A method for enhanced recovery of fluoride in wet phosphoric acid concentration process

Abstract

The present invention discloses a method for strengthening the recovery of fluoride in a wet-process phosphoric acid concentration process. The present invention aims at the technical problem of low fluorine recovery rate in a wet-process phosphoric acid concentration process. In the wet-process phosphoric acid concentration process, an organosilicon-type fluorine overflow agent is added to react fluorine-containing compounds in phosphoric acid with organosilicon to generate fluorine-containing gas. The escaped fluorine-containing gas is passed into water for recovery to obtain a pure fluorine-containing aqueous solution as a high-quality raw material for producing hydrogen fluoride. The recovery rate of fluorine-containing gas is 54.22% when the fluorine overflow agent is not added, and the recovery rate of fluorine-containing gas is increased to 87.84% when the fluorine overflow agent is added. The present invention uses organosilicon as a treatment agent, and the agent can be directly added to a phosphoric acid concentration device, which is easy to industrialize on site and has good industrial application prospects. The present invention strengthens the recovery of fluorine in phosphoric acid and realizes the efficient and comprehensive utilization of associated fluorine resources in phosphate resources.

Description

Technical Field

[0001] The invention relates to the fields of wet-process phosphoric acid production and resource recovery, and in particular to a method for enhanced recovery of fluoride in a wet-process phosphoric acid concentration process. Background Art

[0002] Fluorine is an important strategic resource in my country and is widely used in various fields such as mineral metallurgy, electronics, agriculture and medicine. Fluorine resources exist in various ores on the earth, mainly fluorite and phosphate rock.

[0003] Phosphoric acid is an important chemical raw material in the fields of fertilizer, food, coating, and electronics. Its production methods mainly include wet phosphoric acid process and thermal phosphoric acid process. Thermal phosphoric acid has high requirements on the grade of phosphate ore, high energy consumption, high cost, and high pollution in the production process. At present, the production of phosphoric acid in domestic industry is mainly based on wet phosphoric acid. The most commonly used method for wet phosphoric acid is the dihydrate process, which has a simple process and strong ore adaptability. More than 80% of phosphoric acid in my country is produced by the dihydrate process. However, the crude phosphoric acid produced by the dihydrate process contains P 2 O 5 The content is only 20%-30%. In this process, after acid hydrolysis, part of the fluorine in the phosphate rock overflows in the form of hydrogen fluoride gas, and part reacts with a small amount of silicon dioxide in the phosphate rock to form fluorosilicic acid (H 2 SiF 6 ) and a small amount of silicon tetrafluoride gas. Therefore, the fluorine in phosphate rock, except for a small amount of SiF 4 In addition to overflowing in the form of HF gas, most of it will remain in the phosphoric acid in the form of fluorosilicate ions and fluoride ions, and it is not easy to separate from the phosphoric acid, which will have a significant impact on the phosphoric acid preparation process and downstream products. The reactions that occur in the phosphate rock are as follows:

[0004] 6HF+SiO 2 =H 2 SiF 6 +2H 2 O

[0005] H 2 SiF 6 +SiO 2 →3SiF 4 ↑+H 2 O

[0006] H 2 SiF 6 →SiF 4 ↑+HF↑

[0007] The industrial standard for the content of fluoride in phosphate products is: less than 0.18% for feed grade and less than 0.005% for food grade. Therefore, it is very necessary to strengthen the recovery of fluoride in the process of wet phosphoric acid concentration: on the one hand, it can improve the quality of phosphoric acid products and reduce the corrosion of hydrofluoric acid to equipment in the production of wet phosphoric acid; on the other hand, the recovery of fluorine can also provide a cheap source for the manufacture of hydrofluoric acid, artificial fluorite and other fluorine chemical products.

