CN114804935B - Method and system for preparing biochar-based organic fertilizer from kitchen waste - Google Patents
Method and system for preparing biochar-based organic fertilizer from kitchen waste Download PDFInfo
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Classifications
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- C—CHEMISTRY; METALLURGY
- C05—FERTILISERS; MANUFACTURE THEREOF
- C05F—ORGANIC FERTILISERS NOT COVERED BY SUBCLASSES C05B, C05C, e.g. FERTILISERS FROM WASTE OR REFUSE
- C05F9/00—Fertilisers from household or town refuse
- C05F9/04—Biological compost
-
- C—CHEMISTRY; METALLURGY
- C05—FERTILISERS; MANUFACTURE THEREOF
- C05F—ORGANIC FERTILISERS NOT COVERED BY SUBCLASSES C05B, C05C, e.g. FERTILISERS FROM WASTE OR REFUSE
- C05F9/00—Fertilisers from household or town refuse
- C05F9/02—Apparatus for the manufacture
Abstract
The invention provides a method and a system for preparing a charcoal-based organic fertilizer from kitchen waste, which comprises the following steps: step S1, pretreating kitchen waste to obtain organic slurry; s2, carrying out hydrothermal oxidation reaction and hydrothermal carbonization reaction on the organic slurry and compressed air or oxygen at the temperature of 150-340 ℃ and the pressure of 1-15 Mpa, wherein the oxygen supply is 0.2-20% of the mass of the organic slurry, and the reaction time is 15-300 min, so as to obtain a suspension; s3, carrying out solid-liquid separation on the suspension to obtain a solid organic mud cake and a clear liquid; and S4, performing microbial fermentation composting on the organic mud cake to obtain the biochar-based organic fertilizer. Under the condition of no additional addition of biochar, the invention prepares the biochar-based organic fertilizer by taking kitchen waste as a raw material, so as to meet the treatment requirements of harmless, reduction and recycling of kitchen waste and reduce the preparation cost of the biochar-based organic fertilizer.
Description
Technical Field
The invention relates to the technical field of environmental protection, in particular to a method and a system for preparing a biochar-based organic fertilizer from kitchen waste.
Background
Kitchen waste is waste produced in activities such as daily living, food processing, food service, unit food supply and the like, and comprises discarded unused vegetable leaves, leftovers, pericarps, eggshells, tea leaves, bones and the like, and the components have multisource, promiscuous and uncertain properties. Such waste, if disposed of improperly, can cause serious environmental pollution as well as disease transmission to humans and animals.
The existing kitchen garbage treatment method mainly comprises anaerobic fermentation (such as patent document CN 112851411A), aerobic fermentation (such as patent document CN 106927977A), aerobic composting (such as patent document CN 114057516A), rotary kiln pyrolysis carbonization (such as patent document CN 109400375A) and solid-liquid separation synergistic incineration. However, these methods have the following disadvantages: (1) Anaerobic bacteria in anaerobic fermentation have low decomposition speed to organic matters in cells and tissues, long anaerobic digestion residence time, low efficiency and low recycling degree, and a large amount of biogas residues and biogas slurry remained after anaerobic digestion have high treatment cost and difficult terminal digestion; (2) The aerobic fermentation and aerobic composting method needs to add a large amount of auxiliary materials such as straw, wood dust and the like or utilize energy sources to reduce the water content of kitchen waste to a condition suitable for composting, and has the advantages of large energy consumption, difficult management of odor in the process, long composting time of the aerobic composting, large occupied area, difficult achievement of standard indexes of a large amount of organic fertilizer products, difficult market digestion, high storage and stacking cost and easy secondary pollution; (3) The rotary kiln pyrolysis carbonization method and the solid-liquid separation synergistic incineration method both need to vaporize the kitchen waste water, have high energy consumption, have the emission risk of dioxin harmful gas, have high difficulty in rear end tail gas treatment and high investment cost, and cannot fully utilize resources by directly incinerating organic matters. Therefore, the existing kitchen waste treatment method has the defects of incomplete treatment and digestion, high process energy consumption, difficult tail gas treatment, low economic cost performance, low circular economy index and the like, and cannot meet the policy requirements of harmless, decrement and recycling of higher standards.
