Methanol three-tower triple-effect rectification energy-saving system

Abstract

The utility model provides a methanol three-tower triple-effect rectification energy-saving system, which belongs to the technical field of chemical production and comprises a pre-rectifying tower, a pressurizing tower and an atmospheric tower which are connected in sequence, the top of the pre-rectifying tower is connected with a pre-tower condensing device, and the bottom of the pre-rectifying tower is connected with a pre-tower reboiler; the top of the atmospheric tower is connected with a refined methanol extraction device, the middle of the atmospheric tower is connected with a fusel extraction device, and the bottom of the atmospheric tower is connected with an atmospheric tower reboiler; the bottom of the pressurizing tower is connected with a pressurizing tower reboiler; one path of the pressurized tower top extraction pipeline is connected with the heat source input end of the pre-tower reboiler, the other path of the pressurized tower top extraction pipeline is connected with the heat source input end of the atmospheric tower reboiler, and the heat source output ends of the pre-tower reboiler and the atmospheric tower reboiler are both connected with the pressurized tower reflux device. According to the system, the tower kettle of the pressurizing tower uses steam, and the pre-rectifying tower and the atmospheric tower do not need external heat sources, so that the steam consumption of methanol refining is reduced, the production cost is saved, the methanol refining processing amount is adjustable and is not limited, and the energy-saving and consumption-reducing effects are remarkable.

Description

Technical Field

[0001] The utility model relates to the technical field of chemical production, in particular to a methanol three-tower three-effect distillation energy-saving system. Background Art

[0002] Methanol is an important organic chemical raw material. It can be used as a raw material to produce a variety of chemical products such as formic acid, formaldehyde, acetic acid, methyl formate, methylamine, dimethyl ether, etc. Methanol is a clean fuel. In addition to being directly mixed with gasoline and diesel as fuel, fuel cell technology is attracting more and more attention. Moreover, with the rapid development of methanol derivatives and their downstream products, the demand for methanol is increasing, so the quality of methanol products and the energy saving and consumption reduction of methanol units are attracting more and more attention. Methanol distillation unit is an important processing step in methanol production, and its energy consumption accounts for about 20% of the total energy consumption of methanol production. The quality of methanol distillation technology is directly related to the quality of refined methanol. Advanced, energy-saving and efficient distillation units play an important role in reducing costs, saving energy and reducing consumption, improving product competitiveness and enterprise economic benefits. In the refined methanol product produced by double-tower distillation, the content of ethanol and organic impurities can only be controlled within a certain range. Depending on the quality of crude methanol, the ethanol content in refined methanol is about 100-600 mg / kg; the quality of refined methanol produced by three-tower distillation can generally meet the US AA grade standard, and the mass fraction of ethanol is only 8.0×10 -5 Therefore, the three-tower methanol distillation technology is increasingly being promoted and applied due to its high thermal utilization rate, low consumption, easy operation, good product quality, and high environmental benefits.

[0003] However, in the most commonly used three-tower double-effect distillation system for methanol, although the condensation latent heat of the gas phase at the top of the pressure tower is used as the heat source of the reboiler of the atmospheric tower kettle, the atmospheric tower does not need an external heat source and reduces energy consumption, but with the expansion of the scale of methanol refining, the above three-tower double-effect distillation system still has the problem of high steam consumption per ton of refined alcohol and significant increase in total energy consumption. A variety of improvement schemes have been tried in the prior art, such as adding a five-tower distillation or using heat pump technology, but the five-tower distillation directly leads to other problems such as site, tower investment and condensed water consumption, and heat pump distillation also has problems with equipment investment and power consumption. Therefore, in order to reduce the energy consumption of methanol distillation, it is necessary to improve the process system. Utility Model Content

[0004] The utility model provides a methanol three-tower three-effect distillation energy-saving system, which is used to solve the problems of high steam consumption per ton of refined alcohol, high total energy consumption, and limited methanol refining processing capacity in the existing methanol three-tower double-effect distillation system.

