CN215906119U

CN215906119U - Multi-effect methanol rectification process method device for avoiding ethanol accumulation

Info

Publication number: CN215906119U
Application number: CN202121341004.8U
Authority: CN
Inventors: 蓝仁水; 黄贵明; 董顺利; 汤伟
Original assignee: New Tianjin T & D Co ltd
Current assignee: New Tianjin T & D Co ltd
Priority date: 2021-06-16
Filing date: 2021-06-16
Publication date: 2022-02-25
Anticipated expiration: 2031-06-16

Abstract

The utility model provides a device for a multi-effect methanol rectification process method for avoiding ethanol accumulation, which can effectively avoid impurity components such as ethanol and the like with the boiling point close to that of methanol from entering a subsequent methanol rectification tower, reduce the separation difficulty of the subsequent methanol rectification tower in the multi-effect rectification process and greatly reduce the operation energy consumption. The whole device at least comprises five towers such as a light component removal tower (T210), a first rectifying tower (T220), a second rectifying tower (T230), a third rectifying tower (T240), a last tower (T250) and the like and matched equipment thereof. Can be used for various methanol solvent recovery and rectification processes of methanol synthesis devices to produce national standard high-grade methanol, American standard AA grade methanol products or methanol products with other specifications. Overcomes the defects of the prior art, has remarkable practicability and economic benefit and has wide application prospect.

Description

Multi-effect methanol rectification process method device for avoiding ethanol accumulation

Technical Field

The device of the multi-effect methanol rectification process method for avoiding ethanol accumulation provided by the utility model can be used for various methanol solvent recovery and rectification processes of a methanol synthesis device to produce superior methanol products.

Background

Methanol is an important organic chemical raw material and a novel energy fuel, and has wide application in the fields of chemical industry, light industry and clean energy. In the industrial production process of the synthetic methanol, the energy consumption of the refining process of the crude methanol is one of the key factors influencing the production cost of the methanol. With the increasing shortage of energy resources such as petroleum, coal, natural gas and the like, and the increasing severity of problems such as environmental pollution, greenhouse effect and the like, energy conservation and consumption reduction in industries such as methanol and the like become the key points for the survival of enterprises and the improvement of competitiveness, and are more and more paid attention from various aspects.

FIG. 1 shows a four-tower (three towers plus one tower) methanol rectification process widely used at present, namely, a pre-tower T101, a pressurized tower T102, a first rectification tower T103 and other three towers are adopted, and a recovery tower T104 is added to produce national standard superior products or American standard AA grade methanol products. Removing light components from the top of the pre-tower, rectifying the prognostic crude methanol 10 by a pressurizing tower and a first rectifying tower, respectively obtaining methanol products from a top discharge 24 of the pressurizing tower and a top discharge 14 of the first rectifying tower, and extracting fusel 42 from a side line of the first rectifying tower. The gas phase 21 of the material at the top of the pressurized tower heats the tower kettle of the first rectifying tower. Fusel 42 on the side line of the first rectifying tower and the first rectifying tower bottom liquid 15 enter a recovery tower, a recovered methanol product 29 is obtained from the top of the recovery tower, fusel oil 30 is extracted from the side line of the recovery tower, and wastewater 33 is discharged from the bottom of the recovery tower. Although the technology is mature, the production energy consumption is high, and the equipment scale is huge along with the increasing scale of the device. Is unfavorable for the construction, economy and stable operation of the increasingly large-scale methanol production device.

Chinese patent CN 201420664698.2 discloses a process method of a flexible methanol rectification device capable of producing both MTO-grade and AA-grade methanol, and the core content of the process method is to utilize the heat of condensate of heating steam or the heat exchange of cold and hot liquid in the system to achieve the purpose of energy conservation on the basis of the currently widely adopted four-tower double-effect rectification process. Obviously, the sensible heat transfer between the materials has a very limited effect on reducing the operation energy consumption of the whole rectification system.

CN 201910655239.5 discloses "a refined technology method of crude methanol of improved three-tower triple effect", its characterized in that: the operating pressure of the first rectifying tower and the second rectifying tower is improved, so that the first rectifying tower and the second rectifying tower perform triple-effect heat integration operation. And (3) separating the gas phase at the top of the second rectifying tower to provide heat for the pre-rectifying tower. Compared with CN 201420664698.2, the process method has higher energy-saving effect. However, because the top of the pre-rectifying tower in the system does not produce methanol products, the energy provided by the second rectifying tower for the pre-rectifying tower belongs to a single-effect methanol rectifying process. In the system, methanol products are produced at the tops of the first rectifying tower and the second rectifying tower, and the energy provided by the first rectifying tower for the second rectifying tower only belongs to a double-effect methanol rectifying process, so that the process method has a certain improved energy-saving effect, but the energy-saving effect is not ideal.

CN 201711022448.3 discloses a methanol triple-effect rectification system and a process thereof, and CN 201811025624.3 discloses a vacuum thermal coupling methanol rectification method and a device thereof, which adopt triple-effect heat integration operation on a rectification tower for producing methanol products in the system, wherein the effect with the lowest operation pressure is a vacuum rectification tower. Although the vacuum distillation tower is beneficial to improving the relative volatility of the separation system and obtaining higher purity of the methanol product. However, because the boiling point of methanol is low, the temperature at the top of the tower is very low due to the pressure reduction operation, the heat exchange temperature difference of the condenser at the top of the tower is obviously reduced, the area of the condenser is large, and the loss of the methanol is possibly increased due to a vacuum system. It is known that such a decompression operation necessarily leads to a considerable increase in the size of the corresponding column. For the current increasingly large-scale methanol device, the process can cause the scale of a tower and heat exchange equipment to be very large. Meanwhile, the pre-rectifying towers of the two patent processes are heated by adopting fresh steam, and are not in heat integration operation with the methanol rectifying tower, so that the energy-saving effect is limited to a certain extent.

CN200910068170.2 adopts a process method of rectifying methanol by five tower heat integration devices, crude methanol at the tower bottom of a light component removal tower firstly enters an atmospheric pressure rectifying tower, tower bottom materials of the atmospheric pressure rectifying tower enter a low pressure rectifying tower, tower bottom materials of the low pressure rectifying tower enter a high pressure rectifying tower, methanol products are respectively extracted from the tops of the atmospheric pressure rectifying tower, the low pressure rectifying tower and the high pressure rectifying tower, and tower bottom materials of the high pressure rectifying tower enter a recovery tower; triple-effect heat integration is carried out among the atmospheric distillation tower, the low-pressure distillation tower and the high-pressure distillation tower; double-effect heat integration is carried out between the light component removal tower and the recovery tower. The technological method for rectifying the methanol by adopting five tower heat integration devices provided by CN200910068170.2 can obviously reduce the operation energy consumption, but has certain defects that ethanol and other fusel oil in the crude methanol after light components are removed all sequentially pass through an atmospheric pressure rectifying tower, a low-pressure rectifying tower and a high-pressure rectifying tower; and along with the extraction of methanol products at the tops of the atmospheric distillation tower and the low-pressure distillation tower, the concentrations of ethanol and other fusel oil in the low-pressure distillation tower and the high-pressure distillation tower are sequentially increased, so that the methanol distillation difficulty of the low-pressure distillation tower and the high-pressure distillation tower is gradually increased, and the operation energy consumption of the low-pressure distillation tower and the high-pressure distillation tower is higher.

