System and method for preparing ammonium bicarbonate by ammonia extraction from sludge-kitchen waste combined anaerobic digestion tail water

Abstract

The application discloses a sludge-kitchen combined anaerobic digestion tail water ammonia extraction system and method for preparing ammonium bicarbonate, and belongs to the technical field of environmental protection and resource recycling. The system comprises a mixing system, a kitchen garbage treatment system connected with the feeding end of the mixing system, a sludge treatment system connected with the feeding end of the mixing system, an anaerobic digestion system connected with the discharging end of the mixing system, a biogas treatment system connected with the gas discharging end of the anaerobic digestion system, a biogas slurry storage tank connected with the material discharging port of the anaerobic digestion system, and an ammonia recovery system connected with the liquid discharging end of the biogas slurry storage tank. The in-situ pH technology is used to improve the ammonia removal efficiency of the biogas slurry, the concentration process is used to improve the ammonia gas purity, and then the production efficiency and purity of the ammonium bicarbonate are improved. The application can efficiently treat the kitchen garbage and the sludge, and can be economically and environmentally converted into a high-value-added product, which meets the development trend of the circular economy.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection and resource recycling technology, specifically to a system and method for preparing ammonium bicarbonate from sludge-kitchen wastewater combined anaerobic digestion tailwater. Background Technology

[0002] With global population growth and accelerated urbanization, the amount of urban food waste and sewage sludge generated is increasing daily, making the treatment of these wastes a global environmental challenge. Food waste and sludge are not only voluminous but also contain high levels of moisture, organic matter, and potential pathogens; improper handling can cause serious environmental pollution. Traditional treatment methods such as landfill, incineration, and composting often suffer from low efficiency, low resource recovery rates, and severe secondary pollution. Therefore, developing a new technology that can transform food waste and sludge into valuable products is of great significance.

[0003] Currently, the main technologies for treating food waste include physical, chemical, and biological methods. Physical methods primarily involve pretreatment through physical means such as crushing and sorting, but this method cannot effectively reduce the amount of waste. Chemical methods involve the use of chemical reagents, but have high operating costs and may produce harmful byproducts. Biological methods decompose organic waste through the action of microorganisms, such as anaerobic digestion technology. This technology can achieve energy utilization of resources to a certain extent, but still faces problems such as low methane production and high investment and operating costs.

[0004] In sludge treatment, common methods include anaerobic digestion, aerobic digestion, and composting. These methods can reduce sludge volume to some extent and recover some resources, but they still have problems such as long processing time, low resource utilization rate, and incomplete ammonia nitrogen removal. In particular, ammonia, as an odorous gas, not only pollutes the environment but also wastes resources during sludge treatment.

[0005] Ammonium bicarbonate, an important nitrogen fertilizer, is widely used in agricultural production. Currently, its production mainly relies on fossil fuels, using the Haber process to extract nitrogen from natural gas, which is then reacted with carbon dioxide to produce ammonium bicarbonate. This process not only consumes a large amount of non-renewable resources but also generates significant carbon emissions.

[0006] Faced with increasingly severe environmental pressures and resource shortages, transforming food waste and municipal sludge into valuable resources has become an urgent need. In particular, converting these wastes into fertilizer not only solves the waste disposal problem but also promotes sustainable agricultural development, forming a closed-loop economic model. Ammonium bicarbonate, as a commonly used nitrogen fertilizer, has stable market demand. If its preparation process can be effectively combined with the treatment of food waste and sludge, the comprehensive utilization rate of resources will be greatly improved.

[0007] Although several attempts have been made to use food waste or sludge separately for fertilizer production, such as through composting, anaerobic digestion, and land application, the following limitations exist in combined treatment: Technical compatibility issues: Existing treatment processes are often designed for single waste types, making it difficult to efficiently integrate the treatment of food waste and sludge; Low resource conversion efficiency: Due to differences in material characteristics, combined treatment may result in low efficiency and low resource conversion rates; Secondary pollution risk: Improper treatment methods may generate new pollutants, such as odorous gases and leachate, causing secondary pollution to the environment; Economic considerations: High treatment costs and complex technical requirements make it difficult to widely promote some advanced treatment technologies.

[0008] The invention patent application with application number 201910578302.X discloses a system and method for simultaneous recovery of carbon and nitrogen resources from anaerobic fermentation biogas slurry of kitchen waste. The method includes the following steps: (1) adjusting the pH of the anaerobic fermentation biogas slurry of kitchen waste to 9-10; (2) stirring in an N2 atmosphere and adding Mg dropwise. 2+ Solution and Al 3+ (3) After precipitation occurs, the suspension is subjected to hydrothermal treatment. After the reaction is completed, the precipitate is washed and collected to obtain carbon resource products; (4) The gas generated during the process carries NH3, which reacts with CO2 to form NH4HCO3 products and crystallizes out to obtain nitrogen resource products. This invention simply discloses a method for preparing NH4HCO3 products from biogas slurry of anaerobic fermentation of kitchen waste, but does not specifically disclose the method for preparing NH4HCO3 products by joint anaerobic fermentation of waste, kitchen waste and sludge in this application. Moreover, the method disclosed in this invention has low NH3 recovery efficiency.

