阅读说明：本技术 一种利用二氧化碳制备氟化钙与碳酸氢钾的方法 (Method for preparing calcium fluoride and potassium bicarbonate by using carbon dioxide ) 是由 黄忠 何俊 徐超 张险峰 余双强 胡挺 查炎华 高婷 于 2019-09-23 设计创作，主要内容包括：本发明公开了一种利用二氧化碳制备氟化钙与碳酸氢钾的方法,属于磷化工技术领域。该方法步骤如下：(1)将氟硅酸钾与含钾化合物反应得到粗氟化钾溶液和二氧化硅；(2)在粗氟化钾溶液中加入氟硅酸调整pH得到氟化钾溶液和二氧化硅-氟硅酸钾固体,二氧化硅-氟硅酸钾固体返回到步骤(1)；(3)用二氧化碳将氢氧化钙乳液进行酸化得到碳酸氢钙溶液；(4)将氟化钾溶液与碳酸氢钙溶液进行反应得到氟化钙产品；滤液处理后得到碳酸氢钾产品；(5)碳酸氢钾母液经干燥、煅烧得到碳酸钾,返回到步骤(1)。仅氢氧化钙和少量的含钾化合物就能够将副产磷酸氟钾化合物与氟硅酸和合成氨副产二氧化碳加工成高价值的氟化钙、碳酸氢钾和二氧化硅。(The invention discloses a method for preparing calcium fluoride and potassium bicarbonate by using carbon dioxide, belonging to the technical field of phosphorus chemical industry. The method comprises the following steps: (1) reacting potassium fluosilicate with a potassium-containing compound to obtain a crude potassium fluoride solution and silicon dioxide; (2) adding fluosilicic acid into the crude potassium fluoride solution to adjust the pH value to obtain a potassium fluoride solution and a silicon dioxide-potassium fluosilicate solid, and returning the silicon dioxide-potassium fluosilicate solid to the step (1); (3) acidifying the calcium hydroxide emulsion with carbon dioxide to obtain calcium bicarbonate solution; (4) reacting the potassium fluoride solution with a calcium bicarbonate solution to obtain a calcium fluoride product; treating the filtrate to obtain a potassium bicarbonate product; (5) drying and calcining the potassium bicarbonate mother liquor to obtain potassium carbonate, and returning to the step (1). The by-product potassium fluophosphate compound and the by-product carbon dioxide of fluosilicic acid and synthetic ammonia can be processed into high-value calcium fluoride, potassium bicarbonate and silicon dioxide only by calcium hydroxide and a small amount of potassium-containing compounds.)

1. A method for preparing calcium fluoride and potassium bicarbonate by using carbon dioxide, which is characterized by comprising the following steps:

(1) reacting a potassium fluoride compound which is a byproduct in wet-process phosphoric acid processing with a solution containing a potassium compound, performing solid-liquid separation after the reaction is finished, combining a filtrate with a washing solution obtained by washing a filter cake to obtain a crude potassium fluoride solution, wherein the potassium compound is potassium carbonate obtained in the step (5) and additionally added potassium hydroxide or potassium carbonate; the molar ratio of the potassium-containing compound to the potassium fluosilicate in the potassium fluoride compound is 2.0-2.1: 1.0;

(2) adding fluosilicic acid into the crude potassium fluoride solution obtained in the step (1) to adjust the pH value to 7-8, filtering and separating to obtain a potassium fluoride solution and a silicon dioxide-potassium fluosilicate solid, and returning the silicon dioxide-potassium fluosilicate solid to the step (1);

(3) acidifying the calcium hydroxide emulsion by using carbon dioxide, and filtering to obtain a calcium bicarbonate solution;

(4) reacting the potassium fluoride solution obtained in the step (2) with the calcium bicarbonate solution obtained in the step (3), carrying out solid-liquid separation after the reaction is finished, and washing and drying a filter cake to obtain a calcium fluoride product; the molar ratio of calcium bicarbonate to potassium fluoride is 1.0: 1.8-2.2, concentrating, crystallizing and drying the filtrate to obtain a potassium bicarbonate product;

(5) and (4) evaporating and calcining the potassium bicarbonate mother liquor obtained in the step (4) to obtain potassium carbonate, and returning to the step (1).