Disclosure of Invention

The utility model relates to a device for a multi-effect methanol rectification process method for avoiding ethanol accumulation, which can effectively avoid impurity components such as ethanol and the like with the boiling point close to that of methanol from entering a subsequent methanol rectification tower, reduce the separation difficulty of the subsequent methanol rectification tower in the multi-effect rectification process and greatly reduce the operation energy consumption. Can be used for various methanol solvent recovery and rectification processes of methanol synthesis devices to produce national standard high-grade methanol, American standard AA grade methanol products or methanol products with other specifications.

The utility model provides a device for a multi-effect methanol rectification process method for avoiding ethanol accumulation, which mainly comprises the following steps:

1) at least comprises five towers, such as a lightness-removing tower T210, a first rectifying tower T220, a second rectifying tower T230, a third rectifying tower T240, a last tower T250 and the like.

2) The liquid phase in the bottom of the light component removal tower T210 enters a first rectifying tower T220 and a second rectifying tower T230 respectively.

3) The first rectifying tower T220 feeds the liquid phase which is extracted from the upper side of the material and enters a second rectifying tower T230, and the second rectifying tower T230 feeds the liquid phase which is extracted from the upper side of the material and enters a third rectifying tower T240.

4) The liquid phases at the bottoms of the first rectifying tower T220, the second rectifying tower T230 and the third rectifying tower T240 all enter a last tower T250;

5) three-effect heat integration is adopted among the five towers, and the gas phases at the tops of the first rectifying tower T220 and the last rectifying tower T250 are respectively used as heating heat sources of the tower kettle of the second rectifying tower T230 to provide required heat for the second rectifying tower T230; the gas phase at the top of the second rectifying tower T230 is divided into two parts which are respectively used as heating heat sources of the light component removal tower T210 and the third rectifying tower T240 to provide required heat for the light component removal tower T210 and the third rectifying tower T240.

6) And respectively extracting refined methanol products from the tops of four tower columns, namely a first rectifying tower T220, a second rectifying tower T230, a third rectifying tower T240, a last tower T250 and the like.

By adopting the multi-effect methanol rectification process method for avoiding ethanol accumulation, materials are extracted from the side line of the upper part of the feeding of the first rectification tower and enter the second rectification tower, and dilute methanol containing ethanol/water and fusel oil is discharged from the tower bottom of the first rectification tower; the material extracted from the side line at the feeding upper part of the second rectifying tower enters a third rectifying tower, and the diluted methanol containing ethanol/water and fusel oil is discharged from the tower kettle of the second rectifying tower; the tower bottom of the third rectifying tower also discharges dilute methanol containing ethanol/water and fusel oil; the impurity components such as ethanol and the like with the boiling point close to that of the methanol are effectively prevented from entering the second rectifying tower and the third rectifying tower, the separation difficulty of the second rectifying tower and the third rectifying tower is reduced, and the operation energy consumption can be greatly reduced.

The multi-effect methanol rectification process method for avoiding ethanol accumulation provided by the utility model overcomes the defects of the prior art, has remarkable practicability and economic benefits, and has a wide application prospect.

The process method provided by the utility model comprises the following steps:

the crude methanol raw material 1 is divided into two streams, and a raw material 4 of one stream of raw material 2 preheated by a feed wastewater preheater E2504 is mixed with a raw material 5 of the other stream of raw material 3 preheated by a feed methanol preheater E2503 to form a preheated raw material 6 which enters a lightness-removing tower T210.

Condensing the gas phase 7 at the top of the light component removal tower T210 by a light component removal tower condenser E2102 to obtain a condensate, directly returning the condensate to the top of the light component removal tower T210 as a light component removal tower reflux liquid 9, and discharging a non-condensable gas 8; the bottom material 10 of the light component removal tower T210 is divided into two parts, one part 11 enters a first rectifying tower T220, and the other part 12 enters a second rectifying tower T230.

The first rectifying tower T220 and the second rectifying tower T230 are operated in a heat integration mode, a gas phase 13 at the top of the first rectifying tower T220 enters a shell pass of a reboiler A E2301A of the second rectifying tower, condensed condensate 14 is divided into two strands, one strand is used as a reflux liquid 15 of the first rectifying tower and directly returns to the top of the first rectifying tower T220, and the other strand of condensate 16 is used as a rectified methanol product and is extracted; feeding the material 17 extracted from the upper side of the first rectifying tower T220 into a second rectifying tower T230; the bottom material 18 of the first rectifying tower T220 enters a methanol stripping side L250 of a last tower T250.

The second rectifying tower T230, a lightness-removing tower T210 and a third rectifying tower T240 are subjected to heat integration operation, a gas phase 19 at the top of the second rectifying tower T230 is divided into two streams, one stream 20 enters a lightness-removing tower reboiler E2101 shell pass, the other stream 21 enters a third rectifying tower reboiler E2401 shell pass, condensed condensate 22 and condensed condensate 23 are mixed and then divided into two streams, one stream is used as a second rectifying tower reflux 24 and directly returned to the top of the second rectifying tower T230, and the other stream 25 is used as a rectified methanol product and is extracted; the second rectifying tower T230 feeds the material 26 extracted from the upper side line into a third rectifying tower T240; the bottom material 27 of the second rectifying tower T230 enters a methanol stripping side L250 of a last tower T250.

The condensate 29 of the gas phase 28 at the top of the third rectifying tower T240 condensed by the third rectifying tower condenser E2402 is divided into two parts, one part is taken as the reflux liquid 30 of the third rectifying tower and directly returned to the top of the third rectifying tower T240, and the other part is taken as the rectified methanol product and extracted; the bottom material 32 of the third rectifying tower T240 enters a methanol stripping side L250 of a last tower T250.

The mixed material 33 of the first rectifying tower T220 tower bottom material 18, the second rectifying tower T230 tower bottom material 27 and the third rectifying tower T240 tower bottom material 32 enters a last tower T250 methanol stripping side L250.

The last tower T250 and the second rectifying tower T230 are operated in a heat integration mode, a gas phase 34 at the top of the last tower T250 enters a shell pass of a reboiler B E2301B of the second rectifying tower, condensed condensate 35 is divided into two parts, one part is used as reflux liquid 36 of the last tower and directly returned to the top of the last tower T250, and the other part of condensate 37 is used as a refined methanol product and is extracted; side lines of the last tower T250 near a feed inlet of a methanol stripping side L250 are used for extracting fusel oil 41 with low methanol and ethanol contents; taking the material 43 at the bottom of the L250 tower at the methanol stripping side of the last tower T250 as wastewater for extraction; and taking the material 48 at the bottom of the R250 tower at the ethanol rectification side of the last tower T250 as a recovered ethanol product.

And (3) cooling a refined methanol product 38 obtained by mixing a product 16 at the top of the first rectifying tower T220, a product 25 at the top of the second rectifying tower T230, a product 31 at the top of the third rectifying tower T240 and a product 37 at the top of the last rectifying tower T250 by using a feeding methanol preheater E2503, cooling a cooled material 39 by using a methanol product cooler E2505 to obtain a refined methanol product 40, and sending the refined methanol product 40 out of the device.

Waste water 43 extracted from the bottom of the last tower T250 methanol stripping side L250 is firstly cooled by a feed waste water preheater E2504, cooled material 44 is then cooled by a waste water cooler E2506 to obtain waste water 45 which is divided into two parts, one part is taken as waste water 46 and sent out of the device, and the other part is taken as extract water 47 and returned to the top of the light component removal tower T210.

Fusel oil 41 which is extracted from a side line L250 of a methanol stripping side of the last tower T250 is cooled by a fusel oil cooler E2507 to obtain a fusel oil product 42 which is sent out of the device.

And (3) cooling the recovered ethanol 48 extracted from the bottom of the R250 tower at the ethanol rectification side of the last tower T250 by an ethanol cooler E2508 to obtain a recovered ethanol product 49, and sending the recovered ethanol product out of the device.

