Anaerobic ammoxidation coupled anaerobic digestion system with cooperation of biological denitrification and biogas purification and use method of anaerobic ammoxidation coupled anaerobic digestion system

Abstract

The invention relates to an anaerobic ammonia oxidation coupled anaerobic digestion system with biological denitrification cooperating with biogas purification and a use method thereof. The system comprises an anaerobic digestion tank, a carbon dioxide absorption device and a PN / A unit, the PN / A unit comprises an anaerobic ammonia oxidation reactor and a sequencing batch reactor; the anaerobic digestion tank is used for providing an anaerobic digestion environment for organic solid waste or organic wastewater, a biogas outlet of the anaerobic digestion tank is connected with the carbon dioxide absorption device, and a digestion liquid outlet of the anaerobic digestion tank is connected with a water inlet of the sequencing batch reactor; the carbon dioxide absorption device is used for absorbing carbon dioxide in gas discharged from the biogas outlet through water so as to purify the biogas; the water outlet of the sequencing batch reactor is connected with the water inlet of the anaerobic ammonia oxidation reactor, the water outlet of the anaerobic ammonia oxidation reactor is connected with the carbon dioxide absorption device, and the liquid outlet of the carbon dioxide absorption device is connected with the water inlet of the anaerobic ammonia oxidation reactor to form a liquid circulation loop. According to the invention, integration of biogas purification, denitrification, sulfur removal and pH self-regulation is realized.

Description

Technical Field

[0001] The present invention belongs to the field of biogas energy utilization and high-ammonia nitrogen wastewater treatment, and particularly relates to an anaerobic ammonia oxidation coupled anaerobic digestion system for biological denitrification and coordinated biogas purification and a method for use thereof. Background Art

[0002] The biogas produced by anaerobic digestion processes and landfills is mainly composed of methane (CH4) and carbon dioxide (CO2). The substrate used, the fermentation technology and the collection method will affect the production and composition of the raw biogas. In addition to CH4 and CO2, raw biogas also contains small amounts of ammonia (NH3), hydrogen sulfide (H2S), etc. CO2 is a stubborn gas that reduces the density and calorific value of biogas, but it is not as toxic and corrosive as H2S. The latter is harmful to the environment and corrosive to metal parts such as engines, pumps, compressors, gas tanks and valves. In order to increase the calorific value and reduce harmful components, it is important to clean the raw biogas and upgrade it to a higher fuel standard. This process is called biogas purification and upgrading. At present, industrial-scale CO2 removal is based on physical and chemical technologies, among which washing with water, organic solvents or chemical solutions, pressure swing adsorption, membrane separation and low-temperature CO2 separation are the main methods for biogas physical and chemical purification. All of them can adopt multi-step operations and separate equipment for decarbonization, desulfurization and denitrification. However, they have disadvantages such as complex control, weak impact resistance and serious waste of resources. Therefore, it is urgent to find ultra-low energy consumption and simple biogas purification methods. Summary of the Invention

[0003] In view of the current problems of high energy consumption, chemical waste liquid pollution, multi-unit fragmentation, non-circulation of resources and weak impact resistance in biogas purification and upgrading, the present invention provides an anaerobic ammonium oxidation coupled anaerobic digestion system with high-efficiency biological denitrification and coordinated biogas purification, and its use method. Through the three-unit synergy and material circulation mechanism, anaerobic biogas production, anaerobic ammonium oxidation denitrification and biogas purification are combined, which is a beneficial supplement to traditional waste treatment and efficient utilization of biogas, breaking through the bottleneck of high cost, high pollution and low efficiency of traditional technology, realizing the integration of biogas purification, denitrification, sulfur and pH self-regulation, and providing an innovative solution for distributed biogas projects.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] An anaerobic ammonium oxidation coupled anaerobic digestion system for biological denitrification and biogas purification, comprising an anaerobic digestion tank, a carbon dioxide absorption device, and a PN / A unit; the PN / A unit comprises an anaerobic ammonium oxidation reactor and a sequencing batch reactor;

[0006] The anaerobic digester is used to provide an anaerobic digestion environment for organic solid waste or organic wastewater, the biogas outlet of which is connected to the carbon dioxide absorption device, and the digestate outlet is connected to the water inlet of the sequencing batch reactor;

[0007] The carbon dioxide absorption device is used to absorb carbon dioxide in the gas discharged from the biogas outlet through water to purify the biogas;

[0008] The water outlet of the sequencing batch reactor is connected to the water inlet of the anaerobic ammonium oxidation reactor, the water outlet of the anaerobic ammonium oxidation reactor is connected to the carbon dioxide absorption device, and the liquid outlet of the carbon dioxide absorption device is connected to the water inlet of the anaerobic ammonium oxidation reactor to form a liquid circulation loop.

