Method and system for recovering methanol, dimethyl ether and methyl formate in non-condensable gas of methanol rectifying tower

Abstract

The invention discloses a method for recovering methanol, dimethyl ether and methyl formate in non-condensable gas of a methanol rectifying tower, which belongs to the field of chemistry and comprises the following steps: compressing the non-condensable gas of the methanol rectifying tower, washing and absorbing methanol liquid, carrying out temperature swing adsorption, vaporizing, absorbing carbon dioxide, rectifying and purifying, and liquefying and completely recovering methanol, dimethyl ether and methyl formate in the non-condensable gas of the methanol rectifying tower. And the gas subjected to temperature swing adsorption is combusted in a torch. According to the invention, methanol, dimethyl ether and methyl formate in the non-condensable gas in the methanol rectifying tower are liquefied and fully recovered.

Description

TECHNICAL FIELD

[0001] The present application relates to methanol production, in particular to a method and system for recovering methanol, dimethyl ether and methyl formate in non-condensable gas of methanol distillation column. BACKGROUND

[0002] In the methanol distillation process, the non-condensable gas contains methanol, dimethyl ether and methyl formate. The existing process for treating non-condensable gas is as follows: part of methanol, dimethyl ether and methyl formate in the non-condensable gas is absorbed by water washing, and then the water washing liquid is sent to the methanol distillation column to purify methanol, and the non-condensable gas after water washing is sent to the torch for combustion. The methanol content in the water washing liquid is between 8% and 15%, and the methanol content in the non-condensable gas after water washing is between 5% and 10%; the contents of dimethyl ether and methyl formate in the non-condensable gas after water washing increase by 10% to 20% and reach 20% to 50% due to their low solubility in water.

[0003] The existing treatment method has the following defects:

[0004] (1) The water washing liquid containing 8% to 15% methanol is sent to the methanol distillation column for distillation, which increases the steam consumption of distillation.

[0005] (2) The non-condensable gas after water washing is sent to the torch for combustion, which not only causes waste of methanol, dimethyl ether and methyl formate, but also increases the carbon emission of torch combustion, which is not economical and not environmentally friendly.

[0006] The above background is for the convenience of understanding the present application, and is not the known technology publicly disclosed before the present application. SUMMARY

[0007] In view of the above defects, the present application provides a method for recovering methanol, dimethyl ether and methyl formate in non-condensable gas of methanol distillation column, which aims to improve at least one problem mentioned in the background art.

[0008] The technical solution is as follows: a method for recovering methanol, dimethyl ether and methyl formate in non-condensable gas of methanol distillation column, comprising:

[0009] The non-condensable gas of the methanol distillation column is compressed, washed and absorbed by methanol liquid, subjected to temperature swing adsorption, vaporized, absorbed by carbon dioxide and purified by distillation, and the methanol, dimethyl ether and methyl formate in the non-condensable gas of the methanol distillation column are fully recovered, and the gas after temperature swing adsorption is sent to the torch for combustion.

[0010] Further, the methanol liquid washing and absorption is two-stage washing, wherein the first-stage washing is carried out in an A washing tower, and the second-stage washing is carried out in a B washing tower, part of the washing liquid after washing in the A washing tower is returned, and part of the washing liquid after washing in the A washing tower enters the B washing tower to participate in the second-stage washing, part of the washing liquid after the second-stage washing is returned, and part of the washing liquid after the second-stage washing is vaporized;

[0011] The temperature swing adsorption is a two-stage temperature swing adsorption, wherein the first-stage temperature swing adsorption is carried out in a first-stage adsorption tower group, and the second-stage temperature swing adsorption is carried out in a second-stage adsorption tower group, wherein a part of the first-stage adsorption non-condensable gas after the first-stage temperature swing adsorption is heated and used as desorption gas in the first-stage temperature swing adsorption, and another part is first used as cooling gas in the first-stage adsorption and then heated and used as desorption gas in the second-stage temperature swing adsorption; the gas after the second-stage washing is subjected to the second-stage temperature swing adsorption; the desorption gas after the first-stage temperature swing adsorption and the desorption gas after the second-stage temperature swing adsorption are subjected to the second-stage washing in a B washing tower, and the second-stage adsorption non-condensable gas is used as cooling gas in the second-stage temperature swing adsorption and then sent to a flare for combustion.

[0012] In the vaporization + carbon dioxide absorption + rectification purification, the vaporization is carried out in a vaporization tower, the carbon dioxide absorption is carried out in a carbon dioxide absorption tower, and the rectification purification is carried out in a methyl formate rectification tower; the liquid after the B washing tower is subjected to vaporization in the vaporization tower, absorption in the carbon dioxide absorption tower and rectification in the methyl formate rectification tower, to obtain methanol, dimethyl ether and methyl formate products, respectively.

[0013] Further, in the first-stage washing, the methanol, dimethyl ether and methyl formate mist and foam in the methanol rectification tower non-condensable gas are captured, so that most of the methanol, dimethyl ether and methyl formate gas in the methanol rectification tower non-condensable gas is liquefied and absorbed into liquid methanol.

[0014] In the second-stage washing, the methanol, dimethyl ether and methyl formate mist and foam in the desorption gas from the temperature swing adsorption are captured, so that most of the methanol, dimethyl ether and methyl formate gas in the desorption gas is liquefied and absorbed into liquid methanol.

