Halogen waste gas purification method based on high-efficiency activated carbon

Abstract

The application discloses a kind of halogen waste gas purification methods based on high-efficiency activated carbon, belong to halogen waste gas treatment technical field.The method is sequentially treated halogen waste gas by four-step process of cyclone collision deoiling, high-voltage electrostatic coagulation, cryogenic dehumidification, composite modified activated carbon adsorption;Cryogenic dehumidification uses the demulsification filter material containing attapulgite, chitosan, anhydrous sodium sulfate to treat condensate, and the adsorption process uses the composite modified activated carbon adsorption bed composed of hydrophobic macroporous, oxidized modified mesoporous and transition metal-based supported microporous activated carbon layers arranged according to airflow direction.The application adapts to the working conditions of halogen waste gas high temperature and high humidity, high sticky gum and composite polar odor, effectively solves the problems of easy clogging, easy failure and insufficient adsorption specificity of activated carbon in traditional technology, realizes efficient and synergistic removal of multiple components in halogen waste gas, has high equipment operation stability and industrialization promotion value.

Description

Technical Field

[0001] This invention belongs to the field of brine waste gas treatment technology, specifically a brine waste gas purification method based on high-efficiency activated carbon. Background Technology

[0002] The processing of braised poultry products such as braised goose typically employs techniques like atmospheric pressure steaming, simmering in a rich broth, and heat preservation, continuously releasing large amounts of waste gas during production. This waste gas exhibits three main characteristics: high temperature and high humidity coupling, rich accumulation of highly viscous oily colloids, and complex odor components. Firstly, the relative humidity of the waste gas is consistently maintained above 85% year-round, resulting in a combination of high temperature and high humidity conditions. Secondly, it is rich in micron-sized, highly viscous oil mist formed by animal fats, collagen, and spice colloids. Thirdly, the odor components are complex, encompassing polar malodorous gases such as ammonia and hydrogen sulfide, as well as large molecular flavor substances like terpenes and esters. This waste gas differs from typical restaurant fumes and industrial VOCs, making conventional treatment methods difficult to directly address its characteristics.

[0003] Currently, the industry mostly uses conventional waste gas purification technologies to treat halogenated waste gas, which has limitations in practical application. For example, patent CN111111347B discloses a waste gas purification tower, including a tower body with a grid, spray pipes, activated carbon layer, and demister inside. Wastewater falling drives an impeller to rotate, which in turn moves a lower pressure block, achieving the effect of evenly dispersing dust at the discharge pipe opening and preventing blockage. While this solution solves the problem of particulate matter accumulation at the discharge outlet, its combination of spraying and activated carbon adsorption in treating halogenated waste gas does not fully consider the impact of high humidity during halogenation on adsorption performance. Water vapor easily competes with odor molecules for adsorption, shortening the effective lifespan of the activated carbon. Furthermore, this solution lacks targeted interception methods for highly viscous animal fats and collagen aerosols; oil deposits easily clog the pores of the activated carbon, exacerbating the decline in adsorption performance.

[0004] Patent CN113069876A discloses a waste gas purification device, including a shell, a water washing structure, an adsorption mechanism, and a decomposition mechanism, employing a multi-stage purification process of water washing + adsorption + decomposition. While this solution uses a multi-stage purification design, the single water washing tank combined with a water curtain structure has limited effectiveness in capturing micron-sized, highly viscous oil mist. Furthermore, the activated carbon is not specifically modified to target polar odorous gases such as ammonia and hydrogen sulfide, as well as large-molecule flavoring substances in the halogenated waste gas. This results in insufficient selectivity of the adsorption mechanism for complex odors, and the odor elimination effect needs improvement.

[0005] In summary, existing technologies are ill-suited to the conditions of high temperature and humidity, high viscosity and viscous substances, and the coexistence of complex polar odors in halogenated waste gas. They generally suffer from problems such as easy activation of activated carbon, easy clogging, and insufficient targeted adsorption. Therefore, developing a highly efficient activated carbon purification method for halogenated waste gas that is suitable for these conditions is of paramount importance. Summary of the Invention

[0006] The purpose of this invention is to provide a method for purifying halogenated waste gas based on high-efficiency activated carbon, so as to solve the problems that existing technologies are difficult to adapt to the working conditions of high temperature and high humidity, high viscosity and colloids, and coexistence of complex polar odors in halogenated waste gas, and that activated carbon is prone to clogging, failure, and insufficient adsorption specificity, so as to achieve high-efficiency purification of halogenated waste gas.

