A method for preparing an active soil conditioner using metallurgical solid waste

Abstract

The application discloses a method for preparing active soil conditioner by using metallurgical solid wastes, which is prepared from steel slag, pickling sludge, desulfurization gypsum, blast furnace bag dust and dephosphorization ash as raw materials through crushing, oxidation stabilization, composite activation and granulation modification. The heavy metals are stabilized by calcium peroxide and ultrasonic oxidation, and the soil repair effect is improved by combining humic acid and functional microbial agent. The conditioner is suitable for heavy metal pollution and acidification soil repair, and has the characteristics of high solid waste resource utilization rate, low process energy consumption, environmental friendliness and the like. The process steps include raw material pretreatment, oxidation stabilization, composite activation and granulation modification, and the parameters of each step are accurately controlled to guarantee the comprehensive performance of the conditioner.

Description

Technical Field

[0001] This invention relates to the field of metallurgical solid waste resource utilization and soil remediation technology, specifically to a method for preparing an active soil conditioner using metallurgical solid waste. Background Technology

[0002] Metallurgical industry processes generate a large amount of solid waste, of which steel slag has a utilization rate of less than 30%, pickling sludge contains heavy metals and acidic substances, and desulfurization gypsum accumulation can easily cause dust pollution. Traditional treatment methods for these solid wastes include landfilling and cement mixing, which not only pose the possibility of secondary pollution but also result in low added value of the products.

[0003] Existing soil conditioner technologies have significant shortcomings: single solid waste utilization: for example, patent CN201810617360.4 only uses steel slag desulfurization byproducts, and does not achieve the synergistic treatment of multiple solid wastes; High energy consumption: For example, high-temperature calcination processes (>800℃) lead to increased CO2 emissions and destroy the active ingredients in solid waste; Functional limitations: Existing improvers mostly focus on pH adjustment or nutrient supplementation, and are insufficient in their ability to passivate heavy metals and regulate microbial communities. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing an active soil conditioner using metallurgical solid waste, addressing the shortcomings mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the technical solution provided by the present invention is: a method for preparing an active soil conditioner using metallurgical solid waste, comprising the following process steps: (1) Raw material pretreatment: Steel slag, pickling sludge, desulfurization gypsum, blast furnace bag filter dust and dephosphorization ash are mixed in a mass ratio of 3-5:2-4:1-3:1-2:0.5-1.5 and crushed to a particle size ≤2mm; (2) Oxidative stabilization: Add 5-8% by weight of calcium peroxide to the mixed solid waste obtained in step (1), adjust the pH of the mixed system to 7.5-8.5, stir the reaction for 2-4 hours, and control the reaction temperature to 40-60℃; (3) Composite activation: Add 10-15% of humic acid, 1-3% of diatomaceous earth and 0.5-2% of composite microbial agent by total mass of solid waste to the product obtained in step (2), wherein the composite microbial agent contains phosphate-solubilizing bacteria (Bacillus megaterium) and heavy metal-resistant bacteria (Pseudomonas putida), and activate at 50-70℃ for 6-8 hours; (4) Granulation modification: The activated product obtained in step (3) is mixed with 5-10% of binder and granulated. The binder is sodium carboxymethyl cellulose or polyacrylamide. After granulation, the particle size is controlled at 1-4 mm and dried until the moisture content is ≤5% to obtain the soil conditioner.

[0006] Furthermore, the steel slag is converter steel slag, and after magnetic separation to remove metal impurities, the Fe2O3 content is ≥30%; the pickling sludge needs to be dewatered to a moisture content ≤40%, and the heavy metal content must meet the requirements of Pb≤200mg / kg and Cd≤5mg / kg.

[0007] Furthermore, the number of viable phosphate-solubilizing bacteria in the compound microbial agent is ≥1×10⁻⁶. 8 CFU / g; The heavy metal resistant bacteria are genetically engineered to tolerate concentrations of Cd ≥100 mg / L and Cr ≥200 mg / L.

[0008] Furthermore, in the oxidation stabilization process of step (2), an ultrasonic-assisted reaction is used, with an ultrasonic frequency of 20-40kHz and an ultrasonic power of 200-400W.

[0009] Furthermore, the application method of the soil conditioner is as follows: for soils contaminated with heavy metals, apply 200-500 kg per acre, and mix it with the topsoil to a depth of ≥30 cm; for acidic soils, apply 1-2% sulfur powder to adjust the soil pH to 6.0-7.0.

[0010] With the above structure, the present invention has the following advantages: Detailed Implementation

[0011] The present invention will now be described in further detail.