The biochar-based organic fertilizer is prepared by mixing and fermenting biochar and organic materials derived from plants and/or animals or mixing the biochar and the fermented and decomposed carbon-containing organic materials derived from the plants and/or the animals, so that the biochar-based organic fertilizer needs to be prepared firstly and then mixed with the organic materials, and the process flow is complex and tedious. Secondly, the biochar is a solid product obtained by pyrolyzing biomass materials such as crop straws, wood chips and the like under the environment condition of limiting oxygen or isolating oxygen, but the cost of the straws and the wood chips for separating from the ground is high, so that the price of the biochar-based organic fertilizer is high, and the popularization of the biochar-based organic fertilizer is limited.
Disclosure of Invention
The invention aims to provide a method and a system for preparing a biochar-based organic fertilizer from kitchen waste, which can meet the treatment requirements of harmless, reduction and recycling of kitchen waste without adding additional biochar, and can reduce the preparation cost of the biochar-based organic fertilizer by taking the kitchen waste as a raw material.
In order to solve the problems, the technical scheme of the invention is as follows:
the invention relates to a method for preparing a charcoal-based organic fertilizer from kitchen waste, which is characterized by comprising the following steps:
step S1, pretreating kitchen waste to obtain organic slurry with the water content of 80% -99%;
s2, carrying out hydrothermal oxidation reaction and hydrothermal carbonization reaction on the organic slurry and compressed air or oxygen at the temperature of 150-340 ℃ and the pressure of 1-15 Mpa, wherein the oxygen supply is 0.2-20% of the mass of the organic slurry, and the reaction time is 10-300 min, so as to obtain a suspension;
s3, carrying out solid-liquid separation on the suspension to obtain a solid organic mud cake and a clear liquid;
and S4, performing microbial fermentation composting on the organic mud cake to obtain the biochar-based organic fertilizer.
Further, the clarified liquid is subjected to anaerobic biogas production to obtain biogas.
Preferably, the pretreatment of the kitchen waste in the step S1 comprises crushing, sorting, pulping and homogenizing the kitchen waste, plastics, metals, sand and other undegradable household garbage sundries in the kitchen waste can be removed, and organic matters and water are prepared into homogeneous organic slurry with certain fluidity, wherein the water content of the organic slurry is 88% -95%.
Preferably, the hydrothermal oxidation and hydrothermal carbonization reactions are performed under the action of a catalyst, which is a heterogeneous metal catalyst, for example: a cellular heterogeneous metal catalyst; more preferably, the active ingredient of the catalyst is one or more of cerium, lanthanum, ruthenium or palladium, and the mass fraction of each metal in the catalyst is 0.1% -3%.
Preferably, the mass ratio of the compressed air or oxygen to the organic slurry is (1% -10%): 1, by controlling the oxygen supply, partial organic matters in the organic slurry are oxidized, a large amount of heat is released, the proper conditions and proper reaction degree of hydrothermal oxidation and hydrothermal carbonization reaction are ensured, and the carbon content and organic nutrients in the final product reach the required range.
Preferably, the reaction temperature in the step S2 is 180-280 ℃, and the reaction pressure is 2-9 Mpa. Cellulose and hemicellulose in kitchen waste organic matters are carbonized at 220 ℃ and 300 ℃ respectively, protein is denatured and carbonized at 50-70 ℃ generally, fat is decomposed and carbonized at 200 ℃ or more, and low-molecular saccharides are carbonized at 180 ℃ generally, so that most biomass can be carbonized by setting the reaction temperature in the range of 200-280 ℃, and biomass in kitchen waste can be carbonized step by controlling the reaction temperature, pressure and reaction time. Generally, the higher the temperature and the higher the pressure, the higher the carbonization degree, and the carbon content in the product is increased, but the manufacturing cost and the running cost of the system are greatly increased. The addition of a proper catalyst can reduce the temperature and pressure of the reaction, ensure the quality and yield of the product and reduce the manufacturing and running costs. Preferably, the water content of the organic mud cake is less than or equal to 35 percent.
