A device system and method for resourceful treatment of polysilicon slurry

Abstract

The present application relates to a kind of polycrystalline silicon slag slurry resource processing device system and method, the device system includes sequentially connected along material flow direction mixer, preheater, nitrogen heater, silicon powder impurity remover, tail gas filter, heat exchanger and tail gas spraying device;The silicon powder impurity remover is connected with ton bag;The tail gas spraying device is connected with lye storage device;The circulating nitrogen of tail gas spraying device discharge enters nitrogen storage device, and part of circulating nitrogen in the nitrogen storage device is recycled for the mixer, and part is transported into the ton bag.The device system provided by the present application greatly improves the heat exchange efficiency, while the higher purity silicon powder can be recycled and used as silicon source for front-end process, and the hydrolysis neutralization heat can also be recycled to reduce energy consumption cost.

Description

Technical Field

[0001] This invention relates to the field of polysilicon production technology, specifically to a device system and method for the resource-based treatment of polysilicon slag. Background Technology

[0002] Currently, the demand for polysilicon is growing rapidly due to the continuous development of the electronics and information industry. The mainstream polysilicon production process is the modified Siemens process, which involves a wide variety of raw materials and many steps in the entire production process. It also generates a large amount of slurry by-products, which include hydrogen, trichlorosilane, silicon tetrachloride, hydrogen chloride, silicon dioxide, metal chlorides, etc.

[0003] The main causes of slurry byproducts fall into three categories: 1. Side reactions occurring during the cold hydrogenation process of trichlorosilane synthesis, producing a solid slurry containing silicon powder, trichlorosilane, and silicon tetrachloride; 2. Leaks in the entire production system, allowing some water vapor to penetrate into the system and react with trichlorosilane, producing hydrogen chloride and silicon dioxide, which are then mixed into the slurry; 3. In the polycrystalline silicon reduction furnace, incomplete deposition of crystalline silicon after trichlorosilane reduction results in the silicon being discharged from the system at the bottom of the furnace. After filtration, some trichlorosilane and tetrachlorosilane can be recovered from the slurry, but some liquid byproducts remain attached to the surface of the solid silicon powder. Slurry contaminants readily react with water and air, generating large amounts of flammable, explosive, and toxic gases. Therefore, proper storage and necessary measures for harmless treatment are required, and some byproducts should be recycled and reused.

[0004] The main slurry treatment process currently is hydrolysis neutralization, where the slurry is directly introduced into a hydrolysis neutralization tank containing a lime solution. Trichlorosilane, silicon tetrachloride, and aluminum chloride in the slurry first hydrolyze to produce hydrogen chloride, which then undergoes a neutralization reaction with the lime water. The waste gas, waste liquid, and waste residue generated during this process all require further treatment to be rendered harmless. Not only can the cold hydrogenation raw materials such as trichlorosilane, silicon tetrachloride, and silicon powder not be recovered, but the large amount of heat generated during the hydrolysis neutralization reaction cannot be utilized. Furthermore, to fully neutralize the slurry and prevent boiling over, this process requires the addition of excessive amounts of water and lime solution for cooling, resulting in material waste.

[0005] To address the above issues, CN 110834031A proposes using a bubbling device to improve neutralization efficiency and avoid blockage of the neutralization tower, and utilizes the clarified waste liquid after precipitation as a waste gas scrubbing liquid. However, neither silicon powder nor the heat from hydrolysis neutralization is recovered. CN217016565U uses nitrogen as a seal and employs a jacketed heating system to heat the slurry in the reactor to extract silicon raw materials. This method can reduce the silicon content in the solid slag and lower hydrolysis costs, but due to incomplete heating by the heat transfer oil jacket and the low temperature, it is difficult to completely evaporate the silicon and aluminum chloride impurities in the solid slag, requiring treatment in both the recovered gas and the waste slag. Additionally, some existing technologies use nitrogen heating to strip chlorosilanes, which can completely extract silicon tetrachloride and trichlorosilane, but this does not recover silicon powder or the waste heat from the high-temperature nitrogen. Furthermore, the aluminum chloride stripped from the slurry must be considered for its impact on low-temperature scaling in the pipelines. Therefore, there is still considerable room for process optimization.