[0012] This invention provides a low-cost, low-environmental-impact method for the resource utilization of metallurgical solid waste. Through the synergistic formulation and composite activation process of various solid wastes, a soil conditioner with functions of heavy metal passivation, nutrient slow release, and microbial activation is prepared. The specific technical solution is as follows: I. Core Technology Design Complementary combination of multiple solid waste functions: Steel slag provides Fe 3+ Ca 2+ It can react with SO4 in pickling sludge. 2- The reaction produces ettringite (3CaO·Al2O3·3CaSO4·32H2O), achieving the solidification of heavy metals; desulfurized gypsum (CaSO4·2H2O) and dephosphorizing ash (Ca5(PO4)3OH) work together to release Ca 2+ and PO4 3-This promotes the formation of soil aggregates while reducing the bioavailability of heavy metals; blast furnace baghouse dust (Fe2O3 content ≥40%) adsorbs As through surface hydroxyl adsorption. 3+ Cd 2+ It combines with humic acid to form a stable complex.

[0013] Oxidation-microbial synergistic activation: Calcium peroxide (CaO2) releases O2 and OH under acidic conditions. - It can remove As from pickling sludge 3+ Oxidized into less toxic As 5+ At the same time, it inhibits the release of hydrogen sulfide; heavy metal tolerant bacteria can secrete extracellular polymers (EPS) to encapsulate heavy metal ions, and phosphate-solubilizing bacteria can release organic acids to dissolve insoluble phosphorus, thereby increasing the content of available nutrients in the soil.

[0014] Low-temperature and high-efficiency process design: The ultrasonic-assisted oxidation method reduces energy consumption by 50% compared to traditional processes; the microbial activation process adopts medium-temperature conditions to avoid damage to the activity of the microbial agent by high temperature, and the temperature of the entire process is controlled at ≤70℃.

[0015] II. Process Steps Raw material pretreatment: Steel slag, pickling sludge, desulfurization gypsum, blast furnace bag filter dust, and dephosphorization ash are mixed in a mass ratio of 3-5:2-4:1-3:1-2:0.5-1.5 and crushed to a particle size ≤2mm. The steel slag used is converter steel slag, which, after magnetic separation to remove metallic impurities, has an Fe2O3 content ≥30%. The pickling sludge needs to be dewatered to a moisture content ≤40%, and the heavy metal content must meet the requirements of Pb ≤200mg / kg and Cd ≤5mg / kg.

[0016] Oxidative stabilization: Add 5-8% calcium peroxide to the mixed solid waste, adjust the pH of the mixture to 7.5-8.5, stir the reaction for 2-4 hours, and control the temperature at 40-60℃. Ultrasonic-assisted reaction (frequency 20-40kHz, power 200-400W) is used in this step to accelerate the conversion of heavy metals from their oxidized state to a stable state, while simultaneously promoting hydroxylation of the solid waste particles and enhancing their adsorption performance.

[0017] Compound activation: Add 10-15% humic acid, 1-3% diatomaceous earth, and 0.5-2% compound microbial agent (containing phosphate-solubilizing bacteria Bacillus megaterium and heavy metal-tolerant bacteria Pseudomonas putida) by weight of the total solid waste, and activate at 50-70℃ for 6-8 hours. The viable count of phosphate-solubilizing bacteria in the compound microbial agent should be ≥1×10⁻⁶. 8 CFU / g, heavy metal resistant bacteria are genetically engineered to tolerate Cd and Cr concentrations ≥100mg / L and 200mg / L, respectively.

[0018] Granulation modification: Mix the activated product with 5-10% of binder (sodium carboxymethyl cellulose or polyacrylamide) and granulate, controlling the particle size to 1-4 mm, and dry to a moisture content of ≤5%.

[0019] III. Application Method For soil contaminated with heavy metals, apply 200-500 kg per acre and mix it with the topsoil to a depth of ≥30 cm; for acidic soil, it is necessary to adjust the pH to 6.0-7.0 with 1-2% sulfur powder.

[0020] Example Example 1 Raw material pretreatment: Steel slag, pickling sludge, desulfurization gypsum, blast furnace bag filter dust and dephosphorization ash are mixed in a mass ratio of 3:2:1:1:0.5 and crushed to a particle size ≤2mm; Oxidative stabilization: Add 5% calcium peroxide to the mixed solid waste, adjust the pH of the mixed system to 7.5, stir the reaction for 2 hours, and control the temperature at 40℃; Composite activation: Add 10% humic acid, 1% diatomaceous earth and 0.5% compound microbial agent of the total mass of solid waste, and activate at 50℃ for 6 hours; Granulation modification: The activated product is mixed with 5% binder (sodium carboxymethyl cellulose) and granulated, with the particle size controlled at 1-4 mm, and dried until the moisture content is ≤5%.

