A kitchen waste treatment system and a method for operating the same

Abstract

The present application belongs to the technical field of kitchen waste energy processing, and provides a kitchen waste processing system and a running method thereof. The processing system comprises a solid-liquid separation device, a dryer, a crusher, a hydrothermal reaction kettle, an ammonia recovery unit, a photocatalytic quartz reactor, an ammonia-hydrogen engine, a fuel cell system, a boiler, a steam turbine and a generator. The addition of PCB wastewater in the garbage leachate can improve the light transmittance and photocatalytic effect of the garbage leachate, the catalyst can accelerate the photocatalytic hydrogen production rate, the condensed ammonia is incorporated into the boiler using hydrothermal carbon as fuel, which can accelerate the combustion reaction rate, achieve the purpose of CO2 substantial emission reduction, and help the "carbon neutralization and carbon peak" policy. The whole system structure is reasonable, which can realize the large-scale volume reduction of the garbage, and achieve the technical purpose of the collaborative treatment of kitchen waste, sludge and polychlorinated biphenyl wastewater, and maximize the simultaneous energy and resource utilization of the garbage.

Description

Technical Field

[0001] This invention relates to the field of energy conversion of kitchen waste, and in particular to a kitchen waste treatment system and its operation method. Background Technology

[0002] Currently, food waste is typically disposed of through incineration or landfill. Landfilling is simple and inexpensive, but it leaves behind a large number of bacteria, viruses, and heavy metal contaminants, and leachate can cause long-term pollution of groundwater, resulting in serious secondary pollution. Direct incineration of food waste releases large amounts of harmful gases such as nitrogen oxides into the air, leading to severe air pollution.

[0003] CN202121914391.X discloses a waste treatment system that separates kitchen waste into solid and liquid components, but only processes and recycles the solid components, failing to effectively utilize the liquid components. CN114405963A discloses a simple, hygienic, and environmentally friendly kitchen waste recycling system that achieves the recycling and treatment of solid and liquid components from kitchen waste; however, the use of chemicals to treat leachate cannot guarantee the absence of harmful gas generation. CN113955863A proposes a method for using microorganisms to degrade kitchen waste, but the types of waste that microorganisms can digest and decompose are limited, and undigested interfering substances cannot be effectively utilized.

[0004] Therefore, providing an efficient and environmentally friendly food waste treatment system is of great significance. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems existing in the prior art and provide a kitchen waste treatment system and its operation method.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a kitchen waste treatment system, comprising the following devices: a solid-liquid separation device, a dryer, a crusher, a hydrothermal reactor, an ammonia recovery unit, a photocatalytic quartz reactor, an ammonia-hydrogen engine, a fuel cell system, a boiler, a steam turbine, and a generator.

[0008] The present invention also provides a method for operating the processing system, comprising the following steps:

[0009] (1) Separate kitchen waste in a solid-liquid separation device to obtain solid separation material and landfill leachate;

[0010] (2) The landfill leachate, polychlorinated biphenyl wastewater, catalyst and electron donor solution are mixed in a photocatalytic quartz reactor to react and produce hydrogen.

[0011] (3) The solid separated material and sludge are mixed in a hydrothermal reactor for hydrothermal carbonization to obtain hydrothermal carbon and liquid separated material;

[0012] (4) The liquid separated material is passed into the ammonia recovery unit to obtain condensed ammonia;

[0013] (5) The hydrothermal carbon obtained in step (3) and the partial condensed ammonia obtained in step (4) are mixed in a boiler and burned to obtain flue gas;

[0014] (6) The hydrogen obtained in step (2) and the condensed ammonia obtained in step (4) are mixed and burned in an ammonia-hydrogen engine to obtain flue gas;

[0015] (7) The remaining hydrogen obtained in step (2) is fed into the fuel cell system to generate electricity.

[0016] Preferably, the catalyst in step (2) is a Ni-MOF catalyst, and the preparation method of the Ni-MOF catalyst includes the following steps:

[0017] The Ni-MOF catalyst was obtained by reacting a mixture of nickel nitrate hexahydrate, terephthalic acid, polyvinylpyrrolidone, N,N-dimethylformamide, ethanol, and water.

