A method for dehydrating a gas using salt-containing n-methylpyrrolidone

Abstract

The application belongs to the technical field of separation and purification, and discloses a method for dehydrating gas by using salt-containing N-methyl pyrrolidone. The application uses NMP containing tetraethylammonium chloride salt as an adsorbent for dehydrating gas. The adsorbent is contacted with water-containing gas in countercurrent in an absorption tower, and then a small amount of volatile NMP is removed by evaporation under reduced pressure, so that gas with low water content is obtained. The adsorbent has good thermal stability and is not easy to volatilize. Compared with ion liquid, molecular sieve and other process materials, the adsorbent has lower price and good economy. Meanwhile, the method can dry high-flow gas, and has wide industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of separation and purification, and specifically relates to a method for dehydrating gas using N-methylpyrrolidone containing salt. Background Technology

[0002] There is a wide demand for dehydration and drying in industry. In many industrial scenarios, it is necessary to remove water from gases, such as natural gas dehydration, hydrogen dehydration, acetylene dehydration, and chloromethane dehydration. Taking hydrogen dehydration as an example, dehydration can achieve the following advantages: (1) Protect equipment. The presence of water may have adverse effects on equipment and processes. For example, in hydrogen coolers or catalysts, the presence of water may lead to corrosion, blockage, or reduced catalyst activity. Dehydration treatment can avoid the impact on processes and equipment. (2) Prevent condensation. When the water content in hydrogen reaches the saturation point, if cooling or depressurization operations occur in the process, water may condense, causing damage to pipelines or equipment, and even affecting subsequent processes. (3) Improve purity. Currently, many process scenarios require high purity of hydrogen products. Water is one of the common impurities in hydrogen. In order to improve the purity of hydrogen, dehydration is necessary. (4) Meet process requirements. In scenarios such as hydrogen fuel cells, excessive water content may lead to a decrease in battery performance. Therefore, water must be removed to meet process requirements.

[0003] Currently, the main industrial methods for gas drying include solid dehumidification, cooling dehumidification, and solvent dehumidification. Among solid dehumidification methods, activated alumina adsorption is widely used. Its advantages include a shorter process flow, widespread industrial application, and a product moisture content as low as approximately 200 ppm. Disadvantages include the need to import activated alumina, resulting in high prices, severe wear and deactivation during use, and a short lifespan. Furthermore, the desorption tower requires vacuum operation, necessitating high equipment sealing. Cooling dehumidification is suitable for dehumidifying high-temperature, high-moisture-content natural gas. Its advantages include large processing capacity and low equipment procurement costs. Disadvantages include high power consumption and the inability to achieve extremely low moisture content. The mainstream solvent dehumidification method currently uses triethylene glycol for drying. Its advantages are that triethylene glycol is inexpensive to purchase and the process is mature. The main disadvantages of this process are that triethylene glycol will decompose at temperatures above 204 degrees Celsius, so the temperature of the solvent recovery tower needs to be strictly controlled, which increases the difficulty of tower operation. Also, a lot of triethylene glycol is lost during the production process due to volatility, which not only increases solvent costs but also causes environmental pollution.

[0004] N-Methylpyrrolidone (NMP) is a commonly used organic solvent in industry. Due to its unique structure-activity relationship, it can dissolve almost any organic matter, and is therefore widely used as a solvent and extractant. NMP has a higher boiling point and pyrolysis temperature than triethylene glycol, thus offering advantages over triethylene glycol in that it is less prone to pyrolysis and secondary volatilization. Although NMP has good hygroscopic properties, its dehydration effect is limited in industrial settings with high atmospheric flux and high water content, and a small amount of NMP volatilizes into the gas, affecting product purity, thus limiting its use.

