Two-stage heat exchange dead steam waste heat recovery system based on annular water curtain

Abstract

The invention belongs to the technical field of industrial waste heat recovery, and particularly relates to a two-stage heat exchange dead steam waste heat recovery system based on an annular water curtain, which comprises a first-stage condensation collection heat exchange module, a second-stage condensation collection heat exchange module, a first-stage flash cap and a second-stage flash cap, the first-stage condensation collection heat exchange module is connected with the second-stage condensation collection heat exchange module in series, the first-stage flash cap is installed on the top of the first-stage condensation collection heat exchange module, and the second-stage flash cap is installed on the top of the second-stage condensation collection heat exchange module. Through the two stages of annular water curtains, exhaust steam gradient condensation is achieved, pipeline specification matching and operation control are optimized, the heat exchange efficiency and the system stability are improved, the manual operation intensity is reduced, the problems that an existing single-stage heat exchange efficiency is low, the sealing performance is poor, and parameters are difficult to control are effectively solved, and the energy utilization rate is remarkably increased.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial waste heat recovery, in particular to a two-stage heat exchange steam exhaust waste heat recovery system based on an annular water curtain. BACKGROUND

[0002] In the industrial processes such as alumina production and chemical reactions, a large amount of high-temperature steam exhaust is generated after leaching. These steam exhausts carry a large amount of heat energy. If they are directly discharged, not only will it cause serious energy waste, but also it may lead to problems such as environmental temperature rise and steam condensate water discharge pollution.

[0003] The existing steam exhaust waste heat recovery technology mostly adopts a single-stage heat exchange structure, which has the defects of low heat exchange efficiency, insufficient steam exhaust condensation, and limited waste heat recovery utilization rate. The traditional single-stage heat exchange combined with simple condensation scheme can only realize single heat exchange of steam exhaust and a single temperature medium, and cannot capture the gradient heat energy of steam exhaust from 97℃ to medium and low temperature. As a result, more than 40% of medium and low temperature waste heat is discharged with the steam exhaust, causing serious energy waste. Moreover, the temperature of the medium after heat exchange is mostly lower than 60℃, which cannot meet the demand for hot water above 80℃ in production links such as red mud washing, and additional steam is needed for secondary heating, increasing the operating cost. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application provides a two-stage heat exchange steam exhaust waste heat recovery system based on an annular water curtain. Through a two-stage annular water curtain heat exchange structure, gradient condensation of steam exhaust and full recovery of waste heat are realized. At the same time, the pipeline connection mode and operation control process are optimized to improve the sealing, stability and waste heat recovery efficiency of the system.

[0005] To achieve the above purpose, the present application realizes the following technical scheme: A two-stage heat exchange steam exhaust waste heat recovery system based on an annular water curtain, comprising: a first condensation collection heat exchange module, a second condensation collection heat exchange module, a first flash cap and a second flash cap; The first condensation collection heat exchange module and the second condensation collection heat exchange module are connected in series, the first condensation collection heat exchange module is provided with the first flash cap at the top, and the second condensation collection heat exchange module is provided with the second flash cap at the top. The first flash cap is used to disperse the 97℃ high-temperature steam exhaust into uniform annular airflow, preliminarily reduce the temperature to 90-92℃ and separate the entrained liquid water droplets. The second flash cap is used to perform secondary flash evaporation on the 65℃ medium-temperature steam exhaust, reduce the humidity of the exhaust steam and regulate it into stable laminar flow.

[0006] Preferably, the first flash cap adopts an umbrella-shaped flow guide structure, and the second flash cap adopts a double-layer louvered condensation structure.

[0007] Preferably, the recovery system further comprises a medium conveying unit, the medium conveying unit comprising a booster pump, a hot water pump and an electric flow regulating valve; the booster pump is used to convey 35℃ medium-temperature filtrate water to the first-stage condensation collection heat exchange module at a flow rate of 8m³ / h, the hot water pump is used to convey 35℃ low-temperature filtrate water to the second-stage condensation collection heat exchange module at a flow rate of 10m³ / h; the electric flow regulating valve is respectively arranged corresponding to the first-stage condensation collection heat exchange module and the second-stage condensation collection heat exchange module, and is used to regulate the flow rate of the filtrate water.

