Constituent transformation mechanism of concentrated leachate after incineration at different temperatures

Abstract

Spraying concentrated leachate into an incineration furnace and burning is encouraged by the Chinese government as a harmless method for leachate treatment. In this research, the constituent transformation mechanism was studied, by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectrometry (EDS), of residues after burning the concentrated leachate in a muffle furnace at different temperatures (750 °C, 850 °C, 900 °C, 1000 °C, and 1100 °C). XRD results showed that the main components of the residues were metal chlorides and calcium salt crystals and that the peak position of most of these crystals changed little because their crystal structure was stable at high temperatures. SEM results illustrated that the higher the burning temperature, the smaller the solid particles, and the looser the structures of the residues. EDS analysis showed that S atoms in the concentrated leachate were usually transformed into gaseous compounds during incineration, whereas most of the Cl atoms could be fastened onto solid residues if an appropriate temperature was maintained. This study concluded that 900 °C was the best burning temperature for spraying concentrated leachate into the furnace. In addition, this study suggested that material selection for the nozzle and flue gas pipelines must pay more attention to corrosion caused by gaseous sulfur compounds. Similarly, material selection for the inner wall of the incinerator furnace should pay more attention to corrosion caused by Cl atoms. This means that the municipal solid waste (MSW) incineration power plants should incorporate various and appropriate corrosion-resistant materials according to the different regions of the incinerator.