A low- to medium-concentration malodorous gas purification process

Abstract

The present invention relates to the field of gas purification technology, specifically a medium and low concentration malodorous gas purification process. The present invention overcomes the problem of low waste gas purification efficiency. The present invention passes the malodorous gas into a pretreatment unit to obtain pretreatment gas, then enters the adsorption treatment unit to obtain adsorption treatment gas, then enters the biodegradation unit to obtain biological treatment gas, then enters the deep purification unit to obtain purified gas, and finally discharges it after meeting the indicators. The pretreatment unit can purify waste gas containing acidic / water-soluble pollutants, particulate matter, oil mist and suspended matter; the adsorption treatment unit is mainly aimed at hydrophobic pollutants, such as benzene series, some ketones, thiols, etc.; the biodegradation unit can effectively purify pollutants such as thiols, amines, low-level aldehydes, benzene series, esters, etc.; the deep purification unit can treat residual pollutants, such as high-ring aromatic hydrocarbons, halogenated hydrocarbons, and benzene series, aldehydes, ketone residues; each link together improves the efficiency of waste gas purification.

Description

Technical Field

[0001] The present invention relates to the technical field of gas purification, and in particular to a process for purifying low- to medium-concentration malodorous gases. Background Art

[0002] Microorganisms play a key role in the gas purification process. When waste gas is introduced into the biological purification tower, the rich and diverse microorganisms in the tower quickly capture the pollutants in the waste gas. The waste gas contains various complex pollutants such as benzene compounds, thiols, amines, aldehydes, esters, etc. These pollutants are the nutrient sources for the survival of microorganisms. Microorganisms can effectively treat these pollutants through precise and efficient biodegradation and biosynthesis mechanisms. Under the action of microorganisms, some of the pollutants are converted into nutrients necessary for the growth and reproduction of the microorganisms themselves, helping the microorganisms to thrive; while other parts are completely decomposed into carbon dioxide and water, so that the originally heavily polluted gas is gradually purified and becomes clean gas that meets emission standards.

[0003] Numerous industries generate this type of complex waste gas during their production processes. Sewage treatment plants release waste gas containing pollutants such as mercaptans and amines due to the decomposition of organic matter in wastewater. The food production industry produces aldehydes and esters during food processing and fermentation. The printing industry produces benzene compounds due to the volatilization of ink. The wood processing industry also releases various organic waste gases during processes such as wood drying and gluing. The chemical, coating, printing and dyeing, and rubber products industries generate even larger amounts of waste gas, which seriously pollutes the environment. Purifying these gases is therefore crucial.

[0004] With its unique advantages, biological methods occupy an important position in the field of medium and low concentration waste gas purification. Compared with other purification methods, biological methods have significant characteristics such as low cost and no secondary pollution. For medium and low concentration waste gas, microorganisms can fully exert their purification capabilities in a suitable environment and efficiently convert pollutants in the waste gas. In the biological purification tower, by reasonably controlling environmental conditions such as temperature, humidity, and pH value, an optimal living environment is created for microorganisms, enabling them to purify waste gas stably and continuously, thereby achieving effective treatment of low and medium concentration waste gas from various industries and making an important contribution to environmental protection. However, the problem of low waste gas purification efficiency still exists in the waste gas treatment process, which seriously affects the waste gas treatment effect.

[0005] Therefore, a low- to medium-concentration malodorous gas purification process is proposed. Summary of the Invention

[0006] The purpose of the present invention is to design a low- to medium-concentration malodorous gas purification process. The present invention subjects the malodorous gas to spraying and filtration treatment to obtain pre-treated gas, then subject it to activated carbon adsorption and biological pretreatment to obtain adsorption-treated gas, then subject it to three-layer biological treatment to obtain biologically treated gas, then subject it to photocatalytic treatment and ozone treatment to obtain purified gas, and finally discharge it if it meets the indicators, otherwise it will be re-purified. The pre-treatment unit of the present invention can purify waste gas containing acidic / water-soluble pollutants, particulate matter, oil mist and suspended matter, and also has a certain treatment effect on esters; the adsorption treatment unit is mainly aimed at hydrophobic pollutants that are difficult to degrade, such as benzene series, some ketones, and thiols in waste gas; the biodegradation unit can effectively purify biodegradable pollutants such as thiols, amines, low-level aldehydes, benzene series, esters, etc.; the deep purification unit can treat residual pollutants that are difficult to biodegrade, such as high-ring aromatic hydrocarbons, halogenated hydrocarbons, and trace amounts of benzene series, aldehydes, and ketone residues; each link together improves the efficiency of gas purification.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention provides a process for purifying low- to medium-concentration malodorous gases, the purification process comprising the following steps:

[0009] S1 passes the malodorous gas into the pretreatment unit, and obtains the pretreated gas after spraying and filtering;

[0010] S2 pre-treated gas enters the adsorption treatment unit and is adsorbed and treated by activated carbon and biological pre-treatment to obtain adsorbed gas;

[0011] The S3 adsorption treated gas enters the biodegradation unit and undergoes three-layer biological treatment to obtain biotreated gas. The filter bed in the biodegradation unit is composed of: the upper layer is a filter material containing Pseudomonas, the middle layer is a filter material containing Thiobacillus, and the lower layer is a filter material containing nitrifying bacteria and Alcaligenes faecalis, and is filled with a matrix filler, which includes activated carbon and cellulose.