[0008] At present, the main methods for domestic phosphorus chemical enterprises to recover fluorine from phosphoric acid include chemical precipitation, steam stripping, solvent extraction and vacuum concentration. Among them, the chemical precipitation method mainly uses sodium salt or potassium salt as a defluorinating agent to precipitate the fluoride in phosphoric acid in the form of sodium fluorosilicate or potassium fluorosilicate, and finally the precipitate is filtered and separated to achieve the purpose of defluorination. However, when the chemical precipitation method removes fluoride from phosphoric acid, on the one hand, the defluorination depth is not enough, and the fluorine removal rate is low, generally only 45% to 55%. On the other hand, the fluorine is removed in the form of precipitation and enters the defluorination slag, which cannot be effectively recycled. The steam stripping method is an efficient and deep defluorination method, which mainly changes the saturated vapor pressure of the phosphoric acid solution by exhausting or ventilating, so that the phosphoric acid solution boils and evaporates, and the fluorine in the phosphoric acid is gasified and pumped away by the vacuum pump, thereby achieving the purpose of defluorination. However, this method has high process cost and complex operation, so it has not been widely used in industry. The solvent extraction method is to achieve the purpose of defluorination by mixing a suitable extractant with wet-process phosphoric acid, based on the different solubility of fluorine and other components in the organic phase and the aqueous phase. Commonly used extractants include cyclohexanol, n-butanol and amines. This method can deeply defluorinate without introducing other impurities, but the price of the extractant is expensive, the amount of extractant is large, and the initial investment is large. The vacuum concentration method is currently the most widely used method in industry. It mainly concentrates the phosphoric acid solution by heating so that the fluorine in the phosphoric acid overflows and is recovered in the form of gas. However, there are also defects such as low fluorine recovery rate and large waste of fluorine resources. According to data, the current fluorine recovery rate of leading domestic chemical companies is only about 40%, which not only causes a large waste of precious fluorine resources, but also aggravates environmental pollution. Summary of the invention

[0009] The purpose of the present invention is to provide a method for recovering fluorine from wet-process phosphoric acid. The method adds a fluorine overflow agent to phosphoric acid to enhance the generation of fluorine gas during the concentration process, thereby achieving the purpose of enhancing the recovery of fluorine resources.

[0010] The technical solution adopted by the present invention to solve the above technical problems is:

[0011] A method for enhanced recovery of fluoride in a wet-process phosphoric acid concentration process comprises the following steps:

[0012] S1, contacting and mixing wet-process phosphoric acid with a fluorine overflow agent; the fluorine overflow agent is a silicone type;

[0013] S2, heating and stirring the reaction system to concentrate the wet-process phosphoric acid acid while allowing the fluoride in the wet-process phosphoric acid acid to fully react with the fluorine overflow agent to allow the fluorine-containing gas to overflow;

[0014] S3. The concentrated phosphoric acid mixture obtained by the reaction is filtered to obtain a phosphoric acid product and defluorination residue.

[0015] The organosilicon includes: at least one of organosilicon monomer and silicone oil; the organosilicon monomer includes silane; the silicone oil includes: at least one of linear silicone oil, modified silicone oil and silicone grease. The preferred types of the organosilicon are: hydroxy silicone oil and methyltrichlorosilane.

[0016] The purity range of the organic silicon is 60% to 100%.

[0017] The ratio of wet-process phosphoric acid to fluorine overflow agent in S1 is 1:0.001-0.100; the preferred ratio range is: 1:0.01-0.05.

[0018] The fluorine overflow agent in S1 is added once or in several portions.

[0019] The heating temperature in S2 is 50°C to 200°C; the preferred temperature range is 85°C to 150°C.

[0020] The stirring speed in S2 is 800 rpm to 3000 rpm; preferably, the speed range is 1800 rpm to 2400 rpm.

[0021] The reaction time in S2 is 10 min to 5 h; the preferred reaction time is 40 min to 120 min.

[0022] The fluorine-containing gas overflowing from S2 is absorbed in water to obtain a pure fluorine-containing aqueous solution, which is used as a raw material for producing hydrogen fluoride.

[0023] The mass ratio of wet-process phosphoric acid to initial absorbed water in S2 is 1:0.2-10; the preferred ratio range is 1:2-4.

