Preparation process for preparing calcium fluoride ball material by using fluorine-containing sludge

Abstract

The invention belongs to the technical field of resource utilization of fluorine-containing sludge, and provides a preparation process for preparing calcium fluoride pellets from fluorine-containing sludge, which comprises a dewatering and drying process, an acidification process, a fluorination process, an alkalization process and a granulation process for preparing the calcium fluoride pellets from the fluorine-containing sludge. The calcium fluoride ball material is prepared by removing impurities such as calcium sulfate and silicon dioxide in the fluorine-containing sludge, the calcium sulfate and silicon dioxide impurities in the calcium fluoride are removed by adopting a dewatering and drying process, an acidification process, a fluorination process and an alkalization process, and the method has the advantages and effects of resource utilization of the fluorine-containing sludge and improvement of the purity of the calcium fluoride.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of resource utilization of fluorine-containing sludge, and particularly relates to a preparation process for preparing calcium fluoride spherical material from fluorine-containing sludge. BACKGROUND

[0002] The fluorine-containing waste acid sludge is a byproduct generated in a process of using hydrofluoric acid or an acid containing fluorine ions for processing, and is mainly derived from semiconductor manufacturing, photovoltaic industry, glass etching, metal surface treatment and stainless steel pickling, etc. A large amount of fluorine-containing wastewater is generated in the industrial production process, and the fluorine-containing wastewater is diluted, neutralized with lime, and settled and filtered to form fluorine-containing sludge solid waste. With the rapid development of related industries, a large amount of fluorine-containing wastewater is generated in the production process, and currently, calcium salt or lime is usually added to the fluorine-containing sludge, resulting in an increase in the annual discharge amount of the fluorine-containing sludge. The fluorine-containing sludge mainly contains calcium fluoride, calcium sulfate, silicon dioxide, calcium chloride and related metal impurities such as iron, copper and aluminum, and the fluorine content in the fluorine-containing sludge is high, which poses a serious leaching risk in stacking or landfill, and can cause serious harm to groundwater and the surrounding ecological environment.

[0003] Currently, the fluorine-containing sludge is purified to prepare calcium fluoride, but the calcium fluoride contains a large amount of calcium sulfate and silicon dioxide impurities, and the purity of the calcium fluoride is low, which makes it difficult to utilize the calcium fluoride. Therefore, the application removes the metal impurities such as iron, copper and aluminum, calcium sulfate and silicon dioxide impurities in the calcium fluoride by adopting a dehydration drying process, an acidification process, a fluorination process and an alkalization process, so as to improve the purity of the calcium fluoride and the resource utilization amount of the calcium fluoride in industrial production. SUMMARY

[0004] The application aims to provide a preparation process for preparing calcium fluoride spherical material from fluorine-containing sludge, which has the effects of resource utilization of fluorine-containing sludge and improvement of the purity of calcium fluoride.

[0005] The above technical objective of the application is achieved by the following technical scheme: a preparation process for preparing calcium fluoride spherical material from fluorine-containing sludge, which comprises a dehydration drying process, an acidification process, a fluorination process, an alkalization process and a granulation process.

[0006] The application further provides that the dehydration drying process comprises stirring the fluorine-containing sludge in a mechanical stirrer for 10 min at a speed of 260 r·min -1 , and then dehydrating the uniformly stirred fluorine-containing sludge in a filter press to obtain a fluorine-containing sludge with a water content of less than 35%. The dehydrated fluorine-containing sludge is dried in a dryer at a temperature of 180-230 DEG C for 120 min.

[0007] The further setting of the application is that the concentration of hydrochloric acid in the acidification process is 5-6%, the liquid-solid ratio is 6:1, the slurry is continuously stirred, the stirring speed is 210 r·min -1 , the slurry temperature is controlled at 15-18 DEG C, the pH is controlled at 3-4, and the acidification time is controlled for 40 min.

[0008] The further setting of the application is that the concentration of hydrogen fluoride in the fluorination process is 20%, the liquid-solid ratio is 0.5-0.8:1, the slurry is continuously stirred, the stirring speed is 210 r·min -1 , the slurry temperature is controlled at 25-30 DEG C, the pH is controlled at 2-3.5, and the fluorination time is controlled for 45 min.

[0009] The further setting of the application is that the alkali leaching solvent in the alkali process is sodium hydroxide and calcium chloride, the concentration of sodium hydroxide is 13%, the concentration of calcium chloride is 6%, the liquid-solid ratio is 3:1, the slurry is continuously stirred, the stirring speed is 250 r·min -1 , the slurry temperature is controlled at 68 DEG C, and the alkali time is controlled for 60 min.