[0009] Patent application number 202110383541.7 discloses a system and method for preparing organic acids / organoacid salts from kitchen waste. Specifically, after pretreatment of the kitchen waste, anaerobic acid production is carried out, with alkaline substances added to adjust the pH (pH > 8.0) to obtain a fermentation broth with a high organic acid / organoacid salt content (mass concentration of organic acids / organoacid salts > 5%). The fermentation broth is then steam-evaporated to remove ammonia nitrogen, ultimately yielding dephosphorized and denitrogenated organic acids / organoacid salts. This method cannot effectively utilize the ammonia nitrogen in the fermentation broth, therefore additional pollution-free treatment is required.

[0010] Patent application number 202210453683.0 discloses a method for recovering ammonia nitrogen from kitchen waste and preparing a carbon source for wastewater treatment. This method includes nine systems: a kitchen waste crushing and sorting system, a screw extrusion system, a sand and impurity removal system, a hot water hydrolysis system, an oil extraction system, a solid-liquid separation system, coagulation and sedimentation, and ammonia removal. This method can maximize the recovery of oil and NH3 from kitchen waste, reduce the salt content in kitchen waste, improve the quality of organic carbon sources produced from kitchen waste, maximize resource recycling, and increase the value of kitchen waste recycling products. Although the method mentions that the NH3 released during the production process can be recovered to produce ammonia water or ammonium bicarbonate, it does not disclose how to link the ammonium bicarbonate production system with the kitchen waste treatment system.

[0011] Therefore, it is particularly important to develop a system and method that can efficiently treat food waste and sludge and economically and environmentally transform them into high-value-added products. Summary of the Invention

[0012] In view of the above problems, the present invention discloses a system and method that can efficiently treat kitchen waste and sludge and economically and environmentally transform them into high value-added products, thereby achieving efficient and coordinated treatment of waste, optimizing resource allocation, improving resource conversion efficiency, reducing treatment costs, and reducing environmental pollution, which is in line with the development trend of circular economy.

[0013] To achieve the above objectives, the present invention provides a system and method for preparing ammonium bicarbonate by ammonia extraction from sludge-kitchen wastewater combined with anaerobic digestion.

[0014] The method for preparing ammonium bicarbonate from sludge-kitchen wastewater combined anaerobic digestion effluent includes:

[0015] S1. When collecting kitchen waste, it is classified according to its source. Food scraps collected in the community are classified as kitchen waste, and food scraps collected in restaurants are classified as catering waste.

[0016] S2. Pre-treat kitchen waste, catering waste and sludge separately;

[0017] S3. The pretreated kitchen waste, catering waste and sludge from step S2 are fed into the mixing system in a certain mass ratio. After being mixed evenly, they are fed into the anaerobic digestion system for anaerobic digestion. After anaerobic digestion, the waste is centrifuged and dehydrated to obtain biogas slurry containing ammonia nitrogen.

[0018] In steps S4 and S3, the biogas slurry passes through the impurity removal unit and the heat transfer unit in sequence, and then enters the stripping and desorption tower. In the stripping and desorption tower, ammonia vapor is generated through anaerobic ammonia oxidation. The biogas slurry is then transported to the stripping and desorption tower for further anaerobic ammonia oxidation to generate ammonia vapor. The ammonia vapor generated in the stripping and desorption tower is recovered by the ammonia vapor recovery device at the top of the stripping and desorption tower and sent back to the stripping and desorption tower. Together with the ammonia vapor generated in the stripping and desorption tower, the ammonia vapor is recovered by the ammonia vapor recovery device at the top of the stripping and desorption tower and sent to the condenser.

[0019] S5. After the ammonia vapor in the condenser is condensed, the liquid is transported to the stripping ammonia removal tower via a gas-liquid separator. The ammonia gas is transported to the ammonia concentration tower for concentration and purification by a vacuum pump installed between the ammonia concentration tower and the gas-liquid separator.

[0020] S6. The concentrated ammonia gas from step S5 is transported to the carbonization tower, and a carbon source is simultaneously transported to the carbonization tower. The ammonia gas and the carbon source undergo a neutralization reaction in the aqueous phase to generate ammonium bicarbonate.

[0021] S7. The mixed solution from step S6 is transported to a crystallization tank, where ammonium bicarbonate in the mixed solution crystallizes under low temperature conditions.

[0022] S8. The solid-liquid mixture after crystallization in the crystal slurry tank in step S7 is transported to a centrifuge for physical separation. The resulting liquid is transported to a gas-liquid separator, and the resulting solid is ammonium bicarbonate.

[0023] In step S2, the pretreatment of kitchen waste includes passing the kitchen waste through crushing and screening, magnetic separation, extrusion and dehydration, and sand and impurity removal in sequence.

[0024] Large-diameter fabric particles are removed through crushing and screening, magnetic metals are removed through magnetic separation, solid slag is removed through extrusion and dewatering, and inert materials such as sand and stone are removed through sand and impurity removal.

[0025] In step S2, the pretreatment of food waste includes sequentially passing the food waste through sand and impurity removal, hot water hydrolysis, and oil removal.

[0026] Food waste that has undergone sand removal, heating, and oil removal processes can reduce equipment wear caused by sand and other impurities, lower oil content, reduce the inhibitory effect of oil on the activity of anaerobic microorganisms, improve the biodegradability of organic matter, and enhance the stability of subsequent processing processes and the quality of the final product.

[0027] In step S2, the pretreatment of sludge includes sequentially passing the sludge through sand removal, impurity removal, and pulping treatment.

[0028] By removing sand and impurities and pulping the sludge, the consistency of the pretreated sludge is maintained, thus improving the stability of production.

