Organic waste gas high-efficiency purification and recovery system based on liquid absorption-desorption cycle

Abstract

This application relates to the field of organic waste gas purification technology, specifically to a high-efficiency purification and recovery system for organic waste gas based on a liquid absorption-desorption cycle. The system includes an absorption module, a desorption module, and a heat exchange module. By deploying temperature and pressure sensors at key locations in the desorption tower, the system uses a sliding historical window to predict the tower top temperature trend. Based on the prediction deviation ratio, the system dynamically adjusts the reboiler circulation flow rate and the regenerated liquid output flow rate, and introduces opening clamping constraints and adjustment dead zones. Simultaneously, combined with closed-loop regulation of the bottom liquid level to control the pump inflow rate, the system achieves coupled control of mass conservation and heat balance. This application effectively addresses the interference of VOCs concentration fluctuations on the desorption process. While ensuring the regeneration quality of the absorbent liquid, it significantly reduces system energy consumption through efficient heat exchange between hot and cold materials, improving the stability and economy of organic waste gas recovery.

Description

Technical Field

[0001] This application relates to the field of organic waste gas purification technology, specifically to a high-efficiency purification and recovery system for organic waste gas based on a liquid absorption-desorption cycle. Background Technology

[0002] Chemical industrial parks, as hubs of industrial economy, are also significant sources of volatile organic compound (VOC) pollution. With increasing industrial development and stricter environmental regulations, the demand for VOCs control continues to grow. However, VOCs are characterized by their wide variety, complex composition, diverse properties, strong odor, and high hazard, posing a tremendous challenge to their control.

[0003] Traditional environmental engineering typically employs surface-based technologies such as adsorption-combustion, adsorption-condensation, and adsorption-catalytic conversion to treat VOCs. While these technologies have seen some application, they generally suffer from drawbacks including low efficiency, high treatment costs, significant safety risks, substantial resource waste, and large carbon emissions. Mechanistically, most organic compounds possess characteristic functional groups, and similar functional groups exhibit strong miscibility. Based on this "like dissolves like" property and intermolecular interaction mechanisms, theoretically, highly efficient purification of VOCs waste gas can be achieved.

[0004] Among existing technologies, there is a treatment method based on the principle of "like dissolves like," which uses highly efficient liquid absorbents to remove most of the VOCs from waste gas. However, if this method uses water-based composite absorbents, it will generate wastewater containing a large amount of organic matter, and usually only the solid adsorbent is regenerated by hot air, resulting in a waste of the absorbent itself. Summary of the Invention

[0005] In view of the above, it is necessary to provide a high-efficiency purification and recovery system for organic waste gas based on liquid absorption-desorption cycle to solve the above problems.

[0006] One embodiment of this application provides a high-efficiency purification and recovery system for organic waste gas based on a liquid absorption-desorption cycle, the system comprising: Absorption module: Start the absorption fan and circulation pump 1#. After the VOCs waste gas passes through the pretreatment equipment to remove particulate matter, it enters the absorption tower. The absorption tower sprays VOCs absorption liquid to absorb and purify the VOCs waste gas. The purified gas meets the emission standards. The waste liquid of the absorption tower enters the circulation tank 1# for storage. Desorption module: The waste liquid from the low-temperature absorption tower in the circulation tank 1# is preheated by the heat exchanger using circulation pump 2# and then sent to the desorption tower for distillation and separation; the gaseous material at the top of the desorption tower is cooled by the condenser and then enters the gas-liquid separator; the resulting liquid VOCs are sent to the solvent tank for recycling, and the non-condensable gas is returned to the desorption tower; the regenerated liquid at the bottom of the desorption tower is cooled by the heat exchanger and then sent back to the absorption tower for recycling. Heat exchange module: The high-temperature regenerated absorbent in circulation tank 2# is pumped into the heat exchanger by circulation pump 1#, and exchanges heat with the low-temperature absorbent waste liquid pumped into the desorption tower by circulation pump 2#, so as to achieve cooling of the high-temperature liquid and preheating of the low-temperature liquid; at the same time, the amount of vaporization reflux heating of the reboiler at the bottom of the tower is controlled by adjusting the opening of solenoid valve 1#, and the flow rate of the regenerated absorbent entering the heat exchanger is controlled by adjusting the opening of solenoid valve 2#.

