Styrene resource recovery method from waste gas of artificial stone production line based on adsorption-absorption synergy

Abstract

The present invention belongs to the field of environmental protection VOC tail gas treatment, specifically discloses a method for recycling styrene from waste gas of artificial stone production line based on adsorption-absorption synergy, including artificial stone production line tail gas entering the absorption tower from the tail gas inlet at the bottom of the absorption tower under the suction action of a fan, and sequentially contacting with the absorbent sprayed from top to bottom in countercurrent, most of the styrene is absorbed; the semi-purified tail gas discharged from the top of the absorption tower enters the adsorption tower, and the residual styrene component is further adsorbed, and the purified tail gas from the adsorption tower group is directly discharged through the chimney, and the rich liquid having absorbed the styrene component enters the flash kettle for distillation and recovery of styrene, and the rich liquid is divided into two streams, the first stream is heated to 60-65 ° C and then sent to the flash kettle for parsing and recovery of the styrene component; the second stream is sent to the rich liquid reflux washing tower to capture the fine droplets in the flash steam from the flash kettle. The present invention has low investment and operating costs, good tail gas purification effect, effective coupling of absorption and adsorption, high styrene recovery rate, and is environmentally friendly.

Description

Technical Field

[0001] The present invention belongs to the field of environmental protection and relates to a resource recovery and utilization of polluting components in VOC tail gas. Specifically, it is a resource recovery method for styrene in waste gas of artificial stone production line based on adsorption-absorption synergy. Background Art

[0002] Styrene, a key raw material in the chemical industry, is a crucial monomer in the production of synthetic resins, ion exchange resins, and synthetic rubber, and is widely used. In the production of artificial stone, resin is a key raw material. During the stirring, mixing, molding, and curing processes, large amounts of styrene waste gas are generated, causing serious pollution to the surrounding environment and posing a serious threat to human health.

[0003] In order to control styrene tail gas pollution, the terminal control technologies currently used are all traditional VOCs waste gas treatment technologies, which are divided into destruction technology and recovery technology.

[0004] Destruction technology usually adopts chemical or biochemical methods, including thermal destruction, plasma, photodegradation and biological methods. Recovery technology usually adopts physical methods, including membrane separation, condensation, adsorption and absorption [Ling Fan et al. Experimental comparison of membrane separation, chemical absorption and combined methods for separation of CO2 / CH4. Journal of Power Engineering, 2015, 35(03): 245-250; Liu Yingshu et al. Study on the influence of process parameters on SO2 recovery from flue gas adsorption desulfurization desorption gas by condensation method. Journal of Chemical Industry and Engineering, 2020, 71(12): 5620-5627; Guo Yuchen et al. Research progress in VOCs waste gas treatment technology. Chemical Industry Management, 2019, (07): 114-116].

[0005] In addition, due to the influence of the types and properties of VOCs, it is often difficult to achieve standard VOC emissions using a single technology. Therefore, physical and chemical or physical and chemical combined with biological methods are often used to treat VOCs, which is more economical and efficient than a single technology.

[0006] Almost all organic pollutants can be converted into CO2 and H2O when burned at a certain temperature. The thermal destruction method is a method that utilizes the flammable characteristics of VOCs and fully burns them into harmless substances under the action of fuel or auxiliary materials. It mainly includes direct combustion method, heat storage combustion method and catalytic combustion method [Zhang Ruibo, Yang Yumin. Experimental study on the treatment of VOCs in petrochemical enterprises by combustion method. Energy and Environmental Protection, 2020, 34(02): 53-56]. Direct combustion is to directly burn VOCs as fuel. It is suitable for high-concentration VOCs. For industries with low VOCs concentration and large flux, auxiliary fuel needs to be added, and the operating cost is high [Khan FI, Ghosha lA K. Removal of volatile organic compounds from polluted air[J]. Journal of loss prevention in the process industries, 2000, 13(6): 527-545]. Catalytic combustion involves lowering the activation temperature under the action of a catalyst, catalytically oxidizing VOCs to CO2 and H2O at low temperatures. This method offers high purification efficiency, but it can be susceptible to catalyst poisoning and is suitable for low concentrations and low air volumes. Regenerative combustion, which uses heat exchange technology and thermal storage materials to convert VOCs into CO2 and H2O, is suitable for high air volumes and high-concentration organic waste gases.

[0007] Since the concentration of pollutants in styrene exhaust gas is greatly affected by the production environment and climate, the concentration of styrene in exhaust gas in different seasons is highly correlated, resulting in poor adaptability of traditional VOC exhaust gas treatment process equipment, difficulty in production control, and poor production operation stability, which in turn significantly increases equipment investment and operating costs. Summary of the Invention

[0008] The purpose of the present invention is to solve the above technical problems and provide a process for recovering the styrene component from artificial stone tail gas based on absorption-coupled adsorption, which has a simple system, low investment and operating costs, good tail gas purification effect, effective coupling of absorption and adsorption, energy saving and consumption reduction, and high styrene recovery rate.

[0009] The present invention is based on a method for resource recovery of styrene in waste gas from an artificial stone production line based on adsorption-absorption synergy. The method comprises the following steps: tail gas from the artificial stone production line enters an absorption-adsorption unit under the suction action of a fan, enters an absorption tower from a tail gas inlet at the bottom of the absorption tower, and sequentially contacts with an absorbent sprayed from top to bottom in countercurrent, so that most of the styrene is absorbed; semi-purified tail gas discharged from the top of the absorption tower enters an adsorption tower, and the residual styrene component is further adsorbed; the purified tail gas from the adsorption tower group is directly discharged through a chimney; rich liquid having absorbed the styrene component enters a flash unit for distillation and recovery of styrene; the flash unit comprises a flash kettle and a rich liquid reflux washing tower; the rich liquid is divided into two streams, the first stream is heated to 60-65°C and then sent to the flash kettle for decomposition and recovery of the styrene component; the second stream is sent to the rich liquid reflux washing tower for washing and heat exchange with flash steam and stripping gas from the flash kettle, and fine droplets are captured; the rich liquid from the rich liquid reflux washing tower is sent to the flash kettle for decomposition and recovery of the styrene component.

[0010] The absorbent is divided into at least three spray layers and enters the corresponding at least three packing layers in the absorption tower from the middle of the absorption tower from top to bottom. The absorbent in each spray layer is circulated and sprayed independently, and fresh lean liquid and replenished fresh absorbent are replenished into the absorption tower from the upper layer; the spray liquid of the upper layer flows into the next layer in full flow.

[0011] The absorption-adsorption unit includes an absorption tower and an adsorption tower group. The adsorption tower group includes at least two adsorption towers connected in parallel. The parallel adsorption towers alternately perform adsorption, desorption and cooling processes.

