Adsorption process of DCM waste gas and special adsorption system thereof

Abstract

The invention discloses a DCM waste gas adsorption process and a special adsorption system thereof, and belongs to the technical field of environmental protection. The adsorption system comprises a waste gas adsorption system, a resin desorption system, a desorbed gas recovery system, a resin cooling and drying system, a wastewater treatment system and a safety prevention and control system, all the systems respectively control all adsorbers to independently and sequentially carry out adsorption-desorption-regeneration processes through an automatic control system, full-automatic integration of waste gas adsorption-desorption-regeneration-wastewater treatment is achieved, the purification efficiency can still be maintained to be 99% after the device continuously operates for 7200 h, the resin loss rate is only 3.0%, the operation cost is reduced by more than 65%, and the operation efficiency is greatly improved. Double standard discharge of DCM waste gas and waste water is realized, and remarkable environmental benefits and economic benefits are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental protection, and in particular relates to an adsorption system for adsorbing dichloromethane. Background Art

[0002] Dichloromethane (DCM) has the advantages of low flammability and strong solubility, and is widely used in the pharmaceutical, chemical and semiconductor industries. However, it has a low boiling point and is very easy to volatilize into the surrounding environment. If it is not controlled, it will cause human poisoning on the one hand, and on the other hand, it will decompose under the action of light to produce phosgene and carbon monoxide, thereby destroying the ozone layer. The "List of New Pollutants under Key Control (2023 Edition)" (Ministry of Ecology and Environment Order No. 28) announced by the Ministry of Ecology and Environment on December 29, 2022 listed DCM as one of the new pollutants that require key control. The "Stockholm Convention" also lists DCM as one of the 12 persistent organic pollutants that are prioritized for treatment and control. Therefore, the control of DCM has become one of the environmental problems that need to be solved urgently.

[0003] Commonly used DCM treatment technologies mainly include condensation, absorption, combustion, biological treatment, adsorption, etc. Condensation method: The condensation method is to use a temperature below the boiling point to condense the target pollutants in the exhaust gas into liquid, so as to achieve a certain removal effect, and the condensed liquid can often be reused in production. Generally, this method can be used for exhaust gas with small air volume and high concentration. However, the concentration of organic matter in the exhaust gas after condensation is still high, and further treatment is required to meet the emission requirements. According to relevant engineering experience, for DCM exhaust gas, it has a better condensation effect at -70°C, but at this time, liquid nitrogen and other coolants are needed for condensation, and the investment cost is often expensive, which many small and medium-sized chemical companies generally cannot afford. Absorption method: The absorption method can be divided into chemical absorption and physical absorption. Physical absorption is generally aimed at organic pollutants with good solubility. Chemical absorption can be divided into acid absorption, desorption, redox absorption, etc. In actual engineering applications, one or more chemical absorption methods are often used for specific exhaust gas properties. If the absorption method is used for purification alone, the effect of removing the insoluble DCM pollutants is not ideal. Even if oxidative absorption is carried out by adding oxidants and other measures, its ability to degrade DCM is not very strong, and generally the expected treatment target cannot be achieved, and the DCM degradation rate is low. Incineration method: also known as thermal oxidation method and thermal combustion method, it is a method of using high temperature to decompose organic pollutants into harmless substances. Incineration method is a relatively effective method for treating organic pollutants. After incineration treatment, it can generally achieve a relatively ideal treatment effect. However, if the incineration temperature and residence time are not controlled well, resulting in incomplete combustion, more toxic substances will be produced, especially for chlorine-containing organic matter, which will produce more toxic substances such as dioxins. For DCM, the biggest obstacle to the incineration method is that it is easy to produce highly toxic pollutants such as dioxins after incineration. Although the United States has conducted in-depth research on incineration, it has been found that as long as the incineration temperature is controlled, the residence time must be reached, and the residual oxygen content in the tail gas must be reached, the production of dioxins can be effectively curbed. However, in actual operation, due to the fluctuation of the concentration of exhaust gas, it is difficult to accurately and stably control the incineration process. In addition, the "Safety Technical Requirements for Regenerative Thermal Incinerator Systems" (DB32 / T 4700-2024) and "Technical Specifications for Industrial Organic Waste Gas Treatment Engineering by Regenerative Combustion" (HJ 1093-2020) do not recommend the use of regenerative thermal incinerators (RTO) to treat chlorine-containing organic waste gas. Biological treatment method: Biological treatment to purify organic waste gas mainly utilizes the degradation of microorganisms to convert organic matter in the waste gas into simple inorganic substances (CO2, water, etc.) and cell components. For the treatment of organic waste gas, the commonly used device is the biotrickling filter, but the acclimation cycle of microorganisms is relatively long, and microorganisms are more sensitive to fluctuations in waste gas. Compared with other methods, this process has the characteristics of low operating cost, good safety, and no secondary pollution, and is suitable for the treatment of low and medium concentration organic waste gas.However, DCM has high biological toxicity and is insoluble in water, making it difficult to be degraded by microorganisms. Therefore, if biological methods are used to treat DCM, a longer acclimation period is often required. In addition, if the concentration of DCM waste gas fluctuates greatly, it will also greatly affect the growth and degradation effect of microorganisms. Adsorption method: The adsorption method uses porous solid adsorption materials as adsorbents to adsorb DCM on the surface of the adsorbent to achieve the purpose of removal. After adsorption, heat treatment methods are generally used to remove the adsorbed DCM so that the adsorbent can be regenerated and reused. The adsorption method has the advantages of simple process, high adsorption efficiency, low energy consumption, etc., and is widely used in DCM treatment. Commonly used DCM adsorbents include activated carbon, molecular sieves, and adsorption resins.

[0004] Activated carbon is a widely used adsorbent due to its large specific surface area, good chemical stability, low price, and high DCM adsorption capacity. However, activated carbon is flammable, pores are easily blocked, and regeneration is difficult during the DCM adsorption process. These defects restrict the application of activated carbon in DCM adsorption. Molecular sieves have good selectivity, thermal stability, and a relatively suitable price for DCM adsorption. They are widely available and are adsorbents with great application prospects. However, their moisture resistance is relatively poor and needs further improvement.

[0005] Adsorption resin is an emerging polymer material with concentration, separation and adsorption functions. It is mainly used for the adsorption of organic pollutants in water. In recent years, domestic and foreign scholars have also applied adsorption resins to the adsorption treatment of gaseous pollutants. Using traditional resins as a matrix for differential modification to prepare new resins with special applications that meet the needs of different industrial production can not only optimize the resin structure and improve the adsorption efficiency, but also expand the application field of adsorption resins. It has been widely recognized in the research field and is also a hot topic for in-depth research on adsorption theory in the future. A large amount of literature and engineering operation data show that although traditional adsorption resins have a large specific surface area and good water resistance, their adsorption capacity for DCM is low. At the same time, there is little research on the modification of adsorption resins for DCM adsorption.

