CN111017956B - System for recycling low-temperature methanol washing air and operation method - Google Patents
System for recycling low-temperature methanol washing air and operation method Download PDFInfo
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- CN111017956B CN111017956B CN201911305232.7A CN201911305232A CN111017956B CN 111017956 B CN111017956 B CN 111017956B CN 201911305232 A CN201911305232 A CN 201911305232A CN 111017956 B CN111017956 B CN 111017956B
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- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 title claims abstract description 710
- 238000005406 washing Methods 0.000 title claims abstract description 104
- 238000000034 method Methods 0.000 title claims abstract description 11
- 238000004064 recycling Methods 0.000 title abstract description 7
- 239000007789 gas Substances 0.000 claims abstract description 188
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims abstract description 100
- 229910021529 ammonia Inorganic materials 0.000 claims abstract description 49
- 230000001105 regulatory effect Effects 0.000 claims abstract description 43
- 238000003786 synthesis reaction Methods 0.000 claims abstract description 41
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 34
- 238000011084 recovery Methods 0.000 claims abstract description 33
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 26
- 238000006243 chemical reaction Methods 0.000 claims abstract description 23
- 238000010926 purge Methods 0.000 claims abstract description 10
- 238000007599 discharging Methods 0.000 claims abstract description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 24
- 229910052757 nitrogen Inorganic materials 0.000 claims description 12
- 239000007788 liquid Substances 0.000 claims description 11
- 239000002994 raw material Substances 0.000 claims description 10
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 abstract description 11
- 229910052739 hydrogen Inorganic materials 0.000 abstract description 11
- 239000001257 hydrogen Substances 0.000 abstract description 11
- 238000004519 manufacturing process Methods 0.000 abstract description 7
- 238000004364 calculation method Methods 0.000 abstract description 5
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 abstract description 3
- 229910052717 sulfur Inorganic materials 0.000 abstract description 3
- 239000011593 sulfur Substances 0.000 abstract description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 14
- 229910002092 carbon dioxide Inorganic materials 0.000 description 7
- 239000003034 coal gas Substances 0.000 description 4
- 239000003245 coal Substances 0.000 description 3
- 238000000746 purification Methods 0.000 description 3
- 239000002253 acid Substances 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 238000002309 gasification Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000012824 chemical production Methods 0.000 description 1
- 238000007405 data analysis Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
- C01C1/00—Ammonia; Compounds thereof
- C01C1/02—Preparation, purification or separation of ammonia
- C01C1/04—Preparation of ammonia by synthesis in the gas phase
- C01C1/0405—Preparation of ammonia by synthesis in the gas phase from N2 and H2 in presence of a catalyst
- C01C1/0488—Processes integrated with preparations of other compounds, e.g. methanol, urea or with processes for power generation
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
- C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
- C01B3/025—Preparation or purification of gas mixtures for ammonia synthesis
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
- C01C1/00—Ammonia; Compounds thereof
- C01C1/02—Preparation, purification or separation of ammonia
- C01C1/04—Preparation of ammonia by synthesis in the gas phase
- C01C1/0405—Preparation of ammonia by synthesis in the gas phase from N2 and H2 in presence of a catalyst
- C01C1/0476—Purge gas treatment, e.g. for removal of inert gases or recovery of H2
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/15—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively
- C07C29/151—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases
- C07C29/1512—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases characterised by reaction conditions
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/15—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively
- C07C29/151—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases
- C07C29/1516—Multisteps
- C07C29/1518—Multisteps one step being the formation of initial mixture of carbon oxides and hydrogen for synthesis
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Inorganic Chemistry (AREA)
- Analytical Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Combustion & Propulsion (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention relates to a system for recycling low-temperature methanol washing air and an operation method thereof. A hydrogen recovery pipeline, a regulating valve and a flowmeter are added on a synthetic ammonia low-temperature methanol washing and discharging pipeline; a bypass pipeline of the methanol conversion furnace and a CO regulating valve HV2 are additionally arranged between the inlet and the outlet of the methanol conversion furnace, so that the hydrogen-carbon ratio of the methanol synthesis gas is ensured to be 2.0-3.0, the cold energy of low-temperature methanol washing is not affected, and the sulfur content of the synthesis gas at the low-temperature methanol washing outlet is less than 0.1ppm. When the working pressure of the synthetic ammonia low-temperature methanol washing shift gas washing tower exceeds the working pressure, the purge gas vent valve HV1 is opened, vent gas is generated, the recycle gas front hand valve V2, the recycle gas rear hand valve V3 and the recycle gas regulating valve HV3 are opened, and vent gas is recycled to the methanol device through numerical calculation of the recycle flow meter FI1, the methanol synthesis flow meter FI2 and the hydrogen-carbon ratio analyzer AI2, and the like, so that the high-load production of the methanol device is ensured while the complete recycling of vent gas is ensured.
