Method for harmless treatment of aquaculture pond sediment by low-temperature aerobic pyrolysis and production of spray-dried carrier particles

Abstract

The application discloses a method for harmless treatment of aquaculture pond bottom mud by low-temperature aerobic pyrolysis and production of spray drying carrier particles. The application combines the aquaculture pond bottom mud, carbide slag and straw powder, forms a good mesoporous space structure through pyrolysis of the bottom mud and the straw through a low-temperature aerobic pyrolysis process, generates calcium carbonate through the reaction of the carbide slag with the atmosphere and carbon dioxide generated by pyrolysis to directly provide particle strength, and finally forms calcium-carbon-based particles with certain particle strength and a good mesoporous space system, which can be used for spray drying carriers.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of low-temperature aerobic pyrolysis and resource utilization of aquaculture pond sediment, and specifically relates to a method for harmless low-temperature aerobic pyrolysis of aquaculture pond sediment and production of spray-dried carrier particles. BACKGROUND

[0002] Aquaculture pond sediment is composed of a large amount of minerals and organic matter (unconsumed leftover feed, antibiotics, excrement, and organic matter after the death of various organisms), and is an important carrier for the accumulation and migration and transformation of pollutants. Excessive sediment can form a local anaerobic environment at the bottom of the pond, resulting in the formation of a large amount of products (such as ammonia, hydrogen sulfide, and organic acids) that are toxic to aquaculture organisms. In addition, the complex composition of the sediment also facilitates the breeding of pathogens, and the accumulation of antibiotics induces the formation of antibiotic resistance genes in pathogenic bacteria, leading to frequent occurrence of diseases in aquaculture organisms and seriously affecting the quality and safety of aquaculture products.

[0003] In large-scale agricultural aquaculture, due to high-density breeding and large amounts of feed, pond sediment is prone to accumulation and deposition, and therefore needs to be properly treated. After two to three years of aquaculture in a pond, the sediment needs to be treated by clearing the pond, i.e., after the pond is dried, part of the sediment is dug out and placed on the pond bank, and quicklime is used to disinfect the bottom of the pond to eliminate parasitic and pathogenic organisms in the sediment. Although placing the sediment on the pond bank greatly reduces the cost of treatment and saves manpower and resources, the organic matter and antibiotics in the sediment can still migrate to the aquaculture pond due to water erosion and other hydraulic effects, making the pond cleaning insufficient. Currently, the main ex-situ treatment and disposal technologies for pond sediment in China include aerobic composting, anaerobic digestion, and pyrolysis technology. Pyrolysis technology has a wide application prospect due to its good environmental and economic benefits, but due to the high water content and high inorganic content of the sediment, it is not easy to pyrolyze, and therefore biomass such as straw and garden waste is often added for mixed pyrolysis.

[0004] Chinese patent CN113171750B discloses a method for preparing biochar from sediment and garden waste. The method involves drying and crushing the sediment and garden waste, mixing them with water at a mass ratio of 1:0.25-4, and pyrolyzing them under anaerobic conditions at 300-700°C for 1-5h. The pyrolysis products are then mixed with a modifier (NaOH or FeCl3) and water, and the mixture is dried to obtain the final product, biochar. Although this method can effectively treat sediment and garden waste through pyrolysis and convert them into biochar, it involves multiple drying and anaerobic processes, resulting in high energy consumption. In addition, the method requires the addition of a modifier, which increases the cost of raw materials and makes it unsuitable for large-scale treatment and disposal of aquaculture sediment.

[0005] Chinese patent CN115477527B discloses a biochar ceramsite particle filler production method, which mixes sludge with industrial waste such as fly ash, realizes harmless treatment of sludge through low-temperature aerobic pyrolysis process, and forms biochar ceramsite with space porous structure, which can be used for adsorption of gas-liquid phase multi-medium pollutants. However, the average pore size of the mesoporous of the biochar ceramsite is 6-10 nm, which is relatively small and not suitable for use as a spray drying carrier.

