Middle and low concentration malodorous gas purification process

Abstract

The invention relates to the technical field of gas purification, in particular to a medium-low concentration malodorous gas purification process. The problem that the waste gas purification efficiency is low is solved. The malodorous gas is introduced into the pretreatment unit to obtain pretreated gas, then the pretreated gas enters the adsorption treatment unit to obtain adsorption treated gas, then the adsorption treated gas enters the biodegradation unit to obtain biological treated gas, then the adsorption treated gas enters the deep purification unit to obtain purified gas, and finally the purified gas is discharged after meeting indexes. Wherein the pretreatment unit can be used for purifying waste gas containing acidic / water-soluble pollutants, particulate matters, oil mist and suspended matters; the adsorption treatment unit mainly aims at hydrophobic pollutants, such as benzene series, part of ketones, mercaptan and the like; the biodegradation unit can effectively purify pollutants such as mercaptan, amines, low-grade aldehydes, benzene series and esters; the deep purification unit can be used for treating residual pollutants, such as high-cyclic aromatic hydrocarbon, halogenated hydrocarbon, benzene series, aldehydes and ketone residues; all links jointly improve the waste gas purification efficiency.

Description

Technical Field

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

[0002] Microorganisms play a key role in the process of gas purification. When the 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 series compounds, mercaptans, amine ketones, aldehydes, and esters. These pollutants are exactly the nutrient sources for microorganisms to survive. Through precise and efficient biological decomposition and biosynthesis mechanisms, microorganisms can effectively process these pollutants. Some of these pollutants are converted into nutrients necessary for the growth and reproduction of microorganisms themselves under the action of microorganisms, helping the microorganisms to thrive; while the other part is completely decomposed into carbon dioxide and water, so that the originally severely polluted gas is gradually purified into a clean gas that meets the emission standards.

[0003] Many industries will generate such complex waste gases during the production process. When a sewage treatment plant treats sewage, due to the decomposition of organic matter in the sewage, waste gases containing pollutants such as mercaptans and amines will be released; in the food production industry, during food processing, fermentation and other links, aldehyde and ester waste gases will be generated; in the printing industry, due to the volatilization of ink, benzene series compound waste gases will be generated; in the wood processing industry, during wood drying, gluing and other processes, various organic waste gases will also be released; industries such as chemical engineering, coating, printing and dyeing, and rubber products will generate a large amount of waste gases, which seriously pollute the environment. Therefore, it is crucial to purify these gases.

[0004] The biological method occupies an important position in the field of medium- and low-concentration waste gas purification due to its unique advantages. Compared with other purification methods, the biological method has significant characteristics such as low cost and no secondary pollution. For medium- and low-concentration waste gases, microorganisms can fully exert their purification ability in a suitable environment and efficiently convert the 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 stably and continuously purify the waste gas, thereby effectively treating medium- and low-concentration waste gases from various industries and contributing an important force to environmental protection. However, there is still a problem of low waste gas purification efficiency in the process of waste gas treatment, which seriously affects the waste gas treatment effect.

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

[0006] The object of the present invention is to design a purification process for malodorous gases with medium and low concentrations. In the present invention, the malodorous gas is subjected to spray treatment and filtration treatment to obtain a pretreated gas, then subjected to activated carbon adsorption and biological pretreatment to obtain an adsorbed and treated gas, then subjected to three-layer biological treatment to obtain a biologically treated gas, then subjected to photocatalytic treatment and ozone treatment to obtain a purified gas, and finally discharged after meeting the standards, and if not meeting the standards, it is purified again. The pretreatment unit of the present invention can purify waste gases containing acidic / hydrophilic pollutants, particulate matter, oil mist and suspended matter, and also has a certain treatment effect on esters; the adsorption treatment unit mainly targets recalcitrant hydrophobic pollutants such as benzene series, some ketones, and mercaptans in the waste gas; the biodegradation unit can effectively purify biodegradable pollutants such as mercaptans, amines, lower aldehydes, benzene series, esters, etc.; the deep purification unit can treat recalcitrant residual pollutants such as polycyclic aromatic hydrocarbons, halogenated hydrocarbons, and trace residues of benzene series, aldehydes, and ketones; each link jointly 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 purification process for malodorous gases with medium and low concentrations, and the purification process includes the following steps:

