CN108057319B - Raw material gas recovery method and device - Google Patents
Raw material gas recovery method and device Download PDFInfo
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- CN108057319B CN108057319B CN201810024144.9A CN201810024144A CN108057319B CN 108057319 B CN108057319 B CN 108057319B CN 201810024144 A CN201810024144 A CN 201810024144A CN 108057319 B CN108057319 B CN 108057319B
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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
- 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
- B01D53/1406—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
- B01D53/18—Absorbing units; Liquid distributors therefor
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2257/00—Components to be removed
- B01D2257/50—Carbon oxides
- B01D2257/504—Carbon dioxide
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
- Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
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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]
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Abstract
The invention relates to a raw material gas recovery method and a raw material gas recovery device, and belongs to the technical field of gas separation engineering. A feed gas recovery process comprising the steps of: step one: countercurrent contact of lean solution and raw gas in an absorption module for absorbing carbon dioxide, wherein the obtained solution is rich solution containing the raw gas; step two: the rich liquid and the replacement gas are in countercurrent contact in a recovery module to replace the raw material gas; step three: the recovered raw material gas is returned to the absorption module for continuous recycling. The invention also discloses a raw material gas recovery device which comprises an absorption module and a recovery module which are connected and communicated. The invention replaces the raw material gas in the rich liquid under the high pressure condition by the replacement gas, and the recycled high pressure raw material gas can be directly returned to the raw material gas absorption and decarbonization device or enter the subsequent process treatment.
Description
Technical Field
The invention relates to a raw material gas recovery method and a raw material gas recovery device, and belongs to the technical field of gas separation engineering.
Background
In the industrial production of ammonia synthesis, methanol synthesis, oxo synthesis, hydrogen production, natural gas and the like, carbon dioxide is required to be removed from carbon dioxide-containing raw material gas under high pressure so as to meet the requirements of subsequent processes. The main beneficial component of feed gas in the ammonia synthesis and hydrogen production industries is hydrogen; the main beneficial components of feed gas in the methanol synthesis and oxo industry are hydrogen and carbon monoxide; the main beneficial component of the feed gas in the natural gas process is methane. The current industrial method for recycling the raw material gas mainly comprises the following steps: absorption-desorption decarbonization methods and pressure swing adsorption PSA decarbonization methods, wherein the absorption-desorption decarbonization methods occupy the vast majority of the market. The absorption-desorption decarbonization method can be classified into MDEA method, low temperature methanol washing method, polyethylene glycol dimethyl ether, etc. according to different absorption solvents. When the decarbonizing solution absorbs carbon dioxide in the high-pressure feed gas, a certain amount of the feed gas is dissolved in the absorbing liquid, and the feed gas in the carbon dioxide-rich absorbing liquid (hereinafter referred to as rich liquid) is generally recovered in order to reduce the feed gas loss. In the ammonia-urea synthesis industry, generally, the separated carbon dioxide is also used for urea production, and because the corrosion protection requirement of a urea device requires to inject a certain amount of oxygen into the carbon dioxide, the urea device has strict requirements on the components of raw gas in the carbon dioxide, and if the concentration of flammable and explosive components in the carbon dioxide sent to the urea device is too high, the components can explode, thereby causing production accidents.
The current method for recovering the raw gas in the rich liquid is to decompress the rich liquid to a lower pressure to flash-evaporate the raw gas such as hydrogen, carbon monoxide, methane and the like, and the flash gas rich in the raw gas is returned to a raw gas system after the pressure is increased by a compressor or is treated as a product gas with low added value after the purity of the raw gas in the flash gas is increased by Pressure Swing Adsorption (PSA), membrane separation and other methods. The recovery method needs to adopt a compressor, PSA equipment or special film equipment and the like, adopts a plurality of equipment, has complex process system, high energy consumption and high investment, and has high equipment use and maintenance cost.
For an absorption-desorption system matched with a urea device, the rich liquid needs to enter the desorption system through a pressure difference, so that the flash evaporation pressure of the rich liquid is often limited by a subsequent system, and the raw material gas dissolved in the rich liquid after flash evaporation is finally desorbed together with carbon dioxide to enter a carbon dioxide compression system. Because of the limitation of flash pressure, the content of flammable and explosive components such as hydrogen in the rich liquid after flash evaporation is not easy to control.
