Experimental demonstration of the Ca-Cu looping process

In this work an experimental proof-of-concept of the Ca-Cu process has been carried out. The Ca-Cu process combines sorption-enhanced steam reforming of methane with a Ca-based sorbent with chemical looping of a Cu-based oxygen carrier to provide the energy for the sorbent regeneration. Each process step has been studied separately for different operating pressures and inlet gas compositions, and addition complete cycles (including all three consecutive process steps, viz. the sorption-enhanced reforming step, oxidation step and regeneration step) have been performed to evaluate the technical feasibility of the complete process. The pressure influences the sorption-enhanced reforming step negatively, while the steam-to-carbon ratio does not influence the average outlet H₂ (dry) fraction. When increasing the inlet O₂ concentration during the oxidation step, the amount of CO₂ released increases, whereas increasing the pressure decreases the amount of CO₂ released. In the regeneration step, increasing the H₂ fraction in the feed increases the amount of sorbent that is regenerated, reaching 70 wt% of the sorbent in the bed with 60 vol% H₂ in the feed. More than 285 complete cycles were performed, the solids were still chemically performing well, and the results were still reproducible. Simulations with a pseudo-homogeneous reactor model were performed for all the separate steps. The model does not describe the experimental data well, which was attributed to problems with the packing of the bed at the bottom of the reactor (solids maldistribution), which was confirmed after opening the reactor after the experimental campaign. The problems with the packing of the bed was caused by problems with the chemical–mechanical stability of the oxygen carrier, which became a powder after the experiments due to the high mechanical stresses it was exposed to.