Production of a syngas and CaO by desorption-enhanced reverse water–gas shift of CaCO3 with H2

Abstract

A syngas production method is investigated that combines in a single reactor the enhanced decomposition of CaCO3 with H2 and the reverse water–gas shift (RWGS) of part of the CO2 evolved during calcination. The method exploits Le Chatelier’s principle, to overcome RWGS equilibrium limitations by conducting such reactions with an excess of CaCO3 and at sufficiently high temperatures to maintain the partial pressure of CO2 close to the calcination equilibrium. The decomposition and RWGS reactions result in a ‘desorption-enhanced reverse water–gas shift’ (DERWGS) equilibrium of CaCO3 on H2, observed in experiments performed in a packed-bed reactor operated between 1023 and 1123 K and 1 and 5 atm when feeding H2 to a mixture of CaCO3, with or without a RWGS catalyst. Product gases containing over 25 vol% CO, with an H2/CO molar ratio of 2 and below, were obtained. In experiments without the use of an RWGS catalyst, the DERWGS equilibrium was also approached thanks to the catalytic activity of CaO for RWGS. The syngas analogue obtained from these reactions opens the door to new processes for synthetic fuel production from CaCO3 and renewable H2.