Description
Technical Field
The invention belongs to the field of chemical production, relates to coal gas co-production, and in particular relates to a system for recycling low-temperature methanol washing air and an operation method.
Background
In the coal chemical industry production, coal gas is generally used as a tap, the generated coal gas enters the downstream, the downstream is generally a co-production device, the coal gas is mainly used as a raw material, and methanol, synthetic ammonia and carbon-chemical products are commonly produced at the same time.
As shown in fig. 1, the synthesis ammonia device comprises a synthesis ammonia shift converter 8, a synthesis ammonia shift heat exchanger group 9, a synthesis ammonia low-temperature methanol washing heat exchanger 10, a synthesis ammonia low-temperature methanol washing shift gas washing tower 11, a liquid nitrogen washing 12, a synthesis ammonia press 13 and a synthesis ammonia low-temperature methanol washing unconverted system 14; raw gas produced by coal gasification is used as a raw material, CO and water vapor react under the action of a catalyst and a certain temperature condition through a synthetic ammonia shift converter 8, CO is converted into hydrogen and carbon dioxide gas, so that the content of hydrogen in the raw gas is increased, and the gas is called shift gas; the other raw gas which enters the shift process is directly cooled with the synthesis ammonia shift heat exchanger group 9 without passing through the synthesis ammonia shift furnace 8 to obtain the non-shift gas. The shift gas enters a synthetic ammonia low-temperature methanol washing shift gas washing tower 11 for acid gas removal, then enters a liquid nitrogen washing 12 through a liquid nitrogen washing inlet pipeline 20, is compressed through a synthetic ammonia compressor 13, and finally is sent to downstream for producing liquid ammonia; when the device is started, the shift gas enters a synthetic ammonia low-temperature methanol washing shift gas washing tower 11, a start stop valve XV2 is opened, a liquid nitrogen washing inlet stop valve XV1 is closed, the shift gas passes through a washing tower outlet pipeline 19, and then passes through a synthetic ammonia low-temperature methanol washing heat exchanger 10 for heat exchange and then is discharged through a purified gas discharge pipeline 22 and a purified gas discharge valve HV1; the unconverted gas enters a synthesis ammonia low-temperature methanol washing unconverted system 14 for acid gas removal to produce a carbon-one product 15, and the carbon-one product is sent to a downstream device.
The methanol device shown in fig. 2 comprises a raw material gas separator 1, a raw material gas filter 2, a methanol conversion furnace 3, a methanol conversion heat exchanger group 4, a methanol low-temperature methanol washing heat exchanger 5, a methanol washing tower 6 and a methanol gas compressor 7. The gas pipeline is connected with the middle part of the raw gas separator 1, the top of the raw gas separator 1 is connected with the top of the raw gas filter 2, the bottom of the raw gas filter is connected with the methanol shift converter 3, the outlet pipeline 17 of the methanol shift converter is connected with the methanol shift converter group 4, the outlet of the methanol shift converter group 4 is connected with the shell side inlet of the methanol low-temperature methanol wash heat exchanger 5, the outlet pipeline of the methanol shift converter group 4 is provided with the CO on-line analyzer AI1, the shell side outlet of the methanol low-temperature methanol wash heat exchanger 5 is connected with the middle part of the methanol wash tower 6, the top of the methanol wash tower 6 is connected with the tube side inlet of the methanol low-temperature methanol wash heat exchanger 5, the tube side outlet of the methanol low-temperature methanol wash heat exchanger 5 is connected with the low-temperature methanol wash zone valve V1, the low-temperature methanol wash zone valve V1 is connected with the methanol gas press 7 through the inlet pipeline 18 of the methanol gas press, and the hydrogen-carbon ratio analyzer AI2 and the methanol synthesis flowmeter FI2 are installed on the inlet pipeline 18 of the methanol gas press. The hydrogen-carbon ratio index is controlled to be 2.0-3.0, the hydrogen-carbon ratio is displayed by AI2, the purified gas is compressed by a methanol aerostatic press 7, and finally the purified gas is sent to the downstream to produce methanol.
