A lye recycling system

Abstract

The utility model provides a kind of lye recycling system, it is related to polysilicon technical field.The utility model includes magnetic ring cleaning equipment, circulation pipeline is located on magnetic ring cleaning equipment, wherein, lye collecting pool, evaporator and filter device are sequentially equipped on the circulation pipeline, the flocculation pipe of the calcium hydroxide of filling is equipped on the lye collecting pool, the lye of the output of magnetic ring cleaning equipment enters circulation pipeline and sequentially passes through lye collecting pool, evaporator and filter device.The utility model treats and reuses lye after magnetic ring cleaning, reduces cost.

Description

Technical Field

[0001] This utility model relates to the field of polycrystalline silicon technology, specifically to an alkaline solution recycling system. Background Technology

[0002] In polysilicon production technology, the modified Siemens process is the primary production method. The electrodes and accessories of the polysilicon reduction furnace are the core equipment in polysilicon production, producing the final product, and are also a key factor determining the normal and stable operation of the reduction furnace. The reduction furnace electrodes and accessories are core components in polysilicon production, affecting the stability of the reduction furnace and determining its capacity.

[0003] The insulation between the reduction furnace electrodes and the furnace chassis relies on PTFE sleeves. The silicon nitride magnetic ring also serves to extend the creepage distance between the chassis and the furnace electrode heads during high-voltage breakdown. Because the silicon nitride magnetic ring is located inside the furnace, it is affected by the high temperature and materials, resulting in severe scaling that is difficult to clean, leading to decreased insulation and grounding during high-voltage breakdown and normal production. Therefore, the silicon nitride magnetic ring needs to be removed and replaced periodically. Since silicon nitride magnetic rings are relatively expensive, periodically replacing them, cleaning the surface scale, and recycling them (specific reaction equation: Si + 2NaOH + H₂O = Na₂SiO₃ + 2H₂) can significantly save costs.

[0004] Currently, the magnetic ring cleaning in the reduction section is all done by soaking and cleaning in an alkaline solution tank. During the cleaning process, 1.5 tons of caustic soda flakes need to be added daily. The caustic soda flakes dissolve in water to form an alkaline solution of the appropriate concentration, which is used to soak the magnetic rings and react to remove the silicon on the surface of the magnetic rings. After the reaction, the concentration of the alkaline solution decreases, and it is all sent to the downstream system for acid treatment. The waste alkaline solution needs to be neutralized with acid to generate salts such as Na2SO4, which wastes reagents and increases the operation and maintenance pressure of wastewater treatment facilities, resulting in high costs. Utility Model Content

[0005] The purpose of this invention is to develop an alkaline solution recycling system that can treat and reuse the alkaline solution after cleaning magnetic rings in order to reduce costs.

[0006] This utility model is achieved through the following technical solution:

[0007] An alkali recycling system, comprising:

[0008] Magnetic ring cleaning equipment;

[0009] The circulation pipeline is installed on the magnetic ring cleaning equipment;

[0010] The circulation pipeline is sequentially equipped with an alkaline solution collection tank, an evaporation device, and a filtration device. The alkaline solution collection tank is equipped with a flocculation pipe for adding calcium hydroxide. The alkaline solution output from the magnetic ring cleaning equipment enters the circulation pipeline and passes through the alkaline solution collection tank, the evaporation device, and the filtration device in sequence.

[0011] Optionally, the evaporation device is an MVR evaporator, and the evaporation device is provided with a second steam pipe and a second condenser pipe, and the evaporation device is provided with a heat exchange pipe that communicates with the second steam pipe and the second condenser pipe.

[0012] Optionally, the evaporation device is equipped with a concentration detector, and the second steam pipe is equipped with a regulating valve that cooperates with the concentration detector.

[0013] Optionally, a first transfer pump is provided between the alkali collection tank and the evaporation device.

[0014] Optionally, a collection tank is connected to the evaporation device and the filtration device via a pipeline, and a second delivery pump is provided between the collection tank and the filtration device.

[0015] Optionally, the filtration device is a filter press.

[0016] Optionally, the magnetic ring cleaning device has a box structure with a steam coil at the bottom inside, and a first steam pipe and a first condenser pipe at both ends of the steam coil.

[0017] The beneficial effects of this utility model are:

[0018] This invention enables the recycling of alkali solution, reduces the consumption of caustic soda flakes, lowers costs, reduces wastewater discharge, and reduces the amount of solid waste generated, further reducing costs and environmental damage. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a structural diagram of the present utility model.

[0021] Reference numerals in the attached drawings: 1. Magnetic ring cleaning equipment; 2. First steam pipe; 3. First condenser pipe; 4. Alkali collection tank; 5. Flocculation pipe; 6. First transfer pump; 7. Evaporation device; 8. Concentration detector; 9. Second steam pipe; 10. Regulating valve; 11. Second condenser pipe; 12. Collection tank; 13. Second transfer pump; 14. Filter press. Detailed Implementation

[0022] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0023] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0024] In this invention, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0025] The embodiments of this utility model will now be described in detail with reference to the accompanying drawings.

[0026] like Figure 1 As shown, this utility model discloses an alkali solution recycling system, including a magnetic ring cleaning device 1. The magnetic ring cleaning device 1 has a box structure with a steam coil at the bottom. The steam coil has a first steam pipe 2 and a first condenser pipe 3 at both ends. Steam enters the steam coil through the first steam pipe 2 to heat the alkali solution in the magnetic ring cleaning device 1.

