CN115636393B - Conversion system and method for low-quality coal gas - Google Patents
Conversion system and method for low-quality coal gas Download PDFInfo
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- CN115636393B CN115636393B CN202211214832.4A CN202211214832A CN115636393B CN 115636393 B CN115636393 B CN 115636393B CN 202211214832 A CN202211214832 A CN 202211214832A CN 115636393 B CN115636393 B CN 115636393B
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- 238000006243 chemical reaction Methods 0.000 title claims abstract description 105
- 238000000034 method Methods 0.000 title claims abstract description 27
- 239000003034 coal gas Substances 0.000 title claims abstract description 18
- 239000007789 gas Substances 0.000 claims abstract description 329
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims abstract description 197
- 239000001257 hydrogen Substances 0.000 claims abstract description 129
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 129
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- 229910002092 carbon dioxide Inorganic materials 0.000 claims abstract description 99
- 239000001569 carbon dioxide Substances 0.000 claims abstract description 98
- 238000004519 manufacturing process Methods 0.000 claims abstract description 41
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- 239000007788 liquid Substances 0.000 claims description 36
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- 238000004458 analytical method Methods 0.000 claims description 17
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- 238000000926 separation method Methods 0.000 claims description 17
- 239000012495 reaction gas Substances 0.000 claims description 16
- 238000012546 transfer Methods 0.000 claims description 16
- 239000002250 absorbent Substances 0.000 claims description 15
- 230000002745 absorbent Effects 0.000 claims description 15
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 claims description 13
- 229910000037 hydrogen sulfide Inorganic materials 0.000 claims description 13
- 230000001105 regulatory effect Effects 0.000 claims description 12
- 239000002699 waste material Substances 0.000 claims description 12
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims description 11
- 229910002091 carbon monoxide Inorganic materials 0.000 claims description 11
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 10
- 230000003750 conditioning effect Effects 0.000 claims description 10
- 238000010438 heat treatment Methods 0.000 claims description 10
- 229910052760 oxygen Inorganic materials 0.000 claims description 10
- 239000001301 oxygen Substances 0.000 claims description 10
- 238000001035 drying Methods 0.000 claims description 9
- 239000000446 fuel Substances 0.000 claims description 9
- 239000000463 material Substances 0.000 claims description 7
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 6
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 claims description 6
- 229910052802 copper Inorganic materials 0.000 claims description 6
- 239000010949 copper Substances 0.000 claims description 6
- 239000002808 molecular sieve Substances 0.000 claims description 5
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 claims description 5
- 150000002431 hydrogen Chemical class 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 4
- QPLDLSVMHZLSFG-UHFFFAOYSA-N Copper oxide Chemical compound [Cu]=O QPLDLSVMHZLSFG-UHFFFAOYSA-N 0.000 claims description 3
- 239000005751 Copper oxide Substances 0.000 claims description 3
- 101150090195 cnb-1 gene Proteins 0.000 claims description 3
- 230000001276 controlling effect Effects 0.000 claims description 3
- 229910000431 copper oxide Inorganic materials 0.000 claims description 3
- 230000009467 reduction Effects 0.000 claims description 3
- 239000011787 zinc oxide Substances 0.000 claims description 3
- 229910052573 porcelain Inorganic materials 0.000 claims description 2
- 239000006096 absorbing agent Substances 0.000 claims 1
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 claims 1
- 238000005516 engineering process Methods 0.000 description 13
- 230000009466 transformation Effects 0.000 description 10
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 9
- 239000002245 particle Substances 0.000 description 9
- 229910052717 sulfur Inorganic materials 0.000 description 9
- 239000011593 sulfur Substances 0.000 description 9
- UFWIBTONFRDIAS-UHFFFAOYSA-N Naphthalene Chemical compound C1=CC=CC2=CC=CC=C21 UFWIBTONFRDIAS-UHFFFAOYSA-N 0.000 description 8
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 7
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 6
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 6
- 208000012839 conversion disease Diseases 0.000 description 6
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- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 4
- 238000011084 recovery Methods 0.000 description 4
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- 239000002253 acid Substances 0.000 description 3
- 229910021529 ammonia Inorganic materials 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 239000003245 coal Substances 0.000 description 3
- 238000005262 decarbonization Methods 0.000 description 3
- 229910052763 palladium Inorganic materials 0.000 description 3
- 239000011148 porous material Substances 0.000 description 3
- 229910000029 sodium carbonate Inorganic materials 0.000 description 3
- 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 2
- QMMZSJPSPRTHGB-UHFFFAOYSA-N MDEA Natural products CC(C)CCCCC=CCC=CC(O)=O QMMZSJPSPRTHGB-UHFFFAOYSA-N 0.000 description 2
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 2
- 239000004480 active ingredient Substances 0.000 description 2
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- 229910021591 Copper(I) chloride Inorganic materials 0.000 description 1
- 241000948268 Meda Species 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- IDZYHGDLWGVHQM-UHFFFAOYSA-N aluminum;calcium;sodium;silicate Chemical group [Na+].[Al+3].[Ca+2].[O-][Si]([O-])([O-])[O-] IDZYHGDLWGVHQM-UHFFFAOYSA-N 0.000 description 1
- 238000003763 carbonization Methods 0.000 description 1
- 238000004939 coking Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- OXBLHERUFWYNTN-UHFFFAOYSA-M copper(I) chloride Chemical compound [Cu]Cl OXBLHERUFWYNTN-UHFFFAOYSA-M 0.000 description 1
- 229910052593 corundum Inorganic materials 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000005261 decarburization Methods 0.000 description 1
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Landscapes
- Separation Of Gases By Adsorption (AREA)
Abstract
The invention discloses a low-quality coal gas conversion system and a low-quality coal gas conversion method, wherein the conversion system comprises a pretreatment unit, a conversion unit, a carbon dioxide liquefying unit and a PSA hydrogen production unit; aiming at the characteristic that the effective components and the ineffective components in the low-quality gas respectively account for nearly half, the invention fully recycles the components in the low-quality gas so as to realize a technical route of high-efficiency and energy-saving low-quality gas utilization.
Description
Technical Field
The invention relates to the technical field of low-quality gas utilization, in particular to a low-quality gas conversion system and a low-quality gas conversion method.
Background
In coal chemical industry, such as coal gasification and coal coking technologies, a conventional process route, i.e. a technical route of pretreatment followed by conversion, and then desulfurization, decarburization and hydrogen extraction, is generally adopted for coal gas. The conversion adopts a combination mode of high temperature, medium temperature and low temperature, a series of water spraying and cooling devices are arranged at each stage of conversion, so that invalid components in coal gas, particularly low-quality coal gas, pass through the process, the volume content of effective components (hydrogen+CO) in the low-quality coal gas is low, for example, less than 60vol%, for example, the volumes of the effective components and the invalid components are nearly half, the capacity of the devices in the process is increased in multiple stages, and the energy consumption is increased in multiple stages.
Disclosure of Invention
The invention provides a low-quality gas conversion system and a low-quality gas conversion method for overcoming the defects of the prior art, and aims at the characteristic that the effective components and the ineffective components in the low-quality gas respectively occupy nearly half, so that the components in the low-quality gas are fully recycled, and a high-efficiency and energy-saving low-quality gas utilization technical route is realized.