[0015] Further, the working process of the first-stage adsorption tower group is as follows: the gas washed by the A washing tower enters the first-stage adsorption tower group, and the adsorbent in the regenerated adsorption tower bed layer of the first-stage adsorption tower group absorbs the gas methanol, dimethyl ether and methyl formate, the methanol, dimethyl ether and methyl formate in the gas are concentrated in the adsorbent, the partial pressure of the methanol, dimethyl ether and methyl formate in the adsorbent gradually reaches the liquefaction partial pressure, the gas-liquid mixture of the methanol, dimethyl ether and methyl formate is formed in the adsorbent, when the methanol, dimethyl ether and methyl formate in the upper bed layer of the adsorbent approaches the design index of 0.01%, another regenerated adsorption tower of the first-stage adsorption tower group is switched to operate; the adsorption saturated adsorption tower of the first-stage adsorption tower group is operated by using the gas from the top of the adsorption tower in the adsorption state of the first-stage adsorption tower group to be heated to 150-180 degrees for isobaric backwashing operation, the high-concentration gas-liquid mixture of the methanol, dimethyl ether and methyl formate in the adsorbent is blown out from top to bottom, and after being cooled by a cooler, the liquefaction of the gas-liquid mixture after being washed by the methanol liquid at room temperature in the B washing tower is completed, and the adsorbent is regenerated; the regenerated adsorption tower of the first-stage adsorption tower group is cooled by using the gas from the top of the adsorption tower in the adsorption state of the first-stage adsorption tower group; the adsorption tower of the first-stage adsorption tower group alternately performs adsorption, regeneration and cooling to complete the first-stage adsorption.

[0016] The working process of the second-stage adsorption tower group is as follows: the gas washed by the B washing tower enters the second-stage adsorption tower group, and the adsorbent in the regenerated adsorption tower bed layer of the second-stage adsorption tower group absorbs the gas methanol, dimethyl ether and methyl formate, the methanol, dimethyl ether and methyl formate in the gas are concentrated in the adsorbent, the partial pressure of the methanol, dimethyl ether and methyl formate in the adsorbent gradually reaches the liquefaction partial pressure, the gas-liquid mixture of the methanol, dimethyl ether and methyl formate is formed in the adsorbent, when the methanol, dimethyl ether and methyl formate in the upper bed layer of the adsorbent approaches the design index of 0.01%, another regenerated adsorption tower of the second-stage adsorption tower group is switched to operate; the adsorption saturated adsorption tower of the second-stage adsorption tower group is operated by using the gas from the top of the adsorption tower in the adsorption state of the first-stage adsorption tower group to be heated to 150-180 degrees for isobaric backwashing operation, the high-concentration gas-liquid mixture of the methanol, dimethyl ether and methyl formate in the adsorbent is blown out from top to bottom, and after being cooled by a cooler, the liquefaction of the gas-liquid mixture after being washed by the methanol liquid at room temperature in the B washing tower is completed, and the adsorbent is regenerated; the regenerated adsorption tower of the second-stage adsorption tower group is cooled by using the gas from the top of the adsorption tower in the adsorption state of the second-stage adsorption tower group; the adsorption tower of the second-stage adsorption tower group alternately performs adsorption, regeneration and cooling to complete the second-stage adsorption.

[0017] Further, the initial formation process of the washing liquid in the A washing tower is as follows: the non-condensable gas of the methanol rectifying tower is compressed to form a pressurized fluid, the pressurized fluid is separated in the A washing tower, the gas is sent to the temperature swing adsorption, and the liquid is gradually accumulated in the A washing tower, and the accumulated liquid is the washing liquid of the A washing tower.

[0018] The initial formation of the washing liquid in the B washing tower is that the desorption gas from the TSA is separated in the B washing tower, the gas is sent to the TSA, and the liquid is gradually accumulated in the B washing tower, and the accumulated liquid is the washing liquid of the B washing tower.

[0019] The application also provides a system for recovering methanol, dimethyl ether and methyl formate in non-condensable gas of a methanol rectification tower.

[0020] The technical scheme is: a system for recovering methanol, dimethyl ether and methyl formate in non-condensable gas of a methanol rectification tower, comprising: a compressor, an A washing tower, a first-stage adsorption tower group, a second-stage adsorption tower group and a B washing tower, wherein the A washing tower is in communication with the compressor, the B washing tower and the first-stage adsorption tower group through pipelines respectively, the first-stage adsorption tower group is in communication with the B washing tower and the second-stage adsorption tower group through pipelines respectively, and the second-stage adsorption tower group is in communication with the B washing tower through a pipeline.

[0021] Further, the first-stage adsorption tower group comprises an A adsorption tower, a B adsorption tower and a C adsorption tower, wherein the top and the bottom of each of the A adsorption tower, the B adsorption tower and the C adsorption tower are connected with pipelines in communication with each other, and first, second, third, ninth, tenth and eleventh program-controlled valve groups are installed on the pipelines; the second-stage adsorption tower group comprises a D adsorption tower, an E adsorption tower and an F adsorption tower, wherein the top and the bottom of each of the D adsorption tower, the E adsorption tower and the F adsorption tower are connected with pipelines in communication with each other, and fourth, fifth, sixth, seventh and eighth program-controlled valve groups are installed on the pipelines.

[0022] Further, an A regeneration gas heater is installed on the pipeline of the third program-controlled valve group, and a B regeneration gas heater is installed on the pipeline connecting the first-stage adsorption tower group and the second-stage adsorption tower group.