[0024] The present invention aims at the technical problem of low fluorine recovery rate in the wet phosphoric acid concentration process. In the wet phosphoric acid concentration process, a liquid high chemically active organosilicon type fluorine overflow agent is added to overcome the defects of poor activity and slow reaction rate of diatomaceous earth and white carbon black defluorinating agents, so that the fluorine-containing compounds in phosphoric acid fully react with organosilicon to generate fluorine-containing gas. The overflowed fluorine-containing gas is passed into water for recovery to obtain a pure fluorine-containing aqueous solution as a high-quality raw material for producing hydrogen fluoride. In the wet phosphoric acid original acid concentration process, when no fluorine overflow agent is added, the fluorine recovery rate is 54.22%; when an organosilicon type fluorine overflow agent is added, the fluorine recovery rate is increased to 87.84%. The present invention uses organosilicon as a treatment agent, and the agent can be directly added to the phosphoric acid concentration device, which is easy to industrialize on site and has good industrial application prospects; the present invention strengthens the recovery of fluorine in phosphoric acid and realizes the efficient and comprehensive utilization of associated fluorine resources in phosphate resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a diagram of the apparatus in Comparative Examples 1 to 2 and Examples 1 to 5;

[0026] 1. Oil bath; 2. Three-necked flask with rubber stopper; 3. Straight condenser; 4. Beaker with absorbed water. DETAILED DESCRIPTION

[0027] In order to make the above-mentioned objects, features and advantages of the present invention more clearly understood, the present invention is further described in detail below in combination with specific practical comparisons and implementation cases. The following examples are intended to further explain the present invention, but not to limit the present invention.

[0028] Comparative Example 1:

[0029] 1) Weigh 100 g of wet-process phosphoric acid (fluorine content of 0.66%) solution and add it to a reaction vessel without adding a fluorine overflow agent. The reaction vessel is sealed with a rubber stopper and concentrated at 150° C. The solution is stirred at a speed of 1800 rpm. A condenser is connected through a conduit to collect the overflowed gas into a beaker containing 200 g of initial absorption water. The reaction is carried out for about 40 minutes. When the phosphoric acid solution is concentrated to about half of its original mass, the heating is stopped.

[0030] 2) Record the total mass of the absorption liquid, cool the concentrated phosphoric acid solution to precipitate impurity crystals, filter, record the mass of the concentrated phosphoric acid filtrate and defluorination residue, measure the fluorine content in the phosphoric acid, absorption liquid and defluorination residue, and calculate the recovery rate of fluoride in the absorption liquid.

[0031] 3) After direct evaporation and concentration without adding fluorine overflow agent, the fluorine content in phosphoric acid was 0.266%, the fluorine content in the absorption liquid was 0.149%, the fluorine content in the defluorination residue was 7.685%, and the recovery rate of fluoride in the absorption liquid was 54.22%.

[0032] Comparative Example 2:

[0033] 1) Weigh 100 g of wet-process phosphoric acid (fluorine content of 0.66%) solution and add it to a reaction vessel, and add 2 g of diatomaceous earth (the amount of diatomaceous earth added was optimized through preliminary experiments, and it was found that under the same other reaction raw materials and conditions, the optimal amount of diatomaceous earth added was 2 g), seal the reaction vessel with a rubber stopper, concentrate at 150° C., and stir the solution at a speed of 1800 rpm. Connect a condenser through a conduit, collect the overflowed gas into a beaker containing 200 g of initial absorption water, react for about 40 minutes, and stop heating when the phosphoric acid solution is concentrated to about half of its original mass.

[0034] 2) Record the total mass of the absorption liquid, cool the concentrated phosphoric acid solution to precipitate impurity crystals, filter, record the mass of the concentrated phosphoric acid filtrate and defluorination residue, measure the fluorine content in the phosphoric acid, absorption liquid and defluorination residue, and calculate the recovery rate of fluoride in the absorption liquid.

[0035] 3) After adding fluorine overflow agent diatomaceous earth and evaporating and concentrating, the fluorine content in phosphoric acid was 0.172%, the fluorine content in the absorption liquid was 0.157%, the fluorine content in the defluorination slag was 4.000%, and the recovery rate of fluoride in the absorption liquid was 61.95%.

[0036] Embodiment 1:

[0037] 1) Weigh 100 g of wet-process phosphoric acid (fluorine content of 0.66%) solution into a reaction vessel, add 3 mL of propyltrichlorosilane, seal the reaction vessel with a rubber stopper, concentrate at 150° C., stir the solution at 1800 rpm, connect a condenser via a conduit, collect the overflowed gas into a beaker containing 200 g of absorption water, react for about 40 minutes, and stop heating when the phosphoric acid solution is concentrated to about half of its original mass.