Disclosure of Invention
Aiming at the defects existing in the prior art, the invention provides a novel raw material gas recovery method and a novel raw material gas recovery device. The method is characterized in that the raw material gas in the rich liquid is replaced by the replacement gas under the high pressure condition, and the recovered high pressure raw material gas can be directly returned to the raw material gas absorption and decarbonization device or enter the subsequent process treatment.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
a feed gas recovery process comprising the steps of:
step one: countercurrent contact of lean solution and raw gas in an absorption module for absorbing carbon dioxide, wherein the obtained solution is rich solution containing the raw gas;
step two: the rich liquid and the replacement gas are in countercurrent contact in a recovery module to replace the raw material gas;
step three: the recovered raw material gas is returned to the absorption module for continuous recycling.
Preferably, when the raw material gas is recovered in the third step, the operating pressure of the second step is equal to or higher than the absorption pressure of the raw material gas in the first step, and the recovered raw material gas can be directly returned to the absorption module for continuous recycling.
Preferably, when the raw material gas is replaced in the second step, the operating pressure of the second step may be lower than the absorption pressure of the raw material gas in the first step, and the recovered raw material gas may be returned to the absorption die or enter other raw material gas treatment systems through the pressurizing device.
Preferably, the displacement gas is a mixed gas of one or more of helium, nitrogen and argon.
Preferably, the displacement gas is a mixed gas of carbon dioxide and one or more gases selected from helium, nitrogen and argon.
Preferably, the amount of the displacement gas is 0.1 to 1000Nm 3 /m 3 Rich liquid.
A raw material gas recovery device comprises an absorption module and a recovery module which are connected and communicated;
the upper part of the absorption module is provided with one or more lean liquid inlets, the lower part of the absorption module is provided with a raw material gas inlet, and the top end of the absorption module is also provided with a purified gas outlet;
the upper part of the recovery module is provided with a rich liquid inlet, the lower part of the recovery module is provided with a replacement gas inlet, and the recovery module is also provided with a rich liquid outlet and/or a recovery gas outlet.
Preferably, the absorption module and the recovery module are two independent mass transfer devices, and a recovery pipeline is arranged between the absorption module and the recovery module.
Preferably, the absorption module and the recovery module are integrated in the same mass transfer device, and when the operation pressure of the absorption module is the same as that of the recovery module, the absorption module and the recovery module can be integrated in the same mass transfer device, the recovery module is positioned below the absorption module, and the rich liquid enters the recovery module through the action of gravity.
Preferably, the mass transfer device is a tray column or a packed column.
The beneficial effects of the invention are as follows:
(1) According to the invention, the raw material gas is recovered by adopting the replacement gas, the operation is flexible and controllable, the operation pressure of the second step is equal to or higher than the absorption pressure of the raw material gas in the first step, the recovered raw material gas can be directly returned to the raw material gas system in the first step, gas compression equipment is not needed, the compression energy consumption of the recovered raw material gas is reduced, and the economic benefit is improved. The operating pressure of the second step is lower than the absorption pressure of the raw material gas in the first step, so that the recovery rate of the raw material gas in the rich liquid is higher.
(2) The invention has simple and reliable process flow, uses less equipment, and can reduce investment cost, power cost, equipment use quantity and equipment maintenance cost.
(3) The content of the raw material gas in the rich liquid is easy to control, and the content of the raw material gas in the rich liquid can be reduced by increasing the amount of the displacement gas, so that the concentration of inflammable and explosive components in the desorbed carbon dioxide is reduced.
Drawings
FIG. 1 is a flow chart of a first embodiment of a feed gas recovery apparatus and method of the present invention.
FIG. 2 is a flow chart of a second embodiment of a feed gas recovery apparatus and method of the present invention.
FIG. 3 is a flow chart of a third embodiment of a feed gas recovery apparatus and method of the present invention.
FIG. 4 is a schematic diagram of the structure and process flow of a flash gas pressure withdrawal process system in comparative example one.
FIG. 5 is a flow chart of a fourth embodiment of a feed gas recovery apparatus and method of the present invention.
FIG. 6 is a schematic diagram of the structure and process flow of a flash gas pressure withdrawal process system in comparative example two.
