A method for removing methane in exhaust gas by using organic wastewater to strengthen biofiltration

Abstract

The application discloses a method for removing methane in waste gas by using organic wastewater to strengthen biological filtration, and comprises the following steps: using the organic wastewater as a nutrient solution to start a biological filter; and introducing the methane waste gas into the biological filter to perform biological degradation, thereby completing the removal of the methane in the waste gas. The method for removing the methane in the waste gas by using the organic wastewater to strengthen the biological filtration has the advantages of simple process, convenient operation, low cost, short starting time, high treatment efficiency, good methane removal effect, green environmental protection, easy popularization and the like, is a new method which can be widely used and can realize the collaborative treatment of wastewater and waste gas, has high application value and commercial value, and has great application potential in the fields of actual treatment of organic waste gas containing methane and alleviation of greenhouse effect.

Description

Technical Field

[0001] This invention belongs to the field of air pollution control and environmental protection technology, and relates to a method for treating methane waste gas, specifically a method for removing methane from waste gas by enhancing biological filtration with organic wastewater. Background Technology

[0002] The massive emission of greenhouse gases has led to significant climate change, and how to effectively mitigate the greenhouse effect has attracted widespread attention from governments and the public worldwide. Methane, with its high calorific value, is an indispensable energy source for global economic development and a major contributor to the greenhouse effect; its 20-year global warming potential is 86 times that of carbon dioxide. Methane has numerous sources in the atmosphere, including inevitable leaks and emissions during natural gas production and storage, other industrial production and daily life activities such as fossil fuel production, livestock farming, anaerobic treatment of municipal sludge and high-concentration organic wastewater, and landfill operations. When the methane content in a gas exceeds 40% (v / v), it can generally be used for energy production. However, over 55% of the methane generated in human production and daily life is low-content (<5%, v / v) methane waste gas, such as landfill gas from early or late stages of landfilling, wastewater treatment plants, and waste gas from livestock farms. These low concentrations of methane are not suitable for treatment using thermal oxidation and energy recovery methods. Therefore, it is necessary to adopt green, economical, and effective technologies to purify methane-containing waste gases generated in human production and daily life in order to reduce methane emissions and mitigate their impact on the climate.

[0003] Thermal oxidation methods, such as incineration, are effective technologies for treating organic waste gas. However, these methods suffer from high energy consumption, are unsuitable for treating low-concentration organic waste gas, and are not suitable for applications in petrochemical and other enterprises with strict fire safety requirements. Among biological methods, biofiltration, as a green, economical, and mature approach, has broad application prospects in the field of organic waste gas treatment. However, methane, as a special organic compound, has strong hydrophobicity. In the process of using biofiltration, there are problems such as high gas-liquid mass transfer resistance, low utilization of methane by microorganisms, and poor stability of the biological treatment system. This results in weak methane removal performance of biofiltration, affecting its application in methane waste gas purification. Furthermore, due to the limited uptake and capture capacity of microorganisms for hydrophobic organic compounds, the growth of microorganisms in the biofiltration system is often poor, and the start-up time of the biofiltration system is long, which is also detrimental to achieving rapid treatment of methane waste gas. Therefore, it is essential to develop a method for enhanced biofiltration to remove methane from waste gas with short start-up time, high treatment efficiency, and good methane removal effect. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for removing methane from waste gas by enhancing biological filtration using organic wastewater. This method is simple, easy to operate, low in cost, has a short start-up time, high processing efficiency, good methane removal effect, is green and environmentally friendly, and is easy to promote.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0006] A method for removing methane from exhaust gas using enhanced biological filtration of organic wastewater includes the following steps:

[0007] S1. Use organic wastewater as a nutrient solution to start the biological filter;

[0008] S2. Methane waste gas is passed into a biological filter for biodegradation to remove methane from the waste gas.

[0009] In a further improvement to the above method, in step S1, the organic matter in the organic wastewater is benzene and / or toluene; the mass percentage of the organic matter in the organic wastewater is 0.015% to 0.050%.

