Multi-effect energy-saving methanol rectification process method and device

Abstract

The invention provides a multi-effect energy-saving methanol rectification process method and a multi-effect energy-saving methanol rectification device. The operation energy consumption can be greatly reduced. The whole device at least comprises five towers including a light component removal tower (T300), a first rectifying tower (T310), a second rectifying tower (T320), a third rectifying tower (T330) and a fourth rectifying tower (T340) and matched equipment thereof. The method can be used for recovery of various methanol solvents and rectification processes of methanol synthesis devices to produce national standard superior methanol, American standard AA-grade methanol products or methanol products of other specifications. The defects in the prior art are overcome, the unit steam consumption of the refined methanol product can be reduced to below 0.398, and the method has remarkable practicability and economic benefit and wide application prospect.

Description

Technical Field

[0001] A multi-effect energy-saving methanol rectification process method and device provided by the present invention can be used for the rectification process of various methanol solvent recovery and methanol synthesis devices to produce high-quality methanol products. Background Art

[0002] Methanol is an important organic chemical raw material and new energy fuel, and has wide applications in the fields of chemical industry, light industry and clean energy. In the industrial production process of synthetic methanol, the energy consumption in the refining process of crude methanol is one of the key factors affecting the production cost of methanol. With the increasing shortage of energy resources such as petroleum, coal and natural gas, and the increasingly serious problems of environmental pollution and greenhouse effect, energy conservation and consumption reduction in the methanol and other industries have become the key to the survival and competitiveness improvement of enterprises, and have attracted more and more attention from all aspects.

[0003] Figure 1 It is a currently widely used four-column (three columns plus one column) methanol rectification process method, that is, a pre-column T101, a pressurized column T102, a first rectification column T103 and other three columns are used and then one more recovery column T104 is added to produce national standard high-quality or American standard AA grade methanol products. Light components are removed from the top of the pre-column. After the pre-treated crude methanol 10 is rectified by the pressurized column and the first rectification column, methanol products are obtained respectively from the top of the pressurized column 24 and the top of the first rectification column 14, and fusel oil 42 is drawn from the side line of the first rectification column. The vapor 21 of the material at the top of the pressurized column is used to heat the bottom of the first rectification column. The side-line fusel oil 42 of the first rectification column and the bottom liquid 15 of the first rectification column enter the recovery column, and recovered methanol product 29 is obtained from the top of the recovery column. Fusel oil 30 is drawn from the side line of the recovery column, and waste water 33 is discharged from the bottom of the recovery column. Although this method has mature technology, its production energy consumption is relatively high, and with the increasing scale of the device, its equipment scale appears to be relatively large. It is not conducive to the construction and stable economic operation of the increasingly large-scale methanol production device.

[0004] Chinese Patent CN 201420664698.2 discloses a process method of a "flexible methanol rectification device that can produce both MTO-grade and AA-grade methanol". The core content of which is based on the currently widely used four-column double-effect rectification process, and uses the condensate heat of the heating steam or the heat exchange between hot and cold liquids inside the system to achieve the purpose of energy conservation. Obviously, this sensible heat transfer between materials has a very limited effect on reducing the operation energy consumption of the entire rectification system.

[0005] CN 201910655239.5 discloses "an improved three-column and three-effect crude methanol refining process", which is characterized in that: the operating pressures of the first rectification column and the second rectification column are increased, and three-effect heat integration operation is carried out on the first rectification column, the second rectification column and the pre-rectification column. A gas phase is separated from the top of the second rectification column to provide heat for the pre-rectification column. Compared with CN201420664698.2, this process has a higher energy-saving effect. However, since no methanol product is produced at the top of the pre-rectification column in the system, the energy provided by the second rectification column for the pre-rectification column belongs to a single-effect methanol rectification process. Methanol products are produced at the tops of the first rectification column and the second rectification column in the system, and only the energy provided by the first rectification column for the second rectification column belongs to a double-effect methanol rectification process. Therefore, although this process has a certain improved energy-saving effect, the energy-saving effect is not ideal.

[0006] CN201711022448.3 discloses "a methanol three-effect rectification system and process", and CN 201811025624.3 discloses "a vacuum thermally coupled methanol rectification method and device". They both adopt three-effect heat integration operation for the rectification columns that produce methanol products in the system, and the effect with the lowest operating pressure is a vacuum rectification column. The vacuum rectification column is beneficial to improving the relative volatility of the separation system and obtaining a higher methanol product purity. The pre-rectification columns of these two patented processes still use fresh steam for heating and do not have heat integration operation with the methanol rectification column, so the energy-saving effect is limited to a certain extent.

[0007] CN200910068170.2 adopts a five-column heat integration device for the process of methanol rectification. The crude methanol at the bottom of the pre-rectification column first enters the atmospheric rectification column. The material at the bottom of the atmospheric rectification column enters the low-pressure rectification column. The material at the bottom of the low-pressure rectification column enters the high-pressure rectification column. Methanol products are respectively taken out from the tops of the atmospheric rectification column, the low-pressure rectification column and the high-pressure rectification column. The material at the bottom of the high-pressure rectification column enters the recovery column; three-effect heat integration is carried out among the three columns of the atmospheric rectification column, the low-pressure rectification column and the high-pressure rectification column; double-effect heat integration is carried out between the pre-rectification column and the recovery column. The operating energy consumption of this process is still relatively high, and there is still room for optimization and reduction.

[0008] CN202110667709.7 adopts a five-column double three-effect heat integration device for the process of methanol rectification, and double three-effect heat integration operation is carried out among the de-lighting column (T210), the first rectification column (T220), the second rectification column (T230), the third rectification column (T240), the last column (T250), etc. Compared with the three-effect + double-effect process provided by CN200910068170.2, the operating energy consumption of this process is reduced, but there is still room to further reduce the energy consumption.

[0009] CN202321881315.2 discloses "A five - tower four - effect crude methanol refining device", and CN202310877978.5 discloses "A five - tower four - effect crude methanol refining process and device". The essence of this methanol refining process flow is a three - effect heat - integrated distillation process: The main body of the pre - distillation column (1) is heated by fresh steam. In addition, the sensible heat of the condensate at the top of the pressurized distillation column (3) is used to heat the pre - distillation column, but the effective heat in this part is relatively small. Therefore, the pressurized distillation column provides only a small amount of heat for the pre - distillation column; The pressurized distillation column (3), atmospheric distillation column (4), and vacuum distillation column (2) adopt three - effect heat - integrated operation; The pre - distillation column and the vacuum distillation column adopt double - effect heat - integrated operation; The recovery column (5) and the pressurized distillation column (3) are also heated by fresh steam; The energy consumption of this process operation is relatively high, and the steam specific consumption of the refined methanol product is about 0.62.

[0010] CN202310877976.6 discloses "A five - tower four - effect crude methanol refining process and equipment". The essence of this methanol refining process flow is a three - effect heat - integrated distillation process: The main body of the pre - distillation column (1) is heated by the pressurized gas phase after the gas phase extracted from its top is compressed by a heat pump (60). In addition, the sensible heat of the condensate at the top of the pressurized distillation column (3) is used to heat the pre - distillation column, but the effective heat in this part is relatively small. Therefore, the pressurized distillation column provides only a small amount of heat for the pre - distillation column; The pressurized distillation column (3), atmospheric distillation column (4), and vacuum distillation column (2) adopt three - effect heat - integrated operation, and at the same time, the vacuum distillation column is additionally supplemented with fresh steam for heating; The recovery column (5) and the pressurized distillation column (3) are also heated by fresh steam; Although the steam specific consumption of the refined methanol product in this process is about 0.5, it uses heat pump technology, which greatly increases the power consumption.

[0011] CN202110620943.4 discloses "A multi - effect methanol refining device and its refining process". The tower pressures of the first pressurized distillation column, the second pressurized distillation column, the third pressurized distillation column, and the atmospheric distillation column decrease in sequence, and four - effect heat - integrated operation is adopted. The first pressurized distillation column is heated by fresh steam, and the bottom of the atmospheric column discharges water; The pre - distillation column is heated by fresh steam and is a single - effect operation without participating in heat - integrated operation; The top pressure of the first pressurized distillation column is 25 - 35 bar, and the operating pressure is very high; The energy consumption of this process operation is relatively high, and the steam specific consumption of the refined methanol product is about 0.8.

[0012] CN201910748405.6 discloses "a single-tower steam-driven methanol six-tower four-effect distillation method without by-product fusel oil". The essence of this methanol refining process flow is a four-effect + three-effect heat-integrated distillation process: four-effect heat integration among the vacuum tower (7), atmospheric tower (10), medium-pressure tower (12), and high-pressure tower (14); three-effect heat integration among the vacuum tower (7), pre-separation tower (1), and high-pressure tower (14); only fuel alcohol is produced at the top of the recovery tower; the methanol yield is relatively low, the energy-saving effect is poor, and there is still a large room for optimization. Summary of the Invention

[0013] The object of the present invention is to provide a multi-effect energy-saving methanol distillation process method and device, which can significantly reduce the operating energy consumption, and can overcome the defects of the prior art, such as limited energy-saving effect, complex equipment, etc. The steam specific consumption of the refined methanol product of the present invention can be reduced to below 0.43. The present invention can be used for the distillation process of various methanol solvent recovery and methanol synthesis devices to produce national standard first-class methanol, US standard AA-grade methanol products, or methanol products of other specifications, and has significant practicality and economic benefits, and broad application prospects.

[0014] A multi-effect energy-saving methanol distillation process method provided by the present invention mainly includes the following steps: 1) It includes at least five towers such as the light-component removal tower T300, the first distillation tower T310, the second distillation tower T320, the third distillation tower T330, and the fourth distillation tower T340.

[0015] 2) After the crude methanol is preheated, it enters the light-component removal tower T300, and the liquid phase at the bottom of the light-component removal tower T300 enters the first distillation tower T310.

[0016] 3) The liquid phase at the bottom of the first distillation tower T310 enters the second distillation tower T320.

[0017] 4) The liquid phase at the bottom of the second distillation tower T320 enters the third distillation tower T330.

[0018] 5) The liquid phase at the bottom of the third distillation tower T330 enters the fourth distillation tower T340.

[0019] 6) Five-effect heat integration is adopted among the five towers. The gas phase at the top of the fourth distillation tower T340 is used as the heating heat source at the bottom of the light-component removal tower T300 to provide the required heat for the light-component removal tower T300; the gas phase at the top of the light-component removal tower T300 is used as the heating heat source at the bottom of the third distillation tower T330 to provide the required heat for the third distillation tower T330; the gas phase at the top of the third distillation tower T330 is used as the heating heat source at the bottom of the second distillation tower T320 to provide the required heat for the second distillation tower T320; the gas phase at the top of the second distillation tower T320 is used as the heating heat source at the bottom of the first distillation tower T310 to provide the required heat for the first distillation tower T310.

[0020] 7) The refined methanol products are respectively withdrawn from the tops of four towers, namely the first rectification tower T310, the second rectification tower T320, the third rectification tower T330, and the fourth rectification tower T340.

[0021] According to the process method provided by the present invention, it undergoes the following steps: The crude methanol raw material 1 is divided into two streams. One stream of raw material 4, which is preheated by the feed wastewater preheater E3404, and another stream of raw material 5, which is preheated by the feed methanol preheater E3403, are mixed to form the preheated raw material 6 and enter the light component removal tower T300.

