Abstract: An apparatus and method operable for the continuous monitoring of a gas stream including an optical sensor operable to monitor and/or measure Hg concentrations in a flue gas by calculating the absorbance of the ultraviolet light thereby at a range of wavelength 253.7 nm+/?0.05 nm. The apparatus therefore provides as a spectrally narrow UV light source, a mercury lamp. The spectrally broad UV light source includes a UV LED. A 2×2 coupler is provided to mix the narrow and broad UV light energy which is propagated through the gas stream. The invention recognizes that measurement of radiation absorption at the 254 nm+/?1.5 nm range will result in not only from Hg0, but also from the SO2 component in the flue gas. To compensate for sulphur dioxide, measurement of energy absorption for both specially narrow radiant energy in the 253.7 nm+/?0.

Abstract: An apparatus and method operable for the continuous monitoring of a gas stream including an optical sensor operable to monitor and/or measure Hg concentrations in a flue gas by calculating the absorbance of the ultraviolet light thereby at a range of wavelength 253.7 nm+/?0.05 nm. The apparatus therefore provides as a spectrally narrow UV light source, a mercury lamp. The spectrally broad UV light source includes a UV LED. A 2×2 coupler is provided to mix the narrow and broad UV light energy which is propagated through the gas stream. The invention recognizes that measurement of radiation absorption at the 254 nm+/?1.5 nm range will result in not only from Hg0, but also from the SO2 component in the flue gas. To compensate for sulphur dioxide, measurement of energy absorption for both specially narrow radiant energy in the 253.7 nm+/?0.