Process and apparatus for recovering hydrogen purge gas containing soluble volatile organic compounds

Abstract

A hydrogen purge gas recovery process and device containing soluble volatile organic compounds, high-pressure purge gas is sent into the membrane absorber through pressure reduction and mass transfer with the countercurrent absorption liquid between the membranes, VOC gas is dissolved in the absorption liquid for removal, and the saturated absorption liquid is discharged for reuse; after preliminary removal of VOC through the membrane absorber, the purge gas enters the adsorber for further purification and is sent to the PSA outside the boundary for recovery; after the adsorption bed is saturated, vacuum heating is used for desorption, and the desorption gas is condensed for recovery. The process uses the pressure of the purge gas itself, carries out low-load adsorption treatment through the series connection of high-efficiency membrane absorption, and the water and VOC contents in the outlet hydrogen are extremely low, so that the hydrogen can be directly recovered by the hydrogen PSA, and the VOC is recovered through the absorption liquid and the desorption condenser; the device provided by the application has the advantages of simple process, few control points, safety and stability, small and compact equipment, no secondary pollution, low energy consumption, low investment and operation cost, good economic recovery, etc.

Description

Technical Field

[0001] This invention belongs to the field of volatile organic compound (VOC) separation and removal and gas recovery technology, specifically relating to a process and apparatus for treating and reusing VOC-containing hydrogen purge gas using membrane absorption and adsorption coupling. Background Technology

[0002] Catalytic hydrogenation is widely used in petroleum refining, chemical processing, and pharmaceutical synthesis. In refining and petrochemical processes, catalytic hydrogenation is used to refine products, perform fine separation, and remove impurities such as desulfurization, dearomatization, and demetallization, thereby obtaining more valuable fine petrochemical and chemical products. In practice, there are various forms such as catalytic reforming hydrogenation, hydrogenation refining, and selective hydrogenation.

[0003] Hydrogenation processes typically involve reactions at high pressures and temperatures to increase reaction rates and yields. However, during hydrogenation, the hydrogen concentration in the gas phase gradually decreases due to hydrogen consumption and the accumulation of impurities introduced by the hydrogen, reaction impurities, or light components in the gas phase. This ultimately severely impacts the reaction rate or product purity. Therefore, it is necessary to periodically release a portion of the purge gas through the reactor outlet while simultaneously replenishing it with fresh hydrogen to maintain the purity of the hydrogen in the reaction system. This purge gas is primarily composed of hydrogen but also contains high concentrations of organic components. Industrially, hydrogenation purge gas is usually treated by combustion methods such as flares. However, with the increasing emphasis on comprehensive, continuous environmental monitoring and energy conservation, emission reduction, and carbon reduction both domestically and internationally, direct flaring treatment not only fails to consistently meet standards but also fails to reduce emissions. Various regions have begun to require the use of other reasonable and effective processes for strict compliance with purification and recycling standards.

[0004] For hydrogen purge gas containing volatile organic compounds, the exhaust gas has a certain pressure and is usually intermittent with weak emission regularity. Conventional condensation methods are added at the outlet to minimize losses, depending on process requirements. Hydrogen itself is flammable and explosive, and cannot be purified using typical VOC gas treatment methods. It is necessary to consider removing VOCs without posing a safety risk. Furthermore, for hydrogen recovery, if the hydrogen, after preliminary VOC removal, is sent to the PSA for further purification and reuse, the requirements for inlet pressure and the concentration of hydrocarbons, oils, VOCs, and moisture content before entering downstream processes such as the PSA must be considered. Typically, it cannot be directly fed into the PSA unit of the hydrogen production system and must undergo pretreatment to ensure the inlet requirements are met.

[0005] For hydrogen purge gas with high VOC concentrations but small, intermittent, and unstable emissions, membrane separation for VOC removal is unsuitable due to its low inlet concentration. While traditional PSA processes can theoretically be used, their adsorption processes and materials are better suited for easily removing gaseous organic matter at room temperature. Otherwise, the PSA unit may lack sufficient adsorption capacity, requiring multiple stages or adsorption towers, or regeneration may be difficult and incomplete, affecting the purification rate. Furthermore, the process is lengthy and requires complex systems for pressure regulation, equalization, regeneration negative pressure, and heating, resulting in high investment and operating costs. The economic benefits are minimal for the amount of hydrogen recovered from the purge gas. If absorption processes are used to remove VOCs, pre-treatment gas-liquid entrainment can lead to the presence of absorbent liquids, such as organic absorbents or aqueous solutions, in the gas. These substances must not enter the hydrogen production PSA unit, necessitating complex devices for removing entrained liquids and gases. This process design is challenging and costly. Summary of the Invention

