A vegetable tail vegetable resource utilization treatment method

Abstract

The application relates to the field of agricultural waste resource processing technology, and discloses a vegetable tailing cabbage resource utilization processing method. In view of the problems of easy collapse, local anaerobic fermentation and nitrogen loss of tailing cabbage aerobic fermentation, the method comprises the following steps: adding polymeric ferric sulfate for demulsification and tackiness conditioning after crushing the tailing cabbage; first, adding a premix of calcium superphosphate and magnesium sulfate heptahydrate, and then adding sodium carbonate in a staggered manner to buffer the pH value of the system and build a mineralization structure; then, placing the material in a closed space, converting the internal closed pores of the material into connected pore structures through continuous circulation of controlled low-amplitude positive pressure preservation and instantaneous pressure relief; and finally, performing normal pressure forced aeration aerobic fermentation and discharging the material. The application improves the structural stability and oxygen supply mass transfer efficiency of the fermentation bed, inhibits local spoilage in the early fermentation stage, in-situ fixes ammonia nitrogen through magnesium-phosphorus complex crystallization in the middle and late stages, and improves the total nitrogen retention rate in the whole fermentation cycle.

Description

Technical Field

[0001] This invention relates to the field of agricultural waste resource utilization technology, specifically a method for the resource utilization and treatment of vegetable waste. Background Technology

[0002] Vegetable waste is generated in large quantities during agricultural harvesting, distribution, and processing. Aerobic fermentation to produce fertilizer is a common way to utilize this resource. However, vegetable waste is characterized by high water content, abundant readily degradable organic matter, and a lack of physical support structure. During conventional aerobic fermentation, the pores within the material are prone to collapse and closure due to the weight of the pile and the rapid degradation by microorganisms. This disruption of the physical structure hinders the transport of external air to the deeper layers of the pile, leading to localized anaerobic environments within the material. Under insufficient oxygen supply, readily degradable organic matter rapidly produces volatile fatty acids, which accumulate and cause rancidity in the fermentation system. This not only produces foul-smelling gases but also inhibits the normal metabolic activity of aerobic fermentation microorganisms.

[0003] Meanwhile, vegetable waste is rich in nitrogenous substances such as protein. During the later stages of fermentation, as the temperature of the compost pile rises and nitrogenous organic matter continues to degrade, the nitrogen in the system is easily converted into ammonia, which is then volatilized and lost through forced ventilation. This phenomenon reduces the total nitrogen and other nutrient content in the final fertilizer product, affecting its agricultural value.

[0004] To alleviate the aforementioned problems, traditional processing methods often involve adding large amounts of low-moisture exogenous materials such as straw, rice husks, or sawdust. These materials absorb excess moisture, and their lignin fiber structure provides the porous framework of the compost pile. However, this approach increases the costs of purchasing, transporting, and pre-treating these materials. More significantly, the addition of large amounts of exogenous materials occupies limited space in the fermentation tank, significantly reducing the actual amount of vegetable waste processed per unit fermentation volume, resulting in low overall processing efficiency. Furthermore, relying solely on physical mixing makes it difficult to simultaneously address the combined issues of poor material rheology, easy pore closure, and subsequent nitrogen loss without adding large amounts of exogenous materials. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for the resource utilization and processing of vegetable waste, which solves the problems of high water content and low physical structural strength of vegetable waste, which easily leads to pore collapse and local anaerobic conditions during aerobic fermentation; at the same time, the material is prone to rapid acid production in the early stage of fermentation, causing system rancidity, and ammonia volatilization and nitrogen loss in the middle and late stages, resulting in low fermentation efficiency and substandard fertilizer product quality.

[0006] In a first aspect, the present invention provides a method for the resource utilization and treatment of vegetable waste, which adopts the following technical solution: A method for the resource utilization and treatment of vegetable waste includes the following steps: (1) Crushing and demulsification: The vegetable tails are crushed, and then polyferric sulfate is added evenly to the crushed material. The mixture is sheared and stirred at a speed of 50-70 rpm to obtain processed material A. (2) Staggered addition of skeleton premix and foaming source: Reduce the stirring speed to 10-20 rpm, first uniformly sprinkle skeleton and nitrogen-retaining dry powder premix into the material A and maintain stirring, then uniformly add sodium percarbonate into the material system and continue to maintain stirring to obtain material B. (3) Controlled low-amplitude positive pressure pore formation treatment: Place the processed material B in a closed fermentation space, pump air into the interior to form a controlled low-amplitude positive pressure environment and maintain the pressure. After the pressure maintenance is completed, release the pressure to normal pressure instantly. Repeat the pressure maintenance and instantaneous pressure release steps continuously. (4) Aerobic fermentation and discharge: Forced ventilation aerobic fermentation is carried out under normal pressure. After fermentation is completed, the material is discharged to obtain solid organic fertilizer product. The amounts of each ingredient added per 1000 servings of the aforementioned vegetable scraps, by weight, are as follows: The amount of the polyferric sulfate is 1.0 to 3.0 parts; The skeleton and nitrogen-retaining dry powder premix consists of 20.0-40.0 parts of superphosphate and 10.0-25.0 parts of magnesium sulfate heptahydrate; The sodium percarbonate content is 15.0 to 30.0 parts.

[0007] By adopting the above technical solution, this invention pre-conditions the physical pores and related components of vegetable waste before aerobic fermentation through a combination of physical-mechanical processes and additives. The corresponding reaction process and mechanism are as follows: In step (1), since the crushing of vegetable waste usually releases intracellular substances and forms emulsified colloids, the addition of polyferric sulfate causes hydrolysis to produce polynuclear hydroxyl complexes and iron ions. These can reduce the repulsion potential by neutralizing the negative charge on the surface of the colloid, thus promoting the destabilization of the colloidal particles. Based on this, the adsorption and bridging effect of polymer molecules causes the fine particles to undergo preliminary flocculation, thereby breaking the original water-holding form of the material and promoting the conversion of more bound water into free water.

[0008] In step (2), the degradation of nitrogen-containing organic matter in the early stage of fermentation often produces ammonia gas, which dissolves into the liquid phase to form ammonium ions. The phosphate and magnesium ions released by the dissolution of superphosphate and magnesium sulfate heptahydrate in the premix can react with the above-mentioned ammonium ions in the microenvironment of the material to generate magnesium ammonium phosphate crystals (Mg). 2 +NH4 + +PO4 3-+6H₂O→MgNH₄PO₄·6H₂O↓). This crystallization reaction tends to convert free nitrogen in the system into a relatively stable, insoluble salt, thereby inhibiting the volatilization and loss of ammonia with the gas flow. On the other hand, sodium percarbonate decomposes in water in the system to release hydrogen peroxide and further produce oxygen (2Na₂CO₃·3H₂O₂→2Na₂CO₃+3H₂O+1.5O₂↑). The produced oxygen, limited by the viscosity of the material, forms microbubbles, providing a gaseous basis for subsequent physical pore formation, and the byproduct sodium carbonate can play a certain buffering and regulating role in the acidity introduced by superphosphate in the system.

[0009] In step (3), as positive pressure is established in the sealed space, the microbubbles distributed within the material shrink in volume due to pressure. Under the subsequent instantaneous depressurization operation, the sudden drop in external pressure causes the bubbles to expand rapidly due to pressure imbalance, thereby overcoming the resistance of the surrounding liquid film and rupturing. The pressure fluctuation operation, which is carried out in conjunction with the cycle, easily promotes the convergence and interconnection of originally isolated and closed microbubbles, guiding the formation of a connected pore network inside the material. This improves airflow diffusion conditions and reduces forced ventilation resistance without the need for a large amount of external bulking agent.

