Method for preparing fluosilicic acid from yellow phosphorus slag

Abstract

The invention discloses a method for preparing fluosilicic acid from yellow phosphorus slag, which comprises the following steps: drying the yellow phosphorus slag, pretreating, and carrying out acidolysis reaction on the pretreated yellow phosphorus slag; solid residues in reactants obtained after the reaction are removed, and filtrate containing fluosilicic acid is obtained; adding sodium sulfide into the obtained filtrate to purify and remove impurities, removing heavy metal ions, adjusting the pH value of the filtrate, and filtering again to obtain purified filtrate; and concentrating the purified filtrate under reduced pressure to separate out fluosilicic acid crystals or directly obtain a fluosilicic acid solution. According to the method disclosed by the invention, resource utilization of the yellow phosphorus slag is realized, accumulation of wastes is reduced, and pollution to the environment is reduced; by optimizing process conditions, the recovery rate of fluorine resources is increased, and the production cost is reduced; in addition, the method is simple in process and suitable for large-scale industrial production, has both technical feasibility and industrial application prospects, and provides important technical support for green transformation of the phosphorus chemical industry.

Description

Technical Field

[0001] The present invention belongs to the technical field of phosphorus chemical solid waste resource utilization, and particularly relates to a method for preparing fluosilicic acid from yellow phosphorus slag. Background Art

[0002] Yellow phosphorus slag is a solid waste generated during the industrial production of yellow phosphorus. Yellow phosphorus is mainly prepared by the electric furnace method, in which phosphate rock, coke and silica are reacted at high temperature to generate by-products such as yellow phosphorus, carbon monoxide and calcium silicate. After the reaction melt is cooled and water quenched, the yellow phosphorus slag is discharged from the bottom of the furnace. It is estimated that about 8 - 10 tons of yellow phosphorus slag are by-produced per ton of yellow phosphorus produced, and the main components of yellow phosphorus slag are calcium silicate and a small amount of unreacted phosphate rock, coke and trace yellow phosphorus, etc. Since it contains harmful substances such as phosphorus and fluorine, if not properly treated, it will pollute the environment. Therefore, the resource utilization of yellow phosphorus slag has become a research hotspot.

[0003] At present, the utilization methods of yellow phosphorus slag mainly include low - value - added products such as building materials, cement admixtures and fertilizers. In the field of building materials, yellow phosphorus slag can be used to produce lightweight aggregate building materials, expanded yellow phosphorus slag and yellow phosphorus slag foam glass, which have the characteristics of light weight, heat insulation and heat preservation, etc. However, the production process is complex, energy consumption is high, and the product performance may be inferior to traditional materials. As a cement admixture, yellow phosphorus slag can improve the performance of cement, but the admixture amount is limited, the composition is unstable, and there may be environmental risks. In the field of fertilizers, yellow phosphorus slag can be used as low - grade phosphate fertilizer or soil conditioner, but the fertilizer efficiency is low, and it may contain harmful substances, and long - term use may pollute the soil. Generally speaking, the existing treatment methods generally have problems such as resource waste, environmental pollution and high costs. In the future, it is necessary to develop more efficient and low - cost resource utilization technologies to realize the reduction, harmlessness and resource utilization of yellow phosphorus slag.

[0004] Fluosilicic acid (H 2 SiF 6 ) is an important chemical raw material, which is widely used in the fields of preparing hydrofluoric acid, fluorinated salts, etc. However, the traditional production methods of fluosilicic acid have problems such as complex process, high cost and environmental pollution. Patent CN112390619A discloses "a lightweight aggregate building material produced from yellow phosphorus slag and its production method". Although it realizes the resource utilization of yellow phosphorus slag, it does not fully utilize the fluorine element in yellow phosphorus slag, and at the same time, high - temperature calcination is required during the production process, resulting in high energy consumption.

