A styrene VOCs-containing waste gas treatment device and method

Abstract

The application relates to the technical field of waste gas treatment, and discloses a styrene-containing VOCs waste gas treatment device and method, which comprises a pretreater, a zeolite rotary adsorption and concentration device, a desorption gas closed-loop circulation recovery unit and an emergency catalytic oxidation furnace are arranged on the right side of the pretreater; by constructing a full-inert-gas closed-loop desorption system, oxygen is completely eliminated from the source, the chemical path of styrene oxidative radical polymerization is blocked, the desorption temperature is accurately controlled at 150 DEG C, trace gas-phase polymerization inhibitors are injected into the desorption gas atmosphere, and the double polymerization inhibition measures of capturing accidental radicals are combined, so that styrene hardly has any polymerization reaction in the whole desorption recovery process, the industry problems of system resistance rise, operation instability and even shutdown cleaning caused by polymer blockage of the zeolite rotary wheel, the condenser and the pipeline system are fundamentally solved, and long-period continuous and stable operation of the device is ensured.

Description

Technical Field

[0001] This invention relates to the field of waste gas treatment technology, specifically to a device and method for treating styrene-containing VOCs waste gas. Background Technology

[0002] Styrene is an important monomer in synthetic resins, ion exchange resins, and synthetic rubber. Large quantities of volatile organic compounds containing styrene are emitted during the production processes of chemical and composite material industries. Styrene is chemically extremely reactive; its molecules contain active vinyl groups, making it highly susceptible to free radical polymerization under heat or oxygen exposure, producing viscous polymers.

[0003] In traditional activated carbon adsorption-water vapor desorption processes, high-temperature water vapor not only causes styrene to polymerize violently within the activated carbon channels, leading to rapid deactivation and frequent replacement of the activated carbon, but also results in styrene and water emulsifying in the desorption condensate, generating large amounts of difficult-to-treat styrene-containing wastewater and causing serious secondary pollution. While the zeolite rotor adsorption-concentration combined with regenerative combustion processes can extend the adsorbent lifespan to some extent, styrene can still undergo localized thermal polymerization under the high-temperature and oxygen-deficient conditions in the desorption zone. The generated polymers gradually clog the zeolite channels and gas flow channels, causing a continuous increase in system resistance, a surge in operating energy consumption, and even forcing shutdown for cleaning. Summary of the Invention

[0004] This invention provides a device and method for treating styrene-containing VOCs waste gas, which solves the problems mentioned in the background art.

[0005] The present invention provides the following technical solution: a styrene-containing VOCs waste gas treatment device, including a pre-processor, wherein a zeolite rotary adsorption concentration device, a desorption gas closed-loop circulation recovery unit and an emergency catalytic oxidation furnace are provided on the right side of the pre-processor; The outer wall of the zeolite rotor adsorption concentration device is equipped with a main fan and an exhaust pipe. The interior of the zeolite rotor adsorption concentration device is divided into an adsorption zone, a cooling zone and a desorption zone. The outlet of the pre-processor is connected to the inlet of the adsorption zone, the outlet of the adsorption zone is connected to the inlet of the main fan, and the outlet of the main fan is connected to the exhaust pipe. The desorbed gas closed-loop recycling unit includes a heater, a primary condenser, a secondary condenser, a gas-liquid separator, and a circulating fan. The outlet of the heater is connected to the inlet of the desorption zone. The outlet of the desorption zone is connected sequentially to the primary condenser and the secondary condenser. The outlet of the secondary condenser is connected to the inlet of the gas-liquid separator. The gas phase outlet of the gas-liquid separator is connected to the inlet of the cooling zone via a switching valve group. The outlet of the cooling zone is connected to the inlet of the circulating fan. The outlet of the circulating fan is divided into two paths: one path is connected to the heater inlet via the main circuit to form a closed loop, and the other path is connected to the inlet of the emergency catalytic oxidation furnace via a bypass regulating valve. The liquid phase outlets of the primary and secondary condensers are both connected to the gas-liquid separator. The oil phase outlet of the gas-liquid separator is connected to the styrene recovery tank via an oil phase pump, and the water phase outlet is connected to the wastewater treatment equipment via a water pump. The desorbed gas closed-loop recycling unit is connected to a nitrogen source and is filled with nitrogen. It is also equipped with an online oxygen content detector and a nitrogen supply valve.

[0006] As a preferred embodiment of the present invention, the preprocessor comprises a water washing tower, a demister, and a dry filter connected in sequence by pipelines.

