Fouling of heat exchangers' heat transfer areas is one of the serious problems of certain process plants. A waste incinerating plant is a typical example of such a process plant. The main process stream in a waste incinerating plant (i.e., produced stream of flue gas) and its thermophysical characteristics and properties significantly influence operating, maintenance, and investment costs of installed equipment and its service life. Moreover, properties of flue gas can vary over a wide range. This contribution deals with the issue of the fouling mechanism at the heat transfer area of tubular heat transfer equipment installed in plants for thermal processing of wastes and presents a mathematical model developed for fouling tendency prediction and for prevention in design and operating of tubular heat transfer equipment designed for applications in waste incinerating plants. Obtained results were compared with experimental data published in worldwide available literature and a very good agreement was found.