Gasmet Technologies, a Finnish manufacturer of emission monitoring instruments, has launched a continuous mercury emission monitoring system based on the cold vapor atomic fluorescence measurement principle.
The analyzer is integrated in an air conditioned cabinet together with a vacuum pump, an automatic calibrator and a nitrogen gas generator. The sample gas is extracted from the process duct with a dilution probe and heated sample line specially designed for sampling mercury from harsh process conditions. The analyzer has a detection limit of 0.02 µg/Nm3 and the lowest measuring range for total mercury concentration is 0 – 10 µg/Nm3 , according to Gasmet.
The monitoring system was road-tested on the emission stack of a rotary kiln cement plant with an electrostatic precipitator for particulate emission control. The test period lasted 30 days. The fuels used during the test included coal, petroleum coke and recovered fuels.
During the field trial, the raw mill was periodically stopped and the variation in mercury levels was monitored together with changes in other process parameters.
Average mercury concentration when the raw mill was running was 6 to 8 µg/Nm3 and when the raw mill was stopped, the concentrations could increase to 20 – 40 µg/Nm3. The plant had an emission limit value of 50 µg/Nm3 for total mercury.