A method and system for recovering methanol, dimethyl ether, methyl formate in non-condensable gas of a methanol rectification column

Abstract

The application discloses a method for recycling methanol, dimethyl ether and methyl formate in non-condensable gas of a methanol rectification tower, and belongs to the field of chemistry, which comprises the following steps: compressing the non-condensable gas of the methanol rectification tower, absorbing and washing the non-condensable gas by using methanol liquid, carrying out temperature swing adsorption, vaporizing, absorbing carbon dioxide and purifying by rectification, recycling the methanol, dimethyl ether and methyl formate in the non-condensable gas of the methanol rectification tower, and burning the gas after the temperature swing adsorption by using a flare. The methanol, dimethyl ether and methyl formate in the non-condensable gas of the methanol rectification tower are recycled.

Description

Technical Field

[0001] This invention relates to methanol production, and particularly to a method and system for recovering methanol, dimethyl ether, and methyl formate from non-condensable gas in a methanol distillation column. Background Technology

[0002] During methanol distillation, the generated non-condensable gas contains methanol, dimethyl ether, and methyl formate. Current processes treat this non-condensable gas by washing it with water to absorb some of the methanol, dimethyl ether, and methyl formate. The wash solution is then sent to a methanol distillation column to purify the methanol. The washed non-condensable gas is then sent to a flare for combustion. The methanol content in the wash solution is between 8% and 15%, and the washed non-condensable gas contains 5% to 10% methanol. Because dimethyl ether and methyl formate have only trace solubility in water, their content in the non-condensable gas increases by 10% to 20% after washing, reaching 20% ​​to 50%.

[0003] The existing processing methods have the following drawbacks:

[0004] (1) Sending the washing liquid containing 8%-15% methanol to the methanol distillation column for distillation increases the steam consumption of the distillation process.

[0005] (2) Sending the non-condensable gas after water washing to the flare for combustion not only wastes methanol, dimethyl ether, and methyl formate, but also increases the carbon emissions from the flare combustion, which is neither economical nor environmentally friendly.

[0006] The above background information is provided to facilitate understanding of the present invention and is not intended to be publicly known technology disclosed to the general public prior to the application of this invention. Summary of the Invention

[0007] In view of the above-mentioned defects, the present invention provides a solution that aims to improve at least one of the problems mentioned in the background art.

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

[0009] 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.

[0010] Furthermore, the methanol washing and absorption is a two-stage washing process, wherein the first stage washing is carried out in washing tower A and the second stage washing 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 the second stage washing is refluxed and part of it is devastated.

[0011] 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.

[0012] 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.

[0013] Furthermore, 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 gases in the non-condensable gas of the methanol distillation column are liquefied and absorbed into liquid methanol.

[0014] 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.

[0015] Furthermore, the working process of the first-stage adsorption tower group is as follows: the gas washed by the A scrubbing tower enters the first-stage adsorption tower group, where the adsorbent in the regenerated adsorption tower bed absorbs the 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 the liquefaction partial pressure, forming a gas-liquid mixture of methanol, dimethyl ether, and methyl formate inside the adsorbent. When the methanol, dimethyl ether, and methyl formate in the upper bed of the adsorbent approach the design target of 0.01%, the operation is switched to another regenerated adsorption tower in the first-stage adsorption tower group. The first-stage adsorption tower, after reaching adsorption saturation, undergoes isobaric backflushing by heating the gas exiting from the top of the adsorption tower in the adsorption state to 150-180 degrees Celsius. This backflushing removes a high-concentration gas-liquid mixture of methanol, dimethyl ether, and methyl formate from the adsorbent, blowing it down from top to bottom. 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 cooling the gas exiting from the top of the adsorption tower in the adsorption state. The adsorption towers in the first-stage adsorption tower group alternately undergo adsorption, regeneration, and cooling to complete the first-stage adsorption.

[0016] 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.

[0017] Furthermore, 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, wherein the gas undergoes temperature-switching adsorption, and the liquid gradually accumulates in the A washing tower, and the accumulated liquid is the washing liquid of the A washing tower.

