CN115350566A - Improved low-temperature methanol-washing CO 2 Device and process for desorbing and utilizing desorbed gas - Google Patents
Improved low-temperature methanol-washing CO 2 Device and process for desorbing and utilizing desorbed gas Download PDFInfo
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- CN115350566A CN115350566A CN202210960688.2A CN202210960688A CN115350566A CN 115350566 A CN115350566 A CN 115350566A CN 202210960688 A CN202210960688 A CN 202210960688A CN 115350566 A CN115350566 A CN 115350566A
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- 238000000034 method Methods 0.000 title claims abstract description 51
- 230000008569 process Effects 0.000 title claims abstract description 43
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims abstract description 3138
- 239000007789 gas Substances 0.000 claims abstract description 578
- 238000003795 desorption Methods 0.000 claims abstract description 155
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 112
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 109
- 239000007791 liquid phase Substances 0.000 claims description 176
- 238000010521 absorption reaction Methods 0.000 claims description 153
- 239000002253 acid Substances 0.000 claims description 119
- 229910052717 sulfur Inorganic materials 0.000 claims description 110
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- 229910052757 nitrogen Inorganic materials 0.000 claims description 55
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- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 claims description 19
- 229920006395 saturated elastomer Polymers 0.000 claims description 12
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- 239000002351 wastewater Substances 0.000 claims description 7
- QFHYHYSMAHUARD-UHFFFAOYSA-N [S].CO Chemical compound [S].CO QFHYHYSMAHUARD-UHFFFAOYSA-N 0.000 claims description 6
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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
- B01D53/18—Absorbing units; Liquid distributors therefor
-
- 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
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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
- B01D53/1418—Recovery of products
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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
- B01D53/1456—Removing acid components
-
- 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
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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
- B01D53/1493—Selection of liquid materials for use as absorbents
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2252/00—Absorbents, i.e. solvents and liquid materials for gas absorption
- B01D2252/20—Organic absorbents
- B01D2252/202—Alcohols or their derivatives
- B01D2252/2021—Methanol
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2257/00—Components to be removed
- B01D2257/30—Sulfur compounds
- B01D2257/308—Carbonoxysulfide COS
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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
- Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
- Y02C20/00—Capture or disposal of greenhouse gases
- Y02C20/40—Capture or disposal of greenhouse gases of CO2
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- Oil, Petroleum & Natural Gas (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Gas Separation By Absorption (AREA)
Abstract
The invention discloses an improved low-temperature methanol CO washing method 2 Device and process for desorption and utilization of desorbed gas by adding medium pressure H 2 S concentration tower, medium pressure desorption gas expander, medium pressure desorption gas/sulfur-free methanol-rich heat exchanger, the methanol-rich quencher is changed into a sulfur-free methanol-rich/methanol-rich heat exchanger, the methanol-poor cooler is changed into a winding pipe type heat exchanger, thereby improving CO 2 The gas desorption process, wherein a part of the methanol-rich gas enters the medium pressure H 2 S concentration tower for desorbing CO dissolved in rich methanol by using medium-pressure nitrogen gas stripping 2 Since the pressure during desorption is greatly increased, the desorbed CO is generated 2 The absorbed cold energy is increased, and CO is desorbed 2 The methanol temperature after the reaction is more reduced, and the intermediate pressure H is 2 Medium pressure CO-rich from S concentration column 2 The desorbed gas enters the expansion machine again, and more cold energy is generated through expansion. The invention realizes that the low-temperature methanol washing generates more cold energy,the load of the ice machine is reduced, and meanwhile, the expander drives the generator to output electric energy, so that the power consumption and the circulating water consumption are reduced, the total energy consumption is reduced by 13%, and the aims of saving energy and reducing consumption are fulfilled.
Description
Technical Field
The invention belongs to the technical field of low-temperature methanol washing processes, and particularly relates to an improved device and process for desorbing CO2 and utilizing desorbed gas by using low-temperature methanol washing.
Background
The low-temperature methanol washing process takes cold methanol as a physical absorption solvent, and utilizes the methanol to remove acid gas (CO) at low temperature 2 、H 2 S, COS, etc.) of very high solubilityThe method has excellent characteristics, removes acid gas in the raw material gas and is a physical absorption method; the principle is that methanol under high pressure (2.5-8.2 MPaG) and low temperature (20-55 deg.C) is used to react with sulfide (H) 2 S、COS)，CO 2 The lower the temperature and the higher the pressure of methanol, the better the absorption capacity of methanol on acid gas, and methanol on H 2 、CO、CH 4 Selectively absorbing acid gas components in the crude gas by the characteristic that the solubility of the effective gas components is very low, removing the acid gas components by absorption, then respectively removing carbon dioxide and sulfide by modes of reducing pressure, heat exchange, heating, gas stripping and the like of methanol containing a large amount of acid gas, enabling the process of regenerating the methanol solution to be called as a purification (decarburization, desulfurization and dehydration) process, and finally, the removed sulfur components are generally sent to a downstream sulfur recovery unit, and the removed CO is 2 Washing, emptying methanol in the washing exhaust gas, and finally sending the washing wastewater to a biochemical treatment unit.
At present, the existing low-temperature methanol washing process mainly comprises the following two ways of generating cold energy: firstly, high-pressure methanol-rich is throttled and decompressed directly through a regulating valve to obtain certain temperature reduction, or the methanol-rich is throttled and decompressed through a hydraulic turbine pump (water turbine), the refrigerating efficiency of the hydraulic turbine pump is higher than that of valve throttling, but turbine blades are easy to be damaged by gas cavitation generated by flash evaporation. Second, by CO 2 When the methanol is desorbed from the methanol, the methanol can absorb heat and can generate a large amount of cold, which is also the main cold source of the low-temperature methanol washing process at present.
The low temperature methanol wash requires supplemental cooling for several reasons: 1. absorption of CO 2 The absorption heat will be generated, so the temperature of the methanol liquid will rise, and the rising temperature of the methanol will affect the absorption capacity of the acid gas, therefore, the absorption of CO will be needed 2 Cooling the heated methanol again; 2. the heat exchange has temperature difference to generate cold loss; 3. the low-temperature system inevitably has environmental heat leakage and also generates cold loss; 4. precooling is needed for the regenerated lean methanol; 5. absorption of CO 2 Will generate heat of absorption and desorb CO 2 The amount of heat absorbed is not equal. The cooling capacity needed above is to utilize methanol to wash the inside through CO 2 The cold energy generated by desorption and the cold energy generated by throttling of the methanol-rich liquid also need external cold supplement to maintain the cold energy balance of the system.
At present, the existing low-temperature methanol washing process selects most of CO in order to cool poor methanol to the final absorption temperature 2 The desorption process is set at a low pressure H 2 The stripping of the CO dissolved in methanol is carried out by passing nitrogen through the bottom of an S concentration column (operating at a pressure of generally about 0.1 MPaG) 2 So as to obtain a low temperature sulfur-rich methanol at the bottom of the column of about-60 ℃ and a sulfur-free rich CO at the top of the column also of about-60 DEG 2 The main function of the desorption gas is to cool the regenerated lean methanol at about-35 ℃ to about-50 ℃ without sulfur and rich CO 2 The stripping gas has lower pressure, and is generally directly discharged to the atmosphere after being washed by water after the cold energy is recovered by the heat exchange between the feed heat exchanger and the feed gas at 40 ℃. Sometimes in order to produce CO of very high purity 2 Product gas (purity ≥ 99.5% Vol), provided with a CO at slightly higher operating pressure 2 The product tower has the principle that after the pressure of the methanol is reduced, partial acid gas is flashed, a stream of flash gas is introduced into the tower bottom to strip the methanol, sulfur-free methanol-rich liquid is used as tower top reflux liquid at the tower top to absorb sulfide in the ascending gas, but a large amount of CO contained in the flash gas 2 Is easily re-dissolved in methanol, so the ascending gas driving force of the tower comes from the decompression flash evaporation of rich methanol, rather than promoting CO by breaking the original gas-liquid balance through nitrogen 2 Desorption, stripping to produce pure CO by flash gas 2 CO of product gas 2 The product tower can not add cold quantity to the system and is used for meeting the requirement of downstream CO 2 Demand for product quantity, CO 2 The operating pressure of the product column is typically set at 0.2MPaG, typically not more than 0.25MPaG, so that low pressure H is used regardless of whether it is 2 S concentration tower for stripping CO 2 Or also using CO 2 Product tower to produce relatively pure CO 2 The pressure of gas phase material flow out of the tower is only 0.1-0.2 MPaG. This corresponds to the original high partial pressure of acid gas (CO) in the high pressure feed gas 2 The partial pressure in the original feed gas can reach 1 to3 MPa), after methanol absorption and desorption, the pressure is reduced from high pressure to near normal pressure, and CO is obtained 2 The internal energy in the components is wasted greatly and is not fully utilized, and a large amount of energy (electric energy or power steam) is consumed to enable an ice machine to produce cold energy, so that the cold energy balance in a low-temperature methanol washing area can be maintained.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide an improved low-temperature methanol CO washing method 2 Desorption and a device and a process for utilizing desorption gas, which solve the problem that CO is carried out by adopting low pressure in the prior art 2 The gas stripping desorption of the gas causes the technical problems of the waste of the original internal energy of the acid gas and the high energy consumption of the ice machine.
In order to solve the technical problems, the invention adopts the following technical scheme:
improved low-temperature methanol-washing CO 2 A device for desorbing and utilizing desorbed gas, which comprises an acid gas methanol absorption tower, a circulating methanol cooler, a methanol heat exchanger I, a circulating gas flash tank II and a medium pressure H 2 S concentration column, low pressure H 2 The system comprises an S concentration tower, a methanol-rich flash tank, a methanol-rich pump I, a methanol-rich pump II, a medium-pressure desorption gas/sulfur-free methanol-rich heat exchanger, a sulfur-free methanol-rich/methanol-rich heat exchanger, a medium-pressure desorption gas expander, a generator driven by the expander, a new methanol-poor cooler, a methanol-rich pump III, a methanol heat exchanger II, a methanol heat exchanger III, CO 2 Desorption column, H 2 The system comprises an S fraction separator II, a poor methanol collecting tank, a poor methanol pump, a poor liquid water cooler, a purified gas/methanol heat exchanger I, a circulating gas compressor, a methanol quencher and a methanol-rich filter;
CO of the acid gas methanol absorption tower 2 The 36 th tray liquid phase outlet at the bottom of the fine absorption section passes through the circulating methanol cooler tube bundle and the CO of the acid gas methanol absorption tower 2 The 37 th tray liquid phase inlet at the top of the main absorption section is connected; CO of acid gas methanol absorption tower 2 The liquid phase outlet of the 66 th tower tray at the bottom of the main absorption section passes through the tube bundle of the circulating methanol cooler and the CO of the acid gas methanol absorption tower 2 The 67 th tower tray liquid phase inlet at the top of the coarse absorption section is connected; CO of acid gas methanol absorption tower 2 A part of sulfur-free methanol-rich outlet of a 96 th tray at the bottom of the coarse absorption section is connected with a liquid phase inlet of a circulating gas flash tank I through a tube pass of a medium-pressure desorption gas/sulfur-free methanol-rich heat exchanger, a tube bundle of a methanol heat exchanger I and a tube pass of the sulfur-free methanol-rich/methanol-rich heat exchanger; CO of acid gas methanol absorption tower 2 The other part of the sulfur-free methanol-rich outlet at the bottom of the coarse absorption section is connected with the liquid phase inlet of the 97 th tower tray at the top of the lower section of the acid gas methanol absorption tower; a liquid phase outlet at the bottom of the acid gas methanol absorption tower is connected with a liquid phase inlet of a circulating gas flash tank II through a purified gas/methanol heat exchanger I tube pass and a methanol heat exchanger I tube bundle;
said medium pressure H 2 The gas phase outlet at the top of the S concentration tower is connected with the shell pass inlet of the medium-pressure desorption gas/sulfur-free methanol-rich heat exchanger; liquid phase outlet pipeline branch at bottom of I tank of circulating gas flash tank and medium pressure H 2 The liquid phase inlet at the top of the S concentration tower is connected; liquid phase outlet at bottom of tank I of circulating gas flash tank and low pressure H 2 S, connecting a liquid phase inlet at the top of the concentration tower; liquid phase outlet pipeline branch at bottom of circulating gas flash tank II and medium pressure H 2 The liquid phase inlet of the 15 th tray of the S concentration tower is connected; liquid phase outlet pipeline at bottom of II tank of circulating gas flash tank and low pressure H 2 The liquid phase inlet of the 23 th tray of the S concentration tower is connected; medium pressure H 2 The liquid phase outlet of the 70 th tray at the bottom of the upper section of the S concentration tower is connected with the liquid phase inlet of the methanol-rich flash tank; low pressure H 2 A liquid phase outlet of the 106 th tray at the bottom of the upper section of the S concentration tower is connected with a liquid phase inlet of the methanol-rich flash tank through a methanol-rich pump II and a new methanol-poor cooler tube bundle; gas phase outlet at top of methanol-rich flash tank and low pressure H 2 The gas phase inlet of the 107 th tray at the top of the lower section of the S concentration tower is connected; the liquid phase outlet at the bottom of the methanol-rich flash tank passes through a methanol-rich pump I, a sulfur-free methanol-rich/methanol-rich heat exchanger shell pass, a methanol heat exchanger I shell pass, a circulating methanol heat exchanger I shell pass and medium pressure H 2 The 71 th tower tray liquid phase inlet at the top of the lower section of the S concentration tower is connected; medium pressure nitrogen from air separation and medium pressure H 2 S, connecting a gas phase inlet under the tower tray at the bottommost layer of a tower kettle of the concentration tower; medium pressure H 2 The liquid phase outlet at the bottom of the S concentration tower passes through a medium pressure H 2 S concentration tower bottom liquid level regulating valve and low pressure H 2 The 107 th tray liquid phase inlet at the top of the lower section of the S concentration tower is connected; the shell side outlet of the medium-pressure desorption gas/sulfur-free methanol-rich heat exchanger is connected with the inlet of a medium-pressure desorption gas expander; the outlet of the medium-pressure desorption gas expander passes through the tube bundle of the new lean methanol cooler and the low pressure H 2 S concentration tower top rich in CO 2 Connecting desorption gas pipelines; an output shaft of the medium-pressure desorption gas expander is connected with a generator shaft; the gas phase outlets at the tops of the circulating gas flash tank I and the circulating gas flash tank II are both connected with the inlet of a circulating gas compressor; low pressure H 2 The liquid phase outlet at the bottom of the S concentration tower passes through a rich methanol pump III, a methanol heat exchanger II, a methanol heat exchanger III and CO 2 The liquid phase inlet at the top of the desorption tower is connected; h 2 Liquid phase outlet at bottom of S fraction separator II tank and low pressure H 2 The 132 th tray liquid phase inlet of the S concentration tower is connected; CO2 2 Gas phase outlet and low pressure H at the top of the desorption tower 2 The 125 th tray gas phase inlet of the S concentration tower is connected; and a liquid phase outlet at the bottom of the poor methanol collecting tank is connected with a liquid phase inlet at the top of the acid gas methanol absorption tower through a poor methanol pump, a poor liquid water cooler tube pass, a methanol heat exchanger III tube pass, a methanol heat exchanger II tube pass and a new poor methanol cooler shell pass.
