OVERFEED FIXED-BED COMBUSTION OF WOOD

Research on the combustion of wood on a fixed grate with a separate su pply of combustion air is described in this paper. From the layer of t he wood on the grate, only fixed carbon was burned in the primary comb ustion chamber in the presence of primary air, whereas the volatiles w ere burned subsequently in the secondary combustion chamber in the pre sence of secondary air. A one-dimensional mathematical model describin g the combustion in the overfeed layer of wood chips is given. Theoret ical results were confirmed by the experiments carried out in the expe rimental furnace. The scheme of the experimental device and the result s of experiments and calculations are presented. It was confirmed that the conditions in the layer and the quality of combustion were highly effected by the ratio of the fuel mass flow and mass flows of primary and secondary air. It was found that the ratio between primary and se condary air could be determined on the basis of the measured concentra tion of CO2 in flue gases leaving the burning layer. The optimum ratio of primary and secondary combustion air at any excess air was determi ned. (C) 1998 Elsevier Science Ltd. All rights reserved.