[0018] 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.

[0019] The present invention also provides a system for recovering methanol, dimethyl ether, and methyl formate from the non-condensable gas of a methanol distillation column.

[0020] The technical solution is as follows: A system for recovering methanol, dimethyl ether, and methyl formate from the non-condensable gas of a methanol distillation column as described above, comprising: a compressor, a scrubbing tower A, a first-stage adsorption tower group, a second-stage adsorption tower group, and a scrubbing tower B, wherein the scrubbing tower A is connected to the compressor, the scrubbing tower B, and the first-stage adsorption tower group respectively via pipelines, the first-stage adsorption tower group is also connected to the scrubbing tower B and the second-stage adsorption tower group respectively via pipelines, and the second-stage adsorption tower group is also connected to the scrubbing tower B via a pipeline.

[0021] Furthermore, the first-stage adsorption tower group includes adsorption tower A, adsorption tower B, and adsorption tower C, wherein the top and bottom of each adsorption tower A, adsorption tower B, and adsorption tower C are connected to interconnected pipes, and a first programmable valve group, a second programmable valve group, a third programmable valve group, a ninth programmable valve group, a tenth programmable valve group, and an eleventh programmable valve group are installed on the pipes; the second-stage adsorption tower group includes adsorption tower D, adsorption tower E, and adsorption tower F, wherein the top and bottom of each adsorption tower D, adsorption tower E, and adsorption tower F are connected to interconnected pipes, and a fourth programmable valve group, a fifth programmable valve group, a sixth programmable valve group, a seventh programmable valve group, and an eighth programmable valve group are installed on the pipes.

[0022] Furthermore, an A regeneration gas heater is installed on the installation pipeline of the third programmable 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] Furthermore, 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 via a pipeline. The vaporization tower is also connected to the methyl formate distillation tower and the carbon dioxide absorption tower via pipelines. The carbon dioxide absorption tower and the carbon dioxide desorption tower are connected via pipelines.

[0024] Furthermore, there are two pipes connecting the second-stage adsorption tower group to the B washing 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 washing tower, and the other pipe is connected to the bottom of the B washing tower. There are also two pipes connecting the carbon dioxide absorption tower and the carbon dioxide desorption tower. One pipe is connected to the bottom of the B washing 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 washing 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.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] This invention utilizes compression, washing and absorption, temperature-switching adsorption, vaporization, carbon dioxide absorption, and distillation purification to liquefy and fully recover methanol, dimethyl ether, and methyl formate from the feed gas. Only small amounts of methanol, dimethyl ether, and methyl formate are discharged from the system while meeting emission standards. This reduces losses from traditional flare combustion processes and ensures that methanol, dimethyl ether, and methyl formate in the exhaust gas are discharged under national standards, resulting in significant economic and environmental benefits.

[0027] This invention utilizes the heating of the tail gas at the top of the first-stage adsorption tower to backflush the adsorption bed, resulting in very low energy consumption. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the process flow of the present invention.