When equipment such as liquid nitrogen washing, a synthetic ammonia gas press and the like is maintained or abnormally stopped, because the non-converted gas of the synthetic ammonia low-temperature methanol washing is supplied to the downstream carbon-one product, if the synthetic ammonia low-temperature methanol washing is stopped, the downstream carbon-one product is influenced, if the synthetic ammonia low-temperature methanol washing is not stopped, a certain load is required to be maintained for a conversion gas system of the low-temperature methanol washing in order to maintain the cold balance of the low-temperature methanol washing, and a large amount of hydrogen is discharged.
Disclosure of Invention
The invention aims to maintain the load of unconverted gas and recover the vent gas of converted gas under the condition of ensuring the cold balance of low-temperature methanol washing.
The method comprises the steps of mixing a gas which does not pass through a shift converter with shift converter, mixing the gas with the shift converter, and then entering methanol low-temperature methanol to ensure the mixed content of the gas and the shift converter, wherein the shift gas in the methanol low-temperature methanol washing has the hydrogen content of 93-96%, the CO content of 1-2%, the nitrogen content of 1.2-3%, the sulfur content of less than 1.4 ppm, the CO content of 1.2% and the CO content of 2%, the shift gas in the methanol low-temperature methanol washing has the CO2 content of only 2.6%, the methanol low-temperature methanol washing can meet the requirement of methanol synthesis by adjusting the operation of the methanol low-temperature methanol washing, and the hydrogen content in the shift gas in the methanol low-temperature methanol washing of the synthetic ammonia is high, so that the CO content in the methanol low-temperature methanol washing needs to be improved, the requirement of the methanol synthesis can be ensured, and the gas which does not pass through the shift converter is led out in a methanol shifting device and the shift gas which passes through the shift converter is mixed with the shift converter, and then enters the methanol low-temperature methanol to be improved to ensure the mixed content of the methanol low-temperature and the CO content of 2 to be within the normal range of 0.0.0.
According to the technological requirements and data analysis, the following technical scheme is proposed:
a system for recovering low-temperature methanol washing air; a hydrogen recovery pipeline, a regulating valve and a flowmeter are added on the synthetic ammonia low-temperature methanol washing and emptying pipeline 22; a methanol conversion furnace bypass pipeline 16 and a CO regulating valve HV2 are additionally arranged between the inlet and the outlet of the methanol conversion furnace, so that the hydrogen-carbon ratio of the methanol synthesis gas is ensured to be 2.0-3.0, the cold energy of low-temperature methanol washing is not affected, and the sulfur content of the synthesis gas at the low-temperature methanol washing outlet is less than 0.1ppm.
The further explanation is: the system synthesis ammonia low-temperature methanol washing conversion gas purification gas vent pipeline 22 is connected with a methanol gas compressor inlet pipeline 18, a vent gas recovery pipeline 21 is sequentially provided with a recovered gas front hand valve V2, a recovered gas regulating valve HV3, a recovered flow meter FI1 and a recovered gas rear hand valve V3; a methanol conversion furnace bypass pipeline 16 and a CO regulating valve HV2 are connected between the inlet and the outlet of the methanol conversion furnace and are used for regulating the CO content of the two purified gases after being mixed, thereby meeting the requirement of 2.0-3.0 of the methanol synthesis ratio.
Further described are: the system is characterized in that a shift converter bypass pipeline 16 is connected between an inlet and an outlet of a methanol shift converter, a CO regulating valve HV2 is arranged on the shift converter bypass pipeline, and a CO on-line analyzer AI1 is arranged on an outlet pipeline of a methanol shift heat exchanger group 4; the outlet of the tube side of the methanol low-temperature methanol washing heat exchanger 5 is connected with an inlet pipeline 18 of a methanol gas compressor through a valve V1 of a low-temperature methanol washing area, and a hydrogen-carbon ratio analyzer AI2 and a methanol synthesis flowmeter FI2 are arranged on the inlet pipeline 18 of the methanol gas compressor; the outlet of the synthetic ammonia low-temperature methanol washing heat exchanger 10 is connected with the inlet pipeline 18 of the methanol gas compressor through a vent gas recovery pipeline 21, and a recovered gas front hand valve V2 and a recovered gas regulating valve HV3, a recovered flow meter FI1 and a recovered gas rear hand valve V3 are sequentially arranged on the vent gas recovery pipeline 21.
