Process for co-producing seedling culture substrate and corrosive acid by utilizing hydrothermal carbonization of waste fish or / and shrimp composite cotton straw and seedling culture substrate

Abstract

The invention relates to a process for co-producing a seedling culture substrate and corrosive acid by using waste fish or / and shrimp composite cotton straw through hydrothermal carbonization and the seedling culture substrate. The method comprises the following steps: removing fish or / and shrimp waste grease, and stirring to obtain fish or / and shrimp waste slurry; performing wet grinding on the cotton straws to obtain fiber slurry; obtaining the mass ratio of the fish or / and shrimp waste slurry to the fiber slurry and the hydrothermal reaction constant temperature time according to the hull content, the crude protein content and the cotton straw cellulose content; the method comprises the following steps: mixing fish or / and shrimp waste slurry and fiber slurry according to a mass ratio of 100: (20-40), carrying out a hydrothermal reaction, cooling to 60 DEG C, separating a solid phase from a liquid phase, dehydrating the solid phase, drying to obtain a hydrothermal carbonized product, condensing and recovering the liquid phase, carrying out crystal multi-stage membrane separation, and concentrating to obtain humic acid, wherein the mass ratio of the fish or / and shrimp waste slurry to the fiber slurry is 100: (20-40); and mixing the hydrothermal carbonization product, an acidity regulator and a structure modifier, adding a nitrification inhibitor and a slow release agent, and grinding to obtain the seedling culture substrate.

Description

Technical Field

[0001] This invention relates to the field of seedling substrate preparation technology, and in particular to a process and seedling substrate for the co-production of seedling substrate and corrosive acid by hydrothermal carbonization of waste fish and / or shrimp composite cotton straw. Background Technology

[0002] my country's annual aquaculture production exceeds 65 million tons. Waste fish and / or shrimp generated from various damages during the breeding, transportation, and processing stages account for approximately 5-8% of the total aquaculture output. Byproducts such as fish heads, bones, and viscera generated during processing account for 30-50% of the raw material weight. These wastes are rich in protein, oil, and chitin, and are particularly prone to spoilage and foul odor.

[0003] Hydrothermal carbonization can rapidly convert organic matter under subcritical water conditions. However, in practice, the reaction rates of shrimp shells, fish bones, and soft tissues differ significantly. When using fixed parameters, more shells result in incomplete carbonization and low carbon content, while fewer shells lead to over-reaction and pore collapse. A resource-based chemical plant in Guangdong has demonstrated that fish and shrimp raw materials release large amounts of malodorous gases during hydrothermal carbonization, becoming a major obstacle to industrial application.

[0004] Therefore, in order to address the above problems, the present invention urgently needs to provide a process and seedling substrate for the hydrothermal carbonization of waste fish and / or shrimp composite cotton straw to co-produce seedling substrate and corrosive acid. Summary of the Invention

[0005] The purpose of this invention is to provide a process and seedling substrate for the hydrothermal carbonization of waste fish and / or shrimp combined with cotton stalks to co-produce seedling substrate and corrosive acid. By proposing the process of using waste fish and / or shrimp combined with cotton stalks to co-produce seedling substrate and corrosive acid, this invention solves the technical problems in the prior art where the reaction rates of shrimp shells, fish bones and soft tissues of fish are very different. When using fixed parameters, if there are too many shells, carbonization is not thorough and the carbon content is low; if there are too few shells, the reaction is excessive and the pores collapse, which cannot meet the application requirements.

[0006] This invention provides a process for the hydrothermal carbonization of waste fish and / or shrimp composite cotton straw to co-produce seedling substrate and corrosive acid, comprising the following steps:

[0007] Remove the grease from the fish and / or shrimp waste, add water and stir to obtain a fish and / or shrimp waste slurry;

[0008] Cotton stalks are wet-milled to obtain fiber pulp;

[0009] The shell content, crude protein content, and cotton straw cellulose content of fish or / and shrimp waste slurry were determined. Based on the shell content, crude protein content, and cotton straw cellulose content, the mass ratio of fish or / and shrimp waste slurry to fiber slurry and the hydrothermal reaction isothermal time were obtained.

[0010] Mixing the fish or / and shrimp waste slurry and the fiber slurry, the mass ratio of the fish or / and shrimp waste slurry and the fiber slurry is 100: (20-40), and the hydrothermal reaction is carried out at 180-240℃, and the temperature is reduced to 60℃, and the solid phase and the liquid phase are separated, the solid phase is dehydrated and dried to obtain the hydrothermal carbonization product, and the liquid phase is condensed and recovered, and the humic acid is obtained through multi-stage membrane separation and concentration.

[0011] Mixing the hydrothermal carbonization product, the acid regulator and the structure modifier, adding the nitration inhibitor and the slow-release agent, and grinding to obtain the breeding substrate.

[0012] Preferably, the specific method for obtaining the mass ratio of the fish or / and shrimp waste slurry and the fiber slurry and the constant temperature time of the hydrothermal reaction is obtained according to the shell content, the crude protein content and the cotton stalk cellulose content.

