CN117861253A - Energy-saving and environment-friendly rectification method and rectification system for preparing methanol from coal - Google Patents
Energy-saving and environment-friendly rectification method and rectification system for preparing methanol from coal Download PDFInfo
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- CN117861253A CN117861253A CN202410029725.7A CN202410029725A CN117861253A CN 117861253 A CN117861253 A CN 117861253A CN 202410029725 A CN202410029725 A CN 202410029725A CN 117861253 A CN117861253 A CN 117861253A
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- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 title claims abstract description 904
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- 239000003245 coal Substances 0.000 title claims abstract description 10
- 238000005406 washing Methods 0.000 claims abstract description 171
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 99
- 238000011084 recovery Methods 0.000 claims abstract description 85
- 239000007788 liquid Substances 0.000 claims abstract description 79
- 239000002994 raw material Substances 0.000 claims abstract description 5
- 239000007789 gas Substances 0.000 claims description 101
- 238000010992 reflux Methods 0.000 claims description 75
- 239000007921 spray Substances 0.000 claims description 29
- 238000010438 heat treatment Methods 0.000 claims description 12
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 9
- 239000000463 material Substances 0.000 claims description 5
- 239000002918 waste heat Substances 0.000 claims description 5
- 230000000295 complement effect Effects 0.000 claims 1
- 125000005842 heteroatom Chemical group 0.000 claims 1
- 239000002351 wastewater Substances 0.000 abstract description 34
- 230000008901 benefit Effects 0.000 abstract description 11
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- 230000008569 process Effects 0.000 description 9
- 238000000926 separation method Methods 0.000 description 9
- 239000012071 phase Substances 0.000 description 8
- 239000007791 liquid phase Substances 0.000 description 7
- 230000015572 biosynthetic process Effects 0.000 description 6
- 230000000694 effects Effects 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 6
- 238000003786 synthesis reaction Methods 0.000 description 6
- 238000010521 absorption reaction Methods 0.000 description 4
- 239000001760 fusel oil Substances 0.000 description 4
- ZOCHHNOQQHDWHG-UHFFFAOYSA-N hexan-3-ol Chemical compound CCCC(O)CC ZOCHHNOQQHDWHG-UHFFFAOYSA-N 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 238000004064 recycling Methods 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- 230000009466 transformation Effects 0.000 description 4
- IMNFDUFMRHMDMM-UHFFFAOYSA-N N-Heptane Chemical compound CCCCCCC IMNFDUFMRHMDMM-UHFFFAOYSA-N 0.000 description 3
- 239000007864 aqueous solution Substances 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- 238000006482 condensation reaction Methods 0.000 description 3
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- 150000002148 esters Chemical class 0.000 description 3
- 238000006460 hydrolysis reaction Methods 0.000 description 3
- GBMDVOWEEQVZKZ-UHFFFAOYSA-N methanol;hydrate Chemical compound O.OC GBMDVOWEEQVZKZ-UHFFFAOYSA-N 0.000 description 3
- BBMCTIGTTCKYKF-UHFFFAOYSA-N 1-heptanol Chemical compound CCCCCCCO BBMCTIGTTCKYKF-UHFFFAOYSA-N 0.000 description 2
- PFNHSEQQEPMLNI-UHFFFAOYSA-N 2-methyl-1-pentanol Chemical compound CCCC(C)CO PFNHSEQQEPMLNI-UHFFFAOYSA-N 0.000 description 2
- ISTJMQSHILQAEC-UHFFFAOYSA-N 2-methyl-3-pentanol Chemical compound CCC(O)C(C)C ISTJMQSHILQAEC-UHFFFAOYSA-N 0.000 description 2
- QPRQEDXDYOZYLA-UHFFFAOYSA-N 2-methylbutan-1-ol Chemical compound CCC(C)CO QPRQEDXDYOZYLA-UHFFFAOYSA-N 0.000 description 2
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- RZKSECIXORKHQS-UHFFFAOYSA-N Heptan-3-ol Chemical compound CCCCC(O)CC RZKSECIXORKHQS-UHFFFAOYSA-N 0.000 description 2
- LRHPLDYGYMQRHN-UHFFFAOYSA-N N-Butanol Chemical compound CCCCO LRHPLDYGYMQRHN-UHFFFAOYSA-N 0.000 description 2
- AMQJEAYHLZJPGS-UHFFFAOYSA-N N-Pentanol Chemical compound CCCCCO AMQJEAYHLZJPGS-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
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- QNVRIHYSUZMSGM-UHFFFAOYSA-N hexan-2-ol Chemical compound CCCCC(C)O QNVRIHYSUZMSGM-UHFFFAOYSA-N 0.000 description 2
- ZXEKIIBDNHEJCQ-UHFFFAOYSA-N isobutanol Chemical compound CC(C)CO ZXEKIIBDNHEJCQ-UHFFFAOYSA-N 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
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- ULPMRIXXHGUZFA-UHFFFAOYSA-N (R)-4-Methyl-3-hexanone Natural products CCC(C)C(=O)CC ULPMRIXXHGUZFA-UHFFFAOYSA-N 0.000 description 1
- QNVRIHYSUZMSGM-LURJTMIESA-N 2-Hexanol Natural products CCCC[C@H](C)O QNVRIHYSUZMSGM-LURJTMIESA-N 0.000 description 1
- LCFKURIJYIJNRU-UHFFFAOYSA-N 2-methylhexan-1-ol Chemical compound CCCCC(C)CO LCFKURIJYIJNRU-UHFFFAOYSA-N 0.000 description 1
- PFCHFHIRKBAQGU-UHFFFAOYSA-N 3-hexanone Chemical compound CCCC(=O)CC PFCHFHIRKBAQGU-UHFFFAOYSA-N 0.000 description 1
- UNXHWFMMPAWVPI-QWWZWVQMSA-N D-threitol Chemical compound OC[C@@H](O)[C@H](O)CO UNXHWFMMPAWVPI-QWWZWVQMSA-N 0.000 description 1
- UNXHWFMMPAWVPI-UHFFFAOYSA-N Erythritol Natural products OCC(O)C(O)CO UNXHWFMMPAWVPI-UHFFFAOYSA-N 0.000 description 1
- JGFBQFKZKSSODQ-UHFFFAOYSA-N Isothiocyanatocyclopropane Chemical compound S=C=NC1CC1 JGFBQFKZKSSODQ-UHFFFAOYSA-N 0.000 description 1
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- PWLNAUNEAKQYLH-UHFFFAOYSA-N butyric acid octyl ester Natural products CCCCCCCCOC(=O)CCC PWLNAUNEAKQYLH-UHFFFAOYSA-N 0.000 description 1
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- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 125000004435 hydrogen atom Chemical class [H]* 0.000 description 1
- QQZOPKMRPOGIEB-UHFFFAOYSA-N n-butyl methyl ketone Natural products CCCCC(C)=O QQZOPKMRPOGIEB-UHFFFAOYSA-N 0.000 description 1
- UUIQMZJEGPQKFD-UHFFFAOYSA-N n-butyric acid methyl ester Natural products CCCC(=O)OC UUIQMZJEGPQKFD-UHFFFAOYSA-N 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
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- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention relates to an energy-saving and environment-friendly rectification method and a rectification system for preparing methanol by using coal, wherein the rectification method is based on coupling of a six-tower three-effect rectification device and a low-temperature methanol washing device, so that kettle liquid of the low-temperature methanol washing device is used for washing noncondensable gas of the rectification device, namely raw material crude methanol flows into the rectification device consisting of a pre-tower, a pre-tower noncondensable gas washing tower, a pressurizing tower, an atmospheric tower, a vacuum tower and a vacuum recovery tower, and kettle liquid of the vacuum tower and the vacuum recovery tower are connected into the low-temperature methanol washing device to serve as washing and supplementing liquid. The invention has the advantages that the methanol rectifying device is coupled with the low-temperature methanol washing system, the methanol rectifying system realizes zero discharge of wastewater and zero desalted water supplement, the whole device reduces 13t/h of wastewater discharge and 13t/h of desalted water consumption.