[0005] The utility model provides a methanol three-tower three-effect distillation energy-saving system, comprising: a pre-distillation tower, a pressure tower and an atmospheric pressure tower which are connected in sequence; the top of the pre-distillation tower is connected with a pre-tower condensing device, the bottom of the pre-distillation tower is connected with a pre-tower reboiler, and the bottom material of the pre-distillation tower is the feed of the pressure tower; the top of the atmospheric pressure tower is connected with a refined methanol extraction device, the middle extraction port of the atmospheric pressure tower is connected with a fusel alcohol tank, the bottom of the atmospheric pressure tower is connected with an atmospheric pressure tower reboiler, the bottom material of the atmospheric pressure tower is sent to a wastewater treatment system, and the feed of the atmospheric pressure tower is the bottom material of the pressure tower; the bottom of the pressure tower is connected with a pressure tower reboiler, and the heat source of the pressure tower reboiler is steam; the top extraction pipeline of the pressure tower is divided into two routes, one route is connected with the heat source input end of the pre-tower reboiler, and the other route is connected with the heat source input end of the atmospheric pressure tower reboiler, and the heat source output ends of the pre-tower reboiler and the atmospheric pressure tower reboiler are both connected with the reflux device of the pressure tower.

[0006] Furthermore, a pre-feed heat exchanger is arranged between the pre-distillation tower and the pressure tower, the cold medium inlet of the pre-feed heat exchanger is connected to the bottom of the pre-distillation tower, and the cold medium outlet of the pre-feed heat exchanger is connected to the feed port of the pressure tower; the hot medium inlet of the pre-feed heat exchanger is connected to the bottom of the pressure tower, and the hot medium outlet of the pre-feed heat exchanger is connected to the feed port of the atmospheric pressure tower.

[0007] Furthermore, the pre-tower condensing device includes a first pre-tower condenser, the exhaust port of the first pre-tower condenser is connected to the second pre-tower condenser, the exhaust port of the second pre-tower condenser is connected to the non-condensable gas pipeline, the coolant outlet of the second pre-tower condenser is connected to the gas-liquid separator, the top of the gas-liquid separator is connected to the non-condensable gas pipeline, the bottom of the gas-liquid separator is connected to the inlet of the pre-tower reflux tank, and the inlet of the pre-tower reflux tank is also connected to the coolant outlet of the first pre-tower condenser; the bottom of the pre-tower reflux tank is connected to the reflux port on the upper part of the pre-distillation tower through a pre-tower reflux pump.

[0008] Furthermore, the refined methanol production device includes an atmospheric tower product cooler, which is connected to the atmospheric tower reflux tank, and the bottom of the atmospheric tower reflux tank is respectively connected to the reflux port of the atmospheric tower and the product tank through an atmospheric tower reflux pump.

[0009] Furthermore, the reflux device of the pressure tower includes a pressure tower reflux tank, the heat source output ends of the pre-tower reboiler and the atmospheric tower reboiler are connected to the inlet of the pressure tower reflux tank, the bottom of the pressure tower reflux tank is connected to the reflux port of the pressure tower and the pressure tower product cooler respectively through the pressure tower reflux pump, and the pressure tower product cooler is connected to the product tank.

[0010] Furthermore, a fusel alcohol production device is connected between the middle production port of the atmospheric tower and the fusel alcohol tank, and the fusel alcohol production device includes a fusel alcohol buffer tank, and the bottom of the fusel alcohol buffer tank is connected to the feed port of the stripping tower through a stripping feed pump; a stripping reboiler is provided at the bottom of the stripping tower, and the heat source of the stripping reboiler is steam; the bottom discharge of the stripping tower is sent to a wastewater treatment system; the middle production port of the stripping tower is connected to the fusel alcohol tank through a fusel alcohol cooler; the top production port of the stripping tower is connected to the stripping tower product cooler, the stripping tower product cooler is connected to the stripping tower reflux tank, and the bottom of the stripping tower reflux tank is respectively connected to the reflux port and the product tank of the stripping tower through a stripping tower reflux pump.

[0011] Furthermore, the top extraction pipeline of the pressure tower is also connected to the material inlets of the atmospheric tower product cooler and the stripping tower product cooler respectively.

[0012] Furthermore, the pre-distillation tower, the pressure tower and the atmospheric pressure tower are all plate towers; the pre-tower reboiler, the pressure tower reboiler, the atmospheric pressure tower reboiler and the stripping reboiler are all shell-and-tube heat exchangers.