The invention also comprises the following technical characteristics:
specifically, the acid gas methanol absorption tower can utilize different solubility of different gas components in low-temperature methanol to sectionally react with CO 2 And selectively absorbing the sulfide acid gas component;
the acid gas methanol absorption tower comprises 116 trays which are divided into 4 sections from top to bottom, wherein 1-36 trays are CO 2 The fine absorption section and 37-66 trays are made of CO 2 The main absorption section and 67-96 trays are made of CO 2 The crude absorption section and 97-116 trays are sulfide absorption sections.
In particular, said medium pressure H 2 The S concentration tower comprises 106 trays which are divided into two sections from top to bottom, wherein 1-70 trays are medium-pressure H 2 At the upper section of the S concentration tower, 71-106 trays are medium-pressure H 2 S, the lower section of a concentration tower;
the low pressure H 2 The S-concentrator column includes 138 trays,divided into two sections from top to bottom, wherein 1 to 106 trays have low pressure H 2 The upper section of the S concentration tower adopts 107 to 138 trays as low pressure H 2 S, the lower section of a concentration tower;
medium pressure H 2 S concentration column and low pressure H 2 The S concentration tower is used for leading CO dissolved in low-temperature methanol to be stripped through nitrogen 2 Is desorbed and is washed by sulfur-free rich methanol at the tower top simultaneously, so that H is obtained 2 S is gradually concentrated in methanol flowing downwards to obtain concentrated H at the bottom of the tower 2 S-rich methanol; due to CO 2 The desorption from the methanol absorbs heat, and the temperature of the methanol-rich solution and the desorbed gas discharged from the tower is reduced.
Improved low-temperature methanol-washing CO 2 Desorption and utilization of desorbed gas process for CO scrubbing with said improved low temperature methanol 2 The device for desorbing and utilizing the desorbed gas comprises the following steps:
the raw material gas enters an acid gas methanol absorption tower to remove all acid gas, and lean methanol absorbs CO in sections 2 After the sulfide acid gas component is saturated, the sulfide acid gas component respectively leaves an acid gas methanol absorption tower in a sulfur-free methanol-rich and sulfur-containing methanol-rich material flow mode, two strands of methanol-rich enter a methanol heat exchanger I, wherein the sulfur-containing methanol-rich is firstly precooled to-19.4 ℃ by purified gas which is discharged from the top of the acid gas methanol absorption tower, in the methanol heat exchanger I, two strands of high-pressure methanol-rich are both cooled to-30 ℃ by the methanol-rich from a methanol-rich flash tank, then the sulfur-free methanol-rich continuously enters a tube pass of a sulfur-free methanol/methanol-rich heat exchanger, is further cooled to-36 ℃, the cooled absorbed acid gas to saturated sulfur-free methanol-rich and the saturated sulfur-containing methanol-rich enter a circulating gas flash tank I and a circulating gas flash tank II after being respectively decompressed and throttled by a regulating valve;
the throttled and decompressed sulfur-free rich methanol and sulfur-containing rich methanol are respectively subjected to flash evaporation in a circulating gas flash evaporation tank I and a circulating gas flash evaporation tank II, and H 2 、CO、CH 4 The flash evaporation gas of the effective gas component goes to the inlet of the recycle gas compressor, is subjected to pressure rise by the recycle gas compressor and is cooled by a water cooler of the recycle gas compressor and then is merged with the inlet feed gas;
circulating gas flash drum I tankThe sulfur-free methanol-rich bottom is respectively sent to the medium pressure H 2 S concentration column and low pressure H 2 The liquid inlet at the top of the S concentration tower is used as medium pressure H 2 S concentration column and low pressure H 2 S, concentrating the tower top reflux liquid of the tower; the sulfur-containing rich methanol at the bottom of the circulating gas flash tank II is respectively sent to the medium pressure H 2 S concentration column and low pressure H 2 Liquid inlet of the 15 th tray of the S concentration tower as medium pressure H 2 S concentration column and low pressure H 2 S, concentrating the second reflux of the tower; at medium pressure H 2 S concentration column and low pressure H 2 The tower kettle of the S concentration tower is respectively filled with medium-pressure and low-pressure nitrogen from an air separation unit, and CO dissolved in the rich methanol is treated by the nitrogen 2 Stripping to remove CO 2 Desorbed from the methanol rich due to CO 2 Desorption will absorb heat, so CO 2 Stripping gas and stripping CO 2 The temperature of methanol (a) is all reduced; from medium pressure H 2 70 th tray of S concentration tower and low pressure H 2 The 106 th tray of the S concentration tower respectively flows out all the desorbed part of CO 2 After the low-pressure sulfur-rich methanol is pressurized by a methanol-rich pump II, the low-pressure sulfur-rich methanol and medium-pressure gas stripping expansion gas respectively pass through a new methanol-poor cooler tube bundle to cool the methanol to-50.6 ℃, and then the low-pressure sulfur-rich methanol enters the liquid phase inlet of the methanol-rich flash tank through the regulating valve;
in the methanol-rich flash tank, two sulfur-containing methanol-rich flash tanks are subjected to flash evaporation at an operating pressure slightly higher than the low pressure H 2 S concentration tower operating pressure so that flash gas flashed out can enter low pressure H 2 The gas phase inlet above the 107 th tray on the top of the lower section of the S concentration tower is used for reducing the temperature of the rich methanol and the flash evaporation gas to-55.6 ℃ after flash evaporation, and the flash evaporation gas is sent to the low pressure H 2 S, a gas phase inlet at the top of the lower section of the concentration tower, rich methanol enters a methanol-rich pump I, after the pressure of the rich methanol pump I is increased, the rich methanol firstly goes to a sulfur-free methanol-rich/methanol-rich heat exchanger, the sulfur-free methanol-rich is cooled to-36 ℃, and then respectively goes to a methanol heat exchanger I and a circulating methanol cooler under the regulation of a methanol-rich flow regulating valve of the methanol heat exchanger I and a methanol-rich flow regulating valve of the circulating methanol cooler, and then goes to the methanol heat exchanger I and the circulating methanol coolerCooling due to absorption of CO 2 The two half rich methanol streams are cooled to-35 ℃, the sulfur-free rich methanol stream and the sulfur-containing rich methanol stream are cooled to-30 ℃, the sulfur-free rich methanol stream and the sulfur-containing rich methanol stream are heated to-30.5 ℃ and-19.1 ℃, and the two half rich methanol streams are returned to the medium pressure H after being merged 2 The 71 th tray liquid phase inlet on the top of the lower section of the S concentration tower is continuously stripped by medium-pressure nitrogen from the tower kettle, and the desorbed CO 2 And the stripping nitrogen enters the medium pressure H through the ascending pipe 2 The bottom of the upper section of the S concentration tower is continuously in countercurrent contact with rich methanol flowing from top to bottom, and the CO dissolved in the methanol at the upper section is continuously stripped 2 From medium pressure H 2 Medium pressure CO-rich from top of S concentration tower 2 The desorption gas is sent to a medium-pressure desorption gas/sulfur-free methanol-rich heat exchanger, cooled sulfur-free methanol-rich gas enters an inlet of a medium-pressure desorption gas expander, and medium-pressure CO-rich gas enters the expander 2 The desorbed gas expands outwards to do work, the process is close to isentropic expansion, the temperature of the expanded gas is greatly reduced, meanwhile, the expander drives the generator to generate electricity and output electric energy, and then the electricity and the low-pressure CO-rich gas flow are sent to a new lean methanol cooler from the outlet of the expander to recover cold energy and then are mixed with low-pressure CO 2 The desorbed gas goes to a raw gas cooler to further recover cold and then is sent to a tail gas washing tower; from medium pressure H 2 Sulfur-containing rich methanol from the bottom of the S concentration tower enters low pressure H after being throttled by a liquid level regulating valve 2 The liquid phase inlet of the 107 th tray at the top of the lower section of the S concentration tower is used as low pressure H 2 S the reflux liquid at the lower section of the concentration tower is continuously from the low pressure H 2 Low pressure nitrogen stripping of S concentration tower still at low pressure H 2 S, obtaining high-sulfur methanol rich at the temperature of-45.1 ℃ at the bottom of the concentration tower;
high sulfur methanol rich from low pressure H 2 After the S concentration tower bottom comes out, the pressure is increased by a methanol-rich pump III, the poor methanol is cooled to-40 ℃ through a methanol-rich filter, a methanol heat exchanger II shell pass and a methanol heat exchanger II shell pass to exchange heat with the poor methanol which circulates back, the high-sulfur rich methanol is heated to 31 ℃, and the high-sulfur rich methanol enter CO 2 The liquid phase inlet at the top of the desorption tower is used as CO 2 Reflux liquid at the top of the desorber in CO 2 Introducing a stream of low-pressure nitrogen into the tower kettle of the desorption tower, and continuing to obtain high-sulfur semi-rich methanolCountercurrent contact with stripping nitrogen to allow CO to pass 2 Desorbed from methanol in CO 2 The sulfur-containing CO is obtained at the top of the desorption tower 2 Stripping gas in CO 2 High-sulfur methanol and sulfur-containing CO are obtained at the bottom of the desorption tower 2 Stripping gas to low pressure H 2 S is a 128 th tray gas phase inlet of a concentration tower, high-sulfur methanol is pressurized by a methanol-rich pump IV and then exchanges heat with regenerated poor methanol through a methanol heat exchanger IV tube pass, enters a 8 th tray liquid phase inlet of a thermal regeneration tower, the high-sulfur methanol is heated by a tower bottom reboiler in the thermal regeneration tower to complete regeneration, finally most of the poor methanol after thermal regeneration is recycled heat through a methanol heat exchanger IV shell pass, enters a poor methanol collecting tank, is replenished with a small amount of lost methanol, is boosted through the poor methanol, is gradually cooled to-40 ℃ through a poor liquid water cooler tube pass, a methanol heat exchanger III tube pass and a methanol heat exchanger II tube pass by circulating cooling water and high-sulfur semi-rich methanol, is further cooled to-50.6 ℃ by sulfur-containing semi-rich methanol and expansion desorption gas in a new poor methanol cooler, and then is re-circulated to enter a liquid phase inlet at the top of an acid gas methanol absorption tower, and starts to absorb acid gas in crude synthesis gas again; pressurizing a small part of regenerated poor methanol by a reflux pump of a methanol/water separation tower, passing through a poor methanol filter, recovering the cold energy of a methanol aqueous solution by a reflux cooler I tube pass, then entering a liquid phase inlet at the top of the methanol/water separation tower to be used as a reflux liquid at the top of the methanol/water separation tower, respectively entering the middle section of the methanol/water separation tower by the methanol aqueous solution and tail gas washing water, introducing low-pressure steam into a reboiler at the bottom of the methanol/water separation tower for heating, desorbing the methanol from the water, allowing the pure methanol steam to flow to the middle part of a thermal regeneration tower from a gas phase outlet at the top of the methanol/water separation tower, allowing waste water containing a small amount of methanol to pass through a reflux cooler I shell pass for recovering heat and then to a waste water treatment unit.
Compared with the prior art, the invention has the following technical effects:
1. in the invention, the part of the methanol-rich gas is stripped at a newly increased medium pressure H which can reach 0.5MPaG to 0.75MPaG 2 S concentration is carried out in the lower part of the tower, and the higher the pressure during desorption is, the desorbed CO is 2 The greater the endothermic amount of (A), the more CO is desorbed 2 Rich methanol and desorption gas temperature ofWill be lower. The air stripping pressure is greatly improved for part of the rich methanol in the system, and the generated cold quantity is increased. Through medium pressure H 2 S concentration column and low pressure H 2 The S concentration tower and the two towers are jointly stripped by using nitrogen gas, and finally, the low pressure H can be realized 2 The high-sulfur rich methanol with the temperature as low as minus 45.1 ℃ is obtained at the bottom of the S concentration tower, the temperature of the methanol is about 10 ℃ lower than that of the high-sulfur rich methanol in the classical Linde low-temperature methanol washing process, the poor methanol can be directly cooled to minus 40 ℃, liquid ammonia is not needed to be used for cooling the poor methanol, and the cold requirement of the system is reduced.
2. The invention generates medium-pressure rich CO by newly adding 2 The desorbed gas passes through an expansion machine with a generator, and simultaneously obtains cold energy and electric energy output externally, and the newly generated cold energy and electric energy further reduce the cold energy requirement of the system and the energy consumption of the system.
3. The present invention, by increasing the operating pressure of the stripper, to increase the amount of heat absorbed during desorption is known to those skilled in the art from prior art information or engineering practice. Increasing the operating pressure of the stripper to obtain a stripping gas at a high pressure is known to the person skilled in the art from prior art information or engineering practice. Medium pressure H 2 The S concentration tower uses nitrogen to partially enrich CO contained in methanol under high pressure 2 Performing gas stripping desorption, and producing pure CO by only decompressing the rich methanol to obtain flash evaporation gas adopted by other current patenters 2 CO of (2) 2 The product towers are of different principles and have a medium pressure H 2 The gas component at the top of the S concentration tower is usually CO 2 Concentration of about 82-88%, N 2 12 to 18% in terms of CO 2 The product column overhead gas component is typically CO 2 Vol at a concentration of 99.5% or more, the latter being for CO 2 The throughput requirements, which are generally at much lower operating pressures than the former, do not allow desorption gases at higher pressures, which knowledge is known to the person skilled in the art from prior art data or engineering practice. The medium-pressure desorption gas with high pressure passes through the expander, the medium-pressure gas expands in the expander to do work outwards, the expander drives the generator to generate electricity while the temperature of the outlet gas is reduced, and the technical data of the technical personnel in the field can be obtained from the prior artOr known in engineering practice. The device and the process can be modified based on the prior device, and the purposes of energy conservation and consumption reduction can be achieved after the device and the process are modified according to the description of the device and the process.