[0006] Therefore, in view of the shortcomings of the existing technology, there is an urgent need to provide a device system that can effectively recover silicon powder and other by-products and make full use of the neutralization heat for the resource-based treatment of polycrystalline silicon slag slurry. Summary of the Invention

[0007] The purpose of this invention is to provide a device system and method for the resource-based treatment of polycrystalline silicon slag slurry, which significantly improves heat exchange efficiency, extends equipment service life, makes full use of hydrolysis and neutralization heat to reduce energy consumption costs, and improves the resource recovery rate of each component in polycrystalline silicon slag slurry.

[0008] To achieve this objective, the present invention employs the following technical solution:

[0009] In a first aspect, the present invention provides a device system for the resource utilization treatment of polycrystalline silicon slag slurry. The device system includes a mixer, a preheater, a nitrogen heater, a silicon powder impurity remover, a tail gas filter, a heat exchanger, and a tail gas spraying device connected sequentially along the material flow direction. The silicon powder impurity remover is connected to a ton bag. The tail gas spraying device is connected to an alkaline solution storage device. The circulating nitrogen discharged from the tail gas spraying device enters the nitrogen storage device, and part of the circulating nitrogen in the nitrogen storage device is reused in the mixer and part is transported to the ton bag.

[0010] The device system for resource-based treatment of polycrystalline silicon slag slurry provided by this invention utilizes a preheater and a nitrogen heater to generate high-temperature nitrogen gas. The polycrystalline silicon slag slurry is then fluidized or bubbled in a silicon powder impurity remover. During this process, the polycrystalline silicon slag slurry directly contacts the high-temperature nitrogen gas, enhancing efficient heat exchange and significantly improving heat exchange efficiency. This reduces the processing time for each batch of slag slurry, representing a significant improvement over existing jacketed indirect heat exchange methods. Furthermore, a tail gas filter is used to vaporize and remove trichlorosilane, silicon tetrachloride, and aluminum chloride adhering to the surface of silicon powder in the polycrystalline silicon slag slurry, followed by separate treatment, further improving efficiency. The purity of recovered silicon powder is improved, reducing the footprint and alkali load of the tail gas scrubbing device. The recovered silicon powder is returned to the front-end process as a silicon source for reuse, saving a large amount of raw materials and eliminating the cost of treating it as waste residue. In addition, nitrogen in this invention has multiple functions: fluidizing carrier gas in the silicon powder impurity remover; heating source for the slurry in the silicon powder impurity remover; protective gas for the hydrolysis and neutralization reaction in the tail gas scrubbing device; protective gas for silicon powder during ton bag transportation; and continuous circulation of heat and momentum by nitrogen significantly improves the overall process reaction rate and significantly reduces energy and material consumption.

[0011] Preferably, the mixer is provided with a nitrogen inlet.

[0012] Preferably, the nitrogen heater is connected to the bottom of the silicon powder impurity remover.

[0013] Preferably, the silicon powder impurity remover is provided with a polycrystalline silicon slag slurry inlet.

[0014] Preferably, the exhaust gas filter is provided with a filter powder outlet, and the silicon powder discharged from the filter powder outlet is returned to the silicon powder impurity remover.

[0015] Preferably, the exhaust gas spraying device is provided with a liquid discharge port and a slag discharge port.

[0016] Preferably, the exhaust gas spraying device is provided with a heating jacket, the inlet of the heating jacket is connected to the shell-side outlet of the preheater, the outlet of the heating jacket is connected to the shell-side inlet of the heat exchanger, and the shell-side outlet of the heat exchanger is connected to the shell-side inlet of the preheater.

[0017] This invention employs a circulating water waste heat recovery process. Circulating water flows in from the inlet of the heating jacket of the exhaust gas spray device and then flows out from the outlet. It is then introduced into the shell side of a heat exchanger to absorb heat from the mixed gas, transforming it into circulating steam. This circulating steam is then introduced into the shell side of a preheater to exchange heat with the mixed nitrogen gas. After heat exchange, it condenses back into circulating water, which then re-enters the heating jacket of the exhaust gas spray device for further circulation. This circulating water waste heat recovery process can significantly reduce the energy consumption cost of the nitrogen heater.

[0018] Preferably, the exhaust gas spraying device includes an exhaust gas spraying neutralization tower.

[0019] Preferably, the alkali storage device includes an alkali storage tank.

[0020] Preferably, the nitrogen storage device includes a nitrogen storage tank.