FIG. 7 is a flow chart of a fifth embodiment of a feed gas recovery apparatus and method of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings, in order to make the objects and technical solutions of the present invention more apparent.
Embodiment one:
the first embodiment provides a general structural block diagram and a method flow chart of the invention. As shown in fig. 1, a feed gas recovery device comprises an absorption module 1 and a recovery module 2, wherein the absorption module 1 is an absorption tower, the recovery module 2 is a recovery tower, mass transfer equipment, the recovery tower, preferably a plate tower, a packed tower and other tower devices, a lean solution inlet is formed in the upper part of the absorption module 1, the lean solution also comprises semi-lean solution, a lean solution 101 enters from the upper part of the absorption module 1, a feed gas inlet is formed in the lower part of the absorption module 1, a feed gas 102 enters from the lower part of the absorption module 1, the lean solution 101 and the feed gas 102 are in countercurrent full contact in the absorption tower, and the lean solution 101 absorbs the feed gas 102 to obtain a rich solution 103. The absorption module 1 and the recovery module 2 are connected and communicated, the obtained rich liquid 103 enters the recovery module 2 from the absorption module 1, a rich liquid inlet is arranged at the upper part of the recovery module 2, a replacement gas inlet is arranged at the lower part of the recovery module 2, replacement gas 104 enters from the lower part of the recovery module 2, the rich liquid 103 and the replacement gas 104 are in countercurrent full contact and then replace raw material gas 105, the raw material gas 105 replaced in the embodiment can be returned to a raw material gas system or other raw material gas utilization systems, and the lean liquid in the embodiment is lean liquid desorbed by the carbon dioxide desorption system 3. Thus, the resources can be fully utilized, and the energy consumption is saved. The upper end of the absorption module 1 is provided with a purge gas outlet from which the purge gas 106 is discharged.
Embodiment two:
taking the coke oven gas to prepare synthetic ammonia as an example, the raw material gas treatment capacity of the decarburization section is 37400Nm 3 And (3) per hour (dry basis), wherein the annual operation time is 8000 hours, and the volume concentration of the main components of the raw material gas is as follows: 72.8% hydrogen, 24.8% carbon dioxide, 2.0% nitrogen, 0.2% methane, 0.2% carbon monoxide; the pressure is: 2.95MPa (A); the temperature is as follows: 50 ℃. Decarbonization absorption towerThe operating pressure was 2.9MPa (A), the lean solution 212 was 45% MDEA, the semi-lean solution 213 was 5% piperazine aqueous solution, the semi-lean solution temperature was 69 ℃, the feed rate was 306t/h, the lean solution temperature was 55 ℃, the feed rate was 101t/h, the bottom liquid-rich amount of the absorption module 1 was 471t/h, and the amount of dissolved hydrogen in the rich solution was 635Nm 3 /h。
As shown in fig. 2, a raw material gas recovery device includes an absorption module 1 and a recovery module 2, wherein the absorption module 1 is an absorption tower, and the recovery module 2 is a recovery tower. The absorption tower and the recovery tower are connected by a pipeline, a rich liquid pump 21 is arranged on the pipeline, a lean liquid 212 and a semi-lean liquid 213 enter from the upper part of the absorption tower, a raw material gas 210 enters from the lower part of the absorption tower, the lean liquid 212, the semi-lean liquid 213 and the raw material gas 210 are in countercurrent contact in the absorption tower to obtain a rich liquid 214 and a purified gas 211, the purified gas 211 is discharged from the top of the absorption tower, the rich liquid 214 is sent to the top of the recovery tower through the rich liquid pump 21, the operation pressure of the recovery tower is 3MPa (A), the power of the rich liquid pump 21 is 20kW, and in the embodiment, the replacement gas 217 introduced into the tower kettle of the recovery tower is nitrogen. The displacement gas 217 and the rich liquid 214 are in countercurrent contact in the recovery tower, the displacement gas 217 displaces the raw material gas in the rich liquid to obtain the recovered gas 215, a recovery pipeline is further arranged between the absorption module 1 and the recovery module 2 in the embodiment, the recovered gas 215 is returned to the previous step, namely the recovered gas is returned to the first step to be used as the raw material gas to continuously participate in absorption and decarbonization, the recovered gas in the embodiment is hydrogen, and the amount of the hydrogen recovered at the top of the recovery tower is 610Nm 3 And/h, the hydrogen quantity carried away by the rich liquid is 25Nm 3 And/h, the recovery rate of the raw material gas is 96.1%.
