Waste heat utilization system for chassis of polycrystalline silicon reduction furnace

Abstract

The invention relates to the technical field of polycrystalline silicon production, in particular to a polycrystalline silicon reduction furnace chassis waste heat utilization system which comprises a chassis water tank, a chassis water pump, a reduction furnace chassis, a lithium bromide unit, a heating heat exchanger, a TCS preheater, a TCS vaporizer, a heat pump unit, a steam compressor, a condensate water collecting tank, a condensate water pump and a control system. The chassis water tank stores cooling water, the chassis water pump conveys water to the reduction furnace chassis for cooling, and the cooling water is conveyed through the main water conveying pipe. The main water delivery pipe is connected with the lithium bromide unit, the heating heat exchanger, the TCS preheater and the heat pump unit, and each pipeline is provided with a flow meter and a regulating valve. The TCS vaporizer is connected with the TCS preheater, the heat pump unit is connected with the steam compressor and the low-pressure steam equipment, and the condensate water collecting tank is communicated with the chassis water tank through the condensate water pump. And the control system is connected with the thermometer, the flowmeter and the flow regulating valve to realize intelligent control of the system. Waste heat of the chassis can be fully utilized, and the operation stability of the system is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of polysilicon production technology, and in particular to a waste heat utilization system for the chassis of a polysilicon reduction furnace. Background Technology

[0002] In modern industrial production, efficient energy utilization has become an important goal for enterprises' sustainable development and energy conservation and emission reduction. In many industries such as metallurgy, chemical industry, and power, a large number of equipment generate a lot of waste heat during operation. If this waste heat cannot be effectively recovered and utilized, it will not only cause energy waste, but may also have adverse effects on the environment.

[0003] In the production of semiconductor materials such as polycrystalline silicon and monocrystalline silicon, the reduction furnace is one of the key pieces of equipment. Trichlorosilane is the core raw material for TCS (Polycrystalline Silicon Composition) and a crucial raw material for polycrystalline silicon production. The reduction furnace releases a large amount of heat during operation. The furnace chassis is cooled by heat exchange via a water bath. Because the chassis is equipped with electrodes fitted with PTFE sleeves, the insulation and sealing of the PTFE sleeves decrease as the chassis temperature rises; therefore, the chassis water temperature should not be too high. In existing technologies, the waste heat from the chassis water is mainly utilized through the following methods: First, chassis cooling water below 100℃ is used for chassis heat exchange. The resulting low-grade hot water (below 110℃) provides a heat source for the reboiler of the primary fractionation column in the distillation section, and also provides a heat source for winter air conditioning and overall plant heating. Second, chassis cooling water at 120-133℃ is used for chassis heat exchange. After heat exchange, the chassis cooling water temperature is 130-143℃. Flash evaporation generates low-quality steam with a pressure of 0.1-0.2 MPa. The low-quality steam is used for refrigeration of the lithium bromide unit and provides a heat source for winter air conditioning and heating of the entire plant. However, existing waste heat utilization systems have poor adaptability. When production is adjusted or the system fluctuates, and the number of reduction furnaces in operation changes, excess heat needs to be cooled by circulating water heat exchangers or by air coolers, resulting in heat waste. The low-quality steam generated by flash evaporation of low-grade hot water is only usable by a very small number of heat-consuming equipment due to its low pressure, and cannot be widely utilized. When the number of reduction furnaces in operation increases and there is too much waste heat in the chassis, the excess low-quality steam needs to be vented, resulting in waste. Flash evaporation of chassis cooling water, with the water temperature at 120-133℃ and the return water temperature at 130-143℃, reduces the insulation of the PTFE electrode sleeves, making grounding faults more likely to occur during the operation of the reduction furnace, thus affecting the stable operation of the reduction furnace. Summary of the Invention

[0004] In view of this, the present invention provides a waste heat utilization system for the chassis of a polycrystalline silicon reduction furnace. The main purpose is to make full use of the waste heat of the chassis, improve the waste heat utilization efficiency and the system's ability to regulate waste heat utilization, and ensure the stability of system operation.

[0005] To achieve the above objectives, the present invention mainly provides the following technical solutions:

[0006] An embodiment of the present invention provides a waste heat utilization system for the chassis of a polycrystalline silicon reduction furnace, comprising: a chassis water tank, a chassis water pump, a reduction furnace chassis, a lithium bromide unit, a heating heat exchanger, a TCS preheater, a TCS vaporizer, a heat pump unit, a steam compressor, a condensate collection tank, a condensate pump, and a control system.

