Integration of a pilot-scale serpentinite carbonation process with an industrial lime kiln

• Several technical challenges with scale-up of current process to industrial scale.
• Lack of suitably sized equipment for pilot plant.
• Exergy loss of the gas compression and expansion process was studied.
• Process optimization can minimize exergy loss.

This paper involves integration of a mineral carbonation process developed at Åbo Akademi University with an industrial lime kiln. Optimization of energy integration and flue gas compression is studied by means of exergy analysis. In addition technical challenges of process scale-up from laboratory to pilot scale are discussed. Aspen Plus was used to model the process. The intended pilot scale is to process 620 kg/h lime kiln gas which is almost two orders of magnitude more than processed at laboratory scale. Process integration brings significant improvements to energy economy compared to earlier studies as here also a flue gas compression strategy is addressed and CO2 pre-separation is avoided. The utilization of 500 °C waste heat from the lime kiln leads to exergy demand per ton CO2 sequestered for heat and power of 2595 MJ and 885 MJ, respectively, processing 550 kg rock/h and sequestering 187 kg CO2/h. With the heat and power requirement equivalent to a production of 9 kg CO2/h, this gives a net sequestration of 178 kg CO2/h. The calculations were made for serpentinite rock from a nickel mine in Hitura, Finland, assuming a 90% conversion of Mg from rock to Mg(OH)2 and a 90% carbonation conversion of this.