Many cement plants add high ballast and high ash fuels through the firing system. However, I do not know of any plant that is specifically doing that with iron additive. I also see no reason to do that. There are potential problems of in homogeneity in the clinker. Also you need the iron to form flux in the transition zone, not at the end of the burning zone.

What kind of changes are required in raw mix to increase the granulation with 50 per cent pet coke total CV 4.3 per cent, LSF 93, SM-2.1 per cent, AM-1.0 per cent, in kiln feed?

The granulation problems with pet coke firing arise because of the low viscosity of the flux caused by the sulphur in the pet coke. Therefore raising the silica and alumina modulii should help to improve the granulation.

We regulate our raw material pile at 105-110 LSF. However the LSF of the raw mill's sample becomes 85-90. How can we have such a large difference?

There might be a problem in the sampling station. More likely you have a problem of segregation of the material. This is most likely when you are reclaiming the end-cones of the pile or in the intermediate feed bin between the pile and the raw mill. One solution is to add the end-cone to the next pile rather than sending it to the raw mill. The intermediate bin should be kept at a high level by setting the reclaimer start signal to a high bin level.

We would like to use phospho-gypsum in place of mineral gypsum in our cement plant. Please advice us of its suitability. Phospho-gypsum has 36 per cent moisture and pH is 2.3. The cost of using this material is very low but what are the drawbacks?

I know of no reason why you should not use phosphogypsum. However, you will have to conduct trials to verify that no product quality problems are involved.