[0009] S1 The malodorous gas is introduced into the pretreatment unit, and after spray treatment and filtration treatment, a pretreated gas is obtained;

[0010] S2 The pretreated gas enters the adsorption treatment unit, and after activated carbon adsorption and biological pretreatment, an adsorbed and treated gas is obtained;

[0011] S3 The adsorbed and treated gas enters the biodegradation unit, and after three-layer biological treatment, a biologically treated gas is obtained. The composition of the filter bed in the biodegradation unit is: the upper layer is a filter material containing Pseudomonas, the middle layer is a filter material containing Thiobacillus, the lower layer is a filter material containing Nitrobacter and Alcaligenes faecalis, and a matrix filler is filled. The matrix filler includes activated carbon and cellulose;

[0012] S4 The biologically treated gas enters the deep purification unit, and after photocatalytic treatment and ozone treatment, a purified gas is obtained;

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

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

[0015] Preferably, the specific process of activated carbon adsorption and biological pretreatment is as follows: The composite activated carbon-coated filler and microbial activated carbon are filled into the adsorption treatment unit according to a weight ratio of 3:1. The composite activated carbon-coated filler is at the bottom and the microbial activated carbon is at the top, and the filling height is controlled at 1.2 m - 1.7 m; the pretreated gas is introduced into the adsorption treatment unit from bottom to top, passing through the composite activated carbon-coated filler and microbial activated carbon respectively, for activated carbon adsorption and biological pretreatment. The gas residence time is controlled at 20 s - 40 s, the temperature inside the unit is controlled at 35°C, and the humidity is 55%, to obtain the adsorbed treatment gas; the composite activated carbon-coated filler includes polyurethane foam and a nano-activated carbon coating; the microbial activated carbon includes activated carbon and a composite bacterial solution.

[0016] Preferably, by weight, the preparation method of the composite activated carbon-coated filler is as follows: Dissolve 0.25 parts of copper nitrate and 0.5 parts of iron nitrate in 50 parts of deionized water to form a mixed solution A; slowly drip 0.75 parts of tetrabutyl titanate into 50 parts of ethanol to form a solution B; under vigorous stirring, slowly drip solution B into mixed solution A while adjusting the pH value to 8 to form a mixed sol; put 5 - 10 parts of activated carbon into the mixed sol, stir for 2 h and then transfer to a reaction kettle, react at 150°C - 180°C under self-rising pressure for 12 h, and after the reaction, wash and dry to obtain a composite material; put the composite material into a muffle furnace, calcine at 450°C for 2.5 h, with a heating rate of 5°C / min, and finally obtain a nano-activated carbon composite material; put the nano-activated carbon composite material, 2 parts of silica sol and 0.1 part of sodium polyacrylate into 50 parts of deionized water, stir for 1 h and then ball mill for 5 h to obtain a nano-activated carbon coating; use polyurethane foam as a carrier, immerse the polyurethane foam in the nano-activated carbon coating for 5 min, take it out to obtain an impregnated carrier; dry the impregnated carrier at 60°C for 20 h and then cure it at 160°C for 1.5 h to obtain the composite activated carbon-coated filler.

[0017] Preferably, the preparation method of the microbial activated carbon is as follows: Cultivate thiobacillus and Geotrichum candidum strains respectively. Centrifuge and collect the thalli of the cultivated thiobacillus and Geotrichum candidum, and then resuspend them with sterile normal saline to prepare a composite bacterial solution with a concentration of 10 7 cells / mL; put the activated carbon into the composite bacterial solution, oscillate and soak for 18 h - 22 h, and after inoculation, culture for 7 days to obtain the microbial activated carbon.

[0018] Preferably, the specific process of the three-layer biological treatment is as follows: the adsorption-treated gas is introduced into the biodegradation unit from bottom to top, passing through the lower, middle, and upper layers of the filter bed respectively. The gas passing time is controlled at 100 s - 120 s, and the filter bed temperature is controlled at 30°C - 35°C to obtain the biologically treated gas.