An operation method for recycling low-temperature methanol washing air comprises the following steps:
1. when the working pressure of the synthetic ammonia low-temperature methanol washing shift gas washing tower exceeds the working pressure, the purified gas discharging valve HV1 is opened, and then the air is discharged;
2. opening a recovered gas front hand valve V2 and a recovered gas rear hand valve V3, and opening a recovered gas regulating valve HV3 to 5% -8%;
3. displaying flow through a recovery flow meter FI1, and calculating the numerical value of the CO index to be adjusted of the methanol conversion outlet according to the flow of the recovery flow meter FI1, the numerical value of a methanol synthesis flow meter FI2 and the numerical value of a hydrogen-carbon ratio analyzer AI2 to obtain the CO index to be adjusted of the methanol conversion outlet;
4. the CO content is adjusted by adjusting the opening of the CO adjusting valve HV2, so that the actual value of the CO online analyzer AI1 is consistent with the calculated CO value;
5. calibrating the value of the hydrogen-carbon ratio analyzer AI2 to meet the hydrogen-carbon ratio of the methanol between 2.0 and 3.0;
6. gradually opening the valve position of the recovered gas regulating valve HV3, increasing the opening by 3-5% each time, repeating the steps 3-5, and regulating the opening of the CO regulating valve HV2 to ensure that the hydrogen-carbon ratio of methanol is 2.0-3.0;
7. when the purge gas vent valve HV1 is completely closed, the vent gas is completely recovered, and the recovery gas regulating valve HV3 and the CO regulating valve HV2 remain in current operation.
The invention has the advantages that:
1. on the premise of not adding new equipment, only part of pipelines and valves are added, so that the investment is small and the benefit is large.
2. The invention improves the system maintenance after ammonia synthesis, which is more convenient, does not influence the production of downstream carbon-one products and reduces the stopping loss to the minimum.
3. The invention recovers the vent gas to the methanol device, and ensures the high-load production of the methanol device while ensuring the complete recovery of the vent gas.
Drawings
Fig. 1: existing ammonia synthesis plant flow diagrams.
Fig. 2: flow chart of existing methanol device
Fig. 3: the invention relates to a process flow chart after transformation.
Wherein: a 1-raw material gas separator, a 2-raw material gas filter, a 3-methanol shift converter, a 4-methanol shift heat exchanger group, a 5-methanol low-temperature methanol wash heat exchanger, a 6-methanol wash tower, a 7-methanol gas compressor, an 8-synthesis ammonia shift converter, a 9-synthesis ammonia shift heat exchanger group, a 10-synthesis ammonia low-temperature methanol wash heat exchanger, an 11-synthesis ammonia low-temperature methanol wash shift gas wash tower, a 12-liquid nitrogen wash, a 13-synthesis ammonia compressor, a 14-synthesis ammonia low-temperature methanol wash non-shift system, a 15-carbon product, a 16-shift converter bypass pipeline, a 17-methanol shift converter outlet pipeline, an 18-methanol gas compressor inlet pipeline, a 19-wash tower outlet pipeline, a 20-liquid nitrogen wash inlet pipeline, a 21-vent recovery pipeline, a 22-purge gas vent pipeline, a HV 1-purge gas vent valve, a HV2-CO regulating valve, a HV 3-recovery gas regulating valve, a V1-low-temperature methanol wash zone valve, a V2-recovery gas front hand valve, a V3-recovery gas back hand valve, a FI 1-methanol flowmeter, a 2-synthesis gas flowmeter, an AI1-CO online analyzer and an AI 2-hydrogen-carbon ratio analyzer.
Detailed Description
The invention is described in further detail below with reference to the accompanying drawings:
the introduction of the synthetic low-temperature methanol washing needs to consider two factors, namely, ensuring the hydrogen-carbon ratio of the methanol synthesis and the cold energy of the low-temperature methanol washing.
