Experimental Investigation of the Ca-Cu Process for H2 Production: Evaluation of Reduction/Calcination Strategies

Abstract

The exothermic reduction of the CuO present in a bed of solids (39 % wt. CuO, 20 % wt. CaCO3 and 1.5 % wt. Ni, being the rest inert materials) with a fuel gas, generated a pure CO2 stream once steam was condensed (and free of N2). In this way, a Cu/Ca molar ratio of approximately 2 in the bed of solids allowed for CaCO3 calcination efficiencies of around 95 % molar basis at the reducing gases break-through. This allowed performing consecutive cycles of the main reaction steps involved in the Ca/Cu H2 production process. The mixture CaO-based sorbent, reforming catalyst and Cu-based material was able to produce a gas stream with a 94.0 % vol. H2 at 10 bar during the CH4 sorption enhanced reforming stage. The Cu-based material was oxidized with a highly diluted air stream at 10 bar, reacting in a well defined reaction front. A pure CO2 gas stream was obtained at reactor exit during the calcination/reduction stage with a fuel gas typical composition of a SMR stage at high temperature. The experimental results indicated that it was possible to cool the bed and to produce a syngas with a H2/CO molar ratio of about 3.5 suitable for its use in the calcination/reduction stage, in a SMR stage at high temperature. It was also possible to perform the calcination/reduction and SMR in one single stage.

Review of pressurized chemical looping processes for power generation and chemical production with integrated CO2 capture

“…This process is receiving increased interest due to the predicted high energy efficiency and lower product costs compared to benchmarking CO2 capture technologies [164]. Experimental development studies were completed, mainly focusing on the Ca-Cu material and its performance, testing under the main critical step of the process which combines reduction of CuO and calcination CaCO3 [165][166][167]. A recent review by Fernández et al [168] on the technology provides a complete overview of the progress both on process development, modelling and integration.…”