[0007] The chassis water tank is used to store chassis cooling water;

[0008] The input end of the chassis water pump is connected to the chassis water tank;

[0009] The cooling water inlet of the reduction furnace chassis is connected to the output end of the chassis water pump; the cooling water outlet of the reduction furnace chassis is connected to a main water supply pipe; a thermometer is installed on the main water supply pipe;

[0010] The input end of the lithium bromide generator unit is connected to the main water supply pipe via a pipeline; the output end of the lithium bromide generator unit is connected to the chassis water tank.

[0011] The input end of the heating water heater is connected to the main water supply pipe through pipe two; the output end of the heating water heater is connected to the chassis water tank.

[0012] The input end of the TCS preheater is connected to the main water supply pipe via pipe three; the output end of the TCS preheater is connected to the chassis water tank; a flow meter is installed on pipe three; a flow regulating valve is installed on pipe three.

[0013] The TCS vaporizer is connected to the TCS preheater via pipe four.

[0014] The heat pump unit is connected to the main water supply pipe through pipe five; a flow meter two is installed on pipe five; a flow regulating valve two is installed on pipe five;

[0015] The input end of the steam compressor is connected to the steam outlet of the heat pump unit via pipe six;

[0016] The inlet of the low-pressure steam equipment is connected to the steam outlet of the heat pump unit via pipe seven; the cooling water outlet of the heat pump unit is connected to the chassis water tank.

[0017] The condensate collection tank is connected to the low-pressure steam equipment via pipe eight.

[0018] The input end of the condensate pump is connected to the condensate collection tank; the output end of the condensate pump is connected to the chassis water tank.

[0019] The control system is connected to the thermometer;

[0020] The control system is connected to the flow regulating valve.

[0021] The control system is connected to the second flow regulating valve;

[0022] The control system is connected to the flow meter.

[0023] The control system is connected to the flow meter.

[0024] Furthermore, the control system is connected to the heat pump unit and is used to control the start-up or shutdown of the heat pump unit.

[0025] Furthermore, a low-pressure steam inlet is provided on the chassis water tank.

[0026] Furthermore, the output end of the steam compressor is connected to the medium-pressure steam pipeline network.

[0027] Furthermore, the low-pressure steam equipment is provided with an input port two for inputting low-pressure steam.

[0028] By employing the above technical solution, the waste heat utilization system for the polysilicon reduction furnace chassis of the present invention has at least the following advantages:

[0029] It can make full use of the waste heat of the chassis, improve the efficiency of waste heat utilization and the system's ability to regulate waste heat utilization, and ensure the stability of system operation.

[0030] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of a waste heat utilization system for a polycrystalline silicon reduction furnace chassis, provided as an embodiment of the present invention.

[0032] As shown in the figure:

[0033] 1 is the chassis water tank, 2 is the chassis water pump, 3 is the reduction furnace chassis, 4 is the main water supply pipe, 5 is pipe one, 6 is the lithium bromide unit, 7 is pipe two, 8 is the heating heat exchanger, 9 is pipe three, 10 is the TCS preheater, 11 is the TCS input pipe, 12 is pipe four, 13 is the TCS vaporizer, 14 is the thermometer, 15 is the flow regulating valve one, 16 is the flow meter one, 17 is the flow regulating valve two, 18 is the flow meter two, 19 is pipe five, 20 is the heat pump unit, 21 is pipe seven, 22 is the steam compressor, 23 is pipe six, 24 is the low-pressure steam equipment, 25 is the input port two, 26 is pipe eight, 27 is the condensate collection tank, 28 is the condensate pump, 29 is the low-pressure steam inlet, and 30 is the TCS output pipe. Detailed Implementation

[0034] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the specific embodiments, structures, features, and effects according to the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments. In the following description, different "embodiments" or "embodiments" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0035] like Figure 1 As shown, an embodiment of the present invention provides a waste heat utilization system for a polycrystalline silicon reduction furnace chassis 3, comprising: chassis water tank 1, chassis water pump 2, reduction furnace chassis 3, lithium bromide unit 6, heating heat exchanger 8, TCS preheater 10, TCS vaporizer 13, heat pump unit 20, steam compressor 22, condensate collection tank 27, condensate pump 28, and control system;

