Organic waste gas purification method

Abstract

The invention discloses an organic waste gas purification method, and belongs to the technical field of environmental protection. The method comprises the following steps: step 1, absorbing VOCs in waste gas in a tower by taking water or saline water as an absorbent to form an emulsion; step 2, centrifugally separating the emulsion, coarsening the VOCs emulsion, and separating the VOCs emulsion from a water phase; 3, standing and settling the centrifugate, and recycling the lower saturated water phase in the step 1; and 4, adsorbing the upper oil phase by using crystalline salt for deep dehydration, recovering organic matters, heating and regenerating the crystalline salt for recycling, and introducing regenerated water vapor into the step 1 for purification. VOCs resource recycling is achieved through physical separation, heat balance of the system is maintained through high specific heat capacity of water, and external cooling is not needed; the absorbent is circulated, the dehydrating agent is regenerated, and water vapor is recycled, so that multiple closed loops are realized. Compared with an incineration method and a condensation method, the method has the advantages that the energy consumption is obviously reduced, secondary pollution is avoided, and the method is particularly suitable for purifying middle-concentration and high-concentration organic waste gases such as esters, aromatic hydrocarbons and halogenated hydrocarbons.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection technology, specifically relating to a method for purifying organic waste gas. Background Technology

[0002] Industrial production and plant growth both generate emissions of volatile organic compounds (VOCs), also known as organic waste gases. These organic waste gases pose various health and environmental hazards. Health hazards include irritation of the respiratory system, impact on the nervous system, damage to the liver, kidneys, and blood, interference with the immune and endocrine systems, reproductive and developmental toxicity, and carcinogenic risks. Environmental hazards include the formation of photochemical smog, ozone layer depletion, persistent pollution, and the greenhouse effect.

[0003] Depending on the nature and characteristics of the organic waste gas, its surrounding environment, and the possibility of recovering the organic matter, different purification and recovery methods can be adopted. Commonly used methods include adsorption, combustion, liquid absorption, and condensation. Absorption is suitable for water-soluble or reactive organic matter; adsorption is suitable for low-concentration, high-volume organic waste gas; combustion is suitable for high-concentration or recalcitrant organic matter; condensation is used for high-concentration solvent recovery; and biological methods are environmentally friendly and suitable for low-concentration, easily degradable waste gas.

[0004] However, existing technologies still have many shortcomings. For example, patent CN102716666B discloses a multiphase photocatalytic purification system for treating waste gas. While this technology boasts a high purification rate, the equipment is complex and energy-intensive. Another example is Taiwan patent I511771, which points out that traditional condensation methods often result in a large amount of water in the condensate after treatment, leading to a low concentration of volatile organic compounds and increasing the energy consumption of subsequent purification processes. Furthermore, some technologies employing absorption combined with combustion oxidation, while highly efficient, ultimately convert organic matter into carbon dioxide and water, failing to achieve resource recovery of organic matter and incurring high operating costs.

[0005] Furthermore, the main methods for treating high-concentration organic waste gas are incineration and condensation. While incineration is thorough, it is extremely energy-intensive and wasteful of resources; condensation has stringent concentration requirements and requires significant energy for deep refrigeration. Developing an alternative technology that can both recover resources and eliminate high energy consumption has become a pressing technical challenge in this field. Summary of the Invention

[0006] The purpose of this invention is to provide a method for purifying organic waste gas, which aims to overcome the problems of high energy consumption, low purification efficiency, and resource waste in the prior art, and achieve low energy consumption, high efficiency, and resource utilization.

[0007] The technical solution of the present invention is as follows:

[0008] A method for purifying organic waste gas includes the following steps:

[0009] Step 1, Washing and Absorption: Using water or brine as the absorbent, volatile organic compounds (VOCs) in the waste gas are absorbed within the tower. The VOCs are converted from the gas phase to the liquid phase, releasing heat of absorption. This heat is absorbed by the absorbent, forming a heated emulsion containing VOCs. Salt is added to the brine or water to increase the density of the aqueous phase, thus increasing the density difference between the oil and water phases and enhancing the centrifugal separation effect.

[0010] Step 2, centrifugal separation: The emulsion obtained in Step 1 is sent to a centrifuge, and the VOCs emulsion in the absorption liquid is separated from the aqueous phase under the action of centrifugal force.

[0011] Step 3, Natural sedimentation: The absorbent liquid separated by centrifugation in step 2 is allowed to settle naturally in the storage tank. The absorbent liquid cools naturally during the settling process, and the saturated aqueous phase at the bottom is reused for washing and absorption in step 1.

