Methanol rectification system

Abstract

The utility model belongs to a methanol rectification system. Comprising a crude methanol pipeline which is connected with an inlet of a pre-rectifying tower, a tower kettle liquid outlet of the pre-rectifying tower is connected with an inlet of a pressurized rectifying tower, a tower kettle liquid outlet of the pressurized rectifying tower is connected with an inlet of a low-pressure rectifying tower, and a tower kettle liquid outlet of the low-pressure rectifying tower is connected with an inlet of a negative-pressure rectifying tower. A middle tower side line pipeline of the negative pressure rectifying tower is connected with the recovery rectifying tower; and a gas phase outlet of the pressurized rectifying tower, a gas phase outlet of the low-pressure rectifying tower, a gas phase outlet of the negative-pressure rectifying tower and a gas phase outlet of the recovery rectifying tower are respectively connected with a refined methanol product pipeline. The method has the advantages that five towers are used for rectification, heat can be graded and fully utilized in the rectification process, so that the purpose of reducing total energy consumption as much as possible is achieved, meanwhile, methanol is rectified into a positive substance system, so that decompression operation is beneficial to separation of methanol from substances such as water and ethanol, and energy required by separation can be further reduced.

Description

Technical Field

[0001] The utility model belongs to the technical field of methanol distillation and purification, in particular to a methanol distillation system. Background Art

[0002] Currently, the methanol content in methanol products obtained by directly synthesizing methanol from synthesis gas is generally below 96%. Methanol of this specification cannot meet the raw material requirements of most chemical products. Therefore, methanol distillation is currently the most common way to obtain refined methanol. Its basic principle is to separate most impurities other than methanol in crude methanol by distillation, thereby obtaining a refined methanol product that meets the use requirements.

[0003] The three-tower methanol distillation (co-current double-effect distillation) process currently widely used in methanol refining involves sequential distillation and separation of crude methanol through a pre-distillation tower, a pressure distillation tower, and an atmospheric distillation tower. Methanol products are obtained at the top of the pressure tower and the top of the atmospheric tower, respectively. The separation sequence involves the pre-distillation tower removing light components from the crude methanol. The crude methanol from the bottom of the tower enters the pressure distillation tower. The latent heat of condensation of the methanol vapor at the top of the pressure tower serves as a reboiling heat source for the atmospheric tower, achieving co-current double-effect distillation. Fusel alcohols are withdrawn from the atmospheric tower sideline, and wastewater is discharged from the bottom of the atmospheric tower. This method is a common crude methanol refining process. The methanol distillation process consumes approximately 417-3223.7 MJ / ton of refined methanol product, resulting in high production energy consumption. As the scale of methanol refining expands, total energy consumption also increases significantly. Improving the yield of refined methanol while conserving energy has become a pressing technical challenge. Utility Model Content

[0004] The utility model provides a methanol distillation system, which is used to solve the technical problems raised in the above background technology.

[0005] The technical solution of the utility model is:

[0006] A methanol distillation system comprises a crude methanol pipeline, wherein the crude methanol pipeline is connected to the inlet of a pre-distillation tower, the bottom liquid outlet of the pre-distillation tower is connected to the inlet of a pressure distillation tower, the bottom liquid outlet of the pressure distillation tower is connected to the inlet of a low-pressure distillation tower, the bottom liquid outlet of the low-pressure distillation tower is connected to the inlet of a negative pressure distillation tower, and a side line pipeline in the negative pressure distillation tower is connected to a recovery distillation tower; and the gas phase outlet of the pressure distillation tower, the gas phase outlet of the low-pressure distillation tower, the gas phase outlet of the negative pressure distillation tower, and the gas phase outlet of the recovery distillation tower are respectively connected to a refined methanol product pipeline.

[0007] The beneficial effects of the utility model are as follows: the utility model utilizes the characteristic that methanol distillation is a positive system, and the entire process adopts a reduced pressure operation, which is not only conducive to the separation of methanol from substances such as water and ethanol, but also can further reduce the energy required for separation; further, the utility model utilizes a pre-distillation tower, a pressurized distillation tower, a low-pressure distillation tower, a negative pressure distillation tower and a recovery distillation tower to perform five-tower distillation, so as to achieve the characteristic of improving the yield of refined methanol.

[0008] Preferably, the crude methanol pipeline is connected to the inlet of the pre-distillation tower through the first channel of the first crude alcohol preheater and the first channel of the second crude alcohol preheater; the gas phase outlet of the pre-distillation tower is connected to the non-condensable gas separation tank through the first channel of the pre-tower top condenser, the gas phase outlet of the non-condensable gas separation tank is connected to the gas phase inlet of the extraction tank, the liquid phase outlet of the non-condensable gas separation tank and the liquid phase outlet of the extraction tank are respectively connected to the inlet of the pre-tower reflux tank, and the outlet of the pre-tower reflux tank is connected to the reflux port of the pre-distillation tower through a pre-tower reflux pump; a four-way valve is provided between the bottom liquid outlet of the pre-distillation tower and the inlet of the pressurized distillation tower, the third end of the four-way valve is connected to the inlet of the lower part of the pre-distillation tower through the first channel of the first pre-tower reboiler, and the fourth end of the four-way valve is connected to the inlet of the lower part of the pre-distillation tower through the first channel of the second pre-tower reboiler.