[0007] Preferably, the absorption tower is provided with baffles, two spray zones, and a demister from bottom to top. The spray zones are composed of an upper spray plate and a lower spray plate equipped with spray heads, as well as an upper packing mesh frame and a lower packing mesh frame.

[0008] Preferably, the VOCs absorbent is composed of 100 parts by mass of absorbent and 0.1-2 parts by mass of additive.

[0009] Preferably, the absorbent is at least one selected from 1,4-butanediol, N-methylpyrrolidone (NMP), sulfolane, and polyethylene glycol diethylene oxide methyl ether.

[0010] Preferably, the additives are Tween 80, Tween 20, glycerol, and oxalic acid.

[0011] Preferably, the process of controlling the vaporization reflux heating amount of the reboiler at the bottom of the column by adjusting the opening of solenoid valve 1# is as follows: The control period is preset. Based on the bottom pressure and top temperature of the column in each control period, the top temperature of the column in the future preset time period is predicted to obtain the estimated value of the top temperature. The rate of change of the estimated value of the top temperature of the column relative to the preset standard temperature of the top temperature of the column is calculated to obtain the deviation ratio of the top temperature of the column. The opening degree of solenoid valve #1 is controlled based on the temperature deviation ratio at the top of the tower.

[0012] Preferably, the control of the opening degree of solenoid valve 1# specifically involves: Calculate the difference between value 1 and the ratio of the temperature deviation at the top of the tower, and then multiply it by the current opening degree of solenoid valve 1# to obtain the opening degree value of solenoid valve 1# after adjustment.

[0013] Preferably, the difference between the bottom temperature of the column at each sampling time and the preset bottom standard temperature is used as the input parameter of the bottom reboiler, so that the bottom temperature of the desorption column reaches the bottom standard temperature.

[0014] Preferably, the control of the flow rate of the regenerated absorbent entering the heat exchanger by adjusting the opening of solenoid valve 2# specifically involves: When the temperature deviation ratio at the top of the tower is greater than or equal to the preset first threshold and less than or equal to the preset second threshold, the opening of solenoid valve 2# remains unchanged; otherwise, the opening of solenoid valve 2# is adjusted by adding or subtracting the absolute value of the preset opening percentage; wherein, the second threshold is greater than the first threshold.

[0015] Preferably, the process of adjusting the opening of solenoid valve 2# by adding or subtracting the absolute value of the preset opening percentage is as follows: When the temperature deviation ratio at the top of the tower is less than the preset first threshold, the opening of solenoid valve #2 is reduced; when the temperature deviation ratio at the top of the tower is greater than the preset second threshold, the opening of solenoid valve #2 is increased.

[0016] This application has at least the following beneficial effects: This application utilizes an absorbent based on the principle of "like dissolves like" to absorb VOCs. The absorbent operates at normal temperature and pressure. Compared to incineration technology, this application does not pose a fire or explosion risk, making it safe to use. Furthermore, it fully utilizes heat exchangers for cooling the high-temperature regenerated absorbent and preheating the waste liquid in the low-temperature absorption tower, resulting in greater energy efficiency, economy, and a green and low-carbon approach.

[0017] Secondly, the absorption liquid of this application has a large number of molecular interaction particles in the absorption of VOCs, and it is a physical reaction. The VOCs recovered after desorption can be reused as resources, and the absorption liquid can also be recycled. No secondary pollutants such as wastewater and solid waste are generated.