[0012] Step 4: Deep dehydration: Deeply dehydrate the oil phase in the upper part of the storage tank in Step 3 to obtain organic matter with low water content.

[0013] Preferably, the washing and absorption in step one is performed continuously, while the centrifugation in step two is performed intermittently.

[0014] More preferably, the washing and absorption in step one is carried out continuously in multiple sets of parallel towers, and the absorbent liquid generated by the multiple sets of towers is collected and intermittently sent to a centrifuge for centrifugal separation in step two.

[0015] Preferably, the method does not include a cooling or condensation step for the absorbent or waste gas after the washing and absorption in step one and before the centrifugation in step two.

[0016] Preferably, the deep dehydration in step four is performed by adsorption dehydration using an inorganic salt that readily absorbs water and forms crystals, wherein the inorganic salt is anhydrous sodium sulfate or anhydrous magnesium sulfate.

[0017] More preferably, the deep dehydration in step four specifically includes: (1) adding inorganic salt to the oil phase and stirring to mix so that the inorganic salt absorbs water to form crystalline hydrate; (2) separating the dehydrated oil phase by filtration; and (3) heating the separated crystalline hydrate to dehydrate and regenerate it for recycling.

[0018] More preferably, the water vapor and VOCs generated by heating and dehydrating the crystalline hydrate are absorbed and purified in the washing and absorption process of step one.

[0019] Preferably, the tower is a spray tower, a packed tower, or a plate tower.

[0020] Preferably, the absorbent is water, sodium chloride solution, calcium chloride solution, or seawater.

[0021] Preferably, the centrifuge is a disc centrifuge, a tubular centrifuge, or a horizontal screw centrifuge.

[0022] It should be noted that the "centrifugal coarsening separation" described in this invention refers to the process in which tiny VOCs droplets in an emulsion first collide and merge (coarsening) in a centrifugal force field, increasing their particle size, and then achieving stratification separation by utilizing the density difference between the oil and water phases. Centrifugal force simultaneously achieves the dual functions of coarsening and separation.

[0023] It should also be noted that this invention is applicable to the purification and treatment of water-insoluble or slightly soluble volatile organic compounds, especially to waste gases containing esters, ketones, aromatics, and halogenated hydrocarbons generated during industrial processes such as spraying, coating, and paint stripping. For highly water-soluble alcohol VOCs (such as methanol, ethanol, isopropanol, etc.), because they are easily soluble in the aqueous phase and difficult to effectively recover through centrifugal separation, they are not included in the preferred scope of this invention.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] 1. Low energy consumption: This invention utilizes the high specific heat capacity of water to absorb the heat released by the liquefaction of VOCs, enabling the system to maintain thermal balance without external cooling, thus avoiding the energy consumption of traditional absorption methods that require additional cooling devices due to temperature rise; the entire process only consumes electricity from the centrifuge, which significantly reduces energy consumption compared to incineration and condensation methods.

[0026] 2. Resource recycling: This invention achieves VOCs recovery through physical separation. The recovered organic matter can reach industrial-grade standards after deep dehydration and can be directly reused in the original production process, realizing the internal cycle of "original soup to original food", saving procurement costs and reducing carbon emissions.

[0027] 3. Absorbent recycling: The aqueous phase after natural sedimentation is directly recycled back into the absorption tower, realizing the internal circulation of the absorbent, eliminating secondary wastewater generation, and significantly reducing operating costs.

[0028] 4. Simplified process and strong adaptability: This invention uses physical separation throughout the entire process, without the need for heating, cooling or adding chemical agents. The equipment is simple and easy to operate, and it is suitable for the treatment of medium and high concentration organic waste gas. It can effectively replace incineration and condensation methods.

[0029] 5. Flexible configuration: This invention supports the decoupling of continuous absorption operation and intermittent centrifugal operation, and can realize multiple absorption towers sharing a single centrifugal separation system, which greatly reduces equipment investment and floor space, and is particularly suitable for centralized treatment in industrial parks or waste gas treatment in multiple workshops of enterprises.

[0030] 6. Multiple Closed-Loop System for Ultimate Environmental Protection: In a further optimized version of this invention, anhydrous sodium sulfate and other crystalline salts are used for deep dehydration. The dehydrating agent can be heated and regenerated for reuse. The water vapor generated during regeneration is directly recycled back to the absorption tower to replenish the absorbent, achieving a triple closed-loop design: solvent recovery, dehydrating agent recycling, and water resource reuse. Compared to conventional dehydration technologies, no secondary waste is generated, the system maintains its own water balance, and near-zero emissions are achieved.