[0007] The objective of this invention is achieved through the following technical solution: A method for purifying halogenated waste gas based on high-efficiency activated carbon, characterized by comprising the following steps: S1. The halogenated waste gas to be treated is introduced into the cyclone collision deoiling zone. The oil droplets and condensate droplets in the waste gas are captured by centrifugal force and liquid film collision to obtain pre-dehydrated oily waste gas. S2. The pre-dehydrated oily waste gas is introduced into the high-voltage electrostatic condensation zone. Under the action of a DC electric field of 15-25kV, and with the aid of high-temperature resistant oleophobic agent spraying, the sticky oil film on the electrode plate is broken, so that the oil and grease particles in the waste gas are charged and condensed into a liquid film on the surface of the dust collecting electrode and flow out, thereby obtaining degummed waste gas. S3. The degummed waste gas is introduced into the cryogenic dehumidification zone, and the temperature of the waste gas is reduced to 15-25°C by a finned heat exchanger. The demulsifying filter material in the water collection pan is used to demulsify and remove the gummed material from the condensate, so that the water vapor in the waste gas is condensed and precipitated to obtain low-temperature and low-humidity waste gas. The compound demulsifying filter material includes attapulgite clay, chitosan, and anhydrous sodium sulfate; S4. The low-temperature and low-humidity waste gas is introduced into a composite modified activated carbon adsorption bed, which includes a hydrophobic macroporous activated carbon layer, an oxidized modified mesoporous activated carbon layer, and a transition metal-based supported microporous activated carbon layer arranged sequentially in the airflow direction. After adsorption treatment, purified gas is obtained.

[0008] Preferably, in step S2, the electrode spacing in the high-voltage electrostatic condensation zone is 30-50 mm, the electric field wind speed is 0.8-1.2 m / s, and the spraying rate of the oleophobic agent is 0.05-0.2 L / h.

[0009] Preferably, in step S3, the refrigerant inlet temperature of the finned heat exchanger is 5-10℃, and the residence time of the exhaust gas in the finned heat exchanger is 1.5-3.0s.

[0010] Preferably, in step S3, the mass ratio of attapulgite, chitosan, and anhydrous sodium sulfate in the compound demulsifying filter material is (5-7):(2-4):(1-2). In this scheme, attapulgite provides an adsorption framework, chitosan can break down the emulsified structure of oily and colloidal substances in the condensate, and anhydrous sodium sulfate plays a role in salting out and sedimentation. This is suitable for the characteristics of condensate from halogenated waste gas, making the demulsifying filter material more aligned with actual treatment needs. It can better decompose the oily and colloidal emulsion system in the condensate and reduce the clogging of drainage pipes.

[0011] Preferably, in step S4, the preparation method of the hydrophobic macroporous activated carbon layer is as follows: coal-based activated carbon with a pore size distribution of 50-100 nm is selected, and a diamond-like carbon film is deposited on the surface of the activated carbon using plasma-enhanced chemical vapor deposition (PECVD) at a working pressure of 10-30 Pa and a self-bias voltage of -150 to -300 V for a deposition time of 20-40 min. This method, by depositing a diamond-like carbon film on coal-based activated carbon with a specific pore size distribution using PECVD, can improve the hydrophobic properties of the activated carbon surface, reduce the adhesion of water vapor to the activated carbon surface, and simultaneously, the matched pore size distribution can better adsorb large-molecule oily odors in halogenated waste gas.

[0012] Preferably, in step S4, the preparation method of the oxidized modified mesoporous activated carbon layer is as follows: Fruit shell activated carbon with a pore size distribution of 2-50 nm is selected and placed in a 10%-20% (w / w) ammonium persulfate solution, oxidized at 60-80°C for 4-6 hours, followed by the introduction of polyethyleneimine for surface grafting; wherein the molecular weight of polyethyleneimine is 600-2000, the grafting reaction temperature is 50-70°C, and the reaction time is 8-15 hours. In this scheme, oxygen-containing functional groups are first formed on the surface of the activated carbon through ammonium sulfate oxidation treatment, and then polyethyleneimine of a specific molecular weight is introduced for grafting reaction, allowing suitable adsorption sites to be formed on the surface of the activated carbon, thereby improving the adsorption capacity for polar alkaline odorous gases such as ammonia and hydrogen sulfide.

[0013] Preferably, in step S4, the transition metal-based supported microporous activated carbon layer is a nano-titanium dioxide composite platinum-supported microporous activated carbon layer, the preparation method of which includes: selecting coconut shell activated carbon with a pore size of less than 2 nm, loading nano-titanium dioxide with a mass fraction of 3%-8% and platinum catalyst with a mass fraction of 0.5%-1.5% using an impregnation method, and then reducing the loaded activated carbon in a reducing atmosphere at 200-300℃ and a hydrogen volume percentage of 5%-10%.

[0014] In this scheme, nano-titanium dioxide and platinum catalyst are loaded by impregnation, followed by treatment in a reducing atmosphere, so that the catalyst can be loaded more uniformly and stably on the surface of activated carbon. The synergistic effect of nano-titanium dioxide and platinum catalyst can improve the deep adsorption effect of this type of large molecular odor, and further optimize the purification effect of halogenated waste gas.