[0018] Finally, this application proposes a method for controlling the circulation of liquid phase materials at the bottom of the tower. By controlling the opening of solenoid valve 1# and solenoid valve 2#, the temperature of the desorption tower and the regeneration of the absorbent liquid can be regulated. While ensuring that the temperature requirement at the top of the desorption tower is met, the preheating temperature of the waste liquid in the absorbent tower is increased as much as possible, thereby promoting energy saving in the process. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of the high-efficiency purification and recovery system for organic waste gas based on liquid absorption-desorption cycle provided in this application; Figure 2 This is a schematic diagram of the absorption tower structure provided in this application; Figure 3 A block diagram of the high-efficiency purification and recovery system for organic waste gas based on liquid absorption-desorption cycle provided in this application. Detailed Implementation

[0020] The following description, in conjunction with the accompanying drawings, details the specific scheme of the high-efficiency purification and recovery system for organic waste gas based on liquid absorption-desorption cycle provided in this application.

[0021] This application specifically relates to a highly efficient purification and recovery system for organic waste gas based on a liquid absorption-desorption cycle, the schematic diagram of which is shown below. Figure 1As shown, the system specifically includes: pretreatment equipment, absorption tower, desorption tower, condenser, reboiler at the bottom of the tower, circulating pump, fan, heat exchanger, circulating tank, solvent tank, and piping system. Specifically, 1 is the pretreatment equipment, 2 is the absorption fan, 3 is the absorption tower, 4 is circulating pump #1, 5 is circulating tank #1, 6 is the condenser, 7 is the reboiler at the bottom of the tower, 8 is circulating pump #2, 9 is the desorption tower, 10 is circulating tank #2, 11 is the solvent tank, 12 is the heat exchanger, 13 is the gas-liquid separator, 14 is solenoid valve #1, and 15 is solenoid valve #2.

[0022] The schematic diagram of the absorption tower structure is as follows: Figure 2 As shown. Specifically, 301 is the air inlet, 302 is the demister, 303 is the upper spray plate, 304 is the upper packing mesh frame, 305 is the lower spray plate, 306 is the lower packing mesh frame, 307 is the waste liquid inlet, 308 is the replenishment liquid inlet, 309 is the spray head, 310 is the chimney, and 311 is the baffle plate.

[0023] Please see Figure 3 The diagram illustrates a block diagram of an efficient organic waste gas purification and recovery system based on a liquid absorption-desorption cycle according to an embodiment of this application. The system includes an absorption module, a desorption module, and a heat exchange module.

[0024] This application first proposes a high-efficiency purification and recovery system for organic waste gas based on a liquid absorption-desorption cycle, applied in the field of organic waste gas purification technology. The system includes: Absorption Module: The absorption fan 2 and circulation pump 1# are turned on. After the VOCs waste gas passes through the pretreatment equipment 1 to remove particulate matter, it enters the absorption tower 3. The absorption tower 3 sprays VOCs absorption liquid to absorb and purify the VOCs waste gas. The purified gas meets the emission standards, and the waste liquid of the absorption tower enters the circulation tank 1#5 for storage.

[0025] In this application, the VOCs waste gas refers to waste gas from the production workshop. After the control system issues an activation command, the high-efficiency purification and recovery device for organic waste gas starts the absorption fan 2 and the circulation pump 1#4. The VOCs waste gas, after passing through the pretreatment equipment 1 to remove particulate matter, enters the absorption tower 3. Based on the similarity-dissolves-like properties of organic matter, the absorption tower 3 sprays VOCs absorption liquid to achieve the absorption and purification of the VOCs waste gas, ensuring compliance with emission standards. The waste liquid from the absorption tower is then stored in the circulation tank 1#5.

