Program control device and method for treating VOCs tail gas

Abstract

The invention relates to a program control device and method for treating VOCs tail gas, and aims to improve desorption efficiency and nitrogen flushing replacement efficiency. The device comprises an absorption tower, a condensation storage tank, a condenser, an adsorption unit, a nitrogen purging unit and a vacuum pump unit. The adsorption unit is connected in parallel to the four adsorption tanks through four conveying pipes and corresponding program control valves, the nitrogen purging unit and the vacuum pump unit are connected with the adsorption tanks through purging pipes and vacuum pipes respectively, and program control valves are arranged on the nitrogen purging unit and the vacuum pump unit to achieve automatic control. Through the split-range system, the desorption time is prolonged, the treatment efficiency is improved, and the method is suitable for industrial VOCs tail gas treatment.

Description

Technical Field

[0001] The invention relates to a program-controlled device and method for treating VOCs tail gas. Background Art

[0002] Absorption and adsorption technology is a mature VOCs oil and gas treatment technology. However, with the continuous improvement of environmental protection requirements, the absorption and adsorption technology of ultra-clean emissions has stricter control over the absorption and adsorption process, and more sophisticated selection of adsorbents. The main principle is to use program control technology to achieve step-by-step control of the adsorption and desorption process of the adsorption tank, extend the desorption time, increase nitrogen flushing and replacement, and improve the desorption efficiency, so that the adsorption tank has better adsorption capacity to achieve mg-level emission requirements for the export exhaust gas. The analyzed gas removes the high-concentration VOC separated by adsorption and analysis from the system through condensation absorption. The physical method used by the ultra-clean emission technology of absorption and adsorption reduces carbon emissions in the treatment process and achieves the synergistic benefits of environmental protection and carbon reduction.

[0003] Therefore, how to use the split-stage system to extend the desorption time and improve the desorption efficiency while increasing the nitrogen flushing and replacement efficiency is a technical problem that technicians in this field currently need to solve. Summary of the invention

[0004] The purpose of the present invention is to solve the above deficiencies in the prior art and provide a program-controlled device for treating VOCs tail gas, which uses a split-range system to extend the desorption time and improve the desorption efficiency, while increasing the nitrogen flushing and replacement efficiency. Another purpose of the present invention is to provide a program-controlled method for treating VOCs tail gas. The following is a specific scheme:

[0005] On the one hand, a program-controlled device for treating VOCs tail gas includes an absorption tower, a condensation storage tank, a condenser, an adsorption unit, a nitrogen purge unit and a vacuum pump unit, wherein the condensation storage tank is connected to the downstream of the condenser along the flow direction of the tail gas, and is used to store the condensed tail gas; the condenser is connected to the downstream of the absorption tower along the flow direction of the tail gas, so that the tail gas enters the condensation storage tank after condensation and cooling; the adsorption unit is connected to the downstream of the condenser along the flow direction of the tail gas, and includes a first delivery pipe, a second delivery pipe, a third delivery pipe and a fourth delivery pipe, all of which are used to transport the tail gas, the first delivery pipe, the second delivery pipe, the third delivery pipe and the fourth delivery pipe are connected in parallel with each other, and the first delivery pipe, the second delivery pipe and the third delivery pipe are respectively connected with a first program-controlled valve, a second program-controlled valve, a third program-controlled valve and a fourth program-controlled valve, and the ends of the first delivery pipe, the second delivery pipe, the third delivery pipe and the fourth delivery pipe are respectively connected to a first adsorption tank, a second adsorption tank, a third adsorption tank and a fourth adsorption tank, and the The downstream of the first adsorption tank, the second adsorption tank, the third adsorption tank and the fourth adsorption tank are all connected to the tail gas discharge port; the nitrogen purge unit includes a first purge pipe, a second purge pipe, a third purge pipe and a fourth purge pipe which are connected to the first adsorption tank, the second adsorption tank, the third adsorption tank and the fourth adsorption tank in sequence, and the first purge pipe, the second purge pipe, the third purge pipe and the fourth purge pipe are respectively connected with a fifth program-controlled valve, a sixth program-controlled valve, a seventh program-controlled valve and an eighth program-controlled valve; the vacuum pump unit is connected with the first adsorption tank, the second adsorption tank, the third adsorption tank and the fourth adsorption tank, and the vacuum pump unit includes a first vacuum tube, a second vacuum tube, a third vacuum tube and a fourth vacuum tube, and the first vacuum tube, the second vacuum tube, the third vacuum tube and the fourth vacuum tube are respectively connected with a ninth program-controlled valve, a tenth program-controlled valve, an eleventh program-controlled valve and a twelfth program-controlled valve, so that the air pressure in the first adsorption tank, the second adsorption tank, the third adsorption tank and the fourth adsorption tank is evacuated to vacuum; the twelve program-controlled valves are all connected to the program control system.