[0006] The purpose of this invention is to provide a hydrogen purge gas recovery device and process containing soluble volatile organic compounds, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A process for recovering hydrogen purge gas containing soluble volatile organic compounds includes the following steps:

[0009] Step 1: Hydrogen purge gas containing soluble volatile organic compounds is introduced into one side of the membrane in the membrane absorber, and absorbent is supplied to the other side of the membrane, so that the soluble volatile organic compounds are absorbed by the absorbent.

[0010] Step 2: The gas absorbed in the membrane absorber is sent to the adsorption device for further adsorption of soluble volatile organic compounds. After condensation to remove condensable gases, hydrogen is obtained.

[0011] The soluble volatile organic compounds include one or more of the following: hydrocarbons, alcohols, esters, ethers, and ketones.

[0012] The hydrogen content in the hydrogen purge gas can be above 80%, or even above 90% or 95%.

[0013] The content of soluble volatile organic compounds in the hydrogen purge gas can be 20%, 15%, 10%, or less than 5%.

[0014] The absorbent is an inorganic or organic absorbent. The inorganic absorbent is one or more of water, dilute acid, and dilute alkali; the organic absorbent is one or more of n-hexane, xylene, 1,2-dichloroethane, cyclohexanone, and ethylene glycol.

[0015] The membrane installed in the membrane absorber is a hollow fiber membrane, and the hollow fiber membrane material is one or a combination of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP), polysulfone (PSF / PSU), and polyethersulfone (PESU), with a membrane pore size of 20-500 nm.

[0016] In step 2, the adsorbent used in the adsorption device is one or more of activated carbon, molecular sieve, hydrophobic silica gel, or macroporous resin.

[0017] The hydrogen gas obtained in step 2 contains less than 10 ppm of soluble volatile organic compounds, or less than 15 ppm.

[0018] A hydrogen purge gas recovery device containing soluble volatile organic compounds, comprising:

[0019] Release gas control valve 1 is used to regulate the release gas pressure;

[0020] Membrane absorbers 21 and 2n, wherein a separation membrane is installed and connected to the purge gas control valve 1, are used to remove soluble volatile organic compounds in the purge gas by means of membrane absorption;

[0021] Absorbent storage tanks 31 and 3n are connected to the membrane absorber and are used to supply absorbent into the membrane absorber;

[0022] Adsorbers 6a and 6b are connected to membrane absorbers 21 and 2n and are used to adsorb and separate residual organic matter from the purge gas obtained in membrane absorbers 21 and 2n.

[0023] Condenser 8, connected to adsorbers 6a and 6b, is used to condense the gas obtained in the adsorber and remove condensable gases.

[0024] The separation membrane is a hollow fiber membrane, and the hollow fiber membrane material is one or a combination of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP), polysulfone (PSF / PSU), and polyethersulfone (PESU), with a membrane pore size of 20-500 nm.

[0025] The absorbent storage tanks 31 and 3n are filled with inorganic or organic absorbent liquid. The inorganic absorbent liquid is one or more of water, dilute acid, and dilute alkali. The organic absorbent liquid is one or more of n-hexane, xylene, 1,2-dichloroethane, cyclohexanone, and ethylene glycol.

[0026] One side of the separation membrane is connected to the absorbent storage tanks 31 and 3n, and the other side is connected to the venting control valve 1.

[0027] It also includes: circulation pumps 51 and 5n, which connect one side of the separation membrane to the absorbent storage tanks 31 and 3n, so as to circulate the absorbent between one side of the separation membrane and the absorbent storage tanks 31 and 3n.

[0028] It also includes: absorbent regulating valves 41 and 4n, connected to circulating pumps 51 and 5n, used to regulate the flow rate of absorbent supplied from circulating pumps 51 and 5n.

[0029] The membrane absorbers 21 and 2n are multi-stage.

[0030] The adsorbers 6a and 6b are multi-stage.

[0031] The adsorbers 6a and 6b are filled with one or more of activated carbon, molecular sieves, hydrophobic silica gel, or macroporous resin.