[0010] The further setting of the application is that the granulation process includes that the calcium fluoride separated by filtering after the alkali treatment is subjected to plate and frame filter pressing, the calcium fluoride filter cake is sent to a sunlight room for natural air drying, the air drying is performed until the solid water ratio of the calcium fluoride is less than 4:1, and then the calcium fluoride is sent to a pair roller extrusion granulator for granulation, and the pressure is 30-50 MPa.

[0011] The beneficial effects of the application are:

[0012] (1) In the dehydration and drying process, the fluorine-containing sludge is dried after dehydration, the drying temperature is controlled at 180-230 DEG C, and the drying time is 120 min, in the drying temperature range, the calcium sulfate in the fluorine-containing sludge can be converted into calcium sulfate hemihydrate, because the solubility of calcium sulfate is very low, and the solubility of calcium sulfate hemihydrate is more than 4 times of that of calcium sulfate at 15-20 DEG C; by controlling the drying temperature, the calcium sulfate impurities in the fluorine-containing sludge are converted into calcium sulfate hemihydrate, and the calcium sulfate hemihydrate has the characteristics of fast dissolution rate and high solubility.

[0013] (2) In the acidification process, the solubility of calcium sulfate hemihydrate in the acid solution is significantly higher than that of calcium sulfate, so that more calcium sulfate can be dissolved in the acid solution, the solid-liquid separation is adopted to remove the calcium sulfate in the fluorine-containing sludge, and the purity of calcium fluoride is improved.

[0014] (3) Fluorination process by precise control of hydrogen fluoride concentration, liquid-solid ratio, slurry temperature, pH and time, so that the silicon dioxide in the fluorine-containing sludge fully reacts with hydrogen fluoride to produce silicon tetrafluoride gas, thereby removing the silicon dioxide in calcium fluoride and further improving the purity of calcium fluoride.

[0015] (4) The alkalization process uses sodium hydroxide and calcium chloride as the alkaline leaching solvent to further purify the calcium fluoride solution. Sodium hydroxide can form sodium silicate under alkaline conditions, which can be dissolved in the solution and removed. Calcium chloride can further convert excess fluoride ions in the solution into calcium fluoride precipitate under alkaline conditions, thereby further improving the purity of calcium fluoride.

[0016] (5) The calcium fluoride filter cake is sent to the sunlight room for natural air drying, which is beneficial to reducing energy consumption. The dried calcium fluoride powder is granulated in a roller extrusion granulator to prepare calcium fluoride pellets, which is beneficial to storage and transportation, thereby reducing calcium fluoride dust pollution. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by a person of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0018] Embodiment 1

[0019] A preparation process for preparing calcium fluoride pellets from fluorine-containing sludge according to the present application, the fluorine-containing sludge is stirred by a mechanical stirrer for 10 min at a speed of 260 r·min -1 The uniformly stirred fluorine-containing sludge is dewatered in a filter press with a water content of less than 35%. The dewatered fluorine-containing sludge is dried in a dryer at a temperature of 210℃ for 120 min.

[0020] The dried fluorine-containing sludge is subjected to an acidification process, the hydrochloric acid concentration is 5-6%, the liquid-solid ratio is 6:1, the slurry is continuously stirred at a stirring speed of 210 r·min -1 , the slurry temperature is controlled at 15℃, the pH is controlled at 3-4, and the acidification time is controlled for 40 min.

[0021] After acidification, fluorination is carried out, the hydrogen fluoride concentration is 20%, the liquid-solid ratio is 0.5:1, the slurry is continuously stirred at a stirring speed of 210 r·min -1 , the slurry temperature is controlled at 30℃, the pH is controlled at 2-3.5, and the fluorination time is controlled for 45 min.

[0022] After fluorination, an alkalization treatment process is carried out, the alkali leaching solvent is sodium hydroxide and calcium chloride, the concentration of sodium hydroxide is 13%, the concentration of calcium chloride is 6%, the liquid-solid ratio is 3:1, the slurry is continuously stirred, the stirring speed is 250 r·min -1 , the slurry temperature is controlled at 68 DEG C, and the alkalization time is controlled for 60 min.

[0023] After the alkalization treatment, the filtered and separated calcium fluoride is subjected to plate-frame pressure filtration, the calcium fluoride filter cake is sent into a sunlight room for natural air drying, the air drying is performed until the solid-water ratio of the calcium fluoride is less than 4:1, and then the calcium fluoride filter cake is sent to a pair of roller extrusion granulators for granulation at a pressure of 30 MPa to prepare calcium fluoride spherical materials.

[0024] Example 2:

[0025] The preparation process of the application for preparing calcium fluoride spherical materials from fluorine-containing sludge, the fluorine-containing sludge is stirred for 10 min by a mechanical stirrer at a speed of 260 r·min -1 , the uniformly stirred fluorine-containing sludge is subjected to dewatering in a pressure filter, and the water content is less than 35%. The dewatered fluorine-containing sludge is subjected to drying in a dryer at a temperature of 180 DEG C for 120 min.