[0010] In a further improvement to the above method, in step S1, the organic wastewater is benzene- and / or toluene-containing wastewater generated in the coking, steel, or petrochemical industries.

[0011] In a further improvement to the above method, in step S1, the organic wastewater is sprayed intermittently from top to bottom onto the packing material of the biological filter; the spray volume of the organic wastewater is 1 m³ / s. 3 The methane exhaust gas requires spraying with 0.3L of organic wastewater.

[0012] In a further improvement to the above method, in step S1, the packing material of the biological filter includes biochar material; the volume ratio of biochar material to the total volume of the packing material in the biological filter is 1:4 to 1:2; the biochar material includes one or more of bamboo charcoal, wood charcoal, and fruit shell charcoal.

[0013] In a further improvement to the above method, in step S2, the methane waste gas is continuously introduced from below the packing material of the biofilter; the empty bed residence time of the methane waste gas in the biofilter is 60s to 200s.

[0014] In a further improvement to the above method, in step S2, the methane concentration in the methane waste gas is 200 mg / m³. 3 ~1000mg / m 3 .

[0015] In a further improvement to the above method, step S1, before the biological filter is started, includes the following treatment: inoculating activated sludge into the packing material of the biological filter; the activated sludge comes from activated sludge in the aerobic tank of the oil refinery wastewater treatment plant; the sludge settling ratio of the activated sludge is 25% to 35%, and the sludge volume index is 100 mL / g to 160 mL / g.

[0016] A further improvement to the above method is that, after the activated sludge is inoculated, the activated sludge undergoes an acclimatization treatment; the acclimatization treatment includes the following steps:

[0017] (1) Use organic wastewater as a nutrient solution and spray it onto the packing material of the biological filter;

[0018] (2) Methane waste gas is introduced into the biological filter to cultivate microorganisms in the packing material and complete the acclimatization of activated sludge in the biological filter.

[0019] In a further improvement to the above method, in step (1), the organic wastewater is sprayed from top to bottom onto the packing material of the biological filter in an intermittent spraying manner; the organic matter in the organic wastewater is benzene and / or toluene; the mass percentage of organic matter in the organic wastewater is 0.015% to 0.050%; the organic wastewater is benzene- and / or toluene-containing wastewater generated in the coking, steel or petrochemical industries.

[0020] In a further improvement to the above method, in step (2), the methane waste gas is continuously introduced from below the packing material of the biological filter; the empty bed residence time of the methane waste gas in the biological filter is 60s to 200s; and the methane concentration in the methane waste gas is 200mg / m³. 3 ~1000mg / m 3 The culture time is 15 to 30 days.

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

[0022] (1) In view of the shortcomings of existing biological filtration methods, such as long start-up time and insufficient methane purification capacity, this invention creatively proposes a method for removing methane from waste gas by using organic wastewater to enhance biological filtration. Using organic wastewater as a nutrient solution for microorganisms can not only stimulate the proliferation of microorganisms and increase the demand of microorganisms for carbon sources in the biological filtration system, but also promote the uptake, capture and transformation of methane in waste gas by microorganisms. The enhanced biological filtration purification system constructed in this way has the characteristics of strong methane purification capacity, good purification effect and short start-up time, which is conducive to the biodegradation of organic matter in wastewater and waste gas. Moreover, it can effectively treat organic wastewater and has the characteristics of treating waste with waste, and can achieve synergistic treatment of wastewater and waste gas. At the same time, no additional energy input is required in the entire treatment process, which has the advantages of green economy, safety and energy saving and no secondary pollution, and has great potential for promotion and application. This invention utilizes enhanced biological filtration of organic wastewater to remove methane from waste gas. It has advantages such as simple process, convenient operation, low cost, short start-up time, high treatment efficiency, good methane removal effect, green environmental protection, and easy promotion. It is a new method that can be widely adopted and can achieve the synergistic treatment of wastewater and waste gas. It has high application and commercial value, especially in the practical treatment of methane-containing organic waste gas and in the field of greenhouse effect mitigation.

