Four-tower heat pump heat-coupled methanol rectification method and rectification device

Abstract

The application provides a four-column heat pump heat coupling methanol rectification method, which adopts four-column heat pump heat coupling of a pre-rectification column, a negative pressure rectification column, a pressurized rectification column and a fusel recovery column; the steam at the top of the negative pressure rectification column is heated and pressurized by a compressor I and then provides heat for a negative pressure rectification column reboiler II; part of the steam at the top of the fusel recovery column is heated and pressurized by a compressor II and then provides heat for a fusel recovery column reboiler I; and the application also provides a four-column heat pump heat coupling methanol rectification device, which comprises the pre-rectification column, the negative pressure rectification column, the pressurized rectification column and the fusel recovery column which are connected in sequence; the application fully carries out heat coupling and plays the energy-saving advantage of heat pump technology, reduces the pressure and difficulty of the waste water treatment section when purifying methanol, makes the average steam consumption of each ton of refined methanol lower than the lowest steam consumption level in the industry, saves energy consumption, reduces energy waste and maximizes energy saving.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of chemical engineering and coal chemical engineering, in particular to a four-tower heat pump heat-coupled methanol rectification device. BACKGROUND

[0002] Methanol is an important basic organic chemical raw material and a new type of energy fuel. In industry, methanol is almost entirely synthesized by the method of pressurized catalytic hydrogenation of carbon monoxide. The process includes the procedures of gas making, synthesis and purification, methanol synthesis and crude methanol rectification. The main task of methanol rectification is to remove volatile components such as dimethyl ether, and non-volatile ethanol, higher alcohols and water, to produce refined methanol meeting product requirements. With the vigorous development of the coal chemical industry, the scale of methanol rectification devices is also becoming larger and larger. How to reduce the energy consumption per ton of refined methanol of the methanol refining device has become the key to the survival and improvement of competitiveness of enterprises. The majority of scientific researchers and engineering and technical personnel have conducted in-depth research on this object.

[0003] The three-tower methanol rectification (downstream double-effect rectification) process widely used at present is that crude methanol is sequentially rectified and separated through a pre-rectification tower, a pressurized rectification tower and an atmospheric rectification tower. Methanol products are obtained from the overhead of the pressurized tower and the overhead of the atmospheric tower. The separation sequence is that light components in the crude methanol are removed from the pre-rectification tower, and the pre-overhead crude methanol from the tower sump enters the pressurized rectification tower. The condensation latent heat of the methanol steam at the top of the pressurized tower is used as the reboiling heat source of the atmospheric tower to realize downstream double-effect rectification. The fusel alcohol is taken from the side line of the atmospheric tower, and the waste water is discharged from the bottom of the atmospheric tower. This method is a common crude methanol refining process. The energy consumption of the methanol rectification process is about 2417-3223.7 MJ / ton of refined methanol product. The production energy consumption is relatively high. With the expansion of the scale of methanol refining, the total energy consumption also significantly increases. Energy-saving processes have become the preferred object of the industry.

[0004] In order to reduce the energy consumption of methanol rectification, there are currently various attempts to solve the problem. For example, a high-pressure tower is added to couple with the current pressurized tower to become a five-tower three-effect rectification process, or a heat pump technology is used. The five-tower rectification modification mode directly leads to other problems such as site restriction factors, increased tower investment, insufficient safety distance, etc. For single heat pump rectification, there are also engineering problems such as increased equipment investment and expansion of the power distribution station. The current three-tower three-effect technology and improved three-tower three-effect technology have the advantage of engineering in that, due to the lower separation difficulty of methanol and water and methanol and ethanol under negative pressure conditions, the energy consumption can be significantly reduced.

[0005] In summary, for the methanol rectification system in the prior art, currently mainly multi-effect rectification is adopted, such as five-tower three-effect, five-tower four-effect, three-tower three-effect, improved three-tower three-effect, four-tower four-effect, and in individual cases, a scheme of nesting a heat pump into a certain link is also adopted. The average energy consumption per ton of refined methanol of the scheme of nesting a heat pump is 0.6-0.9 tons of steam. In the article of Wang Dongliang, "New Energy-saving Process of Heat Pump Coupling Methanol Multi-effect Rectification", through the coupling of a heat pump and multi-effect, the energy consumption is further reduced to 0.45-0.50 tons of steam per ton of refined methanol. Each improved technical innovation achieves a significant reduction in energy consumption. Based on the background of global climate change, the price of energy is also rising, and better energy-saving processes and means will gradually be applied. The present application aims to combine the four-tower with the coupling of a heat pump and multi-effect, thereby forming a new technical scheme. SUMMARY

[0006] The present application provides a four-tower heat pump heat coupling methanol rectification method, characterized in that a pre-rectification tower, a negative pressure rectification tower, a pressurized rectification tower and a fusel recovery tower are coupled by a heat pump.

[0007] The steam at the top of the negative pressure rectification tower is heated to the negative pressure rectification tower reboiler II after being compressed and pressurized and heated by a compressor I.

[0008] The light component impurities collected at the top of the pre-rectification tower are sent to a flare system for treatment, and the crude methanol after removal of light component impurities from the pre-rectification tower is sent to the negative pressure rectification tower.

[0009] The refined methanol product is collected at the top of the negative pressure rectification tower, and the material at the bottom of the negative pressure rectification tower is sent to the pressurized rectification tower.

[0010] The refined methanol product is collected at the top of the pressurized rectification tower, the material collected from the side line of the pressurized rectification tower is sent to the fusel recovery tower, and the waste water is collected at the bottom of the pressurized rectification tower.

[0011] The fuel methanol is collected at the top of the fusel recovery tower, and the waste water is collected at the bottom of the fusel recovery tower.

[0012] As a preferred scheme, part of the steam at the top of the pressurized rectification tower is used to heat the pre-rectification tower reboiler I of the pre-rectification tower.

[0013] As a preferred scheme, part of the steam at the top of the fusel recovery tower is heated to the fusel recovery tower reboiler I after being compressed and pressurized and heated by a compressor II.

[0014] As a preferred scheme, part of the steam at the top of the pre-rectification tower is used to heat the waste water treatment device.

[0015] As a preferred solution, the waste water taken out from the bottom of the pressurized rectifying tower and the waste water taken out from the bottom of the fusel oil recovery tower are treated by a waste water evaporator, and the heater provides heat for the waste water evaporator.

[0016] As a preferred solution, the operating pressure of the pre-rectifying tower is 110-130 KPa, the top temperature is 68-72℃, and the bottom temperature is 72-76℃.

[0017] As a preferred solution, the operating pressure of the negative pressure rectifying tower is 60-95 KPa, the top temperature is 50-65℃, and the bottom temperature is 60-70℃.

[0018] As a preferred solution, the operating pressure of the pressurized rectifying tower is 190-300 KPa, the top temperature is 85-93℃, and the bottom temperature is 105-125℃.

[0019] As a preferred solution, the operating pressure of the fusel oil recovery tower is 101-130 KPa, the top temperature is 65-75℃, and the bottom temperature is 102-108℃.