Description
Technical Field
The invention relates to the technical field of crude methanol rectification, in particular to an energy-saving and environment-friendly rectification method and a rectification system for preparing methanol from coal.
Background
The crude methanol rectification is a conventional process method for obtaining a high-purity methanol product at present, and a traditional three-tower methanol rectification process is generally adopted, namely, the crude methanol sequentially passes through a pre-tower, a pressurizing tower and a normal pressure tower 3-tower single-effect rectification process.
The low-temperature methanol washing process is to absorb the acid gas in the mixed gas by using methanol, and then separate the methanol from the acid gas by decompression desorption, gas stripping and heating, thereby achieving the purposes of purifying the mixed gas and recycling the methanol.
The tail gas of the low-temperature methanol washing process contains a trace amount of methanol, and the tail gas is directly discharged into the atmosphere to pollute the environment and cause the loss of methanol solution, and in order to meet the environmental emission standard, the low-temperature methanol washing process adopts a tail gas washing process, namely, the tail gas is absorbed by desalted water, the waste water after washing contains about 5000ppm of methanol, and the waste water is directly sent to a sewage treatment device for treatment and is discharged after being qualified; meanwhile, the temperature of the low-temperature methanol washing tail gas is about 17 ℃, and the temperature of washing water after washing is about 20 ℃, so that the low-temperature methanol washing tail gas has a certain influence on a sewage treatment device (the low water temperature is not beneficial to the bacterial growth of a sewage treatment A/O pool).
At present, the sewage treatment device and the desalted water are fully loaded, and the rectified wastewater and the low-temperature methanol washing tail gas washing tower wastewater are directly discharged to the sewage treatment device, so that the water consumption of the system is increased and the water resource is wasted; the water content of the crude methanol is about 3.5% (wt), the refined methanol production capacity is 49 tons/hour (1180 tons/day), the water content is about 3t/h, the methanol rectification needs to be extracted by adding desalted water from a pre-tower reflux tank (the water content is 15-20% wt after water supplementing), and the water content is about 5t/h; the water is a component in the methanol rectification process, and is finally discharged at the tower bottom of the normal pressure tower, the waste water amount is about 8t/h, the main component of the waste water is 99.9 percent of water, and the alcohol content is 500-1000ppm; therefore, the usage amount of desalted water is greatly required to be reduced, the discharge capacity of the sewage is reduced, and the current situation that the operation difficulty of the sewage device is high is relieved.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides an energy-saving and environment-friendly rectification method and a rectification system for preparing methanol from coal, which are an environment-friendly and energy-saving process system for realizing the quality recycling of wastewater of the device, reducing desalted water of the system and reducing the emission of sewage by coupling a six-tower three-effect rectification device with a low-temperature methanol washing device.
The invention is realized by the following technical scheme: in one aspect, the rectification method for preparing methanol from energy-saving and environment-friendly coal is based on the coupling of a six-tower three-effect rectification device and a low-temperature methanol washing device, so that kettle liquid of the low-temperature methanol washing device is used for washing noncondensable gas of the rectification device, namely raw material crude methanol flows into the rectification device consisting of a pre-tower, a pre-tower noncondensable gas washing tower, a pressurizing tower, an atmospheric tower, a vacuum tower and a vacuum recovery tower, and kettle liquid of the vacuum tower and the vacuum recovery tower is connected into the low-temperature methanol washing device to serve as washing fluid.
Through the technical scheme, the methanol rectification system is coupled with the low-temperature methanol washing system, the methanol rectification system realizes zero discharge of wastewater and zero desalted water supplement, the whole device reduces 13t/h of wastewater discharge, 13t/h of desalted water consumption, 3 yuan/t of wastewater direct treatment cost, 5.9 yuan of desalted water direct production cost/, and 92.56 ten thousands yuan of annual direct economic benefit calculated according to 8000 h; meanwhile, after the 32 pre-tower noncondensable gas absorption tower adopts cold water at 20 ℃ in the tower kettle of the 29 low-temperature methanol tail gas washing tower, the equipment investment of a spray water cooler of the 32 pre-tower noncondensable gas absorption tower is reduced, and meanwhile, better cooling effect is achieved compared with the cooling by adopting a spray water cooler.
Further, the kettle liquid of the pre-tower 6 is respectively conveyed to a pressurizing tower 11, an atmospheric tower 14 and a vacuum tower 17 to be used as feed materials; the operating pressures and temperatures of the pressurizing tower 11, the atmospheric tower 14 and the vacuum tower 17 are adjusted simultaneously, so that energy matching is formed among the three towers to form triple-effect rectification.
Through the technical scheme, the methanol rectifying system is coupled with the low-temperature methanol washing system and is used for recovering the methanol in the discharged air of the pre-tower of the methanol rectifying, and the discharged air of the pre-tower is 360Nm 3 (h) 17% methanol (mol%) 85kg methanol can be recovered per hour; the low-temperature methanol washing wastewater contains 5000ppm of methanol, and is recycled for 5m per hour 3 25kg of methanol can be recovered per hour, 110kg of methanol can be recovered per hour, and 880 tons of methanol can be recovered annually; the methanol is calculated according to 8000h in terms of tax value 2300 yuan/t and annual, and the annual direct economic benefit is 202.4 ten thousand yuan.
Specifically, crude methanol at 75-80 ℃ in the tower kettle of the pre-tower is preheated to 110-120 ℃ through condensate of a reboiler of the pressurizing tower, and the waste heat of the condensate of the pressurizing tower is recovered; the heat source of the pressurized tower kettle is provided by 0.5MPa steam, the using amount is about 35t-36t/h, methanol steam at the top of the pressurized tower is provided, 45% of the tower top steam is regulated and distributed to a pre-tower reboiler through a valve 36, and the other 55% of the tower top steam is sent to an atmospheric tower reboiler to be used as a heating source of the atmospheric tower reboiler; condensing the heated methanol vapor in the pre-tower and the normal pressure tower into a methanol liquid phase, taking a part of the methanol liquid phase as reflux, and controlling the reflux ratio to be 2.2; a part is taken after cooling as a product, and the taking-out proportion is 44% of the total load, about 22t/h. The pressure of the tower is controlled to be 0.65MPaG, the temperature of the top of the tower is 120 ℃, and the temperature of the tower bottom is 135 ℃. The methanol water solution in the tower bottom 20-25 is fed from the tower pressure to the normal pressure tower as the normal pressure tower.
