What is the effect of cooler dust on flame?

The effect of dust recirculating from the cooler in the secondary air is potentially disastrous. I have seen occasions where the dust keeps increasing until the kiln is full of dust and the firing has to stopped while the kiln is emptied of dust. The dust affects the combustion of the fuel in the flame and the problems tends to intensify in a vicious circle. Potential causes are poor combustion in the flame or elevated sulphate content in the clinker. (See April 2003 issue of ICR for an article about dust formation with pet coke firing in cement kilns).

We are having to stop our kiln at frequent intervals because of ring build-ups. When we raise the alumina modulus to 1.7 we have better results. Secondly what's the difference between a snowman and a ring formation.

: Ring formation is caused by the formation of liquids in the kiln at a particular position. These penetrate the refractory lining and cause a localised thickening of the coating. Fe₂O₃ can be a cause of these problems and I am not surprised that raising the alumina modulus has solved the problem. Many cement factories operate with higher alumina modulus than 1.7 and I would recommend keeping the kiln feed mix design with the higher alumina modulus. A snowman is the formation of a large build-up on the first grate of the cooler where the clinker falls from the kiln rather than a build-up in the kiln.