Energy-saving and environment-friendly coal-to-methanol rectification method and rectification system

Abstract

The present application relates to a kind of energy-saving and environment-friendly coal methanol rectification method and rectification system, the rectification method is based on the rectification device of three effects of six towers and low temperature methanol washing device coupling, the kettle liquid of low temperature methanol washing device is used to wash the non-condensable gas of the rectification device, i.e. raw material crude methanol is flowed into the rectification device consisting of pre-column, pre-column non-condensable gas washing tower, pressurized tower, atmospheric tower, vacuum tower, vacuum recovery tower, so that the kettle liquid of vacuum tower and vacuum recovery tower is connected to the low temperature methanol washing device as washing supplement liquid.The present application has the advantages that methanol rectification device is coupled with low temperature methanol washing system, methanol rectification system realizes zero discharge of waste water, zero desalination water supplement, the whole device reduces waste water discharge by 13t / h, reduces desalination water consumption by 13t / h.

Description

Technical Field

[0001] This invention relates to the field of crude methanol distillation technology, and in particular to an energy-saving and environmentally friendly coal-to-methanol distillation method and distillation system. Background Technology

[0002] Crude methanol distillation is a conventional process for obtaining high-purity methanol products. It usually adopts the traditional three-tower methanol distillation process, in which crude methanol is sequentially passed through a pre-tower, a pressurized tower, and an atmospheric tower for single-effect distillation.

[0003] The low-temperature methanol washing process involves absorbing acidic gases from a mixed gas with methanol, followed by depressurization desorption, gas stripping, and heating to separate the methanol from the acidic gases, thereby purifying the mixed gas and recovering methanol.

[0004] The tail gas from the low-temperature methanol washing process contains trace amounts of methanol. Direct discharge into the atmosphere not only pollutes the environment but also results in the loss of methanol solution. To meet environmental emission standards, the low-temperature methanol washing process adopts a tail gas washing process, which uses demineralized water to absorb the methanol in the tail gas. After washing, the wastewater contains about 5000 ppm of methanol and is directly sent to the sewage treatment plant for treatment before being discharged. At the same time, since the tail gas temperature of the low-temperature methanol washing is about 17°C and the washing water temperature is about 20°C, the low temperature has a certain impact on the sewage treatment plant (low water temperature is not conducive to the growth of bacteria in the A / O tank of the sewage treatment plant).

[0005] Currently, the wastewater treatment unit and demineralized water usage are already at full capacity. Wastewater from distillation and wastewater from the low-temperature methanol washing tail gas scrubbing tower are directly discharged to the wastewater treatment unit, resulting in increased system water consumption and waste of water resources. The crude methanol has a water content of about 3.5% (wt). Based on a refined methanol production rate of 49 tons / hour (1180 tons / day), the water content is about 3 t / h. Methanol distillation requires the addition of demineralized water from the pre-column reflux tank for extraction (after water replenishment, the water content is 15-20% wt), resulting in a water content of about 5 t / h. Water is a heavy component in the methanol distillation process and is finally discharged from the bottom of the atmospheric distillation tower, resulting in a wastewater volume of about 8 t / h. The main component of the wastewater is 99.9% water, with an alcohol content of 500-1000 ppm. Therefore, it is urgent to reduce the amount of demineralized water used and the amount of wastewater discharged to alleviate the current operational difficulties of the wastewater treatment unit. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide an energy-saving and environmentally friendly coal-to-methanol distillation method and distillation system. The system couples a six-tower, three-effect distillation unit with a low-temperature methanol washing unit to achieve wastewater recycling, desalination reduction, and wastewater discharge reduction, making it an environmentally friendly and energy-saving process system.

[0007] This invention is achieved through the following technical solution: On the one hand, an energy-saving and environmentally friendly coal-to-methanol distillation method is provided. This distillation method is based on the coupling of a six-tower, three-effect distillation unit with a low-temperature methanol washing unit. The bottom liquid of the low-temperature methanol washing unit is used to wash the non-condensable gas of the distillation unit. Specifically, the raw crude methanol flows into the distillation unit, which consists of a pre-tower, a pre-tower non-condensable gas washing tower, a pressurized tower, an atmospheric tower, a vacuum tower, and a vacuum recovery tower. The bottom liquid of the vacuum tower and the vacuum recovery tower is connected to the low-temperature methanol washing unit as washing replenishment liquid.

[0008] Through the above technical solution, the methanol distillation system is coupled with the low-temperature methanol washing system. The methanol distillation system achieves zero wastewater discharge and zero demineralized water replenishment. The entire unit reduces wastewater discharge by 13t / h and demineralized water consumption by 13t / h. The direct wastewater treatment cost is 3 yuan / t, and the direct production cost of demineralized water is 5.9 yuan / t. Based on 8000h per year, the annual direct economic benefit is 925,600 yuan. At the same time, after the 32 pre-tower non-condensable gas absorption tower adopts the 20℃ cold water from the bottom of the 29 low-temperature methanol tail gas washing tower, the equipment investment of the spray water cooler for the 32 pre-tower non-condensable gas absorption tower is reduced, and the cooling effect is better than that of the spray water cooler.

[0009] Furthermore, the liquid in the pre-column 6 is fed to the pressurized column 11, the atmospheric column 14, and the vacuum column 17 as feed; at the same time, the operating pressure and temperature of the pressurized column 11, the atmospheric column 14, and the vacuum column 17 are adjusted to achieve energy matching between the three columns, so as to form a triple-effect distillation.

[0010] Through the above technical solution, the methanol distillation system is coupled with the low-temperature methanol washing system to recover methanol from the vent air in the methanol distillation pre-distillation tower. The vent air in the pre-distillation tower is 360 Nm³. 3 / h, containing 17% (mol%) methanol, 85kg of methanol can be recovered per hour; low-temperature methanol washing wastewater contains 5000ppm methanol, 5m³ / h can be recovered. 3 It can recover 25 kg of methanol per hour, with a total recovery of 110 kg of methanol per hour and 880 tons of methanol recovered per year. Based on a price of 2,300 yuan / ton including tax and 8,000 hours per year, the direct economic benefit is 2.024 million yuan per year.

