Adsorption tank, VOCs anhydrous desorption recovery system and method

Abstract

The invention relates to the technical field of organic waste gas desorption and recovery, and provides an adsorption tank and a VOCs anhydrous desorption and recovery system and method. The VOCs anhydrous desorption recovery system provided by the invention comprises two adsorption tanks which are connected in parallel, a gas path proportion control module, a desorption recovery module, a hot steam-condensate water supply module and a safety control module, wherein an upper-layer inner coil pipe (a snakelike coil pipe) and a lower-layer inner coil pipe (a central straight pipe and a double-layer reverse spiral pipe) are arranged in each adsorption tank. According to the device, low-water-content recovery, precise safe explosion prevention and efficient desorption of a solvent can be realized in a manner of combining water vapor heating of the inner coil pipe with a compressed air-nitrogen atmosphere, so that the operation cost and safety risk of an enterprise can be reduced, VOCs treatment can be promoted to be upgraded from standard emission to efficient recycling, and the environment pollution is reduced. The method meets the urgent demand of the industry for realizing green transformation, and is suitable for solvent recovery scenes in the industries of printing, chemical engineering, pharmacy, new energy batteries and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of organic waste gas desorption recovery, and in particular to an adsorption tank, a VOCs waterless desorption recovery system and method. BACKGROUND

[0002] Under the background of the coordinated development of industrial production and environmental protection, the upgrading and iteration of VOCs treatment technology has always been the focus of the industry. Among them, the adsorption-desorption-recovery process has become the preferred solution for the treatment of organic waste gas in the printing and packaging, fine chemical, automobile coating, and pharmaceutical manufacturing industries, with the dual values of "pollution control" and "resource recycling". This process captures VOCs in waste gas through high-performance adsorption materials (such as modified resin and activated carbon fiber), achieving waste gas emission standards while recycling the desorbed solvent for production, with a single set of equipment recovering tens to hundreds of tons of solvent per year, significantly reducing the raw material cost of enterprises.

[0003] However, the traditional desorption has exposed the following problems in actual operation, which has become a key bottleneck restricting the high-quality development of the industry: (1) high water content in solvent recovery. Traditional desorption mostly uses the method of directly introducing steam for heating (such as saturated steam directly contacting the adsorption resin), and the "gas-solid direct contact" mode has a fatal flaw. The steam will condense into liquid water during the cooling process, forming a milky liquid or homogeneous mixture system with the desorbed VOCs. Taking ethyl acetate commonly used in the printing industry as an example, its mutual solubility with water leads to a water content in the recovered solvent generally exceeding 5%, and in some high-humidity areas, it even reaches 8%~12%, which requires additional dehydration treatment (such as membrane treatment), increasing the cost and reducing the purity of the solvent. (2) Low desorption efficiency and recovery utilization rate. The mode of direct contact between steam and resin will cause the resin to overheat, affecting the service life of the resin, and it is difficult to completely desorb the VOCs adsorbed on the resin, which will affect the subsequent desorption efficiency and reduce the recovery utilization rate of the solvent. (3) Outstanding safety risks. VOCs are mostly flammable and explosive substances (such as ethyl acetate with an explosion limit of 2.0%~11.5%), and if the mixing ratio with air during desorption is within the explosion limit, it is easy to cause fire or explosion.

[0004] In summary, it is urgent to develop an integrated desorption technology that can achieve "low water content recovery, safety explosion prevention, and high desorption efficiency". SUMMARY

[0005] Therefore, the present application provides an adsorption tank, a VOCs waterless desorption recovery system and method. The adsorption tank provided by the present application can indirectly heat the adsorption resin through the inner coil water vapor heating method, avoiding direct contact between steam and resin. The VOCs waterless desorption recovery system assembled by using the adsorption tank can achieve low water content recovery of VOCs, high desorption efficiency, and precise safety explosion prevention.

[0006] In order to achieve the above-mentioned purposes, the present application provides the following technical solutions. An adsorption tank comprises an upper adsorption bed and a lower adsorption bed; the upper adsorption bed is divided into two sections by a baffle, and an upper inner coil is arranged in each section of the upper adsorption bed; the upper inner coil is a serpentine coil; The lower adsorption bed is also divided into two sections by a baffle, and a lower inner coil is arranged in each section of the lower adsorption bed; the lower inner coil comprises a central straight pipe and an inner layer spiral coil and an outer layer spiral coil wound around the periphery of the central straight pipe; the rotation directions of the inner layer spiral coil and the outer layer spiral coil are opposite; A distributor is arranged at the bottom of each section of the upper adsorption bed and each section of the lower adsorption bed; The adsorption tank is provided with a gas inlet at the bottom and a gas outlet and a steam / cooling water inlet 18 at the top; The upper inner coil and the lower inner coil are connected with the steam / cooling water inlet through an inner coil inlet.

[0007] Preferably, the pipe diameter of the serpentine coil is DN25~40, the length is 2.0~3.0m, and the bending radius of the U-shaped bend is 40~60mm; the number of the serpentine coils in each section of the upper adsorption bed is 10~14, and the distance between two adjacent serpentine coils is 70~90mm; the serpentine coil is inclined by 5~10° along the axial direction of the adsorption tank, and the low end is communicated with the cooling water outlet; In the lower inner coil: the pipe diameter of the central straight pipe is DN40~DN80, the central straight pipe is inclined by 5~10° along the axial direction of the adsorption tank, and the low end is communicated with the cooling water outlet; the pipe diameter of the inner layer spiral coil is DN25~DN50, the spiral diameter is 50%~70% of the tank diameter of the adsorption tank, and the pitch is 1~2 times of the pipe diameter; the pipe diameter of the outer layer spiral coil is DN20~DN40, the spiral diameter is 70%~90% of the tank diameter of the adsorption tank, and the pitch is 1.5~3.0 times of the pipe diameter; the inner layer spiral coil rotates clockwise, and the outer layer spiral coil rotates counterclockwise; The upper inner coil and the lower inner coil are both made of stainless steel.

[0008] Preferably, a gas outlet switching valve is arranged at the gas outlet of the adsorption tank; and the distributor is a hump-type distributor.

[0009] The present application also provides a VOCs anhydrous desorption and recovery system, which comprises: The first adsorption tank and the second adsorption tank are connected in parallel; the first adsorption tank and the second adsorption tank are both the adsorption tank described in the above-mentioned solution; The gas path proportional control module comprises a compressed air source, a nitrogen source, a static mixer and a dryer; the outlets of the compressed air source and the nitrogen source are communicated with the static mixer; the outlet of the static mixer is communicated with the inlet of the dryer; the outlet of the dryer is communicated with the gas inlets of the first adsorption tank and the second adsorption tank respectively; The desorption recovery module comprises a condenser and a solvent recovery tank; the inlet of the condenser is communicated with the gas outlets of the first adsorption tank and the second adsorption tank; the inlet of the solvent recovery tank is communicated with the outlet of the condenser; The hot steam-cooled water supply module comprises a steam generator, a cooling tower and a cooling tower water storage tank; the steam generator and the cooling tower are both communicated with the steam / cooling water inlets of the first adsorption tank and the second adsorption tank through a three-way valve; the cooling tower water storage tank is communicated with the cooling tower; The safety control module comprises a pressure sensor, an oxygen concentration sensor, a first VOCs concentration sensor, a steam temperature sensor, a pressure relief valve, a steam electric regulating valve, a proportional electromagnetic valve, an audible and visual alarm device and a control unit.