[0018] Preferably, the mass ratio of nickel nitrate hexahydrate, terephthalic acid, polyvinylpyrrolidone, N,N-dimethylformamide, ethanol and water is 3.5~4.5:0.5~1.5:4.5~5.5:75~85:75~85:75~85;

[0019] The reaction is carried out at a temperature of 140-160°C for 9-11 hours.

[0020] Preferably, the electron donor solution in step (2) comprises a sodium sulfide solution and a sodium sulfite solution, wherein the concentration of the sodium sulfide solution is 0.3~0.4 mol / L and the concentration of the sodium sulfite solution is 0.2~0.3 mol / L;

[0021] The mass ratio of landfill leachate to polychlorinated biphenyl (PCB) wastewater is 1:8~12;

[0022] The mass ratio of the landfill leachate and polychlorinated biphenyl wastewater to the catalyst, sodium sulfide solution and sodium sulfite solution is 1950~2050:0.5~1.5:190~210:190~210.

[0023] Preferably, the reaction described in step (2) is a sequential reaction involving protection from light and exposure to light;

[0024] The light-shielding reaction takes 25-35 minutes; the xenon lamp power for the light-irradiation reaction is 250-350W, and the time is 2.5-3.5 hours.

[0025] Preferably, the mass ratio of the solid separated material to the sludge in step (3) is 1:3.5~4.5;

[0026] The hydrothermal carbonization is carried out at a temperature of 190~220℃, a pressure of 1.2~1.3MPa, and a time of 1~2h.

[0027] Preferably, the calorific value ratio of hydrothermal carbon to partially condensed ammonia in step (5) is 10:2~3, and the combustion temperature is 900~1100℃.

[0028] Preferably, the mass ratio of the partial hydrogen and partial condensed ammonia in step (6) is 2.5~3.5:6.5~7.5, and the combustion temperature is 1800~2000℃.

[0029] The beneficial effects of this invention are:

[0030] (1) This invention provides a kitchen waste treatment system, comprising the following devices: a solid-liquid separation device, a dryer, a crusher, a hydrothermal reactor, an ammonia recovery unit, a photocatalytic quartz reactor, an ammonia-hydrogen engine, a fuel cell system, a boiler, a steam turbine, and a generator. The entire system has a reasonable structural design, and while treating waste on a large scale with reduced volume, it achieves the technical objective of co-treating kitchen waste, sludge, and polychlorinated biphenyl (PCB) wastewater, maximizing the simultaneous energy and resource utilization of waste.

[0031] (2) The photocatalytic hydrogen production process of this invention is carried out in a photocatalytic quartz reactor. PCB wastewater is added to the landfill leachate for mixing and dilution, which can improve the light transmittance of the landfill leachate and the photocatalytic effect. The catalyst can accelerate the photocatalytic hydrogen production rate of the mixture. At the same time, Na2S and Na2SO3 are added as electron donors. The reactor is first placed in a light-proof environment and stirred until the mixed wastewater (landfill leachate and polychlorinated biphenyl wastewater) and the photocatalyst reach adsorption-desorption equilibrium. After the light is turned on, a large number of photogenerated electrons are absorbed and accumulated on the Ni-MOF conduction band. Subsequently, the photogenerated electrons can generate hydrogen. + It is reduced to H2, which can be used as fuel for ammonia-hydrogen engines and fuel cells.

[0032] (3) The hydrothermal carbonization reaction process of the present invention is carried out in a closed reactor. It is a thermochemical conversion process in which solid raw materials are placed in the reactor and pressure is generated on its own. After a series of chemical reactions such as hydrolysis, dehydration, decarboxylation, polymerization and aromatization, biomass raw materials generate hydrothermal carbon, which can improve the high calorific value and energy utilization rate of kitchen waste.