[0012] S4 biological treatment gas enters the deep purification unit and is treated with photocatalysis and ozone to obtain purified gas;

[0013] The S5 purified gas enters the monitoring emission unit and is discharged if it meets the emission indicators. If it does not meet the indicators, it re-enters the adsorption treatment unit.

[0014] Preferably, the specific process of spraying treatment and filtering treatment is: the malodorous gas is passed into the pretreatment unit from bottom to top, and then sprayed and filtered through the spray tower and the filtering device in turn. The spray tower is equipped with a NaOH solution spray device with a spray intensity of 10-20m 3 / (m 2h), the mass fraction concentration of the NaOH solution is 2%-5%, the inlet temperature is controlled at 15°C, and the temperature in the spray tower is 25°C-35°C; when the gas from the spray tower enters the filtration device, the gas flow rate is controlled at 0.1m / s-0.5m / s, and the filtration device uses a high-efficiency fiber filter with a pore size of 3μm, and finally the pretreated gas is obtained.

[0015] Preferably, the specific process of activated carbon adsorption and biological pretreatment is: the composite activated carbon coating filler and the microbial activated carbon are loaded into the adsorption treatment unit in a weight ratio of 3:1, with the composite activated carbon coating filler at the bottom and the microbial activated carbon at the top, and the loading height is controlled at 1.2m-1.7m; the pretreated gas is passed from bottom to top into the adsorption treatment unit, passing through the composite activated carbon coating filler and the microbial activated carbon respectively, for activated carbon adsorption and biological pretreatment, the gas residence time is controlled to be 20s-40s, the temperature in the control unit is 35°C, and the humidity is 55% to obtain adsorption treated gas; the composite activated carbon coating filler includes polyurethane foam and nano activated carbon coating; the microbial activated carbon includes activated carbon and composite bacterial liquid.

[0016] Preferably, the preparation method of the composite activated carbon coating filler is as follows: dissolving 0.25 parts of copper nitrate and 0.5 parts of ferric nitrate in 50 parts of deionized water to form a mixed solution A; slowly adding 0.75 parts of butyl titanate to 50 parts of ethanol to form a solution B; slowly adding solution B to the mixed solution A under vigorous stirring, while adjusting the pH value to 8 to form a mixed sol; adding 5-10 parts of activated carbon to the mixed sol, stirring for 2 hours, and then transferring to a reactor, reacting at 150°C-180°C under self-increasing pressure for 12 hours, and washing and drying after the reaction. A composite material is obtained; the composite material is placed in a muffle furnace and calcined at 450°C for 2.5 hours with a heating rate of 5°C / min to finally obtain a nano-activated carbon composite material; the nano-activated carbon composite material, 2 parts of silica sol and 0.1 parts of sodium polyacrylate are placed in 50 parts of deionized water, stirred for 1 hour and then ball-milled for 5 hours to obtain a nano-activated carbon coating; polyurethane foam is used as a carrier, and the polyurethane foam is immersed in the nano-activated carbon coating for 5 minutes, and the impregnated carrier is taken out; the impregnated carrier is dried at 60°C for 20 hours and then cured at 160°C for 1.5 hours to obtain a composite activated carbon coating filler.

[0017] Preferably, the preparation method of microbial activated carbon is as follows: culturing Thiobacillus and Geotrichum candidum strains respectively, collecting the cultured Thiobacillus and Geotrichum candidum cells by centrifugation, and then resuspending them in sterile saline to prepare a concentration of 10 7 / mL composite bacterial liquid; put the activated carbon into the composite bacterial liquid, shake and soak for 18h-22h, and culture for 7 days after the inoculation is completed to obtain microbial activated carbon.

[0018] Preferably, the specific process of three-layer biological treatment is: the adsorbed treated gas is passed into the biodegradation unit from bottom to top, passing through the lower, middle and upper layers of the filter bed respectively, controlling the gas passage time to 100s-120s, and the filter bed temperature to 30℃-35℃ to obtain biological treatment gas.

[0019] Preferably, the filter material of the upper layer of the filter bed is a fiber ball inoculated with Pseudomonas, with a thickness of 40cm-60cm; the filter material of the middle layer is a polyurethane foam inoculated with Thiobacillus, with a thickness of 40cm-60cm; the filter material of the lower layer is ceramsite inoculated with nitrifying bacteria and Alcaligenes faecalis, with a thickness of 60cm-80cm; the filter bed is filled with a matrix filler, which includes activated carbon and cellulose, and the weight ratio of activated carbon to cellulose is 1-5:7; the inoculation process is: Pseudomonas, Thiobacillus, nitrifying bacteria and Alcaligenes faecalis are cultured separately, and then the cells are collected by centrifugation, and sterile saline is used to prepare them to a concentration of 10 7 Pseudomonas bacterial solution, Thiobacillus bacterial solution and mixed bacterial solution containing nitrifying bacteria and Alcaligenes faecalis were added, and then the fiber balls, polyurethane foam and ceramsite were immersed in the Pseudomonas bacterial solution, Thiobacillus bacterial solution and mixed bacterial solution respectively. After soaking for 20 hours, they were cultured for 7 days to obtain each layer of filter material.