Preferably, the microbial fermentation compost is one or more of static active oxygen supply compost, mechanical turning static compost and container compost; wherein, the static active oxygen supply composting is to stack solid organic mud cakes under the aerobic condition and ferment by microorganisms to obtain the fertilizer, and the method has low cost; the mechanical turning static composting is to ventilate and dehumidify by using a stirrer or other equipment, so that the solid organic mud cake is uniformly contacted with air, ferment by using aerobic bacteria, quickly decompose composting materials, prevent odor from generating, and normally the fermentation time is 7-10 days, and the turning times are once a day; the container compost is made by using a compost box, and the air flow and the temperature in the container compost can be controlled by using the principle of a bioreactor so as to maintain the optimal aerobic decomposition condition.
The invention also provides a system for preparing the biochar-based organic fertilizer from kitchen waste, which is characterized by comprising the following steps: a pretreatment device; the thermal oxygen wall-breaking carbonization reaction device is connected with the pretreatment device; the solid-liquid separation device is connected with the thermal-oxygen wall-breaking carbonization reaction device; the device comprises a solid-liquid separation device, a microorganism fermentation device and an anaerobic biogas production device, wherein the solid-liquid separation device is connected with a solid-phase discharge port of the microorganism fermentation device;
wherein: the hot oxygen wall breaking carbonization reaction device comprises a slurry tank connected with the pretreatment equipment, and a discharge port of the slurry tank is connected with a feed inlet of a gas-liquid mixer through a pipeline; the gas-liquid mixer is also provided with an air inlet which is connected with compressed air or oxygen supply equipment; the discharge port of the gas-liquid mixer is connected with the tube side inlet of the tube-shell heat exchanger; the tube side outlet of the tube side heat exchanger is connected with a feed inlet of the reaction; the discharge port of the reaction tower is connected with the shell side inlet of the shell-and-tube heat exchanger; the shell side outlet of the shell-and-tube heat exchanger is connected with the feed inlet of the gas-liquid separator; and a liquid phase outlet of the gas-liquid separator is connected with a feed inlet of the solid-liquid separation device.
Compared with the prior art, the invention has the following advantages:
(1) The invention increases the solubility of oxygen in organic slurry by maintaining the high-temperature and high-pressure state during the reaction, provides strong driving force for the hydrothermal oxidation reaction and the hydrothermal carbonization reaction, accelerates the reaction speed and reduces the reaction time.
(2) The invention fully breaks wall and thoroughly kills viruses and various cells in the organic slurry through hydrothermal oxidation reaction, releases the water and organic matters in the viruses and the cells, and the organic matters with partial solubility or insoluble matters undergo oxidation reaction and are decomposed into soluble micromolecular organic matters or carbon dioxide and emit heat; and simultaneously, part of soluble or insoluble organic matters (cellulose, hemicellulose, lignin, protein, fat, low-molecular saccharides and other biomasses) are carbonized into insoluble biochar particles to suspend in liquid through hydrothermal carbonization reaction, and the organic slurry which is viscous and difficult to separate solid from liquid originally becomes suspension which is easy to separate solid from liquid.
(3) According to the invention, the mass ratio of oxygen supply to the organic slurry can be adjusted to adjust the oxygen content in the organic slurry, so that the ratio of the hydrothermal oxidation reaction to the hydrothermal carbonization reaction is changed, and the biochar-based organic fertilizer with different biochar yields can be prepared, so that the requirements of different soil improvement or fertilization can be met;
(4) According to the invention, carbon-containing organic matters in kitchen waste are directly converted into biochar in the hydrothermal carbonization reaction, and the biochar is not required to be additionally added; the kitchen waste can be converted into the biochar-based organic fertilizer, so that the kitchen waste is turned into wealth, and compared with the kitchen waste treatment method in the prior art, toxic and harmful substances are not generated, so that the treatment requirements of harmless, reduced and recycled kitchen waste are met, and the preparation cost of the biochar-based organic fertilizer is greatly reduced;
(5) The suspension obtained after oxidation is filtered by a plate-and-liquid separation filter press to obtain clear liquid with purity, low SS and excellent biodegradability and a solid organic mud cake with water content of less than 35 percent. The content of suspended matters in the clarified liquid obtained by solid-liquid separation is very low (lower than 0.1 g/L), and the clarified liquid is rich in small molecular compounds, and is suitable for anaerobic biogas production by adopting an efficient liquid anaerobic reactor such as IC or UASB. Compared with solid-liquid full-mixing anaerobic biogas production, the anaerobic reaction time can be shortened by more than 70 percent; the investment and running cost of the equipment are reduced by more than 60 percent. The obtained solid organic mud cake contains high content of organic matters and biochar, has high porosity, and does not need to add a large amount of auxiliary materials (wood dust) and additional dehydration in the microbial fermentation process.
