Towards the model based development of a combined wood- and coal gasification reactor

Components such as methane, hydrogen, carbon monoxide, carbon dioxide and water as well as solid charcoal. A secondary but simultaneously running process in this context is coal gasification, where the residual charcoal under oxygen exposure in turn reacts to carbon monoxide or carbon dioxide. Depending on process parameters like temperature, air- or water supply rate, a thermo-chemical system can favour either typical wood gasification, or typical coal-gasification reactions. The assumption is that a device, capable of deliberately switching between the two modes of operation would be more robust and flexible with respect to changing wood input quality. In order to gain more knowledge about the exact conditions required to run the process in either one of the two modes, a thermochemical, fluid-dynamic model of the combined processes was created using system dynamic principles. The transient 1D model is based on species balances, the minimization of molar Gibbs free energy of formation of the chemical compounds as well as kinetic considerations. An experimental wood gasifier was built to validate the predictions of the model regarding the state of the gasification process, based on temperature profile measurements. There is a high degree of agreement between the computational results and experimental data. Furthermore the model provides deep insight into the transient evolution of the different chemical reactions and thus also knowledge about limiting parameters. The latter can be used to improve the process in oncoming design phases