[0010] Preferably, the pressure sensor is used for monitoring the tank pressure of the adsorption tank; the oxygen concentration sensor is arranged between the static mixer and the dryer; the first VOCs concentration sensor is used for monitoring the VOCs concentration in the adsorption tank; the steam electric regulating valve and the steam temperature sensor are both arranged at the outlet end of the steam generator; the pressure relief valve is used for relieving the pressure of the adsorption tank; and the proportional electromagnetic valve is arranged at the front end of the static mixer.

[0011] Preferably, the VOCs anhydrous desorption recovery system further comprises a cooling water storage tank; the cooling water storage tank is communicated with the cooling water discharge outlets of the first adsorption tank and the second adsorption tank; The VOCs anhydrous desorption recovery system further comprises a VOCs inlet pipeline, which is communicated with the gas inlets of the first adsorption tank and the second adsorption tank respectively; and a VOCs inlet on-off valve is arranged on the VOCs inlet pipeline; A pressure stabilizing and reducing valve is further arranged at the outlet end of the steam generator; The cooling tower is further communicated with the condenser; a cooling tower fan and a cooling tower on-off valve are arranged on the pipeline where the cooling tower is communicated with the condenser; The gas outlets of the first adsorption tank and the second adsorption tank are communicated with the condenser through a one-way valve; A compressed air on-off valve and a compressed air flowmeter are arranged at the outlet end of the compressed air source; and a nitrogen source on-off valve and a nitrogen flowmeter are arranged at the outlet end of the nitrogen source; The gas outlet switching valve of the first adsorption tank and the second adsorption tank is connected to two gas paths, one of which is connected to the condenser, and the other is connected to the purified gas exhaust port, and a second VOCs concentration sensor is arranged on the pipeline connected to the purified gas exhaust port.

[0012] The application also provides a method for desorbing and recovering VOCs by using the VOCs anhydrous desorption and recovery system. Step 1: introduce VOCs into the first adsorption tank or the second adsorption tank, and the resin in the first adsorption tank or the second adsorption tank adsorbs VOCs until the resin is saturated; the first adsorption tank and the second adsorption tank are connected in parallel, and when the adsorption resin in one of the two tanks reaches the VOCs adsorption saturation, the control unit controls the tank to stop adsorption and enter the desorption mode, and controls the other tank in standby state to switch to the adsorption state; Step 2: introduce hot steam into the upper and lower inner coils in the VOCs adsorption saturated tank to indirectly heat the resin and desorb VOCs; at the same time, introduce the mixed gas of nitrogen and compressed air into the adsorption tank to blow and recover the desorbed VOCs to the condenser; Step 3: after the VOCs desorption is completed, stop introducing the hot steam, introduce cooling water into the upper and lower inner coils, and introduce the mixed gas of nitrogen and compressed air into the adsorption tank to blow and cool the adsorption tank.

[0013] Preferably, the pressure of the hot steam is 0.1 MPa to 0.27 MPa, and the temperature is 100 to 130 DEG C; the pressure of the hot steam is controlled by a pressure stabilizing valve, and the temperature is controlled by a steam temperature sensor and a steam electric regulating valve.

[0014] Preferably, in step 2, the pressure in the adsorption tank is 3.5 to 4.5 atm, and the pressure in the adsorption tank is controlled by a pressure sensor and a pressure relief valve; in step 2, the oxygen concentration in the adsorption tank is controlled by an oxygen concentration sensor and a proportional electromagnetic valve to be within a safe range; the safe range of the oxygen concentration in step 2 is ≤8 vol%; In step 3, the temperature of the cooling water is ≤25 DEG C, and the cooling time is 30 to 60 minutes.

[0015] Preferably, in the safety control module, the control unit and each execution component form an interlocking logic. When the pressure sensor detects a value > 4.5 atm, the control unit triggers the pressure relief valve to open; When the oxygen concentration sensor detects a value > the safe oxygen concentration, the control unit forces the proportional electromagnetic valve to reduce the proportion of compressed air to ≤ the safe oxygen concentration / 21%; When the VOCs concentration in the tank is monitored to exceed 25% of the lower explosive limit, the nitrogen proportion is automatically increased to > 80%; When the steam temperature sensor detects a value > 120℃, the control unit reduces the opening of the steam electric regulating valve; when the detected value > 130℃, the steam electric regulating valve is closed and an alarm is triggered. When the above safety signal is triggered, the control unit synchronously starts the audible and visual alarm device.

[0016] The application provides an adsorption tank, comprising an upper adsorption bed and a lower adsorption bed; the upper adsorption bed is divided into two sections by a baffle, and an upper inner coil is arranged in each section of the upper adsorption bed, the upper inner coil being a serpentine coil; the lower adsorption bed is divided into two sections by a baffle, and a lower inner coil is arranged in each section of the lower adsorption bed, the lower inner coil comprising a central straight pipe and an inner layer spiral coil and an outer layer spiral coil wound around the periphery of the central straight pipe, the rotation directions of the inner layer spiral coil and the outer layer spiral coil being opposite; a distributor is arranged at the bottom of each section of the upper adsorption bed and each section of the lower adsorption bed; a gas inlet is arranged at the bottom of the adsorption tank, and a gas outlet and a steam / cooling water inlet are arranged at the top of the adsorption tank; the upper inner coil and the lower inner coil are connected with the steam / cooling water inlet through an inner coil inlet. The adsorption tank provided by the application is internally provided with an upper inner coil (serpentine coil) and a lower inner coil (central straight pipe+double-layer reverse spiral pipe), during desorption, hot steam is introduced into the inner coil to indirectly desorb the adsorption resin, so that direct contact between the steam and the resin is avoided, and after desorption, cooling water is introduced into the inner coil to cool the adsorption tank. The adsorption tank of the application can realize water-free desorption and recovery of VOCs, and has high desorption efficiency and solvent recovery rate.

[0017] The application further provides a water-free desorption and recovery system for VOCs, comprising a first adsorption tank and a second adsorption tank connected in parallel, a gas path proportion control module, a desorption and recovery module, a hot steam-condensed water supply module and a safety control module. The water-free desorption and recovery system for VOCs provided by the application can realize continuous processing by alternately operating the first adsorption tank and the second adsorption tank, when the resin in one of the adsorption tanks is saturated with adsorption of VOCs, the control system automatically controls the adsorption tank to stop adsorption and enter the desorption mode, while triggering the other adsorption tank to start and switch to the adsorption state. The application can accurately control the proportion of compressed air and nitrogen through the gas path proportion control module, during desorption, the mixed compressed air and nitrogen according to a safe proportion are used for purging, so that the enriched VOCs are pushed into the condenser for recovery, and the operation safety is ensured.

[0018] The system provided by the application comprises a safety control module, wherein: a pressure sensor monitors the pressure in the tank; an oxygen concentration sensor monitors the oxygen content of the mixed gas, and controls the oxygen concentration in the adsorption tank within a safe range; a steam inlet pipeline is provided with a steam temperature sensor and a steam electric regulating valve connected to the control system, and the control system adjusts the pressure of the pressure reducing valve according to the signal of the steam temperature sensor to control the size of the steam temperature; all signals are connected to the control system, and the sound-light alarm is triggered synchronously to form a multi-layer safety protection.