In order to achieve the above object, the present invention adopts the following technical scheme:
A low quality gas conversion system, the conversion system comprising:
the pretreatment unit is used for removing invalid components in the raw material low-quality gas to obtain clean gas;
The pretreatment unit comprises a TSA impurity removal unit, a PSA denitrification unit and a deacidification gas unit which are sequentially connected, wherein the TSA impurity removal unit is used for carrying out temperature swing adsorption treatment on raw material low-quality gas so as to remove impurities in the raw material low-quality gas and obtain first purified gas; the PSA denitrification unit is used for performing pressure swing adsorption treatment on the first purified gas so as to remove nitrogen in raw material low-quality coal gas and obtain second purified gas; the deacidification gas unit is used for absorbing and removing carbon dioxide and hydrogen sulfide gas in the second purified gas to obtain purified gas;
the conversion unit is used for carrying out conversion treatment on the clean gas so as to obtain a mixed gas flow of hydrogen and carbon dioxide;
The shift unit comprises a first adjusting unit, a shift reactor and a water vapor removal unit, wherein the first adjusting unit is used for adjusting the temperature and/or pressure of the clean gas so as to facilitate shift treatment; the shift reactor is used for shifting carbon monoxide in the clean gas from the first regulating unit to obtain shift gas; the water vapor removal unit is used for removing water in the shift gas to obtain a mixed gas flow of hydrogen and carbon dioxide;
A carbon dioxide liquefaction unit for producing a liquid carbon dioxide product from the hydrogen and carbon dioxide mixed gas stream;
The carbon dioxide liquefying unit comprises a liquefier and a rectifying tower with a reboiler, wherein the liquefier is used for cooling a part of mixed gas flow of hydrogen and carbon dioxide which comes from the water vapor removing unit and is subjected to heat exchange and cooling by the reboiler and the rest part of mixed gas flow of hydrogen and carbon dioxide which comes from the water vapor removing unit so as to liquefy carbon dioxide in the mixed gas flow of hydrogen and carbon dioxide, thereby obtaining a raw material to be rectified and separated; the rectifying tower is used for rectifying and separating the raw materials to be rectified and separated from the liquefier so as to obtain a crude hydrogen product stream at the top of the tower and a liquid carbon dioxide product at the bottom of the tower;
The PSA hydrogen production unit is used for performing pressure swing adsorption separation on impurities in the crude hydrogen product stream from the carbon dioxide liquefaction unit to obtain a hydrogen product;
The PSA hydrogen production unit comprises a second regulating unit, a hydrogen production pressure swing adsorption unit and an optional hydrogen compressor; wherein the second conditioning unit is used for conditioning the temperature and/or pressure of the crude hydrogen product stream from the carbon dioxide liquefaction unit for subsequent pressure swing adsorption treatment; the hydrogen production pressure swing adsorption unit is used for performing pressure swing adsorption separation on impurities in the crude hydrogen product stream from the second regulating unit so as to obtain a hydrogen product; the hydrogen compressor is used for pressurizing the hydrogen product from the hydrogen production pressure swing adsorption unit.
In the present invention, low quality gas refers to gas in which the volume content of the active ingredient (hydrogen+co) is low, such as less than 60vol%, for example, 40 to 60vol%, for example, the active ingredient, the inactive ingredient each account for approximately half, such as 45vol%, 50vol%, or 55vol%; in one embodiment, the low-quality gas has an H 2 content of 22.5 to 28vol% and a CO content of 15 to 24vol%.
According to the conversion system of the invention, in one embodiment, the pretreatment unit further comprises a gas holder and a low-quality gas compressor, wherein the low-quality gas compressor is used for pressurizing raw material low-quality gas from the gas holder and sending the pressurized raw material low-quality gas to the TSA impurity removal unit.
According to the conversion system of the invention, in one embodiment, the TSA impurity removal unit comprises a first regenerated gas inlet pipe, a second regenerated gas inlet pipe, a temperature swing adsorption unit, a first resolved gas outlet pipe and a second resolved gas outlet pipe; the first regenerated gas inlet pipe and the second regenerated gas inlet pipe are arranged in parallel, a heater is arranged on the first regenerated gas inlet pipe and used for heating the resolved gas from the hydrogen production pressure swing adsorption unit and then sending the heated resolved gas into the temperature swing adsorption unit as first regenerated gas, and the second regenerated gas inlet pipe is used for sending the resolved gas from the hydrogen production pressure swing adsorption unit into the temperature swing adsorption unit as second regenerated gas; the temperature swing adsorption unit is used for performing temperature swing adsorption treatment on raw material low-quality gas so as to remove impurities in the raw material low-quality gas, obtain first purified gas, and regenerate by utilizing the resolved gas from the hydrogen production pressure swing adsorption unit after adsorption saturation; the first analysis gas exhaust pipe is arranged in parallel with the second analysis gas exhaust pipe, the first analysis gas exhaust pipe is used for sending out the first regenerated analysis gas exhausted by the temperature swing adsorption unit through the regeneration of the first regenerated gas as fuel after the temperature of the first regenerated analysis gas is reduced through the heat exchange of the second adjusting unit, and the second analysis gas exhaust pipe is used for sending out the second regenerated analysis gas exhausted by the temperature swing adsorption unit through the regeneration of the second regenerated gas as fuel;
Preferably, the second regulating unit comprises a second heat exchanger, and the second heat exchanger is used for heat exchange and cooling of the first regenerated desorption gas and the crude hydrogen which is from the rectifying tower and is heated by heat exchange of the liquefier.
According to the conversion system of the present invention, in one embodiment, the deacidification gas unit includes an absorption tower, a regeneration tower, a desulfurization device, and a carbon dioxide transporter; the absorption tower is used for removing carbon dioxide in the first purified gas by using an N-methyl glycol amine solution as an absorbent to obtain decarbonated gas; the regeneration tower is used for stripping the absorbent from the absorption tower by a stripping method to separate carbon dioxide and sending the regenerated absorbent back to the absorption tower; the desulfurization device is used for removing hydrogen sulfide in the decarbonated gas from the absorption tower to obtain clean gas; the carbon dioxide transporter is used for transporting carbon dioxide from the regeneration tower to the moisture removal unit to recover carbon dioxide.
In the present invention, desulfurization apparatuses for removing hydrogen sulfide are well known in the art, such as desulfurization apparatuses for removing hydrogen sulfide from a gas by a physical absorption method or a chemical absorption method, for example, a chemical absorption method using sodium carbonate or potassium hydroxide as a desulfurization absorption liquid. In one embodiment, the desulfurization device is a supergravity desulfurization device, and the hydrogen sulfide removal is performed by using a supergravity technology.
According to the conversion system of the present invention, in one embodiment, the moisture removal unit comprises a waste pan, a water cooler, a knock-out pot, and an adsorption dryer pot; wherein the waste pan is used to recover heat from the shift gas of the shift reactor; the water cooler is used for further cooling the shift gas from the waste boiler; the liquid separating tank is used for carrying out gas-liquid separation on materials from the water cooler and the carbon dioxide conveyer; the adsorption drying tank is used for carrying out adsorption drying and water removal on the gas-phase material from the liquid separation tank so as to obtain a mixed gas flow of hydrogen and carbon dioxide;
Preferably, the carbon dioxide conveyer is an ejector, and the ejector is used for facilitating partial conversion gas from the water cooler to serve as an ejector flow to convey the carbon dioxide from the regeneration tower into the liquid separation tank.