[0023] Further, the system further comprises a vaporization tower, a carbon dioxide absorption tower, a methyl formate rectification tower and a carbon dioxide desorption tower, the vaporization tower is in communication with the B washing tower through a pipeline, the vaporization tower is in communication with the methyl formate rectification tower and the carbon dioxide absorption tower through pipelines respectively, and the carbon dioxide absorption tower is in communication with the carbon dioxide desorption tower through a pipeline.

[0024] Further, the pipeline, which is in communication with the B washing tower and the second-stage adsorption tower group, has two pipelines, one of which is connected to the top of the B washing tower, and the other is connected to the lower part of the B washing tower; the pipeline, which is in communication with the carbon dioxide absorption tower and the carbon dioxide desorption tower, has two pipelines, one end of one of the pipelines is connected to the bottom of the B washing tower, and the other end is connected to the middle upper part of the carbon dioxide desorption tower, and one end of the other pipeline is connected to the middle upper part of the B washing tower, and the other end is connected to the bottom of the carbon dioxide desorption tower, and the two pipelines are in heat exchange through a heat exchanger.

[0025] Compared with the prior art, the beneficial effects of the present application are that:

[0026] The present application can recover methanol, dimethyl ether and methyl formate in the raw material gas by compression + washing absorption + temperature swing adsorption + vaporization, carbon dioxide absorption and rectification purification, and only a small amount of methanol, dimethyl ether and methyl formate can be discharged from the system under the premise of meeting the emission standard, thereby reducing the loss of traditional process to flare combustion, ensuring that the methanol, dimethyl ether and methyl formate in the exhaust gas are discharged under the national standard, and having obvious economic benefits and environmental protection value.

[0027] The present application can use the tail gas at the top of the first-stage adsorption tower to heat and blow back the adsorption bed, and the energy consumption is very low. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a process flow diagram of the present application.

[0029] In the figure: 1, raw gas pipeline; 2, compressor; 3, A washing tower; 4, first cooler; 5, first circulating pump; 6, methanol liquid level regulating valve; 7, A washing tower outlet pipeline; 8, purge gas pressure reducing regulating valve; 9, B washing tower; 10, second cooler; 11, second circulating pump; 12, B washing tower liquid level regulating; 13, mixed liquid to gasification tower pipeline; 14, gasification tower; 15, carbon dioxide absorption tower; 16, gasification tower reboiler; 17, methyl formate rectification tower; 18, absorption liquid circulating pump; 19, fresh liquid reflux pump; 20, crude methanol pressurizing pump; 21, crude methanol reboiler; 22, methyl formate reflux pump; 23, methyl formate collection tank; 24, product methyl formate outlet pipe; 25, methyl formate condenser; 26, heat exchanger; 27, third cooler; 28, carbon dioxide desorption tower; 29, circulating heater; 30, liquid circulating pump; 31, dimethyl ether reflux pump; 32, dimethyl ether collection tank; 33, product dimethyl ether outlet pipeline; 34, dimethyl ether condenser; 35, desorption gas reflux B pipe; 36, carbon dioxide vent pipe; 37, desorption gas reflux A pipe; 38, secondary regeneration gas pipeline; 39, A adsorption tower; 40, B adsorption tower; 41, C adsorption tower; 42, D adsorption tower; 43, E adsorption tower; 44, F adsorption tower; 45, A regeneration gas heater; 46, B regeneration gas heater; 47, first sequence valve group; 48, second sequence valve group; 49, pressure regulating valve; 50, third sequence valve group; 51, fourth sequence valve group; 52, fifth sequence valve group; 53, sixth sequence valve group; 54, seventh sequence valve group; 55, eighth sequence valve group; 56, adsorption tower cooling gas outlet pipe; 57, tail gas outlet main pipe; 58, pressure regulating valve; 59, flow regulating valve; 60, ninth sequence valve group; 61, tenth sequence valve group; 62, eleventh sequence valve group; 63, secondary washing tower outlet main pipe. DETAILED DESCRIPTION

[0030] As used herein the terms "about 2" and "approximately 2" mean ± 0.2.

[0031] "Made by" is synonymous with "comprising". The terms "comprising", "including", "having" and "with" as used herein, are meant to be open-ended terms that specify the presence of the stated elements. The term "comprising" when used in a clause of the form "A comprising B" should not be interpreted as a limitation that the accompanying statement must be authoritatively interpreted in accordance with 35 U.S.C. § 112(6). Rather, such clauses are to be interpreted in the manner set forth in the Federal Circuit's decisions in the Li v. Whitney and MPEP § 2111.03(a), 2111.03(c) and 2111.03(d) decisions.

[0032] The conjunctive term "comprising" encompasses the presence of unrecited elements or steps of claim limitations. If used in the claims, the transitional phrase "comprising" shall allow the claim to be interpreted to "open" the claim to the inclusion of other non-recited materials or steps, except where expressly recited otherwise. The conjunctive term "consisting of shall exclude any element, step, or component not specified in the claim. If used in the claims, the transitional phrase "consisting of shall make the claim closed, such that it will not include materials other than those recited in the claim, except for normal impurities in the materials. The conjunctive term "consisting essentially of shall exclude any elements, steps, or components not specified in the claim except for those that do not materially affect the basic and novel characteristic(s) of the claimed application. If used in the claims, the transitional phrase "consisting essentially of shall make the claim closed, such that it will not include materials or steps that affect the basic and novel characteristic(s) of the claimed application.