[0015] Compared with the prior art, the beneficial effects of the present invention are: This invention effectively improves upon the problems of easy clogging, easy failure, and insufficient adsorption targeting of activated carbon in the treatment of halogenated waste gas by synergistically employing four-step processes: cyclone collision degreasing, high-voltage electrostatic condensation, cryogenic dehumidification, and composite modified activated carbon adsorption. Specific beneficial effects are as follows: In step S1, the halogenated waste gas is introduced into the cyclone collision deoiling zone, where centrifugal force and collision with the liquid film complete gas-liquid separation, capturing large oil droplets and condensate droplets in the waste gas, and initially removing highly viscous grease and some water vapor. This step can reduce the oil content of the waste gas, reduce the possibility of large oil droplets entering subsequent processes and causing equipment and pipeline blockage, and also reduce the interference of water vapor on subsequent electrostatic condensation and cryogenic dehumidification processes.

[0016] In step S2, the pre-dehydrated oily waste gas is introduced into the high-voltage electrostatic condensation zone. Under the action of a DC electric field, the micron-sized grease particles become charged and condense into a liquid film on the surface of the dust collecting electrode, flowing out. Simultaneously, a high-temperature resistant oleophobic agent is sprayed to break up the sticky oil film on the electrode plate, achieving the removal of micron-sized highly viscous colloids. The non-contact collection method of high-voltage electrostatic condensation can reduce the problems of filter screen clogging and pressure drop. In actual implementation, the electrode plate is prone to forming oil film scale due to the continuous adhesion of grease and colloids. The spraying of the oleophobic agent can not only solve the problem of electric field imbalance caused by such oil film scale, but also reduce equipment downtime caused by insulator condensation and creepage. The waste gas after removing the colloids can also reduce the pore blockage caused by sticky particles adhering to the subsequent activated carbon.

[0017] In step S3, condensation is used to dehumidify the exhaust gas, adjusting the humidity of the halogenated exhaust gas to a range suitable for activated carbon adsorption. This reduces competition from water vapor for adsorption and increases the adsorption capacity of activated carbon for odor components. In actual implementation, condensate water easily carries trace amounts of unremoved grease and colloids, forming an emulsion system. The compounded demulsifying filter material can decompose this emulsion system, reducing the likelihood of condensate water clogging the drainage pipes.

[0018] In step S4, the three-layer graded modified activated carbon can target the adsorption of odor components with different polarities and molecular weights in the halogenated waste gas: the hydrophobic macroporous activated carbon layer blocks residual moisture and adsorbs large-molecule oily odors; the oxidized modified mesoporous activated carbon layer adsorbs polar alkaline odor gases such as ammonia and hydrogen sulfide; and the transition metal-based supported microporous activated carbon layer deeply adsorbs large-molecule flavoring substances such as terpenes and esters. The three carbon layers work synergistically, combining physical and chemical adsorption to improve the removal efficiency of total VOCs and odor intensity.

[0019] In summary, this invention, through the coordinated operation of each process, can adapt to the working conditions of high temperature and humidity, high viscosity and viscous substances, and complex polar odors in brine waste gas. It improves the industry problems of poor purification efficiency, easy failure of activated carbon, and high equipment operation and maintenance costs in the prior art. While achieving the purification of brine waste gas, it extends the replacement cycle of consumables and reduces the frequency of equipment operation and maintenance, and has value for industrial promotion and application. Detailed Implementation

[0020] The following examples and comparative examples all use the continuously emitted braising waste gas from a braised goose processing workshop as the treatment object. The initial parameters of the waste gas are: temperature 55℃, relative humidity 89%, oil content 380mg / m³, ammonia concentration 36mg / m³, hydrogen sulfide concentration 11mg / m³, total VOCs concentration 280mg / m³ (mainly containing terpenes and ester macromolecular flavor substances), and odor intensity level 8.

[0021] Example 1 1. Preparation of some raw materials and composite modified activated carbon adsorption bed.

[0022] (1) Preparation of compound demulsifying filter material: Weigh attapulgite (the attapulgite is 80-200 mesh, modified attapulgite that has been dried at 200℃ and activated by hot air (moisture content ≤5%), with a specific surface area of ​​250-350 m² / g), chitosan, and anhydrous sodium sulfate at a mass ratio of 6:3:1; and use 1%... After dissolving in an aqueous acetic acid solution, it is thoroughly mixed with attapulgite clay and anhydrous sodium sulfate, and stirred until the system forms a kneadable wet powder (no drying is required; the wettability is achieved by utilizing the moisture in the aqueous acetic acid solution). The wet powder is fed into an extrusion granulator and granulated under pressure into 2-4 mm cylindrical particles. The particles are then placed in an 80℃ forced-air drying oven and dried to constant weight to obtain a compound demulsifying filter media (the static demulsification rate is ≥95% after testing). The obtained granular filter media is filled into a polypropylene filter media box to obtain a compound demulsifying filter media module (the filter media box has an opening rate of 60% to facilitate sufficient contact of condensate with the filter media).

[0023] (2) Preparation of hydrophobic macroporous activated carbon layer: Coal-based activated carbon with a pore size distribution of 50-100 nm was selected. Plasma-enhanced chemical vapor deposition was used with methane as the reactant gas and argon as the protective gas. The gas flow ratio was 1:8 and the radio frequency power was 150 W. Under the conditions of working pressure of 20 Pa and self-bias voltage of -200 V, a diamond-like carbon film was deposited on the surface of the activated carbon for 30 min to obtain hydrophobic macroporous activated carbon (the water contact angle was ≥110° after testing). It was then uniformly filled into a stainless steel carbon layer frame to obtain a hydrophobic macroporous activated carbon layer with a thickness of 15 cm.