[0007] As a preferred embodiment of the present invention, the desorbed gas closed-loop circulation recovery unit further includes a temperature sensor and a polymerization inhibitor injection device. The temperature sensor is installed on the pipeline between the outlet of the desorption zone and the first-stage condenser, and the temperature sensor is linked to the heater. The temperature sensor is electrically connected to the heater for feedback control of the heating power. The polymerization inhibitor injection device is connected to the inlet pipeline of the desorption zone.

[0008] As a preferred embodiment of the present invention, the emergency catalytic oxidation furnace includes a gas heat exchanger, a burner, a catalytic bed, and an independent exhaust stack. The outlet of the bypass regulating valve is connected to the cold side inlet of the gas heat exchanger, the cold side outlet of the gas heat exchanger is connected to the inlet of the burner, the outlet of the burner is connected to the inlet of the catalytic bed, the outlet of the catalytic bed is connected to the hot side inlet of the gas heat exchanger, and the hot side outlet of the gas heat exchanger is connected to the independent exhaust stack.

[0009] As a preferred embodiment of the present invention, the sampling point of the online oxygen content detector is located on the outlet pipe of the circulating fan; the nitrogen supply valve is located on the inlet pipe of the circulating fan.

[0010] As a preferred embodiment of the present invention, the oil phase outlet of the gas-liquid separator is located above the oil-water interface, and the water phase outlet is located at the lowest point of the bottom.

[0011] As a preferred embodiment of the present invention, the zeolite rotor adsorption concentration device rotates continuously at a speed of 6 revolutions per hour, and the processes in the adsorption zone, cooling zone and desorption zone are carried out simultaneously.

[0012] A method for treating styrene VOCs waste gas includes the following steps: S1. The collected styrene-containing waste gas is introduced into the pre-processor and sequentially passes through a water washing tower for washing, a demister for demisting, and a dry filter for filtration to remove particulate matter and high-boiling-point substances. After cooling and dehumidification, it is introduced into the adsorption zone of the zeolite rotary adsorption concentration device. Styrene is selectively adsorbed by the zeolite molecular sieve, and the purified gas is pressurized by the main fan and discharged through the exhaust pipe in compliance with standards. S2. Before starting the desorption gas closed-loop circulation recovery unit, nitrogen is introduced through the nitrogen supply valve to replace the oxygen content inside the system to a level lower than the preset safety value; the circulating fan and heater are started to heat the inert gas in the closed loop to 150°C. The heated inert gas enters the desorption zone to desorb styrene and a small amount of water vapor adsorbed on the zeolite; the temperature sensor monitors the outlet gas temperature of the desorption zone in real time and controls the temperature in conjunction with the heater; the polymerization inhibitor injection device injects a small amount of gas-phase polymerization inhibitor into the desorption atmosphere to inhibit styrene polymerization. The gas-phase polymerization inhibitor is either hydroquinone or 2,6-di-tert-butyl-p-cresol, and the injection amount is 10-100 ppm of the circulating gas flow rate. S3. The high-temperature mixed gas containing styrene vapor flowing out of the desorption zone sequentially enters the primary condenser and the secondary condenser; the primary condenser cools the mixed gas to 35°C, and the secondary condenser further cools the mixed gas to 5°C, condensing styrene vapor and water vapor into liquid state, and the gas-liquid mixture enters the gas-liquid separator; in the gas-liquid separator, the condensate automatically separates into layers based on density difference, the upper styrene oil phase is collected by the oil phase pump and transported to the styrene recovery tank for recovery, and the lower water phase is discharged by the water pump to the wastewater treatment equipment for treatment; S4. The low-temperature non-condensable gas separated by the gas-liquid separator has a temperature of 5°C. It enters the cooling zone through the switching valve group to pre-cool the high-temperature zeolite module that has just been transferred from the desorption zone. The gas that has absorbed heat flows out from the outlet of the cooling zone and enters the circulating fan for pressurization. Most of the pressurized gas returns to the heater along the main circuit for reheating, completing the closed-loop circulation. S5. During operation, when the internal pressure of the desorbed gas closed-loop circulation recovery unit increases or the oxygen content online detector detects that the oxygen content has reached the set upper limit, the bypass regulating valve is opened to introduce part of the circulating gas into the emergency catalytic oxidation furnace. The circulating gas flows sequentially through the cold side of the gas heat exchanger for preheating, the burner for heating to 300°C, and the catalytic bed for catalytic oxidation. The residual styrene is completely oxidized and decomposed into carbon dioxide and water. The high-temperature gas after oxidation flows through the hot side of the gas heat exchanger to recover heat and is safely discharged through an independent exhaust stack.

[0013] As a preferred embodiment of the present invention, in step S2, the desorption temperature is maintained at 150°C through the linkage control of the temperature sensor and the heater.

