Method for recovering F from calcium fluoride waste residue

Abstract

The application discloses a method for recycling F in fluorite waste residue, and belongs to the technical field of fluorite recycling. The method comprises the following steps: mixing and reacting phosphorite slurry doped with fluorite waste residue with a first phosphoric acid solution and an acid solution containing sulfuric acid, then performing crystal growing treatment, and performing solid-liquid separation to obtain phosphogypsum and finished product phosphoric acid; the mass ratio of the fluorite waste residue contained in the phosphorite slurry to the phosphorite powder is 0.01:100 to 4:100. The phosphogypsum and the finished product phosphoric acid obtained by the method both contain F, and the effect of recycling F in fluorite is achieved.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of calcium fluoride recycling, and in particular, to a method for recovering F from calcium fluoride waste residue. BACKGROUND

[0002] Calcium fluoride waste residue is mainly derived from inorganic and organic fluorine chemical production enterprises. A large amount of fluorine-containing wastewater is generated in the production and recycling process of traditional phosphorus chemical industry, fluorine chemical industry, photovoltaic power generation, and battery. Fluorine mainly exists in the form of hydrofluoric acid, fluorosilicic acid, and soluble fluoride salt in the wastewater. Direct discharge of fluorine-containing wastewater will pollute the natural environment, etc. Currently, calcium-containing alkaline raw materials such as calcium oxide, calcium hydroxide, and lime milk are usually added to precipitate fluorine ions in the wastewater to treat the fluorine-containing wastewater and obtain calcium fluoride waste residue. However, due to the different anion impurities contained in the fluorine-containing wastewater, different impurities will exist in the corresponding calcium fluoride waste residue, such as calcium carbonate and calcium sulfate. The existence of these impurities will make it difficult to recover F from calcium fluoride.

[0003] In view of this, the present disclosure is proposed. SUMMARY

[0004] The purpose of the present disclosure includes providing a method for recovering F from calcium fluoride waste residue to improve or solve the above technical problems.

[0005] The present disclosure can be achieved as follows:

[0006] The present disclosure provides a method for recovering F from calcium fluoride waste residue, which comprises the following steps: mixing and reacting phosphorite slurry doped with calcium fluoride waste residue with a first phosphoric acid solution and a sulfuric acid-containing acid solution, then performing a crystal growing treatment, and solid-liquid separation to obtain phosphogypsum and finished phosphoric acid.

[0007] The mass ratio of calcium fluoride waste residue to phosphorite powder contained in the phosphorite slurry is 0.01:100 to 4:100.

[0008] In an optional embodiment, the preparation of the phosphorite slurry comprises: mixing a second phosphoric acid solution, calcium fluoride waste residue, and phosphorite powder.

[0009] In an optional embodiment, the concentration of P2O5 in the first phosphoric acid solution is 20wt%-32wt%, and / or the concentration of P2O5 in the second phosphoric acid solution is 20wt%-32wt%.

[0010] In an optional embodiment, the concentration of P2O5 in the first phosphoric acid solution is equal to the concentration of P2O5 in the second phosphoric acid solution.

[0011] In an optional embodiment, the mass ratio of the calcium fluoride waste residue to the second phosphoric acid solution is 1:2 to 1:3, wherein the mass of the calcium fluoride waste residue is based on dry basis.

[0012] In an optional embodiment, the total mass of the first phosphoric acid solution and the second phosphoric acid solution to the mass of the phosphate rock powder in the phosphate rock slurry is 0.5:1 to 2:1, wherein the mass of the phosphate rock powder is based on dry basis.

[0013] In an optional embodiment, at least 80wt% of the calcium fluoride waste residue has a particle size of no more than 150μm.

[0014] In an optional embodiment, at least 80wt% of the phosphate rock powder in the phosphate rock slurry has a particle size of no more than 150μm.

[0015] In an optional embodiment, the acidic solution further comprises a third phosphoric acid solution.

[0016] In an optional embodiment, the mass ratio of the third phosphoric acid solution to the phosphate rock powder in the phosphate rock slurry is 1:1 to 4:1, wherein the mass of the phosphate rock powder is based on dry basis; the concentration of P2O5 in the third phosphoric acid solution is 10wt%-25wt%.

[0017] In an optional embodiment, the mass ratio of the third phosphoric acid solution to sulfuric acid is 1.5:1 to 5:1, wherein the concentration of sulfuric acid is 93wt%-98wt%.

[0018] In an optional embodiment, the phosphate rock slurry and the acidic solution are added to the first phosphoric acid solution at 70°C-85°C for reaction.

[0019] In an optional embodiment, the feeding time of the phosphate rock slurry and the acidic solution is 50min-60min.

[0020] In an optional embodiment, in the reaction liquid obtained by mixing the reaction, the concentration of P2O5 is 20wt%-32wt%, the concentration of SO3 is 15g / L-50g / L, and the liquid-solid ratio is 2:1 to 5:1.

[0021] In an optional embodiment, the crystal growing time is 4h-6h.

[0022] In an optional embodiment, the method further comprises washing the phosphogypsum obtained by solid-liquid separation, and collecting the washing liquid.

[0023] In an optional embodiment, the phosphogypsum is countercurrently washed with hot water.

[0024] In an optional embodiment, the temperature of the hot water is 60°C-80°C, and / or the countercurrent washing is performed for no less than 3 times.

[0025] In an optional embodiment, further comprising: mixing the washing liquid with part of the finished phosphoric acid to prepare a new first phosphoric acid solution or an acidic solution.

[0026] Advantages of the present disclosure include:

[0027] The method provided by the present disclosure can recover F in calcium fluoride waste residue by combining the two-water method wet-process phosphoric acid, doping a certain proportion of calcium fluoride waste residue in the phosphate ore slurry, and reacting F in the calcium fluoride waste residue with SiO2 in the phosphate ore to generate H2SiF6 or exist in the form of free F in the phosphoric acid solution, thereby playing a role in recovering F; F exceeding a certain proportion can react with Mg and Al metal impurities released by acidolysis of the phosphate ore to generate MgAl2F8-MgAlF5 complex precipitates and Na / K to generate Na2SiF6 / K2SiF6 precipitates, which are discharged out of the system with gypsum, causing loss of F; in addition, a small amount of F in the calcium fluoride waste residue can promote the conversion of calcium sulfate dihydrate crystals and improve the yield of phosphogypsum. The above method is relatively simple in operation, low in cost, short in process, and low in energy consumption, and can effectively recover F in the calcium fluoride waste residue. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present disclosure, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0029] Figure 1 The overall process flow chart of the method for recovering F in calcium fluoride waste residue provided by the present disclosure. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the embodiments of the present disclosure clearer, the technical solutions in the embodiments of the present disclosure will be described clearly and completely. The specific conditions not mentioned in the embodiments are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments not mentioned by the manufacturer are all conventional products that can be purchased on the market.

[0031] The method for recovering F in calcium fluoride waste residue provided by the present disclosure will be described in detail below.

[0032] As shown in Figure 1 The present disclosure provides a method for recovering F in calcium fluoride waste residue, which comprises the following steps: mixing phosphate ore slurry doped with calcium fluoride waste residue with a first phosphoric acid solution and an acidic solution containing sulfuric acid and then performing a crystal growing treatment, solid-liquid separation, to obtain phosphogypsum and finished phosphoric acid.

[0033] By combining the wet method of phosphoric acid with the two water method, the calcium fluoride waste residue to be recovered is doped in the phosphate ore slurry. The F in the calcium fluoride waste residue can react with SiO2 in the phosphate ore to generate H2SiF6 or exist in the form of free F in the phosphoric acid solution, thereby playing a role in recovering F. In addition, the F in the calcium fluoride waste residue can promote the conversion of calcium sulfate dihydrate crystals, thereby improving the yield of phosphogypsum.

