A system and method for the combined treatment of biogas combustion exhaust gas and sludge dewatering filtrate.

Abstract

This invention relates to a system and method for the combined treatment of biogas combustion exhaust gas and sludge dewatering filtrate, comprising the following steps: co-treating alkaline sludge filtrate with biogas combustion gas, utilizing the interaction between alkaline wastewater and acidic waste gas to both lower the pH value of the wastewater and simultaneously reduce NO in the waste gas. X SO2 is neutralized in the wastewater, and then total nitrogen and residual gaseous pollutants in the wastewater are removed through an anaerobic ammonia oxidation process. Compared with existing technologies, this invention uses an anaerobic ammonia oxidation process to jointly treat pretreated wastewater and exhaust gas, achieving efficient removal of nitrogen from wastewater and flue gas while ensuring further biochemical degradation of residual components in the flue gas. It features environmental protection and energy saving, waste-to-waste treatment, and significant effects.

Description

Technical Field

[0001] This invention relates to the field of waste gas and wastewater treatment technology, and in particular to a system and method for the combined treatment of biogas combustion tail gas and sludge dewatering filtrate. Background Technology

[0002] Traditional anaerobic digestion of sludge is the most common method for stabilizing municipal sludge, and it also has the advantages of recovering biomass energy (biogas) and improving sludge dewatering performance. The biogas produced can be used for power generation to generate energy, reduce power consumption in the plant, or generate economic benefits by connecting to the grid. However, the exhaust gas produced by burning biogas for power generation contains harmful substances such as nitrogen oxides and sulfur dioxide. The nitrogen oxides are mainly nitric oxide (accounting for more than 90%) and nitrogen dioxide (accounting for 5-10%).

[0003] NO is a colorless and odorless gas with a molecular weight of 30.01. Its melting point is -161℃ and its boiling point is -152℃. NO is slightly soluble in water and is easily oxidized to NO2 in an oxygen-rich environment at room temperature, which is an exothermic reaction. NO2 is a reddish-brown, harmful, and odorous gas with a molecular weight of 46.01 and a density approximately 1.5 times that of air. It is relatively soluble in water and alkalis, forming nitrites and nitrates, as shown in the reaction: 2NO2 + 2OH-. - ==NO2 - +NO3 - Nitrogen dioxide and nitric oxide are absorbed together to form nitrite, the reaction being: NO + NO₂ + 2OH⁻. - ==2NO2 - +H2O.

[0004] Alkaline dewatering of digested sludge has good dewatering effect, low moisture content of sludge cake, and sludge quality that meets the requirements for terminal incineration. However, the sludge filtrate produced is strongly alkaline and has a low C / N ratio. MBR biological treatment results in high carbon source consumption and high operating costs. In addition, acid neutralization consumes a lot of acid and is also costly.

[0005] The anaerobic ammonia oxidation process was developed in 1990 by the Kluyver Biotechnology Laboratory at Delft University of Technology in the Netherlands. This process broke through the basic theoretical concepts of traditional biological nitrogen removal processes. Under anaerobic conditions, ammonia is used as the electron donor and nitrite as the electron acceptor, converting ammonia nitrogen and nitrite nitrogen together into nitrogen gas. The reaction formula is as follows:

[0006] 1NH4 + +1.32NO2 - +0.066HCO3 - +0.13H + →1.02N2+0.26NO3 - +0.066CH2O 0.5 N0.15 +2.03H2O.

[0007] Application No. 202010871879.2, "Flue Gas Denitrification Device and Method," uses chlorine dioxide to oxidize NO in flue gas to NO2, which is then absorbed by reacting with an alkaline solution (such as sodium hydroxide, potassium hydroxide, ammonia, etc.). The absorbed tail gas is then emitted. This method has high operating costs. Application No. 201711100920.0, "A Novel Low-Temperature Oxidation Flue Gas Denitrification System," uses a combination of ozone injectors and alkaline desulfurizing agents (such as CaCO3, NaCO3, or ammonia) to oxidize and absorb NO. This method suffers from significant power consumption during ozone generation and high operating costs. Furthermore, none of the above methods address the efficient and environmentally friendly treatment of the wastewater from NO2 absorption, failing to incorporate the concept of treating waste with waste, and solely focusing on NO in the exhaust gas. X Overall, oxidation and absorption treatments have not demonstrated significant economic and environmental benefits.