[0020] Preferably, the specific process of photocatalysis and ozone treatment is as follows: the deep purification unit includes a photocatalytic reactor and an ozone processor, and the biological treatment gas is introduced into the photocatalytic reactor and the ozone processor from bottom to top to obtain purified gas; in the photocatalytic reactor, an ultraviolet lamp group with a wavelength of 254nm and 185nm is set, the power is 200W, and a TiO2 coating is coated on the inner wall of the photocatalytic reactor. The illumination time is 10min-30min, the temperature is controlled at 20℃-40℃, and the humidity is 40%-60%; the ozone dosage in the ozone processor is 100mg / m 3 -150mg / m 3 The residence time of biological treatment gas is 3min-7min.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. In the pretreatment unit, the present invention sprays NaOH solution in a spray tower to remove acidic / water-soluble pollutants in the exhaust gas, while reducing dust and adjusting the humidity to an appropriate range; the filtering device intercepts oil mist and suspended matter, protecting subsequent unit equipment from clogging or damage due to impurities, providing cleaner and more stable air intake conditions for subsequent treatment units, balancing fluctuations in exhaust gas concentration, and improving the stability of the overall purification process.

[0023] 2. The composite activated carbon coating filler in the adsorption treatment unit consists of polyurethane foam and nano-activated carbon coating. The nano-activated carbon coating is loaded with multiple metal oxides, enhancing the adsorption and catalytic synergy of hydrophobic pollutants. Thiobacillus and Geotrichum candidum in the microbial activated carbon biodegrade sulfur compounds, alcohols, aldehydes, and esters, further reducing pollutant concentrations. Furthermore, the unit buffers load shocks, preventing high-concentration pollutants from entering subsequent units and inhibiting microbial growth, thus ensuring the stable operation of the entire purification system.

[0024] 3. The activated carbon filling the filter bed in the biodegradation unit absorbs residual volatile organic compounds, while cellulose acts as a slow-release carbon source, providing a continuous nutrient supply for the microorganisms. As the gas flows upward through the layered biofilter, nitrifying bacteria in the lower layer convert amine pollutants into nitrates, while Alcaligenes faecalis gradually converts low-level aldehydes into acids, ultimately decomposing them into CO2. Thiobacilli in the middle layer oxidize and decompose mercaptans in the gas, while Pseudomonas in the upper layer degrades residual benzene and esters. This efficient and targeted degradation of multiple biodegradable pollutants significantly reduces the pollutant content in the exhaust gas.

[0025] 4. In the photocatalytic reactor of the deep purification unit, ultraviolet lamps of specific wavelengths drive the TiO2 coating to degrade trace amounts of pollutants such as benzene; the ozone processor produces strong oxidizing hydroxyl radicals to decompose residual pollutants such as aldehydes and ketones, further reducing the concentration of pollutants in the exhaust gas, making the purified gas closer to or reaching the emission standards, and improving the entire purification process's ability to handle complex and difficult-to-degrade pollutants.

[0026] 5. The final purified gas enters the monitoring emission unit, and the emission indicators are monitored in real time. Once it is found that the indicators are not met, the gas will be reintroduced into the adsorption treatment unit for re-purification to avoid the discharge of unqualified gas into the environment, ensuring the environmental protection compliance of the entire odorous gas purification process and effectively preventing environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Graph showing the mercaptan purification rates of gases in Example 15 of the present invention and Comparative Examples 18-21. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] Activated carbon: CAS: 7440-44-0; silica sol was purchased from Guangdong Huihe Silicon Products Co., Ltd.; Thiobacillus, Geotrichum candidum, Pseudomonas, nitrifying bacteria and alkali-producing rods were purchased from Ruichu Biotechnology (Jiangsu) Co., Ltd.; cellulose: CAS: 9004-34-6; fiber balls were purchased from Yixing Shengquan Water Treatment Equipment Co., Ltd.; polyurethane foam was purchased from Jiangsu Shuijingling Environmental Protection New Materials Co., Ltd.; and ceramsite was purchased from Gongyi Haoxin Water Purification Materials Co., Ltd.

[0030] Specific reference Figure 1 The present invention provides a low- to medium-concentration malodorous gas purification process, and the technical solution is as follows:

[0031] The method for determining the composition of exhaust gas in the present invention complies with the national standard. H2S is analyzed according to GB / T 11060.1-1998, NH3 is analyzed according to GB / T 14679-1993, methyl mercaptan, dimethyl sulfide, and ethyl mercaptan are analyzed according to GB / T 14678-1993, and volatile organic compounds are determined using Agilent 6890N. The chromatographic column is an HP-5 capillary column with a length of 30 m and the detector is an FID. The emission standard is GB16297-1996.