[0033] (4) The liquid separated product generated in this invention can be recovered by the ammonia recovery unit. Part of the condensed ammonia can be used as fuel for the ammonia-hydrogen engine, and another part of the condensed ammonia can be mixed into the boiler using hydrothermal carbon as fuel to accelerate the combustion reaction rate and achieve the goal of significantly reducing CO2 emissions. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the kitchen waste treatment system in this invention. Detailed Implementation

[0035] This invention provides a kitchen waste treatment system, comprising the following devices: a solid-liquid separation device, a dryer, a crusher, a hydrothermal reactor, an ammonia recovery unit, a photocatalytic quartz reactor, an ammonia-hydrogen engine, a fuel cell system, a boiler, a steam turbine, and a generator.

[0036] The present invention also provides a method for operating the processing system, comprising the following steps:

[0037] (1) Separate kitchen waste in a solid-liquid separation device to obtain solid separation material and landfill leachate;

[0038] (2) The landfill leachate, polychlorinated biphenyl wastewater, catalyst and electron donor solution are mixed in a photocatalytic quartz reactor to react and produce hydrogen.

[0039] (3) The solid separated material and sludge are mixed in a hydrothermal reactor for hydrothermal carbonization to obtain hydrothermal carbon and liquid separated material;

[0040] (4) The liquid separated material is passed into the ammonia recovery unit to obtain condensed ammonia;

[0041] (5) The hydrothermal carbon obtained in step (3) and the partial condensed ammonia obtained in step (4) are mixed in a boiler and burned to obtain flue gas;

[0042] (6) The hydrogen obtained in step (2) and the condensed ammonia obtained in step (4) are mixed and burned in an ammonia-hydrogen engine to obtain flue gas;

[0043] (7) The remaining hydrogen obtained in step (2) is fed into the fuel cell system to generate electricity.

[0044] In this invention, the catalyst in step (2) is preferably a Ni-MOF catalyst, and the preparation method of the Ni-MOF catalyst includes the following steps:

[0045] The Ni-MOF catalyst was obtained by reacting a mixture of nickel nitrate hexahydrate, terephthalic acid, polyvinylpyrrolidone, N,N-dimethylformamide, ethanol, and water.

[0046] In this invention, the mass ratio of nickel nitrate hexahydrate, terephthalic acid, polyvinylpyrrolidone, N,N-dimethylformamide, ethanol, and water is preferably 3.5~4.5:0.5~1.5:4.5~5.5:75~85:75~85:75~85, more preferably 3.7~4.3:0.7~1.3:4.7~5.3:77~83:77~83:77~83, and even more preferably 3.8~4:0.8~1:4.9~5:78~80:78~80:78~80.

[0047] In this invention, the mixing is preferably carried out by first mixing N,N-dimethylformamide, ethanol and water, and then adding nickel nitrate hexahydrate, terephthalic acid and polyvinylpyrrolidone in sequence, and stirring to obtain a mixed solution.

[0048] In this invention, the stirring speed for the initial mixing is preferably 280~320 r / min, more preferably 290~310 r / min, and even more preferably 295~300 r / min; the initial mixing is sufficient to achieve uniformity; the stirring speed is preferably 280~320 r / min, more preferably 290~310 r / min, and even more preferably 295~300 r / min; the stirring time is preferably 0.8~1.2 h, more preferably 0.9~1.1 h, and even more preferably 1~1.05 h.

[0049] In this invention, the reaction temperature is preferably 140~160℃, more preferably 145~155℃, and even more preferably 147~150℃; the reaction time is preferably 9~11h, more preferably 9.5~10.5h, and even more preferably 10~10.3h.

[0050] In this invention, after the reaction is completed, the system is naturally cooled, and then centrifuged, washed and dried sequentially to obtain the Ni-MOF catalyst.

[0051] In this invention, the target temperature for natural cooling is preferably 20~30℃, more preferably 22~28℃, and even more preferably 23~25℃; the centrifugal washing consists of sequential water washing and anhydrous ethanol washing, and the centrifugal washing speed is preferably 9000~11000 r / min, more preferably 9500~10500 r / min, and even more preferably 9800~10000 r / min; the number of water washings is preferably ≥2 times, more preferably ≥3 times, and even more preferably ≥4 times; the number of anhydrous ethanol washings is preferably ≥3 times, more preferably ≥4 times, and even more preferably ≥5 times; the drying temperature is preferably 70~90℃, more preferably 75~85℃, and even more preferably 77~80℃; the drying time is preferably 11~13h, more preferably 11.5~12.5h, and even more preferably 12~12.3h.