[0029] In step S2, the pretreated kitchen waste has a moisture content of 80-90% and a VSS content (volatile suspended solids content) of 82-95%; the pretreated catering waste has a moisture content of 85-95% and a VSS content of 90-98%; and the pretreated sludge has a moisture content of 85-95% and a VSS content of 25-35%.

[0030] In step S3, the mass ratio of kitchen waste, catering waste and sludge is 1:6.5~7.5:13~14.

[0031] In step S3, the anaerobic digestion conditions are: anaerobic digestion at a temperature of 30~40 ℃ for 20~30 days.

[0032] In step S3, the ammonia nitrogen concentration in the biogas slurry is 800~1000 mg / L.

[0033] In step S4, the impurity removal unit is a coagulation sedimentation tank equipped with an air flotation device, and the heat transfer unit is a heat exchanger. The impurity removal unit removes suspended solids and other impurities from the biogas slurry that may affect subsequent treatment, while the heat transfer unit increases the temperature of the biogas slurry, providing the necessary heat source for ammonia removal.

[0034] In step S4, the heating temperature of the heat transfer unit is 75~85 ℃.

[0035] In step S4, the pH value of the biogas slurry is adjusted to 9-10 before it enters the stripping and analysis tower.

[0036] In step S4, the parameters in the stripping analysis tower are: pressure of -0.05 to -0.08 MPa, temperature of 70 to 80℃, and steam consumption of 70 to 100 kg / t.

[0037] In step S4, the parameters in the stripping ammonia removal tower are: pressure of -0.03 to -0.06 MPa, temperature of 60 to 70℃, and steam consumption of 50 to 90 kg / t.

[0038] In step S4, the ammonia nitrogen concentration of the solution after anaerobic ammonia oxidation in the stripping ammonia removal tower is detected online at the outlet of the stripping ammonia removal tower. When the ammonia nitrogen concentration in the solution is higher than 60 mg / L, the solution after anaerobic ammonia oxidation in the stripping ammonia removal tower is transported to the heat transfer unit; when the ammonia nitrogen concentration in the solution is less than 60 mg / L, the solution after anaerobic ammonia oxidation in the stripping ammonia removal tower is transported to the cryocooler for wastewater treatment.

[0039] In step S5, the carbon source includes a carbonic acid solution or carbon dioxide.

[0040] In step S5, the concentration treatment is carried out at a pressure of -0.03 to -0.06 MPa, a temperature of 20 to 30 ℃, and a steam consumption of 50 to 70 kg / t.

[0041] In step S6, the neutralization reaction specifically includes: the concentrated ammonia gas enters the carbonization tower, and at the same time, a carbonic acid solution or carbon dioxide and water are introduced into the carbonization tower to complete the neutralization reaction at a temperature of 30~40 ℃.

[0042] In step S7, the low temperature is 15~20℃.

[0043] This invention provides a system and method for preparing ammonium bicarbonate through combined treatment of kitchen waste and sludge. By separating kitchen waste collected from residential communities from catering waste collected from restaurants, the quality of raw materials in subsequent processing can be effectively controlled, reducing heterogeneity and improving the quality and yield of the final product. Furthermore, mixing pretreated kitchen waste, catering waste, and sludge in a specific ratio ensures nutritional balance, promotes efficient anaerobic digestion, and achieves effective decomposition of organic waste. Simultaneously, a large amount of biogas is generated, providing necessary raw materials for subsequent ammonia oxidation. Anaerobic ammonia oxidation via in-situ pH deammoniation not only improves ammonia production efficiency but also operates under relatively low temperature and pressure conditions, reducing energy consumption and enhancing production safety and economy. This method is efficient, environmentally friendly, and economical, solving the problem of urban organic waste treatment and promoting sustainable development through resource recovery and energy utilization.

[0044] The system for preparing ammonium bicarbonate by combining food waste treatment and sludge treatment includes: a mixing system; a food waste treatment system connected to the feed end of the mixing system; a sludge treatment system connected to the feed end of the mixing system; an anaerobic digestion system connected to the discharge end of the mixing system; a biogas treatment system connected to the gas discharge end of the anaerobic digestion system; a biogas slurry storage tank connected to the material discharge port of the anaerobic digestion system; an ammonia recovery system connected to the liquid phase discharge end of the biogas slurry storage tank; and a cryogenic cooler connected to the ammonia recovery system.

[0045] The aforementioned food waste treatment system includes a kitchen waste treatment system and a catering waste treatment system;

[0046] The ammonia recovery system comprises, in sequence, a purification unit, a heat transfer unit, a stripping analysis tower, a stripping ammonia removal tower, a condenser, a gas-liquid separator, a vacuum pump, an ammonia concentration tower, a carbonization tower, a crystallization tank, and a centrifuge.

[0047] The kitchen waste treatment system includes a drainage system, a crushing and screening system, a magnetic separation system, a pressing and dewatering system, and a sand and impurity removal system connected in sequence.

[0048] The aforementioned food waste treatment system includes a pulping system, a sand removal system, a hot water hydrolysis system, and an oil extraction system connected in sequence.

[0049] The sludge treatment system includes a sludge removal system and a slurry preparation system. The mixing system includes a mixing tank or a homogenizing tank.

