur-rich methanol; at the same time, before the low-pressure sulfur-rich methanol enters the first pressure recovery device, it is first pressurized, and preferably a first boosting pump with a small lift is set to supplement the insufficient pressure energy, so that the pressure of the high-pressure sulfur-containing methanol flowing out of the high-pressure side of the boosting end of the first pressure recovery device meets the pressure required for the operation of the thermal regeneration tower, thereby reducing the total power consumption of the external motor.

[0041] In a specific embodiment of the present invention, high-pressure carbon-rich methanol enters the high-pressure side inlet of the pressure-reducing end of the second pressure recovery device, and at the same time, the pressurized semi-lean methanol enters the low-pressure side inlet of the boosting end of the second pressure recovery device; in the second pressure recovery device, the "pressure energy" of the high-pressure carbon-rich methanol on the high-pressure side of the pressure-reducing end is first converted into the "mechanical energy" of the rotating shaft, and then converted into the "pressure energy" of the pressurized semi-lean methanol on the low-pressure side of the boosting end. As a result, the pressure of the pressurized semi-lean methanol increases and is converted into high-pressure semi-lean methanol; at the same time, before the low-pressure semi-lean methanol enters the second pressure recovery device 2, it is preferably provided with a second boosting pump with a small head to supplement the insufficient pressure energy, so that the pressure of the high-pressure semi-lean methanol flowing out of the high-pressure side of the boosting end of the second pressure recovery device meets the pressure required for the operation of the absorption tower, thereby reducing the total power consumption of the external motor.

[0042] In some embodiments of the present invention, preferably, the recovery method comprises the following steps:

[0043] (1) subjecting the crude synthesis gas to H2S absorption to obtain pretreated synthesis gas and the high-pressure sulfur-rich methanol; subjecting the pretreated synthesis gas to CO2 absorption to obtain the high-pressure carbon-rich methanol and purified gas;

[0044] (2) converting the high-pressure sulfur-rich methanol and the pressurized sulfur-containing methanol into pressure energy in a first pressure recovery device to obtain the low-pressure sulfur-rich methanol and the high-pressure sulfur-containing methanol;

[0045] (3) subjecting the low-pressure sulfur-rich methanol to a first flash evaporation, and subjecting the obtained flashed sulfur-rich methanol to a first decompression, and then subjecting the obtained low-pressure sulfur-containing methanol to a second flash evaporation, and subjecting the obtained low-pressure sulfur-containing methanol to a first pressurization, to obtain the pressurized sulfur-containing methanol; heating the high-pressure sulfur-containing methanol, and subjecting the obtained high-temperature and high-pressure sulfur-containing methanol to thermal regeneration, and returning the obtained lean methanol to the CO2 absorption;

[0046] (4) converting the high-pressure carbon-rich methanol and the pressurized semi-lean methanol into pressure energy in a second pressure recovery device to obtain the low-pressure carbon-rich methanol and the high-pressure semi-lean methanol;

[0047] (5) The low-pressure carbon-rich methanol is subjected to a third flash distillation, and the obtained carbon-containing methanol after flash distillation is subjected to a second decompression, and then subjected to a fourth flash distillation. The obtained low-pressure semi-lean methanol is subjected to the second pressurization to obtain the pressurized semi-lean methanol; the high-pressure semi-lean methanol is returned and subjected to the CO2 absorption.

[0048] In the present invention, in step (1), the H2S absorption is intended to remove H2S in the crude synthesis gas, and the CO2 absorption is intended to remove CO2 in the crude synthesis gas. Preferably, the conditions for the H2S absorption and the CO2 absorption each independently include: a temperature of -70 to -20°C and a pressure of 3-6MPa. In the present invention, the pressures are all gauge pressures.

[0049] In some embodiments of the present invention, preferably, the molar content of H2S in the crude syngas is 0.2-2.0%, and the molar content of CO2 is 30-80%. In the present invention, the source of the crude syngas has a wide selection range, including but not limited to the crude syngas from the sulfur-tolerant shift unit.

[0050] In some embodiments of the present invention, preferably, the temperature is -30 to 0°C and the pressure is 3-6 MPa.

[0051] In some embodiments of the present invention, preferably, the molar content of H2S in the high-pressure sulfur-rich methanol is 0.2-2%, and the molar content of CO2 is 30-80%.

[0052] In some embodiments of the present invention, preferably, the molar content of H2S in the high-pressure carbon-enriched methanol is 0-0.01%, and the molar content of CO2 is 30-80%.

[0053] In some embodiments of the present invention, preferably, the volume flow ratio of the crude synthesis gas to the high-pressure sulfur-rich methanol is 1:0.05-0.1.

[0054] In some embodiments of the present invention, preferably, the volume flow ratio of the crude synthesis gas to the high-pressure carbon-rich methanol is 1:0.16-0.3.

[0055] In some embodiments of the present invention, preferably, in step (2), the pressure difference ΔP between the high-pressure sulfur-rich methanol and the low-pressure sulfur-rich methanol is (11-12) is 2-5MPa; further preferably, the pressure of the low-pressure sulfur-rich methanol is 0.5-2MPa. (11-12) The more pressure energy recovered by the first pressure recovery device, the higher the recovery efficiency.

[0056] In some embodiments of the present invention, preferably, the pressure difference ΔP between the pressurized sulfur-containing methanol and the high-pressure sulfur-containing methanol is (16-15) is 0.5-2.5MPa; more preferably, the pressure of the pressurized sulfur-containing methanol is 0.5-1MPa; the pressure of the high-pressure sulfur-containing methanol is 1.5-3MPa. In the present invention, the pressure difference ΔP (16-15) It mainly depends on the pressure energy provided by high-pressure sulfur-rich methanol (i.e., ΔP (11-12) ×Q 11 ).