[0022] The light component removal tower T300 and the third rectification tower T330 are in heat integration operation. The gas phase 7 at the top of the light component removal tower T300 enters the shell side of the third rectification tower reboiler E3301. The condensed liquid 9 is directly returned to the top of the light component removal tower T300, and the non-condensable gas 8 is discharged. The bottom material 10 of the light component removal tower T300 enters the first rectification tower T310.

[0023] The gas phase 11 at the top of the first rectification tower T310 is condensed by the first rectification tower condenser E3102, and the condensed liquid 12 is divided into two streams. One stream is used as the reflux liquid 13 of the first rectification tower and directly returned to the top of the first rectification tower T310, and the other stream of condensed liquid 14 is withdrawn as the refined methanol product. The bottom material 15 of the first rectification tower T310 enters the second rectification tower T320.

[0024] The second rectification tower T320 and the first rectification tower T310 are in heat integration operation. The gas phase 16 at the top of the second rectification tower T320 enters the shell side of the first rectification tower reboiler E3101. The condensed liquid 17 is divided into two streams. One stream is used as the reflux liquid 18 of the second rectification tower and directly returned to the top of the second rectification tower T320, and the other stream of condensed liquid 19 is withdrawn as the refined methanol product. The bottom material 20 of the second rectification tower T320 enters the third rectification tower T330.

[0025] The third rectification tower T330 and the second rectification tower T320 are in heat integration operation. The gas phase 21 at the top of the third rectification tower T330 enters the shell side of the second rectification tower reboiler E3201. The condensed liquid 22 is divided into two streams. One stream is used as the reflux liquid 23 of the third rectification tower and directly returned to the top of the third rectification tower T330, and the other stream of condensed liquid 24 is withdrawn as the refined methanol product. The bottom material 25 of the third rectification tower T330 enters the methanol stripping side L340 of the fourth rectification tower T340.

[0026] The fourth rectification column T340 operates with heat integration with the light component removal column T300. The vapor phase 26 at the top of the fourth rectification column T340 enters the shell side of the reboiler E3001 of the light component removal column. The condensed liquid 27 is divided into two streams. One stream is directly returned as the reflux liquid 28 of the fourth rectification column to the top of the fourth rectification column T340, and the other stream of condensed liquid 29 is taken out as the refined methanol product. Near the feed port of the methanol stripping side L340 of the fourth rectification column T340, a side stream is taken out for the fusel oil 33 with very low methanol and ethanol contents; the bottom material 35 of the methanol stripping side L340 of the fourth rectification column T340 is taken out as wastewater; the bottom material 40 of the ethanol rectification side R340 of the fourth rectification column T340 is taken out as the recovered ethanol product.

[0027] The refined methanol product 30 after mixing the top products 14 of the first rectification column T310, the top products 19 of the second rectification column T320, the top products 24 of the third rectification column T330, and the top products 29 of the fourth rectification column T340 is cooled by the feed methanol preheater E3403. The cooled material 31 is further cooled by the methanol product cooler E3405 and then the refined methanol product 32 is sent out of the device.

[0028] The wastewater 35 taken out from the bottom of the methanol stripping side L340 of the fourth rectification column T340 is first cooled by the feed wastewater preheater E3404. The cooled material 36 is further cooled by the wastewater cooler E3406 and then the obtained wastewater 37 is divided into two streams. One stream is sent out of the device as wastewater 38, and the other stream is returned as extraction water 39 to the top of the light component removal column T300.

[0029] The fusel oil 33 taken out from the side stream of the methanol stripping side L340 of the fourth rectification column T340 is cooled by the fusel oil cooler E3407 and then the fusel oil product 34 is sent out of the device.

[0030] The recovered ethanol 40 taken out from the bottom of the ethanol rectification side R340 of the fourth rectification column T340 is cooled by the ethanol cooler E3408 and then the recovered ethanol product 41 is sent out of the device.

[0031] According to the process method provided by the present invention, in the five columns described above, the following five-column five-effect deformation process can be adopted, and it can be selected from: 1) Move the light component removal column T300 between the third rectification column T330 and the second rectification column T320: The vapor phase at the top of the fourth rectification column T340 is used as the heating heat source for the bottom of the third rectification column T330 to provide the required heat for the third rectification column T330; the vapor phase at the top of the third rectification column T330 is used as the heating heat source for the bottom of the light component removal column T300 to provide the required heat for the light component removal column T300; the vapor phase at the top of the light component removal column T300 is used as the heating heat source for the bottom of the second rectification column T320 to provide the required heat for the second rectification column T320; the vapor phase at the top of the second rectification column T320 is used as the heating heat source for the bottom of the first rectification column T310 to provide the required heat for the first rectification column T310.

[0032] 2) Move the light component removal column T300 between the second distillation column T320 and the first distillation column T310: The overhead gas phase of the fourth distillation column T340 serves as the heating heat source for the reboiler of the third distillation column T330, providing the required heat for the third distillation column T330; the overhead gas phase of the third distillation column T330 serves as the heating heat source for the reboiler of the second distillation column T320, providing the required heat for the second distillation column T320; the overhead gas phase of the second distillation column T320 serves as the heating heat source for the reboiler of the light component removal column T300, providing the required heat for the light component removal column T300; the overhead gas phase of the light component removal column T300 serves as the heating heat source for the reboiler of the first distillation column T310, providing the required heat for the first distillation column T310.

[0033] 3) Move the light component removal column T300 after the first distillation column T310: The overhead gas phase of the fourth distillation column T340 serves as the heating heat source for the reboiler of the third distillation column T330, providing the required heat for the third distillation column T330; the overhead gas phase of the third distillation column T330 serves as the heating heat source for the reboiler of the second distillation column T320, providing the required heat for the second distillation column T320; the overhead gas phase of the second distillation column T320 serves as the heating heat source for the reboiler of the first distillation column T310, providing the required heat for the first distillation column T310; the overhead gas phase of the first distillation column T310 serves as the heating heat source for the reboiler of the light component removal column T300, providing the required heat for the light component removal column T300.

[0034] According to the process method provided by the present invention, in the five columns described above, generally, when the light component removal column T300 does not require as much heat as provided by the process flow of the present invention, the following five-effect plus four-effect modified process can be adopted to reduce the supply of heat integration energy for the light component removal column T300, thereby reducing the equipment specifications of the light component removal column T300, reducing investment, and can be selected from: 1) The overhead gas phase of the fourth distillation column T340 is divided into two streams. One stream serves as the heating heat source for the reboiler of the third distillation column T330, providing a part of the required heat for the third distillation column T330, and the other stream serves as the heating heat source for the reboiler of the light component removal column T300, providing the required heat for the light component removal column T300; the overhead gas phase of the light component removal column T300 also serves as the heating heat source for the reboiler of the third distillation column T330, providing the remaining required heat for the third distillation column T330. T340, T300, T330, T320, and T310 form a five-effect heat integration, and T340, T330, T320, and T310 form a four-effect heat integration. The entire device constitutes a distillation process of five columns, five-effect plus four-effect.

[0035] 2) The vapor phase at the top of the third rectification column T330 is divided into two streams. One stream serves as the heating heat source for the reboiler of the second rectification column T320, providing part of the required heat for the second rectification column T320, and the other stream serves as the heating heat source for the reboiler of the light component removal column T300, providing the required heat for the light component removal column T300; the vapor phase at the top of the light component removal column T300 also serves as the heating heat source for the reboiler of the second rectification column T320, providing the remaining required heat for the second rectification column T320. T340, T330, T300, T320, and T310 form a five-effect heat integration, and T340, T330, T320, and T310 form a four-effect heat integration. The entire device constitutes a rectification process with five towers, five effects plus four effects.

[0036] 3) The vapor phase at the top of the second rectification column T320 is divided into two streams. One stream serves as the heating heat source for the reboiler of the first rectification column T310, providing part of the required heat for the first rectification column T310, and the other stream serves as the heating heat source for the reboiler of the light component removal column T300, providing the required heat for the light component removal column T300; the vapor phase at the top of the light component removal column T300 also serves as the heating heat source for the reboiler of the first rectification column T310, providing the remaining required heat for the first rectification column T310. T340, T330, T320, T300, and T310 form a five-effect heat integration, and T340, T330, T320, and T310 form a four-effect heat integration. The entire device constitutes a rectification process with five towers, five effects plus four effects.

[0037] According to the process method provided by the present invention, in the five towers described above, when the energy consumption requirement for the device is not high, the following modified process with five towers and double four effects can be adopted to reduce the operating pressure of some equipment, thereby reducing the pressure rating of some equipment and reducing the investment. It can be selected from: 1) The vapor phase at the top of the fourth rectification column T340 is divided into two streams. One stream serves as the heating heat source for the reboiler of the third rectification column T330, providing the required heat for the third rectification column T330, and the other stream serves as the heating heat source for the reboiler of the light component removal column T300, providing the required heat for the light component removal column T300; the vapor phases at the tops of the third rectification column T330 and the light component removal column T300 respectively serve as the heating heat sources for the reboiler of the second rectification column T320, providing the required heat for the second rectification column T320. T340, T300, T320, and T310 form a four-effect heat integration, and T340, T330, T320, and T310 form a four-effect heat integration. The entire device constitutes a rectification process with five towers and double four effects.

[0038] 2) The bottom of the fourth rectification column T340 and the light - component removal column T300 are heated by external heat sources (such as steam, hot water, heat - conducting oil, or other low - grade heat sources within the system); the top gas phases of the fourth rectification column T340 and the light - component removal column T300 both serve as the heating heat sources for the bottom of the third rectification column T330, providing the required heat for the third rectification column T330. T300, T330, T320, and T310 form a four - effect heat integration, and T340, T330, T320, and T310 form a four - effect heat integration. The entire device constitutes a rectification process of five columns with double four - effect.

[0039] 3) The top gas phase of the third rectification column T330 is divided into two streams. One stream serves as the heating heat source for the bottom of the second rectification column T320, providing the required heat for the second rectification column T320, and the other stream serves as the heating heat source for the bottom of the light - component removal column T300, providing the required heat for the light - component removal column T300; the top gas phase of the second rectification column T320 serves as the heating heat source for the bottom of the first rectification column T310, providing the required heat for the bottom of the first rectification column T310, and the top gas phase of the light - component removal column T300 serves as the heat source for the feed pre - heater of the first rectification column T310. T340, T330, T300, and T310 form a four - effect heat integration, and T340, T330, T320, and T310 form a four - effect heat integration. The entire device constitutes a rectification process of five columns with double four - effect.

[0040] 4) The top gas phase of the second rectification column T320 is divided into two streams. One stream serves as the heating heat source for the bottom of the first rectification column T310, providing the required heat for the first rectification column T310, and the other stream serves as the heating heat source for the bottom of the light - component removal column T300, providing the required heat for the light - component removal column T300. T340, T330, T320, and T300 form a four - effect heat integration, and T340, T330, T320, and T310 form a four - effect heat integration. The entire device constitutes a rectification process of five columns with double four - effect.

