Integrated CO 2 Capture and Utilization by Combining Calcium Looping with CH 4 Reforming Processes: A Thermodynamic and Exergetic Approach.

This study investigates a novel concept to coproduce high-purity H 2 and syngas, which couples steam methane reforming with CaO carbonation to capture the generated CO 2 and dry reforming of methane with CaCO 3 calcination to directly utilize the captured CO 2 . The thermodynamic equilibrium of the reactive calcination stage was evaluated using Aspen Plus via a parametric analysis of various operating conditions, including the temperature, pressure, and CH 4 /CaCO 3 molar ratio. Introducing a CH 4 feed in the calcination stage promoted the driving force and completion of CaCO 3 decomposition at lower temperatures (∼700 °C) compared to applying an inert flow, as a result of in situ CO 2 conversion. A conceptual process design was investigated that employs a system of two moving bed reactors to produce nearly equivalent volumetric flows of pure H 2 and a syngas stream with a H 2 /CO molar ratio close to 1. A solar reactor was examined for the reactive calcination step to cover the energy requirements of endothermic CaCO 3 decomposition and dry reforming. The overall exergy efficiency of the process was found equal to ∼75.9%, a value ∼4.0 and ∼8.0% higher compared to sorption-enhanced reforming with oxy-fuel and solar calciner, respectively, without direct utilization of the captured CO 2 .