[0014] As a preferred technical solution of the present invention, when a trace amount of polymer accumulates in the desorption zone of the zeolite rotor adsorption concentration device, the waste gas feed is temporarily cut off, the inert gas in the desorption gas closed-loop circulation recovery unit is heated to 220°C and kept warm and circulated, or a mixed gas containing solvent vapor and polymerization inhibitor is introduced for in-situ cleaning and regeneration to restore the adsorption activity of the zeolite rotor.

[0015] The present invention has the following beneficial effects: 1. This styrene-containing VOCs waste gas treatment device and method completely eliminates oxygen at the source by constructing a fully inert gas closed-loop desorption system, blocking the chemical pathway of styrene undergoing oxidative free radical polymerization. Combined with precise control of the desorption temperature at 150℃ and the injection of a small amount of gas-phase polymerization inhibitor into the desorption atmosphere to capture accidental free radicals, the styrene hardly undergoes any polymerization reaction during the entire desorption and recovery process. This fundamentally solves the industry problem of increased system resistance, operational instability, and even shutdown for cleaning caused by polymer blockage in zeolite rotors, condensers, and pipeline systems, ensuring long-term continuous and stable operation of the device.

[0016] 2. The styrene-containing VOCs waste gas treatment device and method achieves the step-by-step liquefaction of styrene vapor through staged cooling with a primary condenser and a secondary condenser. The condensate automatically separates into an upper styrene oil phase and a lower water phase in the gas-liquid separator due to density difference. The styrene oil phase can be directly collected and recycled as a production raw material, while the water phase is discharged separately for treatment. This anhydrous separation and recovery method not only obtains styrene monomer with high purity and realizes the effective recycling of resources, but also completely avoids the styrene-containing wastewater generated by condensate emulsification in the traditional water vapor desorption process, eliminating secondary pollution at the source.

[0017] 3. The styrene-containing VOCs waste gas treatment device and method, through the desorption closed-loop circulation loop, the low-temperature non-condensable nitrogen gas after gas-liquid separation is first introduced into the rotor cooling zone to pre-cool the high-temperature zeolite module, and after recovering the system's cold energy, it is returned to the heater for reheating by the circulating fan. This forms a highly efficient closed-loop circulation of heating, desorption, condensation, cooling and reheating, which greatly reduces heating energy consumption and nitrogen consumption. At the same time, the emergency catalytic oxidation furnace, as a bypass end-of-line protection device, intervenes when the system pressure or oxygen content is abnormal and exhaust is required, and thoroughly catalytically oxidizes the exhaust gas to meet emission standards, ensuring the economic efficiency and environmental reliability of the device under all operating conditions. Attached Figure Description

[0018] Figure 1This is a schematic diagram of the process flow of the present invention;

[0019] Figure 2 This is a schematic diagram of the device connection structure of the present invention; Figure 3 This is a schematic diagram of the preprocessor structure of the present invention; Figure 4 This is a schematic diagram of the zeolite rotor adsorption concentration device of the present invention; Figure 5 This is a schematic diagram of the desorbed gas closed-loop recycling unit structure of the present invention; Figure 6 This is a schematic diagram of the emergency catalytic oxidation furnace structure of the present invention; Figure 7 This is a schematic diagram of the device composition of the present invention.