2. The method for preparing calcium fluoride and potassium bicarbonate by using carbon dioxide as claimed in claim 1, wherein in the step (1), the potassium fluoride compound is selected from one or more of potassium fluosilicate prepared by-producing fluosilicic acid, deposits in a phosphoric acid storage tank, scaling substances in a phosphoric acid conveying pipeline, crystals in a phosphogypsum reservoir water return pipeline and defluorination products generated by defluorination of dilute phosphoric acid.

3. The method for preparing calcium fluoride and potassium bicarbonate by using carbon dioxide as claimed in claim 1, wherein the reaction temperature is 20-95 ℃ and the reaction time is 30-120 min in the step (1).

4. The method for preparing calcium fluoride and potassium bicarbonate by using carbon dioxide as claimed in claim 1, wherein the solution of the potassium-containing compound in the step (1) has a concentration of 20-70% by mass.

5. The method for preparing calcium fluoride and potassium bicarbonate by using carbon dioxide as claimed in claim 1, wherein the reaction temperature is 10-40 ℃ in the step (2).

6. The method for preparing calcium fluoride and potassium bicarbonate by using carbon dioxide according to claim 1, wherein in the step (2), the fluosilicic acid is derived from a fluosilicic acid by-product of phosphorus chemical industry.

7. The method for preparing calcium fluoride and potassium bicarbonate by using carbon dioxide as claimed in claim 1, wherein in the step (3), the mass concentration of the calcium bicarbonate solution is 5-14%.

8. The method for preparing calcium fluoride and potassium bicarbonate by using carbon dioxide as claimed in claim 1, wherein in the step (3), the carbon dioxide is carbon dioxide emitted from the synthetic ammonia industry.

9. The method for preparing calcium fluoride and potassium bicarbonate by using carbon dioxide as claimed in claim 1, wherein the reaction temperature is 10-50 ℃ and the reaction time is 10-60min in the step (4).

10. The method for preparing calcium fluoride and potassium bicarbonate by using carbon dioxide according to claim 1, which comprises the following steps:

(1) reacting a potassium fluoride compound which is a byproduct in wet-process phosphoric acid processing with a solution containing a potassium compound, wherein the mass percentage concentration of the solution containing the potassium compound is 20-70%, the reaction temperature is 20-95 ℃, carrying out solid-liquid separation after the reaction is finished, combining a filtrate with a washing solution obtained by washing a filter cake to obtain a crude potassium fluoride solution, and the potassium compound is potassium carbonate obtained in the step (5) and additionally added potassium hydroxide or potassium carbonate; the molar ratio of the potassium-containing compound to the potassium fluosilicate in the potassium fluoride compound is 2.0-2.1: 1.0; the potassium fluoride compound is selected from one or more of potassium fluosilicate prepared by a byproduct of fluosilicic acid, sediment in a phosphoric acid storage tank, scaling substances in a phosphoric acid conveying pipeline, crystals in a phosphogypsum reservoir water return pipeline and a defluorination product generated by defluorination of dilute phosphoric acid;

(2) adding fluosilicic acid serving as a phosphorus chemical byproduct into the crude potassium fluoride solution obtained in the step (1), adjusting the pH to 7-8, controlling the reaction temperature to 10-40 ℃, filtering and separating to obtain a potassium fluoride solution and a silicon dioxide-potassium fluosilicate solid, and returning the silicon dioxide-potassium fluosilicate solid to the step (1);

(3) acidifying the calcium hydroxide emulsion by using carbon dioxide discharged by the synthetic ammonia industry, and filtering to obtain a calcium bicarbonate solution, wherein the mass concentration of the calcium bicarbonate solution is 5-14%;

(4) reacting the potassium fluoride solution obtained in the step (2) with the calcium bicarbonate solution obtained in the step (3) at the reaction temperature of 10-50 ℃, carrying out solid-liquid separation after the reaction is finished, and washing and drying a filter cake to obtain a calcium fluoride product; the molar ratio of calcium bicarbonate to potassium fluoride is 1.0: 1.8-2.2, concentrating, crystallizing and drying the filtrate to obtain a potassium bicarbonate product;

(5) and (4) evaporating and calcining the potassium bicarbonate mother liquor obtained in the step (4) to obtain potassium carbonate, and returning to the step (1).

