Process for purifying and recovering acetylene from BDO purge gas

Abstract

The invention relates to a process for purifying and recovering acetylene from BDO purge gas, which comprises an alkaline washing tower, a water washing tower, a gas-liquid separator, a purification tower and a gas outlet tempering stopper which are connected in sequence to form a system for purifying and recovering acetylene from BDO purge gas. Acetylene in purge gas generated in the ethynylation reaction process of a BDO production device is purified, recycled and reused in an alkali washing, water washing and adsorption mode, configuration is simple, the occupied area is small, operation is convenient, the acetylene gas recycling rate is high, the production cost is greatly reduced, and the acetylene gas recycling device can be widely applied to the technology for producing BDO through an acetylene-aldehyde method.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical gas processing, and in particular relates to a process for purifying and recovering acetylene from BDO purge gas. Background Art

[0002] 1,4-Butanediol, referred to as BDO, is one of the methanol product chains and an important basic organic chemical and fine chemical raw material. Its main derivatives include polybutylene terephthalate, polyurethane resin, spandex, γ-butyrolactone, N-methylpyrrolidone, etc. BDO derivatives are fine chemical products with high added value and are widely used in solvents, medicines, cosmetics, plasticizers, curing agents, pesticides, herbicides, foamed leather, fibers and engineering plastics. The main production technologies of 1,4-butanediol include the Reppe method, butadiene acetate method, propylene oxide method and maleic anhydride method. The Reppe method is also called the acetylene aldehyde method. First, acetylene and formaldehyde are reacted under the action of copper bismuth catalyst to produce crude 1,4-butynediol. Then, the crude 1,4-butynediol is purified and refined, and then reacted with hydrogen under the action of skeleton nickel catalyst to obtain 1,4-butanediol.

[0003] The acetylation reaction in the acetylenic aldehyde process for producing BDO is a cyclic reaction. The unreacted acetylene gas in the acetylation reactor circulates in the system. However, as the reaction proceeds, the impurity gas and organic substances such as formaldehyde and methanol in the circulating acetylene gas will accumulate more and more. Therefore, in order to improve the efficiency of the acetylation reaction, the impurity gas that affects the reaction efficiency is usually vented to the acetylene torch together with part of the acetylene gas for combustion, which wastes the acetylene gas. At the same time, in order to eliminate the black smoke generated by the combustion of acetylene gas, it is necessary to transport steam to the acetylene torch, and in order to ensure that the acetylene torch does not go out, it is necessary to increase the consumption of natural gas or hydrogen.

[0004] Chinese patent CN217829485U proposes a device for purifying and recovering acetylene from BDO exhaust gas. The device uses a pressure swing adsorption system to recover acetylene from BDO exhaust gas. Two or more PSA systems can be set according to the different requirements of downstream sections for acetylene concentration. However, the number of equipment is large, the floor space is large, and the cost is high.

[0005] Chinese patent CN113694698A discloses an acetylene tail gas recovery device for BDO production, including acetylene tail gas washing in a washing tower and then entering a tail gas compressor, passing through a deliquescence system after pressurization, and then entering an absorption tower after removing water and other small droplets, and then the tail gas after being absorbed by low-temperature methanol is sent to an acetylene torch, and the rich liquid enters a regeneration tower for regeneration, and the regenerated liquid at the bottom of the tower is returned to the absorption tower for recycling, and the acetylene is recovered at the top of the tower. The disadvantage of this invention is that it cannot remove unknown aldehydes and alcohols that may be produced in the acetylation reaction, so the purity of acetylene cannot be guaranteed.

[0006] In the basic chemical industry, most companies have realized the "chlor-alkali coal-electricity" integrated circular economy model. Calcium carbide reacts with water to produce acetylene, which can be used in the chlor-alkali industry to produce polyvinyl chloride and in the coal chemical industry as a raw material for producing BDO. Because, in order to improve the circular economy industry chain, it is necessary to invent a process for purifying and recovering acetylene from BDO purge gas, so that the recovered acetylene can be used for both BDO production and polyvinyl chloride production. Summary of the invention

[0007] Based on the problems existing in the prior art, the object of the present invention is to provide a process for purifying and recovering acetylene from BDO purge gas.

[0008] The object of the present invention is achieved through the following technical scheme: a process for purifying and recovering acetylene from BDO purge gas, comprising an alkali washing tower, a water washing tower, a gas-liquid separator, a purification tower, and an outlet gas flashback arrester connected in sequence, wherein the bottom of the alkali washing tower is connected to an alkali washing circulation pump, and the bottom of the water washing tower is connected to a water washing circulation pump and a water cooler, the alkali washing tower and the water washing tower are both packed towers, the purification tower adopts a combination of two purification towers in parallel, and the bottom of each purification tower is connected to a regenerative heat exchanger through a pipeline, and the above constitutes a system for purifying and recovering acetylene from BDO purge gas.

