Highest Temp. Zone

The burning/highest temperature zone os a cement kiln is nothing to do with the coating. The thermal energy in the kiln derives from the fuel burnt in the flame and also from the exothermic formation of the calcium silicates.

The thermal energy from the flame is transferred to the charge by radiation and convection. As the gas flow is up the kiln then the thermal energy transfer by convection will tend to be in front of the flame.

The exothermic thermal energy is inherent in the charge and will be released wherever the calcium silicates are formed. This will significantly in front of the flame for the dicalcium silicate. That is why the burning/highest temperature zone is further up the kiln than the flame.

Dear Clark,

Is this not true that due to very high temperature in burning zone, it will have less tendency to form coating since due to high temp. any coating form will get melted and go into solution. But as the lower transition zone is reached the temperature became relative low and it help in stabilizing coating.

 

Regards,

Gulam Dastgir

 

No, the tendency is for the best coating to form in the buring zone. The fluxes in the charge of material penetrate into the refractory lining. There is a temperature gradient across that refractory lining from the hot face to the shell. The fluxes solidify at the point in that temperature gradient where the temperature falls to below their melting point. This creates a stable coating in the burning zone.