[0006] Therefore, how to further realize efficient dewatering and harmless treatment of high-moisture-content sediment, reduce process energy consumption, and utilize sediment pyrolysis to form spray drying carrier particles with larger mesoporous pores and specific surface area is a problem to be solved. SUMMARY

[0007] The problems to be solved by the above-mentioned prior art are as follows: (1) efficient dewatering and harmless treatment of high-moisture-content sediment; (2) utilizing sediment pyrolysis to form carrier particles with larger mesoporous pores and specific surface area as a spray drying carrier.

[0008] The present application provides a method for low-temperature aerobic pyrolysis harmless treatment of aquaculture pond sediment and production of spray drying carrier particles. The method realizes efficient dewatering and low-temperature aerobic pyrolysis harmless treatment of high-moisture-content sediment through a double-screw extrusion-drying granulation integrated device and a low-temperature aerobic pyrolysis rotary reactor. By adding carbide slag and crushed straw powder, the sediment can form larger mesoporous pores (mesopore diameter of about 23 nm) through low-temperature aerobic pyrolysis, and the straw powder low-temperature aerobic pyrolysis can improve the mesopore diameter and increase the specific surface area of calcium-carbon-based particles (for example, the specific surface area of the calcium-carbon-based particles prepared after adding straw in Example 1 is 13.6764 m 2 / g, and the specific surface area of the calcium-carbon-based particles prepared without adding straw based on Example 1 is 8.0947 m 2 / g). The carbide slag can react with the atmosphere and the carbon dioxide generated by pyrolysis to form calcium carbonate, directly providing particle strength. Finally, through low-temperature aerobic pyrolysis, calcium-carbon-based particles with certain particle strength and mesoporous space structure are obtained, and the good mesoporous system can be used as a spray drying carrier.

[0009] The technical solutions adopted by the present application are as follows:

[0010] The method for low-temperature aerobic pyrolysis harmless treatment of aquaculture pond sediment and production of spray drying carrier particles comprises the following steps:

[0011] Step 1): Mix and stir the aquaculture pond sediment, carbide slag and straw powder;

[0012] Step 2): Extrude and dewater the mixed material in the double-screw extrusion-drying granulation integrated device and pressure form wet base columnar particles;

[0013] Step 3): The above wet-based columnar particles are sent to a low-temperature aerobic pyrolysis rotary reactor. After particle preheating, low-temperature aerobic pyrolysis and instantaneous combustion, the bottom mud of aquaculture ponds is rendered harmless, and calcium-carbon based particles with particle strength and mesoporous spatial structure are obtained. These calcium-carbon based particles with good mesoporous system can be used as a spray drying carrier.

[0014] Furthermore, in step 1): the bottom mud of the aquaculture pond comes from the pond cleaning or maintenance process of the aquaculture pond and has a water content of 90-95%; the calcium carbide slag is the main industrial waste of acetylene produced by electrolysis, and its main component is calcium hydroxide; the straw is crushed into straw powder with a size of 10-20 mesh.

[0015] Furthermore, in step 1), the mass ratio of the materials to be mixed is 5-6:2:2-3 for bottom mud: carbide slag: straw powder.

[0016] Aquaculture pond bottom mud, carbide slag and straw powder are respectively conveyed to the mixer via shaftless screw conveyors;

[0017] The moisture content of the mixed material is 55-70%.

[0018] Furthermore, in step 2): the mixture is conveyed to the twin-screw extrusion and granulation integrated equipment via a shaftless screw conveyor; the twin-screw extrusion and granulation integrated equipment is Chinese Patent CN 117839550 A sludge mixture pressure molding granulation moisture content control equipment.

[0019] Furthermore, in step 2): the mixture is first dehydrated under the action of twin-screw extrusion and frictional evaporation, controlling the moisture content of the mixture to 25-32% to achieve continuous and stable granulation. Dehydration is completed in the moisture control section of the sludge mixture pressure molding granulation moisture content control equipment.

[0020] The mixture is then pressure-formed into wet-based columnar particles with a diameter of 3-10 mm and a length of 5-10 mm, and the moisture content of the wet-based columnar particles is 20-25%. Granulation is completed in the extrusion granulation section of the sludge mixture pressure forming granulation moisture content control equipment.