[0052] In this invention, the electron donor solution in step (2) preferably comprises a sodium sulfide solution and a sodium sulfite solution. The concentration of the sodium sulfide solution is preferably 0.3~0.4 mol / L, more preferably 0.32~0.38 mol / L, and even more preferably 0.33~0.35 mol / L. The concentration of the sodium sulfite solution is preferably 0.2~0.3 mol / L, more preferably 0.22~0.28 mol / L, and even more preferably 0.23~0.25 mol / L.

[0053] In this invention, the mass ratio of landfill leachate to polychlorinated biphenyl wastewater is preferably 1:8~12, more preferably 1:9~11, and even more preferably 1:9.5~10.

[0054] In this invention, the mass ratio of the landfill leachate and polychlorinated biphenyl wastewater to the catalyst, sodium sulfide solution and sodium sulfite solution is preferably 1950~2050:0.5~1.5:190~210:190~210, more preferably 1970~2030:0.7~1.3:195~205:195~205, and even more preferably 1980~2000:0.8~1:198~200:198~200.

[0055] In this invention, the polychlorinated biphenyl wastewater in step (2) can improve the light transmittance and photocatalytic effect of landfill leachate, and the catalyst can accelerate the photocatalytic hydrogen production rate of the mixture.

[0056] In this invention, the reaction in step (2) is preferably a light-avoidance reaction and a light-irradiation reaction carried out sequentially.

[0057] In this invention, the stirring speed of the light-protected reaction is preferably 280~350 r / min, more preferably 290~330 r / min, and even more preferably 300~310 r / min; the time of the light-protected reaction is preferably 25~35 min, more preferably 27~33 min, and even more preferably 30~32 min; the purpose of the light-protected reaction is to allow the mixed wastewater of landfill leachate and polychlorinated biphenyl wastewater to reach adsorption-desorption equilibrium with the catalyst; the power of the xenon lamp for the light-irradiated reaction is preferably 250~350 W, more preferably 270~330 W, and even more preferably 280~300 W; the time is preferably 2.5~3.5 h, more preferably 2.7~3.3 h, and even more preferably 3~3.1 h.

[0058] In this invention, a large amount of solid suspended matter is generated during the treatment of industrial wastewater and domestic sewage, which serves as the source of sludge in step (3).

[0059] In this invention, the mass ratio of the solid separated material to the sludge in step (3) is preferably 1:3.5~4.5, more preferably 1:3.7~4.3, and even more preferably 1:3.8~4.

[0060] In this invention, after the solid separated material and sludge in step (3) are mixed, they are first dried in a dryer, then crushed in a crusher, then hydrothermally carbonized in a hydrothermal reactor, and finally enter a solid-liquid separation device to obtain high-quality energy density hydrothermal carbon and liquid separated material.

[0061] In this invention, the drying temperature is preferably 42~63℃, more preferably 45~60℃, and even more preferably 50~55℃; the drying time is preferably 52~70min, more preferably 55~67min, and even more preferably 60~62min.

[0062] In this invention, the temperature of the hydrothermal carbonization is preferably 190~220℃, more preferably 195~215℃, and even more preferably 200~210℃; the pressure is preferably 1.2~1.3MPa, more preferably 1.22~1.28MPa, and even more preferably 1.23~1.25MPa; and the time is preferably 1~2h, more preferably 1.2~1.8h, and even more preferably 1.5~1.6h.

[0063] In this invention, the hydrothermal carbon in step (3) is naturally cooled and dried, and then used as fuel in the boiler in step (5). The flue gas generated after the fuel is burned heats the liquid water and generates high-temperature steam. Through the method of heating and constant pressure vaporization, the steam is finally converted into superheated steam at the boiler outlet. Then the superheated steam enters the turbine to expand and do work, causing the blades to rotate and drive the generator to generate electricity. Through this system, the chemical energy of kitchen waste is converted into electrical energy. In addition, when the hydrothermal carbon in the boiler is burned, the condensed ammonia obtained from the ammonia recovery unit is introduced into the boiler. The combustion of hydrothermal carbon with ammonia can significantly reduce carbon emissions.

