Styrene waste gas purification method based on absorption coupling adsorption-alternate desorption

Abstract

The invention relates to VOC (volatile organic compound) tail gas treatment in the field of environmental protection, in particular to a styrene waste gas purification method based on absorption coupling adsorption-alternate desorption, which comprises the following steps: styrene tail gas enters an absorption-adsorption unit under the suction action of a fan to remove styrene components, and then is discharged after reaching the standard; the absorption-adsorption unit comprises an absorption tower and an adsorption tower group, the styrene tail gas enters the absorption tower from a tail gas inlet in the lower part of the absorption tower and is in countercurrent contact with an absorbent, semi-purified tail gas obtained by absorbing most styrene is discharged from the top of the absorption tower and enters the adsorption tower group, and residual styrene components are further adsorbed; purified tail gas discharged from the adsorption tower group is directly discharged through a chimney. The method is simple in process, low in investment and operation cost, good in tail gas purification effect, capable of effectively coupling absorption and adsorption, energy-saving, consumption-reducing and high in styrene recovery rate.

Description

Technical Field

[0001] The invention belongs to the field of waste gas treatment and relates to the treatment of VOC tail gas, and specifically is a styrene waste gas purification method based on absorption coupled adsorption-alternating desorption. Background Art

[0002] Styrene is an important monomer in the industry for synthetic resins, ion exchange resins and synthetic rubber. Since the styrene component has a high saturated vapor pressure and strong volatility at room temperature, a large amount of styrene tail gas is generated during the production process.

[0003] The emission of styrene waste gas will cause harm to the environment and human health. In addition, it is a flammable and explosive gas / liquid, irritating to the eyes and upper respiratory tract mucosa, and has an anesthetic effect at high concentrations [Lei Yanmei et al. Experimental study on purification of low-concentration styrene waste gas by biofilm packing tower. Journal of Environmental Engineering, 2006, 7(3):36-39]. Styrene is also one of the important precursors of PM2.5 [Zhao Lei et al. Development and industrial application of deep purification technology of petrochemical VOC waste gas. Environmental Engineering, 2016, (S1):569-571], and will cause serious secondary pollution when entering the atmosphere.

[0004] The treatment of styrene-containing waste gas usually adopts the traditional VOCs waste gas treatment process, which is mainly classified into separation recovery technology and reaction destruction technology.

[0005] Separation and recovery technology uses physical methods to purify styrene gas, such as condensation, adsorption, absorption, etc.

[0006] The condensation method treats styrene gas by low-temperature heat exchange, cooling and condensing gaseous styrene into liquid phase and recovering it. However, the single condensation method for treating styrene gas is not ideal, because if it is to meet national emission standards, a lower temperature is required, which greatly increases power consumption and operating costs; at the same time, the condensed styrene will adhere to the surface of the heat exchanger and seriously affect the cooling efficiency. The condensation method is usually used as a unit operation in the process of treating styrene gas to pre-treat styrene gas, and is often used in combination with absorption, adsorption, and incineration methods to reduce costs. Lin Yu [Lin Yu. Study on the condensation method for treating styrene waste gas and its influencing rules. Modern Chemical Industry, 2018, 38(10): 192-195] et al. used the condensation method to treat styrene waste gas and explored the relevant experimental factors affecting the recovery of styrene waste gas. By adding a quantitative anticoagulant to the styrene solution, styrene was prevented from self-aggregation reaction to form polystyrene, and nitrogen was blown into the condensation device; at the same time, the influence of relevant parameters such as water temperature and waste gas concentration on the treatment efficiency was studied. When low-temperature water was used to condense and purify styrene waste gas, the change of water bath temperature had little effect on the waste gas outlet concentration. When styrene vapor was condensed, the inlet temperature could be kept below 40°C as much as possible.

[0007] Adsorption is the use of certain substances with adsorption capacity such as activated carbon, silica gel, zeolite molecular sieve, activated alumina, etc. to adsorb harmful components to achieve the purpose of eliminating harmful pollution. The treatment effect is not only related to the properties of the adsorbent [Pan Hongyan, Li Zhong, Xia Qibin, et al. Performance of ammonia-modified activated carbon fiber in adsorbing styrene [J]. Functional Materials, 2008, 02): 324-327], but also related to the type, nature, concentration of gaseous pollutants and the temperature and pressure of the adsorption system. The advantages of the adsorption method are high removal efficiency, energy saving, mature technology and less pollution. However, there are also certain limitations. For example, the equipment is large in size, the adsorbent after adsorption saturation is hazardous waste, and the replacement of the adsorbent is prone to secondary pollution and the cost of hazardous waste treatment is high.

[0008] In general, the existing separation and recovery technologies have problems such as great recovery difficulty, low recovery efficiency, and secondary pollution.

[0009] The reaction destruction method purifies styrene gas through chemical or biochemical reactions, including combustion, UV photocatalysis, advanced oxidation, biological method, plasma technology, etc.