[0032] Example 1

[0033] 0.25 parts of copper nitrate and 0.5 parts of ferric nitrate were dissolved in 50 parts of deionized water to form a mixed solution A; 0.75 parts of butyl titanate were slowly added dropwise to 50 parts of ethanol to form a solution B; under vigorous stirring, solution B was slowly added dropwise to the mixed solution A while adjusting the pH value to 8 to form a mixed sol; 5 parts of activated carbon were added to the mixed sol, stirred for 2 hours, and then transferred to a reactor, reacted at 150°C under self-increasing pressure for 12 hours, and washed and dried after the reaction to obtain a composite material; the composite material was placed in a muffle furnace. , calcined at 450℃ for 2.5h with a heating rate of 5℃ / min to finally obtain a nano-activated carbon composite material; the nano-activated carbon composite material, 2 parts of silica sol and 0.1 part of sodium polyacrylate were put into 50 parts of deionized water, stirred for 1h and then ball-milled for 5h to obtain a nano-activated carbon coating; polyurethane foam was used as a carrier, and the polyurethane foam was immersed in the nano-activated carbon coating for 5min, and then taken out to obtain an impregnated carrier; the impregnated carrier was dried at 60℃ for 20h and then cured at 160℃ for 1.5h to obtain a composite activated carbon coating filler.

[0034] Thiobacillus and Geotrichum candidum strains were cultured separately, the cultured Thiobacillus and Geotrichum candidum were collected by centrifugation, and then resuspended with sterile saline to prepare a concentration of 10 7 / mL composite bacterial liquid; activated carbon was placed in the composite bacterial liquid, shaken and soaked for 18 hours, and cultured for 7 days after inoculation to obtain microbial activated carbon.

[0035] Pseudomonas, Thiobacillus, Nitrifying Bacteria and Alcaligenes faecalis were cultured separately, and then the cells were collected by centrifugation and prepared with sterile saline to a concentration of 10 7 Pseudomonas bacterial solution, Thiobacillus bacterial solution and mixed bacterial solution containing nitrifying bacteria and Alcaligenes faecalis were added, and then the fiber balls, polyurethane foam and ceramsite were immersed in the Pseudomonas bacterial solution, Thiobacillus bacterial solution and mixed bacterial solution respectively. After soaking for 20 hours, they were cultured for 7 days to obtain each layer of filter material.

[0036] The upper filter material of the filter bed is fiber balls inoculated with Pseudomonas, with a thickness of 40 cm; the middle filter material is polyurethane foam inoculated with Thiobacillus, with a thickness of 40 cm; the lower filter material is ceramsite inoculated with nitrifying bacteria and Alcaligenes faecalis, with a thickness of 60 cm; the filter bed is filled with matrix filler, which includes activated carbon and cellulose, and the weight ratio of activated carbon to cellulose is 1:7.

[0037] Purification process:

[0038] S1 passes the malodorous gas from bottom to top into the pretreatment unit, and then passes through the spray tower and the filter device for spraying and filtering. The spray tower is equipped with a NaOH solution spray device with a spray intensity of 10m 3 / (m 2 h), the mass fraction concentration of the NaOH solution is 2%, the inlet temperature is controlled at 15°C, and the temperature inside the spray tower is 25°C; when the gas from the spray tower enters the filtration device, the gas flow rate is controlled at 0.1m / s, and the filtration device uses a high-efficiency fiber filter with a pore size of 3μm, and finally the pretreated gas is obtained;

[0039] S2: The composite activated carbon coating filler and the microbial activated carbon are loaded into the adsorption treatment unit in a weight ratio of 3:1, with the composite activated carbon coating filler at the bottom and the microbial activated carbon at the top, and the loading height is controlled at 1.2m; the pretreated gas is passed into the adsorption treatment unit from bottom to top, and passes through the composite activated carbon coating filler and the microbial activated carbon respectively, for activated carbon adsorption and biological pretreatment, and the gas residence time is controlled to be 20s, and the temperature in the control unit is controlled to be 35°C and the humidity is controlled to be 55%, thereby obtaining the adsorbed treated gas;

[0040] S3 passes the adsorbed treated gas from bottom to top into the biodegradation unit, passing through the lower, middle and upper layers of the filter bed respectively, controlling the gas passage time to 100s and the filter bed temperature to 30°C, to obtain the biotreated gas;

[0041] The S4 deep purification unit includes a photocatalytic reactor and an ozone processor. The biological treatment gas is passed from bottom to top into the photocatalytic reactor and the ozone processor to obtain purified gas. In the photocatalytic reactor, a UV lamp group with a wavelength of 254nm and 185nm is set, with a power of 200W. The inner wall of the photocatalytic reactor is coated with a TiO2 coating. The illumination time is 10 minutes, the temperature is controlled at 20℃, and the humidity is 40%. The ozone dosage in the ozone processor is 100mg / m 3 , the residence time of biological treatment gas is 3min;

[0042] The S5 purified gas enters the monitoring emission unit and is discharged if it meets the emission indicators. If it does not meet the indicators, it re-enters the adsorption treatment unit.

[0043] Examples 2-4 refer to the parameter conditions in Example 1, and the specific differences are shown in Table 1.

[0044] Table 1 Parameter conditions of Examples 1-4

[0045]

[0046] Comparative Example 1 refers to the parameter conditions in Example 1, except that the solution sprayed in the spray tower is water.

[0047] Comparative Example 2 refers to the parameter conditions in Example 1, except that no spraying treatment is performed.

[0048] Comparative Example 3 refers to the parameter conditions in Example 1, except that the filtration device uses an ordinary filter screen.

[0049] Comparative Example 4 refers to the parameter conditions in Example 1, except that no filtering treatment is performed.

