Energy consumption study in ultrasonic vibration-assisted pelleting of wheat straw for cellulosic biofuel manufacturing

Cellulosic biofuels are an alternative to petroleum-based transportation fuels. Ultrasonic vibration-assisted (UV-A) pelleting can increase density of cellulosic feedstocks, reduce transportation and storage costs, and increase sugar yield. However, energy consumption in UV-A pelleting has not been fully investigated. This paper presents an experimental study on energy consumption in UV-A pelleting of wheat straw. Effects of pelleting input variables (sieve size used in size reduction, pelleting pressure, ultrasonic power, and pellet weight) and size reduction machine type (knife milling versus hammer milling) are investigated. Results show that energy consumption in UV-A pelleting increased as sieve size, ultrasonic power, and pellet weight increased, and as pelleting pressure decreased. Energy consumption in UV-A pelleting of wheat straw particles processed by knife milling was higher than that in UV-A pelleting of those processed by hammer milling.