[0011] Specifically, the crude methanol at 75-80℃ in the pre-pressurization tower bottom is preheated to 110-120℃ by the condensate in the pressurization tower reboiler, recovering the waste heat of the pressurization tower condensate. The heat source for the pressurization tower bottom is provided by 0.5MPa steam, with a usage of approximately 35-36t / h. Methanol vapor from the top of the pressurization tower is also provided; 45% of the top vapor is distributed to the pre-pressurization tower reboiler via valve 36, and the remaining 55% is sent to the atmospheric reboiler as a heat source for the atmospheric reboiler. The methanol vapor heated in the pre-pressurization and atmospheric reboilers is condensed into liquid methanol; a portion is used as reflux (reflux ratio controlled at 2.2), and a portion is collected after product cooling, accounting for 44% of the total load, approximately 22t / h. The pressurization tower pressure is controlled at 0.65MPaG, the top temperature at 120℃, and the bottom temperature at 135℃. The methanol-water solution at 20-25℃ in the bottom of the pressurization tower is pressurized by the tower pressure and fed to the atmospheric reboiler as feed.

[0012] The atmospheric pressure column is controlled at 50 kPaG, and the reflux ratio is controlled at 2.0. The methanol vapor at 50 kPaG at the top of the atmospheric pressure column enters the reboiler of the vacuum column. After heating the vacuum column, the methanol condenses into liquid. Part of it is refluxed by the reflux pump, and part of it is collected as product. The collected product accounts for 26% of the total load, about 13 t / h. The 60-65% methanol aqueous solution in the column bottom is pressurized by the bottom liquid pump and sent to the vacuum column.

[0013] The vacuum tower pressure is controlled at -60 kPaG, and the reflux ratio is controlled at 2.0. The methanol vapor at the top of the vacuum tower enters the circulating water cooler at the top of the vacuum tower, where the methanol condenses into liquid. Part of the liquid is refluxed by the reflux pump, and part is collected as product, accounting for 26% of the total load, approximately 13 t / h. The wastewater containing 500-1000 ppm methanol in the bottom of the tower is combined with the bottom liquid of the vacuum recovery tower and then pressurized by the bottom liquid pump before being sent to the upper part of the low-temperature methanol washing C2207 for use as washing water.

[0014] Furthermore, the methanol vapor at the top of the pressurized tower 11 also serves as a heating source for the pre-tower 6 and the atmospheric tower 14.

[0015] Furthermore, 45% of the flow rate of methanol vapor from the top of the pressurized tower 11 is fed to the pre-tower reboiler 8 of the pre-tower 6 as a heat source, and 55% of the flow rate of methanol vapor from the top of the pressurized tower 11 is fed to the atmospheric reboiler 13 of the atmospheric tower 14 as a heat source.

[0016] With the above technical solution, if the pre-tower reboiler is regulated by the pre-tower temperature regulating valve 36 to distribute more than 45% of the top steam to the pre-tower reboiler, and the remaining methanol steam is sent to the atmospheric reboiler as a heat source, the pre-tower reflux ratio will be greater than the optimal reflux ratio. This increase in the pre-tower reflux ratio leads to an increase in the methanol steam fed into the pre-tower reboiler, which in turn reduces the amount of methanol steam entering the atmospheric reboiler. This means a decrease in the heat source for the atmospheric reboiler, resulting in a reduction in methanol production. This interlocking effect leads to a further reduction in the heat source for the vacuum reboiler, further decreasing methanol production.

[0017] If less than 45% of the top steam is distributed to the pre-reboiler via the pre-reboiler temperature regulating valve 36, and the remaining methanol steam is sent to the atmospheric reboiler as a heat source, the pre-refluxing ratio will be lower than the optimal reflux ratio. This will reduce the amount of methanol steam fed into the pre-reboiler, decreasing the oxidation time and preventing effective separation of light components. Over time, these light impurities will accumulate in the methanol, leading to substandard methanol distillation.

[0018] The valve opening for 45% of the overhead steam to the pre-column reboiler is based on the effective removal of light components in the pre-column. The optimal reflux ratio of the pre-column increases the load of the atmospheric column, indirectly increases the load of the vacuum column, increases the production capacity of methanol distillation, and reduces the energy consumption per unit product.

[0019] Furthermore, the heat source of the pressurized tower 11 is provided by 0.65 MPaA steam. The pressurized tower reboiler 12 converts the steam into condensate. The condensate enters the pressurized tower feed preheater 10 to preheat the methanol entering the pressurized tower 11. The residual heat of the condensate serves as the heat source for the vacuum recovery tower reboiler 25. The condensate after heat exchange is sent to the condensate recovery system.

[0020] Through the above technical solutions, the heat of the distillation system is fully utilized. At the same time, the addition of a vacuum tower fully utilizes the heat of methanol vapor at the top of the atmospheric distillation tower. The pre-tower reduces steam consumption by about 15 t / h, and the steam consumption for methanol distillation is reduced from 50 t / h to 35-36 t / h. The distillation energy consumption is significantly reduced. The 0.5MPa steam consumption per ton of refined methanol is reduced from 1.05 tons to 0.71 tons, saving 16.66 tons of steam per hour. Based on a cost of 120 yuan per ton of 0.5MPa steam and 8000 hours of operation per year, the direct economic benefit is 15.9936 million yuan per year.

[0021] Furthermore, the top vapors of both the vacuum tower 17 and the vacuum recovery tower 24 are condensed by a top circulating water cooler.

[0022] Furthermore, the low-temperature methanol washing device includes a low-temperature methanol washing tail gas scrubbing tower 29; the bottom liquids of the vacuum tower 17 and the vacuum recovery tower 24 are combined and sent to the low-temperature methanol washing tail gas scrubbing tower 29 as spray water for the low-temperature methanol washing tail gas scrubbing tower 29.

[0023] Another energy-saving and environmentally friendly coal-to-methanol distillation system is provided. Based on the above-mentioned energy-saving and environmentally friendly coal-to-methanol distillation method, the distillation system includes a six-tower, three-effect distillation unit and a low-temperature methanol washing unit.

[0024] The distillation apparatus includes a pre-column 6, a pre-column non-condensable gas scrubbing column 32, a pressurized column 11, an atmospheric column 14, a vacuum column 17, and a vacuum recovery column 24 connected in sequence. The atmospheric column reboiler 13 is connected to the top of the pressurized column 11 and is heated by the steam from the top of the pressurized column 11. The vacuum column reboiler 16 is connected to the top of the atmospheric column 14 and is heated by the steam from the top of the atmospheric column 14. The pressurized column 11, the atmospheric column 14, and the vacuum column 17 constitute a triple-effect distillation system.