[0010] Combustion method is a method of burning combustible organic gas phase pollutants as fuel. The combustion method cannot recover useful substances, and low-concentration exhaust gas needs to be supplemented with fuel gas. In most cases, the concentration of organic matter is low and insufficient to burn without auxiliary fuel. It is generally only applicable to exhaust gas with high concentration of combustible harmful components or high calorific value. Catalytic combustion can only be carried out under the action of precious metals such as platinum and palladium and transition metal oxide catalysts.

[0011] UV photocatalysis, advanced oxidation, biological methods, plasma and other technologies all use special processes to produce advanced oxidants to more thoroughly oxidize and decompose styrene pollutants in the exhaust gas, thereby achieving the purpose of purifying pollutants in the waste gas.

[0012] Technologies such as UV photocatalysis, advanced oxidation, biological methods, and plasma have problems such as bulky equipment, complex process flows, and fire safety. Summary of the invention

[0013] The purpose of the present invention is to solve the above technical problems and to provide a styrene waste gas purification method based on absorption coupled adsorption-alternating desorption, which has the advantages of simple process, low investment and operation costs, good tail gas purification effect, effective coupling of absorption and adsorption, energy saving and consumption reduction, and high styrene recovery rate.

[0014] The process of the present invention is as follows: styrene tail gas enters an absorption-adsorption unit under the suction action of a fan to remove styrene components and then is discharged after meeting standards. The absorption-adsorption unit comprises an absorption tower and an adsorption tower group. The styrene tail gas enters the absorption tower from a tail gas inlet at the lower part of the absorption tower and contacts with an absorbent in countercurrent. Most of the semi-purified tail gas in which styrene is absorbed is discharged from the top of the absorption tower and enters the adsorption tower group. The residual styrene components are further adsorbed, and the purified tail gas from the adsorption tower group is directly discharged through a chimney.

[0015] The absorbent is sprayed from the middle of the absorption tower from top to bottom in at least three stages into the three packing layers in the absorption tower respectively. The absorbent in each spraying 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 stage flows into the next stage in full flow.

[0016] The adsorption tower group includes at least two parallel adsorption towers, which are respectively in the adsorption stage and the desorption and cooling stage. The parallel adsorption towers perform adsorption, desorption and cooling processes alternately.

[0017] The adsorption, desorption and cooling processes alternately performed by the parallel adsorption tower group are as follows:

[0018] The semi-purified tail gas from the absorption tower is continuously sent to 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 out of the absorption tower switches to the adsorption tower in the adsorption stage;

[0019] 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;

[0020] After the desorption is completed, the adsorption tower in the waiting desorption and cooling stage enters the waiting 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 waiting cooling stage into the adsorption tower in the waiting cooling stage. The cooling gas is discharged from the bottom of the tower and sent to the absorption tower. After cooling, it enters the waiting adsorption stage. Multiple adsorption towers alternately perform adsorption, desorption and cooling processes.

[0021] The absorbent used for washing the packing layer in the adsorption tower in the desorption stage comes from the hot lean liquid after the flash kettle is analyzed; in one desorption cycle, the temperature of the absorbent (i.e., the washing and desorption rich liquid) exiting the adsorption tower after spray washing is detected in real time. According to the temperature change of the washing and desorption rich liquid, the desorption process is divided into three phases. The washing and desorption rich liquid temperature rises to 11-15°C lower than the temperature of the hot lean liquid entering the tower, which is the first phase; the washing and desorption rich liquid temperature rises to 5-10°C lower than the temperature of the hot lean liquid entering the tower, which is the second phase; the washing and desorption rich liquid temperature rises to less than 5°C lower than the temperature of the hot lean liquid entering the tower, which is the third phase. After the spray washing enters the third phase, the spray washing time is controlled, and the spray washing is continued until the washing and desorption rich liquid temperature is within 2°C lower than the temperature of the hot lean liquid entering the tower, completing the desorption process.

[0022] In the first time period, the absorbent after washing the packing layer (i.e., the washing and desorption rich liquid) 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.

[0023] The rich liquid at the bottom of the absorption tower that absorbs the styrene component enters the flash kettle for analysis and recovery of the styrene component. The lean liquid from the flash kettle after analysis is divided into two streams by the liquid holding column. The first stream returns to the absorption tower for cyclic spraying to purify the styrene tail gas, and the second stream is sent to the adsorption tower group to wash the packing layer.

[0024] 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.

[0025] 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. A primary flash atomizer is arranged at the upper part of the primary flash chamber, and a primary flash guide plate is arranged at the bottom; a secondary flash atomizer is arranged at the upper part of the secondary flash chamber, and a secondary flash guide plate is arranged in a part of the lower part of the secondary flash chamber located above the semi-lean liquid tank, and the remaining area is communicated with 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 through an air stripping gas guide pipe, and the semi-lean liquid tank is connected to the secondary flash atomizer through a semi-lean liquid heater.