[0034] For reference, the preparation of the phosphate ore slurry includes mixing the second phosphoric acid solution, the calcium fluoride waste residue, and the phosphate ore powder.

[0035] The mass ratio of the calcium fluoride waste residue (on a dry basis) to the phosphate ore powder (on a dry basis) can be 0.01:100 to 4:100, such as 0.01:100, 0.02:100, 0.05:100, 0.1:100, 0.2:100, 0.5:100, 1:100, 1.5:100, 2:100, 2.5:100, 3:100, 3.5:100, or 4:100, etc., and can also be any other value within the range of 0.01:100 to 4:100.

[0036] If the doping amount of the calcium fluoride waste residue in the phosphate ore slurry is too high, it can easily lead to the generation of MgAl2F8-MgAlF5 complex precipitates from the Mg and Al metal impurities released by the acidolysis of the phosphate ore, and the generation of Na2SiF6 / K2SiF6 precipitates from Na / K, which are discharged outside the system with the gypsum, thereby causing the loss of F.

[0037] Before doping, the calcium fluoride waste residue can be pretreated so that at least 80wt% of the calcium fluoride waste residue has a particle size of no more than 150μm. Illustratively, the pretreatment can be grinding the calcium fluoride waste residue.

[0038] To improve the uniformity of the mixing and the sufficiency of the reaction, at least 80wt% of the phosphate ore powder in the phosphate ore slurry has a particle size of no more than 150μm.

[0039] In some optional embodiments, the particle size of the doped calcium fluoride waste residue is substantially consistent with the particle size of the phosphate ore powder.

[0040] In the present disclosure, the concentration of P2O5 in the first phosphoric acid solution can be 20wt%-32wt%, such as 20wt%, 22wt%, 24wt%, 26wt%, 28wt%, 30wt%, or 32wt% etc., and can also be any other value within the range of 20wt%-32wt%.

[0041] The concentration of P2O5 in the second phosphoric acid solution can also be 20wt%-32wt%, such as 20wt%, 22wt%, 24wt%, 26wt%, 28wt%, 30wt%, or 32wt% etc., and can also be any other value within the range of 20wt%-32wt%.

[0042] In some optional embodiments, the concentration of P2O5 in the first phosphoric acid solution is equal to the concentration of P2O5 in the second phosphoric acid solution. In this scheme, the phosphoric acid solution with a preset P2O5 concentration can be uniformly prepared in advance, and then a part of it is used as the first phosphoric acid solution and another part is used as the second phosphoric acid solution. In other embodiments, the concentration of P2O5 in the first phosphoric acid solution is not equal to the concentration of P2O5 in the second phosphoric acid solution, but both are within the range of 20wt%-32wt%. The above-mentioned concentration of P2O5 meets the requirements of wet-process phosphoric acid production.

[0043] In the present disclosure, the mass ratio of calcium fluoride waste residue (on a dry basis) to the second phosphoric acid solution can be 1:2 to 1:3, such as 1:2, 1:2.2, 1:2.5, 1:2.8 or 1:3, etc., and can also be any other value within the range of 1:2 to 1:3.

[0044] By using the second phosphoric acid solution in the above-mentioned dosage range, the carbonates can be effectively removed, and the generated CO2 is beneficial to reduce the foam layer of the reaction system. However, if the dosage of the second phosphoric acid solution is too large, it will affect the mixed phosphate rock slurry, causing the acidity to increase, resulting in the Ca5(PO4)3+7H3PO4=5Ca(H2PO4)2+HF↑ reaction to move forward, and additional tail gas treatment equipment is required.

[0045] The mass ratio of the total mass of the first phosphoric acid solution and the second phosphoric acid solution to the mass of the phosphate rock powder (on a dry basis) in the phosphate rock slurry can be 0.5:1 to 2:1, such as 0.5:1, 0.8:1, 1:1, 1.2:1, 1.5:1, 1.8:1 or 2:1, etc., and can also be any other value within the range of 0.5:1 to 2:1.

[0046] In some embodiments, the moisture content of the phosphate rock slurry is 25wt%-35wt%, such as 25wt%, 28wt%, 30wt%, 32wt% or 35wt%, etc., which can be adjusted by adding water as appropriate.

[0047] After the second phosphoric acid solution reacts with calcium fluoride, a small amount of phosphoric acid remaining can further react with carbonates in the phosphate rock powder to generate CO2, which is beneficial to reduce the foam layer of the reaction system.

[0048] In the present disclosure, the acidic solution also contains a third phosphoric acid solution.

[0049] The mass ratio of the third phosphoric acid solution to the mass of the phosphate rock powder (on a dry basis) in the phosphate rock slurry can be 1:1 to 4:1, such as 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1 or 4:1, etc., and can also be any other value within the range of 1:1 to 4:1.

[0050] The concentration of P2O5 in the third phosphoric acid solution can be 10wt%-25wt%, such as 10wt%, 15wt%, 20wt%, or 25wt%, or other arbitrary values within the range of 10wt%-25wt%.

[0051] Exemplarily, the first phosphoric acid solution, the second phosphoric acid solution, and the third phosphoric acid solution used in the present disclosure can each be independently configured by dilute wet phosphoric acid with a P2O5 concentration of 20wt%-32wt%, concentrated wet phosphoric acid with a P2O5 concentration of 40wt%-50wt%, industrial-grade (or analytical-grade) phosphoric acid with a H3PO4 concentration of 75wt%, or industrial-grade (or analytical-grade) phosphoric acid with a H3PO4 concentration of 85wt% plus water. In addition, it can also be configured by other raw materials capable of forming a phosphoric acid solution.

[0052] The mass ratio of the third phosphoric acid solution to sulfuric acid can be 1.5:1 to 5:1, such as 1.5:1, 2:1, 3:1, 4:1, or 5:1, or other arbitrary values within the range of 1.5:1 to 5:1. Among them, the sulfuric acid is concentrated sulfuric acid, and the concentration thereof can be 93wt%-98wt%, such as 93wt%, 94wt%, 95wt%, 96wt%, 97wt%, or 98wt%, or other arbitrary values within the range of 93wt%-98wt%.

[0053] It should be noted that if the acid solution directly uses sulfuric acid with a concentration of 93wt%-98wt% without the third phosphoric acid solution, it is easy to cause the reaction process to appear a wrapping phenomenon (calcium sulfate is a slightly soluble substance, which can form a thin film on the surface of the phosphate rock particles to wrap the phosphate rock particles, hindering the further progress of the reaction), and it is also easy to cause the local supersaturation of the reaction system to be too high, resulting in a decrease in phosphorus yield. In addition, if the sulfuric acid used is equal to the concentration of sulfate ions contained in the pre-set acid solution, too much water will be brought into the reaction system, resulting in a decrease in acid concentration (P2O5) content. In order to maintain a suitable acid concentration, it is necessary to reduce the excess water through other process steps, but reducing water often only through adjusting the amount of subsequent washing water to achieve, which in turn easily leads to incomplete washing, resulting in an increase in phosphorus loss.

[0054] In the present disclosure, the mixing reaction is carried out at a temperature of 70°C-85°C (such as 70°C, 75°C, 80°C, or 85°C, etc.).

[0055] In some embodiments, the phosphate rock slurry and the acid solution can be added to the first phosphoric acid solution at a temperature of 70°C-85°C for reaction. In operation, the phosphate rock slurry can be slowly added to the first phosphoric acid solution at a temperature of 70°C-85°C, and the acid solution can be slowly added at the same time.

[0056] The feeding time of the phosphate rock slurry and the acidic solution is 50-60 minutes, such as 50 minutes, 55 minutes or 60 minutes. In some embodiments, the feeding time of the phosphate rock slurry is 50-60 minutes, and the feeding time of the acidic solution is 50-60 minutes, which can also be understood as the feeding of the phosphate rock slurry and the acidic solution being completed together within 50-60 minutes.