According to the process method provided by the utility model, a fourth rectifying tower T260 is added on the basis of the five towers to form a six-tower double-triple-effect methanol rectifying device, triple-effect heat integration is adopted among the first rectifying tower T220, the second rectifying tower T230 and the third rectifying tower T240, and triple-effect heat integration is adopted among the light component removal tower T210, the fourth rectifying tower T260 and the last rectifying tower T250.

According to the process method provided by the utility model, a fifth rectifying tower T270 is added on the basis of the six towers to form a seven-tower four-effect and three-effect methanol rectifying device, four-effect heat integration is adopted among the first rectifying tower T220, the second rectifying tower T230, the third rectifying tower T240 and the fifth rectifying tower T270, and three-effect heat integration is adopted among the light component removal tower T210, the fourth rectifying tower T260 and the last tower T250.

According to the process method provided by the utility model, the lower part of the last tower T250 adopts a partition plate tower structure, and the partition plate S250 divides the lower part of the last tower T250 into a methanol stripping side L250 and an ethanol rectification side R250; discharging wastewater 43 from the last tower T250 methanol stripping side L250 tower kettle; withdrawing fusel oil 41 with low methanol and ethanol contents from the side line below a feed inlet of a methanol stripping side L250 of the last tower T250; and (3) recovering an ethanol product 49 from the bottom of the R250 tower at the ethanol rectification side of the last tower T250.

The process provided by the utility model can also be transformed into other heat integration processes for producing methanol:

the first deformation process method comprises the following steps: in the five towers, the tail tower T250 does not adopt a partition plate structure, but adopts a conventional structure, ethanol 48 is extracted and recovered from a position above a feed inlet of the tail tower T250, fusel oil 41 is extracted from a position below the feed inlet, and a tower bottom material 43 of the tail tower T250 is extracted as wastewater.

And a second deformation process method comprises the following steps: a stripping tower T250S is added on the basis of the five towers, and the last tower T250 adopts a conventional structure instead of a partition plate structure; the side-stream liquid material 63 of the last tower T250 enters the top of a stripping tower T250S, the gas material 64 at the top of the stripping tower T250S returns to the last tower T250, and ethanol 48 is recovered from the bottom of a stripping tower T250S.

And a deformation process method III: a recovery tower T280 is added on the basis of the five towers, and the tail tower T250 adopts a conventional structure instead of a partition plate structure; the recovery tower T280 may use the gas phase at the top of the first rectifying tower T220, the second rectifying tower T230 or the last rectifying tower T250 as a heat source, or use other heat sources in the system, or use an external heat source.

And a deformation process method comprises the following steps: on the basis of the five towers, one first rectifying tower T220 is reduced to be a four-tower triple-effect heat integration operation, and the gas phase at the top of the last tower T250 is used as a heating heat source of the tower kettle of the second rectifying tower T230 to provide required heat for the second rectifying tower T230; the gas phase at the top of the second rectifying tower T230 is used as a heating heat source for the bottoms of the light component removal tower T210 and the third rectifying tower T240, and provides required heat for the light component removal tower T210 and the third rectifying tower T240.

According to the process method provided by the utility model, the adopted energy-saving method is selected as follows:

1) the crude methanol raw material can exchange heat with wastewater discharged from a bottom tower L250 on the methanol stripping side of the last tower T250, the crude methanol raw material can also exchange heat with a refined methanol product, and the crude methanol raw material can also exchange heat with a gas phase at the top of a third rectifying tower T240 or a light component removal tower T210;

2) and feeding materials of the first rectifying tower T220, the second rectifying tower T230, the third rectifying tower T240, the fourth rectifying tower T260, the fifth rectifying tower T270, the last tower T250 or the light component removal tower T210 and the like exchange heat with heating steam condensate.

Typical embodiments of such heat exchange between the vapor condensate and the column feeds are:

1) the steam condensate exchanges heat with the feeding materials of the first rectifying tower T220 and the last rectifying tower T250, and preheats the feeding materials of the first rectifying tower T220 and the last rectifying tower T250;

2) and the steam condensate after the heat exchange of the feeding materials of the first rectifying tower T220 and the last rectifying tower T250 exchanges heat with the feeding material of the lightness-removing tower T210, and preheats the feeding material of the lightness-removing tower T210.

The steam condensate can be used for preheating the feeding of the light component removal tower, or feeding the feeding of the first rectifying tower, or feeding the feeding of the second rectifying tower, or feeding the feeding of the third rectifying tower, or feeding the feeding of the last rectifying tower, the steam condensate can be used for preheating any tower in the system or the permutation and combination thereof, the heat exchange mode is only the supplement of the energy-saving process method for rectifying the methanol of the multi-effect heat integration device for avoiding the accumulation of the ethanol, which is provided by the utility model, but not any limitation on the spirit of the utility model, and the technical personnel in the related field can completely carry out the permutation and combination of the heat exchange processes according to the common general knowledge, and various evolution process flows formed by the method can be considered to be in the spirit, the scope and the content of the utility model.

According to the process method provided by the utility model, an absorption tower T290 is additionally arranged, and the tail gas of the light component removal tower T210 is absorbed by the washing water in the absorption tower T290 and then discharged out of the device, so that the methanol in the tail gas is recovered, the yield of the methanol product is improved, and the content of pollutants in the discharged non-condensable gas is reduced. The absorption tower T290 is added as a general method, and any method or a modification method thereof provided by the utility model can adopt the general method to improve the yield of the methanol product and reduce the content of pollutants in the discharged non-condensable gas. When the general method is adopted, a part of extraction water can enter the top of the lightness-removing column T210 by 47; the other part 72 enters the top of the absorption tower T290; the extraction water can also be totally fed into the top of the absorption tower T290.

According to the process method provided by the utility model, the overhead product 16 of the first rectifying tower T220, the overhead product 25 of the second rectifying tower T230, the overhead product 31 of the third rectifying tower T240 and the overhead product 37 of the last rectifying tower T250 can be extracted from the upper side line of each tower.

According to the process method provided by the utility model, the heat sources used by the first rectifying tower reboiler E2201, the last methanol stripping side reboiler E2501 and the last ethanol rectifying side reboiler E2502 can be fresh steam, heat conduction oil or material steam generated in the system.

According to the process method provided by the utility model, the condenser E2102 of the light component removal tower, the condenser E2402 of the third rectifying tower, the methanol product cooler E2505, the wastewater cooler E2506, the fusel oil cooler E2507 and the ethanol cooler E2508 can be air coolers or water coolers; the cooling medium can be circulating water, low-temperature water, chilled water, or other cooling media such as low-temperature materials in the system.

According to the process method provided by the utility model, the discharged material at the bottom of the light component removal tower T210 firstly enters a first rectifying tower T220, or firstly enters a second rectifying tower T230, or firstly enters a third rectifying tower T240, or firstly enters a fourth rectifying tower T260; or respectively enter a first rectifying tower T220 and a second rectifying tower T230; or respectively enters a first rectifying tower T220 and a fourth rectifying tower T260; or respectively enter a first rectifying tower T220, a second rectifying tower T230 and a third rectifying tower T240; or respectively enter a first rectifying tower T220, a second rectifying tower T230, a third rectifying tower T240 and a fourth rectifying tower T260.

According to the attached figure 2, the typical multi-effect methanol rectification process method for avoiding ethanol accumulation provided by the utility model has the advantages that the heat integration mode among the first rectification tower T220, the second rectification tower T230 and the third rectification tower T240 can also be that the tower top gas phase of the third rectification tower T240 heats the reboiler at the tower bottom of the second rectification tower T230; the gas phase at the top of the second rectifying tower T230 heats a reboiler at the bottom of the first rectifying tower T220.

