MODELING OF FIXED-BED COMBUSTION

As part of an investigation of methods for the control of sulphur diox ide emissions from stoker-fired plant, a computer-based model of combu stion within the fuel bed was developed. The model was based on an exi sting model of coal combustion and developed to enable consideration o f the fuel bed conditions in a travelling grate stoker. The model cons iders the fuel from the point of entry on the grate through devolatili sation, combustion and ash cooling. Heat and material balances are car ried out throughout the fuel bed at selected time intervals. This enab les prediction of combustion gas composition and temperature at any po int within the fuel bed. As input the model requires details of coal c omposition, along with basic plant operational parameters such as grat e speed, excess air and fuel burning rate. The model was used to predi ct fuel bed combustion gas composition and temperature profiles. Compa rison with data obtained from operational plant and a novel fixed grat e simulator showed good agreement with model predictions giving confid ence in its representativeness.