Solving raw material challenges [cement industry]

A comprehensive understanding of the chemical and physical aspects of raw material transformation into clinker is an important foundation to increasing production, reducing costs, and improving quality at the cement plant. Clinker formation relies on numerous kiln feed properties and pyroprocessing conditions. Understanding the influential properties of the feed (chemistry, fineness, uniformity, and mineralogy) can lead to improvements in its burnability and therefore in the efficiency of plant operations. The paper discusses clinker formation, its relation to kiln feed properties, and the importance of optimizing burnability by careful mix control, good mix homogeneity, and tailoring the burning process to the raw mix. The burnability and kiln feed are discussed in relation to specific fuel consumption. When the raw materials available make it hard to achieve burnability goals, the use of fluxes and/or mineralizers may be helpful. Fluxes and mineralizers indirectly affect burnability by promoting clinker phase formation to occur earlier; their effect on clinker formation and cement quality is briefly described. Fluoride-containing compounds have proven to be the most effective mineralizers in cement clinkering reactions. However, an excessive amount of fluoride may delay cement setting time. Emphasis is placed on the effects of changes in raw material burnability and clinker formation on kiln operations, finish mill productivity, and the properties of the resulting cement.