[0009] In one embodiment, the anaerobic ammonium oxidation reactor contains autotrophic bacteria Anammox bacteria, and the sequencing batch reactor contains autotrophic bacteria AOB bacteria.

[0010] In one embodiment, the entire system is equipped with a hot water bath circulation device to maintain the operating temperature at 31-35°C.

[0011] In one embodiment, the biogas outlet of the anaerobic digester is connected to the liquid level of the carbon dioxide absorption device, and the gas is passed through the internal spiral blades through the swirl cutting aeration head to generate centrifugal force, breaking the bubbles into 0.5-2mm microbubbles, thereby maximizing the gas-liquid mass transfer area.

[0012] The present invention also provides a method for using the anaerobic ammonium oxidation coupled anaerobic digestion system for biological denitrification and biogas purification, comprising the following steps:

[0013] Step 1: feeding the organic solid waste or organic wastewater into the anaerobic digester for anaerobic digestion reaction, maintaining the temperature at 31-35° C., feeding the generated gas into the carbon dioxide absorption device, and feeding the digestion liquid into the sequencing batch reactor;

[0014] Step 2: The carbon dioxide absorption device absorbs carbon dioxide in the produced gas using water to purify the biogas, and the purified biogas is stored;

[0015] Step 3: The sequencing batch reactor oxidizes part of the ammonia nitrogen in the digestion liquid into NO2 - , generating NH4 + With NO2 - The mixed liquid is sent to the anaerobic ammonium oxidation reactor;

[0016] Step 4, the anaerobic ammonium oxidation reactor, the NH4 + With NO2 - Converted into N2, and at the same time, the carbon dioxide in the liquid of the carbon dioxide absorption device is used to supplement the inorganic carbon source to maintain cell proliferation.

[0017] In one embodiment, in step 1, the gas produced by the anaerobic digester contains 50%-60% methane and 20%-30% carbon dioxide, and the effluent digestion liquid contains NH4 + -N content is 1000-3500 mg / L; in the step 2, in the carbon dioxide absorption device, part of the carbon dioxide dissolves in water and reacts with water to generate carbonic acid, thereby increasing the purity of methane to more than 95% and promoting the decrease of the pH of the solution, and part of the carbon dioxide reacts with the anaerobic ammonium oxidation effluent to generate CO2+2OH - =CO3 2- +H2O.

[0018] In one embodiment, the effluent pH of the anaerobic ammonium oxidation reactor is greater than 9, and the effluent return flow of the anaerobic ammonium oxidation reactor and / or the gas production flow of the anaerobic digester are controlled so that the pH of the liquid in the carbon dioxide absorption device drops to pH less than 8 as aeration continues, and then flows back to the anaerobic ammonium oxidation reactor.

[0019] In one embodiment, the liquid level of the carbon dioxide absorption device is maintained between 2 / 5 and 3 / 5.

[0020] In one embodiment, in step 3, the sequencing batch reactor oxidizes 50% of the ammonia nitrogen into NO2 under the condition of 0.3-0.8 mg / L dissolved oxygen. - , generating NH4 + :NO2 - ≈1:1.32 mixture.

[0021] In one embodiment, in step 4, the effluent from the anaerobic ammonium oxidation reactor is refluxed and discharged, ultimately achieving NH3-N ≤ 45 mg / L in the effluent.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. Through the synergy of three units and the material circulation mechanism, anaerobic biogas production, anaerobic ammonium oxidation denitrification and biogas purification are combined to achieve the integrated purpose of biogas purification, denitrification, sulfur and pH self-regulation.

[0024] 2. For the first time, the effluent from the anaerobic ammonium oxidation reactor is circulated to the gas absorption device, and pH self-regulation is achieved through liquid acidification-buffered reflux, which has the innovative advantage of resource recycling. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of the present invention.

