CN108726520B - Waste heat recovery system of reducing furnace - Google Patents

Abstract

The invention discloses a reducing furnace waste heat recovery system, which comprises a reducing furnace chassis, wherein a cooling cavity is arranged on the reducing furnace chassis, a cooling water inlet pipe and a cooling water outlet pipe are connected to the cooling cavity, and a tail gas heat exchange device is further arranged on a cooling water outlet pipe pipeline; and a tail gas pipe is further arranged on the chassis of the reduction furnace and is communicated with the tail gas heat exchange device. And (3) guiding the cooling water passing through the chassis cooling cavity into the tail gas heat exchange device, heating the cooling water by virtue of the reducing furnace chassis, and then guiding the cooling water into the jacket pipe to exchange heat with the tail gas with higher temperature. The cooling and heat absorption are carried out step by adopting a set of water circulation system, so that the cooling requirements of the chassis and tail gas of the reduction furnace can be met simultaneously, and the number of equipment is reduced; the single cooling water source is convenient for the waste heat recovery equipment to more efficiently recycle heat.

Description

A kind of reduction furnace waste heat recovery system

Technical field

The invention relates to the field of polycrystalline silicon production, and in particular to a reduction furnace waste heat recovery system.

Background technique

The polysilicon reduction furnace is the core equipment for producing final products in polysilicon production, and is also a key link in determining system production capacity and energy consumption. Reducing polysilicon energy consumption and production costs, and improving product quality and production efficiency are effective measures for polysilicon manufacturers to improve product competitiveness.

At present, the reduction process of various polysilicon manufacturers uses medium-temperature water (temperature between 50 and 90°C) to cool the chassis of the reduction furnace. The water from the chassis is cooled by circulating water through a plate heat exchanger or cooled by a lithium bromide hot water refrigeration unit and then recycled. To cool down the tail gas, high-temperature hot water (temperature greater than 120°C) is used alone for cooling, and then the heated high-temperature hot water is flashed into a certain pressure of saturated steam in a flash tank. The tail gas cooling water after flashing continues to be recycled. .

The problem is that the chassis cooling system and the exhaust cooling system each use a cooling water circulation system for cooling, which requires a large number of equipment and high construction costs. At the same time, cooling through plate heat exchangers will not only consume a large amount of circulating water, but also cause a large amount of energy loss, resulting in waste of heat and increased energy consumption.

Contents of the invention

In view of this, this application provides a reduction furnace waste heat recovery system, which diverts the cooling water passing through the cooling cavity of the chassis to the exhaust gas heat exchange device. After relying on the reduction furnace chassis to heat the cooling water, the cooling water is then introduced into the jacket. The tube conducts heat exchange with the higher temperature exhaust gas. Using a water circulation system to cool and absorb heat step by step can simultaneously meet the cooling needs of the reduction furnace chassis and exhaust gas, simplifying the number of equipment; a single source of cooling water facilitates more efficient heat recovery and utilization by the waste heat recovery equipment.

In order to solve the above technical problems, the technical solution provided by the present invention is a reduction furnace waste heat recovery system, which includes a reduction furnace chassis. The reduction furnace chassis is provided with a cooling chamber, and the cooling chamber is connected to a cooling water inlet pipe and a cooling chamber. Water outlet pipe, the cooling water outlet pipe is also provided with an exhaust gas heat exchange device; the reduction furnace chassis is also provided with an exhaust gas pipe, and the exhaust pipe is connected with the exhaust gas heat exchange device.

Preferably, the exhaust gas heat exchange device includes an exhaust gas jacketed pipe and an exhaust gas cooler. When the gas in the exhaust gas pipe flows, it first passes through the exhaust gas jacketed pipe and then passes through the exhaust gas cooler; the water in the cooling water outlet pipe flows It first passes through the exhaust gas cooler and then through the exhaust gas jacket pipe.

Preferably, the cooling water outlet pipe is provided with no less than two water outlets on the exhaust gas cooler, and the distance between the water outlets and the water inlet of the cooling water outlet pipe on the exhaust gas cooler increases in sequence.

Preferably, the cooling water outlet pipe is provided with a temperature monitoring device on the pipeline between the exhaust gas jacket pipe and the exhaust gas cooler for monitoring the temperature of the cooling water entering the exhaust gas jacket pipe; the water outlets are equipped with Electronic valves are used to control the cooling water in the exhaust gas cooler to flow out from different outlets; the temperature monitoring device and the electronic valve are both electrically connected to the main control module, and the main control module is used to receive the water temperature sent by the temperature monitoring device. And adjust the opening and closing of the electronic valve.

Preferably, a cooling water pump is provided on the cooling water inlet pipe, and the cooling water pump is electrically connected to the main control module.

