PROCESS EQUIPMENT UPDATE
to be monitored. Each type of molecule in the gas gives rise to a specific pattern of light absorption. Te more molecules of a given type, the more absorption. By analysing the spectrum of the remaining light, specific gas concentrations can be calculated. Te DOAS method works excellently for atomic mercury (Hg0
), where
extremely low levels can be detected. Tis is extended to apply to total mercury (THg) by introducing a durable catalytic converter. In the complete system, a small amount of flue gas is extracted from the duct and led through the converter. In the converter, all mercury compounds are split up while what already is Hg0
unaffected, resulting in mercury only existing as Hg0
concentration, and thereby after the converter. Te
gas sample is then led to a monitoring cell where a gas analyser easily detects the Hg0
effectively the concentration of total mercury in the flue gas. Te Opsis System 400Hg has been
thoroughly tested and verified in a variety of harsh industrial environments over the past years, with excellent results. It is currently being rolled out to customers
both within the EU and elsewhere in the world. Operators looking for a complete multi-gas monitoring system can take advantage of the fact that a single Opsis system can be extended and configured to measure concentrations of many gaseous substances simultaneously, not only Hg0 and THg but also for example CO, CO2 HCl, HF, NH3
, , NO, NO2 , and SO2 . Tis
is applicable to continuous emissions monitoring in many different industry types, as well as to process control needs, for example to control and protect scrubbers and catalytic converters used in the flue gas cleaning.
Bengt Löfstedt is with Opsis.
www.opsis.se
remains
The Opsis continuous emissions monitoring system for total mercury
www.engineerlive.com 17
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