[0064] In this invention, the target temperature for natural cooling is preferably 20~30℃, more preferably 22~28℃, and even more preferably 23~25℃; the drying temperature is preferably 35~40℃, more preferably 36~39℃, and even more preferably 37~38℃; the drying time is preferably 46~52min, more preferably 47~51min, and even more preferably 49~50min.

[0065] In this invention, the calorific value ratio of hydrothermal carbon to partially condensed ammonia in step (5) is preferably 10:2~3, more preferably 10:2.2~2.8, and even more preferably 10:2.3~2.5; the combustion temperature is preferably 900~1100℃, more preferably 950~1050℃, and even more preferably 980~1000℃.

[0066] In this invention, the mass ratio of the partial hydrogen and the partial condensed ammonia in step (6) is preferably 2.5~3.5:6.5~7.5, more preferably 2.7~3.3:6.7~7.3, and even more preferably 2.8~3:6.8~7; the combustion temperature is preferably 1800~2000℃, more preferably 1850~1950℃, and even more preferably 1900~1930℃.

[0067] In this invention, in step (6), the flue gas generated by combustion in the ammonia-hydrogen engine expands and performs work, driving the piston to move.

[0068] In this invention, in step (7), the fuel cell system directly converts the chemical energy of hydrogen and oxygen into electrical energy, which can supply power to the ammonia-hydrogen engine, forming a thermal-electric composite power system of a zero-carbon internal combustion engine and a fuel cell for power output.

[0069] In this invention, a schematic diagram of the kitchen waste treatment system is shown below. Figure 1 As shown.

[0070] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0071] In the following embodiments, the source of the polychlorinated biphenyl (PCB) wastewater is Shanghai Huasheng Chemical Plant, and the source of the sludge is Shanghai Gaoqiao Petrochemical Company.

[0072] Example 1

[0073] N,N-dimethylformamide, ethanol, and water were stirred at 300 rpm and mixed thoroughly. Then, nickel nitrate hexahydrate, terephthalic acid, and polyvinylpyrrolidone were added sequentially, and the mixture was stirred at 300 rpm for 1 h. The mass ratio of nickel nitrate hexahydrate, terephthalic acid, polyvinylpyrrolidone, N,N-dimethylformamide, ethanol, and water was 4:1:5:80:80:80. The resulting mixed solution was reacted at 150 °C for 10 h. After the reaction was completed, the system was naturally cooled to 25 °C, washed four times with water at 10,000 rpm, then washed five times with anhydrous ethanol at 10,000 rpm, and finally dried at 80 °C for 12 h to obtain the Ni-MOF catalyst.

[0074] Leftover food, rice, and fruit peels are separated in a solid-liquid separation device to obtain solid separation and landfill leachate. The landfill leachate, polychlorinated biphenyl (PCB) wastewater, catalyst, 0.35 mol / L sodium sulfide solution, and 0.25 mol / L sodium sulfite solution are mixed in a photocatalytic quartz reactor (the mass ratio of landfill leachate to PCB wastewater is 1:10, and the mass ratio of the sum of the landfill leachate and PCB wastewater to the catalyst, sodium sulfide solution, and sodium sulfite solution is 2000:1). The mixture (1:200:200) was reacted at 310 r / min in the dark for 30 min, followed by reaction under a 300W xenon lamp for 3 h to obtain hydrogen gas. The solid-liquid mixture and sludge (mass ratio of solid-liquid to sludge 1:4) were mixed and dried in a dryer at 50°C for 60 min, then crushed in a crusher, and finally hydrothermally carbonized in a hydrothermal reactor at 205°C and 1.25 MPa for 1.5 h. After carbonization, the mixture was transferred to a solid-liquid separation device. The process involves obtaining hydrothermal carbon and liquid separation. The liquid separation is then fed into an ammonia recovery unit to obtain condensed ammonia. The hydrothermal carbon is naturally cooled to 25°C and then dried at 38°C for 49 minutes. It is then mixed with a portion of the condensed ammonia (the calorific value ratio of hydrothermal carbon to condensed ammonia is 10:2.5) in a boiler and burned at 1000°C. The resulting flue gas heats the liquid water and produces high-temperature steam. Through constant-pressure vaporization, the steam is converted into superheated steam at the boiler outlet. The superheated steam then enters the turbine, expands, and performs work, causing the blades to rotate and driving the generator to produce electricity. A portion of hydrogen and a portion of the condensed ammonia (the mass ratio of hydrogen to condensed ammonia is 3:7) are mixed in an ammonia-hydrogen engine and burned at 1900°C to obtain flue gas. This flue gas expands and performs work, driving the piston. The remaining hydrogen is fed into a fuel cell system, which directly converts the chemical energy of hydrogen and oxygen into electrical energy, which powers the ammonia-hydrogen engine. This forms a zero-carbon internal combustion engine and fuel cell combined thermal-electric power system for power output.

