Experimental Investigation of the Combustion Characteristics of Briquettes Produced from Sawdust and Coal in a Fixed-Bed Reactor

The utilization of biomass-coal briquettes offers a promising approach for improving the sustainability and performance of solid-fuel combustion systems. This study experimentally investigated the combustion characteristics of sawdust-coal briquettes in a fixed-bed reactor to evaluate the influence of fuel composition on combustion behavior. Briquettes containing 0–60 wt.% coal at 10 wt.% intervals were produced and combusted under a constant air mass flux of 0.10 kg/m2s. Combustion performance was assessed using temperature distribution, mass-loss history, ignition time, flame propagation speed, and burning rate. Temperature profiles exhibited a single dominant peak, indicating substantial overlap of fuel heating, devolatilization, volatile combustion, and char oxidation processes. Peak bed temperatures decreased from 813 °C for briquettes containing 40 wt.% sawdust to 657 °C for pure sawdust briquettes, while combustion duration decreased from 26 to 21 min with increasing sawdust content. Mass-loss rate, flame propagation speed, and burning rate increased with increasing sawdust content, while ignition time decreased progressively. Overall, higher sawdust contents promoted earlier ignition, faster fuel conversion, and greater combustion reactivity, whereas higher coal contents resulted in elevated combustion temperatures and longer combustion durations. These findings provide insights for optimizing biomass-coal briquette formulations for fixed-bed combustion applications.