Drawings
FIG. 1 is a flow diagram of the apparatus and process of the present invention;
the meaning of the individual reference symbols in the figures is:
1. raw gas unpurified from an upstream unit;
2. recycle gas from a recycle gas compressor;
3. spraying raw material gas from a lean methanol pump to prevent the temperature of water vapor in the raw material gas from being reduced and the methanol from being frozen;
4. purified gas from the top of the acid gas methanol absorption tower;
5. from low pressure H 2 Sulfur-free CO-rich of S concentration tower 2 Desorbing gas;
6. a feed gas from the feed gas/water separation tank from which most of the water components are removed;
7. part of sulfur-free saturated rich methanol from the bottom of the middle section of the acid gas methanol absorption tower (going to the top of the lower section of the acid gas methanol absorption tower);
8. a part of sulfur-free saturated rich methanol (going to a methanol heat exchanger I) from the bottom of the middle section of the acid gas methanol absorption tower;
9. sulfur-containing saturated rich methanol from the bottom of the acid gas methanol absorption tower;
10. sulfur-free rich methanol from the recycle gas flash drum I;
11. sulfur-containing rich methanol from the recycle gas flash drum II;
12. from low pressure H 2 S, concentrating the rich methanol at the bottom of the upper section of the tower;
13. from low pressure H 2 S, concentrating high-sulfur methanol rich at the bottom of the tower;
14. from CO 2 Sulfur-containing CO at the top of the desorber 2 Desorbing gas;
15. from CO 2 Sulfur-containing rich methanol at the top of the desorption tower;
16. acid gas components and methanol vapor from the top of the thermal regenerator;
17.H 2 s acid gas;
18. circulating lean methanol from a lean methanol pump;
19. lean methanol from the bottom of the hot regenerator column to the methanol/water separation column as overhead reflux;
20. methanol vapor from the top of the methanol/water separation column;
21. discharging the sewage containing a small amount of methanol components at the bottom of the methanol/water separation tower;
22. semi-rich methanol at the bottom of the top section of the acid gas methanol absorption tower is discharged;
23. semi-rich methanol at the bottom of the upper section of the acid gas methanol absorption tower is discharged;
24. methanol & water solution from the bottom of the feed gas/water separation tank;
25. from H 2 Acid gas condensate at the bottom of the S fraction separator II;
26. sulfur-free methanol-rich feed to low pressure H 2 S, adjusting a valve in front of a concentration tower;
27. sulfur-containing rich methanol into low pressure H 2 S, adjusting a valve in front of the concentration tower;
28. low pressure nitrogen to low pressure H 2 S, a concentration tower;
29. CO removal by low pressure nitrogen 2 A stripper column;
30. desalinated water from a desalinated water pipe network;
31. tail gas after being washed by desalted water;
32. tail gas washing water;
33. medium pressure H 2 S, a concentration tower;
34. sulfur-free methanol-rich medium pressure H 2 S, a flow regulating valve in front of the concentration tower;
35. sulfur-containing rich methanol into medium pressure H 2 S, a flow regulating valve in front of the concentration tower;
36. incoming medium pressure H from air separation 2 S, concentrating medium-pressure nitrogen in a tower kettle of a tower;
37. a medium pressure stripping gas/sulfur-free methanol-rich heat exchanger;
38. a sulfur-free methanol-rich/methanol-rich heat exchanger;
39. a methanol-rich flow regulating valve of the methanol inlet heat exchanger I;
40. a methanol-rich flow regulating valve entering the circulating methanol cooler;
41. flow splitting to remove medium pressure H 2 S, sulfur-free methanol-rich in a concentration tower;
42. shunting to remove low pressure H 2 S, sulfur-free methanol-rich in a concentration tower;
43. flow diversion to remove medium pressure H 2 S, concentrating sulfur-containing rich methanol in a tower;
44. shunting to remove low pressure H 2 S, concentrating sulfur-containing rich methanol in a tower;
45. medium pressure H 2 Medium-pressure sulfur-free CO-rich tower top of S concentration tower 2 Desorbing gas;
46. medium pressure H 2 The middle-pressure methanol-rich at the bottom of the upper section of the S concentration tower (70 th tray);
47. a pressure reducing valve is arranged before the medium-pressure methanol-rich gas enters the methanol-rich flash tank;
48. a pressure reducing valve is arranged before the low-pressure methanol-rich gas enters the methanol-rich flash tank;
49. flash evaporation gas at the top of the methanol-rich flash evaporation tank is discharged;
50. the rich methanol at the bottom of the flash tank for the rich methanol is discharged;
51. rich methanol after heat exchange with sulfur-free rich methanol;
52. shunting the rich methanol to a recycle methanol cooler;
53. shunting methanol rich in methanol in the methanol removal heat exchanger I;
54. rich methanol exiting the recycle methanol cooler;
55. rich methanol is discharged from the methanol heat exchanger I;
56. medium-pressure sulfur-free CO-rich heat exchanger for discharging medium-pressure desorbed gas/sulfur-free methanol-rich heat exchanger 2 Desorbing gas;
57. a medium pressure stripping gas expander;
58. CO-enriched air from medium-pressure desorption gas expander 2 Gas;
59. CO-rich of lean methanol heat exchanger 2 Gas;
60. confluent rich CO 2 Low pressure CO-rich expansion gas 2 Desorbing gas;
61. medium pressure H 2 At the bottom of the S concentration towerSulfur-rich methanol;
62. medium pressure H 2 S, a liquid level regulating valve of a tower kettle of the concentration tower;
63. a generator driven by the expander;
64. an acid gas methanol absorption tower;
65. a circulating methanol cooler;
66. a methanol heat exchanger I;
67. a methanol quencher;
68. a circulating gas flash tank I;
69. a circulating gas flash tank II;
70. low pressure H 2 S, a concentration tower;
71. a methanol-rich flash tank;
72. a methanol-rich pump I;
73. a fresh lean methanol cooler;
74. a methanol-rich pump II;
75. a methanol-rich pump III;
76. a methanol-rich filter;
77. a methanol heat exchanger II;
78. a methanol heat exchanger III;
79.CO 2 a desorber;
80.H 2 an S fraction separator I;
81.H 2 an S fraction separator II;
82. a poor methanol collecting tank;
83. a lean methanol pump;
84. a barren liquor water cooler;
85. a purified gas/methanol heat exchanger I;
86. a feed gas/water separation tank;
87.H 2 an S fraction quencher;
88.H 2 an S fraction heat exchanger;
89.H 2 an S fraction cooler;
90. a thermal regeneration tower reflux pump;
91. a thermal regeneration column;
92. a thermal regeneration column reboiler;
93. a reflux pump of the methanol/water separation tower;
94. a rich methanol pump IV;
95. a lean methanol filter;
96. a reflux cooler I;
97. a methanol heat exchanger IV;
98. a methanol/water separation column;
99. a methanol/water separation column reboiler;
100. a water heat exchanger;
101. a tail gas wash tower;
102. a tail gas washing water pump;
103. a raw gas cooler;
104. a recycle gas compressor;
105. a water cooler of the circulating gas compressor;
flow rates of streams in the above designations the flow rates of the gas-phase streams are in Nm, according to the engineering practice 3 The/h is expressed and the liquid stream is expressed in kg/h.
Detailed Description
In the classical linde low-temperature methanol washing process, the energy consumption of a low-temperature methanol washing unit mainly comes from two aspects: the first is that several methanol circulating pumps in the system, such as a lean methanol pump, a rich methanol pump and the like, and a circulating gas compressor; secondly, the ice maker supplies energy consumed by cold energy to the low-temperature methanol washing unit, the ice maker has the function of re-pressurizing the ammonia gas heated by the hot material flow of the system, the temperature of the ammonia gas is reduced after throttling and pressure reduction, part of the ammonia gas is changed into low-temperature liquid ammonia, the liquid ammonia is used for providing cold energy for the low-temperature methanol washing quenchers, the liquid ammonia is evaporated into the ammonia gas after the material flow is heated, a low-temperature methanol washing device of the classical Linde low-temperature methanol washing process is adopted, the circulation quantity of lean methanol is 223905kg/hr, the total load of the cold energy required by 4 quenchers at 40 ℃ below zero is 4065kwh, the calculation is carried out according to the refrigerating efficiency of the ammonia ice maker which is about 1.53, and the axial power required by the ammonia ice maker is 2656kw. In the above methanol washing process, CO 2 The internal energy in the components is wasted greatly and is not fully utilized, and a large amount of energy (electric energy or power steam) is consumed to enable an ice machine to produce cold energy, so that the cold energy balance in a low-temperature methanol washing area can be maintained.
The invention aims to provide an improved low-temperature methanol CO washing method 2 Desorbing and utilizing the desorbed gas to make part of the rich methanol enter the newly added medium pressure H 2 S concentration tower, in which CO dissolved in rich methanol is desorbed by using middle-pressure nitrogen gas stripping 2 Due to the large increase of pressure during desorption, this part of desorbed CO 2 The absorbed cold is increased, and CO is desorbed 2 The latter methanol is cooled more, this stream is from medium pressure H 2 Medium pressure CO-rich from S-concentration column 2 The desorbed gas enters a newly-added expansion machine again, more cold energy is generated in the expansion machine through expansion, the low-temperature methanol washing unit generates more cold energy per se, the load of the ice machine is reduced by about 33%, meanwhile, the expansion machine drives a generator to output electric energy externally, the power consumption and the circulating water consumption of the system are reduced, the total energy consumption of the improved low-temperature methanol washing system is reduced by 13% according to the conversion of the national energy consumption standard coefficient, and the purposes of energy conservation and consumption reduction are achieved.
The improved low-temperature methanol CO washing method of the invention 2 A desorption device for desorbing and utilizing the desorbed gas, which comprises an acid gas methanol absorption tower, a circulating methanol cooler, a methanol heat exchanger I, a circulating gas flash tank II and a medium pressure H 2 S concentration column, low pressure H 2 The system comprises an S concentration tower, a methanol-rich flash tank, a methanol-rich pump I, a methanol-rich pump II, a medium-pressure desorption gas/sulfur-free methanol-rich heat exchanger, a sulfur-free methanol-rich/methanol-rich heat exchanger, a medium-pressure desorption gas expander, a generator driven by the expander, a new methanol-poor cooler, a methanol-rich pump III, a methanol heat exchanger II, a methanol heat exchanger III, CO 2 Desorption column, H 2 The system comprises an S fraction separator II, a poor methanol collecting tank, a poor methanol pump, a poor liquid water cooler, a purified gas/methanol heat exchanger I, a circulating gas compressor, a methanol quencher and a methanol-rich filter;
CO of acid gas methanol absorption tower 2 The liquid phase outlet of the 36 th tray at the bottom of the fine absorption section passes through the tube bundle of the circulating methanol cooler and the CO of the acid gas methanol absorption tower 2 The 37 th tray liquid phase inlet at the top of the main absorption section is connected; CO of acid gas methanol absorption tower 2 66 th tray liquid at the bottom of the main absorption sectionCO at a phase outlet through a circulating methanol cooler tube bundle and an acid gas methanol absorption tower 2 The 67 th tower tray liquid phase inlet at the top of the coarse absorption section is connected; CO of acid gas methanol absorption tower 2 A part of sulfur-free methanol-rich outlet of a 96 th tray at the bottom of the coarse absorption section is connected with a liquid phase inlet of a circulating gas flash tank I through a tube pass of a medium-pressure desorption gas/sulfur-free methanol-rich heat exchanger, a tube bundle of a methanol heat exchanger I and a tube pass of the sulfur-free methanol-rich/methanol-rich heat exchanger; CO of acid gas methanol absorption tower 2 The other part of the sulfur-free methanol-rich outlet at the bottom of the coarse absorption section is connected with the liquid phase inlet of the 97 th tower tray at the top of the lower section of the acid gas methanol absorption tower; a liquid phase outlet at the bottom of the acid gas methanol absorption tower is connected with a liquid phase inlet of a circulating gas flash tank II through a purified gas/methanol heat exchanger I tube pass and a methanol heat exchanger I tube bundle;
medium pressure H 2 The gas phase outlet at the top of the S concentration tower is connected with the shell pass inlet of the medium-pressure desorption gas/sulfur-free methanol-rich heat exchanger; liquid phase outlet pipeline branch at bottom of I tank of circulating gas flash tank and medium pressure H 2 The liquid phase inlet at the top of the S concentration tower is connected; liquid phase outlet at bottom of I tank of circulating gas flash tank and low pressure H 2 The liquid phase inlet at the top of the S concentration tower is connected; liquid phase outlet pipeline branch at bottom of circulating gas flash tank II and medium pressure H 2 The liquid phase inlet of the 15 th tray of the S concentration tower is connected; liquid phase outlet pipeline at bottom of II tank of circulating gas flash tank and low pressure H 2 The liquid phase inlet of the 23 th tray of the S concentration tower is connected; medium pressure H 2 The liquid phase outlet of the 70 th tray at the bottom of the upper section of the S concentration tower is connected with the liquid phase inlet of the methanol-rich flash tank; low pressure H 2 A liquid phase outlet of the 106 th tray at the bottom of the upper section of the S concentration tower is connected with a liquid phase inlet of the methanol-rich flash tank through a methanol-rich pump II and a new methanol-poor cooler tube bundle; gas phase outlet at top of methanol-rich flash tank and low pressure H 2 The gas phase inlet of the 107 th tray at the top of the lower section of the S concentration tower is connected; the liquid phase outlet at the bottom of the methanol-rich flash tank passes through a methanol-rich pump I, a sulfur-free methanol-rich/methanol-rich heat exchanger shell pass, a methanol heat exchanger I shell pass, a circulating methanol heat exchanger I shell pass and medium pressure H 2 The 71 th tower tray liquid phase inlet at the top of the lower section of the S concentration tower is connected; medium-pressure nitrogen from air separation and medium pressure H 2 Gas phase under one tray at the bottommost layer of tower kettle of S concentration towerAn inlet connection; medium pressure H 2 The liquid phase outlet at the bottom of the S concentration tower passes through a medium pressure H 2 S concentration tower bottom liquid level regulating valve and low pressure H 2 The 107 th tray liquid phase inlet at the top of the lower section of the S concentration tower is connected; the shell side outlet of the medium-pressure desorption gas/sulfur-free methanol-rich heat exchanger is connected with the inlet of a medium-pressure desorption gas expander; the outlet of the medium-pressure desorption gas expander passes through the tube bundle of the new lean methanol cooler and the low pressure H 2 S concentration tower top rich in CO 2 Connecting a desorption gas pipeline; an output shaft of the medium-pressure desorption gas expander is connected with a generator shaft; the gas phase outlets at the tops of the circulating gas flash tank I and the circulating gas flash tank II are both connected with the inlet of a circulating gas compressor; low pressure H 2 The liquid phase outlet at the bottom of the S concentration tower passes through a rich methanol pump III, a methanol heat exchanger II, a methanol heat exchanger III and CO 2 The liquid phase inlet at the top of the desorption tower is connected; h 2 Liquid phase outlet at bottom of S fraction separator II tank and low pressure H 2 The 132 th tray liquid phase inlet of the S concentration tower is connected; CO2 2 Gas phase outlet and low pressure H at the top of the desorption tower 2 The 125 th tray gas phase inlet of the S concentration tower is connected; and a liquid phase outlet at the bottom of the poor methanol collecting tank is connected with a liquid phase inlet at the top of the acid gas methanol absorption tower through a poor methanol pump, a poor liquid water cooler tube pass, a methanol heat exchanger III tube pass, a methanol heat exchanger II tube pass and a new poor methanol cooler shell pass.