[0012] The adsorption, desorption and cooling processes alternately performed by the parallel adsorption towers are as follows:

[0013] The semi-purified tail gas from the absorption tower is continuously fed into the adsorption tower in the adsorption stage for adsorption and then discharged as purified tail gas; when the adsorption tower in any adsorption stage is saturated with adsorption, it switches to the desorption and cooling stage, and the semi-purified tail gas from the absorption tower is simultaneously switched to the adsorption tower in the adsorption stage;

[0014] Spraying hot lean liquid from the upper part of the adsorption tower in the desorption and cooling stage to wash the packing layer, completing the desorption process of the adsorption tower in the desorption and cooling stage;

[0015] After the desorption is completed, the adsorption tower in the desorption and cooling stage enters the cooling stage. The purified tail gas discharged from other adsorption towers in the adsorption stage is introduced from the exhaust port at the top of the adsorption tower in the cooling stage into the adsorption tower in the cooling stage. The cooling gas is discharged from the bottom of the tower. After cooling is completed, it enters the adsorption stage. Multiple adsorption towers alternately perform the adsorption, desorption and cooling processes.

[0016] The absorbent used to wash the packing layer in the adsorption tower during the desorption phase is derived from the hot lean liquid after flash evaporation. During a desorption cycle, the temperature of the rich liquid exiting the adsorption tower after spray washing is monitored in real time. Based on the temperature fluctuations of the rich liquid, the desorption process is divided into three phases: Phase 1, when the rich liquid temperature rises to 11-15°C below the incoming hot lean liquid; Phase 2, when the rich liquid temperature rises to 5-10°C below the incoming hot lean liquid; and Phase 3, when the rich liquid temperature rises to less than 5°C below the incoming hot lean liquid. Once the spray washing enters Phase 3, the spray washing time is controlled and continued until the rich liquid temperature falls within 2°C below the incoming hot lean liquid, completing the desorption process.

[0017] The cooling air temperature out of the tower is detected in real time. When the temperature is 10-15℃ different from the cooling air temperature inlet, the cooling process of the adsorption tower is completed.

[0018] In the first time period, the washing and desorption rich liquid after washing the packing layer is returned to the flash kettle together with the rich liquid at the bottom of the absorption tower for flash evaporation and analysis to recover the styrene component; in the second time period, the absorbent after washing the packing layer is introduced into the bottom spray layer of the absorption tower to participate in the absorption of the styrene component in the original tail gas; in the third time period, the absorbent after washing the packing layer is introduced into the middle spray layer of the absorption tower to participate in the absorption of the styrene component in the original tail gas.

[0019] In the first stage of the desorption stage, the washing and desorption rich liquid after washing the packing layer is all sent to the flash kettle for flash evaporation and decomposition to recover the styrene component; in the second stage of the desorption stage, the washing and desorption rich liquid after washing the packing layer is all sent to the lower section of the absorption tower for spray washing of the artificial stone tail gas; in the third stage of the desorption stage, the washing and desorption rich liquid after washing the packing layer is all sent to the middle section of the absorption tower for spray washing of the artificial stone tail gas.

[0020] The lean liquid from the flash kettle is divided into two streams by the liquid holding column. The first stream returns to the absorption tower for circulation spraying to absorb styrene in the tail gas of the artificial stone production line, and the second stream is sent to the adsorption tower group to spray, wash and desorb the saturated adsorption tower packing layer.

[0021] The first rich liquid drawn from the bottom of the absorption tower exchanges heat with the first lean liquid from the liquid holding column, and then is mixed with the washing and desorption rich liquid from the first period of the adsorption tower group after washing the packing layer, heated to 60-65°C and then sent to the flash kettle.

[0022] The flash kettle is provided with at least two stages of flash chambers from top to bottom, and a liquid storage tank is provided at the bottom.

[0023] The upper section of the flash kettle is a primary flash chamber, and the lower section is a secondary flash chamber. The bottom liquid storage tank is divided into a lean liquid tank and a semi-lean liquid tank by at least one overflow plate. The upper part of the primary flash chamber is provided with a primary flash atomizer and a reflux rich liquid atomizer, and the bottom is provided with a primary flash guide plate. The upper part of the secondary flash chamber is provided with a secondary flash atomizer, and a portion of the lower part of the secondary flash chamber is located above the semi-lean liquid tank and is provided with a secondary flash guide plate, and the remaining area is connected to the lean liquid tank; the front end of the secondary flash guide plate is inserted into the lean liquid tank; the secondary flash guide plate and the overflow plate separate the semi-lean liquid tank from the secondary flash chamber; the gas phase space above the semi-lean liquid tank is connected to the primary flash chamber via a gas stripping gas guide pipe, the semi-lean liquid tank is connected to the secondary flash atomizer via a semi-lean liquid heater, and the primary flash chamber is connected to the semi-lean liquid tank via the primary flash guide pipe.

[0024] The rich liquid at the bottom of the absorption tower is sent to the first-level flash atomizer of the first-level flash chamber together with the absorbent after washing the packing layer, and is sprayed out for flash evaporation; the semi-lean liquid after the first-level flash evaporation falls into the semi-lean liquid tank, is then extracted and heated to 65-70°C, and is sent to the second-level flash atomizer of the second-level flash chamber for spraying for secondary flash evaporation, and the obtained lean liquid falls into the lean liquid tank and is then led out of the flash chamber; the flash steam of the second-level flash chamber and the flash steam of the first-level flash chamber are sent out of the flash kettle under the action of negative pressure and then sent to the flash steam condenser to recover the styrene product.

[0025] The rich liquid from the rich liquid reflux washing tower is divided into two streams. The first stream is sent to the reflux rich liquid atomizer of the flash kettle and sprayed out for flash evaporation. The second stream is mixed with the first rich liquid at the bottom of the absorption tower and the washing and desorption rich liquid after washing the packing layer in the first time period, and then heated to 60-65°C and sent to the first flash atomizer of the first flash chamber for spraying for flash evaporation.

[0026] Inert gas components with a boiling point lower than styrene and insoluble in the absorbent are introduced into the lean liquid tank and semi-lean liquid tank in the flash kettle to further strip the residual styrene components in the lean liquid and semi-lean liquid. These inert gas components are water vapor, or a mixture of water vapor and nitrogen or carbon dioxide.

[0027] The stripping gas escaping from the semi-lean liquid tank is introduced into the primary flash chamber through the stripping gas guide pipe and the demister; the stripping gas escaping from the lean liquid tank directly enters the secondary flash chamber, and the gas phase in the primary flash chamber and the secondary flash chamber is drawn out of the flash kettle under the suction action of the vacuum pump.

[0028] The gas phase out of the flash kettle is washed in a rich liquid reflux washing tower and then sent to a flash steam condenser to separate the condensate and non-condensable gases. The condensate is separated into styrene components and condensed water by a pre-pump oil-water separator. The separated condensed water is heated and vaporized and then introduced as water vapor into the lean liquid tank and semi-lean liquid tank in the flash kettle to strip the styrene components in the lean liquid and semi-lean liquid, thereby realizing the condensed water circulation.

[0029] The non-condensable gas separated by the flash steam condenser is extracted by a vacuum pump and divided into two streams. The first stream is sent to the absorption tower together with the tail gas of the artificial stone production line, and the second stream is sent to the lean liquid tank and semi-lean liquid tank in the flash kettle for gas stripping together with the water vapor.