[0026] The absorption tower is specifically an absorption tower 3 with a chimney. From bottom to top, it is provided with a baffle plate 311, two spray zones, and a demister 302. The baffle plate is located at the bottom of the absorption tower, and the demister is located at the top of the absorption tower. The spray zones are composed of an upper spray plate 303 and a lower spray plate 305 equipped with spray heads 309, as well as an upper packing mesh frame 304 and a lower packing mesh frame 306. After pretreatment, the VOCs waste gas enters the absorption tower through the bottom inlet 301. The VOCs absorbent enters the absorption tower through the replenishment pipe 308 and is sprayed down from the tower through the spray head 309. The VOCs waste gas undergoes a countercurrent contact reaction with the VOCs absorbent sprayed down by the spray head 309 after passing through the baffle plate, thereby absorbing and purifying the VOCs waste gas. After the countercurrent contact reaction, the waste gas is demisted by the demister and then discharged through the chimney 310 in compliance with standards. The waste liquid of the absorption tower is the VOCs absorbent after absorbing the VOCs waste gas in the countercurrent contact reaction, and it flows out of the absorption tower through the waste liquid pipe 307.

[0027] The VOCs absorbent is a composite solution with a high boiling point, stable performance, and large VOCs absorption capacity, consisting of 100 parts by mass of absorbent and 0.1-2 parts by mass of additives. The absorbent is a high-boiling-point VOCs absorbent, specifically at least one of 1,4-butanediol, N-methylpyrrolidone (NMP), sulfolane, and polyethylene glycol diethylene oxide methyl ether. In this embodiment, 1,4-butanediol is used; in other embodiments, 1,4-butanediol, N-methylpyrrolidone (NMP), and sulfolane are used; and in some other embodiments, polyethylene glycol diethylene oxide methyl ether is used.

[0028] The additives are high-boiling-point organic compounds, specifically Tween 80, Tween 20, glycerol, and oxalic acid. The role of these additives is to improve the absorption efficiency of the absorbent for VOCs, enhancing its solubility and increasing the contact area and mass transfer efficiency between the absorbent and VOCs.

[0029] Desorption module: The waste liquid from the low-temperature absorption tower in the circulation tank 1#5 is preheated by the heat exchanger 12 using the circulation pump 2#8 and then sent to the desorption tower 9 for distillation and separation; the gaseous material at the top of the desorption tower 9 is cooled by the condenser 6 and then enters the gas-liquid separator 13. The resulting liquid VOCs are sent to the solvent tank 11 for recycling, and the non-condensable gas is returned to the desorption tower 9. The regenerated liquid at the bottom of the desorption tower 9 is cooled by the heat exchanger 12 and then sent back to the absorption tower 3 for recycling.

[0030] The waste liquid from the low-temperature absorption tower stored in the circulation tank 1#5 is first preheated by the circulation pump 2#8 through the heat exchanger 12, and then enters the desorption tower 9. Based on the different boiling points of the absorbent and VOCs, the desorption tower 9 is used to achieve distillation separation.

[0031] The gaseous material generated at the top of the desorption tower is rich in VOCs. This gaseous material enters condenser 6, where the cooling water temperature is 5℃-10℃. The cooling water in condenser 6 cools the gaseous material, facilitating subsequent storage of the VOCs in liquid form. The outlet of condenser 6 is connected to gas-liquid separator 13. The non-condensable gas (i.e., the gaseous portion) in gas-liquid separator 13 continues to flow into desorption tower 9 through a pipeline. The liquid portion in gas-liquid separator 13 is sent to solvent tank 11 in the plant area, where the VOCs liquid material can be recovered.

[0032] The main component of the liquid phase material at the bottom of the desorption tower is the absorbent. By using the bottom liquid phase material circulation control method, the opening of solenoid valves 1#14 and 2#15 is controlled, thereby realizing the regulation of the temperature of the desorption tower 9 and the regeneration of the absorbent.

[0033] Part of the liquid material at the bottom of the desorption tower is reheated via the bottom reboiler 7 to heat the liquid material to a gaseous state. The outlet of the bottom reboiler 7 is connected to the inlet of the desorption tower, and the reheated material is circulated into the desorption tower 9 to ensure that the desorption tower has sufficient rising high-temperature steam. By controlling the opening of the solenoid valve 1#14, the flow rate of the rising high-temperature steam can be adjusted to control the temperature of the desorption tower.