According to the conversion system of the present invention, in one embodiment, the first conditioning unit comprises a clean gas compressor and a first heat exchanger; wherein the clean gas compressor is used for pressurizing the clean gas; the first heat exchanger is used for enabling the pressurized clean gas to exchange heat with the shift gas leaving the shift reactor to raise the temperature, and sending the shift gas after heat exchange and temperature reduction to the water vapor removal unit.
According to the conversion system of the invention, in one embodiment, a deoxidization reaction catalyst bed layer, a first conversion reaction catalyst bed layer and a second conversion reaction catalyst bed layer are sequentially arranged in the conversion reactor at intervals from top to bottom; the deoxidization reaction catalyst bed layer is provided with a clean gas inlet and a hydrogen inlet for eliminating oxygen in the clean gas through reaction; the first shift reaction catalyst bed layer is provided with a steam inlet for carrying out shift reaction so as to reduce the carbon monoxide content in the reaction gas from the deoxidization reaction catalyst bed layer; the second shift reaction catalyst bed is used for catalyzing shift reaction to further reduce the carbon monoxide content in the reaction gas from the second shift reaction catalyst bed;
a first heat transfer device is arranged between the deoxidization reaction catalyst bed layer and the first shift reaction catalyst bed layer and is used for exchanging heat between the reaction gas from the deoxidization reaction catalyst bed layer and the clean gas from the first regulating unit so as to remove part of heat;
the first shift reaction catalyst bed is internally provided with a second heat transfer device which is used for heating the clean gas from the first heat transfer device so as to remove heat in the first shift reaction catalyst bed and sending the heated clean gas to the clean gas inlet;
Preferably, the hydrogen fed through the hydrogen inlet is from the hydrogen compressor.
In order to achieve the aim of the invention, the invention also provides a method for converting low-quality coal gas by using the conversion system.
In one embodiment of the invention, one or more of adsorbents CNA-421, CNA-316 and CNA-213 used for the temperature swing adsorption treatment by the TSA impurity removing unit are commonly used adsorbents well known in the art, for example, the adsorbents may be CNA-421, CNA-316 and CNA-213 sequentially stacked along the air flow direction; in one embodiment, the three adsorbents are used in amounts that differ by no more than 10% by volume, such as an equal volume pack.
In one embodiment of the invention, the adsorbent used for pressure swing adsorption treatment by the PSA denitrification unit is 5A molecular sieve and HX-CO adsorbent which are sequentially stacked along the airflow direction; in one embodiment, the two volumes are not more than 10% different, such as equal volumes.
In one embodiment of the invention, the adsorbent/filler used for pressure swing adsorption treatment by the PSA hydrogen production unit is AS adsorbent, HXBC-15B, HX A-98H, HXNA-CO adsorbent and inert porcelain balls which are sequentially stacked along the air flow direction; in one embodiment, the five materials are used in volumes that differ by no more than 10%, such as an equal volume pack.
In one embodiment of the present invention, the catalyst used in the deoxidizing reaction catalyst bed is a deoxidizing catalyst, such as an HT type palladium catalyst deoxidizing catalyst, and the deoxidizing catalyst is well known in the art, and a tube type heat exchanger, i.e. a first heat transfer device, is horizontally arranged below the deoxidizing catalyst bed, so that the deoxidizing catalyst bed exchanges heat with the deoxidizing gas, the temperature of the lower end of the first heat transfer device is maintained between 210 ℃ and 220 ℃, and the concentration of CO in the deoxidizing gas reaches 33% -39%.
In one embodiment of the invention, the first shift catalyst bed employs a copper-based shift catalyst to convert CO and water to hydrogen and carbon dioxide by a shift reaction, such shift catalysts being well known in the art, such as a CNB-1 type copper-based shift catalyst, having a catalyst composition: copper oxide is more than or equal to 38 percent, and zinc oxide is more than or equal to 40 percent; alumina 6-8%, such as copper oxide/zinc oxide/alumina 38-52%/40-54%/6-8%, for example, a CNB-type 1 copper-based shift catalyst available from southwest chemical institute; controlling the temperature of the reaction gas leaving the first shift reaction catalyst bed to be 200-210 ℃ and the concentration of CO to be less than 3% (in the invention, the gas content is the volume content unless specified otherwise);
In one embodiment of the invention, the second shift reaction catalyst bed employs a type B207 catalyst; the temperature of the reaction gas leaving the second shift reaction catalyst bed is controlled to be 230-250 ℃ and the concentration of CO is lower than 0.12%.
In the present invention, the concentration means a mass concentration, and the percentage is a mass percentage unless otherwise specified.
Compared with the prior art, the invention has the following advantages:
aiming at the characteristics that the effective components in the low-quality gas are low and the ineffective components occupy nearly half, naphthalene, dust and oil substances are removed before conversion, nitrogen, sulfide and carbon dioxide in the low-quality gas are removed, and industrial nitrogen, sulfur and liquid carbon dioxide can be respectively prepared, so that the low-quality gas is concentrated into high-quality gas, and the capacity of subsequent equipment is halved and the energy consumption is halved.
In addition, the conversion technology is to complete deoxidation, primary conversion and secondary conversion in a conversion reactor, so that the heat exchange process of the two-stage reaction heat and the high-quality gas is well realized. The low-temperature transformation technology is adopted in both the two-stage transformation, and the low-steam ratio transformation technology is applied in the two-stage transformation. And finally, separating hydrogen while obtaining a liquid carbon dioxide product by adopting a low-temperature method, and performing pressure swing adsorption to obtain a final hydrogen product.
The invention fully recycles each component in the low-quality coal gas, changes waste into valuable, realizes zero emission and reaches a high-efficiency and energy-saving low-quality coal gas hydrogen production technical route.
Specifically, aiming at the characteristics that the effective components in the low-quality gas are low, and the ineffective components account for half, for example, the carbon monoxide content is 19%, naphthalene, dust and oil in the low-quality gas are firstly removed, then nitrogen and acid gas (carbon dioxide and hydrogen sulfide gas) are removed, so that the carbon monoxide content is concentrated to 36-38%, the scale of subsequent equipment is reduced by nearly 50%, and the subsequent energy consumption is reduced by half. The conversion technology adopts a high-efficiency conversion reactor, the clean gas sequentially carries out oxygen removal, primary conversion and secondary conversion reactions from top to bottom, and the exchange of the clean gas, the oxygen removal and the primary conversion reaction heat is realized inside. The two-stage conversion adopts a low-temperature conversion technology, steam is added at one time, the two-stage conversion adopts a low-temperature low-steam ratio technology, CO at a CO outlet is converted to 0.12%, the conversion rate is improved by 99.88%, and compared with the traditional conversion technology, the conversion rate is improved, so that zero emission of the conversion technology is achieved. In terms of energy consumption, the water-carbon ratio is optimized from 3.5 of a general conversion technology, the outlet gas-steam ratio is 1.0-1.1, and the water-carbon ratio is 2.75, and the outlet gas-steam ratio is 0.3; the steam is saved by 20-24%, and the annual energy consumption is quite considerable. The transformed carbon dioxide and crude hydrogen are separated from the low temperature by utilizing a carbon dioxide liquefying technology, and industrial nitrogen, sulfur and liquid carbon dioxide are respectively obtained in the technical process, so that zero emission is realized in the whole flow. The recovery rate of the product hydrogen is above 98.3 percent, and the purity is above 99.9 percent.