[0033] When expressing a range, a preferred range, or a range defined by a series of upper preferred values and lower preferred values for an equivalent, concentration, or other value or parameter, it shall be understood that all ranges formed by any pairing of an upper range limit or preferred value with a lower range limit or preferred value, whether or not the range is expressly disclosed, are specifically disclosed. For example, where a range "1-5" is disclosed, the described range should be interpreted to include the ranges "1-4," "1-3," "1-2," "1-2 and 4-5," "1-3 and 5," etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include the endpoints and all integers and fractions within that range.

[0034] The technical solutions of the present application will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0035] Those skilled in the art will understand that the following examples are only used to illustrate the present application, and should not be regarded as limiting the scope of the present application. If the specific conditions are not specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are used. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased on the market.

[0036] "and / or" is used to indicate one or both of the stated conditions can occur, for example, A and / or B includes (A and B) and (A or B).

[0037] Please refer to Figure 1 , Figure 1 is a process flow diagram of the present application.

[0038] In the application, the A adsorption tower 39, the B adsorption tower 40 and the C adsorption tower 41 are the first-stage adsorption tower group, wherein, when the A adsorption tower 39 is in the adsorption state, the B adsorption tower 40 is in the cooling state, and the C adsorption tower 41 is in the desorption regeneration state, and the same applies to the subsequent stages (for example, when the B adsorption tower 40 is in the adsorption state, the A adsorption tower 39 is in the desorption regeneration state, and the C adsorption tower 41 is in the cooling state). For the same adsorption tower in the first-stage adsorption tower group, such as the A adsorption tower 39, the adsorption state, the desorption regeneration state and the cooling state are cyclically performed in sequence.

[0039] In the application, the adsorbents in the first-stage adsorption tower group and the second-stage adsorption tower group are selected from one or more of activated carbon, silica gel and 5A molecular sieve.

[0040] In the application, the D adsorption tower 42, the E adsorption tower 43 and the F adsorption tower 44 are the second-stage adsorption tower group, wherein, when the D adsorption tower 42 is in the adsorption state, the E adsorption tower 43 is in the cooling state, and the F adsorption tower 44 is in the desorption regeneration state, and the same applies to the subsequent stages (for example, when the E adsorption tower 43 is in the adsorption state, the D adsorption tower 42 is in the desorption regeneration state, and the F adsorption tower 44 is in the cooling state). For the same adsorption tower in the second-stage adsorption tower group, such as the D adsorption tower 42, the adsorption state, the desorption regeneration state and the cooling state are cyclically performed in sequence.

[0041] In the application, the purpose of the temperature swing adsorption is to completely adsorb methanol, dimethyl ether and methyl formate in the raw gas into the adsorbent, and the purpose of the rectification purification is to purify methyl formate and dimethyl ether in the mixed liquid to the requirements of commercial products.

[0042] In the application, the cooperation of the purge gas pressure reducing regulating valve 8, the pressure regulating valve 58 and the flow regulating valve 59 is adopted to complete the gas separation and blowing of the first-stage temperature swing adsorption (the first-stage adsorption tower group) and the second-stage temperature swing adsorption (the second-stage adsorption tower group), and the proportion of each is 50%.

[0043] A process for recovering methanol, dimethyl ether and methyl formate in the non-condensable gas of a methanol rectification tower, comprising the following steps:

[0044] S1, compression: the raw gas (with a pressure of 0.02-0.15 MPa) in the raw gas pipeline 1 enters the compressor 2 to be pressurized to 1.0-1.8 MPa (the purpose is to pressurize the non-condensable gas of the methanol rectification tower, which can improve the effect of the methanol washing and the temperature swing adsorption, and at the same time, meet the requirements of the dimethyl ether rectification operation).

[0045] S2, two-stage washing, two-stage adsorption and two-stage desorption:

[0046] S21: First stage washing: the fluid compressed by the compressor 2 enters the A washing tower 3 to be washed by methanol liquid (the A washing tower 3 reduces the content of methanol in the raw gas from 15% to 50% to less than 3%, reduces the content of dimethyl ether from 2% to 15% to less than 5%, and reduces the content of methyl formate from 2% to 15% to less than 3%), the mixed liquid at the bottom of the A washing tower 3 enters the B washing tower 9, and the gas enters the first stage adsorption tower group through the A washing tower outlet pipeline 7.

[0047] S22, first stage adsorption, first stage desorption regeneration and first stage cooling: the gas from the A washing tower outlet pipeline 7 enters the bottom of the A adsorption tower 39 in the first stage adsorption tower group (assuming that the A adsorption tower 39 is in the adsorption state, the C adsorption tower 41 is in the desorption regeneration state, and the B adsorption tower 40 is in the cooling state), the gas at the outlet of the upper part of the A adsorption tower 39 (hereinafter referred to as the first stage adsorption non-condensable gas), 50% of the first stage adsorption non-condensable gas enters the B adsorption tower 40 as the cooling gas, and the other 50% of the first stage adsorption non-condensable gas enters the C adsorption tower 41 through the A regeneration gas heater 45 to perform the sweeping regeneration of the adsorption bed. The first stage adsorption tower group is operated in the adsorption, regeneration and adsorption cycle to complete the first stage adsorption.