[0013] The methanol three-tower three-effect distillation energy-saving system provided by the utility model improves the effective utilization rate of heat flow by replacing the pre-tower reboiler at the bottom of the original pre-distillation tower with steam heating to heating using the material at the top of the pressurized tower. The pre-distillation tower saves the consumption of steam heat source, and both the pre-distillation tower and the atmospheric pressure tower do not need an external heat source. The top water cooler is also saved for the pressurized tower, which has significant effects on energy saving, consumption reduction and production cost reduction, making the methanol refining processing volume adjustable and unrestricted, solving the problems of large distillation load, high steam and cooling water consumption, and achieving the purpose of saving energy and reducing consumption. At the same time, the pre-feed heat exchanger set in the system recovers and couples the heat of the material at the bottom of the pressurized tower, so that the temperature of the material at the bottom of the pre-distillation tower rises, which is more in line with the feed needs of the pressurized tower, so as to improve the distillation purification efficiency and separation effect of the pressurized tower, and also improve the effective utilization rate of heat.

[0014] After the system was put into operation, the steam consumption of the pre-distillation tower was reduced to zero, the reflux ratio of the pre-distillation tower and the pressure tower was reduced, the recovery ratio of the refined methanol product was increased by more than 0.5, the steam consumption was significantly reduced, and the use of circulating water was effectively reduced, reducing the waste of water resources, and achieving significant energy-saving and consumption-reducing effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1A schematic diagram of the structure of a methanol three-tower three-effect distillation energy-saving system provided in one embodiment of the utility model;

[0017] Figure 2 A schematic diagram of the structure of a fusel alcohol extraction device provided in one embodiment of the utility model;

[0018] Figure 3 A schematic structural diagram of a methanol three-tower three-effect distillation energy-saving system provided in another embodiment of the utility model.

[0019] Description of reference numerals:

[0020] 1. Pre-distillation tower, 2. Pressure tower, 3. Atmospheric tower, 4. Fusel alcohol tank, 5. Product tank, 6. Stripping tower, 11. Pre-tower reboiler, 12. Pre-tower first condenser, 13. Pre-tower second condenser, 14. Gas-liquid separator, 15. Pre-tower reflux tank, 16. Pre-tower reflux pump, 21. Pressure tower reboiler, 22. Pre-feed heat exchanger, 23. Pressure tower reflux tank, 24. Pressure tower reflux pump, 25. Pressure tower product cooler, 31. Atmospheric tower reboiler, 32. Atmospheric tower product cooler, 33. Atmospheric tower reflux tank, 34. Atmospheric tower reflux pump, 41. Fusel alcohol buffer tank, 42. Fusel alcohol cooler, 61. Stripping feed pump, 62. Stripping reboiler, 63. Stripping tower product cooler, 64. Stripping tower reflux tank, 65. Stripping tower reflux pump. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the embodiments of the utility model clearer, the technical solution in the embodiments of the utility model is described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work also fall within the scope of protection of the utility model.

[0022] like Figure 1 and Figure 3The utility model provides a methanol three-tower three-effect distillation energy-saving system, comprising: a pre-distillation tower 1, a pressure tower 2 and an atmospheric tower 3 connected in sequence; the top of the pre-distillation tower 1 is connected with a pre-tower condensing device, the bottom of the pre-distillation tower 1 is connected with a pre-tower reboiler 11, and the bottom material of the pre-distillation tower 1 is the feed of the pressure tower 2; the top of the atmospheric tower 3 is connected with a refined methanol extraction device, the middle extraction port of the atmospheric tower 3 is connected with a fusel alcohol tank 4, the bottom of the atmospheric tower 3 is connected with an atmospheric tower reboiler 31, and the atmospheric tower 3 is connected with a pre-tower condensing device. The bottom material of the pressure tower 3 is sent to the wastewater treatment system, and the feed of the atmospheric tower 3 is the bottom material of the pressure tower 2; the bottom of the pressure tower 2 is connected with the pressure tower reboiler 21, and the heat source of the pressure tower reboiler 21 is steam; the top extraction pipeline of the pressure tower 2 is divided into two routes, one is connected to the heat source input end of the pre-tower reboiler 11, and the other is connected to the heat source input end of the atmospheric tower reboiler 31, and the heat source output ends of the pre-tower reboiler 11 and the atmospheric tower reboiler 31 are both connected to the reflux device of the pressure tower 2.