[0008] In summary, the flue gas from biogas power generation contains NO. X SO X Such substances require denitrification and desulfurization treatment before being emitted. Denitrification involves using reducing agents such as ammonia to react with NO. X The gas is reduced to nitrogen under the action of V2O5 / TiO2 catalyst. Desulfurization is carried out by wet / dry alkaline substances for adsorption and neutralization. This process requires dedicated waste gas treatment equipment and has high operating and maintenance costs. Conventional biochemical denitrification technology requires a large amount of carbon source for wastewater with low C / N ratio, and acid needs to be added to adjust the pH for alkaline wastewater, resulting in high operating costs.

[0009] Therefore, there is an urgent need for a system and method that can jointly treat wastewater and exhaust gas, achieve efficient removal of nitrogen from wastewater and flue gas, and ensure further biochemical degradation of residual components in the flue gas. Summary of the Invention

[0010] The purpose of this invention is to overcome the shortcomings of the existing technology by providing a system and method for the combined treatment of biogas combustion exhaust gas and sludge dewatering filtrate. By combining alkaline sludge filtrate with biogas combustion gas, the interaction between alkaline wastewater and acidic waste gas is utilized to lower the pH value of the wastewater and simultaneously reduce NO in the waste gas. X The process neutralizes SO2 in the wastewater, and then removes total nitrogen and residual gaseous pollutants from the wastewater through anaerobic ammonia oxidation. It features environmental protection and energy saving, waste-to-waste treatment, and significant effects.

[0011] The objective of this invention can be achieved through the following technical solutions:

[0012] The first objective of this invention is to provide a system for the combined treatment of biogas combustion exhaust gas and sludge dewatering filtrate. The system includes a biogas generator, a flue gas cooler, an air oxidizer, a gas-liquid absorption tower, a flue gas compressor, a wastewater sedimentation tank, an integrated anaerobic ammonia oxidation reactor, and a membrane treatment unit. The biogas generator, flue gas cooler, air oxidizer, and gas-liquid absorption tower are connected sequentially via pipelines. The gas-liquid absorption tower, flue gas compressor, and integrated anaerobic ammonia oxidation reactor are connected sequentially via pipelines. The integrated anaerobic ammonia oxidation reactor and the membrane treatment unit are connected via pipelines. The integrated anaerobic ammonia oxidation reactor is equipped with aeration branch pipes, which supply oxygen to the reactor and further biochemically degrade and remove residual components in the flue gas.

[0013] Furthermore, the biogas generator, flue gas cooler, air oxidizer, and gas-liquid absorption tower are connected in sequence via a flue gas inlet pipe; the gas-liquid absorption tower, flue gas compressor, and integrated anaerobic ammonia oxidation reactor are connected in sequence via a flue gas outlet pipe; the gas-liquid absorption tower, wastewater sedimentation tank, and integrated anaerobic ammonia oxidation reactor are connected in sequence via a wastewater outlet pipe; the gas-liquid absorption tower is connected to a wastewater inlet pipe, and the alkaline dehydrated filtrate enters the upper part of the gas-liquid absorption tower through the wastewater inlet pipe.

[0014] Furthermore, the flue gas cooler is located at the rear end of the economizer or waste heat boiler in the generator exhaust pipe, and uses a pipeline sprayer for cooling. The water source is the water produced by the membrane treatment unit, and the flue gas temperature is controlled below 100℃ after cooling.

[0015] Furthermore, the air oxidizer includes an air injection port and a pipeline static mixer. The air injection port is connected to the pipeline static mixer to enhance the mixing efficiency of flue gas and air. The volume mixing ratio of air and flue gas in the air oxidizer is 1:1-3:1.