[0057] In the present invention, the first flash evaporation is intended to reduce the CO2 content in the low-pressure sulfur-rich methanol and recover the effective gas (CO and H2) dissolved in the methanol solution. Preferably, in step (3), the conditions of the first flash evaporation include: a temperature of -40 to -10°C and a pressure of 0.5-2MPa; further preferably, the molar content of H2S in the sulfur-rich methanol after the flash evaporation is 0.2-2%, and the molar content of CO2 is 30-80%.

[0058] In the present invention, the first decompression is performed by reducing the pressure of the sulfur-rich methanol after flash evaporation, so that the pressure of the sulfur-rich methanol after decompression meets the pressure requirement of the second flash evaporation.

[0059] In some embodiments of the present invention, preferably, the second flash evaporation conditions include: temperature of -60 to -30°C and pressure of 0.05-0.3 MPa. The second flash evaporation meeting the above range further removes the CO2 content in the decompressed sulfur-rich methanol to obtain low-pressure sulfur-containing methanol.

[0060] In some embodiments of the present invention, preferably, the molar content of H2S in the low-pressure sulfur-containing methanol is 0.5-4%, and the molar content of CO2 is 0.5-2%. In the present invention, the pressure of the low-pressure sulfur-containing methanol is equivalent to the pressure of the second flash, that is, 0.05-0.2MPa.

[0061] In the present invention, the heating is performed by increasing the temperature of the high-pressure sulfur-containing methanol so that the temperature of the high-temperature and high-pressure sulfur-containing methanol meets the temperature requirement of thermal regeneration. Preferably, the temperature of the high-temperature and high-pressure sulfur-containing methanol is 70-100°C.

[0062] In the present invention, the thermal regeneration is intended to reduce the content of H2S and CO2 in high-temperature and high-pressure sulfur-containing methanol to obtain lean methanol substantially free of H2S and CO2. Preferably, the conditions of the thermal regeneration include: a temperature of 70-100°C and a pressure of 0.1-0.4MPa; further preferably, the molar content of H2S in the lean methanol is 0%, and the molar content of CO2 is 0%.

[0063] In some embodiments of the present invention, preferably, in step (4), the pressure difference ΔP between the high-pressure carbon-rich methanol and the low-pressure carbon-rich methanol is (25-26) is 2-5MPaMPa; further preferably, the pressure of the low-pressure carbon-rich methanol is 0.5-2.2MPa. ΔP that meets the above conditions (25-26) The more pressure energy recovered by the first pressure recovery device, the higher the recovery efficiency.

[0064] In some embodiments of the present invention, preferably, the pressure difference ΔP between the pressurized semi-lean methanol and the high-pressure semi-lean methanol is (30-29) is 3-6MPa; further preferably, the pressure of the semi-lean methanol after pressurization is 0.5-2MPa; the pressure of the high-pressure semi-lean methanol is 3.5-7.5MPa. In the present invention, the pressure difference ΔP (30-29) It mainly depends on the pressure energy provided by high-pressure carbon-rich methanol (i.e., ΔP (25-26) ×Q 25 ).

[0065] In the present invention, the third flash evaporation is intended to reduce the CO2 content in the low-pressure carbon-rich methanol and recover the effective gas (CO and H2) dissolved in the methanol solution. Preferably, in step (5), the conditions of the third flash evaporation include: a temperature of -40 to -10°C and a pressure of 0.5-2MPa; further preferably, the molar content of H2S in the carbon-containing methanol after the flash evaporation is 0-0.01%, and the molar content of CO2 is 30-80%.

[0066] In the present invention, the second decompression is performed by reducing the pressure of the carbon-containing methanol after flash evaporation, so that the pressure of the carbon-containing methanol after decompression meets the pressure requirement of the fourth flash evaporation.

[0067] In some embodiments of the present invention, preferably, the conditions of the fourth flash evaporation include: a temperature of -60 to -30°C and a pressure of 0.05-0.3 MPa. The fourth flash evaporation meeting the above range further removes the CO2 content in the carbon-containing methanol after decompression to obtain low-pressure semi-lean methanol.

[0068] In some embodiments of the present invention, preferably, the molar content of H2S in the low-pressure semi-lean methanol is 0-0.01%, and the molar content of CO2 is 5-40%. In the present invention, the pressure of the low-pressure semi-lean methanol is equivalent to the pressure of the fourth flash, that is, the pressure of the low-pressure semi-lean methanol is 0.05-0.3MPa.

[0069] In some embodiments of the present invention, preferably, when the first pressure recovery device fails, the high-pressure sulfur-rich methanol is subjected to the third decompression, and the obtained logistics is sequentially subjected to the first flash evaporation, the first decompression and the second flash evaporation, and the obtained low-pressure sulfur-containing methanol is subjected to the third pressurization, and the obtained logistics is sequentially subjected to the heating and thermal regeneration. In this way, when the first pressure recovery device is not in operation, the lean methanol is ensured to circulate repeatedly between the absorption tower and the thermal regeneration tower.

[0070] In some embodiments of the present invention, preferably, when the second pressure recovery device fails, the high-pressure carbon-rich methanol is subjected to the fourth decompression, and the obtained logistics is sequentially subjected to the third flash evaporation, the second decompression and the fourth flash evaporation, and the obtained low-pressure semi-lean methanol is subjected to the fourth pressurization, and the obtained logistics is returned and subjected to the CO2 absorption. In this way, when the second pressure recovery device is not in operation, the low-pressure semi-lean methanol is ensured to circulate repeatedly between the absorption tower and the reabsorption tower.

[0071] In the present invention, unless otherwise specified, a failure of the pressure recovery device is considered an equipment failure, similar to a pump failure, and generally the device (ie, the pressure recovery device) is provided with a fault signal.

