Abstract: Kiln design that uses a series of at least two subsections with airflow in constant but alternating directions instead of using bi-directional fans that periodically reverse directions. The uninterrupted alternating air flow may be used in continuous drying kilns (CDK) with two sets of carriages carrying spaced stacks of lumber travel in opposite directions through a sequence of chambers. The uninterrupted alternating air flow may be used with a set of at least one pathway for carriages carrying lumber to be dried where all carriages move from a first end of the kiln to a second end of the kiln.

Abstract: An apparatus that employs dual air ducts is described for balancing the return air flow between forward and reverse fan directions in a direct-fired lumber kiln. As freshly heated air enters the kiln, this system forces the air to pass through the stacks of lumber at least once before returning to be reheated. The disclosed apparatus and methods enable more efficient use of energy, reduce drying time and improve the uniformity and precision of the lumber drying process.

Abstract: A continuous drying kiln (CDK) design, in which two sets of carriages carrying spaced stacks of lumber travel in opposite directions through a sequence of chambers in which green lumber is exposed to heated air to dry the lumber to desired conditions. The continuous drying kiln using fans in each chamber to circulate air across the stacked lumber on the two sets of carriages, orthogonal to the direction of carriage travel, in either a first circulation direction or in a second circulation direction. As a carriage moves from chamber to chamber, the circulation direction is reversed.