Effects of the addition of RPF and woody biomass on PM emissions during co-firing with coal

Two Cl-free refuse plastic and paper fuels (RPFs) produced by hydrothermal treatment with Ca(OH)2, as well as two biomasses, were co-fired with bituminous coal in a lab-scale drop tube furnace (DTF). The results indicate that the addition of biomass and RPF partially reduced the emission of SO2, which can readily cause corrosion, deposition and pollution. For the biomass co-firing, the particulate matter (PM) emissions from the black pellet (BP) series were 5.0% higher than those from the white pellet (WP) series because more sticky particles were formed with the increment of Ca-Al-Si and K-Al-Si, which absorbed alkali vapor and fine grains in the gas bulk to inhibit the PM emissions. For RPF, the major origins of sticky particles turned into Ca-Al-Si and Ca-K-Al-Si, the proportion of which was dramatically higher than that from the biomass, resulting in a stiffer suppression of PM formation. In general, the promotion of Ca from additives conversely restrained its transformation into PMs during both biomass and RPF co-firing. It can be concluded that the co-firing of RPF with bituminous coal provides an alternative approach to simultaneously control the emissions of greenhouse gases, gaseous pollutants and PM while remediating plastic waste.