[0023] (2) In this invention, by optimizing the mass percentage of organic matter in the organic wastewater to 0.015% to 0.050%, it is beneficial to improve the purification effect of methane. If the content of organic matter is too high, it will compete with methane and may reduce the conversion effect of methane.

[0024] (3) In this invention, using biochar material as part of the biofilter packing can promote electron transfer in the methane metabolism process of microorganisms and improve the purification efficiency of the biofiltration system for methane. At the same time, by optimizing the total volume ratio of biochar material to packing to 1:4 to 1:2, electron transfer between microorganisms can be promoted and the biodiversity of microorganisms can be improved, which is beneficial to the degradation of pollutants. It is also beneficial to the uniform distribution of airflow in the biofilter and to prevent clogging.

[0025] (4) This invention also includes: inoculating activated sludge into the packing material of the biological filter, wherein the sludge settling ratio of the activated sludge is 25% to 35%, and the sludge volume index is 100 mL / g to 160 mL / g. By optimizing the sludge settling ratio and volume index, the activity of the inoculated sludge can be guaranteed, which is conducive to rapid start-up. It also includes: using organic wastewater as a nutrient solution for microorganisms to acclimate the activated sludge inoculated into the packing material of the biological filter. Acclimatization treatment can promote the rapid proliferation of microorganisms, which can not only shorten the start-up time of the biological filter, but also enhance the ability of microorganisms to absorb, capture, and convert methane waste gas, thus facilitating the rapid purification of methane wastewater by the biological filter. Attached Figure Description

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0027] Figure 1 This is a graph showing the relationship between the inlet and outlet concentrations of methane and the operating time when using organic wastewater to enhance biological filtration to remove methane from exhaust gas in Example 1 of the present invention.

[0028] Figure 2 This is a graph showing the methane removal efficiency over time when using organic wastewater to enhance biological filtration to remove methane from exhaust gas in Example 1 of the present invention.

[0029] Figure 3 This is a diagram showing the methane purification effect when organic wastewater is used to enhance biological filtration to remove methane from exhaust gas in Embodiment 2 of the present invention. Detailed Implementation

[0030] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention. All materials and instruments used in the following embodiments are commercially available.

[0031] Example 1

[0032] A method for removing methane from exhaust gas using enhanced biological filtration of organic wastewater includes the following steps:

[0033] (1) Constructing a biological filter, specifically two sets of cylindrical biological filters with a diameter of 20 cm and a height of 100 cm. The biological filter has two layers of filler material: the upper layer is biochar material, the middle layer is ceramsite, and the lower layer is polyurethane sponge. The volume ratio of the three is 1:1:2.

[0034] (2) The activated sludge in the aerobic tank of the petrochemical plant wastewater treatment station is directly sprayed onto the packing material of the biological filter by a water pump, so that the activated sludge is evenly distributed into the packing material. The activated sludge is yellowish-brown, the sludge settling ratio is 30%, and the sludge volume index is 110mL / g.

[0035] (3) After inoculation, spray 0.3L of nutrient solution per cubic meter of treated waste gas into the biofilter packing material via atomizing nozzles in an intermittent manner, according to the spray volume of 0.3L of nutrient solution per cubic meter of treated waste gas, and start the biofilter. In this step, the toluene wastewater also contains other components for the growth of other microorganisms, which is a conventional formula.

[0036] (4) The concentration is 200 mg / m 3 Methane waste gas is continuously introduced into the biological filter from below the packing material. The empty bed residence time of the methane waste gas in the biological filter is maintained at 120 seconds. The microorganisms in the packing material are cultured for 30 days to complete the acclimatization of the activated sludge in the biological filter.

[0037] (5) The concentration is 700-1000 mg / m 3 Methane waste gas is continuously fed into the biological filter from below the packing material. The empty bed residence time of the methane waste gas in the biological filter is maintained at 120 seconds. The microorganisms in the packing material biodegrade the methane in the waste gas for 20 days to complete the removal of methane from the waste gas.