Preferably, the cooling water outlet pipe after passing through the tail gas heat exchange device is connected to the flash tank, and the cooling water outlet pipe is provided with a pressure regulating valve on the pipeline between the tail gas heat exchange device and the flash tank.

Preferably, the flash tank is connected to a cooling water inlet pipe, and a cooling water pump is provided on the cooling water inlet pipe.

Preferably, the flash tank is provided with a steam pipe for transporting high-temperature steam and a condensed water pipe for returning water generated by condensation of the steam.

Preferably, the steam pipeline is provided with a flash tank pressure regulating valve.

Preferably, the condensate water pipeline is provided with a flash tank liquid level regulating valve.

Compared with the existing technology, the beneficial effects of this application are:

The cooling water passing through the cooling chamber is directed to the exhaust gas heat exchange device. After the cooling water is heated by the reduction furnace chassis, the cooling water is then introduced into the jacket tube to exchange heat with the higher temperature exhaust gas. Through the hierarchical heat exchange of a water circulation system, the waste heat of the reduction furnace chassis and the tail gas pipe can be absorbed simultaneously, thereby improving the heat recovery efficiency.

Although the cooling water flowing out from the cooling cavity has absorbed heat from the chassis, the temperature is still low. Directly introducing it into the exhaust gas jacket pipe to exchange heat with the high-temperature exhaust gas can easily cause uneven thermal expansion due to the excessive temperature difference between water and air, causing equipment damage or damage. Heat absorption cannot be maximized. Therefore, an exhaust gas cooler is set up to conduct a heat exchange between the medium-temperature exhaust gas passing through the exhaust gas jacket tube and the water just flowing out of the cooling chamber, and the heat in the exhaust gas is further recovered; at the same time, the cooling water is heated by the medium-temperature exhaust gas, and the temperature rises, and can be A more suitable temperature enters the exhaust jacketed pipe for heat exchange, and there will be no excessive temperature difference.

The distance between the water outlet and the water inlet of the cooling water outlet pipe on the exhaust gas cooler mentioned here refers to the length of the cooling water pipe flowing in the exhaust gas cooler. The longer the distance the cooling water pipe flows in the exhaust gas cooler, the more sufficient the heat exchange between the cooling water and the exhaust gas will be, and the higher the temperature of the outgoing cooling water will be. Multiple water outlets are set up on the exhaust gas cooler, and different water outlets are connected according to the current required inlet water temperature requirements, so that the temperature of the cooling water entering the exhaust gas jacket can be adjusted, effectively ensuring the smooth operation and heat of the equipment. of full recycling.

The main control module has a temperature threshold preset; the temperature monitoring device monitors the temperature of the cooling water entering the exhaust jacket pipe and sends it to the main control module. When the water temperature value received by the main control module exceeds the threshold, the electronic valve is controlled to open or close so that the cooling water flows out from the appropriate outlet and flows into the exhaust jacketed pipe at a suitable water temperature.

Since the cooling water passes through the cooling chamber and the exhaust gas heat exchange device successively, if the flow rate of the cooling water is changed, the heat exchange efficiency of the cooling chamber and the exhaust gas heat exchange device will change, making it difficult to adjust. After setting up an exhaust gas cooler with multiple water outlets, after the cooling water pump adjusts the water flow under the control of the main control module, the electronic valve on the exhaust gas cooler can also be adjusted accordingly, so that the heat in the cooling cavity The exchange efficiency and the heat exchange efficiency in the exhaust gas heat exchange device can be set and adjusted relatively independently, so that the entire system can maintain better operating conditions.

After the cooling water absorbs heat from the cooling chamber and the exhaust gas heat exchange device, it enters the flash tank through the pressure regulating valve, where a large amount of high-temperature steam flashes out in the flash tank and is exported, thereby realizing heat recovery and utilization.

The high-temperature steam turns into condensed water after dissipating internal energy by performing work on the outside. The condensed water is redirected back to the flash tank and connected to the cooling water pipeline to realize the recycling of water resources.

The output steam volume is controlled by the flash tank pressure regulating valve to stabilize the pressure in the flash tank within a suitable range.

The amount of return cooling water is controlled by the flash tank liquid level regulating valve to ensure that the liquid level in the flash tank is sufficient but does not occupy the volume space in the flash tank excessively, leaving room for flash evaporation of water flowing in from the tail gas jacket pipe. enough space.

Description of drawings

Figure 1 is a schematic structural diagram of the reduction furnace waste heat recovery system of the present invention;

Figure 2 is a schematic diagram of the electrical connection relationship of the reduction furnace waste heat recovery system of the present invention;

Figure 3 is a schematic structural diagram of the exhaust gas cooler of the reduction furnace waste heat recovery system of the present invention.

