Method and apparatus for controlling a dryer

摘要

A method and apparatus for operating a dryer used to reduce the moisture content of sheet material such as a jet veneer dryer. A drying chamber is provided and includes a plurality of individual, juxtaposed drying sections. Each drying section circulates air in a path substantially transverse to the path of movement through the dryer. A single point exhaust system extracts the exhaust from the first drying section. A wet seal section located at the input end of the dryer includes an exhaust passage through which a gas sample is drawn by a sampling fan. Gases within the wet seal section are a combination of ambient air drawn through restricted passages at the entry to the wet seal section and exhaust gas that bleeds into the wet seal section from the drying chamber. A controller monitors the temperature of the sampled gases and ambient air and adjusts the rate of exhaust flow from the main exhaust system as a function of the temperature differential. A preheat apparatus is also provided for transferring sensible heat from the exhaust gases to the incoming material. A reheat subsystem is also provided for maintaining the temperature of the exhaust gas above a predetermined minimum, if required.