A dichloromethane waste gas treatment system and method

Abstract

The present invention provides a dichloromethane waste gas treatment system and method. Among them, the dichloromethane waste gas treatment system includes a first cooling device, an adsorption device, a temperature-variable dehumidification device, and a molecular sieve rotary wheel device that are connected in sequence. By using the dichloromethane waste gas treatment system and method of the present invention to treat dichloromethane waste gas, the concentration of dichloromethane can be reduced to below 20 mg / m<supgt;3< / supgt;, meeting the dichloromethane emission standard, and the cost is controllable.

Description

Technical Field

[0001] The present invention relates to the technical field of gas purification, and in particular to a dichloromethane waste gas treatment system and method. Background Art

[0002] In the production of chemical PC resin, PE diaphragm, and pharmaceutical chemical production processes, a large amount of dichloromethane is used as a solvent, resulting in the emission of high-concentration dichloromethane waste gas. The emission concentration is generally 100 - 200 g / m 3 , for the emission of dichloromethane, industry and local emission requirements have been successively introduced in the petrochemical industry, Shanghai, Sichuan, etc. The strictest standard is that the dichloromethane emission concentration after treatment < 20 mg / m 3 .

[0003] For the waste gas treatment requirement of 10000 Nm 3 / h air volume and 1200 kg / h dichloromethane emission, the processes currently used in the market mainly include granular carbon adsorption, multi-stage deep cooling and other processes.

[0004] The molecular diameter of dichloromethane is relatively small, 0.33 nm. According to the pore size matching principle, it is suitable to use an adsorption material with a small pore size for adsorption. The pore size distribution of granular activated carbon is relatively wide, and the mesopore volume accounts for more than 8%. The adsorption capacity is relatively weak. At the same time, due to the too wide pore size distribution, the desorption tailing phenomenon is serious, the desorption is not complete, and after running for half a year, the performance decays. The outlet concentration after treatment often reaches 500 mg / m 3 or more, making it difficult to meet the requirements of ultra-low emissions; and the ash content of granular activated carbon accounts for more than 5%. The active components in the ash are more likely to cause the decomposition of dichloromethane to produce hydrochloric acid, which aggravates the corrosion of the equipment. The whole activated carbon adsorber is made of titanium metal, and the investment cost is too high.

[0005] When using the three-stage deep cooling process, it is generally cooled to -60°C, and the saturated concentration of dichloromethane is 12.6 g / m 3 , which cannot meet the standard. A process of additional activated carbon re-adsorption still needs to be added at the back end. Due to the limitations of the granular activated carbon adsorption material, it is still difficult to achieve the emission requirement of 20 mg / m 3 , and the investment is more than 20 million yuan. The investment is huge and it is difficult to meet the emission requirements.

[0006] Therefore, there is an urgent need for a dichloromethane waste gas treatment system and method that can effectively reduce the dichloromethane concentration and has controllable costs. Summary of the Invention

[0007] The purpose of the present invention is to provide a dichloromethane waste gas treatment system and method to at least solve the technical problems that the prior art cannot effectively meet the dichloromethane emission standard and has a high cost.

[0008] To achieve the above object, the present invention provides a dichloromethane waste gas treatment system, including a first cooling device, an adsorption device, a temperature-variable dehumidification device, and a molecular sieve rotor device connected in sequence.

[0009] Optionally, activated carbon fiber material is provided inside the adsorption device, and the activated carbon fiber material is used to adsorb dichloromethane.

[0010] Optionally, the adsorption device includes a primary adsorption unit and a secondary adsorption unit. For waste gas with a relatively high concentration of dichloromethane, secondary adsorption can be adopted to reduce the concentration of dichloromethane in the waste gas to a certain concentration (such as 100 mg / m 3 ) or less after two adsorptions.

[0011] Optionally, the dichloromethane waste gas treatment system further includes a second cooling device and a heating device. The primary adsorption unit and / or the secondary adsorption unit are provided with a drying inlet and a drying outlet, and the drying outlet, the second cooling device, the heating device, and the drying inlet are connected in sequence. The second cooling device and the heating device are used to dehumidify the activated carbon fiber material inside the primary adsorption unit and / or the secondary adsorption unit. By cooling and then heating the gas flowing out of the drying outlet, the relative humidity of the gas is reduced, and then it returns to the primary adsorption unit and / or the secondary adsorption unit through the drying inlet, and this cycle is repeated, thereby reducing the humidity of the activated carbon fiber material inside the primary adsorption unit and / or the secondary adsorption unit.