[0026] After drying, the fluorine-containing sludge is subjected to an acidification treatment process, the concentration of hydrochloric acid is 5-6%, the liquid-solid ratio is 6:1, the slurry is continuously stirred, the stirring speed is 210 r·min -1 , the slurry temperature is controlled at 18 DEG C, the pH is controlled at 3-4, and the acidification time is controlled for 40 min.

[0027] After acidification, fluorination treatment is carried out, the concentration of hydrogen fluoride is 20%, the liquid-solid ratio is 0.8:1, the slurry is continuously stirred, the stirring speed is 210 r·min -1 , the slurry temperature is controlled at 25 DEG C, the pH is controlled at 2-3.5, and the fluorination time is controlled for 45 min.

[0028] After fluorination, an alkalization treatment process is carried out, the alkali leaching solvent is sodium hydroxide and calcium chloride, the concentration of sodium hydroxide is 13%, the concentration of calcium chloride is 6%, the liquid-solid ratio is 3:1, the slurry is continuously stirred, the stirring speed is 250 r·min -1 , the slurry temperature is controlled at 68 DEG C, and the alkalization time is controlled for 60 min.

[0029] After the alkalization treatment, the filtered and separated calcium fluoride is subjected to plate-frame pressure filtration, the calcium fluoride filter cake is sent into a sunlight room for natural air drying, the air drying is performed until the solid-water ratio of the calcium fluoride is less than 4:1, and then the calcium fluoride filter cake is sent to a pair of roller extrusion granulators for granulation at a pressure of 30 MPa to prepare calcium fluoride spherical materials.

[0030] Example 3:

[0031] The application discloses a preparation process for preparing calcium fluoride pellets from fluorine-containing sludge. -1 The uniformly stirred fluorine-containing sludge is dewatered in a filter press, and the water content is less than 35%.

[0032] The dried fluorine-containing sludge is subjected to an acidification treatment process, the concentration of hydrochloric acid is 5-6%, the liquid-solid ratio is 6:1, the slurry is continuously stirred, the stirring speed is 210 r·min -1 , the slurry temperature is controlled at 17℃, the pH is controlled at 3-4, and the acidification time is controlled at 40 min.

[0033] The fluorination treatment is performed after the acidification, the concentration of hydrogen fluoride is 20%, the liquid-solid ratio is 0.8:1, the slurry is continuously stirred, the stirring speed is 210 r·min -1 , the slurry temperature is controlled at 28℃, the pH is controlled at 2-3.5, and the fluorination time is controlled at 45 min.

[0034] The alkali treatment process is performed after the fluorination, the alkali leaching solvent is sodium hydroxide and calcium chloride, the concentration of sodium hydroxide is 13%, the concentration of calcium chloride is 6%, the liquid-solid ratio is 3:1, the slurry is continuously stirred, the stirring speed is 250 r·min -1 , the slurry temperature is controlled at 68℃, and the alkali treatment time is controlled at 60 min.

[0035] The filter-separated calcium fluoride after the alkali treatment is subjected to plate-frame filter pressing, the calcium fluoride filter cake is sent to a sunlight room for natural air drying, the air drying is performed until the solid-water ratio of the calcium fluoride is less than 4:1, and the calcium fluoride is sent to a roller extrusion granulator for granulation, so that calcium fluoride pellets are prepared.

[0036] Example 4:

[0037] The application discloses a preparation process for preparing calcium fluoride pellets from fluorine-containing sludge. -1 The uniformly stirred fluorine-containing sludge is dewatered in a filter press, and the water content is less than 35%. The fluorine-containing sludge after dewatering is not subjected to drying treatment. The subsequent acidification process, fluorination process, alkali treatment process and pelletizing process are the same as those in the method of example 1.

[0038] Example 5:

[0039] The application discloses a preparation process for preparing calcium fluoride pellets from fluorine-containing sludge. -1 The uniformly stirred fluorine-containing sludge is dewatered in a filter press, and the water content is less than 35%.

[0040] Example 6

[0041] The application discloses a preparation process for preparing calcium fluoride pellets from fluorine-containing sludge. -1 The uniformly stirred fluorine-containing sludge is dewatered in a filter press, and the water content is less than 35%.

[0042] Example 7

[0043] The application discloses a preparation process for preparing calcium fluoride pellets from fluorine-containing sludge. -1 The uniformly stirred fluorine-containing sludge is dewatered in a filter press, and the water content is less than 35%.