[0021] Furthermore, in step 3): during the low-temperature aerobic pyrolysis process, the drug residues in the bottom sediment, the organic matter from fish feces, and the biomass from the straw are all carbonized and rendered harmless, forming a multi-mesoporous spatial structure inside the columnar particles; simultaneously, the carbon dioxide generated during pyrolysis and the carbon dioxide in the atmosphere react with the carbide slag to form calcium carbonate, providing particle strength to the columnar particles, ultimately forming calcium-carbon-based particles with good mesoporous system and particle strength, which can be used as a spray drying carrier. The low-temperature aerobic pyrolysis rotary reactor is the horizontal rotary aerobic pyrolysis furnace described in CN115477527B.

[0022] Furthermore, in step 3): the temperature for preheating the particles is 100-150℃, and the moisture content of the preheated wet columnar particles is reduced to 15-20%; the temperature for low-temperature aerobic pyrolysis is 350-375℃, and the residence time is 20-30 min; the temperature for instantaneous combustion is 1000-1200℃, and the residence time is 5-15 s.

[0023] Furthermore, the low-temperature aerobic pyrolysis requires determining the required oxygen and carbon dioxide content based on the calcium hydroxide content in the carbide slag and the amount of oxygen needed for the low-temperature aerobic pyrolysis of the bottom mud and straw organic matter. This means determining the addition ratio of air and industrial flue gas. The concentration of oxygen and carbon dioxide in the exhaust gas is monitored in real time by a gas concentration probe at the inlet of the reactor. At the same time, a gas concentration probe is installed at the outlet of the reactor to monitor the concentration of oxygen and carbon dioxide in the exhaust gas in real time, and the ratio of air and industrial flue gas in the intake is adjusted based on the ratio of circulating exhaust gas.

[0024] Furthermore, in step 3): the exhaust gas is cooled by a heat exchanger and the incoming air is preheated at the same time. After the exhaust gas is cooled, it passes through a humus fixed bed to remove pollutant components from the gas. After the gas meets the standards, it is discharged at high altitude.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] (1) This invention solves the problem of dehydration of bottom mud in aquaculture ponds by using twin-screw extrusion technology. It also utilizes low-temperature aerobic pyrolysis technology to achieve the carbonization and harmlessness of drug residues, fish feces and other organic matter, as well as straw biomass in the bottom mud of aquaculture ponds. This invention has low energy consumption, simple and flexible operation, and minimal environmental impact.

[0027] (2) This invention combines aquaculture pond bottom mud, carbide slag and straw powder. Through low-temperature aerobic pyrolysis, the bottom mud and straw are pyrolyzed to form a good mesoporous spatial structure (average pore size of 20 nm). The average mesoporous pore size formed by the low-temperature aerobic pyrolysis of the bottom mud is relatively large, about 23 nm. The straw has a high organic matter content, and aerobic pyrolysis can further improve the pore structure and specific surface area of ​​the calcium carbon-based particles. The reaction of carbide slag with atmosphere and carbon dioxide generated by pyrolysis produces calcium carbonate, which directly provides particle strength. Finally, calcium carbon-based mesoporous particles with a certain particle strength and a good mesoporous system are formed, which can be used as a spray drying carrier.

[0028] (3) This invention produces spray-dried carrier particles by low-temperature aerobic pyrolysis in an atmosphere of CO2 from industrial flue gas and O2 from the air. It organically combines the aerobic pyrolysis of aquaculture pond bottom mud and straw biomass with the fixation of CO2 in industrial flue gas. The low-temperature aerobic pyrolysis achieves the harmlessness of aquaculture pond bottom mud, the fixation of CO2 in industrial flue gas achieves carbon emission reduction, and the production of spray-dried carrier particles achieves resource utilization.