[0009] Preferably, the second channel inlet of the pre-tower top condenser is connected to the first circulating water inlet channel, the second channel outlet of the pre-tower top condenser is connected to the circulating water outlet pipe, the extraction water inlet of the extraction tank is connected to the extraction water pipe, and the gas phase outlet of the extraction tank is connected to the first non-condensable gas pipe; the second end of the four-way is connected to the inlet of the pressurized distillation tower through the pressurized tower feed pump and the first channel of the pressurized tower feed preheater.

[0010] Preferably, the gas phase outlet of the pressurized distillation tower is respectively connected to the second channel of the low-pressure tower reboiler and the second channel of the first pre-tower reboiler, the outlets of the second channel of the low-pressure tower reboiler and the second channel of the first pre-tower reboiler are respectively connected to the pressurized tower reflux tank, the outlet of the pressurized tower reflux tank is respectively connected to the reflux port of the pressurized distillation tower and the second channel of the second crude alcohol preheater through the pressurized tower reflux pump, and the outlet of the second channel of the second crude alcohol preheater is connected to the refined methanol product pipeline.

[0011] Preferably, the bottom liquid outlet of the pressurized distillation tower is connected to the inlet of the low-pressure distillation tower through the first tee and the second channel of the pressurized tower feed preheater, and the third end of the first tee is connected to the lower part of the pressurized distillation tower through the first channel of the pressurized tower reboiler; the steam pipe network is connected to the condensate pipeline through the second channel of the pressurized tower reboiler, and the condensate pipeline is connected to the condensate storage tank through the second channel of the second pre-tower reboiler.

[0012] Preferably, the gas phase outlet of the low-pressure distillation tower is connected to the low-pressure tower reflux pump through the second channel of the negative pressure tower reboiler and the low-pressure tower reflux tank, the outlet of the low-pressure tower reflux pump is respectively connected to the reflux port of the low-pressure distillation tower and the refined methanol product pipeline, the tower bottom liquid outlet of the low-pressure distillation tower is connected to the negative pressure distillation tower through the second tee, the negative pressure tower feed pump and the first channel of the negative pressure tower feed cooler; the third end of the second tee is connected to the inlet of the lower part of the low-pressure distillation tower through the first channel of the low-pressure tower reboiler; the second circulating water inlet pipeline is connected to the circulating water outlet pipeline through the second channel of the negative pressure tower feed cooler.

[0013] Preferably, the gas phase outlet of the negative pressure distillation tower is connected to the negative pressure tower reflux tank through the first channel of the negative pressure tower cooler, the gas phase outlet of the negative pressure tower reflux tank is connected to the vacuum pump separation tank, and the gas phase outlet of the vacuum pump separation tank is connected to the second non-condensable gas pipeline through the negative pressure tower vacuum pump; the liquid phase outlet of the vacuum pump separation tank is refluxed into the negative pressure tower reflux tank through the first channel of the vacuum pump separation tank condenser, and the liquid phase outlet of the negative pressure tower reflux tank is respectively connected to the reflux port of the negative pressure distillation tower and the refined methanol product pipeline through the negative pressure tower reflux pump; the tower bottom liquid outlet of the negative pressure distillation tower is connected to the waste water pipeline through the third tee and the negative pressure tower bottom liquid pump; the third end of the third tee is connected to the lower part of the negative pressure distillation tower through the first channel of the negative pressure tower reboiler; the tower side line pipeline in the middle of the negative pressure distillation tower is connected to the inlet of the recovery distillation tower through the negative pressure tower side line extraction booster pump.

[0014] Preferably, the gas phase outlet of the recovery distillation tower is connected to the recovery tower reflux tank through the first channel of the recovery tower condenser, and the outlet of the recovery tower reflux tank is respectively connected to the reflux port of the recovery distillation tower and the refined methanol product pipeline through the recovery tower reflux pump; the bottom liquid outlet of the recovery distillation tower is connected to the wastewater pipeline through the fourth tee and the recovery tower bottom liquid pump; the third end of the fourth tee is connected to the lower part of the recovery distillation tower through the first channel of the recovery tower reboiler; the steam pipe network is connected to the second channel inlet of the second pre-tower reboiler through the second channel of the recovery tower reboiler; the side line pipeline in the middle of the recovery distillation tower is connected to the fusel alcohol pipeline.