[0010] Preferably, in step (1), the particle size of the crushing process is controlled to be 5-10 mm; the specific process parameters for shearing and mixing are: the stirring shaft speed is set to 50-70 rpm, and the stirring is continuous for 3-8 min.

[0011] By employing the above technical solution, a specific particle size range facilitates the penetration and contact of the reagent while maintaining the basic framework of the material. The purpose of setting the stirring parameters is to provide sufficient shear strength to disperse polyferric sulfate, thereby promoting its flocculation effect, while also preventing excessively high rotation speeds from damaging the nascent floc microstructure.

[0012] Preferably, the skeleton and nitrogen-retaining dry powder premix in step (2) is a pre-prepared mixture. The specific preparation method includes: dry pulverizing superphosphate and magnesium sulfate heptahydrate and passing them through a 60-mesh sieve, and then weighing them according to the ratio; under the conditions of a temperature of 15-25℃ and a relative humidity of less than 40%, putting them into a dry powder mixing device and controlling the spindle speed to be 30-40 rpm for continuous mixing for 10-15 minutes; finally, storing them in a sealed container to prevent moisture and using them within 24 hours after preparation.

[0013] By employing the above technical solutions, the dry pulverization and sieving operations aim to reduce the uneven reaction rate caused by excessively large particles. Mixing and sealing under controlled temperature and humidity conditions primarily reduce the risk of superphosphate absorbing moisture and clumping or premature hydration with magnesium sulfate, thus helping to maintain the reactivity of the reagent at the time of feeding.

[0014] Preferably, the specific timing and process parameters for the staggered addition of the skeleton premix and the foaming source in step (2) are as follows: the stirring speed is adjusted to 10-20 rpm, the skeleton and nitrogen-retaining dry powder premix is ​​sprinkled in first, and stirring is maintained at 10-20 rpm for 3-8 minutes; then the sodium percarbonate is added, and stirring is maintained at 10-20 rpm for 10-20 minutes.

[0015] By adopting the above technical solution, the initial addition of the skeleton premix can establish initial sedimentation sites in the system. The subsequent addition of sodium percarbonate can, to some extent, delay the area of ​​instantaneous contact between sodium percarbonate and a large amount of free water, thus slowing down the rate of decomposition and gas production. Combined with low-speed stirring, it can reduce the probability of newly generated microbubbles being broken up by mechanical force, making them easier to retain inside the material.

[0016] Preferably, in step (2), within 15 minutes after the addition of the sodium percarbonate, the highest temperature rise of the material system is controlled at 6.2 to 8.7°C, and the pH fluctuation range is maintained at 6.32 to 7.22.

[0017] By employing the above technical solution, the range of temperature rise and pH fluctuations is limited, reflecting that the decomposition of sodium percarbonate is in a relatively gradual state. Controllable temperature rise means that exothermic reactions are less likely to damage the flocculated structure of the material, and this weakly acidic to neutral microenvironment is both favorable for the survival of microorganisms in the early stages of fermentation and tends to provide suitable buffering conditions for the crystallization and precipitation of magnesium ammonium phosphate.

[0018] Preferably, the specific process parameters for the controlled low-amplitude positive pressure hole forming process in step (3) are as follows: the controlled low-amplitude positive pressure environment is 0.03 to 0.06 MPa gauge pressure, and the pressure is maintained for 10 to 20 minutes after the set pressure is reached; the instantaneous pressure relief is to reduce the pressure to 0 MPa gauge pressure within 5 to 15 seconds; the pressure holding and instantaneous pressure relief steps are continuously cycled 3 to 5 times.

[0019] By adopting the above technical solution, this gauge pressure range can be selected to compress the microbubble volume without over-compacting the underlying material. Utilizing the sudden pressure drop over a short period to create a pressure differential impact, and repeatedly executing this process, helps to open up previously isolated pore dead zones, gradually constructing interconnected air channels.

[0020] By adopting the above technical solution, specific porosity and pressure drop indicators reflect the degree of change in the physical structure of the material after pressure. The increase in the open area ratio and the decrease in ventilation resistance reflect the formation of gas phase channels, which greatly improves the dense and viscous state of the vegetable waste caused by colloidal water retention, thus facilitating oxygen mass exchange in the subsequent aerobic fermentation stage.

[0021] Preferably, the polyferric sulfate is a solid powder with a total iron content ≥19.0 wt% and a basicity of 8.0–16.0%.

[0022] By adopting the above technical solution, this specification of polyferric sulfate has a high total iron content, which makes it easy to provide coagulation nuclei in the system; the corresponding basicity parameter helps to maintain the polynuclear polymer morphology, so that it can maintain good charge neutralization and bridging flocculation effect in the slightly acidic liquid phase environment of the vegetable waste.

[0023] Preferably, the effective phosphorus pentoxide mass fraction of the superphosphate is ≥12.0 wt%, and the free acid mass fraction is 3.0 to 5.5 wt%.

[0024] By adopting the above technical solution, the available phosphorus contained in superphosphate acts as the anion source for crystallization and precipitation. The small amount of free acid it contains imparts a localized slightly acidic nature to the material, which not only helps to suppress the volatilization and dissipation of free ammonia in the short term, but also acts as a buffer substance in the system to offset some of the alkalinity brought about by the decomposition of sodium percarbonate in the later stage.

[0025] Preferably, the sodium percarbonate is stearic acid-coated microparticles with a particle size of 0.5–1.5 mm and an active oxygen mass fraction ≥13.0 wt%.

[0026] By employing the above technical solution, the hydrophobic stearic acid coating on the surface often limits the rate of water penetration into the core of the agent, thus promoting a slower release of oxygen produced by the decomposition of sodium percarbonate. Matching particle size and reactive oxygen species parameters are primarily used to control the scale of gas production during the decomposition of individual particles, aiming to form a relatively dispersed cluster of microbubbles and reduce the possibility of material pile structure collapse due to excessive local bubble expansion.

[0027] This invention provides a method for the resource utilization and processing of vegetable waste. It has the following beneficial effects: 1. This invention improves the material structure stability and mass transfer efficiency during the fermentation of vegetable waste. By adding polyferric sulfate to demulsify and thicken the vegetable waste slurry, combined with the calcium-based precipitate generated from the reaction of superphosphate and sodium percarbonate, a mechanical support framework is provided for the material. Simultaneously, controlled low-amplitude positive pressure alternating treatment physically tears apart closed air bubbles within the material, transforming them into interconnected channels. This structural change reduces the aeration resistance of the fermentation bed and increases the convective mass transfer efficiency between the deeper layers of the material and the external airflow, thereby reducing the probability of material collapse and localized anaerobic rancidity.

[0028] 2. This invention achieves biochemical environmental buffering and temperature control in the early stages of fermentation. By employing a process of staggered addition of the skeleton premix and the foaming source, the free acid introduced by superphosphate neutralizes the alkalinity released by sodium percarbonate, suppressing the instantaneous and violent decomposition of the foaming source in free water. This process avoids a rapid increase in local temperature and drastic pH fluctuations, establishing relatively stable substrate conditions for the microbial community in the early stages of aerobic fermentation and limiting the abnormal accumulation of volatile fatty acids.

[0029] 3. This invention improves the total nitrogen retention rate and fertilizer efficiency of the product throughout the entire aerobic fermentation cycle. In the later stages of fermentation, ammonia gas produced from the degradation of organic nitrogen in the vegetable waste dissolves in water to form ammonium ions. These ions, along with magnesium ions provided by magnesium sulfate heptahydrate and phosphate ions provided by superphosphate, undergo a complexation crystallization reaction under a slightly alkaline environment to form struvite. This physicochemical mechanism fixes volatile ammonia nitrogen in the fermentation substrate in the form of solid crystals, controlling the volatilization and loss of gaseous nitrogen and increasing the nutrient content of the final fertilizer product. Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0031] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0032] The vegetable waste used in the examples and comparative examples was taken from common cabbage and kale waste leaves. Before use, it was uniformly crushed and homogenized. The tested moisture content was 90 wt%, the mass ratio of total organic carbon to total nitrogen was 20:1, and the initial pH value was 6.0.