[0020] In the diagram: 1. Preprocessor; 2. Zeolite rotor adsorption concentration unit; 3. Desorption gas closed-loop circulation recovery unit; 4. Emergency catalytic oxidation furnace; 11. Water washing tower; 12. Demister; 13. Dry filter; 21. Adsorption zone; 22. Cooling zone; 23. Desorption zone; 24. Main fan; 25. Exhaust pipe; 31. Online oxygen content detector; 32. Nitrogen supply valve; 33. Circulating fan; 34. Bypass regulating valve; 35. Polymer inhibitor injection device; 36. Temperature sensor; 37. Heater; 38. Primary condenser; 39. Secondary condenser; 310. Gas-liquid separator; 311. Switching valve assembly; 312. Oil phase pump; 313. Styrene recovery tank; 314. Water pump; 315. Wastewater treatment equipment; 41. Gas heat exchanger; 42. Burner; 43. Catalytic bed; 44. Independent exhaust stack. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Please see Figures 1-7 A styrene-containing VOCs waste gas treatment device includes a pre-processor 1, and a zeolite rotary adsorption concentration device 2, a desorption gas closed-loop circulation recovery unit 3 and an emergency catalytic oxidation furnace 4 are provided on the right side of the pre-processor 1. The outer wall of the zeolite rotor adsorption concentration device 2 is equipped with a main fan 24 and an exhaust pipe 25. The interior of the zeolite rotor adsorption concentration device 2 is divided into an adsorption zone 21, a cooling zone 22 and a desorption zone 23. The outlet of the pre-processor 1 is connected to the inlet of the adsorption zone 21, the outlet of the adsorption zone 21 is connected to the inlet of the main fan 24, and the outlet of the main fan 24 is connected to the exhaust pipe 25. The desorbed gas closed-loop circulation recovery unit 3 includes a heater 37, a primary condenser 38, a secondary condenser 39, a gas-liquid separator 310, and a circulating fan 33. The outlet of the heater 37 is connected to the inlet of the desorption zone 23. The outlet of the desorption zone 23 is connected sequentially to the primary condenser 38 and the secondary condenser 39. The outlet of the secondary condenser 39 is connected to the inlet of the gas-liquid separator 310. The gas phase outlet of the gas-liquid separator 310 is connected to the inlet of the cooling zone 22 via a switching valve assembly 311. The outlet of the cooling zone 22 is connected to the inlet of the circulating fan 33. The outlet of the circulating fan 33 is divided into two paths. One path connects to the inlet of heater 37 via the main circuit to form a closed loop, while the other path connects to the inlet of emergency catalytic oxidation furnace 4 via bypass regulating valve 34. The liquid phase outlets of primary condenser 38 and secondary condenser 39 are both connected to gas-liquid separator 310. The oil phase outlet of gas-liquid separator 310 is connected to styrene recovery tank 313 via oil phase pump 312, and the water phase outlet is connected to sewage treatment equipment 315 via water pump 314. The desorbed gas closed loop recovery unit 3 is connected to a nitrogen source and is filled with nitrogen. It is also equipped with an online oxygen content detector 31 and a nitrogen supply valve 32.

[0023] In the above structure, through the cooperation of the primary condenser 38, the secondary condenser 39 and the gas-liquid separator 310, most of the styrene is first recovered using the mild cooling capacity of circulating water at 35°C, and then the remaining portion is recovered using the deep cooling capacity of chilled water at 5°C. Utilizing the physical properties that styrene and water are immiscible and have different densities, the direct separation and recovery of the oil phase and the water phase are achieved, completely eliminating the traditional desorption method that produces emulsified wastewater. The cooperation of the gas-liquid separator 310, the cooling zone 22 and the circulating fan 33 allows the clean nitrogen gas at 5°C exiting from the top of the gas-liquid separator to be introduced into the cooling zone 22 before returning to the circulating fan. This pre-cools the zeolite module that has just been transferred from the high-temperature desorption zone, recovering the system's cooling capacity and cooling the zeolite module so that it can be better put into the next round of adsorption. In addition, with the switching valve group 311, the depth of cooling capacity recovery can be flexibly controlled. The desorption closed-loop system is linked to the emergency catalytic oxidation furnace 4 through the bypass regulating valve 34. This combination acts as a safety pressure relief valve and a cleaner for the system. In the stable closed-loop circulation, the emergency system is on standby. When the closed-loop system needs to exhaust gas due to abnormal pressure or oxygen content, the bypass regulating valve 34 will open, allowing a small amount of exhaust gas to enter the catalytic oxidation furnace 4 for purification. This ensures that at any time and under any operating condition, the gas discharged into the atmosphere is treated to meet the standards, guaranteeing environmental compliance throughout the entire process.

[0024] In a preferred embodiment, the preprocessor 1 comprises a water washing tower 11, a demister 12, and a dry filter 13 connected in sequence by pipelines.

[0025] In the above structure, the preprocessor 1 prevents the microporous structure of the zeolite rotor from being blocked by the water washing tower 11, the demister 12 and the dry filter 13. The water washing tower 11 is responsible for washing away paint mist and sticky particles. The demister 12 and the dry filter 13 further intercept moisture and fine dust, ultimately allowing only clean styrene-containing gas to enter the rotor.

[0026] In a preferred embodiment, the desorbed gas closed-loop recycling unit 3 further includes a temperature sensor 36 and a polymerization inhibitor injection device 35. The temperature sensor 36 is located on the pipeline between the outlet of the desorption zone 23 and the primary condenser 38, and the temperature sensor 36 is linked to the heater 37. The polymerization inhibitor injection device 35 is connected to the inlet pipeline of the desorption zone 23.

[0027] In the above structure, the heater 37, temperature sensor 36 and desorption zone 23 work together to precisely control the desorption temperature between 100-200℃. The heater 37 provides a gentle thermal driving force, while the temperature sensor 36 corrects deviations in real time to ensure that the process does not get out of control.