[0012] Optionally, the adsorption device further includes a desorption unit, and the desorption unit is used to regenerate the adsorbed activated carbon fiber material.

[0013] Optionally, the dichloromethane waste gas treatment system further includes a condensation device. The desorption unit is provided with a steam inlet and a steam outlet, and the steam outlet of the desorption unit is connected to the steam inlet of the condensation device. In this application, hot steam is used to regenerate the adsorbed activated carbon fiber material, and the desorbed steam contains dichloromethane, which is recovered and treated through the condensation device.

[0014] Optionally, the condensation device includes a primary condensation unit and a secondary condensation unit. The secondary condensation unit is provided with a non-condensable gas outlet and a condensate outlet. The steam outlet of the analysis unit is connected to the steam inlet of the primary condensation unit. The outlet of the primary condensation unit is connected to the inlet of the secondary condensation unit. The non-condensable gas outlet of the secondary condensation unit is connected to the inlet of the first cooling device. After the analyzed steam is condensed in two stages, the temperature drops to 12 - 20 °C, and it can be subjected to stratified recovery and reuse. Since the non-condensable gas contains dichloromethane, the non-condensable gas is sent to the first cooling device to be treated together with the dichloromethane waste gas to avoid environmental pollution. The condensate outlet of the secondary condensation unit is subjected to stratified treatment. The organic phase dichloromethane is recovered and reused, and the wastewater can be connected to a wastewater treatment device for treatment.

[0015] Optionally, the circulating water of the primary condensation unit and the circulating water of the second cooling device are used in series, which can effectively save the energy consumption of the circulating water.

[0016] Optionally, the primary adsorption unit and / or the secondary adsorption unit can be interchanged with the analysis unit. With this arrangement, after the primary adsorption unit and / or the secondary adsorption unit have adsorbed for a period of time, they are converted into the analysis unit, enabling the activated carbon fiber materials inside the primary adsorption unit and / or the secondary adsorption unit to be regenerated, so that they can be used cyclically. While continuously adsorbing, the adsorption capacity can be restored.

[0017] Optionally, the molecular sieve rotary wheel device includes an adsorption zone, a desorption zone, and a cooling zone.

[0018] Optionally, the molecular sieve rotary wheel device is provided with two gas inlets, corresponding to the adsorption zone and the cooling zone of the molecular sieve rotary wheel device respectively.

[0019] Optionally, the dichloromethane waste gas treatment system further includes a desorption heating device, which is connected to the molecular sieve rotary wheel device and is used to heat the gas in the cooling zone of the molecular sieve rotary wheel device and then send it back to the molecular sieve rotary wheel device for desorbing the molecular sieve rotary wheel. The molecular sieve rotary wheel device uses a disc-shaped molecular sieve rotary wheel that rotates continuously. The gas enters the cooling zone of the molecular sieve rotary wheel device through the temperature and humidity change device to purge the molecular sieve rotary wheel. The gas after purging uses the heat transferred from the desorption zone to preheat the gas temperature to 90 - 100 °C, and then enters the desorption heating device for heating to raise the gas temperature to 140 - 150 °C, and is sent back to the molecular sieve rotary wheel device for desorbing the molecular sieve rotary wheel.

[0020] Optionally, the molecular sieve rotary wheel device is connected to the first cooling device and is used to send the desorbed gas into the first cooling device to be treated together with the dichloromethane waste gas.

[0021] Optionally, the dichloromethane waste gas treatment system further includes a concentration buffer device, which is respectively connected to the first cooling device and the adsorption device. The concentration buffer device is used to balance the concentration of the dichloromethane waste gas, the non-condensable gas and / or the desorbed gas, so that the dichloromethane concentration at the inlet of the adsorption device is relatively stable.

[0022] Optionally, a microporous adsorption material with a high specific surface area, preferably a microporous carbon material with a high specific surface area, is arranged inside the concentration buffer device. The concentration buffer device can adsorb high-concentration dichloromethane gas. When the concentration of dichloromethane gas is low, desorption can be carried out through the concentration difference, so as to balance the fluctuation of the dichloromethane concentration and keep the dichloromethane concentration entering the adsorption device within a stable range.

