Toward an understanding of controlling parameters in softwood and hardwood pellets production

Production of biofuel pellets from hardwood, such as beech, is often very troublesome as observed in large-scale pellet production plants, where reduction of capacity and frequent blocking may be experienced. The problems may be reduced through a laborious optimization procedure of the process conditions and the utilization of softwood and adhesive materials. To optimize and facilitate such a procedure, a deeper understanding of the fundamental physical−chemical mechanisms that control the pelletizing process is sought after by combining small-scale experiments and an advanced pellet production model. Mixtures of beech rich in corrosive alkali chloride salt, pine softwood, brewers spent grains (BSG), and inorganic additives are experimentally tested using a small-scale pellet mill. It was possible to pelletize a beech/pine mixture containing up to 40% (wt) beech. The addition of 15% (wt) BSG to the beech dust significantly facilitated the pelletizing process. The addition of necessary inorganic anti-slag ...