[0050] Preferably, a hardening removal tower is added between the heat transfer unit and the stripping and desorption tower, and a steam heater is installed at the bottom of the hardening removal tower. The main purpose of setting up the hardening removal tower is to address the characteristics of leachate—high hardness, high alkalinity, and easy scaling—by heating the biogas slurry with steam to reduce its alkalinity to a level similar to HCO3. - Decomposes into CO3 2- CO2, etc., and then react with Ca in the biogas slurry. 2+ Mg 2+ Ions of equal hardness combine to form small particles such as calcium carbonate and magnesium carbonate, which reduces the hardness of the biogas slurry.

[0051] Preferably, the tube bundle in the de-hardening tower is made of an inert material, or the surface of the tube bundle is treated with an inert material. CO3 2- With Ca in biogas slurry 2+ Mg 2+ Small particles such as calcium carbonate, formed by the combination of ions of equal hardness, easily form scale inside equipment. In areas with dense tube bundles, the scale hardens over time, making it prone to clogging. Based on the causes of scaling, it is generally believed that the best way to reduce wastewater scaling is to enhance water pretreatment and improve the management of water tanks and treatment equipment. The induction period of salt scaling on heat transfer surfaces is directly related to the heterogeneous nucleation process; scaling hardly occurs on some inert materials. During project operation, scale can be removed through backflushing, and inert materials can be used in densely packed tube bundles prone to scaling, or the surface of the tube bundles can be treated with inert materials to reduce the degree of scaling.

[0052] Preferably, the inert material includes stainless steel, titanium, titanium alloy, polytetrafluoroethylene, hexagonal boron nitride, ceramic, glass lining, glass fiber reinforced plastic, or reinforced stainless steel.

[0053] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0054] 1. This invention, by jointly treating kitchen waste and sewage sludge, not only solves the problem of urban organic waste disposal but also promotes sustainable development practices through resource recycling and energy utilization. This method can convert waste into high-value-added ammonium bicarbonate, achieving resource reuse.

[0055] 2. The system and method for preparing ammonium bicarbonate through combined food waste and sludge treatment provided by this invention optimizes the treatment process and improves treatment efficiency through efficient pretreatment and anaerobic digestion technologies. Simultaneously, the anaerobic ammonia oxidation process using in-situ pH deammoniation not only improves ammonia production efficiency but also reduces energy consumption and treatment costs by operating under relatively low temperature and pressure conditions.

[0056] 3. By processing kitchen waste collected from residential communities and catering waste collected from restaurants separately, this invention can effectively control the quality of reaction raw materials in subsequent processing, reduce the heterogeneity of raw materials, and improve the quality and yield of the final product, ammonium bicarbonate. Attached Figure Description

[0057] Figure 1 This is a schematic diagram of the system for preparing ammonium bicarbonate from sludge-kitchen wastewater combined anaerobic digestion in Embodiment 2 of the present invention.

[0058] Figure 2 This is a schematic diagram of the system for preparing ammonium bicarbonate from sludge-kitchen wastewater combined anaerobic digestion in Example 4 of the present invention. Detailed Implementation

[0059] The technical solution of the present invention will be further described and illustrated below through examples. All raw materials used in the examples are commercially available or prepared using conventional methods.

[0060] Example 1

[0061] A method for preparing ammonium bicarbonate from sludge-kitchen wastewater combined anaerobic digestion effluent includes the following steps:

[0062] S1. When collecting kitchen waste, it is classified according to its source. Food scraps collected in the community are classified as kitchen waste, with a moisture content of 73% and a VSS content of 65.0%. Food scraps collected from restaurants are classified as catering waste, with a moisture content of 85% and a VSS content of 77%.

[0063] S2. Kitchen waste is crushed and screened to remove large particles, then magnetically separated to remove magnetic metals, followed by extrusion dewatering to remove solid slag, and finally sand and impurity removal to remove inert substances. Food waste undergoes sand and impurity removal, hot water hydrolysis, and oil removal. Sludge from urban wastewater treatment plants undergoes sand and impurity removal and pulping. The pre-treated kitchen waste has a moisture content of 86.66% and a VSS content of 88.29%; the pre-treated food waste has a moisture content of 87.98% and a VSS content of 95.53%; the pre-treated sludge has a moisture content of 90.58% and a VSS content of 30.00%.

[0064] S3. The pretreated kitchen waste, catering waste and sludge from step S2 are fed into the mixing system at a mass ratio of 1:6.8:13.4. After uniform mixing, the water content of the mixture is 89.90% and the VSS content is 56.24%. The mixture enters the anaerobic digestion system and is anaerobic digested at 30~40 ℃ for 25 days. The biogas produced by anaerobic digestion enters the biogas treatment system. The mixture after anaerobic digestion is centrifuged and dehydrated to obtain biogas slurry with an ammonia nitrogen concentration of 800~1000 mg / L.

[0065] S4. In step S3, the biogas slurry passes through a coagulation sedimentation tank equipped with an air flotation device. Polyaluminum chloride (PAC), polyacrylamide (PAM), and aminosulfonic acid are added to improve the removal efficiency of suspended solids in the biogas slurry. Then, the biogas slurry flows into a heat transfer unit, where the pH value of the biogas slurry is adjusted to 9-10 and the biogas slurry is heated at a temperature of 75-85 ℃.