[0006] Furthermore, the adsorbent filled inside the adsorption tank is a multi-layer structure, the first layer is an activated carbon material for efficient adsorption of VOCs, the second layer is a silica gel material for high temperature resistant adsorption, and the third layer is a macroporous resin material, which is used for graded adsorption of VOCs components with different molecular weights and boiling points.

[0007] Furthermore, the programmable valve includes an electric actuator, which is connected to a central control unit and monitors the pressure, temperature and gas concentration changes in the system in real time through sensors to automatically adjust the opening time and frequency of the programmable valve so that the programmable device can seamlessly switch between adsorption, desorption and purging.

[0008] Furthermore, the nitrogen purge unit also includes a dual-path nitrogen pipeline, which includes a large-flow pipeline and a small-flow pipeline. The dual-path nitrogen pipeline is further connected with an independent flow control valve, wherein the large-flow pipeline is used to quickly replace the exhaust gas in the tank during the desorption stage of the adsorption tank, and the small-flow pipeline is used to provide a stable nitrogen supply when the tank body returns to normal working pressure.

[0009] Furthermore, the vacuum pump unit includes a first vacuum pump and a second vacuum pump, wherein the first vacuum pump is used to initially extract a large amount of residual gas in the adsorption tank, and the second vacuum pump is used to accurately control the pressure in the tank to an ultra-low vacuum state to prevent overheating and excessive degradation of the adsorbent during the desorption process.

[0010] Furthermore, the program control system is calculated based on the following formula:

[0011] Where Δu is the adjustment amount of the program-controlled valve, e(t) = C target -C(t) is the control error, K p , K i , K d are the proportional, integral and differential control coefficients respectively.

[0012] On the other hand, a program-controlled method for absorbing and adsorbing VOCs tail gas includes the following steps: 1) pre-treating the tail gas containing VOCs through an absorption tower and then entering a condenser, using a cooling system to cool and condense the tail gas, and the condensed tail gas enters a condensation storage tank for storage; 2) transporting the condensed tail gas from the condensation storage tank to an adsorption unit, and the adsorption unit guides the tail gas to a first adsorption tank, a second adsorption tank, a third adsorption tank and a fourth adsorption tank respectively through a program-controlled system, and each adsorption tank is filled with a different type of adsorbent; the flow direction of the tail gas is controlled by a first program-controlled valve, a second program-controlled valve, a third program-controlled valve and a fourth program-controlled valve, and after the adsorption tank is saturated with adsorption, the program-controlled system automatically switches to other unadsorbed tanks. Saturated adsorption tank; 3) when the adsorbent of any adsorption tank reaches the saturated state, the program-controlled system closes the tail gas input of the adsorption tank and starts the nitrogen purge unit, and nitrogen is purged to each adsorption tank in turn through the fifth program-controlled valve, the sixth program-controlled valve, the seventh program-controlled valve and the eighth program-controlled valve, and the adsorbent is replaced by nitrogen to remove the residual gas therein; 4) after nitrogen purge, the vacuum pump unit connected by the first vacuum tube, the second vacuum tube, the third vacuum tube and the fourth vacuum tube respectively opens the ninth program-controlled valve, the tenth program-controlled valve, the eleventh program-controlled valve and the twelfth program-controlled valve to vacuum the adsorption tank, further reduce the air pressure in the adsorption tank, and promote the analysis of VOCs in the adsorbent; exhaust the tail gas.