[0023] Specifically, after the crude methanol material from the synthesis process enters the pre-distillation tower 1, the light component and a small amount of gaseous methanol are extracted from the top of the pre-distillation tower 1, and the aqueous methanol solution A is extracted from the bottom of the pre-distillation tower 1 and enters the pressure tower 2. The refined methanol gas phase material extracted from the top of the pressure tower 2 is divided into two routes: one route is sent to the bottom of the atmospheric tower 3 to provide the required heat for the atmospheric tower reboiler 31; the other route is sent to the bottom of the pre-distillation tower 1 to provide heat for the pre-tower reboiler 11, which is used to heat the pre-distillation tower 1 kettle to about 78°C. After the heat exchange of the two reboilers, the refined methanol gas phase material is cooled into refined methanol condensate and merged into the reflux device of the pressure tower 2. The aqueous methanol solution B is extracted from the bottom of the pressure tower 2 and enters the atmospheric tower 3, the refined methanol material is extracted from the top of the atmospheric tower 3, the fusel alcohol material is extracted from the middle of the atmospheric tower 3, and the wastewater material is extracted from the bottom of the atmospheric tower 3.

[0024] The distillation energy-saving system replaces the pre-tower reboiler 11 at the bottom of the original pre-distillation tower 1 with steam heating to heat the material at the top of the pressure tower 2, and conducts heat coupling with the refined methanol gas phase material extracted from the top of the pressure tower 2, which can effectively improve the reliability of heat coupling and the effective utilization rate of heat flow. The heat of the tower kettle of the pressure tower 2 is stable. After the transformation, it only needs to adjust the reflux ratio and extraction ratio of the pressure tower 2 and the atmospheric pressure tower 3, and normal continuous production can be achieved. Compared with the existing three-tower double-effect distillation system, the entire three-tower three-effect distillation energy-saving system has a small investment in transformation equipment, little change in process flow, high transformation efficiency, and low transformation cost. The pre-distillation tower 1 saves the consumption of steam heat source, and the pre-distillation tower 1 and the atmospheric pressure tower 3 do not need external heat source. The effect of energy saving and consumption reduction and production cost reduction is significant, making the methanol refining processing volume adjustable and unlimited.

[0025] Furthermore, a pre-feed heat exchanger 22 is arranged between the pre-distillation tower 1 and the pressure tower 2, the cold medium inlet of the pre-feed heat exchanger 22 is connected to the bottom of the pre-distillation tower 1, and the cold medium outlet of the pre-feed heat exchanger 22 is connected to the feed port of the pressure tower 2; the hot medium inlet of the pre-feed heat exchanger 22 is connected to the bottom of the pressure tower 2, and the hot medium outlet of the pre-feed heat exchanger 22 is connected to the feed port of the atmospheric pressure tower 3.

[0026] The bottom material of the pre-distillation tower 1 - aqueous methanol solution A is the feed of the pressurized tower 2. The setting of the pre-feed heat exchanger 22 is to use the heat of the bottom material of the pressurized tower 2 - aqueous methanol solution B to heat the bottom material of the pre-distillation tower 1, so that the temperature of the bottom material of the pre-distillation tower 1 rises, which is more in line with the feed requirements of the pressurized tower 2, so as to improve the distillation purification efficiency and separation effect of the pressurized tower 2. The heat recovery and coupling of the bottom material of the pressurized tower 2 are beneficial to the operation and regulation of the pressurized tower 2 and the atmospheric pressure tower 3, and also improve the effective utilization rate of heat.

[0027] Furthermore, the pre-tower condensing device includes a first pre-tower condenser 12, the exhaust port of the first pre-tower condenser 12 is connected to the second pre-tower condenser 13, the exhaust port of the second pre-tower condenser 13 is connected to the non-condensable gas pipeline, the coolant outlet of the second pre-tower condenser 13 is connected to the gas-liquid separator 14, the top of the gas-liquid separator 14 is connected to the non-condensable gas pipeline, the bottom of the gas-liquid separator 14 is connected to the inlet of the pre-tower reflux tank 15, and the inlet of the pre-tower reflux tank 15 is also connected to the coolant outlet of the first pre-tower condenser 12; the bottom of the pre-tower reflux tank 15 is connected to the reflux port on the upper part of the pre-distillation tower 1 through the pre-tower reflux pump 16.