Technical Field

The invention belongs to the technical field of phosphorus chemical industry, and particularly relates to a method for preparing calcium fluoride and potassium bicarbonate by using carbon dioxide, in particular to a method for preparing silicon dioxide, calcium fluoride and potassium bicarbonate by using a byproduct potassium fluoride compound in phosphorus chemical industry and carbon dioxide discharged by fluosilicic acid and synthetic ammonia, so that an ammonium phosphate production enterprise only needs to purchase calcium hydroxide and a small amount of potassium-containing compounds.

Background

The phosphate ore is accompanied with abundant fluorine resources and potassium resources, the fluorine content is generally 2-4%, and the potassium content can be as high as about 1%, so that a large amount of fluorine-containing compounds can be produced in the wet-process phosphoric acid production process, including fluosilicic acid obtained by tail gas absorption, deposits in a phosphoric acid storage tank (hereinafter referred to as deposits), scaling substances in a phosphoric acid conveying pipeline (hereinafter referred to as scaling substances), crystals in a phosphogypsum reservoir water return pipeline (hereinafter referred to as crystals), precipitates generated in the defluorination process of dilute phosphoric acid (hereinafter referred to as defluorination products) and the like, and besides the fluosilicic acid, the main components of the other four fluorine-containing compounds are potassium fluosilicate. Besides the industrial application of fluosilicic acid, the byproducts are processed into products such as hydrogen fluoride, sodium fluosilicate, ammonium fluoride and the like, and other four substances are not fully utilized due to technical limitation, and are generally disposed by being stacked with phosphogypsum. The fluorine-containing compounds which are not utilized have the characteristics of complex components, high fluorine content and large total amount, and are different according to the difference of the fluorine content of the phosphorite. In the scaling compound, the total fluorine content reaches more than 40 percent, and is accompanied by elements such as iron, aluminum, magnesium, calcium, phosphorus and the like; after the sediment is washed to remove the mixed phosphoric acid, the total fluorine content can reach more than 40 percent; the total fluorine content of the crystal can reach about 50 percent; the defluorination product has potassium fluosilicate as main component and small amount of insoluble phosphate. The fluorine content of the fluorine-containing compounds can account for more than 70 percent of the associated fluorine of the phosphorite, for example, the fluorine content of the phosphorite is calculated as 2 percent in wet-process phosphoric acid enterprises which process 400 million tons of phosphorite in one year, if the fluorine compounds are reasonably utilized, 5.6 million tons of fluorine elements can be extracted, and the economic value is close to 6.5 million yuan (calculated by HF). However, the components of fluorine-containing compounds other than fluorosilicic acid have been complicated and no particularly good utilization method has been reported so far. In addition, potassium and fluorine are easy to form potassium fluosilicate with low solubility, so that the potassium and the fluorine are accumulated in a production system continuously without being separated from the system, and when the crystallization concentration is reached, pipelines such as a phosphoric acid conveying pipeline, a phosphogypsum storehouse water return pipeline and the like are easy to block, thereby bringing great difficulty to production and increasing the production cost. Therefore, the method changes fluorine and potassium in the fluorine-containing compounds into valuable substances by a proper means and has very important significance.

Calcium fluoride is a main raw material for producing hydrogen fluoride, is an important raw material for producing enamel, ceramics, optical glass and the like, and has a huge market. The preparation of the calcium fluoride from the fluorine-containing compound is an important way for phosphorite associated fluorine resources. At present, the raw material capable of preparing calcium fluoride from phosphorus ore associated fluorine is mainly fluosilicic acid. Patent CN 201680029715.7 discloses a method for preparing ammonium fluoride from fluorosilicic acid, ammonia and calcium carbonate, wherein fluorosilicic acid and ammonia are reacted to generate ammonium fluoride solution, and the ammonium fluoride solution is reacted with calcium carbonate to generate calcium fluoride, ammonium carbonate and ammonia gas; ammonium carbonate and ammonia gas are recycled to react with fluosilicic acid. Patent CN201110369530.X discloses a method for preparing ammonium fluoride from fluosilicic acid, ammonia and calcium hydroxide, wherein the fluosilicic acid and the ammonia are firstly reacted to generate an ammonium fluoride solution, the ammonium fluoride solution and the calcium hydroxide are reacted to generate calcium fluoride and ammonia water/ammonia gas, and the ammonia water/ammonia gas is recycled to react with the fluosilicic acid. Both patents give access to calcium fluoride products, but are not applicable to deposits, foulants, crystals and defluorinates, and thus have limited applicability to relatively pure fluorosilicic acids. In addition, ammonia which is difficult to recover is used as a circulating medium in both patents, so that the safety and environmental protection risks are high, and safety and environmental protection devices with high requirements are needed; the byproduct ammonia water needs to be heated and evaporated to realize recycling and water balance, and energy consumption is increased; the high cost of ammonia would be another weakness of this type of process.