The technological method and the device for rectifying the methanol by adopting the multi-effect methanol rectifying technological method (five-tower triple-effect heat integration, six-tower double triple-effect heat integration, six-tower four-effect and triple-effect heat integration, seven-tower four-effect and triple-effect heat integration, five-tower four-effect heat integration, four-tower four-effect heat integration or four-tower triple-effect heat integration) device for avoiding the accumulation of the ethanol can be used for producing national standard high-quality methanol, American standard AA grade methanol products or methanol products with other specifications.

According to the process provided by the utility model, the typical operating conditions of each tower are as follows:

the operation pressure range of the top of the light component removal tower T210 is 30-200 kPa.

The operation pressure range of the top of the first rectifying tower T220 is 300-1500 kPa.

The operation pressure range of the top of the second rectifying tower T230 is 110-950 kPa.

The operation pressure range of the top of the third rectifying tower T240 is 30-200 kPa.

The operation pressure range of the top of the last tower T250 is 300-1500 kPa.

The preferred operating conditions for each column are:

the operation pressure at the top of the light component removal tower T210 is 80-160 kpa, the operation temperature at the top of the tower is 50-85 ℃, and the operation temperature at the bottom of the tower is 55-90 ℃;

the operation pressure of the top of the first rectifying tower T220 is 350-960 kPa, the operation temperature of the top of the tower is 100-135 ℃, and the operation temperature of the bottom of the tower is 110-160 ℃;

the operation pressure of the top of the second rectifying tower T230 is 180-500 kPa, the operation temperature of the top of the tower is 80-110 ℃, and the operation temperature of the bottom of the tower is 89-125 ℃.

The operation pressure of the top of the third rectifying tower T240 is 80-180 kpa, the operation temperature of the top of the tower is 58-80 ℃, and the operation temperature of the bottom of the tower is 67-98 ℃.

The operation pressure of the top of the last tower T250 is 350-960 kPa, the operation temperature of the top of the tower is 100-135 ℃, and the operation temperature of the methanol stripping side L250 tower kettle is 140-175 ℃; the operation temperature of the R250 tower kettle at the ethanol rectification side is 110-150 ℃.

The device of the process method mainly comprises five towers of a light component removal tower T210, a first rectifying tower T220, a second rectifying tower T230, a third rectifying tower T240, a last tower T250 and connecting pipelines.

Raw material crude methanol feed lines are respectively connected with cold side inlets of a feed methanol preheater E2503 and a feed wastewater preheater E2504.

Cold side outlets of a feed methanol preheater E2503 and a feed wastewater preheater E2504 are connected to the middle upper part of the lightness-removing column T210; the top of the lightness-removing column T210 is connected with a lightness-removing column condenser E2102, a condensate outlet of the lightness-removing column condenser E2102 is connected with the top of the lightness-removing column T210, and a non-condensable gas outlet of the lightness-removing column condenser E2102 is connected with a non-condensable gas discharge pipeline; the bottom of the light component removal tower T210 is respectively connected with a tube pass inlet of a light component removal tower reboiler E2101, a first rectifying tower T220 and a second rectifying tower T230, and a tube pass outlet of the light component removal tower reboiler E2101 is connected to the tower kettle of the light component removal tower T210.

The top of the first rectifying tower T220 is connected with the shell pass of a second rectifying tower reboiler AE2301A, and the shell pass condensate outlet of the second rectifying tower reboiler AE2301A is respectively connected with the top of the first rectifying tower T220 and the hot side inlet of a feeding methanol preheater E2503; the side draw outlet of the first rectifying tower T220 is connected with a second rectifying tower T230; the bottom of the first rectifying tower T220 is respectively connected with a first rectifying tower reboiler E2201 tube pass inlet and a last tower T250, and a first rectifying tower reboiler E2201 tube pass outlet is connected to the tower kettle of the first rectifying tower T220.

The top of the second rectifying tower T230 is respectively connected with a light component removal reboiler E2101 shell pass and a third rectifying tower reboiler E2401 shell pass, and the light component removal reboiler E2101 shell pass and a third rectifying tower reboiler E2401 shell pass condensate outlet are respectively connected with the top of the second rectifying tower T230 and a hot side inlet of a feeding methanol preheater E2503; the side draw outlet of the second rectifying tower T230 is connected with a third rectifying tower T240; the bottom of the second rectifying tower T230 is respectively connected with a second rectifying tower reboiler AE2301A tube pass inlet, a second rectifying tower reboiler B E2301B tube pass inlet and a last tower T250, and a second rectifying tower reboiler AE2301A tube pass outlet and a second rectifying tower reboiler B E2301B tube pass outlet are connected to the tower kettle of the second rectifying tower T230.

The top of the third rectifying tower T240 is connected with a third rectifying tower condenser E2402, and a condensate outlet of the third rectifying tower condenser E2402 is respectively connected with the top of the third rectifying tower T240 and a hot side inlet of a feeding methanol preheater E2503; the bottom of the third rectifying tower T240 is respectively connected with a tube pass inlet of a third rectifying tower reboiler E2401 and a last tower T250, and a tube pass outlet of the third rectifying tower reboiler E2401 is connected to a tower kettle of the third rectifying tower T240.

The top of the last tower T250 is connected with a second rectifying tower reboiler B E2301B in shell pass, and a second rectifying tower reboiler B E2301B in shell pass condensate outlet is respectively connected with the top of the last tower T250 and a hot side inlet of a feed methanol preheater E2503; the bottom of the last tower T250 methanol stripping side L250 is respectively connected with a last tower methanol stripping side reboiler E2501 tube pass inlet and a hot side inlet of a feed wastewater preheater E2504, and a last tower methanol stripping side reboiler E2501 tube pass outlet is connected with a last tower T250 methanol stripping side L250 tower kettle; a side line extraction pipeline near the feed of the methanol stripping side L250 of the last tower T250 is connected with a hot side inlet of a fusel oil cooler E2507; the bottom of the last tower T250 ethanol rectification side R250 is respectively connected with the last tower ethanol rectification side reboiler E2502 tube pass inlet and the hot side inlet of the ethanol cooler E2508, and the last tower ethanol rectification side reboiler E2502 tube pass outlet is connected with the last tower T250 ethanol rectification side R250 tower kettle.

The hot side outlet of the feed methanol preheater E2503 is connected with the hot side inlet of the methanol product cooler E2505, and the hot side outlet of the methanol product cooler E2505 is connected with a methanol product extraction pipeline.

The hot side outlet of the feed wastewater preheater E2504 is connected with the hot side inlet of the wastewater cooler E2506, and the hot side outlet of the wastewater cooler E2506 is respectively connected with the top of the light component removal tower T210 and a wastewater discharge pipeline; the outlet of the hot side of the fusel oil cooler E2507 is connected with a fusel oil product extraction pipeline; the hot side outlet of the ethanol cooler E2508 is connected with an ethanol product extraction pipeline.

In order to highlight the multi-effect methanol rectification process method for avoiding ethanol accumulation, the utility model omits part of heat exchangers in the process. The technical method provided by the utility model can be implemented by persons skilled in the relevant technical field according to specific device conditions, and various evolved process flows formed by the method can be considered to be in the spirit, scope and content of the utility model. The heat exchanger in the flow diagram is merely schematic, and the specific structure thereof does not limit the utility model.

