A composite filler biofilter column for efficiently degrading volatile organic compound waste gas

Abstract

The application belongs to the environmental protection technical field, and particularly discloses a composite filler biofilter column for efficiently degrading volatile organic compound waste gas, which comprises a supporting layer and a composite filler layer arranged above the supporting layer; the supporting layer comprises a supporting plate embedded in the bottom of the composite filler biofilter column and a gravel layer filled on the supporting plate; and the composite filler layer comprises, from bottom to top, a perlite layer, an activated carbon layer and a magnetite layer in sequence. The composite filler layer of the application makes full use of three fillers with different characteristics, arranges them in order, and plays their respective characteristics, so as to strengthen the adhesion capacity of microbial biofilm, accelerate the formation of the microbial biofilm, and promote the biological degradation.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection technology, specifically relating to a composite packing biofilter column for the efficient degradation of volatile organic compound waste gas. Background Technology

[0002] Volatile organic compounds (VOCs) are the main contributors to the formation of O3 and PM2.5. 2.5 Important precursors to pollution, VOCs are significant contributors to air pollution problems such as photochemical smog and haze, posing serious threats to human health. VOC emissions primarily originate from raw and auxiliary materials used in the production processes of industries such as painting, chemicals, printing, automotive repair, and shipbuilding. Common VOCs include acetates (ethyl acetate), alcohols (methanol, isopropanol), aromatic compounds (benzene, toluene, xylene), and hydrocarbons (propane, hexane). Industrial VOC emissions not only pollute the environment but also pose a certain degree of toxicity to multi-component VOC mixtures, and long-term inhalation can have serious health consequences.

[0003] Chemical techniques such as catalytic oxidation, thermal oxidation, and absorption can effectively remove volatile organic compounds (VOCs), but require large amounts of chemical reagents and may produce toxic byproducts. Physical methods mainly utilize physical processes (such as adsorption) to adsorb pollutants, without altering the chemical properties of the odorous gas itself, but require reprocessing of the adsorbent pollutants, resulting in high operating costs. Biological treatment using biofiltration systems to remove various VOCs is cost-effective, efficient, and environmentally friendly compared to chemical and physical methods, possessing great potential for decomposing and degrading many gaseous pollutants, making it a reliable waste gas treatment method. Compared to the methods mentioned above, biological treatment of VOCs is inexpensive, efficient, environmentally friendly, and has great potential for decomposing and degrading many gaseous pollutants. Biofilters have been one of the simplest and most widely used biological methods for removing gaseous pollutants from gas streams for many years. The reactor is filled with filter media that provides attachment sites for biofilm growth, converting VOCs into harmless products such as water and carbon dioxide. The biodegradation of pollutants in biofilters occurs through a combination of physical, chemical, and biological processes. When pollutants enter a biofilter, they are absorbed by the biofilm surrounding the medium and dissolved in the water layer around the biofilm. The pollutants are then utilized by the microorganisms in the biofilm as a carbon source. The biodegradation capacity is closely related to the properties of the packing material and the biofilm attached to its surface. However, existing biofilters still have some drawbacks: (1) long-term operation of biofilters can lead to excessive biomass accumulation and blockage, resulting in poor removal efficiency; (2) the reuse rate of untreated volatile organic compounds (VOCs) in the biofilter needs to be improved. Based on these two shortcomings, research on enhancing biodegradation and improving the removal of VOCs has received widespread attention.

[0004] Therefore, it is essential to develop a new type of biofilter to meet people's needs. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the existing technology and provide a composite packing biofilter column for efficient degradation of volatile organic compound waste gas.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: a composite packing biological filter column for efficient degradation of volatile organic compound waste gas, comprising a support layer and a composite packing layer disposed above the support layer. The support layer includes a support plate embedded in the bottom of the composite packing biological filter column and a gravel layer filled on the support plate. The composite packing layer comprises, from bottom to top, a perlite layer, an activated carbon layer, and a magnetite layer.

[0007] Preferably, the composite packing biofilter column also includes an air inlet, an air outlet, a return pipe, a leachate drain outlet, a nutrient solution storage tank, and a peristaltic pump.