[0015] The utility model also includes a third circulating water inlet channel, which is respectively connected to the second channel of the negative pressure tower cooler, the second channel of the vacuum pump separation tank condenser and the second channel of the recovery tower condenser, and the second channel outlet of the negative pressure tower cooler, the second channel outlet of the vacuum pump separation tank condenser and the second channel outlet of the recovery tower condenser are respectively connected to the circulating water outlet pipe.

[0016] A methanol distillation system is manufactured according to the above technical solution. The utility model uses five-tower distillation, and can fully utilize heat in a graded manner during the distillation process to achieve the purpose of reducing overall energy consumption as much as possible. At the same time, since methanol distillation is a positive system, the decompression operation is beneficial to the separation of methanol from substances such as water and ethanol, which can further reduce the energy required for separation; the utility model can fully refine crude methanol to achieve the characteristic of improving the yield of refined methanol. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural diagram of the utility model;

[0018] Numbers in the figure: 1, first crude alcohol preheater; 2, second crude alcohol preheater; 3, pre-distillation tower; 4, first pre-tower reboiler; 5, second pre-tower reboiler; 6, pressurized tower feed pump; 7, pre-tower reflux pump; 8, pre-tower reflux tank; 9, pre-tower top condenser; 10, non-condensable gas separation tank; 11, crude methanol pipeline; 12, pressurized tower feed preheater; 13, pressurized tower reboiler; 14, pressurized distillation Tower; 15, pressure tower reflux pump; 16, pressure tower reflux tank; 17, low-pressure tower reboiler; 18, low-pressure distillation tower; 19, negative pressure tower feed pump; 20, negative pressure tower feed cooler; 21, low-pressure tower reflux pump; 22, low-pressure tower reflux tank; 23, negative pressure tower reboiler; 24, negative pressure distillation tower; 25, negative pressure tower kettle liquid pump; 26, negative pressure tower reflux pump; 27, negative pressure tower reflux tank; 28, Negative pressure tower cooler; 29. Recovery tower reboiler; 30. Recovery distillation tower; 31. Steam pipe network; 32. Recovery tower reflux pump; 33. Recovery tower reflux tank; 34. Negative pressure tower vacuum pump; 35. Vacuum pump separation tank; 36. Vacuum pump separation tank condenser; 37. Negative pressure tower side line extraction booster pump; 38. Extraction tank; 39. Recovery tower condenser; 40. Recovery tower bottom liquid pump; 41. Refined methanol product pipeline; 42. Four-way valve; 43. First circulation water inlet channel; 44. Second circulation water inlet pipeline; 45. Third circulation water inlet channel; 46. Circulating water outlet pipeline; 47. Extraction water pipeline; 48. First non-condensable gas pipeline; 49. Second non-condensable gas pipeline; 50. First three-way valve; 51. Second three-way valve; 52. Third three-way valve; 53. Fourth three-way valve; 54. Condensate storage tank; 55. Wastewater pipeline. DETAILED DESCRIPTION

[0019] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is described in detail below with reference to the accompanying drawings. The description in this part is only exemplary and explanatory and should not have any limiting effect on the scope of protection of the present invention.

[0020] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0021] It should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the utility model product is typically placed when in use. These terms are intended solely to facilitate and simplify the description of the utility model and are not intended to indicate or imply that the device or component referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the utility model. Furthermore, the terms "first," "second," and "third," etc., are used solely for distinction and description and should not be construed as indicating or implying relative importance.

[0022] Furthermore, terms such as "horizontal," "vertical," and "overhanging" do not necessarily imply that a component must be absolutely horizontal or overhanging, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but rather that it can be slightly tilted.

[0023] It should also be noted that, in the description of this utility model, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections, electrical connections; direct connections, indirect connections through an intermediate medium, and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this utility model based on the specific circumstances.

[0024] like Figure 1 As shown, the utility model is a methanol distillation system, comprising a crude methanol pipeline 11, the crude methanol pipeline 11 is connected to the inlet of a pre-distillation tower 3, the bottom liquid outlet of the pre-distillation tower 3 is connected to the inlet of a pressure distillation tower 14, the bottom liquid outlet of the pressure distillation tower 14 is connected to the inlet of a low-pressure distillation tower 18, the bottom liquid outlet of the low-pressure distillation tower 18 is connected to the inlet of a negative pressure distillation tower 24, and the side line pipeline in the negative pressure distillation tower 24 is connected to a recovery distillation tower 30; the gas phase outlet of the pressure distillation tower 14, the gas phase outlet of the low-pressure distillation tower 18, the gas phase outlet of the negative pressure distillation tower 24 and the gas phase outlet of the recovery distillation tower 30 are respectively connected to a refined methanol product pipeline 41.