[0036] The chassis water tank 1 stores chassis cooling water; the input end of the chassis water pump 2 is connected to the chassis water tank 1 and is used to supply cooling water to the reduction furnace chassis 3; the cooling water inlet of the reduction furnace chassis 3 is connected to the output end of the chassis water pump 2; the cooling water outlet of the reduction furnace chassis 3 is connected to the main water supply pipe 4; a thermometer 14 is installed on the main water supply pipe 4 to detect the temperature of the water in the main water supply pipe; there are multiple reduction furnace chassis 3; multiple reduction furnace chassis 3 are connected in parallel; multiple reduction furnace chassis 3 operate simultaneously. The input end of the lithium bromide unit 6 is connected to the main water supply pipe 4 through pipe 1 5; the output end of the lithium bromide unit 6 is connected to the chassis water tank 1; the input end of the heating water heater is connected to the main water supply pipe 4 through pipe 2 7; the output end of the heating water heater is connected to the chassis water tank 1; the input end of the TCS preheater 10 is connected to the main water supply pipe 4 through pipe 3 9; the TCS preheater 10 is equipped with a TCS input pipe 11 for TCS to enter. The output end of the TCS preheater 10 is connected to the chassis water tank 1; a flow meter 16 is installed on pipe 3 9; a flow regulating valve 15 is installed on pipe 3 9; the TCS vaporizer 13 is connected to the TCS preheater 10 through pipe 4 12; a TCS output pipe 30 is installed on the TCS vaporizer 13 for TCS output. The heat pump unit 20 is connected to the main water supply pipe 4 via pipe 5 19; a flow meter 2 18 is installed on pipe 5 19; a flow regulating valve 2 17 is installed on pipe 5 19; the input end of the steam compressor 22 is connected to the steam outlet of the heat pump unit 20 via pipe 6 23; the input port 1 of the low-pressure steam equipment 24 is connected to the steam outlet of the heat pump unit 20 via pipe 7 21; the cooling water outlet of the heat pump unit 20 is connected to the chassis water tank 1; the condensate collection tank 27 is connected to the low-pressure steam equipment 24 via pipe 8 26; the input end of the condensate pump 28 is connected to the condensate collection tank 27; the output end of the condensate pump 28 is connected to the chassis water tank 1; the control system is connected to the thermometer 14 to collect the temperature of the cooling water in the main water supply pipe 4; the control system is connected to the flow regulating valve 1 15 to regulate the flow rate; the control system is connected to the flow regulating valve 2 17 to regulate the flow rate; the control system is connected to the flow meter 1 16 to collect the flow data of pipe 3 9. The control system is connected to flow meter 18 to collect flow data from pipe 19. The control system can be a PLC centralized control system, or it can be a system that uses thermometer 14 in conjunction with flow regulating valves 15 and 27 for linkage control.

[0037] One embodiment of the present invention provides a waste heat recovery system for a polycrystalline silicon reduction furnace chassis. In specific implementation, chassis water tank 1, via chassis water pump 2, delivers chassis cooling water at 90-100°C to the reduction furnace chassis 3. After heat exchange with the chassis, the waste heat is carried away, and the temperature is raised to chassis hot water at 100-110°C. Using low-grade hot water at a suitable temperature as chassis cooling water reduces grounding faults in the reduction furnace and improves the stability of the reduction furnace operation. Stable operation of the reduction furnace further reduces production costs. The chassis hot water at 100-110°C after heat exchange is divided into three stages for waste heat recovery. The hot water after heat recovery eventually returns to chassis water tank 1, forming a closed loop. The chassis hot water after heat exchange with the reduction furnace chassis 3 is then transported through the main water pipe 4 for waste heat recovery in stages.

[0038] First-stage waste heat utilization: Hot water enters the lithium bromide unit 6 through pipe 1 (5), where waste heat is used to produce 7°C water, which is then supplied to all 7°C water users in the plant. In winter, hot water from the chassis simultaneously enters the heating heat exchanger 8 through pipe 2 (7), and the heated water is then used for heating throughout the plant.

[0039] Secondary waste heat utilization: If there is still excess heat after the heat exchange of the first-stage equipment, hot water enters the TCS preheater 10 through pipe 39 to preheat the TCS sent to the reduction stage in the previous stage. The preheated TCS enters the TCS vaporizer 13 through pipe 412, where low-pressure steam heats up and vaporizes the TCS, which is then supplied to the subsequent reduction furnace. TCS preheating can reduce the steam consumption of the vaporizer.