[0019] Preferably, the upper-layer filter material of the filter bed is fiber balls inoculated with Pseudomonas, with a thickness of 40 cm - 60 cm; the middle-layer filter material is polyurethane foam inoculated with Thiobacillus, with a thickness of 40 cm - 60 cm; the lower-layer filter material is ceramsite inoculated with Nitrobacter and Alcaligenes faecalis, with a thickness of 60 cm - 80 cm. The filter bed is filled with a matrix filler, and the matrix filler includes activated carbon and cellulose, and the weight ratio of activated carbon to cellulose is 1 - 5:7. The inoculation process is as follows: Pseudomonas, Thiobacillus, Nitrobacter, and Alcaligenes faecalis are cultured respectively, and then the thalli are collected by centrifugation respectively, and are respectively prepared into Pseudomonas bacterial liquid, Thiobacillus bacterial liquid, and a mixed bacterial liquid containing Nitrobacter and Alcaligenes faecalis with a concentration of 10 7 CFU / mL. Then, the fiber balls, polyurethane foam, and ceramsite are respectively immersed in the Pseudomonas bacterial liquid, Thiobacillus bacterial liquid, and mixed bacterial liquid, and after soaking for 20 h, they are cultured for 7 days to obtain the filter materials of each layer.

[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. The biologically treated gas is introduced into the photocatalytic reactor and the ozone processor from bottom to top to obtain the purified gas. In the photocatalytic reactor, an ultraviolet lamp group with wavelengths of 254 nm and 185 nm is set, with a power of 200 W. A TiO 2 coating is applied on the inner wall of the photocatalytic reactor, the illumination time is 10 min - 30 min, the temperature is controlled at 20°C - 40°C, and the humidity is 40% - 60%. The dosage of ozone in the ozone processor is 100 mg / m 3 -150 mg / m 3 , and the residence time of the biologically treated gas is 3 min - 7 min.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1. In the pretreatment unit of the present invention, the NaOH solution in the spray tower is sprayed to remove acidic / hydrophilic pollutants in the waste gas, while reducing dust and adjusting the humidity to a suitable range. The filtering device intercepts oil mist and suspended matter, protects the equipment of the subsequent units, and prevents them from being blocked or damaged by impurities, providing cleaner and more stable inlet conditions for the subsequent treatment units, balancing the fluctuation of the waste gas concentration, and improving the stability of the overall purification process.

[0023] 2. The composite activated carbon coated filler in the adsorption treatment unit includes polyurethane foam and a nano-activated carbon coating. The nano-activated carbon coating is loaded with various metal oxides, enhancing the adsorption and catalytic synergy for hydrophobic pollutants. Thiobacillus and Geotrichum candidum in the microbial activated carbon decompose sulfur-containing compounds, alcohols, aldehydes, and ester pollutants biologically, further reducing the pollutant concentration. At the same time, this unit can buffer the load impact, prevent high-concentration pollutants from instantly entering the subsequent unit and inhibiting the microorganisms, and ensure the stable operation of the entire purification system.

[0024] 3. The activated carbon filled in the filter bed of the biodegradation unit can adsorb residual volatile organic compounds. Cellulose serves as a slow-release carbon source, providing continuous nutrient supply for the microorganisms. The gas passes through the stratified biological filter bed from bottom to top. Nitrifying bacteria in the lower-layer flora convert amine pollutants into nitrates, and Alcaligenes faecalis gradually converts lower aldehydes into acids and finally decomposes them into CO 2 ; Thiobacillus in the middle layer oxidizes and decomposes thiols in the gas; Pseudomonas in the upper layer degrades residual benzene series and esters; achieving efficient and targeted degradation of various biodegradable pollutants and greatly reducing the pollutant content in the waste gas.

[0025] 4. In the photocatalytic reactor of the deep purification unit, an ultraviolet lamp with a specific wavelength drives the TiO 2 coating to degrade trace benzene series and other pollutants; the ozone processor generates strongly oxidizing hydroxyl radicals to decompose residual pollutants such as aldehydes and ketones, further reducing the pollutant concentration in the waste gas, making the purified gas closer to or meet the emission standards, and enhancing the treatment ability of the entire purification process for complex and refractory pollutants.