[0033] Polyferric sulfate is a commercially available industrial-grade powder product with CAS number 10028-22-5. Its total iron content is ≥19.0wt%, and its basicity is between 8.0% and 16.0%.

[0034] The superphosphate is a commercially available industrial-grade powdered fertilizer product with CAS number 8011-76-5. Its effective phosphorus pentoxide mass fraction is ≥12.0wt%, and the free acid (calculated as H3PO4) mass fraction is between 3.0 and 5.5wt%.

[0035] Sodium percarbonate is a commercially available industrial-grade solid stearic acid-coated microparticle product, CAS number 15630-89-4, with a particle size between 0.5 and 1.5 mm and an active oxygen mass fraction ≥ 13.0 wt%.

[0036] Magnesium sulfate heptahydrate is a commercially available industrial-grade powder product with CAS number 10034-99-8 and a main component purity of ≥98.0wt%.

[0037] Preparation Example 1: This preparation example provides a method for preparing a premix of a skeleton and a nitrogen-retaining dry powder, including the following steps: (1) Weighing and crushing: Weigh the superphosphate and magnesium sulfate heptahydrate according to the mass ratio set in each embodiment. Dry crush the superphosphate and magnesium sulfate heptahydrate separately through a crushing device and pass them through a 60-mesh sieve so that the particle size of the two meets the requirements for uniform mixing in the subsequent process.

[0038] (2) Dry powder mixing: Under controlled environmental conditions of 25°C and relative humidity below 40%, the sieved superphosphate and magnesium sulfate heptahydrate are put into a three-dimensional dry powder mixing device. The spindle speed of the three-dimensional dry powder mixing device is controlled to be 40 rpm, and the mixture is continuously mixed for 10 min to obtain a uniformly distributed dry powder mixture of superphosphate and magnesium sulfate heptahydrate.

[0039] (3) Sealed storage: After the dry powder mixture obtained in step (2) is discharged, it is placed in a sealed container for moisture protection and is required to be used within 24 hours after preparation to prevent the free acid in superphosphate from interacting with the crystal water of magnesium sulfate heptahydrate, which would cause the powder to deliquesce and clump, thus obtaining a skeleton and nitrogen-retaining dry powder premix.

[0040] Example 1: This example provides a method for the resource utilization and treatment of vegetable waste, including the following steps: (1) Crushing and Demulsification: 1000 kg of vegetable waste was crushed using a shear crusher to control the characteristic particle size of the crushed material to be 8 mm. The crushed material was then discharged into a twin-shaft paddle mixer. 2.0 kg of polyferric sulfate was evenly added to the material in the mixer. The mixer was turned on, and the stirring shaft speed was set to 60 rpm for continuous stirring for 5 min.

[0041] (2) Addition of skeleton premix and foaming source: Adjust the stirring shaft speed of the twin-shaft paddle mixer to 15 rpm. The skeleton and nitrogen-retaining dry powder premix, which consists of 30.0 kg of superphosphate and 15.0 kg of magnesium sulfate heptahydrate, prepared according to the method of Preparation Example 1, is uniformly fed in using a screw feeder. Stirring is maintained at this speed for 5 min. Then, 20.0 kg of sodium percarbonate is uniformly added, and stirring is maintained at 15 rpm for another 15 min.

[0042] (3) Controlled low-amplitude positive pressure pore formation treatment: After the above treatment, the material is discharged into a closed aerobic fermentation tank through a closed belt conveyor system, and the inlet and outlet isolation valves are closed. The Roots blower system at the bottom is started to pump air into the fermentation tank, so that a controlled low-amplitude positive pressure environment of 0.05 MPa gauge pressure is formed inside the fermentation tank. After reaching the set pressure, the pressure is maintained for 15 minutes. After the pressure holding is completed, the pressure relief valve at the top of the fermentation tank is quickly and fully opened, and the pressure inside the fermentation tank is suddenly reduced to atmospheric pressure, i.e., 0 MPa gauge pressure, within 10 seconds. The above pressure holding and instantaneous pressure relief steps are continuously cycled 4 times.

[0043] (4) Aerobic fermentation and discharge: Turn on the bottom Roots blower to perform forced ventilation at normal pressure and enter the aerobic fermentation stage. Discharge the material when the temperature of the material in the fermentation tank naturally drops back to the ambient temperature and the moisture content of the pile drops to below 40wt%.

[0044] Example 2: This example provides a method for the resource utilization and treatment of vegetable waste, including the following steps: (1) Crushing and Demulsification: 1000 kg of vegetable waste was crushed using a shear crusher, and the characteristic particle size of the crushed material was controlled to be 5 mm. The crushed material was then discharged into a twin-shaft paddle mixer. 1.0 kg of polyferric sulfate was evenly added to the material in the mixer. The mixer was turned on, and the stirring shaft speed was set to 50 rpm, and the mixture was stirred continuously for 3 minutes.

[0045] (2) Addition of skeleton premix and foaming source: Adjust the stirring shaft speed of the twin-shaft paddle mixer to 10 rpm. The skeleton and nitrogen-retaining dry powder premix, which consists of 20.0 kg of superphosphate and 10.0 kg of magnesium sulfate heptahydrate, prepared according to the method of Preparation Example 1, is uniformly fed in using a screw feeder. Stirring is maintained at this speed for 3 min. Then, 15.0 kg of sodium percarbonate is uniformly added, and stirring is maintained at 10 rpm for another 10 min.

[0046] (3) Controlled low-amplitude positive pressure pore formation treatment: After the above treatment, the material is discharged into a closed aerobic fermentation tank through a closed belt conveyor system, and the inlet and outlet isolation valves are closed. The Roots blower system at the bottom is started to pump air into the fermentation tank, so that a controlled low-amplitude positive pressure environment of 0.03 MPa gauge pressure is formed inside the fermentation tank. After reaching the set pressure, the pressure is maintained for 10 minutes. After the pressure holding is completed, the pressure relief valve at the top of the fermentation tank is quickly and fully opened, and the pressure inside the fermentation tank is suddenly reduced to atmospheric pressure, i.e., 0 MPa gauge pressure, within 15 seconds. The above pressure holding and instantaneous pressure relief steps are continuously cycled 3 times.

[0047] (4) Aerobic fermentation and discharge: Turn on the bottom Roots blower to perform forced ventilation at normal pressure and enter the aerobic fermentation stage. Discharge the material when the temperature of the material in the fermentation tank naturally drops back to the ambient temperature and the moisture content of the pile drops to below 40wt%.

[0048] Example 3: This example provides a method for the resource utilization and treatment of vegetable waste, including the following steps: (1) Crushing and Demulsification: 1000 kg of vegetable waste was crushed using a shear crusher, and the characteristic particle size of the crushed material was controlled to be 10 mm. The crushed material was then discharged into a twin-shaft paddle mixer. 3.0 kg of polyferric sulfate was evenly added to the material in the mixer. The mixer was turned on, and the stirring shaft speed was set to 70 rpm, and the mixture was stirred continuously for 8 minutes.

[0049] (2) Addition of skeleton premix and foaming source: Adjust the stirring shaft speed of the twin-shaft paddle mixer to 20 rpm. The skeleton and nitrogen-retaining dry powder premix, which consists of 40.0 kg of superphosphate and 25.0 kg of magnesium sulfate heptahydrate, prepared according to the method of Preparation Example 1, is uniformly fed in using a screw feeder. Stirring is maintained at this speed for 8 min. Then, 30.0 kg of sodium percarbonate is uniformly added, and stirring is maintained at 20 rpm for another 20 min.