[0006] Therefore, how to utilize modified resins in combination with specific processes to adsorb DCM and meet national standards after adsorption treatment has become a problem that needs to be solved urgently. Summary of the invention

[0007] The first purpose of the present invention is to propose an adsorption process for DCM waste gas, which can realize the fully automatic integrated operation of DCM waste gas adsorption-desorption-regeneration-wastewater treatment, reduce the loss of adsorption resin and energy waste, and achieve dual-standard discharge of DCM waste gas and wastewater.

[0008] The second purpose of the present invention is to propose a DCM waste gas adsorption system, which enables each device to operate independently through the design of pipelines and valves, thereby greatly improving the adsorption efficiency of DCM.

[0009] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0010] A DCM waste gas adsorption process includes a waste gas adsorption process, a resin desorption process, a desorption gas recovery process and a waste water treatment process, wherein the DCM waste gas is firstly adsorbed and purified by a waste gas adsorption system, and the purified gas is discharged by the waste gas adsorption system; when the adsorption amount of the waste gas adsorption system reaches saturation, a resin desorption process is performed to desorb and remove the DCM adsorbed in the waste gas adsorption system, and restore the waste gas adsorption system to a normal state; the desorbed DCM enters a desorption gas recovery system, and solid-liquid separation is achieved in the system, and the separated solid DCM is recycled; the separated waste water enters a waste water treatment process, and after being treated by the waste water treatment process, the tail water can be directly discharged from the system, and the adsorption, desorption and regeneration process of the DCM waste gas is achieved;

[0011] The concentration of DCM waste gas before treatment is not less than 10000 mg / m 3 ; The concentration of purified gas after treatment is not higher than 60mg / m 3 .

[0012] A DCM waste gas adsorption system comprises a waste gas adsorption system, a resin desorption system, a desorption gas recovery system, a resin cooling and drying system, and a waste water treatment system.

[0013] Furthermore, the exhaust gas adsorption system comprises a resin absorber a and a resin absorber b, and the bottoms of the resin absorbers a and b are provided with water vapor inlet valves a and water vapor inlet valves b, respectively; the bottoms of the inner cavities of the resin absorbers a and b are provided with high-efficiency gas distributors a and high-efficiency gas distributors b, respectively; the middle of the inner cavities of the resin absorbers a and b are filled with modified adsorption resin; the exhaust gas adsorption system comprises a resin absorber a and b, and the tops of the resin absorbers a and b are provided with outlet valves a and outlet valves b, respectively; the bottoms of the inner cavities of the resin absorbers a and b are provided with high-efficiency gas distributors a and high-efficiency gas distributors b, respectively; the middle of the inner cavities of the resin absorbers a and b are filled with modified adsorption resin (MWCNTs-Li(Ⅰ) / Al(Ⅲ)-AR).

[0014] Furthermore, the resin desorption system includes a resin adsorber a and a resin adsorber b, and the tops of the resin adsorber a and the resin adsorber b are respectively provided with a saturated water vapor inlet valve a and a water vapor inlet valve b; the tops of the inner cavities of the resin adsorber a and the resin adsorber b are respectively provided with a high-efficiency steam distributor a and a high-efficiency steam distributor b; the bottoms of the resin adsorber a and the resin adsorber b are respectively provided with a desorption gas exhaust valve a and a desorption gas exhaust valve b.

[0015] Furthermore, the desorbed gas recovery system includes a high-efficiency condenser a, a high-efficiency condenser b, a high-efficiency condenser c, a condensate stratification tank, a recovery solvent receiving tank and a wastewater receiving tank connected in sequence; the condensed gas from the high-efficiency condenser a, the high-efficiency condenser b, the high-efficiency condenser c, the condensate stratification tank, the recovery solvent receiving tank and the wastewater receiving tank is connected to the inlet of the exhaust gas induced draft fan through a pipeline.

[0016] Furthermore, the resin cooling and drying system comprises a resin adsorber a, a resin adsorber b and a water ring vacuum pump.

[0017] Furthermore, the wastewater treatment system includes a resin adsorber c; an automatic switching valve a and an automatic switching valve b are arranged at the top of the resin adsorber c; an automatic switching valve d and an automatic switching valve c are arranged at the bottom of the resin adsorber c; a high-efficiency steam distributor c is arranged at the top of the inner cavity of the resin adsorber c, and the middle is filled with modified adsorption resin (MWCNTs-Li(Ⅰ) / Al(Ⅲ)-AR).

[0018] Furthermore, the preparation method of the (MWCNTs-Li(Ⅰ) / Al(Ⅲ)-AR) modified adsorption resin is as follows: immersing the adsorption resin in a metal ion solution, washing with water to pH=6-7, and drying to obtain a modified adsorption resin loaded with metal ions; placing MWCNTs in ultrapure water, and preparing a MWCNTs dispersion by ultrasonic dispersion; then immersing the modified adsorption resin loaded with metal ions in the MWCNTs dispersion, and drying again to obtain the (MWCNTs-Li(Ⅰ) / Al(Ⅲ)-AR) modified adsorption resin.

[0019] Furthermore, the metal ion solution is an AlCl3 aqueous solution.

[0020] Furthermore, in the modified adsorption resin loaded with metal ions, the loading amount of metal ions is 5 wt.%.

[0021] Furthermore, in the (MWCNTs-Li(Ⅰ) / Al(Ⅲ)-AR) modified adsorption resin, the MWCNTs loading amount is 2 wt.%.

[0022] Compared with the prior art, the advantages of the present invention are as follows:

[0023] 1) The adsorption system disclosed in the present invention realizes the fully automatic integrated operation of DCM waste gas adsorption-desorption-regeneration-wastewater treatment, and the device can still maintain a purification efficiency of 99% after continuous operation for 7200 hours; the resin loss rate is only 3.0%, which is lower than the technical requirement of "annual resin loss rate of 5%" in the "Technical Specifications for Industrial Organic Waste Gas Treatment Engineering by Resin Adsorption Method" (T / CPCIF 0175-2021).

[0024] 2) The saturated adsorption capacity of the modified adsorption resin (MWCNTs-Li(Ⅰ) / Al(Ⅲ)-AR) prepared by the present invention for DCM is increased from 258.77 mg / g of the unmodified adsorption resin to 644.57 mg / g (an increase of up to 149.09%), and the 24-hour dynamic continuous adsorption efficiency is increased from 84.98% of the unmodified adsorption resin to 99.35%; the adsorption period that meets the emission standards is extended from 2 hours of the unmodified adsorption resin to 14 hours.

[0025] 3) The modified adsorption resin (MWCNTs-Li(Ⅰ) / Al(Ⅲ)-AR) and its adsorption system disclosed in the present invention can make the emission concentration as high as 10000mg / m 3 The DCM waste gas is reduced to 60mg / m after adsorption treatment. 3 The following meet the current most stringent "Pharmaceutical Industry Air Pollutant Emission Standards" (DB32 / 4042-2021) and require no further treatment.