The tower pressure of the atmospheric tower is controlled to 50KPaG, the reflux ratio is controlled to 2.0, methanol steam at the top 50KPaG of the atmospheric tower enters a tower kettle reboiler of the vacuum tower, the methanol is condensed into liquid after heating the vacuum tower, a part of the liquid is refluxed by a reflux pump, and a part of the liquid is extracted as a product, and the extraction is 26% of the total load, about 13t/h; the 60-65% methanol water solution in the tower kettle is pressurized by a kettle liquid pump and then is sent to a vacuum tower.
The tower pressure of the vacuum tower is controlled to be-60 KPaG, the reflux ratio is controlled to be 2.0, methanol steam at the top of the vacuum tower enters a circulating water cooler at the top of the vacuum tower, the methanol is condensed into liquid, a part of the liquid is refluxed by a reflux pump, and a part of the liquid is extracted as a product, and the extraction is 26% of the total load and is about 13t/h; the wastewater containing 500-1000ppm of methanol in the tower bottom is combined with the kettle liquid of the vacuum recovery tower, pressurized by a kettle liquid pump and then sent to the middle upper part of the low-temperature methanol washing C2207 to be used as washing water.
Further, the overhead methanol vapor of the pressurizing column 11 serves as a heating source for both the pre-column 6 and the atmospheric column 14.
Still further, 45% of the flow rate of the overhead methanol vapor of the pressurizing tower 11 is sent to the pre-tower reboiler two 8 of the pre-tower 6 as a heat source, and 55% of the flow rate of the overhead methanol vapor of the pressurizing tower 11 is sent to the atmospheric tower reboiler 13 of the atmospheric tower 14 as a heat source.
Through the technical scheme, if more than 45% of tower top steam is regulated and distributed to the pre-tower reboiler through the pre-tower kettle temperature regulating valve 36, the rest of methanol steam is sent to the normal pressure tower reboiler to be used as a heating source of the normal pressure tower reboiler. The pre-tower reflux ratio will be greater than the optimal reflux ratio, the pre-tower reflux ratio will increase, the methanol vapor input into the pre-tower reboiler will increase, the methanol vapor entering the atmospheric tower methanol reboiler will decrease, meaning that the atmospheric tower bottom heat source will decrease, the yield of methanol products will decrease, the interlocking will lead to a decrease in the vacuum tower bottom heat source, and a decrease in the yield of methanol products.
If less than 45% of the overhead vapor is distributed to the pre-tower reboiler by the pre-tower kettle temperature regulating valve 36, the rest of the methanol vapor is sent to the atmospheric tower reboiler to be used as a heating source of the atmospheric tower reboiler. The pre-tower reflux ratio will be less than the optimal reflux ratio, the pre-tower reflux ratio will be reduced, the methanol vapor input into the pre-tower reboiler is reduced, the oxidation time of the pre-tower is reduced, the light components can not be effectively separated, and along with the extension of time, the light component impurity components will accumulate in the methanol, so that the methanol rectification is failed.
The valve opening of the reboiler from the tower top steam to the pre-tower is effectively removed based on the pre-tower light components, the optimal reflux ratio of the pre-tower, the load of the normal pressure tower is improved, the load of the vacuum tower is indirectly improved, the productivity of methanol rectification is improved, and the energy consumption of unit products is reduced.
Further, the heat source of the tower bottom of the pressurizing tower 11 is provided with heat by 0.65MPaA steam, the pressurizing tower reboiler 12 changes the steam phase into condensate, the condensate enters the pressurizing tower feeding preheater 10 for preheating methanol entering the pressurizing tower 11, the condensate waste heat is used as the heat source of the vacuum recovery tower reboiler 25, and the condensate after heat exchange is sent to the condensate recovery system.
Through the technical scheme, the full utilization of heat of a rectification system is realized, meanwhile, the heat of methanol steam at the top of an atmospheric tower is fully utilized by adding a vacuum tower, the consumption of the pre-tower reduced steam is about 15t/h, the consumption of the methanol rectification steam is reduced from 50t/h to 35-36t/h, the rectification energy consumption is obviously reduced, the consumption of 0.5MPa steam of refined alcohol per ton is reduced from 1.05 ton to 0.71 ton, the consumption of the steam per hour is 16.66t, the consumption of 0.5MPa steam is calculated according to 8000h in 120 yuan for each hour, and the annual direct economic benefit is 1599.36 ten thousand yuan;
further, the overhead vapors of the vacuum column 17 and the vacuum recovery column 24 are condensed by an overhead circulating water cooler.
Further, the low-temperature methanol washing device comprises a low-temperature methanol washing tail gas washing tower 29; the bottoms of the vacuum tower 17 and the vacuum recovery tower 24 are combined and sent to the low-temperature methanol-washing tail gas washing tower 29 to be used as spray water of the low-temperature methanol-washing tail gas washing tower 29.
The rectification system comprises a six-tower three-effect rectification device and a low-temperature methanol washing device;
the rectifying device comprises a pre-tower 6, a pre-tower noncondensable gas washing tower 32, a pressurizing tower 11, an atmospheric tower 14, a vacuum tower 17 and a vacuum recovery tower 24 which are connected in sequence; wherein, the atmospheric tower reboiler 13 is communicated with the top of the pressurizing tower 11, and heat is supplied by the top steam of the pressurizing tower 11; the vacuum tower reboiler 16 is communicated with the top of the atmospheric tower 14, supplies heat by the top steam of the atmospheric tower 14, and forms three-effect rectification by three towers of the pressurizing tower 11, the atmospheric tower 14 and the vacuum tower 17;
the pre-tower 6 is provided with a pre-tower reboiler I7 and a pre-tower reboiler II 8, the pre-tower reboiler I7 is communicated with a heating steam pipeline, the pre-tower reboiler II 8 is communicated with the top of the pressurizing tower 11, and heat is supplied by the top steam of the pressurizing tower 11;
the tower top pipeline of the pre-tower 6 is connected with the air inlet end of the pre-tower noncondensable gas washing tower 32, the liquid inlet end of the pre-tower noncondensable gas washing tower 32 is connected with the low-temperature methanol washing device through a pipeline, and the liquid outlet end of the pre-tower noncondensable gas washing tower 32 is communicated with the reflux tank of the pre-tower 6; the second pre-tower reboiler 8 and the normal pressure tower reboiler 13 are communicated with a reflux pipeline of the pressurizing tower 11 together, and a production pipeline is arranged on the reflux pipeline of the pressurizing tower 11; the top of vacuum tower 17 with vacuum recovery tower 24 all is connected with the circulating water cooler, vacuum recovery tower reboiler 25 and pressurization tower reboiler 12 output intercommunication, vacuum tower 17 lateral line is adopted and is inserted vacuum recovery tower 24, the condensate line of vacuum recovery tower 24 inserts condensate recovery system, vacuum tower 17 with the bottom of vacuum recovery tower 24 is adopted the pipeline and is connected with low temperature methanol washing device.
Further, the operating pressure range of the pre-tower 6 is 0.106 MPaA+/-0.005 MPa, and the reflux amount is 60% of the feed flow; the operating pressure range of the pressurizing tower 11 is 0.76 MPaA+/-0.01 MPa, and the reflux ratio is controlled to be 2.18; the operating pressure range of the atmospheric tower 14 is 0.15 MPaA.+ -. 0.005MPa, and the reflux ratio is 2.0; the operating pressure range of the vacuum column 17 is 0.04 MPaA.+ -. 0.005MPa, and the reflux ratio is 2.0; the operating pressure range of the vacuum recovery column 24 was 0.04 MPaA.+ -. 0.005MPa, and the reflux ratio was 2.33.