[0013] When the shell content is 15-25% and the cotton stalk ratio is 20-30%, the holding time is 70-80 min.

[0014] When the shell content is 26-40% and the cotton stalk ratio is 25-35%, the holding time is 85-100 min.

[0015] When the shell content is 41-55% and the cotton stalk ratio is 30-40%, the holding time is 105-120 min.

[0016] When the shell content is 56-70% and the cotton stalk ratio is 35-45%, the holding time is 125-140 min.

[0017] When the crude protein content is greater than 30%, the above-mentioned holding time is shortened by 5-10 min, but not less than 60 min.

[0018] When the cotton stalk cellulose content is higher than 45%, the holding time is extended by 8-12 min.

[0019] Preferably, the hydrothermal reaction includes three stages.

[0020] The penetration stage, the temperature is increased from room temperature to 120-140℃, the reaction time is 15-25 min, and the pressure is 0.5 MPa.

[0021] The constant temperature stage, the temperature is 180-240℃, the holding time is 70-130 min, and the pressure is 2.5-4.0 MPa.

[0022] The cooling stage, the heating is stopped, and the temperature is reduced to 60℃ at a cooling rate of 15-20℃ / min, the pressure is reduced at a rate of 0.8-1.2 MPa / min, and the time is not more than 30 seconds.

[0023] Preferably, the nitration inhibitor is 0.3-0.6% of the mass of the hydrothermal carbonization product.

[0024] The slow-release agent is 0.1-0.3% of the mass of the hydrothermal carbonization product;

[0025] The acid regulator is 5% of the mass of the hydrothermal carbonization product;

[0026] The structure modifier is 10% of the mass of the hydrothermal carbonization product.

[0027] Preferably, the nitrification inhibitor is dicyandiamide; the acid regulator is vinegar or bamboo vinegar, and the pH value is 2.0-3.5;

[0028] The structure modifier is bentonite or attapulgite powder.

[0029] The interlayer porosity is greater than or equal to 0.40 cm³ / g, and the product after grinding is passed through a 2 mm sieve to obtain the finished product of the seedling substrate.

[0030] Preferably, the specific process for removing fish or / and shrimp waste oil is as follows:

[0031] After the fish or / and shrimp waste is sorted to remove impurities, it is crushed to a particle size of 150-300 μm by a shearing crusher, and then free oil is removed by a screw press to reduce the oil content of the fish or / and shrimp waste to 10-15%;

[0032] Water is added for adjustment, and the water content in the fish or / and shrimp waste slurry is 75-85%.

[0033] Preferably, before wet grinding of the cotton stalks, the cotton stalks are cut to a length of 2-5 cm and soaked in water for 12-24 hours.

[0034] After wet grinding of the cotton stalks, the particle size of the cotton stalks is 200-400 μm.

[0035] Preferably, the process for separating the solid phase and the liquid phase is to open the pressure relief valve to rapidly release the pressure, and the flash steam is recovered by a condenser;

[0036] The solid phase product is dewatered by a plate-and-frame filter press to a water content of 35-45%, and then dried by hot air to a water content of less than or equal to 15% to obtain the hydrothermal carbonization product;

[0037] Preferably, the method for determining the shell content comprises:

[0038] The fish or / and shrimp waste slurry is placed in saturated brine and stirred and allowed to stand, the floating material is the shell component, and the precipitate is the soft tissue, which are respectively dried and weighed to calculate the mass percentage, and the average value is taken by repeating three times, and the determination error is controlled within ±3%.

[0039] The application also provides a seedling substrate obtained based on the process for utilizing waste fish or / and shrimp to produce a seedling substrate and corrosion acid by hydrothermal carbonization of a composite cotton stalk, according to any one of the above.

[0040] The application provides a process for producing fish or / and shrimp waste and cotton stalk composite hydrothermal carbonization co-production of seedling substrate and corrosion acid.

[0041] 1. The process for producing fish or / and shrimp waste and cotton stalk composite hydrothermal carbonization co-production of seedling substrate and corrosion acid provided by the application uses fish or / and shrimp waste and cotton stalk for carbonization together, uses Maillard reaction to inhibit the generation of foul-smelling gas, reduces ammonia volatilization by 75-82%, and makes the workshop environment meet the standards.

[0042] 2. The process for producing fish or / and shrimp waste and cotton stalk composite hydrothermal carbonization co-production of seedling substrate and corrosion acid provided by the application uses cotton stalk to control the pore structure of the product, increases the total porosity by 15-20%, enhances the water holding capacity, uses the bivariate parameter regulation system based on the shell content and the cotton stalk ratio to control the system, the carbon content variation coefficient of the product between batches is less than 7%, the product properties are stable, the process cycle is shortened to 1 / 12 of the traditional composting, the reuse of the hydrothermal reaction liquid reduces the fresh water consumption by 25%, and efficient synergistic resource utilization of fish or / and shrimp waste and cotton stalk is realized.

