Model based optimisation of NO_x-emissions in grate stoker furnaces fired with fuels of unknown, variable composition

摘要

In thermal waste treatment (grate stoker furnaces) the fuel composition changes with time. Naturally this implicates also changing pollutant emissions (e.g. NO_x) with time. Hence, it is the aim to reduce the NO_x-emissions by an automated adjustment of primary measures. This possibility is not implemented in existing control systems. In the following it is described, how this aim was achieved by extension of existing control systems. In the first step the solid fuel conversion on a grate and the gas conversion in a post-combustion chamber with the minimising of NO_x-emissions are calculated. In the second step, in order to automatically emission control it is possible to quantify unknown, varying fuel compositions (input conditions) by measuring the flue gas composition at the exit of the furnace (output conditions). With the developed process model, one can pre-estimate the changing NO_x-minimum expected and therefore it is also possible to pre-estimate set points for the control system (primary measures) early enough.