[0040] Third-stage waste heat utilization: When the flow rate of flow meter 16 on pipeline 39 reaches 300 m³ / h, which roughly corresponds to the cooling water flow rate of the chassis 3 of 5 reduction furnaces, the hot water enters the heat pump unit 20 through pipeline 519. The hot water from the chassis is used to produce 0.3 MPa low-pressure steam. This low-pressure steam is then connected to the low-pressure steam network through pipeline 721 to supply the low-pressure steam equipment 24 throughout the plant. If there is a surplus of low-pressure steam throughout the plant, the 0.3 MPa low-pressure steam produced by the heat pump unit 20 enters the steam compressor 22, which raises the pressure to 0.8-1.0 MPa medium-pressure steam, which is then connected to the medium-pressure steam network for use throughout the plant.

[0041] After the low-pressure steam in the plant's pipeline network is used, the condensate enters the condensate collection tank 27 through pipeline 8 26, and is then transported to the chassis water tank 1 by the condensate pump 28 as a supplement to the condensate after the chassis water circulation system sends out steam.

[0042] One embodiment of the present invention proposes a waste heat recovery system for a polycrystalline silicon reduction furnace chassis. During operation, the system prioritizes meeting the heat demand of the first-stage waste heat recovery equipment. Excess heat is then used in the second and third stages. When the lithium bromide unit's 67°C water meets the plant's overall process requirements and simultaneously supplies heat to the heating water heat exchanger in winter, there is excess waste heat in the chassis water. The flow regulating valve 15 on pipe 39 is set to a control temperature T based on the temperature setting of thermometer 14. When the measured temperature > T, the flow regulating valve 15 on pipe 39 is slowly opened via temperature interlock, allowing the excess chassis hot water to exchange heat with the TCS preheater 10. Since the excess heat in the chassis hot water is not constant, the flow regulating valve 15, which handles the variable flow rate of chassis hot water, exchanges heat with the TCS preheater 10 at the set temperature T. When there is excess heat and the measured temperature > T, the flow regulating valve 15 slowly opens further; when the measured temperature < T°C, the flow regulating valve 15 slowly closes, recovering and utilizing the excess chassis water waste heat.

[0043] When the flow rate of flow meter 16 reaches 300 m³ / h (a suitable value selected based on the total chassis cooling water volume and the load of heat pump unit 20), the system triggers a high flow alarm and starts heat pump unit 20. After starting, heat pump unit 20 immediately switches to automatic operation. Flow regulating valve 17 on pipe 5 is set to control the temperature at T-0.5℃, based on the set value of thermometer 14. When the measured temperature > T-0.5℃, the interlocking control valve 17 slowly opens; when the measured temperature < T-0.5℃, the interlocking control valve 17 slowly closes. Through the temperature interlocking logic, the opening of flow regulating valve 17 precisely controls the flow rate of excess chassis water. Flow regulating valve 17 is adjusted based on temperature value T-0.5℃, while flow regulating valve 15 is adjusted based on temperature value T. Therefore, in the automatic operation state of heat pump unit 20, flow regulating valve 15 in the second stage waste heat utilization is in the closed state, and the second stage waste heat utilization system is in the off state.

[0044] When the flow rate at the inlet flow meter 18 of heat pump unit 20 gradually decreases to 150 m³ / h, the system triggers a low flow rate alarm. The control system determines that the load on heat pump unit 20 is too low, resulting in low efficiency in producing low-pressure steam. The control system then shuts down heat pump unit 20 and switches it to manual mode. Excess heat from the chassis water enters the secondary waste heat recovery system.

[0045] An embodiment of the present invention proposes a waste heat utilization system for the chassis of a polycrystalline silicon reduction furnace. When multiple reduction furnaces are running, due to fluctuations in the production system or production adjustments, a significant amount of waste heat from the chassis will not be wasted by cooling with circulating water or air coolers. The waste heat from the chassis is recovered in stages, which can make full use of the waste heat from the chassis, improve the efficiency of waste heat utilization and the system's ability to regulate waste heat utilization, and ensure the stability of system operation.

[0046] An embodiment of the present invention provides a waste heat utilization system for the chassis of a polycrystalline silicon reduction furnace, which can improve the utilization rate of low-quality steam and avoid steam venting and waste; the low-grade chassis waste heat is converted into medium-pressure steam, which improves the quality of chassis waste heat, reduces the amount of steam purchased, and lowers energy costs.

[0047] An embodiment of the present invention provides a waste heat utilization system for the chassis of a polycrystalline silicon reduction furnace, which can use low-grade hot water at a suitable temperature as cooling water for the chassis, thereby reducing grounding faults in the reduction furnace and improving the stability of the furnace operation.

