A method for producing soil conditioner by electric furnace method from high-phosphorus and high-magnesium flotation phosphorus tailings

Abstract

The application belongs to the technical field of soil conditioner preparation, and particularly relates to a method for producing soil conditioner by using high-phosphorus and high-magnesium floatation phosphorus tailings and an electric furnace method, wherein the method for producing soil conditioner by using high-phosphorus and high-magnesium floatation phosphorus tailings and the electric furnace method are developed, the powder ore can be made into pellets, and the utilization rate of the powder ore is improved; high-temperature melting is used to realize efficient activation of phosphorus, magnesium, calcium, silicon and other nutrient elements in the tailings, and a soil conditioner product capable of supplementing trace elements and improving soil aggregate structure is prepared, which not only can realize high-value utilization of the phosphorus tailings, effectively solve the soil acidification treatment demand, and has important practical significance for promoting resource utilization of the phosphorus tailings.

Description

Technical Field

[0001] This invention belongs to the field of soil conditioner preparation technology, specifically relating to a method for producing soil conditioners using an electric furnace method with high phosphorus and high magnesium flotation phosphorus tailings. Background Technology

[0002] Soil acidification has become one of the most significant obstacles to soil productivity in southern arable land. Soil acidification not only leads to the loss of exchangeable calcium and magnesium but also inhibits crop absorption of these nutrients, resulting in decreased crop yield and quality. Therefore, targeted soil improvement technologies and products are urgently needed. High-phosphorus and high-magnesium flotation tailings are a typical product after secondary separation of flotation tailings. Besides phosphorus, their main components are calcium and magnesium carbonates and silica compounds. Their composition closely matches the needs of acidic soil conditioning, providing a material basis for the preparation of soil conditioners.

[0003] Existing technologies for the resource utilization of phosphorus tailings cover areas such as backfill materials, building materials, phosphorus recovery through reprocessing, calcium and magnesium recovery through chemical methods, and the production of fertilizers and soil conditioners. In the area of ​​soil conditioner preparation, the low-temperature calcination process for phosphorus tailings suffers from limited nutrient activation efficiency. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for producing soil conditioners using an electric furnace process from high-phosphorus and high-magnesium flotation tailings.

[0005] A method for producing soil conditioner from high-phosphorus and high-magnesium flotation tailings using an electric furnace includes the following steps: The flotation tailings powder, medium and low grade phosphate rock powder, silicate flux and binder are mixed in a mass ratio of 70~100:5~20:20~35:3~15 and then pressed into ellipsoids to obtain wet balls. The wet balls are then dried to obtain ore-blended pellets. The ore pellets are melted at 1400~1600℃ for 5~30 minutes to obtain the molten material; The molten material is quenched in water, and after quenching, it is drained, dried, and ground to obtain a powdered product. The powdered product, granulation aid, and functional soil conditioner are mixed, granulated, and dried to obtain the soil conditioner.

[0006] This invention pelletizes ore powder, improving its utilization rate. High-temperature melting efficiently activates nutrients such as phosphorus, magnesium, calcium, and silicon in tailings. If the melting temperature is below 1350℃, the material cannot form a melt flow, and some material adheres to the crucible or remains in powder form, making it impossible to obtain a vitreous material after water quenching. Excessively high melting temperatures (above 1600℃) not only increase energy consumption but also lead to phosphorus volatilization and loss, reducing the effective phosphorus content and activation rate. A melting time of less than 5 minutes prevents sufficient melting and reaction, resulting in a low phosphorus activation rate. Increasing the melting time to more than 30 minutes not only increases energy consumption but also leads to phosphorus volatilization and loss, further reducing the effective phosphorus content. Ultimately, this invention produces a soil conditioner product that supplements micronutrients and improves soil aggregate structure.

[0007] Preferably, the binder is one or more of the following: residual raffinate acid, sludge acid, 1% to 2% sodium carboxymethyl cellulose solution, 3% to 5% calcium lignosulfonate solution, and 1% to 1.5% hydroxypropyl methylcellulose.

[0008] Preferably, the granulation aid is two or more of bentonite, attapulgite, sepiolite, diatomite, and montmorillonite.

[0009] Preferably, the functional soil conditioner is one or more of humic acid solution, amino acid solution, alginate solution, and polyacrylamide solution.

[0010] Preferably, the concentration of the humic acid solution is 5% to 15% by mass, the concentration of the amino acid solution is 10% to 20% by mass, the concentration of the alginate solution is 0.3% to 1% by mass, and the concentration of the polyacrylamide solution is 0.3% to 1% by mass.

