
For many years, the wood-based panel industry has been making great efforts to reduce the release of the glue component formaldehyde from wood-based materials.
This is necessary due to a number of health risks associated with the use of formaldehyde. These risks include eye and respiratory tract irritation, and, with prolonged exposure at high concentrations, an increased risk of cancer.
Over time, wood-based materials containing formaldehyde can release it into the environment due to reactions with air humidity. The wood-based materials industry is therefore endeavouring to reduce the emission of its products through targeted adjustments to process parameters or the addition of formaldehyde scavengers.
In addition, the emissions of the materials produced are monitored closely and at great expense. New formaldehydefree glue systems are also being rapidly developed and tested in initial pilot factories. However, despite these advancements and the drawbacks of formaldehyde use, traditional urea-formaldehyde glues remain economically significant in the industry.
In the laboratories of the wood-based materials industry, standardised test methods for factory production control are used to monitor product emissions, such as the ‘perforator’ (EN 120 / EN ISO 12460-5) or the more modern ‘gas analysis’ method (EN 717-2 / EN ISO 12460-3). What both methods have in common is that test specimens must first be removed from the continuous strand of the woodbased material and typically must be conditioned for one to two days under ambient conditions. Emission testing is then carried out in the laboratory. Production management therefore receives the test results with a delay of one to two days. This is an enormous amount of time when you consider that these results are necessary to ensure that the manufactured product also fulfils the legal requirements. This makes it impossible for process control to react to unforeseen events, which in turn entails the risk of increased reject production. At the same time, precise process control with regard to material emissions is made more difficult by the fact that only a small amount of laboratory test data is generated (around two measurements per day and production line). This leaves great potential for process and cost optimisation untapped.
With the innovative in-line testing system GASANALYSER IL, Fagus-GreCon is currently developing a new measuring method, enabling real-time monitoring of the panel emission during the ongoing production process. The data obtained is processed in a statistical analysis and displayed in real time to predict the subsequent emission values from the laboratory.
IN-SITU LASER SPECTROSCOPY
The analytical centrepiece of the new measuring method is an in-situ laser analyser, which is installed in the extraction system of the diagonal saw of a wood-based panel line.
Physically, the principle of infrared laser spectroscopy is used here, ie the analyser generates laser light with a wavelength specially tuned to formaldehyde. This light is emitted from the laser source through the extraction tube onto a detector. When the laser beam hits formaldehyde in the pipe, an interaction takes place which attenuates the laser light. This decrease in light intensity is recorded on the detector side and converted into the formaldehyde concentration, as the loss of intensity is proportional to the amount of formaldehyde in the gas flow.
The extraction of the diagonal saw is a particularly promising measuring position, as the saw divides the continuous strand of the wood-based material into individual segments and releases a material-specific particle cloud with each cut, which is extracted by a corresponding ventilation system (see Figure 1). Depending on the emission level of the wood-based material, formaldehyde is also released, whereby the amount of formaldehyde released correlates with the emission of the material produced.


Although the measurement data generated in this way correlates with the product emission determined later in the laboratory, it cannot initially be reliably converted into a forecast. For this purpose, a statistical model must be used that takes other factors into account that directly influence the amount of material and formaldehyde in the extraction system. These factors are, for example, the panel thickness, the panel density and some others, which must also be recorded and considered in the further evaluation. Only the statistical evaluation of the process factors together with the formaldehyde concentration measured by the laser analyser enables a reliable prediction of the product emission.
INITIAL FIELD TEST
Both the statistical model and the methodological feasibility in the process have already been tested as part of a field test in a particleboard factory.

The analyser was installed in the extraction system of the diagonal saw of a cutting line and the relevant process-specific parameters were recorded. In parallel, one to two laboratory measurements were carried out daily to determine the gas emission value in accordance with EN ISO 12460-3 and the results obtained were used to train the statistical prediction model.
The results obtained are shown in Figure 3 for a sample size of 20 sample sets. As can be seen, there is a clear correlation between the test value predicted by the model and the gas emission value measured in the laboratory. The deviation between the predicted value and the actual measured value of the laboratory is on average only approximately 6%.

CONCLUSION
The initial field test of the new system has delivered promising results and is now being validated with other customers. Once the validation phase has been completed, this new measuring system will make it possible for the first time to track the formaldehyde emission of wood-based materials in real time in a running production line. As a result, potential process problems that could lead to limit value violations and material waste can be recognised at an early stage and the process can be specifically controlled with regard to product emissions. This presents significant potential for optimising energy consumption (eg, press temperature), production speed and additive usage (eg, formaldehyde scavenger dosing). As a result, the process becomes more efficient, costeffective, and environmentally friendly.