[0025] The crude methanol pipeline 11 is connected to the inlet of the pre-distillation tower 3 through the first channel of the first crude alcohol preheater 1 and the first channel of the second crude alcohol preheater 2; the gas phase outlet of the pre-distillation tower 3 is connected to the non-condensable gas separation tank 10 through the first channel of the pre-tower top condenser 9, the gas phase outlet of the non-condensable gas separation tank 10 is connected to the gas phase inlet of the extraction tank 38, the liquid phase outlet of the non-condensable gas separation tank 10 and the liquid phase outlet of the extraction tank 38 are respectively connected to the inlet of the pre-tower reflux tank 8, and the outlet of the pre-tower reflux tank 8 is connected to the reflux port of the pre-distillation tower 3 through the pre-tower reflux pump 7; a four-way valve 42 is provided between the bottom liquid outlet of the pre-distillation tower 3 and the inlet of the pressurized distillation tower 14, the third end of the four-way valve 42 is connected to the inlet of the lower part of the pre-distillation tower 3 through the first channel of the first pre-tower reboiler 4, and the fourth end of the four-way valve 42 is connected to the inlet of the lower part of the pre-distillation tower 3 through the first channel of the second pre-tower reboiler 5.

[0026] Furthermore, the second channel inlet of the pre-tower top condenser 9 is connected to the first circulating water inlet channel 43, the second channel outlet of the pre-tower top condenser 9 is connected to the circulating water outlet pipe 46, the extraction water inlet of the extraction tank 38 is connected to the extraction water pipe 47, and the gas phase outlet of the extraction tank 38 is connected to the first non-condensable gas pipe 48; the second end of the four-way valve 42 is connected to the inlet of the pressurized distillation tower 14 through the pressurized tower feed pump 6 and the first channel of the pressurized tower feed preheater 12.

[0027] Furthermore, the gas phase outlet of the pressurized distillation tower 14 is respectively connected to the second channel of the low-pressure tower reboiler 17 and the second channel of the first pre-tower reboiler 4, and the outlets of the second channel of the low-pressure tower reboiler 17 and the second channel of the first pre-tower reboiler 4 are respectively connected to the pressurized tower reflux tank 16, and the outlet of the pressurized tower reflux tank 16 is respectively connected to the reflux port of the pressurized distillation tower 14 and the second channel of the second crude alcohol preheater 2 through the pressurized tower reflux pump 15, and the outlet of the second channel of the second crude alcohol preheater 2 is connected to the refined methanol product pipeline 41.

[0028] Furthermore, the bottom liquid outlet of the pressurized distillation tower 14 is connected to the inlet of the low-pressure distillation tower 18 through the first tee 50 and the second channel of the pressurized tower feed preheater 12, and the third end of the first tee 50 is connected to the lower part of the pressurized distillation tower 14 through the first channel of the pressurized tower reboiler 13; the steam pipe network 31 is connected to the condensate pipeline through the second channel of the pressurized tower reboiler 13, and the condensate pipeline is connected to the condensate storage tank 54 through the second channel of the second pre-tower reboiler 5.

[0029] Furthermore, the gas phase outlet of the low-pressure distillation tower 18 is connected to the low-pressure tower reflux pump 21 through the second channel of the negative pressure tower reboiler 23 and the low-pressure tower reflux tank 22, and the outlet of the low-pressure tower reflux pump 21 is respectively connected to the reflux port of the low-pressure distillation tower 18 and the refined methanol product pipeline 41, and the bottom liquid outlet of the low-pressure distillation tower 18 is connected to the negative pressure distillation tower 24 through the second tee 51, the negative pressure tower feed pump 19 and the first channel of the negative pressure tower feed cooler 20; the third end of the second tee 51 is connected to the inlet of the lower part of the low-pressure distillation tower 18 through the first channel of the low-pressure tower reboiler 17; the second circulating water inlet pipeline 44 is connected to the circulating water outlet pipeline 46 through the second channel of the negative pressure tower feed cooler 20.

[0030] Furthermore, the gas phase outlet of the negative pressure distillation tower 24 is connected to the negative pressure tower reflux tank 27 through the first channel of the negative pressure tower cooler 28, and the gas phase outlet of the negative pressure tower reflux tank 27 is connected to the vacuum pump separation tank 35, and the gas phase outlet of the vacuum pump separation tank 35 is connected to the second non-condensable gas pipeline 49 through the negative pressure tower vacuum pump 34; the liquid phase outlet of the vacuum pump separation tank 35 is refluxed to the negative pressure tower reflux tank 27 through the first channel of the vacuum pump separation tank condenser 36, and the liquid phase of the negative pressure tower reflux tank 27 is refluxed to the negative pressure tower reflux tank 27. The outlet is connected to the reflux port of the negative pressure distillation tower 24 and the refined methanol product pipeline 41 respectively through the negative pressure tower reflux pump 26; the bottom liquid outlet of the negative pressure distillation tower 24 is connected to the wastewater pipeline 55 through the third tee 52 and the negative pressure tower bottom liquid pump 25; the third end of the third tee 52 is connected to the lower part of the negative pressure distillation tower 24 through the first channel of the negative pressure tower reboiler 23; the tower side line pipeline in the middle of the negative pressure distillation tower 24 is connected to the inlet of the recovery distillation tower 30 through the negative pressure tower side line extraction pressure pump 37.