In a word, the utility model relates to a multi-effect methanol rectification process method for avoiding ethanol accumulation and various deformation process methods thereof, which can effectively avoid impurity components such as ethanol and the like with the boiling point close to that of methanol from entering a subsequent methanol rectification tower, reduce the separation difficulty of the subsequent methanol rectification tower in the multi-effect rectification process and greatly reduce the operation energy consumption. Can be used for various methanol solvent recovery and rectification processes of methanol synthesis devices to produce national standard high-grade methanol, American standard AA grade methanol products or methanol products with other specifications. Overcomes the defects of the prior art, has remarkable practicability and economic benefit and has wide application prospect.

Drawings

FIG. 1 is a flow diagram of a four-column (three columns plus one column) methanol rectification process used in the prior art.

FIG. 2 is a flow chart of a typical multi-effect methanol rectification process (five-tower three-effect heat integration device) for methanol rectification, which is provided by the utility model and can avoid ethanol accumulation.

Fig. 3 is an evolution process method of fig. 2, namely a first deformation process method, which is a process method provided in fig. 2, in which a fourth rectifying tower T260 is added to form a six-tower double triple-effect methanol rectifying device, triple-effect heat integration is adopted among the first rectifying tower T220, the second rectifying tower T230 and the third rectifying tower T240, and triple-effect heat integration is adopted among the light component removal tower T210, the fourth rectifying tower T260 and the last rectifying tower T250.

Fig. 4 is an evolution process method, namely a deformation process method two, of fig. 3, and with respect to the flow provided in fig. 3, a fifth rectifying tower T270 is added to form a seven-tower four-effect and three-effect methanol rectifying device, four-effect heat integration is adopted among the first rectifying tower T220, the second rectifying tower T230, the third rectifying tower T240 and the fifth rectifying tower T270, and three-effect heat integration is adopted among the light component removal tower T210, the fourth rectifying tower T260 and the last tower T250.

FIG. 5 is a modified process method of FIG. 2, namely modified process method III, and compared with the flow provided by FIG. 2, the last tower T250 does not adopt a partition structure, but adopts a conventional structure, ethanol 48 is recovered by extracting at a position above a feed inlet of the last tower T250, fusel oil 41 is extracted at a position below the feed inlet, and tower bottom material 43 of the last tower T250 is extracted as wastewater.

FIG. 6 is a modified process of FIG. 2, namely modified process four, with the addition of a stripping column T250S, the last column T250 not employing a baffle structure, but rather employing a conventional structure, as opposed to the flow scheme provided in FIG. 2; the side-stream liquid material 63 of the last tower T250 enters the top of a stripping tower T250S, the gas material 64 at the top of the stripping tower T250S returns to the last tower T250, and ethanol 48 is recovered from the bottom of a stripping tower T250S.

FIG. 7 is a modified process of FIG. 2, namely modified process five, wherein a recovery column T280 is added to the process flow provided in FIG. 2, and the final column T250 does not employ a partition structure but rather a conventional structure; the recovery tower T280 may use the gas phase at the top of the first rectifying tower T220, the second rectifying tower T230 or the last rectifying tower T250 as a heat source, or use other heat sources in the system, or use an external heat source.

Fig. 8 is a development process method, namely a deformation process method six, of fig. 2, which is to reduce one first rectification tower T220 to a four-tower triple-effect heat integration operation, and to use the gas phase at the top of the last tower T250 as a heating source for the bottom of the second rectification tower T230 to provide the required heat for the second rectification tower T230, compared with the flow provided in fig. 2; the gas phase at the top of the second rectifying tower T230 is used as a heating heat source for the bottoms of the light component removal tower T210 and the third rectifying tower T240, and provides required heat for the light component removal tower T210 and the third rectifying tower T240.

Fig. 9 is a development process method, namely a modification process method seven, of fig. 2, which is changed to a four-effect heat integration operation of five towers relative to the flow provided in fig. 2, and the gas phase at the top of the last tower T250 is used as a heating heat source for the bottom of the first rectifying tower T220 to provide the required heat for the first rectifying tower T220; the gas phase at the top of the first rectifying tower T220 is used as a heating heat source of the tower kettle of the second rectifying tower T230 to provide required heat for the second rectifying tower T230; the gas phase at the top of the second rectifying tower T230 is used as a heating heat source for the bottoms of the light component removal tower T210 and the third rectifying tower T240, and provides required heat for the light component removal tower T210 and the third rectifying tower T240.

Fig. 10 is an evolution process method, namely a deformation process method eight, of fig. 2, and with respect to the flow provided in fig. 2, a fifth rectification tower T270 is added to form a six-tower four-effect and three-effect methanol rectification device, and the gas phase at the top of the fifth rectification tower T270 serves as a tower bottom heating heat source of the first rectification tower T220 to provide the required heat for the first rectification tower T220; the gas phases at the tops of the first rectifying tower T220 and the last rectifying tower T250 are used as heating heat sources of the tower kettle of the second rectifying tower T230 to provide required heat for the second rectifying tower T230; the gas phase at the top of the second rectifying tower T230 is used as a heating heat source for the bottoms of the light component removal tower T210 and the third rectifying tower T240, and provides required heat for the light component removal tower T210 and the third rectifying tower T240.

Fig. 11 is a modified process method, namely modified process method nine, of fig. 2, which is to reduce one third rectifying tower T240 to four-effect heat integration operation, and to use the gas phase at the top of the last tower T250 as the tower bottom heating heat source of the first rectifying tower T220 to provide the required heat for the first rectifying tower T220, compared with the flow provided in fig. 2; the gas phase at the top of the first rectifying tower T220 is used as a heating heat source of the tower kettle of the second rectifying tower T230 to provide required heat for the second rectifying tower T230; the gas phase at the top of the second rectifying tower T230 is used as a heating heat source of the bottom of the light component removal tower T210 to provide the required heat for the light component removal tower T210.

Fig. 12 is a modified process method, namely a modified process method ten, of fig. 2, which is to add an absorption tower T290 in comparison with the flow provided in fig. 2, and the tail gas of the light component removal tower T210 is absorbed by the washing water in the absorption tower T290 and then discharged from the apparatus, so as to recover the methanol therein, improve the yield of the methanol product, and reduce the content of the pollutants in the discharged non-condensable gas.

As in the evolution process method provided in fig. 10, if the gas phase at the top of the last tower T250 is changed to be heated by the reboiler at the bottom of the fifth rectifying tower T270, the last tower T250, the fifth rectifying tower T270, the first rectifying tower T220, the second rectifying tower T230, and the third rectifying tower T240 form a five-effect heat integration operation; if the gas phases at the tops of the last tower T250 and the fifth rectifying tower T270 are respectively heated by the reboiler at the bottom of the first rectifying tower T220, the last tower T250, the fifth rectifying tower T270, the first rectifying tower T220, the second rectifying tower T230 and the third rectifying tower T240 form four-effect heat integration operation; if the gas phase at the top of the last tower T250 is directly heated by a reboiler at the bottom of the light component removal tower T210, the fifth rectifying tower T270, the first rectifying tower T220, the second rectifying tower T230 and the third rectifying tower T240 form four-effect heat integration operation, and the last tower T250 and the light component removal tower T210 form double-effect heat integration operation.

According to the process provided by the utility model and the modified process, persons skilled in the relevant technical field can implement appropriate heat exchange method of the system internal material flow according to specific device conditions, and various modified process flows formed by the method are considered to be in the spirit, scope and content of the utility model.

Detailed Description

The embodiments of the present invention will be described in detail below with reference to the accompanying drawings, which are illustrative only and not limiting of the utility model.

