The combustion predictive model was developed based on the results of experiments with coal water slurry and coal water slurry containing petrochemicals. Unlike other known models, it takes into account the effect of liquid flammable component (in particular, engine oil waste) on the main mass and heat transfer as well as other physical and chemical processes in the combustion chamber. The main differences, conditions and characteristics of the combustion of coal water slurries containing petrochemicals and without additives have been studied theoretically with different defining parameters: fuel composition, component properties, and furnace chamber temperature. Temperature fields and volumetric concentration distribution of combustion products in the furnace chamber are established for fuel compositions based on water, coal, and industrial oil waste. Temperatures and concentrations for both the initial fuel components and their combustion products are established at different points of the furnace chamber for various component concentrations, properties, and furnace air temperatures. The main research findings are the quantitative differences between the characteristics of ignition and combustion of slurries with and without a liquid fuel component. These differences are critical to illustrate the benefits of using coal water slurries containing petrochemicals in heat and power plants. Adding as little as 10% (relative mass fraction) of waste industrial oils was shown to significantly reduce the ignition delay times and improve the combustion efficiency of fuel compositions. Possible ranges, in which the ignition delay of slurry fuels can be reduced, and the displacement of their ignition zones in the combustion chamber were determined when changing the temperature and the main fuel component - coal (as illustrated by brown and bituminous coals, as well as anthracite).