Fluorine recovery system for fluorine-containing silicon dioxide

Abstract

The utility model relates to the technical field of phosphorus chemical equipment, and particularly discloses a fluorine recovery system for fluorine-containing silicon dioxide. Comprising a first-stage washing system, a second-stage washing system and a plate frame filter, one end of the plate frame filter is provided with a liquid inlet and a liquid outlet, the liquid inlet of the plate frame filter is communicated with a washing system water inlet pipe, the washing system water inlet pipe is provided with a multi-pipeline connecting piece, and the multi-pipeline connecting piece is further communicated with a process water conveying pipe. The liquid outlet is communicated with a washing system recycling pipe, the washing system recycling pipe is provided with a four-way pipe, the four-way pipe and the multi-pipeline connecting piece are provided with valves capable of controlling whether the pipelines are communicated with the plate-and-frame filter or not, and the multi-pipeline connecting piece, the four-way pipe and the valves are utilized and process water is arranged for third-time washing. The technical problems that in the prior art, silicon dioxide after washing contains a large amount of fluorine and is not pure enough, the purity of silicon dioxide cannot be improved, and fluorine is wasted are solved.

Description

Technical Field

[0001] The utility model relates to the technical field of phosphochemical equipment, in particular to a fluorine recovery system for fluorosilicic acid dioxide containing fluorine. Background Art

[0002] Anhydrous hydrogen fluoride is an important chemical product and belongs to the halogen acid products in the manufacture of inorganic acids. Due to the extremely active chemical properties of anhydrous hydrogen fluoride, it can not only react with alkalis, metal oxides, silicates, etc., but also undergo fluorination reactions with organic substances. Therefore, in chemical production, it is not only a catalyst for organic synthesis, but also an important raw material for producing elemental fluorine, inorganic and organic fluorides, various fluorine refrigerants and other products.

[0003] A large amount of fluorosilicic acid will be produced as a by-product of wet-process phosphoric acid produced by the wet process. This part of fluorosilicic acid needs to be treated as wastewater, resulting in wastewater treatment costs. Traditional anhydrous hydrogen fluoride is mainly produced from fluorite. Since fluorite is a non-renewable resource, as its reserves decrease, its price has gradually increased. Therefore, recycling fluorosilicic acid wastewater and utilizing the fluorine element in fluorosilicic acid to produce anhydrous hydrogen fluoride from fluorosilicic acid is a very promising process solution, which is of great significance for the protection of fluorite resources.

[0004] During the process of using fluorosilicic acid to prepare anhydrous hydrogen fluoride, by-product silicon dioxide will be produced. Silicon dioxide exists in liquid fluorosilicic acid in a solid state. Silicon dioxide has various uses in industry and daily life. Collecting and utilizing silicon dioxide can create other additional values. At the same time, since silicon dioxide is in a solid state in liquid concentrated fluorosilicic acid, it can be separated from concentrated fluorosilicic acid by physical methods such as filtration and centrifugation, so as to carry out subsequent treatment and utilization. For example, the patent document with the application number 202322036244.2 discloses a continuous washing device for fluorine-containing silicon dioxide, including a plate and frame filter for filtering silicon dioxide in concentrated fluorosilicic acid. One end of the plate and frame filter is provided with a filtrate outlet and a washing liquid outlet. The inlet end of the filter is connected to the main pipeline through which concentrated fluorosilicic acid flows. The filtrate outlet of the filter is connected to a primary washing water system for cleaning the filter. At the same time, a secondary water washing system for cleaning the filter is also connected to the washing liquid outlet of the plate and frame filter. The purpose of this patent is to solve the problem that when filtering silicon dioxide in concentrated fluorosilicic acid, a large amount of acid solution is needed for washing the silicon dioxide filter cake. Once a large amount of silicon dioxide is filtered, a large amount of acid solution is required, thereby increasing the production cost.

[0005] Although the above-mentioned patent uses a water washing system to wash silica, its washing logic is as follows: The primary water washing system of the water washing system directly uses fluorine-containing wastewater to mix with high-concentration fluosilicic acid for the first washing, and then the secondary water washing system directly uses recycled water for the second washing. However, the excess recycled water in the second washing will continue to be stored in the recycle water tank. After multiple washings, fluorine elements accumulate in the recycle water tank, and the recycled water becomes fluorine-containing wastewater, which is equivalent to using low-concentration fluorine-containing wastewater for the second washing. In actual production, it is found that the total fluorine content in the washed silica filter cake is about 10%-15%. This not only affects the purity of silica but also causes some fluorine to be lost along with silica and cannot be recycled. Summary of the Invention

[0006] The purpose of the present invention is to provide a fluorine recovery system for fluorine-containing silica, so as to solve the technical problems in the above-mentioned prior art that the washed silica still contains a large amount of fluorine, is not pure enough, resulting in the inability to improve the purity of silica and the waste of fluorine.