[0030] The negative pressure in the flash evaporator, flash steam condenser, and pre-pump oil-water separator is controlled to be below 4 kPa absolute pressure. To address the problems in the background art, the inventors have implemented an absorption-adsorption unit, coupling absorption and adsorption, and combined it with a flash evaporation unit to achieve tail gas purification and emission standards for artificial stone production lines and recovery of styrene components in the tail gas. The specific improvements are as follows:

[0031] (1) The flash unit is equipped with a rich liquid reflux washing tower to achieve rich liquid reflux. The flash unit includes a flash kettle and a rich liquid reflux washing tower. The rich liquid reflux washing tower is arranged downstream of the flash kettle gas phase outlet. Under the suction action of the vacuum pump, the flash steam after atomization and flash evaporation of the flash kettle enters the rich liquid reflux washing tower through the flash kettle gas phase outlet. It contacts with the rich liquid from the absorption tower sprayed from the top of the tower through the packing layer in countercurrent, exchanges heat and captures fine droplets.

[0032] By spraying cold rich liquid into the rich liquid reflux scrubber, the rich liquid comes into direct contact with the flash steam, trapping the fine droplets in the flash steam and reducing absorbent loss. This direct contact also cools the flash steam, recovering the coldness of the rich liquid and reducing the cooling required for flash steam condensation.

[0033] On the other hand, within the operating temperature range (30-60°C), the saturated vapor pressure of water is significantly affected by temperature (4.245 kPa at 30°C, 7.381 kPa at 40°C, and 19.932 kPa at 60°C). The incoming rich liquid comes into direct contact with the flash steam, which cools the flash steam and condenses a large amount of water vapor into the rich liquid. The rich liquid then passes through the first-stage flash atomizer and enters the flash kettle for first-stage flash evaporation. Almost all of the water in the rich liquid vaporizes and enters the flash steam. After passing through the rich liquid reflux scrubber, most of it is condensed again. This cycle of water vapor increases the water vapor concentration in the first-stage flash steam, and the reflux rich liquid condenses and absorbs more and more water until an equilibrium state is reached where the reflux rich liquid absorbs water. When the rich liquid, in a moisture equilibrium state, returns to the flash kettle for atomization and flash evaporation, it intensifies the water vapor stripping effect, significantly improving the distillation effect.

[0034] (2) One absorption tower is set up to correspond to at least two parallel adsorption towers, and the parallel adsorption towers alternately perform adsorption, desorption, and cooling processes. Specifically, the semi-purified exhaust gas from the absorption tower is sent to the adsorption tower in the adsorption stage for adsorption and then discharged as purified exhaust gas; when the adsorption tower is saturated, it enters the desorption and cooling stage, and at the same time, the semi-purified exhaust gas is switched to the adsorption tower after desorption and cooling. In this alternating manner, continuous and efficient purification of the exhaust gas from the artificial stone production line is achieved.

[0035] (3) Desorption of hot lean liquid. Hot lean liquid is used to wash and desorb the adsorption tower to be desorbed and cooled. The hot lean liquid is sprayed from the top of the tower to wash and desorb the adsorption filler layer. After desorption is completed, purified exhaust gas is used to enter the purified exhaust gas outlet at the top of the tower to cool the filler layer. The cooling gas is discharged from the semi-purified exhaust gas inlet at the bottom of the adsorption tower and introduced into the absorption tower for further absorption. During the cooling process of the purified exhaust gas, it also has a deep desorption effect on the filler layer. After the purified exhaust gas is cooled, the adsorption tower enters the waiting desorption stage. This alternation can achieve efficient recovery of styrene components in the exhaust gas of the artificial stone production line.

[0036] The absorbent lean liquid for washing and desorbing the packing layer of the adsorption tower stage used for desorption and cooling and the gas used for cooling come from the system itself. Except for replenishing the adsorbent, no new adsorbent needs to be introduced from outside, thus realizing the recycling of the adsorbent.

[0037] (4) A multi-layer structure is set up in the flash evaporator to perform multi-stage flash evaporation, and the equipment structure is compact and safe. A multi-stage flash evaporation chamber is set up in the flash evaporator, and a gas stripping section is set up at the bottom of the evaporator. The multi-stage flash evaporation and gas stripping are organically combined to improve the rich liquid distillation effect, save space, improve the vacuum pump's vacuum effect, and save the operating cost of the gas pump.

[0038] The flash desorption unit's flash evaporation kettle has at least two flash chambers, each connected to a lean liquid tank and a semi-lean liquid tank. The rich liquid is first introduced into the upper, primary flash chamber, where it is flash-evaporated by the primary flash atomizer. The flashed semi-lean liquid then flows through the primary flash guide pipe into the semi-lean liquid tank. The semi-lean liquid is then drawn out, heated by the semi-lean heater, and sent to the lower, secondary flash chamber, where it is sprayed out by the secondary flash atomizer for secondary flash evaporation. The lean liquid then flows through the secondary flash guide plate into the lean liquid tank. The front end of the secondary flash guide plate is inserted below the liquid level in the lean liquid tank, forming a liquid seal that separates the secondary flash chamber from the gas stripping area above the semi-lean liquid tank. This two-stage flash evaporation within a single flash evaporation kettle enhances the desorption process. Furthermore, the primary and secondary flash chambers are isolated from each other, ensuring a consistent flash evaporation effect.

[0039] An aeration head is set in the lean liquid tank and the semi-lean liquid tank. The condensate from which the non-condensable gas and styrene components are separated after flash evaporation is heated and vaporized by a heater, and then introduced into the aeration head in the form of water vapor. The lean liquid tank and the semi-lean liquid tank can be gas-lifted, thus truly realizing the reuse of the condensate. At the same time, the non-condensable gas separated by the flash steam condenser is also divided into two streams, which are respectively returned to the absorption tower and the aeration head, thus also realizing the reuse of the non-condensable gas, saving energy and reducing consumption, and being environmentally friendly.

[0040] (5) The hot lean liquid after flash evaporation is used to desorb the washing packing layer in the adsorption tower that is saturated with adsorption. The washing and desorption rich liquid is introduced into different operating units according to different stages in the washing and desorption cycle. The first-stage washing and desorption rich liquid is returned to the flash evaporator together with the rich liquid at the bottom of the absorption tower for flash evaporation and desorption to recover the styrene component (the styrene concentration of the first-stage washing and desorption rich liquid is higher); the second-stage washing and desorption rich liquid is introduced into the bottom spray layer of the absorption tower to participate in the absorption of the styrene component in the original tail gas (the styrene concentration of the second-stage washing and desorption rich liquid is lower than that of the initial washing and desorption rich liquid); the third-stage washing and desorption rich liquid is introduced into the middle spray layer of the absorption tower to participate in the absorption of the styrene component in the original tail gas (the styrene concentration of the third-stage washing and desorption rich liquid is the lowest), thereby realizing the cascade utilization of the rich liquid and reducing the cost of flash evaporation and desorption.