[0020] The application provides a four-tower heat pump heat-coupled methanol rectifying device, which comprises a pre-rectifying tower, a negative pressure rectifying tower, a pressurized rectifying tower, and a fusel oil recovery tower connected in sequence.

[0021] As a preferred solution, the compressor one is at least two compressor groups connected in parallel, and each compressor group comprises at least one compressor.

[0022] As a preferred solution, the bottom of the fusel oil recovery tower is connected with a fusel oil recovery tower reboiler one and a fusel oil recovery tower reboiler two, the fusel oil recovery tower reboiler one is connected with a fusel oil vertical buffer tank, the fusel oil vertical buffer tank is connected with the top of the fusel oil recovery tower through a heat exchange pipeline three and a fusel tower top pipeline, the heat exchange pipeline three is provided with a compressor two, and the fusel oil vertical buffer tank is further connected with a methanol gas treatment device through a heat exchange pipeline four, and the heat exchange pipeline four is provided with a crude methanol circulating pump.

[0023] As a preferred solution, the compressor two is at least two compressor groups connected in parallel, and each compressor group comprises at least one compressor.

[0024] As a preferred solution, the methanol gas treatment device comprises a fusel alcohol cooler connected with the fusel alcohol tower top pipeline, the heat exchange pipeline three, the fusel alcohol cooler is connected with the fusel alcohol recovery tower reflux tank through the fusel alcohol recovery tower pipeline one, the fusel alcohol recovery tower pipeline one is connected with the heat exchange pipeline four, the fusel alcohol recovery tower reflux tank is connected with the fine methanol cooler one, the fusel alcohol recovery tower reflux tank is also connected with the fine methanol cooler two through the fusel alcohol recovery tower pipeline two, the fusel alcohol recovery tower pipeline two is provided with a fusel alcohol recovery pump, and the fusel alcohol recovery tower pipeline two is connected with the upper part of the fusel alcohol recovery tower through the fusel alcohol recovery tower pipeline three.

[0025] As a preferred solution, the bottom of the pressurized rectifying tower and the bottom of the fusel alcohol recovery tower are connected with the wastewater treatment device.

[0026] As a preferred solution, the wastewater treatment device comprises a wastewater evaporator connected with the bottom of the pressurized rectifying tower through a wastewater pipeline, the wastewater pipeline is provided with a wastewater pump, the top of the wastewater evaporator is connected with a water outlet pipeline, the water outlet pipeline is provided with a condensation cooler, the bottom of the wastewater evaporator is provided with a water outlet pipeline one, the wastewater evaporator is also connected with a heater, the heater is connected with the top of the pre-rectifying tower through a heat exchange pipeline one, and the heater is connected with the pre-rectifying tower gas treatment device through a heat exchange pipeline two; the wastewater evaporator is connected with the bottom of the fusel alcohol recovery tower through a production pipeline.

[0027] As a preferred solution, the wastewater pipeline is connected with a wastewater pipeline one, and the wastewater pipeline one is provided with a wastewater cooler.

[0028] As a preferred solution, the water outlet pipeline is also connected with a condensate reflux pipeline, and the condensate reflux pipeline is connected with the pre-rectifying tower gas treatment device connected with the top of the pre-rectifying tower.

[0029] As a preferred solution, the fusel alcohol recovery tower is connected with the pressurized rectifying tower through a fusel alcohol recovery pipeline, and the fusel alcohol recovery pipeline between the pressurized rectifying tower and the fusel alcohol recovery tower is sequentially provided with a fusel alcohol cooler, a fusel alcohol buffer tank and a fusel alcohol production pump, the top of the fusel alcohol recovery tower is connected with a methanol gas treatment device, the lower part of the fusel alcohol recovery tower is connected with a wastewater treatment device through a production pipeline, and the production pipeline is provided with a fusel alcohol recovery tower tank pump.

[0030] As a preferred solution, the common end bus of the plurality of parallel compressors one is connected with the negative pressure rectifying tower liquid treatment device through a pipeline.

[0031] As a preferred solution, the pre-distillation column gas treatment device comprises a pre-distillation column first condenser, which is connected with a pre-distillation column second condenser through a pre-distillation column pipeline one, the pre-distillation column second condenser is connected with a pre-vapor-liquid separator through a pre-distillation column pipeline two, the pre-vapor-liquid separator is connected with a pre-reflux tank through a pre-distillation column pipeline three, the pre-reflux tank is connected with the top of the pre-distillation column through a pre-distillation column reflux pipeline, a pre-reflux pump is arranged on the pre-distillation column reflux pipeline; the top of the pre-reflux tank is connected with the pre-distillation column first condenser through a pre-distillation column pipeline four; the pre-reflux tank is connected with a water outlet pipeline through the condensate reflux pipeline.

[0032] As a preferred solution, the negative pressure distillation column reboiler two is connected with a negative pressure distillation column liquid treatment device through a heat exchange pipeline six, the negative pressure distillation column liquid treatment device comprises a negative pressure reflux tank connected with the heat exchange pipeline six, the negative pressure reflux tank is connected with the upper part of the negative pressure distillation column through a negative pressure distillation column pipeline one and a negative pressure distillation column pipeline two, the negative pressure reflux tank is connected with a refined methanol tank area through the negative pressure distillation column pipeline one and a negative pressure distillation column pipeline three, a negative pressure column first cooler and a negative pressure column second cooler are arranged on the negative pressure distillation column pipeline three between the negative pressure reflux tank and the refined methanol tank area in sequence; a negative pressure reflux pump is arranged on the negative pressure distillation column pipeline two and the negative pressure distillation column pipeline three; the negative pressure reflux tank is connected with the common end bus through the pipeline, a liquid recovery pipeline is connected with the negative pressure reflux tank, the liquid recovery pipeline is connected with a vacuum system, and a condenser is arranged on the liquid recovery pipeline.

[0033] As a preferred solution, the top of the pressurized distillation column is provided with a pressurized distillation column gas treatment device, the pressurized distillation column gas treatment device comprises a pressurized column cooler, the pressurized column cooler is connected with the top of the pressurized distillation column through a pressurized distillation column pipeline one, the pressurized column cooler is connected with a refined methanol tank area through a pressurized distillation column pipeline two, a pressurized reflux tank, a pressurized reflux pump and a refined methanol cooler are arranged on the pressurized distillation column pipeline two between the pressurized column cooler and the refined methanol tank area in sequence, and the pressurized reflux tank is connected with the pre-distillation column reboiler.

[0034] As a preferred solution, the pressurized distillation column pipeline two is connected with the negative pressure distillation column pipeline three.

[0035] As a preferred solution, the pre-distillation column reboiler comprises a pre-distillation column reboiler one and a pre-distillation column reboiler two, a pre-column vertical buffer tank is arranged at the front of the pre-distillation column reboiler one, the column vertical buffer tank is connected with the pressurized distillation column pipeline one through a heat exchange pipeline seven, and the column vertical buffer tank is also connected with the pressurized reflux tank through a heat exchange pipeline eight; a pre-column heat exchange circulating pump is arranged on the heat exchange pipeline eight.