It is another object of the present invention to provide an improved low temperature methanol scrubbing of CO 2 Compared with the classic Linde low-temperature methanol washing process, the process method can reduce the power consumption of the low-temperature methanol ice washing machine by more than 33 percent, reduce the power consumption in the system and the consumption of circulating cooling water, reduce the total process energy consumption of the system by 13 percent and achieve the purpose of reducing the energy consumption.
Improved low temperature methanol scrubbing of CO of the present invention 2 The desorption and desorption gas utilization process comprises the following steps:
the raw material gas enters an acid gas methanol absorption tower to remove all acid gas, and lean methanol absorbs CO in sections 2 And after the sulfide acid gas component is saturated, respectively using sulfur-free rich methanol and sulfur-containing acid gas componentThe method comprises the following steps that (1) a methanol-rich material flow mode leaves an acid gas methanol absorption tower, two methanol-rich streams enter a methanol heat exchanger I, wherein sulfur-containing methanol-rich is firstly precooled to-19.4 ℃ by purified gas discharged from the top of the acid gas methanol absorption tower, in the methanol heat exchanger I, the two high-pressure methanol-rich streams are cooled to-30 ℃ by methanol-rich from a methanol-rich flash tank, then sulfur-free methanol-rich continuously enters a tube pass of a sulfur-free methanol/methanol-rich heat exchanger, is further cooled to-36 ℃, and the cooled absorbed acid gas to saturated sulfur-free methanol-rich and saturated sulfur-containing methanol-rich respectively enter a circulating gas flash tank I and a circulating gas flash tank II after being decompressed and throttled by regulating valves;
the throttled and decompressed sulfur-free methanol-rich and sulfur-containing methanol-rich are respectively subjected to flash evaporation in a circulating gas flash tank I and a circulating gas flash tank II due to H 2 、CO、CH 4 The effective gas components have low solubility in methanol, so that the effective gas components can be preferentially desorbed from the methanol-rich gas, and most of CO is desorbed 2 And H 2 S, etc. continue to dissolve in the low-temperature rich methanol, mainly H 2 、CO、CH 4 The flash evaporation gas of the effective gas components goes to the inlet of the circulating gas compressor, and is subjected to pressure boosting by the circulating gas compressor and cooling by a water cooler of the circulating gas compressor and then is converged with the inlet feed gas;
the sulfur-free methanol rich at the bottom of the circulating gas flash tank I is respectively sent to the medium pressure H according to the proportion 2 S concentration column and low pressure H 2 Liquid inlet at the top of S concentration tower as medium pressure H 2 S concentration column and low pressure H 2 S concentration tower top reflux liquid, sulfur-free rich methanol as tower top reflux liquid can ensure H from medium pressure and low pressure 2 Rich CO from the top of S concentration tower 2 The desorption gas hardly contains sulfur components; the sulfur-containing rich methanol at the bottom of the circulating gas flash tank II is respectively sent to the medium pressure H according to the proportion 2 S concentration column and low pressure H 2 Liquid inlet of the 15 th tray of the S concentration tower as medium pressure H 2 S concentration column and low pressure H 2 S, concentrating a second reflux liquid of the tower; at medium pressure H 2 S concentration column and low pressure H 2 The tower kettle of the S concentration tower is respectively filled with medium-pressure and low-pressure nitrogen from an air separation unit, and CO dissolved in the rich methanol is treated by the nitrogen 2 Stripping to desorb gasThe methanol-rich counter-current contact, the nitrogen gas destroys the original CO 2 Gas-liquid equilibrium with methanol is achieved, so that CO is generated 2 Continuously desorb from rich methanol due to CO 2 Desorption will absorb heat, so CO 2 Stripping gas and stripping CO 2 The temperature of methanol (a) is all reduced; from medium pressure H 2 70 th tray of S concentration tower and low pressure H 2 Respectively flowing out of the 106 th tray of the S concentration tower to desorb partial CO 2 The unsaturated sulfur-containing methanol is pressurized by a methanol-rich pump II, and then cooled to minus 50.6 ℃ together with medium-pressure stripping expansion gas through a new methanol-poor cooler tube bundle, and then enters the liquid phase inlet of the methanol-rich flash tank after passing through the regulating valve;
in the methanol-rich flash tank, two sulfur-containing methanol-rich flash tanks are flashed, and the operating pressure set behind the regulating valve is slightly higher than the low pressure H 2 S concentration tower operating pressure so that flash gas flashed off can enter low pressure H 2 The gas phase inlet above the 107 th tray on the top of the lower section of the S concentration tower is used for reducing the temperature of the rich methanol and the flash evaporation gas to-55.6 ℃ after flash evaporation, and the flash evaporation gas is sent to the low pressure H 2 S, a gas phase inlet at the top of the lower section of the concentration tower, the rich methanol enters a rich methanol pump I, after the pressure of the rich methanol pump I is increased, the rich methanol firstly goes to a sulfur-free rich methanol/rich methanol heat exchanger, the sulfur-free rich methanol is cooled to-36 ℃, and then the rich methanol respectively goes to a methanol heat exchanger I and a circulating methanol cooler according to the proportion under the regulation of a rich methanol flow regulating valve of the methanol heat exchanger I and a rich methanol flow regulating valve of the circulating methanol cooler to cool the rich methanol and the circulating methanol cooler because CO is absorbed 2 The two half rich methanol streams are cooled to-35 ℃, the sulfur-free rich methanol stream and the sulfur-containing rich methanol stream are cooled to-30 ℃, the sulfur-free rich methanol stream and the sulfur-containing rich methanol stream are heated to-30.5 ℃ and-19.1 ℃, and the two half rich methanol streams are returned to the medium pressure H after being merged 2 The 71 th tray liquid phase inlet at the top of the lower section of the S concentration tower is continuously stripped by medium-pressure nitrogen from the tower kettle, and desorbed CO 2 And the stripping nitrogen enters the medium pressure H through the ascending pipe 2 The bottom of the upper section of the S concentration tower continuously flows from top to bottomMoving rich methanol is in countercurrent contact, and CO dissolved in methanol at the upper section is continuously stripped 2 From medium pressure H 2 Medium pressure CO-rich from top of S concentration tower 2 The desorption gas is sent to a medium-pressure desorption gas/sulfur-free methanol-rich heat exchanger, cooled sulfur-free methanol-rich gas enters an inlet of a medium-pressure desorption gas expander, and medium-pressure CO-rich gas enters the expander 2 The desorbed gas expands outwards to do work, the process is close to isentropic expansion, the temperature of the expanded gas is greatly reduced, meanwhile, the expander drives the generator to generate electricity and output electric energy, and then the electricity and the low-pressure CO-rich gas flow are sent to a new lean methanol cooler from the outlet of the expander to recover cold energy and then are mixed with low-pressure CO 2 The desorbed gas goes to a raw gas cooler to further recover cold and then is sent to a tail gas washing tower; from a medium pressure H 2 Sulfur-containing rich methanol from the bottom of the S concentration tower enters low pressure H after being throttled by a liquid level regulating valve 2 The liquid phase inlet of the 107 th tray at the top of the lower section of the S concentration tower is used as low pressure H 2 The reflux liquid at the lower section of the S concentration tower is continuously from low pressure H 2 Low pressure nitrogen stripping in the tower bottom of S concentration tower at low pressure H 2 S, obtaining high-sulfur methanol rich at the temperature of-45.1 ℃ at the bottom of the concentration tower;
high sulfur methanol rich from low pressure H 2 After the S concentration tower bottom comes out, the pressure is increased through a methanol-rich pump III, the poor methanol is cooled to-40 ℃ through a methanol-rich filter, a methanol heat exchanger II shell pass and the poor methanol circulated back, the subsequent flow is the same as the classical Linde process, the high-sulfur and rich methanol is heated to 31 ℃ and enters CO together with the high-sulfur and rich methanol 2 The liquid phase inlet at the top of the desorption tower is used as CO 2 Reflux liquid at the top of the desorber in CO 2 Introducing a low-pressure nitrogen into the tower kettle of the desorption tower, and continuously making the high-sulfur semi-rich methanol in countercurrent contact with the gas stripping nitrogen to allow CO to be in contact with the gas 2 Desorbed from methanol in CO 2 The sulfur-containing CO is obtained at the top of the desorption tower 2 Stripping gas in CO 2 High-sulfur methanol and sulfur-containing CO are obtained at the bottom of the desorption tower 2 Stripping gas to low pressure H 2 The gas phase inlet of the 128 th tray of the S concentration tower, the high-sulfur methanol is pressurized by a methanol-rich pump IV and then exchanges heat with the regenerated poor methanol through a methanol heat exchanger IV tube pass, the high-sulfur methanol enters the liquid phase inlet of the 8 th tray of the thermal regeneration tower, and the high-sulfur methanol is thermally regeneratedHeating the raw tower by a tower bottom reboiler to complete regeneration, recovering heat of most of the heat-regenerated poor methanol by a methanol heat exchanger IV shell pass, then entering a poor methanol collecting tank, supplementing a small amount of lost methanol, then boosting the pressure of the poor methanol, gradually cooling the poor methanol by circulating cooling water and high-sulfur semi-rich methanol to-40 ℃ by a poor liquid water cooler tube pass, a methanol heat exchanger III tube pass and a methanol heat exchanger II tube pass, further cooling the poor methanol by sulfur-containing semi-rich methanol and expansion desorption gas to-50.6 ℃ in a new poor methanol cooler, then re-circulating the poor methanol to enter an acid gas methanol absorption tower top liquid phase inlet, and re-starting to absorb acid gas in the crude synthesis gas; a small part of regenerated poor methanol is pressurized by a reflux pump of a methanol/water separation tower, then passes through a poor methanol filter, the cold energy of a methanol water solution is recovered by a reflux cooler I tube pass, and then enters a liquid phase inlet at the top of the methanol/water separation tower to be used as a reflux liquid at the top of the methanol/water separation tower, the methanol water solution and tail gas washing water respectively enter the middle section of the methanol/water separation tower, low-pressure steam is introduced into a reboiler at the bottom of the methanol/water separation tower to be heated, methanol is desorbed from water, pure methanol steam goes to the middle part of a thermal regeneration tower from a gas phase outlet at the top of the methanol/water separation tower, wastewater containing a small amount of methanol passes through, and the heat is recovered by a reflux cooler I shell pass and then goes to a wastewater treatment unit.
Description of the device type in the present embodiment:
the raw material gas cooler, the circulating methanol cooler, the methanol heat exchanger I, the new poor methanol cooler and the methanol heat exchanger II are wound tube type heat exchangers, the wound tube type heat exchangers are mainly characterized in that more than one tube pass (shell pass single strand) can be allowed, and a plurality of strands of hot material flows or cold material flows can exchange heat with materials of the shell pass through the tube pass at the same time, and except that the methanol heat exchanger II only has one tube pass, other wound tube type heat exchangers have two tube passes.
Circulating gas compressor water cooler, sulfur-free methanol-rich/methanol-rich heat exchanger, medium-pressure desorption gas/sulfur-free methanol-rich heat exchanger, methanol quencher, methanol-poor cooler, methanol heat exchanger III, H 2 S fraction quencher, H 2 S fraction heat exchanger, H 2 S fraction cooler, methanol heat exchanger IV, thermal regeneration tower boiler and reflux coolerI. The methanol/water separation tower boiler and the water heat exchanger are common shell-and-tube heat exchangers.
Acid gas methanol absorption tower and medium pressure H 2 S concentration column, low pressure H 2 The S concentration tower, the thermal regeneration tower, the methanol/water separation tower and the tail gas washing tower are plate towers, and tower internals are tower trays.
CO 2 The desorption tower is a packed tower, and the internal parts of the tower are regular packing.
The following embodiments of the present invention are provided, and it should be noted that the present invention is not limited to the following embodiments, and all equivalent changes based on the technical solutions of the present invention are within the protection scope of the present invention.
Example 1:
the pressure of the existing raw syngas at the low-temperature methanol washing inlet is 5.6MPaG, the temperature is 40 ℃, and the total gas amount is 174777Nm 3 Hr, wherein the volume fraction is H 2 :59.29％、N 2 :2.03％、CO:2.04％、Ar:0.06％、CH 4 :0.42％、CO 2 :35.45％、H 2 S+COS:0.56％、H 2 0.15 percent of O, and the purpose of the low-temperature methanol washing unit is to remove CO contained in the synthesis gas 2 Purified to below 10ppm, H 2 The content of S + COS is reduced to below 0.1 ppm.
The following Low temperature methanol wash CO intended to be improved by the present invention 2 Desorbing and purifying the raw material gas by using a desorption gas device and a desorption gas process.
The main key equipment of the device comprises an acid gas methanol absorption tower, a circulating methanol cooler, a methanol heat exchanger I, a methanol quencher and a circulating gas flash drum I&II. Medium pressure H 2 S concentration column and low pressure H 2 S concentration tower, methanol-rich gas enter medium pressure&Low pressure H 2 S concentration tower regulating valve, methanol-rich flash tank, methanol-rich pump I and methanol-rich heat exchanger I&A flow regulating valve at the front of the methanol cooler for rich methanol to enter the circulation, a medium-pressure desorption gas/sulfur-free methanol-rich heat exchanger, a sulfur-free methanol-rich/methanol-rich heat exchanger, a medium-pressure desorption gas expander, a generator driven by the expander, a new methanol-poor cooler, a methanol-rich pump III, a methanol-rich filter, a methanol heat exchanger II and a methanol heat exchange deviceIII, CO 2 Desorption column, H 2 The system comprises an S fraction separator II, a poor methanol collecting tank, a poor methanol pump, a poor liquid water cooler, a purified gas/methanol heat exchanger I, a circulating gas compressor, a methanol quencher and a methanol-rich filter.