[0008] Preferably, the recovery system further comprises a condensate water recovery unit, the condensate water recovery unit comprising an inclined condensate water collection cavity and a water seal tank; the inclined condensate water collection cavity is respectively arranged at the bottom of the first-stage condensation collection heat exchange module and the second-stage condensation collection heat exchange module, and is used to collect the condensate water generated by the two-stage modules; the water seal tank is in communication with the two-stage inclined condensate water collection cavities, and is used to receive the condensate water and recycle the condensate water for system water replenishment.

[0009] Preferably, the recovery system further comprises an intelligent monitoring unit, the intelligent monitoring unit comprising a PT100 high-precision temperature sensor and a DCS linkage control system; the PT100 high-precision temperature sensor is respectively installed at the inlet and outlet of the first-stage condensation collection heat exchange module and the second-stage condensation collection heat exchange module, and is used to collect temperature data; the DCS linkage control system is electrically connected with the temperature sensor and the electric flow regulating valve, and when the temperature deviation exceeds 5℃, the medium flow rate of the corresponding module is automatically adjusted.

[0010] Preferably, the first-stage condensation collection heat exchange module is sealingly connected with the outlet of the post-dissolution tank emptying pipe through a standard flange; the outlet of the first-stage condensation collection heat exchange module and the inlet of the second-stage condensation collection heat exchange module are connected through a DN100 seamless steel pipe.

[0011] Preferably, the condensate water pipes of the first-stage condensation collection heat exchange module and the second-stage condensation collection heat exchange module are both of DN50 specification, and the two condensate water pipes are connected to the water seal tank of DN150 specification after being combined.

[0012] A running method of a two-stage heat exchange steam exhaust waste heat recovery system based on an annular water curtain, which adopts the two-stage heat exchange steam exhaust waste heat recovery system based on an annular water curtain as described above, and comprises the following steps: S1, after the system is installed, 0.3MPa compressed air is introduced to maintain pressure for 30 minutes for sealing detection, and air is discharged after confirming that each interface has no leakage; S2, the booster pump is started to convey 35℃ medium-temperature filtrate water to the first-stage condensation collection heat exchange module, the hot water pump is started to convey 35℃ low-temperature filtrate water to the second-stage condensation collection heat exchange module after confirming that the annular water curtain in the first-stage module is stable through the observation window, and the electric flow regulating valve is adjusted to ensure that the flow rates of the two routes of filtrate water are stable. S3, after the elution tank is discharged, open the two-stage module exhaust inlet valve, monitor the temperature data through the DCS linkage control system, manually adjust the flow to make the first-stage module exhaust outlet temperature reach 65 DEG C, the filtrate water outlet temperature reach 50 DEG C, the second-stage module exhaust outlet temperature reach 50 DEG C, and the filtrate water outlet temperature reach 80 DEG C, and then switch to the automatic operation mode.

[0013] The application provides a two-stage heat exchange exhaust steam waste heat recovery system based on an annular water curtain. 1. The two-stage annular water curtain heat exchange structure is adopted, the contact area of the exhaust steam and the water curtain is large, and the contact time is sufficient, so that the gradient condensation of the exhaust steam is realized, and the waste heat recovery utilization rate is significantly improved; the temperature parameters of the first-stage module and the second-stage module are accurately matched, so that the step-by-step recovery of heat energy is ensured.

[0014] 2. The optimization of the DN50 specification condensate pipe and the DN150 specification collecting pipe ensures the smoothness of the condensate water conveying, and avoids the pipe blockage; after the system is installed, strict sealing detection is carried out, so that the leakage problem is effectively prevented, and the stability of the system operation is improved.

[0015] 3. The DCS linkage control system is used for realizing the real-time monitoring and automatic adjustment of the temperature, flow and other parameters, reducing the manual operation intensity, ensuring the accurate control of the operation parameters, and further improving the waste heat recovery effect. DETAILED DESCRIPTION

[0016] Figure 1 It is a system structure schematic view.