[0013] Beneficial effects: The present invention uses a program-controlled system to perform step-by-step control operations on multiple adsorption tanks in the adsorption unit, and the tail gas is processed through condensation, adsorption and other steps to ensure that the VOCs concentration meets the emission standards. After the adsorption tank is saturated with adsorption, the system automatically switches to other unsaturated adsorption tanks, and simultaneously starts the nitrogen purge and vacuum desorption process to regenerate the adsorbent to maintain the efficient operation of the device. The program-controlled system automatically adjusts the valve switch state, gas flow rate, desorption time and other parameters to ensure orderly connection between the work of each unit, ensuring the automation and stability of the entire process;

[0014] The present invention can reduce the VOCs concentration in the tail gas to 20g / Nm 3 The following meet ultra-clean emission standards and strict environmental protection requirements;

[0015] The present invention adopts a highly sensitive program-controlled valve group, and automatically controls the adsorption tank, nitrogen purge unit, vacuum pump, etc. through a central control system, thereby realizing fully automatic switching of the adsorption, desorption, and purge processes, greatly reducing manual intervention and improving operating efficiency;

[0016] Through multi-tank combination and split-range control, the adsorption tanks can work alternately in sequence, avoiding premature saturation of the adsorbent. At the same time, through efficient vacuum desorption and nitrogen purging, the service life of the adsorbent is extended, the nitrogen flushing and replacement efficiency is increased, and the operating cost is reduced;

[0017] This device can adjust the type of adsorbent and process parameters according to the different VOCs tail gas components to meet the needs of various working conditions. The multi-tank design of the adsorption tank can be expanded to 5 to 8 tanks to meet higher processing capacity requirements, with strong adaptability and flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the pipeline principle of a program-controlled device for treating VOCs tail gas;

[0019] Figure 2 It is a schematic diagram of the system structure of a program-controlled device for treating VOCs tail gas;

[0020] Figure 3 It is a flow chart of a program-controlled method for treating VOCs tail gas;

[0021] In the figure: 100, absorption tower, 110, condensation storage tank, 120, condenser, 200, adsorption unit, 201, first delivery pipe, 202, second delivery pipe, 203, third delivery pipe, 204, fourth delivery pipe, 205, first program-controlled valve, 206, second program-controlled valve, 207, third program-controlled valve, 208, fourth program-controlled valve, 300, first adsorption tank, 400, second adsorption tank, 500, third adsorption tank, 600, fourth adsorption tank, 700, tail gas discharge port, 800, nitrogen purge unit, 801, first purge Sweep pipe, 802, second purge pipe, 803, third purge pipe, 804, fourth purge pipe, 805, fifth program-controlled valve, 806, sixth program-controlled valve, 807, seventh program-controlled valve, 808, eighth program-controlled valve, 900, vacuum pump unit, 901, first vacuum tube, 902, second vacuum tube, 903, third vacuum tube, 904, fourth vacuum tube, 905, ninth program-controlled valve, 906, tenth program-controlled valve, 907, eleventh program-controlled valve, 908, twelfth program-controlled valve, 910, first vacuum pump, 920, second vacuum pump. DETAILED DESCRIPTION

[0022] In order to deepen the understanding of the present invention, the present invention will be further described in detail below in conjunction with embodiments and drawings. The embodiments are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention.