[0028] In a preferred embodiment: the emergency catalytic oxidation furnace 4 includes a gas heat exchanger 41, a burner 42, a catalytic bed 43, and an independent exhaust stack 44. The outlet of the bypass regulating valve 34 is connected to the cold side inlet of the gas heat exchanger 41, the cold side outlet of the gas heat exchanger 41 is connected to the inlet of the burner 42, the outlet of the burner 42 is connected to the inlet of the catalytic bed 43, the outlet of the catalytic bed 43 is connected to the hot side inlet of the gas heat exchanger 41, and the hot side outlet of the gas heat exchanger 41 is connected to the independent exhaust stack 44.

[0029] In the above structure, the gas heat exchanger 41 allows the cold exhaust gas to be treated to exchange heat with the hot purified gas from the catalytic bed, using waste heat to preheat the gas to be treated. Its function is to recover heat, significantly reducing the energy consumption of the burner 42, so that the system can maintain low power or fuel consumption even during intermittent operation. The burner 42 precisely heats the preheated exhaust gas to the reaction temperature required for catalytic oxidation, providing energy for subsequent chemical reactions. The catalytic bed 43 is filled with precious metal or metal oxide catalysts. Under the action of the catalyst, residual organic matter such as styrene is completely oxidized and decomposed into harmless carbon dioxide and water at a temperature far lower than that of direct combustion. The hot side of the gas heat exchanger 41 and the independent exhaust pipe 44 are connected. The high-temperature clean gas flows through the hot side of the gas heat exchanger 41, transferring its own heat to the cold side intake gas for cooling, and finally is safely discharged through the independent exhaust pipe. This can recover energy and also avoid thermal damage to the exhaust pipe caused by high-temperature gas.

[0030] In a preferred embodiment: the sampling point of the online oxygen content detector 31 is located on the outlet pipe of the circulating fan 33; the nitrogen supply valve 32 is located on the inlet pipe of the circulating fan 33.

[0031] In the above structure, the online oxygen content detector 31, the nitrogen supply valve 32, the circulating fan 33, and the entire closed-loop system work together. The online oxygen content detector 31 continuously monitors and maintains the oxygen-free state in the system, completely eliminating the possibility of styrene oxidation and polymerization from the source, and further improving the long-term stability of the device without clogging.

[0032] In a preferred embodiment, the oil phase outlet of the gas-liquid separator 310 is located above the oil-water interface, and the water phase outlet is located at the lowest point of the bottom.

[0033] In the above structure, the mixed condensate in the gas-liquid separator 310 is a two-phase system of styrene oil and water. These two phases are immiscible and have a density difference. Positioning the oil phase outlet above the oil-water interface ensures that only the lighter, floating styrene oil phase flows out of this outlet, without entraining the lower water phase. Positioning the water phase outlet at the lowest point ensures that the denser wastewater at the bottom is completely discharged, preventing the formation of dead zones within the tank. This allows the condensate to naturally separate into layers by gravity within the gas-liquid separator, achieving efficient, continuous or intermittent separation of styrene and water without any external power or complex control. The recovered styrene is of high purity and can be directly reused as a production raw material. The separated water is discharged separately to subsequent wastewater treatment equipment, completely avoiding the problem of difficult-to-treat styrene-containing wastewater caused by condensate emulsification in traditional steam desorption processes.

[0034] In a preferred embodiment, the zeolite rotor adsorption concentration device 2 rotates continuously at a speed of 6 revolutions per hour, and the processes of the adsorption zone 21, the cooling zone 22 and the desorption zone 23 are carried out simultaneously.

[0035] In the above structure, while one module is capturing styrene in the waste gas in the adsorption zone 21, another module is simultaneously transferred to the desorption zone 23 to undergo desorption and regeneration with high-temperature inert gas. At the same time, a high-temperature module that has just completed desorption enters the cooling zone 22 for pre-cooling. These three functional zones are spatially independent but seamlessly connected in time, avoiding processing gaps caused by waiting in one zone and preventing a decrease in adsorption efficiency due to the high-temperature module directly transferring to the adsorption zone. This synchronous coordination enables the device to have a constant capacity for treating large volumes of waste gas. Adsorption, desorption, and recovery all proceed smoothly at the same time, fundamentally ensuring the continuity of system operation and the stability of process parameters.