[0050] (3) Controlled low-amplitude positive pressure pore formation treatment: After the above treatment, the material is discharged into a closed aerobic fermentation tank through a closed belt conveyor system, and the inlet and outlet isolation valves are closed. The Roots blower system at the bottom is started to pump air into the fermentation tank, so that a controlled low-amplitude positive pressure environment of 0.06 MPa gauge pressure is formed inside the fermentation tank. After reaching the set pressure, the pressure is maintained for 20 minutes. After the pressure holding is completed, the pressure relief valve at the top of the fermentation tank is quickly and fully opened, and the pressure inside the fermentation tank is suddenly reduced to atmospheric pressure, i.e., 0 MPa gauge pressure, within 5 seconds. The above pressure holding and instantaneous pressure relief steps are continuously cycled 5 times.

[0051] (4) Aerobic fermentation and discharge: Turn on the bottom Roots blower to perform forced ventilation at normal pressure and enter the aerobic fermentation stage. Discharge the material when the temperature of the material in the fermentation tank naturally drops back to the ambient temperature and the moisture content of the pile drops to below 40wt%.

[0052] Example 4: This example provides a method for the resource utilization and treatment of vegetable waste, including the following steps: (1) Crushing and Demulsification: 1000 kg of vegetable waste was crushed using a shear crusher to control the characteristic particle size of the crushed material to be 8 mm. The crushed material was then discharged into a twin-shaft paddle mixer. 1.0 kg of polyferric sulfate was evenly added to the material in the mixer. The mixer was turned on, and the stirring shaft speed was set to 50 rpm for continuous stirring for 8 minutes.

[0053] (2) Addition of skeleton premix and foaming source: Adjust the stirring shaft speed of the twin-shaft paddle mixer to 20 rpm. The skeleton and nitrogen-retaining dry powder premix, which consists of 30.0 kg of superphosphate and 10.0 kg of magnesium sulfate heptahydrate, prepared according to the method of Preparation Example 1, is uniformly fed in using a screw feeder. Stirring is maintained at this speed for 5 min. Then, 20.0 kg of sodium percarbonate is added uniformly, and stirring is maintained at 20 rpm for 15 min.

[0054] (3) Controlled low-amplitude positive pressure pore formation treatment: After the above treatment, the material is discharged into a closed aerobic fermentation tank through a closed belt conveyor system, and the inlet and outlet isolation valves are closed. The Roots blower system at the bottom is started to pump air into the fermentation tank, so that a controlled low-amplitude positive pressure environment of 0.06 MPa gauge pressure is formed inside the fermentation tank. After reaching the set pressure, the pressure is maintained for 10 minutes. After the pressure holding is completed, the pressure relief valve at the top of the fermentation tank is quickly and fully opened, and the pressure inside the fermentation tank is suddenly reduced to atmospheric pressure, i.e., 0 MPa gauge pressure, within 10 seconds. The above pressure holding and instantaneous pressure relief steps are continuously cycled 4 times.

[0055] (4) Aerobic fermentation and discharge: Turn on the bottom Roots blower to perform forced ventilation at normal pressure and enter the aerobic fermentation stage. Discharge the material when the temperature of the material in the fermentation tank naturally drops back to the ambient temperature and the moisture content of the pile drops to below 40wt%.

[0056] Comparative Example 1: Compared with Example 1, the difference is that polyferric sulfate, superphosphate, magnesium sulfate heptahydrate and sodium percarbonate are not added, and controlled low-amplitude positive pressure holding and instantaneous pressure release are not performed. Instead, 30% by volume of sawdust is directly added to the vegetable waste as a physical support material for conventional stirring and fermentation. All other aspects are the same.

[0057] Comparative Example 2: The difference from Example 1 is that polyferric sulfate was not added in step 1, but all other steps were the same.

[0058] Comparative Example 3: Compared with Example 1, the difference is that in step 2, an equal mass of neutral tricalcium phosphate without free acid was used instead of superphosphate, and all other steps were the same.

[0059] Comparative Example 4: Compared with Example 1, the difference is that the timing control of feeding and reaction is broken. Steps 1 and 2 are combined. Polyferric sulfate, the premix composed of superphosphate and magnesium sulfate heptahydrate, and sodium percarbonate are added to the mixer at the beginning of the stirring stage at the same time. All other aspects are the same.

[0060] Comparative Example 5: Compared with Example 1, the difference is that step 3 is missing. After the closed-cell gel material after step 2 is discharged into the fermentation tank, the controlled low-amplitude positive pressure holding and instantaneous pressure release operation is not performed. Instead, atmospheric pressure forced ventilation fermentation is carried out directly. All other aspects are the same.

[0061] Comparative Example 6: Compared with Example 1, the difference is that magnesium sulfate heptahydrate is not added in step 2, that is, the skeleton and nitrogen-retaining dry powder premix only contain superphosphate, and the rest are the same.

[0062] Test Example 1: This test example is used to investigate the rheological characteristics, temperature changes, and pH buffering of vegetable waste during controlled demulsification and acid-base misalignment feeding. The specific experimental steps are as follows: (1) Sampling and preparation of analytes: Sampling and monitoring were carried out during the execution of Examples 1, 3, Comparative Example 2, and Comparative Example 4. For Examples 1, 3, and Comparative Example 2, 500g of the material in the mixer after stirring in step 1 was taken out as the first analyte. For Comparative Example 4, since polyferric sulfate, a premix composed of superphosphate and magnesium sulfate heptahydrate, and sodium percarbonate were added simultaneously at the beginning of stirring, 500g of the material was taken out from the mixer after the one-time addition and stirring for 5 minutes as the first analyte to characterize the overall rheological state under the staggered addition conditions.

[0063] In Step 2 of Examples 1, 3, and Comparative Example 2, the moment when sodium percarbonate came into contact with the material was recorded as 0 min. For Comparative Example 4, the moment when sodium percarbonate and the acidic framework source simultaneously came into contact with the material was recorded as 0 min. The material in the mixer after the corresponding time was used as the second analyte for in-situ temperature and pH monitoring.

[0064] (2) Shear rheological property determination: The first test sample was transferred into the test chamber of a rotary rheometer with a cross-bladed rotor. The constant temperature circulating water bath was set to 25℃, and after standing for 3 minutes to reach equilibrium, a shear scan was performed. The shear rate was 0.1 s⁻¹. -1 linearly increase to 100s -1 The model was fitted using the rheometer's accompanying analysis software, and the initial yield stress and apparent viscosity of the system at a shear rate of 50 s⁻¹ were recorded. Each sample was measured in triplicate, and the average value was taken as the test result.

[0065] (3) In-situ temperature and pH dynamic monitoring: A calibrated industrial-grade long rod composite pH electrode and a K-type thermocouple probe were inserted into the core area of ​​the second analyte through a pre-drilled hole on the top of the mixer, with the probe penetrating approximately 15 cm below the material surface. Temperature and pH values ​​were continuously recorded from 0 min to 15 min at 1 min sampling intervals. Based on the recorded results, the highest temperature rise peak within 15 min was calculated, and the pH fluctuation range during the test period was recorded; the highest temperature rise peak was the difference between the highest temperature during the test and the initial temperature at 0 min.

[0066] The test results are recorded in the table below. Unless otherwise stated, the data in the table are the average values ​​of parallel test results.

[0067] Table 1: Test results of rheological and dynamic physicochemical parameters of each embodiment and comparative example

[0068] According to the data in Table 1, in Examples 1 and 3, the yield stresses of the materials after conditioning with polyferric sulfate and controlled shearing were 98.4 Pa and 142.1 Pa, respectively, and the apparent viscosities were 1452 mPa·s and 1938 mPa·s, respectively. Comparative Example 2, without the addition of polyferric sulfate, had yield stresses and apparent viscosities of 18.5 Pa and 415 mPa·s, respectively, both lower than those in Examples 1 and 3. These results indicate that under the test conditions, the addition of polyferric sulfate and shear mixing treatment may help increase the yield stress and apparent viscosity of the material system, thereby enabling the material to have a certain gas retention capacity during subsequent foaming.