[0041] (6) Setting up a liquid holding column to eliminate "cavitation". Taking into account the problem of "cavitation" when the lean liquid is drawn out from the bottom of the flash kettle, a liquid holding column is set up to increase the pressure before the pump to extract the lean liquid. Since the working pressure of the flash kettle is maintained below 4kPa (absolute pressure), which is much lower than the atmospheric pressure, when the lean liquid is directly drawn out from the bottom of the flash kettle through the pump into the absorption-adsorption unit at normal pressure, the pressure difference before and after the pump is large, and the residual styrene components and dissolved water in the lean liquid will produce "cavitation", which not only affects the stability of the pump operation, but also causes the pump blades to be impacted and corroded. Setting up a liquid holding column to draw the lean liquid from the bottom of the liquid holding column into the absorption tower increases the liquid phase pressure at the pump inlet and effectively overcomes the "cavitation" phenomenon.

[0042] (7) Control the negative pressure of the flash chamber, flash steam condenser and oil-water separator before the pump to be below 4kPa absolute pressure. The reason for choosing a flash pressure below 4kPa is due to the following factors: First, it reduces the polymerization of the recovered styrene component. When the styrene temperature reaches 60℃, the polymerization rate accelerates. When it is below 4kPa, the boiling point of styrene is below 55℃, and the polymerization of styrene at this temperature can be ignored; second, under an absolute pressure of 4kPa, the rich liquid temperature only needs to be controlled at around 60℃ to achieve a high decomposition effect, and the temperature resistance requirements for the equipment and its sealing materials are not high, reducing equipment investment; third, the operating pressure of 4kPa can save investment and operating costs. When the operating pressure is too low, the load of the vacuum pump used increases, and at the same time, the equipment strength and sealing requirements of the vacuum system are higher. When the operating pressure is higher than 4kPa, it is not conducive to the decomposition of styrene.

[0043] (8) Control the amount of condensed water discharged from the oil-water separator before the pump to the condensate tank, increase the oil-water interface level in the oil-water separator before the pump, and discharge excess condensate. Since part of the water vapor brought in by the tail gas during the absorption process is absorbed by the absorbent, during the flash evaporation analysis, the boiling point of water is lower than the boiling point of styrene, and the water vaporizes first and enters the flash steam together with the water vapor introduced. After condensation, it enters the condensate, breaking the water balance of the system, and the excess water needs to be discharged. Keeping the amount of condensed water discharged from the oil-water separator before the pump to the condensate tank constant and raising the oil-water interface to a higher position is conducive to discharging the water absorbed by the absorbent from the tail gas together with the oil phase, thereby reducing the styrene concentration in the water phase; it is conducive to improving the styrene recovery rate. Because the higher the level of the oil-water interface, the more thorough the oil phase separation at the water phase outlet level, thereby reducing the styrene concentration in the water vapor circulating into the flash evaporator.

[0044] (9) Maintaining the balance of water vapor and water in the flash evaporator is beneficial to improving the styrene recovery rate. The amount of aerated water vapor entering the flash evaporator is controlled to be 0.5-0.7% (mass ratio) of the amount of rich liquid entering the evaporator. The excess water brought in by the rich liquid is discharged together with the condensate oil phase through the increase of the oil-water interface in the oil-water separator before the pump to maintain the balance of water vapor and water in the flash evaporator, which is beneficial to improving the styrene recovery rate. Experiments show that when the rich liquid contains a certain amount of water, the styrene desorption rate increases significantly. Since the water vapor partial pressure in the flash steam is much higher than the styrene partial pressure, and the saturated vapor pressure of water is greatly affected by temperature within the operating temperature range (7.381 kPa at 40°C and 19.932 kPa at 60°C), the rotary evaporation experiment shows that the maximum desorption rate is achieved when all the water in the rich liquid is evaporated (that is, when the water phase disappears). This technical solution aerates the lean liquid and semi-lean liquid with water vapor for a long time (about 75kg / h, 3000m3), with a high gas-liquid ratio of about 200-300:1, which is beneficial to further reduce the residual styrene concentration in the lean liquid.

[0045] Beneficial effects:

[0046] The process system is simple and easy to operate, with low investment and operation costs, good tail gas purification effect, effective coupling of absorption and adsorption, energy saving and consumption reduction, high styrene recovery rate, and environmental friendliness. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a process flow chart of the present invention.

[0048] Figure 2 This is a fitting curve diagram of the Henry constant determined experimentally in the present invention.

[0049] 1a: fan; 2: absorption tower; 3a: adsorption tower A; 3b: adsorption tower B; 3c: adsorption tower C; 4a: tertiary spray pump; 4b: secondary spray pump; 4c: primary spray pump; 4d: absorption tower rich liquid pump; 4e: adsorption tower rich liquid pump; 4f: absorption tower lean liquid pump; 4g: adsorption tower lean liquid pump; 4h: lean liquid circulation pump; 4j: lean liquid discharge pump; 4r: primary flash pump; 4s: secondary flash pump; 4t: rich liquid reflux pump; 4u: condensate pump; 5a-1: first desorption rich liquid intermediate tank; 5a-2: first desorption rich liquid intermediate tank; 5a-3 : First desorption rich liquid intermediate tank; 5b: First flash rich liquid tank; 6: Absorption liquid intermediate tank; 7a: Lean liquid cooler for inlet tower; 7b: Lean-rich liquid heat exchanger; 8: Lean liquid tank for inlet tower; 9: Flash steam condenser; 10a: Rich liquid heater; 10b: Semi-lean liquid heater; 10c: Condensate vaporization heater; 11: Vacuum pump; 12a: First flash demister; 12b: Second flash demister; 12c: Stripping demister; 13: Flash kettle; 13-1: Reflux rich liquid atomizer; 13-2: First flash atomizer; 13-3: Second flash atomizer; 13-4: First-stage flash distillation guide plate; 13-5: First-stage flash distillation guide pipe; 13-6: Second-stage flash distillation guide plate; 13-7: Gas stripping gas guide pipe; 13-8: Second-stage flash distillation gas guide pipe; 13-9: Overflow plate; 13-10: Lean liquid tank; 13-11: Semi-lean liquid tank; 13-12: Semi-lean liquid aeration head; 13-13: Lean liquid aeration head; 14: Rich liquid reflux scrubber; 15: Liquid holding column; 15-1: Lean liquid overflow pipe; 16: Vacuum discharge valve; 17: Pre-pump oil-water separator; 18a: Tower A inlet valve; 18b: Tower B inlet valve; 18c : Liquid inlet valve of Tower C; 18e: Air inlet valve of Tower A; 18f: Air inlet valve of Tower B; 18g: Air inlet valve of Tower C; 18h: Smoke exhaust valve of Tower A; 18p: Smoke exhaust valve of Tower B; 18q: Smoke exhaust valve of Tower C; 18r: Liquid drain valve of Tower A; 18s: Liquid drain valve of Tower B; 18t: Liquid drain valve of Tower C; 18u: Cooling gas outlet valve of Tower A; 18v: Cooling gas outlet valve of Tower B; 18w: Cooling gas outlet valve of Tower C; 18x: Cooling gas inlet valve of Tower A; 18y: Cooling gas inlet valve of Tower B; 18z: Cooling gas inlet valve of Tower C; 19: Intermediate oil tank; 20: Condensate tank. DETAILED DESCRIPTION

[0050] The system of the present invention is explained below in conjunction with the accompanying drawings:

[0051] See also Figure 1 The system of the present invention includes an absorption-adsorption unit and a flash evaporation unit. The absorption-adsorption unit includes an absorption tower 2 and an adsorption tower group 3. The tail gas outlet at the top of the absorption tower 2 is connected to the tail gas inlet of the adsorption tower group 3. In this embodiment, the adsorption tower group 3 is composed of three parallel adsorption towers: adsorption tower A 3a, adsorption tower B 3b, and adsorption tower C 3c. The three parallel adsorption towers take turns to perform adsorption, desorption and cooling processes.