Drawings
FIG. 1 is a schematic flow diagram of one embodiment of the conversion system of the present invention.
Detailed Description
The invention is further described below with reference to examples and figures, but the invention is not limited to the examples listed but also comprises equivalent improvements and variants of the solution defined in the claims attached hereto.
As shown in fig. 1, the low-quality gas conversion system of the present invention comprises a pretreatment unit, a conversion unit, a carbon dioxide liquefaction unit and a PSA hydrogen production unit.
The pretreatment unit is used for removing invalid components in raw material low-quality gas to obtain clean gas; the pretreatment unit comprises a TSA impurity removal unit, a PSA denitrification unit 4 and a deacidification gas unit which are sequentially connected, wherein the TSA impurity removal unit is used for carrying out temperature swing adsorption treatment on raw material low-quality gas so as to remove impurities in the raw material low-quality gas and obtain first purified gas; the PSA denitrification unit 4 is used for performing pressure swing adsorption treatment on the first purified gas so as to remove nitrogen in raw material low-quality coal gas and obtain second purified gas; the deacidification gas unit is used for absorbing and removing carbon dioxide and hydrogen sulfide gas in the second purified gas to obtain purified gas. In one embodiment, the pretreatment unit further comprises a gas holder 1 and a low-quality gas compressor 2, wherein the low-quality gas compressor 2 is used for pressurizing raw material low-quality gas from the gas holder 1 and sending the pressurized raw material low-quality gas to the TSA impurity removal unit.
Wherein, gas holder 1 can be the floating roof type gas holder, and dry-type gas holder can be furnished with nitrogen gas, fire protection facility, stores the low-quality gas condition and can be: the temperature is 40 ℃ and the pressure is 0.05Mpa.
In one embodiment, the TSA impurity removal unit includes a first regeneration gas inlet pipe 28, a second regeneration gas inlet pipe 29, a temperature swing adsorption unit 3, a first desorption gas outlet pipe 30, and a second desorption gas outlet pipe 31; the first regenerated gas inlet pipe 28 and the second regenerated gas inlet pipe 29 are arranged in parallel, the first regenerated gas inlet pipe 28 is provided with a heater 32 for heating the desorption gas from the hydrogen production pressure swing adsorption unit 26 and sending the heated desorption gas as a first regenerated gas to the temperature swing adsorption unit 3, and the second regenerated gas inlet pipe 29 is used for sending the desorption gas from the hydrogen production pressure swing adsorption unit 26 as a second regenerated gas to the temperature swing adsorption unit 3; the temperature swing adsorption unit 3 is used for performing temperature swing adsorption treatment on raw material low-quality gas to remove impurities in the raw material low-quality gas, so as to obtain first purified gas, and regenerating the first purified gas by utilizing the desorption gas from the hydrogen production pressure swing adsorption unit 26 after adsorption saturation; the first desorption gas exhaust pipe 30 and the second desorption gas exhaust pipe 31 are arranged in parallel, the first desorption gas exhaust pipe 30 is used for sending out the first regenerated desorption gas exhausted by the temperature swing adsorption unit 3 through the regeneration of the first regenerated gas as fuel after the temperature of the first regenerated desorption gas is reduced through the heat exchange of the second adjusting unit, and the second desorption gas exhaust pipe 31 is used for sending out the second regenerated desorption gas exhausted by the temperature swing adsorption unit through the regeneration of the second regenerated gas as fuel; the second adjusting unit comprises a second heat exchanger 25, and the second heat exchanger 25 is used for heat exchanging and cooling the first regenerated desorption gas and the crude hydrogen which is from the rectifying tower 23 and is heated by heat exchanging of the liquefier 21.
During operation, TSA is purified by temperature swing adsorption to remove hydrocarbons, naphthalene, tar, sulfides and other high-boiling-point impurity components in low-quality gas. The regeneration of the adsorbent in the temperature swing adsorption unit 3 comprises 4 steps: depressurization, heating, cooling and pressurizing. Consists of three towers, operates for 8 hours and regenerates for 16 hours. After regeneration, the first regenerated desorption gas exchanges heat with the second heat exchanger 25 to 40 ℃ and then is combined with the second regenerated desorption gas to be used as fuel in a decarbonization furnace.
Wherein, PSA denitrification unit 4 adopts pressure swing adsorption to prepare nitrogen, adopts the model: the 5A molecular sieve (spherical) and the HX-CO adsorbent can produce nitrogen products with purity of 90-95 percent, and the nitrogen products are sent to a cryogenic liquid nitrogen system for preparing liquid nitrogen. The parsed gas is the purified low-quality gas called the first purified gas (short for high-quality gas) and enters into the deacidification gas unit.
In one embodiment, the deacidification gas unit comprises an absorption tower 5, a regeneration tower 8, a desulfurization device 9 and a carbon dioxide conveyer 10; the absorption tower 5 is used for removing carbon dioxide in the first purified gas by using an N-methyl glycol amine solution as an absorbent to obtain decarbonated gas; the regeneration tower 8 is used for stripping the absorbent from the absorption tower 5 by a stripping method to separate out carbon dioxide and sending the regenerated absorbent back to the absorption tower 5; the desulfurization device 9 is used for removing hydrogen sulfide in the decarbonated gas from the absorption tower to obtain clean gas; the carbon dioxide transporter 10 is used to send carbon dioxide from the regeneration tower 8 to the moisture removal unit for carbon dioxide recovery.
During operation, the absorption tower 5 adopts active MDEA (N-methyl glycol amine) as an absorbent to absorb carbon dioxide, the temperature of the top of the regeneration tower 8 is controlled at 60 ℃, the absorbent from the absorption tower 5 is stripped by a stripping method to separate carbon dioxide, the regenerated absorbent is returned to the absorption tower 5 for recycling, decarbonated gas is sent to the desulfurization device 9 to remove hydrogen sulfide therein to obtain clean gas, and the sulfur-containing compound obtained by desulfurization of the desulfurization device 9 can be recovered by a sulfur removal and sulfur recovery system for sulfur production.
The conversion unit is used for carrying out conversion treatment on the clean gas so as to obtain a mixed gas flow of hydrogen and carbon dioxide; the shift unit comprises a first adjusting unit, a shift reactor 13 and a moisture removal unit, wherein the first adjusting unit is used for adjusting the temperature and/or pressure of the clean gas so as to facilitate shift treatment; the shift reactor 13 is used for shifting carbon monoxide in the clean gas from the first adjusting unit to obtain shift gas; the water vapor removal unit is used for removing water in the shift gas so as to obtain a mixed gas stream of hydrogen and carbon dioxide.
