Method for improving phosphorite reaction activity and fluorine resource recovery rate

Abstract

The invention discloses a method for improving phosphorite reaction activity and fluorine resource recovery rate. The method mainly aims at medium-low-grade collophanite after flotation, and comprises the following steps: firstly, pretreating phosphorite by using fluosilicic acid to prepare high-concentration phosphorite slurry; carrying out premixing reaction on the phosphoric ore pulp and phosphoric acid, and then carrying out crystallization reaction with sulfuric acid with a certain concentration; a flash cooling and flue gas washing system is arranged in each reaction area, so that escape and recovery of fluorine are enhanced; and after the reaction is finished, filtering and washing to obtain phosphoric acid and phosphogypsum. The phosphorite is pretreated by using low-concentration fluosilicic acid recovered in a phosphoric acid concentration section, the phosphorite pre-decomposition pH is adjusted by using fluosilicic acid, carbonate, silicate and quartz impurities in the phosphorite are preferentially dissolved, and micro-channels are formed on the surfaces of phosphorite particles, so that the subsequent use amounts of phosphoric acid and sulfuric acid are reduced, and the content of aluminum phosphate ions in the product is reduced; the phosphorite acidolysis efficiency is improved. Meanwhile, introduction of fluosilicate accelerates escape of fluorine in phosphorite, and the fluorine yield of the system is increased.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of wet-process phosphoric acid, and particularly relates to a method for improving the reaction activity of phosphate rock and the recovery rate of fluorine resources. BACKGROUND

[0002] During the reaction process of phosphate rock in the wet-process phosphoric acid, dissolution and crystallization of the phosphate rock occur. Due to the associated minerals in the phosphate rock and the decomposition rate of the phosphate rock itself, the solubility of the solid product, the supersaturation of the solution and other factors, part of the associated minerals with high activity is prone to preferential acidolysis, and consumes phosphate ions and sulfate ions, thereby reducing or preventing the decomposition efficiency of the phosphate rock. Meanwhile, the nucleation and growth process of calcium sulfate crystals are affected by the problem of insufficient supersaturation of sulfate ions, and the crystal agglomeration or small crystallization occurs, which affects the washing performance of the filter cake and reduces the phosphorus recovery rate. SUMMARY

[0003] In view of the problems in the prior art, the application provides a method for improving the reaction activity of phosphate rock and the recovery rate of fluorine resources. The phosphate rock is pretreated by using fluorosilicic acid. On one hand, the pH value of the phosphate rock pretreatment slurry is reasonably adjusted by using the fluorosilicic acid, and part of the sulfuric acid is replaced. The fluorosilicic acid reacts with calcium, magnesium and other impurities in the phosphate rock to generate calcium fluoride, magnesium fluoride and other precipitates, and accelerates the release of hydrogen fluoride gas. On the other hand, the fluorosilicic acid preferentially decomposes the associated minerals in the phosphate rock, promotes the dissolution of siliceous minerals such as silicates and quartz, and forms micropores on the surface of the phosphate rock particles, thereby reducing the subsequent consumption of phosphoric acid and sulfuric acid. By using the fluorosilicic acid to preferentially treat the phosphate rock, part of the acid-insoluble substances in the phosphate rock are preferentially precipitated and left in the phosphogypsum through flocculation and sedimentation, so that the impurities are prevented from entering the acid system and the quality of the phosphoric acid is improved. Meanwhile, the fluorosilicic acid introduced strengthens the solidification capacity of fluorine in the acidolysis of the phosphate rock, and the associated fluorine resources in the phosphate rock are left in the phosphoric acid. The released hydrogen fluoride is recovered through the setting of a flash cooling and flue gas washing system, and the fluorine recovery rate of the system is improved. The phosphate rock pretreated by the fluorosilicic acid is further decomposed and crystallized with calcium sulfate by using a small amount of phosphoric acid and sulfuric acid, and uniform and large calcium sulfate crystals are generated, thereby strengthening the filtration performance of the phosphogypsum and improving the phosphorus recovery rate of the reaction system.