[0034] Another portion of the liquid material at the bottom of the desorption tower is stored in the circulation tank 2#10. Then, through the circulation pump 1#4, the high-temperature regenerated absorbent stored in the circulation tank 2#10 is cooled by heat exchanger 12 before entering the absorption tower to achieve the regeneration and reuse of the absorbent. The output speed of the regenerated absorbent can be adjusted by controlling the opening of the solenoid valve 2#15.

[0035] Heat exchange module: The high-temperature regenerated absorbent in the circulation tank 2#10 is pumped into the heat exchanger 12 by the circulation pump 1#4, and exchanges heat with the low-temperature absorbent waste liquid pumped into the desorption tower by the circulation pump 2#8, so as to achieve cooling of the high-temperature liquid and preheating of the low-temperature liquid; at the same time, the amount of vaporization reflux heating of the reboiler 7 at the bottom of the tower is controlled by adjusting the opening of the solenoid valve 1#14, and the flow rate of the regenerated absorbent entering the heat exchanger 12 is controlled by adjusting the opening of the solenoid valve 2#15.

[0036] The high-temperature regenerated absorbent pumped from the circulation tank 2#10 by circulation pump 1#4 and the low-temperature absorption tower waste liquid pumped into the desorption tower 9 by circulation pump 2#8 exchange heat in the heat exchanger 12. The high-temperature absorbent is cooled and the low-temperature absorption tower waste liquid is preheated. The two materials achieve efficient heat exchange without the use of additional refrigerant, thereby achieving the purpose of energy saving.

[0037] This module in this application controls the opening degrees of solenoid valves 1#14 and 2#15 to regulate the temperature of the desorption tower 9 and the regeneration of the absorbent liquid. In VOCs waste gas absorption treatment processes, the concentration and flow rate of VOCs significantly affect the concentration of VOCs in the waste liquid of the absorption tower, leading to large fluctuations in VOCs concentration and consequently impacting the temperature inside the absorption tower. This application designates 1 / 5 of the desorption tower's height as the bottom measurement point and 4 / 5 of its height as the top measurement point. Temperature and pressure measuring instruments are installed at both the bottom and top measurement points to acquire the top temperature, top pressure, bottom temperature, and bottom pressure, respectively. The temperature measuring instrument sampling interval is set to 1 second.

[0038] Considering the lag in temperature and pressure changes in the desorption tower, this application uses 3 minutes as the control cycle for the circulation of liquid phase material at the bottom of the tower, that is, the opening degree of solenoid valve 1# and solenoid valve 2# is adjusted once every 3 minutes.

[0039] The bottom of the desorption tower requires high temperatures to drive the evaporation of the liquid phase components, providing the necessary energy for this process. Conversely, the lower temperature at the top helps reduce temperature and pressure differences, thus lowering energy consumption. Appropriate operating parameters for the desorption tower can optimize separation efficiency and enhance the recycling rate of the absorbent. The standard temperature range for the top of the tower is 55℃-65℃, with 60℃ used in this embodiment; the standard temperature range for the bottom of the tower is 120℃-130℃, with 125℃ used in this embodiment.

[0040] The bottom temperature of the desorption tower is mainly related to the reboiler. The higher the power of the reboiler, the greater the increase in the temperature of the liquid phase material flowing through it. This application obtains the bottom temperature of the desorption tower at each sampling time, calculates the difference between the bottom temperature and the standard bottom temperature, uses this as the bottom temperature difference at each sampling time, and feeds it back to the controller of the reboiler to adjust the power of the reboiler at each sampling time so that the bottom temperature of the desorption tower reaches the standard bottom temperature.