Unless otherwise specified, the composition, structure, materials (connecting lines for connecting the towers), reagents, and the like of the process equipment such as the towers, etc., which are not specifically used in the examples, can be obtained from commercial sources, or can be obtained by methods well known to those skilled in the art. The specific experimental procedures and operating conditions involved are generally in accordance with conventional process conditions and conditions as described in the manual or as recommended by the manufacturer.

Application example 1:

the crude methanol feedstock typically has the following composition:

the above ranges of the raw material composition do not constitute any limitation to the present invention, which is applicable to the rectification process of crude methanol raw material of various compositions.

As shown in fig. 2, the crude methanol raw material 1 is divided into two streams, and a raw material 4 obtained by preheating one stream of raw material 2 by a feed wastewater preheater E2504 is mixed with a raw material 5 obtained by preheating the other stream of raw material 3 by a feed methanol preheater E2503 to obtain a preheated raw material 6, and the preheated raw material 6 is introduced into the lightness-removing column T210.

Condensing liquid 9 of a gas phase 7 at the top of the light component removal tower T210 after being condensed by a light component removal tower condenser E2102 is directly returned to the top of the light component removal tower T210 as reflux liquid of the light component removal tower, and discharging non-condensable gas 8; the bottom material 10 of the light component removal tower T210 is divided into two parts, one part 11 enters a first rectifying tower T220, and the other part 12 enters a second rectifying tower T230.

The first rectifying tower T220 and the second rectifying tower T230 are operated in a heat integration mode, a gas phase 13 at the top of the first rectifying tower T220 enters a shell pass of a reboiler AE2301A of the second rectifying tower, condensed condensate 14 is divided into two strands, one strand is used as a reflux liquid 15 of the first rectifying tower and directly returned to the top of the first rectifying tower T220, and the other strand of condensate 16 is used as a rectified methanol product and is extracted; feeding the material 17 extracted from the upper side of the first rectifying tower T220 into a second rectifying tower T230; the bottom material 18 of the first rectifying tower T220 enters a methanol stripping side L250 of a last tower T250.

The heat sources used by the first rectifying tower reboiler E2201, the last methanol stripping side reboiler E2501 and the last ethanol rectifying side reboiler E2502 can be fresh steam, heat conducting oil or material steam generated in the system.

The condensate of the fresh steam added into the system can be used for feeding and preheating the materials for each tower respectively or successively.

The condenser E2102 of the light component removal tower, the condenser E2402 of the third rectifying tower, the methanol product cooler E2505, the wastewater cooler E2506, the fusel oil cooler E2507 and the ethanol cooler E2508 can be air coolers or water coolers; the cooling medium can be circulating water, low-temperature water, chilled water, or other cooling media such as low-temperature materials in the system.

Typical operating conditions for each column in example 1 are given below:

The operation pressure range of the top of the last tower T250 is 300-1500 kPa.

The preferred operating conditions and operating energy consumption for each column in example 1 are given below:

the operation pressure of the top of the light component removal tower T210 is 80-160 kpa, the operation temperature of the top of the tower is 50-85 ℃, and the operation temperature of the bottom of the tower is 55-90 ℃.

The operation pressure of the top of the first rectifying tower T220 is 350-960 kPa, the operation temperature of the top of the tower is 100-135 ℃, and the operation temperature of the bottom of the tower is 110-160 ℃.

In the whole methanol rectifying device, only the first rectifying tower reboiler E2201, the last methanol stripping side reboiler E2501 and the last ethanol rectifying side reboiler E2502 need external heating heat sources, and the rest reboilers, preheaters and other heat sources can be heated by using the internal heat sources and steam condensate of the system.

The external heating source is considered according to the medium-pressure steam, 200 ten thousand tons of American standard AA grade refined methanol products are produced annually on the scale of the device (the operation hours are 8000 hours/year), and according to the four-tower methanol rectification process widely adopted at present, the steam consumption in the methanol rectification process is about 1.4 tons of steam/ton of refined methanol products; the technological method for rectifying the methanol by adopting five tower heat integration devices provided by CN200910068170.2 has the advantages that the steam consumption in the methanol rectification process is about 0.78 ton of steam per ton of refined methanol product; by adopting the multi-effect methanol rectification process method for avoiding ethanol accumulation, provided by the utility model, the steam consumption of the device is lower than 0.65 ton of steam per ton of refined methanol product.

Compared with the four-tower methanol rectification process widely adopted at present, the multi-effect methanol rectification process method for avoiding ethanol accumulation provided by the utility model has the advantages that the energy-saving ratio is as follows:

(1.4-0.65)/1.4×100％≈53.5％

steam can be saved about each year:

(1.4-0.65) ton/ton x 200 ten thousand tons/year-150 ten thousand tons/year.

The steam cost can be saved by 150 yuan per ton of steam each year:

150 ten thousand tons/year × 150 yuan/ton is 22500 ten thousand yuan/year.

Compared with the five-tower heat integration device provided by CN200910068170.2, the multi-effect methanol rectification process method for avoiding ethanol accumulation provided by the utility model has the advantages that the energy-saving ratio is as follows:

(0.78-0.65)/0.78×100％≈16.6％

steam can be saved about each year:

(0.78-0.65) ton/ton x 200 ten thousand ton/year-26 ten thousand ton/year.

The steam cost can be saved by 150 yuan per ton of steam each year:

26 ten thousand tons/year × 150 yuan/ton is 3900 ten thousand yuan/year.

The multi-effect methanol rectification process method capable of avoiding ethanol accumulation provided by the utility model can effectively avoid impurity components such as ethanol and the like with boiling points close to that of methanol from entering a subsequent methanol rectification tower, reduces the separation difficulty of the subsequent methanol rectification tower in the multi-effect rectification process, and can greatly reduce the operation energy consumption. Can be used for various methanol solvent recovery and rectification processes of methanol synthesis devices to produce national standard high-grade methanol, American standard AA grade methanol products or methanol products with other specifications. Overcomes the defects of the prior art, has remarkable practicability and economic benefit and has wide application prospect.

Application example 2:

as shown in fig. 3, which is an evolution process of fig. 2, compared with the flow provided by fig. 2, a fourth rectification column T260 is added to form a six-column and double-triple-effect methanol rectification device, triple-effect heat integration is adopted among the first rectification column T220, the second rectification column T230 and the third rectification column T240, and triple-effect heat integration is adopted among the light component removal column T210, the fourth rectification column T260 and the last column T250.

Application example 3:

as shown in fig. 4, which is an evolution process of fig. 3, with respect to the flow provided in fig. 3, a fifth rectification column T270 is added to form a seven-column, four-effect and three-effect methanol rectification apparatus, four-effect heat integration is adopted among the fifth rectification column T270, the first rectification column T220, the second rectification column T230, and the third rectification column T240, and three-effect heat integration is adopted among the light component removal column T210, the fourth rectification column T260, and the last column T250.

Application example 4:

as shown in FIG. 5, which is an evolution process of FIG. 2, compared with the flow provided by FIG. 2, the last tower T250 does not adopt a partition structure, but adopts a conventional structure, ethanol 48 is recovered from a position near a feed inlet of the last tower T250, fusel oil 41 is recovered from a position below the feed inlet, and a material 43 in the bottom of the last tower T250 is recovered as wastewater.

Application example 5:

as shown in fig. 6, which is an evolution process of fig. 2, a stripping column T250S is added to the process scheme provided in fig. 2, and the last column T250 does not adopt a partition structure but adopts a conventional structure; the side-stream liquid material 63 of the last tower T250 enters the top of a stripping tower T250S, the gas material 64 at the top of the stripping tower T250S returns to the last tower T250, and ethanol 48 is recovered from the bottom of a stripping tower T250S.