[0008] Furthermore, the reflux pipe is located at the top of the composite packing biofilter column, and a gas flow valve is installed on the reflux pipe. The leachate drain outlet is located at the bottom of the composite packing biofilter column.

[0009] Furthermore, the air inlet is connected to the volatile organic compound (VOC) waste gas, which is transmitted from the gas hose to the interior of the composite packing biofilter column and degraded by microorganisms on the packing.

[0010] Furthermore, the outlet is located above the composite packing layer and is connected to the top of the composite packing biofilter column. The treated gas is collected to a gas collection device, and the untreated volatile organic compound gas is drawn back to the composite packing biofilter column by stopping the supply of volatile organic compound waste gas and reversing the gas flow valve.

[0011] Furthermore, the gas flow valve is connected to an automatic volatile organic compound (VOC) concentration detector. When the VOC concentration inside the composite packing biofilter column is too high, the outlet is closed and the gas flow valve is opened. The VOC is then drawn into the gas collection device by the air compressor and then re-entered into the composite packing biofilter column by the pre-fan for biodegradation.

[0012] Preferably, the activated carbon in the activated carbon layer is granular cylindrical carbon.

[0013] Preferably, the gravel particle size in the gravel layer is 15-20 mm, the magnetite particle size in the magnetite layer is 8-12 mm, the activated carbon particle size in the activated carbon layer is 8-12 mm, and the perlite particle size is 6-8 mm.

[0014] Preferably, the magnetite layer, activated carbon layer, and perlite layer are at the same height.

[0015] Preferably, a filler partition plate is provided between the gravel layer and the magnetite layer, between the magnetite layer and the activated carbon layer, and between the activated carbon layer and the perlite layer.

[0016] Furthermore, the packing separator plate is a circular groove, which facilitates the transfer of leachate and biofilm.

[0017] Before using the composite packing biological filter column to treat volatile organic compound (VOC) waste gas, a biofilm formation process is required. Inoculated sludge is sprayed onto the packing layer to adhere to the packing. Then, low-concentration VOC waste gas is introduced for acclimatization treatment, so that microbial strains with high efficiency in degrading VOC waste gas can adhere to the composite packing layer.

[0018] The support plate and the gravel layer together provide a certain mechanical strength to the interior of the filter column to support the packing layer.

[0019] The magnetite in the composite packing layer is a packing material with a fairly dense surface morphology and an excellent rough surface. It can not only provide attachment points for microbial biofilms and improve the contact between microorganisms and pollutants in the liquid phase, which is conducive to the rapid formation of stable microbial biofilms, but also the magnetite itself has certain electrical conductivity. It can act as an electron acceptor / donor to regulate the redox conditions in the environmental system, enhance the extracellular electron transfer of microbial biofilms, promote the growth and metabolism of microorganisms, and enhance the degradation efficiency of microorganisms on volatile organic compounds. The surface layer of the magnetite packing also contains calcium, magnesium and other ions, which can provide certain trace elements for microbial growth.

[0020] The activated carbon in the composite packing layer is mainly composed of carbon, with small amounts of oxygen, hydrogen, sulfur, nitrogen, chlorine, and other elements. Structurally, due to the irregular arrangement of microcrystalline carbon and the presence of pores between the cross-links, carbon structure defects are generated during activation, resulting in low bulk density and a large specific surface area. The porous structure of activated carbon is conducive to biofilm attachment and growth, allowing the attached microbial biofilm to fully contact pollutants in the liquid phase, thereby improving mass transfer efficiency and promoting the degradation of volatile organic compounds.

[0021] The perlite in the composite filler layer is a glassy rock formed from acidic lava from volcanic eruptions through rapid cooling. It possesses a pearly fracture structure and is characterized by low bulk density, low thermal conductivity, high heat resistance, low sound transmission, high surface area, and chemical inertness. It also contains abundant minerals such as silicon, potassium, sodium, iron, and magnesium, all of which are conducive to microbial attachment and biofilm formation for the biodegradation of pollutants. The perlite in the filler layer expands to some extent upon water absorption, which is beneficial in biological filtration as it can store certain nutrients for microorganisms.