Embodiment two:
taking the coke oven gas to prepare synthetic ammonia as an example, the raw material gas treatment capacity of the decarburization section is 37400Nm 3 And (3) per hour (dry basis), wherein the annual operation time is 8000 hours, and the volume concentration of the main components of the raw material gas is as follows: 72.8% hydrogen, 24.8% carbon dioxide, 2.0% nitrogen, 0.2% methane, 0.2% carbon monoxide; the pressure is: 2.95MPa (A); the temperature is as follows: 50 ℃. The operating pressure of the decarbonization absorption tower is 2.9MPa (A), the barren solution 212 adopts 45% MDEA, the semi-barren solution 213 adopts 5% piperazine water solution, the semi-barren solution temperature is 69 ℃, the feeding amount is 306t/h, the barren solution temperature is 55 ℃, the feeding amount is 101t/h, and the absorption module 1The bottom liquid-rich amount was 471t/h, and the amount of dissolved hydrogen in the rich liquid was 635Nm 3 /h。
As shown in fig. 3, a raw gas recovery device includes an absorption module 1 and a recovery module 2, where the absorption module 1 is a decarbonizing section of an upper section and a middle section of an absorption tower, the recovery module 2 is a lower section of the absorption tower, lean solution 312 and semi-lean solution 313 are introduced from the upper part of the absorption module 1, raw gas 310 is introduced from the lower part of the absorption module 1, a rich solution is obtained, a displacement gas 315 is introduced from the lower part of the recovery module 2, the rich solution obtained from the lean solution 312, the semi-lean solution 313 and the raw gas 310 falls into the recovery module 2 under the action of gravity to be in countercurrent contact with the displacement gas 315, and the displacement gas 315 in this embodiment is a mixed gas of nitrogen and carbon dioxide, wherein the nitrogen concentration is 55.6 v%, and the carbon dioxide concentration is 44.4 v%; the recovered gas 314 is hydrogen gas, and the amount of the recovered hydrogen gas is 605 Nm 3 The hydrogen quantity carried away by the rich liquid is 30 Nm 3 And/h, the recovery rate of the raw material gas is 95.3%.
Comparative example one:
comparative example one is a comparative example with examples two and three and figure 4 is a process for recovering feed gas using conventional flash compression. As shown in fig. 4, the lean solution 412 and the semi-lean solution 413 are introduced from the upper portion of the absorption tower 41, the raw gas 410 is introduced from the lower portion of the absorption tower 41, the lean solution 412, the semi-lean solution 413 and the raw gas 410 are contacted in the absorption tower 41 to obtain the purified gas 411 and the rich solution 414, the rich solution 414 coming out of the absorption tower 41 is depressurized and then introduced into the flash tank 42, the operation pressure of the flash tank 42 is 0.62MPa (G), and the flash gas flow rate is 668 Nm 3 /h (dry basis) wherein the hydrogen concentration was 77.2v%, and the recovered hydrogen amount was 515Nm 3 And/h, the amount of hydrogen carried away by the resulting rich liquid 417 is 120Nm 3 And/h. Flash gas 415 was boosted to 3.0MPa (a) by compressor 43, cooled to 50 ℃ and returned to absorber 41 to recover hydrogen therein, and the power of compressor 43 was 49kW. The recovery rate of the raw material gas is 81.1%.
As can be seen from the comparison, compared with the conventional flash gas recovery process, the method does not need a compressor, has the advantages of simple process and low investment cost, and can save electric energy by 23.2-39.2 multiplied by 10 per year in practical application 4 kwh, has better economic benefit. In embodiment twoThe liquid-rich pump is also adopted, so that the arrangement mode and the position of the recovery module are more flexible, and the device is applicable to the transformation of the existing device. The third embodiment is integrated with the absorption tower, so that the occupied area is small and the investment is small.
