Polycrystalline silicon rectification process component separation tower control system
By using cascade control and loop control, the component separation tower of the polycrystalline silicon distillation process is automated, which solves the problems of inaccurate operation, frequent misoperations, high labor load and heat source fluctuation in the existing technology, and improves system stability and product quality.
Patent Information
- Application Number
- CN202520125231.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-20
- Publication Date
- 2026-01-13
- Estimated Expiration
- 2035-01-20
AI Technical Summary
The existing control system for the component separation tower in the polycrystalline silicon distillation process has a low degree of automation, resulting in inaccurate operation, a high probability of misoperation, a heavy workload for employees, poor system integrity, and external heat source fluctuations affecting temperature control stability, thus impacting product quality and system stability.
By employing cascade control and loop control methods, and through real-time monitoring by temperature and pressure sensors, the reflux flow rate, heating medium, and steam quantity are automatically adjusted to achieve stable control of various parameters of the component separation tower, eliminating the influence of operational differences and external heat source fluctuations.
It improved operational accuracy, reduced the probability of misoperation, enhanced system stability and product quality, reduced employee workload, and ensured the stability of material and heat balance.
Smart Images
Figure CN223788091U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of polycrystalline silicon distillation process control technology, and in particular to a control system for a component separation tower in a polycrystalline silicon distillation process. Background Technology
[0002] Currently, distillation is a crucial process in polysilicon production. In distillation, the synthesis liquid from the trichlorosilane synthesis step is separated into chlorosilane liquid and sent to an upgrading component separation tower for further separation. Trichlorosilane is then sent to the raw material chlorosilane tank. The chlorosilane liquid generated in the silicon tetrachloride cold hydrogenation step, after dry dust removal and three-stage condensation, is sent to the raw material chlorosilane tank in the chlorosilane storage step. The aforementioned trichlorosilane synthesis chlorosilane liquid and cold hydrogenation chlorosilane liquid contain silicon tetrachloride, dichlorosilane, and trichlorosilane. Polysilicon production requires pure trichlorosilane, and pure silicon tetrachloride is needed for cold hydrogenation. Dichlorosilane is also produced as a byproduct in the cold hydrogenation and reduction steps, requiring removal during production before being sent to a disproportionation process for consumption.
[0003] I. Synthetic distillation process flow:
[0004] 1. Silicon tetrachloride component separation tower (stage 1 tower)
[0005] The synthesized material first enters the silicon tetrachloride separation tower. After separation in the tower, silicon tetrachloride is collected from the bottom of the tower. The gas at the top of the tower is condensed by the circulating water condenser and becomes liquid chlorosilane, which enters the high-level reflux tank and is then transported by the reflux pump. Part of it is used as top reflux and part is collected as product. The collected components are trichlorosilane and dichlorosilane.
[0006] 2. Dichlorosilane component separation tower (2-stage tower)
[0007] The top product from the silicon tetrachloride separation tower enters the dichlorosilane separation tower. After separation, the top gas is condensed in a circulating water condenser into liquid chlorosilane, which enters a high-level reflux tank. It is then pumped back, with a portion used as top reflux and the remaining dichlorosilane as top product. The bottom product is trichlorosilane, which is pressurized and sent to a high-level purification tower for further purification.
[0008] 3. Remove the first tower (level 3 tower)
[0009] The product from the bottom of the dichlorosilane separation tower enters the high-boiling point removal tower for further purification. After separation, the top product is trichlorosilane, which is sent to the low-boiling point removal tower for further purification. The bottom product is trichlorosilane containing high-boiling-point substances, which is returned to the silicon tetrachloride separation tower for recycling.
[0010] 4. Remove one tower (level 4 tower)
[0011] The top product from the first high-boiling point removal tower enters the first low-boiling point removal tower for low-boiling point removal. After separation, the bottom product is low-boiling point-removed trichlorosilane, which is sent to the second high-boiling point removal tower for further purification. The top product is trichlorosilane containing low-boiling-point compounds, which is returned to the silicon tetrachloride separation tower for recycling.
[0012] 5. Remove the second tower (level 5 tower)
[0013] The bottom product from the first de-lowering column enters the second de-highering column for further de-highering treatment. After separation, the top product is de-highering trichlorosilane, which is sent to the reduction section as the final product of synthetic distillation. The bottom product is trichlorosilane containing high-boiling-point substances, which is returned to the silicon tetrachloride separation column for recycling.
[0014] 6. Silicon tetrachloride removal tower (6-stage tower)
[0015] The bottom product of the silicon tetrachloride separation tower is mainly silicon tetrachloride, including some high-boiling-point substances. This portion of silicon tetrachloride needs to be de-high-boiling-point substances before it can be recycled as feedstock for the cold hydrogenation unit. The silicon tetrachloride leaving the separation tower enters the silicon tetrachloride de-high-boiling-point tower for further treatment. After separation, the top product is the de-high-boiling-point silicon tetrachloride, which is sent to the cold hydrogenation unit. The bottom product is silicon tetrachloride rich in high-boiling-point substances, which is sent to the high and low boiling-point substance recovery unit. The remaining residue after recovery is sent to the hydrolysis and spray treatment unit.
[0016] II. Temperature and Pressure Control
[0017] In distillation processes, temperature and pressure control are crucial, directly impacting product quality and yield. Distillation is a physicochemical process that separates substances based on their boiling point differences; by controlling the pressure and temperature within the distillation column, effective separation of different components can be achieved.
[0018] 1. Temperature Control: Temperature control is crucial for product purity and yield during distillation. A steam heating system is needed to precisely control the temperature at the top, bottom, and other sections of the column to ensure that chlorosilanes are separated at suitable temperatures.
[0019] 2. Pressure control: The stability of system pressure has a direct impact on the gas-liquid balance of the distillation process. It is necessary to use a vacuum system or pressure regulation system to ensure the stability of the pressure inside the column and avoid the impact of pressure fluctuations on the distillation effect.
[0020] III. Material Balance and Impurity Control
[0021] 1. Material balance: Ensure the balance of materials during the distillation process. Through precise metering and monitoring of material flow rate, adjust operating parameters such as feed rate, reflux rate, top recovery rate, and bottom recovery rate in a timely manner to ensure the stable operation of the distillation process.