[0032] It also includes a receiving tank 9, which is connected to the condenser 8, for receiving condensed organic matter and discharging non-condensable gases.

[0033] Beneficial effects of this invention:

[0034] 1. Using a hollow fiber microporous membrane absorber to absorb organic matter in hydrogen purge gas allows the high pressure of the purge gas itself to overcome the huge pressure drop required by the membrane absorber, eliminating the need for additional high-pressure pumps, fans, or other pressurization power facilities, thus saving energy.

[0035] 2. Under high pressure, the huge gas-liquid contact area generated by the numerous micron and submicron pores on the surface of the membrane absorber is much larger than that of traditional packed towers and other absorbers. Therefore, the absorber has a high plate efficiency, a reduced number of absorption stages, and a much smaller equipment size.

[0036] 3. The hollow fiber membrane of the membrane absorber forms a macroscopic gas-liquid barrier effect as the gas-liquid contact surface. Therefore, there is no problem of gas-liquid entrainment or absorption liquid volatilization into the gas phase. As a result, the gas after passing through the membrane absorber basically does not contain absorption liquid components. Therefore, there is no need to set up condensation, defoaming and other removal processes to avoid damaging the downstream hydrogen production system PSA, further simplifying the process and equipment flow.

[0037] 4. After passing through one or more membrane absorbers, the VOC content in the gas entering the back-end adsorption system is already very low. At this point, the back-end adsorption system only serves as a gatekeeper to ensure that the concentration meets the inlet requirements of the hydrogen production PSA system. The processing load is very low, the regeneration frequency and difficulty are very low, the adsorption system can be designed to be very small, and the regeneration system can be simplified, and the operating cost is also much lower.

[0038] 5. Because the front-end membrane absorption efficiency is very high and the back-end adsorption system load is very low, the equipment size of this process device is much smaller than that of traditional processes. The process, equipment and control are simple, there are fewer equipment and pumps, the safety is high, the investment and operation and maintenance costs are low, and the economic benefits are promising. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the device structure of the present invention;

[0040] In the diagram: 1-Relief gas control valve; 21, 2n-Membrane absorbers; 31, 3n-Absorbent storage tanks; 41, 4n-Absorbent regulating valves; 51, 5n-Circulation pumps; 6a-First adsorber; 6b-Second adsorber; 7-Vacuum pump; 8-Condenser; 9-Receiving tank. Detailed Implementation

[0041] This patent addresses hydrogen purge gas containing soluble volatile organic compounds (VOCs), which can include one or more of hydrocarbons, alcohols, esters, ethers, and ketones. The hydrogen content in the purge gas can be above 80%, 90%, or 95%, and the VOC content can be below 20%, 15%, 10%, or 5%.

[0042] The hydrogen purge gas recovery process containing soluble volatile organic compounds provided by this invention includes the following steps:

[0043] S1: The high-pressure hydrogen purge gas containing soluble volatile organic compounds is reduced to the design pressure through the pressure reducing system 1 and then sent into the tube side of the membrane absorber 2. The absorbent is injected into the absorbent storage tank 3.

[0044] S2: The circulating pump 5 introduces the absorbent from the absorbent storage tank 3 into the shell side of the membrane absorber 2. The hydrogen purge gas and the absorbent flow counterclockwise on both sides of the membrane inside the membrane absorber 2 for mass transfer. The soluble organic gas in the hydrogen purge gas comes into efficient contact with the absorbent in the micron-sized pores of the membrane wall and is absorbed, thereby removing the organic matter from the purge gas and sending it to the downstream adsorption system.

[0045] S3: After the absorbent adsorbs organic matter in the hydrogen purge gas, it is sent to the absorbent storage tank 3 by the absorbent regulating valve 4. The absorbent that has absorbed organic matter is returned to the absorbent storage tank 3 for recycling through the pressure regulating valve 4. After the absorbent reaches the designed saturation concentration, it is discharged from the absorbent storage tank 3 to the designated recovery tank as saturated absorbent.

[0046] S4: The hydrogen purge gas from membrane absorber 2 is sent to the downstream adsorption system for further removal of VOC impurities, resulting in purge gas that meets the requirements for hydrogen production.

