Effects of Torrefaction on the Properties of the Cotton Stalk and the Process Optimization

The poor quality of cotton straw (low calorific value and energy density) is a limiting factor for its efficient utilization and development. Therefore, how to upgrade the cotton stalk quality is an essential exploration to break this limitation. The impact of torrefaction on the cotton stalk properties and process optimization were discussed in this paper. Various conditions (the reaction temperature and time) for torrefaction were adopted. Changes in the calorific value, the energy yield, and the mass yield were observed by torrefaction. As the results show, there is a substantial impact of steaming on the performance of the product and could increase the energy density. The optimal treatment conditions (the reaction temperature = 270℃, the residence time was 40 min) were obtained. Better quality cotton stalk product (the calorific value was 19.66 MJ/kg, the energy yield was 72.65%, and the mass yield was 61.60%) could be achieved by torrefaction.