[0026] 4) The modified adsorption resin (MWCNTs-Li(Ⅰ) / Al(Ⅲ)-AR) and its adsorption system disclosed in the present invention can reduce the COD concentration of DCM wastewater with a COD concentration of up to 5000 mg / L to 50 mg / L after adsorption treatment, and the tail water COD index meets the Class A standard of the "Pollutant Discharge Standard for Municipal Wastewater Treatment Plants" (GB 18918-2002) without further treatment.

[0027] 5) The operating cost of the adsorption system disclosed in the present invention is reduced from 3754 yuan / d of the unmodified resin and the original device to 1294 yuan / d, and the operating cost is saved by more than 65%, achieving significant environmental and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is the process flow chart of the laboratory resin adsorption and desorption DCM device.

[0029] Figure 2 This is the adsorption permeation curve of DCM on a single metal modified adsorption resin.

[0030] Figure 3 This is the adsorption permeation curve of DCM on the bimetallic modified adsorption resin.

[0031] Figure 4 This is the adsorption permeation curve of DCM on multi-walled carbon nanotubes (MWCNTs) modified adsorption resin.

[0032] Figure 5 It is a continuous monitoring of the DCM concentration at the inlet and outlet of the waste gas of the unmodified resin adsorption and desorption device (in terms of C) and a purification efficiency trend chart.

[0033] Figure 6 It is a continuous monitoring of DCM concentration at the inlet and outlet of the waste gas of the modified resin adsorption and desorption device (in terms of C) and a purification efficiency trend chart.

[0034] Figure 7 This is the flow chart of the DCM waste gas adsorption and desorption treatment system.

[0035] Among them, 1. Intake valve; 2. Bypass valve; 3. DCM exhaust gas intake valve a; 4. Exhaust valve a; 5. DCM exhaust gas intake valve b; 6. Exhaust valve b; 7. Water vapor intake valve a; 8. Water vapor intake valve b; 9. Desorber discharge valve a; 10. Water vapor intake valve c; 11. Water vapor intake valve d; 12. Desorber exhaust valve b; 13. Automatic switching valve a; 14. Automatic switching valve b; 15. Automatic switching valve c; 16. Automatic switching valve d; 17. Exhaust gas induced draft fan; 18. Surface cooler; 19. High-efficiency condenser a; 20. High-efficiency cooler Condenser b; 21. High-efficiency condenser c; 22. Resin adsorber a; 23. Resin adsorber b; 24. Resin adsorber c; 25. Water ring vacuum pump; 26. Wastewater delivery pump; 27. Solvent delivery pump; 28. High-efficiency steam distributor a; 29. ​​High-efficiency steam distributor b; 30. High-efficiency steam distributor c; 31. High-efficiency gas distributor a; 32. High-efficiency gas distributor b; 33. Condensate stratification tank; 34. Recovery solvent receiving tank; 35. Wastewater receiving tank; A. Pressure monitoring system; B. Temperature monitoring system; C. Flow monitoring system. DETAILED DESCRIPTION

[0036] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with specific embodiments.

[0037] The laboratory resin adsorption and desorption device used in the following examples is as follows Figure 1As shown, the standard air flows out of the standard air bottle and is divided into two paths. One path is controlled by a mass flow controller to control the gas flow Q1 and enters the constant temperature bubbling device containing DCM from the top. The other path is controlled by a mass flow controller to control the gas flow Q2. The two gases are fully mixed in the mixing device to keep the temperature in the bubbling device constant. By adjusting the size of Q1 and Q2, different concentrations of DCM gas can be obtained. The resin adsorption column used is a cylindrical structure with an inner diameter of 100mm and a height of 1000mm. The resin layer filling height is 450mm and the cross-sectional area of ​​the resin layer is 0.00785m 2 , the resin filling volume is 3.5L, and the exhaust gas treatment flow rate is 4.2m 3 / h, the cross-sectional flow velocity is 0.15m / s, the gas residence time is 3s, and the DCM concentration is controlled at 7000mg / m 3 .

[0038] The test methods for the BET specific surface area, micropore volume, total pore volume, post-grinding sphericity, and wet apparent density of the resin adsorbent refer to the "Technical Specifications for Industrial Organic Waste Gas Treatment Engineering by Resin Adsorption Method" (T / CPCIF 0175-2021). The DCM concentration (in terms of C) at the inlet and outlet of the experimental device is measured using a portable VOCs monitoring instrument. The calculation formula for the adsorption efficiency at the inlet and outlet of the experimental device is as follows:

[0039]

[0040] Where: C0 (mg / m 3 ) and C t (mg / m 3 ) are the DCM concentrations at the inlet and outlet of the experimental device, Q0 (Nm 3 / h) and Q t (Nm 3 / h) are the gas flow rates at the inlet and outlet of the experimental device, respectively.

[0041] Example 1

[0042] A DCM waste gas adsorption process includes a waste gas adsorption process, a resin desorption process, a desorption gas recovery process and a waste water treatment process; the specific process is as follows:

[0043] Open the air inlet valve 1, DCM waste gas inlet valve a3 and DCM waste gas inlet valve b5. The DCM waste gas is cooled and dehydrated by the surface cooler 18 through the air inlet pipeline and then sent to the resin adsorber a22 and the resin adsorber b23 through the exhaust gas induced draft fan 17 for adsorption treatment. The high-efficiency gas distributor a31 and the high-efficiency gas distributor b32 arranged at the bottom of the resin adsorber a22 and the resin adsorber b23 can make the DCM waste gas evenly distributed on the cross-section of the resin bed to ensure high-efficiency adsorption. The purified gas that meets the "Pharmaceutical Industry Air Pollutant Emission Standard" (DB32 / 4042-2021) is discharged into the atmosphere through the outlet valve a4 and the outlet valve b6 at the top of the resin adsorber a22 and the resin adsorber b23.

[0044] As the adsorption continues, the resin adsorber whose adsorption amount reaches saturation will enter the desorption process. At this time, the water vapor inlet valve b8 and the water vapor inlet valve d11 are opened, and the saturated water vapor is sprayed from top to bottom into the resin bed of the corresponding resin adsorber through the high-efficiency steam distributor a28 and the high-efficiency steam distributor b29 to desorb the DCM adsorbed on the resin bed. The desorbed gas-liquid mixture containing DCM enters the desorbed gas recovery system through the desorber discharge valve a9 and the desorbed gas discharge valve b12 to carry out the desorbed gas recovery process.

[0045] As the desorbed gas recovery process proceeds, the desorbed gas sequentially passes through the connected high-efficiency condenser a 19, high-efficiency condenser b 20, and high-efficiency condenser c 21 to reach the condensate stratification tank 33. The DCM-containing gas-liquid mixture desorbed in the condensate stratification tank 33 is condensed into a liquid state and physically stratified into DCM and water in the stratification tank. The DCM enters the solvent receiving tank 34 and is transported to the workshop for reuse through the solvent delivery pump 27. The wastewater enters the wastewater receiving tank 35 and is transported to the wastewater treatment system through the wastewater delivery pump 26. The condensed gas from the high-efficiency condenser a 19, the high-efficiency condenser b 20, the high-efficiency condenser c 21, the condensate stratification tank 33, the recovered solvent receiving tank 34, and the wastewater receiving tank 35 is connected to the inlet of the exhaust gas induced draft fan (17) through a pipeline.

