Monitoring wet wood and sawdust
15 Jan 2000
The levels of moisture in sawdust and woodchip used in manufacture of MDF and particle board are very high typically in the range 30-50 % moisture and can vary greatly. This can cause problems for the dryer, which can become overloaded if too much very wet material is fed in at once. On the other hand, if feed rates are too slow, the process is inefficient in terms of time and energy. Accurate knowledge of moisture content after drying is required in order to calculate how much resin is required.
Again, in development of the measurement, Infrared Engineering worked closely with a number of board manufacturers, using data from many different sites in order to optimise the measurement. A large beam patch of 40mm diameter is used to increase the sample size, in order to help overcome the problem of wide variations in moisture content. This and the development of an appropriate algorithm has resulted in a stable measurement which can be used in a feed-forward loop for direct control of the feed rate into the dryer.
