Method for treating kitchen waste and preparing denitrification liquid carbon source and organic fertilizer

Abstract

The invention belongs to the field of garbage treatment, and particularly relates to a method for treating kitchen garbage and preparing a denitrification liquid carbon source and an organic fertilizer, which comprises the following steps: a) mixing kitchen garbage residues after oil extraction with water and a catalyst in a pretreatment tank, and adjusting the pH value to obtain a pretreated mixed solution; b) adding the pretreated mixed solution into a reaction kettle, introducing oxygen-containing gas, and carrying out artificial forced humification conversion to obtain an artificial forced humification reaction solution and residual gas; c) transferring the manual forced humification reaction liquid into a flash tank for pressure relief to obtain flash reaction liquid and flash steam; and d) cooling the flash reaction liquid, and carrying out solid-liquid separation to obtain a liquid component which is a denitrification liquid carbon source and a solid component which is an organic fertilizer. The method provided by the invention solves the problems of high content of humic acid in hydrolysate and hydrothermal carbon in the existing hydrothermal technology and the like, and also overcomes the problems of long treatment period and the like in the traditional wet garbage treatment process.

Description

Technical Field

[0001] The present invention belongs to the field of waste treatment, and particularly relates to a method for disposing of kitchen waste and preparing a denitrifying liquid carbon source and organic fertilizer. Background Art

[0002] With the acceleration of the urbanization process, the output of domestic waste has been continuously increasing, and the daily treatment load of waste treatment stations has been rising. Among them, kitchen waste belongs to perishable wet waste and is difficult to be quickly treated by incineration. The method of sanitary landfill may not only pollute groundwater but also pose a risk of pathogen transmission. Therefore, the state actively promotes the resource utilization of kitchen waste, and currently mainly focuses on the recovery of the oil part. However, the treatment of food residues after oil extraction still faces problems such as low efficiency, environmental pollution, and low resource utilization rate.

[0003] At present, the traditional treatment methods of kitchen waste mainly include biological methods such as anaerobic fermentation and aerobic composting. Anaerobic fermentation can convert food residues into methane for power generation, while aerobic composting can produce organic fertilizer. However, these methods are limited by the microbial activity, have a long treatment cycle, require large fermentation equipment, occupy a large area, are prone to generate odors and the NIMBY effect, and are difficult to be widely promoted on a large scale.

[0004] The hydrothermal treatment technology can effectively avoid the odor and pollution problems generated during the anaerobic fermentation process by reacting the oil-extracted residue with water under high temperature and high pressure conditions. Different temperature ranges of hydrothermal treatment will affect the composition of the final product. At present, a variety of processes have been developed for hydrothermal technology, including biocharification, reaction liquefaction, supercritical water upgrading of heavy oil, supercritical water oxidation, and supercritical water gasification. Under the condition that the hydrothermal temperature is lower than 240 °C, the residue mainly undergoes hydrolysis, dehydration, condensation, polymerization, and aromatization reactions, and finally forms biochar and hydrolysate. Among them, biochar can be widely used in fields such as soil remediation, catalytic reactions, and pollutant adsorption.

[0005] The current hydrothermal treatment methods still have certain limitations. The sugars and proteins in kitchen waste are prone to Maillard reaction and caramelization reaction under high temperature conditions, resulting in the presence of humic acid-like substances with high biological toxicity in the hydrolysate and biochar, thus limiting their applications in the fields of sewage treatment and agriculture. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a method for disposing of kitchen waste and preparing a denitrifying liquid carbon source and organic fertilizer, which solves the problems of high content of humic acid-like substances in the hydrolysate and biochar and limited application scenarios in the existing hydrothermal technology, and also overcomes the problems of long treatment cycles, serious odor emission, and high risk of pathogen transmission in traditional wet waste treatment processes (such as anaerobic fermentation, aerobic composting, and sanitary landfill).

[0007] The present invention provides a method for disposing kitchen waste and preparing a denitrifying liquid carbon source and organic fertilizer, comprising the following steps:

[0008] a) Mix the residual kitchen waste after oil extraction with water and a catalyst in a pretreatment tank, and adjust the pH value to obtain a pretreated mixed liquid;

[0009] In step a), the catalyst is a catalyst with active components containing Al and / or Fe; the pH value of the pretreated mixed liquid is 8-10;

[0010] b) Add the pretreated mixed liquid into a reaction kettle, introduce an oxygen-containing gas for artificial forced humification conversion to obtain an artificial forced humification reaction liquid and residual gas;

[0011] In step b), the temperature of the artificial forced humification conversion is 150-250 °C, and the pressure is 8-12 MPa;

[0012] c) Transfer the artificial forced humification reaction liquid to a flash tank for pressure relief to obtain a flash reaction liquid and flash steam;

[0013] d) After the flash reaction liquid is cooled, solid-liquid separation is carried out. The obtained liquid component is the denitrifying liquid carbon source, and the obtained solid component is the organic fertilizer.

[0014] Preferably, the solid content of the pretreated mixed liquid is 10-20 wt%.

[0015] Preferably, the catalyst is one or more of ammonia-absorbing stone, Fe 2 O 3 、Fe 3 O 4 and FeOCl.