[0036] A method for treating styrene VOCs waste gas includes the following steps: S1. The collected styrene-containing waste gas is introduced into the pre-processor 1, and then sequentially passes through the water washing tower 11 for washing, the demister 12 for demisting, and the dry filter 13 for filtration to remove particulate matter and high-boiling-point substances. After cooling and dehumidification, it is passed into the adsorption zone 21 of the zeolite rotary adsorption concentration device 2. Styrene is selectively adsorbed by the zeolite molecular sieve, and the purified gas is pressurized by the main fan 24 and discharged through the exhaust pipe 25 in compliance with standards. S2. Before starting the desorption gas closed-loop circulation recovery unit 3, nitrogen is introduced through the nitrogen supply valve 32 to replace the oxygen content inside the system to a level lower than the preset safety value; the circulating fan 33 and heater 37 are started to heat the inert gas in the closed loop to 150°C. The heated inert gas enters the desorption zone 23 to desorb styrene and a small amount of water vapor adsorbed on the zeolite; the temperature sensor 36 monitors the outlet gas temperature of the desorption zone in real time and controls the temperature in conjunction with the heater 37; the polymerization inhibitor injection device 35 injects a small amount of hydroquinone into the desorption atmosphere to inhibit styrene polymerization, with the injection amount being 50 ppm of the circulating gas flow rate; S3. The high-temperature mixed gas containing styrene vapor flowing out of the desorption zone 23 sequentially enters the primary condenser 38 and the secondary condenser 39. The primary condenser 38 cools the mixed gas to 35°C, and the secondary condenser 39 further cools the mixed gas to 5°C. Styrene vapor and water vapor are condensed into liquid. The gas-liquid mixture enters the gas-liquid separator 310. In the gas-liquid separator 310, the condensate automatically separates into layers based on the density difference. The upper styrene oil phase is collected by the oil phase pump 312 and transported to the styrene recovery tank 313 for recovery. The lower water phase is discharged by the water pump 314 to the sewage treatment equipment 315 for treatment. S4. The low-temperature non-condensable gas separated by the gas-liquid separator 310 has a temperature of 5°C. It enters the cooling zone 22 through the switching valve group 311 to pre-cool the high-temperature zeolite module that has just been transferred from the desorption zone 23. The gas that has absorbed heat flows out from the outlet of the cooling zone 22 and enters the circulating fan 33 to be pressurized. Most of the pressurized gas returns to the heater 37 along the main circuit for reheating, completing the closed-loop circulation. S5. During operation, when the internal pressure of the desorbed gas closed-loop circulation recovery unit 3 increases or the oxygen content online detector 31 detects that the oxygen content has reached the set upper limit, the bypass regulating valve 34 is opened to introduce part of the circulating gas into the emergency catalytic oxidation furnace 4. The circulating gas flows sequentially through the cold side of the gas heat exchanger 41 for preheating, the burner 42 for heating to 300°C, and the catalytic bed 43 for catalytic oxidation. The residual styrene is completely oxidized and decomposed into carbon dioxide and water. After the oxidized high-temperature gas flows through the hot side of the gas heat exchanger 41 to recover heat, it is safely discharged through the independent exhaust pipe 44.

[0037] In a preferred embodiment: in S2, the desorption temperature is maintained at 150°C through the linkage control of temperature sensor 36 and heater 37.

[0038] In a preferred embodiment: when trace amounts of polymer accumulate in the desorption zone 23 of the zeolite rotor adsorption concentration device 2, the waste gas feed is temporarily cut off, and the inert gas in the desorption gas closed-loop circulation recovery unit 3 is heated to 220°C and kept at that temperature for circulation, or a mixed gas containing solvent vapor and polymerization inhibitor is introduced for in-situ cleaning and regeneration to restore the adsorption activity of the zeolite rotor. The solvent vapor can be toluene or xylene vapor, with a concentration of 0.5-2% (volume fraction) of the desorption gas flow rate, the cleaning temperature is controlled at 180-220°C, and the cleaning time is 2-4 hours.