[0026] 5. The finally purified gas enters the monitoring and emission unit to monitor the emission indicators in real time. Once it is found that the indicators do not meet the standards, the gas is re-introduced into the adsorption treatment unit for re-purification, avoiding the emission of unqualified gas into the environment, ensuring the environmental compliance of the entire malodorous gas purification process, and effectively preventing environmental pollution. Description of the Drawings

[0027] Figure 1 It is a graph of the mercaptan purification rate of the gas in Example 15 of the present invention and Comparative Examples 18 - 21. Detailed Embodiments

[0028] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0029] Activated carbon: CAS: 7440-44-0; silica sol was purchased from Guangdong Huihe Silica Products Co., Ltd.; Thiobacillus, Geotrichum candidum, Pseudomonas, Nitrobacter and Alcaligenes faecalis were purchased from Rechu 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.; ceramsite was purchased from Gongyi Haoxin Water Purification Materials Co., Ltd.

[0030] Specifically refer to Figure 1 , the present invention provides a purification process for medium and low concentration malodorous gases, and the technical solution is as follows:

[0031] In the present invention, the method for measuring the composition of the waste gas complies with the national standard. H 2 S is analyzed by GB / T 11060.1-1998, NH 3 is analyzed by GB / T14679-1993, methyl mercaptan, dimethyl sulfide and ethyl mercaptan are analyzed by GB / T 14678-1993, volatile organic compounds are determined by Agilent 6890N, the chromatographic column is HP-5 capillary column with a length of 30m, and the detector is FID; the emission standard is GB16297-1996 standard.

[0032] Example 1

[0033] Dissolve 0.25 parts of copper nitrate and 0.5 parts of iron nitrate in 50 parts of deionized water to form a mixed solution A; slowly drop 0.75 parts of tetrabutyl titanate into 50 parts of ethanol to form a solution B; under vigorous stirring, slowly drop solution B into mixed solution A while adjusting the pH value to 8 to form a mixed sol; put 5 parts of activated carbon into the mixed sol, stir for 2h and then transfer to a reaction kettle, react at 150 °C under self-elevating pressure for 12h, wash and dry after the reaction to obtain a composite material; put the composite material into a muffle furnace, calcine at 450 °C for 2.5h, and the heating rate is 5 °C / min to finally obtain a nano-activated carbon composite material; put the nano-activated carbon composite material, 2 parts of silica sol and 0.1 part of sodium polyacrylate into 50 parts of deionized water, stir for 1h and then ball mill for 5h to obtain a nano-activated carbon coating; use polyurethane foam as the carrier, immerse the polyurethane foam in the nano-activated carbon coating for 5min, take it out to obtain an impregnated carrier; dry the impregnated carrier at 60 °C for 20h and then cure it at 160 °C for 1.5h to obtain a composite activated carbon coating filler.

[0034] Culture Thiobacillus and Geotrichum candidum strains respectively, centrifuge and collect the thalli of the cultured Thiobacillus and Geotrichum candidum respectively, and then resuspend them with sterile normal saline to prepare a composite bacterial solution with a concentration of 10 7 cells / mL; put the activated carbon into the composite bacterial solution, oscillate and soak for 18h, and culture for 7 days after inoculation to obtain microbial activated carbon.

[0035] Pseudomonas, Thiobacillus, Nitrobacter, and Alcaligenes faecalis were cultured separately. Then, the cells were collected by centrifugation and separately prepared into Pseudomonas bacterial solution, Thiobacillus bacterial solution, and a mixed bacterial solution containing Nitrobacter and Alcaligenes faecalis with a concentration of 10 7 cells / mL. Subsequently, fiber balls, polyurethane foams, and ceramsites were immersed in the Pseudomonas bacterial solution, Thiobacillus bacterial solution, and mixed bacterial solution respectively. After soaking for 20 h, they were cultured for 7 days to obtain each layer of filter media.

[0036] The upper-layer filter media of the filter bed is fiber balls inoculated with Pseudomonas, with a thickness of 40 cm; the middle-layer filter media is polyurethane foams inoculated with Thiobacillus, with a thickness of 40 cm; the lower-layer filter media is ceramsites inoculated with Nitrobacter and Alcaligenes faecalis, with a thickness of 60 cm; the filter bed is filled with matrix fillers, and the matrix fillers include activated carbon and cellulose, and the weight ratio of activated carbon to cellulose is 1:7.