[0016] Preferably, the addition amount of the catalyst is 0.05-0.5 wt% of the total weight of the pretreated mixed liquid.

[0017] Preferably, before the pretreated mixed liquid is added to the reaction kettle, hot gas is introduced into the pretreatment tank to preheat the pretreated mixed liquid; the hot gas includes the residual gas and / or flash steam.

[0018] Preferably, the oxygen content of the oxygen-containing gas ≥ 20%.

[0019] Preferably, the artificial forced humification conversion is carried out under stirring conditions, and the stirring rate is 5000-20000 rpm.

[0020] Preferably, the time of the artificial forced humification conversion is 1-3 h.

[0021] Preferably, the cooling is carried out in a heat exchanger, the cold source is water, and the warm water after heat exchange enters the pretreatment tank to participate in the preparation of the pretreatment mixture.

[0022] Preferably, the residual kitchen waste after oil extraction is obtained by the following method:

[0023] After the kitchen waste is sorted, crushed, centrifuged and left standing, the upper layer of grease is separated, and the lower layer of residual phase is retained;

[0024] The lower layer of residual phase is subjected to decantation treatment to obtain the residual kitchen waste after oil extraction.

[0025] Compared with the prior art, the present invention provides a method for disposing of kitchen waste and preparing a denitrifying liquid carbon source and organic fertilizer, comprising the following steps: a) mixing the residual kitchen waste after oil extraction with water and a catalyst in a pretreatment tank, and adjusting the pH value to obtain a pretreatment mixture; in step a), the catalyst is a catalyst with active components containing Al and / Fe; the pH value of the pretreatment mixture is 8-10; b) adding the pretreatment mixture into a reaction kettle, introducing an oxygen-containing gas for artificial forced humification conversion to obtain an artificial forced humification reaction liquid and surplus gas; in step b), the temperature of the artificial forced humification conversion is 150-250 °C, and the pressure is 8-12 MPa; c) transferring the artificial forced humification reaction liquid to a flash tank for pressure relief to obtain a flash reaction liquid and flash steam; d) cooling the flash reaction liquid and then performing solid-liquid separation, the obtained liquid component is the denitrifying liquid carbon source, and the obtained solid component is the organic fertilizer. The method provided by the present invention solves the problems of high content of humic acid-like substances in the hydrolysis liquid and biochar in the existing hydrothermal technology and limited application scenarios, and at the same time overcomes the problems of long treatment cycle, serious odor emission and high risk of pathogen transmission in traditional wet waste treatment processes (such as anaerobic fermentation, aerobic composting, sanitary landfill). More specifically, the method has at least the following advantages:

[0026] (1) The present invention utilizes the fact that oxygen-containing gas can generate superoxide radicals in an aqueous solution under high temperature and high pressure, and then oxidatively degrades the kitchen waste through the generated radicals; through subsequent methods such as flash pressure relief and solid-liquid separation, a reaction liquid with a COD value higher than 30000 mg / L and hydrothermal carbon rich in fulvic acid can be finally obtained. Among them, the COD value of the reaction liquid is comparable to that of some liquid carbon sources sold on the market, and the utilization efficiency by denitrifying bacteria is higher than that of common carbon sources such as methanol; the obtained hydrothermal carbon not only is rich in fulvic acid, which is helpful for plant germination and root and leaf growth, but also has the effect of improving acidic and alkaline soils. In summary, the products obtained by the method of the present invention are far superior to the kitchen waste raw materials.

[0027] (2) The present invention can achieve rapid reduction of food waste. The solid-liquid mixture obtained through the artificial forced humification technology can be rapidly separated into solid and liquid, and its dehydration rate is more than 100 times that of the original food waste and more than 20 times that of the conventional hydrothermal treatment method. The total processing time of the present invention can be controlled within 5 hours, which is much shorter than the current biological treatment technologies such as anaerobic fermentation and aerobic composting.

[0028] (3) The treatment process of the present invention is green and friendly. The nitrogen heterocyclic substances with strong odors that would be generated by food waste under high temperature and pressure become small molecule volatile organic acids after being treated by the artificial forced humification technology, and no longer release harmful gases to the surrounding environment. Compared with traditional hydrothermal treatment, anaerobic fermentation, aerobic composting and other technologies, the artificial forced humification technology adopted by the present invention brings little NIMBY effect.

[0029] (4) During the treatment process of the present invention, the steam generated by flash evaporation and pressure relief and the warm water obtained by heat exchange and cooling of the flash reaction liquid can provide heat for preheating the pretreatment mixed liquid, thereby improving the heat utilization rate of the overall process and reducing the cost increase caused by unreasonable fuel addition. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0031] Figure 1 Index data diagrams of the liquid carbon source obtained by the artificial forced humification conversion of food waste in Examples 1-2 and Comparative Examples 1-4;

[0032] Figure 2 Small molecule acid component composition data diagrams of the liquid carbon source obtained by the artificial forced humification conversion of food waste in Examples 1-2 and Comparative Examples 1-4;

[0033] Figure 3 Nitrogen component composition data diagrams of the liquid carbon source obtained by the artificial forced humification conversion of food waste in Examples 1-2 and Comparative Examples 1-4;