[0029] In the diagram: 1. Raw material gas pipeline; 2. Compressor; 3. Scrubber A; 4. First cooler; 5. First circulating pump; 6. Methanol level regulating valve; 7. Scrubber A outlet pipeline; 8. Purge gas pressure reducing regulating valve; 9. Scrubber B; 10. Second cooler; 11. Second circulating pump; 12. Scrubber B level regulating valve; 13. Mixed liquid to vaporization tower pipeline; 14. Vaporization tower; 15. Carbon dioxide absorption tower; 16. Vaporization tower reboiler; 17. Formic acid. Ester distillation column; 18. Absorption liquid circulation pump; 19. Fresh liquid reflux pump; 20. Crude methanol pressurization 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. Tertiary cooler; 28. Carbon dioxide stripping column; 29. ​​Circulating heater; 30. Liquid circulation pump; 31. Dimethyl ether reflux pump; 32. Dimethyl ether collection... 33. Dimethyl ether outlet pipeline; 34. Dimethyl ether condenser; 35. Desorption gas return pipe B; 36. Carbon dioxide vent pipe; 37. Desorption gas return pipe A; 38. Secondary regeneration gas pipeline; 39. Adsorption tower A; 40. Adsorption tower B; 41. Adsorption tower C; 42. Adsorption tower D; 43. Adsorption tower E; 44. Adsorption tower F; 45. Regeneration gas heater A; 46. Regeneration gas heater B; 47. First programmable valve group; 48. Secondary programmable valve group. 49. Pressure boosting valve; 50. Third control valve group; 51. Fourth control valve group; 52. Fifth control valve group; 53. Sixth control valve group; 54. Seventh control valve group; 55. Eighth control valve group; 56. Cooling gas outlet pipe of adsorption tower; 57. Tail gas outlet main pipe; 58. Pressure regulating valve; 59. Flow regulating valve; 60. Ninth control valve group; 61. Tenth control valve group; 62. Eleventh control valve group; 63. Secondary scrubbing tower outlet main pipe. Detailed Implementation

[0030] As used in this article:

[0031] "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0032] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0033] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including 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 its endpoints and all integers and fractions within that range.

[0034] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be construed as limiting the scope of this application. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0036] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

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

[0038] In this invention, adsorption tower A 39, adsorption tower B 40, and adsorption tower C 41 form a first-stage adsorption tower group. When adsorption tower A 39 is in the adsorption state, adsorption tower B 40 is in the cooling state, adsorption tower C 41 is in the desorption and regeneration state, and so on (for example, when adsorption tower B 40 is in the adsorption state, adsorption tower A 39 is in the desorption and regeneration state, and adsorption tower C 41 is in the cooling state). For the same adsorption tower in the first-stage adsorption tower group, such as adsorption tower A 39, the adsorption state, desorption and regeneration state, and cooling state are cyclically performed.

[0039] In this invention, 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 this invention, adsorption tower 42 (D), adsorption tower 43 (E), and adsorption tower 44 (F) form a second-stage adsorption tower group. When adsorption tower 42 is in the adsorption state, adsorption tower 43 is in the cooling state, and adsorption tower 44 is in the desorption / regeneration state, and so on (for example, when adsorption tower 43 is in the adsorption state, adsorption tower 42 is in the desorption / regeneration state, and adsorption tower 44 is in the cooling state). For the same adsorption tower in the second-stage adsorption tower group, such as adsorption tower 42 (D), the adsorption state, desorption / regeneration state, and cooling state are cyclically performed.

[0041] In this invention, the purpose of temperature-switching adsorption is to completely adsorb methanol, dimethyl ether, and methyl formate from the raw gas into the adsorbent, and the purpose of distillation purification is to purify methyl formate and dimethyl ether in the mixed liquid to commercial grade requirements.

[0042] In this invention, the purge gas pressure reducing regulating valve 8, pressure regulating valve 58, and flow regulating valve 59 are used in coordination to complete the gas separation purging of the first-stage temperature-switching adsorption (first-stage adsorption tower group) and the second-stage temperature-switching adsorption (second-stage adsorption tower group), with each gas separation ratio accounting for 50%.

[0043] A process for recovering methanol, dimethyl ether, and methyl formate from non-condensable gas in a methanol distillation column includes the following steps:

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

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

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

[0047] S22, First-stage adsorption, first-stage desorption and regeneration, and first-stage cooling: Gas from the outlet pipe 7 of scrubbing tower A enters the first-stage adsorption tower group for adsorption (assuming that adsorption tower A 39 is in adsorption state, adsorption tower C 41 is in desorption and regeneration state, and adsorption tower B 40 is in cooling state). At the bottom of adsorption tower A 39, the gas exiting from the upper part of adsorption tower A 39 (hereinafter referred to as non-condensable gas after first-stage adsorption) is used for cooling. 50% of the non-condensable gas after first-stage adsorption is sent to adsorption tower B 40 as cooling gas, and the other 50% of the non-condensable gas after first-stage adsorption is sent to adsorption tower C 41 via regeneration gas heater 45 to purge and regenerate the adsorption bed. The first-stage adsorption tower group operates in a cycle of adsorption, regeneration, and adsorption to complete the first-stage adsorption.

