The aim of this paper is to increase the understanding of the role of the binary circulating fluidized bed in the process of clean and ecological coal combustion. The operating range of a stable fluidized bed, as a function of gas velocity changes and the flow rate of fine particles, is determined for all possible conditions. Experiments concerning the combustion and desulfurization processes in multi-solid fluidized bed (MSFB) and circulating fluidized bed (CFB) systems give evidence that the residence time of burnt particles in the combustion chamber of MSFB is much extended. This is directly reflected in better combustion conditions, especially those for fine particles, as well as in the process of desulfurization. The advantages of the binary circulating fluidized bed over typical circulating systems make it one of the most efficient methods of clean and ecological coal combustion.