[0038] Control group: The nutrient solution used did not contain toluene, and all other conditions were the same.

[0039] During the domestication and biodegradation process, gas chromatography was used to monitor the methane concentration at the inlet and outlet of the biofilter. The results are as follows: Figure 1 and 2 As shown. By Figure 1 and 2 It was found that the biofilter with toluene as a nutrient solution consistently exhibited higher methane removal performance than the biofilter without it. Furthermore, the biofilter with toluene as a nutrient solution reached a stable state on day 20, while the biofilter without toluene as a nutrient solution required nearly 30 days to reach a stable state. Additionally, after stable operation, increasing the inlet methane concentration to 1000 mg / m³ further improved the performance. 3Biological filters using toluene as a nutrient solution can rapidly adapt to changes in inlet methane concentration and quickly regain stability. Under stable conditions, the methane removal efficiency can reach 80%. In contrast, biological filters without toluene as a nutrient solution exhibit significant lag in adapting to inlet methane concentrations and poor resistance to shock loads, with a methane removal efficiency of only about 50% under stable conditions. Therefore, biological filters using toluene as a nutrient solution have advantages such as shorter start-up time, superior methane removal performance, and stronger resistance to shock loads. Furthermore, detection of toluene in the outlet exhaust gas revealed that the toluene content was below the detection limit, meaning that the introduced toluene-containing wastewater will not cause secondary air pollution. Therefore, introducing toluene-containing organic wastewater into biological filters to provide nutrients for microorganisms is an effective measure to enhance methane removal through biological filtration and is worthy of widespread application.

[0040] Example 2:

[0041] A method for removing methane from exhaust gas using enhanced biological filtration of organic wastewater includes the following steps:

[0042] (1) Construct a biological filter with two layers of packing material, the upper layer being biochar material and the lower layer being polyurethane sponge, with a volume ratio of 1:2.

[0043] (2) The activated sludge in the aerobic tank of the petrochemical plant wastewater treatment station is directly sprayed onto the packing material of the biological filter by a water pump. The activated sludge is yellowish-brown, the sludge settling ratio is 25%, and the sludge volume index is 120mL / g.

[0044] (3) After inoculation, the organic wastewater from petrochemical plants (such as oil refineries) with a benzene content as high as 0.045% is sprayed intermittently through the atomizing nozzles in the biofilter onto the biofilter packing as a nutrient solution for microorganisms, and the biofilter is then started. In this step, the toluene wastewater also contains other components for the growth of other microorganisms, which is a conventional formulation.

[0045] (4) The 500-800 mg / m³ produced by the atmospheric pressure raw material tank 3 Methane waste gas is continuously fed into the biological filter from below the packing material. The empty bed residence time of the methane waste gas in the biological filter is maintained at 100 seconds. The microorganisms in the packing material biodegrade the methane in the waste gas for 40 days to complete the removal of methane from the waste gas.

[0046] During the biodegradation process, gas chromatography was used to monitor the methane concentration at the inlet and outlet of the biofilter. The results are as follows: Figure 3 As shown. By Figure 3It can be seen that during the start-up period (acclimation phase), the methane concentration at the exhaust outlet continuously decreases, and the methane removal performance continuously increases. The biological filter requires 20 days to complete start-up, achieving a methane removal efficiency of 80%, and the outlet methane concentration can be reduced to 150 mg / m³. 3 After that, it can maintain a stable operating state.

[0047] In addition, COD concentration was measured in wastewater discharged from the bottom of the biofilter and sprayed benzene-containing organic wastewater. The results showed that the COD removal efficiency in the wastewater after purification by the biofilter could reach over 85%, meaning that the biofiltration system can effectively remove benzene from the wastewater and achieve synergistic purification of waste gas and wastewater.