[0039] Working principle: Styrene-containing waste gas first passes through the pre-processor 1, where it is purified by a water washing tower 11, a demister 12, and a dry filter 13 to remove particulate matter and high-boiling-point substances. Then, it enters the adsorption zone 21 of the zeolite rotor adsorption concentration device 2. The hydrophobic zeolite molecular sieve selectively captures styrene in the waste gas. The clean gas is discharged through the exhaust pipe 25 via the main fan 24 and rotates continuously at a constant speed. The saturated zeolite module is transferred to the desorption zone 23 filled with nitrogen. In the desorption gas closed-loop circulation recovery unit 3, the inert gas atmosphere completely eliminates oxygen from the source, blocking the chemical path of styrene oxidative free radical polymerization. The heater 37 precisely heats the nitrogen in the closed loop to a temperature of 150°C, which can achieve efficient desorption without triggering violent thermal polymerization. The temperature is controlled by the linkage between the temperature sensor 36 and the heater 37. At the same time, the polymerization inhibitor injection device 35 injects a small amount of gas-phase polymerization inhibitor into the desorption atmosphere to capture the free radicals that are generated by chance, forming a double insurance of temperature control and chemical inhibition of polymerization. In an anaerobic, mild desorption environment, the adsorbed styrene is efficiently and centrally desorbed, achieving a qualitative change from high volume, low concentration to low volume, high concentration. The desorbed styrene vapor then enters the primary condenser 38 and the secondary condenser 39 for staged condensation. Styrene and water vapor are liquefied step by step and then flow into the gas-liquid separator 310. Based on the density difference, they automatically separate into an upper styrene oil phase and a lower water phase. The oil phase is collected by the oil phase pump 312 and sent to the styrene recovery tank 313 for direct reuse, while the water phase is discharged to the wastewater treatment equipment 315 by the water pump 314. The entire process does not produce emulsified wastewater. The low-temperature non-condensable nitrogen gas after gas-liquid separation is introduced into the cooling zone 22 to pre-cool the zeolite module that has just been transferred from the high-temperature desorption zone to recover the system's cooling capacity. The gas that has absorbed heat is pressurized by the circulating fan 33, and most of it returns to the heater 37 along the main loop for reheating, forming a closed-loop cycle of heating, desorption, condensation, cooling, and reheating, which significantly reduces energy consumption and nitrogen consumption. When the desorption closed-loop system experiences pressure or oxygen content exceeding limits due to trace gas infiltration, the bypass regulating valve 34 automatically opens, introducing a small portion of the circulating gas into the emergency catalytic oxidation furnace 4. After preheating by the gas heat exchanger 41, heating by the burner 42, and complete oxidation by the catalytic bed 43, the gas is safely discharged through the independent exhaust stack 44.

[0040] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0041] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended technical solutions and their equivalents.

Claims

1. A styrene-containing VOCs waste gas treatment device, comprising a pre-processor, characterized in that: The right side of the preprocessor is equipped with a zeolite rotor adsorption concentration device, a desorption gas closed-loop circulation recovery unit, and an emergency catalytic oxidation furnace. The outer wall of the zeolite rotor adsorption concentration device is equipped with a main fan and an exhaust pipe. The interior of the zeolite rotor adsorption concentration device is divided into an adsorption zone, a cooling zone and a desorption zone. The outlet of the pre-processor is connected to the inlet of the adsorption zone, the outlet of the adsorption zone is connected to the inlet of the main fan, and the outlet of the main fan is connected to the exhaust pipe. The desorbed gas closed-loop recycling unit includes a heater, a primary condenser, a secondary condenser, a gas-liquid separator, and a circulating fan; The outlet of the heater is connected to the inlet of the desorption zone, the outlet of the desorption zone is connected in sequence to the primary condenser and the secondary condenser, and the outlet of the secondary condenser is connected to the feed inlet of the gas-liquid separator. The gas phase outlet of the gas-liquid separator is connected to the inlet of the cooling zone via a switching valve group. The outlet of the cooling zone is connected to the inlet of the circulating fan. The outlet of the circulating fan is divided into two paths: one path is connected to the inlet of the heater via the main circuit to form a closed loop, and the other path is connected to the inlet of the emergency catalytic oxidation furnace via a bypass regulating valve. The liquid phase outlets of the primary condenser and the secondary condenser are both connected to the gas-liquid separator. The oil phase outlet of the gas-liquid separator is connected to the styrene recovery tank via an oil phase pump, and the water phase outlet is connected to the wastewater treatment equipment via a water pump. The desorbed gas closed-loop circulation recovery unit is connected to a nitrogen source and is filled with nitrogen. It is also equipped with an online oxygen content detector and a nitrogen supply valve.

2. The styrene-containing VOCs waste gas treatment device according to claim 1, characterized in that: The preprocessor consists of a water washing tower, a demister, and a dry filter connected in sequence by pipelines.

3. The styrene-containing VOCs waste gas treatment device according to claim 1, characterized in that: The desorbed gas closed-loop recycling unit also includes a temperature sensor and a polymerization inhibitor injection device. The temperature sensor is installed on the pipeline between the outlet of the desorption zone and the first-stage condenser, and the temperature sensor is linked to the heater. The polymerization inhibitor injection device is connected to the inlet pipeline of the desorption zone.

4. The styrene-containing VOCs waste gas treatment device according to claim 1, characterized in that: The emergency catalytic oxidation furnace includes a gas heat exchanger, a burner, a catalytic bed, and an independent exhaust stack. The outlet of the bypass regulating valve is connected to the cold side inlet of the gas heat exchanger, the cold side outlet of the gas heat exchanger is connected to the inlet of the burner, the outlet of the burner is connected to the inlet of the catalytic bed, the outlet of the catalytic bed is connected to the hot side inlet of the gas heat exchanger, and the hot side outlet of the gas heat exchanger is connected to the independent exhaust stack.

