CN110624370A - Low-temperature methanol washing process CO2Recovery system and method - Google Patents
Low-temperature methanol washing process CO2Recovery system and method Download PDFInfo
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- CN110624370A CN110624370A CN201911007693.6A CN201911007693A CN110624370A CN 110624370 A CN110624370 A CN 110624370A CN 201911007693 A CN201911007693 A CN 201911007693A CN 110624370 A CN110624370 A CN 110624370A
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- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 title claims abstract description 369
- 238000000034 method Methods 0.000 title claims abstract description 27
- 238000005406 washing Methods 0.000 title claims abstract description 16
- 230000008929 regeneration Effects 0.000 claims abstract description 57
- 238000011069 regeneration method Methods 0.000 claims abstract description 57
- 238000000926 separation method Methods 0.000 claims abstract description 57
- 238000003795 desorption Methods 0.000 claims abstract description 51
- 239000007788 liquid Substances 0.000 claims abstract description 49
- 238000010521 absorption reaction Methods 0.000 claims abstract description 38
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 37
- 238000011084 recovery Methods 0.000 claims abstract description 27
- 238000006477 desulfuration reaction Methods 0.000 claims abstract description 20
- 230000023556 desulfurization Effects 0.000 claims abstract description 20
- 238000005261 decarburization Methods 0.000 claims abstract description 6
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 9
- 229910052717 sulfur Inorganic materials 0.000 claims description 9
- 239000011593 sulfur Substances 0.000 claims description 9
- 238000004064 recycling Methods 0.000 claims 1
- 239000007789 gas Substances 0.000 abstract description 83
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 abstract description 14
- 229910000037 hydrogen sulfide Inorganic materials 0.000 abstract description 14
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 abstract description 12
- 229910001873 dinitrogen Inorganic materials 0.000 abstract description 6
- 230000006837 decompression Effects 0.000 abstract 1
- 239000000463 material Substances 0.000 description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 6
- 229910052799 carbon Inorganic materials 0.000 description 6
- 239000003245 coal Substances 0.000 description 6
- 230000001172 regenerating effect Effects 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 5
- 239000002994 raw material Substances 0.000 description 5
- 238000005262 decarbonization Methods 0.000 description 4
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 4
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- PVXVWWANJIWJOO-UHFFFAOYSA-N 1-(1,3-benzodioxol-5-yl)-N-ethylpropan-2-amine Chemical compound CCNC(C)CC1=CC=C2OCOC2=C1 PVXVWWANJIWJOO-UHFFFAOYSA-N 0.000 description 1
- 241001076939 Artines Species 0.000 description 1
- QMMZSJPSPRTHGB-UHFFFAOYSA-N MDEA Natural products CC(C)CCCCC=CCC=CC(O)=O QMMZSJPSPRTHGB-UHFFFAOYSA-N 0.000 description 1
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 239000005431 greenhouse gas Substances 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000003345 natural gas Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/1406—Multiple stage absorption
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/1418—Recovery of products
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/1425—Regeneration of liquid absorbents
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/1456—Removing acid components
- B01D53/1468—Removing hydrogen sulfide
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/1456—Removing acid components
- B01D53/1475—Removing carbon dioxide
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/18—Absorbing units; Liquid distributors therefor
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B17/00—Sulfur; Compounds thereof
- C01B17/16—Hydrogen sulfides
- C01B17/167—Separation
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B17/00—Sulfur; Compounds thereof
- C01B17/16—Hydrogen sulfides
- C01B17/168—Purification
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/50—Carbon dioxide
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/151—Reduction of greenhouse gas [GHG] emissions, e.g. CO2
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Analytical Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Gas Separation By Absorption (AREA)
- Carbon And Carbon Compounds (AREA)
Abstract
The invention discloses CO in a low-temperature methanol washing process2The recovery system comprises an absorption tower and CO2A desorption tower, a first vacuum tank, a thermal regeneration tower and a methanol/water separation tower; the absorption tower is divided into four sections, the lowest section is a desulfurization section, and the upper three sections are decarburization sections; the inlet of the desulfurization section of the absorption tower is connected with the gas outlet of the first gas-liquid separation tank; the outlet of the desulfurization section of the absorption tower is connected with a CO2 desorption tower; an outlet at the upper section of the CO2 desorption tower is connected with an inlet of a first vacuum tank; the gas outlet end of the first vacuum tank is connected with the top gas outlet end of the CO2 desorption tower; the liquid outlet end of the first vacuum tank is connected with the inlet of the heat regeneration tower; the poor methanol outlet at the bottom of the thermal regeneration tower is connected with the inlet of the methanol/water separation tower and the top of the absorption towerAnd (4) a section. The invention separates CO by adopting a vacuum or decompression desorption method2The gas adopts the process flow of replacing nitrogen gas stripping by vacuum desorption, reduces the hydrogen sulfide concentration tower, does not generate tail gas, cancels a tail gas washing tower and almost all CO2Are all desorbed into CO2In the product gas.
