Emission reduction of PM10 via pretreatment combining water washing and carbonisation during rice straw combustion: Focus on the effects of pretreatment and combustion conditions

Abstract

To explore the impact of the changes in pretreatment and combustion conditions on PM10 emissions reduction caused by the combination of water washing and carbonisation (T-W: water washing after torrefaction; W-T: torrefaction after water washing; and HTC: hydrothermal carbonisation) during rice straw combustion, a long leaching time (24 h), large water to biomass ratio (40:1), and oxy-fuel conditions (oxy30 and oxy50) were introduced. Changes in the water washing conditions further increased the removal of inorganic elements (such as K, Cl, and P). Thus, the PM1 emissions reduction further increased. Even if the water washing conditions changed, the emission reduction effect was still HTC > W-T > T-W. Furthermore, the emission reduction effect of W-T 1:40 was high and comparable to that of HTC. When the content of the silicates during combustion was lower than a certain limit after pretreatment, fragmentation dominated and the yields of PM1–10 increased, such as RS W-T 1:40. The change under oxy50 was most pronounced when the combustion conditions changed. The PM1 emission reduction of the three pretreatments was weakened and tended to be similar because of the significant contribution of Si to PM1, and the PM1–10 emissions were noticeably improved owing to severe fragmentation.