The acid gas methanol absorption tower has a total of 116 trays which are divided into 4 sections from top to bottom, which are respectively called as CO 2 Fine absorption section (1-36 trays), CO 2 Main absorption section (37-66 trays), CO 2 A crude absorption section (67 to 96 trays) and a sulfide absorption section (97 to 116 trays). The two sections are connected by a gas-raising pipe. CO2 2 A liquid phase outlet at the bottom of the fine absorption section passes through the circulating methanol cooler tube bundle 1 and the acid gas methanol absorption tower CO 2 The liquid phase inlets at the top of the main absorption section are connected; acid gas methanol absorption tower CO 2 A liquid phase outlet at the bottom of the main absorption section passes through the circulating methanol cooler tube bundle 2 and the acid gas methanol absorption tower CO 2 The liquid phase inlets at the top of the coarse absorption section are connected; acid gas methanol absorption tower CO 2 A sulfur-free methanol-rich outlet at the bottom part of the coarse absorption section is connected with a liquid phase inlet of a circulating gas flash tank I through a tube pass of a medium-pressure desorption gas/sulfur-free methanol-rich heat exchanger, a tube bundle I1 of the methanol heat exchanger and the tube pass of the sulfur-free methanol-rich/methanol-rich heat exchanger; acid gas methanol absorption tower CO 2 And the other part of the sulfur-free methanol-rich outlet at the bottom of the crude absorption section is connected with a liquid phase inlet at the top of the sulfide absorption section of the acid gas methanol absorption tower. The bottom of the sulfide of the acid gas methanol absorption tower is connected with a circulating gas flash tank II through a purified gas/methanol heat exchanger I tube pass and a methanol heat exchanger I tube bundle 2.
Liquid phase outlet pipeline branch at bottom of I tank of circulating gas flash tank and medium pressure H 2 S, connecting liquid phase inlets at the tops of the concentration towers; liquid phase outlet at bottom of tank I of circulating gas flash tank and low pressure H 2 S, connecting liquid phase inlets at the tops of the concentrating towers; liquid phase outlet pipeline branch at bottom of circulating gas flash tank II and medium pressure H 2 The liquid phase inlet of the 15 th tray of the S concentration tower is connected; liquid phase outlet pipeline at bottom of II tank of circulating gas flash tank and low pressure H 2 The liquid phase inlet of the 23 th tray of the S concentration tower is connected; circulating gas flash drum I&II tank top gas phase outlet and circulationThe inlet of the ring air compressor is connected.
Medium pressure H 2 The S concentration tower is divided into two sections from top to bottom, wherein the upper section (1-70 trays) and the lower section (71-106 trays) are connected by a riser. A gas phase outlet at the top of the upper section is connected with an inlet of an intermediate-pressure desorption gas expander through an intermediate-pressure desorption gas/sulfur-free methanol-rich heat exchanger I shell pass; a liquid phase outlet at the bottom of the upper section is connected with a liquid phase inlet 1 of the methanol-rich flash tank; the lower section top liquid phase inlet is connected with a circulating methanol cooler and a shell pass liquid phase outlet of a methanol heat exchanger I; medium pressure H 2 A gas phase inlet of a tower kettle (below the bottommost tray) of the S concentration tower is connected with medium-pressure nitrogen from air separation; medium pressure H 2 The liquid phase outlet at the bottom of the S concentration tower passes through a medium pressure H 2 S concentration tower bottom liquid level regulating valve and low pressure H 2 And the liquid phase inlets at the top of the lower section of the S concentration tower are connected.
Low pressure H 2 The S concentration tower is divided into two sections from top to bottom, wherein the upper section (1-106 trays) and the lower section (107-138 trays) are connected by a riser. The gas phase outlet at the top of the upper section is merged with the expansion desorption gas and then is connected with the feed gas cooler tube bundle 2; a liquid phase outlet at the bottom of the upper section is connected with a liquid phase inlet 2 of the methanol-rich flash tank through a methanol-rich pump II, a new methanol-poor cooler tube bundle 1 and a methanol-rich flash tank; lower section top liquid phase inlet and medium pressure H 2 S, connecting a liquid phase outlet at the bottom of the concentration tower; the lower section top gas phase inlet is connected with a methanol-rich flash tank top gas phase outlet; low pressure H 2 Liquid phase inlet of 132 th tray of S concentration tower and H 2 The liquid phase outlet at the bottom of the S fraction separator II is connected; low pressure H 2 Gas phase inlet of 125 th tray of S concentration tower and CO 2 The gas phase outlet at the top of the desorption tower is connected with the gas phase outlet; low pressure H 2 A gas phase inlet of a tower kettle (below the bottommost tray) of the S concentration tower is connected with low-pressure nitrogen from air separation; low pressure H 2 The liquid phase at the bottom of the S concentration tower passes through a methanol-rich pump, a methanol heat exchanger II, a methanol heat exchanger III and CO 2 The liquid phase inlets at the top of the desorption tower are connected.
Gas phase outlet at top of methanol-rich flash tank and low pressureH 2 The gas phase inlets at the top of the lower section of the S concentration tower are connected; the liquid phase outlet at the bottom of the methanol-rich flash tank passes through a methanol-rich pump I, a sulfur-free methanol-rich/methanol-rich heat exchanger shell pass and a methanol heat exchanger I shell pass&I shell pass and medium pressure H of circulating methanol heat exchanger 2 The liquid phase inlet at the top of the lower section of the S concentration tower (71 th tray) is connected;
an inlet of the medium-pressure desorption gas expander is connected with a medium-pressure desorption gas/sulfur-free methanol-rich shell pass outlet; the outlet of the expansion machine is connected with the inlet of the new lean methanol cooler tube bundle 2, and the output shaft of the expansion machine is connected with the generator.
The new poor methanol cooler is changed into a wound tube type heat exchanger from a shell-and-tube type heat exchanger adopted by the original poor methanol cooler in the type form, and a shell pass inlet is connected with a tube pass outlet of a methanol heat exchanger II; the shell side outlet is connected with a liquid phase inlet at the top of the acid gas methanol absorption tower; the inlet of the tube bundle 1 passes through a methanol-rich pump II and a low pressure H 2 S, connecting a liquid phase outlet at the bottom of the upper section of the concentration tower; the outlet of the tube bundle 1 is connected with the liquid phase inlet 2 of the methanol-rich flash tank; the inlet of the tube bundle 2 is connected with the outlet of the medium-pressure desorption gas expander; outlet of tube bundle 2 and low pressure rich CO 2 The desorbed gas is converged and then is connected with the inlet of the feed gas cooler tube bundle 2;
a liquid phase inlet 1 of the poor methanol collecting tank is connected with supplemented methanol from a methanol tank area, and a liquid phase inlet 2 is connected with a liquid phase outlet 1 at the bottom of the thermal regeneration tower through a methanol heat exchanger IV shell pass; the bottom liquid phase outlet is connected with the top liquid phase inlet of the methanol absorption tower through a lean methanol pump, a lean liquid water cooler tube pass, a methanol heat exchanger III tube pass, a methanol heat exchanger II tube pass and a new lean methanol heat exchanger shell pass.
The acid gas methanol absorption tower can utilize different solubility of different gas components in low-temperature methanol to sectionally react on CO 2 And sulfide (H) 2 S + COS) and other acid gas components are selectively absorbed;
the acid gas methanol absorption tower comprises 116 trays which are divided into 4 sections from top to bottom, wherein 1-36 trays are CO 2 The fine absorption section and 37-66 trays are made of CO 2 The main absorption section and 67-96 trays are made of CO 2 Coarse absorptionThe section, 97-116 trays are sulfide absorption sections; the adjacent two sections are connected through a gas raising pipe; CO2 2 Fine absorption section and CO 2 The liquid phase methanol coming out from the bottom of the main absorption section enters a circulating methanol cooler, and the two streams absorb CO 2 The liquid phase methanol exchanges heat with part of rich methanol in the shell pass of the sulfur-free rich methanol/rich methanol heat exchanger; CO2 2 Part of liquid phase methanol from the bottom of the crude absorption section is cooled by medium pressure desorption gas through a medium pressure desorption gas/sulfur-free methanol-rich heat exchanger tube pass, and CO is discharged from the bottom of the crude absorption section 2 And returning other part of liquid phase methanol from the bottom of the crude absorption section to the sulfide absorption section, flowing out from the bottom of the acid gas methanol absorption tower after sulfide is absorbed, entering the methanol heat exchanger I together with the sulfur-free rich methanol from the tube pass of the medium-pressure desorption gas/sulfur-free methanol-rich heat exchanger, and exchanging heat with other part of rich methanol from the shell pass of the sulfur-free methanol-rich/methanol-rich heat exchanger.
Medium pressure H 2 The S concentration tower comprises 106 trays which are divided into two sections from top to bottom, wherein 1-70 trays are medium-pressure H 2 At the upper section of the S concentration tower, 71-106 trays are medium-pressure H 2 S, the lower section of a concentration tower; the topmost liquid-phase feed to the upper section (1-70 trays) is a portion of sulfur-free methanol-rich from the recycle gas flash drum I, followed by a portion of sulfur-containing methanol-rich from the recycle gas flash drum II to the 15 th tray from the intermediate pressure H 2 The liquid-phase methanol from the bottom of the upper section of the S concentration tower (a 70 th tray) enters a methanol-rich flash tank after passing through a liquid level control valve; medium pressure H 2 The liquid phase feed of the lower section (71-106 trays) of the S concentration tower is that the cold material flow returned from the circulating methanol cooler and the methanol heat exchanger I is rich in methanol, and the medium pressure H is 2 And the two sections of the S concentration tower are connected by a gas lift pipe.
Low pressure H 2 The S concentration tower comprises 138 trays which are divided into two sections from top to bottom, wherein 1-106 trays are low-pressure H 2 The upper section of the S concentration tower adopts 107 to 138 trays as low pressure H 2 S lower section of the concentration tower. The topmost liquid phase feed of the upper section (1-106 trays) is the sulfur-free methanol-rich fraction from the recycle gas flash drum I, and the sulfur-rich methanol fraction from the recycle gas flash drum II is fed to the 23 rd tray from the low pressure H 2 From the bottom of the upper section of the S-concentrator (tray 106)Liquid-phase methanol is pressurized by a methanol-rich pump II, then enters a methanol-rich flash tank after passing through a new methanol-poor cooler tube bundle 1 and a liquid level control valve; low pressure H 2 The top liquid phase feed to the lower section (107-138 trays) of the S concentration column is at medium pressure H 2 The top gas phase feed of the rich methanol from the bottom of the S concentration tower is the flash steam from the top of a methanol-rich flash tank, and the low pressure H is 2 And the two sections of the S concentration tower are connected by a gas lift pipe.
Medium pressure H 2 S concentration column and low pressure H 2 The S concentration tower is used for leading CO dissolved in low-temperature methanol to be stripped through nitrogen gas 2 Is desorbed and is washed by sulfur-free rich methanol at the tower top simultaneously, so that H is obtained 2 S is gradually concentrated in methanol flowing downwards, and H is concentrated at the bottom of the tower 2 S is rich in methanol; due to CO 2 The desorption from the methanol absorbs heat, and the temperature of the methanol-rich solution and the desorbed gas discharged from the tower is reduced.
Medium pressure H 2 S concentration tower, adopting medium pressure nitrogen gas to make gas stripping, because the partial gas stripping rich in methyl alcohol is implemented in medium pressure environment, and the higher the pressure in the desorption process is, then the desorbed CO can be obtained 2 The greater the endothermic heat of (A), the medium pressure CO 2 More heat is absorbed during desorption, so that finally the medium pressure H is removed 2 The bottom of the S concentration tower goes to low pressure H 2 The temperature of the high-sulfur methanol-rich at the top liquid phase inlet of the lower section of the S concentration tower is reduced by about 10 ℃ compared with the temperature of the same liquid phase feed of the original device, and the temperature is at medium pressure H 2 The S concentration tower obtains a stream of medium-pressure rich CO 2 And (5) desorbing gas.
Low pressure H 2 S concentration column, due to low pressure H 2 The temperature of the high-sulfur methanol-rich at the top liquid phase inlet of the lower section of the S concentration tower is reduced by about 10 ℃ compared with the original device, so that low-pressure H is discharged 2 The temperature of the high-sulfur methanol-rich at the bottom of the S concentration tower is reduced by about 10 ℃ compared with the original device.
Methanol-rich flash tank, desorbing part of CO 2 And medium pressure H of the temperature reduction 2 Rich methanol from the upper section of the S concentration tower and part of CO desorbed after heat exchange with poor methanol 2 And reduced low pressure H 2 The rich methanol coming out of the upper section of the S concentration tower enters the rich methanol togetherFlash evaporation is carried out in the flash evaporation tank, the temperature of the rich methanol and the flash evaporation gas is reduced after flash evaporation, the cold energy of the rich methanol is used for cooling CO after the rich methanol is pressurized by a rich methanol pump I 2 Fine absorption section bottom and CO 2 Methanol at the bottom of the main absorption section, sulfur-free rich methanol and sulfur-containing rich methanol.
The medium-pressure stripping gas/sulfur-free methanol-rich heat exchanger is used for preventing medium-pressure stripping gas with too low temperature from entering a medium-pressure stripping gas expander, the temperature of the expanded gas is reduced too much, and if the temperature is too low, CO contained in the gas is reduced too much 2 Can be separated out as solid because the cold energy in the medium-pressure desorption gas needs to be recovered by utilizing the sulfur-free rich methanol, and the material flow temperature at the inlet of the expansion machine is increased.
The medium-pressure desorption gas expander is characterized in that medium-pressure desorption gas passes through the expander, the gas expands in the expander by utilizing the pressure energy of the gas to do work outwards, the process is close to an isentropic process, the temperature of outlet gas is greatly reduced due to the consumption of the internal energy of the gas, cold energy is obtained, the cold energy supplemented to a system by an ice machine can be saved, the energy consumption of the ice machine is saved, and the expander drives a generator driven by the expander to generate electricity through a shaft to obtain electric energy.
The new poor methanol cooler changes the type form of a shell-and-tube heat exchanger adopted by the original poor methanol cooler into a wound tube heat exchanger, and desorbs partial CO compared with the original device 2 The amount of low pressure rich methanol is reduced and the cooling capacity is also reduced, in order to cool the lean methanol to a sufficiently low temperature, part of the CO is desorbed 2 The low pressure methanol rich stream of (2) is passed with the expanded stripping gas through two tube bundles of a fresh methanol lean cooler to cool the lean methanol to-50.6 c.
The methanol heat exchanger II and the methanol heat exchanger III have the functions of exchanging heat between high-sulfur rich methanol at minus 45.1 ℃ sent from the rich methanol pump III and poor methanol cooled to 40 ℃ by water and cooling the poor methanol to minus 40 ℃.
The circulating methanol cooler is a wound tube type heat exchanger because methanol absorbs CO 2 Heat is released, causing the temperature of the methanol solution to rise, and the rising temperature of the methanol causes the methanol to react with CO 2 So that the absorption capacity per unit volume of methanol is made as small as possible in order to secure the absorption effectCan absorb more CO 2 The absorption is cooled by methanol, and the cold source is CO desorption 2 While the cooled methanol-rich.
