*2.1. Sample Preparation*

For this study, one type of bituminous coal typically used at domestic coal-fired thermal power plants and the two biomass types were used as fuels. Trafigura coal, a bituminous coal imported from Australia, served as the coal sample, and the WP and EFB were procured from Canada and Malaysia, respectively. In this paper, bituminous coal is indicated as T coal.

The coal and biomass samples were pulverized using a ball mill and sieved to particle sizes of 75–90 μm and 400–600 μm. These particle sizes are commonly employed in coal-fired power plants in Korea. Before the experiments, proximate and ultimate analyses of the samples were conducted using a TGA-701 system (LECO Co., St. Joseph, MI, USA) and TruSpec element analyzer (LECO Co., St. Joseph, MI, USA) in accordance with the relevant ASTM standards. The procedures specified in the standards ASTM D5142 and ASTM D3176 for coal and in standards ASTM E870 for the two biomasses, respectively. The calorific values were measured using an AC600 (LECO Co., St. Joseph, MI, USA) calorimeter. Table 1 shows the sample analysis results.



a AUS: Australia, CAN: Canada, MAS: Malaysia, %wt.: % by weight, b LHV: low heating value, c VM: volatile matter, d FC: fixed carbon, e Oxygen: by difference.

In addition, ashes were fabricated in accordance with ASTM E1755-01 to examine their chemical compositions depending on the experimental conditions and their melting characteristics through TMA experiments. Accordingly, 1 g of sample dried at 105 ◦C was placed in a ceramic crucible and heated in a temperature-controlled muffle furnace. The sample was heated in an O2 atmosphere from room temperature to 250 ◦C at 10 ◦C/min, and the temperature was maintained for 30 min. Then, the sample was heated again to 575 ◦C (±25 ◦C) at 20 ◦C/min and the final temperature was maintained for 3 h to obtain ash samples, from which the carbon contents of the fuels were completely removed at a lower ash-producing temperature than that of ASTM D1857. This procedure was employed to avoid the volatilization of inorganic materials by the flames during the early combustion process [17]. The chemical composition of each fabricated ash sample was analyzed with a PW2400 XRF (Philips Co., Eindhoven, The Netherlands) at the Korea Basic Science Institute based on the ASTM D4326 method.
