The article proposes a model of the process of ignition and combustion of fine water-coal fuel (FWCF) in a cyclone primary furnace. The model is intended to form an engineering approach to calculating the composition and quantity of combustion products of the FWCF and the definition of the structural and layout characteristics of the actual cyclone primary furnace. Approximation of process modeling is determined by the following assumptions: the quasistationarity of the processes; the constancy of heat capacities and heat transfer coefficients at an average process temperature; isothermal fuel particles; representation of fuel particles in the form of a water-coal drop of a given size; inertness of ash components; record keeping of the determining chemical reactions of interaction with the oxidizing agent; one-dimensional flow. This approach allows to carry out an analytical analysis of the process and to obtain final expressions suitable for engineering calculations.