[0023] Please see Figure 1-3A program-controlled device for treating VOCs tail gas comprises an absorption tower 100, a condensation storage tank 110, a condenser 120, an adsorption unit 200, a nitrogen purge unit 800 and a vacuum pump unit 900. The condensation storage tank 110 is connected to the downstream of the condenser 120 along the flow direction of the tail gas, and is used to store the condensed tail gas; the condenser 120 is connected to the downstream of the absorption tower 100 along the flow direction of the tail gas, so that the tail gas enters the condensation storage tank 110 after condensation and cooling; the adsorption unit 200 is connected to the downstream of the condenser 120 along the flow direction of the tail gas, and comprises a first delivery pipe 201, a second delivery pipe 202, and a third delivery pipe 204, all of which are used to transport the tail gas. The first delivery pipe 203 and the fourth delivery pipe 204, the first delivery pipe 201, the second delivery pipe 202, the third delivery pipe 203 and the fourth delivery pipe 204 are connected in parallel with each other, the first delivery pipe 201, the second delivery pipe 202, the third delivery pipe 203 and the fourth delivery pipe 204 are respectively connected with the first program-controlled valve 205, the second program-controlled valve 206, the third program-controlled valve 207 and the fourth program-controlled valve 208, the first delivery pipe 201, the second delivery pipe 202, the third delivery pipe 203 and the fourth delivery pipe 204 are respectively connected with the first adsorption tank 300, the second adsorption tank 400, the third adsorption tank 500 and the fourth adsorption tank 600, the first adsorption tank 300, the second adsorption tank 400 00, the downstream of the third adsorption tank 500 and the fourth adsorption tank 600 are all connected to the tail gas discharge port 700; the nitrogen purge unit 800 includes a first purge pipe 801, a second purge pipe 802, a third purge pipe 803 and a fourth purge pipe 804 which are connected to the first adsorption tank 300, the second adsorption tank 400, the third adsorption tank 500 and the fourth adsorption tank 600 in sequence, and the first purge pipe 801, the second purge pipe 802, the third purge pipe 803 and the fourth purge pipe 804 are respectively connected to the fifth program-controlled valve 805, the sixth program-controlled valve 806, the seventh program-controlled valve 807 and the eighth program-controlled valve 808; the vacuum pump unit 900 is connected to the first adsorption tank 300 The second adsorption tank 400, the third adsorption tank 500 and the fourth adsorption tank 600 are connected, the vacuum pump unit 900 includes a first vacuum tube 901, a second vacuum tube 902, a third vacuum tube 903 and a fourth vacuum tube 904, the first vacuum tube 901, the second vacuum tube 902, the third vacuum tube 903 and the fourth vacuum tube 904 are respectively connected with a ninth program-controlled valve 905, a tenth program-controlled valve 906, an eleventh program-controlled valve 907 and a twelfth program-controlled valve 908, so that the air pressure in the first adsorption tank 300, the second adsorption tank 400, the third adsorption tank 500 and the fourth adsorption tank 600 are all evacuated to vacuum; the twelve program-controlled valves are all connected to the program-controlled system.

[0024] The adsorbent filled in the adsorption tank is a multi-layer structure. The first layer is an activated carbon material with high efficiency in adsorbing VOCs, the second layer is a silica gel material with high temperature resistance, and the third layer is a macroporous resin material, which is used for graded adsorption of VOCs components with different molecular weights and boiling points. Sensors are installed in the absorption tower, condensation storage tank, condenser, adsorption unit, nitrogen purge unit and vacuum pump unit to measure various data. K is obtained through the sensors. p , K i , K d The coefficient is used as the basis for controlling the program-controlled valve. The program-controlled valve includes an electric actuator, which is connected to the central control unit and monitors the pressure, temperature and gas concentration changes in the system in real time through sensors to automatically adjust the opening time and frequency of the program-controlled valve, so that the program-controlled device can seamlessly switch between adsorption, desorption and purging; the nitrogen purging unit 800 also includes a dual-path nitrogen pipeline, which includes a large flow pipeline and a small flow pipeline, and the dual-path nitrogen pipeline is further connected with an independent flow control valve, wherein the large flow pipeline is used to quickly replace the exhaust gas in the tank during the desorption stage of the adsorption tank, and the small flow pipeline is used to provide a stable nitrogen supply when the tank body returns to normal working pressure; the vacuum pump unit 900 includes a first vacuum pump 910 and a second vacuum pump 920, the first vacuum pump 910 is used to initially extract a large amount of residual gas in the adsorption tank, and the second vacuum pump 920 is used to accurately control the pressure in the tank to an ultra-low vacuum state to prevent overheating and excessive degradation of the adsorbent during the desorption process; the program-controlled system is calculated based on the following formula: Where Δu is the adjustment amount of the program-controlled valve, e(t) = C target -C(t) is the control error, K p , K i , K d are the proportional, integral and differential control coefficients respectively.