[0009] The process flow of purifying and recovering acetylene from BDO purge gas comprises: the purge gas generated in the acetylation reaction process of the BDO production device first enters an alkali washing tower, and is reversely contacted with a sodium hydroxide solution in the alkali washing tower to remove impurities such as carbon dioxide and methanol in the gas, and the sodium hydroxide solution is sent from the bottom of the alkali washing tower to the upper part of the alkali washing tower for recycling through an alkali washing circulation pump; the BDO purge gas flows out from the top of the alkali washing tower and enters a water washing tower, and is reversely contacted with process water in the water washing tower to further remove salt-containing substances in the gas; the crude acetylene after alkali washing and water washing flows out from the top of the water washing tower, enters the upper part of a gas-liquid separator to remove mechanical water, and then enters the bottom of a purification tower to remove unknown organic matter and part of dimethyl ether produced in the acetylation reaction process carried in the crude acetylene; the crude acetylene flows in from the bottom of the purification tower and flows out from the top of the tower, and then passes through a gas outlet backfire arrester and is sent to a subsequent stage for use.

[0010] Furthermore, programmable valves are provided on the inlet and outlet material pipelines of the purification tower and the regeneration heat exchanger. According to the pre-set program, when the purification tower I is in the adsorption process, the purification tower II is in the regeneration state; the regeneration step is to first purge and replace the acetylene in the purification tower II with nitrogen at room temperature, and then use the hot nitrogen heated by steam to regenerate the adsorbent in the purification tower II, the temperature of the hot nitrogen is controlled at 40°C~80°C, and finally the purification tower II is cooled with nitrogen at room temperature, and all the regeneration gas generated during the regeneration process is sent to the system flare for incineration.

[0011] Furthermore, the sodium hydroxide concentration is 2% to 5%.

[0012] Furthermore, the cooling medium of the water cooler is cooling water or cooling liquid at -10°C to -15°C, so that the process water temperature is controlled at 3°C ​​to 8°C.

[0013] The present invention adopts the method of "alkali washing + water washing + adsorption" to purify and recycle the acetylene purge gas generated in the acetylation reaction process of the BDO production device. The invention has simple configuration, small footprint, convenient operation, high acetylene gas recovery rate, and greatly reduces the production cost. The purified and recovered acetylene product gas can be used as a raw material for producing BDO in the coal chemical industry, and can also be used as a raw material for producing vinyl chloride in the chlor-alkali industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a simplified flow chart of the present invention.

[0015] Figure 1 Among them, 1 is an alkali washing tower, 2 is an alkali washing circulation pump, 3 is a water washing tower, 4 is a water washing circulation pump, 5 is a water cooler, 6 is a gas-liquid separator, 7 is a regenerative heat exchanger, 8 is a program-controlled valve, 9 is a purification tower I, 10 is a purification tower II, and 11 is an outlet gas backfire arrester. DETAILED DESCRIPTION Example 1

[0016] See attached Figure 1 A process for purifying and recovering acetylene from BDO purge gas, specifically comprising an alkali washing tower, a water washing tower, a gas-liquid separator, a purification tower, and an outlet gas flashback arrester connected in sequence, wherein the bottom of the alkali washing tower is connected to an alkali washing circulation pump, and the bottom of the water washing tower is connected to a water washing circulation pump and a water cooler, the alkali washing tower and the water washing tower are both packed towers, the purification tower adopts a combination of two purification towers in parallel, and the bottom of each purification tower is connected to a regenerative heat exchanger through a pipeline, and the above constitutes a system for purifying and recovering acetylene from BDO purge gas.

[0017] The process flow of purifying and recovering acetylene from BDO purge gas comprises: the purge gas generated in the acetylation reaction process of the BDO production device first enters an alkali scrubber, and is reversely contacted with a 2% sodium hydroxide solution in the alkali scrubber to remove impurities such as carbon dioxide and methanol in the gas, and the sodium hydroxide solution is sent from the bottom of the alkali scrubber to the top of the alkali scrubber for recycling through an alkali scrubber circulation pump; the BDO purge gas flows out from the top of the alkali scrubber into a water scrubber, and is reversely contacted with process water in the water scrubber to further remove impurities such as carbon dioxide and methanol in the gas. The cooling medium of the water cooler is -15℃ cooling water, so that the process water temperature is controlled at 3℃; the crude acetylene after alkali washing and water washing flows out from the top of the water washing tower, enters the upper part of the gas-liquid separator to remove mechanical water, and then enters the bottom of the purification tower to remove unknown organic matter and part of dimethyl ether produced in the acetylation reaction carried by the crude acetylene; the crude acetylene flows into the bottom of the purification tower and flows out from the top of the tower, and then passes through the outlet gas backfire arrester to obtain the product gas with acetylene content ≥95 (wt)% and is sent to the subsequent stage for use.