[0046] As more and more wastewater is transported to the wastewater treatment system, the automatic switching valve a13 is opened at this time, and the wastewater enters the resin adsorber c24 from top to bottom. A high-efficiency steam distributor c30 is set on the top of the inner cavity of the resin adsorber c24, and the middle is filled with modified system resin (MWCNTs-Li(Ⅰ) / Al(Ⅲ)-AR). The wastewater is purified by the adsorption and purification effect of the resin, and the automatic switching valve d16 is opened. The purified water that meets the standard is discharged from the system through the pipeline.

[0047] Example 2

[0048] An adsorption system for DCM waste gas, such as Figure 7 As shown, it includes a waste gas adsorption system, a resin desorption system, a desorption gas recovery system, a resin cooling and drying system, a wastewater treatment system and a safety prevention control system.

[0049] The exhaust gas adsorption system includes a resin adsorber a22 and a resin adsorber b23, and the tops of the resin adsorber a22 and the adsorber resin adsorber b23 are respectively provided with an outlet valve a4 and an outlet valve b6; the bottoms of the inner cavities of the resin adsorber a22 and the resin adsorber b23 are respectively provided with an efficient gas distributor a31 and an efficient gas distributor b32; the middle of the inner cavities of the resin adsorber a22 and the resin adsorber b23 are filled with modified adsorption resin; the exhaust gas adsorption system includes a resin adsorber a22 and a resin adsorber b23, and the tops of the resin adsorber a22 and the resin adsorber b23 are respectively provided with an outlet valve a4 and an outlet valve b6; the bottoms of the inner cavities of the resin adsorber a22 and the resin adsorber b23 are respectively provided with an efficient gas distributor a31 and an efficient gas distributor b32; the middle of the inner cavities of the resin adsorber a22 and the resin adsorber b23 are filled with modified adsorption resin. The middle part of the inner cavity 23 is filled with modified adsorption resin (MWCNTs-Li(Ⅰ) / Al(Ⅲ)-AR).

[0050] The working process of the waste gas adsorption system is as follows: the DCM waste gas after cooling and dehydration by the surface cooler is sent into the resin adsorber a and resin adsorber b through the DCM waste gas inlet valve a and DCM waste gas inlet valve b by the waste gas induced draft fan for adsorption treatment. The high-efficiency gas distributor arranged at the bottom of the adsorber can make the DCM waste gas evenly distributed on the cross-section of the resin bed to ensure high-efficiency adsorption, and the purified gas that meets the "Pharmaceutical Industry Air Pollutant Emission Standards" (DB32 / 4042-2021) is discharged into the atmosphere through the outlet valve at the top of the adsorber.

[0051] The resin desorption system includes a resin adsorber a22 and a resin adsorber b23, wherein the tops of the resin adsorber a22 and the resin adsorber b23 are respectively provided with a saturated water vapor inlet valve a7 and a water vapor inlet valve b8; the tops of the inner cavities of the resin adsorber a22 and the resin adsorber b23 are respectively provided with a high-efficiency steam distributor a28 and a high-efficiency steam distributor b29; the bottoms of the resin adsorber a22 and the resin adsorber b23 are respectively provided with a desorbed gas exhaust valve a9 and a desorbed gas exhaust valve b12.

[0052] The working process of the resin desorption system is as follows: the adsorber that has reached saturation enters the desorption process, and saturated water vapor is sprayed into the resin bed from top to bottom through a high-efficiency steam distributor to desorb the DCM adsorbed on the resin bed. The desorbed gas-liquid mixture containing DCM enters the desorption gas recovery system through the desorption gas discharge valve.

[0053] The desorbed gas recovery system includes a high-efficiency condenser a19, a high-efficiency condenser b20, a high-efficiency condenser c21, a condensate stratification tank 33, a recovery solvent receiving tank 34 and a wastewater receiving tank 35 which are connected in sequence; the condensed gas from the high-efficiency condenser a19, the high-efficiency condenser b20, the high-efficiency condenser c21, the condensate stratification tank 33, the recovery solvent receiving tank 34 and the wastewater receiving tank 35 is connected to the inlet of the exhaust gas induced draft fan 17 through a pipeline.

[0054] The working process of the desorbed gas recovery system is as follows: the desorbed DCM gas-liquid mixture is condensed into liquid by three-stage condensation and freezing, and the physical stratification of DCM and water is achieved in the stratification tank. After DCM enters the solvent recovery tank, it is transported to the workshop for reuse through the solvent delivery pump, and the wastewater enters the wastewater collection tank and is transported to the wastewater treatment system through the wastewater delivery pump.

[0055] The resin cooling and drying system comprises a resin adsorber a 22, a resin adsorber b 23 and a water ring vacuum pump 25. The resin cooling and drying system uses a water ring vacuum pump to negatively pressure-pump the DCM that is not completely desorbed from the resin bed and the DCM gas-liquid mixture remaining in the adsorber cavity to the desorption gas recovery system, so as to reduce the temperature of the resin bed after desorption.

[0056] The wastewater treatment system includes a resin adsorber c24; an automatic switching valve a13 and an automatic switching valve b14 are arranged at the top of the resin adsorber c24; an automatic switching valve d16 and an automatic switching valve c15 are arranged at the bottom of the resin adsorber c24; a high-efficiency steam distributor c30 is arranged at the top of the inner cavity of the resin adsorber c24, and the middle part is filled with a modified system resin (MWCNTs-Li(Ⅰ) / Al(Ⅲ)-AR).

[0057] The working process of the wastewater treatment system is as follows: DCM wastewater is sent from top to bottom into the adsorber through the wastewater delivery pump for adsorption treatment, and the tail water whose COD meets the Level A standard of "Pollutant Discharge Standard for Urban Wastewater Treatment Plants" (GB 18918-2002) is discharged to the external environment through the outlet valve at the bottom of the adsorber.

[0058] The safety prevention control system includes temperature and pressure flow monitoring, high temperature alarm during adsorption process, low temperature alarm during desorption process and adsorber overpressure protection. Temperature and pressure flow monitoring includes condenser outlet pipe temperature B monitoring, resin bed temperature B and pressure A monitoring, DCM exhaust gas / purified gas temperature B, pressure A and flow C monitoring, saturated water vapor temperature B, pressure A and flow C monitoring, fire water temperature B, pressure A and flow C monitoring; the high temperature alarm during adsorption process is to start the fire water spray cooling urgently when the resin bed temperature B monitoring exceeds 83℃ during adsorption process; the low temperature alarm during desorption process is to start the steam temperature insufficient alarm signal urgently when the resin bed temperature B monitoring is lower than 90℃ during desorption process; adsorber overpressure protection is to automatically open the pressure relief when the pressure monitoring in the adsorption tank exceeds 0.1MPa, and close 1 and open 2 at the same time. The induced draft fan, control valve, detection device and control device involved in the system are connected, and the whole process is automated through the control system.