[0026] The rich liquid discharged from the bottom of the absorption tower is sent to the first flash chamber of the flash kettle together with the rich liquid for washing and desorbing the packing layer in the first period of the desorption stage of the adsorption tower for atomization and spraying for flash evaporation; the semi-lean liquid after the first flash evaporation falls into the semi-lean liquid tank through the first flash evaporation guide pipe, and then is drawn out and heated to 65-70° C. by the semi-lean liquid heater and sent to the second flash chamber of the flash kettle for atomization and spraying for second flash evaporation, and the obtained lean liquid falls into the lean liquid tank and is then led out of the flash chamber; the gas phase of the second flash chamber and the gas phase of the first flash chamber are sent to the flash steam condenser to recover the styrene product after exiting the flash kettle under the action of negative pressure.

[0027] Inert gas components with a boiling point lower than styrene and insoluble in the absorbent are introduced into the lean liquid tank and the semi-lean liquid tank in the flash reactor to further strip the styrene components remaining in the lean liquid and the semi-lean liquid. The inert gas components are water vapor, or a mixture of water vapor and nitrogen or carbon dioxide. A mixture of water vapor and an inert component gas is preferred.

[0028] 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.

[0029] The gas phase out of the flash kettle is sent to the flash steam condenser to separate the condensate and non-condensable gas. The condensate passes through the pre-pump oil-water separator to separate the styrene component and condensed water. The separated condensed water is heated and vaporized and then passed into the lean liquid tank and semi-lean liquid tank in the flash kettle as water vapor to strip the styrene component in the lean liquid and semi-lean liquid, thereby realizing the circulation of condensed water.

[0030] The non-condensable gas separated by the flash steam condenser is divided into two streams after passing through a vacuum pump. The first stream is sent to the absorption tower together with the styrene tail gas, and the second stream is sent to the lean liquid and semi-lean liquid in the flash kettle for gas stripping together with the water vapor.

[0031] Control the negative pressure of the flash kettle, flash steam condenser and oil-water separator before the pump to below 4kPa absolute pressure.

[0032] In view of the problems existing in the background technology, the inventors have made the following improvements:

[0033] (1) An absorption-adsorption unit is set up to couple absorption and adsorption, and further adsorb and recover the styrene remaining in the semi-purified tail gas leaving the absorption tower, thereby maximally recovering the styrene component in the tail gas, effectively purifying the styrene tail gas, and improving the recovery rate of styrene.

[0034] (2) Combined with the flash evaporator, the rich liquid at the bottom of the absorption tower enters the flash evaporator for analysis and recovery of the styrene component. The lean liquid after analysis is divided into two streams. The first stream is cooled and returned to the absorption tower for circulation spraying to absorb the styrene in the styrene tail gas. The second stream is sent to the adsorption tower group in a hot state to elute, desorb and desorb the adsorption tower that has been saturated with adsorption and entered the desorption stage (already saturated with adsorption); the rich liquid from the adsorption tower after elution is returned to the flash evaporator for flash evaporation and analysis.

[0035] (3) The adsorption tower group includes at least two parallel adsorption towers, and the parallel adsorption towers alternately perform adsorption, desorption, and cooling processes, specifically:

[0036] The semi-purified tail gas from the absorption tower is continuously sent to the adsorption tower in the adsorption stage for adsorption and then the purified tail gas is discharged; when the adsorption tower in the adsorption stage is saturated, it switches to the desorption and cooling stage, and the semi-purified tail gas out of the absorption tower switches to another adsorption tower in the adsorption stage;

[0037] The hot lean liquid is sprayed on the upper part of the adsorption tower which has been saturated with adsorption to wash the packing layer, and the temperature of the absorbent (i.e., the washing and desorption rich liquid) out of the adsorption tower after the 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 stages. The washing and desorption rich liquid temperature rises to a range of 11-15°C lower than the temperature of the hot lean liquid entering the tower, which is the first stage; the washing and desorption rich liquid temperature rises to a range of 5-10°C lower than the temperature of the hot lean liquid entering the tower, which is the second stage; the washing and desorption rich liquid temperature rises to a range of less than 5°C lower than the temperature of the hot lean liquid entering the tower, which is the third stage. After the spray washing enters the third stage, the spray washing time is controlled, and the spray washing is continued until the washing and desorption rich liquid temperature is lower than the temperature of the hot lean liquid entering the tower by less than 2°C, and the desorption process is completed;

[0038] After the adsorption tower is desorbed, it enters the cooling stage. Part of the purified tail gas discharged from another adsorption tower is introduced into the tower from the exhaust port at the top of the adsorption tower (i.e., the purified tail gas outlet during the adsorption stage) to cool the packing layer. The cooling gas is discharged from the bottom of the tower, and the tower cooling gas temperature is detected in real time. When the temperature differs from the tower cooling gas temperature by 10-15°C, the cooling process of the adsorption tower is completed.

[0039] Both desorption and cooling use the medium circulation within the system without introducing external media, saving resources, eliminating secondary pollution, and greatly reducing operating costs.

[0040] (4) 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 operation 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 relatively high); 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), so as to realize the cascade utilization of the rich liquid and reduce the cost of flash evaporation and desorption.