[0072] The second aspect of the present invention provides a schematic diagram of a high-level energy recovery system for an acid gas removal device. Figure 1 As shown, the recovery system comprises: an absorption tower 1, a medium-pressure flash tower 3, a reabsorption tower 4 and a thermal regeneration tower 5 connected in sequence;

[0073] The absorption tower 1 includes an H2S absorption section arranged at the bottom and a CO2 absorption section arranged at the top, which are used to absorb H2S and CO2 in sequence on the crude synthesis gas 10 to obtain purified gas;

[0074] A first pressure recovery device 2-1 is provided on the pipeline connecting the low-pressure sulfur-containing methanol outlet of the reabsorption tower 4 and the H2S absorption section, for converting the pressure energy of the pressurized sulfur-containing methanol 15 obtained by passing the low-pressure sulfur-containing methanol 14 through the first pressurizing component 8 with the high-pressure sulfur-rich methanol 11 to obtain high-pressure sulfur-containing methanol 16 and low-pressure sulfur-rich methanol 12;

[0075] The low-pressure sulfur-rich methanol 12 enters the lower part of the medium-pressure flash tower 3 for the first flash evaporation, and the obtained flashed sulfur-rich methanol 20 enters the first pressure reducing valve 13, and the obtained reduced-pressure sulfur-rich methanol 21 enters the lower part of the reabsorption tower 4 for the second flash evaporation to obtain the low-pressure sulfur-containing methanol 14; the high-pressure sulfur-containing methanol 16 enters the heater 6, and the obtained high-temperature and high-pressure sulfur-containing methanol 19 enters the thermal regeneration tower 5, and the obtained lean methanol 18 returns and is reused in the CO2 absorption section;

[0076] A second pressure recovery device 2-2 is provided on the pipeline connecting the low-pressure semi-lean methanol outlet of the reabsorption tower 4 and the CO2 absorption section, which is used to convert the pressure energy of the pressurized semi-lean methanol 29 obtained by passing the low-pressure semi-lean methanol 28 through the second pressurizing component 22 with the high-pressure carbon-rich methanol 25 to obtain low-pressure carbon-rich methanol 26, and the obtained high-pressure semi-lean methanol 30 is returned and reused in the CO2 absorption section;

[0077] The low-pressure carbon-rich methanol 26 enters the upper part of the medium-pressure flash tower 3 for the third flash evaporation, and the obtained carbon-containing methanol 33 after flash evaporation enters the second pressure reducing valve 27, and the obtained carbon-containing methanol 34 after pressure reduction enters the upper part of the reabsorption tower 4 for the fourth flash evaporation to obtain the semi-lean methanol 28;

[0078] The first pressure recovery device 2-1 and the second pressure recovery device 2-2 each independently include: a pressure reducing end and a pressure increasing end, and the high-pressure side impeller of the pressure reducing end and the low-pressure side impeller of the pressure increasing end are connected via a rotating shaft.

[0079] In some embodiments of the present invention, Figure 1 As shown, the first flash evaporation and the third flash evaporation are respectively carried out in the lower part and the upper part of the medium-pressure flash tower 3.

[0080] In some embodiments of the present invention, Figure 1 As shown, the second flash evaporation and the fourth flash evaporation are carried out in the lower part and the upper part of the reabsorption tower 4 respectively.

[0081] In some embodiments of the present invention, preferably, Figure 1 As shown, the first pressurizing component 8 and the second pressurizing component 22 are independently selected from a pressurizing pump and a pressure recovery device. In the present invention, the first pressurizing component and the second pressurizing component are independently selected from a pressurizing pump with a small lift.

[0082] In some embodiments of the present invention, preferably, Figure 1 As shown, a third pressure reducing valve 9 is provided on the pipeline connecting the H2S absorption section and the lower part of the medium-pressure flash tower 3, and a third boosting pump 7 is provided on the pipeline connecting the reabsorption tower 4 and the thermal regeneration tower 5. When a failure occurs in the first pressure recovery device 2-1, the high-pressure sulfur-rich methanol 11 is subjected to a third pressure reduction, and the obtained logistics is subjected to the first flash, the first pressure reduction and the second flash in sequence, and the low-pressure sulfur-containing methanol 14 is subjected to a third boosting, and the obtained logistics is subjected to the heating and regeneration in sequence.

[0083] In the present invention, unless otherwise specified, the first pressure recovery device 2-1, the third pressure reducing valve 9 and the third boosting pump 7 each independently have a working state and a closed state. When the first pressure recovery device 2-1 is in the working state, the third pressure reducing valve 9 and the third boosting pump 7 are both in the closed state; or, when the first pressure recovery device 2-1 is in the closed state, the third pressure reducing valve 9 and the third boosting pump 7 are both in the working state.

[0084] In some embodiments of the present invention, preferably, Figure 1 As shown, a fourth pressure reducing valve 24 is provided on the pipeline connecting the CO2 absorption section and the upper part of the medium-pressure flash tower 3, and a fourth boosting pump 23 is provided on the pipeline connecting the reabsorption tower 4 and the CO2 absorption section. When the second pressure recovery device 2-2 fails, the high-pressure carbon-rich methanol 25 is subjected to the fourth pressure reduction, and the obtained logistics is subjected to the third flash, the second pressure reduction and the fourth flash in sequence. The obtained low-pressure semi-lean methanol 28 is subjected to the fourth boosting, and the obtained logistics is returned to the CO2 absorption.

[0085] In the present invention, unless otherwise specified, the second pressure recovery device 2-2, the fourth pressure reducing valve 24 and the fourth boosting pump 23 each independently have a working state and a closed state. When the second pressure recovery device 2-2 is in the working state, the fourth pressure reducing valve 24 and the fourth boosting pump 23 are both in the closed state; or, when the second pressure recovery device 2-2 is in the closed state, the fourth pressure reducing valve 24 and the fourth boosting pump 23 are both in the working state.