[0017] In the figure, 1 is an elution tank emptying pipe, 2 is a first-stage condensation collection heat exchange module, 3 is a second-stage condensation collection heat exchange module, 4 is an annular baffle, 5 is a condensate water collection cavity, 6 is a PT100 temperature sensor, 7 is an electric flow regulating valve, 8 is a booster pump, 9 is a hot water pump, 10 is a water seal tank, 11 is a DCS control cabinet, 12 is a first-stage flash cap, 13 is a second-stage flash cap, and 14 is a DCS control cabinet. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0019] Please refer to Figure 1The application provides a technical scheme: a two-stage heat exchange steam exhaust waste heat recovery system based on an annular water curtain.

[0020] In an embodiment of the application, the two-stage heat exchange steam exhaust waste heat recovery system based on an annular water curtain 1 comprises a first condensation collection heat exchange module, a second condensation collection heat exchange module, a first flash cap and a second flash cap.

[0021] The first condensation collection heat exchange module and the second condensation collection heat exchange module are connected in series, the first condensation collection heat exchange module is provided with the first flash cap at the top, and the second condensation collection heat exchange module is provided with the second flash cap at the top; the first flash cap is used for dispersing 97 DEG C high-temperature steam exhaust into uniform annular airflow, preliminarily reducing the temperature to 90-92 DEG C and separating liquid water droplets; the second flash cap is used for performing secondary flash evaporation on 65 DEG C medium-temperature steam exhaust, reducing the humidity of the exhaust steam and rectifying the exhaust steam into stable laminar flow. The first flash cap adopts an umbrella-shaped flow guide structure, and the second flash cap adopts a double-layer shutter type condensation structure.

[0022] The recovery system further comprises a medium conveying unit, a condensate water recovery unit and an intelligent monitoring unit, the medium conveying control unit comprises a booster pump, a hot water pump and an electric flow regulating valve; the booster pump is used for conveying 35 DEG C medium-temperature filtrate water to the first condensation collection heat exchange module at a flow rate of 8 m³ / h, and the hot water pump is used for conveying 35 DEG C low-temperature filtrate water to the second condensation collection heat exchange module at a flow rate of 10 m³ / h; the electric flow regulating valve is arranged corresponding to the first condensation collection heat exchange module and the second condensation collection heat exchange module respectively, and is used for regulating the flow rate of the filtrate water conveying.

[0023] The condensate water recovery unit comprises an inclined condensate water collection cavity and a water seal groove; the inclined condensate water collection cavity is arranged at the bottom of the first condensation collection heat exchange module and the second condensation collection heat exchange module respectively, and is used for collecting the condensate water generated by the two-stage module; the water seal groove is in communication with the two-stage inclined condensate water collection cavities, and is used for receiving the condensate water and recycling the condensate water for system water replenishment.

[0024] The intelligent monitoring unit comprises a PT100 high-precision temperature sensor and a DCS linkage control system; the PT100 high-precision temperature sensor is arranged at the inlet and outlet of the first condensation collection heat exchange module and the second condensation collection heat exchange module respectively, and is used for collecting temperature data; the DCS linkage control system is electrically connected with the temperature sensor and the electric flow regulating valve, and when the temperature deviation exceeds 5 DEG C, the medium flow rate of the corresponding module is automatically adjusted.

[0025] Both the primary condensing collection heat exchange module and the secondary condensing collection heat exchange module adopt a ring-shaped water curtain heat exchange structure, and a uniform water curtain is formed through a ring-shaped water distribution device to enable the exhaust steam to fully contact the water curtain and achieve efficient heat exchange condensation. An observation window is arranged on the module for real-time observation of the water curtain formation state; meanwhile, temperature sensors and flow sensors are provided for monitoring the exhaust steam inlet and outlet temperatures and the filtrate water inlet and outlet temperatures, respectively.

[0026] The condensing water pipes of the primary condensing collection heat exchange module and the secondary condensing collection heat exchange module both adopt a DN50 specification, which can meet the condensing water conveying requirements of the single-stage module and ensure smooth condensing water discharge. After the two DN50 specification condensing water pipes are combined, they are connected to a DN150 specification water seal tank. The DN150 specification pipe can adapt to the combined flow of the two condensing water pipes to avoid pipe congestion. The water seal tank is used to collect condensing water and also plays a sealing role to prevent air from entering the system and affecting the heat exchange effect.

