METHOD AND PLANT FOR DRYING WOOD Russian patent published in 1997 - IPC

FIELD: drying technology; drying hardwood. SUBSTANCE: drying is effected by stepwise heating of material by means of temperature-controlled heating elements to required temperature, holding at each stage of heating and regular treatment of wood by vacuum in course of drying. Heating is effected continuously. After required temperature has been achieved it is maintained at this level till completion of drying procedure. Heating with temperature-controlled heating elements is conducted at several zones located lengthwise at gaps. Length of heating zones ranges from half to four thicknesses; length of gaps between heating zones is no less than length of one heating zone. Treatment of wood with vacuum is started simultaneously with heating; duration of vacuum treatment periods is set by minimum time of formation of permissible volume of condensate; duration of intervals is set by time required for complete drainage of condensate. At first stage of heating, temperature is raised to level corresponding to temperature of saturated steam (boiling of water) for specified working pressure of vacuum treatment similar for all stages. Temperature-controlled heating elements of wood drying plant are made form tubes of rectangular section located in parallel in each row and perpendicularly relative to length of material being dried. These tubes may be interconnected within one row forming at least one flat coil provided with heating medium supply and discharge devices. Adjacent tubes of each coil may be rigidly interconnected by means of spacers. EFFECT: enhanced efficiency. 10 cl, 5 dwg