[0036] As a preferred scheme, the bottom of the pressurized rectifying tower is also connected with a pressurized rectifying tower reboiler, the pre-rectifying tower reboiler two, the pressurized rectifying tower reboiler, the negative pressure rectifying tower reboiler one and the fusel alcohol recovery tower reboiler two are heated by external equipment.

[0037] Compared with the prior art, the present application has the following advantages and positive effects:

[0038] (1) The present application adopts the heat pump rectification technology, and through the setting of the negative pressure tower, the reflux ratio of the tower can be greatly reduced, and the energy consumption is saved;

[0039] (2) The negative pressure tower kettle of the present application retains a part of methanol, so that the bubble point of the kettle material is low enough, and the pressurization range of the top is controlled within 150 KPa, thereby obtaining a lower temperature difference, and the selection of the compressor one is more easy, and the actual power consumption is lower, and the COP value of the heat pump system is about 9.65;

[0040] (3) The present application is provided with a pressurized tower, the operating pressure of the tower is 180-300 KPa, and the top temperature is 80-97℃, which can meet the heating heat source required by the pre-rectifying tower kettle reboiler one, realizes the purpose of double-effect rectification, and reduces the steam consumption by more than 40%;

[0041] (4) The fusel alcohol recovery tower of the present application adopts the heat pump rectification technology, the top steam is pressurized and heated after passing through the compressor two, and the fusel alcohol recovery tower reboiler one of the kettle is heated, so that the heat load of the top is reused, and the COP value of the heat pump system of the fusel alcohol recovery tower is about 4.91;

[0042] (5) The comprehensive steam consumption of each ton of refined methanol of the present application is 0.25-0.36 tons, and the average steam consumption of each ton of refined methanol at present is 0.81-1.15 tons, which is close to the lowest steam consumption level in the industry.

[0043] (6) The heat of the top of the negative pressure rectifying tower is recovered as low-pressure steam through the heat pump, which reduces the waste of energy and maximizes energy saving. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 is the structural schematic diagram of the present application;

[0045] Figure 2 is the structural schematic diagram of the pre-rectifying tower, the negative pressure rectifying tower and the pressurized rectifying tower of the present application;

[0046] Figure 3 is the structural schematic diagram of the wastewater treatment device and the fusel alcohol treatment device of the present application;

[0047] 1, pre-rectifying tower 2, pipeline one 3, negative pressure rectifying tower 4, pipeline two

[0048] 5. pressurized rectification column 6. refined methanol tank area 7. waste water evaporator 8. waste water line

[0049] 9. waste water pump 10. waste water cooler 11. water outlet line 12. condensation cooler

[0050] 13. water outlet line 1 14. heater 15. heat exchange line 1 16. heat exchange line 2

[0051] 17. reflux pump 18. fusel alcohol recovery column 19. fusel alcohol recovery line 20. fusel alcohol cooler

[0052] 21. fusel alcohol buffer tank 22. fusel alcohol production pump 23. production line 24. fusel alcohol recovery column kettle pump

[0053] 25. fusel alcohol recovery column reboiler 1 26. fusel alcohol recovery column reboiler 2 27. fusel alcohol vertical buffer tank

[0054] 28. heat exchange line 3 29. compressor 2 30. heat exchange line 4

[0055] 31. crude methanol circulation pump 32. fusel alcohol cooler 1 33. fusel alcohol recovery column line 1

[0056] 34. fusel alcohol return tank reflux tank 35. refined methanol cooler 1 36. fusel alcohol recovery column line 2

[0057] 37. refined methanol cooler 2 38. fusel alcohol reflux pump 39. fusel alcohol recovery column line 3

[0058] 40. pre-rectification column first condenser 41. pre-rectification column line 1 42. pre-rectification column second condenser

[0059] 43. pre-rectification column line 2 44. pre-gas-liquid separator 45. pre-rectification column line 3

[0060] 46. pre-reflux tank 47. pre-rectification column reflux line 48. pre-column reflux pump

[0061] 49. pre-rectification column line 4 50. negative pressure rectification column reboiler 1 51. negative pressure rectification column reboiler 2

[0062] 52. heat exchange line 5 53. heat exchange line 6 54. negative pressure reflux tank

[0063] 55. negative pressure distillation column line 1 56. negative pressure distillation column line 2 57. negative pressure distillation column line 3

[0064] 58. negative pressure column first cooler 59. negative pressure column second cooler 60. interlocking control device

[0065] 61. Vacuum reflux pump 62. Pressurized column cooler 63. Pressurized rectifier column line one

[0066] 64. Pressurized rectifier column line two 65. Pressurized column reflux tank 66. Pressurized column reflux pump

[0067] 67. Rectified methanol cooler 68. Pre-rectifier column reboiler one 69. Pre-rectifier column reboiler two 70. Pre-column vertical surge tank 71. Heat exchange line seven 72. Heat exchange line eight

[0068] 73. Pre-column heat exchange circulation pump 74. Pressurized rectifier column reboiler 75. Compressor one

[0069] 76. Column kettle circulation pump 77. Pre-rectifier column cooler 78. Condensate reflux line

[0070] 79. Waste water line one 80. Common header bus 81. Line 82. Liquid recovery line

[0071] 83. Condenser 84. Reflux line 85. Fusel column overhead line

[0072] 86. Pre-rectifier column preheater. DETAILED DESCRIPTION

[0073] The present application is described in detail below in conjunction with the attached drawings. Figure 1 —ATTACHED DRAWINGS Figure 3 The specific embodiments of the present application will now be described in detail below. It should be appreciated that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of the present application.

[0074] Example One:

[0075] The application provides a four-tower heat pump heat coupling methanol rectification method, which adopts four-tower heat pump heat coupling of a pre-distillation tower 1, a negative pressure rectification tower 3, a pressurized rectification tower 5 and a fusel alcohol recovery tower 18; the bottom of the pre-distillation tower 1 is connected with the feed inlet of the negative pressure rectification tower 3 through a pipeline one 2, a column still circulation pump 76 and a pre-distillation tower cooler 77 are sequentially arranged on the pipeline one 2 between the pre-distillation tower 1 and the negative pressure rectification tower 3, the bottom of the negative pressure rectification tower 3 is connected with the feed inlet of the pressurized rectification tower 5 through a pipeline two 4, the bottom of the negative pressure rectification tower 5 is connected with a negative pressure rectification tower reboiler one 50 and a negative pressure rectification tower reboiler two 51, the top of the negative pressure rectification tower 5 is connected with the negative pressure rectification tower reboiler two 51 through a heat exchange pipeline five 52, a compressor one 75 is arranged on the heat exchange pipeline five 52, preferably, in order to improve stability and reliability, the compressor one 75 is at least two parallel compressor groups, each compressor group at least includes one compressor, when one of the compressor groups has a problem, the device can normally work, the safety is improved, more preferably, the number of the compressor groups is three; the negative pressure rectification tower 5 is connected with the fusel alcohol recovery tower 18 through a fusel alcohol recovery pipeline 19.