Application example 6:

FIG. 7 shows an evolution of the process of FIG. 2, with the addition of a recovery column T280, with respect to the scheme provided in FIG. 2, and with the final column T250 not being of the baffle structure, but of the conventional structure; the recovery tower T280 may use the gas phase at the top of the first rectifying tower T220, the second rectifying tower T230 or the last rectifying tower T250 as a heat source, or use other heat sources in the system, or use an external heat source.

Application example 7:

as shown in fig. 8, which is an evolution process of fig. 2, compared with the flow provided by fig. 2, one first rectification column T220 is reduced to be a four-column triple-effect heat integration operation, and the gas phase at the top of the last column T250 is used as a heating heat source for the bottom of the second rectification column T230 to provide the required heat for the second rectification column T230; the gas phase at the top of the second rectifying tower T230 is divided into two parts which are respectively used as heating heat sources of the light component removal tower T210 and the third rectifying tower T240 to provide required heat for the light component removal tower T210 and the third rectifying tower T240.

Application example 8:

as shown in fig. 9, which is an evolution process of fig. 2, the process is changed to a four-effect heat integration operation of five towers with respect to the flow provided in fig. 2, and the gas phase at the top of the last tower T250 is used as a heating source for the bottom of the first rectification tower T220 to provide the required heat for the first rectification tower T220; the gas phase at the top of the first rectifying tower T220 is used as a heating heat source of the tower kettle of the second rectifying tower T230 to provide required heat for the second rectifying tower T230; the gas phase at the top of the second rectifying tower T230 is divided into two parts which are respectively used as heating heat sources of the light component removal tower T210 and the third rectifying tower T240 to provide required heat for the light component removal tower T210 and the third rectifying tower T240.

Application example 9:

as shown in fig. 10, which is an evolution process of fig. 2, in comparison with the process provided in fig. 2, a fifth rectification column T270 is added to form a six-column, four-effect and three-effect methanol rectification device, and the gas phase at the top of the fifth rectification column T270 is used as a heating source for the bottom of the first rectification column T220 to provide the required heat for the first rectification column T220; the gas phases at the tops of the first rectifying tower T220 and the last rectifying tower T250 are used as heating heat sources of the tower kettle of the second rectifying tower T230 to provide required heat for the second rectifying tower T230; the gas phase at the top of the second rectifying tower T230 is divided into two parts which are respectively used as heating heat sources of the light component removal tower T210 and the third rectifying tower T240 to provide required heat for the light component removal tower T210 and the third rectifying tower T240.

Application example 10:

as shown in fig. 11, which is an evolution process of fig. 2, compared with the flow provided in fig. 2, one third rectifying tower T240 is reduced to be a four-tower and four-effect heat integration operation, and the gas phase at the top of the last tower T250 is used as a heating source for the bottom of the first rectifying tower T220 to provide the required heat for the first rectifying tower T220; the gas phase at the top of the first rectifying tower T220 is used as a heating heat source of the tower kettle of the second rectifying tower T230 to provide required heat for the second rectifying tower T230; the gas phase at the top of the second rectifying tower T230 is used as a heating heat source of the bottom of the light component removal tower T210 to provide the required heat for the light component removal tower T210.

Application example 11:

as shown in fig. 12, which is an evolution process of fig. 2, compared with the flow provided by fig. 2, an absorption tower T290 is added, and the tail gas of the light component removal tower T210 is absorbed by the washing water in the absorption tower T290 and then discharged from the apparatus, so as to recover the methanol therein, improve the yield of the methanol product, and reduce the content of the pollutants in the discharged non-condensable gas.

The utility model provides a multi-effect methanol rectification process method for avoiding ethanol accumulation, which can effectively avoid impurity components such as ethanol and the like with the boiling point close to that of methanol from entering a subsequent methanol rectification tower, reduce the separation difficulty of the subsequent methanol rectification tower in the multi-effect rectification process and greatly reduce the operation energy consumption. The whole device at least comprises five towers of a light component removal tower T210, a first rectifying tower T220, a second rectifying tower T230, a third rectifying tower T240, a last tower T250 and the like and matched equipment thereof. Can be used for various methanol solvent recovery and rectification processes of methanol synthesis devices to produce national standard high-grade methanol, American standard AA grade methanol products or methanol products with other specifications. Overcomes the defects of the prior art, has remarkable practicability and economic benefit and has wide application prospect.

The embodiments are described in detail, and those skilled in the relevant art can implement the technology by making appropriate changes, modifications and combinations according to the method provided by the present invention. It is expressly stated that all such modifications or alterations and subcombinations which would be apparent to persons skilled in the art by making similar changes or variations to the process flow provided by the present invention are deemed to be within the spirit, scope and content of the utility model.

Claims

1. A device for a multi-effect methanol rectification process method for avoiding ethanol accumulation is characterized in that: mainly comprises five towers of a light component removal tower (T210), a first rectifying tower (T220), a second rectifying tower (T230), a third rectifying tower (T240), a last tower (T250) and a connecting pipeline;

the raw material crude methanol feeding pipeline is respectively connected with cold side inlets of a feed methanol preheater (E2503) and a feed wastewater preheater (E2504);

cold side outlets of a feed methanol preheater (E2503) and a feed wastewater preheater (E2504) are connected to the middle part of the light component removal tower (T210); the top of the light component removal tower (T210) is connected with a light component removal tower condenser (E2102), a condensate outlet of the light component removal tower condenser (E2102) is connected with the top of the light component removal tower (T210), and a non-condensable gas outlet of the light component removal tower condenser (E2102) is connected with a non-condensable gas discharge pipeline; the bottom of the light component removal tower (T210) is respectively connected with a tube pass inlet of a light component removal tower reboiler (E2101), a first rectifying tower (T220) and a second rectifying tower (T230), and a tube pass outlet of the light component removal tower reboiler (E2101) is connected to a tower kettle of the light component removal tower (T210);

the tower top of the first rectifying tower (T220) is connected with the shell pass of a second rectifying tower reboiler A (E2301A), and the shell pass condensate outlet of the second rectifying tower reboiler A (E2301A) is respectively connected with the tower top of the first rectifying tower (T220) and the hot side inlet of a feeding methanol preheater (E2503); the side draw outlet of the first rectifying tower (T220) is connected with the second rectifying tower (T230); the bottom of the first rectifying tower (T220) is respectively connected with a tube pass inlet of a first rectifying tower reboiler (E2201) and a last tower (T250), and a tube pass outlet of the first rectifying tower reboiler (E2201) is connected to a tower kettle of the first rectifying tower (T220);

the tower top of the second rectifying tower (T230) is respectively connected with the shell pass of a light component removal tower reboiler (E2101) and the shell pass of a third rectifying tower reboiler (E2401), and the shell pass condensate outlets of the light component removal tower reboiler (E2101) and the shell pass condensate outlet of the third rectifying tower reboiler (E2401) are respectively connected with the tower top of the second rectifying tower (T230) and the hot side inlet of a feeding methanol preheater (E2503); the side draw outlet of the second rectifying tower (T230) is connected with a third rectifying tower (T240); the bottom of the second rectifying tower (T230) is respectively connected with a tube pass inlet of a second rectifying tower reboiler A (E2301A), a tube pass inlet of a second rectifying tower reboiler B (E2301B) and a last tower (T250), and a tube pass outlet of the second rectifying tower reboiler A (E2301A) and a tube pass outlet of the second rectifying tower reboiler B (E2301B) are connected to the tower kettle of the second rectifying tower (T230);

