Exploring Microwave Technology for Energy Efficient Mechanical Pulping and Increased Permeability of Spruce Woodg av Mekaniska Massaprocesser och Ökad Permeabilitet hos Granved

Projects main objectives are modification of Norway spruce wood ultrastructure to save electrical energy during thermomechanical pulping (TMP) and to improve wood permeability by applying microwave (MW) irradiation. Spruce chips will be MW irradiated and pulp and paper production carried out with industry to assess energy savings and maintenance/improvement of pulp and paper properties. Solid spruce wood will be irradiated and impregnated with conventional or novel green formulations to assess increases in permeability and changes in strength and durability. MW treatments will be conducted using impulse and resonance MW irradiation schedules. Alternation of pressure application with specific frequency will be achieved using MW irradiation causing a rapid water expansion in wood pit chambers causing deflection and rapid oscillation of pit membranes and their subsequent destruction and opening of wood structure. Alternatively, application of MW power pulsation frequency equal to the resonance frequency of pit membranes will be used to cause violent membrane deflection and system failure. By using both approaches, wood permeability should be increased with no effect on fibre and wood strength. The application of MW treatments should allow for energy savings with TMP processing as well as increased permeability of solid wood leading to economic gains for the whole industry.