[0037] Purification process:

[0038] S1 The malodorous gas is introduced into the pretreatment unit from bottom to top and sequentially undergoes spraying treatment and filtration treatment through a spray tower and a filtration device. A NaOH solution spraying device is equipped in the spray tower, with a spraying intensity of 10 m 3 / (m 2 ·h), the mass fraction concentration of the NaOH solution is 2%, the inlet liquid temperature is controlled at 15°C, and the temperature in the spray tower is 25°C; when the gas coming out of the spray tower enters the filtration device, the gas flow rate is controlled at 0.1 m / s, and the filtration device uses a high-efficiency fiber filter screen with a pore size of 3 μm to finally obtain the pretreated gas;

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

[0040] S3 The adsorbed treatment gas is introduced into the biodegradation unit from bottom to top and passes through the lower layer, middle layer, and upper layer of the filter bed respectively. The gas passing time is controlled at 100 s, and the filter bed temperature is controlled at 30°C to obtain the biologically treated gas;

[0041] The S4 deep purification unit includes a photocatalytic reactor and an ozone processor. The biologically treated 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 wavelengths of 254 nm and 185 nm is set, with a power of 200 W. A TiO 2 coating is applied on the inner wall of the photocatalytic reactor. The illumination time is 10 min, the temperature is controlled at 20 °C, and the humidity is 40%; the dosage of ozone in the ozone processor is 100 mg / m 3 , and the residence time of the biologically treated gas is 3 min;

[0042] The purified gas enters the monitoring and emission unit. If it meets the emission standards, it is discharged; if it does not meet the standards, 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 carried out.

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

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

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

[0051] Experimental Example 1 Purification effect test

[0052] The waste gas composition is H 2 S1200 mg / m 3 , NH 3 2000 mg / m 3 , methanethiol 60 mg / m 3 , dimethyl sulfide 50 mg / m 3 , ethanethiol 60 mg / m 3 , volatile organic compounds 3600 mg / m 3 ; The purification effect on the waste 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] It can be found from Table 2 that the purification effect of the examples on gases is relatively stable. In Comparative Example 1, the solution sprayed in the spray tower is water. Compared with the NaOH solution used in the examples, water has a poorer absorption effect on acidic gases. H 2 S is an acidic gas and has a relatively low solubility in water, while the NaOH solution can react chemically with H 2 S and absorb H 2 S more effectively. Therefore, when water is used as the spray liquid, the purification effect on H 2 S will be significantly reduced; and the alkaline solution can change the environment of the pretreatment unit, thus affecting the subsequent filtration effect and subsequent steps. In Comparative Example 2, no spray treatment is carried out, and some pollutants in the waste gas cannot be removed in the pretreatment stage and will directly enter the subsequent treatment unit, resulting in an increased burden on the subsequent activated carbon adsorption unit and a decline in the adsorption effect. The living environment of microorganisms in the biological treatment unit will also be affected. In Comparative Example 3, the filtering device uses an ordinary filter screen, and the filtering accuracy and efficiency of the ordinary filter screen are lower than those of the high-efficiency fiber filter screen, and the ability to intercept and remove particulate matter, aerosol, and some pollutants attached to the particulate matter in the waste gas is weak. In Comparative Example 4, no filtering treatment is carried out, and impurities such as particulate matter in the waste gas will directly enter the adsorption treatment unit and the biodegradation unit. On the one hand, it will block the pores of the activated carbon and reduce the adsorption capacity of the activated carbon. On the other hand, it will cover the surface of the biological filter material, hinder the contact between microorganisms and pollutants, inhibit the activity of microorganisms, and reduce the biodegradation effect. In Comparative Example 5, no spray treatment and no filtering treatment are carried out, and the pollutants in the waste gas that are not removed by the spray treatment and a large amount of impurities such as particulate matter directly enter the subsequent treatment unit, which will have a serious negative impact on various links such as activated carbon adsorption and biodegradation, resulting in the rapid failure of the activated carbon and the inability of the biological treatment unit to function properly. It is also difficult for photocatalysis and ozone treatment to effectively remove a large amount of remaining pollutants. Finally, the pollutant concentration in the purified gas will far exceed the emission standard, and the waste gas purification effect is extremely poor. Therefore, in the pretreatment unit, the NaOH solution in the spray tower is used for spraying to remove acidic / hydrophilic pollutants in the waste gas, while reducing dust and adjusting the humidity to a suitable range; the filtering device intercepts oil mist and suspended matter, protects the subsequent unit equipment, prevents it from being blocked or damaged by impurities, provides cleaner and more stable inlet conditions for the subsequent treatment unit, balances the fluctuation of the waste gas concentration, and improves 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 referred to the parameter conditions in Example 3, with the difference that activated carbon was used to replace the composite activated carbon coating filler.