[0041] According to the process method provided by the present invention, the lower part of the fourth rectification column T340 adopts a dividing - wall column structure. The dividing wall S340 divides the lower part of the fourth rectification column T340 into a methanol stripping side L340 and an ethanol rectification side R340; wastewater 35 is discharged from the bottom of the methanol stripping side L340 of the fourth rectification column T340; fusel oil 33 with very low methanol and ethanol contents is side - drawn from the side below the feed inlet of the methanol stripping side L340 of the fourth rectification column T340; the recovered ethanol product 40 is drawn from the bottom of the ethanol rectification side R340 of the fourth rectification column T340.

[0042] According to the process method provided by the present invention, it can also be deformed into other heat - integration processes for producing methanol, and the options are: 1) In the five towers described above, the fourth rectification tower T340 does not adopt a baffle structure but a conventional structure. Ethanol 40 is withdrawn from the position above the feed inlet of the fourth rectification tower T340, fusel oil 33 is withdrawn from the position below the feed inlet, and the bottom material 35 of the fourth rectification tower T340 is withdrawn as wastewater.

[0043] 2) On the basis of the five towers described above, a stripping tower T340S is added. The fourth rectification tower T340 does not adopt a baffle structure but a conventional structure. The side-line liquid material 42 of the fourth rectification tower T340 enters the top of the stripping tower T340S, the gas-phase material 43 at the top of the stripping tower T340S returns to the fourth rectification tower T340, and the recovered ethanol 40 is withdrawn from the bottom of the stripping tower T340S.

[0044] 3) On the basis of the five towers described above, a recovery tower T350 is added. The fourth rectification tower T340 does not adopt a baffle structure but a conventional structure. The recovery tower T350 can use the gas-phase at the top of the first rectification tower T310 or the second rectification tower T320 or the fourth rectification tower T340 as the heat source, or use other heat sources within the system, or use an external heat source.

[0045] According to the process method provided by the present invention, in the five towers described above, when the energy consumption requirement of the device is relatively high, the following five-tower five-effect or six-tower double-five-effect processes for optimizing and deforming the periphery of the light-component removal tower T300 can be adopted to reduce the operating energy consumption: 1) Another light-component rectification tower T300D is added to the light-component removal tower T300, sharing the bottom and the reboiler E3001 of the light-component removal tower T300. The gas-phase at the top of both the light-component removal tower T300 and the light-component rectification tower T300D serves as the heating heat source for the bottom of the third rectification tower T330 to provide the required heat; the refined methanol product is withdrawn from the top of the light-component rectification tower T300D. 2) Another fifth rectification tower T360 is connected in parallel to the light-component removal tower T300. The gas-phase at the top of the fourth rectification tower T340 is divided into two streams. One stream serves as the heating heat source for the bottom of the light-component removal tower T300 to provide the required heat, and the other stream serves as the heating heat source for the bottom of the fifth rectification tower T360 to provide the required heat; the gas-phase at the top of both the light-component removal tower T300 and the fifth rectification tower T360 serves as the heating heat source for the bottom of the third rectification tower T330 to provide the required heat; the refined methanol product is withdrawn from the top of the fifth rectification tower T360. 3) The upper part of the light component removal column T300 adopts a dividing wall column structure. The dividing wall S300 divides the upper part of the light component removal column T300 into a pre-rectification side R300 and a methanol rectification side L300. The top gas phases of both the pre-rectification side R300 and the methanol rectification side L300 serve as the heating heat source for the bottom of the third rectification column T330, providing the required heat for the third rectification column T330. The refined methanol product is withdrawn from the top of the methanol rectification side L300. The lower part and the bottom of the light component removal column T300 have a conventional structure without a dividing wall.

[0046] According to the process method provided by the present invention, the energy-saving method is selected as follows: 1) The crude methanol raw material can be heat-exchanged with the wastewater discharged from the bottom of the methanol stripping side L340 of the fourth rectification column T340, or with the refined methanol product, or with the top gas phase of the first rectification column T310. 2) The feed of each column such as the first rectification column T310, the second rectification column T320, the third rectification column T330, the fourth rectification column T340, or the light component removal column T300 is heat-exchanged with the heating steam condensate.

[0047] Typical implementation methods of the heat exchange between such steam condensate and the feed of each column are as follows: (1) The steam condensate is first heat-exchanged with the feed of the fourth rectification column T340 to preheat the feed of the fourth rectification column T340. (2) The steam condensate after heat-exchanging with the feed of the fourth rectification column T340 is then heat-exchanged with the feed of the light component removal column T300 to preheat the feed of the light component removal column T300.

[0048] (3) The steam condensate after heat-exchanging with the feed of the light component removal column T300 is then heat-exchanged with the feed of the third rectification column T330 to preheat the feed of the third rectification column T330.

[0049] (4) The steam condensate after heat-exchanging with the feed of the third rectification column T330 is then heat-exchanged with the feed of the second rectification column T320 to preheat the feed of the second rectification column T320.

[0050] (5) The steam condensate after heat-exchanging with the feed of the second rectification column T320 is then heat-exchanged with the feed of the first rectification column T310 to preheat the feed of the first rectification column T310.

[0051] The steam condensate can be used to preheat the feed of the light component removal column, or the feed of the first distillation column, or the feed of the second distillation column, or the feed of the third distillation column, or the feed of the fourth distillation column. The steam condensate can preheat any column in the system or their combinations. The above heat exchange method is only a supplement to the energy-saving process method for methanol distillation in the multi-effect heat integration device provided by the present invention, rather than any limitation to the spirit of the present invention. Those skilled in the relevant art can completely make the permutations and combinations of the above heat exchange process according to general knowledge, and all kinds of evolved process flows formed therefrom should be regarded as within the spirit, scope and content of the present invention.

[0052] According to the process method provided by the present invention, the top products 14 of the first distillation column T310, the top products 19 of the second distillation column T320, the top products 24 of the third distillation column T330, and the top products 29 of the fourth distillation column T340 can also be withdrawn from the upper side lines of each column.

[0053] According to the process method provided by the present invention, the heat sources used for the methanol stripping side reboiler E3401 and the ethanol rectification side reboiler E3402 of the fourth distillation column can be fresh steam, heat transfer oil, or the material steam generated inside the system.

[0054] According to the process method provided by the present invention, while the light component removal column T300, the first distillation column T310, the second distillation column T320, the third distillation column T330, and the fourth distillation column T340 adopt heat integration heating, external heat sources can also be used to provide heat for the middle or bottom of the columns. These external heat sources can be fresh steam, hot water, heat transfer oil, or other low-grade heat sources inside the system. Each column can use the aforementioned other low-grade heat sources to heat the middle or bottom of the column simultaneously or separately.

[0055] According to the process method provided by the present invention, the first distillation column condenser E3102, the methanol product cooler E3405, the wastewater cooler E3406, the fusel oil cooler E3407, and the ethanol cooler E3408 can be air coolers or water coolers; the cooling media used can be circulating water, low-temperature water, chilled water, or other cooling media such as low-temperature materials inside the system.

[0056] According to the process method provided by the present invention, the bottom discharge of the light component removal column T300 first enters the first distillation column T310, or the second distillation column T320, or the third distillation column T330; or enters the first distillation column T310 and the second distillation column T320 respectively; or enters the first distillation column T310 and the third distillation column T330 respectively; or enters the second distillation column T320 and the third distillation column T330 respectively; or enters the first distillation column T310, the second distillation column T320 and the third distillation column T330 respectively.

[0057] The energy-saving process method and device for methanol rectification using the device of the multi-effect methanol rectification process method provided by the present invention (five-column five-effect heat integration, or six-column five-effect heat integration, or five-column five-effect plus four-effect heat integration, or six-column five-effect plus four-effect heat integration, or five-column double four-effect heat integration, or six-column double four-effect heat integration) can be used to produce national standard premium methanol, ASTM AA grade methanol products, or methanol products of other specifications.

[0058] According to the process method provided by the present invention, the typical operating conditions of each column are as follows: The top operating pressure range of the light component removal column T300 is 190 - 1200 kPa; The top operating pressure range of the first rectification column T310 is 25 - 150 kPa; The top operating pressure range of the second rectification column T320 is 45 - 300 kPa; The top operating pressure range of the third rectification column T330 is 90 - 600 kPa; The top operating pressure range of the fourth rectification column T340 is 350 - 1800 kPa.

[0059] Unless otherwise specified, all pressures in the present invention refer to absolute pressures.

[0060] The preferred operating conditions of each column are as follows: The top operating pressure of the light component removal column T300 is 320 - 570 kPa, the top operating temperature is 95 - 115 °C, and the bottom operating temperature is 100 - 125 °C.

[0061] The top operating pressure of the first rectification column T310 is 44 - 69 kPa, the top operating temperature is 45 - 55 °C, and the bottom operating temperature is 50 - 65 °C.

[0062] The top operating pressure of the second rectification column T320 is 81 - 135 kPa, the top operating temperature is 59 - 72 °C, and the bottom operating temperature is 68 - 85 °C.

[0063] The top operating pressure of the third rectification column T330 is 162 - 282 kPa, the top operating temperature is 77 - 93 °C, and the bottom operating temperature is 85 - 110 °C.

[0064] The top operating pressure of the fourth rectification column T340 is 490 - 910 kPa, the top operating temperature is 111 - 133 °C, the bottom operating temperature of the methanol stripping side L340 is 152 - 176 °C; the bottom operating temperature of the ethanol rectification side R340 is 116 - 150 °C.

[0065] The device of the process method provided by the present invention mainly includes five towers, namely a light component removal tower T300, a first rectification tower T310, a second rectification tower T320, a third rectification tower T330, and a fourth rectification tower T340, as well as connecting pipelines.

[0066] The raw material crude methanol feed pipeline is respectively connected to the cold-side inlets of the feed methanol preheater E3403 and the feed wastewater preheater E3404.

[0067] The cold-side outlets of the feed methanol preheater E3403 and the feed wastewater preheater E3404 are connected to the middle part of the light component removal tower T300; the top of the light component removal tower T300 is connected to the shell side of the reboiler E3301 of the third rectification tower, the condensate outlet of the shell side of the reboiler E3301 of the third rectification tower is connected to the top of the light component removal tower T300, and the non-condensable gas outlet of the shell side of the reboiler E3301 of the third rectification tower is connected to the non-condensable gas discharge pipeline; the bottom of the light component removal tower T300 is respectively connected to the tube-side inlet of the reboiler E3001 of the light component removal tower and the first rectification tower T310, and the tube-side outlet of the reboiler E3001 of the light component removal tower is connected to the bottom of the light component removal tower T300.

[0068] The top of the first rectification tower T310 is connected to the condenser E3102 of the first rectification tower, and the condensate outlet of the condenser E3102 of the first rectification tower is respectively connected to the top of the first rectification tower T310 and the hot-side inlet of the feed methanol preheater E3403; the bottom of the first rectification tower T310 is respectively connected to the tube-side inlet of the reboiler E3101 of the first rectification tower and the second rectification tower T320, and the tube-side outlet of the reboiler E3101 of the first rectification tower is connected to the bottom of the first rectification tower T310.

[0069] The top of the second rectification tower T320 is connected to the shell side of the reboiler E3101 of the first rectification tower, and the condensate outlet of the shell side of the reboiler E3101 of the first rectification tower is respectively connected to the top of the second rectification tower T320 and the hot-side inlet of the feed methanol preheater E3403; the bottom of the second rectification tower T320 is respectively connected to the tube-side inlet of the reboiler E3201 of the second rectification tower and the third rectification tower T330, and the tube-side outlet of the reboiler E3201 of the second rectification tower is connected to the bottom of the second rectification tower T320.