Description
Technical Field
The invention relates to the technical field of coal chemical industry, in particular to CO in a low-temperature methanol washing process2And (5) recovering the system.
Background
With the rapid development of methanol industry, CO is produced in methanol production2The amount of emissions is also increasing. In the process of preparing methanol from coal, unit product CO2The emission of CO is 3.4-5.4 tons2Per ton of methanol. Compared with the production of methanol from natural gas, the coal-based methanol production has the same production scale and the carbon emission is nearly 8 times higher. The carbon emission generated in the coal-to-methanol production process accounts for 53.38%, the carbon emission generated by the combustion of the fuel of the thermoelectric boiler accounts for 36.25%, and the carbon emission caused by the net purchased power consumption accounts for 10.36%. It can be seen that direct carbon emissions are of CO2Emission source, CO2The emission reduction space is large. Therefore, the research on carbon capture in the process of preparing methanol from coal is of great significance.
At present, in projects of large-scale coal-to-ammonia synthesis, coal-to-methanol synthesis and the like, the recovery rate of CO2 obtained by low-temperature methanol washing is only about 65%, and a large amount of CO in tail gas2Due to the low concentration being directly vented, only a portion is present in the CO2CO in the product gas2Is recycled, not only causes a large amount of greenhouse gas emission, but also causes CO2The waste of resources. For recovering CO discharged from tail gas2PSA recovery or MEA, MDEA and the like can be adopted, and even the raw material gas can be directly compressed and returned. But this requires an additional capture device and is energy intensive.
Disclosure of Invention
In order to overcome the prior artIn view of the foregoing deficiencies of the art, embodiments of the present invention provide a low temperature methanol wash process CO2Recovery system and method for separating CO by vacuum or reduced pressure desorption2The process flow of gas stripping with vacuum desorption instead of nitrogen gas reduces the concentration tower of hydrogen sulfide, and because no tail gas is produced, the tail gas washing tower is also cancelled, the flow is simplified, and almost all CO in the raw material gas2Are all desorbed into CO2The purity of the product gas is as high as more than 99%.
In order to achieve the purpose, the invention provides the following technical scheme:
low-temperature methanol washing process CO2The recovery system comprises an absorption tower and CO2A desorption tower, a first vacuum tank, a thermal regeneration tower and a methanol/water separation tower;
the absorption tower is divided into four sections, the lowest section is a desulfurization section, and the upper three sections are decarburization sections; the inlet of the desulfurization section of the absorption tower is connected with the gas outlet of the first gas-liquid separation tank;
the outlet of the desulfurization section of the absorption tower is connected with a CO2 desorption tower; an outlet at the upper section of the CO2 desorption tower is connected with an inlet of a first vacuum tank;
the gas outlet end of the first vacuum tank is connected with the top gas outlet end of the CO2 desorption tower; the liquid outlet end of the first vacuum tank is connected with the inlet of the heat regeneration tower;
the poor methanol outlet at the bottom of the thermal regeneration tower is connected with the inlet of the methanol/water separation tower and the top of the absorption tower.
Further, the air outlet end of the first vacuum tank is connected with CO through a vacuum pump2The top exhaust end of the desorber.
