WOOD DRYING METHOD AND APPARATUS Russian patent published in 1998 - IPC

FIELD: wood working industry, in particular, working and drying of lumber. SUBSTANCE: method involves forming lumber stack adapted for drying, with lumber stack transmittance being at least 20% by microwave field; exposing lumber stack to microwave energy at opposite sides; heating lumber till temperature within lumber blocks reaches 60-90 C and outside lumber blocks - 2-15 C by means of wicrowave energy and air flow having temperature of 50-90 C and relative humidity of 30-90%; drying lumber at the same temperature and relative humidity; periodically changing lumber moisture content; upon reaching predetermined final moisture content, relieving lumber inner stress by exposing it to moisture and thermal treatment. To do that, lumber temperature is increased to value exceeding drying temperature by 5-10 C but below 100 C. Method further involves holding lumber under mentioned conditions for time interval exceeding moisture and thermal treatment time by 2-3 times; stopping drying process and cooling lumber by outer air of premises where drying unit is positioned. Drying unit has microwave generators, transmitting antennas, each connected to microwave generator outputs, at least one heating member, fan, humidifier, drying chamber with door, false ceiling provided with longitudinal dividing wall, input and exhaust ventilation pipes with gate valves, device for changing lumber moisture content during drying process, lumber stack car, thermometers for measuring temperature within and outside lumber blocks and air temperature in drying chamber, psychrometer, and devices for controlling microwave generator and heating member power, as well as for controlling operation of gate valve drives. EFFECT: increased efficiency, increased drying rate and improved quality of dry stacked material and reduced power consumption. 6 dwg