[0028] The gaseous materials extracted from the top of the pre-distillation tower 1 are mainly low-boiling point components with a lower boiling point than methanol and non-condensable gases dissolved in methanol, such as H 2 ,CO,CO 2 The gaseous materials are condensed by the first condenser 12 and the second condenser 13 of the pre-tower, and then the gas-liquid separation is performed. The liquid phase obtained by separation is refluxed into the pre-distillation tower 1 as reflux liquid, and the gas phase obtained by separation is sent to the waste gas treatment system (such as a flare, etc.) as non-condensable gas. The use of secondary condensation in the top condensation device of the pre-distillation tower 1 can improve the condensation recovery efficiency and reduce the loss rate of methanol.

[0029] Furthermore, the refined methanol extraction device includes an atmospheric tower product cooler 32, which is connected to an atmospheric tower reflux tank 33, and the bottom of the atmospheric tower reflux tank 33 is respectively connected to the reflux port of the atmospheric tower 3 and the product tank 5 through an atmospheric tower reflux pump 34. The material extracted from the top of the atmospheric tower 3 is the refined methanol material. After condensation in the atmospheric tower product cooler 32, a part of it can be refluxed, and the other part can be extracted as a refined product to the product tank 5 for subsequent deep processing or external sale.

[0030] Furthermore, the reflux device of the pressure tower 2 includes a pressure tower reflux tank 23, and the heat source output ends of the pre-tower reboiler 11 and the atmospheric tower reboiler 31 are both connected to the inlet of the pressure tower reflux tank 23, and the bottom of the pressure tower reflux tank 23 is respectively connected to the reflux port of the pressure tower 2 and the pressure tower product cooler 25 through the pressure tower reflux pump 24, and the pressure tower product cooler 25 is connected to the product tank 5.

[0031] The refined methanol gas phase material extracted from the top of the pressure tower 2 is cooled into a liquid phase after heat exchange in the pre-tower reboiler 11 and the atmospheric tower reboiler 31, and enters the pressure tower reflux tank 23, part of which is refluxed to the pressure tower 2, and part of which is extracted as a refined product, and after further cooling in the pressure tower product cooler 25, it is sent to the product tank 5. The heat utilization method at the top of the pressure tower 2 saves the top water cooler for the pressure tower 2, which can save cooling circulating water resources and make full use of the heat energy at the top of the pressure tower 2, achieving the purpose of reducing costs and increasing efficiency.

[0032] like Figure 2 and Figure 3 Furthermore, a fusel alcohol extraction device is connected between the middle extraction port of the atmospheric tower 3 and the fusel alcohol tank 4, and the fusel alcohol extraction device includes a fusel alcohol buffer tank 41, and the bottom of the fusel alcohol buffer tank 41 is connected to the feed port of the stripping tower 6 through a stripping feed pump 61; a stripping reboiler 62 is provided at the bottom of the stripping tower 6, and the heat source of the stripping reboiler 62 is steam; the bottom discharge of the stripping tower 6 is sent to the wastewater treatment system; the middle extraction port of the stripping tower 6 is connected to the fusel alcohol tank 4 through a fusel alcohol cooler 42; the top extraction port of the stripping tower 6 is connected to a stripping tower product cooler 63, and the stripping tower product cooler 63 is connected to a stripping tower reflux tank 64, and the bottom of the stripping tower reflux tank 64 is respectively connected to the reflux port of the stripping tower 6 and the product tank 5 through a stripping tower reflux pump 65.

[0033] The design of the fusel alcohol extraction device is beneficial to reducing the processing load of the atmospheric pressure tower 3 and improving the methanol refining efficiency. The reduction in processing load also enables the atmospheric pressure tower 3 to only use the reboiling heat provided by the top material of the pressure tower 2 during production to meet the processing of the atmospheric pressure tower 3, further reducing the processing energy consumption of the atmospheric pressure tower 3. At the same time, the stripping tower 6 is used to improve the methanol recovery rate. The fusel alcohol recovered in the fusel alcohol tank 4 can also be recycled and utilized as a resource through subsequent treatment.