[0075] In this embodiment, up to the hydrogen production step in the photocatalytic quartz reactor, the hydrogen production rate is 2.5 times that of directly photocatalyzing kitchen waste (without adding PCB wastewater, catalyst, or electron donor solution).

[0076] In this embodiment, carbon emissions are reduced by 50% when the boiler incorporates condensing ammonia for combustion compared to direct combustion without condensing ammonia.

[0077] Example 2

[0078] N,N-dimethylformamide, ethanol, and water were stirred at 320 r / min and mixed thoroughly. Nickel nitrate hexahydrate, terephthalic acid, and polyvinylpyrrolidone were then added sequentially, and the mixture was stirred at 320 r / min for 0.8 h. The mass ratio of nickel nitrate hexahydrate, terephthalic acid, polyvinylpyrrolidone, N,N-dimethylformamide, ethanol, and water was 3.7:0.7:4.7:77:77:75. The resulting mixture was reacted at 145 °C for 9.5 h. After the reaction, the system was naturally cooled to 20 °C, washed five times with water at 9000 r / min, then washed three times with anhydrous ethanol at 9000 r / min, and finally dried at 70 °C for 13 h to obtain the Ni-MOF catalyst.

[0079] Leftover food, rice, and fruit peels are separated in a solid-liquid separation device to obtain solid separation and landfill leachate. The landfill leachate, polychlorinated biphenyl (PCB) wastewater, catalyst, 0.32 mol / L sodium sulfide solution, and 0.23 mol / L sodium sulfite solution are mixed in a photocatalytic quartz reactor (the mass ratio of landfill leachate to PCB wastewater is 1:9, and the mass ratio of landfill leachate to catalyst, sodium sulfide solution, and sodium sulfite solution is 1970:0.8). The mixture (195:195) was reacted at 280 r / min in the dark for 35 min, followed by reaction under a 270 W xenon lamp for 3.3 h to obtain hydrogen. The solid-liquid mixture and sludge (mass ratio of solid-liquid mixture to sludge was 1:3.7) were mixed and dried in a dryer at 42 °C for 70 min, then crushed in a crusher, and finally hydrothermally carbonized in a hydrothermal reactor at 200 °C and 1.2 MPa for 1.8 h. After carbonization, the mixture was transferred to a solid-liquid separation device. The process yields hydrothermal carbon and a liquid separator. The liquid separator is then fed into an ammonia recovery unit to obtain condensed ammonia. The hydrothermal carbon is naturally cooled to 20°C and then dried at 35°C for 52 minutes. It is then mixed with a portion of the condensed ammonia (the calorific value ratio of hydrothermal carbon to condensed ammonia is 10:2.2) in a boiler and burned at 950°C. The resulting flue gas heats the liquid water, producing high-temperature steam. Through constant-pressure vaporization, the steam is ultimately converted into superheated steam at the boiler outlet. The superheated steam then enters the turbine for expansion. The engine performs work, causing the blades to rotate and drive the generator to produce electricity. A portion of hydrogen and a portion of condensed ammonia (with a mass ratio of 2.7:6.5) are mixed in the ammonia-hydrogen engine and burned at 1850°C to produce flue gas. This flue gas expands and performs work, driving the piston. The remaining hydrogen is fed into the fuel cell system, which directly converts the chemical energy of hydrogen and oxygen into electrical energy, supplying power to the ammonia-hydrogen engine. This forms a zero-carbon internal combustion engine and fuel cell combined thermal-electric power system for power output.

