Faculty of Forestry and Wood Technology, University of Zagreb
Abstract
The use of high technology in the manufacture of pellets and their use in modern furnace chambers of boiler plants for remote heating and heating of family houses, are the reason why pellets as the energy source find an ever increasing application. The biggest problem and obstacle for increasing their use is the starting investment in the boiler and pellet tank, which is considerably higher than the heating oil installation. In order to obtain the best possible indicators on economic feasibility of manufacturing wood pellets, a comprehensive research has been carried out in a wood processing plant. Pellets are manufactured from beech and oak residues. Beech accounted for about 90%. In order to get a complete picture of the consumption of electrical power per unit of manufactured pellets and of required power, the operating and idle power was measured at measurement sites during operations of individual electromotors. The measuring results were stored directly into computer and analysed later by a softwarepackage LabVIEW. The machines’ consumption of electrical power in the observed period was derived from the measuring results by numerical integration, based on which the average electrical power was then determined. Regarding the results of measuring carried out on four groups of electromotors, the highest consumption of electrical power has been measured during pressing, and then on electromotor group for the preparation of chips for pelleting. The highest consumption of electrical power has been recorded for the manufacture of one ton of pellets in pressing 138.98 kWh/t and transport system 74.25 kWh/t, which makes a total of 213.23 kWh/t or almost 95% compared to total consumption of electrical power. The measured electrical power for the manufacture of one ton of pellets in pressing hardwood residues, (in this research – beech), is by 100% higher than the electrical power referred to in literature, which relates to softwood. Consequently, the difference should be made in each study between the consumption of electrical power in pressing softwood and hardwood. Lower consumption of electrical power has been recorded with chippers with sharpened knives amounting to 24.3% compared to unsharpened knives