[0026] Table 1 is the results of the implementation of the present invention (comparative data). DETAILED DESCRIPTION

[0027] The embodiments of the present invention are described in detail below with reference to the accompanying drawings and examples.

[0028] Existing biogas purification still has problems such as high energy consumption, waste of resources and weak impact resistance. To this end, the present invention provides an anaerobic ammonium oxidation coupled anaerobic digestion system with high efficiency biological denitrification and biogas purification and its use method. Figure 1 As shown, the system mainly includes an anaerobic digester 1, a carbon dioxide absorption device 2, and a PN / A unit 3. The PN / A unit 3 mainly consists of a PN unit and an Anammox unit. The Anammox unit is an anaerobic ammonium oxidation reactor 15 containing an autotrophic bacterial group Anammox bacteria, and the PN unit is a sequencing batch reactor 14 containing an autotrophic bacterial group AOB bacteria.

[0029] The feed of the anaerobic digester 1 is typical urban organic solid waste or high-concentration organic wastewater, typically a mixed matrix of food waste and excess sludge. The carbon dioxide absorption device 2 is connected to the biogas outlet of the anaerobic digester 1 to purify the biogas and produce HCO3-rich - The liquid after absorption of sulfide and purified biogas (CH4≥95%, CO2≤5%, H2S≤50ppm) enters the gas storage tank 13. The sequencing batch reactor 14 is connected to the high ammonia nitrogen wastewater discharged from the anaerobic digester 1, which contains NH4 + and NO2 - The effluent of the anaerobic ammonium oxidation reactor 15 is used as the inlet water. The effluent of the anaerobic ammonium oxidation reactor 15 is circulated to the carbon dioxide absorption device 2 to absorb HCO3 - The liquid is then returned to the anaerobic ammonium oxidation reactor 15, providing an inorganic carbon source for the Anammox bacteria while also adjusting the pH. This ultimately achieves efficient denitrification and biogas quality improvement, raising CH4 purity to over 95%. This overcomes the drawbacks of traditional processes, such as high chemical consumption and the independent operation of multiple units. It simultaneously achieves biogas purification and efficient denitrification without adding a carbon source and using low energy consumption.

[0030] To maintain the reaction environment, the present invention is equipped with a hot water bath circulation device 5 to maintain the temperature at about 35±1°C, and is equipped with an aeration pump 6 for aeration, a liquid level controller 7 controls the liquid level of the carbon dioxide absorption device 2, a gas flow meter 8 monitors the gas flow, a paperless recorder 9 records the transmembrane pressure (TMP), a peristaltic pump 10, a peristaltic pump 2 11 and a peristaltic pump 3 12 provide liquid transmission power, and a gas storage tank 13 stores the purified methane.

[0031] In the present invention, the anaerobic digester 1 is fed with a mixed matrix of kitchen waste and excess sludge or other urban organic solid waste, high-concentration wastewater, etc. through its feed port 4, and an aeration pump 6 is used to perform intermittent cyclic aeration from bottom to top, so that the anaerobic digestion is fully carried out and the digestion liquid (NH4 +-N 1000-1500mg / L) is pumped into the sequencing batch reactor 14 through a peristaltic pump 10, and 50% of the ammonia nitrogen is oxidized to NO2 under the condition of dissolved oxygen 0.3-0.8mg / L - , generating NH4 + :NO2 - The mixed solution is ≈1:1.32, and the effluent is connected to the anaerobic ammonium oxidation reactor 15 to provide the required NH4 for the Anammox reaction + and NO2 - The generated biogas (containing CH4 50%-60%, CO2 20%-30%, H2S 0.55%-3%) is connected to the liquid level of the carbon dioxide collection device 2. The contact area between water and gas is increased through aeration, which promotes the dissolution and mixing of gas in water. Part of the carbon dioxide dissolves in water and reacts with water to generate carbonic acid (H2CO3), which promotes the decrease of solution pH. The other part reacts with the anaerobic ammonium oxidation effluent (pH>9) to generate CO2+2OH - =CO3 2- With continued aeration, the pH drops further to less than 8. The biogas is then returned to the anaerobic ammonium oxidation reactor 15 via a liquid level controller 7, which controls a peristaltic pump 12, stabilizing the pH required for the anammox reaction (7.0-8.0). Finally, the biogas is measured by a flow meter 8 and collected in a gas storage tank 13 for purification.