[0043] 3. The process for producing fish or / and shrimp waste and cotton stalk composite hydrothermal carbonization co-production of seedling substrate and corrosion acid provided by the application limits the insulation time, determines the shell content, crude protein content and cellulose content of the fish or / and shrimp waste slurry, and obtains the mass ratio of the fish or / and shrimp waste slurry and the fiber slurry and the hydrothermal reaction constant temperature time according to the shell content, the crude protein content and the cellulose content of the cotton stalk, so as to ensure the pore structure of the product and the water and fertilizer retention performance of the seedling substrate. DETAILED DESCRIPTION

[0044] The technical solutions of the application will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor belong to the protection scope of the application.

[0045] The process for producing fish or / and shrimp waste and cotton stalk composite hydrothermal carbonization co-production of seedling substrate and corrosion acid provided by the application comprises the following steps:

[0046] S1) removing fish or / and shrimp waste oil, adding water and stirring to obtain fish or / and shrimp waste slurry;

[0047] S2) wet grinding of cotton stalk to obtain fiber slurry;

[0048] S3) Determining the shell content, crude protein content of fish or / and shrimp waste slurry and cellulose content of cotton stalk, and obtaining the mass ratio of fish or / and shrimp waste slurry and fiber slurry and the constant temperature time of hydrothermal reaction according to the shell content, crude protein content and cellulose content of cotton stalk;

[0049] S4) Mixing the fish or / and shrimp waste slurry and fiber slurry, the mass ratio of which is 100: (20-40), and carrying out hydrothermal reaction at 180-240℃, cooling to 60℃, separating the solid phase and liquid phase, dehydrating and drying the solid phase to obtain hydrothermal carbonization product, and condensing and recovering the liquid phase, separating by multi-stage membrane, concentrating to obtain humic acid;

[0050] S5) Mixing the hydrothermal carbonization product, acid regulator and structure modifier, adding nitration inhibitor and slow-release agent, and grinding to obtain the breeding substrate.

[0051] Specifically, the mass ratio of fish or / and shrimp waste slurry and fiber slurry and the constant temperature time of hydrothermal reaction are obtained according to the shell content, crude protein content and cellulose content of cotton stalk, and the specific method is as follows:

[0052] The shell content is 15-25% and the cotton stalk ratio is 20-30%: the holding time is 70-80 min;

[0053] The shell content is 26-40% and the cotton stalk ratio is 25-35%: the holding time is 85-100 min;

[0054] The shell content is 41-55% and the cotton stalk ratio is 30-40%: the holding time is 105-120 min;

[0055] The shell content is 56-70% and the cotton stalk ratio is 35-45%: the holding time is 125-140 min; when the crude protein content is greater than 30%, the above-mentioned holding time is shortened by 5-10 min, but not less than 60 min;

[0056] When the cellulose content of cotton stalk is higher than 45%, the holding time is extended by 8-12 min.

[0057] Specifically, the hydrothermal reaction includes three stages:

[0058] The penetration stage, the temperature is raised from room temperature to 120-140℃, the reaction time is 15-25 min, and the pressure is 0.5 MPa;

[0059] The constant temperature stage, the temperature is 180-240℃, the holding time is 70-130 min, and the pressure is 2.5-4.0 MPa;

[0060] During the cooling phase, heating is stopped, and the temperature drops to 60°C at a rate of 15-20°C / min. The pressure drop rate is controlled at 0.8-1.2 MPa / min, and the time does not exceed 30 seconds.

[0061] Specifically, the nitration inhibitor is 0.3-0.6% of the mass of the hydrothermal carbonization products;

[0062] The slow-release agent is 0.1-0.3% of the mass of the hydrothermal carbonization product;

[0063] The acid regulator is 5% of the mass of the hydrothermal carbonization product;

[0064] The structural modifier is 10% of the mass of the hydrothermal carbonization product.

[0065] Nitrification inhibitor: dicyandiamide; Acidity regulator: wood vinegar or bamboo vinegar, pH 2.0-3.5;

[0066] The structural modifier is bentonite or attapulgite powder.

[0067] The interlayer porosity is ≥0.40cm³ / g. After grinding, the product is passed through a 2mm sieve to obtain the finished seedling substrate.

[0068] Specifically, the process for removing grease from fish and / or shrimp waste is as follows:

[0069] After sorting and removing impurities, fish and / or shrimp waste is crushed to a particle size of 150-300μm by a shear crusher, and then free oil is removed by a screw press, reducing the oil content of fish and / or shrimp waste to 10-15%.

[0070] After adding water, the water content in the fish and / or shrimp waste slurry should be 75-85%.

[0071] Specifically, before wet grinding of cotton stalks, cut the cotton stalks to a length of 2-5cm and soak them in water for 12-24 hours;

[0072] After wet milling, the cotton stalk particle size is 200-400μm.

[0073] Specifically, the process of separating the solid and liquid phases involves opening the pressure relief valve to quickly release the pressure, and the flash vapor is recovered by the condenser.