[0019] In summary, the VOCs anhydrous desorption recovery system provided by the application can realize anhydrous recovery of solvents (water content ≤0.5%), precise and safe explosion prevention (oxygen concentration fluctuation ≤±1%) and high-efficiency desorption through the combination of the internal coil water vapor heating mode and the compressed air-nitrogen atmosphere mode, which not only can reduce the operation cost and safety risk of enterprises, but also can promote the VOCs treatment from'standard emission' to 'efficient resource utilization', meet the urgent needs of the industry to realize green transformation, and is suitable for solvent recovery scenes in printing, chemical industry, pharmaceutical industry, new energy battery industry and the like.

[0020] Further, the internal coil of the application is made of 316L stainless steel material, and is optimally arranged, so that the heating uniformity is improved by 20%, and the desorption efficiency is as high as 95% or more; anhydrous recovery of solvents is realized, indirect heating of the internal coil avoids the contact between steam and resin, and dry purge gas is introduced, so that the water content of the recovered solvent is ≤0.5%, which can be directly reused, the dehydration process is saved, and the cost is reduced by 30%~50%; resin swelling and aging caused by direct steam flushing are avoided, and the service life is prolonged from 1 year to 2~3 years; the steam temperature is precisely maintained at 100~130℃ through closed-loop control of'sensor + steam electric regulating valve', so that resin aging or VOCs decomposition caused by over-temperature is avoided; the proportion of the mixed gas is dynamically adjusted according to 'compressed air proportion ≤ safety oxygen concentration / 21%', so that the risk of VOCs explosion is avoided from the source; the whole process is automatically controlled, which is suitable for continuous production and reduces manual intervention. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 FIG. 1 is a structural schematic view of the adsorption tank; Figure 2 FIG. 2 is a structural schematic view of the serpentine coil; Figure 3 FIG. 3 is a structural schematic view of the VOCs anhydrous desorption recovery system; Figure 4 FIG. 4 is a structural schematic view of the gas ratio control module; Figure 5 FIG. 5 is a safety control logic block diagram of the safety control module; Wherein: 1-first adsorption tank; 2-second adsorption tank; 3-condenser; 4-solvent recovery tank; 5-steam generator; 6-cooling tower; 7-cooling tower water storage tank; 8-cooling water storage tank; 9-compressed air source; 10-nitrogen source; 11-proportional electromagnetic valve; 12-dryer; 13-VOCs inlet switch valve; 14-control unit; 15-inlet switch valve; 16-second gas inlet, 17-first gas inlet; 18-steam / cooling water inlet; 19-gas outlet; 20-upper adsorption bed; 21-lower adsorption bed; 22-filled resin; 23-upper inner coil; 24-lower inner coil; 25-distributor; 26-inner coil inlet; 27-first cooling water outlet, 28-second cooling water outlet; 29-first cooling water discharge valve; 30-second cooling water discharge valve; 31-fixed support; 32-pressure relief valve; 33-pressure sensor; 34-first VOCs sensor; 35-gas outlet switch valve; 36-three-way valve; 37-pressure stabilizing and reducing valve; 38-steam electric regulating valve; 39-steam temperature sensor; 40-cooling tower fan; 41-cooling tower switch valve; 42-check valve; 43-recovered solvent discharge valve; 44-purified gas exhaust; 45-compressed air switch valve; 46-nitrogen source switch valve; 47-compressed air flowmeter, 48-nitrogen flowmeter; 49-static mixer; 50-oxygen concentration sensor; 51-second VOCs concentration sensor. DETAILED DESCRIPTION

[0022] The present application provides an adsorption tank, a structural schematic diagram as shown in Figure 1 The following will be described in detail. Figure 1

[0023] In the present application, the adsorption tank is a horizontal adsorption tank.

[0024] The adsorption tank provided by the present application comprises an upper adsorption bed 20 and a lower adsorption bed 21; the upper adsorption bed 20 is divided into two sections by a baffle, specifically, is divided into two adsorption bed layers in the horizontal direction (denoted as a first section of upper adsorption bed and a second section of upper adsorption bed) by a vertical baffle; an upper inner coil 23 is arranged in each section of upper adsorption bed, and the upper inner coil 23 is a serpentine coil.

[0025] ​In this invention, the diameter of the serpentine coil is preferably DN25~40, specifically DN32 (outer diameter 42mm), the length is preferably 2.0~3.0m, specifically 2.5m, and the U-bend radius is preferably 40~60mm, specifically 50mm; the number of serpentine coils in each upper adsorption bed 20 section is preferably 10~14, specifically 12, and the spacing between two adjacent serpentine coils is preferably 70~90mm, specifically 80mm; the serpentine coil is preferably inclined at 5~10° along the axial direction of the adsorption tank, with its lower end connected to the cooling water outlet (the lower end is located on one side of the tank wall), specifically the lower end of the serpentine coil is the end closest to the side wall of the adsorption tank; the structural schematic diagram of the serpentine coil is shown below. Figure 2 As shown.

[0026] In this invention, the lower adsorption bed 21 is divided into two sections by a baffle, specifically, it is divided into two horizontal adsorption bed sections by a vertical baffle (denoted as the second lower adsorption bed and the second lower adsorption bed); each lower adsorption bed 21 is provided with a lower inner coil 24, the lower inner coil 24 including a central straight tube and an inner spiral coil and an outer spiral coil wound around the central straight tube, the inner spiral coil and the outer spiral coil rotating in opposite directions; in the lower inner coil 24: the diameter of the central straight tube is preferably DN40~DN80 (… 48~ 89mm), the central straight pipe is inclined at 5~10° along the axial direction of the adsorption tank, and its lower end is connected to the cooling water outlet (the lower end is located on one side of the tank wall); the diameter of the inner spiral coil is DN25~DN50 ( 32~ 57mm), the spiral diameter is 50%~70% of the adsorption tank diameter, and the pitch is 1~2 times the pipe diameter; the outer spiral coil has a pipe diameter of DN20~DN40 ( 25~ The inner spiral coil (48mm) has a diameter of 70% to 90% of the adsorption tank diameter and a pitch of 1.5 to 3.0 times the pipe diameter. The inner spiral coil rotates clockwise, and the outer spiral coil rotates counterclockwise. This invention enhances turbulence by using inner and outer spiral coils with opposite rotation directions. In specific embodiments of this invention, the above parameters can be adjusted based on tank size, medium characteristics, and flow rate. For corrosive media, the wall thickness needs to be increased. When the steam pressure is ≤1.0MPa, the wall thickness of the upper and lower inner coils should be ≥3mm to prevent erosion.

[0027] In the application, the cooling water outlet of the adsorption tank is lower than the lower adsorption bed, and two cooling water outlets are provided, namely a first cooling water outlet 27 and a second cooling water outlet 28, which are arranged on the two sides of the adsorption tank, respectively; the low ends of all the upper and lower inner coils are communicated with the cooling water outlet on the same side; the first cooling water outlet is preferably provided with a first cooling water discharge valve 29, and the second cooling water outlet is preferably provided with a second cooling water discharge valve 30.