[0041] (5) The lean liquid after flash evaporation and analysis in the flash evaporator is led out through the liquid holding column and enters the absorption-adsorption unit. Since the working pressure of the flash evaporator is maintained at 4 kPa (absolute pressure), which is much lower than the atmospheric pressure, when the lean liquid is directly drawn out from the bottom of the flash evaporator through the pump and enters 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. The liquid holding column is set up to lead the lean liquid from the bottom of the liquid holding column into the absorption tower, which increases the liquid phase pressure at the pump inlet and effectively overcomes the "cavitation" phenomenon.

[0042] (6) In order to improve the absorption effect of the absorption tower and reduce the amount of styrene remaining in the lean liquid, the flash evaporation kettle of the flash evaporation analysis unit has at least two flash evaporation chambers, and correspondingly connected lean liquid tanks and semi-lean liquid tanks are set. The rich liquid is first sprayed out through the first-stage flash evaporation atomizer located at the upper part of the first-stage flash evaporation chamber for flash evaporation. The semi-lean liquid after flash evaporation falls into the semi-lean liquid tank through the first-stage flash evaporation guide pipe, and then is drawn out and heated by the semi-lean liquid heater and sent to the second-stage flash evaporation atomizer at the upper part of the lower-stage second-stage flash evaporation chamber for spraying, and the lean liquid falls into the lean liquid tank through the second-stage flash evaporation guide plate. The front end of the second-stage flash evaporation guide plate is inserted below the liquid level of the lean liquid tank to form a liquid seal, which separates the second-stage flash evaporation chamber from the gas stripping area above the semi-lean liquid tank. On the one hand, by setting two-stage flash evaporation in one flash evaporation kettle, the analysis effect is enhanced. On the other hand, the first-stage flash evaporation chamber and the second-stage flash evaporation chamber are not connected to each other, so as to ensure the flash evaporation effect.

[0043] (7) An aeration head is set in the lean liquid tank and the semi-lean liquid tank. The condensed water separated after condensing the flash steam 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 realizing the reuse of condensed water in a real sense.

[0044] (8) The stripping gas is preferably a mixture of water vapor and an inert gas with a boiling point lower than that of styrene and insoluble in the absorbent (such as nitrogen, carbon dioxide, etc.). The aeration of the mixed gas into the flash reactor increases the inert component gas in the non-condensable gas, which can effectively reduce the styrene concentration in the non-condensable gas. By controlling the volume ratio of the inert gas to water vapor in the mixed gas (or controlling the inert gas flow rate), the styrene concentration in the non-condensable gas can be controlled below the explosion limit concentration, thereby ensuring the safety and reliability of the system operation;

[0045] (9) The non-condensable gas separated by the flash steam condenser is divided into two streams, which are respectively sent back to the absorption tower and the aeration head, so as to further recover the styrene component in the non-condensable gas, which is environmentally friendly. On the one hand, the recycling of non-condensable gas can effectively lift the styrene component in the lean liquid and semi-lean liquid. In addition, the temperature of the non-condensable gas drops after condensation in the flash steam condenser, and increases after being sucked and compressed by the vacuum pump. The saturated vapor pressure of styrene at two different temperatures is quite different. The non-condensable gas has a large driving force for lifting when entering the flash kettle, which is beneficial to the analysis of the styrene component. The inert gas component brought in participates in the aeration cycle, which can reduce the amount of inert gas added to the flash kettle and further dilute the styrene concentration in the non-condensable gas. On the other hand, it is beneficial to the recovery of the styrene component. There is still a high concentration of styrene remaining in the non-condensable gas, which is much higher than the styrene concentration in the original tail gas entering the absorption tower. The styrene component returned to the absorption tower will be further absorbed and adsorbed.

[0046] (10) The stripping gas escaping from the semi-lean liquid tank passes through the stripping area and the first-stage flash chamber and exits the flash kettle, thereby enhancing the airflow in the first-stage flash chamber. The stripping gas flow is concentrated in the first-stage flash region, and the styrene gas phase atomized and flashed by the first-stage flash atomizer is taken out, diluting the styrene concentration in the gas phase around the atomized droplets, enhancing the styrene volatilization effect, and improving the flash efficiency. The technical effect of introducing the stripping gas from the lean liquid tank into the upper space of the second-stage flash chamber is the same as above.

[0047] (11) Control the negative pressure of the flash kettle, flash steam condenser and pre-pump oil-water separator to be below 4 kPa absolute pressure. The reason for choosing a flash pressure below 4 kPa is, firstly, to reduce the polymerization of the recovered styrene component. When the styrene temperature reaches 60 °C, the polymerization rate intensifies. When it is below 4 kPa, the boiling point of styrene is lower than 55 °C, and the polymerization of styrene at this temperature can be ignored; secondly, under an absolute pressure of 4 kPa, the rich liquid temperature only needs to be controlled at around 60 °C to achieve a high decomposition effect, and the temperature resistance requirements for the equipment and its sealing materials are not high, reducing equipment investment; thirdly, an operating pressure of 4 kPa 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 4 kPa, it is not conducive to the decomposition of styrene.

[0048] Beneficial effects:

[0049] The invention has simple process, easy operation, low investment and operation cost, 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

[0050] Figure 1 It is a process flow chart of the present invention.

[0051] Figure 2 This is a fitting curve diagram of the Henry constant determined experimentally in the present invention.

