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.

What is the optimal forced air flow on the kiln shell? How does this impact on the refractory life? What is the interval in the shell temperature when I should turn on and turn off a fan?

I would say the optimum forced air flow on the kiln shell is zero. The higher the air flow then the higher is the loss of energy through the shell. This means greater heat requirements in the kiln and more penetration of salts into the refractory and therefore a negative impact on refractory life. However, as the refractory lining wears switching a fan onto the shell can be useful to try to build coating. I would suggest switching the fans on at above 350 degrees C.

We carry out refractory work with screw jacks, maximum 10m lining at a time (ie 5m maximum simultaneously at two different locations in same kiln). As ours is a small plant of 1000tpd, with single kiln of 64m length, deploying a brick lining machine and dismantling machines are not viable in terms of cost for us. What therefore is the maximum length of refractory work can be done at a time, in how many parts, simultaneously, from the various aspects such as safety, life of refractory etc.

I would recommend using the glueing method rather than screw jacks and then you can replace as long a section as you like without the concern of installing and removing the jacks. My understanding is that the glueing method will have no problems with a kiln of 3.95m diameter. However, you would be better to check this with suppliers of the refractory glue when placing your order.