[0050] Comparative Example 5 refers to the parameter conditions in Example 1, except that no spraying treatment and filtration treatment are performed.

[0051] Experimental Example 1: Purification Effect Test

[0052] The exhaust gas composition is H2S1200mg / m 3 , NH32000mg / m 3 , methyl mercaptan 60mg / m 3 , dimethyl sulfide 50mg / m 3 , ethyl mercaptan 60mg / m 3 , volatile organic compounds 3600mg / m 3 ; The purification effect on exhaust gas was tested, and the results are shown in Table 2.

[0053] Table 2 Purification effect test of Examples 1-4 and Comparative Examples 1-5

[0054]

[0055]

[0056] Table 2 shows that the gas purification effect of the embodiment is relatively stable. In Comparative Example 1, the spray tower sprays water. Compared with the NaOH solution used in the embodiment, water is less effective at absorbing acidic gases. H2S is an acidic gas with relatively low solubility in water, while NaOH solution can react chemically with H2S, absorbing it more effectively. Therefore, using water as the spray liquid significantly reduces the H2S purification effect. Furthermore, the alkaline solution can alter the environment of the pretreatment unit, thereby affecting subsequent filtration and subsequent steps. In Comparative Example 2, no spray treatment is performed. Some pollutants in the exhaust gas cannot be removed during the pretreatment stage and directly enter the subsequent treatment unit, increasing the burden on the subsequent activated carbon adsorption unit, reducing adsorption efficiency, and affecting the living environment of microorganisms in the biological treatment unit. In Comparative Example 3, the filtration device uses a conventional filter screen. Conventional filter screens have lower filtration accuracy and efficiency than high-efficiency fiber filters, and their ability to intercept and remove particulate matter, aerosols, and some pollutants attached to particulate matter in the exhaust gas is relatively weak. In Comparative Example 4, without filtration, particulate matter and other impurities in the exhaust gas directly enter the adsorption treatment unit and biodegradation unit. This, on the one hand, clogs the pores of the activated carbon, reducing its adsorption capacity; on the other hand, it coats the surface of the biofilter media, hindering contact between microorganisms and pollutants, inhibiting microbial activity, and reducing biodegradation effectiveness. In Comparative Example 5, without spraying and filtration, pollutants in the exhaust gas that have not been removed by spraying, as well as a large amount of particulate matter and other impurities, directly enter the subsequent treatment units. This has a serious negative impact on various processes, including activated carbon adsorption and biodegradation, causing the activated carbon to rapidly fail, the biological treatment unit to fail to function properly, and photocatalysis and ozone treatment to struggle to effectively remove the large amount of remaining pollutants. Ultimately, the pollutant concentration in the purified gas far exceeds the emission standard, resulting in extremely poor exhaust gas purification results. Therefore, in the pretreatment unit, NaOH solution is sprayed in the spray tower to remove acidic / water-soluble pollutants in the exhaust gas, while reducing dust and adjusting the humidity to an appropriate range; the filter device intercepts oil mist and suspended matter to protect subsequent unit equipment from being blocked or damaged by impurities, providing cleaner and more stable air intake conditions for subsequent treatment units, balancing fluctuations in exhaust gas concentration, and improving the stability of the overall purification process.

[0057] Examples 5-8 refer to the parameter conditions in Example 3, and the specific differences are shown in Table 3.

[0058] Table 3 Parameter conditions of Example 3 and Examples 5-8

[0059]

[0060]

[0061] Comparative Example 6 refers to the parameter conditions in Example 3, except that activated carbon is used instead of the composite activated carbon coating filler.

[0062] Comparative Example 7 refers to the parameter conditions in Example 3, except that no composite activated carbon coating filler is added.

[0063] Comparative Example 8 refers to the parameter conditions in Example 3, except that activated carbon is used instead of microbial activated carbon.

[0064] Comparative Example 9 refers to the parameter conditions in Example 3, except that no microbial activated carbon is added.

[0065] Comparative Example 10 refers to the parameter conditions in Example 3, except that during filling, the composite activated carbon coating filler is on the top and the microbial activated carbon is on the bottom.

[0066] Comparative Example 11 refers to the parameter conditions in Example 3, except that activated carbon adsorption and biological pretreatment are not performed.

[0067] Experimental Example 2: Purification Effect Test

[0068] The exhaust gas purification effect was tested with reference to Experimental Example 1, and the results are shown in Table 4.

[0069] Table 4 Purification effect test of Example 3, Examples 5-8 and Comparative Examples 6-11

[0070]