[0031] Furthermore, the gas phase outlet of the recovery distillation tower 30 is connected to the recovery tower reflux tank 33 through the first channel of the recovery tower condenser 39, and the outlet of the recovery tower reflux tank 33 is respectively connected to the reflux port of the recovery distillation tower 30 and the refined methanol product pipeline 41 through the recovery tower reflux pump 32; the bottom liquid outlet of the recovery distillation tower 30 is connected to the wastewater pipeline 55 through the fourth three-way valve 53 and the recovery tower bottom liquid pump 40; the third end of the fourth three-way valve 53 is connected to the lower part of the recovery distillation tower 30 through the first channel of the recovery tower reboiler 29; the steam pipe network 31 is connected to the second channel inlet of the second pre-tower reboiler 5 through the second channel of the recovery tower reboiler 29; the side line pipeline in the middle of the recovery distillation tower 30 is connected to the fusel alcohol pipeline.

[0032] The utility model also includes a third circulating water inlet channel 45, which is respectively connected to the second channel of the negative pressure tower cooler 28, the second channel of the vacuum pump separation tank condenser 36 and the second channel of the recovery tower condenser 39, and the second channel outlet of the negative pressure tower cooler 28, the second channel outlet of the vacuum pump separation tank condenser 36 and the second channel outlet of the recovery tower condenser 39 are respectively connected to the circulating water outlet pipe 46.

[0033] The utility model also provides a method for a methanol distillation system, the method comprising the following steps:

[0034] Step 1: Crude methanol in the crude methanol pipeline 11 passes through the first channel of the first crude alcohol preheater 1 and the first channel of the second crude alcohol preheater 2 in sequence for heat exchange, and then enters the pre-distillation tower 3 for rectification after the heat exchange reaches 70-75°C. The crude methanol in the crude methanol pipeline 11 has a pressure of 0.400 MPaG and a temperature of room temperature, and has a composition of: CH3OH: 92-97%, H2O: 3-7%, C2H5OH: 0.03-0.08%, CO: 0.05-0.1%, CO2: 0.05-0.15%, and CH3O CH3: 0.03-0.08%.

[0035] Step 2: The crude alcohol in the pre-distillation tower 3 is distilled by providing heat sources through the first pre-tower reboiler 4 and the second pre-tower reboiler 5; the heat source of the first pre-tower reboiler 4 is the gas phase from the pressurized distillation tower 14, which is methanol vapor with a pressure of 0.60 MPaG and a temperature of 121-125°C; the heat source of the second pre-tower reboiler 5 is the steam condensate from the second channel of the pressurized tower reboiler 13 and the second channel of the recovery tower reboiler 29, with a steam condensate pressure of 0.1 MPa(G) and a temperature of 180°C;

[0036] Step 3: The gas phase at the gas phase outlet of the pre-distillation tower 3 is heat exchanged with the circulating water through the first channel of the pre-tower top condenser 9, and the methanol in the gas phase is condensed and enters the non-condensable gas separation tank 10. The non-condensable gas in the non-condensable gas separation tank 10 and the extraction water in the extraction water pipeline 47 enter the extraction tank 38 for extraction, and the extracted gas phase enters the first non-condensable gas pipeline 48 for treatment; the liquid phase in the non-condensable gas separation tank 10 and the liquid phase in the extraction tank 38 enter the pre-tower reflux tank 8 as the reflux liquid of the pre-distillation tower 3, and finally is sent to the pre-distillation tower 3 through the pre-tower reflux pump 7; the gas phase pressure at the gas phase outlet of the pre-distillation tower 3 is: 0.030MPaG, the temperature is 72.0-80.0℃, and the components are: CH3OH: 82-87%, H2O: 7-13%, C2H5OH: 0.0005-0.002%, CO: 0.1 ~0.3%, CO2: 2~4%, CH3OCH3: 0.05~0.1%; the non-condensable gas pressure entering the non-condensable gas separation tank 10 is: 0.030MPaG, the temperature is 40~50℃, and the components are: CH3OH: 20~30%, H2O: 0.1~1%, C2H5OH: 0.0005~0.001%, CO: 3~5%, CO2: 60~70%, CH 3OCH3: 1-3%; the liquid phase pressure in the extraction tank 38 is: 0.030MPaG, the temperature is 63-70°C, and the components are: CH3OH: 85-88%, H2O: 10-14%, C2H5OH: 0.0005-0.0015%, CO: 0.002-0.004%, CO2: 0.2-0.4%, CH3OCH3: 0.005-0.01%;

[0037] Step 4: The bottom liquid in the pre-distillation tower 3 is pressurized by the pressure tower feed pump 6 and preheated by the pressure tower feed preheater 12 and then enters the pressure distillation tower 14; the bottom liquid pressure in the pre-distillation tower 3 is 0.046 MPaG, the temperature is 75-80°C, and the composition is: CH3OH: 85-90%, H2O: 10-15%, C2H5OH: 0.03-0.08%; the bottom liquid is pressurized to 0.410 MPaG by the pressure tower feed pump 6, and the bottom liquid temperature after preheating by the pressure tower feed preheater 12 is 90-110°C;

[0038] Step 5: The pressurized distillation tower 14 performs distillation by providing a heat source through the pressurized tower reboiler 13. The heat source of the pressurized tower reboiler 13 comes from the steam in the steam network 31. The steam has a pressure of 1.0 MPaG, a temperature of 180-190°C, and a composition of 100% H2O.