[0052] The purified tail gas outlet at the top of the adsorption tower group 3 is connected to the chimney for external discharge, and the rich liquid outlet at the bottom of the tower passes through three parallel attached rich liquid intermediate tanks (the first desorption rich liquid intermediate tank 5a-1, the second desorption rich liquid intermediate tank 5a-3 and the first desorption rich liquid intermediate tank 5a-3), and then is divided into three routes through the adsorption tower rich liquid pump 4e. The first route is connected to the flash kettle 13 through the first-stage flash pump 4r, the lean-rich liquid heat exchanger 7b, and the rich liquid heater 10a; the second route is connected to the middle spray layer of the absorption tower 2; and the third route is connected to the bottom spray layer of the absorption tower 2.

[0053] The lean liquid outlet at the bottom of the flash kettle 13 is connected to the absorbent inlet of the adsorption tower group 3 through the liquid holding column 15 and the adsorption tower lean liquid pump 4g. At the same time, the bottom outlet of the liquid holding column 15 is also connected to the absorbent inlet of the absorption tower 2 through the lean liquid circulation pump 4h, the lean-rich liquid heat exchanger 7b, the tower lean liquid cooler 7a, the tower lean liquid tank 8, the absorption tower lean liquid pump 4f, and the first-stage spray pump 4c.

[0054] An overflow port, a lean liquid inlet, and a lean liquid outlet are respectively provided at the upper, middle, and lower parts of the liquid holding column 15. The overflow port is connected to the lean liquid tank 13 via a lean liquid overflow pipe 15-1. The lean liquid inlet is connected to the lean liquid outlet at the bottom of the flash kettle 13. The lean liquid outlet of the liquid holding column 15 is connected to the absorption tower 2.

[0055] The flash unit includes a flash kettle 13 and a rich liquid reflux washing tower 14. The flash kettle 13 has at least two flash chambers. Specifically, the upper section of the flash kettle is a primary flash chamber, the lower section is a secondary flash chamber, and the bottom is divided by an overflow plate 13-9 (or overflow pipe) into a lean liquid tank 13-10 and a semi-lean liquid tank 13-11. The upper part of the primary flash chamber is provided with a primary flash atomizer 13-2 and a primary flash guide plate 13-4 at the bottom; the upper part of the secondary flash chamber is provided with a secondary flash atomizer 13-3 and the lower part is provided with a secondary flash guide plate 13-5, the front end of the secondary flash guide plate 13-5 is inserted into the lean liquid tank 13-10; the primary flash chamber is connected to the semi-lean liquid tank 13-11 via the primary flash guide pipe 13-5. The secondary flash chamber is connected to the lean liquid tank 13-10 through the secondary flash guide plate 13-5, and the stripping area above the semi-lean liquid tank 13-11 is also connected to the primary flash chamber through the stripping gas guide pipe 13-7. A stripping demister 12-7 is provided on the pipeline. The stripping gas pipe 13-7 can be set inside the flash kettle 13 or outside the flash kettle 13, preferably outside the kettle, which can save space in the kettle, reduce the upward flow rate of the flash steam, and facilitate the sedimentation of fine droplets generated by atomization flash evaporation; the semi-lean liquid tank 13-11 is connected to the secondary flash atomizer 13-3 through the secondary flash pump 4s and the semi-lean liquid heater 10b.

[0056] The gas phase outlets of the primary and secondary flash chambers, respectively, pass through corresponding primary and secondary flash demisters 12a and 12b, and are then connected to the lower gas phase (flash steam) inlet of the rich liquid reflux scrubber 14. The top gas phase outlet of the rich liquid reflux scrubber 14 is connected to the flash steam condenser 9. The condensate outlet of the flash steam condenser 9 is connected to the pre-pump oil-water separator 17. The condensate outlet of the pre-pump oil-water separator 17 is connected to the aeration heads 13-13 and 13-12 in the lean liquid tank 13-10 and semi-lean liquid tank 13-11 in the flash kettle 13 via the condensate tank 20, condensate pump 4u, and condensate vaporization heater 10c. The oil phase outlet of the pre-pump oil-water separator 17 is connected in sequence to the vacuum discharge valve 16 and the intermediate oil tank 18. The non-condensable gas outlet of the flash steam condenser 9 is connected to the absorption tower 2 and the aeration heads 13-13 and 13-12 in the lean liquid tank 13-10 and the semi-lean liquid tank 13-11 in the flash kettle 13 respectively.

[0057] The rich liquid outlet at the bottom of the absorption tower 2 is divided into two paths through the absorption tower rich liquid pump 4d. One path is connected to the first-stage flash rich liquid tank 5b, the first-stage flash pump 4r, the lean-rich liquid heat exchanger 7b, and the rich liquid heater 10a to the first-stage flash atomizer 13-2 of the first-stage flash chamber of the flash kettle 13; the other path is connected to the reflux rich liquid atomizer 13-1 connected to the first-stage flash chamber.

[0058] The negative pressure of the flash chamber 13, the flash steam condenser 9, the pre-pump oil-water separator 17 and the condensed water vaporization heater 10c is controlled to be below 4 kPa absolute pressure.

[0059] Process:

[0060] The tail gas from the artificial stone production line enters the absorption tower 2 from the tail gas inlet at the lower part of the absorption tower 2 under the suction action of the fan 1a and contacts with the absorbent in countercurrent. The semi-purified tail gas with most of the styrene absorbed is discharged from the top of the absorption tower 2 and enters the adsorption tower group 3 to further adsorb the residual styrene components. The purified tail gas from the adsorption tower group 3 is directly discharged through the chimney.