[0034] Figure 4 Three-dimensional fluorescence data diagrams of the liquid carbon source obtained by the artificial forced humification conversion of food waste in Examples 1-2 and Comparative Examples 1-4;

[0035] Figure 5Index data graphs of the liquid carbon sources obtained after the artificial forced humification conversion of the food waste in Examples 1, 3, 4, 5 and Comparative Examples 5-11;

[0036] Figure 6 Graphs of the corresponding catalyst metal ion dissolution data obtained after the artificial forced humification conversion of the food waste in Examples 1, 3, 4, 5 and Comparative Examples 5-11;

[0037] Figure 7 Graph of the operation data of the liquid carbon source obtained after the artificial forced humification conversion of the food waste in Example 1 during continuous operation in a small-scale continuous flow denitrification reactor built in the laboratory for 28 days;

[0038] Figure 8 Graph of the denitrification ability data of the liquid carbon source obtained after the artificial forced humification conversion of the food waste in Example 1, the commercially purchased glucose and sodium acetate carbon sources, and the sludge in the vial experiment testing different carbon sources;

[0039] Figure 9 Graph of the signal ratio at wavelengths of 465 nm and 665 nm measured by the ultraviolet spectrophotometer for the leachate of the highly humified organic fertilizers obtained in Examples 1, 6-9, and the results of the seed germination experiment pictures using pure water, the organic fertilizers obtained in Example 1 and Comparative Example 4, and the leachate obtained from the untreated food waste;

[0040] Figure 10 Graph of the experimental result data of the laboratory cultivation of pakchoi using no fertilizer, untreated food waste, the organic fertilizers obtained in Example 1 and Comparative Example 4, commercially purchased farmyard manure, and potassium fulvate as fertilizers;

[0041] Figure 11 Graph of the growth effect diagram of the laboratory cultivation of pakchoi using no fertilizer, untreated food waste, the organic fertilizers obtained in Example 1 and Comparative Example 4, commercially purchased farmyard manure, and potassium fulvate as fertilizers; Detailed implementation manners

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0043] The present invention provides a method for disposing of food waste and preparing a denitrification liquid carbon source and an organic fertilizer, comprising the following steps:

[0044] a) Mix the residual kitchen waste after oil extraction with water and a catalyst in a pretreatment tank, and adjust the pH value to obtain a pretreated mixed solution;

[0045] b) Add the pretreated mixed solution to a reaction kettle, introduce an oxygen-containing gas for artificial forced humification conversion to obtain an artificial forced humification reaction solution and residual gas;

[0046] c) Transfer the artificial forced humification reaction solution to a flash tank for pressure relief to obtain a flash reaction solution and flash steam;

[0047] d) After the flash reaction solution is cooled, perform solid-liquid separation. The liquid component obtained is the denitrification liquid carbon source, and the solid component obtained is organic fertilizer.

[0048] In the method provided by the present invention, in step a), the residual kitchen waste after oil extraction can be obtained by the following method:

[0049] After the kitchen waste is sorted, crushed, centrifuged and left standing, the upper-layer oil is separated, and the lower-layer residual phase is retained;

[0050] The lower-layer residual phase is subjected to decantation treatment to obtain the residual kitchen waste after oil extraction.

[0051] In the method provided by the present invention, in step a), the catalyst is a catalyst whose active ingredient contains Al and / or Fe, preferably one or more of ammonia-absorbing stone, Fe 2 O 3 、Fe 3 O 4 and FeOCl; the addition amount of the catalyst is preferably 0.05-0.5 wt% of the total weight of the pretreated mixed solution, and specifically can be 0.05 wt%, 0.1 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.35 wt%, 0.4 wt%, 0.45 wt% or 0.5 wt%.

[0052] In the method provided by the present invention, in step a), the pH value of the pretreated mixed solution is 8-10, and specifically can be 8, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9 or 10.

[0053] In the method provided by the present invention, in step a), the solid content of the pretreated mixed solution is preferably 10-20 wt%, and specifically can be 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt% or 20 wt%.

[0054] In the method provided by the present invention, in step a), before the pretreatment mixture is discharged for subsequent treatment, it is preferred to first introduce hot gas into the pretreatment tank to preheat the pretreatment mixture; the hot gas preferably includes the surplus gas and / or flash steam.

[0055] In the method provided by the present invention, in step b), the oxygen content of the oxygen-containing gas is preferably ≥20%, more preferably ≥50%, still more preferably ≥70%, and specifically, pure oxygen, a mixture of oxygen and water vapor, air, or a mixture of air and water vapor can be selected.

[0056] In the method provided by the present invention, in step b), the temperature for artificial forced humification conversion is 150 - 250°C, and specifically, it can be 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, or 250°C.

[0057] In the method provided by the present invention, in step b), the pressure for artificial forced humification conversion is 8 - 12 MPa, and specifically, it can be 8 MPa, 8.2 MPa, 8.5 MPa, 8.7 MPa, 9 MPa, 9.2 MPa, 9.5 MPa, 9.7 MPa, 10 MPa, 10.2 MPa, 10.5 MPa, 10.7 MPa, 11 MPa, 11.2 MPa, 11.5 MPa, 11.7 MPa, or 12 MPa.

