Wet Granulation of Pine Wood Powders

Abstract

<abstract><title><italic>Abstract.</italic></title> Wood chips and sawdusts are densified into pellets to increase their bulk flow properties and to reduce the costs of handling, transport, and storage. Utilization of wood pellets in the U.S. is limited due to high pelleting costs and the low price of alternative fuels. Development of a low-cost densification technology can be critical for establishing a competitive solid biofuels market in the U.S. or elsewhere. In this study, a novel wet granulation method was investigated to agglomerate wood powders using a pan-type granulator and to evaluate the physical and bulk flow properties of granules at various liquid binder concentrations and particle sizes. Granulation is the process of agglomerating fine particles (typically smaller than 500 μm) into spherical granules by simultaneously wetting the particle surfaces with a liquid binder and applying shear and rotational forces to facilitate granulation. A laboratory-scale pan granulator was used to granulate pine wood powders of three different mean particle sizes (397, 225, and 135 μm) with an optimal concentration of starch binder. Of the three levels of starch concentration tested (2.5%, 5%, and 7.5%), the binder with 5% starch concentration was found optimal to produce pine granules. Wood powders with a mean particle size of 135 μm produced the highest granule density with strong granules at 5% binder concentration. Wood powders can be successfully densified into good-quality granules using a pan granulator for efficient handling, transport, and storage.