This Open-Access-Book bundles the knowledge gained from 12 years of research in a joint project (CRC/TRR 129 funded by DFG) on the subject of oxyfuel combustion of solid fuels. Oxyfuel combustion uses an atmosphere of CO-, H-O and O-, which fundamentally changes the combustion behavior & with effects on reaction rates, flame stability and transport processes from atomic to industrial scale. Within the project these processes are investigated experimentally and by simulations of different complexity , for example using molecular dynamic simulations, Large-Eddy-Simulation (LES) and direct numerical simulations. The focus is on pyrolysis, particle combustion, reaction kinetics and radiation properties. Within the scope of this research, new experimental as well as new numerical-simulative methods were developed in about 20 closely interlinked projects, which led to a variety of new findings. This makes this book a valuable source of information for all scientists working on the fundamental aspects of the reactive conversion of solid fuels. Editors: The team of editors of this book is composed of the board and the management of the CRC/TRR 129. All editors have been part of the CRC since the first funding period and conduct research at the three universities involved in the project (RWTH Aachen University, Technische Universität Darmstadt, Ruhr-Universität Bochum).