[0005] In view of the above problems, the present invention proposes a green, efficient and low - cost method for resource utilization of yellow phosphorus slag. Summary of the Invention

[0006] In order to solve the above technical problems, the purpose of the present invention is to provide a method for preparing fluorosilicic acid from yellow phosphorus slag, so as to realize the resource utilization of waste and reduce production costs and environmental impact; this method not only effectively solves the environmental problems caused by the accumulation of yellow phosphorus slag, but also provides a new economical and environmentally friendly way for the production of fluorosilicic acid.

[0007] The object of the present invention is achieved by comprising the following steps: (1) drying and pre-treating the yellow phosphorus slag, and then subjecting the pre-treated yellow phosphorus slag to an acid hydrolysis reaction; (2) removing the solid residue from the reactant obtained after the reaction in step (1) to obtain a filtrate containing fluorosilicic acid; (3) Add sodium sulfide (Na 2 S) to purify and remove impurities, remove heavy metal ions (Fe 3 + 、Al 3+ etc.), adjust the pH of the filtrate, filter again to obtain a purified filtrate; impurity removal reaction equation: ; (4) The purified filtrate is concentrated under reduced pressure to precipitate fluosilicic acid crystals, or a fluosilicic acid solution is directly obtained.

[0008] Preferably, the pretreatment in step (1) is to grind the yellow phosphorus slag into fine powder, the particle size of the fine powder is 80 mesh to 100 mesh, and the acid hydrolysis reaction is specifically to mix the obtained fine powder with concentrated sulfuric acid, heat and stir to react; the reaction equation is: .

[0009] Preferably, the concentration of concentrated sulfuric acid is ≥98%, the volume mass ratio of concentrated sulfuric acid to fine powder is 3-10 ml:1 g, the stirring rate is 200 rpm-500 rpm, and the reaction time is 2-5 h.

[0010] Further preferably, the volume mass ratio of concentrated sulfuric acid to fine powder is 4 ml:1 g.

[0011] Further preferably, the reaction of concentrated sulfuric acid with fine powder is carried out in a condensation reflux or absorption tower (water or dilute alkali solution) to prevent HF from escaping, ensure that the gas is redissolved to participate in the reaction, and improve the utilization rate of raw materials.

[0012] Preferably, the acid hydrolysis reaction temperature is maintained at 80°C to 100°C.

[0013] Preferably, the pretreatment in step (1) is to crush and screen yellow phosphorus slag to obtain yellow phosphorus slag with a particle size of 100 mesh to 200 mesh. The acidolysis reaction specifically is to mix the crushed and screened yellow phosphorus slag with water to obtain a yellow phosphorus slag slurry as a desulfurizer, and use the yellow phosphorus slag slurry to remove sulfur dioxide in wet flue gas to obtain a saturated yellow phosphorus slag desulfurization slurry; Among them, calcium sulfate (CaSO 4 ), as a calcium element recovery product, settles at the bottom, and fluorine-containing substances dissolve in the upper reaction solution to form a fluorosilicic acid solution, realizing the efficient separation and resource recovery of fluorine; the reaction equation is as follows: .

[0014] Preferably, the drying temperature in step (1) is 60°C to 120°C.

[0015] Preferably, the mass ratio of water to yellow phosphorus slag is 3 to 10:1, and SO in wet flue gas is removed 2 The desulfurization temperature is controlled at 40°C to 100°C, and the stirring rate is 200 rpm to 500 rpm.

[0016] Preferably, the pH of the obtained yellow phosphorus slag slurry is 9 to 12.5.

[0017] Preferably, the oxygen content in the flue gas is 9% to 25%, and the sulfur dioxide concentration is 4000 mg / m 3 ~6000 mg / m 3 , and the gas flow rate is 300 mL / min to 600 mL / min.

[0018] Preferably, the pH of the filtrate is adjusted to 2 to 3 in step (3).

[0019] Preferably, the concentration of the fluorosilicic acid solution obtained by vacuum concentration in step (4) is 30% to 40%.