[0025] The pre-tower 6 has a first pre-tower reboiler 7 and a second pre-tower reboiler 8. The first pre-tower reboiler 7 is connected to a heating steam pipeline, and the second pre-tower reboiler 8 is connected to the top of the pressurized tower 11 and is heated by the top steam of the pressurized tower 11.

[0026] The top pipeline of the pre-tower 6 is connected to the inlet of the pre-tower non-condensable gas scrubbing tower 32. The liquid inlet of the pre-tower non-condensable gas scrubbing tower 32 is connected to the low-temperature methanol washing device via a pipeline. The liquid outlet of the pre-tower non-condensable gas scrubbing tower 32 is connected to the reflux tank of the pre-tower 6. The pre-tower reboiler 8 and the atmospheric pressure tower reboiler 13 are connected to the reflux pipeline of the pressurized tower 11. The reflux pipeline of the pressurized tower 11 is provided with a collection pipeline. The top of the vacuum tower 17 and the vacuum recovery tower 24 are both connected to a circulating water cooler. The vacuum recovery tower reboiler 25 is connected to the output end of the pressurized tower reboiler 12. The side line of the vacuum tower 17 is collected and connected to the vacuum recovery tower 24. The condensate pipeline of the vacuum recovery tower 24 is connected to the condensate recovery system. The bottom collection pipelines of the vacuum tower 17 and the vacuum recovery tower 24 are connected to the low-temperature methanol washing device.

[0027] Furthermore, the operating pressure range of the pre-tower 6 is 0.106 MPa ± 0.005 MPa, and the reflux rate is 60% of the feed rate; the operating pressure range of the pressurization tower 11 is 0.76 MPa ± 0.01 MPa, and the reflux ratio is controlled at 2.18; the operating pressure range of the atmospheric pressure tower 14 is 0.15 MPa ± 0.005 MPa, and the reflux ratio is 2.0; the operating pressure range of the vacuum tower 17 is 0.04 MPa ± 0.005 MPa, and the reflux ratio is 2.0; the operating pressure range of the vacuum recovery tower 24 is 0.04 MPa ± 0.005 MPa, and the reflux ratio is 2.33.

[0028] Through the above technical solution, the methanol distillation system is coupled with the low-temperature methanol washing system. The methanol distillation system achieves zero wastewater discharge and zero demineralized water replenishment, reducing wastewater discharge and demineralized water consumption by 13 t / h. Simultaneously, the 32 pre-tower non-condensable gas absorber uses 20°C cold water from the bottom of the 29 low-temperature methanol tail gas scrubbing tower, reducing the investment in a spray water cooler for the 32 pre-tower non-condensable gas absorber while achieving better cooling performance. Furthermore, it effectively recovers methanol from the low-temperature methanol washing tail gas scrubbing tower. This ensures full utilization of heat in the distillation system, while the addition of a vacuum tower fully utilizes the methanol vapor heat from the top of the atmospheric pressure tower. The feed for methanol distillation directly uses methanol synthesized at 0.4-0.5 MPaA pressure, saving energy.

[0029] Furthermore, the vacuum tower side stream extracts 3 t / h of fusel oil heavy components containing 50% methanol and sends it to the vacuum recovery tower.

[0030] Through the above technical solution, before the modification, 3 t / h of methanol-containing fusel oil from the atmospheric distillation tower side stream, containing 50% methanol, was sent to the boiler for co-firing as hazardous waste, resulting in a methanol loss of 1.5 t / h. The non-condensable gas vented from the top of the pre-distillation tower contained 2 t / d of methanol, which was not recovered, with a methanol recovery rate of approximately 96.7%. After the modification, all methanol was recovered, increasing the recovery rate to over 99.9%, demonstrating significant economic and environmental benefits. The methanol distillation feed directly uses methanol synthesized at 0.4-0.5 MPaA pressure, eliminating the need for crude methanol feed pump 4 and saving 17.5 kWh of electricity, resulting in an annual electricity saving of 140,000 kWh.

[0031] The beneficial effects of this invention are as follows:

[0032] (1) The methanol distillation system is coupled with the low-temperature methanol washing system. The methanol distillation system achieves zero wastewater discharge and zero demineralized water replenishment. The entire unit reduces wastewater discharge by 13t / h and demineralized water consumption by 13t / h. The direct wastewater treatment cost is 3 yuan / t, and the direct production cost of demineralized water is 5.9 yuan / t. Based on 8000h per year, the annual direct economic benefit is 925,600 yuan. At the same time, after the 32 pre-tower non-condensable gas scrubbing tower adopts the 29 low-temperature methanol tail gas scrubbing tower bottom water at 20℃, the equipment investment of the 32 pre-tower non-condensable gas scrubbing tower spray water cooler is reduced. At the same time, it achieves better cooling effect than using a spray water cooler.

[0033] (2) Coupling of the methanol distillation system with the low-temperature methanol washing system and methanol recovery from the vent air of the methanol distillation pre-distillation tower (360 Nm³). 3 / h, containing 17% (mol%) methanol, 85kg of methanol can be recovered per hour; low-temperature methanol washing wastewater contains 5000ppm methanol, 5m³ / h can be recovered. 3 It can recover 25 kg of methanol per hour, with a total recovery of 110 kg of methanol per hour and 880 tons of methanol recovered per year. Based on a price of 2,300 yuan / ton including tax and 8,000 hours per year, the direct economic benefit is 2.024 million yuan per year.

[0034] (3) The heat of the distillation system is fully utilized. At the same time, the addition of the vacuum tower fully utilizes the heat of methanol vapor at the top of the atmospheric tower. The steam consumption of the pre-tower is reduced by about 15t / h. The steam consumption of methanol distillation is reduced from 50t / h to 35-36t / h. The distillation energy consumption is significantly reduced. The steam consumption of 0.5MPa per ton of refined alcohol is reduced from 1.05 tons to 0.71 tons, saving 16.66t of steam per hour. Based on 0.5MPa steam at 120 yuan per ton and 8000h per year, the direct economic benefit is 15.9936 million yuan per year.

