Model validation of the Ca-Cu looping process

In this work an experimental demonstration and validation of a 1-D pseudo homogeneous reactor model for the Ca-Cu looping process is presented. The Ca-Cu looping process is a highly integrated process based on sorption-enhanced reforming of methane using CaO as sorbent, combined with chemical looping of a Cu-based oxygen carrier to provide the energy for the regeneration of the sorbent. Experiments were carried for all three involved process steps. The sorption-enhanced reforming step was studied at two different scales under different conditions. The effects of different bed compositions, operating temperatures, methane residence times and different steam-to-carbon ratios on the hydrogen production rate have been evaluated. A methane space velocity of 2.26 kg_CH4h⁻¹ kg_cat⁻¹ and a temperature range of 600–650 °C were found to be the most appropriate for optimal performance of the SER step and when increasing the steam-to-carbon ratio the hydrogen fraction produced increased. Moreover, complete cycles (consecutive steps of sorption-enhanced steam reforming, oxidation and reduction/calcination) have been performed in a medium-scale packed bed reactor (0.6 m length), where the three functional materials needed for this process were physically mixed. The Ca-Cu process was successfully demonstrated experimentally, forming 90% of H₂ in the sorption enhanced reforming stage and regenerating well the sorbent in the reduction/calcination step. The experimental results obtained from the experimental campaign have been used to validate a packed bed reactor model and a good agreement between the model and the experimental data was found.