[0028] In the application, the upper inner coil 23 and the lower inner coil 24 are made of stainless steel, specifically 316L stainless steel, which has good corrosion resistance to benzene series, esters, alcohols and some sulfur / halogen-containing organic matter, high temperature resistance (no significant corrosion at ≤200℃), high strength, good weldability and is suitable for spiral pipe processing; the upper inner coil 23 and the lower inner coil 24 are preferably fixed by a fixed support 31.

[0029] In the application, the adsorption tank is provided with a gas inlet at the bottom and a gas outlet 19 and a steam / cooling water inlet 18 at the top; the gas inlet preferably includes a first gas inlet 17 and a second gas inlet 16, the first gas inlet 16 is preferably located at the bottom of the first section of the lower adsorption bed, and the second gas inlet is preferably located at the bottom of the second section of the lower adsorption bed; the first gas inlet 17 and the second gas inlet 16 are communicated with the gas inlet switch valve 15.

[0030] In the application, the upper inner coil 23 and the lower inner coil 24 are connected with the steam / cooling water inlet 18 through the inner coil inlet 26; the gas outlet switch valve 35 is preferably arranged at the gas outlet 19 of the adsorption tank.

[0031] In the application, the distance between the outer wall of the serpentine coil and the outer wall of the outer and inner spiral pipes of the lower inner coil and the inner wall of the adsorption tank body is preferably greater than 80mm, so as to avoid the dead angle of resin filling.

[0032] In the present application, a distributor 25 is arranged at the bottom of each upper adsorption bed 20 and each lower adsorption bed 21; the distributor 25 is preferably a hump distributor; the material of the hump distributor is preferably a steel material resistant to weakly corrosive gases (such as chlorine-containing VOCs), preferably 316L stainless steel; the hole position of the hump distributor is preferably arranged in the upper part of the arc surface of the hump, specifically at a distance of 50-80 mm from the arc top, and the outer hole diameter is preferably less than half of the particle size of the resin particles but not less than 0.1 mm; the hump width (W) of the hump distributor needs to be adapted to the diameter of the resin column in the adsorption bed: when the column diameter is <1.5 m, the hump width is preferably 250-300 mm, and when the column diameter is >1.5 m, the hump width is preferably 300-350 mm, so as to avoid excessive units causing airflow interference, and the distance between adjacent humps is preferably consistent with the width to ensure uniform distribution of the gas chamber. The hump height (H) of the hump distributor is preferably 100-150 mm higher than the bottom of the resin bed; the hump arc surface needs to be smoothly transitioned (avoiding right angles); and the arc vertex is directed towards the upward direction of the airflow. In a specific embodiment of the present application, when the gas treatment capacity is large (>5000 m 3 / h), the number of hump units can be appropriately increased or the hump width can be expanded, while the opening rate is increased to 22%-25% to reduce airflow resistance; when the gas capacity is small (<1000 m 3 / h), the opening rate can be reduced to 15%-18% to avoid low airflow velocity leading to a decrease in mass transfer efficiency.

[0033] In the present application, the height of the upper adsorption bed is preferably 0.3 m, and the height of the lower adsorption bed is preferably 0.5 m; the upper adsorption bed and the lower adsorption bed are both filled with packed resin 22, and the filling amount of the packed resin 22 is preferably one-half to three-quarters of the volume of the adsorption tank; the present application does not have special requirements for the type of packed resin, and any type known to those skilled in the art can be used.

[0034] In a specific embodiment of the present application, the baffles separating the upper adsorption bed and the lower adsorption bed, and the baffles between the upper adsorption bed and the lower adsorption bed are all perforated baffles to facilitate gas flow.

[0035] In the present application, a pressure relief valve 32, a pressure sensor 33, and a first VOCs concentration sensor 34 are also arranged on the adsorption tank, which will be described in detail later.

[0036] The present application also provides a VOCs anhydrous desorption recovery system, and a structure diagram thereof is shown in Figure 3 , which will be described in detail below. Figure 3 .

[0037] The VOCs anhydrous desorption recovery system provided by the application comprises a first adsorption tank 1 and a second adsorption tank 2 connected in parallel.

[0038] The VOCs anhydrous desorption recovery system provided by the application comprises a gas path proportion control module; the gas path proportion control module comprises a compressed air source 9, a nitrogen source 10, a static mixer 49 and a dryer 12; the outlets of the compressed air source 9 and the nitrogen source 10 are communicated with the static mixer 49; the outlet of the static mixer 49 is communicated with the inlet of the dryer 12; the outlet of the dryer 12 is respectively communicated with the gas inlets of the first adsorption tank 1 and the second adsorption tank 2, specifically through the gas inlet of the first adsorption tank 1 and the second adsorption tank 2 and the gas inlet switching valve 15. The gas inlet switching valve 15 is linked with the control unit 14 to realize the alternate switching of the adsorption / desorption state.

[0039] In the application, the nitrogen source 10 is preferably a nitrogen generator, specifically a pressure swing adsorption nitrogen generator, and the purity of the generated nitrogen is preferably ≥99.9%; the drying agent used in the dryer 12 can be one or both of anhydrous CaO and anhydrous CaSO4.

[0040] In the application, the VOCs anhydrous desorption recovery system further comprises a VOCs gas inlet pipeline, which is communicated with the gas inlets of the first adsorption tank 1 and the second adsorption tank 2, specifically through the gas inlet of the first adsorption tank 1 and the second adsorption tank 2 and the gas inlet switching valve 15; the VOCs gas inlet pipeline is provided with a VOCs gas inlet switch valve 13.

[0041] In the application, the outlet end of the compressed air source 9 is preferably provided with a compressed air switch valve 45 and a compressed air flowmeter 47; the outlet end of the nitrogen source 10 is preferably provided with a nitrogen source switch valve 46 and a nitrogen flowmeter 48; in the specific embodiment of the application, the compressed air and the nitrogen enter the proportional electromagnetic valve 11 through the respective flowmeters, and the proportion is adjusted by the control unit according to the flowmeter signal to ensure that the proportion of the compressed air is ≤21% of the safe oxygen concentration; the compressed air and the nitrogen are uniformly mixed through the static mixer 49, and then enter the dryer 12 after the oxygen content is detected by the oxygen concentration sensor 50, and then enter the adsorption tank after drying.

[0042] In addition, the gas path proportion control module further comprises a proportional electromagnetic valve and an oxygen concentration sensor, which will be described in detail later. Figure 4 The schematic diagram of the gas path proportion control module.

[0043] The VOCs anhydrous desorption recovery system provided by the application comprises a desorption recovery module; the desorption recovery module comprises a condenser 3 and a solvent recovery tank 4; the inlet of the condenser 3 is communicated with the gas outlet 19 of the first adsorption tank 1 and the second adsorption tank 2; specifically, the gas outlet 19 of the first adsorption tank 1 and the second adsorption tank 2 is preferably communicated with the condenser 3 through a one-way valve 42, and the one-way valve 42 is arranged to prevent the backflow of condensed liquid. The inlet of the solvent recovery tank 4 is communicated with the outlet of the condenser 3, and the solvent recovery tank 4 is preferably further provided with a solvent recovery discharge valve 43. In the specific embodiment of the application, the VOCs, nitrogen and compressed air after desorption are condensed through the condenser 3, the liquid VOCs are collected into the solvent recovery tank 4, and a small amount of non-condensable gas, nitrogen and compressed air are discharged after reaching the standard through the waste gas treatment device.