[0086] According to a particularly preferred embodiment of the present invention, a method for recovering high-level energy of an acid gas removal device comprises: subjecting low-pressure sulfur-containing methanol and low-pressure semi-lean methanol from a reabsorption process to a first pressurization and a second pressurization, respectively, to obtain pressurized sulfur-containing methanol and pressurized semi-lean methanol;

[0087] The pressurized sulfur-containing methanol and the high-pressure sulfur-rich methanol from the H2S absorption process are subjected to pressure energy conversion in a first pressure recovery device to obtain high-pressure sulfur-containing methanol and low-pressure sulfur-rich methanol;

[0088] The pressurized semi-lean methanol and the high-pressure carbon-rich methanol from the CO2 absorption process are subjected to pressure energy conversion in a second pressure recovery device to obtain high-pressure semi-lean methanol and low-pressure carbon-rich methanol;

[0089] Wherein, the low-pressure sulfur-containing methanol and the high-pressure sulfur-rich methanol satisfy Formula III: [ΔP (11-12) ×Q 11 +ΔP (15-14) ×Q 14 ]=[ΔP (16-14) ×Q14 ]; The low-pressure semi-lean methanol and high-pressure carbon-rich methanol satisfy Formula IV: [ΔP (25-26) ×Q 25 +ΔP (29-28) ×Q 28 ]=[ΔP (30-28) ×Q 28 ];

[0090] Wherein, the first pressure recovery device and the second pressure recovery device each independently include: a pressure reducing end and a pressure increasing end, and the high-pressure side impeller of the pressure reducing end and the low-pressure side impeller of the pressure increasing end are connected via a rotating shaft;

[0091] The recovery method comprises the following steps:

[0092] (1) subjecting the crude synthesis gas to H2S absorption to obtain pretreated synthesis gas and the high-pressure sulfur-rich methanol; subjecting the pretreated synthesis gas to CO2 absorption to obtain the high-pressure carbon-rich methanol and purified gas;

[0093] (2) converting the high-pressure sulfur-rich methanol and the pressurized sulfur-containing methanol into pressure energy in a first pressure recovery device to obtain the low-pressure sulfur-rich methanol and the high-pressure sulfur-containing methanol;

[0094] (3) subjecting the low-pressure sulfur-rich methanol to a first flash evaporation, and subjecting the obtained flashed sulfur-rich methanol to a first decompression, and then subjecting the obtained low-pressure sulfur-containing methanol to a second flash evaporation, and subjecting the obtained low-pressure sulfur-containing methanol to a first pressurization, to obtain the pressurized sulfur-containing methanol; heating the high-pressure sulfur-containing methanol, and subjecting the obtained high-temperature and high-pressure sulfur-containing methanol to thermal regeneration, and returning the obtained lean methanol to the CO2 absorption;

[0095] (4) converting the high-pressure carbon-rich methanol and the pressurized semi-lean methanol into pressure energy in a second pressure recovery device to obtain the low-pressure carbon-rich methanol and the high-pressure semi-lean methanol;

[0096] (5) The low-pressure carbon-rich methanol is subjected to a third flash distillation, and the obtained carbon-containing methanol after flash distillation is subjected to a second decompression, and then subjected to a fourth flash distillation. The obtained low-pressure semi-lean methanol is subjected to the second pressurization to obtain the pressurized semi-lean methanol; the high-pressure semi-lean methanol is returned and subjected to the CO2 absorption.

[0097] The present invention will be described in detail below through examples.

[0098] Example 1

[0099] Recycling system such as Figure 1As shown, the system comprises: an absorption tower 1, a medium-pressure flash tower 3, a reabsorption tower 4 and a thermal regeneration tower 5 connected in sequence; the absorption tower 1 comprises an H2S absorption section arranged at the bottom and a CO2 absorption section arranged at the top; a first pressure recovery device 2-1 is arranged on the pipeline connecting the low-pressure sulfur-containing methanol outlet of the reabsorption tower 4 and the H2S absorption section; a second pressure recovery device 2-2 is arranged on the pipeline connecting the low-pressure semi-lean methanol outlet of the reabsorption tower 4 and the CO2 absorption section;

[0100] A third pressure reducing valve 9 is provided on the pipeline connecting the H2S absorption section and the lower part of the medium-pressure flash tower 3, and a third boosting pump 7 is provided on the pipeline connecting the reabsorption tower 4 and the thermal regeneration tower 5; a fourth pressure reducing valve 24 is provided on the pipeline connecting the CO2 absorption section and the upper part of the medium-pressure flash tower 3, and a fourth boosting pump 23 is provided on the pipeline connecting the reabsorption tower 4 and the CO2 absorption section.

[0101] The recovery method is carried out in the above recovery system, specifically comprising:

[0102] (1) 120000Nm 3 / h of crude synthesis gas 10 (with a molar content of H2S of 0.5% and a molar content of CO2 of 43%; a temperature of -6°C and a pressure of 5.6MPa) is subjected to H2S absorption in the H2S absorption section of the absorption tower 1 (with a temperature of -25°C and a pressure of 5.6MPa) to obtain pretreated synthesis gas and high-pressure sulfur-rich methanol 11 (with a molar content of H2S of 0.9% and a molar content of CO2 of 37%; a temperature of -8°C and a pressure of 5.56MPa); the pretreated synthesis gas is subjected to CO2 absorption to obtain high-pressure carbon-rich methanol 25 (with a molar content of H2S of 0.001% and a molar content of CO2 of 34%; a temperature of -11°C and a pressure of 5.56MPa) and purified gas;

[0103] (2) The high-pressure sulfur-rich methanol 11 is introduced into the high-pressure side inlet of the pressure reducing end of the first pressure recovery device 2-1, and at the same time, the low-pressure sulfur-containing methanol 14 (pressure of 0.2 MPa) from the reabsorption tower 4 first passes through the first booster pump 8 (lift of 90 m) with a small lift to supplement the insufficient pressure energy, and then the boosted sulfur-containing methanol 15 (pressure of 0.9 MPa) enters the low-pressure side inlet of the pressure boosting end of the first pressure recovery device 2-1;