[0076] Part of the steam at the top of the pre-distillation tower 1 is used for heating a waste water treatment device, more specifically, part of the steam at the top of the pre-distillation tower 1 is used for heating a heater 14, the heater 14 is used for heating a waste water evaporator 7; the steam at the top of the negative pressure rectification tower 3 is used for heating the negative pressure rectification tower reboiler two 51 after being pressurized and heated by the compressor one 75, part of the steam at the top of the pressurized rectification tower 5 is used for heating the pre-distillation tower reboiler one 68 of the pre-distillation tower 1, part of the steam at the top of the fusel alcohol recovery tower 18 is used for heating the fusel alcohol recovery tower reboiler one 68 after being pressurized and heated by a compressor two 29; the negative pressure rectification tower 3 and the fusel alcohol recovery tower 18 are heat pump rectified by setting the compressors, the heat at the top of the pressurized rectification tower 5 is used for the pre-distillation tower reboiler one 68, and a combined innovation is carried out; preferably, the compressor two 29 is at least two parallel compressor groups, each compressor group at least includes one compressor; in actual work, a part of methanol is reserved in the column still of the negative pressure rectification tower 3, so that the bubble point of the column still material is low enough, the pressurization range of the top of the tower is controlled to be within 150 KPa, and a lower temperature difference is obtained, so that the selection of the compressor one 75 is easier, the actual power consumption of the compressor one 75 is lower, and the COP value of the heat pump compressor system is 8-12, more preferably 9.65;

[0077] The light component impurities at the top of the pre-distillation tower 1 enter a flare system for treatment, and the crude methanol after removing the light component impurities in the column still of the pre-distillation tower 1 enters the negative pressure rectification tower 3;

[0078] The refined methanol product is taken out from the top of the negative pressure rectification tower 3, and the column still material of the negative pressure rectification tower 3 enters the pressurized rectification tower 5;

[0079] The overhead of the pressurized rectifying column 5 is taken out as a refined methanol product, the side line of the pressurized rectifying column 5 is taken out as a material into the fusel recovery column 18, and the bottom of the pressurized rectifying column 5 is taken out as waste water;

[0080] The overhead of the fusel recovery column 18 is taken out as fuel methanol, and the bottom of the fusel recovery column 18 is taken out as waste water.

[0081] Preferably, the waste water taken out from the bottom of the pressurized rectifying column 5 and the waste water taken out from the bottom of the fusel recovery column 18 are further treated in a waste water treatment device, more specifically, by a waste water evaporator 7, and the heater 14 provides heat for the waste water evaporator 7.

[0082] As a preferred solution, the operating pressure of the pre-rectifying column is 110-130 KPa, the overhead temperature is 68-72℃, and the bottom temperature is 72-76℃.

[0083] As a preferred solution, the operating pressure of the negative pressure rectifying column is 60-95 KPa, the overhead temperature is 50-65℃, and the bottom temperature is 60-70℃.

[0084] As a preferred solution, the operating pressure of the pressurized rectifying column is 190-300 KPa, the overhead temperature is 85-93℃, and the bottom temperature is 105-125℃.

[0085] As a preferred solution, the operating pressure of the fusel recovery column is 101-130 KPa, the overhead temperature is 65-75℃, and the bottom temperature is 102-108℃.

[0086] In this embodiment, the specific control parameters of the pre-rectifying column 1, the negative pressure rectifying column 3, the pressurized rectifying column 5, and the fusel recovery column 18 can be as shown in Table 1:

[0087] Apparatus Theoretical plate number Overhead temperature °C Overhead pressure MPaA Reflux ratio Bottom temperature °C Bottom pressure MPaA Pre-fractionator column 39 72 0.130 16.5 75.2 0.150 Vacuum fractionator column 55 51.7 0.060 1.5 63.5 0.065 Pressurized fractionator column 58 85 0.205 2.2 111.6 0.235 Fusel oil recovery column 40 71.5 0.130 4.9 105.3 0.133

[0088] Table 1

[0089] The purification of crude methanol is illustrated in this embodiment. The general composition of methanol includes: methanol: 80-96%, light component content 0.8-2.5%, water content 2.0-13.0%. The methanol content in the gas phase material collected from the top of the pre-distillation column 1 is 2.5-5.5 w%, the methanol content in the aqueous methanol solution collected from the bottom of the pre-distillation column 1 is 80-85 w%; the content of refined methanol product collected from the top of the negative pressure distillation column 3 is 99.9995-99.9999 w%, the methanol content in the aqueous methanol solution collected from the bottom of the negative pressure distillation column 3 is 50-65 w%; the methanol content in the gas phase material collected from the top of the pressurized distillation column 5 is 99.998-99.999 w%, the methanol content in the aqueous methanol solution collected from the bottom of the pressurized distillation column 5 is 12-15 w%, the methanol content in the fusel alcohol collected from the side line of the pressurized distillation column 5 is 15-20%, the methanol content in the gas phase material collected from the top of the fusel alcohol recovery column 18 is 90-96 w%, and the methanol content in the aqueous methanol solution collected from the bottom of the fusel alcohol recovery column 18 is 50-100 ppm.

[0090] Embodiment two:

[0091] The embodiment provides a four-column heat pump heat-coupled methanol distillation device, which comprises a pre-distillation column 1, a negative pressure distillation column 3, a pressurized distillation column 5 and a fusel alcohol recovery column 18 connected in sequence, and more specifically, the bottom of the pre-distillation column 1 is connected with the feed inlet of the negative pressure distillation column 3 through a pipeline one 2, a column kettle circulating pump 76 and a pre-distillation column cooler 77 are arranged on the pipeline one 2 in sequence between the pre-distillation column 1 and the negative pressure distillation column 3, the bottom of the negative pressure distillation column 3 is connected with the feed inlet of the pressurized distillation column 5 through a pipeline two 4, the bottom of the negative pressure distillation column 5 is connected with a negative pressure distillation column reboiler one 50 and a negative pressure distillation column reboiler two 51, the top of the negative pressure distillation column 5 is connected with the negative pressure distillation column reboiler two 51 through a heat exchange pipeline five 52, and a compressor one 75 is arranged on the heat exchange pipeline five 52. Preferably, in order to improve stability and reliability, the compressor one 75 is at least two parallel compressor groups, each compressor group comprises at least one compressor, and when one of the compressor groups fails, the device can still work normally, thereby improving safety.

[0092] The negative pressure rectifying tower 3 in the embodiment adopts heat pump rectification technology (also known as heat pump compressor rectification technology, and hereinafter referred to as heat pump rectification technology for convenience of description), the vapor at the top of the tower is pressurized and heated by the compressor 75, and then is used to heat the negative pressure rectifying tower reboiler 2 51, so that the heat load at the top of the tower is reused. The COP value of the heat pump system of the negative pressure rectifying tower 3 is 8-12, and is more preferably 9.65. The negative pressure rectifying tower reboiler 1 50 can be heated by conventional external steam, and can provide sufficient heat energy supply when the equipment is started or in special situations such as unstable operation. The negative pressure rectifying tower reboiler 2 51 is heated by the vapor collected from the top of the negative pressure rectifying tower 3, and then enters the negative pressure reflux tank 54 after heat exchange.

