Indirect drying method using two temperature zones

摘要

A method of drying material uses two different temperature zones within a single chamber. The material enters the first temperature zone where it is indirectly heated by structures heated to a first temperature. The material then moves to the second temperature zone where it is indirectly heated by structures heated to a second temperature different from the first temperature. The second temperature may be greater than or less than the first temperature. The method is particularly useful for drying materials that have a tendency to foul the heated structures of a dryer, such as wastewater treatment sludges.