[0057] In the present disclosure, the concentration of P2O5 in the reaction liquid obtained by the mixing reaction is 20-32 wt% (such as 20 wt%, 24 wt%, 26 wt%, 28 wt%, 30 wt% or 32 wt%), the concentration of SO3 is 15-50 g / L (such as 15 g / L, 20 g / L, 25 g / L, 30 g / L, 35 g / L, 40 g / L, 45 g / L or 50 g / L), and the liquid-solid ratio is 2:1 to 5:1 (such as 2:1, 3:1, 4:1 or 5:1). That is, the degree that meets the above conditions is taken as the end point of the mixing reaction.

[0058] The phosphate rock can be decomposed by sulfuric acid in the above reaction process to obtain phosphoric acid, which belongs to the wet-process phosphoric acid production method. The main reaction equations involved in the reaction process are as follows:

[0059] ①, Ca5(PO4)3+ 5H2SO4+ 10H2O = 3H3PO4+ 5CaSO4·2H2O + HF↑, wherein H3PO4 is the finished product phosphoric acid, and CaSO4·2H2O is phosphogypsum;

[0060] ②, CaF2+ H2SO4 = CaSO4 + HF↑, wherein CaSO4 is also phosphogypsum.

[0061] The sub-reaction equation involved in the above ① includes:

[0062] Ca5(PO4)3+ 7H3PO4 = 5Ca(H2PO4)2+ HF↑;

[0063] 5Ca(H2PO4)2+ 5H2SO4+ 5nH2O = 5CaSO4·nH2O + 10H3PO4.

[0064] In the sub-reaction equation, the first step is the reaction of phosphate rock and the first phosphoric acid solution and phosphoric acid in the second phosphoric acid solution to generate monocalcium phosphate, and the generated monocalcium phosphate reacts with a slight excess of sulfuric acid to generate calcium sulfate crystals and phosphoric acid.

[0065] In addition, during the entire reaction process, some side reactions are also involved, for example:

[0066] ③, the impurities such as iron, aluminum, sodium and potassium in the phosphate rock undergo the following reactions:

[0067] Fe2O3 + H3PO4 = FePO4↓ + 3H2O;

[0068] Al2O3 + H3PO4 = AlPO4↓ + 3H2O;

[0069] Na2O + H2SiF6 = Na2SiF6↓ + H2O;

[0070] K2O + H2SiF6 = K2SiF6↓ + H2O.

[0071] IV. Magnesium mainly exists in carbonates, and carbonates in phosphate ores such as dolomite and calcite are first decomposed by sulfuric acid and release carbon dioxide:

[0072] CaCO3 + H2SO4 = CaSO4 + CO2↑ + H2O;

[0073] CaCO3·MgCO3 + H2SO4 = CaSO4 + MgSO4 + CO2↑ + H2O.

[0074] In addition, hydrogen fluoride reacts with SiO2 in phosphate ores:

[0075] 6HF + SiO2 = H2SiF6 + 2H2O;

[0076] H2SiF6 + SiO2 = SiF4↑ + 2H2O;

[0077] HF can also be complexed with metal ions to form various complex salt precipitates, such as:

[0078] 10HF + Al2O3 + 2MgO → 2MgAlF5↓ + 5H2O;

[0079] 8HF + Al2O3 + MgO → 2MgAl2F8↓ + 4H2O, etc.

[0080] It can be seen that F in the gas phase mainly exists in the form of SiF4, and F in the liquid phase mainly exists in the form of H2SiF6 or HF. The partial pressure of SiF4 gas in the escaping gas in the two-water method wet-process phosphoric acid is very small (the escaping F accounts for about 0.5-1% of the total F, and the acidic F-containing water after water absorption is used for water supplement in the fluorine absorption tower during the concentration in the back end, which is ignored in the calculation of the present patent), and the environmental protection treatment is mainly carried out to prevent environmental pollution. 3SiF4 + (n + 2)H2O = SiO2·nH2O↓ + 2H2SiF6.

[0081] In the present disclosure, the growth time can be 4h-6h, such as 4h, 4.5h, 5h, 5.5h or 6h, etc., and can also be any other value within the range of 4h-6h.

[0082] In the present disclosure, the solid-liquid separation can be performed by filtration as an example but not by limitation.

[0083] After the solid-liquid separation, the phosphogypsum and product acid can be obtained.

[0084] In order to further improve the purity of the phosphogypsum and improve the P yield, the solid phase (phosphogypsum) obtained by the solid-liquid separation can be washed, and the washing liquid is collected.

[0085] In some embodiments, the phosphogypsum can be countercurrently washed by hot water. The temperature of the hot water can be 60-80°C, such as 60°C, 65°C, 70°C, 75°C or 80°C, etc. The number of countercurrent washing can be, for example, not less than 3 times, such as 3 times or 4 times, etc. In other embodiments, the number of countercurrent washing can also be adjusted according to actual needs.

[0086] After obtaining the washing liquid, the washing liquid is mixed with part of the finished phosphoric acid to prepare a new first phosphoric acid solution or an acidic solution. The amount of the finished phosphoric acid used for mixing with the washing liquid is set according to the preset concentration of the first phosphoric acid solution or the acidic solution. The washed phosphogypsum is used for stockpiling or comprehensive utilization according to needs.

[0087] Taking 3 times of countercurrent washing as an example, the phosphogypsum is first countercurrently washed by fresh hot water to obtain first washing water and first washed phosphogypsum; the first washing water is used to second countercurrently wash the first washed phosphogypsum to obtain second washing water and second washed phosphogypsum; the second washing water is used to third countercurrently wash the second washed phosphogypsum to obtain third washing water and third washed phosphogypsum. The third washing water is used to mix with part of the finished phosphoric acid to prepare a new first phosphoric acid solution or an acidic solution, and the phosphogypsum after three times of washing is used for stockpiling or comprehensive utilization according to needs.

[0088] As described above, the present disclosure is based on the dihydrate method wet-process phosphoric acid, and calcium fluoride waste residue is doped in the phosphor slurry to recover F in the calcium fluoride waste residue. F in the calcium fluoride reacts with SiO2 in the phosphor to generate H2SiF6 or exists in the phosphoric acid solution in the form of free F to play a role in recovering F. A small amount of F can also promote the conversion of dihydrate calcium sulfate crystals to achieve the multiple effects of recovering F in the calcium fluoride and improving the phosphorus yield. The method provided by the present disclosure has a simple operation process and is easy to realize industrialization, and achieves the multiple effects of comprehensive utilization of calcium fluoride waste residue and improvement of phosphorus yield.

[0089] The features and performances of the present disclosure are further described in detail below in combination with embodiments.

[0090] The phosphorite in the following examples and comparative examples is all from Hubei Yichang, the calcium fluoride residue is all from the residue after the treatment of fluorine-containing wastewater, dried, the wet-process phosphoric acid used is all from the finished product of a certain phosphorus chemical enterprise in Hubei, and the main component composition of the above materials is shown in Table 1.

[0091] Table 1 Composition of material (wt%)

[0092]

[0093]

[0094] Example 1

[0095] The present embodiment provides a method for recovering F in calcium fluoride residue, which comprises the following steps:

[0096] S1: configuring an initial phosphoric acid solution and an acid solution: 825.16 g of wet-process phosphoric acid with P2O5 concentration of 46.56 wt% is weighed and added with 711.62 g of water to configure an intermediate phosphoric acid solution with P2O5 concentration of 25 wt%; 567.79 g of wet-process phosphoric acid with P2O5 concentration of 46.56 wt% is weighed and added with 1194.64 g of water to configure a third phosphoric acid solution with P2O5 concentration of 15 wt%, and the third phosphoric acid solution with P2O5 concentration of 15 wt% is mixed with 830.67 g of concentrated sulfuric acid with concentration of 98 wt% to obtain an acid solution, and the mass ratio of the third phosphoric acid solution with P2O5 concentration of 15 wt% to the concentrated sulfuric acid with concentration of 98 wt% in the acid solution is 2.12:1.

