Thermal camera lumber timber wood continuous kiln

Measurement of wood moisture content in a continuous timber kiln

In the project, a thermal camera was installed on an FB continuous lumber kiln to make moisture content measurements on the timber stacks in the kiln. The project is funded by the Kamprad Family Foundation over a 3-year period. The participants are J G Anderssons Söner AB, RISE, Linnaeus University, Termisk Systemteknik AB and IKEA.

An average daily moisture content diagram showing that the timber in the kiln was dry at the end of August after the summer break, and that the timber's average moisture content and moisture content distribution increased in early September.

The challenge

Wood is often over-dried because online measurement techniques for use in wood dryers are rarely used in Sweden. Such measurement probes must be mounted and unmounted before and after each kiln drying batch, which is considered too time consuming. In addition, a measurement technique that can work in a continuously fed kiln must also be non-contact because of the moving stacks. Consequently, a measurement technique is needed which can perform measurements at a distance, without touching the wood, and which does not need to be handled by the personell.

The project

Previous research has shown that there is a connection between the timber temperature and the timber moisture content. Drying and surface temperature data on spruce have been produced in a previous project in the laboratory, and a model based on that data is used in this project to predict the moisture content of timber in an industrial kiln at JG Anderssons Söner AB. The project's main goal is to develop a functional measurement setup and software to arrive at a measurement technology for the use in all kinds of lumber kilns. A thermal camera was mounted in the middle of a two-zone continuous kiln in the attic and, via surface temperature measurements on the wood and reference surfaces, the average moisture content and the moisture content distribution on each wood package and stack that passes the thermal camera are predicted. The data is compiled and presented continuously to the kiln operator, who can respond to it by adapting the drying process.