the top of the third rectifying tower (T240) is connected with a third rectifying tower condenser (E2402), and a condensate outlet of the third rectifying tower condenser (E2402) is respectively connected with the top of the third rectifying tower (T240) and a hot side inlet of a feeding methanol preheater (E2503); the bottom of the third rectifying tower (T240) is respectively connected with a tube pass inlet of a third rectifying tower reboiler (E2401) and a last tower (T250), and a tube pass outlet of the third rectifying tower reboiler (E2401) is connected to a tower kettle of the third rectifying tower (T240);

the top of the last tower (T250) is connected with the shell pass of a second rectifying tower reboiler B (E2301B), and the shell pass condensate outlet of the second rectifying tower reboiler B (E2301B) is respectively connected with the top of the last tower (T250) and the hot side inlet of a feed methanol preheater (E2503); the bottom of the methanol stripping side (L250) of the last tower (T250) is respectively connected with the tube pass inlet of a reboiler (E2501) at the methanol stripping side of the last tower and the hot side inlet of a feed wastewater preheater (E2504), and the tube pass outlet of the reboiler (E2501) at the methanol stripping side of the last tower is connected with the tower kettle at the methanol stripping side (L250) of the last tower (T250); a side draw pipeline near the methanol stripping side (L250) feeding of the last tower (T250) is connected with a hot side inlet of a fusel oil cooler (E2507); the bottom of the ethanol rectification side (R250) of the last tower (T250) is respectively connected with the tube pass inlet of a reboiler (E2502) at the ethanol rectification side of the last tower and the hot side inlet of an ethanol cooler (E2508), and the tube pass outlet of the reboiler (E2502) at the ethanol rectification side of the last tower is connected to the tower kettle at the ethanol rectification side (R250) of the last tower (T250);

the outlet of the hot side of the feeding methanol preheater (E2503) is connected with the inlet of the hot side of the methanol product cooler (E2505), and the outlet of the hot side of the methanol product cooler (E2505) is connected with a methanol product extraction pipeline;

the hot side outlet of the feed wastewater preheater (E2504) is connected with the hot side inlet of the wastewater cooler (E2506), and the hot side outlet of the wastewater cooler (E2506) is respectively connected with the top of the light component removal tower (T210) and a wastewater discharge pipeline; the hot side outlet of the fusel oil cooler (E2507) is connected with a fusel oil product extraction pipeline; the outlet of the hot side of the ethanol cooler (E2508) is connected with an ethanol product extraction pipeline.

2. The apparatus for a multi-effect methanol rectification process with avoidance of ethanol accumulation as claimed in claim 1 wherein: and a fourth rectifying tower (T260) is added on the basis of the five towers to form a six-tower double triple-effect methanol rectifying device, triple-effect heat integration is adopted among the first rectifying tower (T220), the second rectifying tower (T230) and the third rectifying tower (T240), and triple-effect heat integration is adopted among the light component removal tower (T210), the fourth rectifying tower (T260) and the last tower (T250).

3. The apparatus for a multi-effect methanol rectification process with avoidance of ethanol accumulation as claimed in claim 2 wherein: and a fifth rectifying tower (T270) is added on the basis of the six towers to form a seven-tower four-effect and three-effect methanol rectifying device, four-effect heat integration is adopted among the first rectifying tower (T220), the second rectifying tower (T230), the third rectifying tower (T240) and the fifth rectifying tower (T270), and three-effect heat integration is adopted among the light component removing tower (T210), the fourth rectifying tower (T260) and the last tower (T250).

4. A multi-effect methanol distillation process apparatus as claimed in any of claims 1 to 3 wherein said final column (T250) is configured as a dividing wall column with the dividing wall (S250) dividing the lower portion of the final column (T250) into a methanol stripping side (L250) and an ethanol rectification side (R250); discharging waste water (43) from the bottom of the last tower (T250) methanol stripping side (L250); withdrawing methanol and fusel oil (41) with low ethanol content from the side line below the feed inlet of the methanol stripping side (L250) of the last tower (T250); ethanol (48) is extracted and recovered from the bottom of the last tower (T250) on the ethanol rectification side (R250).

5. The apparatus for a multi-effect methanol distillation process to avoid ethanol accumulation as claimed in claim 1, characterized by an apparatus selected from the group consisting of deformation processes:

modification one: a stripping tower (T250S) is added on the basis of the five towers, and the last tower (T250) adopts a conventional structure instead of a partition plate structure; the liquid phase material (63) at the side line of the last tower (T250) enters the top of a stripping tower (T250S), the gas phase material (64) at the top of the stripping tower (T250S) returns to the last tower (T250), and ethanol (48) is recovered from the tower kettle of the stripping tower (T250S);

and (2) deformation II: a recovery tower (T280) is added on the basis of the five towers, and the last tower (T250) adopts a conventional structure instead of a partition plate structure; the recovery tower (T280) can adopt the gas phase at the top of the first rectifying tower (T220), the second rectifying tower (T230) or the last tower (T250) as a heat source, or adopt other heat sources in the system, or adopt an external heat source;

and (3) deformation: on the basis of the five towers, one first rectifying tower (T220) is reduced, four-tower triple-effect heat integration operation is changed, and the gas phase at the top of the last tower (T250) is used as a heating heat source of the tower kettle of the second rectifying tower (T230) to provide required heat for the second rectifying tower (T230); the gas phase at the top of the second rectifying tower (T230) is used as a heating heat source for the light component removal tower (T210) and the third rectifying tower (T240) to provide required heat for the light component removal tower (T210) and the third rectifying tower (T240).

6. A multi-effect methanol distillation process apparatus to avoid ethanol accumulation as claimed in any of claims 1-3 wherein: and an absorption tower (T290) is added, and the tail gas of the light component removal tower (T210) is absorbed by washing water in the absorption tower (T290) and then discharged out of the device so as to recover the methanol in the tail gas, improve the yield of the methanol product and reduce the content of pollutants in the discharged non-condensable gas.

7. The apparatus for a multi-effect methanol rectification process with avoidance of ethanol accumulation as claimed in claim 1 wherein: typical operating conditions for each column are:

the operation pressure range of the top of the light component removal tower (T210) is 30-200 kPa;

the operation pressure range of the top of the first rectifying tower (T220) is 300-1500 kPa;

the tower top operating pressure range of the second rectifying tower (T230) is 110-950 kPa;

the operation pressure range of the top of the third rectifying tower (T240) is 30-200 kPa;

the operation pressure range of the top of the last tower (T250) is 300-1500 kPa.

8. The multi-effect methanol distillation process plant to avoid ethanol accumulation as claimed in claim 7, characterized in that: the operating conditions of each column were:

the operation pressure at the top of the light component removal tower (T210) is 80-160 kpa, the operation temperature at the top of the tower is 50-85 ℃, and the operation temperature at the bottom of the tower is 55-90 ℃;

the operation pressure of the top of the first rectifying tower (T220) is 350-960 kPa, the operation temperature of the top of the tower is 100-135 ℃, and the operation temperature of the bottom of the tower is 110-160 ℃;

the operation pressure at the top of the second rectifying tower (T230) is 180-500 kPa, the operation temperature at the top of the tower is 80-110 ℃, and the operation temperature at the bottom of the tower is 89-125 ℃;

the operation pressure of the top of the third rectifying tower (T240) is 80-180 kpa, the operation temperature of the top of the tower is 58-80 ℃, and the operation temperature of the tower kettle is 67-98 ℃;

the operation pressure of the top of the last tower (T250) is 350-960 kPa, the operation temperature of the top of the tower is 100-135 ℃, and the operation temperature of the bottom of the methanol stripping side (L250) is 140-175 ℃; the operation temperature of the ethanol rectification side (R250) tower kettle is 110-150 ℃.