Experimental studies of wood chips charactristics influence on boiler performance and pollutant emissions

Abstract

Wood chips are often used as solid fuel in modern biomass boilers. Experiments were conducted on 22 boilers located in Serbia burning wood chips as fuel. The influence of wood chips characteristics is analyzed in relation to the flue gas losses and the thermal efficiency of the boiler. Measured useful heat output of the tested boilers was 460-2585 kW. Moisture content of the wood chips was 19.21-38.23% with a net calorific value of 10177-14139 kJ/kg and ash content of 0.84-3.59%. Thermal efficiency of the boilers was 88.78-94.06%, flue gas losses 5.84-11.13% and flue gas temperature 121.83-188.44?C. Experimental research and analysis of the results showed that an increase in moisture content of wood chips lead to a decrease of net calorific value i.e., decrease in flue gas temperature. Moisture content of wood chips has an influence on both useful heat output and boiler thermal efficiency. The experimental results showed that for a given boiler construction, this impact is not negative. Based on regression analysis, mathematical expressions were derived for the calculation of thermal efficiency and flue gas losses. Throughout the experiments, pollutant emissions were measured, NOx, CO, and particulate matter.