[0025] A program-controlled method for absorbing and adsorbing VOCs tail gas, comprising the following steps: 1) pre-treating the tail gas containing VOCs through an absorption tower 100 and then entering a condenser 120, using a cooling system to cool and condense the tail gas, and the condensed tail gas enters a condensation storage tank 110 for storage; 2) transporting the condensed tail gas from the condensation storage tank 110 to an adsorption unit 200, and the adsorption unit 200 guides the tail gas to a first adsorption tank 300, a second adsorption tank 400, a third adsorption tank 500 and a fourth adsorption tank 600 respectively through a program-controlled system, and each adsorption tank is filled with a different type of adsorbent; the flow direction of the tail gas is controlled by a first program-controlled valve 205, a second program-controlled valve 206, a third program-controlled valve 207 and a fourth program-controlled valve 208, and after the adsorption of the adsorption tank is saturated, the program-controlled system automatically switches to other unsaturated adsorption tanks. Adsorption tank; 3) When the adsorbent of any adsorption tank reaches a saturated state, the program-controlled system closes the tail gas input of the adsorption tank and starts the nitrogen purge unit 800, and nitrogen is purged to each adsorption tank in turn through the fifth program-controlled valve 805, the sixth program-controlled valve 806, the seventh program-controlled valve 807 and the eighth program-controlled valve 808, and the adsorbent is replaced with nitrogen to remove the residual gas therein; 4) After nitrogen purge, the vacuum pump unit 900 connected by the first vacuum tube 901, the second vacuum tube 902, the third vacuum tube 903 and the fourth vacuum tube 904 respectively opens the ninth program-controlled valve 905, the tenth program-controlled valve 906, the eleventh program-controlled valve 907 and the twelfth program-controlled valve 908 to vacuum-evacuate the adsorption tank, further reduce the air pressure in the adsorption tank, and promote the analysis of VOCs in the adsorbent; exhaust the tail gas.

[0026] In a specific embodiment: the absorption tower 100 has a diameter of 1.5 meters and a height of 6 meters. It is made of stainless steel and is suitable for treating exhaust gas containing VOCs such as benzene and alkanes. The condenser 120 adopts a double-tube heat exchanger, the cooling medium is circulating water, the water inlet temperature is 15°C, the water outlet temperature is 20°C, and the heat exchange area of ​​the condenser 120 is 15 square meters, which can reduce the exhaust gas temperature from 80°C to 30°C, causing some VOCs components to condense into liquid. The volume of the condensation storage tank 110 is 3 cubic meters, with a corrosion-resistant design and a liquid level monitoring function. The condensate is transported to the exhaust gas recovery device through an automatic drainage pump. The adsorption unit 200 includes four parallel adsorption tanks, each of which has a diameter of 1 meter, a height of 2 meters, and a volume of about 1.57 cubic meters. The adsorbents are filled with 200 kg of activated carbon, 150 kg of silica gel, and 100 kg of resin, respectively, for graded adsorption of different types of VOCs components. Each adsorption tank is connected to the delivery pipeline and tail gas outlet 700 through a program-controlled valve; the nitrogen purge unit 800 has a dual-channel nitrogen purge system, the diameter of the large-flow nitrogen pipeline is DN50, and the diameter of the small-flow pipeline is DN20. The purge nitrogen flow rate is 300Nm 3 / h, the high-flow purge time is set to 10 minutes, and the low-flow purge time is set to 5 minutes to ensure full regeneration of the adsorbent; the vacuum pump is a two-stage vacuum pump system, and the first-stage suction volume is 1000Nm 3 / h, the second stage is 300Nm 3 / h, the vacuum degree can reach 5kPa, and the vacuum pumping time is set to 20 minutes to ensure complete desorption of the adsorbent.

[0027] In a specific embodiment, the tail gas containing VOCs enters the absorption tower 100 through a pipeline, and the flow rate of the tail gas is 5000Nm 3 / h, temperature is 80℃.