[0093] The top of the pre-distillation tower 1 is connected with a pre-distillation tower gas treatment device, the lower part of the pre-distillation tower 1 is provided with a pre-distillation tower reboiler, the negative pressure rectifying tower reboiler 2 51 is connected with a negative pressure rectifying tower liquid treatment device through a heat exchange pipeline 6 53, the top of the pressurized rectifying tower 5 is provided with a pressurized rectifying tower gas treatment device, the pressurized rectifying tower gas treatment device is connected with a refined methanol tank area 6, and the refined methanol tank area 6 is also connected with the negative pressure rectifying tower liquid treatment device. The lower part of the pressurized rectifying tower 5 is also provided with a pressurized rectifying tower reboiler 74, which is heated by conventional external steam to provide heat energy supply.

[0094] More specifically: the pre-distillation column gas treatment device comprises a pre-distillation column first condenser 40, which is connected with a pre-distillation column second condenser 42 through a pre-distillation column pipeline one 41, the pre-distillation column second condenser 42 is connected with a pre-gas-liquid separator 44 through a pre-distillation column pipeline two 43, the pre-gas-liquid separator 44 is connected with a pre-reflux tank 46 through a pre-distillation column pipeline three 45, the pre-reflux tank 46 is connected with the top of the pre-distillation column 1 through a pre-distillation column reflux pipeline 47, and a pre-reflux pump 48 is arranged on the pre-distillation column reflux pipeline 47; the top of the pre-reflux tank 46 is connected with the pre-distillation column first condenser 40 through a pre-distillation column pipeline four 49; the crude methanol is fully contacted with gas and liquid through high-efficiency DVST tower plates or several sections of fillers in the pre-distillation column 1, the light components and a small part of the methanol in the crude methanol are taken out from the top of the column in a gaseous form, and are sequentially connected with the gas phase inlets of the pre-distillation column first condenser 40 and the pre-distillation column second condenser 42 and the pre-gas-liquid separator 44; the non-condensable gas outlets (CO, CO2, H2, N2, CH4, multi-carbon alkanes, ethyl acetate, dimethyl ether, etc., 40℃, 0.12MPa (A), 3.0-50.0m3 / h) of the pre-distillation column second condenser 42 and the pre-gas-liquid separator 44 enter a subsequent post-treatment and flare system; the condensate outlets of the pre-distillation column first condenser 40 and the pre-gas-liquid separator 44 are connected to enter the pre-reflux tank 46, and after being pressurized by the pre-reflux pump 48, are introduced into the top tower plate of the pre-distillation column 1 to perform reflux; the top of the pre-distillation column 1 is provided with a interlocking control device 60 with the flare system, the pre-distillation column second condenser 42 and the pre-gas-liquid separator 44, so as to control the amount of methanol taken out; preferably, the pre-distillation column pipeline one 41 between the pre-distillation column first condenser 40 and the pre-distillation column second condenser 42 is also connected with the pre-reflux tank 46, so as to release the excess non-condensable gas of the pre-reflux tank 46.

[0095] The negative pressure rectifying tower liquid treatment device comprises a negative pressure reflux tank 54 connected with the heat exchange pipeline six 53, the negative pressure reflux tank 54 is connected with the upper part of the negative pressure rectifying tower 3 through a negative pressure distillation tower pipeline one 55 and a negative pressure distillation tower pipeline two 56, the negative pressure reflux tank 54 is connected with the refined methanol tank area 6 through the negative pressure distillation tower pipeline one 55 and a negative pressure distillation tower pipeline three 57, a negative pressure tower first cooler 58 and a negative pressure tower second cooler 59 are sequentially arranged on the negative pressure distillation tower pipeline three 57 between the negative pressure reflux tank 54 and the refined methanol tank area 6; a negative pressure reflux pump 61 is arranged on the negative pressure distillation tower pipeline two 56 and the negative pressure distillation tower pipeline three 57; the negative pressure reflux tank 54 is connected with a common bus 80 connected with the compressor one 75 in parallel through a pipeline 81, the negative pressure reflux tank 54 is connected with a liquid recovery pipeline 82, the liquid recovery pipeline 82 is connected with a vacuum system, and a condenser 83 is arranged on the liquid recovery pipeline 82; preferably, a interlocking control device 60 is arranged between the liquid recovery pipeline 82 and the heat exchange pipeline five 52, and is used for controlling the top reflux amount of the negative pressure rectifying tower 3; after light components are removed from the pre-distillation tower 1, a methanol solution containing water is collected from the tower kettle and enters the negative pressure rectifying tower 3, in the negative pressure rectifying tower 3, gas-liquid heat and mass transfer are carried out through high-efficiency tower trays or fillers, water, ethanol, fusel alcohol and the like in the methanol are fully removed, the gas phase in the tower top enters the negative pressure rectifying tower reboiler two 51 through the heat exchange pipeline five 52, heat is supplied to the negative pressure rectifying tower reboiler two 51, the liquid phase after heat exchange flows into the negative pressure reflux tank 54, and the non-condensable gas enters the negative pressure tower first cooler 58 and the negative pressure tower second cooler 59 for further condensation and then enters the refined methanol tank area 6 for storage; the liquid in the negative pressure reflux tank 54 is pressurized through the negative pressure reflux pump 61, one part of the liquid returns to the tower top of the negative pressure rectifying tower 3 as reflux liquid, and the other part of the liquid is cooled and then transported to the refined methanol tank area 6.

[0096] The pressurized rectifying tower gas treatment device comprises a pressurized tower cooler 62, the pressurized tower cooler 62 is connected with the top of the pressurized rectifying tower 5 through a pressurized rectifying tower pipeline one 63, the pressurized tower cooler 62 is connected with the refined methanol tank area 6 through a pressurized rectifying tower pipeline two 64, a pressurized tower reflux tank 65, a pressurized tower reflux pump 66 and a refined methanol cooler 67 are sequentially arranged on the pressurized rectifying tower pipeline two 64 between the pressurized tower cooler 62 and the refined methanol tank area 6; preferably, the pressurized rectifying tower pipeline two 64 of the rear section of the refined methanol cooler 67 is connected with the negative pressure distillation tower pipeline three 57, and the refined methanol formed after condensation of the top of the pressurized rectifying tower 5 is transported to the refined methanol tank area 6 together with the refined methanol condensed in the upper part of the negative pressure rectifying tower 3; the pressurized rectifying tower pipeline two 64 between the pressurized tower reflux pump 66 and the refined methanol cooler 67 is connected with the tower top of the negative pressure rectifying tower 5 through a reflux pipeline 84.

[0097] The pre-distillation column reboiler comprises a pre-distillation column reboiler one 68 and a pre-distillation column reboiler two 69, a front part of the pre-distillation column reboiler one 68 is provided with a pre-column vertical buffer tank 70, the pre-column vertical buffer tank 70 is connected with the pressurized distillation column pipeline one 63 through a heat exchange pipeline seven 71, and the column vertical buffer tank 70 is also connected with the pressurized column reflux tank 65 through a heat exchange pipeline eight 72; the heat exchange pipeline eight 72 is provided with a pre-column heat exchange circulating pump 73; part of the steam at the top of the pressurized distillation column 3 enters the pre-column vertical buffer tank 70, then flows out through the pre-column heat exchange circulating pump 73, and enters the pressurized column reflux tank 65 through the heat exchange pipeline eight 75; the safety of the steam heat exchange after pressurization and the stability of the heat exchange heat are improved through indirect heat exchange between the pre-column vertical buffer tank 70 and the pre-distillation column reboiler one 68; a interlocking control device 60 is arranged between the pre-column vertical buffer tank 70 and the heat exchange pipeline eight 72, so as to control the material flow of the heat exchange flow; the pre-distillation column reboiler two 69 can be heated by using conventional external steam, and sufficient heat energy supply can be provided when the equipment is started or in special conditions such as unstable operation.