[0022] 2. Impurity Removal: Chlorosilanes often contain impurities such as boron and phosphorus, which severely affect the performance of polycrystalline silicon products. Multi-stage distillation is necessary to effectively remove these impurities and improve product purity. In this process, the reflux rate of the component separation tower plays a crucial role in impurity removal.
[0023] Currently, the control system for the component separation tower in the distillation process is still manually operated by the main controller. The system has a low degree of automation and requires frequent operation, resulting in a heavy workload for employees who need to spend a lot of time on operation, leaving less time for system monitoring. Furthermore, the operation of different main controllers varies greatly, which is not conducive to the stable operation of the system. The main problems are as follows:
[0024] 1. Insufficient operational precision. For example, different master controllers may have varying degrees of control over temperature and reflux flow rate in the distillation process component separation column system. This can lead to significant fluctuations in reflux flow rate. Excessive reflux flow rate results in a lower temperature at the top of the second-stage column, leading to decreased product quality. Conversely, insufficient reflux flow rate results in a higher temperature, increasing the disproportionation load and severely impacting the stability of the disproportionation product quality. The stability of the distillation process component separation column system is highly dependent on the operating skills and experience of the master controllers. The inconsistencies in the actions of different master controllers result in operational discrepancies, causing process fluctuations that affect system stability and product quality.
[0025] 2. Higher probability of misoperation. For locations with frequent or complex operation controls, employees are prone to misoperation. For example, in the automatic temperature control circuit of the steam regulating valve in the first-stage synthetic distillation column, the main controller needs to input the set temperature once when adjusting the steam flow. If the main controller carelessly inputs an excessively high temperature value during this process, it may cause the component separation column to overheat, leading to overpressure in the first-stage column, posing a significant risk.
[0026] 3. Heavy workload for employees. The main control unit requires frequent manual operation, resulting in a heavy workload for employees. They need to spend a lot of time on repetitive operations, making it impossible to devote more valuable time to more valuable work, such as skills training and risk analysis.
[0027] 4. Poor integrity of manual operation. For example, when the feed rate of the first stage column of synthetic distillation changes, the corresponding steam flow, reflux flow, output flow, vent flow, and reflux flow should change accordingly. However, manual operation requires highly experienced controllers to effectively and predictively adjust the parameters of the entire system. Less experienced controllers will only adjust individual parameters, resulting in poor system integrity. This introduces significant variables into the stability of the distillation system's materials, pressure, temperature, and product quality, hindering stable system operation.
[0028] 5. Large fluctuations in external heat sources. In the polysilicon production process, steam is derived from system byproducts. In actual operation, steam pressure fluctuates significantly, resulting in large fluctuations in steam volume. This leads to large fluctuations in heat in the component separation tower and a decrease in temperature control stability.
[0029] Based on the above, in actual production, in order to ensure the stability of materials, pressure, and temperature during distillation, improve the quality of distillation products, and avoid product quality degradation and safety accidents caused by manual operation, the implementation of full-process automated intelligent control is crucial. Utility Model Content
[0030] This invention aims to provide a control system for a component separation tower in a polycrystalline silicon distillation process. This system enables complete, continuous, and fully automatic control of all parameters of the component separation tower, ensuring stable control of parameters such as feed rate, reflux flow rate, top outflow rate, temperature, and top pressure. This allows the component separation tower to automatically achieve physical and thermal equilibrium based on the feed from the first-stage tower, and to actively overcome external steam interference, thus ensuring stable parameters and consistent distillation quality.
[0031] To achieve the above-mentioned objectives, the technical solution of this utility model is as follows:
[0032] A control system for a component separation tower in a polycrystalline silicon distillation process includes a component separation tower, comprising a primary tower and a secondary tower. Heat exchangers are installed in the reboilers of both the primary and secondary towers. The top outlets of the primary and secondary towers are connected to reflux tanks via top condensers. A reflux pump is connected to the bottom of each reflux tank, and the reflux outlet of the reflux pump is connected to the top of the primary component separation tower. Tail gas discharge pipes are installed at the tops of both the primary and secondary towers. The outlet of the reflux pump from the primary tower is connected to the feed inlet of the secondary tower. Pressure sensors II are installed at the tops of both the primary and secondary towers. Level gauges IIa are installed in both reflux tanks. Level gauges IIb are installed in the reboilers of both the primary and secondary towers. A flow meter IIb and a reboiler discharge regulating valve are installed at the reboiler outlet of the component separation tower.
[0033] The exhaust pipe is connected to an exhaust gas condensation device.
[0034] The tail gas condensation device includes a tail gas condenser and two condensate tanks. The inlet of the tail gas condenser is connected to the tail gas discharge pipe of the component separation tower, and the outlet of the tail gas condenser is connected to the inlet of the condensate tanks. The condensate tanks are equipped with a level gauge III, and the outlet pipe of the condensate tanks is equipped with a condensate pump, a discharge regulating valve III, and a flow meter III.
[0035] The outlet of the condensate pump is connected to the raw material tank via the main pipeline, the extraction regulating valve III is installed on the main pipeline, and the flow meter is installed at the inlet of the raw material tank.
[0036] The condensate tank is equipped with a pressure sensor III, and a pressure relief valve is installed on the top of the condensate tank.
[0037] A pressure sensor IV is installed at the outlet of the condensate pump.
[0038] The outlet of the condensate pump is also connected to the raw material tank via a bypass pipeline. The bypass pipeline is equipped with a valve, and valves are installed at both ends of the regulating valve III on the main pipeline.
[0039] The outlet of the condensate pump is connected to the condensate tank via a return pipeline, and a valve is installed on the return pipeline.
[0040] The exhaust gas condenser is a shell-and-tube heat exchanger.
[0041] The outlet of the reflux pump of the second-stage tower is connected to the anti-disproportionation device;
[0042] The feed inlet of the first-stage tower is connected to the raw material tank;
[0043] Both the exhaust pipe outlets of the first-stage tower and the second-stage tower are equipped with venting regulating valves.
[0044] The reflux outlet of the reflux pump is equipped with a reflux regulating valve and a flow meter IIc; the outflow outlet of the reflux pump is equipped with a tower top outflow regulating valve and a flow meter IId.