[0034] like Figure 3 Furthermore, the top extraction pipeline of the pressure tower 2 is also connected to the material inlet of the atmospheric tower product cooler 32 and the stripping tower product cooler 63. In the case of a large processing volume, the refined methanol gas phase material extracted from the top of the pressure tower 2 can also be directly extracted into the product tank 5 after being cooled by the atmospheric tower product cooler 32 and / or the stripping tower product cooler 63, thereby improving the extraction efficiency of refined methanol.

[0035] Furthermore, the pre-distillation tower 1, the pressure tower 2 and the atmospheric tower 3 are all plate towers; the pre-tower reboiler 11, the pressure tower reboiler 21, the atmospheric tower reboiler 31 and the stripping reboiler 62 are all shell-and-tube heat exchangers. The distillation energy-saving system adopts plate towers, which are convenient for regulating the system and the processing volume of methanol by taking advantage of their large processing capacity, high mass transfer efficiency, convenient cleaning and maintenance, and good operational stability. The shell-and-tube heat exchanger used as a reboiler has the advantages of simple structure, high heat exchange efficiency, easy installation, easy maintenance, and good stability and adjustability of the entire structure.

[0036] The utility model provides a methanol three-tower three-effect distillation energy-saving system. When it is working, after the crude methanol material from the synthesis process enters the pre-distillation tower 1, the gaseous material formed by the light component and a small amount of gaseous methanol is extracted from the top of the pre-distillation tower 1, and the gaseous material is condensed by the first condenser 12 of the pre-tower and the second condenser 13 of the pre-tower respectively. The coolant from the second condenser 13 of the pre-tower is separated into gas and liquid in the gas-liquid separator 14. The separated liquid phase and the coolant of the first condenser 12 of the pre-tower are sent to the pre-tower reflux tank 15, and reflux into the pre-distillation tower 1 as reflux liquid through the pre-tower reflux pump 16. The separated gas phase is sent to the waste gas treatment system (such as a torch, etc.) as non-condensable gas.

[0037] The aqueous methanol solution A is extracted from the bottom of the pre-distillation tower 1, and after heat exchange with the material from the bottom of the pressurized tower 2 in the pre-feed heat exchanger 22, it enters the pressurized tower 2 from the feed port of the pressurized tower 2 for distillation. The pressurized tower reboiler 21 provides heat through steam, and the aqueous methanol solution A completes distillation separation in the pressurized tower 2. The refined methanol gas phase material extracted from the top of the pressurized tower 2 is divided into two routes: one route is sent to the bottom of the atmospheric tower 3 to provide the required heat for the atmospheric tower reboiler 31; the other route is sent to the bottom of the pre-distillation tower 1 to provide heat for the pre-tower reboiler 11, which is used to heat the pre-distillation tower 1 kettle to about 78°C. After heat exchange between the two reboilers, the refined methanol gas phase material is cooled into refined methanol condensate and merged into the pressurized tower reflux tank 23, part of which is sent to the pressurized tower 2 for reflux through the pressurized tower reflux pump 24, and part of which is sent to the pressurized tower product cooler 25 for cooling, and then sent to the refined methanol product tank 5. The aqueous methanol solution B taken out from the bottom of the pressure tower 2 is cooled by the post-feed heat exchanger 22 and then enters the atmospheric pressure tower 3.