[0069] Regarding the changes in temperature and pH, in Example 1, after the addition of the acidic framework source followed by sodium percarbonate, the highest temperature rise within 15 minutes was 6.2℃, and the pH fluctuation range was 6.41–7.22. In Example 3, the highest temperature rise was 8.7℃, and the pH fluctuation range was 6.32–7.15. These results indicate that under the test conditions, when the acidic framework source and the alkaline foaming source are added in stages, the pH fluctuation of the system is relatively small, and the temperature rise is also at a low level.

[0070] Comparative Example 4 involved the simultaneous addition of polyferric sulfate, the framework and nitrogen-retaining dry powder premix, and sodium percarbonate in the initial stage. Within 15 minutes, the highest temperature rise was 18.4°C, and the pH fluctuation range was 5.12 to 8.95. Compared to Example 1, Comparative Example 4 showed significantly increased temperature rise and pH fluctuation range. These results indicate that under the test conditions, the timing of the addition of acidic substances and alkaline foaming sources affects the local acid-base changes and exothermic processes of the system. When using a staggered addition method, the acidic framework source can participate to some extent in the neutralization and buffering of sodium percarbonate hydrolysis products, helping to reduce the rapid increase in local pH and temperature, and providing a more stable reaction environment for subsequent foaming and mineralization deposition processes.

[0071] Test Example 2: This test example is used to investigate the effects of controlled low-amplitude positive pressure holding and instantaneous pressure release on the pore structure and aeration resistance of fermentation materials. The specific experimental steps are as follows: (1) Experimental Subjects and Sampling: The fermentation materials obtained in Examples 1 to 3 and Comparative Example 5 were used as experimental subjects. In step 3 of Examples 1 to 3, samples were taken immediately after the material was discharged into the fermentation tank and before the controlled low-amplitude positive pressure operation was performed, and these were recorded as pre-treatment samples; and samples were taken after all pressure holding and instantaneous pressure release cycles were completed, and these were recorded as post-treatment samples. 1000g of sample was extracted from the core area of ​​the material each time. For Comparative Example 5, which did not involve controlled low-amplitude positive pressure operation, samples were taken before and after the simulated treatment at the same time intervals as in Example 1. The extracted samples were placed in liquid nitrogen for rapid freezing and solidification, and then vacuum freeze-dried at -40℃ for 48h to preserve the original pore morphology of the material as much as possible.

[0072] (2) Determination of open and closed porosity: The freeze-dried block samples were tested using a fully automatic vacuum gas specific gravity bottle analyzer. High-purity helium was used as the replacement medium, and the change in equilibrium pressure of the gas chamber was recorded under constant temperature of 20℃. At the same time, the geometric volume, apparent density, and true density of the fully pulverized samples were measured. Combined with the skeleton volume obtained by helium replacement, the closed porosity and open porosity of each sample were calculated. Each sample was measured independently 4 times, and the average value was taken as the test result.

[0073] (3) Measurement of air permeability resistance: An equal volume of unfreeze-dried raw material was filled into an air column with an inner diameter of 150 mm and a height of 500 mm. Air was introduced into the bottom of the air column at an apparent air velocity of 0.05 m / s. After the airflow distribution stabilized, the static pressure difference between the two ends of the material layer was measured using a differential pressure gauge, and the air pressure drop per unit height of the material layer was calculated.

[0074] The test results are recorded in the table below. Unless otherwise stated, the data in the table are the average values ​​of parallel test results.

[0075] Table 2: Porosity and pressure drop test results before and after treatment for each embodiment and comparative example.

[0076] According to the data in Table 2, in the untreated state, the closed-cell rate of Examples 1 to 3 and Comparative Example 5 was 31.8% to 40.5%, the open-cell rate was 10.9% to 15.3%, and the ventilation pressure drop was 3988 Pa / m to 4502 Pa / m. These results indicate that after the material has undergone chemical foaming but before controlled low-amplitude positive pressure operation, a certain bubble structure has formed inside the material. However, many of these bubbles may still be relatively independent or not fully connected, resulting in high ventilation resistance.

[0077] Comparative Example 5 did not undergo controlled low-amplitude positive pressure holding and instantaneous pressure relief operations. Its closed-cell rate was 35.1% before treatment and 36.4% after treatment; the open-cell rate was 13.2% before treatment and 14.1% after treatment; the ventilation pressure drop was 4150 Pa / m before treatment and 4085 Pa / m after treatment. These data indicate that under the test conditions, after only the same amount of settling time, the changes in the closed-cell rate, open-cell rate, and ventilation pressure drop of the material were relatively small.

[0078] After controlled low-amplitude positive pressure holding and instantaneous pressure relief operations in Examples 1 to 3, the closed-pore ratio decreased from 31.8–40.5% before treatment to 8.2–14.7%, the open-pore ratio increased from 10.9–15.3% before treatment to 28.2–48.1%, and the ventilation pressure drop decreased from 3988–4502 Pa / m before treatment to 894–1532 Pa / m. These results indicate that under the test conditions, controlled low-amplitude positive pressure holding and instantaneous pressure relief operations help increase the proportion of interconnected pores in the material and reduce the material's ventilation resistance.

[0079] From the possible operational process, during the pressure-holding stage, the gas within the closed pores is compressed; during the pressure-relieving stage, the pressure difference between the inside and outside of the pores changes, and the gel-like matrix surrounding the closed air bubbles may be subjected to localized stretching or shearing, causing some adjacent closed pores to connect. As a result, some closed-pore structures within the material can transform into interconnected pore structures, thus forming pore channels that are more conducive to air passage. This change in pore structure can provide better channel conditions for oxygen supply and water migration during subsequent aerobic fermentation.

[0080] Test Example 3: This test example is used to investigate the effects of different feeding sequences and magnesium source conditions on the formation of calcium-based mineralization structures and nitrogen-containing magnesium-phosphorus mineralization structures in the solid phase material during the resource-based fermentation of vegetable waste. The specific experimental steps are as follows: (1) Experimental subjects and sampling: 200g of solid material was extracted from the core area of ​​the closed aerobic fermentation tanks on days 1 and 5 of the fermentation cycle of Example 1, and on day 5 of the fermentation cycles of Comparative Example 4 and Comparative Example 6. The extracted samples were placed in a vacuum freeze dryer and treated at -40℃ for 48h or until constant weight to reduce the influence of dehydration or transformation of the hydrous mineral crystals under high temperature conditions. The dried samples were ground using an agate mortar and pestle and passed through a 200-mesh standard analytical sieve. The material passing through the sieve was collected as the powder sample to be tested.

[0081] (2) Determination of phase and crystal structure: The powder samples to be tested were scanned using a powder X-ray diffractometer. The test conditions were Cu target Kα radiation source, working voltage of 40kV, working current of 40mA; scanning angle 2θ range of 10°~40°, scanning step size of 0.02°, and scanning speed of 5° / min. After the test, the intensity of the characteristic diffraction peak of calcite-type calcium carbonate near 29.4° and the intensity of the characteristic diffraction peak of struvite near 15.8° were extracted. In order to reduce the influence of sampling amount and sample loading difference on the test results, a fixed mass ratio of α-Al2O3 was added to each powder sample to be tested as an internal standard, and the target characteristic peak was normalized by internal standard with the characteristic peak intensity of the internal standard as a reference, and the internal standard normalized relative response intensity of the target peak was recorded.