(6) The organic slurry and the compressed air enter the reaction tower to undergo hydrothermal oxidation reaction and release a large amount of heat, so that sufficient energy is provided for hydrothermal carbonization reaction, and the reacted material and unreacted cold material undergo countercurrent partition wall heat exchange in the shell-and-tube heat exchanger, thereby achieving the dual effects of cooling the hot material and preheating the cold material, and realizing heat self-balance. Except that an external heat source is needed in the starting stage, the processes of cell wall breaking liquefaction, macromolecule decomposition into micromolecules and partial carbonization can be realized without adding an additional heat source in the normal operation stage, so that the energy consumption is greatly saved, and the operation cost is reduced.
Drawings
FIG. 1 is a schematic flow chart of a method for preparing a biochar-based organic fertilizer from kitchen waste in an embodiment of the invention;
FIG. 2 is a schematic diagram of an apparatus for preparing a biochar-based organic fertilizer from kitchen waste in an embodiment of the invention;
Detailed Description
In order that the above objects, features and advantages of the invention will be readily understood, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other.
In addition, the terms "comprising," "including," "having," and "containing" are not limiting, as other steps and other ingredients may be added that do not affect the result. Materials, equipment, reagents are commercially available unless otherwise specified.
As shown in fig. 2, the system for preparing the biochar-based organic fertilizer from kitchen waste comprises: a pretreatment device; the thermal oxygen wall-breaking carbonization reaction device is connected with the pretreatment device; the solid-liquid separation device is connected with the thermal-oxygen wall-breaking carbonization reaction device; the device comprises a solid-liquid separation device, a microorganism fermentation device and an anaerobic biogas production device, wherein the solid-liquid separation device is connected with a solid-phase discharge port of the microorganism fermentation device; the system comprises a thermal oxygen wall-breaking carbonization reaction system, a solid-liquid separation system, a biological fermentation system, an anaerobic biogas production system and a clear liquid anaerobic biogas production system, wherein the thermal oxygen wall-breaking carbonization reaction system is used for performing hydrothermal oxidation reaction and hydrothermal carbonization reaction, the solid-liquid separation system is used for performing solid-liquid separation on suspension liquid, the biological fermentation system is used for performing microbial fermentation composting on solid organic mud cakes, and the anaerobic biogas production system is used for anaerobically producing biogas from clear liquid;
wherein: the hot oxygen wall breaking carbonization reaction device comprises a slurry tank 1 connected with the pretreatment equipment, wherein a discharge port of the slurry tank 1 is connected with a feed port of a gas-liquid mixer 3 through a pipeline; the gas-liquid mixer 3 is also provided with an air inlet which is connected with compressed air or oxygen supply equipment 9; the discharge port of the gas-liquid mixer 3 is connected with the tube side inlet of the tube-shell heat exchanger 4; the tube side outlet of the tube shell type heat exchanger 4 is connected with a feed inlet at the lower part of the reaction tower 5; a discharge hole at the upper part of the reaction tower 5 is connected with a shell side inlet of the shell-and-tube heat exchanger 4; the shell side outlet of the shell-and-tube heat exchanger 4 is connected with the feed inlet of the gas-liquid separator 6; the liquid phase outlet of the gas-liquid separator 6 is connected with the feed inlet of the solid-liquid separation device 8.