[0021] In a second aspect, the present invention provides a method for the resource-based treatment of polycrystalline silicon slag slurry, the method being carried out using the apparatus system described in the first aspect, the method comprising the following steps:

[0022] (1) Nitrogen gas is mixed with circulating nitrogen gas and then subjected to preheating and heating treatments in sequence to obtain hot nitrogen gas;

[0023] (2) The hot nitrogen gas obtained in step (1) is introduced into the polycrystalline silicon slag slurry to obtain a mixed gas of silicon powder, trichlorosilane, silicon tetrachloride and aluminum trichloride; circulating nitrogen gas is introduced into the obtained silicon powder to obtain silicon powder by-product;

[0024] (3) The mixed gas obtained in step (2) is sequentially filtered, heat exchanged and sprayed neutralized to obtain waste liquid and waste residue; the circulating nitrogen gas discharged after the spraying neutralization is recycled to the mixture in step (1) and the silicon powder in step (2).

[0025] The method for resource-based treatment of polycrystalline silicon slag slurry provided by this invention involves heating nitrogen gas and directly contacting it with the polycrystalline silicon slag slurry to fluidize or bubble it, which significantly improves the heat exchange efficiency. At the same time, the high temperature of nitrogen gas is used to vaporize and remove trichlorosilane, silicon tetrachloride, and aluminum chloride adhering to the surface of silicon powder in the polycrystalline silicon slag slurry. These substances are then processed separately, which greatly improves the purity of the recovered silicon powder and fully extracts and separates silicon tetrachloride, trichlorosilane, and aluminum trichloride, thus achieving the goal of resource-based treatment and recycling of polycrystalline silicon slag slurry.

[0026] Preferably, the temperature of the heat treatment in step (1) is 300-500℃, for example, it can be 300℃, 350℃, 400℃, 450℃ or 500℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] Limiting the temperature of the heating treatment to a reasonable range allows nitrogen to play multiple roles after heating, such as a heat source, protective gas, or carrier gas. If the temperature is too high or too low, it will have an adverse effect on the process of resource utilization of polycrystalline silicon slag slurry.

[0028] Preferably, the polycrystalline silicon slurry in step (2) is in a bubbling or fluidized state after being purged with hot nitrogen.

[0029] Preferably, the silicon powder with a particle size ≤100μm obtained after the filtration process in step (3) is returned to the polycrystalline silicon slag slurry in step (2).

[0030] The particle size of the silicon powder is ≤100μm, for example, it can be 100μm, 90μm, 80μm, 70μm or 60μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] Preferably, the heat exchange treatment in step (3) is carried out in a heat exchanger, wherein the tube-side outlet temperature of the heat exchanger is 200-260°C and the shell-side inlet temperature is 60-80°C.

[0032] The tube-side outlet temperature of the heat exchanger is 200-260℃, for example, it can be 200℃, 210℃, 220℃, 240℃ or 260℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0033] In this invention, the temperature of the mixed gas before entering the exhaust gas spraying device is controlled at 200-260℃, which ensures that aluminum chloride will not adhere and form scale in the pipes and heat exchangers, thereby ensuring the long-term efficient operation of the pipes and heat exchangers and extending the equipment life.

[0034] The shell-side inlet temperature of the heat exchanger is 60-80℃, for example, it can be 60℃, 65℃, 70℃, 75℃ or 80℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] Preferably, the neutralizing agent used in the spray neutralization treatment in step (3) includes sodium hydroxide solution and / or lime water solution.

[0036] In the spray neutralization process, trichlorosilane, silicon tetrachloride, and aluminum trichloride in the mixed gas all undergo hydrolysis and neutralization reactions under the action of the neutralizing reagent, generating salts and releasing a large amount of heat. The equations are as follows:

[0037] SiHCl3 + 3H2O = Si(OH)4 + 3HCl

[0038] SiCl4 + 4H2O = Si(OH)4 + 4HCl

[0039] AlCl3 + 3H2O = Al(OH)3 + 3HCl

[0040] AlCl3 + 3H2O = Al(OH)3 + 3HCl

[0041] HCl + MOH - =MCl + H2O

[0042] When using the aforementioned device system for the resource recovery of polycrystalline silicon slag slurry:

[0043] Nitrogen gas is mixed with nitrogen gas discharged from the nitrogen storage device in a mixer, and then enters the tube side of the preheater. After preheating in the preheater, it is introduced into the nitrogen heater and heated to 300-500°C to obtain hot nitrogen gas, which is then introduced into the silicon powder impurity remover. At the same time, polycrystalline silicon slurry is also added to the silicon powder impurity remover. Under the heating of hot nitrogen gas, trichlorosilane, silicon tetrachloride, and aluminum trichloride in the polycrystalline silicon slurry evaporate to form a mixed gas that enters the tail gas filter. The silicon powder after impurity removal from the polycrystalline silicon slurry enters the ton bag, and circulating nitrogen gas from the nitrogen storage device is introduced into the ton bag to form silicon powder by-product.

