Research into factors influencing the formation of particulate matter emissions in a drop tube furnace

• Increasing the temperature from 600 °C to 800 °C increased the number of PM particles by approximately 60 %. • Reducing the fuel size below 0.5 mm led to a 90 % increase in fine particles. • Higher moisture content increased the mass concentration of PM emissions by 80–100 %. • Higher air flow increased PM number by 25–30 % and generally raised PM mass by ∼26 %. • The results show that optimization of combustion parameters can significantly reduce PM emissions. The escalating environmental concerns associated with fossil fuel combustion highlight the urgent need for alternative energy sources, such as Refuse-Derived Fuel (RDF). However, the heterogeneous nature of waste-derived fuels presents considerable challenges, particularly regarding the complex formation of particulate matter (PM) emissions during combustion. This experimental study employed a drop tube furnace to investigate PM emissions from RDF, systematically varying combustion temperature (600–800 °C), fuel particle size (<0.5 mm to >1 mm), moisture content, and air flow rate. Results show that increasing temperature raised the number of fine particles by about 60 %, while the total PM mass concentration remained stable, suggesting a shift toward finer particles despite improved burnout. Reducing fuel particle size increased PM count by 90 % but decreased mass by 40 %, indicating more complete combustion accompanied by enhanced ultrafine particle generation. At a reference temperature of 800 °C, PM 0.1 accounted for 52–78 % of the total mass, underscoring the dominant role of ultrafine particles. Higher moisture content increased PM number by 30–50 % and mass by up to 80–100 %, primarily due to reduced combustion efficiency. Likewise, higher air flow raised PM count by 25–30 % and mass by about 26 %, attributed to stronger turbulence and incomplete burnout. Unlike previous studies primarily focused on homogeneous conventional fuels, this research uniquely investigates particulate matter emissions from RDF in a drop tube furnace. These findings contribute to a deeper understanding of PM formation mechanisms and to the optimization of alternative fuel combustion conditions.