[0024] (3) Preparation of oxidatively modified mesoporous activated carbon layer: Selected coconut shell activated carbon with a pore size distribution of 2-50 nm, placed in a 15% ammonium persulfate solution with a liquid-to-solid ratio of 5:1, and oxidized at 60-80℃ for 5 h. After filtration, it was repeatedly washed with deionized water until the filtrate was neutral, and dried at 105℃ to constant weight. Then, 8% polyethyleneimine aqueous solution with a molecular weight of 1200 was added with a liquid-to-solid ratio of 6:1. The pH of the system was adjusted to 6-7, and the grafting reaction was carried out at 60℃ for 12 h. After filtration, it was dried at 105℃ to constant weight to obtain oxidatively modified mesoporous activated carbon (the acidic functional group content was tested to be 2.5-3.2 mmol / g). It was uniformly filled into a stainless steel carbon layer frame to obtain an oxidatively modified mesoporous activated carbon layer with a thickness of 30 cm.

[0025] (4) Preparation of nano-titanium dioxide composite platinum supported microporous activated carbon layer: ① Using anhydrous ethanol as a solvent, first add chloroplatinic acid and stir until completely dissolved, then add γ-aminopropyltriethoxysilane (coupling agent) and mix and stir until the system is homogeneous; finally, slowly add tetrabutyl titanate and continue stirring to obtain a homogeneous and transparent ethanol impregnation solution; wherein, the mass fraction of tetrabutyl titanate converted to nano-titanium dioxide according to the theoretical yield of TiO2 is 5%, the mass fraction of chloroplatinic acid in the impregnation solution is 1.0%, and the amount of γ-aminopropyltriethoxysilane added is 0.8% of the total mass of the impregnation solution; ② Add coconut shell activated carbon with a pore size of less than 2nm to the above impregnation solution, the liquid-solid ratio of the impregnation solution to the coconut shell activated carbon is 4:1 (mass ratio), and ultrasonically impregnate at a frequency of 50kHz for 2h, stirring at a low speed of 300r / min during the ultrasonic process; after ultrasonic impregnation, slowly add deionized water to the system (molar ratio of tetrabutyl titanate to water is 1:4, dropping rate is 2mL / min, system pH is 0.8%). Hydrolyze the activated carbon at room temperature for 1 hour (controlled at 4.5-5.5%), then filter and dry it at 80℃ to constant weight. Place the dried activated carbon in a tube furnace and reduce it at 250℃ in a hydrogen-argon mixed reducing atmosphere with 8% hydrogen by volume for 4 hours to obtain nano-titanium dioxide composite platinum-stabilized microporous activated carbon. Fill the microporous activated carbon layer with nano-titanium dioxide composite platinum-supported microporous activated carbon with a thickness of 30 cm into a stainless steel carbon layer frame.

[0026] (5) Assembly of composite modified activated carbon adsorption bed: Make a stainless steel adsorption bed body, and fill it in sequence according to the airflow direction with the above-mentioned hydrophobic macroporous activated carbon layer, oxidized modified mesoporous activated carbon layer, and nano titanium dioxide composite platinum supported microporous activated carbon layer. The total height of the adsorption bed is 75cm and the designed filtration velocity is 0.3m / s.

[0027] 2. Assembly of process equipment.

[0028] The cyclone collision degreasing zone, high-pressure electrostatic condensation zone, cryogenic dehumidification zone (with built-in finned heat exchanger), and composite modified activated carbon adsorption bed are sequentially and sealed together via 304 stainless steel pipes to form a closed-loop halogenated waste gas purification device. The entire sealing device is then subjected to negative pressure leak testing to ensure a leakage rate of <3%.

[0029] Among them, ① the outer walls of the above-mentioned connecting pipes are all wrapped with 32°C heat tracing tape, and the heat tracing tape is wrapped with insulation cotton to prevent gaseous grease inside the pipe from condensing and adhering when it cools down. ② A fixed electrode plate and a barbed discharge electrode are installed in the high-voltage electrostatic condensation zone, and an oleophobic agent atomizing spray assembly (including atomizing nozzles and an oleophobic agent storage tank) is installed above the electrode plate. ③ A water collection tray is installed below the finned heat exchanger in the cryogenic dehumidification zone. The above-mentioned compound demulsifying filter media module is fixed in the water collection tray with a slot. The bottom of the water collection tray is connected to a U-shaped water seal drainage pipe. 3. Processing technology for purifying waste gas from braising.