[0005] In recent years, research on the salt effect theory has gained attention, and cases of solvent salt enhancement for separation have been applied in industry, such as ethanol dehydration and C4 separation. Adding a suitable salt to NMP can significantly improve its dehydration effect and reduce its volatility, effectively overcoming its shortcomings. The lack of thermodynamic data on organic solutions containing salt components and the complexity of thermodynamic models are important reasons limiting the enhancement of salt addition processes. Existing electrolyte models struggle to accurately describe the thermodynamic properties of salt-organic solution systems, and thermodynamic models based on the group contribution method require extensive experimental data to regress model parameters. Therefore, it is difficult to select a suitable type from the vast array of salts with diverse properties. Summary of the Invention

[0006] In view of the problems and shortcomings of the existing technology, the purpose of this invention is to provide a method for dehydrating gas by adding salt N-methylpyrrolidone.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: The first aspect of the present invention provides a method for dehydrating gas using N-methylpyrrolidone containing salt, comprising the following steps: after the water-containing gas and the adsorbent are fed into an absorption tower in a countercurrent manner, the top stream of the dehydrated gas is separated from the top of the absorption tower; then the top stream of the dehydrated gas is fed into a flash tank for pressurized condensation treatment to obtain the dehydrated gas; The adsorbent is N-methylpyrrolidone (NMP) containing salt.

[0008] Preferably, the gas is hydrogen.

[0009] More preferably, the pressurized condensation treatment is to remove the small amount of NMP that volatilizes from the dehydrated hydrogen gas.

[0010] The COSMO-SAC model is a predictive molecular thermodynamic model based on statistical mechanics and quantum chemistry. It approximates a real solution as a conductor with shielded charges, calculating the activity coefficient of the mixture by measuring the charge density distribution on the molecular surface, and then using thermodynamic equations to calculate other thermodynamic properties. Since the probability distribution of the charge density on the molecular surface, i.e., the σ-profile, can be calculated using only the molecular structure, the COSMO-SAC model can describe the thermodynamic properties of mixtures without experimental data, making it very convenient to use. Its accuracy has been extensively demonstrated through research and experiments. The COSMO-SAC model can accurately and qualitatively describe the thermodynamic properties of mixture systems, and therefore it is widely used in drug design, ionic liquid screening, and other research.

[0011] Since ionic liquids are essentially liquid molten salts, the COSMO-SAC model is also applicable to the screening of salt mixtures. After screening the Henry's coefficient of water in NMP solution with added salt using the COSMO-SAC model, it was finally determined that tetraethylammonium chloride can effectively enhance the dehydration effect of NMP while reducing the volatility of NMP.

[0012] Preferably, the salt in the adsorbent is tetraethylammonium chloride (TEAC); the tetraethylammonium chloride accounts for 5%-20% of the mass of the salt-containing N-methylpyrrolidone, preferably 10%. Further, the thermodynamic properties of the TEAC, NMP, hydrogen, and water system are described using the COSMO-SAC model, and simulations and calculations have demonstrated its excellent hydrogen dehydration effect.

[0013] Furthermore, in order to achieve the desired dehydration effect while reducing energy consumption and absorbent usage, this process has optimized a series of operating and design parameters, as detailed below: Preferably, the absorption tower is a packed tower; the theoretical number of trays in the absorption tower is 4-6, preferably 5; the pressure of the absorption tower is 1 atm; and the temperature inside the absorption tower is 15-25℃.

[0014] Preferably, the water content in the aqueous hydrogen gas is 5%-10% by mass; the feed inlet of the aqueous hydrogen gas is located at the last tray from the top of the absorption tower; the feed temperature of the aqueous hydrogen gas is 25°C; the feed pressure of the aqueous hydrogen gas is atmospheric pressure; and the feed flow rate of the aqueous hydrogen gas is 2000-2500 kg / h.

[0015] Preferably, the inlet of the adsorbent is located at the first tray from the top of the absorption tower; the feed temperature of the adsorbent is 25°C; the feed pressure of the adsorbent is atmospheric pressure; and the feed flow rate of the adsorbent in the absorption tower is 1000-2000 kg / h.

[0016] Preferably, the flash tank operates at a temperature of 10°C and a pressure of 5 bar.

[0017] Preferably, the adsorbent is reacted countercurrently with water-containing hydrogen to obtain a water-rich adsorbent, and the bottom stream containing the water-rich adsorbent is separated from the bottom of the absorption tower; the bottom stream containing the water-rich adsorbent is heated sequentially by a heat exchanger in the material flow section and a heater before entering a solvent recovery tower for distillation treatment, and the bottom stream containing the recovered adsorbent is separated from the bottom of the solvent recovery tower; the bottom stream containing the recovered adsorbent is first used as a heat exchange medium in the heat exchanger in the material flow section for heat exchange treatment, and then cooled down by a cooler before being fed back into the absorption tower as an adsorbent.