[0031] This invention achieves demulsification and oil-water separation of emulsions in one step through centrifugation and coarsening separation. Compared with traditional processes that require the addition of demulsifiers or heating for demulsification, this invention greatly simplifies the process and reduces costs. Attached Figure Description

[0032] Figure 1 This is a process flow diagram of an organic waste gas purification method according to the present invention. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0034] Example 1: Treatment of spray painting exhaust gas with thinner (mixed solvent)

[0035] This embodiment addresses the organic waste gas generated during the spraying and drying process of an oil-based paint in a hardware factory's spraying workshop, where thinner is used as a diluent. The thinner's main components are a mixture of ethyl acetate, butyl acetate, toluene, xylene, etc., with a waste gas volume of 15000 m³ / h and a VOCs concentration of 1200 mg / m³.

[0036] Step 1: Washing and Absorption: Using clean water as the absorbent, the waste gas is absorbed by countercurrent spraying in a packed tower at a gas-liquid ratio of 2500:1. Esters and aromatic VOCs in the waste gas are absorbed into the water, forming an emulsion. During the absorption process, VOCs convert from the gas phase to the liquid phase, releasing heat of absorption. This heat is absorbed by the absorbent, and the temperature of the absorbent gradually rises from an initial 25℃ and stabilizes at 29-32℃. The esters and aromatics in the thinner are water-insoluble or slightly soluble organic compounds, existing as dispersed oil droplets in the absorbent, forming a stable emulsion.

[0037] Step 2: Centrifugal Separation: The absorbent liquid at the bottom of the tower is pumped into a disc centrifuge for centrifugal separation. Under centrifugal force, the lighter oil phase (thinner-water mixed solvent) accumulates in the inner layer, while the heavier aqueous phase moves to the outer layer, achieving preliminary separation. The centrifuge operates intermittently, starting 3-4 times daily depending on the accumulation of absorbent liquid.

[0038] Step 3: Natural Settling: The absorbent containing residual VOCs discharged from the centrifuge enters the storage tank and is allowed to settle for 8 hours. At this time, the liquid in the storage tank clearly separates into two layers: the upper layer is a rich mixed oil phase (thinner water component), and the lower layer is a relatively clear water phase. The liquid temperature naturally drops to room temperature. The lower water phase is returned to the scrubbing absorption tower via overflow and recycled as an absorbent.

[0039] Step 4, Deep Dehydration: The upper oil phase obtained in Step 3 (containing approximately 8000 ppm of water) is fed into a dehydration tank equipped with a stirrer. Anhydrous sodium sulfate (Glauber's salt) powder is added at 8% of the oil phase mass, and the mixture is stirred at room temperature for 30 minutes. After absorbing the water in the oil phase, the Glauber's salt gradually transforms into sodium sulfate decahydrate crystals, expanding in volume but still maintaining a solid state. The mixture is filtered through a 200-mesh filter bag, and the filtrate is the dehydrated organic solvent. Karl Fischer titration shows that the water content of the dehydrated solvent is consistently below 800 ppm, meeting the requirements for reuse, and is directly sent back to the paint mixing process in the spray painting workshop.

[0040] Treatment effect: Testing showed that the purified exhaust gas outlet concentration was 35 mg / m³, with a removal rate of 97.1%. Gas chromatography analysis of the recovered mixed solvent revealed that the proportions of its main components were similar to those of fresh thinner, meeting the requirements of the spraying process. The entire system generates no secondary wastewater, and its overall energy consumption is only 1 / 12 of that of incineration.

[0041] Example 2: Coating waste gas – Ethyl acetate treatment

[0042] This embodiment treats ethyl acetate-containing waste gas generated during the coating process of a photoelectric polarizer, with an air volume of 10,000 m³ / h and a concentration of 1,500 mg / m³. Ethyl acetate is a typical slightly aqueous ester solvent, widely used in dry lamination processes.

[0043] Step 1, Washing and Absorption: Using a 5% sodium chloride solution as the absorbent, the waste gas is absorbed by countercurrent spraying in a packed tower at a gas-liquid ratio of 2000:1. Brine is used as the absorbent, utilizing the salting-out effect to reduce the solubility of ethyl acetate in water and promote its precipitation in subsequent separation steps. The absorption process is exothermic, and the temperature of the absorbent solution is stabilized at 28-31℃.

