Energy demand in wood processing plants
Computer models were developed to quantify the energy demand in a sawmill and a medium density fibreboard (MDF) plant, based on the production processes. For the sawmill, an empirical model was developed using mill data collected from a local sawmill near Christchurch. The model requires further practical data from more sawmills for validation. For the MDF plant, thermal energy demand was theoretically calculated and electricity demand was simulated empirically based on an energy audit. The MDF energy demand model was validated by plant data and the results showed a satisfactory accuracy with the discrepancies being -5% to 7% for the thermal energy prediction and ±4% for the electricity prediction.
With the inputs of product production and grade, the models are able to predict the energy demand, the log volume required, the wood residues generated and the energy self-sufficiency. The wood residues generated are usually be able to provide more than enough energy to meet demand including heat and electricity in a sawmill, but only 80-90% of the thermal energy demand in an MDF plant. The difference is due to the much lower energy demand in a sawmill.