[0058] In the method provided by the present invention, in step b), the artificial forced humification conversion is preferably carried out under stirring conditions, and the stirring rate is preferably 5000 - 20000 rpm, and specifically, it can be 5000 rpm, 6000 rpm, 7000 rpm, 8000 rpm, 9000 rpm, 10000 rpm, 11000 rpm, 12000 rpm, 13000 rpm, 14000 rpm, 15000 rpm, 16000 rpm, 17000 rpm, 18000 rpm, 19000 rpm, or 20000 rpm.

[0059] In the method provided by the present invention, in step b), the time for artificial forced humification conversion is preferably 1 - 3 h, and specifically, it can be 1 h, 1 h 10 min, 1 h 20 min, 1 h 30 min, 1 h 40 min, 1 h 50 min, 2 h, 2 h 10 min, 2 h 20 min, 2 h 30 min, 2 h 40 min, 2 h 50 min, or 3 h.

[0060] In the method provided by the present invention, in step d), the cooling is preferably carried out in a heat exchanger, and the cold source is preferably water. The warm water after heat exchange can enter the pretreatment tank to participate in the preparation of the pretreatment mixture, so as to reduce the preheating cost of the pretreatment mixture.

[0061] In the method provided by the present invention, in step d), the denitrifying liquid carbon source can be applied to the denitrification tank of a sewage treatment plant; the organic fertilizer can be applied to the remediation of acidic and alkaline soils and the application to crops and flowers after granulation treatment.

[0062] For the sake of clarity, the following will be described in detail through the following examples and comparative examples.

[0063] It should be noted that the raw materials in the following examples and comparative examples are as follows: alumina powder, anhydrous ferric chloride, iron oxide powder, magnetite powder, copper oxide powder, cuprous oxide powder, manganese dioxide, manganese tetroxide, nickel oxide, zinc oxide, sodium hydroxide, sodium acetate, glucose: purchased from Sinopharm Chemical Reagent Co., Ltd.; ammonia-absorbing stone powder: purchased from the Taobao store Henan Guanghui Water Treatment Store; kitchen waste residue: sourced from the Xiaomiao Organic Resource Treatment Center in Hefei, Anhui Province.

[0064] Example 1

[0065] As Figure 1 shown, this example provides a method for disposing of kitchen waste and preparing a denitrifying liquid carbon source and an organic fertilizer, including the following steps:

[0066] Step 1, garbage collection and sorting: Use a garbage transport vehicle to transport the sorted kitchen waste to the Xiaomiao Organic Resource Treatment Center in Hefei, and sort out impurities such as plastics and large bone blocks in the kitchen waste.

[0067] Step 2, oil extraction and three-phase separation: Mechanically crush the sorted kitchen waste, and after centrifugal static treatment, separate the upper-layer oil as crude waste oil for further purification; perform decantation treatment on the lower-layer residual phase to remove most of the water, and leave the water-containing kitchen waste residue for subsequent artificial forced humification technology treatment.

[0068] Step 3, feed pretreatment: Add the water-containing kitchen waste residue and water to the preheating tank in a ratio of 15 wt% of the solid content for mixing, and add 0.15 wt% of ammonia-absorbing stone as a catalyst based on the total weight of the mixture to adjust the pH value of the mixture to about 9; introduce the high-temperature gas generated in the downstream process into the preheating tank to preheat the mixture.

[0069] Step 4, Artificial forced humification technology: Transfer the preheated mixture to a reaction kettle, and introduce high-temperature gas with an oxygen content > 70% into the reaction kettle. Control the temperature of the reaction kettle at 220 °C and the pressure at 10 MPa. The mixture stays in the reaction kettle for 2 h under continuous stirring at 10000 rpm to obtain an artificial forced humification reaction solution; during the operation of the reaction kettle, the remaining gas is transferred to the preheating tank for preheating the mixture.

[0070] Step 5, Flash evaporation and pressure relief: Transfer the artificial forced humification reaction solution to a flash evaporation tank, and reduce the pressure in the tank to near normal atmospheric pressure by flash evaporation. Transfer the high-temperature flash steam released by flash evaporation to the preheating tank for preheating the mixture. The function of the flash evaporation tank is to quickly release the high pressure in the artificial forced humification reaction solution, remove the ammonia nitrogen therein to increase the carbon-nitrogen ratio of the liquid carbon source, and at the same time recycle the heat in the flash steam to reduce the heating cost in the process.

[0071] Step 6, Water-cooled heat exchange: Transfer the pressure-relieved artificial forced humification reaction solution to a heat exchanger, and cool it to room temperature by water cooling. The warm water after heat exchange is injected into the preheating tank as a solvent to dilute and heat the food waste residues. The function of water-cooled heat exchange is to quickly cool the high-temperature artificial forced humification reaction solution to normal temperature for subsequent further solid-liquid separation, and at the same time recover the heat in the artificial forced humification reaction solution to reduce the heating cost in the process.

[0072] Step 7, Mechanical dehydration and solid-liquid separation: Transfer the cooled artificial forced humification reaction solution to a dehydration tank, and use a robotic arm to perform extrusion dehydration. The separated hydrolysis solution can be collected and processed to become a liquid carbon source for use in the denitrification tank of a sewage treatment plant; the separated hydrothermal carbon can be granulated to become a highly humified organic fertilizer for use in the repair of acidic and alkaline soils and the application to crops and flowers.