[0052] 1a: fan; 2: absorption tower; 3a: absorption tower A; 3b: absorption tower B; 3c: absorption tower C; 4a: three-stage spray pump; 4b: two-stage spray pump; 4c: one-stage spray pump; 4d: absorption tower rich liquid pump; 4e: absorption tower rich liquid pump; 4f: absorption tower lean liquid pump; 4g: absorption tower lean liquid pump; 4h: lean liquid circulation pump; 4j: lean liquid discharge pump; 4r: one-stage flash pump; 4s: two-stage flash pump; 4u: condensate pump; 5a-1: first desorption rich liquid intermediate tank, 5a-2: second desorption rich liquid intermediate tank, 5a -3: the third desorption rich liquid intermediate tank; 5b: the first flash rich liquid tank; 6: the absorption liquid intermediate tank; 7a: the lean liquid cooler entering the tower; 7b: the lean-rich liquid heat exchanger; 8: the lean liquid tank entering the tower; 9: the flash steam condenser; 10a: the rich liquid heater; 10b: the semi-lean liquid heater; 10c: the condensed water vaporization heater; 11: the vacuum pump; 12a: the first flash demister; 12b: the second flash demister; 12c: the air stripping demister; 13: the flash kettle; 13-2: the first flash atomizer; 13-3: the second flash atomizer; 13-4: primary flash guide plate; 13-5: primary flash guide pipe; 13-6: secondary flash guide plate; 13-7: gas stripping gas guide pipe; 13-8: secondary flash 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; 15: liquid holding column; 16: vacuum unloading valve; 17: pre-pump oil-water separator; 18a: A tower liquid inlet valve; 18b: B tower liquid inlet valve; 18c: C tower liquid inlet valve; 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

[0053] The system of the present invention is explained below in conjunction with the accompanying drawings:

[0054] See also Figure 1 , including an absorption-adsorption unit and a flash kettle 13, 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, and the adsorption tower group 3 in this embodiment is composed of three parallel adsorption towers 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.

[0055] 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 is connected to the flash kettle 13 through three parallel first desorption rich liquid intermediate tanks 5a-1, second desorption rich liquid intermediate tanks 5a-2, third desorption rich liquid intermediate tanks 5a-3, adsorption tower rich liquid pumps 4e, rich liquid heaters 10a, and primary flash rich liquid tanks 5b. 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 a liquid holding column 15 and an 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 a lean liquid circulation pump 4h, a lean-rich liquid heat exchanger 7b, an inlet lean liquid cooler 7a, an inlet lean liquid tank 8, an absorption tower lean liquid pump 4f, and a primary spray pump 4c. The overflow port at the top of the liquid holding column 15 is connected to the flash kettle 13.

[0056] The rich liquid outlet at the bottom of the absorption tower 2 is connected to the primary flash atomizer 13-2 of the primary flash chamber of the flash kettle 13 through the absorption tower rich liquid pump 4d, the lean-rich liquid heat exchanger 7b, the rich liquid heater 10a, the primary flash rich liquid tank 5b, and the primary flash pump 4r.

[0057] 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 into a lean liquid tank 13-10 and a semi-lean liquid tank 13-11 by an overflow partition 13-9 (or an overflow pipe). The upper part of the primary flash chamber is provided with a primary flash atomizer 13-2, and the bottom is provided with a primary flash guide plate 13-4; 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, and 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 13-1 through the primary flash guide pipe 13-5. 1, the secondary flash chamber is connected to the lean liquid tank 13-10 through the secondary flash guide plate 13-5, and the gas phase space above the semi-lean liquid tank 13-11 is also connected to the primary flash chamber through the gas stripping gas guide pipe 13-7, and a gas stripping demister 12c is arranged on the pipeline. The gas stripping gas pipe 13-7 can be arranged inside the flash kettle 13 or outside the flash kettle 13, preferably outside the kettle, which can save space inside the kettle, reduce the upward flow rate of the flash steam, and is conducive to the precipitation of fine droplets generated by the atomization flash; 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.

[0058] The gas phase outlet of the primary flash chamber and the gas phase outlet of the secondary flash chamber are connected to the flash steam condenser 9 through the corresponding primary flash demister 12a and secondary flash demister 12b, respectively. 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 lean liquid aeration head 13-13 and the semi-lean liquid aeration head 13-12 in the lean liquid tank 13-10 and the semi-lean liquid tank 13-11 in the flash kettle 13 through the condensate tank 20, the condensate pump 4u, and the condensate vaporization heater 10c. The oil phase outlet of the pre-pump oil-water separator 17 is connected to the vacuum discharge valve 16 and the intermediate oil tank 18 in sequence. The non-condensable gas outlet of the flash steam condenser 9 is connected to the lean liquid aeration head 13-13 and the semi-lean liquid aeration head 13-12 in the lean liquid tank 13-10 and the semi-lean liquid tank 13-11 in the absorption tower 2 and the flash kettle 13. The negative pressure of the flash chamber 13, the flash steam condenser 9, the pre-pump oil-water separator 17 and the condensed water vaporizing heater 10c is controlled to be below the absolute pressure of 4 kPa.