[0097] S2: calcium fluoride residue pretreatment: the calcium fluoride residue is ground into powder so that the particle size of at least 80 wt% of the calcium fluoride residue is not more than 150 μm. 30 g of the intermediate phosphoric acid solution is taken as a second phosphoric acid solution, 10 g of the calcium fluoride residue powder is added thereto, and stirred uniformly to remove the carbonate to obtain an intermediate slurry.

[0098] S3: mixing with phosphorite powder: the phosphorite powder is ground so that the particle size of at least 80 wt% of the phosphorite powder is not more than 150 μm, the intermediate slurry is mixed with 1000 g of the above phosphorite powder, and 402.86 g of water is added to adjust the slurry to a phosphorite slurry with moisture content of 30 wt%, and the residual small amount of phosphoric acid in the intermediate slurry can react with the carbonate in the phosphorite powder to generate CO2 to reduce the foam layer of the reaction system. The mass ratio of the dry basis calcium fluoride residue in the intermediate slurry to the dry basis phosphorite powder is 1:100.

[0099] S4: The remaining intermediate phosphoric acid solution in S1 is transferred to a 5L beaker as the first phosphoric acid solution, the beaker is placed in a water bath for heating, and the first phosphoric acid solution is mechanically stirred, the water bath temperature is 85°C, when the temperature of the first phosphoric acid solution reaches 70°C, the phosphorite slurry in S3 is slowly added, and the acid solution in S1 is slowly added at the same time, the total feeding time of the phosphorite slurry and the acid solution is controlled within 60 min, the temperature of the reaction is controlled within 75-80°C, until the concentration of P2O5 in the reaction solution is 25wt%, the concentration of SO3 is 35g / L, and the liquid-solid ratio is 2.5:1. After the reaction is completed, the crystal is maintained for 5h.

[0100] S5: The slurry after the crystal is maintained (crystal-maintained slurry) is filtered to obtain finished phosphoric acid and phosphogypsum. The phosphogypsum is washed with 1500g of 80°C hot water in a countercurrent manner for 3 times to obtain, after washing, the phosphogypsum is stacked or further utilized comprehensively, and the washing solution after washing is mixed with part of the finished phosphoric acid to prepare the first phosphoric acid solution in S1 or mixed with concentrated sulfuric acid to prepare the acid solution in S1.

[0101] In this embodiment, the concentration of P2O5 in the first phosphoric acid solution and the second phosphoric acid solution is 25wt%, and the mass ratio of dry basis calcium fluoride waste residue to dry basis phosphorite powder is 1:100 (i.e., the doping amount of calcium fluoride waste residue is 1wt%).

[0102] Example 2

[0103] The embodiment provides a method for recycling F in calcium fluoride waste residue, which comprises the following steps:

[0104] S1: preparing an initial phosphoric acid solution and an acid solution: 842.81g of wet concentrated phosphoric acid with a P2O5 concentration of 46.56wt% is weighed and mixed with 726.84g of water to prepare an intermediate phosphoric acid solution with a P2O5 concentration of 25wt%; 571.82g of wet concentrated phosphoric acid with a P2O5 concentration of 46.56wt% is weighed and mixed with 1203.10g of water to prepare a third phosphoric acid solution with a P2O5 concentration of 15wt%, the third phosphoric acid solution with a P2O5 concentration of 15wt% is mixed with 837.17g of 98wt% concentrated sulfuric acid to obtain an acid solution, and the mass ratio of the third phosphoric acid solution with a P2O5 concentration of 15wt% to the 98wt% concentrated sulfuric acid in the acid solution is 2.12:1.

[0105] S2: calcium fluoride waste residue pretreatment: the calcium fluoride waste residue is ground into powder to make at least 80wt% of the calcium fluoride waste residue have a particle size of not more than 150μm. 60g of the intermediate phosphoric acid solution is taken as a second phosphoric acid solution, 20g of calcium fluoride waste residue powder is added thereto, and stirred uniformly to remove carbonates to obtain an intermediate slurry.

[0106] S3: Mixing with phosphate rock powder: The phosphate rock powder is ground to have a particle size of at most 150 μm for at least 80 wt% of the phosphate rock powder, the intermediate slurry is mixed with 1000 g of the above phosphate rock powder, and 377.14 g of water is added to adjust the slurry to have a moisture content of 30 wt% of phosphate rock slurry, and the residual small amount of phosphoric acid in the intermediate slurry can react with the carbonate in the phosphate rock powder to generate CO2 to reduce the foam layer of the reaction system. The mass ratio of dry basis calcium fluoride waste residue to dry basis phosphate rock powder in the intermediate slurry is 2:100.

[0107] S4: Same as step S4 in Example 1.

[0108] S5: Same as step S5 in Example 1.

[0109] In this example, the concentration of P2O5 in the first phosphoric acid solution and the second phosphoric acid solution is 25 wt%, and the mass ratio of dry basis calcium fluoride waste residue to dry basis phosphate rock powder is 2:100 (i.e. the doping amount of calcium fluoride waste residue is 2 wt%).

[0110] Example 3

[0111] The present example provides a method for recovering F in calcium fluoride waste residue, which comprises the following steps:

[0112] S1: Preparation of initial phosphoric acid solution and acid solution: 859.86 g of wet concentrated phosphoric acid with a P2O5 concentration of 46.56 wt% is weighed and added with 741.54 g of water to prepare an intermediate phosphoric acid solution with a P2O5 concentration of 25 wt%; 576.42 g of wet concentrated phosphoric acid with a P2O5 concentration of 46.56 wt% is weighed and added with 1212.78 g of water to prepare a third phosphoric acid solution with a P2O5 concentration of 15 wt%, and the third phosphoric acid solution with a P2O5 concentration of 15 wt% is mixed with 843.66 g of concentrated sulfuric acid with a concentration of 98 wt% to obtain an acid solution, and the mass ratio of the 15 wt% phosphoric acid solution to the 98 wt% concentrated sulfuric acid in the acid solution is 2.12:1.

[0113] S2: Pretreatment of calcium fluoride waste residue: The calcium fluoride waste residue is ground into powder to have a particle size of at most 150 μm for at least 80 wt% of the calcium fluoride waste residue. 90 g of the intermediate phosphoric acid solution is taken as the second phosphoric acid solution, 30 g of calcium fluoride waste residue powder is added thereto, and the mixture is stirred uniformly to remove the carbonate to obtain an intermediate slurry.

[0114] S3: Mixing with phosphate rock powder: The phosphate rock powder is ground to have a particle size of at most 150 μm for at least 80 wt% of the phosphate rock powder, the intermediate slurry is mixed with 1000 g of the above phosphate rock powder, and 377.14 g of water is added to adjust the slurry to have a moisture content of 30 wt% of phosphate rock slurry, and the residual small amount of phosphoric acid in the intermediate slurry can react with the carbonate in the phosphate rock powder to generate CO2 to reduce the foam layer of the reaction system. The mass ratio of dry basis calcium fluoride waste residue to dry basis phosphate rock powder in the intermediate slurry is 2:100.

[0115] S4: Same as step S4 in Example 1.

[0116] S5: Same as step S5 in Example 1.

[0117] In this example, the concentration of P2O5 in the first and second phosphoric acid solutions is 25wt%, and the mass ratio of dry basis calcium fluoride waste residue to dry basis phosphate rock powder is 3:100 (i.e., the doping amount of calcium fluoride waste residue is 3wt%).