[0016] Furthermore, the height-to-diameter ratio of the gas-liquid absorption tower is 5:1-10:1; the gas-liquid absorption tower is provided with an inlet at the top and an outlet at the bottom; the inlet is equipped with an anti-clogging nozzle; the gas-liquid absorption tower contains a packing layer, and the outlet at the bottom has a "U" shaped structure to prevent flue gas from entering the outlet.

[0017] Furthermore, the wastewater sedimentation tank adopts one of inclined tube, inclined plate, or horizontal flow sedimentation; PAM solution is added to the wastewater sedimentation tank to accelerate the sedimentation and separation of particulate impurities in the wastewater, and a slag discharge port is provided at the bottom.

[0018] The second objective of this invention is to provide a method for the combined treatment of biogas combustion exhaust gas and sludge dewatering filtrate. This method employs the aforementioned system, combining alkaline sludge filtrate with biogas combustion gas. By utilizing the interaction between alkaline wastewater and acidic waste gas, the pH value of the wastewater is reduced, while the NO in the waste gas is simultaneously eliminated. X SO2 is neutralized in the wastewater, and then the total nitrogen and residual gaseous pollutants in the wastewater are removed by anaerobic ammonia oxidation process.

[0019] Furthermore, the method includes the following steps:

[0020] S1, the biogas generator, flue gas cooler, air oxidizer, and gas-liquid absorption tower are connected sequentially through the flue gas inlet pipe. The flue gas discharged from the biogas generator is cooled by the flue gas cooler before entering the air oxidizer to undergo an oxidation reaction with injected air. This lowers the flue gas temperature and increases the oxygen content, resulting in the removal of most NO₂. X The gas is oxidized to NO2 and then enters the lower part of the gas-liquid absorption tower, where it comes into countercurrent contact with the alkaline dehydrated filtrate 12 entering the upper part of the tower. The chemical reaction between the flue gas and the filtrate in the gas-liquid absorption tower is as follows:

[0021] 2NO2 + 2OH - ==NO2 - +NO3 - +H₂O, NO + NO₂ + 2OH⁻ - ==2NO2 - +H2O;

[0022] S2, the gas-liquid absorption tower, flue gas compressor, aeration branch pipe, and integrated anaerobic ammonia oxidation reactor are connected in sequence through the flue gas outlet pipe. At the top of the gas-liquid absorption tower, the flue gas after reaction is pressurized by the flue gas compressor and enters the aeration branch pipe in the integrated anaerobic ammonia oxidation reactor to supply oxygen to the integrated anaerobic ammonia oxidation reactor and further biochemically degrade and remove the residual components in the flue gas.

[0023] S3, the gas-liquid absorption tower, the wastewater sedimentation tank, and the integrated anaerobic ammonia oxidation reactor are connected in sequence through the wastewater outlet pipe. In the gas-liquid absorption tower, the dehydrated filtrate absorbs NO2 and NO in the flue gas and converts it into nitrite and lowers the pH. At the same time, the CO2 contained in the flue gas also helps to lower the pH. The wastewater after the reaction at the bottom of the gas-liquid absorption tower enters the wastewater sedimentation tank to remove impurities carried in the flue gas and generated by the gas-liquid reaction, and then enters the integrated anaerobic ammonia oxidation reactor.

[0024] S4. The pretreated waste gas and pretreated filtrate undergo a chemical reaction in an integrated anaerobic ammonia oxidation reactor. First, ammonia-oxidizing bacteria convert a portion of the ammonia nitrogen in the water into nitrite nitrogen under aeration conditions. Then, the remaining ammonia nitrogen, nitrite nitrogen, and nitrite nitrogen generated from the absorbed flue gas are converted into nitrogen gas together. The reaction formula is as follows:

[0025] 1NH4 + +1.5O2→NO2 - +2H + +H2O (nitrosation reaction),

[0026] 1NH4 + +1.32NO2 - +0.066HCO3 - +0.13H + →1.02N2+0.26NO3 - +0.066CH2O 0.5 N 0.15 +2.03H2O (anaerobic ammonia oxidation reaction),

[0027] Finally, it undergoes deep processing in the membrane treatment unit.