[0022] Nutrient solution is transported from the nutrient solution storage tank to the composite packing biofilter column via a peristaltic pump. The composite packing biofilter column can be sprayed with nutrient solution from the nutrient tank onto the packing layer via an external peristaltic pump, providing the trace elements needed for microbial biodegradation. A leachate drain at the bottom of the composite packing biofilter column periodically removes the internal leachate, reducing pressure drop.

[0023] Work process:

[0024] When volatile organic compound (VOC) waste gas enters the biofilter column, it is absorbed by the biofilm on the surface of the medium. The microorganisms in the biofilm use the pollutants as a carbon source for decomposition and metabolism, converting the VOCs into harmless oxidation products (such as H2O, CO2, sulfates and nitrates).

[0025] Before using a composite-packed biofilter to treat volatile organic compound (VOC) waste gas, a biofilm formation process is required. Activated sludge is sprayed onto the packing layer to adhere to it. Then, low-concentration VOC waste gas is introduced for acclimatization, allowing highly efficient VOC-degrading microorganisms to attach to the composite packing layer. Stable VOC removal efficiency during the acclimatization phase indicates successful biofilm formation. The inlet concentration of VOC waste gas is then gradually increased. During operation, the concentration at the reactor inlet and outlet is monitored every three days, and nutrient solution is sprayed every two days to maintain the microbial community's trace element levels and the reactor's internal humidity. Every three days, the supply of VOC waste gas to the biofilter is suspended, and the leachate outlet valve is opened to discharge the leachate and detached biofilm from the composite-packed biofilter, reducing internal pressure and clogging levels.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] 1. The composite packing layer of the present invention makes full use of three packing materials with different properties, arranged in an orderly manner, giving full play to their respective characteristics, enhancing the adhesion ability of microbial biofilm, accelerating its formation, and promoting biodegradation.

[0028] 2. The activated carbon and perlite in this invention have a large specific surface area and porosity, which not only facilitates the attachment of a large number of microorganisms and the formation of biofilms, but also adsorbs pollutants to a certain extent, strengthens the interaction between biofilms and pollutants, and promotes the biodegradation of pollutants.

[0029] 3. The magnetite in this invention not only promotes the attachment of microbial biofilms, but also has certain electrical conductivity. It can act as an electron acceptor / donor to regulate the redox conditions in the environmental system, promote the growth and metabolism of microorganisms, and at the same time promote the extracellular electron transfer of microorganisms, thereby enhancing the degradation efficiency of pollutants by microorganisms.

[0030] 4. The reflux pipe and spray device of the present invention can effectively improve the removal of volatile organic compounds (VOCs) waste gas. When the untreated VOCs waste gas is transferred to the uppermost filter layer, the nutrient solution spraying can allow the VOCs waste gas to be captured and degraded again by the microbial biofilm. The remaining untreated VOCs waste gas can be back-suctioned by opening the gas flow valve, so that it returns to the composite packing biofilter column for further degradation. This improves the reuse rate of microbial degradation of VOCs waste gas.

[0031] 5. Compared with a single-filler biological filter, the combination of three types of packing materials in this invention can, to some extent, avoid the problem of increased pressure drop in the filter bed due to packing material blockage after long-term operation, which ultimately leads to reduced removal efficiency. The composite packing material combination not only improves mass transfer efficiency but also prolongs the residence time of pollutants between the biofilm and the packing material, indirectly promoting the biodegradation of volatile organic compounds.

[0032] 6. The composite packing of the present invention has the characteristics of high porosity, large specific surface area and strong resistance to impact load, which ensures efficient treatment of volatile organic compounds while maintaining stable operating performance, provides theoretical support for the efficient treatment of volatile organic compounds in practice, and generates good social and economic benefits. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of the composite packing biofilter column of the present invention.

[0034] In the diagram: 1-Support layer, 2-Composite packing, 1-1-Support plate, 1-2-Gravel layer, 2-1-Perlite layer, 2-2-Activated carbon layer, 2-3-Magnetite layer, 3-Air inlet, 4-Air outlet, 5-Recirculation pipe, 6-Leachate drain outlet, 7-Valve, 8-Nutrient solution storage tank, 9-Peristaltic pump, 6-Leachate drain outlet, 10-Gas flow valve, 11-Gas collection device, 12-Waste gas storage tank, 13-1-First packing partition plate, 13-2-Second packing partition plate, 13-3-Third packing partition plate, 14-Leachate collection device;

[0035] Figure 2 This is a schematic diagram of the backflow of the present invention.