[0023] The present invention also provides a method for treating dichloromethane waste gas. The dichloromethane waste gas is discharged after being cooled, adsorbed, temperature-variable dehumidified, and re-adsorbed by a molecular sieve rotor in sequence.

[0024] Optionally, after the dichloromethane waste gas is cooled, the temperature is 15-35°C.

[0025] Optionally, activated carbon fiber material is used for the adsorption. After the adsorption, the concentration of dichloromethane is reduced to 100 mg / m 3 or less; the adsorption is preferably two-stage adsorption.

[0026] Optionally, a cyclic drying method is adopted to reduce the moisture content on the surface of the activated carbon fiber material.

[0027] Optionally, the temperature of the gas after the temperature-variable dehumidification is 30-35°C, and the humidity is 70-75%.

[0028] Optionally, after the re-adsorption by the molecular sieve rotor, the concentration of dichloromethane is reduced to 20 mg / m 3 or less.

[0029] By using the above dichloromethane waste gas treatment system and method of the present invention to treat dichloromethane waste gas, the concentration of dichloromethane can be reduced to 20 mg / m 3The following meets the dichloromethane emission standard and has controllable costs. In addition, by adopting a circulating drying method, the moisture content on the surface of the activated carbon fiber material is effectively reduced, thereby reducing the load of the subsequent temperature-variable dehumidification device. At the same time, the second cooling device and the primary condensation unit adopt a heat coupling method to maximize the energy consumption savings of the circulating water and reduce the process cost. Third, the adsorption unit and the desorption unit alternate, so that continuous waste gas treatment can be achieved, improving the waste gas treatment efficiency and reducing the cost. Fourth, by adopting a disc-shaped molecular sieve rotor, the heat in the desorption zone can be reused, reducing the energy consumption of the desorption heating device. Fifth, the non-condensable gas and the desorbed gas are returned to the front end of the system and treated together with the dichloromethane waste gas to avoid secondary pollution to the environment during the treatment process. At the same time, through the concentration buffer device for concentration balance, the adsorption efficiency of the adsorption device is effectively improved, and thus the treatment efficiency of the entire treatment system is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0031] Figure 1 FIG. shows a schematic diagram of an optional dichloromethane waste gas treatment system according to an embodiment of the present invention;

[0032] Figure 2 FIG. shows a flowchart of an optional dichloromethane waste gas treatment method according to an embodiment of the present invention.

[0033] DESCRIPTION OF THE REFERENCE NUMERALS:

[0034] 1 - First cooling device; 2A - Primary adsorption unit; 2B - Secondary adsorption unit; 2C - Desorption unit; 3 - Temperature-variable dehumidification device; 4 - Molecular sieve rotor device; 5 - Second cooling device; 6 - Heating device; 7A - Primary condensation unit; 7B - Secondary condensation unit; 8 - Desorption heating device; 9 - Concentration buffer device; 10 - First fan; 11 - Second fan; 121 - Gas inlet valve; 122 - Gas outlet valve; 123 - Drying inlet valve; 124 - Drying outlet valve; 125 - Steam inlet valve; 126 - Steam outlet valve. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] Embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are only used to explain the present invention and should not be construed as a limitation to the present invention.

[0036] In the description of the present invention, it should be understood that the terms "comprising", "including", "provided with", "containing" or any other modification thereof used herein are intended to cover non-exclusive inclusion. For example, a device provided with the listed elements is not necessarily limited to these elements, but may include other elements not expressly listed or elements inherent to such a device.

[0037] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality of" means two or more unless otherwise specifically defined. "And / or" is used to indicate that either or both of the stated situations may occur. For example, A and / or B includes (A and B) and (A or B).

[0038] In the present invention, unless otherwise clearly defined and limited, the terms "installed", "connected", "connected to", "fixed" and other terms should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0039] Embodiment 1

[0040] This embodiment provides a dichloromethane waste gas treatment system, as Figure 1 shown, including a first cooling device 1, a concentration buffer device 9, a first fan 10, a primary adsorption unit 2A, a secondary adsorption unit 2B, a desorption unit 2C, a variable temperature and dehumidification device 3, a molecular sieve rotor device 4, a second cooling device 5, a heating device 6, a second fan 11, a primary condensation unit 7A, a secondary condensation unit 7B, and a desorption heating device 8.