[0062] Comparative Example 7 referred to the parameter conditions in Example 3, with the difference that the composite activated carbon coating filler was not added.

[0063] Comparative Example 8 referred to the parameter conditions in Example 3, with the difference that activated carbon was used to replace microbial activated carbon.

[0064] Comparative Example 9 referred to the parameter conditions in Example 3, with the difference that microbial activated carbon was not added.

[0065] Comparative Example 10 referred to the parameter conditions in Example 3, with the difference that during filling, the composite activated carbon coating filler was on top and the microbial activated carbon was at the bottom.

[0066] Comparative Example 11 referred to the parameter conditions in Example 3, with the difference that no activated carbon adsorption and biological pretreatment were carried out.

[0067] Experimental Example 2 Purification effect test

[0068] Referring to Experimental Example 1, the purification effect on the waste gas was tested, 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] It can be found from Table 4 that the gas purification effects in the examples are all good. In Comparative Example 6, activated carbon was used to replace the composite activated carbon-coated filler. Although activated carbon also has adsorption capacity, the composite activated carbon-coated filler has a more special structure or surface properties and can more effectively adsorb pollutants in the waste gas. After using activated carbon to replace it, the purification effect will decline. In Comparative Example 7, the composite activated carbon-coated filler was not added. Without the adsorption effect of the composite activated carbon-coated filler, the pollutants in the waste gas cannot be effectively adsorbed and removed by this filler, and the purification effect will be significantly worse, and the residual amounts of various components in the waste gas will increase significantly. In Comparative Example 8, activated carbon was used to replace the microbial activated carbon. The microbial activated carbon not only has the adsorption effect of activated carbon, but also contains microorganisms. These microorganisms can further remove pollutants in the waste gas through biodegradation. After using activated carbon to replace the microbial activated carbon, the biodegradation link is lost, and the purification effect will be affected, and the ability to remove pollutants in the waste gas will be reduced. In Comparative Example 9, the microbial activated carbon was not added. Without the adsorption and biodegradation effects of the microbial activated carbon, the pollutants in the waste gas are difficult to be effectively removed, and the purification effect will be greatly reduced. In Comparative Example 10, after changing the filling order, it will cause the waste gas not to contact the most suitable filler first, thereby affecting the purification efficiency and increasing the residual amount of pollutants in the waste gas. In Comparative Example 11, without activated carbon adsorption and biological pretreatment, the waste gas will directly enter the biological treatment unit, inhibiting the microbial activity, and it is difficult for photocatalysis and ozone treatment to effectively remove a large amount of remaining pollutants. In summary, the composite activated carbon-coated filler in the adsorption treatment unit contains various metal oxides, enhancing the adsorption and catalytic synergy of hydrophobic pollutants; Thiobacillus and Geotrichum candidum in the microbial activated carbon biodegrade sulfur-containing compounds, alcohols, aldehydes and ester pollutants, further reducing the pollutant concentration. At the same time, this unit can buffer the load impact, prevent high-concentration pollutants from instantly entering the subsequent unit 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, and the difference is that the upper filter material is not used.

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

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

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

[0079] Comparative Example 16 referred to the parameter conditions in Example 6, with the difference that there was only a matrix filler in the filter bed.

[0080] Comparative Example 17 referred to the parameter conditions in Example 6, with the difference that three - layer biological treatment was not carried out.

