In this study, steady-state combustion in boilers with a fixed bed has been investigated. The solution method and the discretization of the governing equations of two-dimensional turbulent reactive flow in the combustion chamber and one-dimensional coal combustion in the fixed bed are explained. Control volume and finite difference methods are used in the discretization of the equations in the combustion chamber and in the fixed bed, respectively. Kinetic calculations are employed in the solution of turbulent reactive flow equations in the combustion chamber The combustion of coal particles in the fixed bed is ruled by the reaction-controlled mechanism. The distributions of temperature and some of the chemical species through the combustion chamber and the fixed bed are presented. Also, the variation of coal particle size with the fixed bed height is given.