[0048] As can be seen from the above results, in this invention, using organic wastewater as a nutrient solution for microorganisms not only stimulates the proliferation of microorganisms and increases their demand for carbon sources in the biofiltration system, but also promotes the uptake, capture, and conversion of methane in the waste gas by microorganisms. The enhanced biofiltration purification system constructed in this way has the characteristics of strong methane purification capacity, good purification effect, and short start-up time, which is conducive to the biodegradation of organic matter in wastewater and waste gas. Moreover, it can effectively treat organic wastewater, has the characteristics of treating waste with waste, and can achieve synergistic treatment of wastewater and waste gas. At the same time, no additional energy input is required in the entire treatment process, which has the advantages of green economy, safety and energy saving, and no secondary pollution, and has great potential for promotion and application. As can be seen, the method of removing methane from waste gas by enhancing biological filtration using organic wastewater in this invention has the advantages of simple process, convenient operation, low cost, short start-up time, high treatment efficiency, good methane removal effect, green environmental protection, and easy promotion. It is a new method that can be widely adopted and can achieve the synergistic treatment of wastewater and waste gas, with high application and commercial value, especially in the actual treatment of methane-containing organic waste gas and the field of greenhouse effect mitigation.

[0049] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall still fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for removing methane from waste gas using enhanced biological filtration of organic wastewater, characterized in that, Includes the following steps: S1. Using organic wastewater as a nutrient solution, start the biological filter; the organic matter in the organic wastewater is benzene and / or toluene; the mass percentage of organic matter in the organic wastewater is 0.015% to 0.050%; S2. Methane waste gas is introduced into a biological filter for biodegradation to remove methane from the waste gas; the methane waste gas is continuously introduced from below the packing material of the biological filter; the empty bed residence time of the methane waste gas in the biological filter is 60 s to 200 s.

2. The method according to claim 1, characterized in that, In step S1, the organic wastewater is benzene- and / or toluene-containing wastewater generated in the coking, steel or petrochemical industries.

3. The method according to claim 1, characterized in that, In step S1, the organic wastewater is sprayed intermittently from top to bottom onto the packing material of the biological filter; the spray volume of the organic wastewater is 1 m³ / s. 3 The methane exhaust gas requires spraying with 0.3L of organic wastewater.

4. The method according to claim 3, characterized in that, In step S1, the packing material of the biological filter contains biochar material; the volume ratio of biochar material to the total volume of the packing material in the biological filter is 1:4 to 1:2; the biochar material includes one or more of bamboo charcoal, wood charcoal, and fruit shell charcoal.

5. The method according to any one of claims 1 to 4, characterized in that, In step S2, the methane concentration in the methane exhaust gas is 200 mg / m³. 3 ~1000 mg / m 3 .

6. The method according to any one of claims 1 to 4, characterized in that, In step S1, before the biological filter is started, the following treatment is also included: inoculating the packing material of the biological filter with activated sludge; the activated sludge comes from the activated sludge in the aerobic tank of the oil refinery wastewater treatment plant; The activated sludge has a sludge settling ratio of 25% to 35% and a sludge volume index of 100 mL / g to 160 mL / g.

7. The method according to claim 6, characterized in that, After the activated sludge is inoculated, the process further includes acclimatization treatment of the activated sludge; the acclimatization treatment includes the following steps: (1) Use organic wastewater as a nutrient solution and spray it onto the packing material of the biological filter; (2) Methane waste gas is introduced into the biological filter to cultivate microorganisms in the packing material and complete the acclimatization of activated sludge in the biological filter.

8. The method according to claim 7, characterized in that, In step (1), the organic wastewater is sprayed from top to bottom onto the packing material of the biological filter in an intermittent spraying manner; the organic matter in the organic wastewater is benzene and / or toluene; the mass percentage of organic matter in the organic wastewater is 0.015% to 0.050%; the organic wastewater is benzene- and / or toluene-containing wastewater generated in the coking, steel or petrochemical industries. In step (2), the methane waste gas is continuously introduced from below the packing material of the biofilter; the empty bed residence time of the methane waste gas in the biofilter is 60 s to 200 s; and the methane concentration in the methane waste gas is 200 mg / m³. 3 ~1000 mg / m 3 The culture time is 15 to 30 days.

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