Flash calcination of kaolinite rich clay and impact of process conditions on the quality of the calcines: A way to reduce CO2 footprint from cement industry

Use of properly calcined kaolinite rich clay (i.e., metakaolin) to offset part of CO2-intensive clinkers not only reduces CO2 footprint from cement industry but also improves the performance of concrete. However, calcination under inappropriately high temperatures or long retention times may deplete metakaolin into unwanted products (e.g., mullite), which limits the use of the calcines as a supplementary cementitious material. With this regard, a dynamic model of flash calcination of kaolinite rich clay particles is developed using gPROMS (general PROcess Modeling System) to predict the impacts of calcination temperature and residence time on the transformation of the clay particles and to derive a favorable production path that is able to achieve optimum amount of the desired product. Flash calcination tests of the kaolinite rich clay particles are also performed in a pilot-scale gas suspension calciner. The model is validated by the experimental data (e.g., the degree of dehydroxylation and the density of the calcines). Based on the model, the impacts of process conditions and feed properties on the quality of the calcination products are thoroughly examined.