[0047] In step S2, a multi-stage membrane system is set up according to requirements. The outlet of the membrane absorber 21 tube of the first-stage membrane absorption system is connected to the inlet of the membrane absorber 22 tube of the second-stage membrane absorption system through a gas valve. The outlet of the membrane absorber 2n tube of the last-stage membrane absorption system is connected to the downstream adsorption system through a gas valve. The efficiency of removing VOC impurities from hydrogen purge gas is improved through multi-stage adsorption.

[0048] The back-end adsorption system is an adsorber. The adsorber uses pressure swing adsorption, temperature swing adsorption, or temperature swing pressure swing adsorption. The adsorbent used is one or more of activated carbon, molecular sieve, hydrophobic silica gel, or macroporous resin. Multiple materials can be mixed or layered. After the adsorber is saturated, the adsorbed organic matter is drawn out by vacuum pump 7, condensed by condenser 8, and discharged into receiving tank 9. Non-condensable gas is discharged to the tail gas purification device.

[0049] The back-end adsorption system is equipped with a first adsorber 6a and a second adsorber 6b. The inlets of the first and second adsorbers are each connected to the outlet of the membrane adsorption system via gas valves. The outlets of the first and second adsorbers are each connected to the outlet of the purge gas recovery device via gas valves. The adsorption method of the first adsorber 6a and the second adsorber 6b is pressure swing adsorption (PSA), temperature swing adsorption (TSA), or temperature swing pressure swing adsorption (TSA). The adsorbent used is one or more of activated carbon, molecular sieves, hydrophobic silica gel, or macroporous resin, either mixed or layered. Each of the adsorbers 6b is connected to a vacuum pump 7 via a gas valve. The other end of the vacuum pump 7 is connected to a condenser 8, and the condenser 8 is connected to a receiving tank 9. When the first adsorber 6a is working, the gas valve at the inlet of the second adsorber 6b is closed. When the first adsorber 6a is saturated, the gas valves at the inlet and outlet of the first adsorber 6a are closed, while the gas valves at the inlet and outlet of the second adsorber 6b are opened. At the same time, the gas valve connecting the first adsorber 6a to the vacuum pump 7 is opened. The vacuum pump 7 draws out the organic matter adsorbed in the first adsorber 6a, condenses it in the condenser 8, and discharges it into the receiving tank 9. The non-condensable gas is discharged to the tail gas purification device.

[0050] Based on the above technical approach, this patent can employ the following device:

[0051] A hydrogen purge gas recovery device containing soluble volatile organic compounds includes a membrane absorption system and a downstream adsorption system. The membrane absorption system includes a purge gas control valve 1, a membrane absorber 2, an absorbent storage tank 3, an absorbent regulating valve 4, and a circulation pump 5. One end of the membrane absorber 2 is connected to the purge gas control valve 1, and the other end is connected to the downstream adsorption system. One end of the absorbent regulating valve 4 is connected to the shell side of the membrane absorber 2 near the purge gas control valve 1, and the other end is connected to the absorbent storage tank 3. One end of the circulation pump 5 is connected to the absorbent storage tank. 3. The other end is connected to the shell side of the membrane absorber 2 away from the purge gas control valve 1. The hydrogen purge gas containing soluble volatile organic compounds is depressurized through the purge gas control valve 1 and sent to the tube side of the membrane absorber 2. The absorbent is injected into the absorbent storage tank 3 and introduced into the shell side of the membrane absorber 2 by the circulation pump 5. The hydrogen purge gas and the absorbent flow counterclockwise on both sides of the membrane inside the membrane absorber 2 for mass transfer. After the absorbent adsorbs the organic matter in the hydrogen purge gas, it is sent to the absorbent storage tank 3 by the absorbent regulating valve 4. The hydrogen purge gas is sent to the downstream adsorption system for treatment to meet the hydrogen production requirements.

[0052] The membrane absorption system has a multi-stage structure. In the first-stage membrane absorption system, the outlet of the membrane absorber 21 tube is connected to the inlet of the membrane absorber 22 tube in the second-stage membrane absorption system through a gas valve. The outlet of the membrane absorber 2n tube in the last-stage membrane absorption system is connected to the downstream adsorption system through a gas valve.

[0053] The membrane absorber 2 uses a hollow fiber membrane as the membrane module. The hollow fiber membrane material is one or more of the following: polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP), polysulfone (PSF / PSU), and polyethersulfone (PESU). The membrane pore size is 20-500 nm.

