Effect of the torrefaction on the emission of PM10 from combustion of rice husk and its blends with a lignite

Torrefaction is a competitive biomass pretreatment technology. However, its impacts on particulate matter (PM) formation during biomass combustion and co-combustion with coal have little been investigated. This work provides new data on the formation of PM₁₀ (particulate matter with aerodynamic diameters less than or equal to 10 µm) from combustion of raw (RH), torrefied rice husk (TRH) and their blends with a lignite (SZ). All combustion experiments were carried out on a drop-tube furnace at 1300 °C and in air. The combustion-generated PM₁₀ was collected by a Dekati low pressure impactor and classified into 14 size fractions for further quantification and characterization. The results indicate that, compared with the RH, the TRH-derived PM₁₀₊ (particle size above 10?µm) contains more alkalis, leading to a decrease in the production of PM₁ (particle size below 1?µm). During co-combustion, fuel interactions promote the transformation of alkali chlorides to aluminosilicates. A considerable amount of water-soluble Ca and P in PM₁ transforms to PM_1–10 (particle size between 1–10?µm). As a result, the production of PM₁ (on an ash basis) decreases while that of PM_1–10 increases. Co-combustion of coal with torrefied rice husk is found to generate less PM₁ but more PM_1–10 than that with raw rice husk.