[0044] The mixed gas entering the tail gas filter filters out silicon powder with a particle size ≤100μm, which is discharged from the filter powder outlet and then returned to the silicon powder impurity remover for further reaction. The mixed gas is then introduced into a heat exchanger for heat exchange treatment, with the tube-side outlet temperature of the heat exchanger being 200-260℃ and the shell-side inlet temperature being 60-80℃. The gas is then introduced into a tail gas spray device for spray neutralization treatment. A neutralizing agent is added to the tail gas spray device from an alkali storage device. After the reaction, waste liquid and waste residue are obtained and discharged from the system through the liquid outlet and slag outlet of the tail gas spray device, respectively. The circulating nitrogen discharged from the tail gas spray device enters a nitrogen storage device. Part of the circulating nitrogen in the nitrogen storage device is reused in the mixer, and part is transported to the ton bag as a protective gas for silicon powder removal from the system.

[0045] The device system adopts a circulating water waste heat recovery process. Circulating water flows in from the inlet of the heating jacket of the exhaust gas spray device and flows out from the outlet of the heating jacket of the exhaust gas spray device. Then it is introduced into the shell side of the heat exchanger to absorb the heat of the mixed gas and become circulating steam. The circulating steam is then introduced into the shell side of the preheater to exchange heat with the mixed nitrogen. After heat exchange, it condenses into circulating water and then enters the heating jacket of the exhaust gas spray device for circulation.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] (1) The device system for resource recovery treatment of polycrystalline silicon slag slurry provided by the present invention utilizes a preheater and a nitrogen heater to form high-temperature nitrogen gas, and then fluidizes or bubblees the polycrystalline silicon slag slurry in a silicon powder impurity remover. During the process, the polycrystalline silicon slag slurry is in direct contact with the high-temperature nitrogen gas, which greatly improves the heat exchange efficiency and reduces the processing time of each batch of slag slurry. This is a significant improvement over the existing jacketed indirect heat exchange method. The tail gas filter is used to gasify and remove the trichlorosilane, silicon tetrachloride and aluminum chloride adhering to the surface of silicon powder in the polycrystalline silicon slag slurry, and then process them separately, which greatly improves the purity of the recovered silicon powder, reduces the footprint and alkali load of the tail gas spraying device, and the obtained silicon powder is returned to the front-end process for reuse as a silicon source, which saves a lot of production raw materials and eliminates the cost of treating it as waste residue.

[0048] (2) In this invention, the temperature of the mixed gas before entering the tail gas spraying device is controlled within a reasonable range, which can ensure that aluminum trichloride will not adhere to scale in the pipes and heat exchangers, thereby ensuring the long-term efficient operation of the pipes and heat exchangers and extending the equipment life.

[0049] (3) The circulating water waste heat recovery process adopted in this invention, after recovering the hydrolysis neutralization heat of trichlorosilane, silicon tetrachloride and aluminum trichloride, the circulating water is returned to the front end as a nitrogen preheating heat source, which can significantly reduce the energy consumption of the nitrogen heater and reduce energy consumption costs.

[0050] (4) Nitrogen in this invention has multiple functions: as a fluidizing carrier gas for silicon powder impurity remover; as a heating source for slurry in silicon powder impurity remover; as a protective gas for hydrolysis and neutralization reaction in tail gas spray device; as a protective gas for silicon powder in ton bag transportation; nitrogen continuously circulates heat and momentum, which significantly improves the reaction rate of the overall process and significantly reduces energy and material consumption. Attached Figure Description

[0051] Figure 1 This is a schematic diagram of the structure of the device system for the resource utilization treatment of polycrystalline silicon slag slurry provided in Embodiment 1 of the present invention;

