Cement kilns - Clinker firing workshops

Clinker firing is the intermediate step in the three important stages of the cement manufacturing process:

• preparation of raw materials ;

• clinker firing ;

• clinker grinding.

In a systematic approach, the function of the kiln is to transform "raw" material into a semi-finished product known as clinker. Preparing the "raw" material involves mixing and grinding the raw materials to obtain a product with a predefined composition and fineness.

The whole issue of clinker firing is to achieve optimum savings in both capital and operating costs. To meet this twofold objective, technological evolution is a series of responses to the technical and economic evolution of the system's input and output variables:

• diversity of raw materials;

• fuel diversity ;

• socio-economic constraints;

• required clinker performance ;

• environmental constraints ;

• unit production capacities.

Technological developments have enabled us to use an increasingly wide range of raw materials, from natural to synthetic raw materials, and to use less and less traditional fuel mixtures (automobile shredder residues, special industrial waste, oils, tires, etc.), under economic pressure, while reducing emissions (dust, NO _x , SO ₂ ...).

This development has gone hand in hand with a 100-fold increase in unit production capacity over the past fifty years.

The capital cost of a cement plant is high, roughly equivalent to 3 years' sales. As a result, technological advances are only gradually implemented in the industry, either when a new production line is created, or when the capacity of an existing line is increased.

The article "Cement kilns" is the subject of several booklets:

• BE 8 844 Clinker firing plants ;

• BE 8 845 Rotary furnaces ;

• BE 8 846 Clinker coolers.

The subjects are not independent of each other.

Readers will need to refer back to the other issues often enough.