阅读说明：本技术 一种由氟化钙污泥制备高纯氟化钙的方法 (Method for preparing high-purity calcium fluoride from calcium fluoride sludge ) 是由 王百年 陈义雯 常道春 杨保俊 张告时 都晓俊 于 2019-12-11 设计创作，主要内容包括：本发明公开了一种由氟化钙污泥制备高纯氟化钙的方法,是将氟化钙污泥放入烘箱干燥后,经球磨机球磨并过筛,得到筛下物A；取一定量的A,加入一定量的酸溶液搅拌反应,得到固液混合物B,经不同目数的滤布过滤得到滤渣C和滤液D,将上述滤液D进行离心分离,得到沉淀物E；取一定量的沉淀物E,加入氢氧化钠溶液,过滤得到氟化钙和滤液F,将氟化钙烘干粉碎即得到粉末状高纯氟化钙。本发明可以对氟化钙污泥进行有效处置,制备出高纯氟化钙,解决氟资源紧张的问题,具有良好的经济与环境效益以及广阔的应用前景。(The invention discloses a method for preparing high-purity calcium fluoride from calcium fluoride sludge, which comprises the steps of drying the calcium fluoride sludge in an oven, ball-milling by a ball mill, and sieving to obtain a undersize product A; taking a certain amount of A, adding a certain amount of acid solution, stirring and reacting to obtain a solid-liquid mixture B, filtering through filter cloth with different meshes to obtain filter residue C and filtrate D, and carrying out centrifugal separation on the filtrate D to obtain a precipitate E; and (3) adding a certain amount of precipitate E into a sodium hydroxide solution, filtering to obtain calcium fluoride and a filtrate F, and drying and crushing the calcium fluoride to obtain powdery high-purity calcium fluoride. The method can effectively treat the calcium fluoride sludge, prepare high-purity calcium fluoride, solve the problem of shortage of fluorine resources, and has good economic and environmental benefits and wide application prospect.)

1. A method for preparing high-purity calcium fluoride from calcium fluoride sludge is characterized by comprising the following steps:

drying the calcium fluoride sludge in an oven, ball-milling by a ball mill, and sieving to obtain a undersize product A; taking a certain amount of A, adding a certain amount of acid solution, stirring and reacting to obtain a solid-liquid mixture B, filtering through filter cloth with different meshes to obtain filter residue C and filtrate D, and carrying out centrifugal separation on the filtrate D to obtain a precipitate E; and (3) adding a certain amount of precipitate E into a sodium hydroxide solution, filtering to obtain calcium fluoride and a filtrate F, and drying and crushing the calcium fluoride to obtain powdery high-purity calcium fluoride.

2. The method according to claim 1, characterized by comprising the steps of:

step 1: drying sludge: drying the calcium fluoride sludge in an oven, ball-milling by using a ball mill, and sieving by using a 200-mesh sieve to obtain a undersize product A;

step 2: sludge acidification: mixing the undersize product A with water, stirring uniformly, adding hydrochloric acid to dissolve an alkaline precipitate to obtain a solid-liquid mixture B;

and step 3: and (3) filtering: filtering and screening the solid-liquid mixture B by using filter cloth with different particle sizes to obtain filter residue C and filtrate D;

and 4, step 4: centrifuging: carrying out centrifugal washing on the filtrate D to obtain a precipitate E;

and 5: alkali leaching to remove silicon: adding a sodium hydroxide solution into the precipitate E, uniformly stirring, converting silicon dioxide in the sludge into sodium silicate, and filtering to obtain calcium fluoride and a filtrate F;

step 6: drying and crushing: and (3) drying the obtained calcium fluoride in an oven, and crushing the calcium fluoride by using a ball mill to obtain powdery high-purity calcium fluoride.

3. The method of claim 2, wherein:

in the step 2, the mass ratio of the undersize product A to water is 1: 1-1: 10; the molar ratio of the acid equivalent in the hydrochloric acid to the calcium content in the calcium fluoride sludge is 1: 1-3: 1.

4. The method of claim 2, wherein:

in the step 2, the molar concentration of hydrogen ions in the acidification reaction system is 1.0-3.0 mol/L, the acidification reaction time is 90min, and the acidification reaction temperature is room temperature.

