High Temperature In-situ-detection of Atomic Potassium with Nir-diode Lasers

A laser-based in-situ spectrometer using near infrared diode laser at 767 and 770 nm to detect potassium atoms in high-temperature environments is described. The device was used to investigate the thermal dissociation of KCl and to monitor K behind the flue gas filter (300mm diameter, 1000°C) of a 250kW-coal combustor, without the necessity of error prone gas sampling. With a response time of 2 s we achieved detection sensitivities in the order of 10 atoms/cm. The spectrometer should therefore be fast and sensitive enough to detect a malfunction of the flue gas filters via the release of potassium atoms.