[0030] After being collected by the workshop's gas collection hood, the brine-processing waste gas directly enters this purification device. The specific process steps are as follows: S1 Cyclone Collision Oil Removal: The halogenated waste gas to be treated is introduced into the cyclone collision oil removal zone at a speed of 20 m / s along the tangential direction. The cyclone blades are tilted at an angle of 38°. The inner wall of the oil removal zone is formed by external deionized water through atomizing nozzles to form a continuous liquid film (film thickness 2-3 mm). After the waste gas forms a cyclone in the zone, it collides with the liquid film on the wall with the help of centrifugal force, which efficiently captures large oil droplets and condensate droplets in the waste gas. After separation by a 0.7 m³ gas-liquid separation chamber, pre-dehydrated oily waste gas is obtained. The pressure drop in the oil removal zone is controlled at 400 Pa. The captured oil droplets and condensate are collected and treated through the bottom drain port.

[0031] S2 High-voltage electrostatic condensation: Pre-dehydrated oily waste gas is continuously introduced into the high-voltage electrostatic condensation zone. The electrode spacing within the zone is 40mm, the electric field velocity is 1.0m / s, and a 20kV DC electric field is applied, causing the micron-sized oil particles in the waste gas to become charged. Simultaneously, the oleophobic agent atomizing spray assembly is activated [(the spray assembly is isolated from the high-voltage electric field electrodes by a ceramic insulating support; the atomizing nozzles are made of non-metallic anti-static polytetrafluoroethylene material, effectively preventing electric field breakdown and short circuits; the spray assembly includes atomizing nozzles and an oleophobic agent storage tank; the high-temperature resistant oleophobic agent is a mixture of polyglycerol fatty acid ester and fluorinated silicone oil in a mass ratio of 4:1 (fluorinated silicone oil viscosity at 25℃ is 500-800cSt)], followed by a flow rate of 0.075L / h. The spray volume continuously sprays a high-temperature resistant oleophobic agent onto the electrode plate, breaking the sticky oil film on the electrode plate surface. Under the action of Coulomb force, the charged grease particles move towards the dust collecting electrode and condense into a liquid film that flows out, thus obtaining degummed waste gas. The pressure drop in the electrostatic zone is controlled at 150Pa, and the condensed oil film is collected and treated through the bottom drain port.

[0032] S3 Cryogenic Dehumidification: The degummed exhaust gas is continuously introduced into the cryogenic dehumidification zone. The refrigerant inlet temperature of the finned heat exchanger is 8℃, and the residence time of the exhaust gas in the heat exchanger is 2.2s. The exhaust gas temperature is precisely reduced to 20℃, and the saturated water vapor in the exhaust gas condenses and precipitates into the water collection pan below the heat exchanger. The condensate in the water collection pan comes into full contact with the compound demulsifying filter media module. The filter media demulsifies and removes the gum from the condensate, decomposing the oil and gum emulsion system in the condensate. The demulsified condensate is discharged through the U-shaped water seal drainage pipe. After dehumidification and demulsification treatment, low-temperature and low-humidity exhaust gas (relative humidity 60%) is obtained, and the pressure drop in the dehumidification zone is controlled at 300Pa.

[0033] S4 Composite Modified Activated Carbon Adsorption: Low-temperature and low-humidity waste gas is continuously passed through the composite modified activated carbon adsorption bed at a filtration velocity of 0.3 m / s. The waste gas passes through the hydrophobic macroporous activated carbon layer, the oxidized mesoporous activated carbon layer, and the nano-titanium dioxide composite platinum supported microporous activated carbon layer in sequence. After the directional adsorption and synergistic effect of the three carbon layers, purified gas is obtained.

[0034] Example 2 Compared to Example 1, only some parameters were adjusted; the preparation of other raw materials, assembly of the apparatus, and purification process remained the same as in Example 1. The specific adjustments are as follows: 1. Preparation of some raw materials and composite modified activated carbon adsorption bed.

[0035] The compound demulsifying filter media was prepared at a mass ratio of 5:2:1; Hydrophobic macroporous activated carbon layer: deposition time 20 min, carbon layer thickness 12 cm; Oxidation-modified mesoporous activated carbon layer: ammonium persulfate solution mass fraction 10%, polyethyleneimine grafting reaction time 8h, carbon layer thickness 28cm; Nano-titanium dioxide composite platinum supported microporous activated carbon layer: ultrasonic impregnation frequency 40kHz, reduction temperature 200℃, carbon layer thickness 28cm.

[0036] 3. Purification process parameters: S1 swirling collision oil removal exhaust gas velocity is 18m / s, pressure drop is controlled at 350Pa; S2 High-voltage electrostatic condensation electrode plate spacing 30mm, electric field wind speed 0.8m / s, DC electric field 15kV, oleophobic agent spraying rate 0.05L / h, pressure drop control 120Pa; S3 cryogenic dehumidifying refrigerant inlet temperature 5℃, exhaust gas residence time 1.5s, exhaust gas temperature reduced to 15℃, pressure drop controlled at 250Pa; The S4 composite modified activated carbon adsorption filtration velocity is 0.25 m / s.

[0037] Example 3 Compared to Example 1, only some parameters were adjusted; the preparation of other raw materials, assembly of the apparatus, and purification process remained the same as in Example 1. The specific adjustments are as follows: 1. Preparation of some raw materials and composite modified activated carbon adsorption bed.