[0044] Step 2: Centrifugal Separation: The absorbent from the bottom of the column is fed into a tubular centrifuge for centrifugal separation. Under centrifugal force, the ethyl acetate emulsion is coarsened and separated from the aqueous phase. The centrifuge is run intermittently, 2-3 times per day.

[0045] Step 3: Natural sedimentation: The centrifuged absorbent is placed in a storage tank and allowed to settle for 6 hours. After the liquid separates into layers, the lower brine phase is returned to the absorption tower for recycling, while the upper layer is the enriched ethyl acetate oil phase.

[0046] Step 4, Deep Dehydration: The upper ethyl acetate oil phase is dehydrated using anhydrous magnesium sulfate adsorption. Anhydrous magnesium sulfate powder is added at 6% of the oil phase mass, and the mixture is stirred for 20 minutes. The magnesium sulfate absorbs water to form magnesium sulfate heptahydrate crystals. After filtration through a filter bag, the water content of the dehydrating solvent is reduced to below 500 ppm, exceeding the national standard requirement for superior grade products (1000 ppm), and can be directly reused in the compounding process.

[0047] Treatment results: Testing showed that the concentration of the purified exhaust gas at the outlet was 28 mg / m³, with a removal rate of 98.1%. The recovered ethyl acetate, after being mixed with adhesive, showed normal curing reaction with no defects such as bubbles or white spots. The composite strength was no different from that of the fresh solvent.

[0048] Example 3: Treatment of paint stripping waste gas – dichloroethane

[0049] This embodiment addresses the issue of using dichloroethane as a thinner in an air-conditioned cleanroom during the roller coating and end-cap paint stripping process of a printer. This process generates dichloroethane-containing waste gas at a flow rate of 5000 m³ / h and a concentration of 2500 mg / m³. Dichloroethane is a halogenated hydrocarbon solvent with a density greater than water (approximately 1.25 g / cm³), and belongs to a special type of VOCs.

[0050] Step 1: Washing and Absorption: Using clean water as the absorbent, the waste gas is absorbed in a packed tower within the workshop, with a gas-liquid ratio of 1500:1. Dichloroethane is absorbed to form an emulsion; because its density is greater than water, it tends to settle in the absorbent. The absorption process is exothermic, and the absorbent temperature remains stable at 20-23℃.

[0051] Step 2: Centrifugal Separation: The absorbent from the bottom of the column is fed into a horizontal screw centrifuge for centrifugal separation. Under centrifugal force, the heavier dichloroethane oil phase aggregates to the outer layer, while the lighter aqueous phase moves to the inner layer, achieving separation. The centrifuge operates intermittently, twice daily.

[0052] Step 3: Natural Settling: The centrifuged absorbent is placed in a storage tank and allowed to settle for 4 hours. Because dichloroethane is denser than water, the lower layer after settling is a dichloroethane oil phase, and the upper layer is an aqueous phase. The upper aqueous phase is returned to the absorption tower for recycling, while the lower oil phase proceeds to the next step of processing.

[0053] Step 4, Deep Dehydration: The lower dichloroethane oil phase is dehydrated using anhydrous sodium sulfate adsorption. 5% sodium sulfate is added by weight of the oil phase, stirred, and then filtered. After dehydration, the solvent water content is reduced to below 600 ppm, meeting industrial-grade requirements, and can be reused in the paint stripping process.

[0054] Treatment effect: The concentration of the purified exhaust gas at the outlet was 42 mg / m³, with a removal rate of 98.3%. This embodiment demonstrates that the method of the present invention is also applicable to the treatment of VOCs with a density greater than water, requiring only adjustment of the collection methods of the oil and water phases during the sedimentation step.

[0055] Example 4: Closed-loop dehydration cycle of sodium sulfate (preferred solution)

[0056] This embodiment treats the same thinner waste gas as in Embodiment 1, with steps one to three being the same as in Embodiment 1.

[0057] Step 4: Adsorption, dehydration, and regeneration of sodium sulfate:

[0058] (1) Adsorption and dehydration: The upper oil phase (containing about 8000 ppm of water) obtained in step 3 is fed into a dehydration tank with a stirrer, and anhydrous sodium sulfate (sodium sulfate powder) powder is added at 8% of the mass of the oil phase. The mixture is stirred at room temperature for 30 minutes. After absorbing the water in the oil phase, the sodium sulfate powder gradually transforms into sodium sulfate decahydrate crystals.