[0029] (4) This invention utilizes high-moisture-content biomass waste (bottom mud of aquaculture ponds), industrial waste (carbide slag), and agricultural waste (straw) to produce spray-dried carrier particles. The raw materials are readily available, the cost is low, and the process is simple and practical. The plant construction conditions are simple and flexible, the equipment investment is low, it is not easy to cause secondary pollution, and it has little impact on the environment. It has good economic and environmental benefits. Attached Figure Description

[0030] Figure 1 This is a process flow diagram of the method for low-temperature aerobic pyrolysis and harmless treatment of aquaculture pond bottom mud and the production of spray-dried carrier particles according to the present invention. Detailed Implementation

[0031] To make the technical means, creative features, objectives and effects of this invention easier to understand, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings.

[0032] The method for low-temperature aerobic pyrolysis and harmless treatment of aquaculture pond bottom mud and the production of spray-dried carrier particles in this embodiment includes the following:

[0033] Step 1): Mix the aquaculture bottom mud, carbide slag, and straw powder together;

[0034] Furthermore, the bottom mud of the aquaculture pond comes from the pond cleaning or maintenance process and has a water content of 90-95%; the calcium carbide slag is the main industrial waste for producing acetylene by electrolysis, and its main component is calcium hydroxide; the straw is crushed to a size of 10-20 mesh.

[0035] Preferably, in step 1), the material ratio of the mixture is bottom mud: carbide slag: straw in a ratio of 6:2:2 or 5:2:3; the materials are conveyed to the mixer by a shaftless screw conveyor; the moisture content of the mixed material is 55%-70%.

[0036] Step 2): The mixed material is squeezed and dehydrated in a twin-screw extrusion and granulation integrated equipment and pressure molded to form wet-based columnar granules with a certain particle strength.

[0037] Preferably, in step 2), the mixture is conveyed to the twin-screw extrusion and granulation integrated equipment by a shaftless screw conveyor. The material is first dehydrated under the action of twin-screw extrusion and friction evaporation. By controlling the operating parameters such as the twin-screw speed, the moisture content of the mixture is controlled to be 25%-32% to achieve continuous and stable granulation.

[0038] Preferably, in step 2), the mixture with a suitable moisture content enters the pressure forming section of the twin-screw extrusion and granulation integrated equipment and is formed into wet-based columnar particles with a diameter of 3-10 mm and a length of 5-10 mm by pressure forming. The moisture content of the wet-based columnar particles is 20%-25%.

[0039] Step 3): The above wet-based particles are sent to a low-temperature aerobic pyrolysis rotary reactor. After particle preheating, low-temperature aerobic pyrolysis and instantaneous combustion treatment, calcium-carbon-based mesoporous particles with a certain particle strength are obtained. The good mesoporous system can be used as a spray drying carrier.

[0040] Preferably, in step 3), the temperature of the preheating section of the low-temperature aerobic pyrolysis rotary reactor is 100-150℃, and the moisture content of the wet-based columnar particles after preheating is reduced to 15%-20%; the temperature of the low-temperature aerobic pyrolysis section is 350-375℃, and the residence time is 20-30 min; the temperature of the instantaneous combustion is 1000-1200℃, and the residence time is 5-15 s.

[0041] Preferably, in step 3), the low-temperature aerobic pyrolysis section of the low-temperature aerobic pyrolysis rotary reactor needs to determine the ratio of air and industrial flue gas addition based on the content of carbide slag and the oxygen demand of low-temperature aerobic pyrolysis, and monitor it in real time through a gas concentration probe at the front end of the reactor; at the same time, a gas concentration probe needs to be set at the rear end of the reactor to monitor the oxygen and carbon dioxide concentrations of the exhaust gas in real time, and adjust the ratio of air and industrial flue gas in the intake based on the ratio of circulating exhaust gas.

[0042] Preferably, in step 3), the exhaust gas is cooled by a heat exchanger and the incoming air is preheated at the same time. After the exhaust gas is cooled, it passes through a humus fixed bed to remove pollutant components from the gas. After the gas meets the standards, it is discharged at high altitude.