[0044] After drying, the fluorine-containing sludge is subjected to an acidification treatment process, the concentration of hydrochloric acid is 5-6%, the liquid-solid ratio is 6:1, the slurry is continuously stirred, the stirring speed is 210 r·min -1 The slurry temperature is controlled at 15 DEG C, the pH is controlled at 3-4, and the acidification time is controlled at 40 min.

[0045] After acidification, fluorination treatment is performed, the concentration of hydrogen fluoride is 20%, the liquid-solid ratio is 0.5:1, the slurry is continuously stirred, the stirring speed is 210 r·min -1 The slurry temperature is controlled at 30 DEG C, the pH is controlled at 2-3.5, and the fluorination time is controlled at 45 min.

[0046] After fluorination, no alkalization treatment process is performed, the filtered and separated calcium fluoride after the fluorination treatment is subjected to plate-frame pressure filtration, the calcium fluoride filter cake is sent to a sunlight room for natural air drying, the air drying is performed until the water content ratio of the calcium fluoride is less than 4:1, and then the calcium fluoride is sent to a pair-roller extrusion granulator for granulation, and the calcium fluoride is prepared into calcium fluoride spherical material under a pressure of 30 MPa.

[0047] The purity of the calcium fluoride spherical material prepared in Examples 1-7 is shown in Table 1:

[0048] Table 1

[0049] Purity of calcium fluoride balls Example 1 92.85 Example 2 89.16 Example 3 91.34 Example 4 72.51 Example 5 83.36 Example 6 82.99 Example 7 87.05

[0050] The purity of the calcium fluoride spherical material prepared by the process of the patent can reach 92.85%, which is increased by 20.34% compared with the purity of the calcium fluoride without drying treatment process, and is increased by 9.49% and 9.86% compared with the purity of the calcium fluoride dried at 100℃ and 300℃, respectively, and is increased by 5.8% compared with the purity of the calcium fluoride without alkalization treatment process. The purity of 90% of the calcium fluoride can meet the application requirements in the steel industry and the aluminum alloy industry. The calcium fluoride spherical material prepared by the process of the patent improves the purity of the calcium fluoride, so that it can meet the purity requirements in different fields such as construction, ceramics, steel industry and aluminum alloy industry, thereby the resource utilization amount of the calcium fluoride can be increased, the leaching of fluoride in the fluorine-containing sludge can be reduced, and the influence of the fluorine-containing sludge on the beautiful environment for human survival can be avoided.

Claims

1. A process for the production of calcium fluoride spherules from a fluorine-containing sludge, characterized in that: The preparation of calcium fluoride balls from fluorine-containing sludge includes a dewatering and drying process, an acidification process, a fluorination process, an alkalization process and a granulation process.

2. The process for preparing calcium fluoride pellets using fluorine-containing sludge according to claim 1, characterized by: The dewatering and drying process includes stirring the fluorine-containing sludge in a mechanical stirrer for 10 min at a speed of 260 r·min -1 The uniformly stirred fluorine-containing sludge is subjected to dewatering in a filter press, and the water content is less than 35%. The dewatered fluorine-containing sludge is subjected to drying in a dryer, the temperature is controlled at 180-230℃, and the drying time is 120 min.

3. The process for preparing calcium fluoride pellets using fluorine-containing sludge according to claim 1, characterized by: The concentration of hydrochloric acid in the acidification process is 5-6%, the liquid-solid ratio is 6:1, the slurry is continuously stirred, the stirring speed is 210 r·min -1 , the slurry temperature is controlled at 15-18℃, the pH is controlled at 3-4, and the acidification time is controlled for 40 min.

4. The process for preparing calcium fluoride pellets using fluorine-containing sludge according to claim 1, characterized by: The hydrogen fluoride concentration in the fluorination process is 20%, the liquid-solid ratio is 0.5-0.8:1, the slurry is continuously stirred, the stirring speed is 210 r·min -1 , the slurry temperature is controlled at 25-30℃, the pH is controlled at 2-3.5, and the fluorination time is controlled for 45 min.

5. The process for preparing calcium fluoride pellets using fluorine-containing sludge according to claim 1, characterized by: The alkali leaching solvent in the alkali process is sodium hydroxide and calcium chloride, the concentration of sodium hydroxide is 13%, the concentration of calcium chloride is 6%, the liquid-solid ratio is 3:1, the slurry is continuously stirred, the stirring speed is 250 r·min -1 , the slurry temperature is controlled at 68℃, and the alkali time is controlled for 60 min.

6. The process for preparing calcium fluoride pellets using fluorine-containing sludge according to claim 1, wherein: The granulation process includes frame filter pressing of the filtered and separated calcium fluoride after the alkalization treatment, and the calcium fluoride filter cake is sent to a sunlight room for natural air drying until the solid water ratio of the calcium fluoride is less than 4:1, and then sent to a pair of roller extrusion granulators for granulation at a pressure of 30-50 MPa.