[0035] (4) Before the renovation, the side stream of the atmospheric distillation tower containing 3t / h of methanol and 50% fusel oil was sent to the boiler as hazardous waste for co-firing, resulting in a methanol loss of 1.5t / h; the non-condensable gas vented from the top of the pre-tower contained 2t / d of methanol, which was not recovered, and the methanol recovery rate was about 96.7%. After the renovation, all of it was recovered, and the recovery rate was increased to over 99.9%, which has good economic and environmental benefits.

[0036] (5) The feed for methanol distillation is directly supplied by methanol synthesized at 0.4-0.5 MPaA, eliminating the need for a crude methanol feed pump and saving 17.5 kWh of electricity, resulting in an annual electricity saving of 140,000 kWh. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the structure of the present invention;

[0038] Figure 2This is a schematic diagram illustrating the structure of the methanol distillation system of this invention.

[0039] 1. Vacuum pump; 2. Crude methanol intermediate tank; 3. Vacuum pump inlet buffer tank; 4. Crude methanol feed pump; 5. Crude methanol feed preheater; 6. Pre-tower; 7. Pre-tower reboiler one; 8. Pre-tower reboiler two; 9. Pre-tower bottom liquid pump; 10. Pressurized tower feed preheater; 11. Pressurized tower; 12. Pressurized tower reboiler; 13. Atmospheric tower reboiler; 14. Atmospheric tower; 15. Atmospheric tower bottom liquid pump; 16. Vacuum tower reboiler; 17. Vacuum tower; 18. Vacuum tower condenser; 19. 20. Empty tower reflux tank; 21. Vacuum tower reflux pump; 22. Atmospheric pressure tower reflux tank; 23. Atmospheric pressure tower reflux pump; 24. Vacuum tower bottom liquid pump; 25. Vacuum recovery tower; 26. Vacuum recovery tower reboiler; 27. Vacuum recovery tower condenser; 28. Vacuum recovery tower reflux tank; 29. ​​Vacuum recovery tower reflux pump; 30. Low-temperature methanol wash tail gas scrubbing tower; 31. Spray water cooler; 32. Low-temperature methanol wash tail gas scrubbing tower bottom liquid pump; 33. Pre-tower non-condensable gas scrubbing tower; 34. Pre-tower secondary cooler. 34. Condenser; 35. Pre-tower reflux tank; 36. Pre-tower reflux pump; 37. Pre-tower bottom temperature regulating valve; 38. Vacuum recovery tower pressure regulating valve; 39. Vacuum tower pressure regulating valve; 40. Vacuum recovery tower bottom liquid control valve; 41. Low-temperature methanol wash tail gas scrubbing tower bottom liquid control valve; 42. Low-temperature methanol wash tail gas scrubbing tower top spray water control valve; 43. Pre-tower non-condensable gas recovery tower spray water flow rate regulating valve; 44. Atmospheric pressure tower reflux tank; 45. Crude methanol intermediate tank feed valve; 46. Synthetic crude methanol 46. ​​Feed valve; 47. Crude methanol tank discharge valve; 48. Fusel cooler; 49. Fusel storage tank; 50. Vacuum recovery tower feed pump; 51. Pressurized tower bottom liquid valve; 52. Pre-tower inlet valve; 53. Atmospheric tower bottom liquid valve; 54. Pressurized tower feed valve; 55. Refined methanol cooler; 56. Atmospheric tower reflux pump; 57. Distillation wastewater cooler; 58. Methanol synthesis flash evaporator; 59. Low-temperature methanol wash and demineralized water valve; 60. Distillation wastewater cooler. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] Example 1

[0042] An energy-saving and environmentally friendly method for methanol distillation from coal, such as Figure 1 and Figure 2As shown, this distillation method is based on the coupling of a six-tower, three-effect distillation unit with a low-temperature methanol washing unit, so that the bottom liquid of the low-temperature methanol washing unit is used to wash the non-condensable gas of the distillation unit; that is, the raw crude methanol flows into the distillation unit consisting of a pre-tower 6, a pre-tower non-condensable gas washing tower 32, a pressurized tower 11, an atmospheric tower 14, a vacuum tower 17, and a vacuum recovery tower 24, so that the bottom liquid of the vacuum tower 17 and the vacuum recovery tower 24 is connected to the low-temperature methanol washing unit as washing makeup liquid; wherein the low-temperature methanol washing unit includes a low-temperature methanol washing tail gas washing tower 29, a spray water cooler 30, and a low-temperature methanol washing demineralized water valve 59.

[0043] The crude methanol feedstock provided by the methanol synthesis system or the crude methanol intermediate tank 2 enters from the middle of the methanol distillation pre-tower 6. The non-condensable gas at the top of the pre-tower 6 is washed with methanol by the pre-tower non-condensable gas scrubbing tower 32. The methanol content in the gas phase is <1000ppm and is sent to the VOCs treatment system. The methanol aqueous solution after absorption is used as the extraction makeup water for the reflux tank of the pre-tower 6. The washing water of the pre-tower non-condensable gas scrubbing tower 32 is provided by the bottom liquid of the low temperature methanol tail gas scrubbing tower 29.

[0044] The liquid from the pre-column 6 is fed to the pressurized tower 11, the atmospheric tower 14, and the vacuum tower 17 via the pressurized tower feed preheater 10. The methanol vapor from the top of the pressurized tower 11 is sent to the pre-column reboiler 8 and the atmospheric tower reboiler 13 as the heating source for the pre-column reboiler 8 and the atmospheric tower reboiler 13, respectively. After being heated, the methanol vapor in the pre-column reboiler 8 is condensed into liquid methanol, which enters the pressurized tower reflux tank 43. After mixing with the liquid methanol from the atmospheric tower reboiler 13, the mixture is pressurized by the pressurized tower reflux pump 56 and used as the tower reflux liquid. Part of the mixture is cooled by the methanol cooler 55 and sent out as refined methanol product.

[0045] The heat source of the pressurized tower 11 is provided by 0.65 MPaA steam. The steam phase changes into condensate after passing through the pressurized tower reboiler 12. The condensate enters the pressurized tower feed preheater 10 to preheat the methanol entering the pressurized tower 11 to about 110°C. The residual heat of the condensate is used as the heat source of the vacuum recovery tower reboiler 25. The condensate after heat exchange is sent to the condensate recovery system.

[0046] The liquid in the pressurized tower 11 is transported by its own pressure to the atmospheric tower 14 as feed. The methanol vapor at the top of the atmospheric tower 14 serves as the heat source for the vacuum tower reboiler 16. After providing heat to the vacuum tower 17, it is condensed into a liquid phase and enters the atmospheric tower reflux tank 21. After being pressurized by the atmospheric tower reflux pump 22, it is returned to the atmospheric tower 14.