[0043] During the low-temperature aerobic pyrolysis process, drug residues, fish feces, and other organic matter in the bottom sediment, as well as sludge organic matter and straw biomass, are all carbonized and rendered harmless, forming a multi-mesoporous spatial structure inside the columnar particles. At the same time, the carbon dioxide produced by pyrolysis and the carbon dioxide in the atmosphere react with the carbide slag to form calcium carbonate, which provides particle strength to the columnar particles. Finally, calcium-carbon based particles with a certain particle strength and a good mesoporous system are formed, which can be used as a spray drying carrier.

[0044] Example 1:

[0045] (1): Aquaculture bottom mud (moisture content 90%), carbide slag and straw powder (crushed to 15 mesh) are mixed in a ratio of bottom mud: carbide slag: straw of 6:2:2 by conveying them to a horizontal mixer through a shaftless screw conveyor.

[0046] (2): The mixed material is conveyed to the twin-screw extrusion and granulation integrated equipment through a shaftless screw conveyor. The material is first dehydrated under the action of twin screw extrusion and friction evaporation. By controlling the operating parameters such as the twin screw speed, the moisture content of the mixture is controlled to decrease from 60% to 28%-32% to achieve continuous and stable granulation. The mixture with a suitable moisture content enters the pressure forming section of the twin-screw extrusion and granulation integrated equipment and is formed into wet-based columnar particles with a diameter of 8mm and a length of 10mm by pressure forming. The moisture content of the wet-based columnar particles is 25%.

[0047] (3): The above-mentioned wet-based particles are sent to a low-temperature aerobic pyrolysis rotary reactor. The temperature of the preheating section of the low-temperature aerobic pyrolysis rotary reactor is 125℃, and the moisture content of the wet-based columnar particles after preheating is reduced to 20%. The temperature of the low-temperature aerobic pyrolysis section is 375℃, and the residence time is 30min. The instantaneous combustion temperature is 1100℃, and the residence time is 10s. The proportion of air and industrial flue gas added is determined according to the content of carbide slag and the oxygen demand of low-temperature aerobic pyrolysis. The proportion of air and industrial flue gas added is adjusted in real time based on the proportion of circulating tail gas by monitoring the gas concentration probes at the inlet and outlet of the reactor.

[0048] (4) When the exhaust gas is discharged, a heat exchanger is used to exchange heat and cool down the exhaust gas, while preheating the incoming air at the same time. After the exhaust gas is cooled down, the pollutant components in the gas are removed through a humus fixed bed. After the gas meets the standards, it is discharged at high altitude.

[0049] During the low-temperature aerobic pyrolysis process, drug residues, fish feces, and other organic matter in the bottom sediment, as well as sludge organic matter and straw biomass, are all carbonized and rendered harmless, forming a multi-mesoporous spatial structure inside the columnar particles. At the same time, the carbon dioxide produced by pyrolysis and the carbon dioxide in the atmosphere react with the carbide slag to form calcium carbonate, which provides particle strength to the columnar particles. Finally, calcium-carbon based particles with a certain particle strength and a good mesoporous system are obtained, which can be used as a spray drying carrier.

[0050] The mesoporous calcium-carbon based particles prepared in this embodiment have a compressive strength of 100.35 N and a BET-measured specific surface area of ​​13.6764 m². 2 / g, Total pore volume: 0.062519cm³ 3 / g, average pore size: 18.2854nm.

[0051] Example 2:

[0052] (1): Aquaculture bottom mud (moisture content 92%), carbide slag and straw powder (crushed to 10 mesh) are mixed in a ratio of bottom mud: carbide slag: straw of 5:2:3 by conveying them to a horizontal mixer through a shaftless screw conveyor.

[0053] (2): The mixed material is conveyed to the twin-screw extrusion and granulation integrated equipment through a shaftless screw conveyor. The material is first dehydrated under the action of twin screw extrusion and friction evaporation. By controlling the operating parameters such as the twin screw speed, the moisture content of the mixture is controlled to decrease from 55% to 30% to achieve continuous and stable granulation. The mixture with a suitable moisture content enters the pressure forming section of the twin-screw extrusion and granulation integrated equipment and is formed into wet-based columnar particles with a diameter of 5mm and a length of 7mm by pressure forming. The moisture content of the wet-based columnar particles is 25%.