[0059] (2) Solid-liquid separation: The mixture is filtered through a 200-mesh filter bag, and the filtrate is the dehydrated organic solvent. The water content of the dehydrated solvent is determined by Karl Fischer method to be stable below 800 ppm, which meets the requirements for reuse and is directly sent back to the paint mixing process in the spraying workshop.

[0060] (3) Regeneration of crystallized salt: After collecting the sodium sulfate decahydrate crystals trapped in the filter bag, they are spread evenly in a regeneration tray with a heating jacket and heated to 120-150℃ for 2-3 hours. The sodium sulfate decahydrate loses its water of crystallization upon heating and is converted back into anhydrous sodium sulfate powder, which can be recycled for the dehydration of the next batch of solvent. The water vapor generated during the heating process is collected through a pipeline, naturally cooled, and then introduced into the absorbent storage tank of step one as a supplement to the absorbent.

[0061] System water balance calculation: Taking the treatment of 1000kg / h of waste gas as an example, the evaporation loss of the absorption tower is about 15kg / h, and the water recovery volume of the crystallization salt regeneration is about 18kg / h. The amount of recycled water can completely cover the evaporation loss, and the system does not require external replenishment of fresh water.

[0062] Technical benefits: This embodiment achieves a triple closed loop of "solvent recovery + dehydrating agent regeneration + water resource reuse". The sodium sulfate can be repeatedly recycled with a loss rate of less than 5%; the regenerated water vapor is directly reused in the absorption tower, with no secondary wastewater discharge; the entire system only requires replenishment of a small amount of sodium sulfate lost, resulting in extremely low operating costs.

[0063] Example 5: Deep dehydration of anhydrous magnesium sulfate (alternative solution)

[0064] This embodiment treats the same ethyl acetate waste gas as in Example 2, with steps one to three being the same as in Example 2.

[0065] Step 4: Anhydrous Magnesium Sulfate Adsorption and Dehydration: The upper oil phase obtained in Step 3 (containing approximately 8000 ppm of water) is fed into a dehydration tank equipped with a stirrer. Anhydrous magnesium sulfate powder is added at 6% of the oil phase mass, and the mixture is stirred at room temperature for 20 minutes. After absorbing the water from the oil phase, the anhydrous magnesium sulfate transforms into magnesium sulfate heptahydrate crystals, which are fine granules. The mixture is filtered through a 200-mesh filter bag, and the filtrate is the dehydrated organic solvent. The water content of the dehydrated solvent is consistently below 500 ppm, as determined by the Karl Fischer method.

[0066] Crystallized salt regeneration: The magnesium sulfate heptahydrate crystals trapped inside the filter bag are collected and dehydrated by heating at 120-150℃, reverting to anhydrous magnesium sulfate for recycling. Compared to sodium sulfate, magnesium sulfate absorbs water faster and its crystal form is easier to filter, making it particularly suitable for applications requiring high treatment efficiency.

[0067] Comparative Example 1: Treatment with water-soluble VOCs (ethanol)

[0068] This comparative example is used to illustrate that the present invention is not applicable to water-soluble alcohol VOCs.

[0069] Using the same process flow as in Example 1, ethanol-containing waste gas generated by a winery was treated with an air volume of 8000 m³ / h and a concentration of 1000 mg / m³.

[0070] Step 1, Washing and Absorption: Absorb with water. Ethanol will completely dissolve in water, forming a true solution, not an emulsion.

[0071] Step 2, centrifugal separation: Since ethanol is dissolved in water in a molecular state, the centrifuge cannot separate oil and water, and the absorption liquid does not show stratification.

[0072] Step 3, natural sedimentation: After standing for 24 hours, the absorbent liquid remains homogeneous and no oil phase precipitates.

[0073] Step 4, Deep Dehydration: Since there is no oil phase separation, subsequent dehydration cannot be carried out.

[0074] Results: Ethanol could not be recovered using this method; purification relied solely on absorption, which required replacement of the absorbent after saturation, resulting in a large amount of alcohol-containing wastewater. This comparative example demonstrates that the method of this invention is not suitable for the treatment of water-soluble alcohol VOCs.

[0075] Comparative Example 2: Treatment by Conventional Incineration

[0076] Using the same waste gas conditions as in Example 1 (thinner waste gas), a regenerative thermal oxidizer (RTO) was employed for incineration. The incineration temperature was 800°C, and the waste gas was oxidized and decomposed into CO2 and H2O within the furnace.