[0020] Advantages of the present invention: 1. The method of the present invention realizes the resource utilization of yellow phosphorus slag, reduces the accumulation of waste, and reduces environmental pollution; by optimizing process conditions, the recovery rate of fluorine resources is improved, and the production cost is reduced; in addition, the method of the present invention has a simple process and is suitable for large-scale industrial production; 2. The method of the present invention makes full use of the fluorine resources in yellow phosphorus slag, while reducing environmental pollution, solves the dual contradictions of yellow phosphorus slag accumulation pollution and shortage of fluorosilicic acid production resources, has both technical feasibility and industrial application prospects, and provides important technical support for the green transformation of the phosphorus chemical industry; 3. The method of the present invention constructs a synergistic preparation technology system of yellow phosphorus slag-fluorosilicic acid, organically combines the activation treatment of yellow phosphorus slag with the flue gas desulfurization process, and realizes SO 2While the removal rate is >99%, fluosilicic acid is simultaneously generated, providing a new idea for the comprehensive utilization of yellow phosphorus slag and the preparation of fluosilicic acid. Description of the Drawings

[0021] Figure 1 It is a schematic flow chart of the reaction involving concentrated sulfuric acid in the present invention; Figure 2 It is a schematic flow chart of the reaction involving flue gas in the present invention. Detailed Embodiments

[0022] The present invention will be further described below in conjunction with embodiments, but the present invention is not limited in any way. Any transformation or replacement based on the teachings of the present invention falls within the protection scope of the present invention.

[0023] Example 1 The method for preparing fluosilicic acid from yellow phosphorus slag in this example includes the following steps: (1) Dry and crush the yellow phosphorus slag into fine powder, and the particle size of the fine powder is 80 mesh to 100 mesh; (2) Mix the fine powder obtained in step (1) with concentrated sulfuric acid. The concentration of the concentrated sulfuric acid is ≥98%, the volume-mass ratio of the concentrated sulfuric acid to the fine powder is 3 ml:1 g, the stirring rate is 300 rpm, the reaction time is 3 h, and the heating is maintained at 80 °C with stirring for reaction; (3) Remove the solid residue in the reactant obtained in step (2) to obtain a filtrate containing fluosilicic acid; (4) Add sodium sulfide (Na 2 2S) to the filtrate obtained in step (3) to remove heavy metal ions, adjust the pH of the filtrate to 2 - 3, filter again to obtain a purified filtrate, and concentrate the purified filtrate under reduced pressure; after detection, the concentration of the directly obtained fluosilicic acid solution is 30%.

[0024] Example 2 The method for preparing fluosilicic acid from yellow phosphorus slag in this example is based on Example 1, and the difference from Example 1 is that the heating temperature in step (2) is 100 °C; after detection, the concentration of the obtained fluosilicic acid solution is 32%.

[0025] Example 3 The method for preparing fluosilicic acid from yellow phosphorus slag in this example is based on Example 1, and the difference from Example 1 is that the volume-mass ratio of the concentrated sulfuric acid to the fine powder in step (2) is 4 ml:1 g.

[0026] Example 4 The method for preparing fluosilicic acid from yellow phosphorus slag in this example is based on Example 1, and the difference from Example 1 is that the volume-mass ratio of the concentrated sulfuric acid to the fine powder in step (2) is 3 ml:1 g, the stirring rate is 200 rpm, the reaction time is 2 h, and the reaction temperature is maintained at 80 °C.

[0027] Example 5 The method for preparing fluosilicic acid from yellow phosphorus slag in this example is based on Example 1. The differences from Example 1 are as follows: In step (2), the volume-mass ratio of concentrated sulfuric acid to fine powder is 10 ml:1 g, the stirring rate is 500 rpm, the reaction time is 5 h, and the reaction temperature is maintained at 100 °C.

[0028] Example 6 The method for preparing fluosilicic acid from yellow phosphorus slag in this example is based on Example 1. The differences from Example 1 are as follows: In step (2), the volume-mass ratio of concentrated sulfuric acid to fine powder is 6.5 ml:1 g, the stirring rate is 350 rpm, the reaction time is 3.5 h, and the reaction temperature is maintained at 90 °C.

