Evaluation of the Gross and Net Calorific Value of the Selected Wood Species

Abstract

The article deals with the important characteristics of the fuel energy parameters as the heat of combustion and ash contents of selected species of hardwoods and softwoods. In the research there were used the following wood of trees: pine, spruce, beech and maple, with calorific values ascertained separately for wood, bark, leaves and needles. Gross calorific value (another equivalent term is heat of combustion) was determined and calculated according to ISO 1928 “Heat of combustion of solid fuels”. Because the net calorific value of fuel significantly decreases with the moisture, the net calorific value of samples was determined not only in the absolutely dry state, but also at different percentage of moisture. The highest values of heat of combustion have been shown needles of pine wood (21.32 MJ.kg-1), bark of spruce wood (21.21 MJ.kg-1), leaves of beech wood (20.44 MJ.kg-1) and inner wood of spruce tree (20,54 MJ.kg-1). As other important energetic characteristic of wood a contents of ash have been measured and evaluated. Ash values from specimens of tested tree species were in the range from 0.78 up to 5 %. The average value of the residuum is 2.07 %. The lowest value was found for the field maple wood 0.78 % and the highest one for the bark of the same maple 5 %. The highest ash values were measured in most cases for needles and leaves; only for maple it was for the bark. On the other side, the lowest residuals were found for the wood itself.