The decline of PCDDs/PCDFs-ratios from inlet to outlet flue gases (i.e., from 2.76 to 0.71) could be attributed to the better desorption capacity of PCDFs than PCDDs (Chen et al., 2019), which is from solution, more accurately, from SS, caused by the higher vapour pressure of PCDF congeners (Rordorf, 1989; Mader and Pankow, 2003; Li et al., 2004; Ryan et al., 2005).