Investigation on the Na removal and combustion characteristics of the hydrothermal treated Wucaiwan coal char

The effect of the hydrothermal treatment on the Na removal and the combustion characteristics of Wucaiwan char was addressed in this paper. The sodium contained in the raw coal and the char was removed by hydrothermal treatment in a high-pressure autoclave. The content and occurrence modes of sodium contained in the samples before and after the hydrothermal treatment was determined using inductively coupled plasma atomic emission spectrometry (ICP-AES). The combustion characteristics of the sample were investigated using a Thermal Gravimetric Analyzer ( TGA). Meanwhile,the oxidation reaction kinetics of the char was established using Flynn-Wall-Ozawa (FWO) meth- od. The results indicate that the main occurrence modes of the sodium contained in the raw coal and the char samples is water-soluble species and the total sodium removal efficiency of the char by the hydrothermal treatment is higher than that of the raw coal. The appearance of the water-soluble sodium is disadvantageous to the char combustion. The sodium removal efficiency of the char prepared at 600 ℃ by hydrothermal treatment is 82. 59% . The activation energy of the char hydrothermal treated is the lowest and the combustion characteristics index is the best among all char sam- ples.