[0082] (3) Characteristic functional group analysis: Approximately 2 mg of the powder sample to be tested was weighed and mixed with 200 mg of thoroughly dried high-purity potassium bromide powder. The mixture was then ground evenly in an agate mortar and pressed into transparent thin sheets using a tablet press. The tablets were placed in the sample chamber of a Fourier transform infrared spectrometer, and spectral acquisition was performed in transmission mode. The scanning wavenumber range was 4000 cm⁻¹. -1 Up to 400cm -1 Spectral resolution of 4 cm -1 Both the background and sample scans were performed 32 times. After obtaining the absorption spectra, the sample was extracted at 1030 cm⁻¹. -1 The absorption peak of PO stretching vibration near 1400 cm⁻¹ -1 The relative absorbance values ​​corresponding to the absorption peaks of the nearby NH bending vibration.

[0083] The test results are recorded in the table below. The X-ray diffraction data in Table 3 are the relative response intensities obtained after normalization using the α-Al₂O₃ internal standard. Unless otherwise stated, the data in the table are the average values ​​of parallel test results.

[0084] Table 3: Test results of relative response intensities of characteristic diffraction peaks and absorption peaks of solid materials at different fermentation stages in each treatment group

[0085] According to the data in Table 3, in the sample of Example 1 on day 1 of fermentation, the characteristic peak response of calcite-type calcium carbonate was 0.884, and the characteristic peak response of struvite was 0.052; simultaneously, the relative absorbance of the PO absorption peak was 0.751, and the relative absorbance of the NH absorption peak was 0.114. These results indicate that in the early stages of fermentation, a certain degree of calcium-based mineralization structure had already formed in the system, while the characteristic responses related to struvite remained at a low level.

[0086] In Example 1, on day 5 of fermentation, the characteristic peak response of struvite increased from 0.052 to 0.618, and the relative absorbance of the NH absorption peak increased from 0.114 to 0.582; simultaneously, the relative absorbance of the PO absorption peak increased from 0.751 to 0.895. These changes indicate that as fermentation progresses, the release of nitrogen-containing components in the system may lead to further binding between the magnesium source, phosphate, and ammonium nitrogen, enhancing the mineralization response related to magnesium ammonium phosphate in the material. Therefore, it can be inferred that the calcium-based mineralization structure formed in the early stage and the nitrogen-containing magnesium phosphate mineralization structure formed in the middle and later stages of fermentation in Example 1 jointly participated in the construction of the solid-phase framework.

[0087] Comparative Example 4 showed a characteristic peak response of 0.547 for calcite-type calcium carbonate and 0.163 for struvite on day 5 of fermentation, both lower than the corresponding values ​​in Example 1 on day 5. This result indicates that under the test conditions, when polyferric sulfate, the framework and nitrogen-retaining dry powder premix, and sodium percarbonate are added simultaneously, the formation degree of calcium-based mineralization structures and struvite-related mineralization structures in the system is relatively low. This may be due to the simultaneous presence of acidic components, alkaline components, and metal ions in the initial stage, leading to local ion competition or dispersion during the precipitation process.

[0088] Comparative Example 6 showed a characteristic peak response of 0.912 for calcite-type calcium carbonate on day 5 of fermentation, while the characteristic peak response for struvite was only 0.021, and the relative absorbance of the NH absorption peak was 0.108. These results indicate that calcium-based mineralization structures can still form in the system without the addition of magnesium sulfate heptahydrate, but the characteristic response associated with struvite is weaker, suggesting that the presence of a magnesium source is beneficial for the subsequent formation of nitrogen-magnesium-phosphate mineralization structures.

[0089] Based on the above results, under the test conditions, the stepwise addition of acidic framework source, magnesium source and alkaline foaming source is beneficial to the gradual formation of calcium-based mineralization structure and nitrogen-containing magnesium-phosphorus mineralization structure at different fermentation stages, thereby providing conditions for the continuous construction of the solid-phase framework of the material.

[0090] Test Example 4: This test example is used to examine the changes in the pile height of fermentation materials during the treatment cycle, and to evaluate the initial volume maintenance and mid-to-late-stage settling of materials under different treatment conditions. The specific experimental steps are as follows: (1) Experimental subjects and test platform setup: The total amount of materials discharged into a closed aerobic fermentation tank in Examples 1, 2, 4, 5, and 6 were used as experimental subjects. A multi-point ultrasonic ranging sensor array was installed on the inner wall of the top of the fermentation tank, with a ranging accuracy set to ±1 mm, for non-contact monitoring of changes in the height of the material surface. The horizontal plane where the gas distribution plate at the bottom of the fermentation tank is located was used as the zero-point reference for height measurement.

[0091] (2) Monitoring of initial volume maintenance: After the material processed in step 3 is discharged into the fermentation tank and the surface is leveled, the initial material layer height is recorded. The data recording function of the ultrasonic ranging sensor is turned on, and the sampling frequency is once per hour. As the sodium percarbonate hydrolysis reaction proceeds in the early stage of fermentation, the height of the material pile may change due to gas entrainment. The maximum foaming height value monitored in the first 24 hours is recorded. When fermentation has reached 24 hours, the material layer height at this time is recorded, and the initial effective volume maintenance rate is calculated according to the following formula: Initial effective volume retention rate = (Height of material layer after 24 hours of fermentation / Maximum foaming height) × 100%.

[0092] This indicator is used to characterize the height retention of materials after foaming in the early stages of fermentation.

[0093] (3) Monitoring of macroscopic settling in the mid-to-late stages: During the aerobic fermentation stage from 24 hours after fermentation to day 7, sensor monitoring was maintained, and the average material height was recorded once daily. The material layer height at the end of day 7 of fermentation was recorded, and the macroscopic settling rate in the mid-to-late stages was calculated according to the following formula: Macroscopic settling rate in the middle and late stages = (height of material layer after 24 hours of fermentation - height of material layer on day 7 of fermentation) / height of material layer after 24 hours of fermentation × 100%.

[0094] This indicator is used to evaluate the height retention and settling degree of the material pile during the middle and late stages of fermentation.

[0095] The test results are recorded in the table below. Unless otherwise stated, the data in the table are the average values ​​of parallel test results.

[0096] Table 4: Dynamic Test Data of Material Stack Height and Physical Stability Indicators for Each Processing Group

[0097] According to the data in Table 4, the initial effective volume retention rate of Example 1 was 95.61%, and the material layer height after 24 hours of fermentation was 1582.1 mm. The initial effective volume retention rates of Comparative Example 2 and Comparative Example 4 were 82.34% and 76.44%, respectively, both lower than that of Example 1. These results indicate that under the test conditions, conditioning with polyferric sulfate and stepwise addition of acid and alkali may help improve the volume retention capacity of the material in the early stages of fermentation.

[0098] Comparative Example 2, without the addition of polyferric sulfate, achieved a maximum foaming height of 1342.5 mm, which decreased to 1105.4 mm after 24 hours of fermentation. This result indicates that without demulsification and thickening treatment, the material's ability to retain foamed height is relatively weak. Comparative Example 4, using a simultaneous one-time addition method, achieved a maximum foaming height of 1512.6 mm, a material layer height of 1156.2 mm after 24 hours of fermentation, and an initial effective volume retention rate of 76.44%. This result suggests that the timing of adding acidic components and alkaline foaming sources may affect the foaming process and initial volume retention.

[0099] During the later stages of fermentation, the macroscopic settling rate of Example 1 was 10.16%, lower than that of Comparative Example 2 (22.50%), Comparative Example 4 (22.58%), Comparative Example 5 (27.18%), and Comparative Example 6 (37.64%). These results indicate that under the test conditions, the material obtained in Example 1 exhibited a relatively low height decrease during the fermentation period from day 1 to day 7.