[0041] The opening degree of solenoid valve #1 primarily affects the flow rate of high-temperature rising steam within the desorption tower. Increasing the opening degree of solenoid valve #1 increases the amount of liquid material entering the reboiler at the bottom of the tower, resulting in a higher flow rate of high-temperature rising steam within the desorption tower, thus increasing the top temperature. Due to the large volume of the desorption tower, changes in top temperature exhibit a lag, while pressure changes within the tower respond rapidly. An increase in bottom pressure indicates an increase in the amount of gas at the bottom, leading to a corresponding increase in the flow rate of high-temperature rising steam, thereby raising the top temperature of the desorption tower. In this application, the initial opening degree of solenoid valve #1 is set to 50%.

[0042] This application constructs a tower top temperature sequence and a tower bottom pressure sequence in ascending order of sampling times within the control cycle. The tower bottom pressure sequence is used as the exogenous variable sequence for the ARIMAX model. Based on the ARIMAX model, the predicted sequence of the tower top temperature sequence for the next N time periods is obtained: Tower top temperature, tower bottom pressure, and tower top pressure data for the 30 minutes prior to the current time are extracted to construct a sliding historical window sequence. Then, the AIC (Akaike Information Content) criterion is used to dynamically determine the autoregressive order p, the difference order d, and the moving average order q of the model to balance model accuracy and complexity. The least squares method is used to fit the model coefficients online in real time. Finally, the fitted model is combined with the current pressure exogenous variable to calculate and output the predicted mean value Tp of the tower top temperature for the next N time periods. It should be noted that during the initial system startup, if the historical data accumulation is less than 30 minutes, the ARIMAX prediction program is automatically suspended, and a preset constant opening logic is executed for system warm-up. The prediction and control program is activated again after the data window is filled.

[0043] Calculate the mean of all data elements within the prediction sequence as the estimated value of the tower top temperature. In this embodiment, N is taken as 1 min. (The formula is used to...) To obtain the temperature deviation ratio at the top of the desorption tower. In the formula, It is an estimated temperature at the top of the tower. This is the standard temperature at the top of the tower.

[0044] By combining the pressure at the bottom of the column and the temperature at the top, the accuracy of the top temperature prediction can be improved. If the predicted top temperature is higher than the standard top temperature, then... To reduce process energy consumption, the flow rate of high-temperature rising steam in the desorption tower should be reduced, and the opening degree of solenoid valve #1 should be decreased; if the estimated tower top temperature is lower than the standard tower top temperature, i.e. In order to fully separate the VOCs waste gas components in the waste liquid of the absorption tower, the flow rate of high-temperature rising steam in the desorption tower should be increased, and the opening degree of solenoid valve 1 should be increased.

[0045] This application obtains the opening degree of solenoid valve #1 during the current control cycle. Through formula The opening value of solenoid valve #1 after adjustment was calculated. This enables dynamic control of the opening degree of solenoid valve 1#. It should be noted that the opening degree range of solenoid valve 1# is [0, 100%], and this embodiment uses this range to truncate the adjusted opening degree.

[0046] The opening degree of solenoid valve #2 mainly affects the regeneration speed of the absorbent and the heat exchange efficiency of the heat exchanger. The larger the opening degree of solenoid valve #2, the higher the flow rate of the high-temperature regenerated absorbent through the heat exchanger, the better the heat exchange effect, and the higher the preheating temperature of the low-temperature absorbent waste liquid pumped into the desorption tower, resulting in a more significant energy-saving effect.

[0047] The larger the opening degree of solenoid valve 2#, the more significant the energy-saving effect. Therefore, the initial opening degree of solenoid valve 2# in this application is set to 100%. However, the liquid phase material at the bottom of the desorption tower is limited. When the opening degree of solenoid valve 2# is 100%, if the temperature at the top of the desorption tower is too low, there will be less liquid phase material flowing through the reboiler at the bottom of the desorption tower from solenoid valve 1#. This may not be enough to meet the temperature requirements at the top of the desorption tower, which can easily lead to insufficient temperature at the top of the desorption tower and incomplete distillation and separation of waste liquid in the absorption tower.