[0007] To solve the above problems, the technical solution adopted by the present invention is as follows: A fluorine recovery system for fluorine-containing silica includes a primary water washing system, a secondary water washing system, and a plate and frame filter. One end of the plate and frame filter is provided with a liquid inlet and a liquid outlet. The liquid inlet of the plate and frame filter is connected to a washing system inlet pipe. A multi-pipe connector that can be connected to the primary water washing system and the secondary water washing system is provided on the washing system inlet pipe. The multi-pipe connector is also connected to a process water supply pipe that supplies water for the third washing of silica. The liquid outlet is connected to a washing system reuse pipe. A four-way pipe that is connected to the primary water washing system and the secondary water washing system is provided on the washing system reuse pipe. Valves that can control whether the pipe is connected to the plate and frame filter are provided on the four-way pipe and the multi-pipe connector.

[0008] The beneficial effect of this embodiment is as follows:

[0009] 1. In the prior art, when washing silica using a water washing system, the washing process is as follows: the waste water tank of the primary water washing system is used to mix the fluorine-containing waste water with high-concentration fluosilicic acid for the first washing. Then, the circulating water tank of the secondary water washing system directly uses circulating water for the second washing. However, the excess circulating water in the second washing will continue to be stored in the circulating water tank. After the circulating water undergoes multiple washings, fluorine elements accumulate in the circulating water tank, and the circulating water becomes fluorine-containing waste water, which is equivalent to using low-concentration fluorine-containing waste water for the second washing. In actual production, it is found that the total fluorine content in the washed silica filter cake is about 10%-15%. This not only affects the purity of silica but also causes some fluorine to be lost along with silica and cannot be recycled. In this application, a process water delivery pipe is provided, and process water is supplied through the process water delivery pipe for the third washing. The process water contains a small amount of fluorine. During washing, the difference in fluorine content between the process water and the silica is large, forming a greater driving force, enabling the fluorine on the silica to better enter the process water. According to actual production, it is found that the fluorine content in the washed silica has been reduced from about 10%-15% to below 6%.

[0010] 2. In the prior art, when mixing fluorine-containing waste water with high-concentration fluosilicic acid, the concentration of fluosilicic acid is reduced, which is not conducive to the recycling of fluorine elements. In this application, multiple pipe connectors and a four-way pipe are provided, and valves are provided on the multiple pipe connectors and the four-way pipe. By controlling the connection or disconnection of the multiple pipe connectors and the plate frame filter through the valves, the washing process is divided into three washings. Fluosilicic acid is introduced for the first washing, fluorine-containing waste water is introduced for the second washing, and process water is introduced for the third washing. The washing water after the third washing is used as the washing water for the second washing through the four-way pipe, and the washing water after the second washing is used as the washing water for the first washing. This makes the concentration of the washing water gradually increase, forming a fluosilicic acid solution containing high-concentration fluorine, so it can be directly used in the production system. This application not only makes the silica washing cleaner but also recycles fluorine elements.

[0011] Further, the valve is a solenoid valve, and the solenoid valve is electrically connected to a PLC controller.

[0012] Further, the multiple pipe connectors include a four-way pipe and a three-way pipe.

[0013] Further, the primary water washing system includes a waste water tank and a circulating water tank. The waste water tank is provided with a waste water tank outlet pipe connected to the washing system inlet pipe and a waste water tank inlet pipe that can be connected to the washing system return pipe.

[0014] Further, the secondary water washing system includes a washing water tank. The washing water tank includes a washing water tank delivery pipe connected to the washing system inlet pipe and a washing water tank inlet pipe connected to the washing system return pipe.

