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

This study investigates a novel concept to coproduce high-purity H and syngas, which couples steam methane reforming with CaO carbonation to capture the generated CO and dry reforming of methane with CaCO calcination to directly utilize the captured CO. 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/CaCO molar ratio. Introducing a CH feed in the calcination stage promoted the driving force and completion of CaCO decomposition at lower temperatures (∼700 °C) compared to applying an inert flow, as a result of CO 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 and a syngas stream with a H/CO molar ratio close to 1. A solar reactor was examined for the reactive calcination step to cover the energy requirements of endothermic CaCO 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.