[0004] The technical scheme of the application is as follows: A method for improving the reaction activity of phosphate rock and the recovery rate of fluorine resources, the method comprising the following steps: S1: pretreating the phosphate rock by using fluorosilicic acid to prepare a phosphate rock slurry; S2: premixing the phosphate rock slurry with phosphoric acid and then performing a crystallization reaction with sulfuric acid; S3: filtering and washing the reaction product to obtain phosphoric acid and phosphogypsum.

[0005] Preferably, the method is for the low-grade collophanite after flotation, the content of P2O5 in the low-grade collophanite after flotation is 25-35%, the content of carbonate mineral is 5-15%, the content of silicate mineral is 2-10%, and the content of quartz mineral is 1-8%.

[0006] Preferably, in the step S1, the concentration of fluosilicic acid is 10-25%, the pretreatment time is 10-90 min, the pretreatment temperature is 40-80℃, and the pH of the pretreatment slurry is controlled at 2-4, for example, 2, 2.5, 3, 3.5 or 4, so that the microchannels of 1-2 μm are formed inside the phosphate rock particles.

[0007] Further preferably, in the step S1, a foam dispersing agent is added in the pretreatment process to prevent excessive foam caused by the decomposition of carbonate minerals, and the main component of the foam dispersing agent is hydroxyethylidene diphosphonic acid (HEDP), and the addition amount is 5-50 mg / L, for example, 5 mg / L, 15 mg / L, 25 mg / L, 35 mg / L or 50 mg / L.

[0008] Preferably, in the step S1, the concentration of the prepared phosphate rock slurry is 50-80%, for example, 50%, 60%, 65%, 70% or 80%.

[0009] Preferably, in the step S2, the phosphate rock slurry and phosphoric acid are premixed for 30-60 min at a temperature of 50-95℃, and the liquid-solid ratio of the slurry is 1-5:1, for example, 1:1, 2:1, 3:1, 4:1 or 5:1, and the calcium ion concentration of the acid solution is 1-4%, for example, 1%, 2%, 2.5%, 3% or 4%.

[0010] Further preferably, in the step S2, the phosphate rock slurry and phosphoric acid are premixed, and polyacrylamide flocculant is added, and the addition amount of the polyacrylamide flocculant in the premixing process of the phosphate rock slurry and phosphoric acid is 0.5-2 mg / L, for example, 0.5 mg / L, 1 mg / L, 1.5 mg / L, 1.8 mg / L or 2 mg / L. Preferably, in the step S2, the sulfuric acid crystallization reaction time is 30-90 min, the temperature is 60-95℃, for example, 60℃, 70℃, 80℃, 90℃ or 95℃, the liquid-solid ratio of the slurry is 1-5:1, for example, 1:1, 2:1, 3:1, 4:1 or 5:1, the sulfate ion concentration of the acid solution is 2-5%, for example, 2%, 3%, 3.5%, 4% or 5%, and uniform calcium sulfate crystals with an average particle size of 15-45 μm are formed.

[0011] Preferably, in the method, a flash cooling and flue gas washing system is arranged in each of the fluosilicic acid pretreatment reaction, phosphoric acid premixing reaction and sulfuric acid crystallization reaction to strengthen the escape and recovery of fluorine.

[0012] Further preferably, the vacuum degree of the flash cooler arranged in the fluorosilicic acid pretreatment reaction, the phosphoric acid premixing reaction and the sulfuric acid crystallization reaction is 60-86 kPa, for example, it can be 60 kPa, 66 kPa, 72 kPa, 80 kPa or 86 kPa; the temperature difference between the material inlet and outlet of the flash cooler in the three reaction zones is 3-9 ℃, for example, it can be 3 ℃, 6 ℃, 5 ℃, 7 ℃ or 9 ℃.

