The multi-phase pressure (MPP) process. One stage CCA treatment and accelerated fixation process
- Concepts proved by repetitive pilot plant treatments
A J Pendlebury, J A Drysdale, K Nasheri, H Pearson, M E Hedley
Twenty-four charges of radiate pine roundwood or sawn timber were treated using the MPP Process and hot CCA solution. Treated timber met the CCA retention and penetration requirements of the NZ Timber Preservation Council for Hazard Classes H3 to H5. The objectives of the trials were: (1) To "stress" CCA solution by repetitive heating, treating and cooling to determine its stability in the process; (2) to determine any effects of pre-drying regimes on the standard of treatment; (3) to determine the extent of fixation influenced by various treatment variables. At the finish of the trials, the working solution was clear with no propensity to sludging. Preservative element ratios remained constant throughout the trials. Wood moisture content at the time of treatment had, not unexpectedly, most effect on degree of fixation achieved. Kickback liquid contamination with residual CCA and organic carbon was greater when wood moisture contents were high.