[0036] In the diagram: 1-Support layer, 2-Composite packing, 1-1-Support plate, 1-2-Gravel layer, 2-1-Perlite layer, 2-2-Activated carbon layer, 2-3-Magnetite layer, 3-Air inlet, 4-Air outlet, 5-Return pipe, 6-Leachate drain outlet, 7-Valve, 8-Nutrient solution storage tank, 9-Peristaltic pump, 6-Leachate drain outlet, 10-Gas flow valve, 11-Gas collection device, 12-Waste gas storage tank, 13-1-First packing partition plate, 13-2-Second packing partition plate, 13-3-Third packing partition plate, 14-Leachate collection device, 15-Automatic detector, 16-Air compressor, 17-Front fan;

[0037] Figure 3 The following are schematic diagrams of the packing separator plate of the present invention: (a) top view and bottom view, (b) front view, and (c) sectional view.

[0038] Figure 4 Comparison of ethyl acetate removal rates between composite packing and single activated carbon packing;

[0039] Figure 5 Comparison of biomass accumulation between composite packing material and single activated carbon packing material. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in more detail below with reference to the accompanying drawings and specific embodiments. However, the scope of protection of this invention is not limited to these embodiments. The same reference numerals throughout the text always represent the same elements, and similar reference numerals represent similar elements.

[0041] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "horizontal", "vertical", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the perspective view in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0042] like Figure 1As shown, a composite packing biofilter column for efficiently degrading volatile organic compound (VOC) waste gas includes a support layer 1 and a composite packing layer 2 disposed above the support layer 1. The support layer 1 includes a support plate 1-1 embedded at the bottom of the composite packing biofilter column and a gravel layer 1-2 piled on the support plate 1-1. The composite packing layer 2, from bottom to top, includes a perlite layer 2-1, an activated carbon layer 2-2, and a magnetite layer 2-3. The composite packing biofilter column also includes an air inlet 3, an air outlet 4, a return pipe 5, a leachate drain outlet 6, a valve 7, an external nutrient solution storage tank 8, and a peristaltic pump 9. The leachate drain outlet 6 is located at the bottom of the composite packing biofilter column. VOC waste gas enters through a gas hose into the air inlet 3 and is captured by the microbial biofilm on each layer of the composite packing in the composite packing biofilter column. The return pipe 5 is located at the top of the composite packing biofilter column. A gas flow valve 10 is installed on the return pipe 5, and the gas flow valve 10 is connected to an automatic volatile organic compound (VOC) waste gas concentration detector 15. When the VOC waste gas concentration inside the composite packing biofilter column is too high, the outlet 4 is closed, and the gas flow valve 10 is opened. The VOC waste gas is then drawn into the waste gas storage tank 12 by the air compressor 16, and then re-enters the composite packing biofilter column for biodegradation via the pre-fan 17. Figure 2As shown. The leachate drain outlet 6 is located at the bottom of the composite packing biofilter column. The air inlet 3 is connected to the waste gas storage tank 12. Volatile organic waste gas in the waste gas storage tank 12 is transferred through a gas hose to the interior of the composite packing biofilter column where it is degraded by microorganisms on the packing material. The air outlet 4 is located above the composite packing layer and is connected to the top of the composite packing biofilter column. The treated gas is collected here to the gas collection device 11. By stopping the supply of volatile organic waste gas and reversing the gas flow valve 10, the untreated volatile organic gas is drawn back to the composite packing biofilter column. The composite packing biofilter column uses an external peristaltic pump 9 to spray nutrient solution from the nutrient solution storage tank 8 onto the composite packing layer 2, providing the trace elements needed for microbial biodegradation. The leachate drain outlet 6 at the bottom of the composite packing biofilter column periodically discharges the leachate inside, reducing the pressure drop. The leachate collection device 14 can collect the nutrient solution that has not been absorbed by the biofilm of the packing layer and reuse it by spraying again. The gravel in gravel layer 1-2 has a particle size of 15-20 mm, the magnetite in magnetite layer 2-3 has a particle size of 8-12 mm, the activated carbon in activated carbon layer 2-2 is granular cylindrical carbon with a particle size of 8-12 mm, and the perlite in perlite layer 2-1 has a particle size of 6-8 mm. The magnetite, activated carbon, and perlite layers 2-3 are all at the same height. A first packing separator 13-1, a second packing separator 13-2, and a third packing separator 13-3 are respectively installed between each pair of adjacent gravel, perlite, activated carbon, and magnetite layers 2-3. The first, second, and third packing separators 13-1 and 13-2 are all annular grooves to facilitate the transfer of leachate and biofilm.