[0048] In this step, the methanol, dimethyl ether and methyl formate in the gas adsorbed by the A adsorption tower 39 are completely adsorbed by the adsorbent, and the content of the methanol, dimethyl ether and methyl formate in the first stage adsorption non-condensable gas is less than 100 ppm, which is qualified sweeping gas.

[0049] In this step, the desorption gas after the desorption of the C adsorption tower 41 enters the B washing tower 9 after passing through the desorption gas backflow A pipeline 37 and the sweeping gas pressure reducing regulating valve 8, and the gas after the cooling of the B adsorption tower 40 enters the second stage regeneration gas pipeline 38 after being heated by the B regeneration gas heater 46 installed on the second stage regeneration gas pipeline 38, and then enters the second stage adsorption tower group to perform the desorption sweeping.

[0050] In this step, the first stage adsorption tower group realizes that one adsorption tower is in the adsorption state, another adsorption tower is in the desorption regeneration state, and the last adsorption tower is in the cooling state through the first programmable valve group 47, the second programmable valve group 48, the third programmable valve group 50, the ninth programmable valve group 60, the tenth programmable valve group 61 and the eleventh programmable valve group 62.

[0051] In this step, the desorption regeneration effect can be improved by opening the pressure increasing valve 49.

[0052] S23: Second stage washing: the desorption gas from the first stage adsorption tower group enters the B washing tower 9 to be washed, the washed gas enters the second stage washing tower outlet main pipeline 63, the mixed liquid enters the mixed liquid gasification tower pipeline 13, and the mixed liquid from the A washing tower 3 continuously enters the B washing tower 9 as the washing liquid through the first mixed liquid pipeline continuously through the methanol liquid level regulating valve 6.

[0053] S24: Second stage adsorption, second stage desorption and second stage cooling: The gas from the second stage washing tower outlet manifold 63 enters the bottom of the second stage adsorption tower group (assuming that the D adsorption tower 42 is in the adsorption state, the E adsorption tower 43 is in the cooling state, and the F adsorption tower 44 is in the desorption state). After adsorption, the gas at the outlet of the upper part of the D adsorption tower 42 (hereinafter referred to as second stage adsorption non-condensable gas) is used as cooling gas, and the desorption gas of the F adsorption tower 44 is the gas from the second stage regeneration gas pipeline 38. The second stage adsorption tower group is operated in a cycle of adsorption, regeneration and adsorption, and the second stage adsorption is completed.

[0054] In this step, the methanol, dimethyl ether and methyl formate in the D adsorption tower 42 are completely adsorbed by the adsorbent, and the total content of methanol, dimethyl ether and methyl formate in the second stage adsorption non-condensable gas is less than 100 ppm, meeting the emission standard requirements.

[0055] In this step, the second stage adsorption non-condensable gas enters the E adsorption tower 43, and after cooling the E adsorption tower 43, it goes to the tail gas outlet manifold 57 through the adsorption tower cooling gas outlet pipe 56 for discharge. The desorption gas from the F adsorption tower 44 goes to the B washing tower 9 for washing through the desorption gas backflow B pipe 35.

[0056] In this step, the second stage adsorption tower group realizes that one adsorption tower is in the adsorption state, another adsorption tower is in the desorption state, and the last adsorption tower is in the cooling state through the fourth program-controlled valve group 51, the fifth program-controlled valve group 52, the sixth program-controlled valve group 53, the seventh program-controlled valve group 54 and the eighth program-controlled valve group 55.

[0057] S3, vaporization and rectification purification: The mixed liquid from the B washing tower 9 is continuously sent to the vaporization tower 14 through the mixed liquid vaporization tower pipeline 13 by the washing tower B liquid level adjustment 12. In the vaporization tower 14, the carbon dioxide and dimethyl ether in the mixed liquid are vaporized, and the vaporized gas is sent to the carbon dioxide absorption tower 15. The gas treated by the carbon dioxide absorption tower 15 is condensed in the dimethyl ether condenser 34, and finally the dimethyl ether product is obtained through the product dimethyl ether outlet pipeline 33. The mixed liquid at the bottom of the vaporization tower 14 is treated by the methyl formate rectification tower 17, and then the methyl formate product is obtained through the product methyl formate outlet pipeline 24. The crude methanol from the bottom of the methyl formate rectification tower 17 is sent out of the system by the crude methanol pressurizing pump 20 and goes to the methanol rectification tower.

[0058] In this step, the dimethyl ether condensate from the dimethyl ether condenser 34 is collected in the dimethyl ether collection tank 32. The dimethyl ether condensate from the dimethyl ether collection tank 32 is partially sent to the dimethyl ether outlet pipeline 33 under the dimethyl ether reflux pump 31, and the other part is returned to the carbon dioxide absorption tower 15. The liquid from the bottom of the carbon dioxide absorption tower 15 is sent to the carbon dioxide desorption tower 28 for desorption through the absorption liquid circulating pump 18 and the heat exchanger 26.

[0059] In this step, the gas from the top of the methyl formate rectification tower 17 is condensed by the methyl formate condenser 25, and the methyl formate condensate is collected in the methyl formate collection tank 23. A part of the methyl formate liquid in the methyl formate collection tank 23 is returned to the methyl formate rectification tower 17 by the methyl formate reflux pump 22, and the other part is introduced into the product methyl formate outlet pipe 24.