[0045] Temperature sensor IIa is installed at the top of the component separation tower, temperature sensor IIb is installed at the bottom of the tower, and temperature sensor IIc is installed in the middle of the tower.
[0046] The heat exchanger heating medium pipelines of the first-stage tower and the second-stage tower are connected to the main steam pipeline; each heat exchanger heating medium inlet is equipped with a heating medium regulating valve and a temperature sensor IId, and the main steam pipeline is equipped with a pressure sensor I; each heat exchanger heating medium pipeline inlet is equipped with a flow meter IIa.
[0047] The feed inlet of the first-stage tower is equipped with a feed regulating valve I and a flow meter Ib, and the raw material tank is equipped with a level gauge I.
[0048] The beneficial effects of this utility model are:
[0049] 1. In this invention, by optimizing the control logic and employing cascade control, the accuracy of parameter adjustment is ensured, eliminating discrepancies in temperature and reflux flow control between different master controllers in the distillation process component separation tower system. For example, the reflux regulating valve of the two-stage tower is cascaded with the reflux flow and tower top temperature, with tower top temperature control as the main loop and the PID loop operating in a positive-acting manner. A tower top control temperature is set, and the tower top temperature is monitored in real time by a temperature sensor. When there is a positive deviation between the real-time tower top temperature and the set temperature, the reflux flow is increased to automatically adjust the temperature; when there is a negative deviation, the reflux flow is decreased to automatically adjust the temperature. This ensures that the tower top temperature of the component separation tower remains essentially stable at the set value. This avoids operational discrepancies caused by inconsistencies in the actions of different master controllers, which could lead to process fluctuations and affect system stability and product quality.
[0050] 2. In this invention, parameters are controlled via loop control, significantly reducing the probability of main control system malfunctions. For example, the heating medium regulating valve and the column bottom temperature are automatically controlled in a single loop. A column bottom temperature is set, and a temperature sensor monitors the column bottom temperature in real time. When there is a positive deviation between the real-time column bottom temperature and the set temperature, the heating medium regulating valve reduces its output opening to automatically adjust the temperature. When there is a negative deviation between the real-time column bottom temperature and the set temperature, the heating medium regulating valve increases its output opening to automatically adjust the temperature. This ensures that the column bottom temperature of the component separation column remains relatively stable at the set value. Loop control eliminates frequently or complex operation points, significantly reducing the workload of employees, preventing malfunctions, and improving system safety.
[0051] 3. In this invention, the application of loop control and program control enhances the integrity of system operation. For example, when the feed rate of the first-stage column in the synthetic distillation changes, the corresponding steam flow, reflux flow, output flow, venting flow, and reflux flow will change accordingly through loop control and program control. For instance, when the feed rate of the first-stage column increases, the output from the top and bottom of the component separation column will increase. Through loop control, this process can be automatically completed based on the liquid levels in the bottom and reflux tanks, completely eliminating the need for manual operation. This improves the integrity of the operating system and effectively enhances the stability of materials, pressure, temperature, and product quality in the distillation system.
[0052] 4. This invention can eliminate the problem of large fluctuations in external heat sources. For example, the heating medium of the first-stage and second-stage towers is automatically adjusted and controlled by steam. When the steam pressure fluctuates too high, the opening of the steam regulating valve will be automatically reduced according to the set value. When the steam pressure fluctuates too low, the opening of the steam regulating valve will be automatically increased according to the set value, thereby stabilizing the steam volume of the component separation tower and improving the stability of temperature control. Attached Figure Description
[0053] Figure 1 This is a schematic diagram of the control system for the component separation tower in the polycrystalline silicon distillation process of this utility model.
[0054] Figure 2 This is a schematic diagram of the control system structure of the first-stage tower of the component separation tower in the polycrystalline silicon distillation process of this utility model.
[0055] Figure 3 This is a schematic diagram of the control system structure of the two-stage column of the component separation column in the polycrystalline silicon distillation process of this utility model.
[0056] Figure 4 This is a schematic diagram of the exhaust gas condensation device of this utility model.
[0057] The components include: 1. Stage 1 tower; 2. Stage 2 tower; 3. Reflux tank; 4. Heat exchanger; 5. Reflux pump; 6. Top condenser; 7. Disproportionation unit; 8. Feed tank; 9. Main steam pipeline; 10. Pressure sensor II; 11. Level gauge IIa; 12. Level gauge IIb; 13. Flow meter IIb; 14. Bottom outlet control valve; 15. Vent control valve; 16. Reflux control valve; 17. Flow meter IIc; 18. Top outlet control valve; 19. Flow meter IId; 20. Temperature sensor IIa; 21. Temperature sensor IIb; 22. Temperature sensor IIc; 23. 24. Heating medium regulating valve; 25. Temperature sensor IId; 26. Pressure sensor I; 27. Flow meter IIa; 28. Feed regulating valve I; 29. Flow meter Ib; 30. Level gauge I; 101. Tail gas condenser; 102. Tail gas condenser; 103. Condensate tank; 104. Tail gas discharge pipe; 105. Level gauge III; 106. Condensate pump; 107. Outlet regulating valve III; 108. Flow meter III; 109. Main pipeline; 110. Pressure sensor III; 111. Pressure sensor IV; 112. Bypass pipeline; 113. Return pipeline. Detailed Implementation
[0058] The present invention will be further described in detail below with reference to the embodiments, but the implementation of the present invention is not limited thereto.
[0059] Example 1
[0060] This embodiment provides a method such as Figure 1-3The control system for the component separation tower in the polycrystalline silicon distillation process shown includes a component separation tower, which includes a first-stage tower 1 and a second-stage tower 2. Heat exchangers 4 are installed in the bottoms of both the first-stage tower 1 and the second-stage tower 2. The top outlets of the first-stage tower 1 and the second-stage tower 2 are connected to reflux tanks 3 via top condensers 6. A reflux pump 5 is connected to the bottom of the reflux tank 3, and the reflux outlet of the reflux pump 5 is connected to the top of the component separation tower. A tail gas discharge pipe 103 is installed at the top of both the first-stage tower 1 and the second-stage tower 2. The outlet of the reflux pump 5 of the first-stage tower 1 is connected to the feed inlet of the second-stage tower 2. Pressure sensors II 10 are installed at the top of both the first-stage tower 1 and the second-stage tower 2. Level gauges IIa 11 are installed in both reflux tanks 3. Level gauges IIb 12 are installed in the bottoms of both the first-stage tower 1 and the second-stage tower 2. A flow meter IIb 13 and a bottom outlet regulating valve 14 are installed at the bottom outlet of the component separation tower.