[0073] Example 2

[0074] This example provides a method for disposing of food waste and preparing a denitrification liquid carbon source and organic fertilizer. The difference from Example 1 is that the oxygen-containing gas introduced in Step 4 is air.

[0075] Example 3

[0076] This example provides a method for disposing of food waste and preparing a denitrification liquid carbon source and organic fertilizer. The difference from Example 1 is that the type of catalyst added in Step 3 is Fe 2 O 3 。

[0077] Example 4

[0078] This embodiment provides a method for disposing of kitchen waste and preparing a denitrifying liquid carbon source and organic fertilizer. The difference from Embodiment 1 is that the type of catalyst added in Step 3 is Fe 3 O 4 .

[0079] Embodiment 5

[0080] This embodiment provides a method for disposing of kitchen waste and preparing a denitrifying liquid carbon source and organic fertilizer. The difference from Embodiment 1 is that the type of catalyst added in Step 3 is FeOCl.

[0081] Embodiment 6

[0082] This embodiment provides a method for disposing of kitchen waste and preparing a denitrifying liquid carbon source and organic fertilizer. The difference from Embodiment 1 is that the temperature of the reaction kettle in Step 4 is controlled at 160 °C.

[0083] Embodiment 7

[0084] This embodiment provides a method for disposing of kitchen waste and preparing a denitrifying liquid carbon source and organic fertilizer. The difference from Embodiment 1 is that the temperature of the reaction kettle in Step 4 is controlled at 180 °C.

[0085] Embodiment 8

[0086] This embodiment provides a method for disposing of kitchen waste and preparing a denitrifying liquid carbon source and organic fertilizer. The difference from Embodiment 1 is that the temperature of the reaction kettle in Step 4 is controlled at 200 °C.

[0087] Embodiment 9

[0088] This embodiment provides a method for disposing of kitchen waste and preparing a denitrifying liquid carbon source and organic fertilizer. The difference from Embodiment 1 is that the temperature of the reaction kettle in Step 4 is controlled at 240 °C.

[0089] Comparative Example 1

[0090] This comparative example provides a method for disposing of kitchen waste and preparing a denitrifying liquid carbon source and organic fertilizer. The difference from Embodiment 1 is that no catalyst is added to participate in the reaction in Step 3.

[0091] Comparative Example 2

[0092] This comparative example provides a method for disposing of kitchen waste and preparing a denitrifying liquid carbon source and organic fertilizer. The difference from Embodiment 1 is that the gas introduced in Step 3 is high-temperature steam without oxygen, and the oxygen-containing gas introduced in Step 4 is air.

[0093] Comparative Example 3

[0094] This comparative example provides a method for disposing of food waste and preparing a denitrifying liquid carbon source and organic fertilizer. The difference from Example 1 is that high-purity nitrogen is introduced before aeration to expel the residual atmosphere in the reaction kettle, and the gas introduced is high-temperature steam without oxygen.

[0095] Comparative Example 4

[0096] This comparative example provides a method for disposing of food waste and preparing a denitrifying liquid carbon source and organic fertilizer. The difference from Example 1 is that no catalyst is added in Step 3 for the reaction, and high-purity nitrogen is introduced before aeration to expel the residual atmosphere in the reaction kettle, and the gas introduced is high-temperature steam without oxygen.

[0097] Comparative Example 5

[0098] This example provides a method for disposing of food waste and preparing a denitrifying liquid carbon source and organic fertilizer. The difference from Example 1 is that the type of catalyst added in Step 3 is Cu 2 O.

[0099] Comparative Example 6

[0100] This example provides a method for disposing of food waste and preparing a denitrifying liquid carbon source and organic fertilizer. The difference from Example 1 is that the type of catalyst added in Step 3 is CuO.

[0101] Comparative Example 7

[0102] This example provides a method for disposing of food waste and preparing a denitrifying liquid carbon source and organic fertilizer. The difference from Example 1 is that the type of catalyst added in Step 3 is Mn 2 O 3 .

[0103] Comparative Example 8

[0104] This example provides a method for disposing of food waste and preparing a denitrifying liquid carbon source and organic fertilizer. The difference from Example 1 is that the type of catalyst added in Step 3 is Mn 3 O 4 .

[0105] Comparative Example 9

[0106] This example provides a method for disposing of food waste and preparing a denitrifying liquid carbon source and organic fertilizer. The difference from Example 1 is that the type of catalyst added in Step 3 is Co 3 O 4 .

[0107] Comparative Example 10

[0108] This embodiment provides a method for disposing of kitchen waste and preparing a denitrifying liquid carbon source and organic fertilizer. The difference from Embodiment 1 is that the type of catalyst added in Step 3 is Ni 2 O 3 .

[0109] Comparative Example 11

[0110] This embodiment provides a method for disposing of kitchen waste and preparing a denitrifying liquid carbon source and organic fertilizer. The difference from Embodiment 1 is that the type of catalyst added in Step 3 is ZnO.