[0048] This application obtains the temperature deviation ratio at the top of the desorption tower during the control period. The opening value of solenoid valve #2 is dynamically controlled in the following manner: (a) If the temperature deviation at the top of the tower is higher than... If the temperature is below the first threshold, it indicates that the temperature at the top of the column is too low. To prevent insufficient flow of the bottom liquid through solenoid valve 1#, which could lead to inadequate distillation and separation of the waste liquid in the absorption column, this application closes solenoid valve 2# by 15%. , This refers to the opening degree of solenoid valve #2 within the current control cycle. This represents the opening value after adjustment by solenoid valve #2. Here, `max()` is the maximum value function, and the first threshold is -0.2 in this embodiment. This embodiment establishes a feed-discharge linkage logic based on the bottom liquid level by installing a liquid level sensor at the bottom of the desorption tower. The controller performs PID closed-loop regulation of circulating pump #2 based on the liquid level data, causing the pumping flow rate of circulating pump #2 to dynamically change with the total discharge of solenoid valves #1 and #2, thereby eliminating the interference of valve opening adjustment on the bottom liquid level and maintaining the material balance within the desorption tower.

[0049] (ii) If the temperature deviation at the top of the tower is greater than... If the temperature exceeds the second threshold, it indicates a high temperature at the top of the column. The liquid flowing through solenoid valve #2 can provide sufficient high-temperature rising steam to support the temperature at the top. To improve the heat exchanger efficiency and promote energy conservation in the process, this application opens solenoid valve #2 by 15%, i.e. , This refers to the opening degree of solenoid valve #2 within the current control cycle. This represents the opening value of solenoid valve #2 after adjustment. Here, min() is the minimum value function, and the second threshold is set to 0.2 in this embodiment.

[0050] Since frequent adjustments to the process desorption tower can easily lead to "over-adjustment", when the temperature deviation ratio at the top of the tower is greater than or equal to the first threshold and less than or equal to the second threshold, the solenoid valve #2 will no longer be adjusted in the corresponding control cycle.

Claims

1. A high-efficiency purification and recovery system for organic waste gas based on a liquid absorption-desorption cycle, characterized in that, The system includes: Absorption module: Turn on the absorption fan (2) and circulation pump 1# (4). After the VOCs waste gas passes through the pretreatment equipment (1) to remove particulate matter, it enters the absorption tower (3). The absorption tower (3) sprays VOCs absorption liquid to absorb and purify the VOCs waste gas. The purified gas meets the emission standards. The waste liquid of the absorption tower enters the circulation tank 1# (5) for storage. Desorption module: The waste liquid from the low-temperature absorption tower in the circulation tank 1# (5) is preheated by the heat exchanger (12) using the circulation pump 2# (8) and then sent to the desorption tower (9) for distillation and separation; the gaseous material at the top of the desorption tower (9) is cooled by the condenser (6) and then enters the gas-liquid separator (13); the obtained liquid VOCs are sent to the solvent tank (11) for recycling; the non-condensable gas is returned to the desorption tower (9); the regenerated liquid at the bottom of the desorption tower (9) is cooled by the heat exchanger (12) and then sent back to the absorption tower (3) for recycling. Heat exchange module: The high-temperature regenerated absorbent in the circulation tank 2#(10) is pumped into the heat exchanger (12) by the circulation pump 1#(4) and exchanged with the low-temperature absorbent waste liquid pumped into the desorption tower by the circulation pump 2#(8) to achieve the cooling of the high-temperature liquid and the preheating of the low-temperature liquid; at the same time, the amount of vaporization reflux heating of the reboiler (7) at the bottom of the tower is controlled by adjusting the opening of the solenoid valve 1#(14), and the flow rate of the regenerated absorbent entering the heat exchanger (12) is controlled by adjusting the opening of the solenoid valve 2#(15).