Many wet-process phosphoric acid processing enterprises are provided with ammonia synthesis devices, and a large amount of carbon dioxide is discharged every year.

The invention not only researches and invents a method suitable for fluosilicic acid, but also suitable for sediments, scaling substances, crystallisates and defluorination products, overcomes the defects of the utilization technology of the fluorine-containing compound, realizes the recycling economic utilization of byproducts of wet-process phosphoric acid processing enterprises, and is more convenient to be widely applied in industry.

Disclosure of Invention

The invention aims to overcome the technical defect of preparing calcium fluoride by using phosphorite associated fluorine resources in the prior art and provide a more economic and effective method for preparing calcium fluoride and co-producing potassium bicarbonate by using industrial byproduct carbon dioxide. The scheme is as follows:

the invention provides a method for preparing calcium fluoride and potassium bicarbonate by using carbon dioxide, which comprises the following steps:

(1) reacting a potassium fluoride compound (added in a form of solid or slurry) which is a byproduct in wet-process phosphoric acid processing with a solution containing a potassium compound, carrying out solid-liquid separation after the reaction is finished, combining a filtrate with a washing solution obtained by washing a filter cake to obtain a crude potassium fluoride solution, wherein the potassium compound is potassium carbonate (generated in the previous batch if the potassium compound exists) obtained in the step (5) and additionally added potassium hydroxide or potassium carbonate; the molar ratio of the potassium-containing compound to the potassium fluosilicate in the potassium fluoride compound is 2.0-2.1 (calculated by potassium carbonate (the molar amount of potassium hydroxide is 1/2): 1.0.

the main reaction formula is as follows: k₂SiF₆+4KOH→SiO₂↓+6KF +2H₂O or K₂SiF₆+2K₂CO₃→6KF+SiO₂↓+2CO₂↑。

(2) Adding fluosilicic acid into the crude potassium fluoride solution obtained in the step (1) to adjust the pH value to 7-8, filtering and separating to obtain a potassium fluoride solution and a silicon dioxide-potassium fluosilicate solid, and returning the silicon dioxide-potassium fluosilicate solid to the step (1) for recycling.

The main reaction formula is as follows: h₂SiF₆+2KOH→K₂SiF₆↓+2H₂O or H₂SiF₆+K₂CO₃→K₂SiF₆+CO₂↑+H₂O。

(3) Acidifying the calcium hydroxide emulsion with carbon dioxide, and filtering to obtain calcium bicarbonate solution.

The main reaction formula is as follows: 2CO₂+ Ca(OH)₂→Ca(HCO₃)₂。

(4) Reacting the potassium fluoride solution obtained in the step (2) with the calcium bicarbonate solution obtained in the step (3), carrying out solid-liquid separation after the reaction is finished, and evaporating and drying a filter cake to obtain a calcium fluoride product; the molar ratio of calcium bicarbonate to potassium fluoride is 1.0: 1.8-2.2, concentrating, crystallizing and drying the filtrate to obtain a potassium bicarbonate product.

The main reaction formula is as follows: 2KF + Ca (HCO)₃)₂→CaF₂↓+ 2KHCO₃。

(5) And (4) drying and calcining the potassium bicarbonate mother liquor (crystallization mother liquor) obtained in the step (4) to obtain potassium carbonate, and returning to the step (1) for recycling.