[0015] Furthermore, one end of the process water delivery pipe is connected to the water inlet pipe of the washing system, and the other end is connected to a process water tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic structural diagram of an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] The following is a more detailed description through specific embodiments:

[0018] The reference numerals in the accompanying drawings of the specification include: plate-and-frame filter 1, liquid inlet 11, liquid outlet 12, washing tank 2, washing tank water delivery pipe 21, washing tank water inlet pipe 22, process water tank 3, process water delivery pipe 31, waste water tank 4, waste water tank water inlet pipe 41, waste water tank water outlet pipe 42, circulating water tank 43, washing system reuse pipe 5, washing system water inlet pipe 6.

[0019] As shown in the embodiment Figure 1 shown: A fluorine recovery system for fluorosilica dioxide includes a plate-and-frame filter 1, and a liquid inlet 11 and a liquid outlet 12 are provided at one end of the plate-and-frame filter 1. During use, the mixed liquid of concentrated fluorosilicic acid (liquid) and silicon dioxide (solid) generated by using fluorosilicic acid to produce anhydrous hydrogen fluoride flows towards the plate-and-frame filter 1 through the main pipeline after production. The main pipeline (not shown in the figure) is connected to the washing system water inlet pipe 6, and is connected to the liquid inlet 11 of the plate-and-frame filter 1 through the washing system water inlet pipe 6. The washing system water inlet pipe 6 feeds the mixed liquid of concentrated fluorosilicic acid and silicon dioxide into the plate-and-frame filter 1. Silicon dioxide forms a filter cake in the plate-and-frame filter 1, while the concentrated fluorosilicic acid is connected to the washing system reuse pipe 5 through the liquid outlet 12 and returns to the production system of anhydrous hydrogen fluoride for reuse through the washing system reuse pipe 5.

[0020] After separating the concentrated fluorosilicic acid liquid from the silicon dioxide, the silicon dioxide filter cake in the plate-and-frame filter 1 is washed. The entire washing process includes three washes.

[0021] The first wash is completed by a primary water wash system. The primary wash system includes a waste water tank 4 and a circulating water tank 43. A circulating water tank 43 for storing low-concentration pickling water is provided on one side of the waste water tank 4. The water outlet of the circulating water tank 43 is connected to the waste water tank 4. The water in the circulating water tank 43 comes from the low-concentration fluorosilicic acid waste water generated in the production of anhydrous hydrogen fluoride. This part of the water contains fluorine. This part of the low-concentration water is transported into the waste water tank 4 to supplement the waste water in the waste water tank 4. The waste water tank 4 is connected to the washing system water inlet pipe 6 through the waste water tank water outlet pipe 42. Therefore, the washing water in the waste water tank 4 enters the plate-and-frame filter 1 through the washing system water inlet pipe 6 and the liquid inlet 11 to wash the silicon dioxide filter cake. The washed water forms a concentrated fluorosilicic acid solution and returns to the production system of anhydrous hydrogen fluoride through the washing system reuse pipe 5.

[0022] The second washing is completed by a secondary water washing system. The secondary water washing system includes a washing water tank 2, a washing water tank water delivery pipe 21, and a waste water tank water inlet pipe 41. One end of the washing water tank water delivery pipe 21 is connected to the bottom of the washing water tank 2, and the other end is connected to the washing system water inlet pipe 6. Therefore, the washing water in the washing water tank 2 will be pumped into the plate and frame filter 1 to conduct the second washing on the silica cake. The filtrate after washing enters the waste water tank 4 through the waste water tank water inlet pipe 41 and serves as the main source of washing water for the first washing.

[0023] The third washing is completed by process water. The process water is delivered to the washing system water inlet pipe 6 by a process water delivery pipe 31. The process water delivery pipe 31 is directly connected to the main process water pipeline of the factory. A process water tank 3 can also be set up to provide process water to the plate and frame filter 1 as the washing water for the third washing. The washing water after the third washing enters the washing water tank 2 of the secondary water washing system through the washing water tank water inlet pipe 22 and serves as the main washing water for the second washing.

[0024] The washing system water inlet pipe 6 is provided with a multi-pipeline connector. The multi-pipeline connector is composed of a tee and a cross. By using the multi-pipeline connector, the washing system water inlet pipe 6 is connected to the waste water tank water outlet pipe 42 of the waste water tank 4 of the primary water washing system and the washing water tank water delivery pipe 21 of the washing water tank 2 of the secondary water washing system, and can also be directly connected to the process water delivery pipe 31. And an electromagnetic valve is set at each pipeline connection position. The electromagnetic valve is electrically connected to the PLC controller. Therefore, the opening and closing of the electromagnetic valve can be controlled by the PLC controller. Therefore, during the three washings, the washing water entering the plate and frame filter 1 can be controlled by opening and closing the electromagnetic valve to ensure that it is washed step by step according to the setting and the concentration of the washing water gradually increases. The washing system reuse pipe 5 is also provided with a cross pipe. The cross pipe is connected to the waste water tank water inlet pipe 41 of the waste water tank 4 of the primary water washing system and the washing water tank water inlet pipe 22 of the washing water tank 2 of the secondary water washing system. And an electromagnetic valve is also set on the cross pipe. The electromagnetic valve on the cross pipe is also electrically connected to the PLC controller.

