Pre-Processing and Drying
Pre-processing and drying feedstocks are important from the standpoint of transport costs as well as combustion efficiency. The drier the wood, the less water transported. Assuming total transportation vehicle payload capacities stay the same, there will more wood (and less water) delivered per load. This will reduce the transport cost per unit of wood, and reduce the amount of water being handled, transported, and evaporated through combustion.
To facilitate efficient transport, material handling, and utilization at the conversion facility, biomass is further pre-processed during or after harvesting. The optimum treatment of the material depends upon the characteristics of the material, the end-use, and the site management requirements. Pre-processing should address two critical characteristics of biomass: particle size and moisture content.
The desired particle size is defined by the end user of the biomass. A rule of thumb is that the size must be small enough to be conveyed without material binding up or bridging. Several biomass power plants in the US have material specifications that provide for nominal 3- inch material; this means that nearly all of the material does not exceed 3 inches in any dimension. This can be accomplished with either chipping or grinding.
Encyclopedia ID: p1295