[0061] The reflux outlet of the reflux pump 5 is equipped with a reflux regulating valve 16 and a flow meter IIc17; the outflow outlet of the reflux pump 5 is equipped with a tower top outflow regulating valve 18 and a flow meter IId19.
[0062] Temperature sensor IIa20 is installed at the top of each component separation tower, temperature sensor IIb21 is installed at the bottom of the tower, and temperature sensor IIc22 is installed in the middle of the tower; the outlet of the reflux pump 5 of the second-stage tower 2 is connected to the anti-disproportionation device 7, and the feed inlet of the first-stage tower 1 is connected to the raw material tank 8.
[0063] In this invention, the synthesized material first enters stage 1, the silicon tetrachloride separation tower. After separation, silicon tetrachloride is collected from the bottom of the tower. The gaseous phase at the top of the tower is condensed by a circulating water condenser into liquid chlorosilane, which enters the high-level reflux tank 3 and is then pumped by reflux pump 5. Part of the liquid is used as top reflux, and the rest is collected as product. The collected components are trichlorosilane and dichlorosilane. The top product from the silicon tetrachloride separation tower enters stage 2, the dichlorosilane separation tower. After separation, the gaseous phase at the top of the tower is condensed by a circulating water condenser into liquid chlorosilane, which enters the high-level reflux tank 3 and is then pumped by reflux pump 5. Part of the gas is used as top reflux, and the rest is collected as dichlorosilane. The bottom product is trichlorosilane. After pressurization, the bottom product is sent to the high-purity removal tower for further purification.
[0064] In this embodiment, the venting regulating valve 15 is a German Akar bellows regulating valve 1"-150LB, the pressure sensor II 10 is an EJA pressure transmitter 2"-150LB, the level gauges IIa 11 and IIb 12 are EJA differential pressure transmitters 2"-150LB, the flow meter IIb 13 is a Yokogawa vortex flow meter, and the bottom outlet regulating valve 14 IIa is a German Akar bellows regulating valve 1 / 2"-150LB.
[0065] In this embodiment, the reflux regulating valve 16 of stage 1 column 1 is automatically controlled in a single loop with the reflux flow rate; the reflux regulating valve 16 of stage 2 column 2 is cascaded controlled with the reflux flow rate and the top temperature; the top outlet regulating valve 18 of stage 1 column 1 is cascaded controlled with the liquid level of reflux tank 3 and the top outlet flow rate; the top outlet regulating valve 18 of stage 2 column 2 is automatically controlled in a single loop with the liquid level of reflux tank 3; the bottom outlet regulating valves 14Ⅱa of stage 1 column 1 and stage 2 column 2 are cascaded controlled with the bottom liquid level and the bottom outlet flow rate; the component separation column also includes automatic reflux ratio adjustment control and the reflux tank 3 also includes automatic reflux tank 3 level adjustment control.
[0066] The reflux regulating valve 16 and the single-loop automatic control of the reflux flow rate of the first-stage tower 1 include: setting the reflux flow rate; monitoring the reflux flow rate of the component separation tower in real time through the flow meter IIc17 at the reflux outlet of the reflux pump 5 of the first-stage tower 1; when there is a positive deviation between the real-time reflux flow rate value and the set reflux flow rate value, the reflux regulating valve 16II reduces the output opening to automatically adjust the reflux flow rate value; when there is a negative deviation between the real-time reflux flow rate value and the set reflux flow rate value, the reflux regulating valve 16II increases the output opening to automatically adjust the reflux flow rate value; so that the reflux flow rate value of the component separation tower is basically stable at the set value.
[0067] The reflux regulating valve 16 of the second-stage column 2 is cascaded with the reflux flow rate and the column top temperature, including: the column top temperature control is the main loop, and the PID loop operates in a positive-acting mode; the column top control temperature is set, and the column top temperature value is monitored in real time by the temperature sensor IIa20. When there is a positive deviation between the real-time column top temperature value and the set temperature value, the reflux flow rate is increased to automatically adjust the temperature value; when there is a negative deviation between the real-time column top temperature value and the set temperature value, the reflux flow rate is decreased to automatically adjust the temperature value; so that the column top temperature value of the component separation column is basically stable at the set value; the reflux flow rate control is the secondary reflux... The PID loop operates in a reverse-acting manner. The reflux flow rate output of the temperature control main loop is used as the set reflux flow rate. The reflux flow rate of the component separation tower is monitored in real time by the flow meter IIc17 at the reflux outlet of the reflux pump 5 of the second-stage tower. When there is a positive deviation between the real-time reflux flow rate value and the set reflux flow rate value, the reflux regulating valve 16Ⅱ reduces the output opening to automatically adjust the reflux flow rate value. When there is a negative deviation between the real-time reflux flow rate value and the set reflux flow rate value, the reflux regulating valve 16Ⅱ increases the output opening to automatically adjust the reflux flow rate value. This ensures that the reflux flow rate value of the component separation tower remains basically stable at the set value.
[0068] The cascade control of the top outlet regulating valve 18 of the first-stage column 1 with the liquid level and top outlet flow rate of the reflux tank 3 includes: the liquid level control of the reflux tank 3 is the main loop, and the PID loop operates in a positive-acting mode; the control liquid level of the reflux tank 3 is set, and the liquid level value of the reflux tank 3 is monitored in real time by the liquid level gauge IIa11. When there is a positive deviation between the real-time liquid level value of the reflux tank 3 and the set liquid level value, the output of the top outlet flow rate is increased to automatically adjust the liquid level value; when there is a negative deviation between the real-time liquid level value of the reflux tank 3 and the set liquid level value, the output of the top outlet flow rate is decreased to automatically adjust the liquid level value; so that the liquid level value of the reflux tank 3 of the component separation column is basically stable at the set value. The top-of-the-column flow rate control is a secondary loop, and the PID loop operates in a reverse-acting manner. The top-of-the-column flow rate output of the reflux tank 3 level control main loop is used as the set-out flow rate. The top-of-the-column flow rate of the component separation tower is monitored in real time by the top-of-the-column flow rate meter IId19. When there is a positive deviation between the real-time flow rate value and the set-out flow rate value, the top-of-the-column flow rate regulating valve 18IIb decreases its output opening to automatically adjust the top-of-the-column flow rate value. When there is a negative deviation between the real-time flow rate value and the set-out flow rate value, the top-of-the-column flow rate regulating valve 18IIb increases its output opening to automatically adjust the top-of-the-column flow rate value. This ensures that the top-of-the-column flow rate value of the component separation tower remains basically stable at the set value.