[0052] The components are: 1. Mixer; 2. Preheater; 3. Nitrogen heater; 4. Silicon powder remover; 5. Tail gas filter; 6. Heat exchanger; 7. Tail gas spray neutralization tower; 8. Nitrogen inlet; 9. Polysilicon slag slurry inlet; 10. Ton bag; 11. Drain outlet; 12. Slag outlet; 13. Alkali storage tank; 14. Nitrogen storage tank. Detailed Implementation

[0053] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0054] Example 1

[0055] This embodiment provides a device system for the resource-based treatment of polycrystalline silicon slag slurry, such as... Figure 1 As shown, the device system includes a mixer 1, a preheater 2, a nitrogen heater 3, a silicon powder impurity remover 4, a tail gas filter 5, a heat exchanger 6, and a tail gas spray neutralization tower 7, which are connected in sequence along the material flow direction.

[0056] The mixer 1 is provided with a nitrogen inlet 8; the nitrogen heater 3 is connected to the bottom of the silicon powder remover 4; the silicon powder remover 4 is provided with a polycrystalline silicon slag slurry inlet 9; the silicon powder remover 4 is connected to a ton bag 10; the tail gas filter 5 is provided with a filter powder outlet, and the silicon powder discharged from the filter powder outlet is returned to the silicon powder remover 4.

[0057] The tail gas spray neutralization tower 7 is provided with a liquid discharge port 11 and a slag discharge port 12; the tail gas spray neutralization tower 7 is connected to an alkaline storage tank 13; the circulating nitrogen discharged from the tail gas spray neutralization tower 7 enters a nitrogen storage tank 14, part of the circulating nitrogen in the nitrogen storage tank 14 is reused in the mixer 1, and part is transported to the ton bag 10; the tail gas spray neutralization tower 7 is provided with a heating jacket, the inlet of the heating jacket is connected to the shell-side outlet of the preheater 2, the outlet of the heating jacket is connected to the shell-side inlet of the heat exchanger 6, and the shell-side outlet of the heat exchanger 6 is connected to the shell-side inlet of the preheater 2.

[0058] The method for resource recovery of polycrystalline silicon slag slurry using the aforementioned device system includes the following steps:

[0059] (1) Nitrogen gas is mixed with circulating nitrogen gas and then subjected to preheating treatment and heating treatment at 300-500℃ to obtain hot nitrogen gas.

[0060] (2) The hot nitrogen gas obtained in step (1) is introduced into the polycrystalline silicon slag slurry. The polycrystalline silicon slag slurry is in a bubbling or fluidized state after being purged by hot nitrogen gas to obtain a mixed gas of silicon powder, trichlorosilane, silicon tetrachloride and aluminum trichloride. Circulating nitrogen gas is introduced into the obtained silicon powder to obtain silicon powder by-product.

[0061] (3) The mixed gas obtained in step (2) is sequentially filtered, heat exchanged, and neutralized by spraying with sodium hydroxide solution to obtain waste liquid and waste residue; the silicon powder with a particle size ≤100μm obtained after the filtration treatment is returned to the polycrystalline silicon slag slurry in step (2); the heat exchange treatment is carried out in heat exchanger 6, the tube side outlet temperature of heat exchanger 6 is 200-260℃, and the shell side inlet temperature is 60-80℃; the circulating nitrogen gas discharged after the spraying neutralization treatment is reused in the mixture in step (1) and the silicon powder in step (2).

[0062] When using the aforementioned device system for the resource recovery of polycrystalline silicon slag slurry:

[0063] (1) Nitrogen gas and nitrogen gas discharged from nitrogen storage tank 14 are mixed in mixer 1, and then enter the tube side of preheater 2. After being preheated by preheater 2, it is introduced into nitrogen heater 3 and then heated to 300-500℃ by nitrogen heater 3 to obtain hot nitrogen gas, which is then introduced into silicon powder impurity remover 4. At the same time, polycrystalline silicon slag is also added into silicon powder impurity remover 4. Under the heating of hot nitrogen gas, trichlorosilane, silicon tetrachloride and aluminum trichloride in the polycrystalline silicon slag evaporate to form a mixed gas that enters tail gas filter 5. The silicon powder after the polycrystalline silicon slag is impurity removed enters ton bag 10. The circulating nitrogen gas in nitrogen storage tank 14 is introduced into ton bag 10 to form silicon powder by-product.