[0038] The refined methanol material is extracted from the top of the atmospheric tower 3, cooled in the atmospheric tower product cooler 32, and then sent to the atmospheric tower reflux tank 33. Part of it is sent to the atmospheric tower 3 for reflux through the atmospheric tower reflux pump 34, and part of it is extracted as a refined product to the product tank 5. The wastewater material extracted from the bottom of the atmospheric tower 3 is sent to the wastewater treatment system. The fusel alcohol material is extracted from the middle of the atmospheric tower 3 to the fusel alcohol buffer tank 41, and then sent to the stripping tower 6 through the stripping feed pump 61, and the stripping reboiler 62 provides heat for stripping and refining. The bottom discharge of the stripping tower 6 is sent to the wastewater treatment system, the fusel alcohol material taken out from the middle outlet of the stripping tower 6 is sent to the fusel alcohol cooler 42 for cooling, and then enters the fusel alcohol tank 4 for storage, the refined methanol taken out from the top outlet of the stripping tower 6 is sent to the stripping tower reflux tank 64 after being cooled by the stripping tower product cooler 63, and part of it is sent to the stripping tower 6 reflux through the stripping tower reflux pump 65, and part of it is sent to the refined methanol product tank 5. The refined methanol gas phase material taken out from the top extraction pipeline of the pressure tower 2 can also be sent to the atmospheric tower product cooler 32 and / or the stripping tower product cooler 63 for cooling, and then sent to the refined methanol product tank 5.

[0039] The feed rate of the pre-distillation tower 1 is 49-51m 3 / h as an example to operate the system, the top operating temperature of the pre-distillation tower 1 is 72 ° C, the bottom operating temperature is 78 ° C, and the reflux rate is 18.8m 3 / h, reflux ratio is 0.38, steam consumption is 0. The top operating temperature of the pressurized tower 2 is 119℃, the bottom operating temperature is 127℃, and the reflux rate is 54m 3 / h, the top extraction volume is 26-28m 3 / h, reflux ratio is 1.9-2.1, production ratio is 1.6, steam consumption is 40500kg / h. The top operating temperature of atmospheric tower 3 is 63℃, the bottom operating temperature is 109℃, the reflux rate is 27m 3 / h, the top extraction volume is 16-18m 3 / h, the reflux ratio is 1.5-1.68, the production ratio is 1.6, and the steam consumption is 0.

[0040] Compared with the three-tower double-effect distillation system with the same feed amount, the feed amount of the pre-distillation tower 1 of the system of the utility model remains unchanged, the reflux ratio is reduced from 0.55 to 0.38, and the steam consumption is reduced to 0. The reflux ratio of the pressure tower 2 is reduced from 2.2 to about 2.0, and the top extraction volume is increased. The reflux ratio of the atmospheric tower 3 does not change much, and the product extraction ratio is adjusted from 1.1 to 1.6. The steam consumption of the whole system is reduced from 52000kg / h to 40500kg / h, saving 11500kg / h of steam, and the steam consumption per ton of refined methanol is reduced from the original 1.49t to 0.9t, saving 0.5t / h, with significant energy-saving effect. At the same time, in the system of the utility model, the reflux liquid temperature of the pressure tower 2 is reduced, and the cooling water of the pressure tower reflux tank 23 can be shut off, which can save about 20m of circulating water. 3 / h.

[0041] It should be noted that in the present invention, the detailed structure of some devices is not described in detail, but belongs to the prior art known to those skilled in the art, so it will not be repeated here. In addition, the parts not involved in the device are the same as the prior art or can be implemented by the prior art.

[0042] It should be noted that pressure sensors, flow meters or temperature sensors are installed on the transmission pipelines inside the system between different units, devices or equipment. Different valves are also installed, such as pressure relief valves, pressure regulating valves, safety valves, etc., which are used to adjust and stabilize the pressure of the entire system.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model, rather than to limit it; although the utility model has been described in detail with reference to the aforementioned embodiments, ordinary technicians in the field should understand that it is still possible to modify the technical solutions recorded in the aforementioned embodiments, or to replace some or all of the technical features therein with equivalents; and these modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solution of the embodiments of the utility model.

Claims

1. A methanol three-tower three-effect distillation energy-saving system, characterized in that: include: A pre-distillation tower, a pressure tower and an atmospheric tower connected in sequence; the top of the pre-distillation tower is connected to a pre-tower condensing device, the bottom of the pre-distillation tower is connected to a pre-tower reboiler, and the bottom material of the pre-distillation tower is the feed of the pressure tower; the top of the atmospheric tower is connected to a refined methanol extraction device, the middle extraction port of the atmospheric tower is connected to a fusel alcohol tank, the bottom of the atmospheric tower is connected to an atmospheric tower reboiler, the bottom material of the atmospheric tower is sent to a wastewater treatment system, and the feed of the atmospheric tower is the bottom material of the pressure tower; the bottom of the pressure tower is connected to a pressure tower reboiler, and the heat source of the pressure tower reboiler is steam; the top extraction pipeline of the pressure tower is divided into two routes, one route is connected to the heat source input end of the pre-tower reboiler, and the other route is connected to the heat source input end of the atmospheric tower reboiler, and the heat source output ends of the pre-tower reboiler and the atmospheric tower reboiler are both connected to the reflux device of the pressure tower.