[0061] The adsorption tower group 3 in this embodiment is composed of three parallel adsorption towers A 3a, B tower 3b, and C tower 3c, wherein the tail gas inlet, purified tail gas outlet, absorbent inlet, and absorbent outlet of each adsorption tower are connected in parallel; each auxiliary tower is provided with a cooling gas inlet and outlet, the cooling gas inlet is connected to the purified tail gas outlet at the top of the adsorption tower, and the cooling gas outlet is connected to the air inlet of the fan; specifically: the tail gas outlet of the absorption tower 2 is connected to the tail gas inlet of the adsorption tower A 3a, the adsorption tower B 3b, and the adsorption tower C 3c, respectively, and the purified tail gas outlets of the adsorption tower A 3a, the adsorption tower B 3b, and the adsorption tower C 3c are all connected to the chimney; the adsorbent inlets of the adsorption tower A 3a, the adsorption tower B 3b, and the adsorption tower C 3c are all connected to the liquid holding column 15, and the rich liquid outlets of the three towers are all three desorption rich liquid intermediate tanks (the first desorption rich liquid intermediate tank 5a-1, the second desorption rich liquid intermediate tank 5a-3, and the first desorption rich liquid intermediate tank 5a-3). The three adsorption towers alternately perform adsorption, desorption and cooling processes. Specifically, the adsorption and desorption processes of the adsorption tower group 3 are as follows:

[0062] The semi-purified tail gas from the absorption tower is fed from the tail gas inlet into the adsorption tower in the adsorption stage (such as adsorption tower A 3a, adsorption tower B 3b, adsorption tower C 3c), where the purified tail gas is discharged from the tail gas outlet after adsorption. When the adsorption tower in any adsorption stage (such as adsorption tower A 3c) is saturated, the feeding of the semi-purified tail gas of the tower is stopped and the desorption stage is switched. At this time, the semi-purified tail gas is continuously passed into any of the other two towers (adsorption tower B 3b or adsorption tower C 3c) that has completed desorption and cooling. At this time, the hot lean liquid from the liquid holding column 15 enters the desorption tower from the adsorbent inlet. The adsorption tower (adsorption tower A 3c) in the first stage washes the packing layer, and samples and analyzes the circulating washing liquid from the tower regularly. When the styrene concentration in the washing liquid is higher than the set value, the washing and desorption are stopped, and the adsorption tower (adsorption tower A 3c) enters the cooling stage. The purified tail gas from the other two towers (adsorption tower B 3b and adsorption tower C 3c) is introduced to cool the adsorption tower (adsorption tower A 3c), completing an adsorption-desorption-cooling cycle. After the cooling is completed, the tower enters the adsorption tower in the adsorption stage; in conjunction with the switching of the valves on the pipeline, multiple adsorption towers alternately perform the adsorption, desorption and cooling processes;

[0063] The washing and desorption rich liquid after washing the packing layer enters the rich liquid intermediate tank 5a-1, 5a-2, or 5a-3 according to the different stages of the washing and desorption process of the adsorption tower group 3, and is then pumped out by the adsorption tower rich liquid pump 4e. Together with the rich liquid from the bottom of the absorption tower, it is heated to 60-65°C by the rich liquid heater 10a, and then sent to the flash kettle 13 through the first-stage flash rich liquid tank 5b and the first-stage flash pump 4r, or enters the lowest spray layer of the absorption tower 2, or enters the middle spray layer of the absorption tower 2. Specifically:

[0064] The hot lean liquid from the liquid holding column 15 enters the adsorption tower (adsorption tower A 3a) in the desorption stage through the adsorbent inlet to wash the packing layer. The temperature of the absorbent (i.e., the washing and desorption rich liquid) leaving the adsorption tower after spray washing is detected in real time. According to the temperature of the washing and desorption rich liquid, the desorption process is divided into three phases. The first phase is when the temperature of the washing and desorption rich liquid rises to a range of 11-15°C lower than the temperature of the hot lean liquid entering the tower; the second phase is when the temperature of the washing and desorption rich liquid rises to a range of 5-10°C lower than the temperature of the hot lean liquid entering the tower; the third phase is when the temperature of the washing and desorption rich liquid rises to less than 5°C lower than the temperature of the hot lean liquid entering the tower. After the spray washing enters the third phase, the spray washing time is controlled and the spray washing is continued until the temperature of the washing and desorption rich liquid is within 2°C lower than the temperature of the hot lean liquid entering the tower, completing the desorption process.

[0065] According to the temperature of the washing and desorption rich liquid leaving the adsorption tower (adsorption tower A 3a), the washing and desorption rich liquid is introduced into the desorption rich liquid intermediate tank 5a. The washing and desorption rich liquid of the first period is introduced into the desorption rich liquid intermediate tank 5a-1, the washing and desorption rich liquid of the second period is introduced into the desorption rich liquid intermediate tank 5a-2, and the washing and desorption rich liquid of the third period is introduced into the desorption rich liquid intermediate tank 5a-3.

[0066] The washing and desorption rich liquids from the corresponding desorption rich liquid intermediate tanks 5a-1, 5a-2, and 5a-3 are introduced into the rich liquid heater 10a via the absorption tower rich liquid pump 4e to be heated to 60-65°C. The rich liquids are then delivered to the flash kettle 13 via the primary flash evaporation rich liquid tank 5b and the primary flash pump 4r. The bottom spray layer of absorption tower 2 absorbs the styrene component in the raw tail gas, while the middle spray layer of absorption tower 2 also absorbs the styrene component in the raw tail gas. This achieves cascade utilization of the rich liquids, reduces flash evaporation costs, and reduces energy consumption.

[0067] The rich liquid absorption tower rich liquid pump 4d at the bottom of the absorption tower 2 is divided into two streams. One stream is pressurized by the first-stage flash rich liquid tank 5b and the first-stage flash pump 4r, and then sent to the lean and rich liquid heat exchanger 7b together with the absorbent from the adsorption tower group 3 for heat exchange with the lean liquid from the bottom of the flash kettle 13. After leaving the lean and rich liquid heat exchanger 7b, it is sent to the rich liquid heater 10a together with the rich liquid from the rich liquid reflux washing tower 14 for heating, and then sent to the first-stage flash atomizer 13-2 of the flash kettle 13 for spraying; the other stream is sent to the rich liquid reflux washing tower 14 for heat exchange with the gas phase washing exiting the flash kettle 13; the rich liquid flowing out of the bottom of the rich liquid reflux washing tower 14 is divided into two streams, one stream is sent to the reflux rich liquid atomizer 13-1 of the flash kettle 13, and the other stream is sent to the rich liquid heater 10a.

[0068] In the flash kettle 13, the hot rich liquid from the rich liquid heater 10a is first sprayed into the primary flash chamber through the primary flash atomizer 13-2 for flash evaporation. The desorbed flash steam rises and exchanges heat with the cold rich liquid from the rich liquid reflux scrubber 14 sprayed from the reflux rich liquid atomizer 13-1. After that, the mist droplets are removed by the primary flash demister 12a at the top and the liquid is then drawn out. The desorbed semi-lean liquid flows through the primary flash guide plate 13-4 into the primary flash guide pipe 13-5 and then into the semi-lean liquid tank 13-11 at the bottom.

[0069] The semi-lean liquid in the semi-lean liquid tank 13-11 is then pumped out by the secondary flash pump 4s, heated to 65-70°C by the semi-lean liquid heater 10b, and then sent to the secondary flash atomizer 13-3 and sprayed into the secondary flash chamber for secondary flash evaporation. The gas phase in the secondary flash chamber is drawn out through the secondary flash air guide pipe 13-8 and removed by the secondary flash demister 12b. After that, it enters the tower from the lower part of the rich liquid reflux washing tower 14 together with the gas phase out of the primary flash chamber, and contacts the tower in the countercurrent with the cold rich liquid sprayed in from the upper part of the tower. Based on the principle of "particle diameter matching", the sprayed rich liquid can effectively wash and capture the fine droplets in the flash vapor. The flash vapor captured by the cold rich liquid washing is drawn out by the suction action of the exhaust pump 11 and sent to the flash vapor condenser 9. The lean liquid after desorption falls into the lean liquid tank 13-10 along the secondary flash guide plate 13-5 and is then drawn out of the flash kettle 13.