[0025] Looking at the entire washing process as a whole, in the third washing of this application, the cleanest process water is used for washing. The washing water after washing absorbs the residual fluorosilicic acid in the silica to form fluorine-containing water, which is used as the washing water for the second washing of the next batch of silica. The second washing absorbs the fluorosilicic acid in the silica again, causing the concentration of fluorosilicic acid in the fluorine-containing washing water to gradually increase. Therefore, the washing water after the second washing forms a more concentrated fluorine-containing washing water than that after the third washing and is used as the washing water for the first washing of the next batch of silica. During the first washing, the silica is the one separated from concentrated fluorosilicic acid. Therefore, a large amount of fluorosilicic acid and other fluorine-containing substances are adsorbed on the surface of the silica. As a result, the washing water used for washing after the first washing forms a fluorosilicic acid solution containing a high concentration of fluorine and can be directly reused in the production system. This application utilizes the process of step-by-step washing to gradually increase the concentration of fluorine in the washing water, causing the washing water to form a concentrated fluorosilicic acid solution for reuse. Therefore, no fluorine-containing wastewater is formed and discharged to damage the environment, and precious fluorine elements are also recovered.

[0026] From the perspective of silica, the silica is washed three times, and the washing water used each time is cleaner. As a result, the fluorine-containing impurities adsorbed in the silica are washed cleanly, and the fluorine content of the silica after washing in actual production is reduced to less than 6%.

[0027] The above are only the embodiments of the present utility model. Common knowledge such as the specific structures and characteristics known in the solutions is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the structure of the present utility model, several deformations and improvements can be made, which should also be regarded as the protection scope of the present utility model. These will not affect the implementation effect of the present utility model and the practicality of the patent. The protection scope required by this application should be based on the content of its claims, and the specific implementation manners described in the specification can be used to interpret the content of the claims.

Claims

1. A fluorine recovery system for fluorinated silica, comprising a primary water washing system, a secondary water washing system, and a plate and frame filter. One end of the plate and frame filter is provided with a liquid inlet and a liquid outlet, and it is characterized in that: The liquid inlet of the plate-and-frame filter is connected to a washing system water inlet pipe. A multi-pipe connector capable of being connected to a primary water washing system and a secondary water washing system is provided on the washing system water inlet pipe. The multi-pipe connector is also connected to a process water delivery pipe for supplying water for three times of washing of silicon dioxide. The liquid outlet is connected to a washing system recycling pipe. A four-way pipe connected to the primary water washing system and the secondary water washing system is provided on the washing system recycling pipe. Valves capable of controlling whether the pipes are connected to the plate-and-frame filter or not are provided on the four-way pipe and the multi-pipe connector.

2. The fluorine recovery system of fluorinated silica according to claim 1, characterized in that: The valves provided on the four-way pipe and the multi-pipe connector are solenoid valves, and the solenoid valves are electrically connected to a PLC controller.

3. The fluorine recovery system of fluorinated silica according to claim 1, characterized in that: The multi-pipe connector includes a four-way pipe and a three-way pipe.

4. The fluorine recovery system of fluorinated silica according to claim 1, characterized in that: The primary water washing system includes a waste water tank and a circulating water tank. The waste water tank is provided with a waste water tank outlet pipe connected to the washing system water inlet pipe and a waste water tank inlet pipe capable of being connected to the washing system recycling pipe.

5. The fluorine recovery system of fluorinated silica according to claim 1, wherein: The secondary water washing system includes a washing sink. The washing sink includes a washing sink water delivery pipe connected to the washing system water inlet pipe and a washing sink inlet pipe connected to the washing system recycling pipe.

6. The fluorine recovery system of fluorinated silica according to claim 1, wherein: One end of the process water delivery pipe is connected to the washing system water inlet pipe, and the other end is connected to a process water tank.

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