[0028] Further, in step S1, the flue gas undergoing oxidation with the injected air and the dehydrated filtrate are reacted in a gas-liquid ratio of 50:1-150:1 (m³) within the gas-liquid absorption tower. 3 / m 3 The residence time of the dehydrated filtrate in the gas-liquid absorption tower is 30-60 minutes.

[0029] Further, in step S1, the alkaline dehydration filtrate has a pH of 11-13, an ammonia nitrogen concentration of 1000-3000 mg / L, a total alkalinity of 6000-9000 mg / L, and a COD of 2000-5000 mg / L.

[0030] Furthermore, in step S3, PAM (polyacrylamide) solution is added to the wastewater sedimentation tank to accelerate the sedimentation and separation of particulate impurities in the wastewater.

[0031] Furthermore, in step S4, the bacteria in the integrated anaerobic ammonia oxidation reactor are composite encapsulated bacteria; the outer layer of the composite encapsulated bacteria is ammonia oxidizing bacteria, which are in an aerobic environment, come into contact with oxygen and oxidize ammonia nitrogen into nitrite nitrogen; the core of the composite encapsulated bacteria is anaerobic ammonia oxidizing bacteria, which are in an anaerobic environment, and ammonia nitrogen and nitrite nitrogen permeate into the core and are converted into nitrogen gas.

[0032] Furthermore, in step S4, the membrane treatment unit performs deep treatment including the following process: the effluent from the integrated anaerobic ammonia oxidation reactor is separated into sludge and impurities by an external tubular ultrafiltration membrane system, and the ultrafiltration liquid is then subjected to deep treatment by a low-pressure reverse osmosis membrane. The resulting reverse osmosis liquid is used as production water for purposes including flue gas coolers.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The system and method for combined treatment of biogas combustion exhaust gas and sludge dewatering filtrate provided by this invention achieves NO reduction through spray cooling and air oxidation of the waste gas. X Partial oxidation, followed by a gas-liquid reaction with alkaline wastewater, to remove NO from the waste gas. X It absorbs SO2 and simultaneously lowers the pH value of alkaline wastewater.

[0035] 2. The system and method for the combined treatment of biogas combustion tail gas and sludge dewatering filtrate provided by the present invention adopts anaerobic ammonia oxidation process to jointly treat pretreated wastewater and exhaust gas. By utilizing the characteristics of flue gas and wastewater, the two are treated synergistically. Furthermore, by utilizing the low-energy denitrification performance of anaerobic ammonia oxidation, both efficient removal of nitrogen from wastewater and flue gas are achieved, while ensuring further biochemical degradation of residual components in the flue gas.

[0036] 3. The system and method for combined treatment of biogas combustion tail gas and sludge dewatering filtrate provided by the present invention treats waste with waste, which has high environmental and economic benefits and significant effects. Compared with SCR and SNCR processes and oxidation + alkaline absorption liquid methods, this method has lower overall cost, lower terminal tail gas emission concentration, and better synergistic treatment effect. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the structure of a system for the combined treatment of biogas combustion exhaust gas and sludge dewatering filtrate provided by the present invention.

[0038] Explanation of the labels in the diagram:

[0039] 1. Biogas generator; 2. Flue gas cooler; 3. Air oxidizer; 4. Gas-liquid absorption tower; 5. Flue gas compressor; 6. Aeration branch pipe; 7. Wastewater sedimentation tank; 8. Integrated anaerobic ammonia oxidation reactor; 9. Membrane treatment unit; 10. Flue gas inlet pipe; 11. Flue gas outlet pipe; 12. Wastewater inlet pipe; 13. Wastewater outlet pipe. Detailed Implementation

[0040] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0041] Any preparation methods, materials, structures, or composition ratios not explicitly described in this technical solution are considered common technical features disclosed in the prior art.