[0100] Comparative Example 5, which did not undergo low-amplitude positive pressure fracturing, had an initial effective volume retention rate of 94.65%, similar to Example 1, but a later macroscopic settlement rate of 27.18%, higher than Example 1. This result indicates that a high initial volume retention rate does not necessarily correspond to a low later-stage settlement rate; the interconnected pore structure formed by controlled low-amplitude positive pressure holding and instantaneous depressurization operations may help improve subsequent aeration and moisture migration conditions, thereby reducing the magnitude of later-stage reactor settlement.

[0101] Comparative Example 6, without the addition of magnesium sulfate heptahydrate, maintained an initial effective volume retention rate of 95.08%, but its macroscopic settling rate in the middle and later stages was 37.64%. This result indicates that, under conditions lacking a magnesium source, while the initial foaming morphology of the material can maintain a certain height, the height decreases significantly in the middle and later stages of fermentation. Combined with the weak response of struvite in Comparative Example 6 in Test Example 3, it can be inferred that the nitrogen-containing magnesium-phosphate mineralization structure formed with the participation of a magnesium source may play a role in maintaining the pile height in the middle and later stages.

[0102] The results in Table 4 show that, under the test conditions, the conditioning of polyferric sulfate, the stepwise addition of acid and alkali, the controlled low-amplitude positive pressure holding and instantaneous pressure release, and the mineralization process involving magnesium sources can all affect the volume maintenance and sedimentation control of the fermentation material.

[0103] Test Example 5: This test example is used to investigate the changes in pH value, accumulation of volatile fatty acids, and temperature changes in the fermentation process of the fermentation material under different reagent combinations. The specific experimental steps are as follows: (1) Experimental Subjects and Temperature Monitoring: The materials from Examples 1, 4, and Comparative Example 3, which underwent forced ventilation fermentation under normal pressure in a closed aerobic fermentation tank, were used as experimental subjects. Long-handled temperature sensors were placed at the top, middle, and bottom of the material in the fermentation tank to monitor the material temperature in situ. The data acquisition terminal recorded the temperature value of each measuring point once per hour, and the average value of the three measuring points was taken as the core temperature of the material. The continuous period when the core temperature of the material was higher than 55°C was recorded as the high-temperature maintenance period.

[0104] (2) pH and volatile fatty acid determination in the early stage of fermentation: At 0h, 24h, 48h and 72h after fermentation started, approximately 100g of material from the core area of ​​each group was extracted through the side wall sampling port. The fresh material was mixed with deionized water at a mass ratio of 1:10 and extracted by shaking at 200rpm for 30min on a reciprocating shaker. After centrifugation, the supernatant was collected, and the pH value of the extract was measured using a portable pH meter. The remaining supernatant was filtered through a 0.45μm microporous membrane, and the total volatile fatty acid concentration was determined by gas chromatography, on a dry basis, in g / kg. The maximum pH value and the highest volatile fatty acid concentration of each group were recorded in the first 3 days.

[0105] (3) Temperature index statistics: Collect temperature monitoring data from 1 to 7 days of fermentation, extract the highest temperature reached during the fermentation process of each group, and count the cumulative time when the core temperature of the material is higher than 55℃.

[0106] The test results are recorded in the table below. Unless otherwise stated, the data in the table are the average values ​​of parallel test results.

[0107] Table 5: Test data of physicochemical and thermal characteristics of aerobic fermentation microenvironment in each treatment group

[0108] According to the data in Table 5, the maximum pH values ​​of Examples 1 and 4 during the first 3 days of fermentation were 7.52 and 7.31, respectively, and the highest volatile fatty acid concentrations during the first 3 days were 11.45 g / kg and 10.12 g / kg, respectively; the highest temperatures reached during the fermentation process were 68.7℃ and 66.4℃, respectively, and the durations of high temperature maintenance were 4.8 days and 5.2 days, respectively. These results indicate that under the test conditions, the fermentation materials of Examples 1 and 4 still possess a certain capacity for volatile fatty acid accumulation and temperature increase even with relatively small pH changes in the early stages.

[0109] Comparative Example 3 used neutral tricalcium phosphate instead of superphosphate. Its maximum pH value in the first three days was 9.86, higher than that of Examples 1 and 4. Its highest volatile fatty acid concentration in the first three days was 3.24 g / kg, and its highest temperature reached was 42.1℃, without establishing a high-temperature maintenance period above 55℃. These results indicate that under the test conditions, the absence of superphosphate containing free acid significantly increased the pH value in the early stages of the system, affecting the fermentation temperature rise process to some extent.

[0110] The results from each group indicate that the acidic components in superphosphate may play a regulatory role in the alkalinity of the system during the initial stage of sodium percarbonate hydrolysis, thus maintaining the pH value within a relatively mild range during the early stages of fermentation. Simultaneously, the carbonate / bicarbonate system formed by sodium percarbonate hydrolysis may also buffer the accumulation of organic acids during the early stages of fermentation. These acid-base regulatory effects help maintain a suitable fermentation microenvironment and promote the formation of a higher core temperature and a longer duration of high-temperature maintenance in the fermentation system.

[0111] Therefore, under the test conditions, the reagent combination and addition method used in Examples 1 and 4 help to improve the pH value change in the early stage of fermentation and help maintain the accumulation of bioheat during the aerobic fermentation process.

[0112] Test Example 6: This test example is used to investigate the waste product utilization capacity, nitrogen retention, ammonia emissions, and leachate generation of the controlled low-amplitude positive pressure pore formation and dual mineralization framework combined process during fermentation. The specific experimental steps are as follows: (1) Experimental subjects and acquisition of basic parameters: The fermentation materials of Example 1, Comparative Example 1, and Comparative Example 6 throughout their entire fermentation cycle were used as experimental subjects. Among them, Comparative Example 1 was a traditional auxiliary material fermentation process with 30% volumetric sawdust mixed in, and Comparative Example 6 was a treatment process without the addition of magnesium sulfate heptahydrate. The initial total loading volume and the pure mass of the waste food when the materials of each group were discharged into the closed aerobic fermentation tank were measured and recorded. The effective waste food disposal capacity per unit fermentation tank volume was calculated, with the unit being kg / m³. 3 Solid samples were extracted before fermentation started and at the end of day 7 of fermentation. The total nitrogen content on a dry basis was determined by the Kjeldahl method. The total nitrogen retention rate during the entire fermentation cycle was calculated by combining the changes in the total dry matter content of the material.

[0113] (2) Monitoring of gaseous ammonia emissions: The exhaust port at the top of the closed aerobic fermentation tank is connected to an online ammonia analyzer calibrated with standard ammonia. The online ammonia analyzer uses electrochemical ammonia sensing or Fourier transform infrared detection and is equipped with a water vapor pretreatment module or a water vapor compensation module. During the forced ventilation stage from day 1 to day 7 of fermentation, the volume concentration of ammonia in the exhaust gas is continuously measured, and the daily ammonia emission mass is calculated in combination with the standard ventilation flow rate of the Roots blower. The cumulative value of ammonia emission mass during the fermentation cycle is converted to the unit initial dry basis mass of the vegetable waste to obtain the cumulative ammonia emission amount, in g / kg.

[0114] (3) Collection and characterization of liquid leachate: A sealed storage tank was installed at the outlet of the diversion collection tank at the bottom of the fermentation tank. The liquid leachate that was naturally discharged during the fermentation process was collected at regular intervals every day, and the daily volume of leachate produced was recorded. The total yield of leachate during the entire fermentation cycle was calculated and summarized in L / t of vegetable waste. After the leachate samples from each group were mixed evenly, their chemical oxygen demand was determined by the potassium dichromate method and recorded as the average COD of the leachate in mg / L.

[0115] The test results are recorded in the table below. Unless otherwise stated, the data in the table are the average values ​​of parallel test results.