[0070] The top of the third rectification tower T330 is connected to the shell side of the reboiler E3201 of the second rectification tower, and the condensate outlet of the shell side of the reboiler E3201 of the second rectification tower is respectively connected to the top of the third rectification tower T330 and the hot-side inlet of the feed methanol preheater E3403; the bottom of the third rectification tower T330 is respectively connected to the tube-side inlet of the reboiler E3301 of the third rectification tower and the fourth rectification tower T340.

[0071] The top of the fourth rectification column T340 is connected to the shell side of the reboiler E3301 of the third rectification column. The condensate outlet of the shell side of the reboiler E3301 of the third rectification column is respectively connected to the top of the fourth rectification column T340 and the hot side inlet of the feed methanol preheater E3403. The bottom of the methanol stripping side L340 of the fourth rectification column T340 is respectively connected to the tube side inlet of the reboiler E3401 of the methanol stripping side of the fourth rectification column and the hot side inlet of the feed wastewater preheater E3404. The tube side outlet of the reboiler E3401 of the methanol stripping side of the fourth rectification column is connected to the bottom of the methanol stripping side L340 of the fourth rectification column T340. The side draw pipeline near the feed of the methanol stripping side L340 of the fourth rectification column T340 is connected to the hot side inlet of the fusel oil cooler E3407. The bottom of the ethanol rectification side R340 of the fourth rectification column T340 is respectively connected to the tube side inlet of the reboiler E3402 of the ethanol rectification side of the fourth rectification column and the hot side inlet of the ethanol cooler E3408. The tube side outlet of the reboiler E3402 of the ethanol rectification side of the fourth rectification column is connected to the bottom of the ethanol rectification side R340 of the fourth rectification column T340.

[0072] The hot side outlet of the feed methanol preheater E3403 is connected to the hot side inlet of the methanol product cooler E3405, and the hot side outlet of the methanol product cooler E3405 is connected to the methanol product draw pipeline. The hot side outlet of the feed wastewater preheater E3404 is connected to the hot side inlet of the wastewater cooler E3406, and the hot side outlet of the wastewater cooler E3406 is respectively connected to the top of the de-light component column T300 and the wastewater discharge pipeline. The hot side outlet of the fusel oil cooler E3407 is connected to the fusel oil product draw pipeline. The hot side outlet of the ethanol cooler E3408 is connected to the ethanol product draw pipeline.

[0073] To highlight a multi-effect energy-saving methanol rectification process method provided by the present invention, some heat exchangers in the process flow are omitted. According to the process method provided by the present invention, those skilled in the relevant technical fields can completely implement a suitable internal logistics heat exchange method of the system according to the specific device conditions. All kinds of evolved process flows formed thereby should be regarded as within the spirit, scope and content of the present invention. The heat exchangers in the process flow diagram are only for illustration, and their specific structural forms do not constitute any limitation to the present invention.

[0074] The prominent technical features of the present invention are: 1) Adopting a five-column five-effect heat integration structure, through the series connection of five columns including the de-light component column T300 and the first to fourth rectification columns T310-T340, multi-effect heat integration is formed. 2) Utilizing the cascade utilization of gas-phase heat sources, the gas phase at the top of the fourth rectification column T340 provides heat sources for the de-light component column T300, and the gas phases at the tops of the remaining columns provide heat sources for the downstream columns in turn, forming five-effect heat integration. 3) Using the dividing wall column design, the fourth rectification column T340 adopts a dividing wall structure (methanol stripping side L340 and ethanol rectification side R340) to achieve efficient separation of wastewater, fusel oil, and ethanol; 4) Due to the ingenious setting of the flexibility of the process flow, that is, by adjusting the arrangement order of the columns (such as the position change of the light component removal column T300) and the heat source distribution (such as gas phase splitting), deformation processes such as five-effect plus four-effect and double four-effect are achieved to adapt to different energy consumption requirements; 5) The technical solution significantly reduces the steam specific consumption, and the steam specific consumption can be reduced from 1.2 tons of steam per ton of refined methanol product in the traditional process to below 0.398 tons per ton of refined methanol product at the lowest, with an energy-saving ratio of 67%.

[0075] The present invention has made substantial technical progress. Especially when compared with the prior art which mostly adopts three-effect or four-effect heat integration (such as CN202310877978.5), it includes a non-obvious heat integration logic composition technical solution. Through the series connection of five columns and the dividing wall column design, the heat source utilization efficiency is increased to five-effect, breaking through the limitations of the conventional heat cycle; the present invention realizes the dual coordination of the balance between low energy consumption and equipment compactness. By optimizing the heat source distribution between columns (such as using the high-pressure gas phase of the fourth rectification column T340 to heat the light component removal column T300), the dependence on external heat sources is reduced, and at the same time, the over-complication of equipment is avoided (such as the high-pressure column design in CN202110620943.4 resulting in an increase in energy consumption).

[0076] In summary, by adopting a multi-effect energy-saving methanol rectification process method and device provided by the present invention, the operating energy consumption can be significantly reduced. For example, for an annual output of 1 million tons of methanol, the steam cost can be saved by more than 100 million yuan per year, and the steam specific consumption of the refined methanol product can be reduced to below 0.43. The present invention has industrial feasibility and process adaptability, can be used for the rectification process of various methanol solvent recovery and methanol synthesis devices, to produce national standard first-class methanol, American standard AA-grade methanol products, or methanol products of other specifications, with remarkable practicality and economic benefits, and broad application prospects. Description of the Drawings

[0077] Figure 1 is a flow chart of a four-column (three columns plus one column) methanol rectification process method adopted in the prior art.

[0078] Figure 2 is a process flow chart for methanol rectification using a typical multi-effect energy-saving methanol rectification process method (five-column five-effect heat integration device) provided by the present invention.

[0079] Figure 3 is Figure 2 an evolved process method, that is, deformation process method one, relative to Figure 2For the provided process, the light - component removal column T300 is moved between the third distillation column T330 and the second distillation column T320: The gas phase at the top of the fourth distillation column T340 serves as the heating heat source for the reboiler of the third distillation column T330, providing the required heat for the third distillation column T330; The gas phase at the top of the third distillation column T330 serves as the heating heat source for the reboiler of the light - component removal column T300, providing the required heat for the light - component removal column T300; The gas phase at the top of the light - component removal column T300 serves as the heating heat source for the reboiler of the second distillation column T320, providing the required heat for the second distillation column T320; The gas phase at the top of the second distillation column T320 serves as the heating heat source for the reboiler of the first distillation column T310, providing the required heat for the first distillation column T310.

[0080] Figure 4 is Figure 2 an evolved process method, namely the second deformation process method, relative to Figure 2 For the provided process, the light - component removal column T300 is moved between the second distillation column T320 and the first distillation column T310: The gas phase at the top of the fourth distillation column T340 serves as the heating heat source for the reboiler of the third distillation column T330, providing the required heat for the third distillation column T330; The gas phase at the top of the third distillation column T330 serves as the heating heat source for the reboiler of the second distillation column T320, providing the required heat for the second distillation column T320; The gas phase at the top of the second distillation column T320 serves as the heating heat source for the reboiler of the light - component removal column T300, providing the required heat for the light - component removal column T300; The gas phase at the top of the light - component removal column T300 serves as the heating heat source for the reboiler of the first distillation column T310, providing the required heat for the first distillation column T310.

[0081] Figure 5 is Figure 2 an evolved process method, namely the third deformation process method, relative to Figure 2 For the provided process, the light - component removal column T300 is moved after the first distillation column T310: The gas phase at the top of the fourth distillation column T340 serves as the heating heat source for the reboiler of the third distillation column T330, providing the required heat for the third distillation column T330; The gas phase at the top of the third distillation column T330 serves as the heating heat source for the reboiler of the second distillation column T320, providing the required heat for the second distillation column T320; The gas phase at the top of the second distillation column T320 serves as the heating heat source for the reboiler of the first distillation column T310, providing the required heat for the first distillation column T310; The gas phase at the top of the first distillation column T310 serves as the heating heat source for the reboiler of the light - component removal column T300, providing the required heat for the light - component removal column T300.

[0082] Figure 6 is Figure 2 an evolved process method, namely the fourth deformation process method, relative to Figure 2In the provided process, the gaseous phase at the top of the fourth rectification column T340 is divided into two streams. One stream serves as the heating heat source for the bottom of the third rectification column T330, providing a part of the required heat for the third rectification column T330, and the other stream serves as the heating heat source for the bottom of the light component removal column T300, providing the required heat for the light component removal column T300; the gaseous phase at the top of the light component removal column T300 also serves as the heating heat source for the bottom of the third rectification column T330, providing the remaining required heat for the third rectification column T330.

[0083] Figure 7 is Figure 3 an evolved process method, namely the fifth deformation process method. Relative to Figure 3 the provided process, the gaseous phase at the top of the third rectification column T330 is divided into two streams. One stream serves as the heating heat source for the bottom of the second rectification column T320, providing a part of the required heat for the second rectification column T320, and the other stream serves as the heating heat source for the bottom of the light component removal column T300, providing the required heat for the light component removal column T300; the gaseous phase at the top of the light component removal column T300 also serves as the heating heat source for the bottom of the second rectification column T320, providing the remaining required heat for the second rectification column T320.

[0084] Figure 8 is Figure 4 an evolved process method, namely the sixth deformation process method. Relative to Figure 4 the provided process, the gaseous phase at the top of the second rectification column T320 is divided into two streams. One stream serves as the heating heat source for the bottom of the first rectification column T310, providing a part of the required heat for the first rectification column T310, and the other stream serves as the heating heat source for the bottom of the light component removal column T300, providing the required heat for the light component removal column T300; the gaseous phase at the top of the light component removal column T300 also serves as the heating heat source for the bottom of the first rectification column T310, providing the remaining required heat for the first rectification column T310.

[0085] Figure 9 is Figure 2 an evolved process method, namely the seventh deformation process method. Relative to Figure 2 the provided process, the gaseous phase at the top of the fourth rectification column T340 is divided into two streams. One stream serves as the heating heat source for the bottom of the third rectification column T330, providing the required heat for the third rectification column T330, and the other stream serves as the heating heat source for the bottom of the light component removal column T300, providing the required heat for the light component removal column T300; the gaseous phases at the tops of the third rectification column T330 and the light component removal column T300 respectively serve as the heating heat source for the bottom of the second rectification column T320, providing the required heat for the second rectification column T320.

[0086] Figure 10 is Figure 2 an evolved process method, namely the eighth deformation process method. Relative to Figure 2In the provided process, external heat sources are used to heat the bottom of both the fourth rectification column T340 and the light component removal column T300; the top gas phases of the fourth rectification column T340 and the light component removal column T300 are used as the heating heat source for the bottom of the third rectification column T330 to provide the required heat for the third rectification column T330.