[0059] Process:

[0060] Under the suction action of the fan 1a, the styrene tail gas enters the absorption tower 2 from the tail gas inlet at the lower part of the absorption tower 2 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 described in this embodiment is composed of three parallel adsorption towers A 3a, B tower 3b, and C tower 3c, wherein the tail gas inlet of each adsorption tower is connected in parallel, the purified tail gas outlet is connected in parallel, the absorbent inlet is connected in parallel, and the absorbent outlet is 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 1a; the tail gas outlet of the absorption tower 2 is respectively connected to the tail gas inlet of the adsorption tower A 3a, the adsorption tower B 3b, and the adsorption tower C 3c, 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 connected to three parallel first desorption rich liquid intermediate tanks 5a-1, second desorption rich liquid intermediate tanks 5a-2, and third desorption rich liquid intermediate tanks 5a-3. The three adsorption towers perform adsorption and desorption processes in turn. 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 sent from the tail gas inlet to the adsorption tower in the adsorption stage (such as adsorption tower A 3a, adsorption tower B 3b, adsorption tower C 3c), and the purified tail gas is discharged from the tail gas outlet after adsorption; when any adsorption tower in the 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 one of the other two towers (adsorption tower B 3b or adsorption tower C 3c); at this time, the hot lean liquid from the liquid holding column 15 enters the adsorption tower in the desorption stage (adsorption tower A 3a) from the adsorbent inlet to wash the packing layer, and the real-time The temperature of the absorbent (i.e., the washing and desorption rich liquid) leaving the adsorption tower after spray washing is detected. According to the temperature of the washing and desorption rich liquid, the desorption process is divided into three stages. The first stage 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 stage 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 stage is when the temperature of the washing and desorption rich liquid rises to a range of less than 5°C lower than the temperature of the hot lean liquid entering the tower. After the spray washing enters the third stage, the spray washing time is controlled, and the spray washing is continued until the temperature of the washing and desorption rich liquid is less than 2°C lower than the temperature of the hot lean liquid entering the tower, thereby completing the desorption process.

[0063] 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 first stage washing and desorption rich liquid is introduced into the desorption rich liquid intermediate tank 5a-1, the second stage washing and desorption rich liquid is introduced into the desorption rich liquid intermediate tank 5a-2, and the third stage washing and desorption rich liquid is introduced into the desorption rich liquid intermediate tank 5a-3.

[0064] The washing and desorption rich liquid in the corresponding desorption rich liquid intermediate tanks 5a-1, 5a-2, and 5a-3 are respectively introduced into the rich liquid heater 10a to heat to 60-65°C through the absorption tower rich liquid pump 4e, and then sent to the flash kettle 13 through the first-stage flash rich liquid tank 5b and the first-stage flash pump 4r. The bottom spray layer of the absorption tower 2 participates in the absorption of the styrene component in the original tail gas, and the middle spray layer of the absorption tower 2 participates in the absorption of the styrene component in the original tail gas. In this way, the cascade utilization of the rich liquid is achieved, and the cost of flash analysis is reduced.

[0065] After the washing and desorption of the adsorption tower (adsorption tower A 3c) is completed, it enters the cooling stage, and the purified exhaust gas from the adsorption tower (adsorption tower B 3b or adsorption tower C 3c) is introduced to cool the adsorption tower (adsorption tower A 3a), completing an adsorption-desorption-cooling cycle. After the cooling is completed, the tower is switched to the adsorption tower in the adsorption stage again; in conjunction with the switching of the valves on the pipeline, multiple adsorption towers take turns to perform the adsorption, desorption and cooling processes.

[0066] The cooling air temperature out of the tower is detected in real time. When the temperature is 10-15°C different from the cooling air temperature entering the tower, the cooling process of the adsorption tower is completed.

[0067] The rich liquid from the bottom of the absorption tower 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; at the same time, the rich liquid from the bottom of the absorption tower is sent to the lean-rich liquid heat exchanger 7b through the absorption tower rich liquid pump 4d to exchange heat with the lean liquid from the bottom of the flash kettle 13, and then sent to the rich liquid heater 10a together with the absorbent from the adsorption tower group 3.

[0068] In the flash kettle 13: the rich liquid from the primary flash rich liquid tank 5b is first sprayed into the primary flash chamber through the primary flash atomizer 13-2 for flash evaporation. The flash steam after desorption is removed by the primary flash demister 12a at the top and then led out to the flash steam condenser 9. The semi-lean liquid after desorption by the primary flash flows into the primary flash guide pipe 13-5 through the primary flash guide plate 13-4 and finally falls into the semi-lean liquid tank 13-11 at the bottom for collection.

[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 flash steam obtained after analysis is led out through the secondary flash air guide pipe 13-8 and removed by the secondary flash demister 12b, and then led out to the flash steam condenser 9. The lean liquid after analysis falls into the lean liquid tank 13-10 along the secondary flash guide plate 13-5 and then leads out of the flash kettle 13;

[0070] The lean liquid in the lean liquid tank 13-10 can overflow unidirectionally to 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 the corresponding aeration heads 13-13 and 13-12 to further strip the styrene components remaining in the lean liquid and the semi-lean liquid. The stripping gas in the lean liquid tank 13-10 directly enters the secondary flash chamber, and the stripping gas of the semi-lean liquid tank 13-11 is collected from the gas phase space above and then led out by the stripping air guide pipe 13-7, and sent into the primary flash chamber after being defogged by the stripping demister 12c.