[0098] The bottom of the pressurized distillation column 5 is also connected with a pressurized distillation column reboiler 74, the pre-distillation column reboiler two 69, the pressurized distillation column reboiler 74, the negative pressure distillation column reboiler one 50 and the fusel alcohol recovery column reboiler two 26 are heated by external heating equipment, which can be heated by one external heating equipment or separately, and the selection can be made by the skilled person according to the specific conditions, which is not limited in the present application.

[0099] In the embodiment, the total process route adopted is the sequence of the pre-distillation column 1, the negative pressure distillation column 3, the pressurized distillation column 5 and the fusel alcohol recovery column 18, and the methanol is purified, the waste water waste heat evaporation and the condensate water reuse are combined, the heat coupling is fully performed, the energy saving advantage of the heat pump technology is played, the methanol is purified, the pressure and the difficulty of the waste water treatment section are reduced, the average steam consumption of each ton of refined methanol is lower than the lowest steam consumption level in the industry, the energy consumption is saved, the energy waste is reduced, and the energy saving is maximized; the comprehensive steam consumption of the device is 0.25-0.36 tons per ton of refined methanol, and the average steam consumption of each ton of refined methanol is currently between 0.81-1.15 tons, so that the average steam consumption of each ton of refined methanol is lower than the lowest steam consumption level in the industry.

[0100] Embodiment three:

[0101] In the embodiment, the fusel alcohol recovery column 18 is connected with the measuring line of the pressurized distillation column 5, and is used for treating the fusel alcohol collected from the pressurized distillation column 5.

[0102] The fusel alcohol recovery column 18 is connected with the pressurized rectification column 5 through a fusel alcohol recovery pipeline 19, and the fusel alcohol recovery pipeline 19 between the pressurized rectification column 5 and the fusel alcohol recovery column 18 is sequentially provided with a fusel alcohol cooler 20, a fusel alcohol buffer tank 21 and a fusel alcohol extraction pump 22; a top portion of the fusel alcohol recovery column 18 is connected with a methanol gas treatment device; a lower portion of the fusel alcohol recovery column 18 is connected with a wastewater treatment device through an extraction pipeline 23, and the extraction pipeline 23 is provided with a fusel alcohol recovery column bottom pump 24; a bottom portion of the fusel alcohol recovery column 18 is further connected with a fusel alcohol recovery column reboiler one 25 and a fusel alcohol recovery column reboiler two 26; the fusel alcohol recovery column reboiler one 25 is connected with a fusel alcohol vertical buffer tank 27; the fusel alcohol vertical buffer tank 27 is connected with the top portion of the fusel alcohol recovery column 18 through a heat exchange pipeline three 28 and a fusel alcohol column top pipeline 85; the heat exchange pipeline three 28 is provided with a compressor two 29; the fusel alcohol vertical buffer tank 27 is further connected with the methanol gas treatment device through a heat exchange pipeline four 30; the heat exchange pipeline four 30 is provided with a crude methanol circulating pump 31; preferably, the compressor two 29 is at least two parallel compressor sets, and each compressor set comprises at least one compressor.

[0103] The fusel alcohol extracted from the side line port of the pressurized rectification column 5 enters the fusel alcohol recovery column 18 through the fusel alcohol cooler 20, the fusel alcohol buffer tank 21 and the fusel alcohol extraction pump 22 for rectification and purification; a part of the gas extracted from the top portion is used for heating the fusel alcohol recovery column reboiler one 25, and a part is treated through the methanol gas treatment device; the fusel alcohol liquid extracted from the side line contains 30-40% of methanol, and after being injected into the fusel alcohol recovery column 18, the methanol, ethanol, isopropyl alcohol, butanol and other organic matters contained therein can be recovered and used as fuel, i.e. fuel methanol; the fusel alcohol recovery column reboiler two 26 is heated through external conventional steam equipment, which can provide sufficient heat energy supply when the equipment is started or in special cases such as unstable operation.

[0104] In the embodiment, the fusel alcohol recovery column 18 adopts the heat pump rectification technology; the steam at the top portion is pressurized and heated through the compressor two 29 to heat the fusel alcohol recovery column reboiler one 25, so that the heat load at the top portion is reused, and the COP value of the heat pump system of the fusel alcohol recovery column 18 is about 4.91; the fusel alcohol vertical buffer tank 27 and the fusel alcohol recovery column reboiler one 25 are indirectly heat-exchanged, so that the safety and stability of the heat exchange of the pressurized steam are improved.

[0105] Embodiment four:

[0106] The methanol gas treatment device is described in the embodiment, and specifically:

[0107] The methanol gas treatment device comprises a fusel alcohol cooler 32 connected with a fusel alcohol overhead pipeline 85, the fusel alcohol cooler 32 is connected with a fusel alcohol water return reflux tank 34 through a fusel alcohol recovery column pipeline 1 33, the fusel alcohol recovery column pipeline 1 33 is connected with the heat exchange pipeline 4 30, the fusel alcohol water return reflux tank 34 is connected with a fine methanol cooler 1 35, the fusel alcohol water return reflux tank 34 is also connected with a fine methanol cooler 2 37 through a fusel alcohol recovery column pipeline 2 36, a fusel alcohol reflux pump 38 is arranged on the fusel alcohol recovery column pipeline 2 36, the recovery column pipeline 2 36 is connected with the upper part of the fusel alcohol recovery column 18 through a recovery column pipeline 3 39.

[0108] The gas phase at the top of the fusel alcohol recovery column 18 passes through the fusel alcohol cooler 32, the water return reflux tank 34 and the fine methanol cooler 37, and the methanol, ethanol, isopropyl alcohol, butanol and other organic substances in the gas phase are recovered, so that the fuel methanol is obtained.