Implementation four:
taking 50 ten thousand tons/year ammonia synthesis device as an example, the annual operation time is 8000h, and the raw material gas treatment capacity of the decarburization working section is 245000Nm 3 The volume concentration of the main components of the raw material gas is 54.2 percent, the carbon monoxide is 1.0 percent, the carbon dioxide is 43.7 percent, the nitrogen is 0.3 percent, the sulfur dioxide is 0.5 percent, the pressure is 5.87 MPa (A), the temperature entering the absorption module is-13 ℃, and the pressure of the absorption module is 5.72MPa (A); the lean solution is low-temperature methanol with the temperature of minus 62 ℃ and the flow of 315m 3 And/h, the rich liquid flows of the decarburization section and the desulfurization section are 267 m respectively 3 /h and 258 m 3 /h, wherein the dissolved hydrogen is 2152 Nm 3 /h。
As shown in fig. 5, a raw gas recovery device includes an absorption module 1 and a recovery module 2, the absorption module 1 is an absorption tower, the absorption tower includes a decarburization section 52 and a desulfurization section 51, and the recovery module 2 of this embodiment is disposed between the decarburization section 52 and the desulfurization section 51, specifically, the recovery module 2 is disposed at the lower ends of the decarburization section 52 and the desulfurization section 51, respectively. The decarbonization tower 52 is provided with an inlet of a lean solution 512, the desulfurization section 51 is provided with an inlet of a feed gas 510, the feed gas 510 is in countercurrent contact with a sulfur-free rich solution 514 to obtain a sulfur-containing rich solution, the desulfurized feed gas 516 is in countercurrent contact with the lean solution 512 to obtain a rich solution, and part of the sulfur-free rich solution 514 is introduced into the desulfurization section for desulfurizing the feed gas; other sulfur-free rich liquid in the decarburization section enters a decarburization section recovery module to be in countercurrent contact with the replacement gas 518, and the replaced raw gas enters the decarburization section for recycling to obtain sulfur-free rich liquid 513 with low raw gas content; the sulfur-containing rich liquid in the desulfurization section and the replacement gas 517 entering the desulfurization section are in countercurrent contact, and the replaced raw gas enters a stripping section absorption module for recycling, and the sulfur-containing rich liquid 515 is obtained. The displacement gas in this example was nitrogen, and the hydrogen dissolved in the sulfur-free rich liquid 513 and the sulfur-containing rich liquid 515 after the raw material gas recovery were 205 and 198 Nm, respectively 3 And/h, the recovery rate of the raw material gas is 81.3%.
Comparative example two:
comparative example two is a comparative example of example four and fig. 6 is a process diagram of a conventional low temperature methanol rich liquid flash compression recovery feed gas. In the figure, 61 is an absorption tower, the upper section is a decarburization section, the lower section is a desulfurization section, 62 is a sulfur-free methanol-rich cooler, 63 is a sulfur-containing methanol-rich cooler, 64 is a raw gas cooler, 65 is a methanol-rich liquid flash tank, 66 is a sulfur-containing methanol-rich flash tank, 67 is a flash gas compressor, 68 is a post-compression flash cooler, and 69 is an absorption tower decarburization section intercooler; 610 is raw gas, 611 is purified gas after sulfide and carbon dioxide are removed, 612 is low-temperature lean methanol, 613 is sulfur-free rich methanol, 614 is rich methanol for desulfurization, 615 is sulfur-containing rich methanol, 616 is rich methanol flash steam, 617 is sulfur-free rich methanol after flash evaporation, 618 is sulfur-containing rich methanol flash steam, 619 is sulfur-containing rich methanol after flash evaporation, 620 is compressed flash steam.
With continued reference to FIG. 6, the sulfur-free rich liquor 613 of the decarbonizing section and the sulfur-containing rich liquor 615 of the desulfurizing section are cooled to-33 ℃, depressurized to 1.75MPa, flash-evaporated in a flash tank 65 and a flash tank 66 respectively, and the hydrogen 1746 Nm in the flash steam is recovered 3 And/h, the hydrogen amount in the rich liquid after flash evaporation is 406Nm 3 /h; the recovered flash gas was boosted to 5.82MPa (A) by a compressor 67, cooled by a cooler 68, returned to the feed gas system, and absorbed in an absorption column, the compressor shaft power was 230kW, and the feed gas recovery was 81.1%.
