Dehydration of lignite primarily occurs in two stages, namely, removal of surface moisture and decrease in oxygen-containing functional groups and moisture stage. Moisture on the lignite surface could be removed at temperatures below 100 degrees C. However, parts of oxygen-containing functional groups were removed first followed by the removal of the adsorbed moisture at temperatures in the range 100-300 degrees C. Dehydration time increased with an increase in the dehydration load and heat transfer distance. At surface moisture of 7 wt.%, temperature of lignite increased rapidly. Higher temperature of combustion chamber yielded shorter removal times for surface moisture and oxygen-containing functional groups. Based on the rate of increase of lignite temperature and associated heat transfer process, coking chamber could be divided into three zones: the near, middle, and remote zones. The near zone temperature curve was determined to be a convex function (partial derivative T-2/partial derivative tau(2)<= 0); however, the middle zone temperature curve was determined to be a concave function (partial derivative T-2/partial derivative tau(2)>= 0). partial derivative T-2/partial derivative tau(2) = 0 and partial derivative T/partial derivative tau = k were the boundary indices of the middle and remote zones. 100 degrees C isothermal surface movement rate was found to be affected by the heat transfer capacity and dehydration load. Center temperature distribution of coking chamber was made uniform by steam, and temperature of HM7% was the most uniform distribution. (C) 2015 Elsevier B.V. All rights reserved.