In one embodiment, the moisture removal unit comprises a waste pan 11, a water cooler 12, a knock-out pot 19 and an adsorption dryer pot 20; wherein the waste pan 11 is used for recovering heat of shift gas from the shift reactor 13; the water cooler 12 is used for further cooling the shift gas from the waste boiler 11; the liquid separating tank 19 is used for carrying out gas-liquid separation on materials from the water cooler 12 and the carbon dioxide conveyer 10; the adsorption drying tank 20 is used for carrying out adsorption drying and water removal on the gas-phase material from the liquid separation tank 19 so as to obtain a mixed gas flow of hydrogen and carbon dioxide;
The carbon dioxide conveyer 10 is an ejector, and the ejector is used for facilitating partial conversion gas from the water cooler to serve as an ejector flow to convey the carbon dioxide from the regeneration tower 8 into the liquid separating tank 19.
The first regulating unit comprises a clean gas compressor 6 and a first heat exchanger 7; wherein the clean gas compressor 6 is used for pressurizing the clean gas; the first heat exchanger 7 is used for heat exchanging and heating the pressurized clean gas and the shift gas leaving the shift reactor 13, and sending the shift gas after heat exchanging and cooling to the water vapor removal unit.
In one embodiment, a deoxidization reaction catalyst bed 14, a first shift reaction catalyst bed 15 and a second shift reaction catalyst bed 16 are sequentially arranged in the shift reactor 13 at intervals from top to bottom; the deoxidization reaction catalyst bed layer 14 is provided with a clean gas inlet and a hydrogen inlet for eliminating oxygen in the clean gas through reaction; the first shift reaction catalyst bed 15 is provided with a steam inlet for carrying out shift reaction to reduce the carbon monoxide content in the reaction gas from the deoxidization reaction catalyst bed 14; the second shift catalyst bed 16 is used to catalyze shift reactions to further reduce the carbon monoxide content of the reaction gas from the first shift catalyst bed 15;
A first heat transfer device 17 is arranged between the deoxidization reaction catalyst bed 14 and the first shift reaction catalyst bed 15 and is used for exchanging heat between the reaction gas from the deoxidization reaction catalyst bed 14 and the clean gas from the first regulating unit so as to remove part of heat;
A second heat transfer device 18 is arranged in the first shift reaction catalyst bed 15 and is used for heating the clean gas from the first heat transfer device 17 so as to remove heat in the first shift reaction catalyst bed 18 and sending the heated clean gas to the clean gas inlet;
the hydrogen fed through the hydrogen inlet comes from a hydrogen compressor 27.
In operation, the upper section of the shift reactor 13 is a deoxidization reaction zone, and the oxygen content of the air source is: less than 2%, deoxidizing by utilizing the reaction of hydrogen and oxygen, and deoxidizing depth (PPm): less than 1PPm; the minimum hydrogen distribution amount (v/v) is more than 2-3 times of the oxygen content. The outlet temperature of the deoxidization reaction zone is 280-300 ℃, a first heat transfer device 17 is arranged below the deoxidization reaction catalyst, the clean gas exchanges heat with the deoxidization gas, the temperature of the lower end of the first heat transfer device 17 is maintained at 210-220 ℃, and the concentration of CO in the deoxidization gas reaches 33% -39%.
The middle section of the shift reactor 13 is a shift reaction zone, and a copper shift catalyst is adopted as a shift (short for one-stage shift, also called a shift reaction zone) catalyst; the first variant reaction conditions may be: airspeed: less than 5000 (h -1); the pressure is 0.1-5.5 Mpa; temperature: 200-250 ℃; the first transformation reaction generates low-temperature transformation reaction under the action of a catalyst. The second heat transfer device 18 is arranged in the first variable catalyst to maintain the bottom temperature of the first variable catalyst within the range of 210-220 ℃, and the first variable reaction gas exchanges heat with the clean gas and then enters the second variable reaction. The CO conversion rate of the first change is more than 98%, and the concentration of the outlet CO is less than 3%. The first transformation outlet enters a second transformation reaction at 200-210 ℃.
The lower section of the shift reactor 13 is a second shift reaction zone, and a second shift (the second shift reaction zone is also called a second shift reaction zone for short) can catalyze the reaction gas from the first shift by using a B207 shift catalyst to further convert CO; the operating conditions may be: airspeed: less than 5000 (h -1); the pressure is 1-3.5 Mpa; temperature: 200-220 ℃, inlet CO concentration: less than 3%.
The second gas change is cooled by the first heat exchanger 7, cooled by the waste boiler 11, and then enters an ejector nozzle opening of the carbon dioxide conveyer 10 after exchanging heat with the water cooler 12 and leading out a branch line, carbon dioxide of the acid gas regeneration system is ejected into the liquid separation tank 19 for gas-liquid separation, and then enters the adsorption drying tank 20 for dehydration and drying.
Wherein the carbon dioxide liquefaction unit is used for preparing a liquid carbon dioxide product from the mixed gas stream of hydrogen and carbon dioxide; the carbon dioxide liquefying unit comprises a liquefier 21 and a rectifying tower 23 with a reboiler 24, wherein the liquefier 21 is used for cooling a part of mixed gas flow of hydrogen and carbon dioxide which comes from the water vapor removing unit and is subjected to heat exchange and temperature reduction by the reboiler 24 and the rest part of mixed gas flow of hydrogen and carbon dioxide which comes from the water vapor removing unit so as to liquefy carbon dioxide in the mixed gas flow of hydrogen and carbon dioxide, thereby obtaining a raw material to be rectified and separated; the rectifying tower 23 is used for rectifying and separating the raw material to be rectified and separated from the liquefier 21 to obtain a crude hydrogen product stream at the top of the tower and a liquid carbon dioxide product at the bottom of the tower.
When the device is operated, the mixed gas flow of hydrogen and carbon dioxide from the water vapor removal unit is led to a branch line to enter a reboiler 24 at the bottom of a rectifying tower 23, the liquid carbon dioxide at the bottom of the rectifying tower is heated and evaporated and then is combined with a main line to be cooled by a liquefier 21, then the liquid carbon dioxide enters the rectifying tower 23 to separate the carbon dioxide from the hydrogen, the top of the rectifying tower 23 is controlled to be about-30 ℃, the hydrogen at the top of the rectifying tower is decompressed to 0.8-1.6 Mpa through a decompression valve to keep the cold capacity of the top of the tower, the noncondensable gas (hydrogen) separated from the top of the tower enters the liquefier 21 to be used as a cold source to exchange heat and then enters a PSA hydrogen production unit, the temperature of the bottom of the tower is controlled to be-36 to-38 ℃, and the purity of CO 2 reaches 99.9 percent of food grade and is sent to a tank area to be stored.
The cold source of the liquefier 21 can be an ice maker system 22 which is composed of an ammonia press, an oil separator, a condenser, an ammonia storage tank, an ammonia liquid separation tank and the like, and the ice maker system is used for producing liquid ammonia and providing cold for the CO 2 liquefier 21.