[0080] In this embodiment, up to the hydrogen production step in the photocatalytic quartz reactor, the hydrogen production rate is 2.37 times that of directly photocatalyzing kitchen waste (without adding PCB wastewater, catalyst, or electron donor solution).

[0081] In this embodiment, carbon emissions are reduced by 45% when the boiler incorporates condensing ammonia for combustion compared to direct combustion without condensing ammonia.

[0082] Example 3

[0083] N,N-dimethylformamide, ethanol, and water were stirred at 280 r / min and mixed thoroughly. Nickel nitrate hexahydrate, terephthalic acid, and polyvinylpyrrolidone were then added sequentially, and the mixture was stirred at 280 r / min for 1.2 h. The mass ratio of nickel nitrate hexahydrate, terephthalic acid, polyvinylpyrrolidone, N,N-dimethylformamide, ethanol, and water was 4.3:1.3:5.5:83:83:83. The resulting mixture was reacted at 155 °C for 9.5 h. After the reaction, the system was naturally cooled to 28 °C, washed three times with water at 11000 r / min, then washed four times with anhydrous ethanol at 11000 r / min, and finally dried at 90 °C for 11 h to obtain the Ni-MOF catalyst.

[0084] Leftover food, rice, and fruit peels are separated in a solid-liquid separation device to obtain solid separation and landfill leachate. The landfill leachate, polychlorinated biphenyl (PCB) wastewater, catalyst, 0.38 mol / L sodium sulfide solution, and 0.28 mol / L sodium sulfite solution are mixed in a photocatalytic quartz reactor (the mass ratio of landfill leachate to PCB wastewater is 1:11, and the mass ratio of the sum of landfill leachate and PCB wastewater to catalyst, sodium sulfide solution, and sodium sulfite solution is 2030:1). The mixture of solids and sludge (3:205:205) was reacted at 350 r / min in the dark for 25 min, followed by irradiation under a 330 W xenon lamp for 2.7 h to obtain hydrogen. The solids and sludge (mass ratio of solids to sludge was 1:4.5) were mixed and dried in a dryer at 63 °C for 52 min, then crushed in a crusher, and finally hydrothermally carbonized in a hydrothermal reactor at 210 °C and 1.3 MPa for 1.2 h. After carbonization, the mixture was transferred to a solid-liquid separation device. The process yields hydrothermal carbon and a liquid separator. The liquid separator is then fed into an ammonia recovery unit to obtain condensed ammonia. The hydrothermal carbon is naturally cooled to 30°C, then dried at 40°C for 46 minutes. It is then mixed with a portion of the condensed ammonia (the calorific value ratio of hydrothermal carbon to condensed ammonia is 10:2.8) in a boiler and burned at 1050°C. The resulting flue gas heats the liquid water, producing high-temperature steam. Through constant-pressure vaporization, the steam is ultimately converted into superheated steam at the boiler outlet. This superheated steam then enters the turbine for expansion. The expansion of the turbine blades causes them to rotate, which in turn drives the generator to produce electricity. A mixture of hydrogen and condensed ammonia (in a mass ratio of 3.3:7.3) is placed in the ammonia-hydrogen engine and burned at 1950°C to produce flue gas. This flue gas expands and drives the piston. The remaining hydrogen is fed into a fuel cell system, which directly converts the chemical energy of hydrogen and oxygen into electrical energy, powering the ammonia-hydrogen engine. This forms a zero-carbon internal combustion engine and fuel cell combined thermal-electric power system for power output.

[0085] In this embodiment, up to the hydrogen production step in the photocatalytic quartz reactor, the hydrogen production rate is 2.46 times that of directly photocatalyzing kitchen waste (without adding PCB wastewater, catalyst, or electron donor solution).

