Multi-stage dryer for particulate material

A gravity flow dryer for particulate material comprising:

• a first generally vertical drying column having first and second opposed spaced perforate walls;
• first input means for introducing moist particulate material into a top portion of the first drying column;
• first discharge means for removing partially dried heated particulate material from a bottom portion of the first drying column;
• a second generally vertical drying column having first and second opposed spaced perforate walls, the first and second drying columns being spaced apart to provide a plenum chamber between the columns, the first perforate walls of each drying column defining the plenum chamber;
• second input means for introducing partially dried heated particulate material to a top portion of the second drying column, the second input means including a steeping chamber for steeping the partially dried heated particulate material prior to introduction into the second drying column;
• second discharge means for removing dried particulate material from a bottom portion of the second drying column;
• conveyor means for receiving the partially dried heated particulate material from the first discharge means and conveying the partially dried heated particulate material to the second input means;
• means for providing drying air to the plenum chamber whereby the drying air passes into the first and second drying columns through the first perforate walls to heat and dry the particulate material, the drying air being exhausted from the drying columns through the second perforated walls;
• and
• means for directing a flow of cooling air through a portion of the second drying column to cool the dried heated particulate material prior to its removal from the second drying column.