Further, the device also comprises a second gas-liquid separation tank; the top gas outlet of the thermal regeneration tower is connected with the inlet of the second gas-liquid separation tank; and a liquid discharge port of the second gas-liquid separation tank is connected with the thermal regeneration tower.
Further, a liquid outlet of the first gas-liquid separation tank is connected with the methanol/water separation tower through a heat exchanger; the poor methanol outlet at the bottom of the thermal regeneration tower is connected with the methanol/water separation tower through a heat exchanger.
Further, a gas outlet of the methanol/water separation tower is connected with a sulfur recovery system; the liquid outlet of the methanol/water separation tower is connected with the thermal regeneration tower.
Further, the poor methanol outlet at the bottom of the thermal regeneration tower is connected with the top of the absorption tower through an air pump.
Further, the device also comprises a second vacuum tank; the liquid outlet end of the first vacuum tank is connected with the inlet of the second vacuum tank, and the gas outlet end of the second vacuum tank is connected with CO2The top exhaust end of the desorber; the liquid outlet end of the second vacuum tank is connected with the inlet of the heat regeneration tower.
Further, CO2The bottom outlet of the desorption tower is connected with a second vacuum tank.
Further, the operating pressure of the first vacuum tank is 50 kPa-300 kPa; the second vacuum tank is operated at a pressure of 10kPa to 100 kPa.
Low-temperature methanol washing process CO2A recovery process comprising the steps of:
from CO2Rich CO from the desorber2Methanol, rich in H2S methanol enters a first vacuum tank, and CO is separated out through vacuum desorption of the first vacuum tank2Gas admission to CO2Upper end of desorber and CO2Converging the product gas;
separating in a first vacuum tank to obtain H-rich2S, feeding the methanol into a thermal regeneration tower through a pump for thermal regeneration; obtaining poor methanol at the bottom of the thermal regeneration tower and H rich at the top of the thermal regeneration tower2S gas;
after the lean methanol is discharged from the bottom of the thermal regeneration tower, part of the lean methanol is sent to the top of the absorption tower, and part of the lean methanol is sent to a methanol/water separation tower;
h obtained from the top of the thermal regeneration tower2And after gas-liquid separation of S gas, the gas is sent to a sulfur recovery system, and the liquid flows back to a regenerative tower.
The invention has the technical effects and advantages that:
1. the invention greatly improves CO2The yield of the product gas can be adjusted by adjusting the operating temperature and pressure of the vacuum tank, the maximum yield is 92 percent, the yield adjusting range is 61 percent to 92 percent, and CO in the product gas2The concentration can reach 99 percent, and the content of impurities such as sulfide in the product gas reaches the environmental standardPreparing;
2. the invention adopts the process flow of replacing nitrogen gas stripping by vacuum desorption, does not need to additionally add nitrogen gas and reduces the cost.
3. The invention adopts the process flow of replacing nitrogen gas stripping with vacuum desorption, reduces the hydrogen sulfide concentration tower, cancels the tail gas washing tower because no tail gas is generated, and simplifies the process flow.
The invention adopts the process flow of replacing nitrogen gas stripping by vacuum desorption, and can control CO by controlling the operating pressure and temperature2The yield was found.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 shows CO in a coal-to-methanol process of the prior art2A flow chart of a tail gas treatment system.
FIG. 2 shows CO in the process of preparing methanol from coal according to the present invention2A recovery system flow diagram.
FIG. 3 shows CO in the process of preparing methanol from coal according to the present invention2A recovery system flow diagram.
The reference signs are: 1 absorption column, 2CO2Desorption column, 3H2The system comprises an S concentration tower, a 4 thermal regeneration tower, a 5 methanol/water separation tower, a 6 first gas-liquid separation tank, a 7 second gas-liquid separation tank, an 8 air pump, a 9 heat exchanger, a 10 compressor, an 11 material pump, a 30 first vacuum tank and a 31 second vacuum tank.
Detailed Description
The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings. It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.
The following detailed description is exemplary in nature and is intended to provide further details of the invention. Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention.
Comparative example 1
The raw material gas composition and the operation conditions of the same tower adopted in the proportion example are the same as those of the example 1, the low-temperature methanol washing process flow in the prior art is adopted, and the nitrogen stripping method is adopted for H2And (4) concentrating the S.