[0013] The beneficial effects of the present application are: The method for improving the reaction activity of phosphate rock and the fluorine resource recovery rate provided by the present application promotes the dissolution of siliceous minerals silicate and quartz by pretreating the phosphate rock with fluorosilicic acid, and the introduction of fluorosilicic acid strengthens the solidification ability of fluorine in the acidolysis of phosphate rock, thereby improving the reaction activity of phosphate rock and the fluorine recovery rate of the system. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 Example 1: Microscope image of phosphogypsum; Figure 2 Example 1: Microscope image of phosphogypsum; Figure 3 Example 1: Microscope image of phosphogypsum; DETAILED DESCRIPTION

[0015] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and any values should be understood to be approximate. The exact numerical values will depend on the specific application and use. The ranges and values disclosed herein are therefore approximate, and thus can vary by a small amount, for example, by up to 1%, 2%, 5%, or 10% of the stated ranges and values.

[0016] In order to better understand the present application, the content of the present application will be further described below in combination with examples and comparative examples, but the content of the present application is not limited to only the following examples.

[0017] Example 1 For the low-grade phosphate rock with P2O5 content of 26%, carbonate mineral content of 7%, silicate mineral content of 5%, and quartz mineral content of 6% after flotation, first, 15% fluorosilicic acid is used for 30 min, 60°C pretreatment, the pretreatment slurry pH is controlled at 3, and 10 mg / L of hydroxyethylidene diphosphonic acid (HEDP) foam dispersant is added, and a 60% phosphate rock slurry is prepared; the phosphate rock slurry is subjected to a premixed reaction with phosphoric acid for 45 min, at a temperature of 75°C, a slurry liquid-solid ratio of 3:1, and a calcium ion concentration of 4% in the acid liquid, and 1 mg / L of polyacrylamide flocculant is added during the process, and then a crystallization reaction with a certain concentration of sulfuric acid for 60 min, at a temperature of 70°C, a slurry liquid-solid ratio of 3:1, and a sulfuric acid radical concentration of 3% in the acid liquid; a flash cooling and flue gas washing system with a vacuum degree of 70 kPa is arranged in the fluorosilicic acid pretreatment reaction, phosphoric acid premixed reaction, and sulfuric acid crystallization reaction, the temperature difference between the inlet and outlet of the flash cooler is 5°C, and the escape and recovery of fluorine are strengthened; after the reaction, phosphoric acid and phosphogypsum are obtained through filtration and washing.

[0018] Example 2 For the low-grade phosphate rock with P2O5 content of 25%, carbonate mineral content of 12%, silicate mineral content of 6%, and quartz mineral content of 8% after flotation, first, 17% fluorosilicic acid is used for 35 min, 80°C pretreatment, the pretreatment slurry pH is controlled at 2.7, and 40 mg / L of hydroxyethylidene diphosphonic acid (HEDP) foam dispersant is added, and a 55% phosphate rock slurry is prepared; the phosphate rock slurry is subjected to a premixed reaction with phosphoric acid for 45 min, at a temperature of 60°C, a slurry liquid-solid ratio of 4:1, and a calcium ion concentration of 1% in the acid liquid, and 0.7 mg / L of polyacrylamide flocculant is added during the process, and then a crystallization reaction with a certain concentration of sulfuric acid for 50 min, at a temperature of 90°C, a slurry liquid-solid ratio of 4:1, and a sulfuric acid radical concentration of 4% in the acid liquid; a flash cooling and flue gas washing system with a vacuum degree of 80 kPa is arranged in the fluorosilicic acid pretreatment reaction, phosphoric acid premixed reaction, and sulfuric acid crystallization reaction, the temperature difference between the inlet and outlet of the flash cooler is 7°C, and the escape and recovery of fluorine are strengthened; after the reaction, phosphoric acid and phosphogypsum are obtained through filtration and washing.