[0071] The lean liquid exiting the flash kettle 13 is divided into two streams after the liquid level is increased by the liquid holding column 15. 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 in the lean-rich liquid heat exchanger 7b, it is further cooled by the tower lean liquid cooler 7a and sent to the lean liquid inlet tank 8. Finally, it is sent to the absorption tower 2 through the absorption tower lean liquid pump 4f and the first-stage spray pump 4c, sprayed into the tower and contacted with the styrene tail gas in countercurrent to absorb the styrene component in the tail gas. The second stream is sent to the absorption tower group 3 to wash the packing layer through the adsorption tower lean liquid pump 4g.

[0072] The flash steam from the flash kettle 13 is introduced into the flash condenser 9 under the suction action of the vacuum pump 11, and the temperature is reduced to 25-30°C to separate the condensate and non-condensable gas. 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 unloading valve 16, and the inhibitor is added to the intermediate oil tank to mix with the recovered styrene product.

[0073] The separated condensed water is sent to the condensed water tank 20 for collection, and then heated and vaporized by the condensed water vaporization heater 10c, and then passed into 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 as stripping gas for spraying, and the styrene components in the lean liquid and semi-lean liquid are stripped to realize the condensed water circulation. The non-condensable gas separated by the flash steam condenser 9 is increased to 50-60°C after being sucked and compressed by the vacuum pump 11. The saturated vapor pressure of styrene is 5.12kPa, which is 5-6 times that at 25-30°C. It is then divided into two streams, one of which is sent to the absorption tower 2 together with the styrene tail gas, and the other is sent to the flash kettle 13 together with the water vapor for stripping, and is sent to the lean liquid aeration heads 13-13 and the semi-lean liquid 13-12 in the lean liquid tank 13-10 and the semi-lean liquid tank 13-11 for spraying. Specifically, as needed, nitrogen or carbon dioxide can also be mixed into the water vapor for stripping at the same time. The amount of aerated water vapor entering the flash kettle 13 is controlled to be 0.5-0.7% (mass ratio) of the amount of rich liquid entering the kettle. 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 pre-pump oil-water separator 17, so as to maintain the balance of water vapor and water in the flash kettle 13, which is beneficial to improve the styrene recovery rate. Maintaining a high liquid level of the oil-water interface is beneficial to the discharge of excess condensed water together with the oil phase, reducing the styrene concentration in the water phase; it is beneficial to improve the styrene recovery rate. Because the higher the liquid level of the oil-water interface, the more thorough the separation of the oil phase at the liquid level of the water phase discharge port, thereby reducing the styrene concentration in the water vapor circulating into the flash kettle. 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 resolution is achieved when all the water in the rich liquid is evaporated (i.e. when the water phase disappears). This technical solution aerates the lean liquid and semi-lean liquid with water vapor for a long time (about 75 kg / h, 3000 m 3 ), the gas-liquid ratio is high, 200-300:1, which is beneficial to further reduce the residual styrene concentration in the lean solution.

[0074] The absorbent used in the method of the present invention is a high-boiling point organic solvent having a boiling point higher than that of styrene by more than 100° C., preferably diethyl phthalate.

[0075] See also Figure 2 The Henry constant of the solution after diethyl phthalate absorbs styrene is: 23.04kg / (moL·kPa).

[0076] The process 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 purifying styrene waste gas based on absorption-coupled adsorption-alternating desorption, wherein the styrene tail gas enters the absorption-adsorption unit under the suction action of a fan to remove the styrene component and then is discharged out after meeting the standards, characterized in that: The absorption-adsorption unit includes an absorption tower and an adsorption tower group. The styrene tail gas enters the absorption tower from the tail gas inlet at the lower part of the absorption tower and contacts with the absorbent in countercurrent. Most of the semi-purified tail gas in which the styrene is absorbed is discharged from the top of the absorption tower and enters the adsorption tower group. The residual styrene components are further adsorbed, and the purified tail gas from the adsorption tower group is directly discharged through the chimney.

2. The method for purifying styrene waste gas based on absorption coupled adsorption-alternating desorption according to claim 1, characterized in that: The absorbent is sprayed from the middle of the absorption tower from top to bottom in at least three stages into the three packing layers in the absorption tower respectively. The absorbent in each spraying layer is sprayed in an independent cycle. Fresh lean liquid and replenished fresh absorbent are replenished into the absorption tower from the upper layer; the spray liquid of the upper stage flows into the next stage in full flow.

3. The method for purifying styrene waste gas based on absorption coupled adsorption-alternating desorption according to claim 1, characterized in that: The adsorption tower group includes at least two parallel adsorption towers, which are respectively in the adsorption stage and the desorption and cooling stage. The parallel adsorption towers perform adsorption, desorption and cooling processes alternately.