[0064] (2) The mixed gas entering the tail gas filter 5 is filtered to remove silicon powder with a particle size ≤100μm, which is discharged from the filter powder outlet and then returned to the silicon powder impurity remover 4 for further reaction. The mixed gas is introduced into the heat exchanger 6 for heat exchange treatment. The tube side outlet temperature of the heat exchanger 6 is 200-260℃, and the shell side inlet temperature is 60-80℃. Then it is introduced into the tail gas spray neutralization tower 7 for spray neutralization treatment. The neutralizing agent is added to the tail gas spray neutralization tower 7 from the alkali storage tank 13. After the reaction, waste liquid and waste residue are obtained and discharged from the device system through the liquid outlet 11 and the residue outlet 12 of the tail gas spray neutralization tower 7, respectively. The circulating nitrogen discharged from the tail gas spray neutralization tower 7 enters the nitrogen storage tank 14. Part of the circulating nitrogen in the nitrogen storage tank 14 is reused in the mixer 1, and part is transported to the ton bag 10 as silicon powder protective gas to be transported out of the device system.

[0065] (3) The device system adopts a circulating water waste heat recovery process. Circulating water flows in from the inlet of the heating jacket of the tail gas spray neutralization tower 7, and then flows out from the outlet of the heating jacket of the tail gas spray neutralization tower 7. Then it is introduced into the shell side of the heat exchanger 6 to absorb the heat of the mixed gas and become circulating steam. The circulating steam is then introduced into the shell side of the preheater 2 to exchange heat with the mixed nitrogen. After heat exchange, it is condensed into circulating water and then enters the heating jacket of the tail gas spray neutralization tower 7 for circulation.

[0066] The device system provided in this embodiment is used for the resource utilization of polycrystalline silicon slag slurry. The produced silicon powder can be directly recycled into the front-end cold hydrogenation system with a recycling rate of up to 95%. The amount of waste residue is reduced by 30%, a large amount of heat from hydrolysis and neutralization is recovered, and the overall process saves 15% of energy, which has significant economic benefits.

[0067] Example 2

[0068] This embodiment provides a device system for the resource utilization treatment of polycrystalline silicon slag slurry. The method for resource utilization treatment of polycrystalline silicon slag slurry using the device system differs from that in Embodiment 1 in that the temperature of the heating treatment in step (1) is adjusted to 280°C, while the rest is the same as in Embodiment 1.

[0069] The heating temperature was too low to completely vaporize the trichlorosilane, silicon tetrachloride, and aluminum chloride adhering to the surface of the silicon powder in the slurry, thus requiring additional treatment in both the recovered gas and the waste residue. Using the device system provided in this embodiment for the resource recovery of polycrystalline silicon slurry, the produced silicon powder needs to be processed before being reused in the front-end cold hydrogenation system, achieving a reuse rate of 65%. Waste residue emissions are reduced by only 5%, and a large amount of heat from hydrolysis and neutralization is recovered. However, due to the additional processing stage, energy consumption is also required, resulting in an overall energy saving of only 5%.

[0070] Example 3

[0071] This embodiment provides a device system for the resource utilization treatment of polycrystalline silicon slag slurry. The method for resource utilization treatment of polycrystalline silicon slag slurry using the device system differs from that in Embodiment 1 in that the temperature of the heating treatment in step (1) is adjusted to 520°C, while the rest is the same as in Embodiment 1.

[0072] The excessively high temperature of the heating process does not significantly increase the proportion of recovered silicon powder, but it does lead to an increase in overall energy consumption and a decrease in energy efficiency. Using the device system provided in this embodiment for the resource recovery of polycrystalline silicon slag slurry, the produced silicon powder can be reused in the front-end cold hydrogenation system, with a reuse rate of 96%, a 32% reduction in waste discharge, and a large amount of heat recovery from hydrolysis and neutralization, resulting in an overall energy saving of 8%.

[0073] Example 4

[0074] This embodiment provides a device system for the resource utilization treatment of polycrystalline silicon slag slurry. The method for resource utilization treatment of polycrystalline silicon slag slurry using the device system differs from that in Embodiment 1 in that the tube outlet temperature of the heat exchanger 6 in step (3) is adjusted to 190°C, while the rest is the same as in Embodiment 1.

[0075] If the outlet temperature of the heat exchanger tubes is too low, aluminum trichloride will adhere and form scale inside the pipes and heat exchanger, and will also trap silicon powder that adheres to the inner wall of the heat exchanger, thus failing to ensure the long-term efficient operation of the pipes and heat exchanger. Using the device system provided in this embodiment for the resource recovery treatment of polycrystalline silicon slag slurry, the produced silicon powder can be directly recycled into the front-end cold hydrogenation system, with a recycling rate of 80%, a 20% reduction in waste discharge, and the heat from hydrolysis neutralization can be recovered, resulting in an overall energy saving of 20%.