[0111] Effect Evaluation

[0112] (1) Determination of denitrifying carbon source indexes in sewage treatment plants

[0113] For the denitrifying liquid carbon sources of sewage treatment plants prepared in Embodiments 1-9 and Comparative Examples 1-11, tests were carried out on chemical oxygen demand (COD), total organic carbon (TOC), total nitrogen (TN), nitrate nitrogen (NO 3 - -N), nitrite nitrogen (NO 2 - -N), organic nitrogen (TON), and volatile fatty acids (VFA). The results are as Figures 1 to 6 shown and are specifically described as follows:

[0114] In Figure 1 Al 2 O 3 -O 2 group corresponds to Embodiment 1, None-O 2 group corresponds to Comparative Example 1, Al 2 O 3 -Air group corresponds to Embodiment 2, None-Air corresponds to Comparative Example 2, Al 2 O 3 -N 2 group corresponds to Comparative Example 3, None-N 2 group corresponds to Comparative Example 4. It can be seen from Figure 1 that the addition of the catalyst helps to promote the increase of COD of the liquid carbon source in the aerobic system, while it will cause a decrease in COD in the anaerobic system. The co-mixed system of the catalyst and oxygen helps to reduce the total nitrogen content in the reaction solution, thereby increasing the carbon-nitrogen ratio of the liquid carbon source. This is because the catalyst can promote the generation of oxygen-containing active species by oxygen, promote the Maillard reaction between small molecule nitrogen and other small molecules to form humus, and then fix the small molecule amines in the solution in the hydrothermal carbon, achieving the effect of reducing the total nitrogen and increasing the C / N ratio.

[0115] In Figure 2 Al 2 O3 -O 2 Group corresponds to Example 1, None - O 2 Group corresponds to Comparative Example 1, Al 2 O 3 -Air group corresponds to Example 2, None - Air corresponds to Comparative Example 2, Al 2 O 3 -N 2 Group corresponds to Comparative Example 3, None - N 2 Group corresponds to Comparative Example 4. It can be seen from Figure 2 that the addition of the catalyst can improve the VFA content inside the liquid carbon source, and the improvement degree is related to the oxygen concentration introduced. The higher the oxygen concentration, the higher the VFA content inside the liquid carbon source. This is because the oxygen-containing species generated by the catalyst catalyzing oxygen can accelerate the decomposition of food waste, depolymerize the free humic acid in the reaction solution into VFA and small molecule alcohols.

[0116] In Figure 3 Al 2 O 3 -O 2 Group corresponds to Example 1, None - O 2 Group corresponds to Comparative Example 1, Al 2 O 3 -Air group corresponds to Example 2, None - Air corresponds to Comparative Example 2, Al 2 O 3 -N 2 Group corresponds to Comparative Example 3, None - N 2 Group corresponds to Comparative Example 4. It can be seen from Figure 3 that most of the nitrogen inside the liquid carbon source of each experimental example and comparative example consists of organic nitrogen and ammonia nitrogen. The addition of the catalyst can reduce the total nitrogen content in the liquid carbon source and increase the proportion of ammonia nitrogen therein. This is because the oxygen-containing free radicals generated by the catalyst and oxygen can oxidize organic amines into ammonium ions and free them into the solution, thus helping to treat the excess nitrogen in the liquid carbon source.

[0117] In Figure 4 Al 2 O 3 -O 2 Group corresponds to Example 1, None - O 2 Group corresponds to Comparative Example 1, Al 2 O 3 -Air group corresponds to Example 2, None - Air corresponds to Comparative Example 2, Al 2 O 3 -N 2 Group corresponds to Comparative Example 3, None - N 2 Group corresponds to Comparative Example 4. It can be seen from Figure 4It can be seen that the humic acid content in the liquid carbon source significantly decreases in the examples with catalysts and decreases with the increase in the oxygen concentration introduced into the system. This is because the oxygen-containing free radicals generated by the catalyst and oxygen help promote the degradation of humic acid into VFA and small molecule alcohols, making the kitchen waste carbon source more easily absorbed by the microorganisms in the sewage treatment plant.

[0118] In Figure 5 it, the Al 2 O 3 group corresponds to Example 1, the Fe 2 O 3 group corresponds to Example 3, the Fe 3 O 4 group corresponds to Example 4, the FeOCl group corresponds to Example 5, the Cu 2 O group corresponds to Comparative Example 5, the CuO group corresponds to Comparative Example 6, the Mn 2 O 3 group corresponds to Comparative Example 7, the Mn 3 O 4 group corresponds to Comparative Example 8, the Co 3 O 4 group corresponds to Comparative Example 9, the Ni 2 O 3 group corresponds to Comparative Example 10, the Ni 2 O 3 group corresponds to Comparative Example 11. From Figure 5 it can be seen that the COD contents in the liquid carbon source after the reaction with different catalysts are different. Among them, the liquid carbon sources obtained in Example 1 and Example 3 have high COD content and low total nitrogen content, and the corresponding catalysts are more suitable for catalyzing the conversion of kitchen waste into liquid carbon source.