[0066] The heated biogas slurry enters the stripping and desorption tower, flowing from top to bottom. The parameters in the stripping and desorption tower are set as follows: pressure -0.05 to -0.08 MPa, temperature 70 to 80 ℃, and steam consumption 70 to 100 kg / t. In the stripping and desorption tower, the biogas slurry undergoes anaerobic ammonia oxidation to produce ammonia vapor, which flows from bottom to top. The biogas slurry is then transported to the stripping and ammonia removal tower for further anaerobic ammonia oxidation to produce ammonia vapor. The parameters in the stripping and ammonia removal tower are set as follows: pressure -0.03 to -0.06 MPa, temperature 60 to 70 ℃, and steam consumption 50 to 90 kg / t. The ammonia vapor produced in the stripping and ammonia removal tower is recovered by the ammonia vapor recovery device at the top of the stripping and ammonia removal tower and sent back to the stripping and desorption tower. Together with the ammonia vapor produced in the stripping and desorption tower, the ammonia vapor is recovered by the ammonia vapor recovery device at the top of the stripping and desorption tower and sent to the condenser.

[0067] The ammonia nitrogen concentration of the solution after anaerobic ammonia oxidation in the stripping ammonia removal tower is monitored online at the tower's outlet. When the ammonia nitrogen concentration in the solution is higher than 60 mg / L, the solution is transferred to the heat transfer unit to participate in the next round of anaerobic ammonia oxidation deamination treatment. When the ammonia nitrogen concentration in the solution is lower than 60 mg / L, the solution is transferred to the cryocooler and then enters the wastewater treatment system for wastewater treatment.

[0068] S5. The ammonia vapor in the condenser is condensed by the condenser at 30~40 ℃, and then the liquid is transported to the stripping ammonia removal tower by the gas-liquid separator. The ammonia gas is transported to the ammonia concentration tower by the vacuum pump installed between the ammonia concentration tower and the gas-liquid separator. The ammonia gas is concentrated and purified under the conditions of pressure of -0.03 to -0.06 MPa, temperature of 20~30 ℃, and water vapor consumption of 50~70 kg / t.

[0069] S6. The concentrated ammonia gas in step S5 is transported to the carbonation tower. At the same time, a carbonic acid solution or carbon dioxide and water are introduced into the carbonation tower. Under the temperature conditions of 30~40 ℃, the ammonia gas and carbonate ions or carbon dioxide undergo a neutralization reaction in the aqueous phase to generate ammonium bicarbonate.

[0070] S7. The mixed solution from step S6 is transported to a crystallization tank, where ammonium bicarbonate in the mixed solution is crystallized at a low temperature of 15~20 ℃.

[0071] S8. The solid-liquid mixture after crystallization in the crystal slurry tank in step S7 is transported to a centrifuge for physical separation. The resulting liquid is transported to a gas-liquid separator, and the resulting solid is ammonium bicarbonate.

[0072] The ammonium bicarbonate produced in Example 1 was tested according to the acid-base titration method in GB / T6276.1-2008 "Determination of Ammonium Carbonate for Industrial Use". The test results are shown in Table 1. Using the method described in Example 1 for preparing ammonium bicarbonate from sludge-kitchen wastewater combined anaerobic digestion, the daily processing capacity of kitchen waste is approximately 50 t / d; the daily processing capacity of catering waste is approximately 150 t / d; the daily processing capacity of sludge from the municipal wastewater treatment plant is approximately 150 t / d; and the biogas produced is approximately 20 t / d with a volume of approximately 16,100 m³. 3 / d; the amount of wastewater entering the wastewater treatment system is approximately 400 t / d; the amount of ammonium bicarbonate prepared is approximately 415 kg / d.

[0073] Table 1. Detection data of ammonium bicarbonate produced in Example 1

[0074]

[0075] Example 2

[0076] The system for preparing ammonium bicarbonate from sludge-food wastewater combined anaerobic digestion effluent using the preparation method described in Example 1 is as follows: Figure 1As shown, the system includes a mixing system, a food waste treatment system connected to the inlet of the mixing system, a sludge treatment system connected to the inlet of the mixing system, an anaerobic digestion system connected to the outlet of the mixing system, a biogas treatment system connected to the gas outlet of the anaerobic digestion system, a biogas slurry storage tank connected to the material outlet of the anaerobic digestion system, and an ammonia recovery system connected to the liquid phase outlet of the biogas slurry storage tank. A cryogenic cooler is also connected to the ammonia recovery system.

[0077] The aforementioned food waste treatment system includes a kitchen waste treatment system and a catering waste treatment system; the kitchen waste treatment system includes a drainage system, a crushing and screening system, a magnetic separation system, an extrusion dewatering system, and a sand and impurity removal system connected in sequence; the catering waste treatment system includes a pulping system, a sand removal system, a hot water hydrolysis system, and an oil extraction system connected in sequence; the sludge treatment system includes an impurity removal system and a pulping system.

[0078] The ammonia recovery system comprises, in sequence, a purification unit, a heat transfer unit, a stripping analysis tower, a stripping ammonia removal tower, a condenser, a gas-liquid separator, a vacuum pump, an ammonia concentration tower, a carbonization tower, a crystallization tank, and a centrifuge.

[0079] Example 3

[0080] A method for preparing ammonium bicarbonate from sludge-kitchen wastewater combined anaerobic digestion effluent includes the following steps:

[0081] S1. When collecting kitchen waste, it is classified according to its source. Food scraps collected in the community are classified as kitchen waste, with a moisture content of 73% and a VSS content of 65.0%. Food scraps collected from restaurants are classified as catering waste, with a moisture content of 85% and a VSS content of 77%.