[0032] The following is a specific embodiment of the present invention.

[0033] Example 1

[0034] like Figure 1 As shown, this embodiment provides an anaerobic ammonium oxidation coupled anaerobic digestion system with high efficiency biological denitrification and biogas purification and a method for using the system, the main steps of which include:

[0035] 200 mL of the mixed matrix of food waste and excess sludge was added to the anaerobic digestion tank 1 through the feed port 4, and a hot water bath circulation device 5 was equipped to maintain the temperature at 35 ° C. Intermittent circulation aeration was performed from bottom to top through the aeration pump 6 to ensure that the anaerobic digestion was fully carried out. The digestion liquid (NH4 + -N 1000-1500mg / L) is pumped into the sequencing batch reactor 14 through the peristaltic pump 10, and 50% of the ammonia nitrogen is oxidized to NO2 under the condition of 0.3-0.8mg / L dissolved oxygen. - , generating NH4 + :NO2 - The mixed solution is ≈1:1.32, and the effluent is connected to the anaerobic ammonium oxidation reactor 15 to provide the required NH4 for the Anammox reaction + and NO2 -The gas (containing CH4 53%, CO2 44%, H2S 3%) is connected to the liquid level of the carbon dioxide collection device 2 through a pipeline. The contact area between water and gas is increased by aeration, which promotes the dissolution and mixing of gas in water. Part of the carbon dioxide dissolves in water and reacts with water to form carbonic acid (H2CO3), which promotes the decrease of solution pH. Part of the carbon dioxide reacts with the anaerobic ammonium oxidation effluent (pH>9) to form CO2+2OH - =CO3 2- +H2O, as aeration continues, the pH further drops to pH <8, and is refluxed to the anaerobic ammonium oxidation reactor 15 through the liquid level controller 7 linked to the peristaltic pump 12, stabilizing the pH environment required by Anammox (7.0-8.0). The present invention significantly optimizes the gas purification and sewage treatment efficiency through innovative processes: in the biogas purification process, compared with the current mainstream research direction (such as PSA and membrane separation coupling), in order to optimize the traditional process, the CH4 purity is increased from 59% to 93% (↑34%), the CO2 content is reduced from 30% to 4.5%, and the H2S removal rate is >99%, which is close to the complete removal level; in terms of cost and environmental protection, the denitrification process achieves zero reagent consumption, saving 100% of the acid addition cost, and at the same time, the effluent ammonia nitrogen concentration is ≤50mg / L, stably reaching the national Class A emission standard. The specific results are shown in Table 1 below.

[0036] Table 1

[0037] index Traditional crafts The present invention Improvement effect <![CDATA[CH4 purity]]> 59％ 93％ ↑34％ <![CDATA[CO2 content]]> 36％ 4.5％ ↓31.5％ <![CDATA[H2S removal rate]]> <80％ >99％ Nearly complete removal Denitrification cost Acid addition: 0.5 yuan / ton Zero potion consumption Save 100% Ammonia nitrogen in effluent 80-120mg / L ≤50mg / L Reaching Level A standard

Claims

1. An anaerobic ammonium oxidation coupled anaerobic digestion system with biological denitrification and biogas purification, characterized in that: The invention comprises an anaerobic digestion tank (1), a carbon dioxide absorption device (2) and a PN / A unit (3); the PN / A unit (3) comprises an anaerobic ammonium oxidation reactor (15) and a sequencing batch reactor (14); The anaerobic digestion tank (1) is used to provide an anaerobic digestion environment for organic solid waste or organic wastewater, and its biogas outlet is connected to the carbon dioxide absorption device (2), and its digestion liquid outlet is connected to the water inlet of the sequencing batch reactor (14); The carbon dioxide absorption device (2) is used to absorb carbon dioxide in the gas discharged from the biogas outlet through water to purify the biogas; The water outlet of the sequencing batch reactor (14) is connected to the water inlet of the anaerobic ammonium oxidation reactor (15), the water outlet of the anaerobic ammonium oxidation reactor (15) is connected to the carbon dioxide absorption device (2), and the liquid outlet of the carbon dioxide absorption device (2) is connected to the water inlet of the anaerobic ammonium oxidation reactor (15), forming a liquid circulation loop.

