OTC stands for Optimized Two-stage Continuous channel dryer. The air passes through the transmission direction on the first stage and the opposite direction on the second stage.
The goal is to enhance the quality of the dried wood, especially with thicker sawed woods. This makes the last moisture percents like 10% possible. The first OTC-channel drier in Finland was built over 15 years ago.
On the first stage, the water is mostly dried from the cell cavities of the wood. On the second stage the rest of the water is tied into the cells until the wood reaches the wanted moisture level. The air conditions and drying speeds are adjustable in both of the stages.
The moisture of the wood is at the highest in between these stages. During this stage the insides of the thick sawed wood haven’t started shrinking yet, whereas the surface has dried and shrunk. The OTC-channel dryer aims to decrease the amount of tension inside the wood by keeping the relative air moisture levels fairly high. Once the most critical stage has passed and the insides have begun to shrink, the relative moisture of the air decreases and the drying speeds increases.
The drying process is very energy efficient due to the condensed heat that is transferred into energy.