December 9, 2022
Hydration series of refractory castables, the drying process can be roughly divided into three stages.
The first stage is in the temperature from room temperature to 100 degrees Celsius, generally natural drying temperature is about 40 degrees Celsius. But the fastest dehydration temperature of hydrated refractory castable is 50-60℃.
As the temperature increases, the temperature at the solid-liquid interface reaches a boiling point, which is the beginning of the second stage. The temperature of the second stage is 100-170℃. Because a lot of water vapor is produced at this stage, the conduction of water vapor increases the rate of dehydration. At this stage, the castable billet will produce a certain amount of shrinkage from the surface to the inside, which will slow the steam discharge. Some of the hydrates have begun to dehydrate in the range of 100-170℃.
The temperature of the third stage of drying is within the range of 200-400℃. In this temperature range, it is mainly the dehydration of hydrate. In fact, there is a great correlation between the temperature rise rate and the dehydration rate. Under normal circumstances, the binder has calcium aluminate cement refractory castable, the actual removal process is very complex, when close to 100℃, there is free water, with the rise of temperature, the dehydration temperature of the raw material in the trichlorite and its gel is between 210-300℃, the real dehydration temperature of crystallizational water is about 530-550℃. That is to say, hydration refractory casting expected 550℃ dehydration will end.
In the process of dehydration, the relaxation strength of the castable structure decreases. Because there is a lot of water vapor discharge, there will be a lot of pressure in the body of refractory castable billet, and in the baking process, the temperature rises too fast, it is very easy to burst. In order to prevent cracks in the process of baking and drainage of castable, a certain proportion of explosion-proof fiber must be added during production, so as to facilitate the smooth discharge of water in the process of dehydration.
The drying and baking of refractory castable is a very important link. If the temperature rises too fast in the process of temperature rise, the refractory castable will burst and cannot be used normally.