The methanol heat exchanger I is a wound tube type heat exchanger, and a small amount of H is inevitably generated in the process of absorbing acid gas components by methanol 2 、CO、CH 4 The components are also dissolved in methanol in order to recover H dissolved in methanol 2 、CO、CH 4 Equal components, requiring preferential letting H 2 、CO、CH 4 Isocompositional desorption with a major portion of CO2 and H 2 S and the like are still dissolved in the methanol, so that the temperature of the rich methanol needs to be reduced continuously to ensure that the decompressed methanol can react with CO 2 And H 2 S still has enough solubility, and the cold energy source also uses the desorption CO 2 While the cooled methanol-rich.
Circulating gas flash drum I&II, dissolving part of H in the methanol-rich solution in a flash tank 2 、CO、CH 4 Gas component, and a little CO 2 、H 2 And S is desorbed and flashed from the methanol-rich liquid because the pressure of the methanol-rich liquid is reduced, and the flashed vapor enters a circulating gas compressor and is cooled by a water cooler of the circulating gas compressor to be merged with the raw material gas.
The methanol quencher utilizes liquid ammonia as a cold energy source, and the liquid ammonia is provided by an ice maker.
Most of the regenerated poor methanol and the supplemented methanol enter the poor methanol collecting tank together, the poor methanol in the poor methanol collecting tank flows into a poor methanol pump, the poor methanol is pressurized to absorption pressure, is cooled by circulating water in a poor liquid water cooler, then is sent to a methanol heat exchanger II and a methanol heat exchanger III to be continuously cooled by rich methanol, and finally enters a new poor methanol cooler to be continuously cooled to a temperature enough to absorb acid gas.
This example also provides an improved low temperature methanol CO wash 2 The desorption and desorption gas utilization process comprises the following steps:
5.6MPaG from the upstream unit, 40 ℃ and a total gas content of 174777Nm 3 Feed gas 1/h, recycle gas 2 (5.62MPaG, 40 ℃,6381Nm 3 H) are combined and sprayed170kg/h of lean methanol 3 enters the shell side of the raw material gas cooler, the lean methanol is sprayed to prevent water in the raw material gas from freezing due to temperature reduction, and the raw material gas is purified by gas 4 and converged to be rich in CO in the shell side of the raw material gas cooler 2 Low pressure CO-rich expansion gas 2 Cooling desorption gas 60 to-16.8 deg.C, feeding the raw material gas into raw material gas/water separation tank, separating raw material gas from methanol water solution, wherein the raw material gas (5.59 MPaG, -16.8 deg.C, 178976Nm 3 H) entering the bottom of the acid gas methanol absorption tower, cooling to minus 50.6 ℃ poor methanol 18 (6.5 MPaG, -50.6 ℃,223905 kg/h) entering the top of the acid gas methanol absorption tower, in the acid gas methanol absorption tower, the raw material gas is washed by the poor methanol from the top of the tower in sections, and the raw material gas is divided into CO from top to bottom 2 The fine absorption section, the main absorption section, the coarse absorption section and the desulfurization section, all acid gases in the raw material gas are removed when the raw material gas reaches the tower top, and purified gas with qualified acid gas content 4 (5.55 MPaG, 50.2 ℃,111450Nm 3 /h，CO 2 <1ppm，H 2 S+COS<0.1 ppm) out of the top of the acid gas methanol absorption tower. Due to the absorption of CO 2 Heating methanol, and absorbing CO 2 The semi-rich methanol 22 (5.56 MPaG, -25.8 ℃ C., 245826 kg/h) at the bottom of the fine absorption section and the semi-rich methanol 23 (5.57 MPaG, -16.5 ℃ C., 288883 kg/h) at the bottom of the main absorption section are sent to the circulating methanol cooler tube bundle 1&2 cooling, wherein semi-rich methanol 23 is first cooled in a methanol chiller to-25 ℃ by-40 ℃ liquid ammonia, and both semi-rich methanol streams are cooled to-35 ℃ in a recycle methanol chiller by a portion of methanol-rich 52 (0.9 MPaG, -51.4 ℃,170128 kg/h) from the bottom of the methanol-rich flash tank, and then returned separately to the CO quench 2 Top of main absorption section (37 th tray) and CO 2 The top of the coarse absorption stage (tray 67) continues to absorb CO 2 . While lean methanol absorbs CO 2 Until saturated, absorbing CO from acid gas methanol absorption tower 2 The liquid phase outlet at the bottom of the crude absorption section is discharged, 49.99 percent of sulfur-free rich methanol 8 (5.58 MPaG, -12.7 ℃,171141 kg/h) is sent to a medium-pressure desorption gas/sulfur-free rich methanol heat exchanger, 50.01 percent of sulfur-free rich methanol 7 (5.58 MPaG, -12.7 ℃,171210 kg/h) is returned to the top of the desulfurization section of the acid gas methanol absorption tower (97 th tray), the sulfur in the raw material gas is continuously absorbed, and finally, the sulfur-containing rich methanol 8 is returned to the top of the desulfurization section of the acid gas methanol absorption towerMethanol-rich 9 (5.59 MPaG, -9.3 ℃,182405 kg/h) leaves the bottom of the acid gas methanol absorber to the clean gas/methanol heat exchanger I tube side.
Sulfur-free methanol-rich 8 is desorbed by medium-pressure 45 (0.55 MPaG, -41.0 deg.C, 33264Nm in a medium-pressure desorption/sulfur-free methanol-rich heat exchanger 3 H) cooling to 18 ℃ below zero, cooling sulfur-containing rich methanol 9 to 19.4 ℃ below zero by purified gas 4 in a purified gas/methanol heat exchanger I, enabling two strands of rich methanol 8 and 9 to enter two tube bundles of a wound tube type heat exchanger methanol heat exchanger I, enabling two strands of high-pressure rich methanol to be cooled to 30 ℃ below zero by rich methanol from a methanol-rich flash tank in the methanol heat exchanger I, then enabling sulfur-free rich methanol to continuously enter a tube pass of a sulfur-free methanol/rich methanol heat exchanger, further cooling to 36 ℃ below zero, absorbing acid gas after cooling to saturated sulfur-free rich methanol and saturated sulfur-containing rich methanol, respectively reducing the pressure and throttling to 0.86MPaG by a pressure reducing valve, and enabling the cooled absorbed acid gas to enter a circulating gas flash tank I&II。
Throttling and decompressing sulfur-free rich methanol and sulfur-containing rich methanol, respectively in a circulating gas flash drum I&Flash evaporation occurs in II due to H 2 、CO、CH 4 The effective gas components have low solubility in methanol, so that the effective gas components are preferentially desorbed from the methanol-rich gas, and most of CO is generated because the methanol-rich gas is cooled to-30 ℃ and-36 DEG C 2 And H 2 S, etc. continue to dissolve in the low-temperature rich methanol, mainly H 2 、CO、CH 4 Sending the flash vapor with equal components to the inlet of a recycle gas compressor, increasing the pressure to 5.65MPaG by the recycle gas compressor, cooling to 40 ℃ by a water cooler of the recycle gas compressor, and cooling the recycle gas to 2 (5.62MPaG, 40 ℃,6381Nm 3 H) is combined with the inlet feed gas 1.
Sulfur-free methanol-rich, preferably 45% sulfur-free methanol-rich 41 (0.86 MPaG, -35.2 ℃,76262 kg/H) at the bottom of the recycle gas flash drum I is passed to the medium pressure H under the control of the flow regulating valve 34 2 The liquid inlet at the top of the S concentration column and preferably 55% sulfur-free rich methanol 42 (0.86 MPaG, -35.2 ℃,93209 kg/H) are directed to the low pressure H via the control of control valve 26 2 S concentration tower top liquid inlet, using sulfur-free rich methanol as medium-pressure and low-pressure H 2 S concentration tower top reflux liquid due to methanol to H 2 S, COS dissolution of sulfidesResolution ratio CO 2 Much larger, therefore, sulfur-free methanol-rich as overhead reflux can ensure H from medium and low pressure 2 CO-rich gas from the top of S concentration tower 2 The desorption gas hardly contains sulfur components; while the sulfur-containing rich methanol at the bottom of the recycle gas flash drum II, preferably also 45% sulfur-containing rich methanol 43 (0.86 MPaG, -32.0 ℃,79962 kg/H) is passed to the medium pressure H under the control of the flow control valve 35 2 The liquid inlet of the liquid on tray 15 of the S concentration column and preferably 55% of sulfur-containing rich methanol 44 (0.86 MPaG, -32.0 ℃,97731 kg/H) are directed to low pressure H under the control of control valve 27 2 The 23 rd tray inlet of the S concentration tower is used as medium-pressure and low-pressure H 2 S the second reflux of the concentration tower. Preferably medium pressure H 2 The S concentration tower is arranged as follows: medium pressure H 2 S concentration tower top operating pressure is set to 0.55MPaG, medium pressure H 2 The S concentration tower is provided with 106 trays and divided into two sections, wherein the upper section is provided with 70 trays, the lower section is provided with 36 trays, the two sections are communicated by a riser, and the riser of the lower section can enter the bottom of the upper section through the riser. And a low pressure H 2 The operating pressure at the top of the S concentration column was still conventionally set at 0.085MPaG. At medium pressure H 2 S concentration tower kettle and low pressure H 2 The bottom of the S concentration column was purged with medium-pressure nitrogen 36 (0.6 MPaG,35 ℃,6724 Nm) from an air separation unit 3 H) and low-pressure nitrogen 28 (0.3 MPaG,10 ℃,6000Nm 3 H) dissolving CO in methanol-rich solution by nitrogen 2 Stripping, countercurrent contact of desorbed gas and rich methanol, and destruction of CO by nitrogen 2 Gas-liquid equilibrium with methanol is realized, so that CO 2 Continuously desorb from rich methanol due to CO 2 Desorption will absorb heat, so CO 2 Stripping gas and stripping CO 2 The temperature of methanol (b) is decreased. Sulfur-free rich CO 2 Desorption gas 45 (0.55 MPaG, -41.0 ℃,33264Nm 3 H) from medium pressure H 2 The gas phase at the top of the S concentration tower is discharged from a gas phase outlet of the S concentration tower, enters a medium-pressure desorption gas/sulfur-free methanol-rich heat exchanger shell pass, is heated to-21.5 ℃, enters a medium-pressure desorption gas expander 57, is subjected to adiabatic expansion by medium-pressure desorption gas in the expander, pushes the expander to do work outwards, the shaft power output by the expander is 585kw, and the expander drives a matched generator 63 can output 556kw of electric energy and is rich in CO from the medium-pressure desorption gas expander 2 The pressure of the gas 58 is reduced to 0.13MPaG, the temperature is also reduced to-65.5 ℃, and the expanded CO is rich in CO 2 The gas goes to the lean methanol cooler tube bundle 2.
Sulfur-free rich CO 2 Desorption gas 5 (0.085 MPaG, -59.9 ℃,42942Nm 3 H) from low pressure H 2 And a gas phase outlet at the top of the S concentration tower goes to the feed gas cooler. Preferably, from medium pressure H 2 Desorbed part of CO on 70 th tray of S concentration tower 2 Unsaturated medium-pressure sulfur-containing methanol 46 (0.57 MPaG, 40.8 ℃ below zero, 145566 kg/H) flows out of the tower, is decompressed by a liquid level regulating valve 47 and enters a liquid phase inlet 1 of a methanol-rich flash tank, and the low pressure H is 2 The 106 th tray of the S-concentrator desorbs part of the CO 2 The unsaturated low pressure sulfur-containing rich methanol 12 (0.11 MPaG, -59.7 ℃,154237 kg/h) is pressurized by a rich methanol pump II, passed through a lean methanol cooler tube bundle 1, and combined with a medium pressure stripping expansion gas 58 (0.13 MPaG, -65.5 ℃,33264Nm 3 H) cooling the lean methanol 18 to-50.6 ℃ together, and then feeding the sulfur-containing rich methanol 12 into a liquid phase inlet 2 of a methanol-rich flash tank after passing through a throttle valve.
In the methanol-rich flash tank, two sulfur-containing methanol-rich streams are flashed, preferably at an operating pressure of 0.14MPaG, slightly above the low pressure H 2 S concentration tower operating pressure so that flash gas flashed from the methanol-rich flash tank can enter low pressure H 2 The gas phase inlet at the top of the lower section of the S concentration tower reduces the temperature of the rich methanol and the flash steam after flash evaporation to-55.6 ℃ and the flash steam 49 (0.14 MPaG, -55.6 ℃ and 4003 Nm) 3 H) to a low pressure H 2 S concentration tower lower section top (107 th tray) gas phase entrance, and rich methanol 50 (0.14 MPaG, -55.6 ℃,292351 kg/h) enters rich methanol pump I, after the rich methanol pump I boosts the pressure, rich methanol 50 firstly goes to sulfur-free rich methanol/rich methanol heat exchanger shell pass, the sulfur-free rich methanol 8 is further cooled to-36 ℃, then due to the heat-exchanged rich methanol 51 (0.8 MPaG, -51.4 ℃,292351 kg/h) under the regulation of rich methanol flow regulating valve 39 of methanol heat exchanger I and rich methanol flow regulating valve 40 of circulating methanol cooler, preferably according to the proportion of 41%/59%, rich methanol 53, 52 respectively goes to methanol heat exchanger I and circulating methanol cooling valve 40Cooling because of absorbing CO 2 And the warmed semi-rich methanol 22, 23, sulfur-free methanol 8 and sulfur-containing methanol 9, wherein both semi-rich methanol streams are cooled to-35 deg.C, sulfur-free methanol and sulfur-containing methanol are cooled to-30 deg.C, methanol 55 and 54 are warmed to-22.7 deg.C and-30.4 deg.C, and methanol 55 and 54 are combined and returned to medium pressure H 2 The liquid phase inlet at the top of the lower section of the S-concentrator (tray 71).