Through the technical scheme, the methanol rectification system is coupled with the low-temperature methanol washing system, the methanol rectification system realizes zero discharge of wastewater and zero desalted water supplement, the whole device reduces 13t/h of wastewater discharge and 13t/h of desalted water consumption; meanwhile, after the 32 pre-tower noncondensable gas absorption tower adopts cold water at 20 ℃ in the tower kettle of the 29 low-temperature methanol tail gas washing tower, the equipment investment of a spray water cooler of the 32 pre-tower noncondensable gas absorption tower is reduced, and better cooling effect is achieved compared with the cooling by adopting a spray water cooler; meanwhile, the methanol in the low-temperature methanol washing tail gas washing tower can be effectively recovered. The heat of the rectifying system is fully utilized, the heat of the methanol steam at the top of the atmospheric tower is fully utilized by the vacuum tower, the methanol self-pressure of 0.4-0.5MPaA synthesized by methanol is directly adopted as the feeding material of the methanol rectification, and the electric energy is saved.
Further, 3t/h of the heavy component containing 50% of the heteroalcohol of the methanol is extracted from the side line of the vacuum tower and sent to the vacuum recovery tower.
According to the technical scheme, 3t/h of the side line of the methanol rectification atmospheric tower before transformation is carried out, 50% of mixed alcohol containing methanol is taken as dangerous waste to be sent to a boiler for blended combustion, and the methanol loss is 1.5t/h; the empty noncondensable gas at the top of the pre-tower contains 2t/d of methanol, the methanol is not recovered, the yield of the methanol is about 96.7%, the methanol is recovered after transformation, the yield is improved to more than 99.9%, and the method has good economic benefit and environmental protection benefit. The methanol self-pressure of 0.4-0.5MPaA synthesized by methanol is directly adopted as the feeding of methanol rectification, a crude methanol feeding pump 4 is omitted, the electric energy is saved by 17.5kWh, and the electricity consumption is saved by 140000kWh.
The invention has the beneficial effects that:
(1) The methanol rectification system is coupled with the low-temperature methanol washing system, the methanol rectification system realizes zero discharge of wastewater and zero desalted water supplement, the whole device reduces 13t/h of wastewater discharge, 13t/h of desalted water consumption, 3 yuan/t of wastewater direct treatment cost, 5.9 yuan of desalted water direct production cost and 92.56 ten thousand yuan of annual direct economic benefit calculated according to 8000 h; meanwhile, after the cold water at 20 ℃ of the tower bottom of the 29 low-temperature methanol tail gas washing tower is adopted in the 32 pre-tower noncondensable gas washing tower, the equipment investment of a spray water cooler of the 32 pre-tower noncondensable gas washing tower is reduced, and meanwhile, better cooling effect is achieved compared with the cooling by adopting a spray water cooler.
(2) The methanol rectification system is coupled with the low-temperature methanol washing system and is used for recovering methanol in the discharged air of a pre-tower of the methanol rectification, and the discharged air of the pre-tower is 360Nm 3 Per hour, 17 mol% methanol is contained, and the reaction time per hour can be recovered85kg of methanol is collected; the low-temperature methanol washing wastewater contains 5000ppm of methanol, and is recycled for 5m per hour 3 25kg of methanol can be recovered per hour, 110kg of methanol can be recovered per hour, and 880 tons of methanol can be recovered annually; the methanol is calculated according to 8000h in terms of tax value 2300 yuan/t and annual, and the annual direct economic benefit is 202.4 ten thousand yuan.
(3) The heat of the rectification system is fully utilized, the heat of the methanol steam at the top of the atmospheric tower is fully utilized by the vacuum tower, the consumption of the methanol rectification steam is reduced by about 15t/h from 50t/h to 35-36t/h, the rectification energy consumption is obviously reduced, the consumption of 0.5MPa steam for each ton of refined alcohol is reduced to 0.71 ton from 1.05 ton, 16.66t steam is saved per hour, the 0.5MPa steam is calculated according to 8000h in 120-yuan for each year, and the annual direct economic benefit is 1599.36 ten thousand yuan.
(4) Before transformation, 3t/h of the side line of the methanol rectifying atmospheric tower contains 50% of mixed alcohol of methanol as dangerous waste and is sent to a boiler for blending combustion, and the methanol loss is 1.5t/h; the empty noncondensable gas at the top of the pre-tower contains 2t/d of methanol, the methanol is not recovered, the yield of the methanol is about 96.7%, the methanol is recovered after transformation, the yield is improved to more than 99.9%, and the method has good economic benefit and environmental protection benefit.
(5) The methanol self-pressure of 0.4-0.5MPaA synthesized by methanol is directly adopted as the feeding of methanol rectification, a 4-coarse methanol feeding pump is omitted, the electric energy is saved by 17.5kWh, and the electricity consumption is saved by 140000kWh.
Drawings
FIG. 1 is a schematic diagram of the structure of the present invention;
fig. 2 is a schematic diagram of a methanol rectification system embodying the present invention.
1. A vacuum pump; 2. a crude methanol intermediate tank; 3. a vacuum pump inlet buffer tank; 4. a crude methanol feed pump; 5. a crude methanol feed preheater; 6. pre-tower; 7. pre-tower reboiler I; 8. a pre-tower reboiler II; 9. pre-tower kettle liquid pump; 10. a pressurization tower feeding preheater; 11. a pressurizing tower; 12. a pressurized column reboiler; 13. a reboiler of the atmospheric tower; 14. an atmospheric tower; 15. a liquid pump at the bottom of the atmospheric tower; 16. a vacuum column reboiler; 17. a vacuum tower; 18. a vacuum tower condenser; 19. a vacuum tower reflux drum; 20. a vacuum tower reflux pump; 21. a reflux drum of the atmospheric tower; 22. a reflux pump of the atmospheric tower; 23. a vacuum tower kettle liquid pump; 24. a vacuum recovery tower; 25. a vacuum recovery column reboiler; 26. a vacuum recovery column condenser; 27. a reflux groove of the vacuum recovery tower; 28. a vacuum recovery tower reflux pump; 29. a low-temperature methanol washing tail gas washing tower; 30. spray water coolers; 31. a liquid pump of a low-temperature methanol washing tail gas washing tower kettle; 32. a pre-tower noncondensable gas washing tower; 33. a pre-tower secondary condenser; 34. a pre-tower reflux tank; 35. a pre-tower reflux pump; 36. a pre-tower kettle temperature regulating valve; 37. a vacuum recovery tower pressure regulating valve; 38. a vacuum tower pressure regulating valve; 39. a vacuum recovery tower bottom liquid control valve; 40. a low-temperature methanol washing tail gas washing tower kettle liquid control valve; 41. a spray water control valve at the top of the low-temperature methanol washing tail gas washing tower; 42. spray water flow regulating valve of pre-tower noncondensable gas recovery tower; 43. a reflux drum of the atmospheric tower; 44. a crude methanol tundish feed valve; 45. a raw methanol feed valve is synthesized; 46. a crude methanol tank discharge valve; 47. a fusel cooler; 48. a fusel storage tank; 49. a vacuum recovery tower feed pump; 50. a tower bottom liquid valve of the pressurizing tower; 51. feeding the pre-tower into an atmospheric tower valve; 52. feeding the pre-tower into a vacuum tower valve; 53. a tower bottom liquid valve of the atmospheric tower; 54. a pressurized tower feed valve; 55. a refined methanol cooler; 56. a reflux pump of the atmospheric tower; 57. a rectifying wastewater cooler; 58. a methanol synthesis flash tank; 59. a low-temperature methanol washing and desalting water valve; 60. a rectifying waste water cooler.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
The rectification method for preparing methanol from energy-saving environment-friendly coal is based on the coupling of a six-tower three-effect rectification device and a low-temperature methanol washing device, and ensures that kettle liquid of the low-temperature methanol washing device is used for washing noncondensable gas of the rectification device, as shown in figures 1 and 2; the crude methanol as raw material flows into a rectifying device consisting of a pre-tower 6, a pre-tower noncondensable gas washing tower 32, a pressurizing tower 11, an atmospheric tower 14, a vacuum tower 17 and a vacuum recovery tower 24, and kettle liquid of the vacuum tower 17 and the vacuum recovery tower 24 is connected into a low-temperature methanol washing device to be used as washing liquid supplement; wherein the low-temperature methanol washing device comprises a low-temperature methanol washing tail gas washing tower 29, a spray water cooler 30 and a low-temperature methanol washing and water-removing salt water valve 59.