[0118] Example 4

[0119] This example provides a method for recovering F from calcium fluoride waste residue, which comprises the following steps:

[0120] S1: Prepare the initial phosphoric acid solution and the acidic solution: weigh 877.25g of wet concentrated phosphoric acid with a P2O5 concentration of 46.56wt% to prepare an intermediate phosphoric acid solution with a P2O5 concentration of 25wt% by adding 756.53g of water; weigh 580.70g of wet concentrated phosphoric acid with a P2O5 concentration of 46.56wt% to prepare a third phosphoric acid solution with a P2O5 concentration of 15wt% by adding 1221.79g of water, and mix and stir 850.16g of 98wt% concentrated sulfuric acid with the third phosphoric acid solution with a P2O5 concentration of 15wt% to obtain an acidic solution, and the mass ratio of the 15wt% phosphoric acid solution to the 98wt% concentrated sulfuric acid in the acidic solution is 2.12:1.

[0121] S2: Pretreatment of calcium fluoride waste residue: grind the calcium fluoride waste residue into powder so that at least 80wt% of the calcium fluoride waste residue has a particle size of not more than 150μm. Take 120g of the intermediate phosphoric acid solution as the second phosphoric acid solution, add 40g of calcium fluoride waste residue powder thereto, and stir uniformly to remove the carbonate to obtain an intermediate slurry.

[0122] S3: Mix with phosphate rock powder: grind the phosphate rock powder so that at least 80wt% of the phosphate rock powder has a particle size of not more than 150μm, mix the intermediate slurry with 1000g of the above phosphate rock powder, and add 325.71g of water to adjust the slurry to a phosphate rock slurry with a moisture content of 30wt%, and the residual small amount of phosphoric acid in the intermediate slurry can react with the carbonate in the phosphate rock powder to generate CO2 to reduce the foam layer of the reaction system. The mass ratio of dry basis calcium fluoride waste residue to dry basis phosphate rock powder in the intermediate slurry is 4:100.

[0123] S4: Same as step S4 in Example 1.

[0124] S5: Same as step S5 in Example 1.

[0125] In this embodiment, the concentration of P2O5 in the first and second phosphoric acid solutions is 25wt%, the mass ratio of dry basis calcium fluoride waste residue to dry basis phosphate rock powder is 4:100 (i.e. the doping amount of calcium fluoride waste residue is 4wt%).

[0126] Comparative Example 1

[0127] This comparative example provides a method for recovering F from calcium fluoride waste residue, which comprises the following steps:

[0128] S1: Configure the initial phosphoric acid solution and the acid solution: weigh 807.43g of wet concentrated phosphoric acid with a P2O5 concentration of 46.56wt%, add 696.32g of water to configure a first phosphoric acid solution with a P2O5 concentration of 25wt%; weigh 563.90g of wet concentrated phosphoric acid with a P2O5 concentration of 46.56wt%, add 1186.45g of water to configure a third phosphoric acid solution with a P2O5 concentration of 15wt%, and mix 824.18g of 98wt% concentrated sulfuric acid with the 15wt% phosphoric acid solution to obtain an acid solution, the mass ratio of the 15wt% phosphoric acid solution to the 98wt% concentrated sulfuric acid in the acid solution is 2.12:1.

[0129] S2: Configure the phosphate rock slurry: grind the phosphate rock powder to make the particle size of at least 80wt% of the phosphate rock powder not more than 150μm, weigh 1000g of the above phosphate rock powder, and add 428.57g of water to adjust the slurry to a phosphate rock slurry with a moisture content of 30wt%.

[0130] S3: Transfer the first phosphoric acid solution in S1 to a 5L beaker, heat the beaker in a water bath, and mechanically stir the first phosphoric acid solution, the water bath temperature is 85℃, when the temperature of the first phosphoric acid solution reaches 70℃, slowly add the phosphate rock slurry in S2, and simultaneously slowly add the acid solution in S1, the total feeding time of the phosphate rock slurry and the acid solution is controlled within 60min, the reaction temperature is controlled at 75-80℃, until the concentration of P2O5 in the reaction solution is 25wt%, the concentration of SO3 is 35g / L, and the liquid-solid ratio is 2.5:1. After the reaction is completed, the crystals are aged for 5h.

[0131] S4: Same as step S4 in Example 1.

[0132] That is, compared with Example 1, the main difference of this comparative example is that no calcium fluoride waste residue is doped.

[0133] Based on the doping amount of calcium fluoride waste residue being 2wt%, the effects of the P2O5 concentration of the first and second phosphoric acid solutions being 20wt% and the P2O5 concentration of the first and second phosphoric acid solutions being 30wt% are studied.

[0134] Example 5

[0135] The embodiment provides a method for recycling F in calcium fluoride waste residue, which comprises the following steps.

[0136] S1: configuring an initial phosphoric acid solution and an acid solution: 350.62 g of wet concentrated phosphoric acid with a P2O5 concentration of 46.56 wt% is weighed and added with 465.63 g of water to configure an intermediate phosphoric acid solution with a P2O5 concentration of 20 wt%; 651.72 g of wet concentrated phosphoric acid with a P2O5 concentration of 46.56 wt% is weighed and added with 1876.95 g of water to configure a third phosphoric acid solution with a P2O5 concentration of 12 wt%; the third phosphoric acid solution with a P2O5 concentration of 12 wt% is mixed with 837.17 g of concentrated sulfuric acid with a concentration of 98 wt% to obtain an acid solution, and the mass ratio of the 12 wt% phosphoric acid solution to the concentrated sulfuric acid with a concentration of 98 wt% in the acid solution is 3.02:1.

[0137] S2: calcium fluoride waste residue pretreatment: the calcium fluoride waste residue is ground into powder so that the particle size of at least 80 wt% of the calcium fluoride waste residue is not more than 150 μm. 60 g of the intermediate phosphoric acid solution is taken as a second phosphoric acid solution, 20 g of the calcium fluoride waste residue powder is added thereto, and stirring is uniformly performed to remove carbonates to obtain an intermediate slurry.

[0138] S3: mixing with phosphate rock powder: the phosphate rock powder is ground so that the particle size of at least 80 wt% of the phosphate rock powder is not more than 150 μm, the intermediate slurry is mixed with 1000 g of the above phosphate rock powder, and 377.14 g of water is added to adjust the slurry to a phosphate rock slurry with a moisture content of 30 wt%, and a small amount of residual phosphoric acid in the intermediate slurry can react with carbonates in the phosphate rock powder to generate CO2 to reduce the foam layer of the reaction system. The mass ratio of the dry basis calcium fluoride waste residue in the intermediate slurry to the dry basis phosphate rock powder is 2:100.

[0139] S4: the intermediate phosphoric acid solution remaining in S1 is transferred to a 5 L beaker as a first phosphoric acid solution, the beaker is placed in a water bath for heating, and mechanical stirring is performed on the first phosphoric acid solution, the water bath temperature is 85 °C, when the temperature of the first phosphoric acid solution reaches 70 °C, the phosphate rock slurry in S3 is slowly added, and the acid solution in S1 is slowly added at the same time, the feeding time of the phosphate rock slurry and the acid solution is controlled to be 60 min, the temperature of the reaction is controlled to be 75-80 °C, until the concentration of P2O5 in the reaction liquid is 20 wt%, the concentration of SO3 is 45 g / L, and the liquid-solid ratio is 2.5:1. After the reaction is completed, the crystal is maintained for 5 h.

[0140] S5: the slurry after the crystal is maintained is filtered to obtain finished product phosphoric acid and phosphogypsum. The phosphogypsum is washed with 1800 g of hot water with a temperature of 80 °C countercurrently for 3 times to obtain, after the washing, the phosphogypsum is stacked or further comprehensively utilized, and the washing liquid after the washing is mixed with part of the finished product phosphoric acid to prepare the first phosphoric acid solution in S1 or is mixed with concentrated sulfuric acid to configure the acid solution in S1.