[0109] Example five:

[0110] The embodiment describes a waste water treatment device, in particular:

[0111] The bottom of the pressurized rectifying column 5 is connected with a waste water treatment device, the waste water treatment device comprises a waste water evaporator 7, the waste water evaporator 7 is connected with the production pipeline 23, the waste water evaporator 7 is connected with the bottom of the pressurized rectifying column 5 through a waste water pipeline 8, a waste water pump 9 is arranged on the waste water pipeline 8, the top of the waste water evaporator 7 is connected with a water outlet pipeline 1 1, a condensation cooler 12 is arranged on the water outlet pipeline 1 1 ; a water outlet pipeline 1 3 is arranged at the bottom of the waste water evaporator 7; the liquid at the bottom of the pressurized rectifying column 5 enters the waste water evaporator 7, is heated and evaporated, the gas phase is cooled by the condensation cooler 12, and then pure water is formed, which is collected, and the part not evaporated is transported to a sewage treatment plant for biochemical treatment through the water outlet pipeline 1 3; the waste water evaporator 7 is also connected with a heater 14, the heater 14 is used for heating the waste water evaporator 7, the heater 14 is connected with the top of the pre-rectifying column 1 through a heat exchange pipeline 1 5, and the gas phase at the top of the pre-rectifying column 1 is used for heating the heater 14, so that the waste water evaporator 7 is heated; the heater 14 is connected with the pre-rectifying column gas treatment device through a heat exchange pipeline 2 16, more specifically, the heater 14 is connected with a pre-rectifying column pipeline 4 49 through the heat exchange pipeline 2 16, and a reflux pump 1 7 is arranged on the heat exchange pipeline 2 16; more specifically, the condensed liquid after the waste water evaporation is added into the pre-reflux tank 46 of the pre-rectifying column through the pipeline 2 16 and the pre-rectifying column pipeline 4 49, and is used as extraction water.

[0112] The components coming out of the wastewater evaporator 7 are mostly water, but also contain a small amount of methanol and other alcohols, which are condensed and returned to the pre-distillation reflux tank 46. This not only recovers the methanol and other alcohols, reducing the loss of useful materials, but also reduces the difficulty and cost of wastewater treatment. More importantly, it reduces the consumption of soft water and saves water resources.

[0113] Preferably, the wastewater pipeline 8 is also connected to a first wastewater pipeline 79, which is provided with a wastewater cooler 10. The wastewater is cooled by the wastewater cooler 10 and then flows out of the first wastewater pipeline 79 to the biochemical system for treatment.

[0114] Preferably, the water outlet pipeline 11 is also connected to a condensed water reflux pipeline 78, which is connected to a pre-distillation tower gas treatment device at the top of the pre-distillation tower 1. More specifically, the condensed water reflux pipeline 78 is connected to the pre-reflux tank 46. The evaporated condensed water is returned to the pre-reflux tank 46 as extraction water.

[0115] This embodiment processes the liquid produced at the bottom of the pressurized distillation tower 5 to obtain pure water. The heat at the top of the negative pressure pre-distillation tower 3 is recovered as low-pressure steam by the negative pressure distillation tower reboiler 2, reducing energy waste and maximizing energy saving.

[0116] The specific working principle of the present application is as follows: crude methanol enters into the pre-distillation column 1 through the pre-distillation column pre-heater 86, and through the efficient DVST tray or several sections of packing in the column, the light components and a small part of the methanol in the crude methanol are taken out from the top of the pre-distillation column 1 in a gaseous form, a part of the gaseous form is sequentially connected to the gas phase inlet of the pre-distillation column first condenser 40, the pre-distillation column second condenser 42 and the pre-gas-liquid separator 44, the non-condensable gas outlet (CO, CO2, H2, N2, CH4, multi-carbon alkane, ethyl acetate, dimethyl ether, etc., 40℃, 0.12MPa(A), 3.0-50.0m3 / h) of the pre-distillation column second condenser 42 and the pre-gas-liquid separator 44 enters the subsequent post-treatment and flare system, the condensate outlet of the pre-distillation column first condenser 40 and the pre-gas-liquid separator 44 is connected to enter the pre-reflux tank 46, and after being pressurized by the pre-reflux pump 48, it enters the top tray of the pre-distillation column 1 for reflux, and a chain control device 60 is arranged between the top of the pre-distillation column 1 and the flare system; a part of the gaseous form provides heat source for the heater 14 through the heat exchange pipeline one 15; after the crude methanol removes the light component impurities such as acetone and dimethyl ether through the pre-distillation column 1, it enters the negative pressure distillation column 3 through the pipeline one 2, the steam at the top of the negative pressure distillation column 3 is pressurized by the compressor one 75, sprayed into saturation, and then enters the negative pressure distillation column reboiler two 51 to provide heat source for the negative pressure distillation column reboiler two 51, the heat-exchanged liquid phase flows into the negative pressure reflux tank 54, a part of the non-condensable gas enters the negative pressure column first cooler 58 and the negative pressure column first cooler 59 for further condensation and then enters the refined methanol tank area 6 for storage, and the other part of the non-condensable gas is cooled by the condenser 83 and then enters the vacuum system; the liquid in the negative pressure reflux tank 54 is pressurized by the negative pressure reflux pump 61 and returned to the top of the negative pressure distillation column 3 as reflux liquid; the liquid at the bottom of the pressurized distillation column 5 enters the waste water evaporator 7, is heated and evaporated, the gas phase is cooled by the condensing cooler 12 to form pure water, which is collected, and the part not evaporated is transported to the sewage treatment plant for biochemical treatment through the water outlet pipeline one 13; the liquid at the bottom of the pressurized distillation column 5 can also be cooled by the waste water cooler 10 on the waste water pipeline one 79 and then enter the biochemical system for treatment; the heater 14 connected to the waste water evaporator 7 is used to heat the waste water evaporator 7, the gas generated at the top of the pre-distillation column 1 provides heat source for the heater 14, thereby heating the waste water evaporator 7; the fusel alcohol taken out from the side line of the pressurized distillation column 5 enters the fusel alcohol recovery column 18 for rectification and purification through the fusel alcohol cooler 20, the fusel alcohol buffer tank 21 and the fusel alcohol take-out pump 22, a part of the gas taken out from the top is used to heat the fusel alcohol recovery column reboiler two 26, and a part is treated by the methanol gas treatment device; the fusel alcohol liquid taken out from the side line contains 30-40% of methanol, which is injected into the fusel alcohol recovery column 18, and the methanol, ethanol, isopropyl alcohol, butanol and other organic substances in it can be recovered and used as fuel.

[0117] In the first to fourth embodiments, the conventional three-tower downstream double-effect process of the prior art can be directly improved:

[0118] For example, in a certain methanol plant, the conventional three-tower downstream double-effect process is used, the feed quantity is 71.1 t / h, and when the operating parameters reach the optimum, the energy consumption is 1.25 tons of steam / rectified methanol.

[0119] In order to reduce the methanol steam consumption, the four-tower heat pump heat-coupled rectification route described in the application is used, a negative pressure rectification tower 3 is added, the methanol steam at the top of the pressurized rectification tower 5 is used to provide heat source for the pre-rectification tower reboiler one 68, and the negative pressure rectification tower reboiler one 50 of the negative pressure rectification tower 3 uses the methanol steam at the top thereof, which is pressurized and heated by the compressor one 75 and then reused by itself, thereby saving 68 t / h of steam energy consumption. Considering the electric energy consumption of the compressor one 75 of 4550 kw, the COP value of the heat pump reaches about 8.6. The normal steam consumption of the pre-rectification tower 1 is 17.14 tons / h, and during the commissioning process, the gaseous phase rectified methanol steam at the top of the pressurized rectification tower 5 is used to provide heat for the newly added pre-rectification tower reboiler one 68, the addition of the water steam of the pre-rectification tower 1 is gradually reduced, and finally the water steam consumption of the pre-rectification tower 1 is reduced to zero. The high-quality rectified methanol at the top can be produced, and the proportion of the high-quality rectified methanol in the total rectified methanol is about 17.44%.