[0082] S2. Kitchen waste is crushed and screened to remove large particles, then magnetically separated to remove magnetic metals, followed by extrusion dewatering to remove solid slag, and finally sand and impurity removal to remove inert substances. Food waste undergoes sand and impurity removal, hot water hydrolysis, and oil removal. Sludge from urban wastewater treatment plants undergoes sand and impurity removal and pulping. The pre-treated kitchen waste has a moisture content of 86.66% and a VSS content of 88.29%; the pre-treated food waste has a moisture content of 87.98% and a VSS content of 95.53%; the pre-treated sludge has a moisture content of 90.58% and a VSS content of 30.00%.

[0083] S3. The pretreated kitchen waste, catering waste and sludge from step S2 are fed into the mixing system at a mass ratio of 1:6.8:13.4. After uniform mixing, the water content of the mixture is 89.90% and the VSS content is 56.24%. The mixture enters the anaerobic digestion system and is anaerobic digested at 30~40 ℃ for 25 days. The biogas produced by anaerobic digestion enters the biogas treatment system. The mixture after anaerobic digestion is centrifuged and dehydrated to obtain biogas slurry with an ammonia nitrogen concentration of 800~1000 mg / L.

[0084] S4. In step S3, the biogas slurry passes through a coagulation sedimentation tank equipped with an air flotation device. Polyaluminum chloride (PAC), polyacrylamide (PAM) and aminosulfonic acid are added to improve the removal efficiency of suspended solids in the biogas slurry. Then, the biogas slurry flows into a heat transfer unit to heat and adjust the pH value. The heating temperature is 75~85 ℃ and the pH value is 9~10.

[0085] The heated biogas slurry enters the hardening removal tower, which is equipped with a heater at the bottom, set at a temperature of 75-85°C. This heater heats the biogas slurry flowing in from the top of the tower, reducing the alkalinity of the biogas slurry to HCO3-. - Decomposes into CO3 2- CO2, etc., and then react with Ca in the biogas slurry. 2+ Mg 2+ Ions of equal hardness combine to form small particles such as calcium carbonate and magnesium carbonate, which reduces the hardness of the biogas slurry.

[0086] The biogas slurry treated by the hardening tower flows into the stripping and stripping tower from the top, with the flow direction from top to bottom. The parameters in the stripping and stripping tower are set as follows: pressure -0.05 to -0.08 MPa, temperature 70 to 80 ℃, and steam consumption 70 to 100 kg / t. In the stripping and stripping tower, the biogas slurry undergoes anaerobic ammonia oxidation to produce ammonia vapor, which flows from bottom to top. The biogas slurry is then transported to the stripping and ammonia removal tower for further anaerobic ammonia oxidation to produce ammonia vapor. The parameters in the stripping and ammonia removal tower are set as follows: pressure -0.03 to -0.06 MPa, temperature 60 to 70 ℃, and steam consumption 50 to 90 kg / t. The ammonia vapor produced in the stripping and ammonia removal tower is recovered by the ammonia vapor recovery device at the top of the stripping and ammonia removal tower and sent back to the stripping and stripping tower. Together with the ammonia vapor produced in the stripping and stripping tower, the ammonia vapor is recovered by the ammonia vapor recovery device at the top of the stripping and ammonia removal tower and sent to the condenser.

[0087] The ammonia nitrogen concentration of the solution after anaerobic ammonia oxidation in the stripping ammonia removal tower is monitored online at the tower's outlet. When the ammonia nitrogen concentration in the solution is higher than 60 mg / L, the solution is transferred to the heat transfer unit to participate in the next round of anaerobic ammonia oxidation deamination treatment. When the ammonia nitrogen concentration in the solution is lower than 60 mg / L, the solution is transferred to the cryocooler and then enters the wastewater treatment system for wastewater treatment.

[0088] S5. The ammonia vapor in the condenser is condensed at 30~40 ℃, and then the liquid is transported to the stripping ammonia removal tower via a gas-liquid separator. The ammonia gas is transported to the ammonia concentration tower by a vacuum pump installed between the ammonia concentration tower and the gas-liquid separator. The ammonia is concentrated and purified under the conditions of pressure of -0.03 to -0.06 MPa, temperature of 20~30 ℃, and steam consumption of 50~70 kg / t.

[0089] S6. The concentrated ammonia gas in step S5 is transported to the carbonation tower. At the same time, a carbonic acid solution or carbon dioxide and water are introduced into the carbonation tower. Under the temperature conditions of 30~40 ℃, the ammonia gas and carbonate ions or carbon dioxide undergo a neutralization reaction in the aqueous phase to generate ammonium bicarbonate.

[0090] S7. The mixed solution from step S6 is transported to a crystallization tank, where ammonium bicarbonate in the mixed solution is crystallized at a low temperature of 15~20 ℃.

[0091] S8. The solid-liquid mixture after crystallization in the crystal slurry tank in step S7 is transported to a centrifuge for physical separation. The resulting liquid is transported to a gas-liquid separator, and the resulting solid is ammonium bicarbonate.

[0092] The purity of the ammonium bicarbonate produced in Example 3 was tested according to GB / T6276 "Determination of Ammonium Carbonate for Industrial Use", and the test results are shown in Table 2. Using the method described in Example 3 for preparing ammonium bicarbonate from sludge-food wastewater combined anaerobic digestion, the daily processing capacity of food waste is approximately 50 t / d; the daily processing capacity of catering waste is approximately 150 t / d; the daily processing capacity of sludge from the municipal wastewater treatment plant is approximately 150 t / d; and the biogas produced is approximately 20 t / d, with a volume of approximately 16,100 m³. 3 / d; the amount of wastewater entering the wastewater treatment system is approximately 400 t / d; the amount of ammonium bicarbonate produced is approximately 350 t / d.