[0069] The single-loop automatic control of the liquid level in the top outlet regulating valve 18 and reflux tank 3 of the second-stage column 2 includes: a PID loop with positive action. The control liquid level of reflux tank 3 is set, and the liquid level value of reflux tank 3 is monitored in real time by the level gauge IIa11. When there is a positive deviation between the real-time liquid level value of reflux tank 3 and the set liquid level value, the output opening of the top outlet regulating valve 18IIb is increased to automatically adjust the liquid level value; when there is a negative deviation between the real-time liquid level value of reflux tank 3 and the set liquid level value, the output opening of the top outlet regulating valve 18IIb is decreased to automatically adjust the liquid level value; thus, the liquid level value of reflux tank 3 of the component separation column is basically stabilized at the set value.
[0070] The cascade control of the bottom discharge regulating valve 14 of stage 1 and stage 2 towers with the bottom liquid level and bottom discharge flow rate includes: the bottom liquid level control is the main loop, and the PID loop operates in a positive-acting mode; the bottom control liquid level is set, and the bottom liquid level value is monitored in real time by the level gauge IIb12. When there is a positive deviation between the real-time bottom liquid level value and the set liquid level value, the bottom discharge flow rate is increased to automatically adjust the liquid level value; when there is a negative deviation between the real-time bottom liquid level value and the set liquid level value, the bottom discharge flow rate is decreased to automatically adjust the liquid level value; so that the bottom liquid level value of the component separation tower is basically stable at the set value. The bottom flow rate control is a secondary loop, and the PID loop operates in a reverse-acting manner. The bottom flow rate output of the main loop of the bottom level control is used as the set bottom flow rate. The bottom flow rate of the component separation tower is monitored in real time by the bottom flow rate meter IIb13. When there is a positive deviation between the real-time bottom flow rate value and the set bottom flow rate value, the bottom flow rate regulating valve 14IIa decreases the output opening to automatically adjust the bottom flow rate value. When there is a negative deviation between the real-time bottom flow rate value and the set bottom flow rate value, the bottom flow rate regulating valve 14IIa increases the output opening to automatically adjust the bottom flow rate value. This ensures that the bottom flow rate of the component separation tower remains basically stable at the set value.
[0071] The component separation column also includes automatic reflux ratio adjustment control, which automatically adjusts the reflux ratio according to the top flow rate of the component separation column to ensure stable reflux, ensure distillation effect, and reduce energy consumption; including:
[0072] S401: Input the reflux ratio (the ratio of reflux flow rate to the top-collected flow rate) setting;
[0073] S402: The flow rate setpoint of the reflux regulating valve 16 loop of the component separation tower is automatically adjusted to be the product of the reflux ratio setpoint and the flow rate taken out from the top of the tower;
[0074] S403: The reflux regulating valve 16Ⅱ's PID control loop operates in a reverse-acting manner; the real-time value of the reflux flow rate at the top of the tower is monitored in real time by the flow meter Ⅱc17. When there is a positive deviation between the real-time value of the reflux flow rate and the set value of the reflux flow rate, the reflux regulating valve 16Ⅱ reduces the output opening to automatically adjust the reflux flow rate; when there is a negative deviation between the real-time value of the reflux flow rate and the set value of the reflux flow rate, the reflux regulating valve 16Ⅱ increases the output opening to automatically adjust the reflux flow rate; thus, the reflux flow rate value of the component separation tower is basically kept stable at the set value.
[0075] The reflux tank 3 also includes an automatic level adjustment control to prevent frequent changes in the liquid level during short-term extraction from affecting downstream processes. It can also automatically adjust the liquid level in the reflux tank 3. The automatic level adjustment control of the reflux tank 3 includes:
[0076] S701: Setting parameters: setting interval time, setting the upper limit of the flow setting value of the top sampling regulating valve 18Ⅱb loop, setting the lower limit of the flow setting value, setting the upper limit, upper limit, lower limit and lower limit of the liquid level of the reflux tank 3;
[0077] When the liquid level in reflux tank 3 is greater than or equal to the upper limit or less than or equal to the lower limit, the flow rate setting adjustment value SP1 of the circuit of the top sampling regulating valve 18Ⅱb of the component separation tower is set.
[0078] When the liquid level in reflux tank 3 is greater than or equal to the high limit or less than or equal to the low limit, the flow rate setting adjustment value SP2 of the circuit of the top sampling regulating valve 18Ⅱb of the component separation tower is set.
[0079] S702: When the liquid level in reflux tank 3 is greater than or equal to the upper limit and less than the upper-high limit, the flow setting value of the control valve 18Ⅱb loop at the top of the component separation tower is increased by SP1; after adjustment, the program continues to make real-time judgments after the stabilization interval.
[0080] When the liquid level in reflux tank 3 is greater than the lower limit and less than or equal to the lower limit L, the flow rate setpoint of the top sampling regulating valve 18Ⅱb loop of the component separation tower is reduced by SP1; after adjustment, the program continues to make real-time judgments after the stabilization interval.
[0081] S703: When the liquid level in reflux tank 3 is greater than or equal to the high limit, the flow rate setting value of the top sampling regulating valve 18Ⅱb loop of the component separation tower is increased by SP2; after adjustment, the program continues to make real-time judgments after the stabilization interval.
[0082] When the liquid level in reflux tank 3 is less than or equal to the lower limit, the flow rate setting value of the top product control valve 18Ⅱb loop of the component separation tower is reduced by SP2; after adjustment, the program continues to make real-time judgments after a stabilization interval T1. In this embodiment, the liquid level is periodically judged according to the set conditions and set time, and the flow rate setting value of the top product control valve 18Ⅱb loop of the component separation tower is automatically adjusted to avoid multiple manual adjustments in a short period of time and to ensure the stability of the product output.
