1156 posts
Burning Question 79
If air cooled slag is used as a raw material for kiln , replacing uncalcined calcium carbonate, will the calcium silicates, aluminates, etc. revert back to free state, so they can reform clinker crystals of cement design proportions? Will the existing sicates go to C2S state with the increased temperature and time. In other words could this slag combined with correction proportions of silica, iron, alumina, calcium be used as a primary raw material for a kiln feed? If there is a reversion of the state of the compound will there be a requirement for additional heat (as opposed to the exothermic heat released to compound formation) ? Would there be any big colour changes if air cooled slag was used as a primary raw material.
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1156 posts
Re: Burning
The process of adding air-cooled slag to the kiln inlet has been patented by TXI under the name Cemstar. The minerals in the slag do not convert back to the free state. They are already intermediate states in the formation of Portland cement clinker and all that is required is the completion of exothermic combination to C3S. No additional heat is required, also there are no reported changes in the colour of the cement subsequently made from the clinker.
1156 posts
1156 posts
Re: Burning
It is difficult to diagnose the problem over the internet, however these problems are often caused by inefficient combustion of the fuel in the main burner, long flames and poor heat flux in the kiln. I suggest you increase the axial primary to the maximum and see if that helps.