United Conversion Process Coupling CO2 Mineralization with Thermochemical Hydrogen Production

In this work, to achieve both clean energy production and carbon emission reduction, a united conversion to couple CO2 mineralization with thermochemical hydrogen production is proposed. Natural magnesium silicate minerals are used to fix CO2 in the form of carbonate minerals, whereas H2O is dissociated to produce H-2 in the thermochemical cycle. The integration provides a new solution to the challenges of the high energy consumption and poor economic value of conventional CO2 mineralization processes, and the technical feasibility has been proven. Moreover, the energy economy and CO2 conversion capacity were investigated. Hydrolyzation and carbonation experiments were performed in a homemade reactor, and it was found that an optimal MgI2 hydrolyzation rate of 75% could be achieved without alkali consumption. A detailed simulation of the whole system was also developed. The optimal energy conversion efficiency of the cycle reached 47.6%, which is higher than most of the published theoretical energy efficiency values for sulfur-iodine thermochemical cycles. A modified calculation of the net energy requirement for CO2 mineralization was carried out. Finally, a comparison and an evaluation of the energy efficiencies were made based on the calculation. In the optimal case, the modified net energy requirement is 1.4 MJ/kg CO2, which means that this method is competitive compared to those of previous works.