[0083] Example 2
[0084] The difference between this embodiment and Embodiment 1 is that, in this embodiment, as... Figure 4 As shown, the tail gas emission pipe 103 is connected to a tail gas condensation device 30. The outlets of the tail gas emission pipes 103 of both the first-stage tower 1 and the second-stage tower 2 are equipped with venting regulating valves 15. The tail gas condensation device includes a tail gas condenser 101 and two condensate tanks 102. The inlet of the tail gas condenser 101 is connected to the tail gas emission pipe 103 of the component separation tower, and the outlet of the tail gas condenser 101 is connected to the inlet of the condensate tank 102. The condensate tank 102 is equipped with a level gauge III 104. The outlet pipe of the condensate tank 102 is equipped with a condensate pump 105, a collection regulating valve III 106, and a flow meter III 107.
[0085] The rest of the structure is the same as in Example 1.
[0086] In this embodiment, the venting regulating valve 15 is a German Akar bellows regulating valve 1"-150LB.
[0087] In this embodiment, the top vent flow control of the first-stage tower 1 and the second-stage tower 2 is also included, and the tail gas condensation device 30 includes a tail gas vent condensate system feeding control method.
[0088] The vent flow control at the top of the first-stage tower 1 and the second-stage tower 2 includes: single-loop automatic control of the top vent regulating valve 15Ⅱ and the top pressure, with the PID loops all operating in a positive-acting manner; setting the top control pressure, and monitoring the top pressure value in real time through pressure sensor Ⅱ10; when there is a positive deviation between the real-time top pressure value and the set pressure value, the vent regulating valve 15Ⅱ increases the output opening to automatically adjust the pressure value; when there is a negative deviation between the real-time top pressure value and the set pressure value, the vent regulating valve 15Ⅱ decreases the output opening to automatically adjust the pressure value; thus ensuring that the top pressure value of the component separation tower remains basically stable at the set value.
[0089] The exhaust gas condensation device 30 includes an exhaust gas venting condensate system feeding control method, which includes:
[0090] S801: When the liquid level in the tail gas condensate tank 102 is higher than 65%, the condensate pump 105 starts automatically, the tail gas condenser 101 outlet outlet regulating valve III 106 is switched to manual mode, and the opening of the regulating valve III 106 is set to 70%; after 10 seconds, the regulating valve III 106 switches to automatic mode, the set outlet flow rate is 13t / h, and the regulating valve automatically adjusts the opening according to the deviation between the real-time outlet flow rate and the set value; S802: When the liquid level in the tail gas condensate tank 102 is lower than 20%, the condensate pump 105 stops automatically, the tail gas condenser 101 outlet outlet regulating valve III 106 is switched to manual mode, and the regulating valve III 106 is closed.
[0091] S803: During operation, if the current of the condensate pump 105 is lower than 8A and continues for 10 seconds, the condensate pump 105 will stop running, the outlet regulating valve Ⅲ106 of the tail gas condenser 101 will be switched to manual mode, and the outlet regulating valve Ⅲ106 will be closed.
[0092] In this embodiment, the level gauge Ⅲ104 of the condensate tank 102 adopts an EJA differential pressure transmitter 2"-150LB, the outlet regulating valve Ⅲ106 adopts a Samson bellows regulating valve DN100 PN40, and the flow meter Ⅲ107 adopts an E+H mass flow meter.
[0093] In this embodiment, when the liquid level of the tail gas condensate tank 102 is higher than 65% in step S801, the conditions for discharge are met, and the condensate pump 105 starts automatically; the outlet regulating valve III 106 of the tail gas condenser 101 is switched to manual mode and the opening of the regulating valve III 106 is set to 70% to avoid large flow fluctuations at the moment of pump start-up, which could cause the regulating valve to fail to adjust automatically, potentially resulting in pump pressure loss or cavitation and damage to the equipment; the 10-second duration is to ensure stable flow, normal pump start-up, and automatic adjustment of the regulating valve; in step S102, when the liquid level of the tail gas condensate tank 102 is lower than 20%, the feeding ends, the condensate pump 105 stops automatically, and the outlet regulating valve III 106 of the tail gas condenser 101 is switched to manual mode and closed to prevent material backflow.
[0094] In step S803, if the current of the condensate pump 105 is lower than 8A and continues for 10 seconds before automatically stopping, it is based on the pump's underload current protection to avoid damaging the equipment.
[0095] In this embodiment, the exhaust gas from the component separation tower is condensed and reused to improve resource utilization and reduce environmental pollution. The exhaust gas from the 1st to 6th stage component separation towers is vented to the exhaust gas condenser 101, where it is condensed from a gaseous state to a liquid state and collected in the condensate tank 102. Finally, it is pumped into the raw material tank area for reuse, thus realizing the recycling of resources.
[0096] Example 3
[0097] The difference between this embodiment and embodiment 2 is that, in this embodiment, a pressure sensor Ⅲ109 is installed inside the condensate tank 102, and a pressure relief valve is installed on the top of the condensate tank 102. The rest of the structure is the same as in embodiment 2.
[0098] In this embodiment, the tail gas from the component separation tower is not completely condensed when it is discharged into the condensate tank 102 after being condensed by the tail gas condenser 101. It still has a certain pressure. By installing a pressure sensor Ⅲ109 in the condensate tank 102 to detect the pressure in the condensate tank 102, when the pressure is greater than the set maximum value, the pressure relief valve opens to release pressure and ensure the safety of the condensate tank 102.
[0099] Example 4
[0100] The difference between this embodiment and embodiment 2 is that, in this embodiment, a pressure sensor Ⅳ110 is provided at the outlet of the condensate pump 105, while the rest of the structure is the same as in embodiment 2.
[0101] In this embodiment, a pressure sensor Ⅳ110 is installed at the outlet of the condensate pump 105 to monitor the operation of the condensate pump 105 and detect whether there are any abnormalities such as pressure loss or stalling.