[0074] The solid product is dehydrated to a moisture content of 35-45% by a plate and frame filter press, and then dried with hot air to a moisture content of ≤15% to obtain the hydrothermal carbonization product.

[0075] Specifically, methods for determining shell content include:

[0076] Fish and / or shrimp waste slurry was placed in saturated brine, stirred, and allowed to stand. The floating matter was the shell material, and the precipitate was the soft tissue. The materials were dried, weighed, and the mass percentage was calculated. The experiment was repeated three times and the average value was taken. The measurement error was controlled within ±3%.

[0077] The present invention also provides a seedling substrate based on the process described in any one of the above-mentioned methods, which utilizes waste fish and / or shrimp composite cotton straw for hydrothermal carbonization to co-produce seedling substrate and corrosive acid.

[0078] The present invention proposes a process for the co-production of seedling substrate and corrosive acid by hydrothermal carbonization of waste fish and / or shrimp combined with cotton stalks. The process utilizes the waste from fish and / or shrimp and cotton stalks for co-carbonization, and uses the Maillard reaction to suppress the generation of malodorous gases, reducing ammonia volatilization by 75-82%, thus ensuring that the workshop environment meets the standards.

[0079] This invention proposes a process for the hydrothermal carbonization of waste fish and / or shrimp combined with cotton stalks to co-produce seedling substrate and corrosive acid. By using cotton stalks to control the pore structure of the product, the total porosity is increased by 15-20%, and the water holding capacity is enhanced. Based on a dual-variable parameter control system of shell content and cotton stalk ratio, the batch-to-batch carbon content variation coefficient is less than 7%, the product properties are stable, the process cycle is shortened to 1 / 12 of traditional composting, and the reuse of hydrothermal reaction liquid reduces fresh water consumption by 25%, thus achieving efficient and synergistic resource utilization of waste fish and shrimp and cotton stalks.

[0080] This invention determines the shell content, crude protein content, and cotton stalk cellulose content of fish or / and shrimp waste slurry by limiting the heat preservation time. Based on the shell content, crude protein content, and cotton stalk cellulose content, the mass ratio of fish or / and shrimp waste slurry to fiber slurry and the hydrothermal reaction isothermal time are obtained to ensure the pore structure of the product and the water and fertilizer retention performance of the seedling substrate.

[0081] Example 1

[0082] The process of using waste fish and / or shrimp combined with cotton straw for hydrothermal carbonization to co-produce seedling substrate and corrosive acid includes the following steps:

[0083] 101) After sorting out plastics, metals and other impurities from fish waste (50 kg, containing fish heads, fish bones and internal organs), crush it to a particle size of 150-300μm using a shear crusher, and then remove free oils using a screw press to reduce the oil content of the fish waste to 10%. After removing the oil from the fish or / and shrimp waste, add water and stir to adjust the moisture content to 80% to obtain fish waste slurry.

[0084] 102) Cut cotton stalks to a length of 2-5cm, soak them in water for 12 hours, and then wet grind the cotton stalks to obtain fiber slurry. The cotton stalk particle size is 200-400μm.

[0085] 103) Determine the shell content, crude protein content, and cotton stalk cellulose content of the fish waste slurry. Based on the shell content, crude protein content, and cotton stalk cellulose content, obtain the mass ratio of fish waste slurry to fiber slurry and the hydrothermal reaction isothermal time. The shell content is 20%, the cellulose content is 38%, and the crude protein content is 20%.

[0086] 104) Mix fish waste slurry and fiber slurry at a mass ratio of 100:30, controlling the total solid-liquid ratio at 1:4. Load the mixture into a 1m³ vertical mixing vessel and purge with nitrogen for 6 minutes. Start the heating program:

[0087] During the permeation phase, the temperature was raised from room temperature to 120°C, the reaction lasted for 15 minutes, and the pressure was 0.5 MPa.

[0088] During the constant temperature stage, the temperature was 180℃, the holding time was 70 minutes, and the pressure was 2.5 MPa.

[0089] During the cooling phase, heating is stopped, and the temperature drops to 60°C at a rate of 15°C / min. The pressure drop rate is controlled at 0.8 MPa / min, and the time does not exceed 30 seconds.

[0090] The solid and liquid phases are separated, the solid phase is dehydrated and dried to obtain hydrothermal carbonization products, the liquid phase is condensed and recovered, and then separated by multi-stage membrane separation and concentration to obtain humic acid.

[0091] 105) Mix the hydrothermal carbonization products, acid regulators, and structure modifiers, add nitrification inhibitors and slow-release agents, grind, and obtain seedling substrate.

[0092] In this embodiment, the nitration inhibitor is 0.3% of the mass of the hydrothermal carbonization product, and the nitration inhibitor is dicyandiamide;

[0093] The slow-release agent is 0.1% of the mass of the hydrothermal carbonization product, and the slow-release agent is polyvinyl alcohol;

[0094] The acidity regulator is 5% of the mass of the hydrothermal carbonization product, and the acidity regulator is wood vinegar with a pH value of 2.0;

[0095] The structural modifier is 10% of the mass of the hydrothermal carbonization product, and the structural modifier is bentonite.