[0027] The booster pump is used to deliver medium-temperature filtrate water to the primary condensing collection heat exchange module, and the hot water pump is used to deliver low-temperature filtrate water to the secondary condensing collection heat exchange module. The electric flow regulating valve is electrically connected with the DCS linkage control system for precise regulation of the flow of the two filtrate water pipes. The DCS linkage control system integrates the detection data of the temperature sensors and the flow sensors to realize real-time monitoring and automatic adjustment of the system operating parameters.

[0028] The operation method of the two-stage heat exchange exhaust steam waste heat recovery system based on a ring-shaped water curtain, which is realized based on the above system, specifically includes the following steps: S1. After the system is installed, 0.3MPa compressed air is introduced for 30 minutes for sealing detection, and after confirming that there is no leakage at each interface, the air is discharged; S2. The booster pump is started to deliver 35℃ medium-temperature filtrate water to the primary condensing collection heat exchange module. After confirming that the ring-shaped water curtain in the primary module is stable through the observation window, the hot water pump is started to deliver 35℃ low-temperature filtrate water to the secondary condensing collection heat exchange module. The electric flow regulating valve is adjusted to ensure stable flow of the two filtrate water pipes; S3. After the exhaust steam discharge of the elution tank is stable, the exhaust steam inlet valves of the two-stage module are opened. The temperature data are monitored through the DCS linkage control system, and the flow is manually adjusted to make the exhaust steam outlet temperature of the primary module reach 65℃, the filtrate water outlet temperature reach 50℃, the exhaust steam outlet temperature of the secondary module reach 50℃, and the filtrate water outlet temperature reach 80℃. Then, the system is switched to automatic operation mode.

[0029] Specifically; In step S1, after the system is installed, first, 0.3 MPa compressed air is introduced for pressure maintaining treatment, and the pressure maintaining time lasts for 30 minutes. In this process, the system pressure change is monitored through the pressure sensor, and it is checked whether there is leakage at the key positions such as the pipeline interfaces and the module connection. After confirming that there is no leakage, the compressed air in the system is completely discharged to ensure that the system sealing meets the operation requirements.

[0030] In step S2, the booster pump is started, and the 35℃ medium-temperature filtrate water is delivered to the primary condensing collection heat exchange module. The water curtain formation condition is observed through the observation window on the module. After confirming that the annular water curtain in the primary module is stable, the hot water pump is started, and the 35℃ low-temperature filtrate water is delivered to the secondary condensing collection heat exchange module. The electric flow regulating valve is adjusted through the DCS linkage control system, and the flow rate of the two filtrate water is stabilized in the set range according to the feedback data of the flow sensor, so as to provide stable water source conditions for subsequent heat exchange.

[0031] In step S3, after the exhaust steam discharge of the elution tank is stable, the exhaust steam inlet valves of the primary condensing collection heat exchange module and the secondary condensing collection heat exchange module are slowly opened, so that the exhaust steam enters the primary module and the secondary module in sequence for heat exchange. The DCS linkage control system is used to monitor the exhaust steam inlet and outlet temperature and the filtrate water inlet and outlet temperature of the two modules in real time, and the electric flow regulating valve is manually adjusted, so that the exhaust steam outlet temperature of the primary module reaches 65℃, the filtrate water outlet temperature reaches 50℃, the exhaust steam outlet temperature of the secondary module reaches 50℃, and the filtrate water outlet temperature reaches 80℃. When the temperature parameters are stable at the set values, the system is switched to the automatic operation mode, and the DCS linkage control system automatically adjusts the flow rate and the valve opening degree according to the detection data to maintain the stable operation of the system.

[0032] The application adopts a two-stage annular water curtain heat exchange structure, the contact area between the exhaust steam and the water curtain is large, and the contact time is sufficient, so that the gradient condensation of the exhaust steam is realized, and the waste heat recovery utilization rate is significantly improved. The temperature parameters of the primary module and the secondary module are accurately matched to ensure the step-by-step recovery of heat energy. Through the optimization of the DN50 specification condensing water pipe and the DN150 specification collection pipe, the smoothness of the condensing water delivery is ensured, and the pipe blockage is avoided. After the system is installed, the sealing detection is strictly performed to effectively prevent the leakage problem, improve the stability of the system operation, and realize the real-time monitoring and automatic adjustment of the temperature, flow rate and other parameters by means of the DCS linkage control system, reduce the manual operation intensity, ensure the accurate control of the operation parameters, and further improve the waste heat recovery effect.