[0071] Table 4 shows that the gas purification effects in all examples are good. In Comparative Example 6, activated carbon was used instead of the composite activated carbon-coated filler. Although activated carbon also has adsorption capacity, the composite activated carbon-coated filler has a more specialized structure and surface properties, making it more effective in adsorbing pollutants from the exhaust gas. Therefore, the purification effect was reduced after the activated carbon was used as a substitute. In Comparative Example 7, the composite activated carbon-coated filler was omitted. Without the adsorption function of the composite activated carbon-coated filler, pollutants in the exhaust gas could not be effectively adsorbed and removed by the filler, resulting in a significant decrease in the purification effect and a significant increase in the residual amount of various components in the exhaust gas. In Comparative Example 8, activated carbon was used instead of microbial activated carbon. Microbial activated carbon not only has the adsorption function of activated carbon but also contains microorganisms that can further remove pollutants from the exhaust gas through biodegradation. Replacing the microbial activated carbon with activated carbon eliminates this biodegradation process, affecting the purification effect and reducing the ability to remove pollutants from the exhaust gas. In Comparative Example 9, the microbial activated carbon was omitted. Without the adsorption and biodegradation functions of the microbial activated carbon, pollutants in the exhaust gas were difficult to effectively remove, significantly reducing the purification effect. In Comparative Example 10, after changing the loading order, the exhaust gas will not be able to contact the most suitable filler first, thereby affecting the purification efficiency and increasing the residual amount of pollutants in the exhaust gas. In Comparative Example 11, without activated carbon adsorption and biological pretreatment, the exhaust gas will directly enter the biological treatment unit, inhibiting the activity of microorganisms, and photocatalysis and ozone treatment will be difficult to effectively remove a large amount of residual pollutants. In summary, the composite activated carbon coating filler in the adsorption treatment unit contains a variety of metal oxides, which enhances the adsorption and catalytic synergy of hydrophobic pollutants; Thiobacillus and Geotrichum candidum in the microbial activated carbon biodegrade sulfur-containing compounds, alcohols, aldehydes and esters, further reducing the concentration of pollutants. At the same time, the unit can buffer the load shock, prevent high-concentration pollutants from instantly entering the subsequent units and inhibiting microorganisms, and ensure the stable operation of the entire purification system.

[0072] Examples 9-12 refer to the parameter conditions in Example 6, and the specific differences are shown in Table 5.

[0073] Table 5 Parameter conditions of Example 6 and Examples 9-12

[0074]

[0075] Comparative Example 12 refers to the parameter conditions in Example 6, except that no upper filter material is used.

[0076] Comparative Example 13 refers to the parameter conditions in Example 6, except that the middle layer filter material is not used.

[0077] Comparative Example 14 refers to the parameter conditions in Example 6, except that the lower layer filter material is not used.

[0078] Comparative Example 15 refers to the parameter conditions in Example 6, except that the upper filter material is polyurethane foam inoculated with Thiobacillus, the middle filter material is ceramsite inoculated with nitrifying bacteria and Alcaligenes faecalis, and the lower filter material is fiber balls inoculated with Pseudomonas.

[0079] Comparative Example 16 refers to the parameter conditions in Example 6, except that only the matrix filler is included in the filter bed.

[0080] Comparative Example 17 refers to the parameter conditions in Example 6, except that the three-layer biological treatment is not performed.

[0081] Experimental Example 3: Purification Effect Test

[0082] The exhaust gas purification effect was tested with reference to Experimental Example 1, and the results are shown in Table 6.

[0083] Table 6 Purification effect test of Example 6, Examples 9-12 and Comparative Examples 12-17

[0084]

[0085] It can be seen from Table 6 that the purification effect of the embodiment is relatively stable. In Comparative Example 12, not using the upper filter material will lead to a decrease in the treatment effect on some exhaust gas components. The upper filter material degrades benzene series and esters during the entire treatment process. Pseudomonas decomposes benzene series and esters as carbon sources and energy sources through metabolic activities. In Comparative Example 13, not using the middle filter material, lacking Thiobacillus, it is impossible to effectively remove sulfur-containing compounds such as thiols. In Comparative Example 14, not using the lower filter material will increase the content of various components in the treated exhaust gas. Nitrifying bacteria can convert amines into nitrates, and Alcaligenes faecalis converts aldehydes into acids, and finally into carbon dioxide and water, effectively removing amine and aldehyde pollutants in the exhaust gas. In Comparative Example 15, the distribution order of the filter materials was changed. Although the treatment capacity of each pollutant decreased, the treatment effect among the comparative examples was the best. In Comparative Example 16, the filter bed contained only matrix filler, without the addition of specific microorganisms or filter media. This significantly reduced the exhaust gas purification effect. The matrix filler itself had limited exhaust gas treatment capacity, lacking the decomposition and conversion effects of microorganisms. In Comparative Example 17, without the three-layer biological treatment, the synergistic effect of microorganisms in different layers of filter media could not be fully utilized to treat the exhaust gas. The three-layer biological treatment system is an optimized treatment system, with microorganisms in different layers having distinct treatment advantages for different exhaust gas components. Missing any layer or not performing the layered treatment would disrupt this synergistic effect, resulting in poor purification of various exhaust gas components. In summary, the activated carbon filled in the filter bed in the biodegradation unit can adsorb residual volatile organic compounds, and cellulose serves as a slow-release carbon source to provide a continuous nutrient supply for microorganisms; the gas passes through the layered biological filter bed from bottom to top, and the nitrifying bacteria in the lower bacterial community convert amine pollutants into nitrates, and Alcaligenes faecalis gradually converts low-level aldehydes into acids, which are eventually decomposed into CO2; the Thiobacillus in the middle layer oxidizes and decomposes the thiols in the gas; and the Pseudomonas in the upper layer degrades the residual benzene series and esters; achieving efficient and targeted degradation of a variety of biodegradable pollutants, greatly reducing the pollutant content in the exhaust gas.