[0059] Example 3

[0060] The preparation method of adsorption resin (AR) comprises the following steps:

[0061] (1) Polymerization reaction: Styrene, 1,2-diphenylethylene, water, benzoyl peroxide (initiator), and liquid wax (porogen) are added to a polymerization reactor and stirred evenly at room temperature; dispersant cellulose, gelatin, and anti-emulsifier methylene blue are fully dissolved in water and added to the above polymerization reactor, and the temperature is first raised to 80° C. and kept for 4 hours, then raised to 85° C. and kept for 4 hours, and then raised to 98° C. and kept for 4 hours, and finally lowered to 30° C. to complete the reaction. After the reaction is completed, the polymer is separated and washed with water, and the polymer with the porogen is sent to a drying process, and the temperature is controlled at 60° C. and dried for 1 hour to obtain an intermediate; the intermediate is sent to an extraction column, and the porogen liquid wax in the intermediate is extracted multiple times with an extractant methylal, and after the extraction is completed, it is rinsed with water multiple times, and the rinsed intermediate is dried at 80° C. for 10 hours to obtain a semi-finished product I with a water content of less than 1%;

[0062] (2) Chlorination reaction: under room temperature, add semi-finished product I, chloromethyl ether and water into a chlorination reactor, stir for 2 hours to make them evenly mixed, add catalyst ferric chloride under stirring, and carry out radicalization reaction at 45°C; after the reaction is completed, cool to room temperature, filter out the mother liquor, rinse with methanol and water for multiple times, and after rinsing, dry at 80°C and 10 to obtain semi-finished product II with a water content of less than 1%;

[0063] (3) Post-crosslinking: The semi-finished product II and the swelling agent ethylene dichloride are placed in a crosslinking reactor, mixed and stirred for expansion for 5 hours, and then aluminum chloride is added. The temperature is raised to 75°C for post-crosslinking reaction for 24 hours. After the ethylene dichloride is distilled off, water is added for rinsing until the pH value is 6-7, and then dried at 80°C for 10 hours to obtain the adsorption resin.

[0064] The preparation method of the single metal ion modified adsorption resin comprises the following steps:

[0065] (1) Preparation of single metal solutions: AlCl3 aqueous solution, LiCl aqueous solution, MgCl2 aqueous solution, FeCl3 aqueous solution, CaCl2 aqueous solution and AgNO3 aqueous solution were prepared respectively with a concentration of 0.1 mol / L;

[0066] (2) Modification by impregnation method: At room temperature, the adsorption resin product is immersed in different metal salt solutions prepared in step (1), respectively, washed with water to pH = 6-7 after 24 hours, and then dried at 80°C for 10 hours to obtain a single metal modified adsorption resin; the number of impregnation times of the adsorption resin is controlled by comparing the mass of the adsorption resin before and after impregnation, and a single metal ion modified adsorption resin (Al(Ⅲ)-AR, Li(Ⅰ)-AR, Mg(Ⅱ)-AR, Ca(Ⅱ)-AR, Fe(Ⅲ)-AR, Ag(Ⅰ)-AR) with a metal ion loading of 5 wt.% is obtained.

[0067] Example 4

[0068] The preparation method of the double metal ion modified adsorption resin comprises the following steps:

[0069] (1) Preparation of bimetallic solution: First, prepare 0.2 mol / L AlCl3 aqueous solution, LiCl aqueous solution and MgCl2 aqueous solution respectively, then mix equal volumes of AlCl3 aqueous solution and LiCl aqueous solution, AlCl3 aqueous solution and MgCl2 aqueous solution, LiCl aqueous solution and MgCl2 aqueous solution respectively to prepare a bimetallic solution, with a metal ion molar ratio of 1:1;

[0070] (2) Modification by impregnation: At room temperature, the adsorption resin product was immersed in different bimetallic solutions prepared in step (1), washed with water to pH = 6-7 after 24 hours, and then dried at 80°C for 10 hours to obtain a bimetallic modified adsorption resin. The number of impregnations of the adsorption resin was controlled by comparing the mass of the adsorption resin before and after impregnation, and a bimetallic ion modified adsorption resin (Li(Ⅰ) / Al(Ⅲ)-AR>Mg(Ⅱ) / Al(Ⅲ)-AR>Mg(Ⅱ) / Li(Ⅰ)-AR) with a loading of 5wt.% was obtained.

[0071] Example 5

[0072] The preparation method of multi-walled carbon nanotubes (MWCNTs) modified adsorption resin comprises the following steps:

[0073] First, the unmodified adsorption resin (AR) and the double metal ion modified adsorption resin (Li(Ⅰ) / Al(Ⅲ)-AR>Mg(Ⅱ) / Al(Ⅲ)-AR>Mg(Ⅱ) / Li(Ⅰ)-AR) were immersed in methanol solution for 24 h; MWCNTs were placed in ultrapure water, and 5 mg / mL MWCNTs dispersion was prepared by ultrasonic dispersion; the above adsorption resin was immersed in the MWCNTs dispersion and ultrasonicated at room temperature for 8 h to fix the MWCNTs in the pores of the adsorption resin, and then ultrapure water was used to remove the surface of the adsorption resin. The excess MWCNTs were then washed with water until the pH value was 6-7, and then dried at 80°C for 10 hours to obtain a MWCNTs-modified adsorption resin. The number of ultrasonic times of the adsorption resin was controlled by comparing the mass of the adsorption resin before and after ultrasound to obtain MWCNTs-modified adsorption resins (MWCNTs-AR, MWCNTs-Mg(Ⅱ) / Li(Ⅰ)-AR, MWCNTs-Mg(Ⅱ) / Al(Ⅲ)-AR, MWCNTs-Li(Ⅰ) / Al(Ⅲ)-AR) with a MWCNTs loading of 2 wt.%.

[0074] Example 6

[0075] The effect of single metal ion modification (Li(Ⅰ), Ca(Ⅱ), Al(Ⅲ), Fe(Ⅲ), Mg(Ⅱ), Ag(Ⅰ)) on the adsorption performance of ultra-high cross-linked adsorption resin (AR) is shown in Table 1.

[0076] Table 1 Pore structure and other related parameters of single metal ion modified adsorption resin

[0077]

[0078] As can be seen from Table 1, the BET specific surface area, micropore volume and total pore volume of the adsorption resin modified by single metal salt impregnation are slightly smaller than those of the unmodified adsorption resin, but there is no statistical difference; the parameters such as the roundness rate, average pore size and wet apparent density after grinding are basically equivalent to those of the unmodified adsorption resin.