[0019] Example 3 For the low-grade phosphate rock with P2O5 content of 30%, carbonate mineral content of 10%, silicate mineral content of 5%, and quartz mineral content of 7% after flotation, first, 14% fluorosilicic acid is used for 80 min, 45°C pretreatment, the pretreatment slurry pH is controlled at 4, and 42 mg / L of hydroxyethylidene diphosphonic acid (HEDP) foam dispersant is added, and a 55% phosphate rock slurry is prepared; the phosphate rock slurry is subjected to a premixing reaction with phosphoric acid for 40 min, at a temperature of 85°C, a slurry liquid-solid ratio of 3:1, and a calcium ion concentration of 3% in the acid liquid, and in the process, 1.3 mg / L of polyacrylamide flocculant is added, and then a crystallization reaction with a certain concentration of sulfuric acid is performed for 90 min, at a temperature of 80°C, a slurry liquid-solid ratio of 3:1, and a sulfuric acid radical concentration of 4% in the acid liquid; a flash cooling and flue gas washing system with a vacuum degree of 65 kPa is arranged in the fluorosilicic acid pretreatment reaction, phosphoric acid premixing reaction, and sulfuric acid crystallization reaction, the temperature difference between the inlet and outlet of the flash cooler is 5°C, and the escape and recovery of fluorine are strengthened; after the reaction, phosphoric acid and phosphogypsum are obtained through filtration and washing.

[0020] Example 4 For the low-grade phosphate rock with P2O5 content of 30%, carbonate mineral content of 13%, silicate mineral content of 7%, and quartz mineral content of 6% after flotation, first, 22% fluorosilicic acid is used for 15 min, 53°C pretreatment, the pretreatment slurry pH is controlled at 3.7, and 40 mg / L of hydroxyethylidene diphosphonic acid (HEDP) foam dispersant is added, and a 60% phosphate rock slurry is prepared; the phosphate rock slurry is subjected to a premixing reaction with phosphoric acid for 45 min, at a temperature of 70°C, a slurry liquid-solid ratio of 2:1, and a calcium ion concentration of 2% in the acid liquid, and in the process, 2 mg / L of polyacrylamide flocculant is added, and then a crystallization reaction with a certain concentration of sulfuric acid is performed for 45 min, at a temperature of 80°C, a slurry liquid-solid ratio of 4:1, and a sulfuric acid radical concentration of 2% in the acid liquid; a flash cooling and flue gas washing system with a vacuum degree of 80 kPa is arranged in the fluorosilicic acid pretreatment reaction, phosphoric acid premixing reaction, and sulfuric acid crystallization reaction, the temperature difference between the inlet and outlet of the flash cooler is 6°C, and the escape and recovery of fluorine are strengthened; after the reaction, phosphoric acid and phosphogypsum are obtained through filtration and washing.

[0021] Example 5 For the medium and low grade collophanite with P2O5 content of 35%, carbonate mineral content of 8%, silicate mineral content of 9% and quartz mineral content of 5% after flotation, first, 15% fluorosilicic acid is used for 20 min, 55℃ pretreatment, the pretreatment slurry pH is controlled at 3.1, and 15 mg / L of hydroxyethylidene diphosphonic acid (HEDP) foam dispersant is added, and a 65% phosphate rock slurry is prepared; the phosphate rock slurry is subjected to a premixed reaction with phosphoric acid for 50 min, at a temperature of 75℃, a slurry liquid-solid ratio of 4:1, and a calcium ion concentration of 2% in the acid liquid, and in the process, 0.9 mg / L of polyacrylamide flocculant is added, and then a crystallization reaction with a certain concentration of sulfuric acid for 50 min, at a temperature of 80℃, a slurry liquid-solid ratio of 2:1, and a sulfuric acid radical concentration of 4% in the acid liquid; a flash cooling and flue gas washing system with a vacuum degree of 78 kPa is arranged in the fluorosilicic acid pretreatment reaction, the phosphoric acid premixed reaction and the sulfuric acid crystallization reaction, the temperature difference between the inlet and outlet of the flash cooler is 6℃, and the escape and recovery of fluorine are strengthened; after the reaction, phosphoric acid and phosphogypsum are obtained through filtration and washing.