[0093] Table 2. Detection data of ammonium bicarbonate produced in Example 3

[0094]

[0095] Example 4

[0096] The system for preparing ammonium bicarbonate from sludge-food wastewater combined anaerobic digestion effluent using the preparation method described in Example 3 is as follows: Figure 2 As shown, the system includes a mixing system, a food waste treatment system connected to the inlet of the mixing system, a sludge treatment system connected to the inlet of the mixing system, an anaerobic digestion system connected to the outlet of the mixing system, a biogas treatment system connected to the gas outlet of the anaerobic digestion system, a biogas slurry storage tank connected to the material outlet of the anaerobic digestion system, and an ammonia recovery system connected to the liquid phase outlet of the biogas slurry storage tank. A cryogenic cooler is also connected to the ammonia recovery system.

[0097] The aforementioned food waste treatment system includes a kitchen waste treatment system and a catering waste treatment system;

[0098] The ammonia recovery system includes, in sequence, a purification unit, a heat transfer unit, a stripping analysis tower, a stripping ammonia removal tower, a condenser, a gas-liquid separator, a vacuum pump, an ammonia concentration tower, a carbonization tower, a crystallization tank, and a centrifuge;

[0099] The kitchen waste treatment system includes a drainage system, a crushing and screening system, a magnetic separation system, an extrusion dewatering system, and a sand and impurity removal system connected in sequence; the catering waste treatment system includes a pulping system, a sand removal system, a hot water hydrolysis system, and an oil extraction system connected in sequence; the sludge treatment system includes an impurity removal system and a pulping system.

[0100] A hardening removal tower is installed between the heat transfer unit and the gas desorption tower, and a steam heater is installed at the bottom of the hardening removal tower. The main purpose of installing the hardening removal tower is to further optimize the properties of the leachate, which has high hardness, high alkalinity, and is prone to scaling, by heating the biogas slurry with steam. The tube bundle in the hardening removal tower is made of an inert material, or the tube bundle is surface-treated with an inert material. CO3 2- With Ca in biogas slurry 2+ Mg 2+ Small particles such as calcium carbonate, formed by the combination of ions of equal hardness, easily form scale inside equipment. In areas with dense tube bundles, the scale hardens over time, making it prone to clogging. Currently, it is generally believed that the best way to reduce wastewater scaling is to enhance water pretreatment and improve the management of water tanks and treatment equipment. The induction period of salt scaling on heat transfer surfaces is directly related to the heterogeneous nucleation process; scaling hardly occurs on some inert materials. During project operation, scale can be removed through backflushing. In areas with dense tube bundles prone to scaling, inert materials can be used, or the tube bundles can be surface-treated with inert materials to reduce the degree of scaling.

[0101] The inert materials include stainless steel, titanium and its alloys, polytetrafluoroethylene, hexagonal boron nitride, ceramics, glass lining, glass fiber reinforced plastics, or reinforced stainless steel.

[0102] It should be understood that the above embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A method for producing ammonium bicarbonate by ammonia extraction from sludge- kitchen waste combined anaerobic digestion effluent, characterized in that, The application relates to a kitchen waste treatment method. S1, during kitchen waste recovery, food residues recovered in a community are classified as kitchen waste, and food residues recovered in a restaurant are classified as restaurant waste; S2, the kitchen waste, the restaurant waste and sludge are pretreated respectively; S3, the pretreated kitchen waste, the pretreated restaurant waste and the pretreated sludge in step S2 are mixed in a mixing system according to a mass ratio of 1:6.5-7.5:13-14, and then are evenly mixed and fed into an anaerobic digestion system to perform anaerobic digestion, and then are centrifugally dewatered to obtain biogas slurry containing ammonia nitrogen; S4, the biogas slurry in step S3 is sequentially subjected to a dedusting unit and a heat transfer unit, is fed into a stripping and resolving tower, and is subjected to anaerobic ammonia oxidation to generate ammonia steam under the conditions of a pressure of-0.05 to-0.08 MPa, a temperature of 70-80 DEG C and a water vapor consumption of 70-100 kg / t, is fed into a stripping and ammonia removal tower to perform further anaerobic ammonia oxidation to generate ammonia steam under the conditions of a pressure of-0.03 to-0.06 MPa, a temperature of 60-70 DEG C and a water vapor consumption of 50-90 kg / t, the ammonia steam generated in the stripping and ammonia removal tower is recovered by an ammonia steam recovery device at the top of the stripping and ammonia removal tower and is fed into the stripping and resolving tower to be recovered together with the ammonia steam generated in the stripping and resolving tower and is fed into a condenser, the solution after anaerobic ammonia oxidation in the stripping and ammonia removal tower is subjected to online ammonia nitrogen concentration detection at the discharge end of the stripping and ammonia removal tower, when the ammonia nitrogen concentration in the solution is higher than 60 mg / L, the solution after anaerobic ammonia oxidation in the stripping and ammonia removal tower is fed into the heat transfer unit, and when the ammonia nitrogen concentration in the solution is not higher than 60 mg / L, the solution after anaerobic ammonia oxidation in the stripping and ammonia removal tower is fed into a deep freezer and is subjected to sewage treatment; S5, the ammonia steam in the condenser is condensed, the liquid is fed into the stripping and ammonia removal tower through a gas-liquid separation tank, and the ammonia gas is fed into an ammonia concentration tower through a vacuum pump arranged between the ammonia concentration tower and the gas-liquid separation tank to be concentrated and purified under the conditions of a pressure of-0.03 to-0.06 MPa, a temperature of 20-30 DEG C and a water vapor consumption of 50-70 kg / t; S6, the concentrated ammonia gas in step S5 is fed into a carbonization tower, and a carbon source is fed into the carbonization tower, the ammonia gas and the carbon source are subjected to a neutralization reaction in an aqueous phase to generate ammonium bicarbonate; S7, the mixed solution in step S6 is fed into a crystal slurry tank to make the ammonium bicarbonate in the mixed solution crystallize under a low-temperature environment; S8, the crystallized solid-liquid mixture in the crystal slurry tank in step S7 is fed into a centrifuge to be physically separated, the obtained liquid is fed into a gas-liquid separation tank, and the obtained solid is ammonium bicarbonate.