Reference signs: reduction furnace chassis 11, cooling chamber 111, tail gas pipe 12, cooling water inlet pipe 21, cooling water pump 22, cooling water outlet pipe 3, water outlet 31, water inlet 32, temperature monitoring device 33, tail gas jacket pipe 41. Tail gas cooler 42, flash tank 5, pressure regulating valve 51, steam pipeline 52, flash tank pressure regulating valve 521, condensate pipe 53, flash tank level regulating valve 531, main control module 6.

Detailed ways

In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Please refer to the accompanying drawings. The embodiment of the present invention provides a reduction furnace waste heat recovery system, which includes a reduction furnace chassis 11. The reduction furnace chassis 11 is provided with a cooling cavity 111. The cooling cavity 111 is connected to a cooling water inlet pipe 21 and a cooling water outlet. The water pipe 3 and the cooling water outlet pipe 3 are also provided with an exhaust gas heat exchange device; the reduction furnace chassis 11 is also provided with an exhaust gas pipe 12, and the exhaust pipe 12 is connected with the exhaust gas heat exchange device. The exhaust gas heat exchange device includes an exhaust gas jacketed pipe 41 and an exhaust gas cooler 42. When the gas in the exhaust gas pipe 12 flows, it first passes through the exhaust gas jacketed pipe 41 and then passes through the exhaust gas cooler 42; when the water in the cooling water outlet pipe 3 flows, It first passes through the exhaust gas cooler 42 and then passes through the exhaust gas jacket pipe 41 .

The cooling water outlet pipe 3 is provided with three water outlets 31 on the exhaust gas cooler 42. The distance between the water outlets 31 and the water inlet 32 of the cooling water outlet pipe 3 on the exhaust gas cooler 42 increases in sequence. The cooling water outlet pipe 3 is provided with a temperature monitoring device 33 on the pipeline between the exhaust gas jacket pipe 41 and the exhaust gas cooler 42 for monitoring the temperature of the cooling water entering the exhaust gas jacket pipe 41; the water outlets 31 are equipped with electronic The valve is used to control the cooling water in the exhaust gas cooler 42 to flow out from different outlets 31; the temperature monitoring device 33 and the electronic valve are both electrically connected to the main control module 6, and the main control module 6 is used to receive signals from the temperature monitoring device 33. water temperature and adjust the opening and closing of the electronic valve. A cooling water pump 22 is provided on the cooling water inlet pipe 21 , and the cooling water pump 22 is electrically connected to the main control module 6 .

The cooling water outlet pipe 3 after passing through the tail gas jacket pipe 41 is connected to the flash tank 5. The flash tank 5 is connected to the cooling water inlet pipe 21. The cooling water outlet pipe 3 is between the tail gas jacket pipe 41 and the flash tank 5. There is a pressure regulating valve 51 on the pipeline. The flash tank 4 is provided with a steam pipe 52 for transporting high-temperature steam and a condensed water pipe 53 for returning water generated by condensation of the steam. The steam pipeline 52 is provided with a flash tank pressure regulating valve 521, and the condensate water pipeline 53 is provided with a flash tank liquid level regulating valve 531.

When the system is running, the cooling water pump 22 drives the cooling water to flow in the cooling water pipe. The cooling water flows from the cooling water inlet pipe 21 into the cooling cavity 111 of the reduction furnace chassis 11, exchanges heat with the reduction furnace chassis 11, and takes away the heat accumulated by the reduction furnace chassis 11 due to the thermal radiation in the reduction furnace. The cooling water that has absorbed the heat in the reduction furnace chassis 11 flows out from the cooling water outlet pipe 3. At this time, the cooling water temperature is less than 90°C. The outflowing cooling water enters the exhaust gas cooler 42, exchanges heat with the medium-temperature exhaust gas, and the water temperature is increased. It flows out from the set water outlet 31 according to the opening and closing of the electronic valve, and is introduced into the exhaust gas jacket pipe 41 to mix with the high-temperature exhaust gas. The exhaust gas undergoes heat exchange. At this time, the cooling water entering the exhaust gas jacket pipe 41 has a boiling point increased by the pressure of the container, and the temperature is about 120°C. What needs to be explained here is that the exhaust gas is high-temperature exhaust gas when it comes out of the reduction furnace. After heat exchange in the exhaust gas jacket pipe 41, it becomes medium-temperature exhaust gas, and then after further heat exchange in the exhaust gas cooler 42, it becomes low-temperature exhaust gas. The air pipe 12 is discharged; the high temperature, medium temperature and low temperature mentioned above are the relative temperatures of the exhaust gas at different stages. The cooling water absorbs heat from the tail gas jacket pipe 41 and then enters the flash tank 5 through the pressure regulating valve 51. The temperature of the cooling water at this time is above 150°C. The cooling water in the high temperature and high pressure state drops suddenly in the flash tank due to the pressure drop. , flash evaporation occurs to generate high-temperature steam, which is sent out through the steam pipe 52 for utilization. The condensed water condensed after the steam performs work is led back to the flash tank 5 through the condensed water pipe 53, and enters the cooling water circulation system again through the cooling water inlet pipe 21 to continuously cool the reduction furnace chassis.