[0027] The magnetic ring cleaning equipment 1 is equipped with a circulation pipeline, on which an alkaline solution collection tank 4, an evaporation device 7, a collection tank 12, and a filter press 14 are sequentially arranged. The low-concentration alkaline solution discharged from the magnetic ring cleaning equipment 1 enters the alkaline solution collection tank 4, and then passes through the evaporation device 7, the collection tank 12, and the filter press 14 in sequence before entering the magnetic ring cleaning equipment 1.

[0028] The alkaline solution collection tank 4 is equipped with a flocculation pipe 5 on its side. The flocculation pipe 5 injects flocculant into the alkaline solution collection tank 4. The flocculant is calcium hydroxide.

[0029] A first transfer pump 6 is provided between the alkali collection tank 4 and the evaporation device 7. The first transfer pump 6 pumps the low-concentration alkali solution in the alkali collection tank 4 to the evaporation device 7.

[0030] Evaporation device 7 is an MVR evaporator. It is equipped with a concentration detector 8 to detect the concentration of NaOH in the solution. Evaporation device 7 has a second steam pipe 9 and a second condenser pipe 11. Heat exchange tubes connected to the second steam pipe 9 and the second condenser pipe 11 are located inside the evaporation device 7. A regulating valve 10, which works in conjunction with the concentration detector 8, is installed on the second steam pipe 9. Based on the NaOH concentration measured by the concentration detector 8, the regulating valve 10 controls the steam flow rate in the second steam pipe 9, thereby controlling the heat source of the heat exchange tubes within the evaporation device 7. When the NaOH concentration is low, the steam flow rate in the second steam pipe 9 is increased, increasing the evaporation rate of the solution by the evaporation device 7 and thus increasing the NaOH concentration. Conversely, when the NaOH concentration is high, the steam flow rate in the second steam pipe 9 is decreased, reducing the evaporation rate of the solution by the evaporation device 7 and thus decreasing the NaOH concentration.

[0031] The high-concentration alkaline solution output from the evaporator 7 enters the collection tank 12. A second transfer pump 13 is provided between the collection tank 12 and the filter press 14. The second transfer pump 13 pumps the high-concentration alkaline solution in the collection tank 12 to the filter press 14. After the alkaline solution is filtered in the filter press 14, it is returned to the magnetic ring cleaning equipment 1 for recycling.

[0032] At room temperature, static immersion of magnetic rings cannot actively remove the strong-adhesion silica scale, especially the microporous structure inside the magnetic ring is not thoroughly cleaned. To avoid this phenomenon, the magnetic ring cleaning equipment 1 heats the alkaline solution through a steam coil to keep its temperature at 80~90℃.

[0033] The low-concentration alkaline solution discharged from the magnetic ring cleaning device 1 enters the alkaline solution collection tank 4, and calcium hydroxide is added through the flocculation pipe 5 for flocculation treatment. The reaction equation is: Na2SiO3+Ca(OH)2=CaSiO3↓+2NaOH. After flocculation treatment, the low-concentration alkaline solution is transported to the evaporation device 7.

[0034] Evaporation is carried out in evaporator 7. The steam feed rate is controlled by regulating valve 10 to control the heat source in evaporator 7, thereby controlling the concentration of alkaline solution. After evaporation, the high-concentration alkaline solution enters the collection tank 12 and is then pumped to the filter press 14 to filter out the solids. Finally, it enters the magnetic ring cleaning equipment 1 for recycling.

[0035] This invention treats and reuses alkali solution, reducing the daily consumption of caustic soda flakes from 1.5 tons to 0.33 tons, a reduction of approximately 78%. Based on 330 days of operation per year, this results in annual savings of approximately 870,000 yuan in reagent costs. Annual wastewater discharge is reduced from 12,000 m³ to 960 m³, a reduction of approximately 92%, and solid waste generation is reduced from 2.8 tons / month to 0.98 tons / month.

[0036] The above embodiments are merely preferred embodiments of this utility model and are not intended to limit the technical solutions of this utility model. Any technical solution that can be implemented based on the above embodiments without creative effort should be considered to fall within the scope of protection of this utility model patent.

Claims

1. An alkali solution recycling system, characterized in that, include: Magnetic ring cleaning equipment; The circulation pipeline is installed on the magnetic ring cleaning equipment; The circulation pipeline is sequentially equipped with an alkali collection tank, an evaporation device, and a filtration device. The alkali collection tank is equipped with a flocculation pipe for adding calcium hydroxide. The alkali solution output from the magnetic ring cleaning equipment enters the circulation pipeline and passes through the alkali collection tank, the evaporation device, and the filtration device in sequence.

2. The alkali reuse system according to claim 1, characterized in that, The evaporation device is an MVR evaporator, which is equipped with a second steam pipe and a second condenser pipe, and has a heat exchange pipe connected to the second steam pipe and the second condenser pipe inside.

3. The alkali reuse system according to claim 2, characterized in that, The evaporation device is equipped with a concentration detector, and the second steam pipe is equipped with a regulating valve that works in conjunction with the concentration detector.

4. The alkali reuse system according to claim 1, characterized in that, A first transfer pump is provided between the alkali collection tank and the evaporation device.

5. The alkali reuse system according to claim 1, characterized in that, A collection tank is connected to the evaporation device and the filtration device by a pipeline, and a second delivery pump is provided between the collection tank and the filtration device.

6. The alkali reuse system according to claim 1, characterized in that, The filtration device is a filter press.

7. The alkali reuse system according to any one of claims 1 to 6, characterized in that, The magnetic ring cleaning equipment has a box structure with a steam coil at the bottom. The steam coil has a first steam pipe and a first condenser pipe at both ends.

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