As can be seen from the comparison of the second comparative example and the third example, compared with the conventional flash gas recovery process, the method does not need a compressor, has simple process and low investment cost, and saves 184X 10 electric energy annually in practical application 4 kwh, has better economic benefit.
Fifth embodiment:
as shown in fig. 7, a raw gas recovery device comprises an absorption module 1 and a recovery module 2, wherein the absorption module 1 is an absorption tower, the absorption tower comprises a decarburization section of an upper section, a desulfurization section of a middle section and a desulfurization section of a lower section, a lean solution inlet and a semi-lean solution inlet are formed in the upper part of the decarburization section, and a lean solution 712 and a semi-lean solution 713 enter the decarburization section from the lean solution inlet and the semi-lean solution inlet respectively; the decarburization section is provided with a mid-section cooler 75 and a desulfurization section feed cooler 74; the lower part of the desulfurization section is provided with a raw material gas inlet from which raw material gas 710 enters the desulfurization section; lean liquid 712 and semi-lean liquid 713 entering absorption module 1 are sufficiently contacted with feed gas 710 in countercurrent, and sulfur-free rich liquid 716 and sulfur-containing rich liquid 718 are obtained, respectively. The recovery module 2 is a recovery tower, and the recovery tower comprises a sulfur-free methanol-rich raw material gas recovery tower 73 and a sulfur-containing methanol-rich raw material gas recovery tower 72 which are arranged up and down; the sulfur-free methanol-rich raw material gas recovery tower 73 and the sulfur-containing methanol-rich raw material gas recovery tower 72 are respectively provided with a replacement gas inlet and a rich liquid outlet, and a replacement gas 722 and a replacement gas 721 respectively enter the sulfur-free methanol-rich raw material gas recovery tower 73 and the sulfur-containing methanol-rich raw material gas recovery tower 72 from the replacement gas inlet; the upper end of the sulfur-free methanol-rich raw material gas recovery tower 73 is provided with a raw material gas outlet which is communicated with the decarburization section, and the replaced raw material gas 714 can be returned to the absorption module 1 for recycling. The upper part of the sulfur-free methanol-rich raw material gas recovery tower 73 is provided with a sulfur-containing rich liquid inlet which is communicated with the decarbonization section, the rich liquid 716 obtained in the decarbonization section can be directly introduced into the recovery module for use, and the replacement gas 722 enters the sulfur-free methanol-rich raw material gas recovery tower 73 from the replacement gas inlet to be in countercurrent contact with the rich liquid 716 for replacement of raw material gas; the upper part of the sulfur-containing and methanol-rich raw material gas recovery tower 72 is provided with a rich liquid inlet which is communicated with the desulfurization section, the rich liquid 718 obtained in the desulfurization section can be directly introduced into the recovery module for use, the replacement gas 721 enters the sulfur-containing and methanol-rich raw material gas recovery tower 72 from the replacement gas inlet and is in countercurrent contact with the rich liquid 718 to replace the raw material gas 717, and the replaced raw material gas 717 can be returned to the absorption tower for recycling.