[0054] The absorbent can be an inorganic or organic absorbent. The inorganic absorbent is one or more of water, dilute acid, and dilute alkali; the organic absorbent is one or more of n-hexane, xylene, 1,2-dichloroethane, cyclohexanone, and ethylene glycol.

[0055] The back-end adsorption system is an adsorber, and the adsorption method of the adsorber is pressure swing adsorption, temperature swing adsorption or temperature swing pressure swing adsorption. The adsorbent used is one or more of activated carbon, molecular sieve, hydrophobic silica gel or macroporous resin, which are mixed or layered.

[0056] The adsorber 6 is connected to the vacuum pump 7 via a gas valve. The other end of the vacuum pump 7 is connected to the condenser 8, and the condenser 8 is connected to the receiving tank 9. The vacuum pump 7 draws out the organic matter adsorbed in the adsorber 6, which is then condensed by the condenser 8 and discharged into the receiving tank 9. The non-condensable gas is discharged to the tail gas purification device.

[0057] The back-end adsorption system is equipped with a first adsorber 6a and a second adsorber 6b. The air inlet of the first adsorber 6a and the air inlet of the second adsorber are each connected to the air outlet of the membrane adsorption system through an air valve. The air outlet of the first adsorber 6a and the air outlet of the second adsorber are each connected to the air outlet of the purge gas recovery device through an air valve. The adsorption method of the first adsorber 6a and the second adsorber 6b is pressure swing adsorption, temperature swing adsorption or temperature swing pressure swing adsorption. The adsorbent used is one or more of activated carbon, molecular sieve, hydrophobic silica gel or macroporous resin, which are mixed or layered.

[0058] The first adsorber 6a and the second adsorber 6b are each connected to the vacuum pump 7 via a gas valve. The other end of the vacuum pump 7 is connected to the condenser 8, and the condenser 8 is connected to the receiving tank 9. The vacuum pump 7 draws out the organic matter adsorbed in the adsorber 6, which is then condensed by the condenser 8 and discharged into the receiving tank 9. The non-condensable gas is discharged to the tail gas purification device.

[0059] In practice, this can be achieved in the following way:

[0060] like Figure 1 As shown, a multi-stage membrane adsorption system is set up according to design requirements. Hydrogen-containing purge gas 'a' is reduced to the design pressure through the purge gas control valve and then introduced into the first-stage membrane absorption system. In the first-stage membrane absorption system, the hydrogen purge gas 'a' enters the tube side of the membrane absorber 21 through the inlet of the membrane absorber 21. Absorbent liquid 'b' is injected into the absorbent liquid storage tank 31. The circulation pump 51 introduces the absorbent liquid 'b' into the shell side of the membrane absorber 21. By controlling the circulation pump 51 and the absorbent liquid regulating valve 41, the inlet pressure of the absorbent liquid 'b' in the shell side of the membrane absorber 21 is ensured to be 0.02-0.1 MPa higher than the inlet pressure of the hydrogen-containing purge gas 'a' in the tube side. This allows the hydrogen purge gas and the absorbent liquid to flow counterclockwise on both sides of the membrane inside the membrane absorber for mass transfer. The soluble organic gases in the hydrogen purge gas come into efficient contact with the absorbent liquid and are absorbed in the micron-sized pores of the membrane wall, thereby removing the organic matter from the purge gas. The treated hydrogen purge gas is then sent to the next stage membrane absorption system. The absorbent liquid b, which has absorbed organic matter, returns to the absorbent liquid storage tank 31 through the absorbent liquid regulating valve 4. After the absorbent liquid b is saturated with adsorption, it is discharged from the absorbent liquid storage tank 31 as saturated absorbent liquid c.

[0061] After being processed by the multi-stage membrane adsorption system, the hydrogen purge gas is introduced into the downstream adsorption system via a gas valve. The downstream adsorption system includes a first adsorber 6a and a second adsorber 6b. The inlets of the first adsorber 6a and the second adsorber 6b are each connected to the outlet of the membrane adsorption system via gas valves. The outlets of the first adsorber 6a and the second adsorber 6b are each connected to the outlet of the purge gas recovery device via gas valves. The gas valves control that only one adsorber is in operation at any given time. Once an adsorber in operation is saturated, it is closed via a gas valve, and the other adsorber is opened. The gas valve of the saturated adsorber is opened, and the vacuum pump 7 removes the adsorbed organic matter. The desorbed gas containing high concentrations of organic gas discharged from the vacuum is condensed by the condenser 8 and discharged into the receiving tank 9. The condensate f goes to a designated recovery tank outside the boundary, and the non-condensable gas e goes to a tail gas purification device outside the boundary for regeneration and recycling. Hot hydrogen gas g can be injected into the adsorber while the vacuum pump is running to further enhance the desorption effect of the process.