[0079] Depend on Figure 2 It can be seen that the adsorption and penetration time of DCM on the single metal-loaded modified adsorption resin has changed significantly compared with the unmodified adsorption resin. The adsorption and penetration time of DCM on Li(Ⅰ)-AR, Ca(Ⅱ)-AR, Al(Ⅲ)-AR, Fe(Ⅲ)-AR, and Mg(Ⅱ)-AR is significantly prolonged compared with the unmodified adsorption resin, and the adsorption and penetration time of DCM on Ag(Ⅰ)-AR is significantly shortened. The order of the adsorption and penetration time of DCM on the adsorption resins modified with different metal loads is: Al(Ⅲ)-AR>Li(Ⅰ)-AR>Mg(Ⅱ)-AR>Ca(Ⅱ)-AR>Fe(Ⅲ)-AR>Ag(Ⅰ)-AR.

[0080] The saturated adsorption capacity of various adsorbents for DCM was calculated based on the adsorption permeation curves as shown in Table 2. The adsorption capacity of different modified metal ion modified adsorption resins for DCM is in the following order: Al(Ⅲ)-AR>Li(Ⅰ)-AR>Mg(Ⅱ)-AR>Ca(Ⅱ)-AR>Fe(Ⅲ)-AR>unmodified AR>Ag(Ⅰ)-AR. Among them, the adsorption capacity of Al(Ⅲ)-AR is the largest at 436.83 mg / g, which is 68.81% higher than that of unmodified AR; the adsorption capacity of Ag(Ⅰ)-AR is the smallest at only 230.55 mg / g, which is lower than the saturated adsorption capacity of unmodified HIAR. The saturated adsorption capacities of Li(Ⅰ)-AR, Mg(Ⅱ)-AR, Ca(Ⅱ)-AR, Fe(Ⅲ)-AR, etc. are in the middle, but are all higher than the saturated adsorption capacity of unmodified AR.

[0081] When different metal ions are loaded on the surface of the ultra-high cross-linked adsorption resin, its surface acid-base hardness changes. When Al(Ⅲ), Li(Ⅰ), Mg(Ⅱ), Ca(Ⅱ), and Fe(Ⅲ) belonging to hard acids are loaded on the resin surface, the local hard acidity of the resin surface will be enhanced. Since DCM belongs to a hard base, according to the HSAB theory "hard affinity hard" principle, the resin with hard acid metal ions loaded on the surface has enhanced adsorption capacity for hard base substances and DCM, showing a higher adsorption capacity for DCM; Ag(Ⅰ) belongs to a soft acid, and its loading locally enhances the soft acidity of the adsorption resin. According to the HSAB theory "soft and hard collocation is unstable", the adsorption capacity of the adsorption resin with soft acid metal ions loaded on the surface for DCM, a hard base substance, is weakened. According to Pearson's classification, Al(Ⅲ), Li(Ⅰ), and Mg(Ⅱ) are all hard acids with relatively large absolute hardness coefficients, which is consistent with the better adsorption performance shown in the experimental results.

[0082] Table 2 Saturated adsorption of DCM on single metal ion modified adsorption resin

[0083]

[0084] Example 7

[0085] It can be concluded from Example 6 that the adsorption resin modified by Al(Ⅲ), Li(Ⅰ), and Mg(Ⅱ) has better adsorption performance. Therefore, in order to further investigate the effect of co-doping of the above three metal ions, the effect of double metal ion (Li(Ⅰ) / Al(Ⅲ)-AR>Mg(Ⅱ) / Al(Ⅲ)-AR>Mg(Ⅱ) / Li(Ⅰ)-AR) modification on the adsorption performance of ultra-high cross-linked adsorption resin (AR) is shown in Table 3 below.

[0086] Table 3 Pore structure and other related parameters of double metal ion modified adsorption resin

[0087]

[0088] As can be seen from Table 3, the BET specific surface area, micropore volume and total pore volume of the adsorption resin modified by double metal salt impregnation are slightly smaller than those of the unmodified adsorption resin, but there is no statistical difference; the parameters such as the roundness rate, average pore size and wet apparent density after grinding are basically the same as those of the unmodified adsorption resin.

[0089] Depend on Figure 3 It can be seen that the adsorption and penetration time of DCM on the bimetallic loaded modified adsorption resin has changed significantly compared with the unmodified adsorption resin. The adsorption and penetration time of DCM on Mg(Ⅱ) / Li(Ⅰ)-AR, Mg(Ⅱ) / Al(Ⅲ)-AR, and Li(Ⅰ) / Al(Ⅲ)-AR are significantly prolonged compared with the unmodified adsorption resin. The order of the adsorption and penetration time of DCM on the bimetallic loaded modified adsorption resin is: Li(Ⅰ) / Al(Ⅲ)-AR>Mg(Ⅱ) / Al(Ⅲ)-AR>Mg(Ⅱ) / Li(Ⅰ)-AR.

[0090] contrast Figure 2 and Figure 3 Compared with the single metal loaded modified adsorption resin, the adsorption and penetration time of DCM on the double metal loaded modified adsorption resin is significantly prolonged. The saturated adsorption capacity of various adsorbents for DCM is calculated according to the adsorption and penetration curves as shown in Table 4. The adsorption capacity of the double metal ion modified adsorption resin for DCM is as follows: Li(Ⅰ) / Al(Ⅲ)-AR>Mg(Ⅱ) / Al(Ⅲ)-AR>Mg(Ⅱ) / Li(Ⅰ)>unmodified AR. Among them, the maximum adsorption capacity of Li(Ⅰ) / Al(Ⅲ)-AR is 567.64 mg / g, which is 119.36% higher than that of unmodified AR, indicating that the adsorption effect of Li(Ⅰ) / Al(Ⅲ)-AR and Mg(Ⅱ) / Al(Ⅲ)-AR is better. According to Pearson classification, the order of absolute hardness coefficient is Al(Ⅲ)>Li(Ⅰ)>Mg(Ⅱ), which is consistent with the better adsorption performance shown in the results.

[0091] Table 4 Saturated adsorption of DCM on double metal ion modified adsorption resin

[0092]

[0093]

[0094] Example 8

[0095] It can be concluded from Example 7 that the adsorption resin modified by Li(Ⅰ) / Al(Ⅲ)-AR and Mg(Ⅱ) / Al(Ⅲ)-AR has better adsorption performance. Therefore, in order to further investigate the effect of doping multi-walled carbon nanotubes (MWCNTs) on the adsorption performance enhancement of the resin, the effects of AR, MWCNTs-AR, MWCNTs-Mg(Ⅱ) / Li(Ⅰ)-AR, MWCNTs-Mg(Ⅱ) / Al(Ⅲ)-AR and MWCNTs-Li(Ⅰ) / Al(Ⅲ)-AR on the adsorption performance were tested, and the results are shown in Table 5 below.

