Computational fluid dynamics study of sequential hydrothermal carbonization and CO2-gasification of municipal solid waste-coconut husk-derived hydrochar for tunable syngas production

• Hydrothermally carbonized municipal solid waste and coconut husk suit as fuels. • Hydrochar gasification is favorable at higher conversion rate based on kinetics. • The impacts of several operating parameters on syngas quality are studied. • Computational fluid model showed reduced gasification efficiency deviation at 1173 K. • Optimal carbon dioxide injection rate is 0.63 m/s for the present study. The present work is a numerical and experimental investigation of carbon dioxide gasification on a hydrothermally carbonized blend of municipal solid waste and coconut husk. The kinetic data were first validated through experiments with applicable computations using kinetic approximation techniques. Updraft gasification was modeled in a two-dimensional domain using an Euler-Lagrangian approach and k-ε viscous function to investigate the syngas fractions concerning the actual kinetic rates. The CO 2 as a combusting agent parametrically influenced the syngas components concerning the reaction temperature, gas yield, gasification efficiency, and turbulent conditions. Numerical results showed a reduced gasification efficiency from 74.31 % to 31.59 % when the reaction temperature was slightly raised from 1073 K to 1173 K, with the smallest deviation from the experimental result. The gaseous component ratios: H 2 /CO increased by 35.7 % and CO/CO 2 decreased by 90.2 % from 1073 K to 1173 K at 0.43 m/s injection rate, which reduced the lower heating values by 57.5 % but had a negligible effect on the gas yield. Also, the simulation showed a peak turbulent intensity at 0.63 m/s, inferring a sudden increase in the superficial velocity. Due to the faster heat dissipation at 0.83 m/s, an eddy viscosity affects the formation of velocity gradient and momentum transfer within the reactor walls.