2. The methanol three-tower three-effect distillation energy-saving system according to claim 1 is characterized in that: A pre-feed heat exchanger is arranged between the pre-distillation tower and the pressurizing tower, the cold medium inlet of the pre-feed heat exchanger is connected to the bottom of the pre-distillation tower, and the cold medium outlet of the pre-feed heat exchanger is connected to the feed port of the pressurizing tower; the hot medium inlet of the pre-feed heat exchanger is connected to the bottom of the pressurizing tower, and the hot medium outlet of the pre-feed heat exchanger is connected to the feed port of the atmospheric pressure tower.

3. The methanol three-tower three-effect distillation energy-saving system according to claim 1 is characterized in that: The pre-tower condensing device comprises a first pre-tower condenser, the exhaust port of the first pre-tower condenser is connected to the second pre-tower condenser, the exhaust port of the second pre-tower condenser is connected to the non-condensable gas pipeline, the coolant outlet of the second pre-tower condenser is connected to a gas-liquid separator, the top of the gas-liquid separator is connected to the non-condensable gas pipeline, the bottom of the gas-liquid separator is connected to the inlet of a pre-tower reflux tank, and the inlet of the pre-tower reflux tank is also connected to the coolant outlet of the first pre-tower condenser; the bottom of the pre-tower reflux tank is connected to the reflux port on the upper part of the pre-distillation tower through a pre-tower reflux pump.

4. The methanol three-tower three-effect distillation energy-saving system according to claim 1 is characterized in that: The refined methanol extraction device comprises an atmospheric tower product cooler, which is connected to an atmospheric tower reflux tank, and the bottom of the atmospheric tower reflux tank is respectively connected to the reflux port and product tank of the atmospheric tower through an atmospheric tower reflux pump.

5. The methanol three-tower three-effect distillation energy-saving system according to claim 4 is characterized in that: The reflux device of the pressure tower includes a pressure tower reflux tank, the heat source output ends of the pre-tower reboiler and the atmospheric pressure tower reboiler are both connected to the inlet of the pressure tower reflux tank, the bottom of the pressure tower reflux tank is respectively connected to the reflux port of the pressure tower and the pressure tower product cooler through a pressure tower reflux pump, and the pressure tower product cooler is connected to the product tank.

6. The methanol three-tower three-effect distillation energy-saving system according to claim 4, characterized in that: A fusel alcohol extraction device is connected between the middle extraction port of the atmospheric tower and the fusel alcohol tank, and the fusel alcohol extraction device comprises a fusel alcohol buffer tank, and the bottom of the fusel alcohol buffer tank is connected to the feed port of the stripping tower through a stripping feed pump; a stripping reboiler is provided at the bottom of the stripping tower, and the heat source of the stripping reboiler is steam; the bottom discharge of the stripping tower is sent to the wastewater treatment system; the middle extraction port of the stripping tower is connected to the fusel alcohol tank through a fusel alcohol cooler; the top extraction port of the stripping tower is connected to the stripping tower product cooler, and the stripping tower product cooler is connected to the stripping tower reflux tank, and the bottom of the stripping tower reflux tank is respectively connected to the reflux port of the stripping tower and the product tank through a stripping tower reflux pump.

7. The methanol three-tower three-effect distillation energy-saving system according to claim 6, characterized in that: The top extraction pipeline of the pressure tower is also connected to the material inlet of the atmospheric tower product cooler and the stripping tower product cooler respectively.

8. The methanol three-tower three-effect distillation energy-saving system according to claim 6 or 7, characterized in that: The pre-distillation tower, the pressure tower and the atmospheric pressure tower are all plate towers; the pre-tower reboiler, the pressure tower reboiler, the atmospheric pressure tower reboiler and the stripping reboiler are all shell-and-tube heat exchangers.

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