[0038] 2) Record the total mass of the absorption liquid, cool the concentrated phosphoric acid solution to precipitate impurity crystals, filter, record the mass of the concentrated phosphoric acid filtrate and defluorination residue, measure the fluorine content in the phosphoric acid, absorption liquid and defluorination residue, and calculate the recovery rate of fluoride in the absorption liquid.

[0039] 3) After adding 3 mL / 100 g of fluorine overflow agent propyltrichlorosilane and evaporating and concentrating, the fluorine content in phosphoric acid was 0.110%, the fluorine content in the absorption liquid was 0.227%, the fluorine content in the defluorination residue was 2.035%, and the recovery rate of fluoride in the absorption liquid reached 78.63%, which was increased by 24.41% compared with the case without addition.

[0040] Embodiment 2:

[0041] 1) Weigh 100 g of wet-process phosphoric acid (fluorine content of 0.66%) solution into a reaction vessel, add 3 mL of methyltrichlorosilane, seal the reaction vessel with a rubber stopper, concentrate at 150° C., stir the solution at 1800 rpm, connect a condenser via a conduit, collect the overflowed gas into a beaker containing 300 g of initial absorption water, react for about 40 minutes, and stop heating when the phosphoric acid solution is concentrated to about half of its original mass.

[0042] 2) Record the total mass of the absorption liquid, cool the concentrated phosphoric acid solution to precipitate impurity crystals, filter, record the mass of the concentrated phosphoric acid filtrate and defluorination residue, measure the fluorine content in the phosphoric acid, absorption liquid and defluorination residue, and calculate the recovery rate of fluoride in the absorption liquid.

[0043] 3) When 3 mL / 100 g of fluorine overflow agent methyltrichlorosilane was added and the initial absorbed water was 300 g, after evaporation and concentration, the fluorine content in phosphoric acid was 0.113%, the fluorine content in the absorption liquid was 0.161%, the fluorine content in the defluorination residue was 1.987%, and the recovery rate of fluoride in the absorption liquid reached 78.61%.

[0044] Embodiment 3:

[0045] 1) Weigh 100 g of wet-process phosphoric acid (fluorine content of 0.66%) solution into a reaction vessel, add 3 mL of hydroxy silicone oil, seal the reaction vessel with a rubber stopper, concentrate at 150° C., stir the solution at 2400 rpm, connect a condenser through a catheter, collect the overflowed gas into a beaker containing 200 g of initial absorption water, react for about 40 minutes, and stop heating when the phosphoric acid solution is concentrated to about half of its original mass.

[0046] 2) Record the total mass of the absorption liquid, cool the concentrated phosphoric acid solution to precipitate impurity crystals, filter, record the mass of the concentrated phosphoric acid filtrate and defluorination residue, measure the fluorine content in the phosphoric acid, absorption liquid and defluorination residue, and calculate the recovery rate of fluoride in the absorption liquid.

[0047] 3) When 3 mL / 100 g of fluorine overflow agent hydroxy silicone oil was added and the stirring speed was 2400 rpm, after evaporation and concentration, the fluorine content in phosphoric acid was 0.102%, the fluorine content in the absorption liquid was 0.241%, the fluorine content in the defluorination residue was 0.954%, and the recovery rate of fluoride in the absorption liquid reached 86.65%, which was 32.43% higher than that without addition.

[0048] Embodiment 4:

[0049] 1) Weigh 100 g of wet-process phosphoric acid (fluorine content of 0.66%) solution into a reaction vessel, add 3 mL of vinyltrichlorosilane, seal the reaction vessel with a rubber stopper, concentrate at 85° C., stir the solution at 1800 rpm, connect a condenser via a conduit, collect the overflowed gas into a beaker containing 200 g of initial absorption water, react for about 120 min, and stop heating when the phosphoric acid solution is concentrated to about half of its original mass.

[0050] 2) Record the total mass of the absorption liquid, cool the concentrated phosphoric acid solution to precipitate impurity crystals, filter, record the mass of the concentrated phosphoric acid filtrate and defluorination residue, measure the fluorine content in the phosphoric acid, absorption liquid and defluorination residue, and calculate the recovery rate of fluoride in the absorption liquid.