[0022] Comparative Example 1 The present comparative example provides a method for improving the reaction activity of phosphate rock and the recovery rate of fluorine resources, which is the same as Example 1 except that fluorosilicic acid is not used for premixing with the phosphate rock.

[0023] Comparative Example 2 The present comparative example provides a method for improving the reaction activity of phosphate rock and the recovery rate of fluorine resources, which is the same as Example 1 except that nitric acid is used for premixing with the phosphate rock.

[0024] Comparative Example 3 The present comparative example provides a method for improving the reaction activity of phosphate rock and the recovery rate of fluorine resources, which is the same as Example 1 except that the pH of the pretreatment slurry is not strictly controlled within a suitable range.

[0025] Comparative Example 4 The present comparative example provides a method for improving the reaction activity of phosphate rock and the recovery rate of fluorine resources, which is the same as Example 1 except that hydroxyethylidene diphosphonic acid (HEDP) foam dispersant is not added in the fluorosilicic acid premixing stage.

[0026] Comparative Example 5 The present comparative example provides a method for improving the reaction activity of phosphate rock and the recovery rate of fluorine resources, which is the same as Example 1 except that polyacrylamide flocculant is not added in the phosphoric acid pretreatment process.

[0027] Comparative Example 6 The present comparative example provides a method for improving the reaction activity of phosphate rock and the recovery rate of fluorine resources, which is the same as Example 1 except that the polyacrylamide flocculant is replaced by polyaluminum chloride as the flocculant.

[0028] Comparative Example 7 The present comparative example provides a method for improving the reactivity of phosphate ore and the recovery rate of fluorine resources, which is the same as example 1 except that the flash cooling and flue gas washing system is not set in the fluorosilicic acid pretreatment reaction stage.

[0029] The methods provided in application examples 1-5 and comparative examples 1-3 were used to detect phosphoric acid and phosphogypsum. The impurities Al and F in the phosphoric acid were determined by ICP and F ion electrode, and the residual total P2O5 and F content in the phosphogypsum was determined. The results are shown in Table 1. Fluorine recovery rate = (mF content in phosphate ore - mF content in phosphogypsum - mF content in phosphoric acid) / mF content in phosphate ore * 100%.

[0030] Table 1

[0031] As can be seen from Table 1, after the phosphate ore is pretreated by a certain concentration of fluorosilicic acid, the dissolution of siliceous minerals such as silicates and quartz in the phosphate ore is accelerated, the dissolution efficiency of the phosphate ore is improved, and the subsequent use amount of phosphoric acid and sulfuric acid is reduced. At the same time, the flash cooling device added during the fluorosilicic acid, phosphoric acid and sulfuric acid acidolysis process accelerates the escape efficiency of fluorine in the slurry, and promotes the solidification of sodium potassium fluorosilicate in the phosphogypsum through temperature reduction, greatly reduces the content of free fluorine in the phosphoric acid and the phosphogypsum, reduces the content of Al ions in the phosphoric acid, and improves the fluorine recovery rate of the system, while having the effects of removing Al from the phosphoric acid and reducing P and F in the phosphogypsum.

[0032] As can be seen from the gypsum micrographs of example 1 and comparative examples 1 and 5, on the one hand, the phosphate ore is not pretreated by fluorosilicic acid, the content of fluorosilicate ions in the reaction system is low, which leads to the fact that the solidification and removal of impurities cannot be achieved in the subsequent flash cooling process, the content of sodium, potassium, aluminum and other impurities in the slurry is high, which affects the crystallization of calcium sulfate, resulting in fine particle crystals and long rod-shaped crystals; on the other hand, the strong acid flocculating agent is not reasonably added in the reaction system, the gypsum crystals are in the form of fine particle crystals with a size less than 10 μm, which seriously affects the impurity removal effect of the phosphoric acid and the washing and filtering performance of the gypsum.