[0044] In the application, the gas outlet switching valve 35 of the first adsorption tank 1 and the second adsorption tank 2 is preferably connected to two gas paths respectively, one of which is connected to the condenser 3, and the other of which is connected to the purified gas exhaust port 44, and the pipeline connected to the purified gas exhaust port 44 is provided with a second VOCs concentration sensor 51.

[0045] The VOCs anhydrous desorption recovery system provided by the application comprises a hot steam-condensed water supply module; the hot steam-condensed water supply module comprises a steam generator 5, a cooling tower 6 and a cooling tower water storage tank 7; the steam generator 5 and the cooling tower 6 are both communicated with the steam / cooling water inlet 18 of the first adsorption tank 1 and the second adsorption tank 2 through a three-way valve 36; the cooling tower water storage tank 7 is communicated with the cooling tower 6. The cooling tower 6 is preferably further communicated with the condenser 3, and the pipeline communicated with the cooling tower 6 and the condenser 3 is preferably provided with a cooling tower fan 40 and a cooling tower on-off valve 41.

[0046] In the application, the VOCs anhydrous desorption recovery system further comprises a cooling water storage tank 8; the inlet of the cooling water storage tank 8 is communicated with the cooling water discharge outlet of the first adsorption tank 1 and the second adsorption tank 2; at the same time, the outlet of the cooling water storage tank 8 is communicated with the cooling tower water storage tank 7, so as to realize the circulation of the cooling water.

[0047] The VOCs anhydrous desorption recovery system provided by the application comprises a safety control module; the safety control module comprises a pressure sensor 33, an oxygen concentration sensor 50, a first VOCs concentration sensor 34, a steam temperature sensor 39, a pressure relief valve 32, a steam electric regulating valve 38, a proportional electromagnetic valve 11, an audible and visual alarm device and a control unit 14. In the application, the pressure sensor 33 is used for monitoring the pressure in the adsorption tank, and specifically, one pressure sensor 33 is arranged in each of the first adsorption tank 1 and the second adsorption tank 2; the oxygen concentration sensor 50 is arranged between the static mixer 49 and the dryer 12 and is used for monitoring the oxygen concentration of the mixed gas; the first VOCs concentration sensor 34 is used for monitoring the VOCs concentration in the adsorption tank, and specifically, one first VOCs concentration sensor 34 is arranged in each of the first adsorption tank 1 and the second adsorption tank 2; the steam electric regulating valve 38 and the steam temperature sensor 39 are both arranged at the outlet end of the steam generator 5, and the measurement range of the steam temperature sensor is preferably 0-200 ℃, and the accuracy is ±1 ℃; the pressure relief valve 32 is used for discharging pressure of the adsorption tank, and specifically, one pressure relief valve is arranged in each of the first adsorption tank 1 and the second adsorption tank 2; and the proportional electromagnetic valve 11 is arranged at the front end of the static mixer 49.

[0048] In the application, the outlet end of the steam generator 5 is further provided with a pressure stabilizing and reducing valve 37.

[0049] In the application, the control unit 14 receives signals of various sensors and controls various valves and the audible and visual alarm device; and the control unit 14 is preferably a PLC control system.

[0050] The application further provides a method for desorbing and recovering VOCs by using the VOCs anhydrous desorption recovery system. Step 1: VOCs are introduced into the first adsorption tank 1 or the second adsorption tank 2, and the resin in the first adsorption tank 1 or the second adsorption tank 2 adsorbs VOCs until the resin is saturated; the first adsorption tank 1 and the second adsorption tank 2 are arranged in parallel, and when the adsorption resin in one of the adsorption tanks is saturated with VOCs, the adsorption tank is controlled to stop adsorption and enter the desorption mode, and the other adsorption tank in standby state is controlled to switch to the adsorption state; Step 2: hot steam is introduced into the upper inner coil 23 and the lower inner coil 24 in the adsorption tank saturated with VOCs to indirectly heat the resin and desorb VOCs; and a mixed gas of compressed air and nitrogen is introduced into the adsorption tank to blow the desorbed VOCs to the condenser 3 for condensation and recovery of the solvent; Step 3: after the VOCs desorption is completed, the introduction of hot steam is stopped, cooling water is introduced into the upper inner coil 23 and the lower inner coil 24, and a mixed gas of nitrogen and compressed air is introduced into the adsorption tank for blowing and cooling to cool the adsorption tank.

[0051] In the present application, VOCs enter the adsorption tank through the gas inlet after passing through the VOCs inlet valve 13 and the inlet switch valve 15 in turn. The standard for reaching the VOCs adsorption saturation in step 1 is preferably that the VOCs concentration in the tank is greater than 50 mg / m 3 ; after the first VOCs concentration sensor 34 detects that the VOCs concentration in the tank is greater than 50 mg / m 3 , the signal is transmitted to the PLC control system, and the PLC control system immediately performs the switching operation.

[0052] In the present application, the pressure of the hot steam in step 2 is preferably 0.1 MPa~0.27 MPa, and the temperature is preferably 100~130℃; the pressure of the hot steam is preferably controlled by the pressure stabilizing valve 37, and the temperature is controlled by the steam temperature sensor 39 and the steam electric regulating valve 38. In a specific embodiment of the present application, the opening of the steam electric regulating valve 38 is preferably adjusted when the steam temperature is >120℃, and the steam electric regulating valve 38 is closed and an alarm is given when the temperature is >130℃; the hot steam enters the upper and lower coils through the steam / cooling water inlet, and indirectly heats the resin through the coil wall, so that the VOCs are desorbed from the resin. In a specific embodiment of the present application, the temperature of the hot steam can be adjusted according to the boiling point of VOCs, such as 110~120℃ hot steam for ethyl acetate.

[0053] In the present application, the volume ratio of compressed air in the mixed gas of nitrogen and compressed air in step 2 is ≤ the safe oxygen concentration / 21%, and the mixed gas is dried by the dryer 12 and then introduced from the bottom of the adsorption tank, and the desorbed VOCs are blown upward through the top gas outlet 19 and enter the condenser 13 to be condensed into liquid solvent (water content ≤0.5%), and the nitrogen and compressed air are discharged after waste gas treatment, specifically, the uncondensed gas can be emptied after detecting that the VOCs residue is less than 10 mg / m 3 .

[0054] In the present application, the pressure in the adsorption tank in step 2 is preferably 3.5-4.5 atm, and the pressure in the adsorption tank is controlled by the pressure sensor 33 and the pressure relief valve 32 in linkage, when the pressure > 4.5 atm, the pressure relief valve 32 is automatically opened to ensure that the pressure is stable at 3.5-4.5 atm; the oxygen concentration in the adsorption tank in step 2 is controlled by the oxygen concentration sensor 50 and the proportional electromagnetic valve 11 in linkage to keep it within a safe range; the safe oxygen concentration is determined according to the explosion limit of VOCs, for example, for VOCs with an explosion lower limit of ≤5 vol%, the safe oxygen concentration is ≤8 vol% (which can cover the safety requirements of most common VOCs), and the maximum proportion of compressed air in the corresponding mixed gas is 38.1 vol%, and the minimum proportion of nitrogen is 61.9 vol% (calculation: the oxygen content in compressed air is 21 vol%, assuming the oxygen concentration in the mixed gas is ≤8 vol%, then the maximum proportion of compressed air = 8% / 21% ≈ 38.1%, i.e. the proportion of nitrogen ≥ 61.9 vol%).

