Modelling trace and alkali mobilisation in the rotary cement kiln

Abstract

Thermodynamic data for the main phases formed in cement clinker provided in the MTOX database have been supplemented to provide an optimised model of each phase which includes cross-solution of the main oxides CaO, Al₂O₃, SiO₂ and FeO. Additionally, solution of the alkalis and MgO is modelled, together with dilute solutions of ZnO, Cr₂O₃ and NiO. The database has been translated to FactSage format and used to test a model of a cement kiln, in which thermodynamic equilibrium calculations are linked via the FactSage macro facility to a spreadsheet representation of zones in the kiln. In this model recycle within the kiln and kinetic control of processes can be simulated. Buildup of alkali is predicted, with Zn, Ni and Cr largely immobile.

Keywords:

• CEMENT
• KILN
• VOLATILISATION
• MODEL
• EQUILIBRIUM