Raw material crude methanol provided by a methanol synthesis system or a crude methanol intermediate tank 2 enters from the middle part of a methanol rectifying pre-tower 6, and after the top non-condensable gas of the pre-tower 6 is used for washing the methanol by a pre-tower non-condensable gas washing tower 32, the methanol in the gas phase is less than 1000ppm, and the gas phase is sent to a VOCS treatment system; the absorbed methanol water solution is used as extraction water for a reflux tank of a pre-tower 6; the wash water from the pre-tower noncondensable gas wash tower 32 is provided by the bottoms from the low temperature methanol wash tail gas wash tower 29.
The kettle liquid of the pre-tower 6 is respectively sent to a pressurizing tower 11, an atmospheric tower 14 and a vacuum tower 17 through a pressurizing tower feeding preheater 10, and methanol steam at the top of the pressurizing tower 11 is respectively sent to a pre-tower reboiler II 8 and an atmospheric tower reboiler 13 as heating sources of the pre-tower reboiler II 8 and the atmospheric tower reboiler 13; the second pre-tower reboiler 8 is heated and then condensed into methanol liquid, the methanol liquid enters the pressurizing tower reflux tank 43, is mixed with the methanol liquid from the normal pressure tower reboiler 13, is pressurized by the pressurizing tower reflux pump 56 and is used as tower reflux liquid, and part of the methanol liquid is cooled by the methanol cooler 55 and is sent out as refined methanol product.
The heat source of the tower bottom of the pressurizing tower 11 is provided with heat by 0.65MPaA steam, the steam phase of the steam is changed into condensate through the pressurizing tower reboiler 12, the condensate enters the pressurizing tower feeding preheater 10 for preheating the methanol entering the pressurizing tower 11 to about 110 ℃, the condensate waste heat is used as the heat source of the vacuum recovery tower reboiler 25, and the condensate after heat exchange is sent to a condensate recovery system.
The bottom liquid of the pressurizing tower 11 is conveyed to the atmospheric tower 14 as a feeding material through self-pressure, methanol steam at the top of the atmospheric tower 14 is used as a heat source of a vacuum tower reboiler 16, heat is provided for a vacuum tower 17, then the liquid phase is condensed into a liquid phase, and the liquid phase enters an atmospheric tower reflux tank 21, and the liquid phase is pressurized by a constant-pressure tower reflux pump 22 and then flows back to the atmospheric tower 14.
The kettle liquid of the atmospheric tower 14 is conveyed to a vacuum tower 17 by a constant-pressure tower kettle liquid pump 15, and methanol at the top of the vacuum tower 17 enters a vacuum tower reflux tank 19 after being cooled by a vacuum tower condenser 18 and is refluxed to the vacuum tower 17 by a vacuum tower reflux pump 20.
Fusel oil is extracted from the side line of the vacuum tower 17, cooled by a fusel oil cooler 47, enters a fusel storage tank 48, pressurized by a vacuum recovery tower feed pump 49 and enters the vacuum recovery tower 24. The methanol vapor at the top of the vacuum recovery tower 24 enters a vacuum recovery tower reflux tank 27 after being condensed by a vacuum recovery tower condenser 26, and is refluxed to the vacuum recovery tower by a vacuum recovery tower reflux pump 28.
The liquid level of the tower kettle of the vacuum recovery tower 24 is regulated by a vacuum recovery tower kettle liquid control valve 39, and then is combined with the kettle liquid of the vacuum tower 17, and is sent to a low-temperature methanol washing tail gas washing tower 29 through a vacuum tower kettle liquid pump 23, and is used as spray water of the low-temperature methanol washing tail gas washing tower 29.
The methanol rectification wastewater of the vacuum tower kettle liquid pump 23 is cooled by a rectification wastewater cooler 60 and then is cooled by a spray water cooler 30 to be used as spray water at the middle upper part of the low-temperature methanol washing tail gas washing tower 29; after being pressurized by a low-temperature methanol washing tail gas washing tower kettle liquid pump 31, one part of the washing water after being absorbed is used after the flow rate is regulated by a pre-tower noncondensable gas recovery tower spray water regulating valve 42, and the other part of the washing water is used as the top spray water of the low-temperature methanol washing tail gas washing tower 29 after the flow rate is regulated by a low-temperature methanol washing tail gas washing tower top spray water control valve 41; the liquid level of the tower bottom of the low-temperature methanol washing tail gas washing tower 29 is regulated by a low-temperature methanol washing tail gas washing tower bottom liquid control valve 40. When the methanol rectification is not running, the top spray water of the low-temperature methanol washing tail gas washing tower 29 is provided by desalted water through a low-temperature methanol washing desalted water valve 59, and tower kettle water is directly sent to sewage treatment and is not sent to a rectification system.
The noncondensable gas of the vacuum tower 17 is separated by the buffer tank 3 at the inlet of the vacuum pump, the vacuum pump 1 is used for vacuumizing, and the vacuum pump is used for exhausting gas and then enters the pre-tower noncondensable gas washing tower 32 for recycling methanol. The top pressure of the vacuum column 17 is controlled by a vacuum column pressure regulating valve 38; the vacuum recovery column 24 overhead pressure is controlled by a vacuum recovery column pressure regulating valve 37. Wherein, the pre-tower inlet normal pressure tower valve 51 and the pre-tower inlet vacuum tower valve 52 are used when the liquid level of the normal pressure tower 14 and the vacuum tower 17 is established in the driving stage; the first pre-tower reboiler 7 is used when steam is added during starting.
On the basis of the technical scheme, the operating pressure range of the pre-tower 6 is 0.106 MPaA+/-0.005 MPa, and the reflux quantity is 60% of the feeding flow; the operating pressure range of the pressurizing tower 11 is 0.76 MPaA.+ -. 0.01MPa, and the reflux ratio is controlled to 2.18; the operating pressure range of the atmospheric tower 14 is 0.15 MPaA.+ -. 0.005MPa, and the reflux ratio is 2.0; the operating pressure range of the vacuum column 17 was 0.04 MPaA.+ -. 0.005MPa, and the reflux ratio was 2.0; the operating pressure range of the vacuum recovery column 24 was 0.04 MPaA.+ -. 0.005MPa, and the reflux ratio was 2.33.