[0018] Furthermore, the temperature difference between the hot and cold stream outlets of the heat exchanger in the logistics room is 5°C.

[0019] Preferably, the heater heats the bottom stream containing water-rich adsorbent to 120°C; the cooler uses 10°C circulating cooling water; and the cooler cools the bottom stream containing recovered adsorbent to 25°C.

[0020] Preferably, the solvent recovery tower is a distillation tower (plate tower); the solvent recovery tower has 8-10 theoretical plates, preferably 10; the feed inlet of the bottom feed stream containing water-rich adsorbent is located at the 5th plate from the top of the solvent recovery tower.

[0021] Preferably, the pressure at the top of the solvent recovery tower is approximately 100 kPa (atmospheric pressure); the top output rate of the solvent recovery tower is 200 kg / h, and the mass reflux ratio is 1-5; the reboiler at the bottom of the solvent recovery tower is heated by 220°C high-pressure steam to maintain the bottom temperature at 170-185°C; and the condenser at the top of the solvent recovery tower is cooled by circulating cooling water to maintain the condenser temperature at 70-80°C.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention is the first to use NMP containing tetraethylammonium chloride as an adsorbent for gas dehydration. The adsorbent is brought into countercurrent contact with the water-containing gas in the absorption tower, and a small amount of volatilized NMP is removed by vacuum distillation to obtain a gas with low water content. In one embodiment, taking hydrogen dehydration as an example, 2000 kg / h of hydrogen containing 10% water by mass is brought into countercurrent contact with NMP containing 10% TEAC in the packing of the absorption tower. After dehydration and drying, the water content of the product gas at the top of the absorption tower can reach 1 ppm, and the dehydration effect is good. Therefore, the use of tetraethylammonium chloride enhances the dehydration effect of NMP, reduces the volatilization of NMP, and is more green and efficient than traditional desiccants.

[0023] (2) Based on extensive review of relevant domestic and international literature and combined with previous research on gas drying and dehydration conducted by our laboratory, this invention proposes a hydrogen dehydration and drying process using a suitable N-methylpyrrolidone solution with added tetraethylammonium chloride as the desiccant, after considering factors such as quantum chemical calculations and actual prices. The corresponding process was designed. Furthermore, using NMP with added TEAC as the adsorbent has three major advantages: 1) It has the advantages of solvent absorption, capable of drying large flow rates of gas. Simultaneously, the addition of tetraethylammonium chloride salt to NMP provides good thermal stability and low volatility, improving the drying effect while solving problems such as easy pyrolysis and secondary volatilization of triethylene glycol in traditional triethylene glycol drying processes; 2) Recovery is carried out under relatively mild conditions, and solvent loss is significantly reduced, effectively reducing the company's operating costs; 3) Compared to ionic liquids, molecular sieves, and other process raw materials, the price is lower, resulting in good economic efficiency; 4) It does not require changes to existing process equipment, and has broad industrial application prospects.

[0024] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the system of the present invention that uses N-methylpyrrolidone containing salt to dehydrate hydrogen; Among them, B1 is the absorption tower, B2 is the heat exchanger in the material flow room, B3 is the heater, B4 is the solvent recovery tower, B5 is the transfer pump, B6 is the cooler, and B7 is the flash tank. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0028] Example 1: A system for dehydrating hydrogen using N-methylpyrrolidone containing salt. This embodiment provides a system for dehydrating hydrogen using N-methylpyrrolidone containing salt, such as... Figure 1 As shown, it includes an absorption tower B1, a material flow heat exchanger B2, a heater B3, a solvent recovery tower B4, a transfer pump B5, a cooler B6, and a flash tank B7.

[0029] Absorption tower B1 has an adsorbent inlet at the first tray from the top of the tower, a water-containing hydrogen inlet at the last tray from the top of the tower, a dehydrated hydrogen outlet at the top of the tower, and a water-rich adsorbent outlet at the bottom of the tower.

[0030] On the one hand, the dehydrated hydrogen outlet of the absorption tower B1 is connected to the feed inlet of the flash tank B7. The top of the flash tank B7 is equipped with a hydrogen outlet, and the bottom of the tower is equipped with an adsorbent outlet.