[0062] The following are examples of treatment methods for hydrogen purge gases produced by different hydrogenation processes:

[0063] Example 1

[0064] In the process of synthesizing 1,4-butanediol (BDO) from maleic anhydride, the hydrogenation unit periodically releases purge gas. Besides hydrogen, the purge gas mainly contains approximately 6.0 wt% methanol, with trace amounts of other organic matter. Operating conditions: pressure 5.9 MPa, temperature 55℃. The downstream hydrogen production system PSA inlet organic matter concentration requirement is ≤10 ppm, and pressure ≥2.4 MPa. A two-stage PVDF hollow fiber membrane absorber is used, with water as the absorbent. The inlet pressure of the first-stage membrane absorber is 2.8 MPa. After the second-stage membrane absorption, the organic matter concentration in the purge gas is only 200 ppm. After further removal by a first-stage adsorption column containing a mixture of 13X molecular sieve and granular activated carbon, the organic matter concentration in the outlet hydrogen is reduced to 8.5 ppm, the pressure is 2.45 MPa, and the moisture content is very low, allowing it to be directly and harmlessly fed into the downstream hydrogen production PSA. The adsorption unit is regenerated using vacuum desorption, and the desorption condensate and membrane absorbent are returned to the production distillation unit.

[0065] Example 2

[0066] In the production of the pharmaceutical intermediate levophosphonic acid, propadienephosphonic acid is selectively hydrogenated using a Linde catalyst to synthesize propylenephosphonic acid. During this process, the exhaust gas is hydrogen gas containing a high concentration of ethanol and trace amounts of toluene. The ethanol content is approximately 4.0% (v / v), and the toluene content is 25.0 ppm (approximately 100 mg / m³). 3Operating conditions: pressure 33 kPa, temperature approximately 48℃. The downstream hydrogen production system PSA inlet organic matter concentration requirement is ≤15 ppm, pressure ≥2.3 MPa. A two-stage PP hollow fiber membrane absorber is used, with water as the absorbent. After two-stage membrane absorption, the exhaust gas concentration is only 150 ppm for ethanol and 85 mg / m³ for toluene. 3 The ethanol and toluene are then removed by a two-layer adsorption column packed with granular activated carbon and macroporous resin. The total organic matter concentration at the outlet is less than 10 ppm. After the adsorber, a hydrogen booster fan is added to pressurize the gas before sending it to the hydrogen production PSA recovery unit. The adsorption unit is regenerated by using a vacuum while simultaneously introducing a small amount of hot hydrogen for desorption. The high-concentration water produced by membrane absorption is pumped back to the production unit for reuse, and the desorption condensate is returned to the ethanol storage tank.

[0067] Example 3

[0068] In the hydrogenation of dimethyl oxalate to ethylene glycol, a portion of the purge gas is periodically discharged from the hydrogen recirculation compressor. Its composition is: 95% (v) H2, approximately 1.21% (v) methanol, and the remainder nitrogen and argon. Operating conditions: pressure 2.85 MPa (G), temperature approximately 55°C. The downstream hydrogen recovery PSA system requires an inlet organic matter concentration ≤10 ppm and a pressure ≥2.3 MPa. A single-stage PP hollow fiber membrane absorber is used. The absorbent is crude ethylene glycol after light hydrocarbon removal. After membrane absorption, the methanol concentration in the exhaust gas is approximately 200 ppm. The absorbent then enters a single-stage 13X packed adsorption column for adsorption. The outlet methanol concentration is below 20 ppm, and the pressure is 2.5 MPa (G), which can be directly sent to the PSA process of the decarbonization gas to hydrogen production unit for recovery. The adsorption unit is regenerated using vacuum desorption. The desorption condensate is recovered from the crude methanol tank, and the saturated absorbent is returned to the crude ethylene glycol intermediate tank.

[0069] In addition to the above embodiments, the present invention also includes other embodiments. All technical solutions formed by equivalent transformation or equivalent substitution should fall within the protection scope of the claims of the present invention.