[0054] (3): The above-mentioned wet-based particles are sent to a low-temperature aerobic pyrolysis rotary reactor. The temperature of the preheating section of the low-temperature aerobic pyrolysis rotary reactor is 150℃, and the moisture content of the wet-based columnar particles after preheating is reduced to 18%. The temperature of the low-temperature aerobic pyrolysis section is 365℃, and the residence time is 25min. The instantaneous combustion temperature is 1200℃, and the residence time is 15s. The proportion of air and industrial flue gas added is determined according to the content of carbide slag and the oxygen demand of low-temperature aerobic pyrolysis. The proportion of air and industrial flue gas added is adjusted in real time by monitoring the gas concentration probes at the inlet and outlet of the reactor and based on the proportion of circulating tail gas.

[0055] (4) When the exhaust gas is discharged, a heat exchanger is used to exchange heat and cool down the exhaust gas, while preheating the incoming air at the same time. After the exhaust gas is cooled down, the pollutant components in the gas are removed through a humus fixed bed. After the gas meets the standards, it is discharged at high altitude.

[0056] During the low-temperature aerobic pyrolysis process, drug residues, fish feces, and other organic matter in the bottom sediment, as well as sludge organic matter and straw biomass, are all carbonized and rendered harmless, forming a multi-mesoporous spatial structure inside the columnar particles. At the same time, the carbon dioxide produced by pyrolysis and the carbon dioxide in the atmosphere react with the carbide slag to form calcium carbonate, which provides particle strength to the columnar particles. Finally, calcium-carbon based particles with a certain particle strength and a good mesoporous system are obtained, which can be used as a spray drying carrier.

[0057] The mesoporous calcium-carbon based particles prepared in this embodiment have a compressive strength of 120.35 N and a BET-measured specific surface area of ​​14.7327 m². 2 / g, total pore volume: 0.069541cm³ 3 / g, average pore size: 19.3815nm.

[0058] Example 3:

[0059] (1): Aquaculture bottom mud (moisture content of 90%), carbide slag and straw powder (crushed to 12 mesh) are mixed in a ratio of bottom mud: carbide slag: straw of 5:2:3 by conveying them to a horizontal mixer through a shaftless screw conveyor.

[0060] (2): The mixed material is conveyed to the twin-screw extrusion and granulation integrated equipment through a shaftless screw conveyor. The material is first dehydrated under the action of twin screw extrusion and friction evaporation. By controlling the operating parameters such as the twin screw speed, the moisture content of the mixture is controlled to decrease from 58% to 28% to achieve continuous and stable granulation. The mixture with a suitable moisture content enters the pressure forming section of the twin-screw extrusion and granulation integrated equipment and is formed into wet columnar particles with a diameter of 3mm and a length of 5mm by pressure forming. The moisture content of the wet columnar particles is 23%.

[0061] (3): The above-mentioned wet-based particles are sent to a low-temperature aerobic pyrolysis rotary reactor. The temperature of the preheating section of the low-temperature aerobic pyrolysis rotary reactor is 100℃, and the moisture content of the wet-based columnar particles after preheating is reduced to 20%. The temperature of the low-temperature aerobic pyrolysis section is 370℃, and the residence time is 28min. The instantaneous combustion temperature is 1150℃, and the residence time is 12s. The proportion of air and industrial flue gas added is determined according to the content of carbide slag and the oxygen demand of low-temperature aerobic pyrolysis. The proportion of air and industrial flue gas added is adjusted in real time based on the proportion of circulating tail gas by monitoring the gas concentration probes at the inlet and outlet of the reactor.

[0062] (4) When the exhaust gas is discharged, a heat exchanger is used to exchange heat and cool down the exhaust gas, while preheating the incoming air at the same time. After the exhaust gas is cooled down, the pollutant components in the gas are removed through a humus fixed bed. After the gas meets the standards, it is discharged at high altitude.

