Dryer apparatus and dryer control system

Abstract

An improved dryer ( ) and drying methods are provided which increase overall dryer efficiency by maintaining substantially constant output air stream adiabatic saturation ratio and temperature values during the course of drying, notwithstanding the occurrence of upset conditions. The dryer ( ) includes a dryer body ( ), an input air heater assembly ( ) including an air heater ( ), and a control assembly ( ). The dryer body ( ) has a drying zone ( ), with product inputs and outputs ( ) as well as an input ( ) for a heated air stream and an output ( ) for the cooled, moisture-laden output air stream. The dryer control assembly ( ) includes temperature and humidity sensors ( ) coupled to controllers ( ) and a PLC ( ). The controller ( ) is coupled with an exhaust fan/damper unit ( ) while controller ( ) is connected with a fuel valve ( ). In operation, the temperature and humidity of the output air stream are continuously measured by the sensors ( ), and the controllers ( ) are operable to adjust the exhaust fan/damper unit ( ) to regulate the relative proportion of output air exhausted to the atmosphere and recycled via conduit ( ) for mixing with the input air stream, and also regulate the energy input to the dryer. Maintaining a substantially constant output air stream adiabatic saturation ratio and temperature allows dryer operation at significantly higher efficiencies as compared with prior systems.