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 are facing severe problem of balling ball size is sometimes around 2m dia which chokes the hammer crusher and we are forced to stop the kiln. What are the possible reasons form such big balls, how is a kiln operater responsible for this, how a kiln operator can avoid such balls through process changes, how we can avoid the balls by changing the chemical composition of kiln feed.

We hear of these problems with increasing regularity. At one factory the problem was associated with an increase in the Mn₂O₃ content of the kiln feed associated with one of their additives. There are also instances where an increase in the MgO content of the kiln feed gives rise to balling problems. However, the most likely cause is a difference in the clinkering range of the material in the kiln brought about by variation in the sulphate content. A heavy coating tends to form and the material is then dammed behind this coating and agglomerates into a large clinker ball. You must ensure that there are good combustion conditions in the main burner of the kiln to minimise the recirculating sulphates. The other process response is likely to be an adjustment in either the alighnment or the primary air supply to the main burner of the kiln. Regarding the chemistry then any changes which adjust the liquid content will change the clinkering range in the kiln. Addition of calcium fluoride to the kiln feed is also helpful.