[0028] The tail gas after being treated by the absorption tower 100 enters the condenser 120, where the tail gas is cooled to 30°C by circulating water, and some high-boiling-point VOCs are condensed into liquid and flow into the condensate storage tank 110. The condensate in the storage tank is monitored by a liquid level sensor and discharged regularly;

[0029] After being processed in the condenser 120, the tail gas enters any one of the four adsorption tanks in sequence through the program control system. Each adsorption tank is filled with different adsorbents such as activated carbon, silica gel and resin, which can grade and adsorb different types of VOCs such as benzene, alkanes, esters, etc. The system automatically adjusts the adsorption time by setting the outlet concentration target of VOCs. When the tail gas concentration reaches the set target, the program control system switches to the next adsorption tank;

[0030] When the adsorbent in a certain adsorption tank is saturated, the program control system automatically closes the air inlet of the adsorption tank and opens the nitrogen purge unit 800. The large flow of nitrogen is 300Nm 3 / h for 10 minutes to quickly replace the residual gas in the tank, and then switch to a low-flow nitrogen purge with a flow rate of 100Nm 3 / h for 5 minutes to ensure that the residual gas in the adsorbent is completely replaced;

[0031] After the nitrogen purge is completed, the system starts the vacuum pump and desorbs the saturated adsorption tank through the programmable valve control. The vacuum pump reduces the pressure in the tank to 5kPa. The initial pumping time is 15 minutes, followed by a more precise desorption, which lasts for 5 minutes to ensure that the VOCs in the adsorbent are completely desorbed and discharged from the system;

[0032] The exhaust gas treated by the adsorption unit 200 is discharged into the atmosphere through the exhaust port. An online monitoring system is installed at the exhaust port to monitor the VOCs concentration in the exhaust gas in real time. When the VOCs concentration in the exhaust gas exceeds 20g / Nm 3 When the system is in a state of emergency, it will automatically alarm and make corresponding adjustments.

[0033] Overall, the unit is able to efficiently handle 5000Nm 3 / h of VOCs tail gas, the outlet concentration is stably controlled at 20g / Nm 3 The following meets the ultra-clean emission standards; the rapid response of the program-controlled system ensures seamless switching between adsorption and desorption processes, improves processing efficiency and reduces energy consumption; the dual-path nitrogen purge and two-stage vacuum desorption system improve purge efficiency, extend its service life and reduce operating costs.

[0034] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A program-controlled device for treating VOCs tail gas, characterized in that: It includes an absorption tower, a condensation storage tank, a condenser, an adsorption unit, a nitrogen purge unit and a vacuum pump unit. The condensation storage tank is connected to the downstream of the condenser along the flow direction of the exhaust gas and is used to store the condensed exhaust gas; the condenser is connected to the downstream of the absorption tower along the flow direction of the exhaust gas so that the exhaust gas enters the condensation storage tank after condensation and cooling; the adsorption unit is connected to the downstream of the condenser along the flow direction of the exhaust gas, including a first delivery pipe, a second delivery pipe, a third delivery pipe and a fourth delivery pipe, all of which are used to transport the exhaust gas. The first delivery pipe, the second delivery pipe, the third delivery pipe and the fourth delivery pipe are connected in parallel with each other, and the first delivery pipe, the second delivery pipe and the third delivery pipe are respectively connected with a first program-controlled valve, a second program-controlled valve, a third program-controlled valve and a fourth program-controlled valve, and the ends of the first delivery pipe, the second delivery pipe, the third delivery pipe and the fourth delivery pipe are respectively connected to a first adsorption tank, a second adsorption tank, a third adsorption tank and a fourth adsorption tank, and the first adsorption tank, the second adsorption tank, The downstream of the third adsorption tank and the fourth adsorption tank are both connected to the tail gas discharge port; the nitrogen purge unit includes a first purge pipe, a second purge pipe, a third purge pipe and a fourth purge pipe which are connected to the first adsorption tank, the second adsorption tank, the third adsorption tank and the fourth adsorption tank in sequence, and the first purge pipe, the second purge pipe, the third purge pipe and the fourth purge pipe are respectively connected with a fifth program-controlled valve, a sixth program-controlled valve, a seventh program-controlled valve and an eighth program-controlled valve; the vacuum pump unit is connected with the first adsorption tank, the second adsorption tank, the third adsorption tank and the fourth adsorption tank, and the vacuum pump unit includes a first vacuum tube, a second vacuum tube, a third vacuum tube and a fourth vacuum tube, and the first vacuum tube, the second vacuum tube, the third vacuum tube and the fourth vacuum tube are respectively connected with a ninth program-controlled valve, a tenth program-controlled valve, an eleventh program-controlled valve and a twelfth program-controlled valve, so that the air pressure in the first adsorption tank, the second adsorption tank, the third adsorption tank and the fourth adsorption tank is evacuated to vacuum; the twelve program-controlled valves are all connected to the program control system.

