Combustion reactivity of chars pyrolyzed from low-rank coal using a fixed bed reactor installed with internals

Abstract

Pyrolysis of low-rank coal could contribute toward the goal of upgrading coal quality, chemical feedstock and fuel production. This research investigated the combustion reactivity of char pyrolyzed from a low-rank sub-bituminous coal using a conventional fixed bed reactor and a novel reactor with internals at 0 kPa and − 40 kPa gauge pressures. Proximate and ultimate analyses showed that the novel reactor reduced char’s fuel ratio by 46% and 54% at 0 kPa and − 40 kPa respectively. The chars derived from the novel reactor also had a higher order of carbonaceous structure and active sites, as supported by the increment in both IG/IALL and ID3/(IG+ID2+ID3) area ratios obtained from a Raman spectrometry analysis. From a non-isothermal combustion analysis, it was found that the ignition temperature of char derived from the novel reactor was 24–40 °C and 30–45 °C lower at 0 kPa and − 40 kPa respectively. A micro fluidized bed reactor analyzer was used for an isothermal differential analysis and it showed that chars produced from the novel reactor had an average combustion activation energy of around 77.3 kJ·mol−1, which was 23% and 10% lower than chars obtained from the conventional reactor at 0 kPa and − 40 kPa respectively. Overall, the novel reactor produces chars with more desirable combustion quality and, therefore, provides the opportunity for more low-rank coal to be upgraded and utilized more effectively as a fuel source for energy sustainability.