[0087] Figure 11 Yes Figure 3 An evolved process method, namely the ninth deformation process method. Relative to Figure 3 the provided process, the top gas phase of the third rectification column T330 is divided into two streams. One stream is used as the heating heat source for the bottom of the second rectification column T320 to provide the required heat for the second rectification column T320, and the other stream is used as the heating heat source for the bottom of the light component removal column T300 to provide the required heat for the light component removal column T300; the top gas phase of the second rectification column T320 is used as the heating heat source for the bottom of the first rectification column T310 to provide the required heat for the bottom of the first rectification column T310, and the top gas phase of the light component removal column T300 is used as the heat source for the feed preheater of the first rectification column T310.

[0088] Figure 12 Yes Figure 4 An evolved process method, namely the tenth deformation process method. Relative to Figure 4 the provided process, the top gas phase of the second rectification column T320 is divided into two streams. One stream is used as the heating heat source for the bottom of the first rectification column T310 to provide the required heat for the first rectification column T310, and the other stream is used as the heating heat source for the bottom of the light component removal column T300 to provide the required heat for the light component removal column T300.

[0089] Figure 13 Yes Figure 2 An evolved process method, namely the eleventh deformation process method. Relative to Figure 2 the provided process, the fourth rectification column T340 does not adopt a baffle structure but a conventional structure. Ethanol 40 is recovered from the position above the feed inlet of the fourth rectification column T340, and fusel oil 33 is recovered from the position below the feed inlet. The bottom material 35 of the fourth rectification column T340 is taken out as wastewater.

[0090] Figure 14 Yes Figure 2 An evolved process method, namely the twelfth deformation process method. Relative to Figure 2 the provided process, a stripping column T340S is added. The fourth rectification column T340 does not adopt a baffle structure but a conventional structure; the side-line liquid material 42 of the fourth rectification column T340 enters the top of the stripping column T340S, the top gas material 43 of the stripping column T340S returns to the fourth rectification column T340, and the recovered ethanol 40 is taken out from the bottom of the stripping column T340S.

[0091] Figure 15 Yes Figure 2An evolution process method, namely deformation process method thirteen, relative to Figure 2 In the provided process, an additional recovery column T350 is added. The fourth distillation column T340 does not adopt a baffle structure but a conventional structure; the recovery column T350 can use the top gas phase of the first distillation column T310 or the second distillation column T320 or the fourth distillation column T340 as the heat source, or use other heat sources within the system, or use an external heat source.

[0092] Figure 16 Is Figure 2 An evolution process method, namely deformation process method fourteen, relative to Figure 2 In the provided process, an additional light component removal column T300D is added to the light component removal column T300. It shares the reboiler E3001 at the bottom of the column with the light component removal column T300. The top gas phases of both the light component removal column T300 and the light component removal distillation column T300D are used as the heating heat source for the bottom of the third distillation column T330 to provide the required heat for the third distillation column T330; refined methanol products are drawn from the top of the light component removal distillation column T300D.

[0093] Figure 17 Is Figure 2 An evolution process method, namely deformation process method fifteen, relative to Figure 2 In the provided process, an additional fifth distillation column T360 is connected in parallel to the light component removal column T300. The top gas phase of the fourth distillation column T340 is divided into two streams. One stream is used as the heating heat source for the bottom of the light component removal column T300 to provide the required heat for the light component removal column T300, and the other stream is used as the heating heat source for the bottom of the fifth distillation column T360 to provide the required heat for the fifth distillation column T360; the top gas phases of both the light component removal column T300 and the fifth distillation column T360 are used as the heating heat source for the bottom of the third distillation column T330 to provide the required heat for the third distillation column T330; refined methanol products are drawn from the top of the fifth distillation column T360.

[0094] Figure 18 Is Figure 2 An evolution process method, namely deformation process method sixteen, relative to Figure 2 In the provided process, the upper part of the light component removal column T300 adopts a dividing wall column structure. The dividing wall S300 divides the upper part of the light component removal column T300 into a pre-distillation side R300 and a methanol distillation side L300; the top gas phases of both the pre-distillation side R300 and the methanol distillation side L300 are used as the heating heat source for the bottom of the third distillation column T330 to provide the required heat for the third distillation column T330; refined methanol products are drawn from the top of the methanol distillation side L300; the lower part and the bottom of the light component removal column T300 are of a non-dividing wall conventional structure.

[0095] Figure 19 Is Figure 2 An evolution process method, namely deformation process method seventeen, relative toFigure 2 For the provided process, while the light component removal column T300, the first distillation column T310, the second distillation column T320, and the third distillation column T330 adopt heat integration heating, external heat sources can also be used to provide heat to the column kettle. These external heat sources can be fresh steam, hot water, heat transfer oil, or other low-grade heat sources within the system.

[0096] According to the process method provided by the present invention and the above-mentioned variant process methods, those skilled in the relevant technical fields can completely implement appropriate internal system logistics heat exchange methods according to specific device conditions. All kinds of evolved process flows formed thereby should be regarded as within the spirit, scope, and content of the present invention. Specific Embodiments

[0097] The specific implementation embodiments of the present invention are described in detail with reference to the accompanying drawings as follows, but are only for illustration and not for limiting the present invention. Unless otherwise specified, the composition, structure, materials (such as connection pipelines for connecting various tower components), reagents, etc. of the process equipment such as tower components not specifically indicated in the embodiments can be obtained from commercial channels or by methods well-known to those of ordinary skill in the art. The specific experimental methods and operating conditions involved usually follow the conventional process conditions and the conditions described in the manuals, or the conditions recommended by the manufacturers.

[0098] Application Example 1: The typical composition of the crude methanol raw material is as follows: Component Mass Percentage (%) Carbon monoxide 0.035 Carbon dioxide 1.065 Water 4.575 Methanol 94.000 Dimethyl ether 0.048 Methyl formate 0.040 Acetone 0.004 Ethanol 0.150 n-Propanol 0.048 n-Butanol 0.010 Isobutanol 0.010 n-Pentanol 0.012 Methyl ethyl ketone 0.003 Total 100.00.

[0099] The above raw material composition range does not constitute any limitation to the present invention. The present invention can be used in the distillation process of crude methanol raw materials with various compositions.

[0100] Such as Figure 2As shown, the raw methanol feedstock 1 is divided into two streams. One stream of feedstock 2 is preheated by the feed wastewater preheater E3404 to form feedstock 4, which is mixed with another stream of feedstock 3 preheated by the feed methanol preheater E3403 to form feedstock 5. The preheated feedstock 6 then enters the light component removal column T300.

[0101] The light component removal column T300 operates with heat integration with the third distillation column T330. The vapor phase 7 at the top of the light component removal column T300 enters the shell side of the third distillation column reboiler E3301. The condensed liquid 9 is directly returned to the top of the light component removal column T300, and the non-condensable gas 8 is discharged. The bottom material 10 of the light component removal column T300 enters the first distillation column T310.

[0102] The vapor phase 11 at the top of the first distillation column T310 is condensed by the first distillation column condenser E3102, and the condensed liquid 12 is divided into two streams. One stream is used as the reflux liquid 13 of the first distillation column and is directly returned to the top of the first distillation column T310, and the other stream of condensed liquid 14 is taken out as the refined methanol product. The bottom material 15 of the first distillation column T310 enters the second distillation column T320.

[0103] The second distillation column T320 operates with heat integration with the first distillation column T310. The vapor phase 16 at the top of the second distillation column T320 enters the shell side of the first distillation column reboiler E3101. The condensed liquid 17 is divided into two streams. One stream is used as the reflux liquid 18 of the second distillation column and is directly returned to the top of the second distillation column T320, and the other stream of condensed liquid 19 is taken out as the refined methanol product. The bottom material 20 of the second distillation column T320 enters the third distillation column T330.

[0104] The third distillation column T330 operates with heat integration with the second distillation column T320. The vapor phase 21 at the top of the third distillation column T330 enters the shell side of the second distillation column reboiler E3201. The condensed liquid 22 is divided into two streams. One stream is used as the reflux liquid 23 of the third distillation column and is directly returned to the top of the third distillation column T330, and the other stream of condensed liquid 24 is taken out as the refined methanol product. The bottom material 25 of the third distillation column T330 enters the methanol stripping side L340 of the fourth distillation column T340.

[0105] The fourth distillation column T340 operates with heat integration with the light component removal column T300. The vapor phase 26 at the top of the fourth distillation column T340 enters the shell side of the light component removal column reboiler E3001. The condensed liquid 27 is divided into two streams. One stream is used as the reflux liquid 28 of the fourth distillation column and is directly returned to the top of the fourth distillation column T340, and the other stream of condensed liquid 29 is taken out as the refined methanol product. Near the feed inlet of the methanol stripping side L340 of the fourth distillation column T340, a side stream of fusel oil 33 with very low methanol and ethanol content is taken out. The bottom material 35 of the methanol stripping side L340 of the fourth distillation column T340 is taken out as wastewater. The bottom material 40 of the ethanol distillation side R340 of the fourth distillation column T340 is taken out as the recovered ethanol product.

[0106] The refined methanol product 30 after mixing the overhead products 14 of the first distillation column T310, the overhead products 19 of the second distillation column T320, the overhead products 24 of the third distillation column T330, and the overhead products 29 of the fourth distillation column T340 is cooled by the feed methanol preheater E3403. The cooled material 31 is further cooled by the methanol product cooler E3405 to obtain the refined methanol product 32, which is then sent out of the unit.

[0107] The wastewater 35 drawn from the bottom of the methanol stripping side L340 of the fourth distillation column T340 is first cooled by the feed wastewater preheater E3404. The cooled material 36 is further cooled by the wastewater cooler E3406, and the resulting wastewater 37 is divided into two streams. One stream is sent out of the unit as wastewater 38, and the other stream is returned to the top of the light component removal column T300 as extraction water 39.

[0108] The fusel oil 33 drawn from the side stream of the methanol stripping side L340 of the fourth distillation column T340 is cooled by the fusel oil cooler E3407 to obtain the fusel oil product 34, which is then sent out of the unit.

[0109] The recovered ethanol 40 drawn from the bottom of the ethanol rectification side R340 of the fourth distillation column T340 is cooled by the ethanol cooler E3408 to obtain the recovered ethanol product 41, which is then sent out of the unit.

[0110] The heat sources for the reboiler E3401 on the methanol stripping side of the fourth distillation column and the reboiler E3402 on the ethanol rectification side of the fourth distillation column can be fresh steam, heat transfer oil, or the material steam generated within the system.

[0111] The condensate of the fresh steam added to the system can be used to preheat the feeds to each column separately or successively.

[0112] The first distillation column condenser E3102, the methanol product cooler E3405, the wastewater cooler E3406, the fusel oil cooler E3407, and the ethanol cooler E3408 can be air coolers or water coolers; the cooling media used can be circulating water, low-temperature water, chilled water, or other cooling media such as the low-temperature materials within the system.

[0113] The following gives the typical operating conditions of each column in Example 1: The operating pressure range at the top of the light component removal column T300 is 190 - 1200 kPa; The operating pressure range at the top of the first distillation column T310 is 25 - 150 kPa; The operating pressure range at the top of the second distillation column T320 is 45 - 300 kPa; The operating pressure range at the top of the third distillation column T330 is 90 - 600 kPa; The operating pressure range at the top of the fourth rectification column T340 is 350 - 1800 kPa.

[0114] The following are the preferred operating conditions for each column in Example 1: The operating pressure at the top of the light component removal column T300 is 320 - 570 kPa, the operating temperature at the top is 95 - 115 °C, and the operating temperature at the bottom of the column is 100 - 125 °C.