5. The method of claim 2, wherein:

in the step 3, the mesh number of the filter cloth used in the filtering and screening process is 200-1000 meshes.

6. The method of claim 2, wherein:

in the step 4, the centrifugal rotating speed is 1000-5000 r/min, the centrifugal time is 15min, and the washing times are 3.

7. The method of claim 2, wherein:

in the step 5, the mass fraction of the sodium hydroxide solution is 15-40%, the mass ratio of the sodium hydroxide solution to the precipitate E is 2-5: 1, the reaction time is 30-120 min, and the reaction temperature is 70-95 ℃.

Technical Field

The invention belongs to the field of calcium fluoride sludge treatment in the photovoltaic photoelectric industry, and particularly relates to a method for preparing high-purity calcium fluoride from calcium fluoride sludge.

Background

The development of the photovoltaic photoelectric industry in China is rapid, the market share accounts for more than 50% of the world, and the generated fluorine-containing wastewater is neutralized by calcium oxide or calcium hydroxide to generate a large amount of calcium fluoride sludge, wherein the calcium fluoride accounts for more than 40%. The main component of the calcium fluoride sludge is CaF₂、CaCO₃、Ca(OH)₂、CaSO₄、SiO₂、CaSiO₃And impurities such as sand and stone. Calcium fluoride has low toxicity and is slightly soluble in water, and secondary fluorine pollution can be caused by improper disposal, so that the fluorine content of surface water exceeds the standard and the like. Therefore, the disposal of calcium fluoride is urgent.

At present, most calcium fluoride sludge is finally stored or solidified in a centralized stacking mode, and only a small amount of calcium fluoride sludge is comprehensively utilized and recycled to prepare calcium fluoride. Calcium fluoride has the characteristics of high corrosive risk and leaching risk, and landfill treatment and solidification treatment are not ideal treatment modes, so that a reasonable and feasible technical method for comprehensively utilizing and recycling calcium fluoride sludge is imperative.

The comprehensive utilization and recovery method is to use calcium fluoride sludge as an additive to replace partial raw materials or improve the product performance. If calcium fluoride sludge is added into the raw material, the stability of the mineral phase structure after the ceramic is sintered can be improved; partial calcium source required by cement production can be provided by replacing partial raw materials with calcium fluoride sludge; calcium fluoride sludge can be used to replace river sand required in concrete production; calcium fluoride sludge is used as an additive for solidification and stabilization of solid waste incineration fly ash; calcium fluoride sludge is used as a metallurgical flux in the steel industry. Although the treatment and disposal process can reduce a certain amount of calcium fluoride sludge, the problems of low consumption, complex treatment, waste of certain fluorine resources, environmental pollution and the like still exist.

Fluorite is an important nonmetallic mineral, and the main component of the fluorite is CaF₂Of high grade(97-98%) is called acid-making grade, mainly used for producing hydrogen fluoric acid and aluminum smelting, and half of the output of fluorite is used as hydrogen-making fluoric acid and derivatives thereof in the world at present, so that the demand of chemical industry in China on acid-making grade fluorite is huge and obviously increased. In addition, a small amount of fluorite is added during glass melting, so that the fluxing effect can be achieved, the fluorite can reduce the viscosity of glass liquid, the homogenization and clarification of the glass are facilitated, and the quality of the glass is improved. The addition of fluorite during glass melting is also an effective energy-saving measure, but the fluorite for the glass flux has the quality requirement of CaF₂>80 percent, so the preparation of high-purity calcium fluoride from calcium fluoride sludge to replace fluorite ore has wide market prospect.

The purification method of fluorite or calcium fluoride sludge is generally a flotation enrichment method, and refers to CaF₂The oleic acid trapping agent is added into the suspension formed by the oleic acid trapping agent and water, the acidic water glass is selected as an inducer to avoid the influence of calcium, magnesium and iron ions, and the purpose of air flotation separation is achieved by utilizing the surface property difference of materials, but the consumption of the flotation agent is large and the economic benefit is poor; meanwhile, a large amount of impurity mud and sewage containing metal ions and silicon dioxide are generated, and secondary pollution is brought to the environment.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a method for preparing high-purity calcium fluoride from calcium fluoride sludge. The method can effectively treat the calcium fluoride sludge, prepare high-purity calcium fluoride, solve the problem of shortage of fluorine resources, and has good economic and environmental benefits and wide market application prospect.

