Alkali metal compounds in coal sometimes play a role for corrosion and/or erosion in combustion boilers. Therefore, it is necessary to understand detail kinetics and behaviors of the alkali metal compounds during coal combustion, and to develop the control technologies for them during combustion. Combustion tests for several types of coal are conducted, using an electrically heated drop tube furnace with a low pressure impactor (LPI), which can separate the particulates with size ranged from 0.03 to 11 mu m. As direct measurement of behaviors of alkali metal compounds during combustion is difficult, however, behavior of vapors of Na compounds in H-2-air flame is also simulated by detail kinetics calculation, using the CHEMKIN code. To control the alkali metal compounds during coal combustion, while, a little amount of kaolin that is used as a sorbent for the alkali metal compounds, is mixed with the coal, and is burned together. (C) 2007 Elsevier B.V. All rights reserved.