Areas that were investigated were the factors that cause corrosion in kilns, coatings to reduce or prevent corrosion, methods of protecting and sealing the kiln insulation, and elements of kiln design that cause corrosion. Experiments were conducted both in the test kilns at UT and on site at several large commercial installations. Effective coatings and other measures for reducing and correcting corrosion problems were identified during this work. Water spray system During the final stages of drying lumber, steam is sprayed into the kiln to raise the relative humidity. This process is known as conditioning.
Conditioning serves to relieve internal stresses that are produced during kiln drying.
To raise the shell MC, the humidity or wet bulb temperature has to be quickly raised in the kiln without increasing the dry bulb temperature. When steam is sprayed into the kiln, the combination of the latent heat from the steam and the heat given off by the absorption of water by the wood causes the dry bulb temperature to overshoot set point, resulting in slow or poor conditioning of the lumber. Some kiln operators find it necessary to open the kiln, allow the lumber to cool, and then re-heat and humidify the kiln, thereby wasting both time and energy. Researchers at UT were able to successfully adapt water spray systems previously used in green house humidification to replace steam spray for control and conditioning in a kiln. The kiln spray system consists of a high pressure pump that forces the conditioning water through special small diameter orifices to produce a droplet size in the range of 30 microns in diameter.