Aim of the investigation was the determination of heavy metal concentrations, especially RoHS-relevant substances.
The task was to measure dust and gaseous emissions for the first time. Since there are no existing regulations or standards for carrying out these measurements or for limit values, an accredited analysis method was used that is often used to determine airbag emissions. In addition, the ignition residue was examined.
Representative samples with a size of about a postcard (approx. 50 g) were taken from the modules and "burned" in the laboratory furnace under controlled conditions. The tests were carried out at a heating rate of 10 °C/min at 600 °C, 900 °C and 1.100 °C (with a holding time of 1 hour), using both air and "burned" air with only 1% oxygen. The high-alloy reactor with an inner diameter of 80 mm was flowed through at an air flow rate of 15 L/min. A total of 21 tests were carried out.
Results of heavy metal emissions:
The Cd-Te module showed the most striking results: At 600 °C, the measurable cadmium release in dust was negligible. At 1.100 °C, however, the cadmium release increased to over 1 gram per kilogram of captured dust (approx. 0,15 wt.% Cd in the dust). All other modules emitted heavy metals to a much lower extent. The observed gas concentrations were low overall.
In addition, the ash residues chemically analyzed. The heavy metals found in the residues corresponded to the respective chemistry of the module types. In the ground melt residues, the heavy metal concentration was up to 0,12 m%.
Conclusion and recommendations:
Based on these initial results, we recommend conducting further experiments with entire modules under real fire conditions to gain more detailed insights specifically into heavy metal emissions.