Sometimes we need to produce special, low alkali clinker. In order to achieve good results we need to waste all dust from the kiln and to burn the kilnfeed harder than for the ordinary clinker. But in this case we are loosing almost all coating on the bricks. The questions: How and what could we change in our kilnfeed in order to protect the bricks even in case of low alkali clinker?

I think you are operating long wet kilns? If so you could add some chloride to the kiln feed to promote the volatility of the alkalis in the kiln. That will drive more off from the clinker and result in lower alkali content at lower temperatures. However, that may increase your impact on the environment. I would need to know more about your process and situation before recommending that.

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.