Drying Kinetics of Solid Biomass

The growing costs of conventional energy resources has significantly changed the economies and led to an increased demand for biomass. Biomass in its natural state has a high moisture content, which reduces the combustion efficiency and may cause problems in its processing. One of the most widely used forms of solid biomass concerns pellets that are often manufactured from saw dust. The manufacturing process requires that the raw material should be supplied in controllable conditions of humidity (in the order of 10%, dry basis); otherwise the final product will have poor mechanical properties. So it is essential to do the drying process to reduce the moisture content to acceptable values and to improve the efficiency of using of this product. In this way becomes necessary to study the various parameters that influence the drying process of biomass. For this purpose a drying wind tunnel was built. The facility consists of a ventilator, an electrical heating system and settling chamber and a testing chamber. This facility allows the study of the influence of moisture content and initial grain size of samples and the temperature and air velocity in the drying process of biomass. Air is supplied into a sample of biomass and its temperature and humidity are monitored along time. The humidity is measured by weighting the sample at regular intervals. Measurements were carried out on pine sawdust that was sieved into samples of various particle size. The temperature and air velocity was varied for each sample and the drying kinetics were used to derive working correlations from the experimental data. The results have shown that the gas temperature is the most important parameter in the drying of sawdust. The data was also correlated with dimensionless parameters.