[0104] In the first pressure recovery device 2-1, the "pressure energy" of the high-pressure sulfur-rich methanol 11 on the high-pressure side of the pressure reducing end is first converted into the "mechanical energy" of the rotating shaft, and then converted into the "pressure energy" of the pressurized sulfur-containing methanol 15 on the low-pressure side of the pressure increasing end, thereby, the pressure of the pressurized sulfur-containing methanol 15 is increased and converted into high-pressure sulfur-containing methanol 16 (pressure is 1.82MPa); the above-mentioned high-pressure sulfur-containing methanol 16 enters the heater 6, and the obtained high-temperature and high-pressure sulfur-containing methanol 19 (temperature is 88°C) enters the thermal regeneration tower 5 for thermal regeneration (temperature is 86°C, pressure is 0.28MPa), and the obtained lean methanol 18 (H2S molar content is 0%, CO2 molar content is 0%) is cooled and returned to the absorption tower 1 to absorb acid gas impurities in the crude synthesis gas again;

[0105] (3) The pressure of the high-pressure sulfur-rich methanol solution 11 is converted from high pressure to low pressure and flows out from the first pressure recovery device 2-1, and the obtained low-pressure sulfur-rich methanol 12 (pressure of 1.86 MPa) enters the lower part of the medium-pressure flash tower 3 for the first flash (temperature of -27°C, pressure of 1.8 MPa), and the obtained flashed sulfur-rich methanol 20 (molar content of H2S is 0.9%, molar content of CO2 is 35%) enters the first pressure reducing valve 13, and the obtained reduced-pressure sulfur-rich methanol 21 enters the lower part of the reabsorption tower 4 for the second flash (pressure of 0.2 MPa), to obtain low-pressure sulfur-rich methanol 14 (molar content of H2S is 1.4%, molar content of CO2 is 0.9%, pressure of 0.2 MPa);

[0106] (4) The high-pressure carbon-rich methanol 25 is introduced into the high-pressure side inlet of the pressure reducing end of the second pressure recovery device 2-2, and at the same time, the low-pressure semi-lean methanol 28 (pressure of 0.2 MPa) from the reabsorption tower 4 is supplemented by the second booster pump 22 (lift of 90 m) with a small lift to supplement the insufficient pressure energy, so that the pressurized semi-lean methanol 29 (pressure of 2.08 MPa) is obtained and enters the low-pressure side inlet of the boosting end of the second pressure recovery device 2-2; in the second pressure recovery device 2-2, the "pressure energy" of the high-pressure carbon-rich methanol 25 on the high-pressure side of the pressure reducing end is first converted into the "mechanical energy" of the rotating shaft, and then converted into the "pressure energy" of the pressurized semi-lean methanol 29 on the low-pressure side of the boosting end, thereby, the pressure of the pressurized semi-lean methanol 29 is increased, and it is converted into a high-pressure semi-lean methanol solution 30 (pressure of 6.9 MPa) and then enters the absorption tower 1 again to absorb CO2 in the crude synthesis gas;

[0107] (5) The pressure of the high-pressure carbon-rich methanol 25 is converted from high pressure to low pressure and flows out from the second pressure recovery device 2-2, and the low-pressure carbon-rich methanol 26 (pressure is 1.86 MPa) enters the upper part of the medium-pressure flash tower 3 for the third flash (temperature is -30°C, pressure is 1.8 MPa), and the obtained flashed carbon-containing methanol 33 (molar content of H2S is 0.001%, molar content of CO2 is 34%) enters the second pressure reducing valve 27, and the obtained reduced-pressure carbon-containing methanol 34 enters the upper part of the reabsorption tower 4 for the fourth flash (pressure is 0.2 MPa) to obtain low-pressure semi-lean methanol 28 (molar content of H2S is 0.001%, molar content of CO2 is 25%, pressure is 0.2 MPa);

[0108] (6) When the first pressure recovery device 2-1 is set to fail, the high-pressure sulfur-rich methanol 11 enters the third pressure reducing valve 9, and the resulting logistics enters the lower part of the medium-pressure flash tower 3, and the low-pressure sulfur-rich methanol 14 enters the third booster pump 7, and the resulting logistics enters the heater 6, and the obtained high-temperature and high-pressure sulfur-containing methanol 19 enters the thermal regeneration tower 5 for thermal regeneration;

[0109] When a fault occurs in the second pressure recovery device 2-2, the high-pressure carbon-rich methanol 25 enters the fourth pressure reducing valve 24, and the resulting logistics enters the upper part of the medium-pressure flash tower 3, and the low-pressure semi-lean methanol 28 enters the fourth booster pump 23, and the resulting logistics returns to the absorption tower 1.

[0110] Comparative Example 1

[0111] According to the recovery system of Example 1, except that Figure 2 As shown, the recovery system does not contain a first pressure recovery device and a second pressure recovery device;

[0112] The recovery method of Example 1 is the same as that of Example 1, except that steps (2) to (6) are omitted.