The main reaction formula is as follows: 2KHCO₃→K₂CO₃+H₂O +CO₂↑。

Wherein, in the step (1), the potassium fluoride compound is selected from one or more of potassium fluosilicate prepared by-product fluosilicic acid, sediment in a phosphoric acid storage tank, scaling substances in a phosphoric acid conveying pipeline, crystal substances in a phosphogypsum storehouse return pipeline, defluorination products generated by defluorination of dilute phosphoric acid and the like.

Wherein, in the step (1), the reaction temperature is 20-95 ℃ and the reaction time is 30-120 min.

Wherein, in the step (1), the percentage concentration of the solution containing the potassium compound is 20-70% so as to dissolve the fluorine potassium compound.

Wherein, in the step (1), the pH value of the system after the reaction is controlled to be 10-13.

Wherein, in the step (1), the filter cake is used as a coating material (mainly containing silicon dioxide and containing no or little metal salt) of the compound fertilizer.

Wherein, in the step (2), the reaction temperature is 10-40 ℃.

Wherein, in the step (2), the fluosilicic acid is the fluosilicic acid byproduct from the phosphorus chemical industry.

Wherein, in the step (3), the mass concentration of the calcium bicarbonate solution is 5-14%.

Wherein, in the step (3), the carbon dioxide is carbon dioxide discharged by the synthetic ammonia industry.

Wherein, in the step (4), the reaction temperature is 10-50 ℃ and the reaction time is 10-60 min.

Specifically, the method provided by the invention comprises the following steps:

(1) and (3) reacting a potassium fluoride compound which is a byproduct in wet-process phosphoric acid processing with a potassium compound-containing solution, wherein the mass percentage concentration of the potassium compound-containing solution is 20-70%, the reaction temperature is 20-95 ℃, carrying out solid-liquid separation after the reaction is finished, combining a filtrate with a washing solution obtained by washing a filter cake to obtain a crude potassium fluoride solution, and the potassium compound is potassium carbonate obtained in the step (5) and additionally added potassium hydroxide or potassium carbonate. Wherein, the molar ratio of the potassium-containing compound to the potassium fluosilicate in the potassium fluoride compound is 2.0-2.1: 1.0. wherein the fluorine potassium compound is selected from one or more of potassium fluosilicate prepared by byproduct fluosilicic acid, sediment in a phosphoric acid storage tank, scaling substances in a phosphoric acid conveying pipeline, crystal substances in a phosphogypsum reservoir return pipeline, defluorination products generated by defluorination of dilute phosphoric acid and the like.

(2) Adding fluosilicic acid serving as a byproduct of phosphorus chemical industry into the crude potassium fluoride solution obtained in the step (1), adjusting the pH value to 7-8, controlling the reaction temperature to 10-40 ℃, filtering and separating to obtain a potassium fluoride solution and silicon dioxide-potassium fluosilicate solid, and returning the silicon dioxide-potassium fluosilicate solid to the step (1).

(3) Acidifying the calcium hydroxide emulsion by using carbon dioxide discharged by the synthetic ammonia industry, and filtering to obtain a calcium bicarbonate solution, wherein the mass concentration of the calcium bicarbonate solution is 5-14%.

(4) Reacting the potassium fluoride solution obtained in the step (2) with the calcium bicarbonate solution obtained in the step (3) at the reaction temperature of 10-50 ℃, carrying out solid-liquid separation after the reaction is finished, and washing and drying a filter cake to obtain a calcium fluoride product; the molar ratio of calcium bicarbonate to potassium fluoride is 1.0: 1.8-2.2, concentrating the filtrate (the mass concentration of the filtrate can be concentrated to 40% or more, and the concentration is adjusted according to the target yield of potassium bicarbonate (the higher the concentration degree is, the higher the yield of potassium bicarbonate) and the amount of potassium bicarbonate in the step (1), crystallizing and drying to obtain the potassium bicarbonate product.

(5) And (4) evaporating and calcining the potassium bicarbonate mother liquor obtained in the step (4) to obtain potassium carbonate, and returning to the step (1).

The invention has the following innovation points:

(1) the potassium carbonate generated in the reaction is used as a circulating reaction medium, the loss rate is low, and the experimental result shows that the loss rate is not more than 1%.

