PROCESS EQUIPMENT UPDATE
New standards are focusing the waste incineration industry’s attention on mercury monitoring
EMERCURYMISSIONS MONITORING
Bengt Löfstedt explains why monitoring of total mercury emissions has become a focus area within the waste incineration industry, and how to meet the monitoring needs
H
istorically, mercury (Hg) has found its use in many products such as thermometers, batteries and fl uorescent lamps. However,
mercury is extremely toxic and, therefore, it has in modern days been banned from use in most applications. By example, the Minamata Convention on Mercury from 2013 has been designed to prevent releases of mercury and mercury compounds to protect human health and the environment. It is signed and ratifi ed by well above 100 countries around the world. Nevertheless, mercury continues to
be released into the environment. Major anthropogenic sources are coal-fi red power plants due to the natural occurrence of mercury in coal, and waste incineration facilities. In the latter case, the mercury emissions are due to old mercury- containing products ending up in the waste to be burnt. Emissions of mercury from combustion facilities can be reduced by appropriate fl ue gas cleaning equipment. To drive the
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installation and use of such equipment, legislation can dictate emission limits. A recent example of this is found within the European Union, where the Industrial Emissions Directive (the IED) was supplemented by a new set of so-called Associated Emission Levels for waste incineration in December 2019. T ese are referred to as the BAT-AELs of the WI-BATC, where BAT stands for “best available techniques” and BATC for “BAT conclusions”. One of the new BAT-AELs states that the total mercury emissions, expressed as a daily average of a normalised gaseous mercury concentration in the fl ue gas, are possible to keep below 5 µg/m3 and in all cases must be kept below 20 µg/m3
. T e mercury concentration
must be monitored continuously unless the waste can be proven to contain a low and stable level of mercury content. Such proof can be hard or impossible to obtain, in particular in cases of mixed-waste or hazardous-waste incineration.
What then remains is to make sure that
the fl ue gas cleaning equipment is installed and working, and then monitor the remaining mercury emissions continuously. T is must all be up and running not later than by the end of 2023, when the new BAT-AELs come into eff ect.
When it comes to the monitoring part,
total mercury is needed, preferably with a proven reliability and a low total cost of ownership. Here is where Opsis off ers an ideal solution: the Opsis System 400Hg. T e Opsis System 400Hg is based on a technology called diff erential optical absorption spectroscopy (DOAS). A beam of light is led through the gas mixture
the word “total” in total mercury must be considered. T e mercury BAT-AEL applies not just to atomic (metallic) mercury in the fl ue gas but to all gaseous mercury, including compounds such as the relatively commonly occurring mercury chloride (HgCl2 (CH3Hg+
) and methylmercury ). Accordingly, a monitor of
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