Annual Guide 2022 I SOURCE TESTING ASSOCIATION
What is continuous mercury
monitoring? Continuous mercury monitoring is the process of determining in real time the concentration of mercury and mercury derivatives in the emitted gas stream from an industrial process.
Figure 1. Mercury content in fl ue emission gas in a European waste incinerator.
However, if using periodic sampling, the measured concentration will be highly dependent on the moment the measurement is taken. The periodic measured value is not likely to represent the true daily emissions based in part on random chance and the temporary state of the process.
If you take the diagram above, based on 30–60-minute sampling times you could end up reporting very low emission results, or conversely very high emission results. Neither set of results would be comparable with the true state of emissions. Therefore, periodic sampling just won’t cut it. Passing several periodic tests to prove low and stable emissions and continue showing low values twice a year will be a cumbersome and a highly uncertain task.
In comparison, continuous mercury monitoring systems provide process operators a real-time view of their mercury emissions. Continuous mercury monitoring systems also provide signal outputs proportional to the mercury emissions that can then be used for improved control of abatement systems, process optimization and ultimately demonstrating compliance to the sites’ environmental permit and legislation.
A quality continuous mercury monitoring system allows near instant reporting of the current concentration of mercury, which helps plants maintain compliance with regulations, as well as fi nd potential problems more quickly.
The Gasmet CMM and CMM AutoQAL systems represent the benchmark in continuous mercury monitoring. They have the lowest certifi ed QAL1 measuring range of 0-5 µg/m3
, as certifi ed
by TÜV and MCERTS. In addition, the Gasmet CMM AutoQAL has the ability to perform an automated QAL3 zero and span check.
In waste incineration, emission monitoring systems need to have a QAL1 certifi ed range of no more than 1.5 times the emission limit. This means emission limits down to 3.5 µg/m3
can be met
with the Gasmet CMM AutoQAL. This is lower than the lowest concentration of the new WI BREF requirements (5-20 µg/m3 ensuring a future-proof solution.
),
The functionality of continuous mercury monitoring systems needs to be checked for both zero and span drift to ensure continued quality of the measurement. Mercury chloride (HgCl2
test gas is used to perform the span check, and a zero check is performed using nitrogen gas with no mercury present. This is called QAL3 check.
The Gasmet CMM AutoQAL automates the entire QAL3 process. There is no need for third party testers or additional work from the plant staff. The Gasmet CMM AutoQAL has both an automatic HgCl2
span gas generator and a nitrogen zero gas generator that runs the QAL3 checks at user-defi ned intervals. )
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