[0120] The heat pump rectification mode is used for the fusel alcohol recovery tower 18, the compression electric energy consumption is 350 kw, no steam is consumed, the comprehensive water steam consumption of the rectified methanol is 0.31-0.35 t / ton of rectified methanol, the electric energy consumption is according to the electricity price of 0.6 yuan / kw.h, the steam price is according to 200 yuan / ton, the steam consumption per ton of rectified methanol is 0.24 tons of steam, and the comprehensive consumption is 0.55-0.59 tons of steam / ton of rectified methanol. With the increase of the carbon trading price, the steam price will further increase, the electric price will further decrease with the development of new energy technology, and the comprehensive benefits of the process will be more obvious.

[0121] As described above, since the technical scheme is used, the application has the following advantages and positive effects:

[0122] (1) The heat pump rectification technology is used in the application, the reflux ratio of the tower can be greatly reduced by arranging the negative pressure tower, and the energy consumption is saved;

[0123] (2) The negative pressure tower of the application retains a part of the methanol, so that the bubble point of the tower kettle material is low enough, the pressurization range of the top of the tower is controlled within 150 KPa, and then a lower temperature difference is obtained, the selection of the compressor one is easier, the actual power consumption is lower, and the COP value of the heat pump system is about 9.65;

[0124] (3) the present application is provided with a pressurized tower, the operating pressure of the tower is 180-300Kpa, the tower top temperature is 80-97℃, which can meet the heating heat source required by the pre-distillation tower reboiler one, realizes the purpose of double-effect distillation, and reduces the primary steam consumption by more than 40%;

[0125] (4) the heat pump distillation technology is used in the fusel recovery tower of the present application, the tower top steam is pressurized and heated by the compressor two, and then heat is supplied to the reboiler one of the tower bottom fusel recovery tower, so that the heat load of the tower top is reused, and the COP value of the heat pump system of the fusel recovery tower is about 4.91;

[0126] (5) the comprehensive steam consumption of each ton of refined methanol of the present application is 0.25-0.36 tons, and the average steam consumption of each ton of refined methanol is currently 0.81-1.15 tons, which is close to the lowest steam consumption level in the industry;

[0127] (6) the heat of the tower top of the negative pressure distillation tower is recovered as low-pressure steam through the heat pump, which reduces the waste of energy and maximizes energy saving.

[0128] The above-mentioned devices, connection relationships, etc. which are not specifically described belong to the prior art, and the present application will not be specifically described here.

[0129] The preferred mode of the present application is described in detail above in combination with the drawings, but the present application is not limited to the specific details in the above-described embodiments, and various simple modifications can be made to the technical solutions of the present application within the technical concept of the present application, which all belong to the protection scope of the present application.

[0130] In addition, it should be noted that each specific technical feature described in the above specific embodiments can be combined in any appropriate manner without contradiction, and in order to avoid unnecessary repetition, various possible combinations of the present application will not be described again.

[0131] In addition, any combination of various different embodiments of the present application can also be made, as long as it does not deviate from the idea of the present application, and the application should also be considered as disclosed content of the present application.

Claims

1. A four-tower heat pump thermally coupled methanol distillation method, characterized in that, A four-tower heat pump thermal coupling system is adopted, consisting of a pre-distillation tower (1), a negative pressure distillation tower (3), a pressurized distillation tower (5), and a fusel oil recovery tower (18). The steam at the top of the negative pressure distillation column (3) is pressurized and heated by compressor one (75) to heat the reboiler two (51) of the negative pressure distillation column; The light component impurities collected from the top of the pre-distillation column (1) are processed in the flare system. Part of the steam from the top of the pre-distillation column (1) is used to heat the wastewater treatment device. The crude methanol from the bottom of the pre-distillation column (1) after removing the light component impurities enters the negative pressure distillation column (3). The top of the negative pressure distillation column (3) produces refined methanol. The steam at the top of the negative pressure distillation column (3) is pressurized and heated by compressor one (75) to heat the reboiler two (51) of the negative pressure distillation column. The material in the bottom of the negative pressure distillation column (3) enters the pressurized distillation column (5). The pressurized distillation column (5) produces refined methanol at the top. Part of the steam from the top of the pressurized distillation column (5) is used to heat the reboiler (68) of the pre-distillation column (1). The material from the side stream of the pressurized distillation column (5) enters the fusel oil recovery column (18). Wastewater is produced from the bottom of the pressurized distillation column (5). The top of the fusel oil recovery tower (18) produces fuel methanol. Part of the steam from the top of the fusel oil recovery tower (18) is pressurized and heated by compressor two (29) to heat the reboiler one (25) of the fusel oil recovery tower. Wastewater is produced from the bottom of the fusel oil recovery tower (18).

2. The four-tower heat pump thermally coupled methanol distillation method according to claim 1, characterized in that, The operating pressure of the negative pressure distillation column (3) is 60-95 kPa, the top temperature is 50-65℃, and the bottom temperature is 60-70℃.

3. The four-tower heat pump thermally coupled methanol distillation method according to claim 1, characterized in that, The operating pressure of the pressurized distillation column (5) is 190-300 kPa, the top temperature is 85-93℃, and the bottom temperature is 105-125℃.

4. The four-tower heat pump thermally coupled methanol distillation method according to claim 1, characterized in that, The operating pressure of the fusel oil recovery tower (18) is 101-130 kPa, the top temperature is 65-75℃, and the bottom temperature is 102-108℃.

5. A four-tower heat pump thermally coupled methanol distillation apparatus using the four-tower heat pump thermally coupled methanol distillation method according to any one of claims 1-4, characterized in that, The structure includes a pre-distillation column (1), a negative pressure distillation column (3), a pressurized distillation column (5), and a fusel oil recovery column (18) connected in sequence. The bottom of the negative pressure distillation column (3) is connected to a negative pressure distillation column reboiler one (50) and a negative pressure distillation column reboiler two (51). The top of the negative pressure distillation column (3) is connected to the negative pressure distillation column reboiler two (51) through a heat exchange pipeline five (52). A compressor one (75) is provided on the heat exchange pipeline five (52).

6. The four-tower heat pump thermally coupled methanol distillation apparatus according to claim 5, characterized in that, The bottom of the fusel oil recovery tower (18) is connected to a fusel oil recovery tower reboiler one (25) and a fusel oil recovery tower reboiler two (26). The fusel oil recovery tower reboiler one (25) is connected to a fusel oil vertical buffer tank (27). The fusel oil vertical buffer tank (27) is connected to the top of the fusel oil recovery tower (18) through a heat exchange pipeline three (28) and a fusel oil tower top pipeline (85). A compressor two (29) is provided on the heat exchange pipeline three (28). The fusel oil vertical buffer tank (27) is also connected to a methanol gas processing device through a heat exchange pipeline four (30). A crude methanol circulation pump (31) is provided on the heat exchange pipeline four (30).

7. A four-tower heat pump thermally coupled methanol distillation apparatus according to claim 6, characterized in that, The compressor one (75) and compressor two (29) are at least two compressor sets connected in parallel, and each compressor set includes at least one compressor.

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