[0033] The above examples are only preferred technical solutions of the present application, and should not be regarded as limiting the present application. The examples in the present application and the features in the examples can be combined with each other as long as they do not conflict. The protection scope of the present application should be based on the technical solutions claimed in the claims, including equivalent replacement solutions of the technical features claimed in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present application.

Claims

1. A method for improving the reactivity of phosphate rock and the recovery rate of fluorine resources, characterized in that: The method includes the following steps: S1: Phosphate rock is pretreated with fluorosilicic acid to prepare phosphate rock slurry; S2: Phosphate rock slurry is premixed with phosphoric acid and then crystallized with sulfuric acid; S3: After the reaction is complete, phosphoric acid and phosphogypsum are obtained by filtration and washing.

2. The method for improving the reactivity of phosphate rock and the recovery rate of fluorine resources according to claim 1, characterized in that: The method is for low- to medium-grade collophane after flotation, where the P2O5 content is 25-35%, the carbonate mineral content is 5-15%, the silicate mineral content is 2-10%, and the quartz mineral content is 1-8%.

3. The method for improving the reactivity of phosphate rock and the recovery rate of fluorine resources according to claim 1, characterized in that, In step S1, the concentration of fluorosilicic acid is 10-25%, the pretreatment time is 10-90 min, the pretreatment temperature is 40-80℃, and the pH of the pretreated slurry is controlled at 2-4.

4. The method for improving the reactivity of phosphate rock and the recovery rate of fluorine resources according to claim 2, characterized in that, In step S1, a foam dispersant needs to be added during the pretreatment process. The foam dispersant is hydroxyethylidene diphosphonic acid, and the amount added is 5~50 mg / L.

5. The method for improving the reactivity of phosphate rock and the recovery rate of fluorine resources according to claim 1, characterized in that, In step S1, the concentration of the prepared phosphate rock slurry is 50-80%.

6. The method for improving the reactivity of phosphate rock and the recovery rate of fluorine resources according to claim 1, characterized in that, In step S2, the reaction time of the phosphate rock slurry and phosphoric acid premix is ​​30-60 min, the temperature is 50-95℃, the slurry liquid-solid ratio is (1-5):1, and the calcium ion concentration of the acid solution is 1-4%.

7. The method for improving the reactivity of phosphate rock and the recovery rate of fluorine resources according to claim 6, characterized in that, In step S2, the phosphate rock slurry is premixed with phosphoric acid, and polyacrylamide flocculant is added. During the premixing process of the phosphate rock slurry and phosphoric acid, 0.5~2 mg / L of polyacrylamide flocculant is added.

8. The method for improving the reactivity of phosphate rock and the recovery rate of fluorine resources according to claim 1, characterized in that, In step S2, the sulfuric acid crystallization reaction time is 30-90 min, the temperature is 60-95℃, the liquid-solid ratio of the slurry is (1-5):1, the sulfate concentration of the acid solution is 2-5%, and uniform calcium sulfate crystals with an average particle size of 15-45 μm are formed.

9. The method for improving the reactivity of phosphate rock and the recovery rate of fluorine resources according to claim 1, characterized in that, In the method, each reaction zone in the fluorosilicic acid pretreatment reaction, phosphoric acid premixing reaction, and sulfuric acid crystallization reaction is equipped with a flash cooling and flue gas scrubbing system to enhance the release and recovery of fluorine.

10. The method for improving the reactivity of phosphate rock and the recovery rate of fluorine resources according to claim 9, characterized in that, The flash coolers in the fluorosilicic acid pretreatment reaction, phosphoric acid premixing reaction, and sulfuric acid crystallization reaction have a vacuum degree of 60~86kPa; the temperature difference between the material inlet and outlet of the flash coolers in the three reaction zones is 3~9℃.

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