[0115] The operating pressure at the top of the first rectification column T310 is 44 - 69 kPa, the operating temperature at the top is 45 - 55 °C, and the operating temperature at the bottom of the column is 50 - 65 °C.

[0116] The operating pressure at the top of the second rectification column T320 is 81 - 135 kPa, the operating temperature at the top is 59 - 72 °C, and the operating temperature at the bottom of the column is 68 - 85 °C.

[0117] The operating pressure at the top of the third rectification column T330 is 162 - 282 kPa, the operating temperature at the top is 77 - 93 °C, and the operating temperature at the bottom of the column is 85 - 110 °C.

[0118] The operating pressure at the top of the fourth rectification column T340 is 490 - 910 kPa, the operating temperature at the top is 111 - 133 °C, the operating temperature at the bottom of the methanol stripping side L340 is 152 - 176 °C; the operating temperature at the bottom of the ethanol rectification side R340 is 116 - 150 °C.

[0119] The following gives a typical operating condition for each column in Example 1: The operating pressure at the top of the light component removal column T300 is 440 kPa, the operating temperature at the top is 107 °C, and the operating temperature at the bottom of the column is 113 °C.

[0120] The operating pressure at the top of the first rectification column T310 is 58 kPa, the operating temperature at the top is 51 °C, and the operating temperature at the bottom of the column is 57 °C.

[0121] The operating pressure at the top of the second rectification column T320 is 110 kPa, the operating temperature at the top is 67 °C, and the operating temperature at the bottom of the column is 77 °C.

[0122] The operating pressure at the top of the third rectification column T330 is 222 kPa, the operating temperature at the top is 86 °C, and the operating temperature at the bottom of the column is 98 °C.

[0123] The operating pressure at the top of the fourth rectification column T340 is 695 kPa, the operating temperature at the top is 123 °C, the operating temperature at the bottom of the methanol stripping side L340 is 165 °C; the operating temperature at the bottom of the ethanol rectification side R340 is 136 °C.

[0124] For the entire methanol distillation unit, only the methanol stripping side reboiler E3401 and the ethanol rectification side reboiler E3402 of the fourth distillation column require an external heating heat source. The heat sources required for the remaining reboilers and preheaters can be heated using the internal heat sources and steam condensate of the system.

[0125] The external heating heat source is considered as medium-pressure steam. The plant scale is based on an annual output of 1 million tons of methanol product of American Standard AA grade (operating hours are 8000 hours / year). According to the currently widely used four-column methanol distillation process, the steam consumption in the methanol distillation process is approximately 1.2 tons of steam per ton of refined methanol product; using the five-column heat integration device provided by CN200910068170.2 for the methanol distillation process method, the steam consumption in the methanol distillation process is approximately 0.75 tons of steam per ton of refined methanol product; using the multi-effect energy-saving methanol distillation process method provided by the present invention, the steam consumption of the device is less than 0.43 tons of steam per ton of refined methanol product.

[0126] For the multi-effect energy-saving methanol distillation process method provided by the present invention, compared with the currently widely used four-column methanol distillation process, the energy-saving ratio is: (1.2 - 0.43) / 1.2×100%≈64% The steam that can be saved annually is approximately: (1.2 - 0.43) tons / ton×1 million tons / year = 770,000 tons / year.

[0127] Calculated at 150 yuan per ton of steam, the steam cost that can be saved annually is: 770,000 tons / year×150 yuan / ton = 115.5 million yuan / year.

[0128] For the multi-effect energy-saving methanol distillation process method provided by the present invention, compared with the methanol distillation process method using the five-column heat integration device provided by CN200910068170.2, the energy-saving ratio is: (0.75 - 0.43) / 0.75×100%≈42.6% The steam that can be saved annually is approximately: (0.75 - 0.43) tons / ton×1 million tons / year = 320,000 tons / year.

[0129] Calculated at 150 yuan per ton of steam, the steam cost that can be saved annually is: 320,000 tons / year×150 yuan / ton = 48 million yuan / year.

[0130] A multi-effect energy-saving methanol distillation process method provided by the present invention can significantly reduce the operating energy consumption. It can be used in the distillation processes of various methanol solvent recovery and methanol synthesis units to produce national standard premium methanol, American standard AA-grade methanol products, or methanol products of other specifications. It overcomes the defects of the prior art, and the steam specific consumption of refined methanol products can be reduced to below 0.43, with remarkable practicability and economic benefits, and broad application prospects.

[0131] Application Example 2: As Figure 3 shown, it is Figure 2 an evolved process method of Figure 2 For the provided process flow, the light component removal tower T300 is moved between the third distillation tower T330 and the second distillation tower T320: The gas phase at the top of the fourth distillation tower T340 is used as the heating heat source for the reboiler of the third distillation tower T330 to provide the required heat for the third distillation tower T330; The gas phase at the top of the third distillation tower T330 is used as the heating heat source for the reboiler of the light component removal tower T300 to provide the required heat for the light component removal tower T300; The gas phase at the top of the light component removal tower T300 is used as the heating heat source for the reboiler of the second distillation tower T320 to provide the required heat for the second distillation tower T320; The gas phase at the top of the second distillation tower T320 is used as the heating heat source for the reboiler of the first distillation tower T310 to provide the required heat for the first distillation tower T310.

[0132] Application Example 3: As Figure 4 shown, it is Figure 2 an evolved process method of Figure 2 For the provided process flow, the light component removal tower T300 is moved between the second distillation tower T320 and the first distillation tower T310: The gas phase at the top of the fourth distillation tower T340 is used as the heating heat source for the reboiler of the third distillation tower T330 to provide the required heat for the third distillation tower T330; The gas phase at the top of the third distillation tower T330 is used as the heating heat source for the reboiler of the second distillation tower T320 to provide the required heat for the second distillation tower T320; The gas phase at the top of the second distillation tower T320 is used as the heating heat source for the reboiler of the light component removal tower T300 to provide the required heat for the light component removal tower T300; The gas phase at the top of the light component removal tower T300 is used as the heating heat source for the reboiler of the first distillation tower T310 to provide the required heat for the first distillation tower T310.

[0133] Application Example 4: As Figure 5 shown, it is Figure 2 an evolved process method of Figure 2In the provided process, the light component removal column T300 is moved behind the first distillation column T310: The gas phase at the top of the fourth distillation column T340 serves as the heating heat source for the bottom of the third distillation column T330, providing the required heat for the third distillation column T330; the gas phase at the top of the third distillation column T330 serves as the heating heat source for the bottom of the second distillation column T320, providing the required heat for the second distillation column T320; the gas phase at the top of the second distillation column T320 serves as the heating heat source for the bottom of the first distillation column T310, providing the required heat for the first distillation column T310; the gas phase at the top of the first distillation column T310 serves as the heating heat source for the bottom of the light component removal column T300, providing the required heat for the light component removal column T300.

[0134] Application Example 5: As Figure 6 shown, it is Figure 2 an evolved process method of Figure 2 the provided process. For the provided process, the gas phase at the top of the fourth distillation column T340 is divided into two streams. One stream serves as the heating heat source for the bottom of the third distillation column T330, providing a part of the required heat for the third distillation column T330, and the other stream serves as the heating heat source for the bottom of the light component removal column T300, providing the required heat for the light component removal column T300. The gas phase at the top of the light component removal column T300 also serves as the heating heat source for the bottom of the third distillation column T330, providing the remaining required heat for the third distillation column T330.

[0135] Application Example 6: As Figure 7 shown, it is Figure 3 an evolved process method of Figure 3 the provided process. For the provided process, the gas phase at the top of the third distillation column T330 is divided into two streams. One stream serves as the heating heat source for the bottom of the second distillation column T320, providing a part of the required heat for the second distillation column T320, and the other stream serves as the heating heat source for the bottom of the light component removal column T300, providing the required heat for the light component removal column T300. The gas phase at the top of the light component removal column T300 also serves as the heating heat source for the bottom of the second distillation column T320, providing the remaining required heat for the second distillation column T320.

[0136] Application Example 7: As Figure 8 shown, it is Figure 4 an evolved process method of Figure 4 the provided process. For the provided process, the gas phase at the top of the second distillation column T320 is divided into two streams. One stream serves as the heating heat source for the bottom of the first distillation column T310, providing a part of the required heat for the first distillation column T310, and the other stream serves as the heating heat source for the bottom of the light component removal column T300, providing the required heat for the light component removal column T300. The gas phase at the top of the light component removal column T300 also serves as the heating heat source for the bottom of the first distillation column T310, providing the remaining required heat for the first distillation column T310.

[0137] Application Example 8: As Figure 9 shown, it is Figure 2 an evolved process method. Compared with the process provided by Figure 2 , the gas phase at the top of the fourth distillation column T340 is divided into two streams. One stream serves as the heating heat source for the bottom of the third distillation column T330, providing the required heat for the third distillation column T330, and the other stream serves as the heating heat source for the bottom of the light component removal column T300, providing the required heat for the light component removal column T300; the gas phases at the tops of the third distillation column T330 and the light component removal column T300 respectively serve as the heating heat source for the bottom of the second distillation column T320, providing the required heat for the second distillation column T320.

[0138] Application Example 9: As Figure 10 shown, it is Figure 2 an evolved process method. Compared with the process provided by Figure 2 , both the bottoms of the fourth distillation column T340 and the light component removal column T300 are heated by external heat sources; the gas phases at the tops of the fourth distillation column T340 and the light component removal column T300 both serve as the heating heat source for the bottom of the third distillation column T330, providing the required heat for the third distillation column T330.

[0139] Application Example 10: As Figure 11 shown, it is Figure 3 an evolved process method. Compared with the process provided by Figure 3 , the gas phase at the top of the third distillation column T330 is divided into two streams. One stream serves as the heating heat source for the bottom of the second distillation column T320, providing the required heat for the second distillation column T320, and the other stream serves as the heating heat source for the bottom of the light component removal column T300, providing the required heat for the light component removal column T300; the gas phase at the top of the second distillation column T320 serves as the heating heat source for the bottom of the first distillation column T310, providing the required heat for the bottom of the first distillation column T310, and the gas phase at the top of the light component removal column T300 serves as the heat source for the feed preheater of the first distillation column T310.

[0140] Application Example 11: As Figure 12 shown, it is Figure 4 an evolved process method. Compared with the process provided by Figure 4 , the gas phase at the top of the second distillation column T320 is divided into two streams. One stream serves as the heating heat source for the bottom of the first distillation column T310, providing the required heat for the first distillation column T310, and the other stream serves as the heating heat source for the bottom of the light component removal column T300, providing the required heat for the light component removal column T300.

[0141] Application Example 12: As Figure 13As shown, it is Figure 2 an evolved process method relative to Figure 2 the provided process. For the fourth rectification column T340, instead of using a baffle structure, a conventional structure is adopted. Ethanol 40 is recovered from the position above the feed inlet of the fourth rectification column T340, fusel oil 33 is taken out from the position below the feed inlet, and the bottom material 35 of the fourth rectification column T340 is taken out as wastewater.