[0113] That is, the high-pressure sulfur-rich methanol 11 enters the third pressure reducing valve 9, and the obtained low-pressure sulfur-rich methanol 12 (pressure is 1.86MPa) enters the lower part of the medium-pressure flash tower 3 for the first flash evaporation (temperature is -27°C, pressure is 1.8MPa), and the obtained flashed sulfur-rich methanol 20 (molar content of H2S is 0.9%, molar content of CO2 is 35%) enters the first pressure reducing valve 13, and the obtained reduced-pressure sulfur-rich methanol 21 enters the lower part of the reabsorption tower 4 for the second flash evaporation (pressure is 0.2MPa) to obtain low-pressure sulfur-containing methanol 14 (molar content of H2S is 0.9%, molar content of CO2 is 35%). The molar content of H2S is 1.4%, the molar content of CO2 is 0.9%, and the pressure is 0.2MPa) enters the third booster pump 7 (with a head of 195m), and the obtained high-pressure sulfur-containing methanol 16 (with a pressure of 1.82MPa) enters the heater 6, and the obtained high-temperature and high-pressure sulfur-containing methanol 19 (with a temperature of 88°C) enters the thermal regeneration tower 5 for thermal regeneration (with a temperature of 86°C and a pressure of 0.28MPa), and the obtained lean methanol 18 (with a molar content of H2S of 0%, a molar content of CO2 of 0%) is returned to the absorption tower 1 after cooling to absorb the acidic gas impurities in the crude synthesis gas again.

[0114] The high-pressure carbon-rich methanol 25 enters the fourth pressure reducing valve 24, and the obtained low-pressure carbon-rich methanol 26 (pressure is 1.86 MPa) enters the upper part of the medium-pressure flash tower 3 for the third flash (temperature is -30°C, pressure is 1.8 MPa), and the obtained flashed carbon-containing methanol 33 (the molar content of H2S is 0.001%, the molar content of CO2 is 34%) enters the second pressure reducing valve 27, and the obtained reduced-pressure carbon-containing methanol 34 enters the upper part of the reabsorption tower 4 for the fourth flash (pressure is 0.2 MPa), and the low-pressure semi-lean methanol 28 (the molar content of H2S is 0.001%, the molar content of CO2 is 25%, and the pressure is 0.2 MPa) enters the fourth booster pump 23 (head is 698m), and the obtained high-pressure semi-lean methanol 30 (pressure is 6.26 MPa) enters the absorption tower 1 to absorb CO2 in the crude synthesis gas.

[0115] Compared with Comparative Example 1, Example 1 adopts a first booster pump with a head of 90m to replace the third booster pump with an original head of 195m, and adopts a second booster pump with a head of 90m to replace the fourth booster pump with an original head of 698m. The kinetic energy and pressure energy of the liquid flow are converted into mechanical energy so that the pump head can be significantly reduced. 165KW and 310KW of power are recovered at the two places respectively, reducing power consumption. In addition, the technology has a simple structure, a small footprint, a wide operating range, is not affected by system fluctuations and abnormal operations, and has a high energy recovery rate.

[0116] Comparative Example 2

[0117] According to the recovery system of Example 1, except that Figure 3As shown, the recovery system replaces the first pressure recovery device 2-1 and the second pressure recovery device 2-2 with the first hydraulic turbine device 01-1 and the second hydraulic turbine device 01-2 respectively;

[0118] The recovery method of Example 1 is the same as that of Example 1, except that steps (2) to (6) are omitted, i.e.,

[0119] The pressure of the high-pressure sulfur-rich methanol 11 is reduced after entering the first hydraulic turbine device 01-1 to obtain low-pressure sulfur-rich methanol 12 (pressure is 1.86MPa). The high-level energy of the high-pressure sulfur-rich methanol 11 is recovered through the first hydraulic turbine device 01-1. The recovered energy assists in driving the third booster pump 7 to increase the pressure of the low-pressure sulfur-containing methanol 14 (pressure is 0.2MPa) from the reabsorption tower 4 and convert it into high-pressure sulfur-containing methanol 16 (pressure is 1.82MPa); then it enters the heater 6 to obtain high-temperature and high-pressure sulfur-containing methanol 19, which enters the thermal regeneration tower 5 for thermal regeneration. The obtained lean methanol 18 is cooled and returned to the absorption tower 1 to absorb the acid gas impurities in the crude synthesis gas again;

[0120] The low-pressure sulfur-rich methanol 12 enters the medium-pressure flash tower 3 for the first flash evaporation, and the obtained flashed sulfur-rich methanol 20 enters the first pressure reducing valve 13, and the obtained reduced-pressure sulfur-rich methanol 21 enters the lower part of the reabsorption tower 4 for the second flash evaporation (pressure is 0.2 MPa), to obtain the low-pressure sulfur-containing methanol 14;

[0121] The pressure of the high-pressure carbon-rich methanol 25 (operating pressure of 5.56 MPa) is reduced after entering the second hydraulic turbine device 01-2 to obtain low-pressure carbon-rich methanol 26 (pressure of 1.86 MPa). The high-level energy of the high-pressure carbon-rich methanol is recovered by the second hydraulic turbine device 01-2. The recovered energy assists in driving the fourth booster pump 23 to increase the pressure of the low-pressure semi-lean methanol 28 from the reabsorption tower 4, and converts it into high-pressure semi-lean methanol 30 (pressure of 6.26 MPa) and returns to the absorption tower 1 to absorb the CO2 gas in the crude synthesis gas again.

[0122] The low-pressure carbon-rich methanol 26 enters the upper part of the medium-pressure flash tower 3 for the third flash evaporation, and the carbon-containing methanol 33 obtained after flash evaporation enters the second pressure reducing valve 27. The carbon-containing methanol 34 obtained after reduced pressure enters the upper part of the reabsorption tower 4 for the fourth flash evaporation (pressure is 0.2 MPa) to obtain the low-pressure semi-lean methanol 28;

[0123] In comparative example 2, a hydraulic turbine device is used to recover high-level energy to assist in driving a pump, with 110KW and 205KW of power recovered at two locations respectively.

[0124] Therefore, compared with Comparative Example 2, Example 1 adopts the recovery method provided by the present invention, which has more recovered power and higher energy recovery rate.