[0031] On the other hand, the water-rich adsorbent outlet of the absorption tower B1 is connected to the inlet of the solvent recovery tower B4 via the heat exchanger B2 and heater B3 in sequence; the bottom outlet of the solvent recovery tower B4 enters the heat exchange medium inlet of the heat exchanger B2 via the transfer pump B5, and the heat exchange medium outlet of the heat exchanger B2 is connected to the adsorbent inlet of the absorption tower B1 via the cooler B6; the top outlet of the solvent recovery tower B4 is connected to the external zone via the cooler.

[0032] Among them, absorption tower B1 is a packed tower, and solvent recovery tower B4 is a distillation tower (plate tower); the theoretical number of plates in absorption tower B1 is 4-6, and the pressure is an absolute pressure of 101.325 kPa; the theoretical number of plates in solvent recovery tower B4 is 10, and the mass reflux ratio is 5.

[0033] Example 2: Investigating the effect of the number of trays in absorption tower B1 on the hydrogen dehydration effect. To investigate the effect of the number of trays in absorber B1 on the hydrogen dehydration effect, the inventors conducted the following simulation calculations using ASPEN plus V14, based on experimental verification of the accuracy of the thermodynamic model. These simulations are from Examples 2-1 to 2-5, with the theoretical number of trays in absorber B1 corresponding to 2-6, respectively. The measured hydrogen water content results are shown in Table 1.

[0034] Example 2-1 This embodiment provides a method for dehydrating hydrogen gas using N-methylpyrrolidone containing salt, including the following steps: (1) After feeding water-containing hydrogen (water and hydrogen mass fractions of 10% and 90% respectively) and adsorbent (mass ratio of TEAC to NMP of 1:9) into absorption tower B1 for countercurrent contact, the top feed stream containing dehydrated hydrogen is separated from the top of the absorption tower, and the bottom feed stream containing water-rich adsorbent is separated from the bottom of the absorption tower; then the top feed stream containing dehydrated hydrogen is fed into flash tank B7 for pressurized condensation treatment to remove NMP volatilized with hydrogen, and dehydrated hydrogen is obtained; The absorption tower is a packed tower with a temperature of 25℃, two theoretical trays, and an absolute pressure of 101.325 kPa. Hydrogen containing water is fed into the absorption tower from the last tray at the top, at a feed temperature of 25℃ and a mass flow rate of 2000 kg / h. The adsorbent is fed into the absorption tower from the first tray at the top, at a feed temperature of 25℃ and a mass flow rate of 2000 kg / h.

[0035] (2) The bottom stream containing water-rich adsorbent is heated to 120°C by heat exchanger B2 and heater B3 in sequence and then enters solvent recovery tower B4 for distillation to remove water. The bottom stream containing recovered adsorbent is separated from the bottom of solvent recovery tower B4, and water vapor is separated from the top of solvent recovery tower B4 at a flow rate of 210 kg / h. The bottom stream containing recovered adsorbent is first used as heat exchange medium by transfer pump B5 and then enters heat exchanger B2 in the material flow room for heat exchange treatment. Then it is cooled down to 25°C and 1 bar by cooler B6 and then fed back into absorption tower B1 as absorbent.

[0036] The solvent recovery tower is a distillation tower (plate tower) with 10 theoretical plates and a mass reflux ratio of 5.

[0037] In Examples 2-2 to 2-5, the theoretical number of plates in absorption tower B1 is 3-6 respectively, and other conditions are the same as in Example 2-1. The specific parameters and hydrogen water content data are shown in Table 1 below.

[0038] Table 1. Effect of different theoretical plate numbers on hydrogen water content in absorber B1 Table 1 shows that the more trays in the absorption tower, the better the hydrogen drying effect. When the theoretical number of trays reaches 5, the water content of hydrogen with a 10% water content is reduced to 0.1 ppm after treatment by the absorption tower, resulting in higher overall performance. Therefore, an absorption tower with 5 trays is preferred. Example 3: Investigating the effect of adsorbent feed flow rate on hydrogen dehydration efficiency To investigate the effect of adsorbent feed flow rate on hydrogen dehydration, the inventors conducted the following experiments, namely Examples 2-4 and Examples 3-1 to 3-9, with corresponding adsorbent feed flow rates of 1000-2000 kg / h. The measured hydrogen water content results are shown in Table 2.