[0076] Example 5

[0077] This embodiment provides a device system for the resource utilization treatment of polycrystalline silicon slag slurry. The method for resource utilization treatment of polycrystalline silicon slag slurry using the device system differs from that in Embodiment 1 in that the tube outlet temperature of the heat exchanger 6 in step (3) is adjusted to 270°C, while the rest is the same as in Embodiment 1.

[0078] The excessively high outlet temperature of the heat exchanger tubes leads to less gas heat recovery, resulting in a significant increase in downstream cooling water volume and energy consumption. Using the device system provided in this embodiment for polycrystalline silicon slag slurry resource recovery, the produced silicon powder can be directly reused in the front-end cold hydrogenation system, achieving a 95% reuse rate. Waste emissions are reduced by 30%, and the heat from hydrolysis neutralization can be recovered, resulting in an overall energy saving of 10%.

[0079] Example 6

[0080] This embodiment provides a device system for the resource utilization treatment of polycrystalline silicon slag slurry. The method for resource utilization treatment of polycrystalline silicon slag slurry using the device system differs from that in Embodiment 1 in that the device system does not employ a circulating water waste heat recovery process; otherwise, it is the same as in Embodiment 1.

[0081] Using the device system provided in this embodiment for the resource recovery of polycrystalline silicon slag slurry, the produced silicon powder can be directly recycled to the front-end cold hydrogenation system, with a recycling rate of 95% and a 30% reduction in waste discharge. However, since the circulating water waste heat recovery process is not adopted, the heat of hydrolysis and neutralization cannot be recovered, resulting in high energy consumption.

[0082] Comparative Example 1

[0083] This comparative example provides a device system for the resource utilization treatment of polycrystalline silicon slag slurry. The difference from Example 1 is that the preheater 2 is not provided, but all other aspects are the same as in Example 1.

[0084] Using the device system provided in this comparative example for the resource recovery treatment of polycrystalline silicon slag slurry, the produced silicon powder can be directly recycled into the front-end cold hydrogenation system, with a recycling rate of 90% and a 25% reduction in waste slag emissions. However, due to the lack of a preheater, the energy consumption of the heater is high, and the goal of energy saving cannot be achieved.

[0085] Comparative Example 2

[0086] This comparative example provides a device system for the resource utilization treatment of polycrystalline silicon slag slurry. The difference from Example 1 is that the exhaust gas filter 5 is not installed, but all other aspects are the same as in Example 1.

[0087] The device system provided in this comparative example is used for the resource recovery of polycrystalline silicon slag slurry. The produced silicon powder can be directly recycled into the front-end cold hydrogenation system with a recycling rate of 85%. However, since no tail gas filter is installed, the waste residue needs to be post-processed, which is complex and costly, and is not conducive to the realization of resource recovery.

[0088] In summary, the device system for the resource recovery treatment of polycrystalline silicon slag slurry provided by this invention utilizes a preheater and a nitrogen heater to generate high-temperature nitrogen gas. The polycrystalline silicon slag slurry is then fluidized or bubbled in a silicon powder impurity remover. During this process, the polycrystalline silicon slag slurry directly contacts the high-temperature nitrogen gas, significantly improving heat exchange efficiency and reducing the processing time for each batch of slag slurry. This represents a substantial improvement over existing jacketed indirect heat exchange methods. Furthermore, the tail gas filter removes trichlorosilane, silicon tetrachloride, and aluminum chloride adhering to the surface of the silicon powder in the polycrystalline silicon slag slurry through gasification and separate processing, significantly improving the purity of the recovered silicon powder. This reduces the footprint and alkali load of the tail gas spraying device. The resulting silicon powder is returned to the upstream process as a silicon source for reuse, saving a significant amount of raw materials and eliminating the costs associated with treating it as waste slag.

[0089] In this invention, the temperature of the mixed gas before entering the exhaust gas spraying device is controlled within a reasonable range, which can ensure that aluminum trichloride will not adhere and form scale in the pipes and heat exchangers, thereby ensuring the long-term efficient operation of the pipes and heat exchangers and extending the equipment life.