[0033] In use: start the compressed air supply device, 0.3 MPa compressed air into the system, close all outlet valves, pressure 30 minutes. During the period through the DCS linkage control system to monitor the system pressure, while arranging personnel inspection of each interface, junction, confirm no pressure drop, no air leakage phenomenon, open the exhaust valve to exhaust air.

[0034] Start the booster pump, 35 ℃ medium temperature filtrate water through the pipeline to the first stage condensation collection heat exchange module, the operator through the observation window to observe the formation of the annular water curtain, after the water curtain uniform, stable, start the hot water pump, to the secondary condensation collection heat exchange module to transport 35 ℃ low temperature filtrate water. Through the DCS linkage control system to adjust the electric flow regulating valve, the filtrate water flow of the first module is adjusted to 5 m³ / h, and the filtrate water flow of the second module is adjusted to 8 m³ / h, and the flow is maintained stable.

[0035] When the dissolving after-tank exhaust pressure is stable at 0.1-0.2 MPa, slowly open the exhaust inlet valve of the two-stage module, and control the exhaust inlet flow to be 1000 m³ / h. Through the DCS linkage control system to monitor the temperature data, manually adjust the electric flow regulating valve, gradually adjust the filtrate water flow, so that the exhaust outlet temperature of the first module is stable at 65 ℃, the filtrate water outlet temperature is stable at 50 ℃, the exhaust outlet temperature of the second module is stable at 50 ℃, and the filtrate water outlet temperature is stable at 80 ℃. At this time, the system is switched to automatic operation mode, and the DCS linkage control system automatically adjusts the opening degree of the electric flow regulating valve according to the real-time feedback of the temperature sensor, so that the above temperature parameters are stable The condensate water generated by the two-stage module is collected through the DN50 condensate water pipe and then flows into the DN150 water seal tank. The condensate water in the water seal tank is periodically discharged and recycled for industrial production or heating scenarios.

[0036] Periodically check the sealing condition of the pipeline interface and valve to prevent leakage; clean the water outlet of the annular water distribution device to avoid impurities blocking the formation of the water curtain; periodically calibrate the temperature sensor and flow sensor to ensure accurate detection data; regularly maintain the booster pump and hot water pump, check the motor running state, lubricating oil level, etc., to ensure the normal operation of the power equipment.

[0037] The application adopts a two-stage annular water curtain heat exchange structure, the contact area of the exhaust steam and the water curtain is large, and the contact time is sufficient, so that the gradient condensation of the exhaust steam is realized, and the waste heat recycling rate is significantly improved; the temperature parameters of the first module and the second module are accurately matched, so that the heat energy is recycled step by step.

[0038] Secondly, through the optimization of DN50 specification condensate pipe and DN150 specification collection pipe, the smoothness of condensate water transportation is ensured, and pipe blockage is avoided; after the system is installed, strict sealing detection is carried out, leakage problem is effectively prevented, and the stability of system operation is improved. And with the help of DCS linkage control system, real-time monitoring and automatic adjustment of temperature, flow and other parameters are realized, the manual operation intensity is reduced, at the same time, the accurate control of operation parameters is ensured, and the waste heat recovery effect is further improved.

[0039] The foregoing description of specific exemplary embodiments of the application is presented for the purpose of illustration and description and is not intended to limit the application to the precise form described, and it is apparent that many modifications and variations are possible in light of the above teachings. The embodiments were chosen and described in order to explain the principles of the application and its practical application, to thereby enable others skilled in the art to best utilize the application, and various changes and modifications can be made thereto without departing from the intended scope of the application, as set forth in the appended claims.

Claims

1. A two-stage heat exchange waste steam heat recovery system based on an annular water curtain, characterized in that, include: Primary condensation heat exchange module, secondary condensation heat exchange module, primary flash cap and secondary flash cap; The primary condensation and heat exchange module and the secondary condensation and heat exchange module are connected in series. The primary flash cap is installed on the top of the primary condensation and heat exchange module, and the secondary flash cap is installed on the top of the secondary condensation and heat exchange module. The primary flash cap is used to disperse the 97°C high-temperature exhaust steam into a uniform annular airflow, initially cooling it to 90-92°C and separating entrained liquid water droplets. The secondary flash cap is used to perform secondary flash evaporation on the 65°C medium-temperature exhaust steam, reducing the humidity of the exhaust steam and rectifying it into a stable laminar flow.