[0086] Examples 13-16 refer to the parameter conditions in Example 10, and the specific differences are shown in Table 7.

[0087] Table 7 Parameters and conditions of Example 10 and Examples 13-16

[0088]

[0089] Comparative Example 18 refers to the parameter conditions in Example 10, except that the TiO2 coating is not applied inside the photocatalytic reactor.

[0090] Comparative Example 19 refers to the parameter conditions in Example 10, except that no photocatalytic treatment is performed.

[0091] Comparative Example 20 refers to the parameter conditions in Example 10, except that no ozone treatment is performed.

[0092] Comparative Example 21 refers to the parameter conditions in Example 10, except that no photocatalysis and ozone treatment are performed.

[0093] Experimental Example 4: Purification Effect Test

[0094] The purification effect of the exhaust gas was tested with reference to Experimental Example 1. The results are shown in Table 8. The mercaptan purification rates of the gases in Example 15 and Comparative Examples 18-21 are as follows: Figure 1 shown.

[0095] Table 8 Purification effect test of Example 10, Examples 13-16 and Comparative Examples 18-21

[0096]

[0097]

[0098] From Table 8 and Figure 1It can be found that the purification effects of the embodiments are all good. In Comparative Example 18, the TiO2 coating is not coated in the photocatalytic reactor. The TiO2 coating plays a key role in the photocatalytic process. It can generate photogenerated electron-hole pairs under the irradiation of ultraviolet light, and then generate active species such as hydroxyl radicals with strong oxidizing properties, which are used to degrade pollutants in the exhaust gas. Without the TiO2 coating, the photocatalytic reactor cannot effectively produce these active species, and the degradation ability of some difficult-to-degrade organic pollutants and some residual sulfur-containing and nitrogen-containing pollutants in the exhaust gas will be significantly reduced. In Comparative Example 19, no photocatalytic treatment is performed. Photocatalytic treatment is an important link in removing difficult-to-degrade pollutants in the exhaust gas in the deep purification unit. Without photocatalytic treatment, some organic pollutants remaining in the exhaust gas, such as high-boiling-point volatile organic compounds, some aromatic hydrocarbon compounds, etc., cannot be further decomposed into harmless small molecules through photocatalytic oxidation reactions. In Comparative Example 20, ozone treatment is not performed. Ozone has strong oxidizing properties and can decompose residual organic pollutants and some inorganic pollutants in the exhaust gas. Without ozone treatment, some pollutants such as aldehydes, ketones, and some sulfur-containing compounds in the exhaust gas that have not been completely removed by the previous treatment links cannot be oxidized and degraded by ozone. In Comparative Example 21, since photocatalysis and ozone treatment in the deep purification unit complement each other and deeply purify the exhaust gas together, without these two treatment steps, various volatile organic compounds, residual sulfur-containing and nitrogen-containing compounds in the exhaust gas cannot be effectively removed. Therefore, in the photocatalytic reactor of the deep purification unit, ultraviolet lamps of specific wavelengths drive the TiO2 coating to degrade trace pollutants such as benzene series; the ozone processor produces strongly oxidizing hydroxyl radicals to decompose residual pollutants such as aldehydes and ketones, further reducing the concentration of pollutants in the exhaust gas, making the purified gas closer to or reaching the emission standards, and improving the entire purification process's ability to treat complex and difficult-to-degrade pollutants.