[0018] Programmable valves are provided on the inlet and outlet material pipelines of the purification tower and the regeneration heat exchanger. According to the pre-set program, when the purification tower I is in the adsorption process, the purification tower II is in the regeneration state; the regeneration step is to first purge and replace the acetylene in the purification tower II with nitrogen at room temperature, and then use the hot nitrogen heated by steam to regenerate the adsorbent in the purification tower II, the temperature of the hot nitrogen is controlled at 40°C, and finally the purification tower II is cooled with nitrogen at room temperature, and the regeneration gas generated during the regeneration process is all sent to the system flare for incineration. Example 2

[0019] Refer to the attached Figure 1 A process for purifying and recovering acetylene from BDO purge gas, specifically comprising an alkali washing tower, a water washing tower, a gas-liquid separator, a purification tower, and an outlet gas flashback arrester connected in sequence, wherein the bottom of the alkali washing tower is connected to an alkali washing circulation pump, and the bottom of the water washing tower is connected to a water washing circulation pump and a water cooler, the alkali washing tower and the water washing tower are both packed towers, the purification tower adopts a combination of two purification towers in parallel, and the bottom of each purification tower is connected to a regenerative heat exchanger through a pipeline, and the above constitutes a system for purifying and recovering acetylene from BDO purge gas.

[0020] The process flow of purifying and recovering acetylene from BDO purge gas comprises: the purge gas generated in the acetylation reaction process of the BDO production device first enters an alkali scrubber, and is reversely contacted with a sodium hydroxide solution with a concentration of 4% in the alkali scrubber to remove impurities such as carbon dioxide and methanol in the gas, and the sodium hydroxide solution is sent from the bottom of the alkali scrubber to the top of the alkali scrubber for recycling through an alkali scrubber circulation pump; the BDO purge gas flows out from the top of the alkali scrubber into a water scrubber, and is reversely contacted with process water in the water scrubber to further remove impurities such as carbon dioxide and methanol in the gas. The cooling medium of the water cooler is -13℃ cooling water, so that the process water temperature is controlled at 6℃; the crude acetylene after alkali washing and water washing flows out from the top of the water washing tower, enters the upper part of the gas-liquid separator to remove mechanical water, and then enters the bottom of the purification tower to remove unknown organic matter and part of dimethyl ether produced in the acetylation reaction carried by the crude acetylene; the crude acetylene flows into the bottom of the purification tower and flows out from the top of the tower, and then passes through the outlet gas backfire arrester to obtain the product gas with acetylene content ≥95 (wt)% and is sent to the subsequent stage for use.

[0021] Programmable valves are provided on the inlet and outlet material pipelines of the purification tower and the regeneration heat exchanger. According to the pre-set program, when the purification tower II is in the adsorption process, the purification tower I is in the regeneration state; the regeneration step is to first purge and replace the acetylene in the purification tower II with nitrogen at room temperature, and then regenerate the adsorbent in the purification tower II with hot nitrogen heated by steam, the temperature of the hot nitrogen is controlled at 60°C, and finally, the purification tower II is cooled with nitrogen at room temperature, and all the regeneration gas generated during the regeneration process is sent to the system flare for incineration. Example 3

[0022] See attached Figure 1 A process for purifying and recovering acetylene from BDO purge gas, specifically comprising an alkali washing tower, a water washing tower, a gas-liquid separator, a purification tower, and an outlet gas flashback arrester connected in sequence, wherein the bottom of the alkali washing tower is connected to an alkali washing circulation pump, and the bottom of the water washing tower is connected to a water washing circulation pump and a water cooler, the alkali washing tower and the water washing tower are both packed towers, the purification tower adopts a combination of two purification towers in parallel, and the bottom of each purification tower is connected to a regenerative heat exchanger through a pipeline, and the above constitutes a system for purifying and recovering acetylene from BDO purge gas.

