At the present time, boiler units are subject to high environmental requirements and in this regard, great attention is paid to energy boilers with circulating fluidized bed (CFB). Since the processes in the furnaces of boilers with CFB studied insufficiently, in this paper the task is to conduct a study of furnace processes by numerical simulation. The Euler-Lagrangian approach is used as a research method, which allows to estimate the fractional distribution of particles in the furnace volume. The laboratory setup with CFB for burning brown coal of Shiva-Ovo Deposit of Mongolia is accepted as object of research. In the process of variant studies three dimensional functional dependences were obtained qualitatively and adequately describing the processes of combustion organization in the combustion chamber with CFB.