[0086] In this embodiment, carbon emissions are reduced by 47.5% when the boiler incorporates condensing ammonia for combustion compared to direct combustion without condensing ammonia.

[0087] As can be seen from the above embodiments, the present invention provides a food waste treatment system, comprising the following devices: a solid-liquid separation device, a dryer, a crusher, a hydrothermal reactor, an ammonia recovery unit, a photocatalytic quartz reactor, an ammonia-hydrogen engine, a fuel cell system, a boiler, a steam turbine, and a generator. The entire system has a reasonable structural design, achieving the technical objective of co-treating food waste, sludge, and polychlorinated biphenyl (PCB) wastewater while simultaneously reducing the volume of waste on a large scale, thus maximizing the energy and resource utilization of waste.

[0088] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for processing kitchen garbage, characterized by, The method comprises the following steps: (1) separating the kitchen garbage in a solid-liquid separation device to obtain solid separation and garbage leachate; (2) mixing the garbage leachate, polychlorinated biphenyl wastewater, catalyst and electron donor solution in a photocatalytic quartz reactor to react to obtain hydrogen; (3) mixing the solid separation and sludge in a hydrothermal reaction kettle to perform hydrothermal carbonization to obtain hydrothermal carbon and liquid separation; (4) passing the liquid separation into an ammonia recovery unit to obtain condensed ammonia; (5) mixing the hydrothermal carbon obtained in step (3) and part of the condensed ammonia obtained in step (4) in a boiler to burn to obtain flue gas; (6) mixing part of the hydrogen obtained in step (2) and part of the condensed ammonia obtained in step (4) in an ammonia-hydrogen engine to burn to obtain flue gas; (7) passing the remaining hydrogen obtained in step (2) into a fuel cell system to generate electric energy; The electron donor solution in step (2) comprises a sodium sulfide solution and a sodium sulfite solution, the concentration of the sodium sulfide solution is 0.3-0.4 mol / L, and the concentration of the sodium sulfite solution is 0.2-0.3 mol / L; The mass ratio of the garbage leachate and polychlorinated biphenyl wastewater is 1:8-12; The mass ratio of the garbage leachate and polychlorinated biphenyl wastewater to the catalyst, sodium sulfide solution and sodium sulfite solution is 1950-2050:0.5-1.5:190-210:190-210.

2. The treatment method of claim 1, wherein, The catalyst in step (2) is a Ni-MOF catalyst, and the preparation method of the Ni-MOF catalyst comprises the following steps: Mixing nickel nitrate hexahydrate, terephthalic acid, polyvinylpyrrolidone, N,N-dimethylformamide, ethanol and water to react to obtain the Ni-MOF catalyst.

3. The treatment method of claim 2, wherein, The mass ratio of the nickel nitrate hexahydrate, terephthalic acid, polyvinylpyrrolidone, N,N-dimethylformamide, ethanol and water is 3.5-4.5:0.5-1.5:4.5-5.5:75-85:75-85:75-85; The reaction temperature of the Ni-MOF catalyst preparation method is 140-160 DEG C, and the time is 9-11 h.

4. The treatment method of claim 3, wherein, The reaction in step (2) is a light-avoiding reaction and a light irradiation reaction in sequence; The time of the light-avoiding reaction is 25-35 min, the xenon lamp power of the light irradiation reaction is 250-350 W, and the time is 2.5-3.5 h.

5. The treatment method of claim 4, wherein, The mass ratio of the solid separation and sludge in step (3) is 1:3.5-4.5; The temperature of the hydrothermal carbonization is 190-220 DEG C, the pressure is 1.2-1.3 MPa, and the time is 1-2 h.

6. The treatment method of claim 5, wherein, In step (5), the heat value ratio of the hydrothermal carbon and part of the condensed ammonia is 10:2-3, and the burning temperature is 900-1100 DEG C.

7. The treatment method of claim 6, wherein, In step (6), the mass ratio of part of the hydrogen and part of the condensed ammonia is 2.5-3.5:6.5-7.5, and the burning temperature is 1800-2000 DEG C.

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