Chapter 10 deals with heterogeneous combustions. The chapter can be broadly divided into three parts – coal combustion, solid propellant and catalytic combustion. It begins with a discussion on heterogeneous combustion. Then the coal burning models like one-film and two-film models are discussed in detail. Algorithms are suggested for using the models. Different types of coal combustions, like lump coal firing to fluidised bed combustion, are discussed. An overview discussion on solid propellant is provided to give the readers a proper basis to begin future study in this area. The chapter concludes with a brief discussion on catalytic combustion, and the role and working principle of catalysts are illuminated there.