[0047] The liquid in the bottom of the atmospheric column 14 is pumped to the vacuum column 17 by the atmospheric column bottom pump 15. The methanol at the top of the vacuum column 17 is cooled by the vacuum column condenser 18 and then enters the vacuum column reflux tank 19, and is returned to the vacuum column 17 by the vacuum column reflux pump 20.

[0048] Fusel oil is collected from the side stream of vacuum tower 17, cooled by fusel oil cooler 47, and then enters fusel oil storage tank 48. After being pressurized by vacuum recovery tower feed pump 49, it enters vacuum recovery tower 24. Methanol vapor at the top of vacuum recovery tower 24 is condensed by vacuum recovery tower condenser 26 and then enters vacuum recovery tower reflux tank 27. It is then returned to vacuum recovery tower by vacuum recovery tower reflux pump 28.

[0049] The liquid level in the bottom of the vacuum recovery tower 24 is adjusted by the vacuum recovery tower bottom liquid control valve 39 and then combined with the liquid in the bottom of the vacuum tower 17. The liquid is then pumped by the vacuum tower bottom liquid pump 23 to the low-temperature methanol washing tail gas scrubbing tower 29 as the spray water for the low-temperature methanol washing tail gas scrubbing tower 29.

[0050] The methanol distillation wastewater from the vacuum tower bottom pump 23 is cooled by the distillation wastewater cooler 60 and then by the spray water cooler 30 before being used as the upper and middle spray water for the low-temperature methanol wash tail gas scrubbing tower 29. The wash water after methanol absorption is pressurized by the low-temperature methanol wash tail gas scrubbing tower bottom pump 31. Part of this water is used after its flow rate is regulated by the pre-tower non-condensable gas recovery tower spray water regulating valve 42, and the other part is used as the top spray water for the low-temperature methanol wash tail gas scrubbing tower 29 after its flow rate is regulated by the low-temperature methanol wash tail gas scrubbing tower top spray water control valve 41. The bottom liquid level of the low-temperature methanol wash tail gas scrubbing tower 29 is regulated by the low-temperature methanol wash tail gas scrubbing tower bottom liquid control valve 40. When methanol distillation is not running, the top spray water for the low-temperature methanol wash tail gas scrubbing tower 29 is supplied by demineralized water through the low-temperature methanol wash demineralized water replenishment valve 59, and the bottom water is directly sent to wastewater treatment and is no longer sent to the distillation system.

[0051] The non-condensable gas from vacuum tower 17 is separated by vacuum pump inlet buffer tank 3, then evacuated by vacuum pump 1, and the exhaust gas from the vacuum pump enters the pre-tower non-condensable gas scrubbing tower 32 to recover methanol. The top pressure of vacuum tower 17 is controlled by vacuum tower pressure regulating valve 38; the top pressure of vacuum recovery tower 24 is controlled by vacuum recovery tower pressure regulating valve 37. The pre-tower inlet atmospheric pressure tower valve 51 and the pre-tower inlet vacuum tower valve 52 are used to establish liquid levels in atmospheric pressure tower 14 and vacuum tower 17 during the start-up phase; the pre-tower reboiler 7 is used when adding steam during start-up.

[0052] Based on the above technical solutions, the operating pressure range of the pre-tower 6 is 0.106MPa ± 0.005MPa, and the reflux rate is 60% of the feed rate; the operating pressure range of the pressurization tower 11 is 0.76MPa ± 0.01MPa, and the reflux ratio is controlled at 2.18; the operating pressure range of the atmospheric tower 14 is 0.15MPa ± 0.005MPa, and the reflux ratio is 2.0; the operating pressure range of the vacuum tower 17 is 0.04MPa ± 0.005MPa, and the reflux ratio is 2.0; the operating pressure range of the vacuum recovery tower 24 is 0.04MPa ± 0.005MPa, and the reflux ratio is 2.33.

[0053] An energy-saving and environmentally friendly coal-to-methanol distillation system, based on the above-mentioned energy-saving and environmentally friendly coal-to-methanol distillation method, the distillation system includes a six-tower, three-effect distillation unit and a low-temperature methanol washing unit;

[0054] like Figure 1 and Figure 2 As shown, the six-tower, three-effect distillation unit includes a pre-tower 6, a pre-tower non-condensable gas scrubbing tower 32, a pressurized tower 11, an atmospheric tower 14, a vacuum tower 17, and a vacuum recovery tower 24 connected in sequence. The atmospheric tower reboiler 13 is connected to the top of the pressurized tower 11 and is heated by the steam from the top of the pressurized tower 11. The vacuum tower reboiler 16 is connected to the top of the atmospheric tower 14 and is heated by the steam from the top of the atmospheric tower 14. The pressurized tower 11, the atmospheric tower 14, and the vacuum tower 17 constitute a three-effect distillation unit.

[0055] The low-temperature methanol washing unit includes a low-temperature methanol washing tail gas scrubbing tower 29, a spray water cooler 30, a low-temperature methanol washing tail gas scrubbing tower bottom liquid pump 31, a pre-tower non-condensable gas recovery tower spray water regulating valve 42, a low-temperature methanol washing tail gas scrubbing tower top spray water control valve 41, a low-temperature methanol washing tail gas scrubbing tower bottom liquid control valve 40, and a low-temperature methanol washing demineralized water replenishment valve 59. The atmospheric pressure tower reboiler 13 is connected to the top of the pressurized tower 11 and is heated by the steam from the top of the pressurized tower 11; the vacuum tower reboiler 16 is connected to the top of the atmospheric pressure tower 14 and is heated by the steam from the top of the atmospheric pressure tower 14. Simultaneously, the operating pressures and temperatures of the pressurized tower 11, atmospheric pressure tower 14, and vacuum tower 17 are adjusted to achieve energy matching among the three towers, thus forming a triple-effect distillation system.

[0056] The pre-tower 6 has a first pre-tower reboiler 7 and a second pre-tower reboiler 8. The first pre-tower reboiler 7 is connected to the heating steam pipeline, and the second pre-tower reboiler 8 is connected to the top of the pressurized tower 11 and is heated by the top steam of the pressurized tower 11.