Back to medium pressure H 2 The rich methanol at the top of the lower section of the S concentration tower is continuously stripped by the medium-pressure nitrogen from the tower kettle, and the desorbed CO 2 And the stripping nitrogen enters the medium pressure H through the ascending pipe 2 Continuously countercurrent contacting with methanol-rich flowing from top to bottom at the bottom of the upper section of the S concentration tower, and continuously stripping CO dissolved in methanol at the upper section 2 At the end, from medium pressure H 2 Sulfur-containing methanol-rich 61 (0.58 MPaG, -37.3 ℃,246795 kg/H) from the bottom of S concentration column is passed through medium pressure H 2 A liquid level regulating valve 62 of the tower bottom of the S concentration tower and sending the liquid to low pressure H 2 The liquid phase inlet at the top of the lower section of the S-concentration tower (107 th tray) is used as low pressure H 2 S the reflux liquid at the lower section of the concentration tower is continuously from the low pressure H 2 Low pressure nitrogen stripping of the S concentration tower bottom due to CO in rich methanol 2 The partial stripping is carried out in a medium-pressure environment, since the higher the pressure during desorption, the higher the desorbed CO 2 The greater the heat absorption of (A), the medium pressure CO 2 More heat is absorbed during desorption and returns to low pressure H 2 The temperature of the methanol-rich at the top of the lower section of the S concentration tower (107 th tray) is lower than that of the classical Linde process, and the temperature of the methanol-rich in the improved process is as low as-37.3 ℃, and the methanol-rich can be carried out at low pressure H 2 And (4) obtaining high-sulfur methanol rich at the temperature of-45.1 ℃ at the bottom of the S concentration tower. While in the classical linde process, a low pressure H is returned 2 The methanol-rich temperature of the top of the lower section of the S concentration tower as reflux liquid is-28.1 ℃, and the low pressure H is 2 The temperature of the high-sulfur methanol-rich liquid flowing out of the bottom of the S concentration tower is-35.2 ℃, so that the improved low-temperature methanol washing CO is realized 2 Compared with the classical Linde process, the improved process increases new cold energy to be utilized in the system, and reduces the cold energy required to be provided by the ice machine.
High sulfur methanol-rich 13 (0.125 MPaG, -45.1 deg.C, 231568 kg/H) from low pressure H 2 After the liquid phase flows out from the bottom liquid phase outlet of the S concentration tower, the liquid phase is pressurized by a methanol-rich pump III, and then is subjected to heat exchange with the poor methanol 18 which is circulated back by a methanol-rich filter, a methanol heat exchanger II shell pass and a methanol heat exchanger II shell pass, preferably, the circulating poor methanol is directly cooled to-40 ℃ by high-sulfur rich methanol 13 with the temperature as low as-45.1 ℃, and the high-sulfur rich methanol 13 is heated to 22 ℃ and then enters CO 2 The liquid phase inlet at the top of the desorption tower is used as CO 2 Reflux liquid at the top of the desorber, preferably in CO 2 A stream of low-pressure nitrogen 29 (0.3 MPaG,10 ℃,1200 Nm) is introduced into the tower bottom of the desorption tower 3 /h)，CO 2 The operating pressure of the top of the desorption tower is set to be 0.16MPaG, and the high-sulfur semi-rich methanol flowing from top to bottom continuously contacts with the rising stripping nitrogen in a countercurrent way to allow CO to be separated 2 Desorbed from methanol in CO 2 The sulfur-containing CO is obtained at the top of the desorption tower 2 Stripping gas 14 in CO 2 The high-sulfur methanol-rich 15 is obtained at the bottom of the desorption tower. Sulfur-containing CO 2 Desorption gas 14 (0.16MPaG, 30.5 ℃,4578Nm 3 H) to a low pressure H 2 The gas phase inlet of the 125 th tray of the S concentration tower, high-sulfur rich methanol 15 (0.161MPaG, 28.1 ℃,226193 kg/h) is pressurized by a methanol-rich pump IV, and then is subjected to heat exchange with regenerated lean methanol by a methanol heat exchanger IV tube pass to heat up to 85 ℃, and then enters the liquid phase inlet of the 8 th tray of the thermal regeneration tower.
Preferably, the operation pressure of the top of the thermal regeneration tower is set to be 0.23MPaG, low-pressure steam is introduced into the shell side of a reboiler at the bottom of the thermal regeneration tower, the consumption of the low-pressure steam is 10.96t/H (0.45 MPaG, saturation), high-sulfur methanol is heated by the steam in the tube side of the reboiler at the bottom of the tower, and all H in the methanol is heated by the steam at the moment 2 S，CO 2 The components are completely desorbed from the methanol, the regeneration of poor methanol is completely finished at the bottom of the thermal regeneration tower, and H 2 S，CO 2 When the acid gas component continuously rises, and the H dissolved in the methanol is gradually dissolved in the rising process 2 S，CO 2 The methanol vapor is collected in the ascending gas, and is added into a gas phase inlet of a 25 th tray of the thermal regeneration tower to assist the gas stripping by a stream of methanol vapor from the top of the methanol/water separation tower. Finally acid gas component and component AAlcohol vapour composition gas 16 (0.23MPaG, 10 ℃,10870Nm 3 H) out of the overhead gas phase outlet of the thermal regeneration column to H 2 Cooling the tube pass of the S fraction heat exchanger to 40 ℃ by circulating cooling water of the shell pass, condensing most of methanol steam into condensate at the moment, and feeding the condensate and uncondensed acid gas into H 2 And in the S fraction separator I, the methanol condensate enters a reflux pump of the thermal regeneration tower, is pressurized by the reflux pump and then returns to a liquid phase inlet at the top of the thermal regeneration tower to be used as reflux liquid at the top of the thermal regeneration tower. Uncondensed acid gases continue on to H 2 Tube pass of S fraction heat exchanger and H 2 S fraction quencher, H bounded by zone 2 Cooling S fraction and liquid ammonia to-35 deg.C, and passing through H 2 S fraction separator II separates condensed H 2 After S fraction condensate, high concentration H not condensed 2 S gas 17 (0.165 MPaG, -35 ℃,1294Nm 3 H) through H 2 S fraction heat exchanger shell pass and H 2 After the cold energy is recovered by the heat exchange of the S fraction, the S fraction goes to a sulfur recovery unit, and H 2 The S fraction condensate 25 (0.165 MPaG, 36 ℃ C., 349 kg/H) is passed to a low pressure H 2 S-concentrator 132 tray liquid phase inlet.
The regenerated lean methanol is completed from the bottom of the thermal regeneration tower, wherein 98.7% of the lean methanol enters a lean methanol collecting tank after being subjected to heat recovery through a methanol heat exchanger IV shell pass, 80.1kg/h of methanol is supplemented, the reason for supplementing the methanol is that a small amount of methanol steam enters purified gas and a small amount of methanol is dissolved in outside blow-down water to cause methanol loss, most of the regenerated methanol and the supplemented methanol become lean methanol for circulation 18 (0.MP0aG, 45 ℃,223905 kg/h), the lean methanol for circulation is boosted through the lean methanol, is gradually cooled to minus 40 ℃ through a lean liquid water cooler tube pass, a methanol heat exchanger III tube pass and a methanol heat exchanger II tube pass by circulating cooling water and high-sulfur semi-rich methanol, is further cooled to minus 50.6 ℃ by sulfur-containing semi-rich methanol and expansion desorption gas in a new lean methanol cooler shell pass, and is recirculated to enter a liquid phase inlet at the top of an acid gas methanol absorption tower, and absorption of crude acid gas is restarted.
From the bottom of the thermal regeneration column, another 1.3% of the methanol-depleted fraction 19 (0.277MPaG, 101.6 ℃,2911 kg/h) which had been subjected to regeneration was passed to a methanol/water separation columnAfter being pressurized by a reflux pump, the reflux liquid is used as reflux liquid of the methanol/water separation tower after being subjected to heat exchange with a methanol water solution 24 through a reflux cooler I tube side and enters a liquid phase inlet at the top of the methanol/water separation tower. The methanol/water separation tower has the functions of recovering methanol in the methanol water solution and tail gas washing water, reducing the content of methanol in the externally discharged sewage as much as possible and preventing environmental pollution. The methanol aqueous solution 24 (5.6 MPaG, 16.8 ℃ below zero, 206 kg/h) and the tail gas washing water 32 (0.01MPaG, 14.0 ℃ below zero, 5457 kg/h) respectively flow back to the shell side of the cooler I and the tube side of the water heat exchanger, and enter the liquid phase inlet 1 of the 10 th tray of the methanol/water separation tower after exchanging heat with the reflux liquid 19 and the discharged wastewater 21&Introducing low-pressure steam into the reboiler shell side at the bottom of the methanol/water separation tower, wherein the consumption of the low-pressure steam is 1.82t/h (0.45 MPaG, saturated), separating most of methanol dissolved in water from water in the reboiler shell side at the bottom of the methanol/water separation tower, continuously increasing the methanol steam to ensure that the methanol dissolved in water is continuously enriched into the rising steam, and finally, introducing high-purity methanol steam 20 (0.26MPaG, 100.8 ℃,1995Nm & lt/EN & gt) 3 H) out of the top gas phase outlet of the methanol/water separation tower and to the gas phase inlet of the 25 th tray of the thermal regeneration tower. At the bottom of the methanol/water separation column, the discharged wastewater 21 (0.29MPaG, 141.3 ℃,5731 kg/h) still containing a small amount of methanol is discharged to a wastewater treatment unit for treatment after the heat in the wastewater is recovered.
TABLE 1 comparison of Power consumption and utilities for the inventive Process and the classical Linde Low temperature methanol washing Process
For an air separation system that provides both oxygen and nitrogen, since nitrogen is a byproduct of oxygen production, producing a certain amount of nitrogen we can consider not calculating energy consumption separately, and increasing a portion of the low pressure nitrogen while maintaining oxygen production may not require increasing energy consumption or may only require increasing energy consumptionLittle energy consumption is added, and in addition, little energy consumption is consumed to compress the low-pressure nitrogen to the medium-pressure nitrogen. Improved low temperature methanol scrubbing of CO 2 Increased 6724Nm required for desorption and desorption gas-utilizing processes 3 Medium pressure nitrogen,/h and 1120Nm 3 The required additional energy consumption for the air separation system is only 220kw per hour of low-pressure nitrogen. Ammonia-ice machines using electric drive, then improved low temperature methanol scrubbing of CO 2 The power consumption required by the desorption and desorption gas utilization process and the classical Linde low-temperature methanol washing process is as follows:
table 2 electricity consumption required for the process of the invention and the classical linde low temperature methanol wash process
As can be seen from the comparison of the data in the table, when the same specification of raw material gas needs to be processed, compared with the classical Linde low-temperature methanol washing process, the improved low-temperature methanol washing CO is adopted 2 Desorption and process utilization of desorption gas 2 The system comprises an S concentration tower, a medium-pressure desorption gas expander, a generator matched with the expander, a medium-pressure desorption gas/sulfur-free methanol-rich heat exchanger, a sulfur-free methanol-rich heat exchanger instead of an original methanol-rich quencher, and a winding pipe type heat exchanger instead of an original methanol-poor cooler, so that the load of an ice machine is reduced by about 33%, the power consumption and the circulating water consumption of the system are reduced, and the methanol-poor quencher in the original Linde flow is reduced. Although an intermediate pressure H is added as a whole 2 Investment of the S concentration tower (the investment of small and medium-sized equipment such as an increased medium-pressure desorption gas expander and the like is basically equivalent to the investment of a reduced ice maker and the like), but because the system energy consumption is greatly reduced, the improved low-temperature methanol is used for washing CO according to the price that the current industrial average electricity price is 0.55 yuan/kwh and the annual running time of the device is 8000 hours 2 Desorption and use of desorbed gasThe above-mentioned equipment of the process can reduce 569.8 ten thousand yuan of operation cost every year, and the equipment investment increased due to improvement can be expected to be recovered in about 2 years.
Table 3 energy consumption conversion factor of general rule of comprehensive energy consumption calculation according to national standard GBT2589-2020
| Normalized coal coefficient (equivalent) kgce | |
| Electric kwh | 0.3017 |
| Low pressure steam kg | 0.1286 |
| Circulating cooling water t | 0.143 |
TABLE 4 conversion of the consumption of the process of the present invention and the classical Linde low temperature methanol wash process to standard coal consumption
Therefore, it can be seen from the calculation results that the improved low temperature methanol scrubbing CO of the present invention 2 The desorption and desorption gas utilization process has obvious advantages in energy consumption, compared with the classical Linde low-temperature methanol washing process, the total energy consumption of the system is reduced by about 13 percent, and the purposes of energy conservation and consumption reduction are achieved.
Claims (4)
1. Improved low-temperature methanol-washing CO 2 The device for desorbing and utilizing the desorbed gas is characterized by comprising an acid gas methanol absorption tower, a circulating methanol cooler, a methanol heat exchanger I, a circulating gas flash tank II and medium pressure H 2 S concentration column, low pressure H 2 The system comprises an S concentration tower, a methanol-rich flash tank, a methanol-rich pump I, a methanol-rich pump II, a medium-pressure desorption gas/sulfur-free methanol-rich heat exchanger, a sulfur-free methanol-rich/methanol-rich heat exchanger, a medium-pressure desorption gas expander, a generator driven by the expander, a new methanol-poor cooler, a methanol-rich pump III, a methanol heat exchanger II, a methanol heat exchanger III, CO 2 Desorption column, H 2 The system comprises an S fraction separator II, a poor methanol collecting tank, a poor methanol pump, a poor liquid water cooler, a purified gas/methanol heat exchanger I, a circulating gas compressor, a methanol quencher and a methanol-rich filter;
CO of the acid gas methanol absorption tower 2 The liquid phase outlet of the 36 th tray at the bottom of the fine absorption section passes through the tube bundle of the circulating methanol cooler and the CO of the acid gas methanol absorption tower 2 The 37 th tray liquid phase inlet at the top of the main absorption section is connected; CO of acid gas methanol absorption tower 2 The liquid phase outlet of the 66 th tower tray at the bottom of the main absorption section passes through the tube bundle of the circulating methanol cooler and the CO of the acid gas methanol absorption tower 2 The 67 th tower tray liquid phase inlet at the top of the coarse absorption section is connected; CO of acid gas methanol absorption tower 2 A part of sulfur-free methanol-rich outlet of a 96 th tray at the bottom of the coarse absorption section is connected with a liquid phase inlet of a circulating gas flash tank I through a tube pass of a medium-pressure desorption gas/sulfur-free methanol-rich heat exchanger, a tube bundle of a methanol heat exchanger I and a tube pass of the sulfur-free methanol-rich/methanol-rich heat exchanger; CO of acid gas methanol absorption tower 2 The other part of the sulfur-free methanol-rich outlet at the bottom of the coarse absorption section is connected with the liquid phase inlet of the 97 th tower tray at the top of the lower section of the acid gas methanol absorption tower; a liquid phase outlet at the bottom of the acid gas methanol absorption tower is connected with a liquid phase inlet of a circulating gas flash tank II through a purified gas/methanol heat exchanger I tube pass and a methanol heat exchanger I tube bundle;
said medium pressure H 2 The gas phase outlet at the top of the S concentration tower is connected with the shell pass inlet of the medium-pressure desorption gas/sulfur-free methanol-rich heat exchanger; liquid phase outlet pipeline branch at bottom of I tank of circulating gas flash tank and medium pressure H 2 S concentration towerThe top liquid phase inlet is connected; liquid phase outlet at bottom of tank I of circulating gas flash tank and low pressure H 2 The liquid phase inlet at the top of the S concentration tower is connected; liquid phase outlet pipeline branch at bottom of circulating gas flash tank II and medium pressure H 2 The liquid phase inlet of the 15 th tray of the S concentration tower is connected; the liquid phase outlet pipeline at the bottom of the circulating gas flash tank II is communicated with the low pressure H 2 The liquid phase inlet of the 23 th tray of the S concentration tower is connected; medium pressure H 2 The liquid phase outlet of the 70 th tray at the bottom of the upper section of the S concentration tower is connected with the liquid phase inlet of the methanol-rich flash tank; low pressure H 2 A liquid phase outlet of the 106 th tray at the bottom of the upper section of the S concentration tower is connected with a liquid phase inlet of the methanol-rich flash tank through a methanol-rich pump II and a new methanol-poor cooler tube bundle; gas phase outlet at top of methanol-rich flash tank and low pressure H 2 The gas phase inlet of the 107 th tray at the top of the lower section of the S concentration tower is connected; the liquid phase outlet at the bottom of the methanol-rich flash tank passes through a methanol-rich pump I, a sulfur-free methanol-rich/methanol-rich heat exchanger shell pass, a methanol heat exchanger I shell pass, a circulating methanol heat exchanger I shell pass and medium pressure H 2 The 71 th tower tray liquid phase inlet at the top of the lower section of the S concentration tower is connected; medium pressure nitrogen from air separation and medium pressure H 2 S, connecting a gas phase inlet under the bottommost tray of the tower kettle of the concentration tower; medium pressure H 2 The liquid phase outlet at the bottom of the S concentration tower passes through a medium pressure H 2 S concentration tower bottom liquid level regulating valve and low pressure H 2 The 107 th tray liquid phase inlet at the top of the lower section of the S concentration tower is connected; the shell side outlet of the medium-pressure desorption gas/sulfur-free methanol-rich heat exchanger is connected with the inlet of a medium-pressure desorption gas expander; the outlet of the medium-pressure desorption gas expander passes through the tube bundle of the new lean methanol cooler and the low pressure H 2 S concentration tower top rich in CO 2 Connecting desorption gas pipelines; an output shaft of the medium-pressure desorption gas expander is connected with a generator shaft; the gas phase outlets at the tops of the circulating gas flash tank I and the circulating gas flash tank II are both connected with the inlet of a circulating gas compressor; low pressure H 2 The liquid phase outlet at the bottom of the S concentration tower passes through a rich methanol pump III, a methanol heat exchanger II, a methanol heat exchanger III and CO 2 The tower top liquid phase inlet of the desorption tower is connected; h 2 Liquid phase outlet at bottom of S fraction separator II tank and low pressure H 2 The 132 th tray liquid phase inlet of the S concentration tower is connected; CO2 2 Gas phase outlet at the top of the desorption tower and low pressure H 2 Gas phase on 125 th tray of S concentration towerA port connection; and a liquid phase outlet at the bottom of the poor methanol collecting tank is connected with a liquid phase inlet at the top of the acid gas methanol absorption tower through a poor methanol pump, a poor liquid water cooler tube pass, a methanol heat exchanger III tube pass, a methanol heat exchanger II tube pass and a new poor methanol cooler shell pass.