[0048] An embodiment of the present invention proposes a waste heat utilization system for the chassis of a polycrystalline silicon reduction furnace, which increases the controllability of waste heat in the reduction furnace and improves the stability of the entire thermal energy system; it makes full use of the low-grade hot water that carries away the waste heat from the chassis of the reduction furnace in stages, achieving the goal of energy saving and consumption reduction, while reducing the failure rate of chassis hot water affecting the operation of the reduction furnace, improving the stable operation of the reduction furnace, thereby further reducing production costs and improving system operating efficiency.

[0049] Preferably, the control system is connected to the heat pump unit 20 and is used to control the start-up or shutdown of the heat pump unit 20, which helps to achieve automated control.

[0050] Preferably, the chassis water tank 1 is provided with a low-pressure steam inlet 29, which can appropriately increase the temperature when the reduction furnace is started, which is beneficial to the start-up of the reduction furnace.

[0051] Preferably, the output end of the steam compressor 22 is connected to a medium-pressure steam pipeline network to deliver the generated medium-pressure steam to other processes.

[0052] Preferably, the low-pressure steam equipment 24 is provided with an inlet 25 for inputting low-pressure steam to ensure the stable operation of the low-pressure steam equipment 24.

[0053] To further clarify, while the terms "first," "second," etc., may be used herein to describe various elements, these terms should not limit the elements. These terms are used only to distinguish one element from another. For example, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element; these terms are used only to distinguish one element from another. This does not depart from the scope of the exemplary embodiments. Similarly, "element one," "element two," and so on do not represent the order of elements; these terms are used only to distinguish one element from another. As used herein, the term "and / or" includes any and all combinations of one or more associated listed items.

[0054] In the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0055] All standard parts used in this invention can be purchased from the market, and irregular parts can be customized according to the description and drawings. The specific connection methods of each part adopt conventional methods such as bolts, rivets, and welding that are mature in the prior art. The machinery, parts and equipment adopt conventional models in the prior art, and the circuit connection adopts conventional connection methods in the prior art, which will not be described in detail here.

[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A waste heat utilization system for the chassis of a polycrystalline silicon reduction furnace, characterized in that, Includes: chassis water tank, chassis water pump, reduction furnace chassis, lithium bromide unit, heating heat exchanger, TCS preheater, TCS vaporizer, heat pump unit, steam compressor, condensate collection tank, condensate pump and control system; The chassis water tank is used to store chassis cooling water; The input end of the chassis water pump is connected to the chassis water tank; The cooling water inlet of the reduction furnace chassis is connected to the output end of the chassis water pump; the cooling water outlet of the reduction furnace chassis is connected to a main water supply pipe; a thermometer is installed on the main water supply pipe; The input end of the lithium bromide generator unit is connected to the main water supply pipe via a pipeline; the output end of the lithium bromide generator unit is connected to the chassis water tank. The input end of the heating water heater is connected to the main water supply pipe through pipe two; the output end of the heating water heater is connected to the chassis water tank. The input end of the TCS preheater is connected to the main water supply pipe via pipe three; the output end of the TCS preheater is connected to the chassis water tank; a flow meter is installed on pipe three; a flow regulating valve is installed on pipe three. The TCS vaporizer is connected to the TCS preheater via pipe four. The heat pump unit is connected to the main water supply pipe through pipe five; a flow meter two is installed on pipe five; a flow regulating valve two is installed on pipe five; The input end of the steam compressor is connected to the steam outlet of the heat pump unit via pipe six; The inlet of the low-pressure steam equipment is connected to the steam outlet of the heat pump unit via pipe seven; the cooling water outlet of the heat pump unit is connected to the chassis water tank. The condensate collection tank is connected to the low-pressure steam equipment via pipe eight. The input end of the condensate pump is connected to the condensate collection tank; the output end of the condensate pump is connected to the chassis water tank. The control system is connected to the thermometer; The control system is connected to the flow regulating valve. The control system is connected to the second flow regulating valve; The control system is connected to the flow meter. The control system is connected to the flow meter.

2. The waste heat utilization system for the polycrystalline silicon reduction furnace chassis according to claim 1, characterized in that, The control system is connected to the heat pump unit and is used to control the start-up or shutdown of the heat pump unit.

3. The waste heat utilization system for the polycrystalline silicon reduction furnace chassis according to claim 1, characterized in that, The chassis water tank is equipped with a low-pressure steam inlet.

4. The waste heat utilization system for the polycrystalline silicon reduction furnace chassis according to claim 1, characterized in that, The output end of the steam compressor is connected to the medium-pressure steam pipeline network.

5. The waste heat utilization system for the polycrystalline silicon reduction furnace chassis according to claim 1, characterized in that, The low-pressure steam equipment is equipped with an input port two for inputting low-pressure steam.

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