[0125] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for recovering high-level energy of an acid gas removal device, characterized in that: The recovery method comprises: The low-pressure sulfur-containing methanol (14) and the low-pressure semi-lean methanol (28) from the reabsorption process are subjected to a first pressurization and a second pressurization, respectively, to obtain pressurized sulfur-containing methanol (15) and pressurized semi-lean methanol (29); The pressurized sulfur-containing methanol (15) and the high-pressure sulfur-rich methanol (11) from the H2S absorption process are subjected to pressure energy conversion in a first pressure recovery device (2-1) to obtain high-pressure sulfur-containing methanol (16) and low-pressure sulfur-rich methanol (12); The pressurized semi-lean methanol (29) and the high-pressure carbon-rich methanol (25) from the CO2 absorption process are subjected to pressure energy conversion in a second pressure recovery device (2-2) to obtain high-pressure semi-lean methanol (30) and low-pressure carbon-rich methanol (26); Wherein, the low-pressure sulfur-containing methanol (14) and the high-pressure sulfur-rich methanol (11) satisfy Formula I: [ΔP (11-12) ×Q 11 ]≤[ΔP (16-14) ×Q 14 ]; The low-pressure semi-lean methanol (28) and the high-pressure carbon-rich methanol (25) satisfy Formula II: [ΔP (25-26) ×Q 25 ]≤[ΔP (30-28) ×Q 28 ].

2. The recycling method according to claim 1, wherein: The low-pressure sulfur-containing methanol (14) and the high-pressure sulfur-rich methanol (11) satisfy Formula III: [ΔP (11-12) ×Q 11 +ΔP (15-14) ×Q 14 ]=[ΔP (16-14) ×Q 14 ]; The low-pressure semi-lean methanol (28) and the high-pressure carbon-rich methanol (25) satisfy Formula IV: [ΔP (25-26) ×Q 25 +ΔP (29-28) ×Q 28 ]=[ΔP (30-28) ×Q 28 ]; And / or, the first pressure recovery device (2-1) and the second pressure recovery device (2-2) each independently comprise: a pressure reducing end and a pressure increasing end, and the high-pressure side impeller of the pressure reducing end and the low-pressure side impeller of the pressure increasing end are connected via a rotating shaft; And / or, the recovery method comprises the following steps: (1) subjecting the crude synthesis gas (10) to H2S absorption to obtain pretreated synthesis gas and the high-pressure sulfur-rich methanol (11); subjecting the pretreated synthesis gas to CO2 absorption to obtain the high-pressure carbon-rich methanol (25) and purified gas; (2) converting the high-pressure sulfur-rich methanol (11) and the pressurized sulfur-containing methanol (15) into pressure energy in a first pressure recovery device (2-1) to obtain the low-pressure sulfur-rich methanol (12) and the high-pressure sulfur-containing methanol (16); (3) subjecting the low-pressure sulfur-rich methanol (12) to a first flash evaporation, and subjecting the obtained flashed sulfur-rich methanol (20) to a first decompression, and then subjecting the obtained low-pressure sulfur-containing methanol (14) to a first pressurization, to obtain the pressurized sulfur-containing methanol (15); heating the high-pressure sulfur-containing methanol (16), and subjecting the obtained high-temperature and high-pressure sulfur-containing methanol (19) to thermal regeneration, and returning the obtained lean methanol (18) to the CO2 absorption; (4) converting the high-pressure carbon-rich methanol (25) and the pressurized semi-lean methanol (29) into pressure energy in a second pressure recovery device (2-2) to obtain the low-pressure carbon-rich methanol (26) and the high-pressure semi-lean methanol (30); (5) The low-pressure carbon-rich methanol (26) is subjected to a third flash distillation, and the obtained flashed carbon-containing methanol (33) is subjected to a second decompression, and then subjected to a fourth flash distillation. The obtained low-pressure semi-lean methanol (28) is subjected to a second pressurization to obtain the pressurized semi-lean methanol (29); the high-pressure semi-lean methanol (30) is returned and subjected to the CO2 absorption.

3. The recycling method according to claim 2, wherein: In step (1), The conditions for H2S absorption and CO2 absorption each independently include: a temperature of -70 to -20°C and a pressure of 3-6MPa; and / or, the temperature of the crude synthesis gas (10) is between -30 and 0°C and the pressure is between 3 and 6 MPa; and / or, the volume flow ratio of the crude synthesis gas (10) to the high-pressure sulfur-rich methanol (11) is 1:0.05-0.1; And / or, the volume flow ratio of the crude synthesis gas (10) and the high-pressure carbon-rich methanol (25) is 1:0.16-0.

3.

4. The recovery method according to claim 2 or 3, wherein: In step (2), The pressure difference ΔP between the high-pressure sulfur-rich methanol (11) and the low-pressure sulfur-rich methanol (12) (11-12) 2-5MPa; and / or, the pressure of the low-pressure sulfur-rich methanol (12) is 0.5-2 MPa; and / or, the pressure difference ΔP between the pressurized sulfur-containing methanol (15) and the high-pressure sulfur-containing methanol (16) (16-15) 0.5-2.5MPa; And / or, the pressure of the pressurized sulfur-containing methanol (15) is 0.5-1 MPa; the pressure of the high-pressure sulfur-containing methanol (16) is 1.5-3 MPa.

5. According to the recovery method according to any one of claims 2 to 4, in step (3), The conditions of the first flash distillation include: The temperature is -40 to -10°C and the pressure is 0.5-2MPa; And / or, the conditions of the second flash evaporation include: a temperature of -60 to -30°C and a pressure of 0.05-0.3 MPa; and / or, the temperature of the high temperature and high pressure sulfur-containing methanol (19) is 70-100° C.; And / or, the conditions for the thermal regeneration include: a temperature of 70-100° C. and a pressure of 0.1-0.4 MPa.