[0063] During the low-temperature aerobic pyrolysis process, drug residues, fish feces, and other organic matter in the bottom sediment, as well as sludge organic matter and straw biomass, are all carbonized and rendered harmless, forming a multi-mesoporous spatial structure inside the columnar particles. At the same time, the carbon dioxide produced by pyrolysis and the carbon dioxide in the atmosphere react with the carbide slag to form calcium carbonate, which provides particle strength to the columnar particles. Finally, calcium-carbon based particles with a certain particle strength and a good mesoporous system are obtained, which can be used as a spray drying carrier.

[0064] The mesoporous calcium-carbon based particles prepared in this embodiment have a compressive strength of 99.73 N and a BET-measured specific surface area of ​​14.3073 m². 2 / g, total pore volume: 0.066732cm³ 3 / g, average pore size: 20.8819nm.

[0065] Comparative Example 1:

[0066] According to Example 1 of Chinese Patent CN115477527B, a method for producing biochar ceramic granule filler is as follows:

[0067] A small amount of lime is added to the dewatered cake of biomass waste with a moisture content of 80%, and pretreated by heating and stirring at 60°C. The pretreated material is then placed in a plate and frame filter press to further reduce the moisture content to 50% as the main material, accounting for 50%. Fly ash, phosphogypsum, and lime are prepared in a mass ratio of approximately 8:1:1. Waste plastic residue is crushed to less than 2mm and added to an intermittently operating horizontal mixing tank at a mass ratio of 6% of the main and auxiliary materials, respectively, using screw conveyors for thorough mixing. The uniformly mixed material is then evenly fed into the inlet of a twin-screw extruder. The extruder die uses a 5mm perforated plate and is equipped with an automatic scraper. The mixture is pressure-formed into wet-based columnar particles with a diameter of 5mm and a length of 5-10mm (moisture content 30-40%). The granular particles are conveyed to the inlet of the horizontal rotary aerobic pyrolysis furnace via a belt conveyor. The wet-based columnar particles are preheated to 150°C and their moisture content reduced to 25% in the waste heat tail gas preheating and drying section. They then enter the low-temperature aerobic pyrolysis section, where the temperature gradually rises to 300°C, and the particles slowly rotate and remain in the furnace for 40 minutes. Finally, the particles enter the instantaneous combustion section, where natural gas or other combustible gases are used as fuel at 250-350°C. Using annular porous burner technology, the particles undergo short-term combustion treatment at 250-350°C to burn off liquid phase products. Finally, the dry-based particle product is discharged from the pyrolysis furnace outlet and air-cooled. The dry-based particles are then humidified in a wet curing tank using water mist and electrically heated to maintain the temperature at 50°C for 5 days, resulting in a biochar ceramsite product with good mechanical strength.

[0068] The final product is a biochar ceramsite filler with a certain mechanical strength. The apparent density of the biochar ceramsite is 1.097 g / cm³. 3 Adsorption capacity: 12.26 mg / g, compressive strength: 16.76 N, BET specific surface area: 13.9053 m² 2 / g, total pore volume: 0.028698cm³ 3 / g, mesoporous pore volume: 0.027715cm³ 3 / g, average pore size: 8.2552nm (mainly mesoporous).

[0069] It can be seen that the average pore size of the biochar ceramic particles prepared by Comparative Example 1 is small (8.2552 nm), and the compressive strength is poor.

[0070] The organic matter in the liquid fertilizer concentrate has a large molecular weight. If the pore size of the spray drying carrier is small, it will be detrimental to the mass transfer process of organic matter during spray drying. However, the mesoporous sediment-based calcium carbon-based particles of the present invention have an increased average mesopore size compared with the biochar ceramic particles of Comparative Example 1, which is beneficial as spray drying carrier particles for liquid fertilizer concentrate.