The PSA hydrogen production unit is used for performing pressure swing adsorption separation on impurities in a crude hydrogen product stream from the carbon dioxide liquefaction unit to obtain a hydrogen product; the PSA hydrogen production unit includes a second conditioning unit, a hydrogen production pressure swing adsorption unit 26, and an optional hydrogen compressor 27; wherein the second conditioning unit is used for conditioning the temperature and/or pressure of the crude hydrogen product stream from the carbon dioxide liquefaction unit for subsequent pressure swing adsorption treatment; the hydrogen production pressure swing adsorption unit is used for performing pressure swing adsorption separation on impurities in the crude hydrogen product stream from the second regulating unit so as to obtain a hydrogen product; the hydrogen compressor 27 is used to boost the pressure of the hydrogen product from the hydrogen-producing pressure swing adsorption unit. The analysis gas from the hydrogen production pressure swing adsorption unit is heated and then is sent to the temperature swing adsorption unit 3 as first regeneration gas, and the unheated analysis gas from the hydrogen production pressure swing adsorption unit is sent to the temperature swing adsorption unit 3 as second regeneration gas; the adsorption towers of the hydrogen production pressure swing adsorption unit 26 in the PSA hydrogen production unit are combined by 9 towers, wherein 3 towers operate, 6 towers regenerate, and hydrogen is produced and sent to a hydrogen pipe network by a hydrogen compressor.
Examples
The flow rate of the low-quality gas is 200000Nm 3/h, and the composition of the low-quality gas is%vol (dry basis )：H2：22.5～28;CH4：1～3;CO：15～24;CO2：4～9;N2：40～46;H2S：≤1200mg/Nm3.
The low-quality gas is lifted to the pressure of 0.45Mpa and the temperature of 50 ℃ by a screw compressor, enters a TSA temperature swing adsorption unit, and high-boiling-point impurity components such as hydrocarbon, naphthalene, tar, sulfide and the like in the low-quality gas are removed by sequentially stacked adsorbents 1-3, wherein the model 1 of the adsorbent is as follows: CNA-421; appearance: white spherical particles; the crushing strength (N/particle) is more than or equal to 80.2; bulk density (g/ml): 0.68 to 0.72; water absorption (%) 43-51; specific surface area (m 2/g): 251 to 306; particle size (mm): phi 3-5; the water content (%) of the product is less than or equal to 2.0; pore volume (cm 3/g): 0.4 to 0.5; adsorbent 2 model CNA-316: appearance: pale yellow transparent or translucent spherical shape; water adsorption amount rh=20% >8.2; rh=50% >20.4; rh=90% >30.3; the granularity (mm) phi is 1-3; abrasion ratio (%) <5.0; heating decrement (%) <2.0; bulk density (g/ml): 0.75 to 0.80; siO 2 content (%) >98.5; particle size percent of pass (%) >90.0; the qualification rate of spherical particles is more than 84.0; 3 model of adsorbent: CNA-213; form gauge Φ (mm): columnar particles, 4.0+ -0.2; bulk density (g/ml): 0.61-0.65; intensity: (%) is greater than or equal to 96; ash content: (%) is less than or equal to 7; moisture: (%) is less than or equal to 1.5.
Regeneration of the adsorbent in the TSA temperature swing adsorption unit is divided into 4 steps: depressurization, heating, cooling and pressurizing. Consists of three columns, each column operated for 8 hours and regenerated for 16 hours. The regenerated gas comprises a second regenerated gas and a first regenerated gas, the first regenerated gas exchanges heat with the heat exchanger 2 to 40 ℃, then is combined with the second regenerated gas into a decarbonization furnace to be used as fuel, the regenerated gas of the PSA hydrogen production unit is provided with an electric heater, the electric heater is heated to 150 ℃, TSA is subjected to high Wen Jiexi, and the analysis gas is used as fuel to be removed from the carbonization furnace.
The low-quality coal gas from TSA enters into PSA denitrification unit, PSA pressure swing adsorption nitrogen production system is adopted, 5A molecular sieve (spherical) and HX-CO adsorbent are adopted, wherein the 5A molecular sieve is calcium sodium aluminosilicate, and the aperture of crystal is(0.5 Nm); diameter (mm): 1.6 to 2.5; static water adsorption (not less than%): 21.5; bulk density (. Gtoreq.g/ml): 0.68; compressive strength (. Gtoreq.N/particle): 82; abrasion rate (less than or equal to percent): 0.1; packaging water content (less than or equal to percent): 1.5.HX-CO adsorbent: mCuCl. NNa 2O·Al2O3·xSiO2, wherein CuCl (wt%) is not less than 20; appearance: off-white, appearance: cylindrical phi (1.8-2.2) x (3-8); compressive strength (. Gtoreq.N/particle): 20, a step of; abrasion rate (less than or equal to percent): 1.5; bulk density (. Gtoreq.g/ml): 0.82; packaging water content (less than or equal to percent): 1.5; the nitrogen product with purity of 90-95% is produced and sent to a cryogenic liquid nitrogen system for preparing liquid nitrogen. The low-quality gas obtained by purifying the desorption gas is called clean gas, and enters a deacidification gas unit for removing acid gas. 8 sets of PSA pressure swing adsorption nitrogen making towers are used in parallel, two pressure equalizing methods are adopted, and desorption gas is used for regenerating and purging.
The method comprises the steps of absorbing carbon dioxide in a first purified gas by using active MDEA (N-methyl glycol amine) as an absorbent in an absorption tower, controlling the temperature of the top of the regeneration tower to be 60 ℃, stripping the absorbent from the absorption tower 5 by a stripping method to separate carbon dioxide, sending the regenerated absorbent back to the absorption tower 5 for recycling, sending the separated carbon dioxide to an inlet of a receiving chamber of an ejector, sending decarbonated gas to a desulfurization device 9 to remove hydrogen sulfide in the decarbonated gas to obtain clean gas (for example, sodium carbonate is used as desulfurization absorption liquid in a supergravity separation device, the concentration of sodium carbonate is 12g/l, the vapor-liquid ratio is 18.84l/m 3, the supergravity factor is 94.44, the desulfurization rate is over 96 percent, and PDS is used as a desulfurization catalyst), and then the sulfur-containing compound obtained by desulfurization in the desulfurization device 9 can be recovered by a sulfur removal and sulfur recovery system.
The low-quality coal gas after desulfurization and decarbonization enters a clean coal gas compressor to be pressurized to 1.25Mpa at the temperature of 80-100 ℃, then exchanges heat with the converted gas at the second conversion outlet to 120 ℃ and enters a conversion reactor, the conversion reactor is square column-shaped, and the clean coal gas sequentially carries out deoxidation reaction, primary conversion reaction and secondary conversion reaction from top to bottom.
In the deoxidization reaction zone, an HT-type palladium catalyst deoxidization catalyst is adopted, and the grain diameter is as follows: phi 3-phi 5; palladium content (%): 0.02-5; mechanical strength (. Gtoreq.N/particle): 50; bulk specific gravity (g/ml): 0.8+ -0.05; oxygen content of air source: less than 2%; deoxidization depth (PPm): less than 1PPm; the minimum hydrogen distribution amount (v/v) is more than 2-3 times of the oxygen content. The deoxidization reaction zone is at 220 ℃, 1.25Mpa and space velocity: the reaction is carried out with hydrogen under the condition of 2500h -1, the outlet temperature is 280-300 ℃, a first heat transfer device consisting of a plurality of tube bundles is arranged below the deoxidizing catalyst, so that the heat exchange between the clean gas and the deoxidizing gas is realized, the bottom temperature of the deoxidizing catalyst is maintained at 210-220 ℃, the concentration of CO in deoxidized gas after deoxidizing is concentrated to 33-39%, and the deoxidized gas enters a variable reaction zone.
