Evaluation of the efficiency of industrial kiln type CCA fixation chambers
A Taylor, P A Cooper
Six commercial CCA treating plants in Canada were assessed for the fixation efficiency of their hot air fixation chambers. The wood temperature was measured with thermocouples over the fixation period at different locations in the chamber and at the end of the fixation cycle, the degree of chromium fixation was determined by a boring leaching procedure. There was a great variation in the effectiveness of the chambers, related to the heat transfer efficiency of the kilns. Both an adequate steam supply and efficient air circulation are essential to ensure quality fixation in a reasonable time frame. In plants without this, the wood deep in the lumber piles is still in a mainly unfixed state when removed from the fixation chamber. In contrast, for CCA treated wood allowed to fix under ambient temperature conditions, the interior of bulk piled lumber fixes faster than the outer wood or stickered wood. This results from the cooling effect of water evaporation from the exposed lumber as it dries.
Keywords: CCA; FIXATION; KILN FIXATION CHAMBERS; ACCELERATED FIXATION; TEMPERATURE