Electrification of clay calcination for cement decarbonization: Model development and process study

Reducing CO 2 emissions from cement production is essential for climate change mitigation. Electrically heated clay calcination is a novel process that enables the use of renewable electricity to produce calcined clay as a supplementary cementitious material (SCM), offering a practical route to lower clinker use and reducing the carbon footprint of cement. However, the performance of this process has not yet been thoroughly evaluated. In this study, a steady-state Aspen Plus process model of electrically heated clay calcination was developed to evaluate how changes in process layout, operating conditions, and clay feed properties affect process performance, quantified as energy demand, local temperatures, and clay calcination degree. Electrification allows heat recovery by recirculation of a portion of the process gas. At pilot scale with kaolinite-rich clay and targeting a calcination degree of 95%, gas recirculation reduced specific energy demand from 2238 to 1631 kJ/kg of calcined clay and lowered the required hot-gas supply temperature from 1010 to 917 °C. The preheating configuration with two cyclones showed the lowest energy demand. Higher feed rate decreased specific energy demand but increased the required hot-gas supply temperature; a higher gas-to-solid ratio had the opposite effect. Clay characteristics such as clay composition, kinetic model, and clay type were varied to understand their impact on process performance. The model was further applied to a full-scale process to assess scale effects, demonstrating reduced specific energy demand at the industrial scale. • Developed process model assesses operating conditions, feed properties, and layout • Adequate process layout using a convective heater required 917 °C and 1631 kJ/kg input • Energy recovery through gas recirculation reduced energy demand by 37% • 2:1 clay required higher calcination temperature but lower specific energy input • Optimal operation requires balancing hot-gas temperature and energy demand