Further, a slurry conveying pump 2 is arranged on a pipeline connected with the slurry tank 1 and the gas-liquid mixer 3; and a suspension conveying pump 7 is arranged on a pipeline connected with the gas-liquid separator 6 and the solid-liquid separation device 8.
Preferably, the reaction tower 5 is filled with a solid catalyst, and the catalyst is a heterogeneous metal catalyst, for example: honeycomb heterogeneous metal combustion catalysts.
The slurry tank 1 stores organic slurry, the slurry transfer pump 2 is used for transferring the organic slurry into the gas-liquid mixer 3, and the compressed air or oxygen supply device 9 is used for transferring the compressed air or oxygen into the gas-liquid mixer. Preferably, the slurry delivery pump 2 and the compressed air or oxygen supply device 9 control the flow rate of the organic slurry and the flow rate of the compressed air or oxygen through a frequency converter, so as to control the mass ratio of the organic slurry to the oxygen in the hot oxygen wall-breaking carbonization reaction system.
The shell-and-tube heat exchanger 4 is a multistage serial shell-and-tube heat exchanger, and flows in the tube pass of the shell-and-tube heat exchanger to perform reverse partition heat exchange with the reacted hot material flowing in the shell pass of the shell-and-tube heat exchanger to play a double effect of cooling the hot material and preheating the cold material. After the unreacted cold materials are preheated to the required temperature, the materials enter the reaction tower 5 to undergo hydrothermal oxidation reaction, a large amount of heat is released, and sufficient energy is provided for the hydrothermal carbonization reaction; and discharging the reacted thermal material from a discharge port at the upper part of the reaction tower 5 into the shell-and-tube heat exchanger 4 for cooling and heat recovery, so that the self-balance of the heat of the thermal-oxygen wall-breaking carbonization reaction device is realized. Except that an external heat source is needed to preheat the system to the required reaction temperature in the starting stage, the thermal-oxygen wall-breaking carbonization reaction device can realize the processes of 'cell wall-breaking liquefaction, macromolecular decomposition into micromolecules and partial carbonization' without adding an additional heat source in the normal operation stage, thereby greatly saving energy consumption and reducing operation cost.
The gas-liquid separator 6 is used for separating a gas phase and a solid-liquid phase of a reaction product; the separated gas is sent to a subsequent tail gas treatment system, and is safely discharged after reaching the standard; the solid-liquid phase obtained by separation is the suspension.
The solid-liquid separation device is one or more of a plate-and-frame filter press, a pressurized vertical leaf filter, a centrifuge or an automatic filter press; the slurry is subjected to oxidation reaction and carbonization reaction, so that good wall breaking, dehydration and liquefaction effects are obtained, the material properties are changed fundamentally, no medicine is needed, good solid-liquid separation can be realized by adopting the solid-liquid separation system, and solid mud cakes and clear liquid with the water content of less than 35% are obtained.
The thermal-oxygen wall-breaking carbonization reaction system can realize continuous feeding and discharging for 24 hours, can continuously and automatically operate, and has 24-hour continuous operation capability in kitchen waste disposal and biochar-based organic fertilizer preparation processes.