Claims

1. A process for recovering hydrogen purge gas containing soluble volatile organic compounds, comprising the following steps: Step 1: Hydrogen purge gas containing soluble volatile organic compounds is introduced into one side of the membrane in the membrane absorber, and absorbent is supplied to the other side of the membrane, so that the soluble volatile organic compounds are absorbed by the absorbent. Step 2: The gas absorbed in the membrane absorber is sent to the adsorption device for further adsorption of soluble volatile organic compounds. After condensation to remove condensable gases, hydrogen is obtained. The soluble volatile organic compounds include one or more of hydrocarbons, alcohols, esters, ethers, and ketones; The hydrogen purge gas contains more than 80% hydrogen. The soluble volatile organic compound content in the hydrogen purge gas is less than 20%. The absorbent is an inorganic absorbent or an organic absorbent. The inorganic absorbent is one or more of water, dilute acid, and dilute alkali. The organic absorbent is one or more of n-hexane, xylene, 1,2-dichloroethane, cyclohexanone, and ethylene glycol.

2. The hydrogen purge gas recovery process containing soluble volatile organic compounds according to claim 1, characterized in that: The membrane installed in the membrane absorber is a hollow fiber membrane, and the hollow fiber membrane material is one or more of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP), polysulfone (PSF / PSU), and polyethersulfone (PESU), with a membrane pore size of 20-500 nm.

3. The hydrogen purge gas recovery process containing soluble volatile organic compounds according to claim 1, characterized in that: In step 2, the adsorbent used in the adsorption device is one or more of activated carbon, molecular sieve, hydrophobic silica gel, or macroporous resin; the hydrogen obtained in step 2 contains less than 15 ppm of soluble volatile organic compounds.

4. A device for recovering hydrogen purge gas containing soluble volatile organic compounds, comprising: The venting control valve (1) is used to regulate the venting pressure; A membrane absorber (21, 2n) is installed with a separation membrane and connected to a purge gas control valve (1) for removing soluble volatile organic compounds from the purge gas by means of membrane absorption; Absorbent storage tanks (31, 3n) are connected to the membrane absorber and are used to supply absorbent into the membrane absorber; Adsorbers (6a, 6b) are connected to membrane absorbers (21, 2n) and are used to adsorb and separate residual organic matter from the purge gas obtained in the membrane absorbers (21, 2n). A condenser (8) is connected to an adsorber (6a, 6b) and is used to condense the gas obtained in the adsorber to remove condensable gases.

5. The hydrogen purge gas recovery device containing soluble volatile organic compounds according to claim 4, characterized in that: The separation membrane is a hollow fiber membrane, and the hollow fiber membrane material is one or more of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP), polysulfone (PSF / PSU), and polyethersulfone (PESU), with a membrane pore size of 20-500 nm. The absorbent storage tanks (31, 3n) are filled with inorganic or organic absorbent liquid. The inorganic absorbent liquid is one or more of water, dilute acid, and dilute alkali; the organic absorbent liquid is one or more of n-hexane, xylene, 1,2-dichloroethane, cyclohexanone, and ethylene glycol.

6. The hydrogen purge gas recovery device containing soluble volatile organic compounds according to claim 4, characterized in that: One side of the separation membrane is connected to the absorbent storage tank (31, 3n), and the other side is connected to the venting control valve (1); It also includes: a circulation pump (51, 5n) that connects one side of the separation membrane to the absorbent storage tank (31, 3n) to allow the absorbent to circulate between the one side of the separation membrane and the absorbent storage tank (31, 3n); It also includes: an absorbent regulating valve (41, 4n), connected to the circulating pump (51, 5n), used to regulate the flow rate of the absorbent supplied from the circulating pump (51, 5n).

7. The hydrogen purge gas recovery device containing soluble volatile organic compounds according to claim 4, characterized in that: The membrane absorbers (21, 2n) are multi-stage. The adsorbers (6a, 6b) are multi-stage.

8. The hydrogen purge gas recovery device containing soluble volatile organic compounds according to claim 4, characterized in that: The adsorbers (6a, 6b) are filled with one or more of activated carbon, molecular sieves, hydrophobic silica gel, or macroporous resin. It also includes a receiving tank (9), which is connected to the condenser (8) to receive condensed organic matter and discharge non-condensable gas.

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