[0055] In step 3, the desorption end criteria are preferably that the VOCs concentration in the adsorption tank ≤10 mg / m 3 ; the temperature of the cooling water is preferably ≤25℃, and in the mixed gas of nitrogen and compressed air in step 3, the volume fraction of nitrogen is preferably ≥95%, specifically 95%-99.99%; after the mixed gas of nitrogen and compressed air is purged, it can be discharged through a temporary discharge valve or a simple treatment device; the cooling time is preferably 30-60 minutes, and the cooling is preferably to cool the temperature of the adsorption tank to 30-40℃.

[0056] After cooling, stop the flow of cooling water and mixed gas, and prepare for the next adsorption cycle.

[0057] In the present application, in the safety control module, the control unit and each execution component form an interlocking logic (safety logic diagram as shown in Figure 5 ). When the pressure sensor 33 detects a value > 4.5 atm, the control unit triggers the pressure relief valve to open; When the oxygen concentration sensor 50 detects a value > the safe oxygen concentration, the control unit forces the proportional electromagnetic valve 11 to reduce the proportion of compressed air to ≤ the safe oxygen concentration / 21%; When the first VOCs concentration sensor 34 monitors that the VOCs concentration in the tank exceeds 25 vol% of its explosion lower limit, the proportion of nitrogen is automatically increased to ≥80 vol%; When the steam temperature sensor 39 detects a value > 120℃, the control unit reduces the opening of the steam electric regulating valve 38; when the detected value > 130℃, the steam electric regulating valve 38 is closed and an alarm is triggered; When the above safety signals are triggered, the control unit simultaneously starts the audible and visual alarm device.

[0058] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0059] Example 1 In this embodiment, the VOCs anhydrous desorption and recovery system includes a first adsorption tank 1, a second adsorption tank 2, a condenser 3, a solvent recovery tank 4, a steam generator 5, a cooling tower 6, a cooling tower water storage tank 7, a water storage tank 8, a compressed air source 9, a nitrogen source 10, and corresponding detection and control components and a control unit 14 (PLC control system) configured in parallel. All components are connected via pipelines to form a closed-loop processing system, such as... Figure 1 As shown. The first adsorption tank 1 and the second adsorption tank 2 are filled with resin 22. The adsorption bed inside the tank is divided into an upper adsorption bed 20 and a lower adsorption bed 21. The upper adsorption bed 20 and the lower adsorption bed 21 are each divided into two sections by baffles. Each upper adsorption bed section is equipped with an upper inner coil 23, and each lower adsorption bed section is equipped with a lower inner coil 24. The upper inner coil 23 is a serpentine coil, and the lower inner coil 24 is a "central straight tube + double-layer reverse spiral tube". The upper inner coil 23 and the lower inner coil 24 are connected to the steam / cooling water inlet 18 through the inner coil inlet 26, and the inner coil outlets are connected to the first cooling water outlet 27 and the second cooling water outlet 28. A first cooling water discharge valve 29 and a second cooling water discharge valve 30 are respectively installed at the first cooling water outlet 27 and the second cooling water outlet 28. Finally, the upper inner coil 23 and the lower inner coil 24 are fixed using a fixing bracket 31. The top of the first adsorption tank 1 and the second adsorption tank 2 are provided with an adsorption tank gas outlet 19, and the bottom is provided with an adsorption tank first gas inlet 16 and a second gas inlet 17. A pressure sensor 33, a pressure relief valve 32, and a first VOCs concentration sensor 34 are installed on the tanks. The control unit 14 (PLC control system) is electrically connected to each sensor, valve, and equipment, and is particularly linked to the inlet / outlet switching valves of the two adsorption tanks to achieve automatic control through alternating "adsorption and desorption" control.

[0060] Compressed air source 9 is connected to proportional solenoid valve 11 via compressed air source switch valve 45 and compressed air flow meter 47 in sequence. Nitrogen source 10 is connected to proportional solenoid valve 11 via nitrogen source switch valve 46 and nitrogen flow meter 48 in sequence. The outlet of proportional solenoid valve 11 is connected to dryer 12 via static mixer 49 and oxygen concentration sensor 50. The dried mixed gas is connected to the gas inlets of the two adsorption tanks (first gas inlet 17 and second gas inlet 16).

[0061] The steam generator 5 is connected to the steam / cooling water inlet 18 through the stable pressure reducing valve 37, the steam electric regulating valve 38, the steam temperature sensor 39 and the three-way valve 36 in sequence; the cooling tower 6 is connected to the steam / cooling water inlets 18 of the two adsorption tanks through the cooling tower switch valve 41, the cooling tower 6 forms a cycle with the cooling tower water storage tank 7, and the cooling tower 6 is provided with the cooling tower fan 40; the steam / cooling water inlet 18 is provided with the three-way valve 36 for switching the supply of steam and cooling water, and the three-way valve 36 is communicated with the steam generator 5 in the heating stage and is communicated with the cooling tower 6 in the cooling stage.

[0062] The adsorption tank gas outlet 19 and the gas outlet switch valve 35 are connected to two gas paths respectively: one path is connected to the condenser 3 through the one-way valve 42, the outlet of the condenser 3 is connected to the solvent recovery tank 4, and the solvent recovery tank 4 is provided with the solvent recovery tank discharge valve 43; the other path is directly connected to the purified gas exhaust 44, and the second VOCs concentration sensor 51 is arranged on the exhaust gas pipeline to monitor the emission concentration of the adsorbed and purified gas.

[0063] The VOCs inlet valve 13 is connected to the gas inlets (the first gas inlet 17 and the second gas inlet 16) of the two adsorption tanks.

[0064] The control unit 14 is electrically connected with each sensor, valve and device to realize automatic control.

[0065] The complete VOCs desorption and recovery process using the above system is as follows: 1) Each component is assembled according to the above connection relationship, it is ensured that the pipeline is unobstructed, the control unit 14 is in normal signal transmission with the pressure sensor 33, the first VOCs concentration sensor 34, the oxygen concentration sensor 50, the steam temperature sensor 39 and the like, the safe oxygen concentration is set (for example, 8 vol% for benzene series VOCs), the upper limit of the compressed air proportion is 38.1 vol% (8% / 21%), the steam temperature control range is 100-130℃, and the upper limit of the tank pressure is 4.5 atm.

[0066] 2) In the adsorption stage, the control unit 14 defaults to control one of the adsorption tanks (denoted as tank A) to be in the adsorption state, and the other adsorption tank (denoted as tank B) to be in the standby state. The gas inlet switch valve 15 is switched to the VOCs inlet direction, the VOCs inlet valve 13 and the gas outlet switch valve 35 are switched to the purified gas exhaust route, and other valves are closed. The VOCs waste gas to be treated enters the adsorption tank through the adsorption tank gas inlets (the first gas inlet 16 and the second gas inlet 17), is adsorbed and purified through the filled resin 22, is discharged from the purified gas exhaust 44 through the adsorption tank gas outlet 19 and the gas outlet switch valve 35, and the second VOCs concentration sensor 51 on the exhaust gas pipeline monitors the emission concentration in real time.