[0051] 3) After adding 3 mL / 100 g of the fluorine overflow agent vinyl trichlorosilane and heating to 85° C. and concentrating, the fluorine content in the phosphoric acid was 0.100%, the fluorine content in the absorption liquid was 0.214%, the fluorine content in the defluorination residue was 2.599%, and the recovery rate of fluoride in the absorption liquid reached 77.59%.

[0052] Embodiment 5:

[0053] 1) Weigh 100 g of wet-process phosphoric acid (fluorine content of 0.66%) solution and add it to a reaction container, seal the reaction container with a rubber stopper, add 3 mL of methyltrichlorosilane to the phosphoric acid solution in multiple portions, concentrate at 85° C., and stir the solution at a speed of 1800 rpm. Connect a condenser through a conduit, collect the overflowed gas into a beaker containing 200 g of initial absorption water, react for about 120 minutes, and stop heating when the phosphoric acid solution is concentrated to about half of its original mass.

[0054] 2) Record the total mass of the absorption liquid, cool the concentrated phosphoric acid solution to precipitate impurity crystals, filter, record the mass of the concentrated phosphoric acid filtrate and defluorination residue, measure the fluorine content in the phosphoric acid, absorption liquid and defluorination residue, and calculate the recovery rate of fluoride in the absorption liquid.

[0055] 3) After adding 3 mL / 100 g of fluorine overflow agent methyltrichlorosilane in multiple times and evaporating and concentrating, the fluorine content in phosphoric acid was 0.112%, the fluorine content in the absorption liquid was 0.242%, the fluorine content in the defluorination residue was 1.767%, and the recovery rate of fluoride in the absorption liquid reached 87.84%, which was 33.62% higher than that without addition.

[0056] The comparative examples and embodiments above indicate that the experimental conditions of the present invention are more suitable. Under the current optimal conditions, the addition of an organosilicon-based fluorine overflow agent can reduce the fluoride content in the original acid of wet-process phosphoric acid to 0.112%, and the recovery rate of fluoride in the absorption liquid reaches 87.84%, which is 33.62% higher than that without addition; under low temperature (75°C to 90°C) concentration conditions, organosilicon can also effectively recover fluoride in wet-process phosphoric acid, and its reaction environment can meet industrial requirements, with huge application potential.

[0057] The above-mentioned implementation cases are only for further specific and detailed description of the present invention, but they cannot limit the scope of the present invention. Any modification, deformation and improvement made by those skilled in the art without departing from the concept of the present invention should be within the scope of the present invention.

Claims

1. A method for enhanced recovery of fluoride in a wet-process phosphoric acid concentration process, characterized in that: The following steps are involved: S1, contacting and mixing wet-process phosphoric acid with a fluorine overflow agent; the fluorine overflow agent is an organosilicon: propyltrichlorosilane, methyltrichlorosilane, hydroxy silicone oil or vinyltrichlorosilane; S2, heating and stirring the reaction system to concentrate the wet-process phosphoric acid acid while allowing the fluoride in the wet-process phosphoric acid acid to fully react with the fluorine overflow agent to allow the fluorine-containing gas to overflow; S3. The concentrated phosphoric acid mixture obtained by the reaction is filtered to obtain a phosphoric acid product and defluorination residue.

2. The method according to claim 1, characterized in that The purity range of the organosilicon is 60% to 100%.

3. The method according to claim 1, characterized in that: The mass ratio of wet-process phosphoric acid and fluorine overflow agent in S1 is 1:0.001~0.

100.

4. The method according to claim 1 or 3, characterized in that: The fluorine overflow agent in S1 is added once or in several portions.

5. The method according to claim 1, characterized in that: The heating temperature in S2 is 50°C to 200°C.

6. The method according to claim 1 or 5, characterized in that: The stirring speed in S2 is 800 rpm to 3000 rpm.

7. The method according to claim 1 or 5, characterized in that: S2 reaction time is 10min~5h.

8. The method according to claim 1, characterized in that: The fluorine-containing gas overflowing from S2 is absorbed in water to obtain a pure fluorine-containing aqueous solution, which is used as a raw material for producing hydrogen fluoride.

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