The researchers studied how Thai lignite char burns by heating it up and measuring its weight loss. They found that the combustion process is influenced by pore diffusion at high heating rates. The activation energy for the chemical reaction is around 21.31 kcal/gmol, while for pore diffusion control, it is about 12.60 kcal/gmol. These values differ slightly from previous studies, likely due to differences in the type of lignite and how the sample was prepared.