The rectification system comprises a six-tower three-effect rectification device and a low-temperature methanol washing device;
as shown in fig. 1 and 2, the six-tower three-effect rectification device comprises a pre-tower 6, a pre-tower noncondensable gas washing tower 32, a pressurizing tower 11, an atmospheric tower 14, a vacuum tower 17 and a vacuum recovery tower 24 which are connected in sequence; wherein, the atmospheric tower reboiler 13 is communicated with the top of the pressurizing tower 11, and heat is supplied by the top steam of the pressurizing tower 11; the vacuum tower reboiler 16 is communicated with the top of the atmospheric tower 14, supplies heat by the top steam of the atmospheric tower 14, and forms three-effect rectification by three towers of the pressurizing tower 11, the atmospheric tower 14 and the vacuum tower 17;
the low-temperature methanol washing device comprises a low-temperature methanol washing tail gas washing tower 29, a spray water cooler 30, a low-temperature methanol washing tail gas washing tower kettle liquid pump 31, a pre-tower noncondensable gas recovery tower spray water regulating valve 42, a low-temperature methanol washing tail gas washing tower top spray water control valve 41, a low-temperature methanol washing tail gas washing tower kettle liquid control valve 40 and a low-temperature methanol washing and water-removing salt water valve 59. Wherein, the atmospheric tower reboiler 13 is communicated with the top of the pressurizing tower 11, and heat is supplied by the top steam of the pressurizing tower 11; the vacuum tower reboiler 16 is communicated with the top of the atmospheric tower 14, heat is supplied by the top steam of the atmospheric tower 14, and the operating pressure and temperature of the pressurizing tower 11, the atmospheric tower 14 and the vacuum tower 17 are adjusted, so that energy matching is formed among the three towers, and three-effect rectification is formed.
The pre-tower 6 is provided with a pre-tower reboiler I7 and a pre-tower reboiler II 8, the pre-tower reboiler I7 is communicated with a heating steam pipeline, the pre-tower reboiler II 8 is communicated with the top of the pressurizing tower 11, and heat is supplied by the top steam of the pressurizing tower 11;
the tower top pipeline of the pre-tower 6 is connected with the air inlet end of the pre-tower noncondensable gas washing tower 32, the liquid inlet end of the pre-tower noncondensable gas washing tower 32 is connected with the low-temperature methanol washing device through a pipeline, and the liquid outlet end of the pre-tower noncondensable gas washing tower 32 is communicated with the reflux groove of the pre-tower 6; the pre-tower reboiler II 8 and the normal pressure tower reboiler 13 are communicated with a reflux pipeline of the pressurizing tower 11 together, and a recovery pipeline is arranged on the reflux pipeline of the pressurizing tower 11; the tops of the vacuum tower 17 and the vacuum recovery tower 24 are both connected with a circulating water cooler, a vacuum recovery tower reboiler 25 is communicated with the output end of the pressurizing tower reboiler 12, the side line of the vacuum tower 17 is extracted and connected into the vacuum recovery tower 24, the condensate pipeline of the vacuum recovery tower 24 is connected into a condensate recovery system, and the bottom extraction pipelines of the vacuum tower 17 and the vacuum recovery tower 24 are connected with a low-temperature methanol washing device.
As shown in fig. 1, the methanol synthesis system includes a methanol synthesis flash tank 58; during normal production, 0.5-0.6MPa crude methanol from the methanol synthesis flash tank 58 enters the pre-tower 6 after being regulated by a synthesis crude methanol feed valve 45; when the process production is abnormal, the crude methanol of 0.5-0.6MPa synthesized by the methanol enters the crude methanol intermediate tank 2 through the crude methanol intermediate tank feed valve 44, is pressurized by the crude methanol feed pump 4, is regulated by the crude methanol intermediate tank discharge valve 46, and enters the pre-tower 6 after being preheated to 60-64 ℃ by the crude methanol feed preheater 5.
The pre-tower 6 is provided with a pre-tower reboiler I7 and a pre-tower reboiler II 8; the heat source of the tower bottom of the pre-tower 6 is provided with heat by 0.5MPaA steam, the steam phase of the pre-tower reboiler 7 is changed into condensate, the crude methanol of 75-80 ℃ of the tower bottom of the pre-tower 6 is preheated to 110-120 ℃ by the condensate of the pressurizing tower reboiler 12, and the condensate is recovered; the methanol steam at the top of the pre-tower 6 is used for preheating the methanol of the crude methanol feed preheater 5 and then cooling the most of the methanol into liquid, a small amount of uncooled methanol is cooled to 40 ℃ by the pre-tower secondary cooler 33, enters the pre-tower reflux tank 34, is pressurized by the pre-tower reflux pump 35 and then is totally refluxed, the noncondensable gas of the pre-tower reflux tank 34 is used for washing the methanol by the pre-tower noncondensable gas washing tower 32, the reflux quantity is controlled to be 0.6 (31.5 t/h) of the feeding quantity, the noncondensable gas at the top of the tower is reversely contacted with water of 5t/h from the low-temperature methanol washing C2207 tower kettle, the water is used for washing the methanol in the empty noncondensable gas phase, the methanol in the gas phase is less than 1000ppm, the absorbed aqueous solution of the methanol is used as extraction water supplement of the pre-tower reflux tank 34, and the 5t/h washing water is provided by kettle liquid of the low-temperature methanol washing tower 29 at about 20 ℃. The methanol in the pre-tower 6 is added and regulated by extraction water, the methanol content in the tower kettle is 15-20 wt percent, and the methanol is conveyed to a pressurizing tower 11 through a pre-tower kettle liquid pump 9 to be used as the pressurizing tower for feeding, and the tower pressure of the pre-tower is controlled to be about 7 kpa.
Pressurizing the pre-tower 6 kettle liquid by a pre-tower kettle liquid pump 9, delivering the pressurized tower 11, controlling the flow of methanol steam at the top of the pressurized tower 11 to enter a pre-tower reboiler II 8 by a pre-tower kettle temperature regulating valve 36, taking the methanol steam as a heating source of the pre-tower 6 kettle, condensing the heated methanol steam into methanol liquid, entering a pressurizing tower reflux tank 43, mixing the methanol liquid with the methanol liquid from an atmospheric tower reboiler 13, pressurizing the mixture by a pressurizing tower reflux pump 56, taking the mixture as tower reflux liquid, and controlling the reflux ratio to be 2.2; part of the methanol is cooled by a methanol cooler 55 and sent as a refined methanol product, and the extraction ratio is 44% of the total load, about 22t/h. The heat source of the tower kettle of the pressurizing tower 11 is provided with heat by 0.65MPaA steam, the usage amount is about 35t-36t/h, the steam phase of the pressurizing tower reboiler 12 is changed into condensate, the condensate enters the pressurizing tower feeding preheater 10 to preheat the methanol entering the pressurizing tower 11 to about 110 ℃, the pressurizing tower pressure is controlled to be 0.65MPaG, the tower top temperature is 120 ℃, the tower bottom temperature is 135 ℃, the condensate waste heat is used as the heat source of the vacuum recovery tower reboiler 25, and the condensate after heat exchange is sent to a condensate recovery system.