1. Ensuring the calculation thought of the hydrogen-carbon ratio of methanol synthesis
The gas component produced by coal gasification comprises 20-26% of hydrogen and 60-68% of CO (dry basis), and the increased hydrogen content of the discharged air introduced by low-temperature methanol washing of the methanol can be supplemented by introducing a stream of gas which does not pass through a shift converter, so that the requirement of methanol synthesis on the hydrogen-carbon ratio is met. The theoretical calculation thinking is that firstly, the flow of the discharged air is assumed, the gas quantity and the component entering the low-temperature methanol washing inlet are calculated according to the component and the flow of the discharged air and the total gas quantity and the component of the methanol gas inlet press, the gas quantity required to be converted into the CO pipeline is calculated according to the gas component and the gas quantity and the design component of the methanol conversion furnace outlet, and then whether the pipeline exceeds the design flow rate is calculated according to the pipe diameter of the pipeline.
2. Cold balance problem of low temperature methanol washing
As can be seen from production experience, if the low-temperature methanol washing load is above 80%, when the CO2 content in the component of the actual low-temperature methanol washing inlet is compared with the design, the influence on the cold washing amount of the low-temperature methanol is larger when the actual CO2 content is lower than 3% of the design, otherwise, the influence is negligible when the CO2 content is not lower than 3% of the design, so that the theoretical calculation thought is that firstly, the flow of the discharged air is assumed, the air amount and the component entering the low-temperature methanol washing inlet are calculated according to the component and the flow of the discharged air and the total air amount and the component of the methanol air inlet press, and then compared with the design of the low-temperature methanol washing, so as to judge whether the cold washing amount of the low-temperature methanol can be balanced.
The connection mode is as follows:
a system for recycling low-temperature methanol washing and releasing air comprises a raw material gas separator 1, a raw material gas filter 2, a methanol shift converter 3, a methanol shift heat exchanger group 4, a methanol low-temperature methanol washing heat exchanger 5, a methanol washing tower 6, a methanol gas compressor 7, a synthetic ammonia low-temperature methanol washing heat exchanger 10, a synthetic ammonia low-temperature methanol washing shift gas washing tower 11 and liquid nitrogen washing 12. The gas pipeline is connected with the middle part of the raw gas separator 1, the top of the raw gas separator 1 is connected with the top of the raw gas filter 2, the bottom of the raw gas filter is divided into two parts, one part is connected with the methanol shift converter 3, the other part is a shift converter bypass pipeline 16, the other part is connected with a methanol shift converter outlet pipeline 17, a CO regulating valve HV2 is arranged on the shift converter bypass pipeline, the methanol shift converter outlet pipeline 17 is connected with the methanol shift heat exchanger group 4, the outlet of the methanol shift heat exchanger group 4 is connected with the shell side inlet of the methanol low-temperature methanol wash heat exchanger 5, the shell side outlet of the methanol low-temperature methanol wash heat exchanger 5 is connected with the middle part of the methanol wash tower 6, the top of the methanol wash tower 6 is connected with the tube side inlet of the methanol low-temperature methanol wash heat exchanger 5, the tube side outlet of the methanol low-temperature methanol wash heat exchanger 5 is connected with a low-temperature methanol wash boundary region valve V1, the low-temperature methanol wash boundary region valve V1 is connected with the methanol gas compressor 7 through a methanol compressor inlet pipeline 18, and the methanol gas compressor inlet pipeline 18 is provided with a hydrogen-carbon ratio analyzer AI2 and a methanol synthesis flowmeter FI2.
The top of the synthetic ammonia low-temperature methanol washing shift gas washing tower 11 is connected to the inlet of the synthetic ammonia low-temperature methanol washing heat exchanger 10 through a washing tower outlet pipeline 19, a start-up cut-off valve XV2 is installed on the washing tower outlet pipeline 19, a liquid nitrogen washing inlet pipeline 20 is connected before the start-up cut-off valve XV2, an air release recovery pipeline 21 is connected to the outlet of the synthetic ammonia low-temperature methanol washing heat exchanger 10, the air release recovery pipeline 21 is connected with a methanol gas compressor inlet pipeline 18, a recovered gas front hand valve V2, a recovered gas regulating valve HV3, a recovered flow meter FI1, a recovered gas rear hand valve V3 are sequentially installed on the air release recovery pipeline 21 before the recovered gas front hand valve V2, a purified gas air release pipeline 22 is connected, and a purified gas air release valve HV1 is installed on the purified gas air release pipeline 22.