When the temperature monitoring device 33 detects that the temperature of the water flowing into the exhaust gas jacket pipe 41 does not meet the requirements, the main control module 6 controls the electronic valve of the water outlet 31 to open or close, so that the heat exchange rate of the cooling water in the exhaust gas cooler 42 is improved. Change, thereby realizing the adjustment and control of the cooling water temperature flowing into the exhaust gas clamping sleeve 41, ensuring the stable and efficient operation of the waste heat recovery system.

Please refer to Figure 3. According to the pipeline distance between the water outlet 31 and the water inlet 32, set the water outlet 31 as the water outlets 31a, 31b, and 31c from the nearest to the far. Under normal circumstances, the electronic valve of the water outlet 31b is opened, and the water outlet 31b is opened. The electronic valves of the water inlet 31a and the water outlet 31c are in a closed state. When the cooling water temperature received by the main control module 6 from the temperature monitoring device 33 is too low, it controls the electronic valve of the water outlet 31b to close and the electronic valve of the water outlet 31c to open. Because the cooling water flows over a longer distance in the exhaust gas cooler 42 before flowing out from the water outlet 31c, and the heat exchange with the exhaust gas is more complete, the cooling water flowing out from the water outlet 31c has a higher temperature than the cooling water flowing out from the water outlet 31b. . When the cooling water temperature received by the main control module 6 from the temperature monitoring device 33 is too high, it controls the electronic valve of the water outlet 31b to close and the electronic valve of the water outlet 31a to open. Because the cooling water has a shorter flow distance in the exhaust gas cooler 42 before flowing out from the water outlet 31a, and the degree of heat exchange with the exhaust gas is lower, the temperature of the cooling water flowing out from the water outlet 31a is lower than that of the cooling water flowing out from the water outlet 31b. water. This system is used to control the degree of heat exchange between the cooling water and the exhaust gas, thereby adjusting the temperature of the cooling water entering the exhaust gas holding sleeve 41.

The above are only preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be regarded as limitations of the present invention, and the protection scope of the present invention should be subject to the scope defined by the claims. For those of ordinary skill in the art, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims (5)

1. A reduction furnace waste heat recovery system, including a reduction furnace chassis, characterized in that a cooling cavity is provided on the reduction furnace chassis, and a cooling water inlet pipe and a cooling water outlet pipe are connected to the cooling cavity. The water outlet pipe is also provided with an exhaust gas heat exchange device; the reduction furnace chassis is also provided with an exhaust gas pipe, and the exhaust pipe is connected with the exhaust gas heat exchange device; The exhaust gas heat exchange device includes an exhaust gas jacket tube and an exhaust gas cooler. When the gas in the exhaust gas pipe flows, it first passes through the exhaust gas jacket tube and then passes through the exhaust gas cooler; when the water in the cooling water outlet pipe flows, it first passes through The exhaust gas cooler then passes through the exhaust gas jacket pipe; The cooling water outlet pipe is provided with no less than two water outlets on the exhaust gas cooler, and the distance between the water outlets and the water inlet of the cooling water outlet pipe on the exhaust gas cooler increases in sequence; The cooling water outlet pipe is equipped with a temperature monitoring device on the pipeline between the exhaust gas jacket pipe and the exhaust gas cooler, which is used to monitor the temperature of the cooling water entering the exhaust gas jacket pipe; the water outlets are equipped with electronic valves. It is used to control the cooling water in the exhaust gas cooler to flow out from different outlets; the temperature monitoring device and the electronic valve are both electrically connected to the main control module, and the main control module is used to receive the water temperature sent by the temperature monitoring device and control the electronic valve. Adjust the opening and closing of the valve; The cooling water outlet pipe after passing through the tail gas heat exchange device is connected to the flash tank. The cooling water outlet pipe is provided with a pressure regulating valve on the pipeline between the tail gas heat exchange device and the flash tank. 2. The reduction furnace waste heat recovery system according to claim 1, characterized in that a cooling water pump is provided on the cooling water inlet pipe, and the cooling water pump is electrically connected to the main control module. 3. The reduction furnace waste heat recovery system according to claim 1, wherein the flash tank is connected to a cooling water inlet pipe, and a cooling water pump is provided on the cooling water inlet pipe. 4. The reduction furnace waste heat recovery system according to claim 3, wherein the flash tank is provided with a steam pipe for transporting high-temperature steam and a condensate water pipe for refluxing water generated by steam condensation. . 5. The reduction furnace waste heat recovery system according to claim 4, wherein the steam pipeline is provided with a flash tank pressure regulating valve, and the condensate water pipeline is provided with a flash tank liquid level regulating valve.