[0057] The top pipeline of pre-tower 6 is connected to the inlet of pre-tower non-condensable gas scrubbing tower 32. The liquid inlet of pre-tower non-condensable gas scrubbing tower 32 is connected to the low-temperature methanol washing device via a pipeline. The liquid outlet of pre-tower non-condensable gas scrubbing tower 32 is connected to the reflux tank of pre-tower 6. Pre-tower reboiler 8 and atmospheric pressure tower reboiler 13 are connected to the reflux pipeline of pressurized tower 11. A collection pipeline is provided on the reflux pipeline of pressurized tower 11. The top of vacuum tower 17 and vacuum recovery tower 24 are both connected to circulating water coolers. Vacuum recovery tower reboiler 25 is connected to the output end of pressurized tower reboiler 12. The side line of vacuum tower 17 is collected and connected to vacuum recovery tower 24. The condensate pipeline of vacuum recovery tower 24 is connected to the condensate recovery system. The bottom collection pipelines of vacuum tower 17 and vacuum recovery tower 24 are connected to the low-temperature methanol washing device.

[0058] like Figure 1As shown, the methanol synthesis system includes a methanol synthesis flash tank 58. During normal production, crude methanol at 0.5-0.6 MPa from the methanol synthesis flash tank 58 enters the pre-tower 6 after being regulated by the crude methanol feed valve 45. When the process is abnormal, crude methanol at 0.5-0.6 MPa from the methanol synthesis enters the crude methanol intermediate tank 2 through the crude methanol intermediate tank feed valve 44. After being pressurized by the crude methanol feed pump 4 and simultaneously regulated by the crude methanol intermediate tank discharge valve 46, it is preheated to 60-64°C by the crude methanol feed preheater 5 before entering the pre-tower 6.

[0059] Pre-tower 6 has a pre-tower reboiler 1 (7) and a pre-tower reboiler 2 (8). The heat source for the bottom of pre-tower 6 is provided by 0.5 MPa A steam. The steam in pre-tower reboiler 1 (7) is converted into condensate. The crude methanol at 75-80°C in the bottom of pre-tower 6 is preheated to 110-120°C by the condensate in the pressurized reboiler 12, and the condensate is recovered. The methanol vapor at the top of pre-tower 6 is used to preheat the methanol in the crude methanol feed preheater 5, and most of it is cooled into liquid. A small amount of uncooled methanol is cooled to 40°C by the pre-tower secondary cooler 33 and enters the pre-tower reflux tank 34. It is then pumped by the pre-tower reflux pump 35. After compression, the non-condensable gas from the pre-tower reflux tank 34 is washed with methanol in the pre-tower non-condensable gas scrubbing tower 32. The reflux rate is controlled at 0.6 times the feed rate (31.5 t / h). The non-condensable gas at the top of the tower comes into counter-current contact with 5 t / h of water from the bottom of the low-temperature methanol washing tower C2207. The water washes the methanol in the vented non-condensable gas phase, and the methanol content in the gas phase is <1000 ppm. This water is then sent to the VOCs treatment system. The absorbed methanol-water solution is used as makeup water for extraction in the pre-tower reflux tank 34. The 5 t / h of washing water is provided by the bottom liquid of the low-temperature methanol washing tower 29 at around 20°C. The methanol in the pre-tower 6 is adjusted by adding extraction water, and the methanol content in the bottom of the tower is 15-20% wt. The methanol is then pumped to the pressurization tower 11 as feed for the pressurization tower via the pre-tower bottom liquid pump 9. The tower pressure of the pre-tower is controlled at around 7 kPa.

[0060] The liquid in the pre-tower 6 is pressurized by the pre-tower bottom liquid pump 9 and sent to the pressurized tower 11. The methanol vapor at the top of the pressurized tower 11 enters the pre-tower reboiler 8 at a flow rate controlled by the pre-tower bottom temperature regulating valve 36, with about 45% of the methanol vapor being used as a heating source for the bottom of the pre-tower 6. After heating, the methanol vapor condenses into liquid methanol and enters the pressurized tower reflux tank 43. It mixes with the liquid methanol from the atmospheric pressure tower reboiler 13 and is then pressurized by the pressurized tower reflux pump 56 to become the tower reflux liquid, with a reflux ratio controlled at 2.2. Part of it is cooled by the methanol cooler 55 and sent out as refined methanol product, with a recovery rate of 44% of the total load, approximately 22 t / h. The heat source for the bottom of the pressurized tower 11 is provided by 0.65MPaA steam, with a usage of about 35t-36t / h. The steam phase-change of the pressurized tower reboiler 12 is converted into condensate. The condensate enters the pressurized tower feed preheater 10 to preheat the methanol entering the pressurized tower 11 to about 110°C. The tower pressure is controlled at 0.65MPaG, the top temperature is 120°C, and the bottom temperature is 135°C. The residual heat of the condensate is used as the heat source for the vacuum recovery tower reboiler 25. The condensate after heat exchange is sent to the condensate recovery system.

[0061] The 20-25% methanol-water solution in the bottom liquid of the pressurized tower 11 is pumped to the atmospheric tower 14 as feed under its own pressure. The pressure of the atmospheric tower is controlled at 50 kPaG, the reflux ratio is controlled at 2.0, and the pressure at the top of the atmospheric tower is 50 kPaG. The methanol vapor at the top of the atmospheric tower 14 serves as the heat source for the vacuum tower reboiler 16. After providing heat to the vacuum tower 17, it condenses into a liquid phase and enters the atmospheric tower reflux tank 21. After being pressurized by the atmospheric tower reflux pump 22, it is refluxed back to the atmospheric tower 14.