[0081] Experimental Example 3 Purification Effect Test

[0082] Referring to Experimental Example 1, the purification effect on the waste gas was tested, 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] As can be seen from Table 6, the purification effect of the examples is relatively stable. In Comparative Example 12, not using the upper filter material will lead to a decrease in the treatment effect on some waste gas components. The upper filter material degrades benzene series compounds and esters during the whole treatment process. Pseudomonas metabolizes benzene series compounds and esters as carbon sources and energy sources for decomposition. In Comparative Example 13, not using the middle filter material and lacking Thiobacillus, sulfur-containing compounds such as mercaptans cannot be effectively removed. In Comparative Example 14, not using the lower filter material will increase the content of various components in the treated waste gas. Nitrobacter 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 waste gas. In Comparative Example 15, changing the distribution order of the filter materials, although the treatment ability for each pollutant decreases, it has the best treatment effect among the comparative examples. In Comparative Example 16, there is only the matrix filler in the filter bed, without adding specific microorganisms and filter materials, which will greatly reduce the waste gas purification effect. The matrix filler itself has limited treatment ability for waste gas, lacking the decomposition and transformation effects of microorganisms. In Comparative Example 17, without three-layer biological treatment, the synergistic effect of microorganisms in different layers of filter materials cannot be fully utilized to treat waste gas. The three-layer biological treatment is an optimized treatment system. Microorganisms in different layers have their own treatment advantages for different waste gas components. Lacking any layer or not performing stratified treatment will destroy this synergistic effect, resulting in a worse purification effect for various components in the waste gas. In summary, the activated carbon filled in the filter bed in the biodegradation unit can adsorb residual volatile organic compounds, and cellulose, as a slow-release carbon source, provides continuous nutrient supply for microorganisms; the gas passes through the stratified biological filter bed from bottom to top. Nitrobacter in the lower-layer flora converts amine pollutants into nitrates, and Alcaligenes faecalis gradually converts lower aldehydes into acids, and finally decomposes into CO 2 ; Thiobacillus in the middle layer oxidizes and decomposes mercaptans in the gas; Pseudomonas in the upper layer degrades residual benzene series compounds and esters; realizing the efficient and targeted degradation of various biodegradable pollutants, greatly reducing the pollutant content in the waste 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 Parameter Conditions of Example 10 and Examples 13 - 16

[0088]

[0089] Comparative Example 18 refers to the parameter conditions in Example 10, with the difference that the TiO 2 coating is not applied in the photocatalytic reactor.

[0090] Comparative Example 19 refers to the parameter conditions in Example 10, with the difference that photocatalytic treatment is not carried out.

[0091] Comparative Example 20 referred to the parameter conditions in Example 10, with the difference that ozone treatment was not carried out.

[0092] Comparative Example 21 referred to the parameter conditions in Example 10, with the difference that photocatalysis and ozone treatment were not carried out.

[0093] Experimental Example 4 Purification Effect Test

[0094] Referring to Experimental Example 1 to test the purification effect on the waste gas, the results are shown in Table 8. The mercaptan purification rates of the gas in Example 15 and Comparative Examples 18 - 21 are as 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 1 it can be found that the purification effects of the examples are all good. In Comparative Example 18, the TiO 2 coating was not applied in the photocatalytic reactor. The TiO 2 coating plays a key role in the photocatalytic process. It can generate photoexcited electrons - hole pairs under the irradiation of ultraviolet light, and then generate reactive species such as hydroxyl radicals with strong oxidizing ability, which are used to degrade pollutants in the waste gas. Without the TiO 2 coating, the photocatalytic reactor cannot effectively generate these reactive species, and the degradation ability for some refractory organic pollutants and some residual sulfur - and nitrogen - containing pollutants in the waste gas will decrease significantly. In Comparative Example 19, photocatalytic treatment was not carried out. Photocatalytic treatment is an important link for removing refractory pollutants in the waste gas in the deep purification unit. Without photocatalytic treatment, some residual organic pollutants in the waste gas, such as high - boiling - point volatile organic compounds and some aromatic hydrocarbon compounds, cannot be further decomposed into harmless small - molecule substances through photocatalytic oxidation reactions. In Comparative Example 20, ozone treatment was not carried out. Ozone has strong oxidizing ability and can decompose residual organic pollutants and some inorganic pollutants in the waste gas. Without ozone treatment, some pollutants such as aldehydes, ketones, and some sulfur - containing compounds that were not completely removed in the previous treatment steps in the waste gas 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 jointly carry out deep purification of the waste gas, without these two treatment steps, various volatile organic compounds, residual sulfur - and nitrogen - containing compounds, etc. in the waste gas cannot be effectively removed. Therefore, in the photocatalytic reactor of the deep purification unit, a specific - wavelength ultraviolet lamp drives the TiO 2The coating degrades trace pollutants such as benzene series compounds; the ozone processor generates strongly oxidizing hydroxyl radicals to decompose residual pollutants such as aldehydes and ketones, further reducing the concentration of pollutants in the waste gas, making the purified gas closer to or meet the emission standards, and enhancing the treatment capacity of the entire purification process for complex and difficult-to-degrade pollutants.