[0042] During the conceptualization process of this technical solution, it was fully recognized that the flue gas from biogas power generation contains NO. X SO X Before being discharged, these substances require denitrification and desulfurization treatments. The denitrification section typically uses reducing agents such as ammonia / urea to react with NO. X The sulfur dioxide is reduced to nitrogen under the action of V2O5 / TiO2 catalyst. Desulfurization is achieved through wet / dry adsorption and neutralization using alkaline substances. This process requires dedicated waste gas treatment equipment and incurs certain operating and maintenance costs. Compared with conventional SCR and SNCR methods, the method of flue gas oxidation + alkaline absorption does not demonstrate significant economic and environmental benefits or the concept of treating waste with waste. Furthermore, it does not address how to efficiently treat the NO2-containing wastewater. Conventional biological denitrification technologies require a large amount of external carbon source for such low C / N ratio wastewater, and acid adjustment is needed for alkaline wastewater, resulting in high operating costs. Therefore, the applicant proposes a combined treatment approach: combining alkaline sludge filtrate with biogas combustion. This utilizes the interaction between alkaline wastewater and acidic waste gas to lower the pH of the wastewater and neutralize NOx and SO2 in the wastewater. Then, anaerobic ammonia oxidation is used to remove total nitrogen and residual gaseous pollutants from the wastewater. This approach is characterized by environmental protection and energy saving, treating waste with waste, and significant effectiveness.

[0043] The exhaust gas from the biogas generator is pretreated with the alkaline sludge dewatering filtrate to remove NO from the waste gas. X After gaseous pollutants are converted and dissolved in wastewater, they are then treated biochemically using anaerobic ammonia oxidation, which solves the problems of denitrification and desulfurization of generator flue gas, and at the same time achieves efficient denitrification treatment of filter press liquid.

[0044] After anaerobic digestion, the sludge produces biogas and biogas residue. In addition to maintaining the heating required by the system, the remaining biogas can be used to generate electricity through a generator. The dewatered filtrate produced after the biogas residue is dewatered has the characteristics of low C / N ratio, high pH and high ammonia nitrogen.

[0045] In the following examples, commercially available anaerobic ammonia-oxidizing bacteria were used. These bacteria were granular, red in appearance, spherical, and 0.5-2.0 mm in diameter. Anaerobic ammonia-oxidizing bacteria are autotrophic bacteria that use carbon dioxide or carbonate as a carbon source, ammonium salts as electron donors, and nitrite as electron acceptors. The composite-encapsulated bacteria employed a one-stage operating process: the outer layer consists of ammonia-oxidizing bacteria that oxidize ammonium ions to nitrite under aerobic aeration; the inner core consists of anaerobic ammonia-oxidizing bacteria in an anaerobic environment, where ammonia and nitrite permeate into the core and are converted into nitrogen gas.

[0046] Example

[0047] like Figure 1 As shown, this embodiment provides a system for the combined treatment of biogas combustion exhaust gas and sludge dewatering filtrate. The system includes a biogas generator 1, a flue gas cooler 2, an air oxidizer 3, a gas-liquid absorption tower 4, a flue gas compressor 5, a wastewater sedimentation tank 7, an integrated anaerobic ammonia oxidation reactor 8, and a membrane treatment unit 9. The biogas generator 1, flue gas cooler 2, air oxidizer 3, and gas-liquid absorption tower 4 are connected sequentially through a flue gas inlet pipe 10; the gas-liquid absorption tower 4, flue gas compressor 5, and integrated anaerobic ammonia oxidation reactor 8 are connected sequentially through a flue gas outlet pipe 11. The gas-liquid absorption tower 4, wastewater sedimentation tank 7, and integrated anaerobic ammonia oxidation reactor 8 are connected sequentially via wastewater outlet pipe 13; the gas-liquid absorption tower 4 is connected to wastewater inlet pipe 12, and the alkaline dewatering filtrate enters the upper part of the gas-liquid absorption tower 4 through wastewater inlet pipe 12; the integrated anaerobic ammonia oxidation reactor 8 and membrane treatment unit 9 are connected via pipelines; the integrated anaerobic ammonia oxidation reactor 8 is equipped with aeration branch pipe 6, which is used to supply oxygen to the integrated anaerobic ammonia oxidation reactor 8 and further biochemically degrade and remove residual components in the flue gas.

[0048] The flue gas cooler 2 is located at the rear end of the economizer or waste heat boiler in the generator exhaust pipe. It uses a pipeline sprayer to cool the flue gas. The water source is the water produced by the membrane treatment unit 9. After cooling, the flue gas temperature is controlled below 100℃.

