ZLV Online

Abstract

The effect of moisture content of firewood using the energy efficiency model of low and medium temperature processing boilers with the power input up to 500 kW is analysed in the paper. The results of the effect of moisture content of burnt wood with the moisture content in the range W = 10–60% on boiler energy efficiency during cooling the flue gas in a boiler at the temperature ranging from t = 120 °C to 250 °C and emission production with the concentration of CO = 2500 mg.m-3 and soot TZLC = 150 mg.m-3 associated with the boiler requirements of Class 3 in accordance with the standard EN 303:2012 are presented. Following the analyses, the fact that the energy efficiency of a boiler decreases from η = 89.81% to η = 82.95% due to increase in the moisture content of wood from w = 10% to 60% while flue gas is cooled to the temperature of t = 120 °C can be observed. When the flue gas is cooled to the temperature of t = 250 °C, there is decrease in energy efficiency from η = 79.25% to η = 64.58%. Negative effect of moisture content of burnt wood on the boiler energy efficiency depending upon the moisture content of firewood and the temperature of flue gas is described using the formula: η = [(-0.0027∙W2 + 0.0564∙W + 89.373) – (0,001∙W + 0.068)∙(tsp – 120)].