[0070] Due to the presence of overflow plate 13-9, the lean liquid in the lean liquid tank 13-10 can overflow unidirectionally into the semi-lean liquid tank 13-11. Water vapor is introduced into the lean liquid tank 13-10 and the semi-lean liquid tank 13-11 through corresponding aeration heads 13-13 and 13-12 to further strip the residual styrene components in the lean and semi-lean liquids. The stripping gas in the lean liquid tank 13-10 directly enters the secondary flash chamber, while the stripping gas from the semi-lean liquid tank 13-11 is collected from the stripping zone above and drawn through the stripping gas duct 13-7. It is then demisted by the stripping demister 12-7 and then delivered to the primary flash chamber.

[0071] The lean liquid column exiting the flash kettle 13 is pressurized and divided into two streams. The first stream is used as an absorbent and passes through the lean liquid circulation pump 4h. After heat exchange with the rich liquid from the absorption tower 2 in the lean-rich liquid heat exchanger 7b, it is further cooled by the tower lean liquid cooler 7a and sent to the tower lean liquid tank 8. Finally, it is sent to the absorption tower lean liquid pump 4f and the first-level spray pump 4c to be sprayed out to wash and absorb the exhaust gas of the artificial stone production line; the second stream is sent to the adsorption tower group 3 to wash the packing layer through the adsorption tower lean liquid pump 4g.

[0072] The gas phase from the rich liquid reflux washing tower 14 is sent to the flash condenser 9 to separate the condensate and non-condensable gases. The condensate is separated into styrene components and water through the pre-pump oil-water separator 17. The separated styrene components are sent to the intermediate oil tank 19 for collection through the vacuum discharge valve 16, and an inhibitor is added to the intermediate oil tank to be mixed with the recovered styrene product; the amount of condensed water discharged from the pre-pump oil-water separator 17 to the condensate tank 20 is kept balanced, the oil-water interface is raised to a higher position, and the excess water absorbed by the absorption liquid from the tail gas is discharged. The water is discharged together with the oil phase, thereby reducing the styrene concentration in the water phase; this is conducive to improving the styrene recovery rate (because the higher the liquid level of the oil-water interface, the more thorough the oil phase separation at the liquid level of the water phase discharge outlet, thereby reducing the styrene concentration in the water vapor circulating into the flash kettle), maintaining the water vapor and water balance in the flash kettle 13, and helping to improve the styrene recovery rate.

[0073] The separated condensed water is collected in condensate tank 20 and then heated and vaporized by condensate vaporizer 10c. It is then introduced as steam into aeration heads 13-13 and 13-12 in the lean liquid tank 13-10 and semi-lean liquid tank 13-11 within flash kettle 13, where it is then sprayed out. This strips the styrene component from the lean and semi-lean liquids, enabling condensate recycling and reducing wastewater discharge. Carbon dioxide or nitrogen can also be added to the steam entering aeration heads 13-13 and 13-12, as needed.

[0074] The non-condensable gas separated by the flash steam condenser 9 is divided into two streams after passing through the vacuum pump 11. One stream is sent to the absorption tower 2 together with the tail gas of the artificial stone production line, and the other stream is sent to the aeration heads 13-13 and 13-12 in the lean liquid tank 13-10 and the semi-lean liquid tank 13-11 together with the water vapor used for gas stripping entering the flash kettle 13 and sprayed out.

[0075] The absorbent used in the present invention is a high-boiling-point organic solvent having a boiling point 100° C. or higher than that of styrene, and is preferably diethyl phthalate.

[0076] See also Figure 2 The Henry constant of the solution after diethyl phthalate absorbs styrene is: 23.04kg / (moL·kPa).

[0077] The system of the present invention can recover more than 98% of the styrene components in styrene tail gas, purify the tail gas to meet emission standards, and consume less than 0.1kg / t-styrene. Compared with the distillation process, it saves more than 50% of energy consumption and reduces the recovery cost by more than 50%.

Claims

1. A method for recycling styrene from waste gas of an artificial stone production line based on adsorption-absorption synergy, comprising: the tail gas of the artificial stone production line enters an absorption-adsorption unit under the suction action of a fan, enters the absorption tower from the tail gas inlet at the bottom of the absorption tower, and sequentially contacts with the absorbent sprayed from top to bottom in countercurrent, so that most of the styrene is absorbed; the semi-purified tail gas discharged from the top of the absorption tower enters the adsorption tower group, and the residual styrene component is further adsorbed, and the purified tail gas from the adsorption tower group is directly discharged through a chimney; the rich liquid at the bottom of the absorption tower that has absorbed the styrene component enters the flash evaporation unit for distillation to recover the styrene, characterized in that: The flash unit includes a flash kettle and a rich liquid reflux washing tower. The rich liquid is divided into two streams. The first stream is heated to 60-65°C and then sent to the flash kettle for decomposition and recovery of styrene components. The second stream is sent to the rich liquid reflux washing tower for washing and heat exchange with the flash steam and stripping gas from the flash kettle and captures fine droplets. The rich liquid from the rich liquid reflux washing tower is sent to the flash kettle for decomposition and recovery of styrene components. The absorption-adsorption unit includes an absorption tower and an adsorption tower group, the adsorption tower group includes at least two adsorption towers connected in parallel, and the parallel adsorption towers alternately perform adsorption, desorption, and cooling processes; The adsorption, desorption and cooling processes alternately performed by the parallel adsorption towers are as follows: The semi-purified tail gas from the absorption tower is continuously fed into the adsorption tower in the adsorption stage for adsorption and then discharged as purified tail gas; when the adsorption tower in any adsorption stage is saturated with adsorption, it switches to the desorption and cooling stage, and the semi-purified tail gas from the absorption tower is simultaneously switched to the adsorption tower in the adsorption stage; Spraying hot lean liquid from the upper part of the adsorption tower in the desorption and cooling stage to wash the packing layer, completing the desorption process of the adsorption tower in the desorption and cooling stage; After the desorption is completed, the adsorption tower in the desorption and cooling stage enters the cooling stage. The purified tail gas discharged from other adsorption towers in the adsorption stage is introduced from the exhaust port at the top of the adsorption tower in the cooling stage into the adsorption tower in the cooling stage. The cooling gas is discharged from the bottom of the tower and sent to the absorption tower. After cooling, it enters the adsorption stage. Multiple adsorption towers alternately perform the adsorption, desorption and cooling processes. The absorbent used to wash the packing layer in the adsorption tower during the desorption phase is derived from the hot lean liquid after flash evaporation. During a desorption cycle, the temperature of the washing and desorption rich liquid exiting the adsorption tower after spray washing is monitored in real time. Based on the temperature variation of the washing and desorption rich liquid, the desorption phase is divided into three phases: the first phase, when the washing and desorption rich liquid temperature rises to a range of 11-15°C below the temperature of the hot lean liquid entering the tower; the second phase, when the washing and desorption rich liquid temperature rises to a range of 5-10°C below the temperature of the hot lean liquid entering the tower; and the third phase, when the washing and desorption rich liquid temperature rises to less than 5°C below the temperature of the hot lean liquid entering the tower. After the spray washing enters the third phase, the spray washing time is controlled and spray washing is continued until the washing and desorption rich liquid temperature is within 2°C below the temperature of the hot lean liquid entering the tower, completing the desorption process. The cooling air temperature out of the tower is detected in real time. When the temperature is 10-15℃ different from the cooling air temperature in the tower, the cooling process of the adsorption tower is completed. In the first stage of the desorption stage, the washing and desorption rich liquid after washing the packing layer is all sent to the flash kettle for flash evaporation and decomposition to recover the styrene component; in the second stage of the desorption stage, the washing and desorption rich liquid after washing the packing layer is all sent to the lower section of the absorption tower for spray washing of the artificial stone tail gas; in the third stage of the desorption stage, the washing and desorption rich liquid after washing the packing layer is all sent to the middle section of the absorption tower for spray washing of the artificial stone tail gas.