2. A program-controlled device for absorbing VOCs tail gas according to claim 1, characterized in that: The adsorbent filled inside the adsorption tank has a multi-layer structure. The first layer is an activated carbon material that efficiently adsorbs VOCs, the second layer is a silica gel material that is resistant to high temperature adsorption, and the third layer is a macroporous resin material, which is used for graded adsorption of VOCs components with different molecular weights and boiling points.

3. A program-controlled device for absorbing VOCs tail gas according to claim 1, characterized in that: The program-controlled valve includes an electric actuator that is connected to a central control unit and monitors the pressure, temperature and gas concentration changes in the system in real time through sensors to automatically adjust the opening time and frequency of the program-controlled valve so that the program-controlled device can seamlessly switch between adsorption, desorption and purging.

4. A program-controlled device for absorbing VOCs tail gas according to claim 1, characterized in that: The nitrogen purge unit also includes a dual-path nitrogen pipeline, which includes a large-flow pipeline and a small-flow pipeline. The dual-path nitrogen pipeline is further connected with an independent flow control valve, wherein the large-flow pipeline is used to quickly replace the exhaust gas in the adsorption tank during the desorption stage of the adsorption tank, and the small-flow pipeline is used to provide a stable nitrogen supply when the tank body returns to normal working pressure.

5. A program-controlled device for absorbing VOCs tail gas according to claim 1, characterized in that: The vacuum pump unit includes a first vacuum pump and a second vacuum pump. The first vacuum pump is used to initially extract a large amount of residual gas in the adsorption tank, and the second vacuum pump is used to accurately control the pressure in the tank to an ultra-low vacuum state to prevent overheating and excessive degradation of the adsorbent during the desorption process.

6. A program-controlled device for absorbing VOCs tail gas according to claim 1, characterized in that: The program control system is calculated based on the following formula: Where Δu is the adjustment amount of the program-controlled valve, e(t) = C target -C(t) is the control error, K p , K i , K d are the proportional, integral and differential control coefficients respectively.

7. A program-controlled method for absorbing and adsorbing VOCs tail gas, using the program-controlled device for absorbing and adsorbing VOCs tail gas according to any one of claims 1 to 6, characterized in that: The following steps are involved: 1) The tail gas containing VOCs is pre-treated through the absorption tower and then enters the condenser, and the cooling system is used to cool and condense the tail gas, and the condensed tail gas enters the condensation storage tank for storage; 2) The condensed tail gas is transported from the condensation storage tank to the adsorption unit, and the adsorption unit guides the tail gas to the first adsorption tank, the second adsorption tank, the third adsorption tank and the fourth adsorption tank through the program control system, and each adsorption tank is filled with different types of adsorbents; the flow direction of the tail gas is controlled by the first program control valve, the second program control valve, the third program control valve and the fourth program control valve. After the adsorption of the adsorption tank is saturated, the program control system automatically switches to other unsaturated adsorption tanks; 3) When any adsorption tank is When the adsorbent reaches the saturated state, the program-controlled system closes the tail gas input of the adsorption tank and starts the nitrogen purge unit, and nitrogen is purged to each adsorption tank in turn through the fifth program-controlled valve, the sixth program-controlled valve, the seventh program-controlled valve and the eighth program-controlled valve, and the adsorbent is replaced with nitrogen to remove the residual gas therein; 4) After the nitrogen purge, the vacuum pump unit connected to the first vacuum tube, the second vacuum tube, the third vacuum tube and the fourth vacuum tube respectively opens the ninth program-controlled valve, the tenth program-controlled valve, the eleventh program-controlled valve and the twelfth program-controlled valve to vacuum the adsorption tank, further reduce the air pressure in the adsorption tank, and promote the analysis of VOCs in the adsorbent; 5) exhaust the tail gas.

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