Research of willow preparation and utilization for energy purposes

Abstract

For the middle and short rotation energy plants chopping, the conical screw chopper is the most appropriate to use, because this chopper cut plant stems by conical screw with a sharpened outer edge, therefore can cut the longer chips. There were investigated the biometric characteristics of willow stems and physical-mechanical properties of chaff, such as humidity, bulk density, fall and natural crumble angles, chaff fractional composition, ash content as well as the calorific value. Determined bulk density of osier willow chaff decreased from 136.4 to 123.9 kg m-3 DM, and the natural crumble angle changed from 39 to 47 degrees, whereas the fall angle – from 66 to 78 degrees. After evaluation of willow chaff fractional composition it was estimated that the largest part of fraction was received on the sieves with the diameter of 8 and 16 mm holes – from 62.1 to 75.8%, and very small amount of the dust was formed – from 0.02 to 0.08%. Research results of willow chaff ash content and calorific value shows that the estimated ash content was relatively low and reached only 1.44%, it shows that the chaff of such energy plants as willows burns relatively well and in comparison with other energy plants, determined the lower calorific value of willow chaff dry mass was relatively big – 18.5 MJ/kg. Presented research results show that the usage of osier willows for bio-fuel is justified very well. Chopped by conical screw chopper plants can be used in the boiler rooms of average or big power (more than 0.5 MW), which have special burning devices suitable for burning the wet and partially dried bio-fuel.