[0096] The interlayer porosity is ≥0.40cm³ / g. After grinding, the product is passed through a 2mm sieve to obtain the finished seedling substrate.

[0097] Specifically, the process for removing grease from fish waste is as follows:

[0098] After adding water to adjust the moisture content, the water content in the fish waste slurry is 75%.

[0099] The process of separating the solid and liquid phases involves opening the pressure relief valve to quickly release the pressure, and the flash vapor is recovered by the condenser.

[0100] The solid product is dehydrated to a moisture content of 35% by a plate and frame filter press, and then dried with hot air to a moisture content of ≤15% to obtain the hydrothermal carbonization product.

[0101] Specifically, methods for determining shell content include:

[0102] Fish waste slurry was placed in saturated brine, stirred, and allowed to stand. The floating matter was the shell component, and the precipitate was the soft tissue. The components were dried, weighed, and the mass percentage was calculated. The process was repeated three times and the average value was taken. The measurement error was controlled within ±3%.

[0103] The performance parameters of the obtained seedling substrate are shown in Table 1.

[0104] In this embodiment, 45 kg of flash steam condensate was collected, filtered through a 200-mesh sieve, and then concentrated using an ultrafiltration membrane (molecular weight cutoff 1000 Da) to obtain 8.2 kg of humic acid concentrate (solid content 12.5%, fulvic acid content 9.1%).

[0105] Workshop environmental monitoring showed that the peak ammonia concentration during the reaction process was 12 mg / m³, which was 77% lower than that of the single fish treatment (control example 1), and no characteristic odor substances such as methanethiol were detected.

[0106] In this embodiment, odor substance detection is performed by gas sampling-gas chromatography to determine the concentrations of characteristic substances such as NH3, methanethiol, and indole.

[0107] The pore structure was determined in this embodiment using a mercury porosimeter and nitrogen adsorption-desorption method to analyze total porosity and pore size distribution.

[0108] The seedling experiment in this embodiment used tomatoes and peppers as test crops to measure germination rate, root length and seedling vigor index.

[0109] Nutrient slow-release property in this embodiment: nitrogen release curve was determined using the soil column leaching method.

[0110] Example 2

[0111] The process of using waste fish and / or shrimp combined with cotton straw for hydrothermal carbonization to co-produce seedling substrate and corrosive acid includes the following steps:

[0112] 201) The whiteleg shrimp (60 kg) was crushed to a particle size of 180-250 μm by a shear crusher, and then free oil was removed by a screw press to reduce the oil content of the shrimp waste to 15%. After removing the oil from the shrimp waste, water was added and stirred to adjust the moisture content to 80% to obtain fish and / or shrimp waste slurry.

[0113] 202) Cut cotton stalks to a length of 2-5cm, soak them in water for 24 hours, and then wet grind the cotton stalks to obtain fiber slurry. The cotton stalk particle size is 200-400μm.

[0114] 203) The shell content, crude protein content, and cotton straw cellulose content of shrimp waste slurry were determined. The mass ratio of shrimp waste slurry to fiber slurry and the hydrothermal reaction isothermal time were obtained based on the shell content, crude protein content, and cotton straw cellulose content. The shell content was 65%, the cellulose content was 45%, and the crude protein content was 22%.

[0115] 204) Mix shrimp waste slurry and fiber slurry at a mass ratio of 100:35, controlling the total solid-liquid ratio at 1:3.5. Pour the mixture into a 1m³ vertical mixing reactor and purge with nitrogen for 6 minutes. Start the heating program:

[0116] During the permeation phase, the temperature was raised from room temperature to 140°C, the reaction lasted for 25 minutes, and the pressure was 0.5 MPa.

[0117] During the constant temperature stage, the temperature was 240℃, the holding time was 135 minutes, and the pressure was 4.0 MPa.

[0118] During the cooling phase, heating is stopped, and the temperature drops to 60°C at a rate of 20°C / min. The pressure drop rate is controlled at 1.2 MPa / min, and the time does not exceed 30 seconds.

[0119] The solid and liquid phases are separated, the solid phase is dehydrated and dried to obtain hydrothermal carbonization products, the liquid phase is condensed and recovered, and then separated by multi-stage membrane separation and concentration to obtain humic acid.

[0120] 205) Mix the hydrothermal carbonization products, acid regulators, and structure modifiers, add nitrification inhibitors and slow-release agents, grind, and obtain seedling substrate.

[0121] The nitration inhibitor is 0.6% of the mass of the hydrothermal carbonization product; the nitration inhibitor is dicyandiamide.

[0122] The slow-release agent is 0.3% of the mass of the hydrothermal carbonization product, and the slow-release agent is polyvinyl alcohol;

[0123] The acidity regulator is 5% of the mass of the hydrothermal carbonization product, and the acidity regulator is bamboo vinegar with a pH value of 3.5;

[0124] The structural modifier is 10% of the mass of the hydrothermal carbonization product, and the structural modifier is attapulgite powder.