[0011] Preferably, the mass ratio of the flotation phosphorus tailings powder, granulation aid, and functional soil conditioner is 70~100:1~10:3~10.

[0012] Preferably, the pressing pressure is 8 MPa to 30 MPa.

[0013] Preferably, the particle size of the low-grade phosphorus is ≤1mm; the particle size of the silicate flux is ≤1mm.

[0014] The soil conditioner prepared by the method described above.

[0015] The application of the soil conditioner in alleviating soil acidification.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: Existing technologies such as phosphorus recovery through re-selection and calcium and magnesium recovery through chemical methods suffer from certain disposal costs, low overall technical levels, and poor sustainability. In the preparation of soil conditioners, the low-temperature calcination process in phosphorus tailings has limited nutrient activation efficiency; the blast furnace activation method for phosphorus ore typically uses lump ore, and the crushing process results in the waste of fine ore. This invention develops a method for preparing soil conditioners using an electric furnace after blending and pelletizing high-phosphorus and high-magnesium flotation phosphorus tailings. This method can form fine ore into pellets, improving the utilization rate of fine ore. Through high-temperature melting, the efficient activation of nutrients such as phosphorus, magnesium, calcium, and silicon in the tailings is achieved, producing a soil conditioner product that can supplement micronutrients and improve soil aggregate structure. This not only realizes the high-value utilization of phosphorus tailings and effectively addresses the needs of soil acidification remediation, but also has significant practical implications for promoting the large-scale disposal of phosphorus tailings and building a resource recycling system of "solid waste utilization - soil improvement".

[0017] In the preparation of soil conditioners, existing technologies still use the blast furnace method for phosphate rock. However, the activation of phosphate rock in the blast furnace method has problems such as waste of ore powder and reduction of effective phosphorus content due to phosphorus volatilization. The electric furnace method of this invention does not require the use of solid fuels such as coke and coal, thus avoiding the interference of fuel ash on material batching from the source and ensuring the stability of product composition. The operation process is simple, and for the same grade of phosphate rock raw materials, the effective P2O5 content in the product is higher than that of the blast furnace method. The unit product production cost (mainly including raw materials, energy consumption and manufacturing costs) is lower than that of the blast furnace method. Detailed Implementation

[0018] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are conventional methods.

[0019] In this invention, the high-phosphorus and high-magnesium flotation tailings contain 10-15 wt% P2O5, 30-36 wt% CaO, 12-15 wt% MgO, and 6-10 wt% SiO2.

[0020] The content of P2O5 in medium- and low-grade high-silica phosphate rock is 20-26 wt%, CaO content is 30-35 wt%, MgO content is 0.5-2 wt%, and SiO2 content is 30-35 wt%.

[0021] A method for producing soil conditioner using high-phosphorus and high-magnesium flotation phosphate tailings as raw material via electric furnace process includes the following steps: Raw material pretreatment: Dry the high-phosphorus and high-magnesium flotation tailings to a moisture content of <1%, then grind and sieve for later use; crush the medium and low-grade phosphate ore to a particle size of ≤1mm; crush and sieve the silicate flux to obtain powder with a particle size of ≤1mm for later use. Ore blending: The pretreated flotation tailings powder, medium and low grade phosphate rock powder and silicate flux are blended in a mass ratio of 70~100:5~20:20~35 and mixed evenly for later use. Pelletizing process: After adding a binder to the above ingredients, they are put into a briquetting machine and pressed into ellipsoids at 8Mpa~30Mpa. The binder introduces a certain amount of moisture. During the pelletizing process, some ungranulated powdery material will be generated. The powder is returned to the mixer to obtain wet pellets. The wet pellets are dried to obtain ore-blended pellets.

[0022] High-temperature melting treatment in electric furnace: The dried ore pellets are placed in a high-temperature electric furnace and melted at 1400~1600℃ for 5~30 minutes to prepare molten material; Water quenching, drying and grinding process: The molten material is subjected to high-pressure water jet for rapid cooling and water quenching. The water-quenched glass material is then drained, dried and ground to obtain a powdered product. Granulation process: The obtained powdered product is granulated with granulation aids and functional soil conditioner, and then granulated in a granulator. The powder is returned to the mixer, and the granulated product is dried to obtain granular soil conditioner product.