The purification gas discharge valve HV1 of the synthesis ammonia low-temperature methanol washing and shift gas washing tower is in an automatic state and is set to be 3.1MPa, after the downstream shutdown, the pressure of the synthesis ammonia low-temperature methanol washing and shift gas washing tower can be increased, the purification gas discharge valve HV1 can be automatically opened to maintain the set pressure, at the moment, the discharge gas can exist, and the operation method of the discharge gas recovery is as follows:
the method comprises the steps of opening a recovered gas front hand valve V2 and a recovered gas rear hand valve V3 on site, manually opening a recovered gas regulating valve HV3 to 5% -8% in a central control mode, feeding a flow value back to a DCS (the DCS control system is adopted by a company) through a recovered flow meter FI1, a methanol synthesis flow meter FI2 and a hydrogen-carbon ratio analyzer AI2, calculating a CO index value to be regulated by a methanol conversion outlet through the flow of the recovered flow meter FI1, displaying the CO index value on the DCS, regulating the CO index value according to the methanol conversion outlet by an operator, regulating the content of CO through regulating the opening of the CO regulating valve HV2, enabling the actual value of the CO online analyzer AI1 to be consistent with the calculated CO index value, and correcting the value through the hydrogen-carbon ratio analyzer AI2 to meet the condition that the hydrogen-carbon ratio of methanol is between 2.0 and 3.0.
Gradually opening the valve position of the recovered gas regulating valve HV3, increasing the opening by 3-5% each time, and regulating the opening of the CO regulating valve HV2 according to the operation to ensure that the hydrogen-carbon ratio of methanol is 2.0-3.0. When the purge gas vent valve HV1 is completely closed, the vent gas is completely recovered, and the recovery gas regulating valve HV3 and the CO regulating valve HV2 remain in current operation.
Example 1: the inlet conditions of low-temperature methanol washing with methanol of 10000Nm3/h vent gas and 180000Nm3/h of methanol shift gas are calculated by a manager as follows:
as can be seen from Table 1, the CO content of the methanol low-temperature methanol wash port was designed to be 19.61% and the actual content was 22.19%; the gas 9290Nm3/h is required to be mixed, the pipeline is calculated as DN100 according to the transformation of the CO mixing pipeline, and the flow rate is calculated as 15m/s, so that the gas amount can be mixed as 22900Nm3/h, and the requirement can be met; the CO2 content of the low-temperature methanol washing inlet is 35.59 percent, is 34.19 percent practically, and has little influence on the cold washing capacity of the low-temperature methanol, so that the scheme is feasible.
Example 2: the inlet conditions of low-temperature methanol washing with methanol of 20000Nm3/h vent gas and 180000Nm3/h methanol shift gas were calculated by a manager as follows:
as shown in the table above, the CO content of the methanol low-temperature methanol washing inlet is designed to be 19.61%, and the actual content is 24.23%; the gas 16410Nm3/h is required to be mixed, and the gas amount which can be mixed according to the change of the hydrogen mixing pipeline is 22900Nm3/h, so that the requirements can be basically met; the CO2 content of the low-temperature methanol washing inlet is 35.59 percent, which is 33.19 percent practically, and the low-temperature methanol washing cold quantity is not greatly influenced, so that the scheme is feasible.
According to the calculation and design scheme, a hydrogen recovery pipeline, a regulating valve and a flowmeter are added on a synthetic ammonia low-temperature methanol washing and driving pipeline on the basis that the two sets of equipment and valves shown in the figures 1 and 2 are kept unchanged.
The improvement scheme is as follows: a vent gas recovery pipeline 21 is newly added on a synthetic ammonia low-temperature methanol washing shift gas purifying gas vent pipeline 22 and is introduced into a methanol gas compressor inlet pipeline 18, a recovered gas front hand valve V2 and a recovered gas regulating valve HV3 are sequentially installed on the vent gas recovery pipeline, a recovered flow meter FI1 and a recovered gas rear hand valve V3; a methanol conversion furnace bypass pipeline 16 and a CO regulating valve HV2 are additionally arranged at the inlet and the outlet of the methanol conversion furnace and are used for regulating the CO content of the two purified gases after being mixed, thereby meeting the requirement of 2.0-3.0 of the methanol synthesis ratio.
