Energy-saving control system for reducing tail gas recovery

Abstract

The utility model discloses an energy -conserving control system of reduction tail gas recovery, including reduction furnace, condensing unit, adsorption tower, cold water heat exchanger and hot water heat exchanger, the outer periphery of adsorption tower is equipped with the outer coil, the water outlet of desalted water tank is divided into two ways, one way passes through the pipeline and is communicated with the import of cold water pump, and the export of cold water pump is communicated with the hot medium import of cold water heat exchanger through the pipeline, and the hot medium export of cold water heat exchanger is communicated with the water inlet of outer coil through the pipeline, another way passes through the pipeline and is communicated with the import of hot water pump, and the export of hot water pump is communicated with the cold medium import of hot water heat exchanger through the pipeline, and the cold medium export of hot water heat exchanger is communicated with the water inlet of outer coil through the pipeline. Advantages lie in: when resolving, through the heat exchange effect of hot water heat exchanger, through the flow of high pressure steam and low pressure steam of adjusting into hot water heat exchanger, and then adjust the desalted water outlet temperature in hot water heat exchanger, can save high pressure steam, reduce energy loss.

Description

Technical fields:

[0001] This utility model relates to the field of exhaust gas recovery, specifically to an energy-saving control system for recovering and restoring exhaust gas. Background technology:

[0002] During the production of polysilicon, the reduction furnace generates a large amount of exhaust gas. Typically, the exhaust gas first enters a condenser to condense the chlorosilanes (mainly silicon tetrachloride, silicon trichloride, and dichlorosilane) contained in the exhaust gas. The non-condensable gas then enters an adsorption tower, where activated carbon adsorbs gaseous impurities (methane, hydrogen chloride) from the non-condensable gas. After prolonged operation, the adsorbed gaseous impurities in the adsorption tower need to be released. This requires switching from a low-temperature, high-pressure adsorption process to a high-temperature, low-pressure desorption process. This often necessitates a prolonged supply of large amounts of high-pressure steam to maintain the set temperature. However, after the switch, maintaining the set temperature is sufficient; continuous supply of large amounts of high-pressure steam is unnecessary. Since enterprises typically use a single high-pressure steam heat source with a continuous steam supply, this process leads to unnecessary waste of high-pressure steam. Furthermore, when steam demand is high, manual reduction is required. However, frequent manual adjustments to steam consumption have the following disadvantages: they involve numerous operations for central control and on-site personnel, and sometimes require temporary hoses to drain condensate, which is time-consuming, labor-intensive, and poses safety hazards. Frequent manual steam adjustments can negatively impact steam-generating equipment such as electrode boilers, pressurizing equipment like steam compressors, and related desuperheating and pressure-reducing devices. In severe cases, this can cause equipment shutdowns. Additionally, frequent adjustments to steam output result in energy loss. Moreover, a failure of the steam heat source necessitates an emergency shutdown, affecting the system's reliability and stability. Utility Model Content:

[0003] In order to solve the above problems, the purpose of this utility model is to provide an energy-saving control system for the recovery of exhaust gas.

[0004] This utility model is implemented by the following technical solution:

[0005] An energy-saving control system for recovering reduction tail gas includes a reduction furnace, a condensing unit, an adsorption tower unit, and a hot water heat exchanger.

[0006] The exhaust gas outlet of the reduction furnace is connected to the air inlet of the condenser unit via a pipeline. The exhaust gas outlet of the condenser unit is connected to the air inlet of the compressor via a pipeline. The exhaust gas outlet of the compressor is connected to the air inlet of the adsorption tower via a pipeline. The exhaust gas outlet of the adsorption tower is connected to the hydrogen inlet of the reduction furnace via a pipeline.

[0007] An external coil is installed around the periphery of the adsorption tower. The outlet of the demineralized water tank is divided into two paths. One path is connected to the inlet of the cold water pump via a pipeline. The outlet of the cold water pump is connected to the inlet of the heat medium of the cold water heat exchanger via a pipeline. The outlet of the heat medium of the cold water heat exchanger is connected to the inlet of the external coil via a pipeline. The other path is connected to the inlet of the hot water pump via a pipeline. The outlet of the hot water pump is connected to the inlet of the cold medium of the hot water heat exchanger via a pipeline. The outlet of the cold medium of the hot water heat exchanger is connected to the inlet of the external coil via a pipeline. The outlet of the external coil is connected to the inlet of the demineralized water tank via a pipeline.