[0023] Example 1 A method for preparing a soil conditioner includes the following steps: Raw material pretreatment: Dry the high-phosphorus and high-magnesium flotation tailings to a moisture content of <1%, then grind and sieve for later use; crush the medium and low-grade phosphate ore to a particle size of ≤1mm; crush and sieve the silicate flux to obtain powder with a particle size of ≤1mm for later use. Raw materials weighed: 80g of flotation phosphate tailings powder, 20g of medium-low grade phosphate rock powder, 20g of silicate flux, 12g of residual raffinate, 6g of bentonite and 7g of humic acid solution with a concentration of 10%.

[0024] Ore blending: Weigh out the pretreated flotation tailings powder, medium and low grade phosphate rock powder, and silicate flux and mix them evenly for later use. Pelletizing process: After adding residual raffinate to the above ingredients, they are added to a pelletizing machine and pressed into ellipsoids. The powder is returned to the mixer to obtain wet pellets. The wet pellets are dried to obtain ore pellets.

[0025] High-temperature melting treatment in electric furnace: The dried ore pellets are placed in a high-temperature electric furnace and melted at 1450℃ for 10 minutes to prepare molten material; Water quenching, drying and grinding process: The molten material is quenched in water, and the quenched glass material is drained, dried and ground to obtain a powdered product. Granulation process: The obtained powdered product is added to bentonite and humic acid solution, and then granulated in a granulator. The powder is returned to the mixer, and the granulated product is dried to obtain granular soil conditioner.

[0026] The active ingredients in the powdered product are: P2O5 12.8%, CaO 33.7%, MgO 12.5%, and SiO2 35.0%.

[0027] The activation rates of the elements in the powdered product were determined as follows: phosphorus activation rate was 98.7%, calcium activation rate was 96.5%, magnesium activation rate was 93.8%, and silicon activation rate was 85.4%.

[0028] The main components of granular soil conditioner are: P2O5 11.3%, CaO 31.7%, MgO 10.8%, and SiO2 31.6%.

[0029] Example 2 A method for preparing a soil conditioner includes the following steps: Raw material pretreatment: Dry the high-phosphorus and high-magnesium flotation tailings to a moisture content of <1%, then grind and sieve for later use; crush the medium and low-grade phosphate ore to a particle size of ≤1mm; crush and sieve the silicate flux to obtain powder with a particle size of ≤1mm for later use. Raw materials weighed: 90g of flotation phosphate tailings powder, 10g of medium-low grade phosphate rock powder, 30g of silicate flux, 8g of sludge acid, 5g of attapulgite clay and 6g of amino acid solution with a concentration of 15%.

[0030] Ore blending: Weigh out the pretreated flotation tailings powder, medium and low grade phosphate rock powder, and silicate flux and mix them evenly for later use. Pelletizing process: The above ingredients are added with sludge acid and then put into a briquetting machine to be pressed into ellipsoids. The powder is returned to the mixer to obtain wet pellets. The wet pellets are dried to obtain ore pellets.

[0031] High-temperature melting treatment in electric furnace: The dried ore pellets are placed in a high-temperature electric furnace and melted at 1475℃ for 5 minutes to prepare molten material; Water quenching, drying and grinding process: The molten material is quenched in water, and the quenched glass material is drained, dried and ground to obtain a powdered product. Granulation process: Add attapulgite clay and amino acid liquid to the obtained powdered product, granulate it in a granulator, return the powder to the mixer, and dry the granulated product to obtain granular soil conditioner.

[0032] The active ingredients in the powdered product are: P2O5 12.4%, CaO 31.5%, MgO 12.0%, and SiO2 34.2%.

[0033] The activation rates of the elements in the powdered product were determined as follows: phosphorus activation rate was 95.8%, calcium activation rate was 93.7%, magnesium activation rate was 92.7%, and silicon activation rate was 81.5%.

[0034] The main components of granular soil conditioner are: P2O5 10.7%, CaO 28.5%, MgO 10.2%, and SiO2 32.8%.

[0035] Example 3 A method for preparing a soil conditioner includes the following steps: Raw material pretreatment: Dry the high-phosphorus and high-magnesium flotation tailings to a moisture content of <1%, then grind and sieve for later use; crush the medium and low-grade phosphate ore to a particle size of ≤1mm; crush and sieve the silicate flux to obtain powder with a particle size of ≤1mm for later use. Raw materials weighed: 95g of flotation phosphate tailings powder, 5g of medium-low grade phosphate rock powder, 35g of silicate flux, 9g of sodium carboxymethyl cellulose solution, 6g of sepiolite and 8g of alginate solution, with a concentration of 0.7% by mass and a concentration of 1% by mass for sodium carboxymethyl cellulose solution.