[0039] The gas phase at the gas phase outlet of the pressure distillation tower 14 enters the low-pressure tower reboiler 17 to provide a distillation heat source for the low-pressure distillation tower 18, and the first pre-tower reboiler 4 provides a heat source for the pre-distillation tower 3. After cooling, it enters the pressure tower reflux tank 16. Under the action of the pressure tower reflux pump 15, a part of it enters the pressure distillation tower 14 as reflux liquid, and the other part is sent to the refined methanol product pipeline 41 as refined methanol; the gas phase pressure at the gas phase outlet of the pressure distillation tower 14 is 0.60 MPaG, the temperature is 121-125°C, and the composition is: CH3OH: 99.9%; a part of the bottom liquid at the bottom liquid outlet of the pressure distillation tower 14 passes through the pressure tower reboiler 13 for heat exchange and then flows back to the pressure distillation tower 14, and the other part passes through the pressure tower feed preheater 12 to be cooled to 75-78°C and then enters the low-pressure distillation tower 18 for distillation;

[0040] Step 6: The gas phase generated during the distillation process in the low-pressure distillation tower 18 is condensed by the negative pressure tower reboiler 23 and then enters the low-pressure tower reflux tank 22. The low-pressure tower reflux pump 21 pressurizes the liquid phase in the low-pressure tower reflux tank 22. A portion of the pressurized liquid enters the low-pressure distillation tower 18 as reflux liquid, and the other portion is sent to the refined methanol product pipeline 41 as refined methanol.

[0041] The gas phase pressure generated during the distillation process of the low-pressure distillation tower 18 is 0.025-0.03 MPaG, the temperature is 70-75°C, and the composition is: CH3OH: 99.9%; the gas phase is cooled to 68-70°C after passing through the negative pressure tower reboiler 23, and the gas phase fraction is 0; the pressure is 0.80-0.90 MPaG after being pressurized by the low-pressure tower reflux pump 21; at the same time, the negative pressure tower reboiler 23 provides a heat source for the negative pressure distillation tower 24; a part of the bottom liquid of the low-pressure distillation tower 18 is heated by the low-pressure tower reboiler 17 and refluxed into the low-pressure distillation tower 18, and the other part is pressurized to 0.40-0.50 MPaG by the negative pressure tower feed pump 19, and then cooled to 58-60°C by the negative pressure tower feed cooler 20, and then enters the negative pressure distillation tower 24 for distillation;

[0042] Step 7: The gas phase generated during the distillation process of the negative pressure distillation tower 24 enters the negative pressure tower cooler 28 for cooling under the action of the negative pressure tower vacuum pump 34, and enters the negative pressure tower reflux tank 27 for gas-liquid separation after condensation. The gas phase enters the vacuum pump separation tank 35 for further gas-liquid separation, and the gas phase in the vacuum pump separation tank 35 enters the second non-condensable gas pipeline 49 through the negative pressure tower vacuum pump 34 for treatment; the liquid phase in the vacuum pump separation tank 35 enters the negative pressure tower reflux tank 27, and the liquid phase in the negative pressure tower reflux tank 27 is pressurized by the negative pressure tower reflux pump 26, and a part of it enters the negative pressure distillation tower 24 as reflux liquid, and the other part is sent to the refined methanol product pipeline 41 as refined methanol; the refined methanol in the negative pressure distillation tower 24 The gas phase pressure generated during the distillation process is -0.055 to -0.035 MPaG, the temperature is 45 to 50°C, and the composition is: CH3OH: 97 to 99.0%; the gas phase composition entering the second non-condensable gas pipeline 49 is: CH3OH: 66.7%, air: 33%; a portion of the liquid phase generated during the distillation process in the negative pressure distillation tower 24 is heated by the negative pressure tower reboiler 23 and refluxed into the negative pressure distillation tower 24, and the other portion is pressurized by the negative pressure tower bottom liquid pump 25 and transported to the wastewater pipeline 55 for subsequent treatment; the methanol solution enriched in ethanol and fusel alcohols in the negative pressure distillation tower 24 is transported to the recovery distillation tower 30 through the tower side line pipeline with the negative pressure tower side line extraction pressure pump 37;