[0099] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A process for purifying low to medium concentration malodorous gases, characterized by: The purification process comprises the following steps in parts by weight: S1 passes the malodorous gas into the pretreatment unit, and obtains the pretreated gas after spraying and filtering; S2: The pre-treated gas enters the adsorption treatment unit and is adsorbed and treated with activated carbon and biological pretreatment to obtain adsorbed gas; The specific process of the activated carbon adsorption and biological pretreatment is as follows: the composite activated carbon coating filler and the microbial activated carbon are loaded into the adsorption treatment unit in a weight ratio of 3:1, with the composite activated carbon coating filler at the bottom and the microbial activated carbon at the top, and the loading height is controlled to be 1.2m-1.7m; the pretreated gas is passed from bottom to top into the adsorption treatment unit, and passes through the composite activated carbon coating filler and the microbial activated carbon respectively, to perform the activated carbon adsorption and biological pretreatment, the gas residence time is controlled to be 20s-40s, the temperature in the control unit is controlled to be 35°C, and the humidity is controlled to be 55%, to obtain the adsorption treatment gas; the composite activated carbon coating filler includes polyurethane foam and nano-activated carbon coating; the microbial activated carbon includes activated carbon and composite bacterial liquid; The preparation method of the composite activated carbon coating filler is as follows: 0.25 parts of copper nitrate and 0.5 parts of ferric nitrate are dissolved in 50 parts of deionized water to form a mixed solution A; 0.75 parts of butyl titanate are slowly added dropwise to 50 parts of ethanol to form a solution B; under vigorous stirring, the solution B is slowly added dropwise to the mixed solution A, and the pH value is adjusted to 8 to form a mixed sol; 5-10 parts of the activated carbon are added to the mixed sol, stirred for 2 hours, and then transferred to a reactor, reacted at 150°C-180°C under self-increasing pressure for 12 hours, and washed and dried after the reaction to obtain a composite material; The composite material is placed in a muffle furnace and calcined at 450°C for 2.5 hours at a heating rate of 5°C / min to finally obtain a nano-activated carbon composite material; the nano-activated carbon composite material, 2 parts of silica sol and 0.1 parts of sodium polyacrylate are placed in 50 parts of deionized water, stirred for 1 hour and then ball-milled for 5 hours to obtain the nano-activated carbon coating; the polyurethane foam is used as a carrier, and the polyurethane foam is immersed in the nano-activated carbon coating for 5 minutes, and then taken out to obtain an impregnated carrier; the impregnated carrier is dried at 60°C for 20 hours and then cured at 160°C for 1.5 hours to obtain the composite activated carbon coating filler; The preparation method of the microbial activated carbon is as follows: culturing Thiobacillus and Geotrichum candidum strains respectively, centrifuging the cultured Thiobacillus and Geotrichum candidum to collect the bacterial bodies respectively, and then resuspending them in sterile physiological saline to prepare a concentration of 10 7 / mL of the composite bacterial liquid; placing the activated carbon into the composite bacterial liquid, shaking and soaking for 18h-22h, and culturing for 7 days after the inoculation to obtain the microbial activated carbon; S3: the adsorbed treated gas enters the biodegradation unit and undergoes three-layer biological treatment to obtain biotreated gas. The filter bed in the biodegradation unit is composed of: an upper layer of filter material containing Pseudomonas, a middle layer of filter material containing Thiobacillus, and a lower layer of filter material containing nitrifying bacteria and Alcaligenes faecalis, and is filled with a matrix filler, wherein the matrix filler includes the activated carbon and cellulose. The biologically treated gas in step S4 enters a deep purification unit and undergoes photocatalytic treatment and ozone treatment to obtain purified gas; In step S5, the purified gas enters the monitoring emission unit and is discharged if it meets the emission index. Otherwise, it re-enters the adsorption treatment unit if it does not meet the index.

2. The process for purifying low- to medium-concentration malodorous gases according to claim 1, characterized in that: The specific process of the spray treatment and filtration treatment is as follows: the malodorous gas is passed into the pretreatment unit from bottom to top, and the spray treatment and the filtration treatment are carried out in sequence through a spray tower and a filtration device, the spray tower is equipped with a NaOH solution spray device, the spray intensity is 10-20m³ / (m²・h), the mass fraction concentration of the NaOH solution is 2%-5%, the inlet temperature is controlled at 15°C, and the temperature in the spray tower is 25°C-35°C; when the gas coming out of the spray tower enters the filtration device, the gas flow rate is controlled at 0.1m / s-0.5m / s, the filtration device uses a high-efficiency fiber filter with a pore size of 3μm, and finally the pretreated gas is obtained.

3. The process for purifying low- to medium-concentration malodorous gases according to claim 1, characterized in that: The specific process of the three-layer biological treatment is: the adsorbed treatment gas is passed into the biodegradation unit from bottom to top, passing through the lower layer, middle layer and upper layer of the filter bed respectively, controlling the gas passage time to 100s-120s, and the filter bed temperature to 30℃-35℃ to obtain the biological treatment gas.

4. A low-concentration malodorous gas purification process according to claim 3, characterized in that: The filter material on the upper layer of the filter bed is a fiber ball inoculated with Pseudomonas, with a thickness of 40cm-60cm; the filter material on the middle layer is a polyurethane foam inoculated with Thiobacillus, with a thickness of 40cm-60cm; the filter material on the lower layer is ceramsite inoculated with nitrifying bacteria and Alcaligenes faecalis, with a thickness of 60cm-80cm; the filter bed is filled with a matrix filler, which includes activated carbon and cellulose, and the weight ratio of the activated carbon to the cellulose is 1-5:7; the inoculation process is: the Pseudomonas, the Thiobacillus, the nitrifying bacteria and the Alcaligenes faecalis are cultured respectively, and then the cells are collected by centrifugation respectively, and sterile physiological saline is used to prepare the concentrations of 10 7 Pseudomonas bacterial solution, Thiobacillus bacterial solution and a mixed bacterial solution containing the nitrifying bacteria and the Alcaligenes faecalis are prepared, and then the fiber balls, the polyurethane foam and the ceramsite are immersed in the Pseudomonas bacterial solution, the Thiobacillus bacterial solution and the mixed bacterial solution respectively, soaked for 20 hours and then cultured for 7 days to obtain each layer of filter material.

5. The process for purifying low- to medium-concentration malodorous gases according to claim 1, characterized in that: The specific process of the photocatalytic and ozone treatment is as follows: the deep purification unit includes a photocatalytic reactor and an ozone processor, and the biological treatment gas is passed from bottom to top into the photocatalytic reactor and the ozone processor to obtain the purified gas; in the photocatalytic reactor, an ultraviolet lamp group with a wavelength of 254nm and 185nm is set, and the power is 200W, a TiO2 coating is coated on the inner wall of the photocatalytic reactor, the illumination time is 10min-30min, the temperature is controlled at 20℃-40℃, and the humidity is 40%-60%; the ozone dosage in the ozone processor is 100mg / m³-150mg / m³, and the residence time of the biological treatment gas is 3min-7min.

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