2. The method for preparing ammonium bicarbonate by ammonia extraction from sludge- kitchen combined anaerobic digestion effluent according to claim 1, characterized in that, In step S2, the pretreatment of the kitchen waste includes sequentially subjecting the kitchen waste to crushing and screening treatment, magnetic separation treatment, extrusion dewatering treatment and sand and impurity removal treatment; the pretreatment of the food waste includes sequentially subjecting the food waste to sand and impurity removal treatment, thermal hydrolysis treatment and oil removal treatment; the pretreatment of the sludge includes sequentially subjecting the sludge to sand and impurity removal treatment and slurry treatment; the moisture content of the pretreated kitchen waste is 80-90%, and the VSS content is 82-95%; the moisture content of the pretreated food waste is 85-95%, and the VSS content is 90-98%; the moisture content of the pretreated sludge is 85-95%, and the VSS content is 25-35%.

3. The method for preparing ammonium bicarbonate by ammonia extraction from sludge- kitchen combined anaerobic digestion effluent according to claim 1, characterized in that, In step S3, the ammonia nitrogen concentration of the biogas slurry is 800-1000 mg / L.

4. The method for preparing ammonium bicarbonate by ammonia extraction from sludge- kitchen combined anaerobic digestion effluent according to claim 1, characterized in that, In step S4, the impurity removal unit is a coagulation sedimentation tank provided with a flotation device, and the heat transfer unit is a heat exchanger; the biogas slurry is heated in the heat transfer unit, and the pH value of the biogas slurry is adjusted; the heating temperature is 75-85 ℃, and the pH value of the biogas slurry is 9-10.

5. The method for preparing ammonium bicarbonate by ammonia extraction from sludge- kitchen combined anaerobic digestion effluent according to claim 1, characterized in that, In step S5, the carbon source includes carbonic acid solution or carbon dioxide.

6. The method for preparing ammonium bicarbonate by ammonia extraction from sludge- kitchen combined anaerobic digestion effluent according to claim 1, characterized in that, In step S6, the neutralization reaction includes the following specific process: the concentrated ammonia gas enters the carbonation tower, and carbonic acid solution or carbon dioxide and water are introduced into the carbonation tower at a temperature of 30-40 ℃ to complete the neutralization reaction.

7. The method for preparing ammonium bicarbonate by ammonia extraction from sludge- kitchen combined anaerobic digestion effluent according to claim 1, characterized in that, In step S7, the low temperature is 15-20 ℃.

8. The process for ammonium bicarbonate production by ammonia extraction from sludge-kitchen waste combined anaerobic digestion effluent according to any one of claims 1 to 7, characterized in that, The system for preparing ammonium bicarbonate by recovering ammonia from sludge-food waste combined anaerobic digestion tail water includes a mixing system, a food waste treatment system connected to the feed end of the mixing system, a sludge treatment system connected to the feed end of the mixing system, an anaerobic digestion system connected to the discharge end of the mixing system, a biogas treatment system connected to the gas discharge end of the anaerobic digestion system, a biogas slurry tank connected to the material discharge port of the anaerobic digestion system, an ammonia recovery system connected to the liquid discharge end of the biogas slurry tank, and a deep cooler connected to the ammonia recovery system. The food waste treatment system includes a kitchen waste treatment system and a food waste treatment system. The ammonia recovery system includes, in sequence, an impurity removal unit, a heat transfer unit, a hard removal tower, a stripping and resolution tower, a stripping and ammonia removal tower, a condenser, a gas-liquid separation tank, a vacuum pump, an ammonia concentration tower, a carbonation tower, a crystal slurry tank and a centrifuge.

9. The method for preparing ammonium bicarbonate by ammonia extraction from sludge- kitchen combined anaerobic digestion effluent according to claim 8, characterized in that, A hard removal tower is additionally arranged between the heat transfer unit and the stripping and resolution tower, and a steam heater is arranged at the bottom of the hard removal tower. The material of the pipe bundle in the hard removal tower is an inert material, or the pipe bundle is surface treated with an inert material. The inert material includes stainless steel, titanium, titanium alloy, polytetrafluoroethylene, hexagonal boron nitride, ceramic, glass lining, glass fiber reinforced plastic or reinforced stainless steel.

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