[0008] The steam outlets of both the high-pressure steam pipeline and the low-pressure steam pipeline are connected to the heat medium inlet of the hot water heat exchanger via pipelines, and the heat medium outlet of the hot water heat exchanger is connected to the inlet of the drain pipe.

[0009] A high-pressure steam regulating valve and a low-pressure steam regulating valve are respectively installed at the steam outlet of the high-pressure steam pipeline and the low-pressure steam pipeline; a temperature sensor is installed at the cold medium outlet of the hot water heat exchanger; a cold water valve is installed at the hot medium outlet of the cold water heat exchanger, and a hot water valve is installed at the cold medium outlet of the hot water heat exchanger.

[0010] The signal output terminal of the temperature sensor is connected to the signal input terminal of the controller, and the signal output terminal of the controller is connected to the signal input terminals of the cold water valve, the hot water valve, the high-pressure steam regulating valve, and the low-pressure steam regulating valve, respectively.

[0011] Furthermore, it also includes a high-pressure flash tank and a low-pressure flash tank; the steam condensate outlet of the condensate drain pipe is divided into two paths, which are respectively connected to the inlet of the high-pressure flash tank and the low-pressure flash tank, and the steam outlet of the high-pressure flash tank and the low-pressure flash tank are respectively connected to the high-pressure steam pipeline and the low-pressure steam pipeline.

[0012] Advantages of this utility model:

[0013] This invention utilizes the heat exchange function of a hot water heat exchanger. By regulating the flow rates of high-pressure and low-pressure steam entering the heat exchanger, the outlet temperature of the demineralized water from the heat exchanger is adjusted, thereby providing the necessary heat to the adsorption tower. When the heat source requirement is low, the flow rate of high-pressure steam can be reduced as needed, saving high-pressure steam and reducing energy loss. The automatic adjustment of the high-pressure and low-pressure steam usage minimizes the impact on the main steam network, effectively reducing the frequent power adjustments required by related equipment to cope with fluctuations in the steam network, thus extending the service life of the equipment. Simultaneously, ensuring a continuous steam heat source through the heat exchanger improves fault tolerance and effectively prevents system failure due to a problem with a single heat source. Attached image description:

[0014] Figure 1 This is a schematic diagram of the system connection in this embodiment;

[0015] Figure 2 This is the control principle diagram of this embodiment.

[0016] In the diagram: 1. Reduction furnace; 2. Condensing unit; 3. Adsorption tower; 4. Hot water heat exchanger; 5. High-pressure flash tank; 6. Low-pressure flash tank; 7. External coil; 8. Demineralized water tank; 9. High-pressure steam pipeline; 10. Low-pressure steam pipeline; 11. Drainage pipe; 12. Cold water valve; 13. Cold water heat exchanger; 14. Hot water valve; 15. High-pressure steam regulating valve; 16. Low-pressure steam regulating valve; 17. Temperature sensor; 18. Compressor; 19. Controller; 20. Cold water pump; 21. Hot water pump. Detailed implementation method:

[0017] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0018] Example 1:

[0019] like Figures 1 to 2 As shown, an energy-saving control system for recovering reduction tail gas includes a reduction furnace 1, a condenser unit 2, an adsorption tower 3, a cold water heat exchanger 13, and a hot water heat exchanger 4; it also includes a high-pressure flash tank 5 and a low-pressure flash tank 6.

[0020] The exhaust outlet of the reduction furnace 1 is connected to the inlet of the condenser unit 2 via a pipeline. The outlet of the condenser unit 2 is connected to the inlet of the compressor 18 via a pipeline. The outlet of the compressor 18 is connected to the inlet of the adsorption tower 3 via a pipeline. The outlet of the adsorption tower 3 is connected to the hydrogen inlet of the reduction furnace 1 via a pipeline.