[0049] The air oxidizer 3 includes an air injection port and a duct static mixer. The air injection port is connected to the duct static mixer to enhance the mixing efficiency of flue gas and air. The volume mixing ratio of air to flue gas in the air oxidizer 3 is 2:1.

[0050] The gas-liquid absorption tower 4 has an inlet at the top and an outlet at the bottom; the inlet is equipped with an anti-clogging nozzle; the gas-liquid absorption tower 4 contains a packing layer, and the outlet at the bottom has a "U" shaped structure to prevent flue gas from entering the outlet.

[0051] Wastewater sedimentation tank 7 adopts one of the horizontal flow sedimentation tanks; PAM solution is added to wastewater sedimentation tank 7 to accelerate the sedimentation and separation of particulate impurities in wastewater, and a slag discharge port is provided at the bottom of wastewater sedimentation tank 7.

[0052] This embodiment also provides a method for the combined treatment of biogas combustion exhaust gas and sludge dewatering filtrate, using the above-mentioned system, as detailed below:

[0053] Within a sludge treatment plant, a portion of the biogas produced from the anaerobic digestion of sludge is used for power generation. The generator exhaust emission index is: NO. X 400mg / m 3 SO2 is 20 mg / m³ 3 The emissions exceed the air pollutant emission standards for relevant industry facilities, necessitating the addition of external denitrification facilities for flue gas, which consumes reducing agents and catalysts. Simultaneously, the anaerobic digestion sludge undergoes alkaline dewatering, and the dewatered sludge cake is treated through incineration, producing dewatered filtrate (alkaline dewatered filtrate) with the following characteristics: pH 11.5, ammonia nitrogen concentration 1000 mg / L, nitrite nitrogen concentration 0 mg / L, nitrate nitrogen concentration 0 mg / L, total alkalinity 6000 mg / L, and COD 2000 mg / L. This filtrate is characterized by high pH and a low C / N ratio, requiring the addition of large amounts of acid for pH adjustment and additional carbon sources for conventional biological treatment. Both the flue gas and wastewater treatment processes incur significant operating costs, require substantial maintenance, and are environmentally unfriendly.

[0054] Using this technical solution, the flue gas from the biogas generator 1 is cooled and oxidized by the flue gas cooler 2 and the air oxidizer 3, reducing the flue gas temperature to 50℃. This process also removes NO, mainly NO, from the flue gas. X The NO2 generated in the flue gas is converted to NO2 and then enters the gas-liquid absorption tower 4 for a counter-current reaction with the alkaline dehydrated filtrate. The absorption tower has a height-to-diameter ratio of 10:1, a gas-to-liquid ratio of 100:1, and a filtrate residence time of 1 hour. The NO2 generated in the flue gas is absorbed to form nitrite (NO2). - This process reduces the pH of the wastewater. Gas detection was performed at the flue gas outlet of gas-liquid absorption tower 4: NO... X Concentration reduced to 100 mg / m³ 3 SO2 was not detected, meeting emission standards. Water quality testing was conducted at the wastewater outlet of gas-liquid absorption tower 4: ammonia nitrogen concentration was 950 mg / L, nitrite nitrogen concentration was 70 mg / L, nitrate nitrogen concentration was 10 mg / L, and the wastewater pH decreased to 9.5.