[0099] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A low to medium concentration malodorous gas purification process, characterized in that: The purification process comprises the following steps: S1 passes the malodorous gas into a pretreatment unit, and obtains pretreated gas after spraying and filtering; S2: The pre-treated gas enters the adsorption treatment unit, and is adsorbed and treated by activated carbon and biological pre-treatment to obtain adsorbed gas; S3: the adsorbed treated gas enters the biodegradation unit, and after three layers of biological treatment, the biotreated gas is obtained. 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, 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; S4 The biological treatment gas enters the deep purification unit and obtains purified gas after photocatalytic treatment and ozone treatment; S5: The purified gas enters the monitoring emission unit, and is discharged if it meets the emission index, and re-enters the adsorption treatment unit if it does not meet the index.

2. A low-concentration malodorous gas purification process according to claim 1, characterized in that: The specific process of the spray treatment and filtration treatment is: the malodorous gas is introduced into the pretreatment unit from bottom to top, and the spray treatment and the filtration treatment are carried out through the spray tower and the filtration device in sequence. The spray tower is equipped with a NaOH solution spray device, and the spray intensity is 10-20m 3 / (m 2 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 filtering device, the gas flow rate is controlled at 0.1m / s-0.5m / s, and the filtering device adopts a high-efficiency fiber filter with a pore size of 3μm, and finally the pretreated gas is obtained.

3. A low-concentration malodorous gas purification process according to claim 1, characterized in that: 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, passes through the composite activated carbon coating filler and the microbial activated carbon respectively, and performs the 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%, so as 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.

4. A low-concentration malodorous gas purification process according to claim 3, characterized in that: 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 dropped into 50 parts of ethanol to form a solution B; under vigorous stirring, the solution B is slowly dropped into the mixed solution A, and the pH value is adjusted to 8 to form a mixed sol; 5-10 parts of activated carbon are put into the mixed sol, stirred for 2 hours, and then transferred to a reactor, reacted at 150°C-180°C for 12 hours under self-increasing pressure, 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 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 part 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, 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 the composite activated carbon coating filler.

5. A low-concentration malodorous gas purification process according to claim 3, characterized in that: The preparation method of the microbial activated carbon comprises: culturing Thiobacillus and Geotrichum candidum strains respectively, centrifuging the cultured Thiobacillus and Geotrichum candidum to collect the bacterial bodies respectively, and then resuspending them with sterile physiological saline to prepare a concentration of 10 7 / mL of the composite bacterial liquid; placing the activated carbon in the composite bacterial liquid, shaking and soaking for 18h-22h, and culturing for 7 days after inoculation to obtain the microbial activated carbon.

6. A low-concentration malodorous gas purification process according to claim 1, characterized in that: The specific process of the three-layer biological treatment is: the adsorbed treated 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, the gas passage time is controlled to be 100s-120s, the filter bed temperature is controlled at 30℃-35℃, and the biological treatment gas is obtained.

7. A low-concentration malodorous gas purification process according to claim 6, characterized in that: 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, the matrix filler 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 them into a concentration of 10 7 / mL of Pseudomonas bacterial solution, Thiobacillus bacterial solution and a mixed bacterial solution containing the nitrifying bacteria and the alcaligenes faecalis, then the fiber ball, the polyurethane foam and the ceramsite are immersed in the Pseudomonas bacterial solution, the Thiobacillus bacterial solution and the mixed bacterial solution respectively, and then cultured for 7 days after soaking for 20 hours to obtain each layer of filter material.

8. The low to medium concentration malodorous gas purification process 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, 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, a UV lamp group with a wavelength of 254nm and 185nm is set, 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 dosage of ozone in the ozone processor is 100mg / m 3 -150mg / m 3 The residence time of the biological treatment gas is 3min-7min.

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