Application of Zn-ferrite towards thermochemical utilization of carbon dioxide: A thermodynamic investigation

Highlights: • Zn-ferrite-based CDS cycle in thermodynamically studied for the first time. • The energy demand of the heating of inert sweep gas and separation of gases is considered. • The solar energy required to drive the cycle increases due to the rise in the inert sweep gas flowrate. • The energy required for the heating of ZnFe₂O₄, inert sweep gas, and CO₂ plays a vital role. • Maximum ${\eta }_{\mathrm{solar}-to-fuel}$ is attained when gas-to-gas heat recovery effectiveness was held at 0.9. This study reports a thermodynamic analysis of ZnFe₂O₄ based CO₂ splitting cycle. The model developed is evaluated by using HSC Chemistry software. Effects of the influence of the ratio of the molar flow rate of inert sweep gas to the molar flow rate of ZnFe₂O₄, thermal reduction temperature, and gas-to-gas heat recovery effectiveness on thermal energy required to drive the cycle and the solar-to-fuel energy conversion efficiency are investigated at reduction nonstoichiometry of 0.1. The decrease in the reduction temperature is significant when the ratio of the molar flow rate of inert sweep gas to the molar flow rate of ZnFe₂O₄ increases from 10 to 30. At a steady gas-to-gas heat recovery effectiveness equal to 0.7, a rise in the ratio of the molar flow rate of inert sweep gas to the molar flow rate of ZnFe₂O₄ from 10 to 90 is responsible for an increase in the thermal energy required to drive the cycle above 184.9 kW by a factor of 1.45 and decrease in the solar-to-fuel energy conversion efficiency by 4%. At gas-to-gas heat recovery effectiveness equal to 0, the difference between the thermal energy required to drive the cycle at the ratio of the molar flow rate of inert sweep gas to the molar flow rate of ZnFe₂O₄ equal to 10 and 100 is 346.5 kW. However, as the gas-to-gas heat recovery effectiveness increases to 0.9, this difference decreases to 11.8 kW. Because of this, the reduction in the solar-to-fuel energy conversion efficiency also drops to 0.6%. Therefore, a maximum possible solar-to-fuel energy conversion efficiency equal to 16.8% can be achieved.