The primary (one-stage) catalyst adopts a copper CNB-1 type conversion catalyst (purchased from southwest chemical industry institute) with a bulk density (g/ml) of 1.2+0.5; radial strength: greater than 250N/cm; abrasion: less than 8%; size: phi 5 x (3-4) nm; bulk density (g/ml) 0.75. The conversion rate of the first change is more than 90%, the concentration of CO at the outlet is lower than 3%, and the reaction gas at 240 ℃ at the first change outlet enters the second change reaction zone after heat exchange. The second heat transfer device is arranged in the variable catalyst from top to bottom according to the linear rule of the exothermic reaction of the variable catalyst, the heat exchange and the temperature equalization of the reaction heat of the variable gas and the clean gas are completed, and the bottom temperature of the variable catalyst is maintained at 210-220 ℃. The first gas enters the second reaction zone.
The second transformation (two-stage transformation) adopts a catalyst with low steam ratio (model: B207; pore volume (cm 3/g): 0.42; specific surface area (m 2/g): 256.53; pore diameter: 2.3nm; crush strength (N/particle) > 180; bulk density (g/ml) 1.4; space velocity 4500 (h -1); 1.2mpa, 200-220 deg.c and 2.75 water-carbon ratio; inlet CO concentration: 3, the outlet concentration reaches 0.12%; second variable outlet steam-gas ratio: 0.3. the second variable gas is cooled to 180 ℃ by heat exchange, the temperature is reduced to 135 ℃ by a waste boiler, a branch line is led out after heat exchange with a water cooler, the branch line enters a nozzle opening of a carbon dioxide injector, carbon dioxide from a flash tank is led into a liquid separating tank, and gas-liquid separation is carried out in the liquid separating tank together with main line variable gas.
Then the mixture enters an adsorption drying tank, and a JK-K2 composite active alumina adsorbent is adopted in the tank: grain size (+mm): phi 3-phi 5; bulk specific gravity (g/ml): 0.68 to 0.7; compressive strength (N/particle): 110; abrasion rate (less than or equal to percent): 0.3; specific surface (m 2/g): 360. The static water adsorption is more than or equal to 20 percent. After the conversion gas is removed and dried, part of the conversion gas firstly enters a reboiler at the bottom of the rectifying tower, liquid carbon dioxide is heated and evaporated and then is combined with a main line into a liquefier to be cooled to minus 38 ℃ and enters the rectifying tower to rectify the carbon dioxide, the top of the rectifying tower is controlled to minus 30 ℃, therefore, the hydrogen stripping at the top of the rectifying tower is controlled to 0.8-1.6 Mpa through a pressure reducing valve, the cold capacity of the top of the rectifying tower is kept, and noncondensable gas (hydrogen) separated from the top of the rectifying tower enters the liquefier to be used as a cold source for heat exchange and then enters a PSA hydrogen production unit. And the temperature of the bottom of the tank is controlled to be minus 36 to minus 38 ℃, and the food grade with the purity of CO 2 reaching 99.9 percent is sent to a tank area for storage. The system cooling capacity is provided by an ice machine system, and the crude hydrogen cooling capacity of the rectifying tower exchanges heat with gaseous carbon dioxide in normal time, and the insufficient cooling capacity is provided by the ice machine.
The hydrogen production pressure swing adsorption unit of the PSA hydrogen production unit is composed of 9 towers, 3 towers operate and 6 towers regenerate, wherein the adsorbent is filled with AS adsorbent, HXBC-15B, HX A-98H, HXNA-CO adsorbent in equal volume from the bottom to the top. The purity of hydrogen produced by the PSA hydrogen production unit is 99.6 percent, and the hydrogen produced by the PSA hydrogen production unit is sent to a hydrogen pipe network.
The devices or elements of the present invention may be processing apparatuses, devices or elements having corresponding functions, which are known in the art, and will not be described in detail. Not specifically described herein, those skilled in the art will know or understand the present technology, and detailed description thereof will not be given.
It is to be understood that the above examples of the present invention are provided by way of illustration only and not by way of limitation of the embodiments of the present invention. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. Not all embodiments are exhaustive. All obvious variations or modifications which come within the spirit of the invention are desired to be protected.
For example, (1) the shift reactor may be an isothermal shift reactor, which falls within the scope of protection of this patent; (2) The hot potassium method can be adopted to replace the active MEDA method, and belongs to the protection scope of the patent.
Claims (13)
1. A low quality gas conversion system, the conversion system comprising:
the pretreatment unit is used for removing invalid components in the raw material low-quality gas to obtain clean gas;
The pretreatment unit comprises a TSA impurity removal unit, a PSA denitrification unit and a deacidification gas unit which are sequentially connected, wherein the TSA impurity removal unit is used for carrying out temperature swing adsorption treatment on raw material low-quality gas so as to remove impurities in the raw material low-quality gas and obtain first purified gas; the PSA denitrification unit is used for performing pressure swing adsorption treatment on the first purified gas so as to remove nitrogen in raw material low-quality coal gas and obtain second purified gas; the deacidification gas unit is used for absorbing and removing carbon dioxide and hydrogen sulfide gas in the second purified gas to obtain purified gas;
the conversion unit is used for carrying out conversion treatment on the clean gas so as to obtain a mixed gas flow of hydrogen and carbon dioxide;
The shift unit comprises a first adjusting unit, a shift reactor and a water vapor removal unit, wherein the first adjusting unit is used for adjusting the temperature and/or pressure of the clean gas so as to facilitate shift treatment; the shift reactor is used for shifting carbon monoxide in the clean gas from the first regulating unit to obtain shift gas; the water vapor removal unit is used for removing water in the shift gas to obtain a mixed gas flow of hydrogen and carbon dioxide;
A carbon dioxide liquefaction unit for producing a liquid carbon dioxide product from the hydrogen and carbon dioxide mixed gas stream;
The carbon dioxide liquefying unit comprises a liquefier and a rectifying tower with a reboiler, wherein the liquefier is used for cooling a part of mixed gas flow of hydrogen and carbon dioxide which comes from the water vapor removing unit and is subjected to heat exchange and cooling by the reboiler and the rest part of mixed gas flow of hydrogen and carbon dioxide which comes from the water vapor removing unit so as to liquefy carbon dioxide in the mixed gas flow of hydrogen and carbon dioxide, thereby obtaining a raw material to be rectified and separated; the rectifying tower is used for rectifying and separating the raw materials to be rectified and separated from the liquefier so as to obtain a crude hydrogen product stream at the top of the tower and a liquid carbon dioxide product at the bottom of the tower;
The PSA hydrogen production unit is used for performing pressure swing adsorption separation on impurities in the crude hydrogen product stream from the carbon dioxide liquefaction unit to obtain a hydrogen product;
The PSA hydrogen production unit comprises a second regulating unit, a hydrogen production pressure swing adsorption unit and an optional hydrogen compressor; wherein the second conditioning unit is used for conditioning the temperature and/or pressure of the crude hydrogen product stream from the carbon dioxide liquefaction unit for subsequent pressure swing adsorption treatment; the hydrogen production pressure swing adsorption unit is used for performing pressure swing adsorption separation on impurities in the crude hydrogen product stream from the second regulating unit so as to obtain a hydrogen product; the hydrogen compressor is used for pressurizing the hydrogen product from the hydrogen production pressure swing adsorption unit.