[0141] In this example, the concentration of P2O5 in the first phosphoric acid solution and the second phosphoric acid solution is 20wt%, and the mass ratio of dry basis calcium fluoride waste residue to dry basis phosphate rock powder is 2:100 (i.e., the doping amount of calcium fluoride waste residue is 2wt%).

[0142] Comparative Example 2

[0143] This comparative example provides a method for recovering F in calcium fluoride waste residue, which comprises the following steps:

[0144] S1: configure the initial phosphoric acid solution and the acid solution: weigh 322.90g of wet concentrated phosphoric acid with a P2O5 concentration of 46.56wt%, add 428.81g of water to configure a first phosphoric acid solution with a P2O5 concentration of 20wt%; weigh 641.50g of wet concentrated phosphoric acid with a P2O5 concentration of 46.56wt%, add 1847.52g of water to configure a third phosphoric acid solution with a P2O5 concentration of 12wt%, and mix 824.18g of 98wt% concentrated sulfuric acid with the 12wt% phosphoric acid solution to obtain an acid solution, the mass ratio of the 12wt% phosphoric acid solution to the 98wt% concentrated sulfuric acid in the acid solution is 3.02:1.

[0145] S2: configure the phosphate rock slurry: grind the phosphate rock powder so that at least 80wt% of the phosphate rock powder has a particle size of not more than 150μm, weigh 1000g of the above phosphate rock powder, and add 428.57g of water to slurry the phosphate rock powder to obtain a phosphate rock slurry with a moisture content of 30wt%.

[0146] S3: transfer the first phosphoric acid solution in S1 to a 5L beaker, heat the beaker in a water bath, and mechanically stir the first phosphoric acid solution, the water bath temperature is 85℃, when the temperature of the first phosphoric acid solution reaches 70℃, slowly add the phosphate rock slurry in S2, and simultaneously slowly add the acid solution in S1, the total feeding time of the phosphate rock slurry and the acid solution is controlled within 60min, the temperature of the reaction is controlled within 75-80℃, until the concentration of P2O5 in the reaction solution is 20wt% and the concentration of SO3 is 45g / L, and the liquid-solid ratio is 2.5:1. After the reaction is completed, the crystals are aged for 5h.

[0147] S4: the same as step S4 in Example 5.

[0148] That is, compared with Example 5, the main difference of this comparative example is that no calcium fluoride waste residue is doped.

[0149] Example 6

[0150] This example provides a method for recovering F in calcium fluoride waste residue, which comprises the following steps:

[0151] S1: Preparation of initial phosphoric acid solution and acid solution: 1170.27 g of wet concentrated phosphoric acid with P2O5 concentration of 46.56 wt% was weighed and mixed with 645.99 g of water to prepare an intermediate phosphoric acid solution with P2O5 concentration of 30 wt%; 656.64 g of wet concentrated phosphoric acid with P2O5 concentration of 46.56 wt% was weighed and mixed with 872.01 g of water to prepare a third phosphoric acid solution with P2O5 concentration of 20 wt%; the third phosphoric acid solution with P2O5 concentration of 20 wt% was mixed with 837.17 g of concentrated sulfuric acid with concentration of 98 wt% to obtain an acid solution, and the mass ratio of the 20 wt% phosphoric acid solution to the 98 wt% concentrated sulfuric acid in the acid solution was 1.82:1.

[0152] S2: Pretreatment of calcium fluoride waste residue: the calcium fluoride waste residue was ground into powder so that at least 80 wt% of the calcium fluoride waste residue had a particle size of not more than 150 μm. 60 g of the intermediate phosphoric acid solution was taken as a second phosphoric acid solution, and 20 g of the calcium fluoride waste residue powder was added thereto and stirred uniformly to remove carbonates to obtain an intermediate slurry.

[0153] S3: Mixing with phosphate rock powder: the phosphate rock powder was ground so that at least 80 wt% of the phosphate rock powder had a particle size of not more than 150 μm; the intermediate slurry was mixed with 1000 g of the above phosphate rock powder, and 377.14 g of water was added to adjust the slurry to a phosphate rock slurry with a moisture content of 30 wt%; a small amount of residual phosphoric acid in the intermediate slurry could react with carbonates in the phosphate rock powder to generate CO2 to reduce the foam layer of the reaction system. The mass ratio of dry basis calcium fluoride waste residue to dry basis phosphate rock powder in the intermediate slurry was 2:100.

[0154] S4: The remaining intermediate phosphoric acid solution in S1 was transferred to a 5 L beaker as a first phosphoric acid solution, the beaker was placed in a water bath for heating, and the first phosphoric acid solution was mechanically stirred; the water bath temperature was 85 °C; when the temperature of the first phosphoric acid solution reached 70 °C, the phosphate rock slurry in S3 was slowly added, and the acid solution in S1 was slowly added at the same time; the total feeding time of the phosphate rock slurry and the acid solution was controlled to be 50 min-60 min; the temperature of the reaction was controlled to be 75 °C-80 °C; until the concentration of P2O5 in the reaction liquid was 25 wt%, the concentration of SO3 was 25 g / L, and the liquid-solid ratio was 2.5:1; and the reaction was completed, and the crystal was maintained for 5 h.

[0155] S5: The slurry after the crystal maintenance was filtered to obtain finished product phosphoric acid and phosphogypsum; the phosphogypsum was washed with 1300 g of hot water at 80 °C countercurrently for 3 times to obtain washed phosphogypsum; the washed phosphogypsum was stacked or further utilized; and the washing liquid after the washing was mixed with part of the finished product phosphoric acid to prepare the first phosphoric acid solution in S1 or mixed with concentrated sulfuric acid to prepare the acid solution in S1.

[0156] In this example, the concentration of P2O5 in the first and second phosphoric acid solutions is 30wt%, and the mass ratio of dry basis calcium fluoride waste residue to dry basis phosphate rock powder is 2:100 (i.e., the doping amount of calcium fluoride waste residue is 2wt%).

[0157] Comparative Example 3

[0158] This comparative example provides a method for recovering F in calcium fluoride waste residue, which comprises the following steps:

[0159] S1: Configure the initial phosphoric acid solution and the acid solution: weigh 1132.11g of wet concentrated phosphoric acid with a P2O5 concentration of 46.56wt%, add 624.92g of water to configure a first phosphoric acid solution with a P2O5 concentration of 30wt%; weigh 642.83g of wet concentrated phosphoric acid with a P2O5 concentration of 46.56wt%, add 853.67g of water to configure a third phosphoric acid solution with a P2O5 concentration of 20wt%, and mix 824.18g of 98wt% concentrated sulfuric acid with the 20wt% phosphoric acid solution to obtain an acid solution, the mass ratio of the 20wt% phosphoric acid solution to the 98wt% concentrated sulfuric acid in the acid solution is 1.82:1.

[0160] S2: Configure the phosphate rock slurry: grind the phosphate rock powder so that at least 80wt% of the phosphate rock powder has a particle size of not more than 150μm, weigh 1000g of the above phosphate rock powder, and add 428.57g of water to slurry the phosphate rock powder to obtain a phosphate rock slurry with a moisture content of 30wt%.

[0161] S3: Transfer the first phosphoric acid solution in S1 to a 5L beaker, heat 1300g of the beaker in a water bath, and mechanically stir the first phosphoric acid solution, the water bath temperature is 85℃, when the temperature of the first phosphoric acid solution reaches 70℃, slowly add the phosphate rock slurry in S2, and simultaneously slowly add the acid solution in S1, the total feeding time of the phosphate rock slurry and the acid solution is controlled within 60min, the reaction temperature is controlled at 75-80℃, until the concentration of P2O5 in the reaction solution is 30wt%, the concentration of SO3 is 25g / L, and the liquid-solid ratio is 2.5:1. After the reaction is completed, the crystals are aged for 5h.