6. The recovery method according to any one of claims 2 to 5, wherein: In step (4), The pressure difference ΔP between the high-pressure carbon-rich methanol (25) and the low-pressure carbon-rich methanol (26) (25-26) 2-5MPa; and / or, the pressure of the low-pressure carbon-rich methanol (26) is 0.5-2.2 MPa; and / or, the pressure difference ΔP between the pressurized semi-lean methanol (29) and the high-pressure semi-lean methanol (30) (30-29) 3-6MPa; And / or, the pressure of the supercharged semi-lean methanol (29) is 0.5-2 MPa; the pressure of the high-pressure semi-lean methanol (30) is 3.5-7.5 MPa.

7. The recovery method according to any one of claims 2 to 6, wherein: In step (5), The conditions of the third flash evaporation include: temperature of -40 to -10°C and pressure of 0.5 to 2 MPa; And / or, the conditions of the fourth flash evaporation include: a temperature of -60 to -30°C and a pressure of 0.05-0.3 MPa.

8. The recovery method according to any one of claims 2 to 7, wherein: When the first pressure recovery device (2-1) fails, the high-pressure sulfur-rich methanol (11) is subjected to the third decompression, and the obtained logistics is sequentially subjected to the first flash evaporation, the first decompression and the second flash evaporation, and the obtained low-pressure sulfur-containing methanol (14) is subjected to the third pressurization, and the obtained logistics is sequentially subjected to the heating and thermal regeneration; And / or, when the second pressure recovery device (2-2) fails, the high-pressure carbon-rich methanol (25) is subjected to the fourth decompression, and the resulting logistics is sequentially subjected to the third flash evaporation, the second decompression and the fourth flash evaporation, and the low-pressure semi-lean methanol (28) is subjected to the fourth pressurization, and the resulting logistics is returned to the CO2 absorption.

9. A high-level energy recovery system for an acid gas removal device, characterized in that: The recovery system comprises: an absorption tower (1), a medium-pressure flash tower (3), a reabsorption tower (4) and a thermal regeneration tower (5) connected in sequence; The absorption tower (1) comprises an H2S absorption section arranged at the bottom and a CO2 absorption section arranged at the top, and is used to sequentially absorb H2S and CO2 from the crude synthesis gas (10); A first pressure recovery device (2-1) is provided on the pipeline connecting the low-pressure sulfur-containing methanol outlet of the reabsorption tower (4) and the H2S absorption section, for converting the pressure energy of the pressurized sulfur-containing methanol (15) obtained by passing the low-pressure sulfur-containing methanol (14) through the first pressurizing component (8) with the high-pressure sulfur-rich methanol (11) to obtain high-pressure sulfur-containing methanol (16) and low-pressure sulfur-rich methanol (12); The low-pressure sulfur-rich methanol (12) enters the lower part of the medium-pressure flash tower (3) for a first flash evaporation, and the obtained flashed sulfur-rich methanol (20) enters the first pressure reducing valve (13), and the obtained reduced-pressure sulfur-rich methanol (21) enters the lower part of the reabsorption tower (4) for a second flash evaporation to obtain the low-pressure sulfur-containing methanol (14); the high-pressure sulfur-containing methanol (16) enters the heater (6), and the obtained high-temperature and high-pressure sulfur-containing methanol (19) enters the thermal regeneration tower (5), and the obtained lean methanol (18) returns and is reused in the CO2 absorption section; A second pressure recovery device (2-2) is provided on the pipeline connecting the low-pressure semi-lean methanol outlet of the reabsorption tower (4) and the CO2 absorption section, for converting the pressure energy of the pressurized semi-lean methanol (29) obtained by passing the low-pressure semi-lean methanol (28) through the second pressurizing component (22) with the high-pressure carbon-rich methanol (25) to obtain low-pressure carbon-rich methanol (26), and returning the obtained high-pressure semi-lean methanol (30) to be reused in the CO2 absorption section; The low-pressure carbon-rich methanol (26) enters the upper part of the medium-pressure flash tower (3) for a third flash, and the obtained flashed carbon-containing methanol (33) enters the second pressure reducing valve (27), and the obtained reduced-pressure carbon-containing methanol (34) enters the upper part of the reabsorption tower (4) for a fourth flash, to obtain the semi-lean methanol (28); Wherein, the first pressure recovery device (2-1) and the second pressure recovery device (2-2) each independently include: a pressure reducing end and a pressure increasing end, and the high-pressure side impeller of the pressure reducing end and the low-pressure side impeller of the pressure increasing end are connected via a rotating shaft.

10. The recycling system according to claim 9, wherein: The first pressurizing component (8) and the second pressurizing component (22) are each independently selected from a pressurizing pump and a pressure recovery device; And / or, a third pressure reducing valve (9) is provided on the pipeline connecting the H2S absorption section and the lower part of the medium-pressure flash tower (3), and a third boosting pump (7) is provided on the pipeline connecting the reabsorption tower (4) and the thermal regeneration tower (5), so as to be used for, when a failure occurs in the first pressure recovery device (2-1), subjecting the high-pressure sulfur-rich methanol (11) to a third pressure reduction, and subjecting the obtained logistics to the first flash, the first pressure reduction and the second flash in sequence, and subjecting the obtained low-pressure sulfur-containing methanol (14) to a third boosting, and subjecting the obtained logistics to the heating and regeneration in sequence; And / or, a fourth pressure reducing valve (24) is provided on the pipeline connecting the CO2 absorption section and the upper part of the medium-pressure flash tower (3), and a fourth boosting pump (23) is provided on the pipeline connecting the reabsorption tower (4) and the CO2 absorption section, which is used for, when the second pressure recovery device (2-2) fails, subjecting the high-pressure carbon-rich methanol (25) to a fourth pressure reduction, and subjecting the obtained logistics to the third flash, the second pressure reduction and the fourth flash in sequence, and subjecting the obtained low-pressure semi-lean methanol (28) to a fourth boosting, and then returning the obtained logistics to the CO2 absorption.

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