[0021] Example 2 Raw material pretreatment: Steel slag, pickling sludge, desulfurization gypsum, blast furnace bag filter dust, and dephosphorization ash are mixed in a mass ratio of 5:4:3:2:1.5 and crushed to a particle size ≤2mm; Oxidative stabilization: Add 8% calcium peroxide to the mixed solid waste, adjust the pH of the mixed system to 8.5, stir the reaction for 4 hours, and control the temperature at 60℃; Composite activation: Add 15% humic acid, 3% diatomaceous earth and 2% compound microbial agent by weight of solid waste, and activate at 70°C for 8 hours; Granulation modification: The activated product is mixed with 10% binder (polyacrylamide) and granulated, with the particle size controlled at 1-4 mm, and dried until the moisture content is ≤5%.

[0022] Example 3 Raw material pretreatment: Steel slag, pickling sludge, desulfurization gypsum, blast furnace bag filter dust, and dephosphorization ash are mixed in a mass ratio of 4:3:2:1.2:1 and crushed to a particle size ≤2mm; Oxidative stabilization: Add 7% calcium peroxide to the mixed solid waste, adjust the pH of the mixed system to 8, stir the reaction for 3 hours, and control the temperature at 50℃; Composite activation: Add 13% humic acid, 2% diatomaceous earth and 1% compound microbial agent by weight of solid waste, and activate at 60℃ for 7 hours; Granulation modification: The activated product is mixed with 8% binder (sodium carboxymethyl cellulose) and granulated, with the particle size controlled at 1-4 mm, and dried until the moisture content is ≤5%.

[0023] The present invention and its embodiments have been described above. This description is not restrictive, and the actual structure is not limited thereto. In conclusion, if those skilled in the art, inspired by this description, design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the scope of protection of this invention.

Claims

1. A method for preparing an active soil conditioner using metallurgical solid waste, characterized in that: The process includes the following steps: (1) Raw material pretreatment: Steel slag, pickling sludge, desulfurization gypsum, blast furnace bag filter dust and dephosphorization ash are mixed in a mass ratio of 3-5:2-4:1-3:1-2:0.5-1.5 and crushed to a particle size ≤2mm; (2) Oxidative stabilization: Add 5-8% by weight of calcium peroxide to the mixed solid waste obtained in step (1), adjust the pH of the mixed system to 7.5-8.5, stir the reaction for 2-4 hours, and control the reaction temperature to 40-60℃; (3) Composite activation: Add 10-15% of humic acid, 1-3% of diatomaceous earth and 0.5-2% of composite microbial agent by total mass of solid waste to the product obtained in step (2), wherein the composite microbial agent contains phosphate-solubilizing bacteria (Bacillus megaterium) and heavy metal-resistant bacteria (Pseudomonas putida), and activate at 50-70℃ for 6-8 hours; (4) Granulation modification: The activated product obtained in step (3) is mixed with 5-10% of binder and granulated. The binder is sodium carboxymethyl cellulose or polyacrylamide. After granulation, the particle size is controlled at 1-4 mm and dried until the moisture content is ≤5% to obtain the soil conditioner.

2. The method for preparing an active soil conditioner using metallurgical solid waste according to claim 1, characterized in that: The steel slag is converter steel slag, and after magnetic separation to remove metal impurities, the Fe2O3 content is ≥30%; the pickling sludge needs to be dewatered to a moisture content ≤40%, and the heavy metal content must meet the requirements of Pb≤200mg / kg and Cd≤5mg / kg.

3. The method for preparing an active soil conditioner using metallurgical solid waste according to claim 1, characterized in that: The number of viable phosphate-solubilizing bacteria in the compound microbial agent is ≥1×10⁻⁶. 8 CFU / g; The heavy metal resistant bacteria are genetically engineered to tolerate concentrations of Cd ≥100 mg / L and Cr ≥200 mg / L.

4. The method for preparing an active soil conditioner using metallurgical solid waste according to claim 1, characterized in that: In step (2), the oxidation stabilization process is carried out with ultrasonic-assisted reaction, with an ultrasonic frequency of 20-40kHz and an ultrasonic power of 200-400W.

5. The method for preparing an active soil conditioner using metallurgical solid waste according to claim 1, characterized in that: The application method of the soil conditioner is as follows: for soils contaminated with heavy metals, apply 200-500 kg per mu, and mix it with the topsoil to a depth of ≥30 cm; for acidic soils, apply 1-2% sulfur powder to adjust the soil pH to 6.0-7.0.