Enhanced H2 production from biomass coupled with CO2 capture using CaO
The steam gasification of biomass, when coupled with in situ CO2 capture using CaO, is a promising process for the renewable production of H2. A H2-rich stream is resultant from the conversion of biomass with steam at moderate temperatures (~700°C), by manipulating the equilibrium composition of the conversion products with the removal of CO2, as soon as it is formed. CaO reacts directly with CO2 to form solid CaCO3. A high-temperature process can subsequently be used to regenerate CaO, producing a pure stream of CO2. From a theoretical basis, we predict an increase in the H2 concentration in the product stream from 50 to 85%-vol, when CaO is used to capture CO2. However, there are significant practical challenges due to heat and mass transfer limitations that must be addressed in the design of novel biomass conversion reactors, suitable for this integrated conversion process.
This work is specifically focussed on obtaining the fundamental data necessary to design and scale-up novel gasification reactors, for enhanced H2 production from biomass. Gasification experiments were conducted using a modified thermogravimetric analyser, coupled with a mass spectrometer (TGA-MS). Pure cellulose was used as a model biomass fuel and a comparative analysis of the weight loss and mass spectroscopic data obtained during the thermal decomposition of cellulose was used to elucidate the important mechanistic pathways. Furthermore, we report on a methodology for assessing the multicycle performance of a highly reactive CaO sorbent.