In Romania, sawdust is rated as one of the main renewable energy source, due to its high potential, being used for heat production and in the wood industry. Currently, sawdust is used for heat production in natural form or compacted form as briquettes or pellets. In all of these cases, sawdust processing is necessary to achieve a high energy efficiency of the conversion process into heat. All activities in the sawdust processing stage involve energy use. Thus, in the present paper, an energetic analysis of the sawdust pelletizing process has been performed. The objective of the energetic analysis is the identification of the main activities with high energy consumption and the determination of the total energy amount obtained at the end of the process (useful energy). The identification and quantification of the energy consumptions associated with each activity of the pelletizing process provides the possibility to identify solutions for decreasing energy use and thus an increase of the energy efficiency of the process. It also offers the possibility of calculating the energy balance of the process and it constitutes a method to evaluate the energy efficiency of the pelletizing process. Due to the complexity of the process and the multitude of contingency factors, the systemic analysis has been considered to be the best approach to present research. In the context of systemic analysis, an independent system, generic called „PELET” was assimilated with the sawdust pelletizing process. The specific stages of the pelletizing process were considered subsystems of the independent system. The input variables represent the total energy consumptions associated with the activities of the subsystems. The output variables represent the total energy embodied in sawdust pellets, obtained at the end of the pelletizing process. Using the flow energy chart of the process, we have developed explicit mathematical equations used for the evaluation of energy consumptions of each activity of the considered subsystems. These equations were computed based on energy consumption of the specific equipment and machinery used in the process. All activities involve an energy consumption which was calculated using the technical characteristics and maximum energy utilization of the specific equipment. From the analysis of the results the system with the highest energy consumption was identified as the “Processing” subsystem. The analysis of the “Processing” subsystem structure shows that high energy consumption is mainly due to pelletizing and drying activities. Also, high energy consumption has been identified in “Intermediate Transport Subsystem”, mainly due to the pellets loading equipment in transportation vehicle. However the energy balance showed a high energy efficiency of the sawdust pelletizing process.

energy efficiency; sawdust pellets; pelletizing process; systemic approach

Presentation: oral