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 H₂ 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.