Referring to FIG. 1, the feed gas has been previously washed with water in a shift system to remove NH therefrom3The content is reduced to below 1ppm, and the water is separated in a first gas-liquid separation tank 6 and then enters a desulfurization section of a lower tower of an absorption tower 1, the absorption tower 1 is divided into four sections, the lowest section is a desulfurization section, the upper three sections are decarburization sections, and raw gas in the desulfurization section is subjected to CO-rich raw gas2Washing with methanol solution to remove H2S, COS and part of CO2The components are added into a decarbonization section, the gas entering the decarbonization section does not contain sulfur, the gas is washed by lean methanol liquid at the top of the C-01 tower, and purified gas is led out from the top of the tower and absorbs H2S and CO2Then, the methanol coming out of the tower desulfurization section of the absorption tower 1 is sent into CO2Desorption column 2, CO2CO is obtained from the top of the desorption tower 22And (4) product gas 13.
From CO2CO is enriched at the upper section of the desorption tower 22Methanol is introduced into H2S concentration column 3, H2S concentration tower 3 operating pressure 300KPa, temperature-50 deg.C, and obtaining rich H by nitrogen stripping2S methanol from H2The S concentration tower 3 enters a thermal regeneration tower 4 for thermal regeneration, and the nitrogen flow is CO in the feed gas210% of (C), tail gas 14 from H2Directly discharged from the top of the S concentration tower 3 and rich in H2The S methanol is thermally regenerated by a thermal regeneration tower 4, poor methanol is obtained at the bottom of the tower, and H-enriched methanol is obtained at the top of the tower2S gas.
And after part of poor methanol comes out from the bottom of the thermal regeneration tower 4, the poor methanol is sent to the top of the absorption tower 1 after heat exchange and temperature reduction.
H obtained from the top of the thermal regeneration tower 42S gas is separated by a second gas-liquid separation tank 7 and then is sent to a sulfur recovery system, and liquid flows back to H2And an S concentration tower 3.
The aqueous methanol from the bottom of the thermal regeneration tower 4 also contains CO2And the methanol is sent to the middle part of a methanol/water separation tower 5, poor methanol obtained at the top of the methanol/water separation tower 5 flows back to a regenerative tower 4, and water with the methanol content reaching the emission standard is obtained at the bottom of the methanol/water separation tower 5 and is discharged out of the system.
CO2The yield is only 63%, the gas flow rate of the obtained product is 15226Nm/h, most of CO2Directly discharged from the tail gas 14, the tail gas composition is shown in table 3 below:
TABLE 3 Tail gas composition
| Composition of | Content% (mol) |
| CO2 | 77.9 |
| H2 | 0.0021 |
| N2 | 21.7 |
| H2S | 0.0024 |
| CH4 | 0.0019 |
| CO | 0.017 |
| CH4O | 0.0049 |
| Others | 0.3717 |
Example 1:
the invention provides CO in a low-temperature methanol washing process2The recovery system comprises an absorption tower 1, a CO2 desorption tower 2, a thermal regeneration tower 4 and a methanol/water separation tower 5.
The absorption tower 1 is divided into four sections, wherein the lowest section is a desulfurization section, and the upper three sections are decarburization sections; the inlet of the desulfurization section of the absorption tower 1 is connected with a first gas-liquid separation tank 6;
the outlet of the desulfurization section of the absorption tower 1 is connected with CO2A desorption tower 2; CO22An outlet at the upper section of the desorption tower 2 is connected with an inlet of a first vacuum tank 30;
the gas outlet end of the first vacuum tank 30 is connected with CO through a compressor 102The top exhaust end of the desorption tower 2; the liquid outlet end of the first vacuum tank 30 is connected with the inlet of the second vacuum tank 31, and the gas outlet end of the second vacuum tank 31 is connected with CO through the compressor 102The top exhaust end of the desorption tower 2; the liquid outlet end of the second vacuum tank 31 is connected with the inlet of the heat regeneration tower 4;
a gas outlet at the top of the thermal regeneration tower 4 is connected with an inlet of a second gas-liquid separation tank 7; the poor methanol outlet at the bottom of the thermal regeneration tower 4 is connected with the inlet of the methanol/water separation tower 5 and the top of the absorption tower 1.