[0023] The process flow of purifying and recovering acetylene from BDO purge gas comprises: the purge gas generated in the acetylation reaction process of the BDO production device first enters an alkali scrubber, and is reversely contacted with a 5% sodium hydroxide solution in the alkali scrubber to remove impurities such as carbon dioxide and methanol in the gas, and the sodium hydroxide solution is sent from the bottom of the alkali scrubber to the top of the alkali scrubber for recycling through an alkali scrubber circulation pump; the BDO purge gas flows out from the top of the alkali scrubber into a water scrubber, and is reversely contacted with process water in the water scrubber to further remove impurities such as carbon dioxide and methanol in the gas. The cooling medium of the water cooler is -10℃ cooling water, so that the process water temperature is controlled at 8℃; the crude acetylene after alkali washing and water washing flows out from the top of the water washing tower, enters the upper part of the gas-liquid separator to remove mechanical water, and then enters the bottom of the purification tower to remove unknown organic matter and part of dimethyl ether produced in the acetylation reaction carried by the crude acetylene; the crude acetylene flows into the bottom of the purification tower and flows out from the top of the tower, and then passes through the outlet gas backfire arrester to obtain the product gas with acetylene content ≥95 (wt)% and is sent to the subsequent stage for use.

[0024] Programmable valves are provided on the inlet and outlet material pipelines of the purification tower and the regeneration heat exchanger. According to the pre-set program, when the purification tower II is in the adsorption process, the purification tower I is in the regeneration state; the regeneration step is to first purge and replace the acetylene in the purification tower II with nitrogen at room temperature, and then use the hot nitrogen heated by steam to regenerate the adsorbent in the purification tower II, the temperature of the hot nitrogen is controlled at 80°C, and finally the purification tower II is cooled with nitrogen at room temperature, and the regeneration gas generated during the regeneration process is all sent to the system flare for incineration.

[0025] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A process for purifying and recovering acetylene from BDO purge gas, characterized in that: The device comprises an alkali washing tower, a water washing tower, a gas-liquid separator, a purification tower, and an outlet gas flashback arrester which are connected in sequence. The bottom of the alkali washing tower is connected to an alkali washing circulation pump, the bottom of the water washing tower is connected to a water washing circulation pump and a water cooler, and the bottom of the purification tower is also connected to a regenerative heat exchanger through a pipeline. The purification tower adopts a combination of two purification towers in parallel, and the above constitutes a system for purifying and recovering acetylene from BDO purge gas; The process flow for purifying and recovering acetylene from BDO purge gas comprises: the purge gas generated during the acetylation reaction of the BDO production device first enters an alkali scrubber, and is reversely contacted with a sodium hydroxide solution in the alkali scrubber to remove impurities such as carbon dioxide and methanol in the gas, and the sodium hydroxide solution is sent from the bottom of the alkali scrubber to the top of the alkali scrubber for recycling through an alkali scrubber circulation pump; the BDO purge gas flows out from the top of the alkali scrubber into a water scrubber, and is reversely contacted with process water in the water scrubber to further remove salt-containing substances in the gas; The crude acetylene after alkali washing and water washing flows out from the top of the water washing tower, enters the upper part of the gas-liquid separator to remove mechanical water, and then enters the bottom of the purification tower to remove unknown organic matter and part of dimethyl ether produced in the acetylation reaction carried in the crude acetylene; the crude acetylene flows into the bottom of the purification tower and flows out from the top of the tower, and then passes through the outlet gas backfire arrester and is sent to the subsequent section for use.

2. The process for purifying and recovering acetylene from BDO purge gas according to claim 1, characterized in that: Programmable valves are provided on the inlet and outlet material pipelines of the purification tower and the regeneration heat exchanger. According to the pre-set program, when the purification tower I is in the adsorption process, the purification tower II is in the regeneration state; the regeneration step is to first purge and replace the acetylene in the purification tower II with nitrogen at room temperature, and then use the hot nitrogen heated by steam to regenerate the adsorbent in the purification tower II, the temperature of the hot nitrogen is controlled at 40°C~80°C, and finally the purification tower II is cooled with nitrogen at room temperature, and the regeneration gas generated during the regeneration process is all sent to the system flare for incineration.

3. The process for purifying and recovering acetylene from BDO purge gas according to claim 1, characterized in that: The alkali washing tower and the water washing tower are both packed towers.

4. The process for purifying and recovering acetylene from BDO purge gas according to claim 1, characterized in that: The sodium hydroxide concentration is 2% to 5%.

5. The process for purifying and recovering acetylene from BDO purge gas according to claim 1, characterized in that: The cooling medium of the water cooler is cooling water or cooling liquid at -10°C to -15°C, so that the process water temperature is controlled at 3°C ​​to 8°C.

6. The process for purifying and recovering acetylene from BDO purge gas according to claim 1, characterized in that: The acetylene content in the acetylene product gas at the outlet of the gas backfire arrester is ≥95 (wt)%.

Images