GB655064A - Improved method of and apparatus for dehydrating wood and wood products - Google Patents

Abstract

655,064. Treating wood. HUDSON, M. S. Jan. 26, 1948, No. 2298. Convention date, Feb. 26, 1945. Addition to 655,062. [Class 140] [Also in Group XIII] In a modification of the apparatus for drying wood as described in Specification 655,063, which is in turn a modification of apparatus described in the parent Specification, the mixture of water vapour and drying medium is received from the drying chamber 107 by a complete condenser 109 which condenses the vapours to liquid phase. The liquids are then separated in a separator 110, the drying medium being collected in a tank 111 whence it is returned to the evaporator 108. Drying medium is supplied to the evaporator from storage (not shown), through line 112 and valve 113 to line 114 which leads to a pump 115 and line 116. Heat is supplied to the evaporator by steam-heated tubes 131 and cooling water is supplied to the condenser 109 through line 135. The pump 115 recirculates drying medium and water condensate formed in condenser 109 drains to the separator through line 127 and may then be drained to waste by opening threeway valve 139 to line 140, the valve 139 being then opened to line 141 to drain any organic condensate to the tank 111. The pump 115 is now stopped, the lines 114 and 116 closed and when the evaporator reaches the boiling point of the organic drying medium the drying operation may be started. Valves 142 are opened to introduce drying medium from the evaporator 108 to the drying chamber 107 through lines 143 and valves 144 are opened into the vapour header 145 which leads into lines 120, 147 to the condenser. The return tank 111 is heated by steam coils 154 and its liquid level may be gauged by a sight glass 155, photo-electric cells 156, 157 operating to control the pump 115 electrically so that when the liquid reaches the level of the upper cell the pump operates until the liquid reaches the lower level. The separator 110 also works automatically, electrode pairs 165, 166 being disposed therein. These electrodes complete circuits to the valves 158, 161 when immersed in the water layer being separated, which acts as a conductor. The condensate drains continuously but if the interface level rises, valve 161 is closed so that only water is discharged and the interface level falls. When it falls below electrodes 166, valve 161 opens again to discharge organic condensate to tank 111. A vacuum period may be imposed after the drying to recover organic material from the outer layer of the wood.