Thermal plasma gasification of organic waste stream coupled with CO2-sorption enhanced reforming employing different sorbents for enhanced hydrogen production

Abstract

In the past few years, rising concerns vis-à-vis global climate change and clean energy demand have brought worldwide attention to developing the ‘biomass/organic waste-to-energy’ concept as a zero-emission, environment-friendly and sustainable pathway to simultaneously quench the global energy thirst and process diverse biomass/organic waste streams. Bioenergy with carbon capture and storage (BECCS) can be an influential technological route to curb climate change to a significant extent by preventing CO₂ discharge. One of the pathways to realize BECCS is via in situ CO₂-sorption coupled with a thermal plasma gasification process. In this study, an equilibrium model is developed using RDF as a model compound for plasma assisted CO₂-sorption enhanced gasification to evaluate the viability of the proposed process in producing H₂ rich syngas. Three different classes of sorbents are investigated namely, a high temperature sorbent (CaO), an intermediate temperature sorbent (Li₄SiO₄) and a low temperature sorbent (MgO). The distribution of gas species, H₂ yield, dry gas yield and LHV are deduced with the varying gasification temperature, reforming temperature, steam-to-feedstock ratio and sorbent-to-feedstock for all three sorbents. Moreover, optimal values of different process variables are predicted. Maximum H₂ is noted to be produced at 550 °C for CaO (79 vol%), 500 °C for MgO (29 vol%) and 700 °C (55 vol%) for Li₄SiO₄ whereas the optimal SOR/F ratios are found to be 1.5 for CaO, 1.0 for MgO and 2.5 for Li₄SiO₄. The results obtained in the study are promising to employ plasma assisted CO₂-sorption enhanced gasification as an efficacious pathway to produce clean energy and thus achieve carbon neutrality.