Drying, heating and maintenance of cement kiln castables
The hardened or dried castable still has residual physical and chemical water, and then it is heated to 300℃ to vaporize and dehydrate, and all the water will be discharged. Because the castable has a dense structure, the heating rate should be slow to avoid rapid temperature rise. The stress caused by the rapid evaporation of high and moisture causes the damage of the castable.
The drying and heating system of the kiln system sometimes cannot meet the drying requirements of the preheater and calciner (grate cooler, kiln hood and tertiary air duct meet the drying and heating system of the kiln system, and are not listed separately), therefore, The baking heating system of the kiln system mentioned below should be combined with the requirements of this section. If the temperature of the kiln system reaches 600°C (subject to the temperature of the exhaust gas at the kiln tail), the primary preheater does not meet the drying requirements, and the heat preservation time of the kiln system at 600°C should be extended.
The curing time of the latter batch of refractory castables is not less than 24h at a temperature of about 25°C (for low cement castables, the curing time should be extended to 48h as appropriate). After the castable has gained a certain strength, remove the formwork and support. Baking can be carried out after 24h drying. If the curing temperature is too low, the curing time needs to be extended.
Take the temperature of the exhaust gas at the kiln tail as the standard, and use a heating rate of 15°C/h until it reaches 200°C, and keep it for 12 hours.
Raise the temperature to 400°C at a heating rate of 25°C/h, and keep the temperature for no less than 6h.
Raise the temperature to 600°C and keep the temperature for no less than 6h. The following two conditions are the necessary and sufficient conditions for the baking of the calciner and preheater system:
When the temperature of the refractory castable in the pouring hole of the cyclone preheater close to the silicon cover reaches 100℃, the drying time shall not be less than 24h.
At the manhole door of the first-level cyclone preheater, a clean glass piece was used to contact the flue gas, and no moisture leakage on the glass was observed. The heat preservation time was 6 hours.