2. The conversion system according to claim 1, wherein the pretreatment unit further comprises a gas holder and a low-grade gas compressor for pressurizing the raw low-grade gas from the gas holder and delivering the pressurized raw low-grade gas to the TSA de-impurity unit.
3. The conversion system according to claim 1 or 2, wherein the TSA de-impurity unit comprises a first regeneration gas inlet pipe, a second regeneration gas inlet pipe, a temperature swing adsorption unit, a first desorption gas outlet pipe, and a second desorption gas outlet pipe; the first regenerated gas inlet pipe and the second regenerated gas inlet pipe are arranged in parallel, a heater is arranged on the first regenerated gas inlet pipe and used for heating the resolved gas from the hydrogen production pressure swing adsorption unit and then sending the heated resolved gas into the temperature swing adsorption unit as first regenerated gas, and the second regenerated gas inlet pipe is used for sending the resolved gas from the hydrogen production pressure swing adsorption unit into the temperature swing adsorption unit as second regenerated gas; the temperature swing adsorption unit is used for performing temperature swing adsorption treatment on raw material low-quality gas so as to remove impurities in the raw material low-quality gas, obtain first purified gas, and regenerate by utilizing the resolved gas from the hydrogen production pressure swing adsorption unit after adsorption saturation; the first analysis gas exhaust pipe and the second analysis gas exhaust pipe are arranged in parallel, the first analysis gas exhaust pipe is used for sending out the first regenerated analysis gas exhausted by the temperature swing adsorption unit through the regeneration of the first regenerated gas as fuel after the temperature of the first regenerated analysis gas is reduced through the heat exchange of the second adjusting unit, and the second analysis gas exhaust pipe is used for sending out the second regenerated analysis gas exhausted by the temperature swing adsorption unit through the regeneration of the second regenerated gas as fuel.
4. A conversion system according to claim 3, wherein the second conditioning unit comprises a second heat exchanger for heat exchanging and cooling the first regenerated stripping gas with crude hydrogen from the rectifying column which has been warmed by heat exchange with the liquefier.
5. The conversion system according to any one of claims 1-2 and 4, wherein the deacidification gas unit comprises an absorber, a regenerator, a desulfurization device, and a carbon dioxide transporter; the absorption tower is used for removing carbon dioxide in the first purified gas by using an N-methyl glycol amine solution as an absorbent to obtain decarbonated gas; the regeneration tower is used for stripping the absorbent from the absorption tower by a stripping method to separate carbon dioxide and sending the regenerated absorbent back to the absorption tower; the desulfurization device is used for removing hydrogen sulfide in the decarbonated gas from the absorption tower to obtain clean gas; the carbon dioxide transporter is used for transporting carbon dioxide from the regeneration tower to the moisture removal unit to recover carbon dioxide.
6. The conversion system according to claim 5, wherein the moisture removal unit comprises a waste pan, a water cooler, a knock-out pot, and an adsorption dryer pot; wherein the waste pan is used to recover heat from the shift gas of the shift reactor; the water cooler is used for further cooling the shift gas from the waste boiler; the liquid separating tank is used for carrying out gas-liquid separation on materials from the water cooler and the carbon dioxide conveyer; the adsorption drying tank is used for carrying out adsorption drying and water removal on the gas-phase material from the liquid separating tank so as to obtain a mixed gas flow of hydrogen and carbon dioxide.
7. The conversion system of claim 6, wherein the carbon dioxide transporter is an eductor for facilitating a portion of the shift gas from the water cooler to send carbon dioxide from the regeneration tower as an eductor stream to the knock out pot.
8. The conversion system according to any one of claims 1-2, 4, and 6-7, wherein the first conditioning unit comprises a clean gas compressor and a first heat exchanger; wherein the clean gas compressor is used for pressurizing the clean gas; the first heat exchanger is used for enabling the pressurized clean gas to exchange heat with the shift gas leaving the shift reactor to raise the temperature, and sending the shift gas after heat exchange and temperature reduction to the water vapor removal unit.
9. The conversion system according to claim 8, wherein a deoxidization reaction catalyst bed, a first shift reaction catalyst bed and a second shift reaction catalyst bed are sequentially arranged in the shift reactor at intervals from top to bottom; the deoxidization reaction catalyst bed layer is provided with a clean gas inlet and a hydrogen inlet for eliminating oxygen in the clean gas through reaction; the first shift reaction catalyst bed layer is provided with a steam inlet for carrying out shift reaction so as to reduce the carbon monoxide content in the reaction gas from the deoxidization reaction catalyst bed layer; the second shift reaction catalyst bed is used for catalyzing shift reaction to further reduce the carbon monoxide content in the reaction gas from the second shift reaction catalyst bed;
a first heat transfer device is arranged between the deoxidization reaction catalyst bed layer and the first shift reaction catalyst bed layer and is used for exchanging heat between the reaction gas from the deoxidization reaction catalyst bed layer and the clean gas from the first regulating unit so as to remove part of heat;
the first shift reaction catalyst bed is provided with a second heat transfer device which is used for heating the clean gas from the first heat transfer device so as to remove heat in the first shift reaction catalyst bed and send the heated clean gas to the clean gas inlet.
10. The conversion system according to claim 9, wherein the hydrogen fed through the hydrogen inlet is from the hydrogen compressor.
11. A method of low quality gas conversion using the conversion system of any one of claims 1-10.
12. The method according to claim 11, wherein the adsorbent used for the temperature swing adsorption treatment by the TSA impurity removal unit is a CNA-421 type, a CNA-316 type and a CNA-213 type adsorbent sequentially stacked in the gas flow direction;
The adsorbent used for pressure swing adsorption treatment by the PSA denitrification unit is 5A molecular sieve and HX-CO adsorbent which are sequentially piled up along the airflow direction;
The adsorbents adopted in the pressure swing adsorption treatment by the PSA hydrogen production unit are AS adsorbent, HXBC-15B, HX A-98H, HXNA-CO adsorbent and inert porcelain balls which are sequentially piled up along the air flow direction.
13. The method according to claim 11 or 12, wherein the catalyst used in the deoxidizing reaction catalyst bed is an HT-2 type deoxidizing catalyst, and the deoxidizing reaction is carried out at 220 ℃,1.25Mpa; airspeed: 2500h -1 is reacted with hydrogen, the outlet temperature is 280-300 ℃, a tube type heat exchanger is arranged below the deoxidizing catalyst, the heat exchange is carried out on the clean gas and the deoxidizing gas, the temperature of the bottom layer of the deoxidizing catalyst is maintained at 210-220 ℃, and the concentration of CO in the clean gas reaches 33% -39%;
the first shift reaction catalyst bed layer adopts a copper CNB-1 type catalyst; catalyst composition: copper oxide/zinc oxide/aluminum oxide is 38%/40%/6-8%; controlling the temperature of the reaction gas leaving the first shift reaction catalyst bed layer to be 200-210 ℃ and the concentration of CO to be lower than 3%;
The second shift reaction catalyst bed adopts a B207 catalyst; the temperature of the reaction gas leaving the second shift reaction catalyst bed is controlled to be 230-250 ℃ and the concentration of CO is lower than 0.12%.
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