Claims (2)
1. A system for recovering low-temperature methanol washing air; the device comprises a raw material gas separator, a raw material gas filter, a methanol conversion furnace, a methanol conversion heat exchanger group, a methanol low-temperature methanol washing heat exchanger, a methanol washing tower, a methanol gas compressor, a synthetic ammonia low-temperature methanol washing heat exchanger, a synthetic ammonia low-temperature methanol washing conversion gas washing tower and liquid nitrogen washing; the gas pipeline is connected with the middle part of the raw gas separator, the top of the raw gas separator is connected with the top of the raw gas filter, the bottom of the raw gas filter is divided into two parts, one part of the raw gas separator is connected with the methanol shift converter, the other part of the raw gas filter is a shift converter bypass pipeline which is connected with the outlet pipeline of the methanol shift converter, a CO regulating valve HV2 is arranged on the shift converter bypass pipeline, the outlet pipeline of the methanol shift converter is connected with the methanol shift heat exchanger group, the outlet of the methanol shift heat exchanger group is connected with the shell side inlet of the methanol low-temperature methanol wash heat exchanger, the outlet of the methanol low-temperature methanol wash heat exchanger is connected with the tube side inlet of the methanol low-temperature methanol wash heat exchanger, the outlet of the methanol low-temperature methanol wash heat exchanger is connected with a valve V1 of the low-temperature methanol wash limit region, the valve V1 of the low-temperature methanol wash limit region is connected with a methanol gas compressor through the inlet pipeline of the methanol gas compressor, and a hydrogen-carbon ratio analyzer AI2 and a methanol synthesis flowmeter FI2 are arranged on the inlet pipeline of the methanol gas compressor; the top of the synthetic ammonia low-temperature methanol washing shift gas washing tower is connected to the inlet of a synthetic ammonia low-temperature methanol washing heat exchanger through a washing tower outlet pipeline, a start-up cut-off valve XV2 is arranged on the washing tower outlet pipeline, a liquid nitrogen washing inlet pipeline is connected before the start-up cut-off valve XV2, the outlet of the synthetic ammonia low-temperature methanol washing heat exchanger is connected with a vent gas recovery pipeline, the vent gas recovery pipeline is connected with a methanol gas compressor inlet pipeline, a recovery gas front hand valve V2 and a recovery gas regulating valve HV3 are sequentially arranged on the vent gas recovery pipeline, a recovery flowmeter FI1, a recovery gas rear hand valve V3 and a purge gas vent pipeline are connected on the vent gas recovery pipeline before the recovery gas front hand valve V2, and the purge gas vent valve HV1 is arranged on the purge gas vent pipeline; and a CO online analyzer AI1 is arranged on an outlet pipeline of the methanol conversion heat exchanger group.
2. A method of operating a system for recovering low temperature methanol purge air as claimed in claim 1, comprising the steps of:
1) When the working pressure of the synthetic ammonia low-temperature methanol washing shift gas washing tower exceeds the working pressure, the purified gas discharging valve HV1 is opened, and then the air is discharged;
2) Opening a recovered gas front hand valve V2 and a recovered gas rear hand valve V3, and opening a recovered gas regulating valve HV3 to 5% -8%;
3) Displaying flow through a recovery flow meter FI1, and calculating the numerical value of the CO index to be adjusted of the methanol conversion outlet according to the flow of the recovery flow meter FI1, the numerical value of a methanol synthesis flow meter FI2 and the numerical value of a hydrogen-carbon ratio analyzer AI2 to obtain the CO index to be adjusted of the methanol conversion outlet;
4) The CO content is adjusted by adjusting the opening of the CO adjusting valve HV2, so that the actual value of the CO online analyzer AI1 is consistent with the calculated CO value;
5) Calibrating the value of the hydrogen-carbon ratio analyzer AI2 to meet the hydrogen-carbon ratio of the methanol between 2.0 and 3.0;
6) Gradually opening the valve position of the recovered gas regulating valve HV3, increasing the opening by 3-5% each time, repeating the steps 3-5, and regulating the opening of the CO regulating valve HV2 to ensure that the hydrogen-carbon ratio of methanol is 2.0-3.0;
7) When the purge gas vent valve HV1 is completely closed, the vent gas is completely recovered, and the recovery gas regulating valve HV3 and the CO regulating valve HV2 remain in current operation.
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