2. The two-stage heat exchange waste steam recovery system based on an annular water curtain according to claim 1, characterized in that: The primary flash cap adopts an umbrella-shaped flow guiding structure, and the secondary flash cap adopts a double-layer louvered condensation structure.

3. The two-stage heat exchange waste steam recovery system based on an annular water curtain according to claim 1, characterized in that: The recycling system also includes a media conveying unit, which includes a booster pump, a hot water pump, and an electric flow regulating valve. The booster pump is used to convey 35°C medium-temperature filtrate water to the primary condensate collection heat exchange module at a flow rate of 8 m³ / h, and the hot water pump is used to convey 35°C low-temperature filtrate water to the secondary condensate collection heat exchange module at a flow rate of 10 m³ / h. The electric flow regulating valve is respectively set for the primary condensate collection heat exchange module and the secondary condensate collection heat exchange module, and is used to regulate the filtrate water conveying flow rate.

4. A two-stage heat exchange waste steam heat recovery system based on an annular water curtain according to claim 1, characterized in that: The recycling system also includes a condensate recovery unit, which includes an inclined condensate collection chamber and a water seal trough. The inclined condensate collection chamber is respectively located at the bottom of the primary condensate collection heat exchange module and the secondary condensate collection heat exchange module, and is used to collect the condensate generated by the two modules. The water seal trough is connected to the two inclined condensate collection chambers and is used to receive the condensate and reuse it for system makeup water.

5. A two-stage heat exchange waste steam heat recovery system based on an annular water curtain according to claim 1, characterized in that: The recycling system also includes an intelligent monitoring unit, which includes a PT100 high-precision temperature sensor and a DCS linkage control system. The PT100 high-precision temperature sensor is installed at the inlet and outlet of the primary condensation collection heat exchange module and the inlet and outlet of the secondary condensation collection heat exchange module to collect temperature data. The DCS linkage control system is electrically connected to the temperature sensor and the electric flow regulating valve. When the temperature deviation exceeds 5°C, it automatically adjusts the medium flow of the corresponding module.

6. A two-stage heat exchange waste steam recovery system based on an annular water curtain according to claim 1, characterized in that: The primary condensation collection heat exchange module is sealed to the outlet of the evacuation tank drain pipe via a standard flange; the outlet of the primary condensation collection heat exchange module and the inlet of the secondary condensation collection heat exchange module are connected by a DN100 seamless steel pipe.

7. A two-stage heat exchange waste steam heat recovery system based on an annular water curtain according to claim 4, characterized in that: The condensate pipes of both the primary condensate collection heat exchange module and the secondary condensate collection heat exchange module are DN50, and the two condensate pipes are connected to a DN150 water seal tank.

8. The operation method of the two-stage heat exchange waste steam recovery system based on an annular water curtain according to any one of claims 1-7, characterized in that, Includes the following steps: S1. After the system is installed, pressurize it with 0.3MPa compressed air for 30 minutes to test its sealing performance. After confirming that there are no leaks at any of the interfaces, release the air. S2. Turn on the booster pump to deliver 35°C medium-temperature filtrate water to the first-stage condensation heat exchange module. After confirming through the observation window that the annular water curtain in the first-stage module is stable, turn on the hot water pump to deliver 35°C low-temperature filtrate water to the second-stage condensation heat exchange module. Adjust the electric flow regulating valve to ensure that the flow rates of the two filtrate water lines are stable. S3. After the exhaust steam from the dissolution tank stabilizes, open the exhaust steam inlet valves of the two-stage modules. Monitor the temperature data through the DCS linkage control system and manually adjust the flow rate to make the exhaust steam outlet temperature of the first-stage module reach 65℃ and the filtrate water outlet temperature reach 50℃, and the exhaust steam outlet temperature of the second-stage module reach 50℃ and the filtrate water outlet temperature reach 80℃. Then switch to automatic operation mode.

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