Kiln

Cement manufacturing technology is evolving at an impressive pace.

An important catalyst to this evolution is the demand for improved energy efficiency and reduced plant maintenance overheads.

This has led to concentration of the endothermic reaction in the stationary preheater stage (i.e. cyclones and precalciners).

The role of the rotary kiln focuses more and more on the exothermic reaction that converts C₂S+CaO to C₃S, enabling kilns to have shorter lengths and smaller diameters without loss of production capacity.

Today, many producers use the cement kiln as an incinerator – to burn a wide variety of waste materials that are a source of low-cost energy. Such widespread use of alternative fuel affects the goals and priorities of cement kiln engineering, and raises new kinds of problems for the refractories that are used.

For the high-temperature areas, usually lined with basic bricks, there is a great demand for higher refractoriness, alkali-and thermal shock resistance, and better resistance to clinker liquid phase corrosion. The right refractories can make a great contribution to successful clinker production. However, factors such as combustion engineering and raw meal mix need to be well controlled too.

In this section, we address refractory requirements for the rotary kiln. We discuss dry-process kilns first, as they represent the majority of kilns now in use. The refractory requirements of wet- and semi-dry process kilns are essentially similar after the inlet stage.

Before we look inside, let’s look at the rotary kiln’s outside – specifically the  tire rings.

A critical consideration in the start-up of a cold kiln is allowing the tire rings' expansion to keep pace with that of the kiln shell.

If kiln warm-up is too rapid, the restraint of the colder tire rings may cause shell deformation and crushing of the refractories. The tire rings' subsequent expansion to full operating dimensions, if not compensated, will cause a 'rolling ovality' in the kiln shell. Refractories not already damaged by the earlier deformation will suffer severe radial abrasion, with potentially catastrophic lining loss as a result.

Click on the menu bar at left to learn more about each stage of the kiln.