Absorption column 1, CO2Material flow channels are respectively arranged among the desorption tower 2, the thermal regeneration tower 4, the methanol/water separation tower 5, the first gas-liquid separation tank 6, the second gas-liquid separation tank 7, the air pump 8, the heat exchanger 9, the compressor 10, the first vacuum tank 30 and the second vacuum tank 31, and the material flow channels are respectively numbered as 12, 13, 14, 15, 16, 21, 22, 23, 24, 32, 33, 34, 35, 41, 51 and 61.
Referring to fig. 2, the coal-to-methanol process CO of the embodiment2The recovery system comprises an absorption tower 1 and CO2The desorption column, the first vacuum tank 30, the second vacuum tank 31, the thermal regeneration column 4 and the methanol/water separation column 5 are basically the same in composition as the prior art described in fig. 1, and for the same parts, see the description of fig. 1 in comparative example 1 for details, which is the description thereofThe flow rate of the low-temperature methanol liquid injected into the top of the middle absorption tower 1 is 180t/h, the temperature is-50 ℃, the pressure is 500KPa, the operation pressure of the absorption tower 1 is 400KPa, and the temperature is-50 ℃.
The present invention differs from the prior art of fig. 1 in that: from CO2CO is enriched at the upper section of the desorption tower 22Methanol enters a first vacuum tank 30 from a material flow channel 22 and a material flow channel 23, and CO is separated by vacuum desorption2The gas is compressed by the compressor 10 through the material flow channel 32 and then enters the upper end of the desorption tower and CO2The product gas is converged in a material flow channel 21, the operating pressure of the desorption tower is 350KPa, the temperature is-35 ℃, and the rich H is obtained at the bottom of the tower2S methanol, and CO is obtained at the tower top2Product gas, CO2H-rich in the bottom of desorber 22S methanol enters a second vacuum tank 31 through a material flow channel 24, and CO is separated out through vacuum desorption2The gas is pressurized by the compressor 10 and then enters the upper end of the desorption tower and CO2The product gas is merged and used as CO2The operating pressure of the product gas and the material pump 11 is 400KPa, the liquid outlet end of the first vacuum tank 30 is connected with the liquid inlet end of the second vacuum tank 31, and the product gas which is separated from the first vacuum tank 30 and contains part of CO2The methanol enters a second vacuum tank 31 through a material flow channel 24 for further desorption and separation, and is separated from CO2CO-containing gas coming out of the lower section of the desorption tower 22Methanol is fed into the second vacuum tank 31, the flow rate of the methanol is 35t/h, the operation pressure of the second vacuum tank 31 is 100kPa, the temperature is-40 ℃, the operation pressure of the second vacuum tank 31 is 50kPa, and the temperature is-40 ℃.
After separation in two vacuum tanks, the second vacuum tank 31 is discharged to obtain rich H2And (3) feeding the S methanol into a thermal regeneration tower 4 through a material pump 11 for thermal regeneration, wherein the operating pressure of the material pump 11 is 400 KPa.
And after part of poor methanol comes out from the bottom of the thermal regeneration tower 4, the poor methanol is sent to the top of the absorption tower 1 after heat exchange and temperature reduction.
H obtained from the top of the thermal regeneration tower 42And the S gas is separated by a second gas-liquid separation tank 7 and then is sent to a sulfur recovery system, and the liquid flows back to the regenerative tower 4.
The aqueous methanol from the bottom of the thermal regeneration tower 4 also contains CO2Is sent to the middle part of a methanol/water separation tower 5, and the tower of the methanol/water separation tower 5Poor methanol obtained at the top flows back to the regenerative tower 4, water with the methanol content reaching the discharge standard is obtained at the bottom of the methanol/water separation tower 5 and is discharged out of the system.
The feed gas conditions are shown in table 1:
TABLE 1 raw gas State
The resulting product gas flow was 32577Nm/h, the composition is shown in Table 2 below, CO2The yield reaches 92 percent.