[0062] The 60-65% methanol-water solution from the bottom liquid of atmospheric column 14 is pumped to vacuum column 17 by atmospheric column bottom liquid pump 15. Vacuum column 17 has a pressure controlled at -60 kPaG and a reflux ratio controlled at 2.0. Methanol vapor from the top of vacuum column 17 enters the vacuum column top circulating water cooler; that is, the methanol from the top of vacuum column 17 is cooled by vacuum column condenser 18 and then enters vacuum column reflux tank 19, and is refluxed back to vacuum column 17 by vacuum column reflux pump 20. A side stream from vacuum column 17 produces 3 t / h of fusel oil heavy components containing 50% methanol, representing 26% of the total load, approximately 13 t / h. After cooling by fusel oil cooler 47, it enters fusel oil storage tank 48, is pressurized by vacuum recovery column feed pump 49, and then enters vacuum recovery column 24. The methanol vapor from the top of vacuum recovery column 24 is condensed by vacuum recovery column condenser 26 and then enters vacuum recovery column reflux tank 27, and is refluxed back to vacuum recovery column by vacuum recovery column reflux pump 28. The liquid level in the bottom of vacuum recovery tower 24 is adjusted by vacuum recovery tower bottom liquid control valve 39, and then combined with the wastewater containing 500-1000 ppm methanol in the bottom liquid of vacuum tower 17. This wastewater is then pumped via vacuum tower bottom liquid pump 23 to low-temperature methanol washing tail gas scrubbing tower 29 as spray water for the low-temperature methanol washing tail gas scrubbing tower 29. The vacuum in vacuum tower 17 and vacuum recovery tower 24 is provided by the crude methanol ejector entering the crude methanol intermediate tank 2.

[0063] The methanol distillation wastewater from the vacuum tower bottom pump 23 is cooled by the distillation wastewater cooler 60 and then by the spray water cooler 30 before being used as the upper and middle spray water for the low-temperature methanol wash tail gas scrubbing tower 29. The wash water after methanol absorption is pressurized by the low-temperature methanol wash tail gas scrubbing tower bottom pump 31. Part of this water is used after its flow rate is regulated by the pre-tower non-condensable gas recovery tower spray water regulating valve 42, and the other part is used as the top spray water for the low-temperature methanol wash tail gas scrubbing tower 29 after its flow rate is regulated by the low-temperature methanol wash tail gas scrubbing tower top spray water control valve 41. The bottom liquid level of the low-temperature methanol wash tail gas scrubbing tower 29 is regulated by the low-temperature methanol wash tail gas scrubbing tower bottom liquid control valve 40. When methanol distillation is not running, the top spray water for the low-temperature methanol wash tail gas scrubbing tower 29 is supplied by demineralized water through the low-temperature methanol wash demineralized water replenishment valve 59, and the bottom water is directly sent to wastewater treatment and is no longer sent to the distillation system.

[0064] The non-condensable gas from vacuum tower 17 is separated by vacuum pump inlet buffer tank 3, then evacuated by vacuum pump 1, and the exhaust gas from the vacuum pump enters the pre-tower non-condensable gas scrubbing tower 32 to recover methanol. The top pressure of vacuum tower 17 is controlled by vacuum tower pressure regulating valve 38; the top pressure of vacuum recovery tower 24 is controlled by vacuum recovery tower pressure regulating valve 37. The pre-tower inlet atmospheric pressure tower valve 51 and the pre-tower inlet vacuum tower valve 52 are used to establish liquid levels in atmospheric pressure tower 14 and vacuum tower 17 during the start-up phase.

[0065] Comparative Example 1

[0066] The wastewater from methanol distillation mainly consists of methanol and water, but trace components remain undetected. Besides water and methanol, gas chromatography-mass spectrometry (GC-MS) analysis of the crude methanol revealed 23 detectable impurities, including ethanol, isobutanol, threitol, 3-hexanol, methyl butyrate, 2-methylbutanol, 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, and 2-methylhexanol. If an atmospheric distillation process is adopted, and the water from the low-temperature methanol wash tail gas scrubbing tower is used as makeup water for methanol distillation extraction and recycled, according to water balance calculations, the wastewater discharge from the low-temperature methanol wash tail gas scrubbing tower after this coupling is approximately 1-3 t / h, significantly lower than the 8 t / h discharge before coupling. However, with accumulated operating time, these trace components will continuously accumulate in the distillation system's bottom, ultimately causing the methanol product to be substandard. To ensure the quality of the methanol product from the methanol distillation system, it is necessary to supplement 3-5 t / h of demineralized water from the methanol distillation system and increase the drainage from the low-temperature methanol wash tail gas scrubbing tower to maintain the stability of trace impurities in the methanol distillation tower bottom and ensure the quality of the methanol product. After coupling, the problems of large wastewater discharge and large demineralized water makeup water are not effectively solved. This coupling method does not bring good energy-saving and environmental protection effects and also poses a certain risk of plant shutdown.

[0067] Effect Analysis

[0068] Vacuum distillation lowers the bubble point of a mixture, thereby reducing the separation temperature and decreasing condensation reactions of methanol and hydrolysis of esters at high temperatures in the distillation column, thus reducing the generation of trace impurities in heavy components in the distillation column. This is particularly beneficial for long-process methanol distillation systems using 5 or 6 columns, where the process length is increased and the high-temperature residence time is longer. Vacuum distillation lowers the distillation column temperature, reducing the condensation reactions of methanol and hydrolysis of esters at high temperatures, and thus reducing impurities in heavy components in the distillation column. Lower pressure results in higher relative volatility between the components being separated, making separation easier. Vacuum distillation increases the relative volatility between components, making them easier to separate. It also facilitates the separation of water-soluble trace heavy components, improving the separation efficiency of distillation impurities and reducing trace components in the distillation column wastewater.

[0069] First, the current methanol distillation wastewater discharge tower adopts a vacuum separation mode, thereby reducing the separation temperature, reducing the condensation reaction of methanol in the tower bottom at high temperature, the hydrolysis of esters and other reactions, and reducing the generation of trace impurities of heavy components in the tower bottom.

[0070] Secondly, vacuum distillation increases the relative volatility between components, making them easier to separate. Vacuum distillation increases the relative volatility of water and impurity components, facilitating the separation of water and trace heavy components, improving the separation efficiency of distillation impurity components, maintaining these impurity components at controllable levels, and allowing them to be further distilled from the side stream along with the fusel oil into the vacuum recovery tower, thus reducing the trace components in the vacuum tower bottom wastewater.

[0071] Due to the improved separation efficiency and the suppression of side reactions by cooling, a wastewater discharge rate of 2-3 t / h can meet the balance of impurity components in the distillation process, ensuring the product quality of methanol distillation. For the separation of toxic substances, vacuum distillation can prevent material leakage, reduce environmental pollution, and is significant in protecting human health.