[0071] The above description is merely a preferred embodiment of the present invention and does not constitute a limitation on the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for harmless treatment of aquaculture pond sediment by low-temperature aerobic pyrolysis and production of spray-dried carrier particles, characterized in that, The method comprises the following steps: Step 1): mixing and stirring the aquaculture pond sediment, carbide slag and straw powder; Step 2): extruding and dewatering the mixed material in a double-screw extruding and granulating integrated device and pressure forming to form wet base columnar particles; Step 3): sending the wet base columnar particles to a low-temperature aerobic pyrolysis rotary reactor, preheating the particles, low-temperature aerobic pyrolysis and instantaneous combustion to realize the harmless treatment of the aquaculture pond sediment; the preheating temperature of the particles is 100-150 DEG C, the water content of the preheated wet base columnar particles is reduced to 15-20%; the low-temperature aerobic pyrolysis temperature is 350-375 DEG C, and the residence time is 20-30 min; the instantaneous combustion temperature is 1000-1200 DEG C, and the residence time is 5-15 s; During the low-temperature aerobic pyrolysis process, the drug residues, fish manure organic matter and biomass of the straw in the sediment are carbonized and harmless, and a multi-mesopore space structure is formed in the columnar particles; at the same time, the carbon dioxide produced by pyrolysis and the carbon dioxide in the atmosphere reacts with the carbide slag to form calcium carbonate, providing particle strength for the columnar particles; Finally, calcium-carbon-based particles with particle strength and mesoporous space structure are obtained, and the good mesoporous system of the calcium-carbon-based particles can be used as a spray drying carrier.

2. The method for harmless treatment and production of spray-dried carrier particles of aquaculture pond bottom mud by low-temperature aerobic pyrolysis according to claim 1, characterized in that, In step 1), the aquaculture pond sediment comes from the pond cleaning or maintenance process of the aquaculture pond, and the water content is 90-95%; the carbide slag is the main industrial waste of acetylene electrolysis, and the main component is calcium hydroxide; the straw is crushed to 10-20 mesh straw powder.

3. The method for harmless treatment and production of spray-dried carrier particles of aquaculture pond bottom mud by low-temperature aerobic pyrolysis according to claim 2, characterized in that, In step 1), the mass ratio of the mixed and stirred material is 5-6:2:2-3 of sediment:carbide slag:straw powder; The aquaculture pond sediment, carbide slag and straw powder are transported by shaftless screw to the stirrer respectively; The water content of the mixed and stirred material is 55-70%.

4. The method for harmless treatment and production of spray-dried carrier particles of aquaculture pond bottom mud by low-temperature aerobic pyrolysis according to any one of claims 1 to 3, characterized in that, In step 2), the mixed material is transported by shaftless screw to the double-screw extruding and granulating integrated device; the double-screw extruding and granulating integrated device is a sludge mixture pressure forming and granulating water content control device.

5. The method for harmless treatment and production of spray-dried carrier particles of aquaculture pond bottom mud by low-temperature aerobic pyrolysis according to claim 4, characterized in that, In step 2), the mixed material is first dewatered under the action of double-screw extrusion and friction evaporation, and the water content of the mixed material is controlled to 25-32% to realize continuous and stable granulation; The mixed material is then pressure formed into 3-10 mm diameter and 5-10 mm length wet base columnar particles, and the water content of the wet base columnar particles is 20-25%.

6. The method for aquaculture pond sediment low-temperature aerobic pyrolysis harmlessness and production of spray-dried carrier particles according to claim 1, characterized in that, In the low-temperature aerobic pyrolysis, the oxygen content and carbon dioxide content required for the oxygen content and carbon dioxide content of the calcium hydroxide content in the carbide slag and the oxygen required for the low-temperature aerobic pyrolysis of the sediment and straw organic matter are determined, i.e. the addition ratio of air and industrial flue gas is determined, the oxygen and carbon dioxide concentration in the inlet gas is monitored in real time by the gas concentration probe at the front end of the reactor; at the same time, a gas concentration probe is arranged at the rear end of the reactor to monitor the oxygen and carbon dioxide concentration of the tail gas in real time, and the air and industrial flue gas ratio of the inlet gas is adjusted based on the circulating tail gas ratio.

7. The method for aquaculture pond sediment low-temperature aerobic pyrolysis harmlessness and production of spray-dried carrier particles according to claim 1, characterized in that, In step 3), the discharged tail gas is cooled and preheated at the same time by using a heat exchanger, the cooled tail gas is removed through a humus soil fixed bed to remove the pollutant components in the gas, and the tail gas is discharged into the high altitude after being determined to meet the standard.

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