4. The method for purifying styrene waste gas based on absorption coupled adsorption-alternating desorption as claimed in claim 3, characterized in that: The adsorption, desorption and cooling processes alternately performed by the adsorption tower group are as follows: The semi-purified tail gas from the absorption tower is continuously sent to 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 is synchronously 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 waiting desorption and cooling stage enters the waiting 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 waiting cooling stage into the adsorption tower in the waiting cooling stage. The cooling gas is discharged from the bottom of the tower and sent to the absorption tower. After cooling, it enters the waiting adsorption stage. Multiple adsorption towers alternately perform adsorption, desorption and cooling processes. The absorbent used for washing the packing layer in the adsorption tower in the desorption stage comes from the hot lean liquid after the flash kettle is analyzed; in one desorption cycle, the temperature of the washing and desorption rich liquid out of the adsorption tower after spray washing is detected in real time, and the desorption process is divided into three stages according to the temperature change of the washing and desorption rich liquid. The first stage 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 stage 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 stage is when the temperature of the washing and desorption rich liquid rises to a range of less than 5°C lower than the temperature of the hot lean liquid entering the tower. After the spray washing enters the third stage, the spray washing time is controlled, and the spray washing is continued until the temperature of the washing and desorption rich liquid is lower than the temperature of the hot lean liquid entering the tower by less than 2°C, and the desorption process is completed; In the first time period, the 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 analysis and recovery of the styrene component; in the second time period, the rich liquid 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 rich liquid 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.

5. The method for purifying styrene waste gas based on absorption coupled adsorption-alternating desorption according to claim 1, characterized in that: The rich liquid at the bottom of the absorption tower that absorbs the styrene component enters the flash kettle for analysis and recovery of the styrene component. The lean liquid from the flash kettle after analysis is divided into two streams by the liquid holding column. The first stream returns to the absorption tower for cyclic spraying to purify the styrene tail gas, and the second stream is sent to the adsorption tower group to wash the packing layer.

6. The method for purifying styrene waste gas based on absorption coupled adsorption-alternating desorption according to claim 5, 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.

7. The method for purifying styrene waste gas based on absorption coupled adsorption-alternating desorption according to claim 6, 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. A primary flash atomizer is arranged on the upper part of the primary flash chamber, and a primary flash guide plate is arranged on the bottom; a secondary flash atomizer is arranged on the upper part of the secondary flash chamber, and a secondary flash guide plate is arranged in the area above the semi-lean liquid tank in the lower part of the secondary flash chamber, and the remaining area is communicated with 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 through an air stripping gas guide pipe, the semi-lean liquid tank is connected to the secondary flash atomizer through a semi-lean liquid heater, and the primary flash chamber is connected to the semi-lean liquid tank through a primary flash guide pipe.

8. The method for purifying styrene waste gas based on absorption coupled adsorption-alternating desorption according to claim 7, characterized in that: The rich liquid discharged from the bottom of the absorption tower is sent to the first flash chamber of the flash kettle together with the rich liquid for washing and desorbing the packing layer in the first period of the desorption stage of the adsorption tower for atomization and spraying for flash evaporation; the semi-lean liquid after the first flash evaporation falls into the semi-lean liquid tank through the first flash evaporation guide pipe, and then is drawn out and heated to 65-70° C. by the semi-lean liquid heater and sent to the second flash chamber of the flash kettle for atomization and spraying for second flash evaporation, and the obtained lean liquid falls into the lean liquid tank and is then led out of the flash chamber; the gas phase of the second flash chamber and the gas phase of the first flash chamber are sent to the flash steam condenser to recover the styrene product after exiting the flash kettle under the action of negative pressure.

9. The method for purifying styrene waste gas based on absorption coupled adsorption-alternating desorption according to claim 8, characterized in that: Inert gas components with a boiling point lower than styrene and insoluble in absorbent are introduced into the lean liquid tank and the semi-lean liquid tank in the flash kettle to further strip the residual styrene components in the lean liquid and the semi-lean liquid, wherein the inert gas components are water vapor, or a mixed gas of water vapor and nitrogen or carbon dioxide; the stripping gas escaping from the semi-lean liquid tank is introduced into the primary flash chamber through a stripping gas air guide pipe and a 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 a vacuum pump; the gas phase out of the flash kettle is sent to a flash steam condenser to separate the condensate and the non-condensable gas.

10. The method for purifying styrene waste gas based on absorption coupled adsorption-alternating desorption according to claim 9, characterized in that: The condensate is separated into styrene components and condensed water by a pre-pump oil-water separator, and the separated condensed water is heated and vaporized and introduced into the lean liquid tank and the semi-lean liquid tank in the flash kettle as water vapor to strip the styrene components in the lean liquid and the semi-lean liquid, thereby realizing condensed water circulation; the non-condensable gas separated by the flash steam condenser is divided into two streams after passing through a vacuum pump, the first stream is sent to an absorption tower together with the styrene tail gas, and the second stream is sent to the lean liquid and the semi-lean liquid in the flash kettle together with the water vapor to strip the styrene components.

Images