Table 2 product gas composition:
| composition of | Content% (mol) |
| CO2 | 99.1 |
| H2 | 0.21 |
| N2 | 0.10 |
| H2S | 0.0023 |
| H2O | 0 |
| Ar | 0 |
| CH4 | 0.19 |
| CO | 0.017 |
| CH4O | 0.01 |
| COS | 0 |
Example 2:
referring to FIG. 3, the second vacuum tank 31 was eliminated from example 1, the feed composition and other operating conditions were the same as in example 1, and the feed gas had been previously washed with water in the shift system to remove NH therefrom3The content is reduced to below 1ppm, and the water is separated in a gas-liquid separation tank 6 and then enters a desulfurization section of a lower tower of an absorption tower 1, the absorption tower 1 is divided into four sections, the lowest section is a desulfurization section, the upper three sections are decarburization sections, and raw gas in the desulfurization section is subjected to CO-rich raw gas2Washing with methanol solution to remove H2S, COS and part of CO2The components are added into a decarbonization section, the gas entering the decarbonization section does not contain sulfur, the gas is washed by lean methanol liquid at the top of the C-01 tower, and purified gas is led out from the top of the tower and absorbs H2S and CO2Then, the methanol coming out of the tower desulfurization section of the absorption tower 1 is sent into CO2Desorption column 2, CO2CO is obtained from the top of the desorption tower 22Producing gas;
from CO2Rich CO coming out of the desorption tower 22Methanol, rich in H2S methanol is introduced into a first vacuum tank 30, and CO is separated out by vacuum desorption2The gas is compressed by compressor 10 and enters into CO2Upper end of desorber 2 and CO2The product gas is converged and the CO is separated out by vacuum desorption2The gas is compressed by compressor 10 and then mixed with CO2The product gas 21 is merged and used as CO2The product gas is separated by a first vacuum tank 30 to obtain rich H2S methanol enters a thermal regeneration tower 4 through a pump for thermal regeneration, poor methanol is obtained at the bottom of the tower, and H-rich methanol is obtained at the top of the tower2S gas.
And after part of poor methanol comes out from the bottom of the thermal regeneration tower 4, the poor methanol is sent to the top of the absorption tower 1 after heat exchange and temperature reduction.
H obtained from the top of the thermal regeneration tower 42And the S gas is separated by a second gas-liquid separation tank 7 and then is sent to a sulfur recovery system, and the liquid flows back to the regenerative tower 4.
The aqueous methanol from the bottom of the thermal regeneration tower 4 also contains CO2And the methanol is sent to the middle part of a methanol/water separation tower 5, poor methanol obtained at the top of the methanol/water separation tower 5 flows back to a regenerative tower 4, and water with the methanol content reaching the emission standard is obtained at the bottom of the methanol/water separation tower 5 and is discharged out of the system.
The obtained product gas flow is 28943Nm/h, CO2The yield is 81 percent, and CO in the product gas2The composition reaches more than 99 percent.
Example 3
The operation pressure of the vacuum tank was changed to 300kPa for the first vacuum tank 30 and 100kPa for the second vacuum tank 31, and the flow of the raw material composition and other operation conditions used in this example was the same as in example 1, CO2The yield is 77%, and CO in the product gas2The composition reaches more than 99 percent.
Example 4
The operation pressure of the vacuum tank was changed to 50kPa for the first vacuum tank 30 and 10kPa for the second vacuum tank 31, and the flow of the raw material composition and other operation conditions used in this example was the same as in example 1, CO2The yield is 94%, and CO in the product gas2The composition reaches more than 99 percent.
It will be appreciated by those skilled in the art that the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The embodiments disclosed above are therefore to be considered in all respects as illustrative and not restrictive. All changes which come within the scope of or equivalence to the invention are intended to be embraced therein.
