Operating procedures for furnace drying

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Plan for heating the furnace before operation 1. Basis for preparation: PID diagram 2. Purpose of preparation: The purpose of heating is to remove the moisture contained in refractory bricks, plastic materials, and mortar, thereby preventing cracks and fragmentation in the refractory materials and creating favorable conditions for using the furnace once it is put into operation. 3. Requirements for the furnace 3.1 All equipment and pipelines for starting up the heating furnace must be installed. 3.2 After the installation and curing of the refractory materials are complete, carefully inspect the refractory materials inside the furnace; there should be no obvious cracks or defects, and they must be intact. Appropriate expansion gaps should be left as specified. 3.3 Clean all debris from the heating furnace before starting up, and seal the manholes. 3.4 The temperature and pressure control instruments related to the startup furnace have been put into use and are operating efficiently. 3.5 Natural gas has been led to the front of valve FG1014-3″, and a blind flange is installed behind the valve to isolate it from the gas system. 3.6 The temperature and pressure control instruments as well as the flame monitors related to the startup furnace have been put into use, and they are flexible and effective. The FSLL1257 interlock has been removed. 3.7 The gas pipeline has been purged with air and passed the airtightness test. 3.8 Verify that the air valves of the burners can be operated smoothly, that the chimney dampers can be moved freely, and that the valve positions indicated by the indicators correspond to the actual position of the dampers. 4. Oven heating step 4.1 Introduce nitrogen from the HV1050 drain point, and open all valves on the heating furnace’s gas pipeline to fill it with nitrogen for displacement, until the oxygen content is below 0.5%. 4.2 After nitrogen displacement is successful, open the stop valve on FG1014-3″, remove the blind plate behind the valve, and displace the nitrogen with natural gas; stop the process once the methane concentration exceeds 85%. 4.3 After the natural gas replacement is completed and approved, check that all shut-off valves along the gas pipeline up to the large and small burners are closed; any blind plates in place should be removed. 4.4 Fully open the chimney dampers and allow natural ventilation for 30 minutes. Use a combustible gas detector to check the level of combustible gases inside the furnace. 4.5 Adjust the opening of the chimney baffle to an appropriate level. 4.6 Confirm that the fuel gas main pipe of the furnace to be started up has been depressurized; monitor the pressure indicator PI-1152 on the main fuel gas pipe and the pressure indicator PI-1156 on the ignition line, to ensure that the gas pressure is reduced below the set value of 2.8 KPag specified by PSLL-1155. The PALL-1155 alarm on the DCS relates to the ignition wire, while the PSLL-1152 alarm is triggered by PALL-1152. 4.7 Close all burner cocks, ignition line valves, and vent valves. The operator confirms that all manual valves on the main line and the ignition line are closed. 4.8 The operator activates the on-site manual switch HS-1215, and the ignition procedure begins. The program checks that the manual stop functions HS-1257 and HS-1257A are working properly. If these conditions are met, the light XL-1215 on the panel at the site, which indicates that the ignition line fuel gas valve can be opened, will light up. 4.9 The logic program energizes the ignition line dual shut-off valve and the exhaust valve solenoid XY-1255. The stop valves XV-1255A/B are opened, the discharge valve XV1255C is closed, and fuel gas is used to pressurize the ignition line. Open the ball valve of the small burner and ignite it. 4.10 Within the next 3 minutes, this program will deactivate the low-low and high-high pressure interlock switches for the ignition line (PSLL-1155 and PSHH-1156). After 3 minutes, the program turns off the XL-1215 “OK” light and reactivates the low-low and high-high interlock switches for the ignition line. 4.11 If the operator fails to light the small burner within three minutes, the low fuel gas pressure interlock will activate, and the procedure must be started over from the beginning. 4.12 After lighting one burner, the remaining five small burners are lit gradually according to the temperature rise, in order to achieve a uniform heat distribution on the inner wall of the furnace. 4.13 TI1397 was heated from room temperature to 120°C at a rate of up to 15°C per hour, over a period of 6 hours. 4.14 If the temperature cannot reach 120°C after lighting the 6 small ignition burners, then light the large burner. 4.15 Confirm that the pilot burner is lit; set the DCS manual operator HIC-1050 to zero, and control the amount of fuel gas via control valve HV-1050, starting with the minimum flame. 4.16 The program check showed that TSHH-1396 was normal. If the conditions are met, the program turns on the “Allow opening of main fuel pipeline valve” light on the field panel, XL-1210. The program activates the solenoid valve XY-1250 of the double shut-off valves and the vent valve on the main fuel pipeline, causing the two shut-off valves XV-1250A/B to open while the vent valve XV-1250C closes, thereby filling the main fuel pipeline with fuel gas. 4.17 Over the next 5 minutes, the program will deactivate the low-low and high-high pressure switches (PSLL-1152 and PSHH-1150) on the main combustion pipeline, giving the field operators sufficient time to ignite the main burner and stabilize the pressure in that pipeline. 5 minutes later, the program turns off the “OK” indicator light XL-1210 and restores the low-low and high-high interlocks for the main fuel gas pipeline pressure. 4.18 Light three large burners at once, igniting them in a diagonal pattern. At the beginning, a low flame should be used, and the opening of the air valve should be adjusted to control the combustion in the burner. 4.19 When the flue gas temperature reaches 120°C, it is maintained at this temperature for 18 hours. 4.20 After reaching a constant temperature, the temperature is raised to 250°C at a rate of no more than 15°C per hour, over a period of about 8 hours. 4.21 When the flue gas temperature reaches 250°C, maintain it at this level for 16 hours. 4.22 At 250°C, ignition tests shall be conducted on all burners, but one by one to prevent overheating or localized overheating. 4.23 After 16 hours at a constant temperature, the drying process is completed. Some burners are turned off gradually, and the temperature is reduced at a rate of 28°C per hour until it reaches 120°C; all burners are then turned off, and the flue gas dampers, burner air valves, and inspection ports are closed completely, allowing the furnace to cool down naturally. 4.24 After all burners have been turned off, close all stop valves on the gas pipeline leading to the burners, and isolate the gas pipeline with blind flanges. 5. Inspection after baking 5.1 Once the furnace chamber has cooled to room temperature, open the manhole to check whether the refractory bricks and plastic refractory materials inside the chamber have fallen off; conduct a similar inspection of the burners and observation ports. 5.2 If cracks are found in the lining during inspection, they must be repaired using the original materials used for constructing the furnace. If the area that needs repair exceeds 5% of the furnace’s lining, the furnace must be re-dried according to the established procedures. 6. Safety Precautions 6.1 Gas pipelines must be properly purged with nitrogen. 6.2 The furnace chamber must have its combustible gases analyzed; ignition is permitted only after they meet the required standards. 6.3 Strictly control the heating rate; if the temperature exceeds the limit and rapid cooling is not possible, maintain a constant temperature immediately or adjust the burner to restore the normal heating rate or temperature. 6.4 During furnace drying, the burners should be ignited in turn. 6.5 The fire must not be turned off during the furnace drying process. 6.6 If the heating furnace shuts down and cannot be restarted immediately, the dampers should be opened for ventilation, and the combustible gases in the furnace chamber should be analyzed; only after they meet the requirements can the ignition process be carried out again. After ignition, raise the temperature at a rate of 30°C per hour until it reaches the temperature at which combustion stops, and then continue raising the temperature according to the heating curve. 6.7 If the manual stop button for starting the startup heater is pressed, HS-1257 (control room) or HS-1257A (site) will activate, causing the startup heater to stop.