Effects of different biomass feedstocks on the pelleting process and pellet qualities

Abstract

Regional and seasonal biomass feedstocks are emerging materials to be used for pelleting and require higher flexibility and robustness for mechanical devices. In this study, chemical components were reviewed and the physical properties of feedstocks were measured. Densification experiments were conducted on the single pelleting press, pelleting process and pellet qualities were evaluated. Results show pelleting process has relationships with physical properties and pellet qualities are essentially determined by the chemical components. Feedstocks were divided into different types based on the classifications of compression and extrusion force during the process. Herbaceous stalks and woody plants have the best densification effects to increase pellet density by 6–10 times and the largest energy consumption at 15–20 kg/kJ. De-oil cakes consume less energy at 6–7 kg/kJ and have the lowest expansion, those are conducive to reducing friction with the die wall and the finest pellet course. Orange peels rich in pectin have higher pellet strength at the compression force of 273 N and the largest expansion ratio. Pellets from nutshells have the worst performance for the lowest moisture content. This study could provide instructions for designing the pelleting devices and optimizing the pelleting process.