[0039] In Examples 3-1 to 3-9, the feed flow rate of the adsorbent was 1000-1800 kg / h, and other conditions were the same as in Examples 2-4. The specific parameters and hydrogen water content data are shown in Table 2 below.

[0040] Table 2 Effect of adsorbent feed flow rate on hydrogen water content As shown in Table 2, the higher the feed flow rate of the adsorbent, the better the water removal effect of hydrogen. Therefore, considering the overall benefits, a feed flow rate of 2000 kg / h for water-containing hydrogen is preferred.

[0041] Example 4: Investigating the effect of adsorbent feed flow rate on hydrogen dehydration efficiency when the feed temperature of the absorption tower is 20℃. To investigate the effect of different adsorbent feed flow rates on hydrogen dehydration efficiency at an absorption tower feed temperature of 20℃, the inventors conducted the following experiments, namely Examples 4-1 to 4-6, with corresponding adsorbent feed flow rates of 1500-1000 kg / h. The measured hydrogen water content results are shown in Table 3.

[0042] Example 4-1 The method for dehydrating hydrogen using N-methylpyrrolidone containing salt is basically the same as that in Examples 2-4, except that: in step (1), the temperature of the absorption tower is 20°C; the feed temperature of the water-containing hydrogen is 20°C, and the mass flow rate is 1500 kg / h; the mass fractions of TEAC and NMP in the adsorbent are 5% and 95% respectively, and the feed temperature of the adsorbent is 20°C, with a mass flow rate of 1500 kg / h. In step (2), the recovered adsorbent is cooled to 20°C in a cooler, and water vapor is separated from the top of the solvent recovery tower B4 at a flow rate of 150 kg / h.

[0043] In Examples 4-2 to 4-6, the feed flow rate of the adsorbent was 1400-1000 kg / h, and other conditions were the same as in Example 4-1. The specific parameters and hydrogen water content data are shown in Table 3 below.

[0044] Table 3 Effect of adsorbent feed flow rate on hydrogen water content Table 3 shows that the higher the adsorbent feed flow rate, the better the hydrogen dehydration effect. However, comparing Examples 4-1 and 3-6, under the same adsorbent feed flow rate, the dehydration effect at a feed temperature of 25°C is clearly better. Therefore, considering the overall benefits, 25°C is preferred as both the absorption tower temperature and the feed temperature.

[0045] Example 5: Investigating the effect of adsorbent salt content on hydrogen dehydration efficiency when the feed temperature of the absorption tower is 20℃. To investigate the effect of different adsorbent salt contents on hydrogen dehydration efficiency when the feed temperature of the absorption tower is 20℃, the inventors conducted the following experiments, namely Examples 4-1 and 5-1 to 5-3, with corresponding adsorbent salt contents of 5%, 6%, 7%, and 8%, respectively. The measured hydrogen water content results are shown in Table 4.

[0046] The salt content of the adsorbent in Examples 5-1 to 5-3 was 6%, 7% and 8% respectively, and other conditions were the same as in Example 4-1. The specific parameters and hydrogen water content data are shown in Table 4 below.

[0047] Table 4. Effect of adsorbent feed flow rate on hydrogen water content As shown in Table 4, the higher the salt content of the adsorbent, the better the water removal effect of hydrogen. Therefore, adsorbents with a salt content of 8% or higher are preferred for water removal treatment.

[0048] Example 6: Investigating the effect of absorber pressure on hydrogen dehydration efficiency when the feed temperature is 30℃. To investigate the effect of different absorption tower pressures on hydrogen dehydration efficiency when the feed temperature of the absorption tower is 30℃, the inventors conducted the following experiments, namely Examples 6-1 to 6-9, with corresponding absorption tower pressures ranging from 101 to 500 kPa. The measured hydrogen water content results are shown in Table 5.

[0049] Example 6-1 The method for dehydrating hydrogen using N-methylpyrrolidone containing salt is basically the same as that in Examples 2-4, except that: in step (1), the temperature of the absorption tower is 30°C, the theoretical number of plates is 3; the feed temperature of the water-containing hydrogen is 30°C; the mass fractions of TEAC and NMP in the adsorbent are 5% and 95% respectively, and the feed temperature of the adsorbent is 30°C. In step (2), water vapor is separated from the top of the solvent recovery tower B4 at a flow rate of 200 kg / h; the bottom material containing the recovered adsorbent is cooled to 30°C by the cooler B6.