[0067] 3) Desorption stage, when the first VOCs concentration sensor 34 detects that the resin in the A tank is saturated (i.e. VOCs concentration > 50 mg / m 3 ) 3, the inlet switching valve 15 switches to the purge channel, the three-way valve 36 switches to the steam direction. Start the steam generator 5, the steam is adjusted to 0.1 MPa~0.27 MPa by the pressure stabilizing and reducing valve 37, then enters the upper and lower inner coils 23 and 24 through the steam electric regulating valve 38 and the steam temperature sensor 39, heats the filled resin 22 through indirect heat transfer, and the steam temperature is maintained at 120℃±5℃ by the steam electric regulating valve 38 linked by the control unit 14 (the valve is closed when the temperature exceeds 120℃, and the valve is closed when the temperature exceeds 130℃). At the same time, control the B tank to enter the adsorption mode.

[0068] 4) Synchronously open the compressed air source on-off valve 45 and the nitrogen source on-off valve 46, the compressed air (entering the static mixer 49 through the compressed air flow meter 47 and the nitrogen flow meter 48 from the compressed air source 9 and the nitrogen source 10 respectively, the proportional electromagnetic valve 11 adjusts the proportion according to the PLC instruction to ensure that the proportion of compressed air is ≤38.1vol%). The mixed gas is detected by the oxygen concentration sensor 50 (oxygen content ≤8vol%) and then enters the dryer 12, and after drying, the mixed gas enters from the adsorption tank gas inlet (the first gas inlet 16 and the second gas inlet 17), carries the desorbed VOCs, and then flows into the condenser 3 through the one-way valve 42 after the gas outlet switching valve 35, and then flows into the solvent recovery tank 4, and then the solvent recovery tank 4 is full and can be tanked and transported through the valve 43. The uncondensed gas (containing nitrogen and compressed air) is treated by the subsequent waste gas treatment device and discharged according to the standard.

[0069] 5) During the desorption process, the pressure sensor 33 monitors the pressure in the tank in real time, and if it exceeds 4.5atm, the control unit 14 immediately triggers the pressure relief valve 32 to open and reduce the pressure; if the oxygen content detected by the oxygen concentration sensor 50 is > 8vol%, the proportional electromagnetic valve 11 automatically reduces the proportion of compressed air and increases the proportion of nitrogen until the oxygen content is ≤8vol%, and at the same time the audible and visual alarm device is started.

[0070] 6) Cooling stage: when the first VOCs concentration sensor 34 detects that the VOCs concentration in the A tank is ≤10 mg / m 3When the desorption ends, the steam generator 5 and the compressed air source switch valve 45 are closed, the cooling tower switch valve 41 is opened, the cooling water in the cooling tower water storage tank 7 enters the upper layer inner coil 23 and the lower layer inner coil 24 through the steam / cooling water inlet 18, the cooling tower fan 40 is started to enhance heat dissipation, and the steam condensate and the cooling water after heat absorption are collected through the first cooling water outlet 27 and the second cooling water outlet 28, and then flow into the cooling water storage tank 8 through the first cooling water discharge valve 29 and the second cooling water discharge valve 30 for temporary storage, and then flow back to the cooling tower water storage tank 7 for circulation. The nitrogen source switch valve 46 is not closed, and a small amount of mixed gas mainly containing nitrogen (the volume fraction of nitrogen is more than 95%) is introduced for purging and cooling, and the gas is discharged after passing through the adsorption tank gas outlet 19.

[0071] When the A tank is in the cooling stage, the temperature in the A tank is reduced to 30-40°C, the cooling tower switch valve 41 and the nitrogen source switch valve 46 are closed, the control unit 14 switches back to the adsorption mode, the VOCs inlet valve 13 and the adsorption tank gas outlet 19 are opened, and the next round of adsorption is prepared.

[0072] 7) The recovered VOCs solvent is collected through the solvent recovery tank discharge valve 43 at regular intervals, and resource utilization is realized.

[0073] In this embodiment, most of the VOCs to be recovered have a very small water content, good desorption efficiency, high solvent recovery rate, small temperature difference of the packed resin around the heating inner coil, stable tank pressure of 3.5-4.5 atm during continuous operation, and oxygen concentration control accuracy of ±0.5%, which fully meets the safety and environmental protection requirements.

[0074] In summary, the system and method provided by the present application can avoid direct contact between water vapor and adsorption resin during desorption, ensure that the water content of the recovered solvent is ≤0.5%, make the VOCs and other gas mixtures outside the explosion limit by accurately controlling the ratio of compressed air and nitrogen, realize safe desorption, control the pressure in the adsorption tank to be 3.5-4.5 atm to avoid overpressure risk, use the inner coil for rapid cooling to shorten the equipment cycle time, and use two adsorption tanks in parallel configuration with “VOCs concentration > 50 mg / m 3 ” as the switching threshold, realize alternating adsorption / desorption by the PLC control system, solve the “adsorption interruption” problem during single-tank operation, and realize 24-hour continuous treatment.

[0075] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. An adsorption tank, characterized in that, It includes an upper adsorption bed (20) and a lower adsorption bed (21); the upper adsorption bed (20) is divided into two sections by a baffle, and each section of the upper adsorption bed is provided with an upper inner coil (23), which is a serpentine coil; The lower adsorption bed (21) is divided into two sections by a baffle. Each section of the lower adsorption bed (21) is provided with a lower inner coil (24). The lower inner coil (24) includes a central straight tube and an inner spiral coil and an outer spiral coil wrapped around the central straight tube. The inner spiral coil and the outer spiral coil rotate in opposite directions. A distributor (25) is provided at the bottom of each upper adsorption bed (20) and each lower adsorption bed (21); The adsorption tank is provided with a gas inlet at the bottom and a gas outlet (19) and a steam / cooling water inlet (18) at the top. Both the upper inner coil (23) and the lower inner coil (24) are connected to the steam / cooling water inlet (18) through the inner coil inlet (26).

2. The adsorption tank according to claim 1, characterized in that, The diameter of the serpentine coil is DN25~40, the length is 2.0~3.0m, and the bending radius of the U-bend is 40~60mm; the number of serpentine coils in each upper adsorption bed (20) is 10~14, and the distance between two adjacent serpentine coils is 70~90mm; the serpentine coil is inclined at 5~10° along the axial direction of the adsorption tank, and the lower end is connected to the cooling water outlet; In the lower inner coil (24): the diameter of the central straight pipe is DN40~DN80, the central straight pipe is inclined at 5~10° along the axial direction of the adsorption tank, and the lower end is connected to the cooling water outlet; the diameter of the inner spiral coil is DN25~DN50, the spiral diameter is 50%~70% of the diameter of the adsorption tank, and the pitch is 1~2 times the pipe diameter; the diameter of the outer spiral coil is DN20~DN40, the spiral diameter is 70%~90% of the diameter of the adsorption tank, and the pitch is 1.5~3.0 times the pipe diameter; the inner spiral coil rotates clockwise, and the outer spiral coil rotates counterclockwise; Both the upper inner coil (23) and the lower inner coil (24) are made of stainless steel.

