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

Abstract 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 PM 10 (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 PM 10 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 PM 10+ (particle size above 10 µm) contains more alkalis, leading to a decrease in the production of PM 1 (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 PM 1 transforms to PM 1 – 10 (particle size between 1–10 µm). As a result, the production of PM 1 (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 PM 1 but more PM 1 – 10 than that with raw rice husk.