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

[0049] In this step, the desorbed gas after being desorbed by adsorption tower 41 goes to washing tower 9 by desorbed gas return pipe A 37 and purge gas pressure reducing regulating valve 8; the gas after entering adsorption tower 40 and cooling it enters secondary regeneration gas pipeline 38, is heated by B regeneration gas heater 46 installed on it, and then enters the second-stage adsorption tower group for purging and desorption.

[0050] In this step, the first-stage adsorption tower group achieves the following 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: one adsorption tower is in the adsorption state, another adsorption tower is in the desorption and regeneration state, and the last adsorption tower is in the cooling state.

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

[0052] S23: Second stage washing: The desorbed gas from the first stage adsorption tower group enters the B washing tower 9 for washing. The washed gas enters the outlet main pipe 63 of the second stage washing tower. The mixed liquid enters the mixed liquid to gasification tower pipeline 13. The mixed liquid from the A washing tower 3 is continuously fed into the B washing tower 9 as washing liquid through the first mixed liquid pipeline via the methanol level regulating valve 6.

[0053] S24: Second-stage adsorption, second-stage desorption and regeneration, and second-stage cooling: Gas from the outlet manifold 63 of the second-stage scrubbing tower enters the second-stage adsorption tower group (assuming that adsorption tower 42 D is in adsorption mode, adsorption tower 43 E is in cooling mode, and adsorption tower 44 F is in desorption and regeneration mode). After adsorption, the gas at the upper outlet of adsorption tower 42 D (hereinafter referred to as the non-condensable gas after second-stage adsorption) is used as cooling gas. The desorption gas of adsorption tower 44 F is the gas from the second-stage regeneration gas pipeline 38. The second-stage adsorption tower group performs adsorption, regeneration, and adsorption cycle operations to complete the second-stage adsorption.

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

[0055] In this step, the non-condensable gas after the second-stage adsorption enters adsorption tower E 43. After being cooled, the gas passes through the cooling gas outlet pipe 56 and is discharged through the tail gas outlet main pipe 57. The desorbed gas from adsorption tower F 44 is sent to washing tower B 9 for washing via desorbed gas return pipe B 35.

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

[0057] S3, Vaporization and Distillation Purification: The mixed liquid from washing tower 9 is continuously fed into vaporization tower 14 via the mixed liquid to vaporization tower pipeline 13 through the level regulation 12 of washing tower B. In vaporization tower 14, the carbon dioxide and dimethyl ether in the mixed liquid are vaporized. The vaporized gas is sent to carbon dioxide absorption tower 15. After treatment in carbon dioxide absorption tower 15, the gas enters dimethyl ether condenser 34 for condensation, and finally, dimethyl ether product is obtained through product dimethyl ether outlet pipeline 33. The mixed liquid at the bottom of vaporization tower 14 is treated by methyl formate distillation tower 17 and then obtained as methyl formate product through product methyl formate outlet pipeline 24. The crude methanol from the bottom of methyl formate distillation tower 17 is sent out of the system to the methanol distillation tower by crude methanol pressurization pump 20.

[0058] In this step, the dimethyl ether condensate from the dimethyl ether condenser 34 is collected in the dimethyl ether collection tank 32. Part of the dimethyl ether condensate from the collection tank 32 is pumped by the dimethyl ether reflux pump 31 into the dimethyl ether outlet pipe 33, while 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 via the absorption liquid circulation pump 18 and the heat exchanger 26.