5. The styrene-containing VOCs waste gas treatment device according to claim 1, characterized in that: The sampling point of the online oxygen content detector is located on the outlet pipe of the circulating fan; the nitrogen supply valve is located on the inlet pipe of the circulating fan.

6. The styrene-containing VOCs waste gas treatment device according to claim 1, characterized in that: The oil phase outlet of the gas-liquid separator is located above the oil-water interface, and the water phase outlet is located at the lowest point of the bottom.

7. The styrene-containing VOCs waste gas treatment device according to claim 1, characterized in that: The zeolite rotor adsorption concentration device rotates continuously at a speed of 6 revolutions per hour, and the adsorption zone, cooling zone and desorption zone processes are carried out simultaneously.

8. A method for treating styrene-containing VOCs waste gas, comprising using the styrene-containing VOCs waste gas treatment device according to any one of claims 1-7, characterized in that, Includes the following steps: S1. The collected styrene-containing waste gas is introduced into the pre-processor and sequentially passes through a water washing tower for washing, a demister for demisting, and a dry filter for filtration to remove particulate matter and high-boiling-point substances. After cooling and dehumidification, it is introduced into the adsorption zone of the zeolite rotary adsorption concentration device. Styrene is selectively adsorbed by the zeolite molecular sieve, and the purified gas is pressurized by the main fan and discharged through the exhaust pipe in compliance with standards. S2. Before starting the desorption gas closed-loop circulation recovery unit, nitrogen is introduced through the nitrogen supply valve to replace the oxygen content inside the system to a level lower than the preset safety value; the circulating fan and heater are started to heat the inert gas in the closed loop to 150°C. The heated inert gas enters the desorption zone to desorb styrene and a small amount of water vapor adsorbed on the zeolite; the temperature sensor monitors the outlet gas temperature of the desorption zone in real time and controls the temperature in conjunction with the heater; a small amount of gas-phase polymerization inhibitor is injected into the desorption atmosphere through the polymerization inhibitor injection device to inhibit styrene polymerization. The gas-phase polymerization inhibitor is either hydroquinone or 2,6-di-tert-butyl-p-cresol, and the injection amount is 10-100 ppm of the circulating gas flow rate. S3. The high-temperature mixed gas containing styrene vapor flowing out of the desorption zone sequentially enters the primary condenser and the secondary condenser; the primary condenser cools the mixed gas to 35°C, and the secondary condenser further cools the mixed gas to 5°C, condensing styrene vapor and water vapor into liquid state, and the gas-liquid mixture enters the gas-liquid separator; in the gas-liquid separator, the condensate automatically separates into layers based on density difference, the upper styrene oil phase is collected by the oil phase pump and transported to the styrene recovery tank for recovery, and the lower water phase is discharged by the water pump to the wastewater treatment equipment for treatment; S4. The low-temperature non-condensable gas separated by the gas-liquid separator has a temperature of 5°C. It enters the cooling zone through the switching valve group to pre-cool the high-temperature zeolite module that has just been transferred from the desorption zone. The gas that has absorbed heat flows out from the outlet of the cooling zone and enters the circulating fan for pressurization. Most of the pressurized gas returns to the heater along the main circuit for reheating, completing the closed-loop circulation. S5. During operation, when the internal pressure of the desorbed gas closed-loop circulation recovery unit increases or the oxygen content online detector detects that the oxygen content has reached the set upper limit, the bypass regulating valve is opened to introduce part of the circulating gas into the emergency catalytic oxidation furnace. The circulating gas flows sequentially through the cold side of the gas heat exchanger for preheating, the burner for heating to 300°C, and the catalytic bed for catalytic oxidation. The residual styrene is completely oxidized and decomposed into carbon dioxide and water. The high-temperature gas after oxidation flows through the hot side of the gas heat exchanger to recover heat and is safely discharged through an independent exhaust stack.

9. The method for treating styrene-containing VOCs waste gas according to claim 8, characterized in that: In step S2, the desorption temperature is maintained at 150°C through the linkage control of the temperature sensor and the heater.

10. A method for treating styrene-containing VOCs waste gas according to claim 8, characterized in that: When trace amounts of polymer accumulate in the desorption zone of the zeolite rotor adsorption concentration device, the waste gas feed is temporarily cut off, the inert gas in the desorption gas closed-loop circulation recovery unit is heated to 220°C and kept at that temperature for circulation, or a mixed gas containing solvent vapor and polymerization inhibitor is introduced for in-situ cleaning and regeneration to restore the adsorption activity of the zeolite rotor.

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