[0060] In this step, the non-condensed gas (total content of methanol, dimethyl ether and methyl formate is 0.01%) of the dimethyl ether condenser 34, the non-condensed gas of the carbon dioxide stripping tower 28 and the non-condensed gas of the methyl formate condenser 25 are introduced into the carbon dioxide vent pipe 36 and then into the tail gas outlet main pipe 57 for discharge.

[0061] In this step, the liquid from the bottom of the carbon dioxide stripping tower 28 is returned to the carbon dioxide absorption tower 15 by the fresh liquid reflux pump 19, the heat exchanger 26 and the third cooler 27, and the liquid from the middle of the carbon dioxide stripping tower 28 is returned to the carbon dioxide stripping tower 28 after being pumped by the liquid circulating pump 30 and the circulating heater 29.

[0062] In this step, the vaporization tower 14 is connected with the vaporization tower reboiler 16, and the methyl formate rectification tower is connected with the crude methanol reboiler 21.

[0063] In the present application, the working process of the first-stage adsorption tower group is as follows: the adsorbent in the regenerated adsorption bed of the first-stage adsorption tower group absorbs the gaseous methanol, dimethyl ether and methyl formate, and the methanol, dimethyl ether and methyl formate in the gas are concentrated in the adsorbent. The partial pressure of the methanol, dimethyl ether and methyl formate in the adsorbent gradually reaches the liquefaction partial pressure, and a gas-liquid mixture of methanol, dimethyl ether and methyl formate is formed inside the adsorbent. When the methanol, dimethyl ether and methyl formate in the upper bed of the adsorbent approach the design index of 0.01%, the operation is switched to the other regenerated adsorption bed of the first-stage adsorption tower group. The adsorption-saturated adsorption bed of the first-stage adsorption tower group is operated by the gas from the top of the adsorption bed in the adsorption state of the first-stage adsorption tower group, which is heated to 150-180 degrees for isobaric backwashing operation. The high-concentration gas-liquid mixture of methanol, dimethyl ether and methyl formate in the adsorbent is blown out from top to bottom, cooled by a cooler, and then liquefied after being washed by the methanol liquid at room temperature in the B washing tower, so that the adsorbent is regenerated. The regenerated adsorption bed of the first-stage adsorption tower group is cooled by the gas from the top of the adsorption bed in the adsorption state of the first-stage adsorption tower group. The adsorption bed of the first-stage adsorption tower group alternately performs adsorption, regeneration and cooling to complete the first-stage adsorption.

[0064] In the present application, at the initial stage of system operation, methanol liquid is not required to be additionally introduced into the A washing tower 3, the pressurized fluid from the compressor 2 is separated in the A washing tower 3, the gas is removed from the A washing tower outlet pipeline 7 for adsorption, and the liquid is gradually accumulated in the A washing tower 3 (the accumulated liquid is the methanol liquid), and after the liquid level is accumulated to the required level, the methanol liquid level regulating valve 6 is opened for liquid level regulation. Similarly, at the initial stage of system operation, methanol liquid is not required to be additionally introduced into the B washing tower 9, the desorbed gas from the first-stage adsorption tower group and the desorbed gas from the second-stage adsorption tower group are separated in the B washing tower 9, the gas is removed from the B washing tower 9 gas outlet through the second-stage washing tower outlet main pipeline 63, the liquid is gradually accumulated in the B washing tower 9, and after the liquid level is accumulated to the required level, the B washing tower liquid level regulating valve 12 is opened for liquid level regulation, and in the process of accumulation of the washing liquid, the washing liquid from the A washing tower 3 may also be involved.

[0065] In one or more specific embodiments of the present application, in order to ensure the smooth blowing of the A adsorption tower 39, the B adsorption tower 40, the C adsorption tower 41, the D adsorption tower 42, the E adsorption tower 43 and the F adsorption tower 44, the operating pressure of the B washing tower 9 is < the operating pressure of the A washing tower.

[0066] In one or more specific embodiments of the present application, the operating pressure of the A washing tower is 0.3-0.5 MPa.

[0067] In one or more specific embodiments of the present application, in order to ensure the yield and purity of dimethyl ether, the operating pressure of the gasification tower 14 is ≥1.0 MPa.

[0068] In one or more specific embodiments of the present application, in order to ensure the yield and purity of methyl formate, the operating pressure of the methyl formate rectification tower 17 is 0.3-0.5 MPa.

[0069] In the present application, the methanol washing tower of the A washing tower 3 and the B washing tower 9 captures the methanol, dimethyl ether and methyl formate mist droplets, so that most of the methanol, dimethyl ether and methyl formate gas in the raw material gas is liquefied and absorbed into the liquid methanol, and in this process, the temperature of the methanol liquid gradually increases due to the liquefaction of the methanol, dimethyl ether and methyl formate gas. Therefore, in one or more specific embodiments of the present application, the first mixed liquid pipeline is connected with a first liquid return pipeline, the first liquid return pipeline is provided with a first circulating pump 5 and a first cooler 4, and the mixed liquid gasification tower pipeline 13 is provided with a second circulating pump 11 and a second cooler 10. The temperature of the liquid methanol is reduced by the circulating pump + cooler mode, and the temperature of the methanol circulating liquid is preferably below 40 degrees.

[0070] Example 1

[0071] In this embodiment, the raw material gas is processed by the process of Figure 1 The parameters of the raw material gas are shown in Table 1.

[0072] Table 1

[0073]

[0074]

[0075] Implementation Figure 1 After the process, the obtained methyl formate, crude methanol and dimethyl ether are as shown in Table 2 below.