[0055] Wastewater from the lower part of the gas-liquid absorption tower 4 enters the wastewater sedimentation tank 7, where a small amount of PAM solution is added for flocculation to remove impurities before entering the integrated anaerobic ammonia oxidation reactor 8. Simultaneously, flue gas from the upper part of the gas-liquid absorption tower 4 is pressurized by the flue gas compressor 5 (pressure value corresponds to water depth; generally, 1 meter water depth corresponds to 10 kPa pressure, and the compressor selection is related to the design water depth) before entering the integrated anaerobic ammonia oxidation reactor 8 for aeration. Inside the integrated anaerobic ammonia oxidation reactor 8, composite encapsulated bacteria first convert a portion of ammonia nitrogen into nitrite nitrogen. Then, the remaining ammonia nitrogen, nitrite nitrogen, and nitrite nitrogen generated from the absorbed flue gas are converted into nitrogen gas together. At the same time, residual components in the flue gas are further biochemically degraded and removed. The water is then treated by membrane treatment unit 9 (external tubular ultrafiltration membrane + low-pressure reverse osmosis membrane). The deep treatment by the membrane treatment unit includes the following processes: the effluent from the integrated anaerobic ammonia oxidation reactor 8 passes through an external tubular ultrafiltration membrane system to separate sludge and impurities. The ultrafiltration liquid then undergoes deep treatment by a low-pressure reverse osmosis membrane. The resulting reverse osmosis liquid is used as production water for processes including flue gas cooler 2. The water quality of the permeate from membrane treatment unit 9 is tested: ammonia nitrogen concentration 8.7 mg / L, nitrite nitrogen concentration 2.8 mg / L, nitrate nitrogen concentration 17 mg / L, and total nitrogen removal efficiency 97%, which meets the requirements for recycled water in the process unit.

[0056] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for the combined treatment of biogas combustion exhaust gas and sludge dewatering filtrate, characterized in that, The method includes the following steps: After the flue gas from the biogas generator (1) is cooled down by the flue gas cooler (2), it enters the air oxidizer (3) and undergoes an oxidation reaction with the injected air. Then it enters the lower part of the gas-liquid absorption tower (4) and comes into reverse contact with the alkaline dehydration filtrate that enters the upper part of the gas-liquid absorption tower (4). At the top of the gas-liquid absorption tower (4), the flue gas after reaction is pressurized by the flue gas compressor (5) and enters the aeration branch pipe (6) in the integrated anaerobic ammonia oxidation reactor (8) to supply oxygen to the integrated anaerobic ammonia oxidation reactor (8) and further biochemically degrade and remove the residual components in the flue gas. Inside the gas-liquid absorption tower (4), the dehydrated filtrate absorbs NO2 and NO in the flue gas and converts it into nitrite and lowers the pH. At the same time, the CO2 contained in the flue gas also helps to lower the pH. The wastewater after the reaction at the bottom of the gas-liquid absorption tower (4) enters the wastewater sedimentation tank (7) to remove the impurities carried in the flue gas and generated by the gas-liquid reaction, and then enters the integrated anaerobic ammonia oxidation reaction tank (8). The pretreated flue gas and the pretreated filtrate undergo a chemical reaction in an integrated anaerobic ammonia oxidation reactor (8). First, ammonia oxidizing bacteria convert a portion of the ammonia nitrogen in the water into nitrite nitrogen under aeration conditions. Then, the remaining ammonia nitrogen, nitrite nitrogen, and nitrite nitrogen generated from the flue gas are converted into nitrogen gas together. Finally, the gas is further treated by the membrane treatment unit (9). A method for the combined treatment of biogas combustion exhaust gas and sludge dewatering filtrate using a system; The system includes a biogas generator (1), a flue gas cooler (2), an air oxidizer (3), a gas-liquid absorption tower (4), a flue gas compressor (5), a wastewater sedimentation tank (7), an integrated anaerobic ammonia oxidation reactor (8), and a membrane treatment unit (9). The biogas generator (1), flue gas cooler (2), air oxidizer (3), and gas-liquid absorption tower (4) are connected in sequence by pipelines; The gas-liquid absorption tower (4), flue gas compressor (5), and integrated anaerobic ammonia oxidation reactor (8) are connected in sequence by pipelines; The gas-liquid absorption tower (4), wastewater sedimentation tank (7), and integrated anaerobic ammonia oxidation reactor (8) are connected in sequence by pipelines; The integrated anaerobic ammonia oxidation reactor (8) and membrane treatment unit (9) are connected by pipelines; The integrated anaerobic ammonia oxidation reactor (8) is equipped with an aeration branch pipe (6), which is used to supply oxygen to the integrated anaerobic ammonia oxidation reactor (8) and further biochemically degrade and remove residual components in the flue gas. The system achieves NO reduction by spray cooling and air oxidation of the waste gas. X Partial oxidation, followed by a gas-liquid reaction with alkaline wastewater, to remove NO from the waste gas. X It absorbs SO2 and simultaneously lowers the pH value of alkaline wastewater; In step S1, the alkaline dehydration filtrate has a pH of 11-13, an ammonia nitrogen concentration of 1000-3000 mg / L, a total alkalinity of 6000-9000 mg / L, and a COD of 2000-5000 mg / L.