[0077] Calculations show that the comprehensive energy consumption for treating one ton of waste gas using this process is 96 kWh, and the equipment investment is 1.8 million yuan, which are 10 times and 3.5 times that of Example 1 of this invention, respectively. Furthermore, the organic matter is not recovered, resulting in resource waste.

[0078] Comparative Example 3: Conventional condensation method

[0079] The same exhaust gas conditions (ethyl acetate) as in Example 2 were used, and a two-stage condensation process was employed, with the first stage at 5°C and the second stage at -20°C.

[0080] Calculations show that the comprehensive energy consumption for treating one ton of waste gas using this process is 42 kWh, and the equipment investment is 1.35 million yuan, which are 5 times and 2.8 times that of Example 2 of this invention, respectively. The recovered ethyl acetate has a water content of approximately 2% and requires further distillation and purification before it can be reused.

[0081] Description of other implementation methods

[0082] It should be noted that the deep dehydration method described in this invention preferably employs physical adsorption or crystallization dehydration, such as adsorption and dehydration using salts that readily absorb water and crystallize, such as anhydrous sodium sulfate and anhydrous magnesium sulfate. While concentrated sulfuric acid is hygroscopic, it also possesses strong dehydrating, oxidizing, and sulfonating properties. When in contact with organic solvents such as esters and aromatics, it may trigger side reactions such as carbonization, sulfonation, and hydrolysis, leading to deterioration of the recovered solvent quality and posing serious safety risks and equipment corrosion problems. Therefore, it is not suitable for this invention.

[0083] The above examples and comparative examples demonstrate that the method of the present invention has excellent purification effects and resource recovery value for water-insoluble or slightly soluble VOCs such as esters, aromatics, and halogenated hydrocarbons. Its overall energy consumption and investment costs are significantly lower than those of incineration and condensation methods, and the recovered solvent can meet reuse requirements after deep dehydration. In the preferred embodiment, the use of anhydrous sodium sulfate and other crystalline salts for dehydration, along with the regeneration of the dehydrating agent and water vapor reuse, further reduces operating costs, achieves multiple closed-loop processes, and possesses extremely high industrial application value.

Claims

1. A method for purifying organic waste gas, characterized in that, Includes the following steps: Step 1, Washing and Absorption: Using water or brine as the absorbent, the volatile organic compounds (VOCs) in the waste gas are absorbed in the tower to form an emulsion containing VOCs. Step 2, centrifugal separation: The emulsion obtained in Step 1 is sent to a centrifuge, and under the action of centrifugal force, the VOCs emulsion in the absorption liquid is coarsened and separated from the aqueous phase; Step 3, Natural sedimentation: The absorbent liquid separated by centrifugation in step 2 is allowed to settle naturally in the storage tank, and the saturated aqueous phase at the bottom is reused for washing and absorption in step 1. Step 4: Deep dehydration: Deeply dehydrate the oil phase in the upper part of the storage tank in Step 3 to obtain organic matter with low water content.

2. The method according to claim 1, characterized in that, The washing and absorption in step one are performed continuously, while the centrifugation in step two is performed intermittently.

3. The method according to claim 2, characterized in that, The washing and absorption of the same VOCs in step one is carried out continuously in multiple sets of parallel towers. The absorbent liquid generated by the multiple sets of towers is collected and intermittently sent to a centrifuge for centrifugal separation in step two.

4. The method according to claim 1, characterized in that, The method described above does not include a cooling or condensation step for the absorbent or waste gas after the washing and absorption in step one and before the centrifugation in step two.

5. The method according to claim 1, characterized in that, The deep dehydration in step four is performed by adsorption and dehydration using inorganic salts that readily absorb water and form crystals. The inorganic salts are anhydrous sodium sulfate or anhydrous magnesium sulfate.

6. The method according to claim 5, characterized in that, The deep dehydration in step four specifically includes: adding inorganic salt to the oil phase, stirring and mixing to allow the inorganic salt to absorb water and form crystalline hydrates; separating the dehydrated oil phase by filtration; and heating the separated crystalline hydrates to dehydrate and regenerate them for recycling.

7. The method according to claim 6, characterized in that, The water vapor and VOCs generated during the heating and dehydration of the crystalline hydrate are recycled and purified in the washing and absorption process of step one.

8. The method according to claim 1, characterized in that, The tower is a spray tower, a packed tower, or a plate tower.

9. The method according to claim 1, characterized in that, The absorbent is water, sodium chloride solution, calcium chloride solution, or seawater.

10. The method according to claim 1, characterized in that, The centrifuge is a disc centrifuge, a tubular centrifuge, or a horizontal screw centrifuge.

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