[0076] Table 2

[0077]

[0078] The foregoing merely illustrates the principles of the application. It will thus be appreciated that those skilled in the art will be able to devise various arrangements which, although not explicitly described or shown herein, embody the principles of the application and are thus within its spirit and scope. Any modification of the base embodiment, which comes within the scope of the claims and which forms the equivalent of what is claimed, is to be read into the claims as alternative written description to provide a complete description of all modification that come within the scope of the base application.

[0079] Furthermore, to the extent that the term "includes" is used in either the detailed description or the claims, such term is intended to be inclusive in a manner similar to the term "comprising" as "comprising" is interpreted when employed as a transitional word in the introductory clauses of the claims. Moreover, where the term "excludes" is used in either the detailed description or the claims, such term is intended to be exclusive, for example, in a claim limiting the scope of the present application by stating that "the present application does not include." In addition, where the term "does not include" is used in either the detailed description or the claims, such term is intended to be exclusive, for example, in a claim limiting the scope of the present application by stating that "the present application does not include."

Claims

1. A method for recovering methanol, dimethyl ether, and methyl formate from non-condensable gas in a methanol distillation column, characterized in that, include: The non-condensable gas in the methanol distillation column is purified by compression, methanol liquid washing and absorption, temperature-switching adsorption, vaporization + carbon dioxide absorption + distillation. Methanol, dimethyl ether and methyl formate in the non-condensable gas in the methanol distillation column are fully recovered by liquefaction. The gas after temperature-switching adsorption is sent to the flare for combustion.

2. The method for recovering methanol, dimethyl ether, and methyl formate from non-condensable gas in a methanol distillation column according to claim 1, characterized in that, The methanol washing and absorption process consists of two stages: the first stage is carried out in washing tower A, and the second stage is carried out in washing tower B. Part of the washing liquid after washing in washing tower A is refluxed, and part of it enters washing tower B to participate in the second stage washing. Part of the washing liquid after washing in the second stage is refluxed, and part of it is devastated. The temperature-switching adsorption is a two-stage temperature-switching adsorption. The first stage of temperature-switching adsorption is carried out in the first-stage adsorption tower group, and the second stage of temperature-switching adsorption is carried out in the second-stage adsorption tower group. In this case, the non-condensable gas after the first-stage adsorption is heated and used as the desorption gas in the first-stage temperature-switching adsorption, and the other part is first used as the cooling gas in the first-stage adsorption, and then heated and used as the desorption gas in the second-stage temperature-switching adsorption. The gas after the second-stage washing is then subjected to the second-stage temperature-switching adsorption. The desorption gas after the first-stage temperature-switching adsorption and the desorption gas after the second-stage temperature-switching adsorption enter the B washing tower for the second-stage washing. The non-condensable gas after the second-stage adsorption is used as the cooling gas in the second-stage temperature-switching adsorption and then goes to the flare for combustion. In the vaporization + carbon dioxide absorption + distillation purification process, vaporization is carried out in a vaporization tower, carbon dioxide absorption is carried out in a carbon dioxide absorption tower, and distillation purification is carried out in a methyl formate distillation tower. The liquid washed by the B washing tower is vaporized in the vaporization tower, absorbed in the carbon dioxide absorption tower, and distilled in the methyl formate distillation tower to obtain methanol, dimethyl ether, and methyl formate products, respectively.

3. The method for recovering methanol, dimethyl ether, and methyl formate from non-condensable gas in a methanol distillation column according to claim 2, characterized in that, In the first stage of washing, methanol, dimethyl ether, and methyl formate droplets in the non-condensable gas of the methanol distillation column are captured, so that most of the methanol, dimethyl ether, and methyl formate gas in the non-condensable gas of the methanol distillation column are liquefied and absorbed into liquid methanol; In the second stage of washing, methanol, dimethyl ether, and methyl formate droplets from the desorption gas adsorbed by temperature variation are captured, so that most of the methanol, dimethyl ether, and methyl formate gases in the desorption gas are liquefied and absorbed into liquid methanol.