2. The method for combined treatment of biogas combustion exhaust gas and sludge dewatering filtrate according to claim 1, characterized in that, The biogas generator (1), flue gas cooler (2), air oxidizer (3), and gas-liquid absorption tower (4) are connected in sequence through a flue gas inlet pipe (10); The gas-liquid absorption tower (4), flue gas compressor (5), and integrated anaerobic ammonia oxidation reactor (8) are connected in sequence through flue gas outlet pipe (11); The gas-liquid absorption tower (4), wastewater sedimentation tank (7), and integrated anaerobic ammonia oxidation reactor (8) are connected in sequence through wastewater outlet pipe (13); The gas-liquid absorption tower (4) is connected to the wastewater inlet pipe (12), and the alkaline dehydration filtrate enters the upper part of the gas-liquid absorption tower (4) through the wastewater inlet pipe (12).

3. The method for combined treatment of biogas combustion exhaust gas and sludge dewatering filtrate according to claim 1, characterized in that, The flue gas cooler (2) is located at the rear end of the economizer or waste heat boiler in the generator exhaust pipe and is cooled by a pipe sprayer.

4. The method for combined treatment of biogas combustion exhaust gas and sludge dewatering filtrate according to claim 1, characterized in that, The air oxidizer (3) includes an air injection port and a pipeline static mixer, wherein the air injection port is connected to the pipeline static mixer; The volume mixing ratio of air and flue gas in the air oxidizer (3) is 1:1-3:

1.

5. The method for combined treatment of biogas combustion exhaust gas and sludge dewatering filtrate according to claim 1, characterized in that, The height-to-diameter ratio of the gas-liquid absorption tower (4) is 5:1-10:1; The gas-liquid absorption tower (4) is provided with an inlet at the top and an outlet at the bottom; The water inlet is equipped with an anti-clogging nozzle; The gas-liquid absorption tower (4) contains a packing layer and the lower outlet has a "U" shaped structure to prevent flue gas from entering the outlet.

6. The method for combined treatment of biogas combustion exhaust gas and sludge dewatering filtrate according to claim 1, characterized in that, The wastewater sedimentation tank (7) adopts one of the following: inclined tube, inclined plate, or horizontal flow sedimentation tank; The wastewater sedimentation tank (7) is equipped with a slag discharge port at the bottom.

7. The method for combined treatment of biogas combustion exhaust gas and sludge dewatering filtrate according to claim 1, characterized in that, The gas and dehydrated filtrate after oxidation reaction with the injected air have a gas-liquid ratio of 50:1-150:1 by volume in the gas-liquid absorption tower (4), and the residence time of the dehydrated filtrate in the gas-liquid absorption tower (4) is 30min-60min.

8. The method for combined treatment of biogas combustion exhaust gas and sludge dewatering filtrate according to claim 1, characterized in that, PAM solution is added to the wastewater sedimentation tank (7) to accelerate the sedimentation and separation of particulate impurities in the wastewater.

9. The method for combined treatment of biogas combustion tail gas and sludge dewatering filtrate according to claim 1, characterized in that, The bacteria in the integrated anaerobic ammonia oxidation reactor (8) are complex encapsulated bacteria; The outer layer of the composite encapsulated bacteria is an ammonia-oxidizing bacterium, which is in an aerobic environment, comes into contact with oxygen, and oxidizes ammonia nitrogen into nitrite nitrogen; the core of the composite encapsulated bacteria is an anaerobic ammonia-oxidizing bacterium, which is in an anaerobic environment, where ammonia nitrogen and nitrite nitrogen permeate into the core and are converted into nitrogen gas.

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