[0021] An external coil 7 is installed around the periphery of the adsorption tower 3. The outlet of the demineralized water tank 8 is divided into two paths. One path is connected to the inlet of the cold water pump 20 through a pipeline. The outlet of the cold water pump 20 is connected to the inlet of the hot medium of the cold water heat exchanger 13 through a pipeline. The outlet of the hot medium of the cold water heat exchanger 13 is connected to the inlet of the external coil 7 through a pipeline. The other path is connected to the inlet of the hot water pump 21 through a pipeline. The outlet of the hot water pump 21 is connected to the inlet of the cold medium of the hot water heat exchanger 4 through a pipeline. The outlet of the cold medium of the hot water heat exchanger 4 is connected to the inlet of the external coil 7 through a pipeline. The outlet of the external coil 7 is connected to the inlet of the demineralized water tank 8 through a pipeline.

[0022] The steam outlets of both the high-pressure steam pipeline 9 and the low-pressure steam pipeline 10 are connected to the heat medium inlet of the hot water heat exchanger 4 via pipelines, and the heat medium outlet of the hot water heat exchanger 4 is connected to the inlet of the drain pipe 11.

[0023] The condensate outlet of the drainage pipe 11 is divided into two paths, which are connected to the inlets of the high-pressure flash tank 5 and the low-pressure flash tank 6, respectively. The steam outlets of the high-pressure flash tank 5 and the low-pressure flash tank 6 are connected to the high-pressure steam pipeline 9 and the low-pressure steam pipeline 10, respectively.

[0024] High-pressure steam regulating valve 15 and low-pressure steam regulating valve 16 are respectively installed at the steam outlet of high-pressure steam pipeline 9 and low-pressure steam pipeline 10; temperature sensor 17 is installed at the cold medium outlet of hot water heat exchanger 4; cold water valve 12 is installed at the hot medium outlet of cold water heat exchanger 13, and hot water valve 14 is installed at the cold medium outlet of hot water heat exchanger 4.

[0025] The signal output terminal of temperature sensor 18 is connected to the signal input terminal of controller 19. The signal output terminal of controller 19 is connected to the signal input terminals of cold water valve 12, hot water valve 14, high-pressure steam regulating valve 15 and low-pressure steam regulating valve 16 respectively.

[0026] Job Description:

[0027] During the operation of reduction furnace 1, the exhaust gas enters condenser 2 to condense the chlorosilanes (mainly silicon tetrachloride, silicon trichloride, and dichlorosilane) contained in the exhaust gas. The non-condensable gas is then compressed by compressor 20 and enters adsorption tower 3, where activated carbon adsorbs gaseous impurities (methane, hydrogen chloride) from the non-condensable gas. The resulting high-purity hydrogen is then returned to reduction furnace 1 as feed gas to participate in the reaction again. After prolonged operation, adsorption tower 3 needs to be regenerated to release the adsorbed gaseous impurities. To ensure uninterrupted continuous operation of the system during the regeneration phase, 3 to 4 adsorption towers 3 are often connected in parallel, with at least one adsorption tower 3 always in standby mode.