[0038] The compound demulsifying filter media was prepared at a mass ratio of 7:4:2. Hydrophobic macroporous activated carbon layer: deposition time of 40 min by plasma-enhanced chemical vapor deposition, carbon layer thickness of 18 cm; Oxidation-modified mesoporous activated carbon layer: ammonium persulfate solution mass fraction 20%, polyethyleneimine grafting reaction time 15h, carbon layer thickness 32cm; Nano-titanium dioxide composite platinum supported microporous activated carbon layer: ultrasonic impregnation frequency 60kHz, reduction temperature 300℃, carbon layer thickness 32cm.

[0039] 2. Purification process parameters: S1 swirling collision oil removal exhaust gas velocity is 22m / s, pressure drop is controlled at 450Pa; S2 High-voltage electrostatic condensation electrode spacing 50mm, electric field wind speed 1.2m / s, DC electric field 25kV, oleophobic agent spraying rate 0.1L / h, pressure drop control 180Pa; S3 Cryogenic dehumidifying refrigerant inlet temperature 10℃, exhaust gas residence time 3.0s, exhaust gas temperature reduced to 25℃, pressure drop controlled at 350Pa; S4 Composite modified activated carbon adsorption filtration wind speed 0.35m / s.

[0040] Comparative Example 1 Compared to Example 1, only the S2 high-voltage electrostatic condensation step is removed, while the remaining raw material preparation, device assembly, and process parameters are the same as in Example 1; specifically, the pre-dehydrated oily waste gas after the S1 cyclone collision deoiling is directly introduced into the S3 cryogenic dehumidification zone.

[0041] Comparative Example 2 Compared to Example 1, the compound demulsifying filter media is replaced with single chitosan, while the preparation of other raw materials, assembly of the device, and process parameters are the same as in Example 1; specifically, in the S3 cryogenic dehumidification zone water collection tray, the compound demulsifying filter media module is replaced with an equal volume of pure chitosan filter media module.

[0042] Comparative Example 3 Compared to Example 1, the oleophobic agent atomizing spray component in the high-voltage electrostatic coagulation zone is removed, while the remaining raw material preparation, device assembly, and process parameters are the same as in Example 1. Specifically, in the S2 high-voltage electrostatic coagulation zone, only the electrode plate and DC electric field are retained. The oleophobic agent atomizing spray component is not installed, and the oleophobic agent spraying operation is not performed. The cohesive material is coagulated solely by the electric field.

[0043] Comparative Example 4 Compared to Example 1, the oxidatively modified mesoporous activated carbon layer was replaced with a conventional phosphoric acid modification process, while the preparation of other raw materials, equipment assembly, and process parameters were the same as in Example 1. Specifically, the oxidatively modified mesoporous activated carbon layer was prepared using conventional methods of existing technology: selected fruit shell activated carbon of the same pore size was placed in a 1 mol / L phosphoric acid solution with an acid-to-carbon mass ratio of 3:1, refluxed at 85°C for 8 hours, washed until neutral, and then dried.

[0044] Comparative Example 5 Compared to Example 1, the nano-titanium dioxide composite platinum-supported microporous activated carbon layer was replaced with a conventional copper nitrate-manganese nitrate metal oxide-supported activated carbon layer. The preparation of other raw materials, equipment assembly, and process parameters were the same as in Example 1. Specifically, coconut shell activated carbon with the same pore size was selected and impregnated in a mixed solution of copper nitrate and manganese nitrate in a molar ratio of 2:1, with a total metal ion concentration of 0.3 mol / L. After impregnation for 18 h, it was calcined at 380°C under a nitrogen atmosphere for 4 h to replace the original nano-titanium dioxide composite platinum-supported microporous activated carbon layer.

[0045] Comparative Example 6 Compared to Example 1, specifically: the hydrophobic macroporous activated carbon layer is replaced with a macroporous activated carbon layer of equal height and volume (pore size distribution same as Example 1); the oxidized modified mesoporous activated carbon layer is replaced with a mesoporous activated carbon layer of equal height and volume (pore size distribution same as Example 1); and the transition metal-based supported microporous activated carbon layer is replaced with a microporous activated carbon layer of equal height and volume (pore size distribution same as Example 1). All other raw material preparation, apparatus assembly, and process parameters are consistent with Example 1.

[0046] Comparative Example 7 Compared to Example 1, all pretreatment stages, including S1 cyclone collision deoiling, S2 high-voltage electrostatic condensation, and S3 cryogenic dehumidification, were directly eliminated. The halogenated waste gas was collected by a gas collection hood and then directly introduced into the unmodified graded activated carbon adsorption bed in Comparative Example 6 (the hydrophobic macroporous activated carbon layer was replaced with an unmodified macroporous activated carbon layer of the same height and volume with the same pore size, the oxidized mesoporous activated carbon layer was replaced with an unmodified mesoporous activated carbon layer of the same height and volume with the same pore size, and the transition metal-based supported microporous activated carbon layer was replaced with an unmodified microporous activated carbon layer of the same height and volume with the same pore size). The remaining adsorption bed operating parameters and detection methods were the same as in Example 1.