[0041] Among them, the primary adsorption unit 2A, the secondary adsorption unit 2B, and the desorption unit 2C have the same structure, each being provided with a gas inlet and outlet, a drying inlet and outlet, and a steam inlet and outlet. Among them, the gas inlet is provided with a gas inlet valve 121, the gas outlet is provided with a gas outlet valve 122, the drying inlet is provided with a drying inlet valve 123, the drying outlet is provided with a drying outlet valve 124, the steam inlet is provided with a steam inlet valve 125, and the steam outlet is provided with a steam outlet valve 126. All of them are internally provided with activated carbon fiber materials; the gas inlet valves 121 are all connected to the first fan 10, the gas outlet valves 122 are all connected to the temperature-variable dehumidification device 3, the drying inlet valves 123 are all connected to the second cooling device 5, the drying outlet valves 124 are all connected to the second fan 11, the steam inlet valves 125 are all connected to a steam pipeline (not shown), and the steam outlet valves 126 are all connected to the primary condensation unit 7A; by controlling each valve, the interactive cyclic switching between primary adsorption, secondary adsorption, and desorption can be realized, enabling the adsorption unit to be desorbed after adsorption and restoring its adsorption capacity, and without the need to suspend the waste gas treatment, effectively improving the waste gas treatment efficiency and reducing the process cost.

[0042] In this embodiment, taking the primary adsorption unit 2A, the secondary adsorption unit 2B, and the desorption unit 2C to respectively realize primary adsorption, secondary adsorption, and desorption as an example, open the gas inlet valve 121 and the drying outlet valve 124 of the primary adsorption unit 2A, and close the gas outlet valve 122, the drying inlet valve 123, the steam inlet valve 125, and the steam outlet valve 126 of the primary adsorption unit 2A; open the gas outlet valve 122 and the drying inlet valve 123 of the secondary adsorption unit 2B, and close the gas inlet valve 121, the drying outlet valve 124, the steam inlet valve 125, and the steam outlet valve 126 of the secondary adsorption unit 2B; open the steam inlet valve 125 and the steam outlet valve 126 of the desorption unit 2C, and close the gas inlet valve 121, the gas outlet valve 122, the drying inlet valve 123, and the drying outlet valve 124 of the desorption unit 2C. When it is necessary to desorb the primary adsorption unit 2A, just open the steam inlet valve 125 and the steam outlet valve 126 of the primary adsorption unit 2A, and close the gas inlet valve 121, the gas outlet valve 122, the drying inlet valve 123, and the drying outlet valve 124 of the primary adsorption unit 2A. At the same time, open the gas outlet valve 122 and the drying inlet valve 123 of the desorption unit 2C, and close the gas inlet valve 121, the drying outlet valve 124, the steam inlet valve 125, and the steam outlet valve 126 of the secondary adsorption unit 2C to make the desorption unit 2C play the role of secondary adsorption, and so on. By controlling the relevant valves of the primary adsorption unit 2A, the secondary adsorption unit 2B, and the desorption unit 2C, the interactive cyclic switching between primary adsorption, secondary adsorption, and desorption is realized.

[0043] Using the dichloromethane waste gas treatment system of this embodiment to treat dichloromethane waste gas, the process is as follows:

[0044] The dichloromethane waste gas is cooled by the first cooling device 1. Among them, the first cooling device 1 can be a deep cold water cooling device. After being cooled by the first cooling device 1, the gas temperature is reduced to 15 - 35 °C. Then, the gas enters the concentration buffer device 9 for concentration balancing, so that the concentration of dichloromethane in the gas after being treated by the concentration buffer device 9 is maintained within a stable range. Among them, the concentration buffer device 9 is internally provided with a microporous adsorption material with a specific surface area ≥ 1200 m² / g. Subsequently, the gas enters the primary adsorption unit 2A through the gas inlet valve 121 of the first fan 10 and the primary adsorption unit 2A for primary adsorption, and enters the second cooling device 5 for cooling through the drying outlet valve 124 of the primary adsorption unit 2A. After being heated by the heating device 6, it enters the secondary adsorption unit 2B through the drying inlet valve 123 of the second fan 11 and the secondary adsorption unit 2B for secondary adsorption. The concentration of dichloromethane in the gas after secondary adsorption is reduced to 100 mg / m 3 Below; the gas after secondary adsorption enters the temperature-variable dehumidification device 3 through the gas outlet valve 122 of the secondary adsorption unit 2B. The gas temperature is reduced to 20 - 25 °C with water at 7 - 12 °C, and then heated to 30 - 35 °C with steam, and the humidity is 70 - 75%; the gas after temperature-variable dehumidification enters the molecular sieve rotor device 4 for molecular sieve rotor re-adsorption, and the concentration of dichloromethane in the gas is reduced to 20 mg / m 3 Below and is discharged.

[0045] For the desorption unit 2C, hot steam enters the desorption unit 2C through the steam inlet valve 125 of the desorption unit 2C to regenerate the activated carbon fiber material therein. The desorbed steam enters the primary condensation unit 7A through the steam outlet valve 126 of the desorption unit 2C and is cooled with circulating water at 32 - 37 °C; then it enters the secondary condensation unit 7B for secondary condensation. After two-stage condensation, the temperature of the desorbed steam is reduced to 12 - 20 °C, and it can be separated and recycled. Among them, the non-condensable gas enters the first cooling device 1 and is treated together with the dichloromethane waste gas. The condensate containing dichloromethane is discharged from the condensate outlet of the secondary condensation unit 7B and can be separated. The organic phase dichloromethane is recovered and reused, and the wastewater is connected to the wastewater treatment device for treatment. The desorption time is generally 5 - 10 min. After the desorption is completed, the primary adsorption unit 2A, the secondary adsorption unit 2B, and the desorption unit 2C are alternately switched.

[0046] The desorption heating device 8 is used to desorb the molecular sieve rotor in the molecular sieve rotor device 4. The molecular sieve rotor device 4 is provided with an adsorption zone, a desorption zone, and a cooling zone, and internally provided with a disc-shaped molecular sieve rotor. The molecular sieve rotor rotates continuously. The gas enters the cooling zone of the molecular sieve rotor device 4 through the variable temperature and dehumidification device 3, purges the molecular sieve rotor, and the purged gas uses the heat rotated from the desorption zone to preheat the temperature of the gas to 90 - 100 °C, and then enters the desorption heating device 8 for heating, heating the gas temperature to 140 - 150 °C, and transmitting it back to the molecular sieve rotor device 4 to desorb the molecular sieve rotor. The desorbed gas is sent to the first cooling device 1 and is processed together with the dichloromethane waste gas.

[0047] The high specific surface area microporous adsorption material in the concentration buffer device can balance the dichloromethane concentration in the mixed gas of the dichloromethane waste gas, the non-condensable gas generated by the secondary condensation unit 7B, and the gas generated by the rotor desorption, so as to balance the dichloromethane concentration of the mixed gas within a certain range and ensure the relative stability of the gas concentration after treatment.

[0048] Preferably, the second cooling device 5 adopts the method of circulating water + deep cold water. The circulating water is used in series with the circulating water of the primary condensation unit 7A. The internal circulation drying for a certain time can reduce the instantaneous utility load. Since the analysis and drying are not carried out simultaneously, the circulating water adopted by the second cooling device 5 can be used in series with the circulating water of the primary condensation unit 7A, and there is no need to provide additional circulating water, which can save a large amount of energy consumption of the circulating water and reduce the process cost.

[0049] Example 2

[0050] This example provides a method for treating dichloromethane waste gas, as Figure 2 shown, using the dichloromethane waste gas treatment system of the present invention, including the following steps:

[0051] The dichloromethane waste gas is cooled by the first cooling device 1, and the gas temperature is reduced to 15 - 35 °C; after being adsorbed by the activated carbon fiber material in two stages, the dichloromethane concentration in the gas is reduced to 100 mg / m 3 or less; after being dehumidified by the variable temperature and dehumidification device 3, the temperature of the gas is 30 - 35 °C and the humidity is 70 - 75%; then, through the molecular sieve rotor device 4 for molecular sieve rotor re-adsorption, the dichloromethane concentration in the gas is reduced to 20 mg / m 3 or less.

[0052] Example 3

[0053] This example provides a method for treating dichloromethane waste gas. Specifically, taking 10000 Nm 3 / h air volume, the waste gas treatment requirement for dichloromethane emission of 1200 kg / h, the waste gas emission temperature is 50 °C, the relative humidity is 30%, after the waste gas is cooled by surface cooling, the gas temperature drops to 30 °C; activated carbon fiber material is used for two-stage adsorption, and a total of three boxes are designed, one box for primary adsorption, one box for secondary adsorption, and the third box enters the regeneration and desorption state. The three boxes are cycled and switched repeatedly to realize the exchange of adsorption-desorption. The switching time is 5-10 min. After two-stage adsorption by activated carbon fiber material, the dichloromethane emission concentration < 100 mg / m 3 , the temperature and humidity after two-stage adsorption by activated carbon fiber material are 80 °C, 100% RH - 50 °C, 50% RH; after temperature-variable dehumidification, the temperature and humidity of the gas are 30 °C, 70% RH; high-efficiency molecular sieve rotors are used for re-adsorption, and the concentration of dichloromethane after treatment reaches 10 mg / m 3 or less. Among them, the molecular sieve rotor adopts a continuous rotating circular cake structure, and realizes the continuous conversion of adsorption and desorption through continuous rotation. The dichloromethane gas after desorption enters the front end for cooling and re-adsorption after cooling.

[0054] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0055] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A dichloromethane waste gas treatment system, characterized in that, It includes a first cooling device, a concentration buffer device, a first fan, an adsorption device, a temperature-variable dehumidification device, a molecular sieve rotor device, a second cooling device, a heating device, a second fan, a condensation device, and a desorption heating device; Among them, the adsorption device includes a primary adsorption unit, a secondary adsorption unit, and a desorption unit, all of which are internally provided with activated carbon fiber materials; The condensation device includes a primary condensation unit and a secondary condensation unit. The secondary condensation unit is provided with a non-condensable gas outlet and a condensate outlet; The primary adsorption unit, the secondary adsorption unit, and the desorption unit have the same structure and are all provided with gas inlets and outlets, drying inlets and outlets, and steam inlets and outlets. Among them, the gas inlet is provided with a gas inlet valve, the gas outlet is provided with a gas outlet valve, the drying inlet is provided with a drying inlet valve, the drying outlet is provided with a drying outlet valve, the steam inlet is provided with a steam inlet valve, and the steam outlet is provided with a steam outlet valve; the gas inlet valves are all connected to the first fan, the gas outlet valves are all connected to the temperature-variable dehumidification device, the drying inlet valves are all connected to the second cooling device, the drying outlet valves are all connected to the second fan, the steam inlet valves are all connected to the steam pipeline, and the steam outlet valves are all connected to the primary condensation unit; during operation, first open the gas inlet valve and the drying outlet valve of the primary adsorption unit, and close the gas outlet valve, the drying inlet valve, the steam inlet valve, and the steam outlet valve of the primary adsorption unit; open the gas outlet valve and the drying inlet valve of the secondary adsorption unit, and close the gas inlet valve, the drying outlet valve, the steam inlet valve, and the steam outlet valve of the secondary adsorption unit; open the steam inlet valve and the steam outlet valve of the desorption unit, and close the gas inlet valve, the gas outlet valve, the drying inlet valve, and the drying outlet valve of the desorption unit; when it is necessary to desorb the primary adsorption unit, open the steam inlet valve and the steam outlet valve of the primary adsorption unit, and close the gas inlet valve, the gas outlet valve, the drying inlet valve, and the drying outlet valve of the primary adsorption unit. At the same time, open the gas outlet valve and the drying inlet valve of the desorption unit, and close the gas inlet valve, the drying outlet valve, the steam inlet valve, and the steam outlet valve of the secondary adsorption unit to make the original desorption unit play the role of secondary adsorption, and so on. By controlling the relevant valves of the primary adsorption unit, the secondary adsorption unit, and the desorption unit, the interactive cyclic switching of primary adsorption, secondary adsorption, and desorption is realized, so that the adsorption unit can be desorbed after adsorption, restore the adsorption capacity, and there is no need to suspend the waste gas treatment; The drying outlet of the primary adsorption unit and / or the secondary adsorption unit, the second cooling device, the heating device, and the drying inlet are connected in sequence; the second cooling device and the heating device are used to dehumidify the activated carbon fiber materials inside the primary adsorption unit and / or the secondary adsorption unit; The analysis unit is used to regenerate the adsorbed activated carbon fiber material; the gas outlet of the analysis unit is connected to the steam inlet of the condensation device; the steam outlet of the analysis unit is connected to the steam inlet of the first-stage condensation unit, the outlet of the first-stage condensation unit is connected to the inlet of the second-stage condensation unit, and the non-condensable gas outlet of the second-stage condensation unit is connected to the inlet of the first cooling device; the circulating water of the first-stage condensation unit and the circulating water of the second cooling device are used in series. The molecular sieve rotary wheel device includes an adsorption zone, a desorption zone, and a cooling zone; the desorption heating device is connected to the molecular sieve rotary wheel device and is used to heat the gas in the cooling zone of the molecular sieve rotary wheel device and then return it to the molecular sieve rotary wheel device to desorb the molecular sieve rotary wheel. The molecular sieve rotary wheel device is also connected to the first cooling device and is used to send the desorbed gas into the first cooling device to be treated together with the dichloromethane waste gas. The concentration buffer device is internally provided with a microporous adsorption material with a high specific surface area; the concentration buffer device is respectively connected to the first cooling device and the adsorption device and is used to balance the concentration of the dichloromethane waste gas and the non-condensable gas and / or the desorbed gas, so that the dichloromethane concentration at the inlet of the adsorption device is relatively stable.

2. A method for treating dichloromethane waste gas, characterized in that, The dichloromethane waste gas is discharged after passing through the system according to claim 1 and successively undergoing cooling, adsorption, temperature-variable dehumidification, and molecular sieve rotary wheel re-adsorption. Specifically, the dichloromethane waste gas is cooled by the first cooling device, and the gas temperature is reduced to 15 - 35°C; then, the gas enters the concentration buffer device for concentration balancing, so that the concentration of dichloromethane in the gas after being treated by the concentration buffer device is maintained within a stable range. Among them, the concentration buffer device is internally provided with a microporous adsorption material with a specific surface area ≥ 1200 m² / g; subsequently, the gas enters the primary adsorption unit through the first fan and the gas inlet valve of the primary adsorption unit for primary adsorption, and enters the second cooling device through the drying outlet valve of the primary adsorption unit for cooling. After being heated by the heating device, the gas enters the secondary adsorption unit through the second fan and the drying inlet valve of the secondary adsorption unit for secondary adsorption. The concentration of dichloromethane in the gas after secondary adsorption is reduced to 100 mg / m 3 ³ or less; the gas after secondary adsorption enters the temperature-variable dehumidification device through the gas outlet valve of the secondary adsorption unit. The gas temperature is reduced to 20 - 25°C with 7 - 12°C water, and then heated to 30 - 35°C with steam, and the humidity is 70 - 75%; the gas after temperature-variable dehumidification enters the molecular sieve rotor device for molecular sieve rotor re-adsorption, and the concentration of dichloromethane in the gas is reduced to 20 mg / m 3 ³ or less and then discharged; For the analysis unit, hot steam enters the analysis unit through the steam inlet valve of the analysis unit to regenerate the activated carbon fiber material therein. The steam after analysis enters the first-stage condensation unit through the steam outlet valve of the analysis unit and is cooled by circulating water at 32-37°C; then it enters the second-stage condensation unit for secondary condensation. After two-stage condensation, the temperature of the steam after analysis drops to 12-20°C, and it can be subjected to stratified recovery and reuse. Among them, the non-condensable gas enters the first cooling device and is treated together with the dichloromethane waste gas. The condensate containing dichloromethane is discharged from the condensate outlet of the second-stage condensation unit and can be subjected to stratified treatment. The organic phase dichloromethane is recovered and reused, and the wastewater is connected to a wastewater treatment device for treatment; after the analysis is completed, the first-stage adsorption unit, the second-stage adsorption unit, and the analysis unit are alternately switched.

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