[0036] Ore blending: Weigh out the pretreated flotation tailings powder, medium and low grade phosphate rock powder, and silicate flux and mix them evenly for later use. Pelletizing process: After adding sodium carboxymethyl cellulose solution to the above ingredients, they are added to a pelletizing machine and pressed into ellipsoids. The powder is returned to the mixer to obtain wet pellets. The wet pellets are then dried to obtain ore pellets.

[0037] High-temperature melting treatment in electric furnace: The dried ore pellets are placed in a high-temperature electric furnace and melted at 1550℃ for 20 minutes to prepare molten material; Water quenching, drying and grinding process: The molten material is quenched in water, and the quenched glass material is drained, dried and ground to obtain a powdered product. Granulation process: The obtained powdered product is added with sepiolite and alginate solution, and then granulated in a granulator. The powder is returned to the mixer, and the granulated product is dried to obtain granular soil conditioner.

[0038] The active ingredients of the powdered product are: P2O5 11.6%, CaO 32.8%, MgO 13.0%, and SiO2 32.3%.

[0039] The activation rates of the elements in the powdered product were determined as follows: phosphorus activation rate was 96.5%, calcium activation rate was 96.4%, magnesium activation rate was 97.8%, and silicon activation rate was 83.6%.

[0040] The main components of granular soil conditioner are: P2O 59.5%, CaO 29.4%, MgO 11.2%, and SiO 28.7%.

[0041] The purpose of this invention is to efficiently activate phosphorus, magnesium, calcium and silicon elements in phosphate rock. The activation rates of the powdered product are: phosphorus activation rate ≥95%, calcium activation rate 90%~98%, magnesium activation rate 90%~99%, and silicon activation rate ≥80%.

[0042] The active ingredients in the powdered product are: P2O5 11%–13%, CaO 30%–34%, MgO 12%–13%, and SiO2 30%–35%.

[0043] The main components of the prepared granular soil conditioner are: P2O 59%~12%, CaO 24%~32%, MgO 9%~12%, and SiO2 24%~33%.

[0044] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the melting temperature is 1000°C.

[0045] Analysis of the molten material showed that the activation rates of phosphorus (79.2%), calcium (81.0%), magnesium (83.8%), and silicon (0%) were lower than those in Example 1.

[0046] If the melting temperature is less than 1350℃, the material cannot form a melt flow due to the low melting temperature. Some of the material will stick in the crucible or remain in the form of powder, and cannot be obtained as a glassy material after water quenching.

[0047] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the melting temperature is 1600°C.

[0048] The active ingredients in the powdered product are: P2O5 12.0%, CaO 32.5%, MgO 12.1%, and SiO2 35.3%.

[0049] The activation rates of the elements in the powdered product were determined as follows: phosphorus activation rate was 96.3%, calcium activation rate was 95.6%, magnesium activation rate was 92.8%, and silicon activation rate was 89.9%.

[0050] The main components of granular soil conditioner are: P2O5 10.6%, CaO 30.4%, MgO 10.1%, and SiO2 31.8%.

[0051] Excessive melting temperature not only increases energy consumption but also leads to the loss of elements through volatilization, resulting in a decrease in effective phosphorus content and a slight decrease in phosphorus activation rate.

[0052] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that the melting time is 5 minutes.

[0053] The active ingredients of the powdered product are: P2O5 10.4%, CaO 31.9%, MgO 11.7%, and SiO2 32.0%.

[0054] The activation rates of the elements in the powdered product were determined as follows: phosphorus activation rate was 89.2%, calcium activation rate was 94.8%, magnesium activation rate was 91.7%, and silicon activation rate was 87.6%.

[0055] The main components of granular soil conditioner are: P2O 59.4%, CaO 29.3%, MgO 10.6%, and SiO 29.2%.

[0056] If the melting time is too short, the material cannot fully melt and react, resulting in a low phosphorus activation rate.

[0057] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that the melting time is 30 min.

[0058] The active ingredients of the powdered product are: P2O5 11.0%, CaO 32.6%, MgO 11.5%, and SiO2 33.8%.

[0059] The activation rates of the elements in the powdered product were determined as follows: phosphorus activation rate was 99.0%, calcium activation rate was 98.7%, magnesium activation rate was 94.7%, and silicon activation rate was 88.6%.

[0060] The main components of granular soil conditioner are: P2O5 10.4%, CaO 29.8%, MgO 10.2%, and SiO2 31.2%.