The 20-25% methanol aqueous solution of the kettle liquid of the pressurizing tower 11 is conveyed to the normal pressure tower 14 as a feed through self-pressure, the pressure of the normal pressure tower is controlled to 50KPaG, the reflux ratio is controlled to 2.0, the top of the normal pressure tower is controlled to 50KPaG, the methanol steam at the top of the normal pressure tower 14 is used as a heat source of the vacuum tower reboiler 16, after providing heat for the vacuum tower 17, the condensed liquid phase enters the normal pressure tower reflux tank 21, and the normal pressure tower reflux pump 22 pressurizes and then returns to the normal pressure tower 14.
60-65% methanol aqueous solution of kettle liquid of the atmospheric tower 14 is conveyed to a vacuum tower 17 through an atmospheric tower kettle liquid pump 15, the tower pressure of the vacuum tower 17 is controlled to be-60 KPaG, the reflux ratio is controlled to be 2.0, and methanol vapor at the tower top of the vacuum tower 17 enters a circulating water cooler at the tower top of the vacuum tower; namely, the methanol at the top of the vacuum tower 17 enters a vacuum tower reflux groove 19 after being cooled by a vacuum tower condenser 18, and is refluxed to the vacuum tower 17 by a vacuum tower reflux pump 20. 3t/h of mixed alcohol heavy component containing 50% of methanol is extracted from the side line of the vacuum tower 17, and the extraction is 26% of the total load, about 13t/h; cooled by a fusel oil cooler 47, enters a fusel tank 48, is pressurized by a vacuum recovery tower feed pump 49, and enters the vacuum recovery tower 24. The methanol vapor at the top of the vacuum recovery tower 24 enters a vacuum recovery tower reflux tank 27 after being condensed by a vacuum recovery tower condenser 26, and is refluxed to the vacuum recovery tower by a vacuum recovery tower reflux pump 28. The liquid level of the tower bottom of the vacuum recovery tower 24 is regulated by a vacuum recovery tower bottom liquid control valve 39, and then is combined with waste water containing 500-1000ppm of methanol in the tower bottom liquid of the vacuum tower 17, and is sent to a low-temperature methanol washing tail gas washing tower 29 by a vacuum tower bottom liquid pump 23, and is used as spray water of the low-temperature methanol washing tail gas washing tower 29. Wherein the vacuum of the vacuum column 17 and the vacuum recovery column 24 is provided by a crude methanol ejector into the crude methanol intermediate tank 2.
The methanol rectification wastewater of the vacuum tower kettle liquid pump 23 is cooled by a rectification wastewater cooler 60 and then is cooled by a spray water cooler 30 to be used as spray water at the middle upper part of the low-temperature methanol washing tail gas washing tower 29; after being pressurized by a low-temperature methanol washing tail gas washing tower kettle liquid pump 31, one part of the washing water after being absorbed is used after the flow rate is regulated by a pre-tower noncondensable gas recovery tower spray water regulating valve 42, and the other part of the washing water is used as the top spray water of the low-temperature methanol washing tail gas washing tower 29 after the flow rate is regulated by a low-temperature methanol washing tail gas washing tower top spray water control valve 41; the liquid level of the tower bottom of the low-temperature methanol washing tail gas washing tower 29 is regulated by a low-temperature methanol washing tail gas washing tower bottom liquid control valve 40. When the methanol rectification is not running, the top spray water of the low-temperature methanol washing tail gas washing tower 29 is provided by desalted water through a low-temperature methanol washing desalted water valve 59, and tower kettle water is directly sent to sewage treatment and is not sent to a rectification system.
The noncondensable gas of the vacuum tower 17 is separated by the buffer tank 3 at the inlet of the vacuum pump, the vacuum pump 1 is used for vacuumizing, and the vacuum pump is used for exhausting gas and then enters the pre-tower noncondensable gas washing tower 32 for recycling methanol. The top pressure of the vacuum column 17 is controlled by a vacuum column pressure regulating valve 38; the vacuum recovery column 24 overhead pressure is controlled by a vacuum recovery column pressure regulating valve 37. The pre-tower inlet normal pressure tower valve 51 and the pre-tower inlet vacuum tower valve 52 are used for establishing liquid levels of the normal pressure tower 14 and the vacuum tower 17 in the driving stage.
Comparative example 1
The wastewater from methanol rectification is mainly methanol and water, but has trace components which are not detected. In addition to water and methanol, the crude methanol contains 23 detectable impurities of ethanol, isobutanol, threitol, 3-hexanol, methyl butyrate, 2-methyl butanol, 2-methyl 3-pentanol, 3-hexanone, 2-hexanol, hydrogen, methane, argon, carbon dioxide, n-heptane, n-pentanol, n-butanol, n-heptanol, 3-heptanol, n-hexanol, 3-hexanol, 2-methyl-3-pentanol, 2-methyl-1-pentanol, 2-methyl hexanol by gas chromatography-mass spectrometry. If an atmospheric rectification process is adopted, water of a low-temperature methanol washing tail gas washing tower is combined to be used as methanol rectification extraction water supplementing circulation, after the coupling is adopted according to water balance calculation, the waste water amount discharged from the outside of the low-temperature methanol washing tail gas washing tower is about 1-3t/h, compared with 8t/h of water discharged before the coupling, the water discharge is obviously reduced, along with accumulation of operation time, the micro components are continuously accumulated in a rectifying system tower kettle, finally, the methanol rectified product is unqualified, and in order to ensure the qualification of the methanol product of a methanol rectification system, desalted water of 3-5t/h is needed to be supplemented from the methanol rectification, the water discharge of the low-temperature methanol washing tail gas washing tower is increased, so that the stability of micro impurities in the methanol rectifying tower kettle is maintained, and the qualification of the methanol rectification product is ensured. After coupling, the problems of large wastewater discharge and large desalted water supplementing amount are not effectively solved, and the coupling mode cannot bring good energy-saving and environment-friendly effects, and meanwhile, a certain risk exists to cause the device to stop.
Effect analysis
The bubble point of the mixture can be reduced by the reduced pressure rectification, so that the separation temperature is reduced, the condensation reaction of methanol at the high temperature of the tower kettle, the hydrolysis reaction of esters and the like are reduced, and the generation of trace impurities of heavy components at the tower kettle is reduced. Particularly, for the methanol rectification with a long process of 5 towers or 6 towers, the process is prolonged, the high-temperature residence time is longer, the negative pressure rectification is adopted, the temperature of the tower kettle is reduced, the condensation reaction, the hydrolysis reaction of esters and the like of the methanol in the tower kettle at the residence time at the high temperature are reduced, and the impurities in the heavy components in the tower kettle are reduced. The lower the pressure, the greater the relative volatility between the separated mixtures and the easier the separation. By rectification under reduced pressure, the relative volatilities between the components will increase, the more readily the components will separate. The reduced pressure rectification is beneficial to separating micro-heavy components dissolved in water, improves the separation efficiency of rectification impurity components, and reduces micro-components contained in the wastewater at the tower bottom.
Firstly, the existing methanol rectification wastewater discharge tower adopts a vacuum separation mode, thereby reducing the separation temperature, reducing the condensation reaction of methanol at the high temperature of the tower kettle, the hydrolysis reaction of esters and the like, and reducing the generation of trace impurities of heavy components at the tower kettle;
secondly, through vacuum rectification, the relative volatility among the components is increased, and the components are easier to separate. Through vacuum rectification, the relative volatility of water and impurity components is increased, the separation of water and micro-components is facilitated, the separation efficiency of the rectified impurity components is improved, the impurity components are maintained at controllable content, the impurity components enter a vacuum recovery tower from a side line along with fusel oil for further rectification, and the micro-components contained in waste water in the tower bottom of the vacuum tower are reduced.