[0119] In Figure 6 it, the Al 2 O 3 group corresponds to Example 1, the Fe 2 O 3 group corresponds to Example 3, the Fe 3 O 4 group corresponds to Example 4, the FeOCl group corresponds to Example 5, the Cu 2 O group corresponds to Comparative Example 5, the CuO group corresponds to Comparative Example 6, the Mn 2 O 3 group corresponds to Comparative Example 7, the Mn 3 O 4 group corresponds to Comparative Example 8, the Co 3 O 4 group corresponds to Comparative Example 9, the Ni 2 O 3 group corresponds to Comparative Example 10, the Ni 2 O 3 group corresponds to Comparative Example 11. FromFigure 6 As can be seen, the dissolution degrees of the metals used in the liquid carbon sources after the reactions with different catalysts are different. Among them, the catalysts used in Examples 1, 3, 4, and 5 are mainly composed of common Fe and Al series transition metal elements. They are not only inexpensive and have little toxicity to the environment, but also have little dissolution during the artificial forced humification process. This makes the catalysts synthesized from this series of metal oxides more suitable as the carbon source for the artificial forced humification technology. In Comparative Examples 5-11, the dissolution content of their catalysts is very high, indicating that these heavy metal catalysts are prone to corrosion during the artificial forced humification process, and the dissolved metal ions are harmful to the environment and are not suitable as the catalysts for artificial forced humification.

[0120] (2) Determination of the denitrification ability of the artificial forced humification carbon source

[0121] For the liquid carbon source prepared in Example 1 and sodium acetate and glucose purchased on the market, the denitrification ability of the carbon source was determined. Specifically: The reactor was made of plexiglass with an effective volume of 1 L; C / N was 6, and HRT was 8 h; the inoculated sludge was from Qingxi Wastewater Treatment Plant in Hefei; the simulated wastewater selected NaNO 3 as the electron acceptor with a concentration of 50 mg / L; the other components in the wastewater included: 1 g / L NaHCO 3 , 25 mg / L KH 2 PO 4 , 75 mg / L MgSO 4 , 50 mg / L NaCl, 20 mg / L CaCl 2 and 1 mg / L trace elements; among them, the trace element solution included: 14 mg / L H 3 BO 3 , 190 mg / L NiCl 3 ·6H 2 O, 250 mg / L CuSO 4 ·5H 2 O, 990 mg / L MnCl 2 ·4H 2 O, 240 mg / L CoCl 2 ·6H 2 O, 220 mg / L NaMoO 4 ·2H 2 O, 430 mg / L ZnSO 4 ·7H 2 O, 50 mg / L NaWO 4 · 2 H 2O; The initial pH of the simulated wastewater was adjusted to 7.2 ± 0.1 using 0.1 mol / L HCl; the dissolved oxygen (DO) of the simulated wastewater was controlled below 0.5 mg / L by purging nitrogen.

[0122] The experimental results are as Figures 7 to 8 shown and are specifically described as follows: Through Figure 7 it can be seen that the nitrate nitrogen removal rate of the effluent of the liquid carbon source obtained by artificial forced humification can be stabilized at about 90%, and the nitrate nitrogen removal rate can be further increased to nearly 99% after 20 days. Through Figure 8 it can be seen that compared with carbon sources such as commercial sodium acetate and glucose commonly used in sewage treatment plants, the nitrate nitrogen removal efficiency of the liquid carbon source obtained by artificial forced humification is lower than that of sodium acetate and higher than that of glucose. From the above experimental results, it can be seen that the liquid carbon source obtained by artificial forced humification has the ability to become a denitrifying carbon source.

[0123] (3) Determination of indexes of highly humified organic fertilizer

[0124] For the highly humified organic fertilizer prepared in Example 1 and the untreated food waste, tests were carried out on indexes such as organic matter, total nutrients, seed germination rate, fecal coliform count, and Ascaris mortality rate. The results are shown in Table 1.

[0125] Table 1

[0126]

[0127] It can be seen from Table 1 that all indexes of the highly humified organic fertilizer obtained in Example 1 meet the current technical requirements for biological stimulants.

[0128] (4) Determination of biological toxicity of highly humified organic fertilizer

[0129] For the highly humified organic fertilizers prepared in Examples 1, 6 - 9, the conventional hydrothermal fertilizer prepared in Comparative Example 1, the untreated food waste, and the blank control, germination experiments were carried out. Specifically: 20 plump pakchoi seeds were evenly placed in a petri dish with a radius of 10 cm, 1 ml of the 2 - hour leaching solution of the corresponding fertilizer was added, and they were placed in a constant temperature incubator at 20°C for dark cultivation for 48 h. The root length of the seeds was measured, and then the seed germination rate of each fertilizer was calculated according to the growth of the blank control sample. Then, the ultraviolet absorption at wavelengths of 465 nm and 665 nm in the leaching solution of each fertilizer was measured by an ultraviolet spectrophotometer, and the E 4 / E 6 value was calculated to evaluate the degree of maturity of each fertilizer.