[0047] Experimental Example To verify the treatment efficiency of the brine waste gas purification method of the present invention, experiments were conducted on Examples 1-3 and Comparative Examples 1-7. All experiments were repeated three times in parallel, with a relative standard deviation (RSD) ≤ 5%. The average value was taken as the final result (as shown in Table 1). Specific detection indicators and methods are as follows: 1. Removal effect of core pollutants in brine processing exhaust gas: ① Grease removal rate: The grease content of the original waste gas and the treated waste gas was determined by infrared spectrophotometry and calculated according to the formula: Grease removal rate = (Original waste gas grease content - Treated waste gas grease content) / Original waste gas grease content × 100%; ② Ammonia removal rate: The ammonia concentration was determined by Nessler's reagent spectrophotometry and calculated according to the above formula; ③ Hydrogen sulfide removal rate: The concentration of hydrogen sulfide was determined by methylene blue spectrophotometry and calculated according to the above formula; ④ Total VOCs removal rate (including terpenes and esters): The total VOCs concentration was determined by gas chromatography, and the concentrations of terpenes and esters were determined separately by gas chromatography-mass spectrometry (GC-MS). The results were calculated according to the formula above. ⑤ Odor intensity: The three-point comparison odor bag method is used for measurement, and the level is 1-8. The lower the value, the better the odor removal effect.

[0048] 2. Operational stability of the activated carbon adsorption bed: Pressure drop of activated carbon bed after 30 days of operation: The pressure difference between the inlet and outlet of the adsorption bed was measured using a micro differential pressure gauge, and the final pressure drop value was recorded after 30 days of continuous operation. The lower the pressure drop, the better the operation stability, indicating that the pores of the activated carbon are not blocked by colloidal substances.

[0049] 3. Operational stability of equipment in the high-voltage electrostatic condensation zone: Continuous trouble-free operation time in the electrostatic zone: Record the continuous operation time of the high-voltage electrostatic condensation zone from startup to plate scaling / electric field imbalance. The longer the duration, the better the adaptability to high-viscosity adhesive conditions.

[0050] Table 1: Note: "-" in Table 1 indicates that this test was not conducted because the core performance indicators of the relevant groups did not meet the requirements of the halogenated waste gas treatment conditions, and there was no need for further testing.

[0051] As can be seen from Table 1: Examples 1-3 effectively solve the problems of easy clogging, easy failure, and insufficient adsorption targeting of activated carbon in traditional brine waste gas treatment technologies. They are suitable for the high temperature, high humidity, high viscosity, and complex polar odor conditions of brine waste gas, meeting the requirements of industrial purification of brine waste gas. Specifically, the removal rates of grease are all >98%, ammonia removal rates are all ≥96.2%, hydrogen sulfide removal rates are all ≥96.8%, total VOCs removal rates are all ≥96.8%, and terpene and ester removal rates are all ≥96.3%, achieving efficient and synergistic removal of multiple pollutants in brine waste gas. The pressure drop of the activated carbon bed after 30 days of operation is ≤850Pa, which greatly improves the operational stability of activated carbon and extends the service life of consumables. The continuous fault-free operation time of the electrostatic zone is >350h, ensuring the stable operation of the pretreatment section and reducing the frequency of equipment maintenance.

[0052] In Comparative Example 1, the removal of the S2 high-voltage electrostatic coagulation step prevented the effective removal of micron-sized grease and colloids, leading to rapid blockage of the activated carbon bed pores by the colloids. This resulted in a sharp increase in pressure drop after 30 days and a significant decrease in the removal efficiency of various odor pollutants. In Comparative Example 2, replacing the compound demulsifying filter media with single chitosan eliminated the synergistic demulsification effect of the components, reducing the decomposition effect on the grease and colloid emulsion system in the condensate. This resulted in a decrease in the removal rate of total VOCs and characteristic components, and an increase in odor intensity. In Comparative Example 3, the removal of the oleophobic agent atomizing spray component in the high-voltage electrostatic coagulation zone caused rapid scaling and oil film formation on the plates, leading to an imbalance in the electric field. The continuous fault-free operation time in the electrostatic zone was only 48 hours, with frequent equipment shutdowns, which indirectly increased the pressure drop of the activated carbon bed and slightly reduced the adsorption effect. In Comparative Example 4, replacing the oxidically modified mesoporous activated carbon layer with a conventional phosphoric acid modification process failed to create suitable adsorption sites, reducing the adsorption capacity for polar alkaline odorous gases such as ammonia and hydrogen sulfide, thus becoming a bottleneck in odor removal. Consequently, the removal rates of total VOCs and characteristic components decreased. In Comparative Example 5, replacing the nano-titanium dioxide composite platinum-supported microporous activated carbon layer with a conventional copper nitrate-manganese nitrate metal oxide loading process resulted in poor catalyst loading stability and synergistic adsorption effect. The deep adsorption capacity for terpenes and ester macromolecular flavor substances was insufficient, leading to poor total VOCs removal rate and odor intensity. In Comparative Example 6, replacing the three-layer modified activated carbon layer with an unmodified activated carbon layer of the same pore size resulted in the loss of the hydrophobic and deep catalytic adsorption properties brought by the modification. Relying solely on staged packing could not achieve effective adsorption of complex odors, and the removal rates of all pollutants decreased. In Comparative Example 7, because all pretreatment stages were eliminated and the raw halogenated waste gas was directly introduced into the unmodified graded activated carbon adsorption bed, the highly viscous grease and a large amount of water vapor directly blocked the pores of the activated carbon, causing the activated carbon to deactivate rapidly. The removal rates of various pollutants decreased significantly, and the pressure drop after 30 days surged to 3200 Pa. The odor intensity still reached level 6, which fully demonstrates the synergistic effect of the pretreatment stage and the modified activated carbon adsorption bed in this invention.