[0029] Example 7 Using yellow phosphorus slag (containing CaF, CaSiO 3 , CaO, SiO 2 , etc.) generated during the treatment process of a domestic phosphorus chemical plant as raw materials; the method for preparing fluosilicic acid from yellow phosphorus slag in this example includes the following steps: (1) Place the yellow phosphorus slag in a drying oven, with a drying temperature of 120 °C and drying for 6 hours to remove the moisture therein; (2) Mechanically crush and grind the dried yellow phosphorus slag, and sieve it through a 100-200 mesh sieve to obtain yellow phosphorus slag with a particle size of 100-200 mesh; (3) Mix the yellow phosphorus slag obtained in step (2) with water, with a mass ratio of water to yellow phosphorus slag of 5:1, to obtain a yellow phosphorus slag slurry desulfurizer and load it into an absorption device. Use the yellow phosphorus slag slurry desulfurizer to remove sulfur dioxide in wet flue gas (the flue gas is introduced into the absorption device). The oxygen content in the flue gas is 10%, the sulfur dioxide concentration is 5000 mg / m 3 , the gas flow rate is 500 mL / min, use a constant temperature water bath to control the desulfurization temperature at 80 °C, and the stirring rate is 300 rpm; every 30 min, use a flue gas analyzer to detect the concentration of SO 2 after drying, and calculate the desulfurization rate; after the reaction ends, obtain a saturated yellow phosphorus slag slurry desulfurizer; (4) Remove the solid residue of the saturated yellow phosphorus slag slurry desulfurizer to obtain a filtrate containing fluosilicic acid; (5) Adjust the pH of the filtrate containing fluosilicic acid to 2-3, add sodium sulfide (Na 2 2 S) to remove heavy metal ions (such as Fe 2+ 3+ , Al 3+ 3+ etc.), and then filter to obtain a purified filtrate containing fluosilicic acid; (6) Perform vacuum concentration on the purified filtrate obtained in step (5), control the evaporation temperature at 70 °C, and directly obtain a fluosilicic acid solution; The flue gas treated by this method has SO 2 ≤25 mg / m 3 , the initial pH of the yellow phosphorus slag slurry desulfurizer is 9.75, the pH after desulfurization is 1.7, the desulfurization rate is 100% for 18 h, and at the same time, the concentration of the fluosilicic acid solution obtained is 31%.

[0030] Example 8 The method for preparing fluosilicic acid from yellow phosphorus slag in this example is based on Example 7. The differences from Example 7 are as follows: in step (1), the drying temperature is 150 °C and the drying time is 5 h; in step (3), the sulfur dioxide concentration is 6000 mg / m 3 , and a constant temperature water bath is used to control the desulfurization temperature at 70 °C; The flue gas treated by this method has SO 2 ≤25 mg / m 3 , the initial pH of the yellow phosphorus slag slurry desulfurizer is 9.75, the pH after desulfurization is 1.7, and the desulfurization rate is 100% for 14 h.

[0031] Example 9 The method for preparing fluosilicic acid from yellow phosphorus slag in this example is based on Example 7. The differences from Example 7 are as follows: in step (1), the drying temperature is 60 °C; in step (3), the mass ratio of water to yellow phosphorus slag is 3:1, and SO in the wet flue gas is removed 2 The desulfurization temperature is controlled at 40 °C, the stirring rate is 200 rpm, the oxygen content is 9%, and the sulfur dioxide concentration is 4000 mg / m 3 , and the gas flow rate is 300 mL / min.

[0032] Example 10 The method for preparing fluosilicic acid from yellow phosphorus slag in this example is based on Example 7. The differences from Example 7 are as follows: in step (1), the drying temperature is 120 °C; in step (3), the mass ratio of water to yellow phosphorus slag is 10:1, and SO in the wet flue gas is removed 2 The desulfurization temperature is controlled at 100 °C, the stirring rate is 500 rpm, the oxygen content is 25%, and the sulfur dioxide concentration is 6000 mg / m 3 , and the gas flow rate is 600 mL / min.

