News
Major advance for control system close at hand
Valutec’s development project involving control of continuous kilns has come a long way in the past year. One key to a more automated drying process, where clear and rapid signals from the timber package adjust the drying process, could be so-called ”Adaptive-Continuous Control”. This method has been tested, with good results, and is already being used for continuous kilns in both Sweden and Central Europe.
Moelven Edane’s new 2-zone FB continuous kiln has served as the test bed over the past six months. The project group, headed by Valutec’s Development Manager Thomas Wamming and also including kiln operators Lars Persson and Stig-Erik Larsson, has tested a number of different sensor positions, among other things, to find the clearest possible signals to the control system.
“In continuous kilns with edge control, attention has not been focused so much on the position of the air that comes out. The function of the sensor there has been to ensure that we are reasonably on the right track. In order for ”Adaptive-Continuous Control” to be effective, we need to find correct positions,” says Wamming.
One challenge is that the sensor picks up signals from both the timber and the surroundings, for example, in the form of leakage air.
“Effective ”Adaptive-Continuous Control” can better handle the variations in the timber coming in and also yield a more stable moisture ratio in the end. However, the input signals must be clear. The primary benefit, as we see it, is for inexperienced kiln operators. Experienced operators who know their kiln and their timber can generally handle any variations caused by the sensor picking up signals originating from something other than the timber,” says Wamming.
“It’s comparable to having an automatic gearbox instead of having to change gear yourself when driving. It simplifies things,” he explains.
At Edane, Valutec has now identified positions for the sensors that Thomas says feel “genuinely interesting”. Two months of data has now been compiled and the continuity of the results being delivered also looks good.
“With the way we have constructed the kiln for Edane they are ready to move forward with automatic connection to the control system once it’s complete.”
Internal development work is proceeding in parallel at Valutec to update their Valmatics control system, with the objective of making control based on average value a new function in future versions.
“We are working on this and will launch it once it is fully completed. We are still in the development stage. There is a technical limitation that, among other things, involves managing the sensor positions specifically. You can’t just expect to press a button and start a new method of control, no matter what machine you are talking about. You have to ensure first that the practical details and the system itself work together,” says Thomas.
Today several sawmills in Sweden as well as Austrian Hasslacher is using ”Adaptive-Continuous Control”.
FACTS: Moelven Edane’s continuous kiln has a capacity of 40,000 m3 per year. It is an FB continuous kiln, in which drying takes place in two separate zones. The first zone provides quicker humidifying, which reduces the risk of dry cracks at the input end. The second zone acts as an equalisation zone and reduces moisture distribution. The kiln is made from stainless steel and equipped with pressure frames and heat recovery systems, among other features.