[0059] In this step, the gas coming out from the top of the methyl formate distillation column 17 is condensed by the methyl formate condenser 25, and the methyl formate condensate enters the methyl formate collection tank 23 for collection. Part of the methyl formate liquid in the methyl formate collection tank 23 is returned to the methyl formate distillation column 17 by the methyl formate reflux pump 22, and the other part enters the product methyl formate outlet pipe 24.

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

[0061] In this step, the liquid coming out from the bottom of the carbon dioxide stripping tower 28 returns to the carbon dioxide absorption tower 15 via the fresh liquid reflux pump 19, heat exchanger 26 and third cooler 27, while the liquid coming out from the middle of the carbon dioxide stripping tower 28 returns to the carbon dioxide stripping tower 28 via the liquid circulation pump 30 and circulation heater 29.

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

[0063] In this invention, the working process of the first-stage adsorption tower group is as follows: The adsorbent in the regenerated adsorption tower bed of the first-stage adsorption tower group 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 the liquefaction partial pressure, forming a gas-liquid mixture of methanol, dimethyl ether, and methyl formate inside the adsorbent. When the methanol, dimethyl ether, and methyl formate content in the upper bed of the adsorbent approaches the design target of 0.01%, the operation is switched to another regenerated adsorption tower in the first-stage adsorption tower group; the adsorption of the first-stage adsorption tower group is saturated. In the adsorption tower of the first-stage adsorption tower group, the gas exiting from the top of the adsorption tower in the adsorption state is heated to 150-180 degrees Celsius for isobaric backflushing. The high-concentration gas-liquid mixture of methanol, dimethyl ether, and methyl formate in the adsorbent is blown out from top to bottom. After being cooled by a cooler, it goes to the B washing tower where it is washed with room-temperature methanol liquid and liquefied, thus regenerating the adsorbent. The regenerated adsorption tower of the first-stage adsorption tower group is cooled by the gas exiting from the top of the adsorption tower in the adsorption state of the first-stage adsorption tower group. The adsorption towers of the first-stage adsorption tower group alternately perform adsorption, regeneration, and cooling to complete the first-stage adsorption.

[0064] In the present invention, in the initial stage of system operation, the A scrubbing tower 3 does not require additional introduction of methanol liquid. The pressurized fluid coming from the compressor 2 is separated in the A scrubbing tower 3. The gas goes to adsorption through the outlet pipeline 7 of the A scrubbing tower, and the liquid accumulates gradually in the A scrubbing tower 3 (the accumulated liquid is methanol liquid). After the liquid level accumulates to the required level, the methanol liquid level regulating valve 6 is opened for liquid level regulation. Similarly, in the initial stage of system operation, the B scrubbing tower 9 also does not require additional introduction of methanol liquid. The desorbed gas coming out of the first-stage adsorption tower group and the desorbed gas coming out of the second-stage adsorption tower group are separated in the B scrubbing tower 9. The gas is discharged through the outlet main pipe 63 of the secondary scrubbing tower from the gas outlet of the B scrubbing tower 9, and the liquid accumulates gradually in the B scrubbing tower 9. After the liquid level accumulates to the required level, the B scrubbing tower liquid level regulator 12 is opened for liquid level regulation. During the accumulation process of the washing liquid, the washing liquid coming from the A scrubbing tower 3 may also be involved.

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

[0066] In one or more specific embodiments of the present invention, the operating pressure of the A scrubbing tower is 0.3 - 0.5 Mpa.

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

[0068] In one or more specific embodiments of the present invention, 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 invention, since the A scrubbing tower 3 and B scrubbing tower 9 are methanol scrubbing towers, they capture methanol, dimethyl ether, and methyl formate droplet gas foams, and most of the methanol, dimethyl ether, and methyl formate gases in the raw material gas are liquefied and absorbed into the liquid methanol. In this process, the temperature of the methanol liquid will gradually increase due to the liquefaction of methanol, dimethyl ether, and methyl formate gases. Therefore, in one or more specific embodiments of the present invention, the first mixed liquid pipeline is connected with a first return liquid pipe, and a first circulation pump 5 and a first cooler 4 are installed on the first return liquid pipe. A second circulation pump 11 and a second cooler 10 are installed on the pipeline 13 for the mixed liquid to go to the gasification tower. The temperature of the liquid methanol is reduced by the way of circulation pump + cooler, and preferably the temperature of the methanol circulating liquid is below 40 degrees.