[0125] The interlayer porosity is ≥0.40cm³ / g. After grinding, the product is passed through a 2mm sieve to obtain the finished seedling substrate.

[0126] Specifically, the process for removing grease from fish and / or shrimp waste is as follows:

[0127] After adding water to adjust the moisture content, the slurry from fish and / or shrimp waste has a moisture content of 85%.

[0128] Specifically, the process of separating the solid and liquid phases involves opening the pressure relief valve to quickly release the pressure, and the flash vapor is recovered by the condenser.

[0129] The solid product is dehydrated to a moisture content of 45% by a plate and frame filter press, and then dried with hot air to a moisture content of ≤15% to obtain the hydrothermal carbonization product.

[0130] Specifically, methods for determining shell content include:

[0131] Shrimp waste slurry was placed in saturated brine, stirred, and allowed to stand. The floating matter was the shell material, and the precipitate was the soft tissue. The two were dried, weighed, and the mass percentage was calculated. The process was repeated three times and the average value was taken. The measurement error was controlled within ±3%.

[0132] The performance parameters of the obtained seedling substrate are shown in Table 1.

[0133] In this embodiment, 45 kg of flash steam condensate was collected, filtered through a 200-mesh sieve, and then concentrated using an ultrafiltration membrane (molecular weight cutoff of 1000 Da) to obtain 8.9 kg of humic acid concentrate with a free amino acid content of 6.3%.

[0134] Workshop environmental monitoring showed that the peak ammonia concentration during the reaction process was 14 mg / m³, which was 75% lower than that of the single shrimp treatment (control example 2), and no characteristic odor substances such as methanethiol were detected.

[0135] The detection method is the same as in Example 1.

[0136] Example 3

[0137] The process of using waste fish and / or shrimp combined with cotton straw for hydrothermal carbonization to co-produce seedling substrate and corrosive acid includes the following steps:

[0138] 301) After sorting fish (25kg, including fish head, fish bones, and internal organs) and shrimp waste (30kg, whiteleg shrimp) to remove plastic, metal and other impurities, crush them to a particle size of 150-300μm using a shear-type 88-crusher, and then remove free oil using a screw press to reduce the oil content of the fish and shrimp waste to 13%. After removing the oil from the fish and shrimp waste, add water and stir to adjust the moisture content to 80% to obtain fish and shrimp waste slurry.

[0139] 302) Cut cotton stalks to a length of 2-5cm, soak them in water for 20 hours, and then wet grind the cotton stalks to obtain fiber slurry. The cotton stalk particle size is 200-400μm.

[0140] 303) Determine the shell content, crude protein content, and cotton straw cellulose content of fish and shrimp waste slurry. Based on the shell content, crude protein content, and cotton straw cellulose content, obtain the mass ratio of fish and shrimp waste slurry to fiber slurry and the isothermal time of hydrothermal reaction, wherein the shell content is 35%, the cellulose content is 42%, and the crude protein content is 25%.

[0141] With a hull content of 26-40% and a cotton stalk ratio of 25-35%, the heat preservation time is 85-100 minutes.

[0142] 304) Mix fish and shrimp waste slurry and fiber slurry at a mass ratio of 100:30, controlling the total solid-liquid ratio at 1:4. Load the mixture into a 1m³ vertical mixing reactor and purge with nitrogen for 6 minutes. Start the heating program:

[0143] During the permeation phase, the temperature was raised from room temperature to 130°C, the reaction lasted for 20 minutes, and the pressure was 0.5 MPa.

[0144] During the isothermal stage, the temperature was 200℃, the holding time was 90 minutes, and the pressure was 3.0 MPa.

[0145] During the cooling phase, heating is stopped, and the temperature drops to 60°C at a rate of 17°C / min. The pressure drop rate is controlled at 1.0 MPa / min, and the time does not exceed 30 seconds.

[0146] The solid and liquid phases are separated, the solid phase is dehydrated and dried to obtain hydrothermal carbonization products, the liquid phase is condensed and recovered, and then separated by multi-stage membrane separation and concentration to obtain humic acid.

[0147] 205) Mix the hydrothermal carbonization products, acid regulators, and structure modifiers, add nitrification inhibitors and slow-release agents, grind, and obtain seedling substrate.

[0148] Specifically, the nitration inhibitor is 0.5% of the mass of the hydrothermal carbonization products;

[0149] The slow-release agent is 0.2% of the mass of the hydrothermal carbonization product;

[0150] The acid regulator is 5% of the mass of the hydrothermal carbonization product;

[0151] The structural modifier is 10% of the mass of the hydrothermal carbonization product.

[0152] Nitrification inhibitor: dicyandiamide; Acidity regulator: bamboo vinegar, pH 3.5;

[0153] The structural modifier is attapulgite powder.

[0154] The interlayer porosity is ≥0.40cm³ / g. After grinding, the product is passed through a 2mm sieve to obtain the finished seedling substrate.

