Energy Assessment of Ethanol-Enhanced Steam Reforming by Means of Li4SiO4 Carbon Capture

High-temperature solid looping cycles for carbon capture provide a number of benefits when coupled with fuel reforming because they may combine the fuel reactor where the fuel is decarbonized with the CO₂ sorption step in the capture cycle. The heat released in the carbonation reaction may be used to run the endothermic steam reforming occurring in the same reactor, leading to an overall autothermic reaction. Another benefit derived from the presence of a CO₂ sorbent is the shifting of the equilibrium to greater hydrogen yields. A very promising approach is the utilization of Li₄SiO₄ because this sorbent does not present a cyclic degradation as pronounced as the traditional Ca-based sorbents. The extremely high cost of Li₄SiO₄ may be overcome through the production of the sorbent from rice husk, a kind of agriculture waste, which provides the silica source. Furthermore, rice husk Li₄SiO₄ exhibits better sorption properties compared to that of pure Li₄SiO₄ because of the alkaline element content from rice husks. In the State Key Laboratory of Coal Combustion, the kinetics of this enhanced process has been characterized. Different configurations may be adopted to integrate this capture process in a precombustion process for enhanced hydrogen production and minimize the energy penalty associated with sorbent regeneration. A fixed bed system has been modeled to assess the energy requirements of the system and the available energy for integration. By application of the experimental results obtained for Li₄SiO₄ kinetics, the developed model allows for the estimation of syngas compositions, production rate, and energy flows. This model represents an interesting tool for the assessment of further applications of the enhanced reforming of gaseous fuels through in situ carbon capture with Li₄SiO₄.