Claims

1. A method for purifying halogenated waste gas based on high-efficiency activated carbon, characterized in that, Includes the following steps: S1. The halogenated waste gas to be treated is introduced into the cyclone collision deoiling zone. The oil droplets and condensate droplets in the waste gas are captured by centrifugal force and liquid film collision to obtain pre-dehydrated oily waste gas. S2. The pre-dehydrated oily waste gas is introduced into the high-voltage electrostatic condensation zone. Under the action of a DC electric field of 15-25kV, and with the aid of high-temperature resistant oleophobic agent spraying, the sticky oil film on the electrode plate is broken, so that the oil and grease particles in the waste gas are charged and condensed into a liquid film on the surface of the dust collecting electrode and flow out, thereby obtaining degummed waste gas. S3. The degummed waste gas is introduced into the cryogenic dehumidification zone, and the temperature of the waste gas is reduced to 15-25°C by a finned heat exchanger. The demulsifying filter material in the water collection pan is used to demulsify and remove the gummed material from the condensate, so that the water vapor in the waste gas is condensed and precipitated to obtain low-temperature and low-humidity waste gas. The compound demulsifying filter material includes attapulgite clay, chitosan, and anhydrous sodium sulfate; S4. The low-temperature and low-humidity waste gas is introduced into a composite modified activated carbon adsorption bed, which includes a hydrophobic macroporous activated carbon layer, an oxidized modified mesoporous activated carbon layer, and a transition metal-based supported microporous activated carbon layer arranged sequentially in the airflow direction. After adsorption treatment, purified gas is obtained.

2. The method for purifying halogenated waste gas based on high-efficiency activated carbon according to claim 1, characterized in that, In step S2, the electrode spacing in the high-voltage electrostatic condensation zone is 30-50mm, the electric field wind speed is 0.8-1.2m / s, and the spraying rate of the oleophobic agent is 0.05-0.2L / h.

3. The method for purifying halogenated waste gas based on high-efficiency activated carbon according to claim 1, characterized in that, In step S3, the refrigerant inlet temperature of the finned heat exchanger is 5-10℃, and the residence time of the exhaust gas in the finned heat exchanger is 1.5-3.0s.

4. The method for purifying halogenated waste gas based on high-efficiency activated carbon according to claim 1, characterized in that, In step S3, the mass ratio of attapulgite, chitosan and anhydrous sodium sulfate in the compound demulsifying filter material is (5-7):(2-4):(1-2).

5. The method for purifying halogenated waste gas based on high-efficiency activated carbon according to claim 1, characterized in that, In step S4, the preparation method of the hydrophobic macroporous activated carbon layer is as follows: coal-based activated carbon with a pore size distribution of 50-100nm is selected, and a diamond-like carbon film is deposited on the surface of the activated carbon using plasma-enhanced chemical vapor deposition at a working pressure of 10-30Pa and a self-bias voltage of -150~-300V for a deposition time of 20-40min.

6. The method for purifying halogenated waste gas based on high-efficiency activated carbon according to claim 1, characterized in that, In step S4, the preparation method of the oxidized modified mesoporous activated carbon layer is as follows: select coconut shell activated carbon with a pore size distribution of 2-50 nm, place it in a 10%-20% ammonium persulfate solution, oxidize it at 60-80℃ for 4-6 h, and then introduce polyethyleneimine for surface grafting reaction; wherein, the molecular weight of polyethyleneimine is 600-2000, the grafting reaction temperature is 50-70℃, and the reaction time is 8-15 h.

7. The method for purifying halogenated waste gas based on high-efficiency activated carbon according to claim 1, characterized in that, In step S4, the transition metal-based supported microporous activated carbon layer is a nano-titanium dioxide composite platinum-supported microporous activated carbon layer. Its preparation method includes: selecting coconut shell activated carbon with a pore size of less than 2 nm, loading nano-titanium dioxide with a mass fraction of 3%-8% and platinum catalyst with a mass fraction of 0.5%-1.5% using an impregnation method, and then reducing the loaded activated carbon in a reducing atmosphere of 200-300℃ and 5%-10% hydrogen by volume.

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