[0102] Example 5
[0103] Compared with Embodiment 2, the difference in this embodiment is that, in this embodiment, the outlet of the condensate pump 105 is also connected to the raw material tank through a bypass pipeline 111, and a valve is installed on the bypass pipeline 111. Valves are respectively installed at both ends of the regulating valve Ⅲ 106 on the main pipeline 108; the outlet of the condensate pump 105 is connected to the condensate tank 102 through a return pipeline 112, and a valve is installed on the return pipeline 112; the rest of the structure is the same as in Embodiment 2.
[0104] In this embodiment, when the main pipeline 108 fails due to a malfunction of the extraction regulating valve Ⅲ106 or the main pipeline 108, the valves at both ends of the extraction regulating valve Ⅲ106 on the main pipeline 108 are closed, and the valve on the bypass pipeline 111 is opened. The condensate tank 102 is connected to the raw material tank through the bypass pipeline 111 to ensure the normal operation of the system.
[0105] When the condensate tank 102 is connected to the raw material tank through the bypass line 111, the valve on the return line 112 is opened. Part of the condensate pumped out by the condensate pump 105 enters the raw material tank through the bypass line 111, and part of it flows back into the condensate tank 102 through the return line 112. By adjusting the opening degree of the valves on the return line 112 and the bypass line 111, the flow rate of the condensate tank 102 can be regulated.
[0106] Example 6
[0107] Compared with Example 1, the difference in this embodiment is that, in this embodiment, the heating medium pipelines of the heat exchangers 4 of the first-stage tower 1 and the second-stage tower 2 are connected to the main steam pipeline 9; the heating medium inlet of the heat exchangers 4 is equipped with a heating medium regulating valve 23 and a temperature sensor IId 24, and the main steam pipeline 9 is equipped with a pressure sensor I 25; the inlet of the heating medium pipeline of the heat exchangers 4 is equipped with a flow meter IIa 26; the rest of the structure is the same as in Example 1.
[0108] In this embodiment, the heating medium regulating valve 23 of the first-stage tower 1 and the second-stage tower 2 are connected to the single-loop automatic control of the tower bottom temperature and the automatic steam adjustment control.
[0109] The automatic steam adjustment control includes the following steps:
[0110] S101: Setting parameters: setting sampling time, trigger time, steam main pipe set pressure difference value PI-SP and heating medium regulating valve 23 valve opening adjustment setting value OUT-SP;
[0111] S102: The pressure in the steam main is monitored in real time by pressure sensor I25, and the average value of the pressure of the first 6 samplings is calculated.
[0112] S103: Calculate the difference between the current pressure of the steam main and the average pressure of the steam main, and set judgment condition 1 and judgment condition 2;
[0113] The judgment condition 1 is: the difference between the current pressure of the steam main pipe and the average pressure of the steam main pipe is greater than or equal to the set pressure difference PI-SP of the steam main pipe;
[0114] The judgment condition 2 is: when the difference between the current pressure of the steam main pipe and the average pressure of the steam main pipe is less than the set pressure difference PI-SP of the steam main pipe;
[0115] S104: If neither condition 1 nor condition 2 is met, continue to make real-time judgments;
[0116] When condition 1 is met within a continuous time T2, the circuit mode of heating medium regulating valve 23 is switched to manual, and the valve opening is reduced to OUT-SP; after stabilizing for 2 seconds, the circuit mode of heating medium regulating valve 23 is switched to automatic, and the flow rate setting value of the previous automatic mode is restored.
[0117] When condition 2 is met within a continuous time T2, the circuit mode of the heating medium regulating valve 23 is switched to manual, and the valve opening is increased to OUT-SP; after stabilizing for 2 seconds, the circuit mode of the heating medium regulating valve 23 is switched to automatic, and the flow rate setting value of the previous automatic mode is restored.
[0118] The single-loop automatic control of the heating medium regulating valve 23 and the column bottom temperature includes: the PID loop operates in a reverse-acting manner; the column bottom control temperature is set, and the column bottom temperature value is monitored in real time by the temperature sensor IIb21. When there is a positive deviation between the real-time column bottom temperature value and the set temperature value, the heating medium regulating valve 23 reduces the output opening to automatically adjust the temperature value; when there is a negative deviation between the real-time column bottom temperature value and the set temperature value, the heating medium regulating valve 23 increases the output opening to automatically adjust the temperature value; so that the column bottom temperature value of the component separation column is basically stable at the set value.
[0119] Example 7
[0120] Compared with Example 1, the difference in this embodiment is that the feed inlet of the first-stage tower 1 is equipped with a feed regulating valve I27 and a flow meter Ib28, and the raw material tank 8 is equipped with a level gauge I29; the rest of the structure is the same as in Example 1.
[0121] In this embodiment, the first-stage tower 1 also includes automatic feed control, comprising the following steps:
[0122] S201: Setting parameters: Set the adjustment interval time of the feed setpoint of the PID loop of feed regulating valve I27; in the automatic mode of the PID loop of feed regulating valve I27, set the upper and lower limits of the feed flow rate setpoint; set the upper-high limit, upper limit, lower limit and lower-low limit of the liquid level of raw material tank 8.
[0123] S202: Single-loop automatic control of feed regulating valve I27 and feed flow rate, with a PID loop operating in a reverse-acting manner; the feed flow rate of the component separation tower is monitored in real time. When there is a positive deviation between the real-time feed flow rate and the set flow rate, feed regulating valve I27 decreases its output opening to automatically adjust the feed flow rate; when there is a negative deviation between the real-time feed flow rate and the set flow rate, feed regulating valve I27 increases its output opening to automatically adjust the feed flow rate; when it is necessary to decrease the output opening of feed regulating valve I27 and the set feed flow rate reaches the lower limit, no adjustment is made; when it is necessary to increase the output opening of feed regulating valve I27 and the set feed flow rate reaches the upper limit, no adjustment is made; thus, the feed flow rate of the component separation tower is kept basically stable at the set value.
[0124] S203: When the liquid level in raw material tank 8 is greater than or equal to the upper limit and the liquid level is less than the upper limit, the feed flow rate setting value of the PID loop of feed regulating valve I27 is increased by SP1; after adjustment, the program continues to make real-time judgments after the adjustment interval.