[0096] Table 5 Pore structure and other related parameters of multi-walled carbon nanotubes (MWCNTs) modified adsorption resin

[0097]

[0098] As shown in Table 5, the BET specific surface area, micropore volume and total pore volume of the adsorption resin modified by multi-walled carbon nanotubes (MWCNTs) are slightly smaller than those of the unmodified adsorption resin, but there is no statistical difference; the parameters such as the roundness rate, average pore size and wet apparent density after grinding are basically the same as those of the unmodified adsorption resin.

[0099] Depend on Figure 4 It can be seen that the adsorption and penetration time of DCM on the multi-walled carbon nanotube (MWCNTs) modified adsorption resin has changed significantly compared with the unmodified adsorption resin, and the adsorption and penetration time of DCM is significantly prolonged compared with the unmodified adsorption resin. Figure 3 and Figure 4 It can be seen that compared with the adsorption resin modified by bimetallic loading, the adsorption penetration time of DCM on the multi-walled carbon nanotubes (MWCNTs) modified adsorption resin is significantly prolonged.

[0100] The saturated adsorption capacity of various adsorbents for DCM calculated based on the adsorption permeation curve is shown in Table 6 below. Compared with the unmodified AR, the saturated adsorption capacity of MWCNTs-Li(Ⅰ) / Al(Ⅲ)-AR increased by 149.09%, indicating that the adsorption resin enhanced by multi-walled carbon nanotubes (MWCNTs) has a better adsorption effect on DCM. The reason is that the small size and good flexibility of carbon nanotubes are combined with the porous and macroporous properties of the adsorption resin, and the MWCNTs are dispersed into the pores of the adsorption resin by ultrasonic force, so that the MWCNTs are blocked in the pores of the adsorption resin and prevented from dissociating. The introduction of carbon nanotubes greatly improves the adsorption capacity of the adsorption resin.

[0101] Table 6 Saturated adsorption capacity of multi-walled carbon nanotubes (MWCNTs) modified adsorption resin

[0102]

[0103] Example 9

[0104] According to Examples 6 to 8, the best modified adsorption resin is MWCNTs-Li(Ⅰ) / Al(Ⅲ)-AR.

[0105] Taking MWCNTs-Li(Ⅰ) / Al(Ⅲ)-AR as an example, engineering application is carried out as follows:

[0106] A pharmaceutical raw material manufacturing company was taken as the research object. The company used DCM as the solvent in the condensation reaction, cyclization reaction, extraction, dissolution and concentration of imipenem intermediates. The DCM waste gas was collected separately and treated by resin adsorption. The waste gas treatment air volume was 1000m 3 / h, the DCM emission concentration is about 12000mg / m 3 The post-treatment emission standard complies with the "Pharmaceutical Industry Air Pollutant Emission Standard" (DB32 / 4042-2021), that is, the NMHC emission concentration is not higher than 60 mg / m 3 .

[0107] The adsorption system for adsorbing dichloromethane in Example 1 of the present invention is used to transform the original DCM waste gas adsorption and desorption device, and the main transformation parts are as follows:

[0108] ①Add a DCM wastewater adsorption and desorption device, specifically add an adsorber with a tank size of Φ1000*2000 and a modified adsorption resin filled in the adsorber for 1m 3 ;

[0109] ② The unmodified resin in the original adsorber was replaced with modified resin, the resin volume was the same, and the other parameters were not adjusted.

[0110] The import and export were continuously monitored for 24 hours using FID detection equipment. Figure 6 As shown, the average inlet DCM concentration is 12748 mg / m 3 (in terms of C), the average DCM concentration at the outlet is 83 mg / m 3 (in terms of C), the average purification efficiency is as high as 99.35%, which is much higher than the purification efficiency of unmodified adsorption resin. When the dynamic adsorption time reaches 840min, the instantaneous concentration of DCM at the outlet reaches 60mg / m 3(measured in C), indicating that the outlet of the device can meet the "Pharmaceutical Industry Air Pollutant Emission Standards" (DB32 / 4042-2021) within 14 hours of dynamic adsorption, that is, the adsorption and desorption device using modified adsorption resin can meet the emission requirements. The COD of the raw water of DCM wastewater is about 5000mg / L. After the DCM wastewater is treated with modified adsorption resin, the effluent COD drops to 50mg / L. The COD index in the wastewater meets the chemical park sewage treatment plant takeover standard or the sewage discharge into the urban sewer water quality standard, and no further treatment is required. For this reason, the company sets an adsorption cycle at 12h, performs saturated steam desorption twice a day, consumes a total of 2.5 tons of saturated steam, and the 2.5 tons of DCM wastewater generated are again adsorbed and desorbed by modified resin to meet the emission requirements.

[0111] The operating costs of the device are as follows:

[0112] ① The cost of saturated steam consumption is 2.5 tons / d×300 yuan / ton=750 yuan / d;

[0113] ② The electricity cost of the electrical equipment is 6KW×24h / d×1 yuan / KWh=144 yuan / d;

[0114] ③ The cost of low-temperature water consumed by the refrigeration system is 400 yuan / d;

[0115] ④The above operating costs total 1,294 yuan / d.

[0116] Compared with the original process, the device saves the cost of wastewater disposal, natural gas, and liquid alkali consumption, and the operating cost is reduced by 68.20% while meeting the emission standards. In addition, after 7200 hours of continuous use, the loss rate of the modified resin is 3.0%, which meets the technical requirements of Article 6.3.3.4 of the "Technical Specifications for Industrial Organic Waste Gas Treatment by Resin Adsorption Method" (T / CPCIF 0175-2021) "The annual loss rate of the resin should be less than 5%", indicating that the modified resin has good thermal stability.

[0117] Comparative Example 1

[0118] The unmodified resin is used for adsorption and desorption treatment of DCM waste gas. Except for the lack of DCM waste gas adsorption and desorption device, the other designs of the original adsorption and desorption system are the same as those of the original system. Figure 7 Basically similar, its design parameters are as follows:

[0119] ①The adsorber adopts a vertical one-absorption-one-desorption design. The adsorber tank size is Φ1600*2800. Each set of adsorber is filled with 2m3 of unmodified adsorption resin. 3 , the flow velocity of the adsorber design cross section is 0.15m / s, and the gas residence time is 6s;

[0120] ② No DCM wastewater adsorption and desorption system is set up;

[0121] ③The heat exchange area of ​​the first-stage condenser is 30m 2 , spiral wound tube heat exchanger 10m 2 , spiral plate cooler 3m 2 , Surface cooler 50m 2 .

