CEM India - Abstract

Abstract Information :

Mercury is a toxic heavy metal naturally present in our environment. The mercury emission of coal-fired power plants is of growing global concern. Since 2013 the UNEP Minamata Convention on Mercury has been signed and ratified by more than 160 countries. The objective of the Convention is to protect human health and the environment from anthropogenic emissions and releases of mercury. Coal burning is one of the most significant anthropogenic sources of mercury emissions to the atmosphere with a total contribution of 85 %.

Today, only a few countries have set national standards for mercury emissions from coal-fired power plants. In the United States, all coal-fired plants have to be compliant with a mercury emission limit of 1.5 µg/Nm3 (hard coal) resp. 4.8 µg/Nm3 (lignite). In Germany, national regulations limit the mercury emission to 0.03 µg/Nm3 (daily average). The final draft of the revised Best Available Techniques Reference (BREF) Document for large combustion plants (LCP) sets new standards for future European mercury emission limit values: 1-4 µg/Nm3 (hard coal) and 1-7 µg/Nm3 (lignite) as yearly average are proposed.

The current Chinese Emission Standard of air pollutants for thermal power plants has set emission limits for mercury for the first time and defined a limit for mercury emissions of 30 µg/Nm3. India as one of the world's fastest growing economies has recently also taken measures for reducing mercury emissions from thermal power plants. The latest Environmental Standard for thermal power plants specifies a limit value of 0.03 mg/m3 for all units with a capacity of 500 MW or more.

For continuous monitoring of mercury emissions in flue gases cost-efficient and reliable analysers are required. Mercury emissions from combustion processes occur as a mixture of elemental mercury Hg(0) and oxidised mercury Hg(II). Since all available techniques are based on the detection of elemental mercury, oxidised mercury compounds have to be reduced to elemental mercury. For the analysis of elemental mercury different measuring techniques are available. A mercury analyser with a thermo-catalytic reactor for reduction of Hg(II) to Hg(0) using Cold Vapour Atom Absorption Spectroscopy (CVAAS) will be presented. The technique is widely used and allows the separate measurement of Hg(0) and Hg(II). Monitoring the ratio between Hg(0) and Hg(II) enables plant operators optimizing the flue gas cleaning process by implementing specific and efficient measures for mercury removal from the flue gas.

The presented technology allows the cost-efficient real time monitoring of mercury emissions and cost reduction for mercury removal from flue gas.