Undergraduate Research

Branson Wetzstein

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Evaluation of Additives and Storage Conditions on Southern Yellow Pine Energy Pellets

Senior forestry major Branson Wetzstein assisted in using pelletizing additives that were interesting to various pelleting industries to determine if pelleting production could be improved along with pellet characteristics. Southern pine energy pellet production is a growing industry in the United States and supplies overseas countries with millions of dollars of materials to run industrial boilers. In recent years, the pellet industry has found that the use of additives in the pellets can help improve pellet durability, improve BTU content, and lower the energy requirement needed to create the pellets. The goal of the research is to test pellet qualities based on additives, storage temperatures, and storage inflows. In addition, additives were compared for their effect on energy cost to produce vs energy yield of the pellet. Pellets were produced using a Sprout Walden (Andritz Sprout) model 501H with a 125 HP motor. Energy content of the pellets was evaluated with an adiabatic bomb calorimeter ASTM 5373 (2013a). The electrical power consumption was measured with an Extech model 382090 3-phase power analyzer. The amount of pellets created was recorded and the amount of energy required to form the pellets was determined in terms of kWh/ton. The feed rate, the moisture of the feed falling into the pelletizer, and the resultant moisture of the pellets was found and recorded. Moisture content assessment followed the ASTM E871 standard. Overall out of three types of pellets created (control, bio-oil additive, cornstarch additive), the pellets with the cornstarch additive at 1.8 wt% required less energy to form and also had the best durability. The control had the highest energy content, however the ratio of energy content to the energy used was the lowest. The cornstarch had the highest ratio of energy content to the amount of energy used. While airflow through the barrels influenced moisture content of the pellets, the bulk density and durability characteristics did not change. Based on the findings, the bio-oil additive can improve profit margins if it can be created without extra cost; however, issues regarding durability (91.5%) will have to be addressed before commercial companies can adopt bio-oil as an additive.