[0028] When adsorption tower 3 is in adsorption mode, the openings of both the high-pressure steam regulating valve 15 and the low-pressure steam regulating valve 16 are adjusted to their minimum opening (1%) to prevent pipe freezing. The hot water valve 14 is closed, and the cold water valve 12 is opened, allowing the demineralized water cooled by the cold water heat exchanger 13 to enter the outer coil 7, keeping the water in the outer coil 7 at a low temperature, thus maintaining a low-temperature adsorption state inside adsorption tower 3. When switching to desorption mode, to meet the temperature requirements for state switching in adsorption tower 3, the cold water valve 12 is first closed, the hot water valve 14 is opened, and the opening of the low-pressure steam regulating valve 16 is increased to 60%, increasing the flow of low-pressure steam into the hot water heat exchanger 4 to heat the demineralized water entering the hot water heat exchanger 4. This ensures that the temperature of the newly entering water in the outer coil 7 is higher than the existing water temperature in the outer coil 7, gradually replacing the cold water in the outer coil 7 with the newly entered hot water. After 5 minutes, the opening of the high-pressure steam regulating valve 15 is... Gradually increase the pressure to 60%, and begin introducing a large amount of high-pressure steam to heat the demineralized water entering the hot water heat exchanger 4, thereby increasing the water temperature entering the external coil 7. When the temperature sensor 17 detects that the outlet water temperature of the hot water heat exchanger 4 reaches 180℃, stop increasing the opening of the high-pressure steam regulating valve 15, and the adsorption tower 3 begins desorption. The total desorption time is 200 minutes. During this period, the opening of the high-pressure steam regulating valve 15 and the low-pressure steam regulating valve 16 can be adjusted according to the outlet water temperature of the hot water heat exchanger 4. When the temperature exceeds 200℃, the opening of the high-pressure steam regulating valve 15 is reduced; when the temperature is below 185℃, the opening of the low-pressure steam regulating valve 16 is increased; when the temperature is below 180℃, the opening of the high-pressure steam regulating valve 15 is increased. Each adjustment is 10%, ensuring that as much low-pressure steam as possible is used for heating while meeting the outlet water temperature requirements, in order to save high-pressure steam. After the analysis is completed, the valve openings of both the high-pressure steam regulating valve 15 and the low-pressure steam regulating valve 16 are adjusted to their minimum opening (1%), and the hot water valve 14 is closed and the cold water valve 12 is opened, putting the adsorption tower 3 into standby mode. Furthermore, in this embodiment, high-pressure steam and low-pressure steam refer to relatively high and relatively low pressure, without strict pressure range limitations.

[0029] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. An energy-saving control system for recovering reduced exhaust gas, characterized in that, This includes reduction furnaces, condensing units, adsorption towers, chilled water heat exchangers, and hot water heat exchangers; The exhaust gas outlet of the reduction furnace is connected to the air inlet of the condenser unit via a pipeline. The exhaust gas outlet of the condenser unit is connected to the air inlet of the compressor via a pipeline. The exhaust gas outlet of the compressor is connected to the air inlet of the adsorption tower via a pipeline. The exhaust gas outlet of the adsorption tower is connected to the hydrogen inlet of the reduction furnace via a pipeline. An external coil is installed around the periphery of the adsorption tower. The outlet of the demineralized water tank is divided into two paths. One path is connected to the inlet of the cold water pump via a pipeline. The outlet of the cold water pump is connected to the inlet of the heat medium of the cold water heat exchanger via a pipeline. The outlet of the heat medium of the cold water heat exchanger is connected to the inlet of the external coil via a pipeline. The other path is connected to the inlet of the hot water pump via a pipeline. The outlet of the hot water pump is connected to the inlet of the cold medium of the hot water heat exchanger via a pipeline. The outlet of the cold medium of the hot water heat exchanger is connected to the inlet of the external coil via a pipeline. The outlet of the external coil is connected to the inlet of the demineralized water tank via a pipeline. The steam outlets of both the high-pressure steam pipeline and the low-pressure steam pipeline are connected to the heat medium inlet of the hot water heat exchanger via pipelines, and the heat medium outlet of the hot water heat exchanger is connected to the inlet of the drain pipe. A high-pressure steam regulating valve and a low-pressure steam regulating valve are respectively installed at the steam outlet of the high-pressure steam pipeline and the low-pressure steam pipeline; a temperature sensor is installed at the cold medium outlet of the hot water heat exchanger; a cold water valve is installed at the hot medium outlet of the cold water heat exchanger, and a hot water valve is installed at the cold medium outlet of the hot water heat exchanger. The signal output terminal of the temperature sensor is connected to the signal input terminal of the controller, and the signal output terminal of the controller is connected to the signal input terminals of the cold water valve, the hot water valve, the high-pressure steam regulating valve, and the low-pressure steam regulating valve, respectively.

2. The energy-saving control system for recovering reduced exhaust gas according to claim 1, characterized in that, It also includes a high-pressure flash tank and a low-pressure flash tank; the condensate outlet of the drainage pipe is divided into two paths, which are respectively connected to the inlet of the high-pressure flash tank and the low-pressure flash tank, and the steam outlet of the high-pressure flash tank and the low-pressure flash tank are respectively connected to the high-pressure steam pipeline and the low-pressure steam pipeline.

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