[0162] S4: The same as step S4 in Example 6.

[0163] That is, compared with Example 6, the main difference of this comparative example is that no calcium fluoride waste residue is doped.

[0164] Considering the interference of impurity ions such as Mg and Al in the initial phosphoric acid solution, the following is verified with analytical pure phosphoric acid.

[0165] Example 7

[0166] This example provides a method for recovering F in calcium fluoride waste residue, which comprises the following steps:

[0167] S1: Preparation of initial phosphoric acid solution and acid solution: 637.22 g of 85wt% analytical pure phosphoric acid was weighed and mixed with 932.43 g of water to prepare an intermediate phosphoric acid solution with a P2O5 concentration of 25wt%; 432.33 g of 85wt% analytical pure phosphoric acid was weighed and mixed with 1342.58 g of water to prepare a third phosphoric acid solution with a P2O5 concentration of 15wt%; the third phosphoric acid solution with a P2O5 concentration of 15wt% was mixed with 837.17 g of 98wt% concentrated sulfuric acid to obtain an acid solution, and the mass ratio of the third phosphoric acid solution with a P2O5 concentration of 15wt% to the 98wt% concentrated sulfuric acid in the acid solution was 2.12:1.

[0168] S2: Pretreatment of calcium fluoride waste residue: The calcium fluoride waste residue was ground into powder so that at least 80wt% of the calcium fluoride waste residue had a particle size of not more than 150 μm. 60 g of the intermediate phosphoric acid solution was taken as a second phosphoric acid solution, and 20 g of the calcium fluoride waste residue powder was added thereto and stirred uniformly to remove the carbonate and obtain an intermediate slurry.

[0169] S3: Mixing with phosphate rock powder: The phosphate rock powder was ground so that at least 80wt% of the phosphate rock powder had a particle size of not more than 150 μm, and the intermediate slurry was mixed with 1000 g of the above phosphate rock powder, and 377.14 g of water was added to adjust the slurry to a phosphate rock slurry with a moisture content of 30wt%, and the residual small amount of phosphoric acid in the intermediate slurry could react with the carbonate in the phosphate rock powder to generate CO2 to reduce the foam layer of the reaction system. The mass ratio of the dry basis calcium fluoride waste residue to the dry basis phosphate rock powder in the intermediate slurry was 2:100.

[0170] S4: Same as step S4 in Example 1.

[0171] S5: Same as step S5 in Example 1.

[0172] In this example, the initial phosphoric acid was analytical pure phosphoric acid, the P2O5 concentration in the first phosphoric acid solution and the second phosphoric acid solution was 25wt%, and the mass ratio of the dry basis calcium fluoride waste residue to the dry basis phosphate rock powder was 2:100 (i.e. the doping amount of the calcium fluoride waste residue was 2wt%).

[0173] Comparative Example 4

[0174] This comparative example provides a method for recovering F from calcium fluoride waste residue, which comprises the following steps:

[0175] S1: configuration of initial phosphoric acid solution and acid solution: take 610.47 g of H3PO4 with a concentration of 85wt% of analytical pure phosphoric acid, add 893.28 g of water to configure a first phosphoric acid solution with a P2O5 concentration of 25wt%; take 426.35 g of H3PO4 with a concentration of 85wt% of analytical pure phosphoric acid, add 1324.00 g of water to configure a third phosphoric acid solution with a P2O5 concentration of 15wt%, mix the 15wt% third phosphoric acid solution with 824.18 g of 98wt% concentrated sulfuric acid and stir uniformly to obtain an acid solution, the mass ratio of 20wt% phosphoric acid solution to 98wt% concentrated sulfuric acid in the acid solution is 2.12:1.

[0176] S2: configuration of phosphate rock slurry: same as example 7.

[0177] S3: transfer the first phosphoric acid solution in S1 to a 5L beaker, heat the beaker in a water bath, and mechanically stir the first phosphoric acid solution, the water bath temperature is 85℃, when the temperature of the first phosphoric acid solution reaches 70℃, slowly add the phosphate rock slurry in S2, and simultaneously slowly add the acid solution in S1, the total feeding time of the phosphate rock slurry and the acid solution is controlled within 60 min, the reaction temperature is controlled at 75-80℃, until the P2O5 concentration in the reaction liquid is 30wt%, the SO3 concentration is 35g / L, and the liquid-solid ratio is 2.5:1. After the reaction is completed, the crystal is maintained for 5h.

[0178] S4: same as step S4 in example 7.

[0179] That is, the present comparative example is mainly different from example 7 in that no calcium fluoride waste residue is doped.

[0180] Comparative example 5

[0181] The present comparative example provides a method for recovering F from calcium fluoride waste residue, which comprises the following steps:

[0182] S1: configuration of initial phosphoric acid solution and acid solution: take 894.57 g of wet concentrated phosphoric acid with a P2O5 concentration of 46.56wt%, add 771.48 g of water to configure an intermediate phosphoric acid solution with a P2O5 concentration of 25wt%; take 585.03 g of wet concentrated phosphoric acid with a P2O5 concentration of 46.56wt%, add 1230.90 g of water to configure a third phosphoric acid solution with a P2O5 concentration of 15wt%, mix the 15wt% third phosphoric acid solution with 856.65 g of 98wt% concentrated sulfuric acid and stir uniformly to obtain an acid solution, the mass ratio of 15wt% phosphoric acid solution to 98wt% concentrated sulfuric acid in the acid solution is 2.12:1.

[0183] S2: Pretreatment of calcium fluoride waste residue: The calcium fluoride waste residue is ground into powder so that the particle size of at least 80 wt% of the calcium fluoride waste residue is not more than 150 μm. Take 150 g of the intermediate phosphoric acid solution as the second phosphoric acid solution, add 50 g of calcium fluoride waste residue powder thereto, and stir uniformly to remove the carbonate to obtain an intermediate slurry.

[0184] S3: Mixing with phosphate rock powder: The phosphate rock powder is ground so that the particle size of at least 80 wt% of the phosphate rock powder is not more than 150 μm, the intermediate slurry is mixed with 1000 g of the above phosphate rock powder, and 300.00 g of water is added to slurry into a phosphate rock slurry with a moisture content of 30 wt%, the residual small amount of phosphoric acid in the intermediate slurry can react with the carbonate in the phosphate rock powder to generate CO2 to reduce the foam layer of the reaction system. The mass ratio of dry basis calcium fluoride waste residue to dry basis phosphate rock powder in the intermediate slurry is 5:100.

[0185] S4: Same as step S4 in Example 1.

[0186] S5: Same as step S5 in Example 1.

[0187] In this comparative example, the concentration of P2O5 in the first phosphoric acid solution and the second phosphoric acid solution is 25 wt%, and the mass ratio of dry basis calcium fluoride waste residue to dry basis phosphate rock powder is 5:100 (i.e. the doping amount of calcium fluoride waste residue is 5 wt%).

[0188] Comparative Example 6

[0189] This comparative example provides a method for recovering F from calcium fluoride waste residue, which comprises the following steps:

[0190] S1: Preparation of initial phosphoric acid solution and acid solution: Take 911.89 g of wet concentrated phosphoric acid with a P2O5 concentration of 46.56 wt% and add 786.42 g of water to prepare an intermediate phosphoric acid solution with a P2O5 concentration of 25 wt%; take 589.35 g of wet concentrated phosphoric acid with a P2O5 concentration of 46.56 wt% and add 1239.99 g of water to prepare a third phosphoric acid solution with a P2O5 concentration of 15 wt%, mix the 15 wt% third phosphoric acid solution with 863.15 g of 98 wt% concentrated sulfuric acid and stir uniformly to obtain an acid solution, the mass ratio of 15 wt% phosphoric acid solution to 98 wt% concentrated sulfuric acid in the acid solution is 2.12:1.