(2) The raw material range is widened from the conventional fluosilicic acid to the sediment in an acid storage tank, the scaling in a phosphoric acid conveying pipeline, the crystal in a phosphogypsum storehouse water return pipeline, the potassium fluosilicate and the defluorination product generated in the defluorination process of the dilute phosphoric acid, and the application range covers the byproduct fluorine-containing compound in the wet-process phosphoric acid processing process; the method is not only suitable for phosphorite associated fluorine resources, but also suitable for the by-product fluosilicic acid produced in the preparation of hydrogen fluoride from fluorite, the by-product fluosilicic acid produced in the rare earth industry and the like.

(3) The potassium resource associated with the phosphorite can be processed into high-value potassium bicarbonate, about 0.71 ton of potassium bicarbonate can be obtained as a byproduct when 1 ton of calcium fluoride is produced by using sediments, scaling substances, crystals or defluorination products, and the high-value utilization of fluorine and potassium can be realized simultaneously.

(4) If the fluosilicic acid is used for production, low-value potassium sulfate, potassium chloride and other soluble potassium salts can be converted into high-value potassium carbonate and potassium bicarbonate, and finally, only a small amount of potassium hydroxide or potassium carbonate needs to be purchased to enter the fluorine extraction reaction, so that the production cost is greatly saved.

(5) The reaction of the potassium fluoride solution and calcium bicarbonate for preparing calcium fluoride has the characteristics of mild conditions and high speed, is easy for industrial production, and greatly reduces the energy consumption.

(6) The silicon dioxide as a byproduct becomes a coating material of the compound fertilizer, and all resources can be reasonably utilized.

(7) The industrial byproduct carbon dioxide and the associated fluorine and potassium resources of the phosphorite are skillfully and tightly combined, so that the carbon emission of the ammonia synthesis device is reduced (about 1.13 tons of carbon dioxide emission are reduced per 1 ton of calcium fluoride produced), and considerable economic benefits can be brought to enterprises.

Compared with the prior art for utilizing the phosphorus ore associated with fluorine resources, the method has the following advantages:

(1) the raw material range is widened, and almost all fluorine-containing compounds which are byproducts in the wet-process phosphoric acid processing process are included, so that the utilization of the phosphorite associated fluorine resource is not limited to fluosilicic acid any more.

(2) Compared with the technology of sulfuric acid decomposition fluosilicic acid in Guizhou Vanfu blue sky, no large amount of dilute sulfuric acid is generated, a large-scale phosphoric acid device is not required, a wet-process phosphoric acid device of any scale is suitable, and the concentration of associated fluorine resources of phosphorite (in the form of potassium fluosilicate) can be simply realized; the hydrogen fluoride can be produced only by producing the calcium fluoride and combining the existing fluorite method hydrogen fluoride production process; the whole process of the calcium fluoride is neutral or alkaline, the requirement on equipment materials is low, and the investment is saved;

(3) compared with the processes of ammonium fluoride, ammonia and calcium hydroxide/calcium carbonate, the method does not need to use ammonia which is expensive, volatile, flammable and explosive, and basically has no potential safety and environmental protection hazards; in addition, ammonia does not need to be evaporated from the ammonia solution in the process, so that the energy consumption is reduced; the ammonia-free recovery device and the requirement on the tightness of the equipment reduce the equipment investment.

In conclusion, the technical value of the invention is to overcome the defect that the existing process can not utilize wet-process phosphoric acid except for fluosilicic acid to produce the byproduct of the fluorine-containing compound, and the fluorine-containing compound can be fully utilized; the economic value lies in that the waste fluorine-containing compound, phosphorite associated potassium resource, industrial byproduct carbon dioxide and the like can be simultaneously processed into high-value calcium fluoride, potassium bicarbonate, potassium carbonate and silicon dioxide by using calcium hydroxide and a small amount of potassium-containing compound, so that the comprehensive and efficient utilization of fluorine, silicon, potassium and carbon resources is realized.

Drawings

The foregoing and additional aspects and advantages of the present invention will become apparent from the following detailed description of the embodiments, which, taken in conjunction with the accompanying drawings, illustrate by way of example the present invention.

FIG. 1 is a process flow diagram of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings.