Influence of rice husk dosage on PM emissions during the co-firing of coal with refuse derived fuel

Abstract

A self-designed drop tube furnace (DTF) was constructed to investigate the particulate matter (PM) emissions generated from blending 0–30 wt% refuse derived fuel (RDF) and 0–20 wt% rice husks (RH) with bituminous coal during co-firing. The physiochemical characteristics of PM were determined using XRD, XRF, and SEM-EDS, and the creation of the liquid components at varying temperatures was investigated using theoretical thermodynamic calculations based on fuel composition and combustion atmospheres. The results demonstrated that blending 0–30 wt% RDF with coal did not result in significant PM emissions. PM0.5 and PM2.5 yields declined by 31.5% and 39.5%, respectively, with the addition of 20 wt% RH. By solely adding RDF, more Ca-Al-Si and K/Ca-Si formed viscous surfaces or particle bodies that could capture Ca/K vapor released from the volatiles of RDF in the gas bulk. Si-rich and Al-Si species from coal were consumed and transformed into Na/K-Ca-Al-Si to enhance the production of the liquid phase by the abundant Si in the volatiles of RH. Two possible paths of mineral transformations during co-firing were discussed to prove that alkali metals and alkaline earth metals preferentially condensed on Si-rich and Al-Si species to form liquid substances and capture the vapor and grains in the gas bulk, rather than combining with nonmetallic elements to generate precursors for PM generation via the evaporation–condensation mechanism. This study contributes to the search for an efficient pathway to realize simultaneous waste utilization and greenhouse gas reduction.