The combustion of solid particulate fuels involves the interplay of particle phase, fluid flow, and thermochemistry, where investigating and quantifying the influence of each aspect of this interaction triangle is essential to modelling and understanding the combustion processes. This chapter presents an in-depth experimental investigation of particle-flow-chemistry interactions in solid fuels, with a focus on high-volatile bituminous coal and biomass. The fundamental physico-chemical processes of solid fuel combustion are outlined, illustrated by the behaviour of a single solid fuel particle in a hot gaseous environment. Two experimental configurations are described: a laminar flat flame burner for controlled particle-particle interaction studies, and a turbulent hot gas test rig for the investigation of the interplay of turbulent carrier flows and particulate fuels. Various optical diagnostic techniques were advanced and applied to obtain detailed data on particle and gas-phase interactions. The experimental investigations provide valuable insights and unique data that are essential for validating and improving combustion models, thus contributing significantly to the understanding and modelling of solid fuel combustion.