Heating furnace drying

Thread Content

Preparatory work: 1. Wear proper personal protective equipment: gloves, safety helmet, etc. Prepare the appropriate tools: a light gun, an F wrench, an adjustable wrench, a walkie-talkie, etc. Issue a work order. 2 The construction of the furnace body, waste heat recovery system, chimney, etc. has been completed and passed inspection. The furnace lining materials, namely refractory castables and fiber plastics, were cured in accordance with the specified procedures. The furnace wall is dried in natural conditions for more than 5 days. 3. The hydraulic tests of each furnace tube were successful; the fuel gas system, purification air system, non-purification air system, and other related systems have been thoroughly flushed and purged, with satisfactory airtightness and proper functionality. The fuel gas system is isolated from other systems that are not yet in use by blind flanges. 4 blowers and exhaust fans have passed acceptance testing and individual commissioning tests. 5 The related instruments, DCS, and furnace interlock systems have been tested and are ready to meet the requirements for furnace drying. 6 Prepare the furnace heating curve according to the heating temperature specified by the manufacturer, and after joint inspection by relevant personnel, confirm that the conditions for furnace heating are met. 7 All fire-fighting equipment has been installed, and flammable and explosive items around the furnace area have been removed. 8. Notify the laboratory to prepare for the analysis of parameters such as combustible gas levels and oxygen content. Commission the fuel gas system. 9 The furnace should be preheated before formal baking. The stove is powered by steam. First, close the air valve tightly in front of the furnace, open the flue damper to 1/3–1/6, adjust the steam flow, drain any remaining water, and supply steam to the furnace tubes. Control the steam volume, gradually raise the furnace temperature to 130°C, maintain it at this temperature for 24 hours before starting the ignition process to heat up the furnace. During the heating period, if the temperature is difficult to achieve, increase the steam supply or light some permanent lamps appropriately. Ignition and furnace heating steps: 1. Adjust the dampers of the furnace’s flue and air ducts to the appropriate positions, and slightly open the natural ventilation doors to maintain a negative pressure in the furnace chamber at -10 to -20 Pa. 2. The fuel gas is vented to the flare for condensate removal and purging; the laboratory technician is contacted to analyze the oxygen content in the fuel gas, with a permissible level of no more than 0.5%. 3. Furnace steam injection was initiated, and steam was visible from the chimney for over 10 minutes. 4. Stop the purge steam, contact the lab technician to analyze the combustible gas content in the furnace; a level of no more than 0.5% is considered acceptable. Then remove the blind flange on the gas line before the heater nozzle. 5. Slightly open the burner air valve to 1/3–1/6, light the ignition rod outside the furnace, extend the ignition rod through the ignition hole near the pilot lamp, slowly open the pilot lamp gas valve to ignite it, and adjust the flame combustion using the secondary air valve. 6. Control the gas pressure of the permanent light and the number of ignition nozzles to ensure uniform temperature in the furnace; gradually raise the furnace temperature to 320°C at a rate of 7–8°C/h, and maintain this temperature for 24 hours. Then, the temperature is raised to 450°C at a rate of 7–8°C/h, and held at that temperature for 24 hours. 7 Raise the temperature strictly in accordance with the furnace heating curve specified in the furnace design. If the temperature cannot be increased, more nozzles can be added or the gas pressure can be appropriately raised. During the heating process, adjust the flame combustion by controlling the burner dampers, and also adjust the opening of the flue dampers to ensure that the negative pressure in the furnace meets the required levels. 9 During ignition and furnace heating, adjust the opening of the blower inlet damper or the air preheater bypass in order to raise the temperature at the air preheater outlet as much as possible. However, it is necessary to ensure that the temperature at the air preheater outlet does not exceed the allowable limit, and likewise, that the temperature at the air preheater inlet also remains within safe limits. This is done to protect the heat exchangers in the air preheater while carrying out dehydration processes in the air preheater and chimney. 10 Cooling down: Depending on the material of the furnace tubes, select an appropriate constant temperature; after reaching this temperature, cool down at a rate of 14–15°C/h until the temperature reaches 250°C. Turn off all burners, close all air valves and flue dampers, and extinguish the fire in the heating furnace to seal it. Once the furnace temperature drops below 100°C, open the natural ventilation doors and flue dampers to enable natural ventilation for cooling. Precautions: 1. During the gas evacuation and venting process of the equipment, all types of welding and heating operations are strictly prohibited, and all vehicles are forbidden from using the surrounding roads. With the installation of the gas introduction device, fire management within the facility is upgraded, and it is necessary to obtain a level-1 fire permit in strict accordance with the regulations. After the combustible gas analysis in Furnace 2 is satisfactory, ignition should be carried out promptly. Due to certain delays, it is necessary to re-analyze whether the combustible gas is qualified. If the burner goes out after being lit or the main burner fails to ignite, the gas valve should be closed promptly, steam should be blown into the furnace, and ignition should be attempted again only after the conditions are satisfactory for analysis. 3. Do not face the ignition hole when lighting it; when checking, keep your body away from the ignition hole to prevent backfire from causing injury. 4 When using the main burner to dry the furnace, in order to ensure even drying throughout the furnace chamber, the main burners should be ignited in a uniform manner, and those that are being used for ignition should be adjusted promptly. 5. Adjust the burner air damper plates slowly to prevent issues such as incomplete combustion, flameout, or fluctuations in furnace pressure. The temperatures at each temperature measurement point in the 6 furnaces should be as balanced as possible to prevent the flame from hitting the furnace tubes directly, and overheating must be strictly avoided. 7 Once the main burners are burning normally, the interlock system associated with the heating furnace is activated. 8 During the furnace drying process, the temperature should be increased and decreased strictly in accordance with the specified drying curve; regular inspections should be carried out, records should be kept on time, any abnormal situations should be addressed promptly, and the actual temperature rise curve should be plotted. 9 During furnace drying, if steam supply is stopped, the heating rate can be reduced to ensure that the temperature at the pipe outlet does not exceed 300°C. If the gas supply is interrupted or the heating furnace goes out for other reasons, the gas valve should be closed immediately, along with the flue dampers, air vents, and observation windows, in order to prevent equipment damage caused by a too rapid drop in furnace temperature. Once the gas supply is restored, the furnace can be restarted and heated up again. 10 During furnace drying, the steam outlet temperature should be controlled at: no more than 450°C for carbon steel pipes, and no more than 500°C for stainless steel pipes.