Mineral carbonation with thermally activated serpentine; the implication of serpentine preheating temperature and heat integration

Abstract

In this paper, heat integration was coupled with serpentine preheating temperature optimization and was for the first time applied to a mineral carbonation process. For this, a process was selected with the aim to minimise its heat demand. Aspen® Energy Analyzer software was used for heat integration with pinch analysis. The mineral carbonation plant considered here processes 100 tonnes of serpentine per hour, with Mg content of 237 kg per tonne of rock, corresponding to 0.88 million tonnes per year to treat 0.5 million tonnes of CO2 emitted from a cement plant. In the base case considered for heat integration, 50% of the serpentine magnesium content was converted to hydromagnesite using 30% of the flue gas CO2 which means that 5.85 tonnes of rocks were required to capture 1 tonne of CO2.The serpentine preheating temperature, was optimized as 400 °C. Application of heat integration at this solid preheat temperature reduced the process heat demand by 25% compared to our previous study, as 5.0 GJ per tonne of CO2 captured or 9.5 GJ per tonne of CO2 avoided. This corresponds to 0.86 GJ per tonne of ore as the process heat demand was only attributed to the mineral activation. In addition, the impact of process parameters including the solid-liquid ratio and the dissolution reaction extent on the heat integration strategy was evaluated. It was found that solids concentrations as low as 5% substantially reduced the sequestration efficiency as the process waste heat was not sufficient at the optimized solid preheat temperature. Furthermore, the uncertainty behind unknown parameters such as activated serpentine heat capacity and solid heat transfer coefficient was evaluated to validate the study.