4. The method for recovering methanol, dimethyl ether, and methyl formate from non-condensable gas in a methanol distillation column according to claim 2, characterized in that, The first-stage adsorption tower group operates as follows: Gas washed by scrubbing tower A enters the first-stage adsorption tower group. The adsorbent in the regenerated adsorption tower bed absorbs methanol, dimethyl ether, and methyl formate. The methanol, dimethyl ether, and methyl formate in the gas are concentrated in the adsorbent. The partial pressures of methanol, dimethyl ether, and methyl formate in the adsorbent gradually reach liquefaction pressures, forming a gas-liquid mixture of methanol, dimethyl ether, and methyl formate inside the adsorbent. When the methanol, dimethyl ether, and methyl formate concentrations in the upper bed of the adsorbent approach the design target of 0.01%, the operation switches to another regenerated adsorption tower in the first-stage adsorption tower group. In the first-stage adsorption tower group, the adsorption tower saturated with adsorption gas is heated to 150-180 degrees Celsius and subjected to isobaric backflushing. This process blows a high-concentration gas-liquid mixture of methanol, dimethyl ether, and methyl formate from the adsorbent downwards. After cooling in a cooler, the mixture is washed with room-temperature methanol in the B washing tower and liquefied, thus regenerating the adsorbent. The regenerated adsorption tower in the first-stage adsorption tower group is then cooled by the gas exiting the top of the adsorption tower in the first-stage adsorption tower group. The adsorption towers in the first-stage adsorption tower group alternately undergo adsorption, regeneration, and cooling to complete the first-stage adsorption process. The second-stage adsorption tower group operates as follows: Gas washed by scrubbing tower B enters the second-stage adsorption tower group. The adsorbent in the regenerated adsorption tower bed absorbs methanol, dimethyl ether, and methyl formate. The methanol, dimethyl ether, and methyl formate in the gas are concentrated in the adsorbent, and the partial pressures of methanol, dimethyl ether, and methyl formate in the adsorbent gradually reach liquefaction pressures, forming a gas-liquid mixture of methanol, dimethyl ether, and methyl formate inside the adsorbent. When the methanol, dimethyl ether, and methyl formate concentrations in the upper bed of the adsorbent approach the design target of 0.01%, the operation switches to another regenerated adsorption tower in the second-stage adsorption tower group. In the second-stage adsorption tower group, the adsorption tower saturated with adsorption gas is heated to 150-180 degrees Celsius and subjected to isobaric backflushing. This process blows out a high-concentration gas-liquid mixture of methanol, dimethyl ether, and methyl formate from the adsorbent from top to bottom. After being cooled by a cooler, the mixture is washed with room-temperature methanol in the B washing tower and liquefied, thus regenerating the adsorbent. In the second-stage adsorption tower group, the regenerated adsorption tower is cooled by the gas exiting the top of the adsorption tower. The adsorption towers in the second-stage adsorption tower group alternately undergo adsorption, regeneration, and cooling to complete the second-stage adsorption.

5. The method for recovering methanol, dimethyl ether, and methyl formate from non-condensable gas in a methanol distillation column according to claim 2, characterized in that, In the A washing tower, the initial formation process of the washing liquid is as follows: the pressurized fluid formed by the compression of non-condensable gas in the methanol distillation tower is separated in the A washing tower, where the gas undergoes temperature-switching adsorption and the liquid gradually accumulates in the A washing tower. The accumulated liquid is the washing liquid of the A washing tower. In the B washing tower, the initial formation process of the washing liquid is as follows: the desorbed gas adsorbed from the temperature-switching adsorption is separated in the B washing tower, where the gas goes to the temperature-switching adsorption, and the liquid gradually accumulates in the B washing tower. The accumulated liquid is the washing liquid of the B washing tower.

6. A system for recovering methanol, dimethyl ether, and methyl formate from non-condensable gas in a methanol distillation column according to any one of claims 1-5, characterized in that, include: The system includes a compressor, a scrubbing tower A, a first-stage adsorption tower group, a second-stage adsorption tower group, and a scrubbing tower B. Scrubbing tower A is connected to the compressor, scrubbing tower B, and the first-stage adsorption tower group via pipelines. The first-stage adsorption tower group is also connected to scrubbing tower B and the second-stage adsorption tower group via pipelines. The second-stage adsorption tower group is also connected to scrubbing tower B via a pipeline.

7. The system for recovering methanol, dimethyl ether, and methyl formate from non-condensable gas in a methanol distillation column according to claim 6, characterized in that, The first-stage adsorption tower group includes adsorption tower A, adsorption tower B, and adsorption tower C. Each of adsorption towers A, B, and C has interconnected pipes at its top and bottom, and these pipes are equipped with a first, second, third, ninth, tenth, and eleventh programmable valve group. The second-stage adsorption tower group includes adsorption tower D, adsorption tower E, and adsorption tower F. Each of adsorption towers D, E, and F has interconnected pipes at its top and bottom, and these pipes are equipped with a fourth, fifth, sixth, seventh, and eighth programmable valve group.

8. The system for recovering methanol, dimethyl ether, and methyl formate from non-condensable gas in a methanol distillation column according to claim 7, characterized in that, A regeneration gas heater (A) is also installed on the installation pipeline of the third programmable valve group, and a regeneration gas heater (B) is installed on the pipeline connecting the first-stage adsorption tower group and the second-stage adsorption tower group.

9. The system for recovering methanol, dimethyl ether, and methyl formate from non-condensable gas in a methanol distillation column according to claim 6, characterized in that, It also includes a vaporization tower, a carbon dioxide absorption tower, a methyl formate distillation tower, and a carbon dioxide desorption tower. The vaporization tower is connected to the B washing tower through a pipeline. The vaporization tower is also connected to the methyl formate distillation tower and the carbon dioxide absorption tower through pipelines. The carbon dioxide absorption tower and the carbon dioxide desorption tower are connected through a pipeline.

10. The system for recovering methanol, dimethyl ether, and methyl formate from non-condensable gas in a methanol distillation column according to claim 9, characterized in that, There are two pipes connecting the second-stage adsorption tower group to the B scrubbing tower. Both pipes are connected to the bottom of the second-stage adsorption tower group. One pipe is connected to the top of the B scrubbing tower, and the other pipe is connected to the bottom of the B scrubbing tower. There are two pipes connecting the carbon dioxide absorption tower and the carbon dioxide desorption tower. One pipe is connected to the bottom of the B scrubbing tower at one end and to the upper middle part of the carbon dioxide desorption tower at the other end. The other pipe is connected to the upper middle part of the B scrubbing tower at one end and to the bottom of the carbon dioxide desorption tower at the other end. These two pipes exchange heat through a heat exchanger.

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