2. The method for recycling styrene from waste gas of artificial stone production line based on adsorption-absorption synergy according to claim 1, characterized in that: The absorbent is divided into at least three spray layers and enters the corresponding at least three packing layers in the absorption tower from the middle of the absorption tower from top to bottom. The absorbent in each spray layer is circulated and sprayed independently, and fresh lean liquid and replenished fresh absorbent are replenished into the absorption tower from the upper layer; the spray liquid of the upper layer flows into the next layer in full flow.

3. The method for recycling styrene from waste gas of artificial stone production line based on adsorption-absorption synergy according to claim 2, characterized in that: The lean liquid from the flash kettle is divided into two streams by the liquid holding column. The first stream returns to the absorption tower for circulation spraying to absorb styrene in the tail gas of the artificial stone production line, and the second stream is sent to the adsorption tower group to spray, wash and desorb the saturated adsorption tower packing layer.

4. The method for recycling styrene from waste gas of artificial stone production line based on adsorption-absorption synergy according to claim 3, characterized in that: The first rich liquid drawn from the bottom of the absorption tower exchanges heat with the first lean liquid from the liquid holding column, and then is mixed with the washing and desorption rich liquid from the first period of the adsorption tower group after washing the packing layer, heated to 60-65°C and then sent to the flash kettle.

5. The method for recycling styrene from waste gas of artificial stone production line based on adsorption-absorption synergy according to claim 1, characterized in that: The flash kettle is provided with at least two stages of flash chambers from top to bottom, and a liquid storage tank is provided at the bottom.

6. The method for recycling styrene from waste gas of artificial stone production line based on adsorption-absorption synergy according to claim 5, characterized in that: The upper section of the flash kettle is a primary flash chamber, and the lower section is a secondary flash chamber. The bottom liquid storage tank is divided into a lean liquid tank and a semi-lean liquid tank by at least one overflow plate. The upper part of the primary flash chamber is provided with a primary flash atomizer and a reflux rich liquid atomizer, and the bottom is provided with a primary flash guide plate. The upper part of the secondary flash chamber is provided with a secondary flash atomizer, and a portion of the lower part of the secondary flash chamber is located above the semi-lean liquid tank and is provided with a secondary flash guide plate, and the remaining area is connected to the lean liquid tank; the front end of the secondary flash guide plate is inserted into the lean liquid tank; the secondary flash guide plate and the overflow plate separate the semi-lean liquid tank from the secondary flash chamber; the gas phase space above the semi-lean liquid tank is connected to the primary flash chamber via a gas stripping gas guide pipe, the semi-lean liquid tank is connected to the secondary flash atomizer via a semi-lean liquid heater, and the primary flash chamber is connected to the semi-lean liquid tank via the primary flash guide pipe.

7. The method for recycling styrene from waste gas of artificial stone production line based on adsorption-absorption synergy according to claim 6, characterized in that: The rich liquid at the bottom of the absorption tower is sent to the first-level flash atomizer of the first-level flash chamber together with the absorbent after washing the packing layer, and is sprayed out for flash evaporation; the semi-lean liquid after the first-level flash evaporation falls into the semi-lean liquid tank, is then extracted and heated to 65-70°C, and is sent to the second-level flash atomizer of the second-level flash chamber for spraying for secondary flash evaporation, and the obtained lean liquid falls into the lean liquid tank and is then led out of the flash chamber; the flash steam of the second-level flash chamber and the flash steam of the first-level flash chamber are sent out of the flash kettle under the action of negative pressure and then sent to the flash steam condenser to recover the styrene product.

8. The method for recycling styrene from waste gas of artificial stone production line based on adsorption-absorption synergy according to claim 7, characterized in that: The rich liquid from the rich liquid reflux washing tower is divided into two streams. The first stream is sent to the reflux rich liquid atomizer of the flash kettle and sprayed out for flash evaporation. The second stream is mixed with the first rich liquid at the bottom of the absorption tower and the washing and desorption rich liquid after washing the packing layer in the first time period, and then heated to 60-65°C and sent to the first flash atomizer of the first flash chamber for spraying for flash evaporation.

9. The method for recycling styrene from waste gas of artificial stone production line based on adsorption-absorption synergy according to claim 8, characterized in that: Inert gas components with a boiling point lower than styrene and insoluble in the absorbent are introduced into the lean liquid tank and semi-lean liquid tank in the flash kettle to further strip the residual styrene components in the lean liquid and semi-lean liquid. These inert gas components are water vapor, or a mixture of water vapor and nitrogen or carbon dioxide.

10. The method for recycling styrene from waste gas of artificial stone production line based on adsorption-absorption synergy according to claim 9, characterized in that: The stripping gas escaping from the semi-lean liquid tank is introduced into the primary flash chamber through the stripping gas guide pipe and the demister; the stripping gas escaping from the lean liquid tank directly enters the secondary flash chamber, and the gas phase in the primary flash chamber and the secondary flash chamber is drawn out of the flash kettle under the suction action of the vacuum pump.

11. The method for recycling styrene from waste gas of an artificial stone production line based on adsorption-absorption synergy according to claim 10, characterized in that: The gas phase out of the flash kettle is washed in a rich liquid reflux washing tower and then sent to a flash steam condenser to separate the condensate and non-condensable gases. The condensate is separated into styrene components and condensed water by a pre-pump oil-water separator. The separated condensed water is heated and vaporized and then introduced into the lean liquid tank and semi-lean liquid tank in the flash kettle as water vapor to strip the styrene components in the lean liquid and semi-lean liquid, thereby realizing condensed water circulation. The non-condensable gases separated by the flash steam condenser are extracted by a vacuum pump and divided into two streams. The first stream is sent to an absorption tower together with the tail gas of the artificial stone production line, and the second stream is sent to the lean liquid tank and semi-lean liquid tank in the flash kettle together with the water vapor for stripping.

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