[0061] Increasing the melting time not only increases energy consumption but also leads to the loss of elements through volatilization, resulting in a decrease in the effective phosphorus content, while the phosphorus activation rate remains largely unchanged.

[0062] In summary, if the melting temperature is below 1350℃, the material cannot form a molten flow due to the low temperature; some material adheres to the crucible or remains in powder form, making it impossible to obtain a glassy material through water quenching. If the melting temperature is too high, exceeding 1600℃, it not only increases energy consumption but also leads to phosphorus volatilization and loss, reducing the effective phosphorus content and activation rate. If the melting time is too short, less than 5 minutes, the material cannot fully melt and react, resulting in a low phosphorus activation rate. Increasing the melting time, exceeding 30 minutes, not only increases energy consumption but also leads to phosphorus volatilization and loss, reducing the effective phosphorus content, but the phosphorus activation rate remains largely unchanged.

[0063] To further demonstrate the effectiveness of the granular soil conditioner prepared according to this invention, a field application test was conducted using the soil conditioner prepared in Example 1. The results are as follows:

[0064] Control group: CK (conventional fertilization + no soil conditioner); Treatment group (conventional fertilization + 50 kg / mu of granular soil conditioner from Example 1). Conventional fertilization involved using compound fertilizer as base fertilizer at a rate of 50 kg / mu.

[0065] When applied to grape crops in acidic soils, the soil pH increased from 5.5 to 5.9. Compared with the control (CK), the soil exchangeable calcium content increased by 10.6%, and the exchangeable magnesium content increased by 8.6%. Grape yield increased by 30.8%, and the weight of a single grape, soluble solids, and total sugar increased by 48.0%, 8.2%, and 18.0%, respectively.

[0066] The soil conditioner prepared by the method of the present invention is rich in phosphorus, calcium, magnesium and silicon. After being applied to the soil, it can replace hydrogen ions and aluminum ions on the soil colloids, and increase the exchangeable calcium, magnesium and cation exchange capacity of the soil, thereby alleviating soil acidification and improving soil structure.

[0067] It should be noted that when numerical ranges are mentioned in the claims of this invention, it should be understood that the two endpoints of each numerical range and any value between the two endpoints can be selected. To avoid redundancy, the present invention describes preferred embodiments.

[0068] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0069] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for producing soil conditioner from high-phosphorus and high-magnesium flotation tailings using an electric furnace, characterized in that, Includes the following steps: The flotation tailings powder, medium and low grade phosphate rock powder, silicate flux and binder are mixed in a mass ratio of 70~100:5~20:20~35:3~15 and then pressed into ellipsoids to obtain wet balls. The wet balls are then dried to obtain ore-blended pellets. The ore pellets are melted at 1400~1600℃ for 5~30 minutes to obtain the molten material; The molten material is quenched in water, and after quenching, it is drained, dried, and ground to obtain a powdered product. The powdered product, granulation aid, and functional soil conditioner are mixed, granulated, and dried to obtain the soil conditioner.

2. The method according to claim 1, characterized in that, The binder is one or more of the following: residual raffinate, sludge acid, 1%–2% sodium carboxymethyl cellulose solution, 3%–5% calcium lignosulfonate solution, and 1%–1.5% hydroxypropyl methyl cellulose solution.

3. The method according to claim 1, characterized in that, The granulation aid is two or more of the following: bentonite, attapulgite, sepiolite, diatomite, and montmorillonite.

4. The method according to claim 1, characterized in that, The functional soil conditioner is one or more of the following: humic acid solution, amino acid solution, alginate solution, and polyacrylamide solution.

5. The method according to claim 4, characterized in that, The concentration of the humic acid solution is 5% to 15% by mass, the concentration of the amino acid solution is 10% to 20% by mass, the concentration of the alginate solution is 0.3% to 1% by mass, and the concentration of the polyacrylamide solution is 0.3% to 1% by mass.

6. The method according to claim 1, characterized in that, The mass ratio of the flotation phosphorus tailings powder, granulation aid and functional soil conditioner is 70~100:1~10:3~10.

7. The method according to claim 1, characterized in that, The pressing pressure is 8 MPa to 30 MPa.

8. The method according to claim 1, characterized in that, The particle size of the medium- and low-grade phosphorus is ≤1mm; the particle size of the silicate flux is ≤1mm.

9. The soil conditioner prepared by the method according to any one of claims 1 to 8.

10. The application of the soil conditioner according to claim 9 in alleviating soil acidification.