Example 1
A method for preparing a biochar-based organic fertilizer from kitchen waste is shown in a figure 1, and comprises the following steps:
step S1, crushing, sorting, pulping and homogenizing pretreatment are carried out on 100 tons of kitchen waste, plastics, metals, sand and other undegradable household garbage sundries in the kitchen waste are removed, organic matters and dilution water are prepared into 220 tons of homogeneous organic slurry with certain fluidity and water content of 91.8%, and the homogeneous organic slurry is stored in a slurry tank 1;
step S2, 220 tons of organic slurry is fed into the gas-liquid mixer 3 at a speed of 10 square/hour through the slurry conveying pump 2; simultaneously, compressed air is sent into the gas-liquid mixer 3 to be mixed with organic slurry at the speed of 720 square per hour through the air compressor 9; then the organic slurry is sent into a reaction tower 5 filled with a cellular heterogeneous metal lanthanum catalyst (lanthanum content is 2.37%) through a tube pass of a shell-and-tube heat exchanger 4, and is kept at a reaction temperature of 210 ℃ and a pressure of 3.5Mpa for hydrothermal oxidation reaction and thermal carbonization reaction for 30min to obtain 218 tons of suspension;
the hydrothermal oxidation reaction is used for fully breaking the walls of viruses and various cells in the organic slurry and thoroughly killing the viruses and various cells, releasing the water and organic matters in the viruses and the cells, and carrying out oxidative decomposition reaction on part of soluble or insoluble organic matters to obtain soluble micromolecular organic matters or carbon dioxide and giving out heat; the hydrothermal carbonization reaction is to carbonize soluble or insoluble organic matters (cellulose, hemicellulose, lignin, protein, fat, low molecular saccharides and other biomass) into insoluble biochar particles to suspend in liquid, and the organic slurry which is viscous and difficult to separate solid from liquid originally becomes suspension which is easy to separate solid from liquid;
s3, carrying out solid-liquid separation on the suspension by adopting a diaphragm plate-and-frame filter press 8, wherein the maximum filtering pressure is 1Mpa, and the maximum squeezing pressure is 1.4Mpa, so as to obtain 6.3 tons of solid organic mud cakes with the water content of 28.9% and 211.7 tons of clarified liquid; the clarified liquid is prepared into biogas with the methane content of 6800 percent and biogas slurry with the methane content of 56 percent by a UASB anaerobic biogas generating system, and the biogas slurry is discharged after reaching the standard by a water treatment system;
and S4, carrying out microbial fermentation composting on 6.3 tons of solid organic mud cakes for 3 months by adopting mechanical turning static composting to obtain 5.6 tons of biochar-based organic fertilizer.
Example 2
A method for preparing a biochar-based organic fertilizer from kitchen waste comprises the following steps:
step S1, crushing, sorting, pulping and homogenizing pretreatment are carried out on 100 tons of kitchen waste, plastics, metals, sand and other undegradable household garbage sundries in the kitchen waste are removed, organic matters and dilution water are prepared into 226 tons of homogeneous organic slurry with certain fluidity and water content of 90.9%, and the homogeneous organic slurry is stored in a slurry tank 1;
step S2, 226 tons of organic slurry is fed into the gas-liquid mixer 3 at a speed of 10 square/hour through the slurry conveying pump 3; simultaneously, compressed air is sent into the gas-liquid mixer 3 to be mixed with organic slurry at the speed of 780 standard square per hour through the air compressor 9; then the organic slurry is sent into a reaction tower 5 filled with a honeycomb heterogeneous metal ruthenium-cerium catalyst (ruthenium content is 0.15 percent and cerium content is 1.25 percent) through a tube pass of a shell-and-tube heat exchanger 4, and is kept at a reaction temperature of 250 ℃ and a pressure of 6Mpa for hydrothermal oxidation reaction and hydrothermal carbonization reaction, wherein the reaction time is 30min, thus 223 tons of suspension is obtained;
s3, carrying out solid-liquid separation on the suspension by adopting a plate-and-frame filter press 8 to obtain 5.4 tons of solid organic mud cakes with the water content of 28.5 percent and 220.6 tons of clarified liquid, preparing biogas with the methane content of 58 percent in 5900 percent and biogas slurry by using a UASB anaerobic biogas production system, and discharging the biogas slurry after reaching the standard by using a water treatment system;
and S4, carrying out microbial fermentation composting on 5.4 tons of solid organic mud cakes for 3 months by adopting mechanical turning static composting to obtain 4.6 tons of biochar-based organic fertilizer.
