I am working on a project for my university studying the different technologies used in the cement production process from different companies, and I would like to know if any corporation has already constructed its process with a fluidised bed cement kiln for commercial operation and could reach acceptable efficiency. Also, I am researching for the system with most number of steps at the preheater, and the performance of the process compared to other ones.

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.

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.

The shell temperature profile varies with the kiln process (precalciner, preheater, long dry, wet etc.), type of refractories installed (due to different conductivities), the residual thickness of the refractories (which reduces with wear during service), and the thickness of coating on the refractories (which changes dependent on process conditions). For an in-line calciner kiln I would expect shell temperatures of around 200 degrees C for the first 30 per cent of the kiln length where you will have the more insulating refractories installed. The girth gear will be in the region and the shell at this approximate temperature. I would then expect the shell temperature to rise to around 300 degrees C in the upper transition zone from 30 to 60 per cent of the kiln length. The refractories are likely to have little coating in this area. In the burning zone from 60 to 90 per cent of kiln length the shell temperature will be very variable due to coating formation. It could be as low as 150 degrees, but if the coating breaks away and the residual lining thickness is low then it could rise to over 400 degrees.