2. The anaerobic ammonium oxidation coupled anaerobic digestion system for biological denitrification and biogas purification according to claim 1, characterized in that: The anaerobic ammonium oxidation reactor (15) contains the autotrophic bacteria Anammox bacteria, and the sequencing batch reactor (14) contains the autotrophic bacteria AOB bacteria.

3. The anaerobic ammonium oxidation coupled anaerobic digestion system for biological denitrification and biogas purification according to claim 1, characterized in that: The entire system is equipped with a hot water bath circulation device to maintain the operating temperature at 31-35°C.

4. The anaerobic ammonium oxidation coupled anaerobic digestion system for biological denitrification and biogas purification according to claim 1, characterized in that: The biogas outlet of the anaerobic digester (1) is connected to the liquid level below the carbon dioxide absorption device (2). The gas is passed through the internal spiral blades through the swirl cutting aeration head to generate centrifugal force, breaking the bubbles into 0.5-2mm microbubbles, thereby maximizing the gas-liquid mass transfer area.

5. The method for using the anaerobic ammonium oxidation coupled anaerobic digestion system for biological denitrification and biogas purification according to any one of claims 1 to 4, characterized in that: The following steps are involved: Step 1: sending organic solid waste or organic wastewater into the anaerobic digestion tank (1) for anaerobic digestion reaction, maintaining the temperature at 31-35°C, sending the generated gas into the carbon dioxide absorption device (2), and sending the digestion liquid into the sequencing batch reactor (14); Step 2, the carbon dioxide absorption device (2) uses water to absorb carbon dioxide in the produced gas to purify the biogas, and the purified biogas is stored; Step 3, the sequencing batch reactor (14) oxidizes part of the ammonia nitrogen in the digestion liquid into NO2 - , generating NH4 + With NO2 - The mixed liquid is sent to the anaerobic ammonium oxidation reactor (15); Step 4, the anaerobic ammonium oxidation reactor (15) converts the NH4 + With NO2 - Converted into N2, and at the same time, the carbon dioxide in the liquid of the carbon dioxide absorption device (2) is used to supplement the inorganic carbon source to maintain cell proliferation.

6. The method for using the anaerobic ammonium oxidation coupled anaerobic digestion system for biological denitrification and biogas purification according to claim 5, characterized in that: In terms of volume, in the gas produced in the anaerobic digestion tank (1) in step 1, 50%-60% contains methane and 20%-30% carbon dioxide, and in the digestion liquid discharged, NH4 + -N content is 1000-3500 mg / L; in the step 2, in the carbon dioxide absorption device (2), part of the carbon dioxide dissolves in water and reacts with water to generate carbonic acid, thereby increasing the purity of methane to more than 95% and promoting the decrease of the pH value of the solution, and part of the carbon dioxide reacts with the anaerobic ammonium oxidation effluent to generate CO2+2OH - =CO3 2- +H2O.

7. The method for using the anaerobic ammonium oxidation coupled anaerobic digestion system for biological denitrification and biogas purification according to claim 6, characterized in that: The pH of the effluent from the anaerobic ammonium oxidation reactor (15) is greater than 9, and the effluent return rate of the anaerobic ammonium oxidation reactor (15) and / or the gas production rate of the anaerobic digestion tank (1) are controlled so that the pH of the liquid in the carbon dioxide absorption device (2) decreases to pH less than 8 as aeration continues, and then flows back to the anaerobic ammonium oxidation reactor (15).

8. The method for using the anaerobic ammonium oxidation coupled anaerobic digestion system for biological denitrification and biogas purification according to claim 6 or 7, characterized in that: The liquid level of the carbon dioxide absorption device (2) is maintained between 2 / 5 and 3 / 5.

9. The method for using the anaerobic ammonium oxidation coupled anaerobic digestion system for biological denitrification and biogas purification according to claim 5, characterized in that: In step 3, the sequencing batch reactor (14) oxidizes 50% of the ammonia nitrogen into NO2 under the condition of 0.3-0.8 mg / L dissolved oxygen. - , generating NH4 + :NO2 - ≈1:1.32 mixture.

10. The method for using the anaerobic ammonium oxidation coupled anaerobic digestion system for biological denitrification and biogas purification according to claim 5, characterized in that: In the step 4, the effluent from the anaerobic ammonium oxidation reactor (15) achieves NH3-N≤45 mg / L.

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