[0072] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An energy-saving and environmentally friendly method for methanol distillation from coal, characterized in that, This distillation method is based on the coupling of a six-tower, three-effect distillation unit with a low-temperature methanol washing unit. The bottom liquid of the low-temperature methanol washing unit is used to wash the non-condensable gas of the distillation unit. Specifically, the raw crude methanol flows into the distillation unit consisting of a pre-tower (6), a pre-tower non-condensable gas washing tower (32), a pressurized tower (11), an atmospheric tower (14), a vacuum tower (17), and a vacuum recovery tower (24). The bottom liquid of the vacuum tower (17) and the vacuum recovery tower (24) is then fed into the low-temperature methanol washing unit as the washing liquid for the pre-tower non-condensable gas washing tower (32). 45% of the flow rate of methanol vapor at the top of the pressurized tower (11) is fed to the second pre-tower reboiler (8) of the pre-tower (6) as a heat source, and 55% of the flow rate of methanol vapor at the top of the pressurized tower (11) is fed to the atmospheric reboiler (13) of the atmospheric tower (14) as a heat source. The methanol vapor at the top of the atmospheric column (14) serves as the heat source for the vacuum column reboiler (16). After providing heat to the vacuum column (17), it condenses into a liquid phase and enters the atmospheric column reflux tank (21). After being pressurized by the atmospheric column reflux pump (22), it flows back to the atmospheric column (14). Fusel oil is drawn from the side stream of the vacuum tower (17), cooled by the fusel oil cooler (47), and then enters the fusel oil storage tank (48). After being pressurized by the vacuum recovery tower feed pump (49), it enters the vacuum recovery tower (24). The low-temperature methanol washing device includes a low-temperature methanol washing tail gas scrubbing tower (29); the bottom liquid of the vacuum tower (17) and the vacuum recovery tower (24) are combined and sent to the low-temperature methanol washing tail gas scrubbing tower (29) as the spray water of the low-temperature methanol washing tail gas scrubbing tower (29); The absorbed methanol aqueous solution is used as the extraction makeup water for the reflux tank of the pre-tower (6); the washing water of the pre-tower non-condensable gas scrubbing tower (32) is provided by the bottom liquid of the low temperature methanol tail gas scrubbing tower (29).

2. The energy-saving and environmentally friendly coal-to-methanol distillation method according to claim 1, characterized in that, The pre-coil liquid in the pre-coil tower (6) is fed to the pressurized tower (11), the atmospheric tower (14) and the vacuum tower (17) respectively; at the same time, the operating pressure and temperature of the pressurized tower (11), the atmospheric tower (14) and the vacuum tower (17) are adjusted to make energy matching between the three towers, so as to form a triple-effect distillation.

3. The energy-saving and environmentally friendly coal-to-methanol distillation method according to claim 1, characterized in that, The heat source of the pressurized tower (11) is provided by 0.65 MPaA steam. The pressurized tower reboiler (12) turns the steam into condensate. The condensate enters the pressurized tower feed preheater (10) to preheat the methanol entering the pressurized tower (11). The residual heat of the condensate is used as the heat source of the vacuum recovery tower reboiler (25). The condensate after heat exchange is sent to the condensate recovery system.

4. The energy-saving and environmentally friendly coal-to-methanol distillation method according to claim 1, characterized in that, The top vapor of both the vacuum tower (17) and the vacuum recovery tower (24) is condensed by the top circulating water cooler.

5. An energy-saving and environmentally friendly coal-to-methanol distillation system, characterized in that, Based on the energy-saving and environmentally friendly coal-to-methanol distillation method according to any one of claims 1-4, the distillation system includes a six-tower, three-effect distillation unit and a low-temperature methanol washing unit. The distillation apparatus includes a pre-column (6), a pre-column non-condensable gas scrubbing column (32), a pressurized column (11), an atmospheric column (14), a vacuum column (17), and a vacuum recovery column (24) connected in sequence. The atmospheric column reboiler (13) is connected to the top of the pressurized column (11) and is heated by the top steam of the pressurized column (11). The vacuum column reboiler (16) is connected to the top of the atmospheric column (14) and is heated by the top steam of the atmospheric column (14). The pressurized column (11), the atmospheric column (14), and the vacuum column (17) constitute a triple-effect distillation system. The pre-tower (6) has a first pre-tower reboiler (7) and a second pre-tower reboiler (8). The first pre-tower reboiler (7) is connected to a heating steam pipeline, and the second pre-tower reboiler (8) is connected to the top of the pressurized tower (11) and is heated by the top steam of the pressurized tower (11). The top pipeline of the pre-tower (6) is connected to the inlet of the pre-tower non-condensable gas scrubbing tower (32). The liquid inlet of the pre-tower non-condensable gas scrubbing tower (32) is connected to the low-temperature methanol washing device via a pipeline. The liquid outlet of the pre-tower non-condensable gas scrubbing tower (32) is connected to the reflux tank of the pre-tower (6). The pre-tower reboiler 2 (8) and the atmospheric pressure tower reboiler (13) are connected to the reflux pipeline of the pressurized tower (11). The reflux pipeline of the pressurized tower (11) is equipped with a product pipeline. The top of the vacuum tower (17) and the vacuum recovery tower (24) are both connected to a circulating water cooler. The reboiler (25) of the vacuum recovery tower is connected to the output end of the reboiler (12) of the pressurized tower. The side line of the vacuum tower (17) is connected to the vacuum recovery tower (24). The condensate pipeline of the vacuum recovery tower (24) is connected to the condensate recovery system. The bottom pipelines of the vacuum tower (17) and the vacuum recovery tower (24) are connected to the low-temperature methanol washing device.

6. The energy-saving and environmentally friendly coal-to-methanol distillation system according to claim 5, characterized in that, The operating pressure range of the pre-tower (6) is 0.106 MPa ± 0.005 MPa, and the reflux rate is 60% of the feed rate; the operating pressure range of the pressurization tower (11) is 0.76 MPa ± 0.01 MPa, and the reflux ratio is controlled at 2.18; the operating pressure range of the atmospheric tower (14) is 0.15 MPa ± 0.005 MPa, and the reflux ratio is 2.0; the operating pressure range of the vacuum tower (17) is 0.04 MPa ± 0.005 MPa, and the reflux ratio is 2.0; the operating pressure range of the vacuum recovery tower (24) is 0.04 MPa ± 0.005 MPa, and the reflux ratio is 2.

33.

7. The energy-saving and environmentally friendly coal-to-methanol distillation system according to claim 5, characterized in that, The vacuum tower side stream extracts 3 t / h of fusel oil heavy components containing 50% methanol, which is then sent to the vacuum recovery tower.

Images