[0090] The circulating water waste heat recovery process adopted in this invention recovers the hydrolysis neutralization heat of trichlorosilane, silicon tetrachloride and aluminum trichloride, and then returns the circulating water to the front end as a nitrogen preheating heat source, which can significantly reduce the energy consumption of the nitrogen heater and reduce energy costs.

[0091] Nitrogen gas in this invention has multiple functions: as a fluidizing carrier gas in the silicon powder impurity remover; as a heating source for the slurry in the silicon powder impurity remover; as a protective gas for the hydrolysis and neutralization reaction in the tail gas spray device; and as a protective gas for silicon powder during ton bag transportation. Nitrogen gas continuously circulates and transports heat and momentum, which significantly improves the overall process reaction rate and significantly reduces energy and material consumption.

[0092] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A device system for the resource-based treatment of polycrystalline silicon slag slurry, characterized in that, The device system includes a mixer, a preheater, a nitrogen heater, a silicon powder impurity remover, a tail gas filter, a heat exchanger, and a tail gas spraying device connected sequentially along the material flow direction; the silicon powder impurity remover is connected to a ton bag; the tail gas spraying device is connected to an alkaline solution storage device; the circulating nitrogen discharged from the tail gas spraying device enters the nitrogen storage device, and part of the circulating nitrogen in the nitrogen storage device is reused in the mixer, and part is transported to the ton bag; The exhaust gas spraying device is equipped with a heating jacket. The inlet of the heating jacket is connected to the shell-side outlet of the preheater, the outlet of the heating jacket is connected to the shell-side inlet of the heat exchanger, and the shell-side outlet of the heat exchanger is connected to the shell-side inlet of the preheater.

2. The device system according to claim 1, characterized in that, The mixer is equipped with a nitrogen inlet.

3. The device system according to claim 1 or 2, characterized in that, The nitrogen heater is connected to the bottom of the silicon powder remover.

4. The device system according to claim 1, characterized in that, The silicon powder impurity remover is equipped with a polycrystalline silicon slag slurry inlet.

5. The device system according to claim 1, characterized in that, The exhaust gas filter is provided with a filter powder outlet, and the silicon powder discharged from the filter powder outlet is returned to the silicon powder impurity remover.

6. The device system according to claim 1, characterized in that, The exhaust gas spraying device is equipped with a liquid discharge port and a slag discharge port.

7. The device system according to claim 1, characterized in that, The exhaust gas spraying device includes an exhaust gas spraying neutralization tower.

8. The device system according to claim 1, characterized in that, The alkali storage device includes an alkali storage tank.

9. The device system according to claim 1, characterized in that, The nitrogen storage device includes a nitrogen storage tank.

10. A method for the resource-based treatment of polycrystalline silicon slag slurry, characterized in that, The method is performed using the apparatus system according to any one of claims 1-9, and the method includes the following steps: (1) Nitrogen gas is mixed with circulating nitrogen gas and then subjected to preheating and heating treatments in sequence to obtain hot nitrogen gas; (2) The hot nitrogen gas obtained in step (1) is passed into the polycrystalline silicon slag slurry to obtain a mixed gas of silicon powder, trichlorosilane, silicon tetrachloride and aluminum trichloride; circulating nitrogen gas is passed into the obtained silicon powder to obtain silicon powder by-product. (3) The mixed gas obtained in step (2) is sequentially filtered, heat exchanged and sprayed to neutralize, resulting in waste liquid and waste residue; the circulating nitrogen discharged after the spraying and neutralization is recycled to the mixture in step (1) and the silicon powder in step (2).

11. The method according to claim 10, characterized in that, The temperature of the heat treatment in step (1) is 300-500℃.

12. The method according to claim 10 or 11, characterized in that, The polycrystalline silicon slurry described in step (2) is in a bubbling or fluidized state after being purged with hot nitrogen.

13. The method according to claim 10, characterized in that, The silicon powder with a particle size ≤100μm obtained after filtration in step (3) is returned to the polycrystalline silicon slag slurry in step (2).

14. The method according to claim 10, characterized in that, The heat exchange process described in step (3) is carried out in a heat exchanger, wherein the tube-side outlet temperature of the heat exchanger is 200-260℃ and the shell-side inlet temperature is 60-80℃.

15. The method according to claim 10, characterized in that, The neutralizing agents used in the spray neutralization treatment in step (3) include sodium hydroxide solution and / or lime water solution.

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