The separation effect is improved, the side reaction is inhibited by cooling, the waste water discharge amount of 2-3t/h can meet the balance of rectification impurity components, and the product quality of methanol rectification is ensured. For the separation of toxic substances, the vacuum rectification can prevent the leakage of materials, reduce the pollution to the environment and has a certain meaning in the aspect of protecting the health of human bodies.
Finally, it should be noted that: the foregoing description is only illustrative of the preferred embodiments of the present invention, and although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the embodiments described, or equivalents may be substituted for elements thereof, and any modifications, equivalents, improvements or changes may be made without departing from the spirit and principles of the present invention.
Claims (10)
1. The rectification method is characterized in that a rectification device based on six-tower three-effect is coupled with a low-temperature methanol washing device, so that kettle liquid of the low-temperature methanol washing device is used for washing noncondensable gas of the rectification device, namely raw material crude methanol flows into the rectification device consisting of a pre-tower (6), a pre-tower noncondensable gas washing tower (32), a pressurizing tower (11), an atmospheric tower (14), a vacuum tower (17) and a vacuum recovery tower (24), and kettle liquid of the vacuum tower (17) and the vacuum recovery tower (24) is connected into the low-temperature methanol washing device to serve as washing complementary liquid of the pre-tower noncondensable gas washing tower (32).
2. The energy-saving and environment-friendly coal-to-methanol rectification method according to claim 1, wherein kettle liquid of the pre-tower (6) is respectively conveyed to a pressurizing tower (11), an atmospheric tower (14) and a vacuum tower (17) as feed materials; and simultaneously, the operating pressure and the operating temperature of the pressurizing tower (11), the normal pressure tower (14) and the vacuum tower (17) are adjusted to form energy matching among the three towers so as to form triple-effect rectification.
3. The energy-saving and environment-friendly coal-to-methanol rectification method as claimed in claim 1, wherein the top methanol vapor of the pressurizing tower (11) is used as a heating source of the pre-tower (6) and the normal pressure tower (14) at the same time.
4. The energy-saving and environment-friendly coal-based methanol rectification method as claimed in claim 3, wherein 45% of the flow rate of the methanol vapor at the top of the pressurizing tower (11) is conveyed to a pre-tower reboiler two (8) of the pre-tower (6) as a heat source, and 55% of the flow rate of the methanol vapor at the top of the pressurizing tower (11) is conveyed to an atmospheric tower reboiler (13) of the atmospheric tower (14) as a heat source.
5. The energy-saving and environment-friendly coal-to-methanol rectification method according to claim 1, wherein heat is provided by 0.65MPaA steam from a tower kettle heat source of the pressurizing tower (11), the steam is converted into condensate by a pressurizing tower reboiler (12), the condensate enters a pressurizing tower feeding preheater (10) for preheating methanol entering the pressurizing tower (11), condensate waste heat is used as a heat source of a vacuum recovery tower reboiler (25), and the condensate after heat exchange is sent to a condensate recovery system.
6. The energy-saving and environment-friendly coal-to-methanol rectification method as claimed in claim 1, wherein the top vapors of the vacuum tower (17) and the vacuum recovery tower (24) are condensed by a top circulating water cooler.
7. The energy-saving and environment-friendly coal-to-methanol rectification method as claimed in claim 1, wherein the low-temperature methanol washing device comprises a low-temperature methanol washing tail gas washing tower (29); and the kettle liquid of the vacuum tower (17) and the kettle liquid of the vacuum recovery tower (24) are combined and sent to the low-temperature methanol washing tail gas washing tower (29) to be used as spray water of the low-temperature methanol washing tail gas washing tower (29).
8. An energy-saving and environment-friendly molded coal methanol rectification system, which is characterized by comprising a six-tower three-effect rectification device and a low-temperature methanol washing device based on the energy-saving and environment-friendly molded coal methanol rectification method as claimed in any one of claims 1 to 7;
the rectifying device comprises a pre-tower (6), a pre-tower noncondensable gas washing tower (32), a pressurizing tower (11), an atmospheric tower (14), a vacuum tower (17) and a vacuum recovery tower (24) which are connected in sequence; wherein, the atmospheric tower reboiler (13) is communicated with the top of the pressurizing tower (11), and heat is supplied by the top steam of the pressurizing tower (11); the vacuum tower reboiler (16) is communicated with the tower top of the normal pressure tower (14), heat is supplied by the tower top steam of the normal pressure tower (14), and three towers of the pressurizing tower (11), the normal pressure tower (14) and the vacuum tower (17) form three-effect rectification;
the pre-tower (6) is provided with a pre-tower reboiler I (7) and a pre-tower reboiler II (8), the pre-tower reboiler I (7) is communicated with a heating steam pipeline, the pre-tower reboiler II (8) is communicated with the top of the pressurizing tower (11), and heat is supplied by the top steam of the pressurizing tower (11);
the tower top pipeline of the pre-tower (6) is connected with the air inlet end of the pre-tower noncondensable gas washing tower (32), the liquid inlet end of the pre-tower noncondensable gas washing tower (32) is connected with the low-temperature methanol washing device through a pipeline, and the liquid outlet end of the pre-tower noncondensable gas washing tower (32) is communicated with the reflux tank of the pre-tower (6); the pre-tower reboiler II (8) and the normal pressure tower reboiler (13) are communicated with a reflux pipeline of the pressurizing tower (11), and a recovery pipeline is arranged on the reflux pipeline of the pressurizing tower (11); the top of vacuum tower (17) with vacuum recovery tower (24) all is connected with circulating water cooler, vacuum recovery tower reboiler (25) and pressurization tower reboiler (12) output intercommunication, vacuum tower (17) lateral line is adopted and is inserted vacuum recovery tower (24), the condensate line of vacuum recovery tower (24) is connected into condensate recovery system, vacuum tower (17) with the bottom of vacuum recovery tower (24) is adopted the pipeline and is connected with low temperature methanol washing device.
9. The energy-saving and environment-friendly coal-to-methanol rectification system according to claim 8, wherein the operation pressure range of the pre-tower (6) is 0.106MPa plus or minus 0.005MPa, and the reflux amount is 60% of the feed flow; the operating pressure range of the pressurizing tower (11) is 0.76MPaA plus or minus 0.01MPa, and the reflux ratio is controlled to be 2.18; the operating pressure range of the atmospheric tower (14) is 0.15 MPaA+/-0.005 MPa, and the reflux ratio is 2.0; the operating pressure range of the vacuum tower (17) is 0.04MPaA plus or minus 0.005MPa, and the reflux ratio is 2.0; the operating pressure range of the vacuum recovery column (24) was 0.04 MPaA.+ -. 0.005MPa, and the reflux ratio was 2.33.
10. The energy-saving and environment-friendly coal-to-methanol rectifying system according to claim 8, wherein 3t/h of the heavy component containing 50% of the hetero alcohol is extracted from the side line of the vacuum tower and is sent to the vacuum recovery tower.
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| CN202410029725.7A Pending CN117861253A (en) | 2024-01-08 | 2024-01-08 | Energy-saving and environment-friendly rectification method and rectification system for preparing methanol from coal |
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