[0155] Specifically, the process for removing grease from fish and shrimp waste is as follows:

[0156] After adding water to adjust the moisture content, the water content in the fish and shrimp waste slurry is 85%.

[0157] Specifically, the process of separating the solid and liquid phases involves opening the pressure relief valve to quickly release the pressure, and the flash vapor is recovered by the condenser.

[0158] The solid product is dehydrated to a moisture content of 40% by a plate and frame filter press, and then dried with hot air to a moisture content of ≤15% to obtain the hydrothermal carbonization product.

[0159] Specifically, methods for determining shell content include:

[0160] Fish and shrimp waste slurry was placed in saturated brine, stirred, and allowed to stand. The floating matter was the shell material, and the precipitate was the soft tissue. The materials were dried, weighed, and the mass percentage was calculated. The experiment was repeated three times and the average value was taken. The measurement error was controlled within ±3%.

[0161] The performance parameters of the obtained seedling substrate are shown in Table 1.

[0162] In this embodiment, 45 kg of flash steam condensate was collected, filtered through a 200-mesh sieve, and then concentrated using an ultrafiltration membrane (molecular weight cutoff 1000 Da) to obtain 8.5 kg of humic acid concentrate (solid content 12.9%, fulvic acid content 8.9%).

[0163] Workshop environmental monitoring showed that the peak ammonia concentration during the reaction process was 13 mg / m³, and no characteristic odor substances such as methanethiol were detected.

[0164] The detection method is the same as in Example 1.

[0165] Comparative Example 1

[0166] The only difference between this comparative example and Example 1 is that no cotton stalks were added. The parameters of the seedling substrate obtained are shown in Table 1.

[0167] The peak ammonia concentration of the product was 52 mg / m³, and the concentration of methanethiol was detected at 8.5 mg / m³. There was a noticeable odor in the workshop, and the ammonia odor continued to be released during storage.

[0168] Compared with Example 1, Comparative Example 1 lacked cotton stalks, which could not effectively suppress the volatilization of ammonia. The peak concentration of ammonia in the product was 52 mg / m³, and the concentration of methanethiol was detected at 8.5 mg / m³. There was a noticeable odor in the workshop, and the ammonia odor was continuously released during storage. At the same time, the total porosity and water-holding porosity of the obtained seedling substrate were lower than those of Example 1, which could not meet the requirements for use.

[0169] Comparative Example 2

[0170] The only difference between this comparative example and Example 1 is that the heat preservation time is 90 minutes. The obtained seedling substrate parameters are shown in Table 1.

[0171] The peak concentration of ammonia in the product was 56 mg / m³, and the concentration of methanethiol was detected at 9.2 mg / m³. There was a noticeable odor in the workshop, and the ammonia odor continued to be released during storage.

[0172] The difference between this comparative example and Example 1 is that the heat preservation time is 90 minutes, which is longer than that of Example 1. As can be seen from Table 1, the total porosity and water-holding porosity both decreased to some extent, indicating that the heat preservation time is too long, which will affect the total porosity and continuous porosity. This is because the heat preservation time is too long in the high temperature environment, which will lead to excessive carbonization, pore collapse and a decrease in the water and fertilizer retention performance of the seedling substrate, making the product unqualified.

[0173] Comparative Example 3

[0174] The only difference between this comparative example and Example 1 is that the heat preservation time is 60 minutes. The obtained seedling substrate parameters are shown in Table 1.

[0175] The difference between this comparative example and Example 1 is that the heat preservation time is 60 minutes, which is shorter than that of Example 1. As can be seen from Table 1, the total porosity and water-holding porosity both decreased to some extent, indicating that the heat preservation time is too short, which will also affect the total porosity and continuous porosity. Insufficient heat preservation time will prevent the effective formation of pores and reduce the water and fertilizer retention performance of the seedling substrate, thus failing to meet the usage requirements.

[0176] Table 1 Performance parameters of seedling substrate

[0177]

[0178] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A process for co-producing seedling substrate and corrosive acid by hydrothermal carbonization of waste fish and / or shrimp composite cotton straw, characterized in that: Includes the following steps: Remove the grease from the fish and / or shrimp waste, add water and stir to obtain a fish and / or shrimp waste slurry; Cotton stalks are wet-milled to obtain fiber pulp; The shell content, crude protein content, and cotton straw cellulose content of fish or / and shrimp waste slurry were determined. Based on the shell content, crude protein content, and cotton straw cellulose content, the mass ratio of fish or / and shrimp waste slurry to fiber slurry and the hydrothermal reaction isothermal time were obtained. Fish and / or shrimp waste slurry and fiber slurry are mixed at a mass ratio of 100:(20-40). The mixture is subjected to a hydrothermal reaction at 180-240℃, cooled to 60℃, and the solid and liquid phases are separated. The solid phase is dehydrated and dried to obtain hydrothermal carbonization products. The liquid phase is condensed and recovered, separated by multi-stage membrane separation, and concentrated to obtain humic acid. The hydrothermal carbonization products, acid regulators, and structure modifiers are mixed, and nitrification inhibitors and slow-release agents are added. The mixture is then ground to obtain the seedling substrate.

