Influence of reaction parameters of hydrothermal carbonization on the gasification performance of hydrothermally carbonized biomass

For a renewable and sustainable energy production the use of biomass feedstock offers a huge potential to replace or reduce the consumption of fossil energy sources. The utilization of biomass however, poses challenges caused by the huge diversity of these feedstocks. A modern approach to address these problems is biomass upgrading by HTC and subsequent gasification. This process offers a flexible use of the gas for power generation or SNG synthesis with less feedstock limitations. This study focuses on the influence of temperature and residence time of hydrothermal carbonization on the gasification properties of the resulting coal. After carbonization the coals were subsequently pyrolyzed and analyzed in H₂O atmosphere by thermogravimetric analysis to obtain activation energies and reaction rates for steam gasification. The biomass has been carbonized in a temperature range from 180 °C to 280 °C and residence times from 0,5 to 12 hours at the respective temperatures. In accordance with previous studies coalification and therefore heating values of the biomass were increased with reaction severity. The fuel properties of the produced coals were in the range of lignite. The gasification reactivity of the resulting char after pyrolysis was found to be affected by the reaction parameters and decreasing with increased reaction severity. The activation energies obtained from the reaction rates were modeled with the Arrhenius equation and were also found to decrease with increasing reaction severity. This trend contradicts the behavior of the reaction rates and suggests a different approach to model the activation energies. The reaction orders for all samples were found to be in the range of 0,44 – 0,55.