2. The improved low temperature methanol CO wash of claim 1 2 The device for desorbing and utilizing the desorbed gas is characterized in that the acid gas methanol absorption tower can utilize different solubility of different gas components in low-temperature methanol to sectionally react with CO 2 And selectively absorbing the sulfide acid gas component;
the acid gas methanol absorption tower can be divided into 4 sections from top to bottom, wherein the sections are respectively CO 2 Fine absorption section, CO 2 Main absorption section, CO 2 A coarse absorption section and a sulfide absorption section.
3. The improved low temperature methanol CO wash of claim 1 2 Device for desorbing and using a desorption gas, characterized in that the medium pressure H is 2 The S concentration tower can be divided into two sections from top to bottom, and the middle pressure H 2 Upper section of S concentration column, and medium pressure H 2 S is condensed the lower section of the tower, this tower recommends to use the tray as the column internals, can also use regular packing or random packing as the column internals;
the low pressure H 2 The S concentration tower can be divided into two sections from top to bottom, and the low pressure H is 2 Upper section of S concentration column, and low pressure H 2 S, the lower section of a concentration tower;
medium pressure H 2 S concentration column and low pressure H 2 The S concentration tower is used for leading CO dissolved in low-temperature methanol to be stripped through nitrogen 2 Desorbed and washed by sulfur-free rich methanol at the tower top simultaneously to ensure that H 2 S is gradually concentrated in methanol flowing downwards to obtain concentrated H at the bottom of the tower 2 S-rich methanol; due to CO 2 The desorption from the methanol absorbs heat, and the temperature of the methanol-rich solution and the desorbed gas discharged from the tower is reduced.
4. Improved low-temperature methanol-washing CO 2 By desorption and use of desorbed gasesProcess characterized in that it is CO-scrubbed by means of the improved low-temperature methanol of claim 1 2 The device for desorbing and utilizing the desorbed gas comprises the following steps:
the raw material gas enters an acid gas methanol absorption tower to remove all acid gas, and lean methanol absorbs CO in sections 2 After the sulfide acid gas component is saturated, the sulfide acid gas component respectively leaves an acid gas methanol absorption tower in a sulfur-free methanol-rich and sulfur-containing methanol-rich material flow mode, two strands of methanol-rich enter a methanol heat exchanger I, wherein the sulfur-containing methanol-rich is firstly precooled to-19.4 ℃ by purified gas which is discharged from the top of the acid gas methanol absorption tower, in the methanol heat exchanger I, two strands of high-pressure methanol-rich are both cooled to-30 ℃ by the methanol-rich from a methanol-rich flash tank, then the sulfur-free methanol-rich continuously enters a tube pass of a sulfur-free methanol/methanol-rich heat exchanger, is further cooled to-36 ℃, the cooled absorbed acid gas to saturated sulfur-free methanol-rich and the saturated sulfur-containing methanol-rich enter a circulating gas flash tank I and a circulating gas flash tank II after being respectively decompressed and throttled by a regulating valve;
the throttled and decompressed sulfur-free rich methanol and sulfur-containing rich methanol are respectively subjected to flash evaporation in a circulating gas flash evaporation tank I and a circulating gas flash evaporation tank II, and H 2 、CO、CH 4 The flash evaporation gas of the effective gas component goes to the inlet of the recycle gas compressor, is subjected to pressure boosting by the recycle gas compressor and is cooled by a water cooler of the recycle gas compressor and then is converged with the feed gas at the inlet;
the sulfur-free methanol rich at the bottom of the I tank of the circulating gas flash tank is respectively sent to the medium pressure H 2 S concentration column and low pressure H 2 The liquid inlet at the top of the S concentration tower is used as medium pressure H 2 S concentration column and low pressure H 2 S, concentrating the tower top reflux liquid of the tower; the sulfur-containing rich methanol at the bottom of the circulating gas flash tank II is respectively sent to the medium pressure H 2 S concentration column and low pressure H 2 Liquid inlet of the 15 th tray of the S concentration tower as medium pressure H 2 S concentration column and low pressure H 2 S, concentrating the second reflux of the tower; at medium pressure H 2 S concentration column and low pressure H 2 The tower kettle of the S concentration tower is respectively filled with medium-pressure nitrogen and low-pressure nitrogen from an air separation unit, and CO dissolved in the rich methanol is treated by the nitrogen 2 Stripping to remove CO 2 Stripping from rich methanolTo, due to CO 2 Desorption will absorb heat, so CO 2 Stripping gas and stripping CO 2 The temperature of methanol (a) is all reduced; from medium pressure H 2 70 th tray of S concentration tower and low pressure H 2 Respectively flowing out of the 106 th tray of the S concentration tower to desorb partial CO 2 The unsaturated sulfur-containing methanol is pressurized by a methanol-rich pump II, and then cooled to minus 50.6 ℃ together with medium-pressure stripping expansion gas through a new methanol-poor cooler tube bundle, and then enters the liquid phase inlet of the methanol-rich flash tank after passing through the regulating valve;
in the methanol-rich flash tank, two sulfur-containing methanol-rich flash tanks are subjected to flash evaporation at an operating pressure slightly higher than the low pressure H 2 S concentration tower operating pressure so that flash gas flashed off can enter low pressure H 2 S gas phase inlet above 107 trays on the top of the lower section of the concentration tower, rich methanol and flash steam are cooled after flash evaporation, and the flash steam is sent to low pressure H 2 S, a gas phase inlet at the top of the lower section of the concentration tower, the rich methanol enters a rich methanol pump I, after the pressure of the rich methanol pump I is increased, the rich methanol firstly goes to a sulfur-free rich methanol/rich methanol heat exchanger, the sulfur-free rich methanol is cooled to-36 ℃, and then the rich methanol respectively goes to a methanol heat exchanger I and a circulating methanol cooler under the regulation of a rich methanol flow regulating valve of the methanol heat exchanger I and a rich methanol flow regulating valve of the circulating methanol cooler to cool the rich methanol and the rich methanol respectively because CO is absorbed 2 The two half rich methanol streams are cooled to-35 ℃, the sulfur-free rich methanol stream and the sulfur-containing rich methanol stream are cooled to-30 ℃, the sulfur-free rich methanol stream and the sulfur-containing rich methanol stream are heated to-30.5 ℃ and-19.1 ℃, and the two half rich methanol streams are returned to the medium pressure H after being merged 2 The 71 th tray liquid phase inlet at the top of the lower section of the S concentration tower is continuously stripped by medium-pressure nitrogen from the tower kettle, and desorbed CO 2 And the stripping nitrogen enters the medium pressure H through the ascending pipe 2 Continuously countercurrent contacting with methanol-rich flowing from top to bottom at the bottom of the upper section of the S concentration tower, and continuously stripping CO dissolved in methanol at the upper section 2 From medium pressure H 2 Medium pressure CO-rich from top of S concentration tower 2 Desorption gas to medium pressure desorption gasCooling the sulfur-free methanol-rich heat exchanger, feeding the cooled sulfur-free methanol-rich heat exchanger into an inlet of a medium-pressure desorption gas expander, and medium-pressure enriching CO in the expander 2 The desorbed gas expands outwards to do work, the process is close to isentropic expansion, the temperature of the expanded gas is greatly reduced, meanwhile, the expander drives the generator to generate electricity and output electric energy, and then the electricity and the low-pressure CO-rich gas flow are sent to a new lean methanol cooler from the outlet of the expander to recover cold energy and then are mixed with low-pressure CO 2 The desorbed gas goes to a raw gas cooler to further recover cold and then is sent to a tail gas washing tower; from medium pressure H 2 Sulfur-containing rich methanol from the bottom of the S concentration tower enters low pressure H after being throttled by a liquid level regulating valve 2 The liquid phase inlet of the 107 th tray at the top of the lower section of the S concentration tower is used as low pressure H 2 The reflux liquid at the lower section of the S concentration tower is continuously from low pressure H 2 Low pressure nitrogen stripping in the tower bottom of S concentration tower at low pressure H 2 S, obtaining high-sulfur methanol rich at the temperature of-45.1 ℃ at the bottom of the concentration tower;
high sulfur methanol rich from low pressure H 2 After the S concentration tower bottom comes out, the pressure is increased by a methanol-rich pump III, the poor methanol is cooled to-40 ℃ through a methanol-rich filter, a methanol heat exchanger II shell pass and a methanol heat exchanger II shell pass to exchange heat with the poor methanol which circulates back, the high-sulfur rich methanol is heated to 31 ℃, and the high-sulfur rich methanol enter CO 2 The liquid phase inlet at the top of the desorption tower is used as CO 2 Reflux liquid at the top of the desorber in CO 2 Introducing a stream of low-pressure nitrogen into the tower kettle of the desorption tower, and continuously making the high-sulfur semi-rich methanol in countercurrent contact with the stripping nitrogen to allow CO to be in countercurrent contact with the stripping nitrogen 2 Desorbed from methanol in CO 2 The sulfur-containing CO is obtained at the top of the desorption tower 2 Stripping gas in CO 2 High-sulfur methanol and sulfur-containing CO are obtained at the bottom of the desorption tower 2 Stripping gas to low pressure H 2 S concentration tower 128 tower tray gas phase entrance, and high sulfur methanol is pressurized by rich methanol pump IV, and then exchanges heat with regenerated poor methanol through methanol heat exchanger IV tube pass, enters thermal regeneration tower 8 tower tray liquid phase entrance, high sulfur methanol is heated by tower bottom reboiler in thermal regeneration tower, completes regeneration, finally most poor methanol after thermal regeneration is recovered heat through methanol heat exchanger IV shell pass, enters poor methanol collecting tank, after supplementing a small amount of lost methanol, and then is pressurized by poor methanolGradually cooling the lean solution water cooler tube pass, the methanol heat exchanger tube pass III and the methanol heat exchanger tube pass II to-40 ℃ by circulating cooling water and high-sulfur semi-rich methanol, further cooling the lean solution water cooler by sulfur-containing semi-rich methanol and expansion stripping gas to-50.6 ℃, then re-circulating the cooled lean solution water cooler tube pass into a liquid phase inlet at the top of an acid gas methanol absorption tower, and re-starting to absorb acid gas in the crude synthesis gas; a small part of regenerated poor methanol is pressurized by a reflux pump of a methanol/water separation tower, then enters a liquid phase inlet at the top of the methanol/water separation tower after cold energy of a methanol water solution is recovered by a reflux cooler I tube pass through a poor methanol filter, and is used as reflux liquid at the top of the methanol/water separation tower, the methanol water solution and tail gas washing water respectively enter the middle section of the methanol/water separation tower, low-pressure steam is introduced into a reboiler at the bottom of the methanol/water separation tower for heating, methanol is desorbed from water, pure methanol steam goes to the middle part of a thermal regeneration tower from a gas phase outlet at the top of the methanol/water separation tower, and wastewater containing a small amount of methanol goes to a wastewater treatment unit after heat energy is recovered by a reflux cooler I shell pass.
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| CN101874967A (en) * | 2009-12-18 | 2010-11-03 | 中国五环工程有限公司 | Process for removing acid gas with low-temperature methanol solution |
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| CN106520212A (en) * | 2016-11-09 | 2017-03-22 | 中石化宁波工程有限公司 | Acid gas reabsorption technology matched with coal water slurry gasification |
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| WO2010057581A1 (en) * | 2008-11-19 | 2010-05-27 | Linde Aktiengesellschaft | Method and device for washing agent regeneration in physical gas scrubbing |
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| CN204211704U (en) * | 2014-10-27 | 2015-03-18 | 上海国际化建工程咨询公司 | A kind of device of low-temperature rectisol energy-saving and production-increase |
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| CN116517654A (en) * | 2023-05-08 | 2023-08-01 | 襄阳航力机电技术发展有限公司 | Comprehensive utilization method of low-temperature methanol washing energy |
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