2. The process for co-producing seedling substrate and corrosive acid by hydrothermal carbonization of waste fish and / or shrimp composite cotton straw according to claim 1, characterized in that: The specific method for determining the mass ratio of fish or / and shrimp waste slurry to fiber slurry and the hydrothermal reaction isothermal time based on shell content, crude protein content, and cotton straw cellulose content is as follows: With a hull content of 15-25% and a cotton stalk ratio of 20-30%, the heat preservation time is 70-80 minutes. With a hull content of 26-40% and a cotton stalk ratio of 25-35%, the heat preservation time is 85-100 minutes. With a hull content of 41-55% and a cotton stalk ratio of 30-40%, the heat preservation time is 105-120 minutes. With a hull content of 56-70% and a cotton stalk ratio of 35-45%, the heat preservation time is 125-140 minutes. When the crude protein content is greater than 30%, the corresponding heat preservation time should be shortened by 5-10 minutes, but not less than 60 minutes; When the cellulose content of cotton stalks is higher than 45%, the heat preservation time should be extended by 8-12 minutes.

3. The process for co-producing seedling substrate and corrosive acid by hydrothermal carbonization of waste fish and / or shrimp composite cotton straw according to claim 1, characterized in that: The hydrothermal reaction consists of three stages: During the permeation phase, the temperature is raised from room temperature to 120-140℃, the reaction time is 15-25 minutes, and the pressure is 0.5 MPa. During the constant temperature stage, the temperature is 180-240℃, the holding time is 70-130min, and the pressure is 2.5-4.0MPa. During the cooling phase, heating is stopped, and the temperature drops to 60°C at a rate of 15-20°C / min. The pressure drop rate is controlled at 0.8-1.2 MPa / min, and the time does not exceed 30 seconds.

4. The process for co-producing seedling substrate and corrosive acid by hydrothermal carbonization of waste fish and / or shrimp composite cotton straw according to claim 1, characterized in that: The nitration inhibitor is 0.3-0.6% of the mass of the hydrothermal carbonization products; The slow-release agent is 0.1-0.3% of the mass of the hydrothermal carbonization product; The acid regulator is 5% of the mass of the hydrothermal carbonization product; The structural modifier is 10% of the mass of the hydrothermal carbonization product.

5. The process for co-producing seedling substrate and corrosive acid by hydrothermal carbonization of waste fish and / or shrimp composite cotton straw according to claim 1, characterized in that: Nitrification inhibitor: dicyandiamide; Acidity regulator: wood vinegar or bamboo vinegar, pH 2.0-3.5; The structural modifier is bentonite or attapulgite powder; The interlayer porosity is ≥0.40cm³ / g. After grinding, the product is passed through a 2mm sieve to obtain the finished seedling substrate.

6. The process for co-producing seedling substrate and corrosive acid by hydrothermal carbonization of waste fish and / or shrimp composite cotton straw according to claim 1, characterized in that: The specific process for removing grease from fish and / or shrimp waste is as follows: After sorting and removing impurities, fish and / or shrimp waste is crushed to a particle size of 150-300μm by a shear crusher, and then free oil is removed by a screw press, reducing the oil content of fish and / or shrimp waste to 10-15%. After adding water, the water content in the fish and / or shrimp waste slurry should be 75-85%.

7. The process for co-producing seedling substrate and corrosive acid by hydrothermal carbonization of waste fish and / or shrimp composite cotton straw according to claim 1, characterized in that: Before wet grinding of cotton stalks, cut the cotton stalks to a length of 2-5cm and soak them in water for 12-24 hours; After wet milling, the cotton stalk particle size is 200-400μm.

8. The process for co-producing seedling substrate and corrosive acid by hydrothermal carbonization of waste fish and / or shrimp composite cotton straw according to claim 1, characterized in that: The process of separating the solid and liquid phases involves opening the pressure relief valve to quickly release the pressure, and the flash vapor is recovered by the condenser. The solid product is dehydrated to a moisture content of 35-45% by a plate and frame filter press, and then dried with hot air to a moisture content of ≤15% to obtain the hydrothermal carbonization product.

9. The process for co-producing seedling substrate and corrosive acid by hydrothermal carbonization of waste fish and / or shrimp composite cotton straw according to claim 1, characterized in that: Methods for determining shell content include: Fish and / or shrimp waste slurry was placed in saturated brine, stirred, and allowed to stand. The floating matter was the shell material, and the precipitate was the soft tissue. The materials were dried, weighed, and the mass percentage was calculated. The experiment was repeated three times and the average value was taken. The measurement error was controlled within ±3%.

10. A seedling substrate obtained by a process based on any one of claims 1-9, which utilizes waste fish and / or shrimp composite cotton straw for hydrothermal carbonization to co-produce seedling substrate and corrosive acid.

Images