2. The high-efficiency purification and recovery system for organic waste gas based on liquid absorption-desorption cycle as described in claim 1, characterized in that, The absorption tower (3) is provided with baffles (311), two spray zones and a demister (302) from bottom to top. The spray zones are composed of an upper spray plate (303) and a lower spray plate (305) equipped with spray heads (309), as well as an upper packing mesh frame (304) and a lower packing mesh frame (306).

3. The high-efficiency purification and recovery system for organic waste gas based on liquid absorption-desorption cycle as described in claim 1, characterized in that, The VOCs absorption liquid consists of 100 parts by mass of absorbent and 0.1-2 parts by mass of additive.

4. The high-efficiency purification and recovery system for organic waste gas based on liquid absorption-desorption cycle as described in claim 3, characterized in that, The absorbent is specifically at least one of 1,4-butanediol, N-methylpyrrolidone (NMP), sulfolane, and polyethylene glycol diethylene oxide methyl ether.

5. The high-efficiency purification and recovery system for organic waste gas based on liquid absorption-desorption cycle as described in claim 3, characterized in that, The additives are specifically Tween 80, Tween 20, glycerol, and oxalic acid.

6. The high-efficiency purification and recovery system for organic waste gas based on liquid absorption-desorption cycle as described in claim 1, characterized in that, The process of controlling the vaporization reflux heating amount of the reboiler (7) at the bottom of the tower by adjusting the opening of solenoid valve 1# (14) is as follows: The control period is preset. Based on the bottom pressure and top temperature of the column in each control period, the top temperature of the column in the future preset time period is predicted to obtain the estimated value of the top temperature. The rate of change of the estimated value of the top temperature of the column relative to the preset standard temperature of the top temperature of the column is calculated to obtain the deviation ratio of the top temperature of the column. The opening degree of solenoid valve 1#(14) is controlled based on the temperature deviation ratio at the top of the tower.

7. The high-efficiency purification and recovery system for organic waste gas based on liquid absorption-desorption cycle as described in claim 6, characterized in that, The control of the opening degree of solenoid valve 1# (14) is specifically as follows: Calculate the difference between the value 1 and the ratio of the temperature deviation at the top of the tower, and then multiply it by the current opening degree of solenoid valve 1# (14) to obtain the opening degree value of solenoid valve 1# (14) after adjustment.

8. The high-efficiency purification and recovery system for organic waste gas based on liquid absorption-desorption cycle as described in claim 6, characterized in that, The difference between the bottom temperature of the column at each sampling time and the preset standard bottom temperature is used as the input parameter of the bottom reboiler (7) so that the bottom temperature of the desorption column reaches the standard bottom temperature.

9. The high-efficiency purification and recovery system for organic waste gas based on liquid absorption-desorption cycle as described in claim 6, characterized in that, The flow rate of the regenerated absorbent entering the heat exchanger (12) is controlled by adjusting the opening of solenoid valve 2# (15), specifically as follows: When the temperature deviation ratio at the top of the tower is greater than or equal to the preset first threshold and less than or equal to the preset second threshold, the opening degree of solenoid valve 2#(15) remains unchanged; otherwise, the opening degree of solenoid valve 2#(15) is adjusted by adding or subtracting the absolute value of the preset opening degree percentage; wherein, the second threshold is greater than the first threshold.

10. The high-efficiency purification and recovery system for organic waste gas based on liquid absorption-desorption cycle as described in claim 9, characterized in that, The process of adjusting the opening of solenoid valve 2#(15) by adding or subtracting the absolute value of the preset opening percentage is as follows: When the temperature deviation ratio at the top of the tower is less than the preset first threshold, the opening of solenoid valve 2#(15) is reduced; when the temperature deviation ratio at the top of the tower is greater than the preset second threshold, the opening of solenoid valve 2#(15) is increased.

Images