[0033] Example 11 The method for preparing fluosilicic acid from yellow phosphorus slag in this example is based on Example 7. The differences from Example 7 are as follows: in step (1), the drying temperature is 90 °C; in step (3), the mass ratio of water to yellow phosphorus slag is 6.5:1, and SO in the wet flue gas is removed 2 The desulfurization temperature is controlled at 70 °C, the stirring rate is 350 rpm, the oxygen content is 17%, and the sulfur dioxide concentration is 5000 mg / m 3 , and the gas flow rate is 450 mL / min.

Claims

1. A method for preparing fluorosilicic acid from yellow phosphorus slag, characterized in that The following steps are involved: (1) drying and pre-treating the yellow phosphorus slag, and then subjecting the pre-treated yellow phosphorus slag to an acid hydrolysis reaction; (2) removing the solid residue from the reactant obtained after the reaction in step (1) to obtain a filtrate containing fluorosilicic acid; (3) adding sodium sulfide to the filtrate obtained in step (2) to purify and remove impurities, remove heavy metal ions, adjust the pH of the filtrate, and filter again to obtain a purified filtrate; (4) The purified filtrate is concentrated under reduced pressure to precipitate fluosilicic acid crystals, or a fluosilicic acid solution is directly obtained.

2. The method for preparing fluorosilicic acid from yellow phosphorus slag according to claim 1, characterized in that The pretreatment in step (1) is to grind the yellow phosphorus slag into fine powder, the particle size of the fine powder is 80 mesh to 100 mesh, and the acid hydrolysis reaction is specifically to mix the obtained fine powder with concentrated sulfuric acid, heat and stir the reaction.

3. The method for preparing fluorosilicic acid from yellow phosphorus slag according to claim 2, characterized in that The concentration of concentrated sulfuric acid is ≥98%, the volume mass ratio of concentrated sulfuric acid to fine powder is 3-10 ml:1 g, the stirring rate is 200 rpm-500 rpm, and the reaction time is 2-5 h.

4. The method for preparing fluorosilicic acid from yellow phosphorus slag according to claim 2, characterized in that The acid hydrolysis reaction temperature is maintained at 80°C to 100°C.

5. The method for preparing fluorosilicic acid from yellow phosphorus slag according to claim 1, characterized in that The pretreatment described in step (1) is to crush and screen the yellow phosphorus slag to obtain yellow phosphorus slag with a particle size of 100 mesh to 200 mesh. The acidolysis reaction is specifically to mix the crushed and screened yellow phosphorus slag with water to obtain yellow phosphorus slag slurry as a desulfurizer, and use the yellow phosphorus slag slurry to remove sulfur dioxide in the wet flue gas to obtain a saturated yellow phosphorus slag desulfurization slurry.

6. The method for preparing fluorosilicic acid from yellow phosphorus slag according to claim 5, characterized in that The mass ratio of water to yellow phosphorus slag is 3-10:1, the desulfurization temperature for removing SO2 from wet flue gas is controlled to be 40°C-100°C, and the stirring speed is 200rpm-500rpm.

7. The method for preparing fluorosilicic acid from yellow phosphorus slag according to claim 5, characterized in that The pH value of the obtained yellow phosphorus slurry is 9-12.

5.

8. The method for preparing fluorosilicic acid from yellow phosphorus slag according to claim 5, characterized in that The oxygen content in the flue gas is 9%~25%, and the sulfur dioxide concentration is 4000mg / m 3 ~6000mg / m 3 , gas flow rate 300mL / min~600mL / min.

9. The method for preparing fluorosilicic acid from yellow phosphorus slag according to claim 1, characterized in that Step (3) adjusts the pH of the filtrate to 2-3.

10. The method for preparing fluorosilicic acid from yellow phosphorus slag according to claim 1, characterized in that The concentration of the fluorosilicic acid solution obtained by concentrating under reduced pressure in step (4) is 30% to 40%.

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