[0191] S2: Pretreatment of calcium fluoride waste residue: The calcium fluoride waste residue is ground into powder so that the particle size of at least 80 wt% of the calcium fluoride waste residue is not more than 150 μm. Take 180 g of the intermediate phosphoric acid solution as the second phosphoric acid solution, add 60 g of calcium fluoride waste residue powder thereto, and stir uniformly to remove the carbonate to obtain an intermediate slurry.

[0192] S3: Mixing with Phosphate Rock Powder: Grind the phosphate rock powder to ensure that at least 80 wt% of the phosphate rock powder has a particle size not exceeding 150 μm. Mix the intermediate slurry with 1000 g of the above phosphate rock powder and add 274.29 g of water to adjust the slurry to a moisture content of 30 wt%. The small amount of residual phosphoric acid in the intermediate slurry can react with the carbonates in the phosphate rock powder to generate CO2, reducing the foam layer in the reaction system. The mass ratio of dry-based calcium fluoride waste residue to dry-based phosphate rock powder in the intermediate slurry is 6:100.

[0193] S4: Same as step S4 in Example 1.

[0194] S5: Same as step S5 in Example 1.

[0195] In this comparative example, the concentration of P2O5 in both the first and second phosphoric acid solutions was 25 wt%, and the mass ratio of dry-based calcium fluoride waste residue to dry-based phosphate rock powder was 6:100 (that is, the doping amount of calcium fluoride waste residue was 6 wt%).

[0196] Experimental Example 1

[0197] The main component composition, final phosphorus yield, and fluorine yield of the phosphogypsum and finished phosphoric acid obtained from Examples 1-4, Comparative Examples 1, 5, and 6 were compared. The results are shown in Table 2. In Table 2, the units for phosphorus yield and fluorine yield are %, and the units for the rest are wt%.

[0198] The content of total F, P2O5 and other elements was determined in accordance with GB / T 5484-2012 Chemical Analysis Methods for Gypsum.

[0199] The formula for calculating phosphorus yield is as follows:

[0200] The formula for calculating the fluorine yield is as follows:

[0201] Table 2 Comparison Results

[0202]

[0203] Table 2 shows that, under the condition that the P2O5 concentration in both the primary and secondary phosphoric acid solutions is 25 wt%, the phosphorus recovery and total fluorine recovery are relatively high when the calcium fluoride waste residue content is between 2 wt% and 3 wt%. The content of impurities such as magnesium and aluminum in the phosphoric acid is slightly lower than that without calcium fluoride waste residue. When the calcium fluoride waste residue content exceeds 4 wt%, the fluorine recovery decreases significantly, the sodium and aluminum ion content in the finished phosphoric acid decreases significantly, and the magnesium and aluminum ion content in the gypsum increases, indicating that Na2AlF6 and Na2SiF6 may have formed. 6、 Precipitates such as MgAl2F8-MgAlF5 may form. Under these conditions, the impact of phosphoric acid scaling must be considered.

[0204] Test Example 2

[0205] The main component compositions in the phosphogypsum and finished phosphoric acid obtained from the above Examples 5-7 and Comparative Examples 2-4, and the final phosphorus yield and fluorine yield were compared according to the method of Test Example 1, and the results are shown in Table 3, wherein the units of phosphorus yield and fluorine yield are %, and the units of the remaining components are wt%.

[0206] Table 3 Comparison results

[0207]

[0208] As can be seen from Table 3, whether the concentration of P2O5 in the first phosphoric acid solution and the second phosphoric acid solution is 20 wt%, or the concentration of P2O5 in the first phosphoric acid solution and the second phosphoric acid solution is 30 wt%, the phosphorus yield and total F yield corresponding to the calcium fluoride waste residue content of 2 wt% can be increased by about 1% compared to the undoped calcium fluoride waste residue. From the results of using analytical pure phosphoric acid to configure the first phosphoric acid solution and the second phosphoric acid solution, among the impurity metal ions contained in the phosphoric acid, the content of sodium increases, the content of potassium and iron changes little, and the content of magnesium and aluminum decreases.

[0209] In summary, the method provided by the present disclosure has a simple operation process and is easy to realize industrialization, and can achieve the multiple effects of comprehensive utilization of calcium fluoride waste residue and improvement of phosphorus yield.

[0210] The above only describes the preferred embodiments of the present disclosure and is not intended to limit the present disclosure. For those skilled in the art, the present disclosure can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A method for recovering F from calcium fluoride waste residue, characterized by, The method comprises the following steps: The phosphorite slurry doped with calcium fluoride waste residue is mixed with a first phosphoric acid solution and an acidic solution containing sulfuric acid, and then subjected to a crystal growing treatment, solid-liquid separation, to obtain phosphogypsum and finished phosphoric acid; The preparation of the phosphorite slurry comprises mixing a second phosphoric acid solution, calcium fluoride waste residue and phosphorite powder; The mass ratio of the calcium fluoride waste residue to the phosphorite powder in the phosphorite slurry is 0.01:100 to 4:

100.

2. The method of claim 1, wherein, The concentration of P2O5 in the first phosphoric acid solution is 20wt%-32wt%, and / or the concentration of P2O5 in the second phosphoric acid solution is 20wt%-32wt%.

3. The method of claim 2, wherein, The concentration of P2O5 in the first phosphoric acid solution is equal to the concentration of P2O5 in the second phosphoric acid solution.

4. The method of claim 1, wherein, The mass ratio of the calcium fluoride waste residue to the second phosphoric acid solution is 1:2 to 1:3, wherein the mass of the calcium fluoride waste residue is based on dry basis.

5. The method of claim 1, wherein, The total mass of the first phosphoric acid solution and the second phosphoric acid solution to the mass of the phosphorite powder in the phosphorite slurry is 0.5:1 to 2:1, wherein the mass of the phosphorite powder is based on dry basis.

6. The method of claim 1, wherein, At least 80wt% of the calcium fluoride waste residue has a particle size of no more than 150μm. Or, at least 80wt% of the phosphorite powder in the phosphorite slurry has a particle size of no more than 150μm.

7. The method of claim 1, wherein, The acidic solution further contains a third phosphoric acid solution.

8. The method of claim 7, wherein, The mass ratio of the third phosphoric acid solution to the phosphorite powder in the phosphorite slurry is 1:1 to 4:1, wherein the mass of the phosphorite powder is based on dry basis; and the concentration of P2O5 in the third phosphoric acid solution is 10wt%-25wt%.

9. The method of claim 7, wherein, The mass ratio of the third phosphoric acid solution to the sulfuric acid is 1.5:1 to 5:1, wherein the concentration of the sulfuric acid is 93wt%-98wt%.

10. The method of claim 1, wherein, The phosphorite slurry and the acidic solution are added to the first phosphoric acid solution at 70℃-85℃ for reaction.

11. The method of claim 10, wherein, The feeding time of the phosphorite slurry and the acidic solution is 50min-60min.

12. The method of claim 1, wherein, In the reaction liquid obtained by mixing reaction, the concentration of P2O5 is 20wt%-32wt%, the concentration of SO3 is 15g / L-50g / L, and the liquid-solid ratio is 2:1 to 5:

1.

13. The method of claim 1, wherein, The crystal growing time is 4h-6h.

14. The method of claim 1, wherein, The method further comprises washing the phosphogypsum obtained by solid-liquid separation and collecting the washing liquid.

15. The method of claim 14, wherein, The phosphogypsum is countercurrently washed with hot water.

16. The method of claim 15, wherein, The temperature of the hot water is 60℃-80℃, and / or the countercurrent washing is performed for no less than 3 times.

17. The method of claim 14, wherein, The method further comprises: Mixing the washing liquid with part of the finished phosphoric acid to prepare a new first phosphoric acid solution or acidic solution.

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