The invention relates to a method for preparing high-purity calcium fluoride from calcium fluoride sludge, which comprises the steps of putting the calcium fluoride sludge into an oven for drying, ball-milling by a ball mill, and sieving by a 200-mesh sieve to obtain a undersize product A; taking a certain amount of A, adding a certain amount of acid solution, stirring and reacting to obtain a solid-liquid mixture B, filtering to obtain filter residue C and filtrate D, and carrying out centrifugal separation on the filtrate D to obtain a precipitate E; and (3) adding a certain amount of precipitate E into a sodium hydroxide solution, filtering to obtain calcium fluoride and a filtrate F, and drying and crushing the calcium fluoride to obtain powdery high-purity calcium fluoride. The method specifically comprises the following steps:

step 1: drying sludge: drying the calcium fluoride sludge in an oven, ball-milling by using a ball mill, and sieving by using a 200-mesh sieve to obtain a undersize product A;

step 2: sludge acidification: mixing the undersize product A with water, stirring uniformly, adding hydrochloric acid to dissolve an alkaline precipitate to obtain a solid-liquid mixture B;

and step 3: and (3) filtering: filtering and screening the solid-liquid mixture B by using filter cloth with different particle sizes to obtain filter residue C (containing insoluble impurity impurities) and filtrate D (mainly containing calcium fluoride with fine particle size and soluble impurities);

and 4, step 4: centrifuging: carrying out centrifugal washing on the filtrate D to obtain a precipitate E;

and 5: alkali leaching to remove silicon: adding a sodium hydroxide solution into the precipitate E, uniformly stirring, converting silicon dioxide in the sludge into sodium silicate, and filtering to obtain calcium fluoride and a filtrate F;

step 6: drying and crushing: and (3) drying the obtained calcium fluoride in an oven, and crushing the calcium fluoride by using a ball mill to obtain powdery high-purity calcium fluoride.

In the step 2, the mass ratio of the undersize product A to water is 1: 1-1: 10; the molar ratio of the acid equivalent in the hydrochloric acid to the calcium content in the calcium fluoride sludge is 1: 1-3: 1.

In the step 2, the molar concentration of hydrogen ions in the acidification reaction system is 1.0-3.0 mol/L, the acidification reaction time is 90min, and the acidification reaction temperature is room temperature.

In the step 3, the mesh number of the filter cloth used in the filtering and screening process is 200-1000 meshes.

In the step 4, the centrifugal rotating speed is 1000-5000 r/min, the centrifugal time is 15min, and the washing times are 3.

In the step 5, the mass fraction of the sodium hydroxide solution is 15-40%, the mass ratio of the sodium hydroxide solution to the precipitate E is 2-5: 1, the reaction time is 30-120 min, and the reaction temperature is 70-95 ℃.

The beneficial technical effects of the invention are as follows:

compared with the prior art, the method takes industrial solid waste calcium fluoride sludge as a raw material, and removes impurities in the sludge through step-by-step impurity removal operation to obtain high-grade and high-purity calcium fluoride; the invention has simple process and is easy to realize continuous batch production; sludge with different component contents can be reasonably treated by adjusting the addition amount of a reagent; the method can effectively treat the calcium fluoride sludge, can also prepare high-purity calcium fluoride, solves the problem of shortage of fluorine resources, and has good economic and environmental benefits. The calcium fluoride sample obtained by the method has the calcium fluoride content of more than 98 percent, belongs to high-grade acid-making artificial fluorite, can be used for producing hydrofluoric acid and derivatives thereof, and has wide market application prospect.

Drawings

FIG. 1 is a schematic view of the process used in the present invention.

Fig. 2 and 3 are XRD patterns of calcium fluoride sludge and sample high-purity calcium fluoride.

Detailed Description

The present invention will be described in detail with reference to the accompanying drawings and examples.

In the embodiment, calcium fluoride sludge generated in the photovoltaic industry is used as a raw material, the purity of calcium fluoride in raw sludge is 60%, and the calcium fluoride is treated according to the experimental method, and the specific steps are shown in the embodiment.