[0122] The results of continuous monitoring of import and export for 24 hours using FID detection equipment are as follows: Figure 5 As shown, the average inlet DCM concentration is 13217 mg / m 3 (in terms of C), the average concentration of DCM at the outlet is 1986 mg / m 3 (in terms of C), the average purification efficiency is only 84.98%, and the purification efficiency of the device is not less than 95% only for 5 hours. When the dynamic adsorption time reaches 120 minutes, the instantaneous concentration of DCM at the outlet reaches 60mg / m 3 (measured in C), that is, the device only has 2 hours of adsorption time to meet the "Pharmaceutical Industry Air Pollutant Emission Standards" (DB32 / 4042-2021), analysis, regeneration and drying time, and the shortest adsorption switching time in engineering is generally not less than 4 hours, indicating that there is a 2-hour device outlet within the 4-hour continuous dynamic adsorption cycle that cannot meet the emission requirements. For this reason, the company will connect the DCM tail gas treated by the device to RTO for further treatment. Due to some problems with RTO in treating chlorine-containing organic waste gas, the company sets an adsorption cycle at 4 hours, performs saturated steam desorption 6 times a day, consumes a total of 6 tons of saturated steam, and produces 6 tons of DCM wastewater. The operating cost of the device is calculated as follows:

[0123] ① The cost of saturated steam consumption is 6 tons / d×300 yuan / ton=1800 yuan / d;

[0124] ② The wastewater treatment fee is 6 tons / d×200 yuan / ton=1200 yuan / d;

[0125] ③RTO further processes DCM tail gas and consumes natural gas cost of 25m 3 / 10,000m 3 Air·h×1000m 3 ×3.5 yuan / m 3 ×24h / d=210 yuan / d;

[0126] ④ The consumption of liquid alkali for DCM oxidation to generate HCl is 100 yuan / d;

[0127] ⑤ The electricity cost of the electrical equipment is 6KW×24h / d×1 yuan / KWh=144 yuan / d;

[0128] ⑥ The cost of low-temperature water consumed by the refrigeration system is 300 yuan / d;

[0129] ⑦The above operating costs total 3754 yuan / d.

[0130] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A DCM waste gas adsorption process, characterized in that: It includes waste gas adsorption process, resin desorption process, desorption gas recovery process and wastewater treatment process. DCM waste gas is firstly adsorbed and purified by the waste gas adsorption system, and the purified gas is discharged by the waste gas adsorption system. When the adsorption capacity of the waste gas adsorption system reaches saturation, the resin desorption process is carried out to desorb and remove the DCM adsorbed in the waste gas adsorption system, and restore the normal state of the waste gas adsorption system. The desorbed DCM enters the desorption gas recovery system, and the solid-liquid separation is realized in the system, and the separated solid DCM is recycled. The separated wastewater enters the wastewater treatment process, and after being treated by the wastewater treatment process, the tail water can be directly discharged from the system, realizing the adsorption, desorption and regeneration process of DCM waste gas. The concentration of DCM waste gas before treatment is not less than 10000 mg / m 3 ; The concentration of purified gas after treatment is not higher than 60mg / m 3 .

2. A dedicated adsorption system for the adsorption process of DCM waste gas as claimed in claim 1, characterized in that: The invention comprises a waste gas adsorption system, a resin desorption system, a desorption gas recovery system, a resin cooling and drying system, and a wastewater treatment system. The waste gas adsorption system comprises a resin adsorber a (22) and a resin adsorber b (23). The bottoms of the resin adsorber a (22) and the resin adsorber b (23) are provided with an air inlet valve a (3) and an air inlet valve b (5) respectively; the tops of the resin adsorber a (22) and the adsorber resin adsorber b (23) are provided with an air outlet valve a (4) and an air outlet valve b (6) respectively; the bottoms of the inner cavities of the resin adsorber a (22) and the resin adsorber b (23) are provided with a high-efficiency gas distributor a (31) and a high-efficiency gas distributor b (32) respectively; and the middle of the inner cavities of the resin adsorber a (22) and the resin adsorber b (23) are filled with a modified adsorption resin (MWCNTs-Li (Ⅰ) / Al (Ⅲ)-AR).

3. The adsorption system for DCM exhaust gas according to claim 2, characterized in that: The resin desorption system comprises a resin adsorber a (22) and a resin adsorber b (23), wherein the tops of the resin adsorber a (22) and the tops of the resin adsorber b (23) are respectively provided with a saturated water vapor inlet valve a (7) and a water vapor inlet valve b (8); the tops of the inner cavities of the resin adsorber a (22) and the tops of the inner cavities of the resin adsorber b (23) are respectively provided with a high-efficiency steam distributor a (28) and a high-efficiency steam distributor b (29); and the bottoms of the resin adsorber a (22) and the bottoms of the resin adsorber b (23) are respectively provided with a desorption gas exhaust valve a (9) and a desorption gas exhaust valve b (12).

4. The adsorption system for DCM exhaust gas according to claim 2, characterized in that: The desorbed gas recovery system comprises a high-efficiency condenser a (19), a high-efficiency condenser b (20), a high-efficiency condenser c (21), a condensate stratification tank (33), a recovery solvent receiving tank (34) and a waste water receiving tank (35) which are connected in sequence; the condensed gas from the high-efficiency condenser a (19), the high-efficiency condenser b (20), the high-efficiency condenser c (21), the condensate stratification tank (33), the recovery solvent receiving tank (34) and the waste water receiving tank (35) is connected to the inlet of the exhaust gas induced draft fan (17) through a pipeline.

5. The adsorption system for DCM exhaust gas according to claim 2, characterized in that: The resin cooling and drying system comprises a resin adsorber a (22), a resin adsorber b (23) and a water ring vacuum pump (25).

6. The adsorption system for DCM exhaust gas according to claim 2, characterized in that: The wastewater treatment system comprises a resin adsorber c (24); an automatic switching valve a (13) and an automatic switching valve b (14) are arranged at the top of the resin adsorber c (24); an automatic switching valve d (16) and an automatic switching valve c (15) are arranged at the bottom of the resin adsorber c (24); a high-efficiency steam distributor c (30) is arranged at the top of the inner cavity of the resin adsorber c (24), and the middle part is filled with modified adsorption resin (MWCNTs-Li (Ⅰ) / Al (Ⅲ) -AR).

7. The DCM waste gas adsorption system according to claim 2, characterized in that: The preparation method of the (MWCNTs-Li(Ⅰ) / Al(Ⅲ)-AR) modified adsorption resin is as follows: immersing the adsorption resin in a metal ion solution, washing with water until the pH value is 6 to 7, and drying to obtain a modified adsorption resin loaded with metal ions; MWCNTs are placed in ultrapure water and an MWCNTs dispersion is prepared by ultrasonic dispersion; then a modified adsorption resin loaded with metal ions is immersed in the MWCNTs dispersion and dried again to obtain a (MWCNTs-Li(Ⅰ) / Al(Ⅲ)-AR) modified adsorption resin.

8. The DCM exhaust gas adsorption system according to claim 7, characterized in that: The metal ion solution is an AlCl3 aqueous solution.

9. The DCM exhaust gas adsorption system according to claim 7, characterized in that: In the modified adsorption resin loaded with metal ions, the metal ion loading amount is 5 wt.%.

10. The DCM exhaust gas adsorption system according to claim 7, characterized in that: In the (MWCNTs-Li(Ⅰ) / Al(Ⅲ)-AR) modified adsorption resin, the MWCNTs loading amount is 2 wt.%.

Images