[0043] Step 8: The recovery distillation tower 30 uses the heat source of the recovery tower reboiler 29 to realize distillation; a part of the bottom liquid in the distillation process of the recovery distillation tower 30 enters the recovery tower reboiler 29 to exchange heat with the steam from the steam pipe network 31, and the bottom liquid after heat exchange enters the recovery distillation tower 30 for distillation; the steam condensate after heat exchange in the recovery tower reboiler 29 enters the second pre-tower reboiler 5 to provide a heat source for the pre-distillation tower 3; the other part of the bottom liquid is pressurized by the recovery tower bottom liquid pump 40 and enters the waste water pipeline 55 for subsequent treatment; the bottom liquid entering the waste water pipeline 55 has the following components: CH3OH: 0.001%, H2O: 99.99%; recovery distillation The middle and lower part of the tower 30 is enriched with fusel alcohol, which is sent to the subsequent fusel alcohol intermediate tank section through the side line pipeline in the tower and the fusel alcohol pipeline; the top gas phase of the recovery distillation tower 30 enters the recovery tower condenser 39 for condensation, and the condensate is refluxed into the recovery tower reflux tank 33 by gravity. After being pressurized by the recovery tower reflux pump 32, a part of it enters the recovery distillation tower 30 as reflux liquid, and the other part is sent to the refined methanol product pipeline 41 as refined methanol; the top gas phase pressure of the recovery distillation tower 30 is 0.01 MPaG, the temperature is 65-70°C, and the composition is: CH3OH: 99.9%; the pressure after pressurization by the recovery tower reflux pump (32) is 0.65 MPaG.

[0044] It should be noted that, in this article, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements that are inherent to such process, method, article or apparatus.

[0045] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. The above are only preferred implementation methods of the present invention. It should be pointed out that due to the limitations of textual expression, there are objectively infinite specific structures. For ordinary technicians in this technical field, without departing from the principles of the present invention, they can make several improvements, modifications or changes, and can also combine the above technical features in an appropriate manner; these improvements, changes or combinations, or the direct application of the concept and technical solution of the utility model to other occasions without improvement, should be regarded as the scope of protection of the present utility model.

Claims

1. A methanol distillation system, characterized in that: The system comprises a crude methanol pipeline (11), the crude methanol pipeline (11) is connected to the inlet of a pre-distillation tower (3), the bottom liquid outlet of the pre-distillation tower (3) is connected to the inlet of a pressure distillation tower (14), the bottom liquid outlet of the pressure distillation tower (14) is connected to the inlet of a low-pressure distillation tower (18), the bottom liquid outlet of the low-pressure distillation tower (18) is connected to the inlet of a negative pressure distillation tower (24), and the side line pipeline in the negative pressure distillation tower (24) is connected to a recovery distillation tower (30); The gas phase outlet of the pressure distillation tower (14), the gas phase outlet of the low-pressure distillation tower (18), the gas phase outlet of the negative pressure distillation tower (24) and the gas phase outlet of the recovery distillation tower (30) are respectively connected to the refined methanol product pipeline (41).

2. A methanol distillation system according to claim 1, characterized in that: The crude methanol pipeline (11) is connected to the inlet of the pre-distillation tower (3) through the first channel of the first crude alcohol preheater (1) and the first channel of the second crude alcohol preheater (2); The gas phase outlet of the pre-distillation tower (3) is connected to the non-condensable gas separation tank (10) through the first channel of the pre-tower top condenser (9), the gas phase outlet of the non-condensable gas separation tank (10) is connected to the gas phase inlet of the extraction tank (38), the liquid phase outlet of the non-condensable gas separation tank (10) and the liquid phase outlet of the extraction tank (38) are respectively connected to the inlet of the pre-tower reflux tank (8), and the outlet of the pre-tower reflux tank (8) is connected to the reflux port of the pre-distillation tower (3) through the pre-tower reflux pump (7); A four-way (42) is provided between the bottom liquid outlet of the pre-distillation tower (3) and the inlet of the pressurized distillation tower (14); the third end of the four-way (42) is connected to the inlet of the lower part of the pre-distillation tower (3) through the first channel of the first pre-tower reboiler (4); and the fourth end of the four-way (42) is connected to the inlet of the lower part of the pre-distillation tower (3) through the first channel of the second pre-tower reboiler (5).

3. A methanol distillation system according to claim 2, characterized in that: The second channel inlet of the pre-tower top condenser (9) is connected to the first circulating water inlet channel (43), the second channel outlet of the pre-tower top condenser (9) is connected to the circulating water outlet pipe (46), the extraction water inlet of the extraction tank (38) is connected to the extraction water pipe (47), and the gas phase outlet of the extraction tank (38) is connected to the first non-condensable gas pipe (48); the second end of the four-way (42) is connected to the inlet of the pressurized distillation tower (14) through the pressurized tower feed pump (6) and the first channel of the pressurized tower feed preheater (12).

