What is the cooling rate for shutting down a delayed coking heater?

Generally, the rate of temperature change should be set at around 40–50 degrees Celsius as the maximum. . . :lol

Heating rate for startup: Heat at a rate of 20°C/h until reaching 150°C, then maintain that temperature for 8 hours. Heat at a rate of 30°C/h to 250°C, and maintain the temperature for 6 hours. Heat at a rate of 30°C/h to 350°C, and maintain the temperature for 6 hours. Heat at a rate of 30°C/h to 420°C, and maintain the temperature for 4 hours. Heat up at a rate of 30°C/h to 460°C, then switch the four-way valve to switch to bottom feeding. For cooling: once the temperature at the furnace outlet drops to 460°C, switch the four-way valve again and cool down at a rate of 40°C/h. Keep a pilot light lit to maintain a furnace temperature of 300°C, which facilitates cleaning the furnace tubes.

When raising the temperature, it can be done slowly; when lowering it, it is essential to ensure that the furnace tubes can be purged

Our plan: Reduce the furnace outlet temperature to 440°C, switch the four-way valve, and rapidly cool it down (within a few minutes) to 360°C; then lower the temperature at a rate of 40–50°C until it reaches around 250°C, at which point the furnace is shut down (due to low gas pressure triggering safety measures). A pilot light is kept running to maintain a furnace temperature of 300°C.

Cooling rate: From 500 to 350 degrees, the main gas valve should be turned off immediately to achieve rapid cooling (the corresponding permanent flames can also be turned off directly). Only 4–6 main flames should remain burning in the furnace; thereafter, the temperature should drop at a rate of 40 degrees per hour. It is important to ensure that the main flames continue to burn properly throughout this process, in case they need to be used for burning things that have stuck. Heating rate at startup: Up to 250°C, the temperature is increased at a rate of 50°C/h until reaching 250°C, after which it is held constant for 5 hours. Heat at a rate of 40°C/h to 350°C, and maintain the temperature for 5 hours. The temperature is raised to 450°C at a rate of 30°C/h; without maintaining a constant temperature, the four-way valve is switched immediately to switch to bottom feeding, allowing for a rapid rise in temperature to the production temperature. When the unit was put into operation, the purge with clean gas was completed, and the temperature reached around 180°C; therefore, I believe that maintaining a constant temperature of 150°C is not effective. If a constant temperature of 150°C is desired, could it be interpreted as allowing the material to sit and lose water? Originally, we maintained a constant temperature of 120°C; the circulation at the bottom of the tower was not activated, and dehydration was carried out by venting directly from the bottom of the tower. Later, due to stricter environmental regulations, this practice was discontinued, as venting from the bottom of the tower resulted in a large amount of oil being released!

Thank you to all the experts for their answers. I searched online but couldn’t find any information regarding the method for cooling down the furnace. Generally, we follow this procedure to shut down the furnace and cool it down: starting from 760 degrees, we reduce the temperature by 80 degrees per hour until it reaches 450 degrees (which takes 4 hours)； Start at 450 degrees, reduce it to 350 degrees over 1 hour, then turn off the heat and allow it to cool naturally. My question is: if the cooling rate of the heating furnace is too fast, it may cause significant damage to the insulation layer of the furnace bricks, and in severe cases, this could lead to their detachment. But it’s not possible to find out what specific rate is appropriate. This post was last edited by czx000323 on 2009-3-2 19:04.]