The Product Yields and Characteristics of Corncob Wastes Under Torrefaction Atmospheres

From the viewpoint of energy and environmental conservation, biomass has become a promising energy source due to its carbon-fixing and neutral-emission properties. Torrefaction is employed to improve the characteristics of biomass under an oxygen-free or nitrogen atmosphere. The cost of biomass pretreatment and difficulty of process control are increased in order to practically maintain an oxygen-free and closed environment. This study is conducted to understand the product yields and characteristics of solid products of corncob wastes as biomass after 1 hr of torrefaction by using nitrogen, carbon dioxide, air plus carbon dioxide as carrier gases, and at the temperatures of 250°C and 300°C, respectively. The product safety and storage properties before and after torrefaction are revealed by flash points and hygroscopicity. The results show that the product characteristics approach those of coal at higher temperatures and the product yields and retained energy of solid products also decrease as temperatures rise, regardless of what the carrier gases are. The physical and chemical characteristics of solid products are similar when carbon dioxide is used as a carrier gas compared to nitrogen, while poorer when air plus carbon dioxide is used.