[0070] Example 1

[0071] This example uses Figure 1 the process to treat the raw material gas, and the parameters of the raw material gas are as shown in Table 1 below.

[0072] Table 1

[0073]

[0074]

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

[0076] Table 2

[0077]

[0078] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0079] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the foregoing claims, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A method for recovering methanol, dimethyl ether, methyl formate from non-condensable gases in a methanol rectification column, characterized in that, Comprise: The non-condensable gas of the methanol rectification column is compressed, washed and absorbed by liquid methanol, subjected to temperature swing adsorption, vaporized, absorbed by carbon dioxide, and purified by rectification; The washing and absorption by liquid methanol is two-stage washing, wherein the first-stage washing is performed in an A washing tower, the second-stage washing is performed in a B washing tower, the washing liquid after the washing of the A washing tower is partially returned and partially introduced into the B washing tower to participate in the second-stage washing, and the washing liquid after the second-stage washing is partially returned and partially sent to vaporization; The temperature swing adsorption is two-stage temperature swing adsorption, wherein the first-stage temperature swing adsorption is performed in a first-stage adsorption tower group, and the second-stage temperature swing adsorption is performed in a second-stage adsorption tower group, wherein the gas after the washing of the A washing tower is introduced into the first-stage adsorption tower group, the first-stage non-condensable gas after the first-stage temperature swing adsorption is partially heated to serve as desorption gas in the first-stage temperature swing adsorption, and the other part is first used as cooling gas in the first-stage adsorption and then heated to serve 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 introduced into the B washing tower to perform the second-stage washing, the total content of methanol, dimethyl ether and methyl formate in the second-stage non-condensable gas is less than 100 ppm, and the second-stage non-condensable gas is used as cooling gas in the second-stage temperature swing adsorption and then sent to a flare for combustion; In the vaporization, carbon dioxide absorption and rectification purification, the vaporization is performed in a vaporization tower, the carbon dioxide absorption is performed in a carbon dioxide absorption tower, and the rectification purification is performed in a methyl formate rectification tower; the vaporization tower is in communication with the methyl formate rectification tower and the carbon dioxide absorption tower respectively through pipelines; the carbon dioxide absorption tower is in communication with a carbon dioxide desorption tower through a pipeline; the liquid after the washing of the B washing tower is vaporized in the vaporization tower, absorbed by the carbon dioxide absorption tower and purified by rectification in the methyl formate rectification tower to obtain methanol, dimethyl ether and methyl formate products respectively, wherein the gas vaporized in the vaporization tower is treated by the carbon dioxide absorption tower to obtain the dimethyl ether product, the mixed liquid at the bottom of the vaporization tower is treated by the methyl formate rectification tower to obtain the methyl formate product, and crude methanol is obtained at the bottom of the methyl formate rectification tower.

2. The method according to claim 1, wherein in the first-stage washing, the mist and foam of methanol, dimethyl ether and methyl formate in the non-condensable gas of the methanol rectification column are captured to liquefy and absorb most of the gas of methanol, dimethyl ether and methyl formate in the liquid methanol; In the second-stage washing, the mist and foam of methanol, dimethyl ether and methyl formate in the desorption gas from the temperature swing adsorption are captured to liquefy and absorb most of the gas of methanol, dimethyl ether and methyl formate in the liquid methanol.

