John Howard Northrop
Engineers at Winn Rd, Portland, ME

5357881, Oct 25, 1994

Feb 9, 1993

8/016161

Andrew W. Elcik - Raymond ME
John J. Devine - Portland ME
John H. Northrop - Falmouth ME
Kurt T. Dunn - Topsham ME
John F. Healey - Sanford ME

Northrop Engineering Corporation - Portland ME

F23G 704

110346

This invention comprises a combined cellulose sludge dryer and burner in which the drying procedure is positively and automatically controlled in response to the moisture content of the dewatered raw sludge supplied to the dryer headbox and carried through a drying chamber to discharge a dried sludge having but a 15% moisture content and suitable to be burned to provide the hot air for the drying procedure. With the sludge being critical as to charring, a temperature of 300 degrees Fahrenheit to prevent pre-burning and charring of the sludge has to be maintained in the drying chamber and positive and automatic control for the hot air to maintain the temperature is done by checking differences between input and output temperatures of the dryer and diluting the air produced by the burner by the use of a heat exchanger and air dampers. The extracted wet air from the drying chamber and diverted over-supply of air to the drying chamber are delivered through a scrubber and chimney to the atmosphere. A series of opposing hot air and wet air extracting ducts are provided in the drying chamber for the handling of the drying air to direct it from beneath the travelling wire screen conveyor through the sludge particles thereon and passed to the extracting air ducts thereabove whereby to increase speed for drying sludge and the efficiency of temperature control equipment.