[0050] In Examples 6-2 to 6-9, the pressure of the absorption tower was 110-500 kPa, and other conditions were the same as in Example 6-1. The specific parameters and hydrogen water content data are shown in Table 5 below.

[0051] Table 5. Effect of absorption tower pressure on hydrogen water content Table 5 shows that the higher the pressure of the absorption tower, the better the water removal effect of hydrogen. However, even with increasing the absorption tower temperature, reducing the number of absorption tower plates, and reducing the salt content in the absorbent, the water content of hydrogen still reaches 1.9 ppm when the absorption tower pressure is 500 kPa. Therefore, considering the overall benefits, 25°C is the preferred absorption tower temperature and feed temperature.

[0052] In summary, this invention effectively overcomes the shortcomings of the prior art and has high industrial applicability. The above embodiments are intended to illustrate the substantive content of this invention, but are not intended to limit the scope of protection of this invention. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this invention without departing from the essence and scope of protection of this invention.

Claims

1. A method for dehydrating gas using N-methylpyrrolidone containing salt, characterized in that, Includes the following steps: After the water-containing gas and the adsorbent are fed into the absorption tower in a countercurrent manner, the top stream containing the dehydrated gas is separated from the top of the absorption tower; then the top stream containing the dehydrated gas is fed into a flash tank for pressurized condensation treatment to obtain the dehydrated gas. The adsorbent is N-methylpyrrolidone containing salt; the salt in the adsorbent is tetraethylammonium chloride.

2. The method according to claim 1, characterized in that, The tetraethylammonium chloride accounts for 5%-20% of the mass of the salt-containing N-methylpyrrolidone.

3. The method according to claim 2, characterized in that, The gas is hydrogen; the mass fraction of water in the aqueous hydrogen is 5%-10%.

4. The method according to claim 3, characterized in that, The absorption tower is a packed tower; the pressure at the top of the absorption tower is 1 atm; the temperature inside the absorption tower is 15-25℃; and the theoretical number of trays in the absorption tower is 4-6.

5. The method according to claim 4, characterized in that, The feed inlet for the water-containing hydrogen is located at the last theoretical plate from the top of the absorption tower; the feed temperature for the water-containing hydrogen is 25°C; the feed pressure for the water-containing hydrogen is atmospheric pressure; and the feed flow rate for the water-containing hydrogen is 2000-2500 kg / h.

6. The method according to claim 5, characterized in that, The inlet of the adsorbent is located at the first theoretical plate from the top of the absorption tower; the feed temperature of the adsorbent is 25°C; the feed pressure of the adsorbent is atmospheric pressure; and the feed flow rate of the adsorbent is 1000-2000 kg / h.

7. The method according to claim 6, characterized in that, The adsorbent is reacted countercurrently with water-containing hydrogen to obtain a water-rich adsorbent. In the method, after the water-containing gas and the adsorbent are fed into the absorption tower in a countercurrent manner, the bottom stream containing the water-rich adsorbent is separated from the bottom of the absorption tower, and then heated sequentially through the material exchanger and heater before entering the solvent recovery tower for distillation. The bottom stream containing the recovered adsorbent is separated from the bottom of the solvent recovery tower. The bottom stream containing the recovered adsorbent first enters the material exchanger as a heat exchange medium for heat exchange treatment, and then is cooled down by a cooler before being fed back into the absorption tower as adsorbent.

8. The method according to claim 7, characterized in that, The flash tank operates at a temperature of 10°C and a pressure of 5 bar; the heater heats the bottom stream containing water-rich adsorbent to 120°C; the cooler cools the bottom stream containing recovered adsorbent to 25°C.

9. The method according to claim 8, characterized in that, The solvent recovery tower is a distillation tower; the theoretical number of plates in the solvent recovery tower is 8-10; the top pressure of the solvent recovery tower is atmospheric pressure; the top yield of the solvent recovery tower is 200 kg / h, and the mass reflux ratio is 1-5; the bottom temperature of the solvent recovery tower is 170-185℃; and the top temperature of the solvent recovery tower is 70-80℃.

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