[0130] The experimental results are as Figure 9 shown and are specifically described as follows: Figure 9Among them, KW represents the unreacted kitchen waste, HT-220 represents conventional hydrothermal treatment at 220°C (Comparative Example 4), WCO-160 represents artificial forced humification conversion at 160°C (Example 6), WCO-180 represents artificial forced humification conversion at 180°C (Example 7), WCO-200 represents artificial forced humification conversion at 200°C (Example 8), WCO-220 represents artificial forced humification conversion at 220°C (Example 1), and WCO-240 represents artificial forced humification conversion at 240°C (Example 9). By Figure 9 It can be seen that the highly humified organic fertilizer E obtained from Examples 1, 6 to 9 4 / E 6 values are all around 2.5 - 3, far lower than the fertilizer values obtained by conventional hydrothermal treatment, indicating that the humification degree of the artificially forced humified organic fertilizer is high, and the seed germination rates are all above 80%. The seed germination rate of the organic fertilizer prepared in Example 1 is 118%, which fully shows that the artificially forced humified organic fertilizer helps to promote seed germination and has less toxicity to organisms.

[0131] (5) Determination of the growth of plants with highly humified organic fertilizer

[0132] For the highly humified organic fertilizer prepared in Example 1, the conventional hydrothermal fertilizer prepared in Comparative Example 1, untreated kitchen waste, farmyard manure purchased on the market, fulvic acid potassium fertilizer, and NPK chemical fertilizer, laboratory plant growth experiments were carried out. Specifically: The soil for growing pakchoi was first passed through a 4 mm filter screen to ensure the uniformity of the soil. On average, 500 ml of water was added to every 5 kg of soil to obtain soil with a water content of about 23%. After thoroughly mixing it, it was added to flower pots, and each flower pot contained 300 g of soil and 6 plump pakchoi seeds. Due to the different nutrient contents of each fertilizer, the application rates were also different to ensure that the nutrient contents in the potted plants were similar. Among them, the application rate of chemical fertilizer was 0.5 g, and the application rates of the others were all 2 g / pot. The fertilizer was evenly scattered in a ring at the place where the seeds were buried. On average, 10 ml of pure water was added every 3 days. Each experimental group had 3 pots. After 58 days, the growth of the plants was photographed, and the fresh weight, root length, root weight, stem weight and other indicators of the plants were weighed.

[0133] The experimental results are as Figures 10 to 11As shown, the growth conditions of pakchoi over 58 days with the highly humified organic fertilizer prepared in Example 1, the conventional hydrothermal fertilizer prepared in Comparative Example 1, untreated food waste, commercially available farmyard manure, fulvic acid potassium fertilizer, and NPK chemical fertilizer are as follows: highly humified organic fertilizer prepared in Example 1 > untreated food waste > commercially available farmyard manure > blank control > conventional hydrothermal > commercially available fulvic acid potassium fertilizer. Among them, the plants cultivated with the highly humified organic fertilizer prepared in Example 1 have lush leaves, good growth, and rarely show yellowing of leaves, which is better than the commercially available farmyard manure. This shows that the highly humified organic fertilizer prepared in Example 1 has a good effect on promoting plant growth.

[0134] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for treating kitchen waste and preparing denitrification liquid carbon source and organic fertilizer, characterized in that: The following steps are involved: a) mixing the oil-extracted kitchen waste residues with water and a catalyst in a pretreatment tank, and adjusting the pH value to obtain a pretreatment mixed solution; In step a), the catalyst is a catalyst containing Al and / or Fe as active ingredients; the pH value of the pre-treated mixed solution is 8 to 10; b) adding the pretreated mixed solution into a reactor, introducing oxygen-containing gas to carry out artificial forced humification conversion, and obtaining an artificial forced humification reaction solution and residual gas; In step b), the temperature of the artificial forced humification conversion is 150-250° C. and the pressure is 8-12 MPa; c) transferring the artificial forced humification reaction liquid to a flash tank for pressure relief to obtain a flash reaction liquid and flash steam; d) the flash reaction liquid is cooled and then solid-liquid separated, the obtained liquid component is a denitrification liquid carbon source, and the obtained solid component is an organic fertilizer.

2. The method according to claim 1, characterized in that The solid content of the pre-treated mixed solution is 10-20 wt %.

3. The method according to claim 1, characterized in that The catalyst is one or more of ammonia adsorbent, Fe2O3, Fe3O4 and FeOCl.

4. The method according to claim 1, characterized in that The added amount of the catalyst is 0.05-0.5 wt % of the total weight of the pre-treated mixed solution.

5. The method according to claim 1, characterized in that: Before the pretreatment mixed liquid is added to the reactor, hot gas is introduced into the pretreatment tank to preheat the pretreatment mixed liquid; the hot gas includes the residual gas and / or flash steam.

6. The method according to claim 1, characterized in that The oxygen content of the oxygen-containing gas is ≥20%.

7. The method according to claim 1, characterized in that The artificial forced humification conversion is carried out under stirring conditions, and the stirring rate is 5000-20000 rpm.

8. The method according to claim 1, characterized in that: The time of the artificial forced humification conversion is 1 to 3 hours.

9. The method according to claim 1, characterized in that: The cooling is carried out in a heat exchanger, the cold source is water, and the warm water after heat exchange enters the pretreatment tank to participate in the preparation of the pretreatment mixed liquid.

10. The method according to claim 1, characterized in that The kitchen waste residue after oil extraction is obtained by the following method: After the food waste is sorted, crushed, centrifuged and left to stand, the upper layer of fat is separated and the lower layer of residual phase is retained; The lower residual phase is subjected to decantation treatment to obtain the oil-extracted kitchen waste residue.

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