4. A methanol distillation system according to claim 3, characterized in that: The gas phase outlet of the pressurized distillation tower (14) is respectively connected to the second channel of the low-pressure tower reboiler (17) and the second channel of the first pre-tower reboiler (4); the outlets of the second channel of the low-pressure tower reboiler (17) and the second channel of the first pre-tower reboiler (4) are respectively connected to the pressurized tower reflux tank (16); the outlet of the pressurized tower reflux tank (16) is respectively connected to the reflux port of the pressurized distillation tower (14) and the second channel of the second crude alcohol preheater (2) through the pressurized tower reflux pump (15); the outlet of the second channel of the second crude alcohol preheater (2) is connected to the refined methanol product pipeline (41).

5. A methanol distillation system according to claim 4, characterized in that: The bottom liquid outlet of the pressure distillation tower (14) is connected to the inlet of the low-pressure distillation tower (18) through the first tee (50) and the second channel of the pressure tower feed preheater (12), and the third end of the first tee (50) is connected to the lower part of the pressure distillation tower (14) through the first channel of the pressure tower reboiler (13); The steam pipe network (31) is connected to the condensate pipe through the second channel of the pressure tower reboiler (13), and the condensate pipe is connected to the condensate storage tank (54) through the second channel of the second pre-tower reboiler (5).

6. A methanol distillation system according to claim 5, characterized in that: The gas phase outlet of the low-pressure distillation tower (18) is connected to the low-pressure tower reflux pump (21) through the second channel of the negative pressure tower reboiler (23) and the low-pressure tower reflux tank (22), the outlet of the low-pressure tower reflux pump (21) is respectively connected to the reflux port of the low-pressure distillation tower (18) and the refined methanol product pipeline (41), and the bottom liquid outlet of the low-pressure distillation tower (18) is connected to the negative pressure distillation tower (24) through the second tee (51), the negative pressure tower feed pump (19) and the first channel of the negative pressure tower feed cooler (20); The third end of the second tee (51) is connected to the inlet of the lower part of the low-pressure distillation tower (18) through the first channel of the low-pressure tower reboiler (17); The second circulating water inlet pipe (44) is connected to the circulating water outlet pipe (46) through the second channel of the negative pressure tower feed cooler (20).

7. A methanol distillation system according to claim 6, characterized in that: The gas phase outlet of the negative pressure distillation tower (24) is connected to the negative pressure tower reflux tank (27) through the first channel of the negative pressure tower cooler (28), the gas phase outlet of the negative pressure tower reflux tank (27) is connected to the vacuum pump separation tank (35), and the gas phase outlet of the vacuum pump separation tank (35) is connected to the second non-condensable gas pipeline (49) through the negative pressure tower vacuum pump (34); the liquid phase outlet of the vacuum pump separation tank (35) is refluxed into the negative pressure tower reflux tank (27) through the first channel of the vacuum pump separation tank condenser (36), and the liquid phase outlet of the negative pressure tower reflux tank (27) is respectively connected to the reflux port of the negative pressure distillation tower (24) and the refined methanol product pipeline (41) through the negative pressure tower reflux pump (26); The bottom liquid outlet of the negative pressure distillation tower (24) is connected to the wastewater pipeline (55) through the third tee (52) and the negative pressure tower bottom liquid pump (25); the third end of the third tee (52) is connected to the lower part of the negative pressure distillation tower (24) through the first channel of the negative pressure tower reboiler (23); The side line pipeline in the middle of the negative pressure distillation tower (24) is connected to the inlet of the recovery distillation tower (30) through the negative pressure tower side line extraction pressure pump (37).

8. A methanol distillation system according to claim 7, characterized in that: The gas phase outlet of the recovery distillation tower (30) is connected to the recovery tower reflux tank (33) through the first channel of the recovery tower condenser (39), and the outlet of the recovery tower reflux tank (33) is connected to the reflux port of the recovery distillation tower (30) and the refined methanol product pipeline (41) respectively through the recovery tower reflux pump (32); The bottom liquid outlet of the recovery distillation tower (30) is connected to the wastewater pipeline (55) through the fourth tee (53) and the recovery tower bottom liquid pump (40); the third end of the fourth tee (53) is connected to the lower part of the recovery distillation tower (30) through the first channel of the recovery tower reboiler (29); the steam pipe network (31) is connected to the second channel inlet of the second pre-tower reboiler (5) through the second channel of the recovery tower reboiler (29); The side line pipeline in the middle of the recovery distillation tower (30) is connected to the fusel alcohol pipeline.

9. A methanol distillation system according to claim 8, characterized in that: The invention also includes a third circulating water inlet channel (45), which is respectively connected to the second channel of the negative pressure tower cooler (28), the second channel of the vacuum pump separation tank condenser (36), and the second channel of the recovery tower condenser (39), and the second channel outlet of the negative pressure tower cooler (28), the second channel outlet of the vacuum pump separation tank condenser (36), and the second channel outlet of the recovery tower condenser (39) are respectively connected to the circulating water outlet pipe (46).

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