Example 3
A method for preparing a biochar-based organic fertilizer from kitchen waste comprises the following steps:
step S1, crushing, sorting, pulping and homogenizing pretreatment are carried out on 100 tons of kitchen waste, plastics, metals, sand and other undegradable household garbage sundries in the kitchen waste are removed, organic matters and dilution water are prepared into 221 tons of homogeneous organic slurry with certain fluidity and water content of 91.9%, and the homogeneous organic slurry is stored in a slurry tank 1;
step S2, delivering 221 tons of organic slurry into the gas-liquid mixer 3 at a speed of 10 square/hour through the slurry delivery pump 3; simultaneously, compressed air is sent into the gas-liquid mixer 3 to be mixed with organic slurry at the speed of 980 square per hour through the air compressor 9; the organic slurry is sent into a reaction tower 5 through the tube side of a shell-and-tube heat exchanger 4, and no catalyst is filled in the reaction tower 5; carrying out hydrothermal oxidation reaction and hydrothermal carbonization reaction at the reaction temperature of 280 ℃ and the pressure of 8Mpa for 60min to obtain 219 tons of suspension;
s3, carrying out solid-liquid separation on the suspension by adopting a plate-and-frame filter press 8 to obtain 4.7 tons of solid organic mud cakes with 29.7 percent of water content and 216.3 tons of clarified liquid, preparing 4600 square methane and biogas slurry with 57 percent of methane content by a UASB anaerobic biogas production system, and discharging the biogas slurry after reaching the standard by a water treatment system;
and S4, carrying out microbial fermentation composting on 4.7 tons of solid organic mud cakes for 3 months by adopting mechanical turning static composting to obtain 4.1 tons of biochar-based organic fertilizer.
The biochar-based organic fertilizers obtained in examples 1 to 3 were each tested, and the test methods were referred to the "biochar-based organic fertilizer-NY/T3618-2020" of the agricultural industry standard of the people's republic of China, and the results obtained are shown in table 1.
TABLE 1 detection results of biochar-based organic fertilizer
From the results of the detection of the biochar-based organic fertilizer in example 1 and example 2, it is understood that the biochar-based organic fertilizer satisfying both type I and type II standards can be prepared using the process parameters of example 1 and example 2. Compared with the embodiment 1, the embodiment 2 increases part of energy consumption in the preparation process, the quality fraction (based on the fixed carbon content) and the quality of the biochar-based organic fertilizer are improved, and the market demands of different biochar-based organic fertilizers are met by adjusting production technical parameters. Wherein, the higher the reaction temperature, the higher the reaction pressure, the higher the carbonization degree in the organic slurry and the higher the mass fraction of the biochar. As is clear from a comparison of example 3 with examples 1-2, when no catalyst is filled, the temperature and pressure required for the reaction are higher, the reaction time is longer, the product yield is lower, the product quality is inferior to that when the catalyst is filled, and the production cost per unit product is higher.
Although the present disclosure is described above, the scope of protection of the present disclosure is not limited thereto. Various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the disclosure, and these changes and modifications will fall within the scope of the invention.
Claims (3)
1. The method for preparing the biochar-based organic fertilizer from kitchen waste is characterized by comprising the following steps of:
step S1, pretreating kitchen waste to obtain organic slurry with the water content of 80% -99%;
s2, carrying out hydrothermal oxidation reaction and hydrothermal carbonization reaction on the organic slurry and oxygen in compressed air at the temperature of 200-280 ℃ and the pressure of 2-9 Mpa, wherein the reaction time is 30-90 min, so as to obtain suspension; the compressed air and the organic slurry are fed simultaneously, and the feeding rate ratio per hour is (780-980) standard compressed air: 10 parts of organic slurry;
s3, carrying out solid-liquid separation on the suspension to obtain a solid organic mud cake and a clear liquid;
s4, performing microbial fermentation composting on the organic mud cake to obtain a biochar-based organic fertilizer;
the hydrothermal oxidation reaction and the hydrothermal carbonization reaction are carried out under the condition of a catalyst, the catalyst is a heterogeneous metal catalyst, the active ingredients of the catalyst are one or more of cerium, lanthanum, ruthenium or palladium, and the mass fraction of each metal in the catalyst is 0.1-3%.
2. The method according to claim 1, wherein the pre-treatment of the kitchen waste in step S1 comprises crushing, sorting, pulping and homogenizing the kitchen waste; the water content of the organic slurry is 88-95%.
3. The method according to claim 1, wherein the microbial fermentation compost is static actively oxygen-fed compost or/and mechanically turned-over static compost.
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