3. The adsorption tank according to claim 1, characterized in that, The gas outlet (19) of the adsorption tank is equipped with a gas outlet switching valve (35); the distributor (25) is a hump-type distributor.

4. A VOCs anhydrous desorption and recovery system, characterized in that, include: A first adsorption tank (1) and a second adsorption tank (2) connected in parallel; the first adsorption tank (1) and the second adsorption tank (2) are both adsorption tanks as described in any one of claims 1 to 3; A gas path proportional control module; the gas path proportional control module includes a compressed air source (9), a nitrogen source (10), a static mixer (49), and a dryer (12); the outlets of the compressed air source (9) and the nitrogen source (10) are both connected to the static mixer (49); the outlet of the static mixer (49) is connected to the inlet of the dryer (12); the outlet of the dryer (12) is connected to the gas inlets of the first adsorption tank (1) and the second adsorption tank (2), respectively; Desorption and recovery module; the desorption and recovery module includes a condenser (3) and a solvent recovery tank (4); the inlet of the condenser (3) is connected to the gas outlet (19) of the first adsorption tank (1) and the second adsorption tank (2); the inlet of the solvent recovery tank (4) is connected to the outlet of the condenser (3); A hot steam-condensate supply module; the hot steam-condensate supply module includes a steam generator (5), a cooling tower (6) and a cooling tower water storage tank (7); the steam generator (5) and the cooling tower (6) are both connected to the steam / cooling water inlets (18) of the first adsorption tank (1) and the second adsorption tank (2) through a three-way valve (36); the cooling tower water storage tank (7) is connected to the cooling tower (6); Safety control module; the safety control module includes a pressure sensor (33), an oxygen concentration sensor (50), a first VOCs concentration sensor (34), a steam temperature sensor (39), a pressure relief valve (32), a steam electric regulating valve (38), a proportional solenoid valve (11), an audible and visual alarm device, and a control unit (14).

5. The VOCs anhydrous desorption and recovery system according to claim 4, characterized in that, The pressure sensor (33) is used to monitor the pressure inside the adsorption tank; the oxygen concentration sensor (50) is located between the static mixer (49) and the dryer (12); the first VOCs concentration sensor (34) is used to monitor the VOCs concentration inside the adsorption tank; the steam electric regulating valve (38) and the steam temperature sensor (39) are both located at the outlet end of the steam generator (5); the pressure relief valve (32) is used to relieve pressure on the adsorption tank; the proportional solenoid valve (11) is located at the front end of the static mixer (49).

6. The VOCs anhydrous desorption and recovery system according to claim 5, characterized in that, The VOCs anhydrous desorption and recovery system also includes a cooling water storage tank (8); the cooling water storage tank (8) is connected to the cooling water outlet of the first adsorption tank (1) and the second adsorption tank (2); The VOCs anhydrous desorption and recovery system also includes a VOCs inlet pipeline, which is connected to the inlets of the first adsorption tank (1) and the second adsorption tank (2) respectively; a VOCs inlet switch valve (13) is provided on the VOCs inlet pipeline. The outlet end of the steam generator (5) is also equipped with a pressure stabilizing and pressure reducing valve (37). The cooling tower (6) is also connected to the condenser (3), and a cooling tower fan (40) and a cooling tower switch valve (41) are installed on the pipeline connecting the cooling tower (6) and the condenser (3). The gas outlets (19) of the first adsorption tank (1) and the second adsorption tank (2) are connected to the condenser (3) through a one-way valve (42); The outlet end of the compressed air source (9) is provided with a compressed air switch valve (45) and a compressed air flow meter (47); the outlet end of the nitrogen source (10) is provided with a nitrogen source switch valve (46) and a nitrogen flow meter (48). The gas outlet switching valve (35) of the first adsorption tank (1) and the second adsorption tank (2) are respectively connected to two gas paths, one path is connected to the condenser (3) and the other path is connected to the purified gas exhaust port (44), and a second VOCs concentration sensor (51) is installed on the pipe connected to the purified gas exhaust port (44).

7. A method for desorbing and recovering VOCs using the anhydrous VOCs desorption and recovery system according to any one of claims 4 to 6, characterized in that, Includes the following steps: Step 1: Introduce VOCs into the first adsorption tank (1) or the second adsorption tank (2) until the resin in the first adsorption tank (1) or the second adsorption tank (2) adsorbs VOCs to saturation; the first adsorption tank (1) and the second adsorption tank (2) are connected in parallel. After the adsorption resin in one of the adsorption tanks reaches VOCs adsorption saturation, control the adsorption tank to stop adsorption and enter the desorption mode, and at the same time control the other adsorption tank in the standby state to switch to the adsorption state; Step 2: Hot steam is introduced into the upper inner coil (23) and lower inner coil (24) of the adsorption tank saturated with VOCs to indirectly heat the resin and desorb the VOCs; at the same time, a mixture of nitrogen and compressed air is introduced into the adsorption tank to purge the desorbed VOCs to the condenser (3) and condense and recover the solvent. Step 3: After VOCs desorption is completed, stop the hot steam supply and introduce cooling water into the upper inner coil (23) and lower inner coil (24). At the same time, introduce a mixture of nitrogen and compressed air into the adsorption tank to purge and cool it down.

8. The method according to claim 7, characterized in that, The pressure of the hot steam is 0.1MPa~0.27MPa and the temperature is 100~130℃. The pressure of the hot steam is controlled by a pressure reducing and stabilizing valve (37), and the temperature is controlled by a steam temperature sensor (39) and a steam electric regulating valve (38).

9. The method according to claim 7, characterized in that, In step 2: the pressure inside the adsorption tank is 3.5~4.5 atm, and the pressure inside the adsorption tank is controlled by the linkage of the pressure sensor (33) and the pressure relief valve (32); in step 2, the oxygen concentration inside the adsorption tank is controlled by the linkage of the oxygen concentration sensor (50) and the proportional solenoid valve (11) to maintain it within a safe range; the safe range of oxygen concentration in step 2 is ≤8 vol%. The temperature of the cooling water in step 3 is ≤25℃, and the cooling time is 30~60 minutes.

10. The method according to claim 7 or 8, characterized in that, In the safety control module, the control unit and each execution component form an interlocking logic: When the pressure sensor (33) detects a value > 4.5 atm, the control unit triggers the pressure relief valve to open; When the oxygen concentration sensor (50) detects a value greater than the safe oxygen concentration, the control unit forces the proportional solenoid valve (11) to reduce the proportion of compressed air to ≤ safe oxygen concentration / 21%; When the first VOCs concentration sensor (34) detects that the VOCs concentration in the tank exceeds 25 vol% of its lower explosive limit, the nitrogen ratio is automatically increased to ≥80 vol%. When the steam temperature sensor (39) detects a value > 120°C, the control unit reduces the opening of the steam electric regulating valve (38); when the detected value > 130°C, the steam electric regulating valve (38) is closed and an alarm is triggered. When the aforementioned safety signal is triggered, the control unit simultaneously activates the audible and visual alarm device.

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