3. The method according to claim 1, wherein in the first-stage washing, the mist and foam of methanol, dimethyl ether and methyl formate in the non-condensable gas of the methanol rectification column are captured to liquefy and absorb most of the gas of methanol, dimethyl ether and methyl formate in the liquid methanol; ​ The working process of the first-stage adsorption tower group is as follows: the adsorbent in the regenerated bed of the first-stage adsorption tower group absorbs the gas 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 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 of the adsorbent approaches the design index of 0.01%, another regenerated adsorption tower of the first-stage adsorption tower group is switched to operation; 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, so that 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 liquefied after being cooled by a cooler and washed by the methanol liquid at room temperature in the B washing tower, 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; 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 bed of the second-stage adsorption tower group absorbs the gas 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 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 of the adsorbent approaches the design index of 0.01%, another regenerated adsorption tower of the second-stage adsorption tower group is switched to operation; 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, so that 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 liquefied after being cooled by a cooler and washed by the methanol liquid at room temperature in the B washing tower, 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.

4. The method for recovering the methanol, dimethyl ether and methyl formate in the non-condensable gas of the methanol rectification tower according to claim 1, wherein the initial formation process of the washing liquid in the A washing tower is as follows: the pressurized fluid formed by compressing the non-condensable gas of the methanol rectification tower is separated in the A washing tower, the gas is removed for temperature swing adsorption, and the liquid is gradually accumulated in the A washing tower to form the washing liquid of the A washing tower. ​ 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.

5. A system for recovering methanol, dimethyl ether, methyl formate from non-condensable gases in a methanol rectification column, which performs the method of any one of claims 1-4, characterized in that, Comprise: The compressor, the A washing tower, the first-stage adsorption tower group, the second-stage adsorption tower group and the B washing tower, wherein the A washing tower is respectively communicated with the compressor, the B washing tower and the first-stage adsorption tower group through pipelines, the first-stage adsorption tower group is respectively communicated with the B washing tower and the second-stage adsorption tower group through pipelines, and the second-stage adsorption tower group is communicated with the B washing tower through a pipeline.

6. The system for recovering methanol, dimethyl ether, methyl formate in non-condensable gas from a methanol rectification column according to claim 5, characterized in that, The first-stage adsorption tower group comprises the A adsorption tower, the B adsorption tower and the 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, and the pipelines are respectively installed with the first program-controlled valve group, the second program-controlled valve group, the third program-controlled valve group, the ninth program-controlled valve group, the tenth program-controlled valve group and the eleventh program-controlled valve group; the second-stage adsorption tower group comprises the D adsorption tower, the E adsorption tower and the 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, and the pipelines are respectively installed with the fourth program-controlled valve group, the fifth program-controlled valve group, the sixth program-controlled valve group, the seventh program-controlled valve group and the eighth program-controlled valve group.

7. The system for recovering methanol, dimethyl ether, methyl formate in non-condensable gas from a methanol rectification column according to claim 6, characterized in that, The third program-controlled valve group is further installed with the A regenerated gas heater, and the B regenerated gas heater is installed on the pipeline communicating the first-stage adsorption tower group with the second-stage adsorption tower group.

8. The system for recovering methanol, dimethyl ether, methyl formate in non-condensable gas from a methanol rectification column according to claim 5, characterized in that, Further comprising a vaporization tower, a carbon dioxide absorption tower, a methyl formate rectification tower and a carbon dioxide desorption tower, wherein the vaporization tower is communicated with the B washing tower through a pipeline.

9. The system for recovering methanol, dimethyl ether, methyl formate in non-condensable gas from a methanol rectification column according to claim 8, characterized in that, The pipeline communicating the second-stage adsorption tower group with the B washing tower has two pipelines, both of which are communicated with the bottom of the second-stage adsorption tower group, one of which is connected to the top of the B washing tower, and the other of which is connected to the lower part of the B washing tower; the pipeline communicating the carbon dioxide absorption tower with the carbon dioxide desorption tower has two pipelines, one end of one of which is connected to the bottom of the carbon dioxide absorption tower, and the other end of which is connected to the upper middle part of the carbon dioxide desorption tower, one end of the other pipeline is connected to the upper middle part of the carbon dioxide absorption tower, and the other end of which is connected to the bottom of the carbon dioxide desorption tower, and the two pipelines are heat-exchanged through a heat exchanger.

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