[0142] Application Example 13: As Figure 14 shown, it is Figure 2 an evolved process method relative to Figure 2 the provided process. One stripping column T340S is added. For the fourth rectification column T340, instead of using a baffle structure, a conventional structure is adopted. The side-line liquid material 42 of the fourth rectification column T340 enters the top of the stripping column T340S. The vapor material 43 at the top of the stripping column T340S returns to the fourth rectification column T340, and the recovered ethanol 40 is taken out from the bottom of the stripping column T340S.

[0143] Application Example 14: As Figure 15 shown, it is Figure 2 an evolved process method relative to Figure 2 the provided process. One recovery column T350 is added. For the fourth rectification column T340, instead of using a baffle structure, a conventional structure is adopted. The recovery column T350 can use the vapor at the top of the first rectification column T310 or the second rectification column T320 or the fourth rectification column T340 as a heat source, or use other heat sources within the system, or use an external heat source (fresh steam, hot water, heat transfer oil, or other low-grade heat sources within the system).

[0144] Application Example 15: As Figure 16 shown, it is Figure 2 an evolved process method relative to Figure 2 the provided process. One more light component removal rectification column T300D is added to the light component removal column T300. It shares the bottom and the light component removal column reboiler E3001 with the light component removal column T300. The vapor at the top of both the light component removal column T300 and the light component removal rectification column T300D serves as the heating heat source for the bottom of the third rectification column T330, providing the required heat for the third rectification column T330. The refined methanol product is taken out from the top of the light component removal rectification column T300D. Using this process to process the same raw crude alcohol as in Application Example 1, the same AA-grade methanol product according to the US standard is produced, and the steam consumption of the device can be lower than 0.398 tons of steam per ton of refined methanol product.

[0145] Application Example 16: As Figure 17 shown, it is Figure 2An evolved process method, relative to Figure 2 In the provided process, a fifth distillation column T360 is connected in parallel to the light component removal column T300. The gas phase at the top of the fourth distillation column T340 is divided into two streams. One stream serves as the heating heat source for the bottom of the light component removal column T300 to provide the required heat for the light component removal column T300, and the other stream serves as the heating heat source for the bottom of the fifth distillation column T360 to provide the required heat for the fifth distillation column T360; the gas phases at the tops of the light component removal column T300 and the fifth distillation column T360 both serve as the heating heat source for the bottom of the third distillation column T330 to provide the required heat for the third distillation column T330; refined methanol products are withdrawn from the top of the fifth distillation column T360.

[0146] Application Example 17: As Figure 18 shown, it is Figure 2 An evolved process method, relative to Figure 2 In the provided process, the upper part of the light component removal column T300 adopts a dividing wall column structure. The dividing wall S300 divides the upper part of the light component removal column T300 into a pre-distillation side R300 and a methanol distillation side L300; the gas phases at the tops of the pre-distillation side R300 and the methanol distillation side L300 both serve as the heating heat source for the bottom of the third distillation column T330 to provide the required heat for the third distillation column T330; refined methanol products are withdrawn from the top of the methanol distillation side L300; the lower part and the bottom of the light component removal column T300 are of a non-dividing wall conventional structure.

[0147] Application Example 18: As Figure 19 shown, it is Figure 2 An evolved process method, relative to Figure 2 In the provided process, while the light component removal column T300, the first distillation column T310, the second distillation column T320, and the third distillation column T330 adopt heat integration heating, external heat sources can also be used to provide heat for the bottom of the columns. These external heat sources can be fresh steam, hot water, heat transfer oil, or other low-grade heat sources within the system: T300 is heated by E3003 using other low-grade heat sources (low-pressure steam, hot water, heat transfer oil, or other low-grade heat sources within the system); T310 is heated by E3105 using other low-grade heat sources (low-pressure steam, hot water, heat transfer oil, or other low-grade heat sources within the system); T320 is heated by E3203 using other low-grade heat sources (low-pressure steam, hot water, heat transfer oil, or other low-grade heat sources within the system); T330 is heated by E3303 using other low-grade heat sources (low-pressure steam, hot water, heat transfer oil, or other low-grade heat sources within the system). Each column can use the aforementioned other low-grade heat sources to heat the column middle or the bottom simultaneously or separately.

[0148] The present invention provides a multi-effect energy-saving methanol rectification process method and device, which can significantly reduce the operating energy consumption. The entire device includes at least five towers such as a light component removal tower T300, a first rectification tower T310, a second rectification tower T320, a third rectification tower T330, and a fourth rectification tower T340 and their supporting equipment. It can be used for the rectification process of various methanol solvent recovery and methanol synthesis devices to produce national standard premium methanol, ASTM AA grade methanol products, or methanol products of other specifications. It overcomes the defects of the prior art, and the steam specific consumption of the refined methanol product can be reduced to below 0.43, with remarkable practicability and economic benefits, and broad application prospects.

[0149] Specifically described in combination with embodiments, those skilled in the relevant art can make appropriate modifications, changes, and combinations according to the method provided by the present invention to implement this technology. It should be particularly noted that all these similar modifications, changes, and recombinations to the process flow provided by the present invention are obvious to those skilled in the art and are regarded as within the spirit, scope, and content of the present invention.

Claims

1. A multi-effect energy-saving methanol distillation process, characterized in that Steps included: 1) At least five towers including a light component removal tower (T300), a first distillation tower (T310), a second distillation tower (T320), a third distillation tower (T330) and a fourth distillation tower (T340); 2) After being preheated, crude methanol enters the light component removal tower (T300), and the liquid phase in the bottom of the light component removal tower (T300) enters the first distillation tower (T310); 3) The liquid phase from the bottom of the first distillation tower (T310) enters the second distillation tower (T320); 4) The liquid phase from the bottom of the second distillation tower (T320) enters the third distillation tower (T330); 5) The liquid phase from the bottom of the third distillation tower (T330) enters the fourth distillation tower (T340); 6) Five-effect heat integration is adopted between the five towers. The top gas phase of the fourth distillation tower (T340) is used as a heat source for heating the bottom of the light component removal tower (T300) to provide the required heat for the light component removal tower (T300); the top gas phase of the light component removal tower (T300) is used as a heat source for heating the bottom of the third distillation tower (T330) to provide the required heat for the third distillation tower (T330); the top gas phase of the third distillation tower (T330) is used as a heat source for heating the bottom of the second distillation tower (T320) to provide the required heat for the second distillation tower (T320); the top gas phase of the second distillation tower (T320) is used as a heat source for heating the bottom of the first distillation tower (T310) to provide the required heat for the first distillation tower (T310); 7) Refined methanol products are respectively extracted from the tops of the first distillation tower (T310), the second distillation tower (T320), the third distillation tower (T330) and the fourth distillation tower (T340).

2. The process according to claim 1, characterized in that The deformation process that can be used is selected from: 1) In the five towers, the light component removal tower (T300) is moved between the third distillation tower (T330) and the second distillation tower (T320): the top gas phase of the fourth distillation tower (T340) is used as a heat source for heating the bottom of the third distillation tower (T330) to provide the required heat for the third distillation tower (T330); the top gas phase of the third distillation tower (T330) is used as a heat source for heating the bottom of the light component removal tower (T300) to provide the required heat for the light component removal tower (T300); the top gas phase of the light component removal tower (T300) is used as a heat source for heating the bottom of the second distillation tower (T320) to provide the required heat for the second distillation tower (T320); the top gas phase of the second distillation tower (T320) is used as a heat source for heating the bottom of the first distillation tower (T310) to provide the required heat for the first distillation tower (T310); 2) In the five towers, the light component removal tower (T300) is moved between the second distillation tower (T320) and the first distillation tower (T310): the top gas phase of the fourth distillation tower (T340) is used as a heat source for heating the bottom of the third distillation tower (T330), providing the required heat for the third distillation tower (T330); the top gas phase of the third distillation tower (T330) is used as a heat source for heating the bottom of the second distillation tower (T320), providing the required heat for the second distillation tower (T320); the top gas phase of the second distillation tower (T320) is used as a heat source for heating the bottom of the light component removal tower (T300), providing the required heat for the light component removal tower (T300); the top gas phase of the light component removal tower (T300) is used as a heat source for heating the bottom of the first distillation tower (T310), providing the required heat for the first distillation tower (T310); 3) In the five towers, after the light component removal tower (T300) is moved to the first distillation tower (T310): the top gas phase of the fourth distillation tower (T340) is used as a heat source for heating the bottom of the third distillation tower (T330), providing the required heat for the third distillation tower (T330); the top gas phase of the third distillation tower (T330) is used as a heat source for heating the bottom of the second distillation tower (T320), providing the required heat for the second distillation tower (T320); the top gas phase of the second distillation tower (T320) is used as a heat source for heating the bottom of the first distillation tower (T310), providing the required heat for the first distillation tower (T310); the top gas phase of the first distillation tower (T310) is used as a heat source for heating the bottom of the light component removal tower (T300), providing the required heat for the light component removal tower (T300).

3. The process according to claim 1, characterized in that The deformation process that can be used is selected from: 1) In the five towers, the gas phase at the top of the fourth distillation tower (T340) is divided into two streams, one stream is used as a heat source for heating the bottom of the third distillation tower (T330) to provide a part of the required heat for the third distillation tower (T330), and the other stream is used as a heat source for heating the bottom of the light component removal tower (T300) to provide the required heat for the light component removal tower (T300); the gas phase at the top of the light component removal tower (T300) is also used as a heat source for heating the bottom of the third distillation tower (T330) to provide the remaining required heat for the third distillation tower (T330); 2) In the five towers, the gas phase at the top of the third distillation tower (T330) is divided into two streams, one stream is used as a heat source for heating the bottom of the second distillation tower (T320) to provide a part of the required heat for the second distillation tower (T320), and the other stream is used as a heat source for heating the bottom of the light component removal tower (T300) to provide the required heat for the light component removal tower (T300); the gas phase at the top of the light component removal tower (T300) is also used as a heat source for heating the bottom of the second distillation tower (T320) to provide the remaining required heat for the second distillation tower (T320); 3) In the five towers, the gas phase at the top of the second distillation tower (T320) is divided into two streams, one stream is used as a heat source for heating the bottom of the first distillation tower (T310) to provide a part of the required heat for the first distillation tower (T310), and the other stream is used as a heat source for heating the bottom of the light component removal tower (T300) to provide the required heat for the light component removal tower (T300); the gas phase at the top of the light component removal tower (T300) is also used as a heat source for heating the bottom of the first distillation tower (T310) to provide the remaining required heat for the first distillation tower (T310).