[0125] S204: When the liquid level in raw material tank 8 is greater than the lower limit and the liquid level is less than or equal to the lower limit, the feed flow rate setting value of the PID loop of feed regulating valve I27 is reduced by SP1; after adjustment, the program continues to make real-time judgments after the adjustment interval.
[0126] S205: When the liquid level in raw material tank 8 is greater than or equal to the high limit, the feed flow rate setting value of the PID loop of feed regulating valve I27 is increased by SP2; after adjustment, the program continues to make real-time judgments after the adjustment interval.
[0127] S206: When the liquid level in raw material tank 8 is ≤ the lower limit, the feed flow rate setting value of the PID loop of feed regulating valve I27 is reduced by SP2; after adjustment, the program continues to make real-time judgments after the adjustment interval.
[0128] It is understood that this utility model has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of this utility model. Furthermore, under the teachings of this utility model, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of this utility model. Therefore, this utility model is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of this utility model.
Claims
1. A control system for a component separation tower in a polycrystalline silicon distillation process, characterized in that: The system includes a component separation tower, comprising a first-stage tower (1) and a second-stage tower (2). Both the first-stage tower (1) and the second-stage tower (2) are equipped with heat exchangers (4) at their bottoms. The top outlets of the first-stage tower (1) and the second-stage tower (2) are connected to reflux tanks (3) via top condensers (6). A reflux pump (5) is connected to the bottom of the reflux tank (3). The reflux outlet of the reflux pump (5) is connected to the top of the component separation tower. Both the first-stage tower (1) and the second-stage tower (2) are equipped with exhaust pipes (103). The outlet of the reflux pump (5) of the first-stage tower (1) is connected to the feed inlet of the second-stage tower (2). Pressure sensor II (10) is installed at the top of both the first-stage tower (1) and the second-stage tower (2). Level gauge IIa (11) is installed in both the reflux tank (3). Level gauge IIb (12) is installed in the bottom of both the first-stage tower (1) and the second-stage tower (2). Flow meter IIb (13) and bottom outlet regulating valve (14) are installed at the bottom outlet of the component separation tower.
2. The control system for the component separation tower in the polycrystalline silicon distillation process according to claim 1, characterized in that: The exhaust pipe (103) is connected to an exhaust gas condensation device (30).
3. The control system for the component separation tower in the polycrystalline silicon distillation process according to claim 2, characterized in that: The tail gas condensation device (30) includes a tail gas condenser (101) and two condensate tanks (102). The inlet of the tail gas condenser (101) is connected to the tail gas discharge pipe (103) of the component separation tower, and the outlet of the tail gas condenser (101) is connected to the inlet of the condensate tank (102). The condensate tank (102) is equipped with a level gauge III (104). The outlet pipe of the condensate tank (102) is equipped with a condensate pump (105), a collection regulating valve III (106), and a flow meter III (107).
4. The control system for the component separation tower in the polycrystalline silicon distillation process according to claim 3, characterized in that: The outlet of the condensate pump (105) is connected to the raw material tank through the main pipeline (108), the extraction regulating valve III (106) is installed on the main pipeline (108), and the flow meter is installed at the feed inlet of the raw material tank.
5. The control system for the component separation tower in the polycrystalline silicon distillation process according to claim 3, characterized in that: A pressure sensor Ⅲ (109) is installed inside the condensate tank (102), and a pressure relief valve is installed on the top of the condensate tank (102).
6. The control system for the component separation tower in the polycrystalline silicon distillation process according to claim 3, characterized in that: The outlet of the condensate pump (105) is equipped with a pressure sensor Ⅳ (110).
7. The control system for the component separation tower in the polycrystalline silicon distillation process according to claim 4, characterized in that: The outlet of the condensate pump (105) is also connected to the raw material tank through a bypass pipeline (111). The bypass pipeline (111) is equipped with a valve, and the main pipeline (108) has valves at both ends of the regulating valve III (106).
8. The control system for the component separation tower in the polycrystalline silicon distillation process according to claim 7, characterized in that: The outlet of the condensate pump (105) is connected to the condensate tank (102) through a return pipeline (112), and a valve is installed on the return pipeline (112).
9. The control system for the component separation tower in the polycrystalline silicon distillation process according to claim 3, characterized in that: The exhaust gas condenser (101) is a shell-and-tube heat exchanger.
10. The control system for the component separation tower in the polycrystalline silicon distillation process according to claim 1, characterized in that: The reflux pump (5) of the second-stage tower (2) is connected to the anti-disproportionation device (7) at the outlet.
11. The control system for the component separation tower in the polycrystalline silicon distillation process according to claim 1, characterized in that: The feed inlet of the first-stage tower (1) is connected to the raw material tank (8).
12. The control system for the component separation tower in the polycrystalline silicon distillation process according to claim 1, characterized in that: The exhaust pipes (103) outlets of the first-stage tower (1) and the second-stage tower (2) are both equipped with venting regulating valves (15).
13. The control system for the component separation tower in the polycrystalline silicon distillation process according to claim 1, characterized in that: The reflux outlet of the reflux pump (5) is equipped with a reflux regulating valve (16) and a flow meter IIc (17); the outlet of the reflux pump (5) is equipped with a tower top outlet regulating valve (18) and a flow meter IId (19).
14. The control system for the component separation tower in the polycrystalline silicon distillation process according to claim 1, characterized in that: Temperature sensor IIa (20) is installed at the top of each component separation tower, temperature sensor IIb (21) is installed at the bottom of the tower, and temperature sensor IIc (22) is installed in the middle of the tower.
15. The control system for the component separation tower in the polycrystalline silicon distillation process according to claim 1, characterized in that: The heat exchanger (4) heating medium pipelines of the first-stage tower (1) and the second-stage tower (2) are connected to the main steam pipeline (9); the heating medium inlet of the heat exchanger (4) is equipped with a heating medium regulating valve (23) and a temperature sensor IId (24), and the main steam pipeline (9) is equipped with a pressure sensor I (25); the inlet of the heating medium pipeline of the heat exchanger (4) is equipped with a flow meter IIa (26).
16. The control system for the component separation tower in the polycrystalline silicon distillation process according to claim 4, characterized in that: The feed inlet of the first-stage tower (1) is equipped with a feed regulating valve I (27) and a flow meter Ib (28), and the raw material tank (8) is equipped with a level gauge I (29).