Claims (10)
1. Low-temperature methanol washing process CO2Recovery system, its characterized in that: comprises an absorption tower (1) and CO2A desorption tower (2), a first vacuum tank (30), a thermal regeneration tower (4) and a methanol/water separation tower (5);
the absorption tower (1) is divided into four sections, wherein the lowest section is a desulfurization section, and the upper three sections are decarburization sections; the inlet of the desulfurization section of the absorption tower (1) is connected with the gas outlet of the first gas-liquid separation tank (6);
the outlet of the desulfurization section of the absorption tower (1) is connected with a CO2 desorption tower (2); an outlet at the upper section of the CO2 desorption tower (2) is connected with an inlet of a first vacuum tank (30);
the gas outlet end of the first vacuum tank (30) is connected with the top gas outlet end of the CO2 desorption tower (2); the liquid outlet end of the first vacuum tank (30) is connected with the inlet of the heat regeneration tower (4);
the poor methanol outlet at the bottom of the thermal regeneration tower (4) is connected with the inlet of the methanol/water separation tower (5) and the top of the absorption tower (1).
2. The low temperature methanol wash process CO of claim 12Recovery system, its characterized in that: the air outlet end of the first vacuum tank (30) is connected with CO through a vacuum pump (10)2The top exhaust end of the desorption tower (2).
3. The low temperature methanol wash process CO of claim 12Recovery system, its characterized in that: the device also comprises a second gas-liquid separation tank (7); the top gas outlet of the thermal regeneration tower (4) is connected with the inlet of the second gas-liquid separation tank (7); the liquid discharge port of the second gas-liquid separation tank (7) is connected with the thermal regeneration tower (4).
4. The low temperature methanol wash process CO of claim 12Recovery system, its characterized in that: the liquid outlet of the first gas-liquid separation tank (6) is connected with the methanol/water separation tower (5) through a heat exchanger (9); the poor methanol outlet at the bottom of the thermal regeneration tower (4) is connected with the methanol/water separation tower (5) through a heat exchanger (9).
5. The low temperature methanol wash process CO of claim 12Recovery system, its characterized in that: a gas outlet of the methanol/water separation tower (5) is connected with a sulfur recovery system; the liquid outlet of the methanol/water separation tower (5) is connected with the thermal regeneration tower (4).
6. The low temperature methanol wash process CO of claim 12Recovery system, its characterized in that: the bottom poor methanol outlet of the thermal regeneration tower (4) is connected with the top of the absorption tower (1) through an air pump (8).
7. The low temperature methanol wash process CO of claim 12Recovery system, its characterized in that: further comprising a second vacuum tank (31); the liquid outlet end of the first vacuum tank (30) is connected with the inlet of the second vacuum tank (31), and the gas outlet end of the second vacuum tank (31) is connected with CO2The top exhaust end of the desorption tower (2); the liquid outlet end of the second vacuum tank (31) is connected with the inlet of the heat regeneration tower (4).
8. The low temperature methanol wash process CO of claim 12Recovery system, its characterized in that: CO22The outlet at the bottom of the desorption tower (2) is connected with a second vacuum tank (31).
9. The low temperature methanol wash process CO of claim 12Recovery system, its characterized in that: the operating pressure of the first vacuum tank (30) is 50kPa to 300 kPa; the second vacuum tank (31) has an operating pressure of 10 to 100 kPa.
10. Low-temperature methanol washing process CO2Recovery process, characterized in that a low temperature methanol wash process CO according to any of claims 1 to 92A recycling system comprising the steps of:
from CO2Rich in CO from the desorption tower (2)2Methanol, rich in H2S methanol enters a first vacuum tank (30), and CO is separated out through vacuum desorption of the first vacuum tank (30)2Gas admission to CO2Desorption tower(2) Upper end with CO2Converging the product gas;
h-enriched gas obtained after separation in a first vacuum tank (30)2S methanol enters a thermal regeneration tower (4) through a pump for thermal regeneration; the poor methanol is obtained at the bottom of the thermal regeneration tower (4), and the rich H is obtained at the top of the thermal regeneration tower2S gas;
after the poor methanol comes out from the bottom of the thermal regeneration tower (4), part of the poor methanol is sent to the top of the absorption tower (1), and part of the poor methanol is sent to a methanol/water separation tower (5);
h obtained from the top of the thermal regeneration tower (4)2And after gas-liquid separation of the S gas, the gas is sent to a sulfur recovery system, and the liquid flows back to a heat regeneration tower (4).
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