[0116] Table 6: Test Data of Resource Utilization and Environmental Emission Indicators for Each Treatment Group

[0117] Based on the data in Table 6, Example 1 represents the typical process conditions selected after considering the overall dosage of reagents, energy consumption, and treatment effect. In terms of processing capacity, the effective waste vegetable disposal capacity of Example 1 is 852.4 kg / m³. 3 The effective waste disposal capacity of Comparative Example 1 was 556.8 kg / m³. 3 The above results indicate that, under the test conditions, compared with the treatment method involving the mixing of sawdust, Example 1 can accommodate higher quality vegetable waste material under the same fermentation tank volume.

[0118] Regarding nitrogen retention and ammonia emissions, Example 1 showed a total nitrogen retention rate of 88.5% and a cumulative ammonia emission of 2.15 g / kg; Comparative Example 1 showed a total nitrogen retention rate of 64.2% and a cumulative ammonia emission of 8.41 g / kg; and Comparative Example 6 showed a total nitrogen retention rate of 51.6% and a cumulative ammonia emission of 14.28 g / kg. These results indicate that under the test conditions, Example 1 exhibited a higher total nitrogen retention rate and lower cumulative ammonia emissions compared to Comparative Examples 1 and 6.

[0119] Combined with the results of Comparative Example 6, it can be seen that, without the addition of magnesium sulfate heptahydrate, the cumulative ammonia emission was higher than that of Example 1, and the total nitrogen retention rate was lower. This result suggests that the addition of a magnesium source may facilitate the formation of a nitrogen-containing magnesium phosphate mineralization structure between ammonium nitrogen and phosphate in the system, thereby increasing the retention ratio of some nitrogen in the solid phase.

[0120] Regarding leachate production, the total leachate yield of Example 1 was 15.2 L / t of vegetable waste, with an average COD of 4512 mg / L; the total leachate yield of Comparative Example 1 was 45.4 L / t of vegetable waste, with an average COD of 12560 mg / L; and the total leachate yield of Comparative Example 6 was 65.0 L / t of vegetable waste, with an average COD of 18455 mg / L. These results indicate that under the test conditions, the leachate production and COD of Example 1 were lower than those of Comparative Example 1 and Comparative Example 6.

[0121] Based on the high settling rate in the later stages of Comparative Example 6 in Test Example 4, it can be inferred that when the structural stability of the material is insufficient in the later stages, the connectivity of the pile pores and the state of moisture migration may be affected, leading to an increase in leachate production. The interconnected pore structure formed by the controlled low-amplitude positive pressure operation in Example 1, as well as the mineralized framework structure formed during fermentation, may together help improve the material aeration and moisture migration conditions, and reduce leachate production.

[0122] The results in Table 6 show that, under the test conditions, the combined process of controlled low-amplitude positive pressure pore formation and dual mineralization framework used in Example 1 has shown good overall effects in increasing the amount of waste vegetables consumed per unit volume, increasing the total nitrogen retention rate, reducing ammonia emissions, and reducing leachate generation.

[0123] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for the resource utilization and treatment of vegetable waste, characterized in that, Includes the following steps: (1) Crushing and demulsification: The vegetable tails are crushed, and then polyferric sulfate is added evenly to the crushed material. The mixture is sheared and stirred at a speed of 50-70 rpm to obtain processed material A. (2) Staggered addition of skeleton premix and foaming source: Reduce the stirring speed to 10-20 rpm, first uniformly sprinkle skeleton and nitrogen-retaining dry powder premix into the material A and maintain stirring, then uniformly add sodium percarbonate into the material system and continue to maintain stirring to obtain material B. (3) Controlled low-amplitude positive pressure pore formation treatment: Place the treatment material B in a closed fermentation space, pump air into the interior to form a controlled low-amplitude positive pressure environment and maintain the pressure. After the pressure maintenance is completed, release the pressure to normal pressure instantly. The pressure holding and instantaneous pressure release steps are performed continuously in a loop; (4) Aerobic fermentation and discharge: Forced ventilation aerobic fermentation is carried out under normal pressure. After fermentation is completed, the material is discharged to obtain solid organic fertilizer product. The amounts of each ingredient added per 1000 servings of the aforementioned vegetable scraps, by weight, are as follows: The amount of the polyferric sulfate is 1.0 to 3.0 parts; The skeleton and nitrogen-retaining dry powder premix consists of 20.0-40.0 parts of superphosphate and 10.0-25.0 parts of magnesium sulfate heptahydrate; The sodium percarbonate content is 15.0 to 30.0 parts.

2. The method for resource utilization and treatment of vegetable waste according to claim 1, characterized in that, In step (1), the particle size of the crushing process is controlled to be 5-10 mm; The specific process parameters for the shearing and mixing are as follows: the stirring shaft speed is set to 50-70 rpm, and the stirring is carried out continuously for 3-8 minutes.

3. The method for resource utilization and treatment of vegetable waste according to claim 1, characterized in that, The skeleton and nitrogen-retaining dry powder premix mentioned in step (2) are a pre-prepared mixture, and its specific preparation method includes the following steps: (a) Weighing and crushing: Dry crush the superphosphate and magnesium sulfate heptahydrate separately and pass them through a 60-mesh sieve. Then weigh the crushed and sieved superphosphate and magnesium sulfate heptahydrate separately according to the proportion. (b) Dry powder mixing: Under the conditions of temperature of 15-25℃ and relative humidity of less than 40%, superphosphate and magnesium sulfate heptahydrate are added into the dry powder mixing equipment, the spindle speed is controlled at 30-40 rpm, and the mixture is continuously mixed for 10-15 min to obtain the skeleton and nitrogen-retaining dry powder premix. (c) Sealed storage: Place the skeleton and nitrogen-retaining dry powder premix in a sealed container to prevent moisture and use within 24 hours after preparation.

4. The method for resource utilization and treatment of vegetable waste according to claim 1, characterized in that, The specific timing and process parameters for the staggered addition of the skeleton premix and the foaming source in step (2) are as follows: Adjust the stirring speed to 10-20 rpm, first sprinkle in the premix of the skeleton and nitrogen-retaining dry powder, and maintain stirring at 10-20 rpm for 3-8 minutes; Then add the sodium percarbonate and continue stirring at 10-20 rpm for 10-20 minutes.

5. The method for resource utilization and treatment of vegetable waste according to claim 1, characterized in that, In step (2), within 15 minutes after the addition of sodium percarbonate, the highest temperature rise of the material system is controlled at 6.2 to 8.7°C, and the pH fluctuation range is maintained at 6.32 to 7.

22.

6. The method for resource utilization and treatment of vegetable waste according to claim 1, characterized in that, The specific process parameters for the controlled low-amplitude positive pressure hole forming process in step (3) are as follows: The controlled low-amplitude positive pressure environment is a gauge pressure of 0.03 to 0.06 MPa, and the pressure is maintained for 10 to 20 minutes after the set pressure is reached; The instantaneous pressure relief refers to the sudden reduction of pressure to 0 MPa gauge pressure within 5 to 15 seconds. The pressure holding and instantaneous pressure release steps are performed continuously in a cycle of 3 to 5 times.

7. The method for resource utilization and treatment of vegetable waste according to claim 1, characterized in that, The polyferric sulfate is a solid powder with a total iron content ≥19.0 wt% and a basicity of 8.0–16.0%.

8. The method for resource utilization and treatment of vegetable waste according to claim 1, characterized in that, The effective phosphorus pentoxide mass fraction of the superphosphate is ≥12.0 wt%, and the free acid mass fraction is 3.0 to 5.5 wt%.

9. A method for resource utilization and treatment of vegetable waste according to claim 1, characterized in that, The sodium percarbonate is stearic acid-coated microparticles with a particle size of 0.5–1.5 mm and an active oxygen mass fraction ≥13.0 wt%.

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