Taking a 165 ten thousand tons/year methanol device as an example, the annual operation time is 8000h, and the raw material gas treatment capacity of the purification section is 765243Nm 3 And (3) the concentration of the main components of the raw material gas is respectively as follows: 46.1% hydrogen, 20.2% carbon monoxide, 32.8% carbon dioxide, 0.4% nitrogen, 0.3% sulfur dioxide, operating pressure: 3.14MPa (A), the raw material gas 710 enters an absorption tower after heat exchange and cooling, the temperature is-21 ℃, and the absorption pressure of the absorption tower is 3.0MPa (A); lean solution 712 is low-temperature methanol, semi-lean solution 713 is low-temperature semi-lean methanol, low-temperature lean methanol temperature is-53 ℃, and flow is 1129 m 3 And/h, the temperature of the low-temperature semi-lean solution is-55 ℃, and the flow is 1055 m 3 And/h. Rich liquor 716 is sulfur-free in decarbonizing sectionRich liquor 718 is sulfur-containing rich liquor in desulfurization section, and the flow rates of the rich liquor 716 and the rich liquor 718 are 1961 m respectively 3 /h and 717 m 3 /h, wherein the dissolved carbon monoxide is 5686Nm 3 Hydrogen gas of 4292 Nm/h 3 And/h. The pressure at the top of the sulfur-containing methanol-rich raw material gas recovery tower 72 and the sulfur-free methanol-rich raw material gas recovery tower 73 is 3.05MPa (A), which is slightly higher than the raw material gas absorption pressure in the absorption tower by 3.0MPa (A), and the pressure at the top of the tower is higher than the absorption pressure, so that the recovered raw material gas can be directly returned into the absorption tower without gas compression equipment. The displacement gas adopts nitrogen with the temperature of minus 33 ℃, the recovered raw material gas 714 returns to the bottom of the decarbonization section of the absorption tower, the recovered raw material gas 717 returns to the bottom of the desulfurization section of the absorption tower, and the carbon monoxide 3834Nm is recovered altogether 3 Per hour, hydrogen 4256Nm 3 /h。
The foregoing has shown and described the basic principles, principal features and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that the above embodiments and descriptions are merely illustrative of the principles of the present invention, and various changes and modifications may be made without departing from the spirit and scope of the invention, which is defined in the appended claims. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (8)
1. A feed gas recovery process comprising the steps of:
step one: countercurrent contact of lean solution and raw gas in an absorption module for absorbing carbon dioxide, wherein the obtained solution is rich solution containing the raw gas;
step two: the rich liquid and the replacement gas are in countercurrent contact in the recovery module to replace the raw material gas, and the content of the raw material gas in the rich liquid can be reduced by increasing the replacement gas consumption, so that the concentration of flammable and explosive components in the desorbed carbon dioxide is reduced;
step three: the recovered raw material gas returns to the absorption module to be recycled; when the raw material gas is recovered in the third step, the operating pressure of the second step is equal to or higher than the absorption pressure of the raw material gas in the first step, and the recovered raw material gas can be directly returned to the absorption module for continuous recycling.
2. The method for recovering a raw material gas according to claim 1, wherein the displacement gas is a mixed gas of one or more of helium, nitrogen and argon.
3. The method for recovering a raw material gas according to claim 1, wherein the displacement gas is a mixed gas of carbon dioxide and one or more gases selected from helium, nitrogen and argon.
4. The method for recovering a raw gas according to claim 1, wherein the amount of the displacement gas is 0.1 to 1000Nm 3 /m 3 Rich liquid.
5. A recovery apparatus for carrying out the feed gas recovery method of claims 1 to 4, characterized by comprising an absorption module and a recovery module connected and communicated;
the upper part of the absorption module is provided with one or more lean liquid inlets, the lower part of the absorption module is provided with a raw material gas inlet, and the top end of the absorption module is also provided with a purified gas outlet;
the upper portion of recovery module is provided with rich liquid import, the lower part of recovery module is provided with the replacement gas import, recovery module still is provided with rich liquid export and/or recovery gas export.
6. The feed gas recovery device of claim 5 wherein the absorber module and the recovery module are two separate mass transfer apparatuses, and a recovery conduit is provided between the absorber module and the recovery module.
7. The feed gas recovery device of claim 5 wherein the absorber module and the recovery module are integrated within the same mass transfer apparatus.
8. The feed gas recovery device according to claim 6 or 7, wherein the mass transfer means is a tray column or a packed column.
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| CN101177267A (en) * | 2007-10-31 | 2008-05-14 | 武汉凯迪电力环保有限公司 | Method for preparing food-grade carbon-dioxide by using power station smoke gas and system thereof |
| 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 |
| CN104437004A (en) * | 2014-11-25 | 2015-03-25 | 赛鼎工程有限公司 | Method suitable for controlling concentration of hydrogen sulfide tail gas in low-temperature methanol washing process |
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| CN101177267A (en) * | 2007-10-31 | 2008-05-14 | 武汉凯迪电力环保有限公司 | Method for preparing food-grade carbon-dioxide by using power station smoke gas and system thereof |
| 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 |
| CN104437004A (en) * | 2014-11-25 | 2015-03-25 | 赛鼎工程有限公司 | Method suitable for controlling concentration of hydrogen sulfide tail gas in low-temperature methanol washing process |
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