[0043] To enable those skilled in the art to understand this application in detail, the operation process of the composite packing biofilter column for efficiently degrading volatile organic compound (VOC) waste gas is described below: Before using the composite packing biofilter column to treat VOC waste gas, a biofilm formation process is required. Inoculated activated sludge is sprayed onto the packing layer to adhere to it. Then, low-concentration VOC waste gas is introduced for acclimatization treatment, allowing microbial strains with high efficiency in degrading VOC waste gas to adhere to the composite packing layer. The biofilm formation is considered complete when the VOC removal effect stabilizes during the acclimatization stage. The inlet concentration is then gradually increased; in this embodiment, the inlet concentration of ethyl acetate used for treating VOC waste gas is 224–448 g / m³. 3 The gas flow rate is 0.1–0.3 m³ / s. 3 / h. During operation, the ethyl acetate concentration at the reactor inlet and outlet was monitored every three days, and 1L of nutrient solution was sprayed every two days to maintain the trace element level of the microbial community and the humidity inside the reactor. Every three days, the supply of ethyl acetate waste gas to the biofilter was suspended, and the leachate outlet valve was opened to discharge the leachate and detached biofilm from the composite packing biofilter, reducing the internal pressure and clogging levels. In this embodiment, the concentration of ethyl acetate was detected to be 24–40 g / m³. 3 The average removal rate was 84.7%, indicating a good degradation effect.

[0044] The above are merely preferred embodiments of the present invention and are not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the present invention, should fall within the protection scope of the present invention.

Claims

1. A composite packing biofilter column for efficient degradation of volatile organic compound (VOC) waste gas, characterized in that, The filter includes a support layer and a composite packing layer above the support layer. The support layer includes a support plate embedded in the bottom of the composite packing biofilter and a gravel layer filled on the support plate. The composite packing layer, from bottom to top, includes a perlite layer, an activated carbon layer, and a magnetite layer. The composite packing biofilter also includes an air inlet, an air outlet, a return pipe, a leachate drain outlet, a nutrient solution storage tank, and a peristaltic pump. The return pipe is located at the top of the composite packing biofilter and is equipped with a gas flow valve. The leachate drain outlet is located at the bottom of the composite packing biofilter. The gas flow valve is connected to an automatic volatile organic compound (VOC) concentration detector. When the VOC concentration inside the composite packing biofilter is too high, the air outlet is closed, the gas flow valve is opened, and the VOC is drawn into a gas collection device by an air compressor. Then, a pre-fan allows the VOC to re-enter the composite packing biofilter for biodegradation. The gravel in the gravel layer has a particle size of 15-20 mm. The magnetite particles in the magnetite layer are 8-12 mm in diameter, the activated carbon particles in the activated carbon layer are 8-12 mm in diameter, and the perlite particles in the perlite layer are 6-8 mm in diameter. Filler partition plates are provided between the gravel layer and the magnetite layer, between the magnetite layer and the activated carbon layer, and between the activated carbon layer and the perlite layer.

2. The composite packing biofilter column as described in claim 1, characterized in that, The air inlet is connected to the volatile organic compound (VOC) waste gas, which is transmitted from the gas hose to the interior of the composite packing biofilter column and degraded by microorganisms on the packing.

3. The composite packing biofilter column as described in claim 1, characterized in that, The air outlet is located above the composite packing layer and is connected to the top of the composite packing biofilter column.

4. The composite packing biofilter column as described in claim 1, characterized in that, The activated carbon in the activated carbon layer is granular cylindrical carbon.

5. The composite packing biofilter column as described in claim 1, characterized in that, The packing separator plate is a circular groove.

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