4. The process according to claim 1, characterized in that The deformation process that can be used is selected from: 1) In the five towers, the top gas phase of the fourth distillation tower (T340) is divided into two streams, one stream is used as a heat source for heating the bottom of the third distillation tower (T330) to provide the required heat for the third distillation tower (T330), and the other stream is used as a heat source for heating the bottom of the light component removal tower (T300) to provide the required heat for the light component removal tower (T300); the top gas phases of the third distillation tower (T330) and the light component removal tower (T300) are respectively used as heat sources for heating the bottom of the second distillation tower (T320) to provide the required heat for the second distillation tower (T320); 2) In the five towers, the bottoms of the fourth distillation tower (T340) and the light component removal tower (T300) are heated by external heat sources (fresh steam, hot water, heat transfer oil, or other low-grade heat sources inside the system); the top gas phases of the fourth distillation tower (T340) and the light component removal tower (T300) are used as heat sources for heating the bottom of the third distillation tower (T330), providing the required heat for the third distillation tower (T330); 3) In the five towers, the top gas phase of the third distillation tower (T330) is divided into two streams, one stream is used as a heat source for heating the bottom of the second distillation tower (T320) to provide the required heat for the second distillation tower (T320), and the other stream is used as a heat source for heating the bottom of the light component removal tower (T300) to provide the required heat for the light component removal tower (T300); the top gas phase of the second distillation tower T320 is used as a heat source for heating the bottom of the first distillation tower T310 to provide the required heat for the bottom of the first distillation tower T310, and the top gas phase of the light component removal tower T300 provides a heat source for the feed preheater of the first distillation tower T310; 4) In the five towers, the top gas phase of the second distillation tower (T320) is divided into two streams, one stream is used as a heat source for heating the bottom of the first distillation tower (T310) to provide the required heat for the first distillation tower (T310), and the other stream is used as a heat source for heating the bottom of the light component removal tower (T300) to provide the required heat for the light component removal tower (T300).

5. The process according to claim 1, characterized in that The lower part of the fourth distillation tower (T340) adopts a partition tower structure, and the partition (S340) divides the lower part of the fourth distillation tower (T340) into a methanol distillation side (L340) and an ethanol distillation side (R340); waste water (35) is discharged from the bottom of the methanol distillation side (L340) of the fourth distillation tower (T340); fusel oil (33) with very low methanol and ethanol content is produced from the side line below the feed inlet of the methanol distillation side (L340) of the fourth distillation tower (T340); and ethanol product (40) is produced and recovered from the bottom of the ethanol distillation side (R340) of the fourth distillation tower (T340).

6. The process according to claim 1, characterized in that Transformation to other heat-integrated processes for methanol production, selected from: 1) In the five towers, the fourth distillation tower (T340) does not adopt a partition structure but a conventional structure, and the fourth distillation tower (T340) produces recovered ethanol (40) at a position above the feed inlet, produces fusel oil (33) at a position below the feed inlet, and the bottom material (35) of the fourth distillation tower (T340) is produced as wastewater; 2) On the basis of the five towers, a stripping tower (T340S) is added, and the fourth distillation tower (T340) does not adopt a baffle structure but a conventional structure; the side line liquid material (42) of the fourth distillation tower (T340) enters the top of the stripping tower (T340S), the top gaseous material (43) of the stripping tower (T340S) returns to the fourth distillation tower (T340), and the bottom of the stripping tower (T340S) is extracted and recovered ethanol (40); 3) A recovery tower (T350) is added on the basis of the five towers, and the fourth distillation tower (T340) does not adopt a partition structure but a conventional structure; the recovery tower (T350) can use the top gas phase of the second distillation tower (T320) or the third distillation tower (T330) or the fourth distillation tower (T340) as a heat source, or use other heat sources in the system, or use an external heat source.

7. The process according to claim 1, characterized in that The periphery of the light component removal tower (T300) can be transformed into other heat-integrated processes for methanol production, selected from: 1) On the basis of the five towers, a light component removal distillation tower (T300D) is added to the light component removal tower (T300), and the light component removal tower (T300) and the light component removal tower (T300) share the tower kettle and the light component removal tower reboiler (E3001). The top gas phases of the light component removal tower (T300) and the light component removal distillation tower (T300D) are used as heat sources for heating the tower kettle of the third distillation tower (T330), providing the required heat for the third distillation tower (T330); the refined methanol product is produced from the top of the light component removal distillation tower (T300D); 2) On the basis of the five towers, the light component removal tower (T300) is connected in parallel with a fifth distillation tower (T360), and the top gas phase of the fourth distillation tower (T340) is divided into two streams, one stream is used as a heat source for heating the bottom of the light component removal tower (T300) to provide the required heat for the light component removal tower (T300), and the other stream is used as a heat source for heating the bottom of the fifth distillation tower (T360) to provide the required heat for the fifth distillation tower (T360); the top gas phases of the light component removal tower (T300) and the fifth distillation tower (T360) are both used as heat sources for heating the bottom of the third distillation tower (T330) to provide the required heat for the third distillation tower (T330); refined methanol products are produced from the top of the fifth distillation tower (T360); 3) On the basis of the five towers, the upper part of the light component removal tower (T300) adopts a baffle tower structure, and the baffle (S300) divides the upper part of the light component removal tower (T300) into a pre-distillation side (R300) and a methanol distillation side (L300); the top gas phases of the pre-distillation side (R300) and the methanol distillation side (L300) are used as heat sources for heating the bottom of the third distillation tower (T330), providing the required heat for the third distillation tower (T330); the refined methanol product is produced from the top of the methanol distillation side (R300); the lower part of the light component removal tower (T300) and the bottom of the tower are conventional structures without baffles.

8. The process according to any one of claims 1 to 7, characterized in that: The discharge from the bottom of the light component removal tower (T300) first enters the first distillation tower (T310), or first enters the second distillation tower (T320), or first enters the third distillation tower (T330); or enters the first distillation tower (T310) and the second distillation tower (T320) respectively; or enters the first distillation tower (T310) and the third distillation tower (T330) respectively; or enters the second distillation tower (T320) and the third distillation tower (T330) respectively; or enters the first distillation tower (T310), the second distillation tower (T320) and the third distillation tower (T330) respectively.

9. The process according to claim 1, characterized in that: Typical operating conditions for each tower are: The operating pressure range of the light component removal tower (T300) top is 190~1200 kPa; The operating pressure range of the top of the first distillation tower (T310) is 25 to 150 kPa; The top operating pressure range of the second distillation tower (T320) is 45-300 kPa; The top operating pressure range of the third distillation tower (T330) is 90-600 kPa; The top operating pressure range of the fourth distillation tower (T340) is 350-1800 kPa; The preferred operating conditions of each tower are: The light component removal tower (T300) has a top operating pressure of 320-570 kPa, a top operating temperature of 95-115°C, and a bottom operating temperature of 100-125°C. The top operating pressure of the first distillation tower (T310) is 44-69 kPa, the top operating temperature is 45-55°C, and the bottom operating temperature is 50-65°C; The second distillation tower (T320) has a top operating pressure of 81-135 kPa, a top operating temperature of 59-72°C, and a bottom operating temperature of 68-85°C. The top operating pressure of the third distillation tower (T330) is 162-282 kPa, the top operating temperature is 77-93 °C, and the bottom operating temperature is 85-110 °C; The top operating pressure of the fourth distillation tower (T340) is 490~910kPa, the top operating temperature is 111~133℃, the bottom operating temperature of L340 on the methanol distillation side is 152~176℃; the bottom operating temperature of R340 on the ethanol distillation side is 116~150℃.

10. A device for a multiple-effect methanol distillation process, characterized in that: It mainly includes five towers, namely, the light component removal tower (T300), the first distillation tower (T310), the second distillation tower (T320), the third distillation tower (T330), the fourth distillation tower (T340) and connecting pipelines; The raw material crude methanol feed pipeline is connected to the cold side inlet of the feed methanol preheater (E3403) and the feed wastewater preheater (E3404) respectively; The cold side outlets of the feed methanol preheater (E3403) and the feed wastewater preheater (E3404) are connected to the middle of the light component removal tower (T300); the top of the light component removal tower (T300) is connected to the shell side of the third distillation tower reboiler (E3301), the shell side condensate outlet of the third distillation tower reboiler (E3301) is connected to the top of the light component removal tower (T300), and the shell side non-condensable gas outlet of the third distillation tower reboiler (E3301) is connected to the non-condensable gas discharge pipeline; the bottom of the light component removal tower (T300) is respectively connected to the tube side inlet of the light component removal tower reboiler (E3001) and the first distillation tower (T310), and the tube side outlet of the light component removal tower reboiler (E3001) is connected to the bottom of the light component removal tower (T300); The top of the first distillation tower (T310) is connected to the first distillation tower condenser (E3102), and the condensate outlet of the first distillation tower condenser (E3102) is respectively connected to the top of the first distillation tower (T310) and the hot side inlet of the feed methanol preheater (E3403); the bottom of the first distillation tower (T310) is respectively connected to the tube side inlet of the first distillation tower reboiler (E3101) and the second distillation tower (T320), and the tube side outlet of the first distillation tower reboiler (E3101) is connected to the kettle of the first distillation tower (T310); The top of the second distillation tower (T320) is connected to the shell side of the reboiler (E3101) of the first distillation tower, and the shell side condensate outlet of the reboiler (E3101) of the first distillation tower is respectively connected to the top of the second distillation tower (T320) and the hot side inlet of the feed methanol preheater (E3403); the bottom of the second distillation tower (T320) is respectively connected to the tube side inlet of the reboiler (E3201) of the second distillation tower and the third distillation tower (T330), and the tube side outlet of the reboiler (E3201) of the second distillation tower is connected to the kettle of the second distillation tower (T320); The top of the third distillation tower (T330) is connected to the shell side of the reboiler (E3201) of the second distillation tower, and the shell side condensate outlet of the reboiler (E3201) of the second distillation tower is respectively connected to the top of the third distillation tower (T330) and the hot side inlet of the feed methanol preheater (E3403); the bottom of the third distillation tower (T330) is respectively connected to the tube side inlet of the reboiler (E3301) of the third distillation tower and the fourth distillation tower (T340); The top of the fourth distillation tower (T340) is connected to the shell side of the reboiler (E3301) of the third distillation tower, and the shell side condensate outlet of the reboiler (E3301) of the third distillation tower is respectively connected to the top of the fourth distillation tower (T340) and the hot side inlet of the feed methanol preheater (E3403); the bottom of the methanol stripping side (L340) of the fourth distillation tower (T340) is respectively connected to the pipe side inlet of the reboiler (E3401) on the methanol stripping side of the fourth distillation tower and the hot side inlet of the feed wastewater preheater (E3404), and the pipe side outlet of the reboiler (E3401) on the methanol stripping side of the fourth distillation tower is connected to the fourth distillation tower. The bottom of the methanol distillation side (L340) of the tower (T340); the side line extraction pipeline near the feed of the methanol distillation side (L340) of the fourth distillation tower (T340) is connected to the hot side inlet of the fusel oil cooler (E3407); the bottom of the ethanol distillation side (R340) of the fourth distillation tower (T340) is respectively connected to the tube side inlet of the reboiler (E3402) of the ethanol distillation side of the fourth distillation tower and the hot side inlet of the ethanol cooler (E3408), and the tube side outlet of the reboiler (E3402) of the ethanol distillation side of the fourth distillation tower is connected to the bottom of the ethanol distillation side (R340) of the fourth distillation tower (T340); The hot side outlet of the feed methanol preheater (E3403) is connected to the hot side inlet of the methanol product cooler (E3405), and the hot side outlet of the methanol product cooler (E3405) is connected to the methanol product extraction pipeline; The hot side outlet of the feed wastewater preheater (E3404) is connected to the hot side inlet of the wastewater cooler (E3406), and the hot side outlet of the wastewater cooler (E3406) is respectively connected to the top of the light component removal tower (T300) and the wastewater discharge pipeline; the hot side outlet of the fusel oil cooler (E3407) is connected to the fusel oil product production pipeline; the hot side outlet of the ethanol cooler (E3408) is connected to the ethanol product production pipeline.

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