10th Workshop on Mercury Emissions from Coal (MEC10), Clearwater, Florida, 22-25 April 2014

The 10th annual MEC (Mercury Emissions from Coal) meeting was held in the glorious sunshine of Clearwater Beach, Florida, USA. Almost 50 delegates from as far as Australia, Japan, China, Poland, and Slovenia attended to exchange the latest information on mercury emissions, legislation, measurement and control. As always, the MEC meeting was attended by experts in the field and so the discussion periods were extremely lively and enjoyable as well as a little volatile in some cases. The papers from the meeting will be available on the MEC website by 16 May.

In addition to two days of excellent papers, the final day of MEC was an open forum discussion on the work of the UNEP (United Nations Environment Programme) Coal Partnership Area and the feed in of expertise to the process of the Working Group writing the BAT/BEP (best available technology/best environmental practice) document in support of the new Minamata Convention on global mercury reduction.

The BAT/BEP guidance for reducing mercury emissions from the coal combustion sector is being produced by an international Working Group coordinated by UNEP. However, the main text summarising the technology options will be collated by the IEA CCC based on the POG (Process Optimisation Guidance document, available as a free download from the IEA CCC and UNEP), which is also largely based on IEA CCC reports. However, this work needs to be updated and expanded to include more information on industrial boilers and, where possible, cost data. The POG also lacks information on mercury measurement (to confirm the correct operation of control systems) and so new material is being sourced on this topic.

A chapter of the BAT/BEP guidance document is also being written on how to determine BAT/BEP – some form of “decision tree” or flow diagram would work, but would need to be produced in such a way as to be non-prescriptive. The document is there for guidance and is not intended to influence the decision making process.

It is intended that the BAT/BEP guidance will be supported by case studies which provide “success stories” of how mercury has been controlled at coal-fired plants in the real world. Users would search for case studies relevant to their situation and learn from these. The MEC delegation discussed the issue for several hours, providing insight and guidance which simply would not be available in any other forum.

The MEC delegates came up with several recommendations for the UNEP Working Group. In terms of the number of case studies required in order to provide relevant data across the sector, a working total was estimated at about 50. These should be searchable based on several basic differences:

A – amount of mercury reduction required – high, medium, low

Whilst countries such as those in N America and the EU may be looking towards >70 or 80% control targets, developing regions may move more slowly due to technological, economic and political challenges. Many regions still face issues with particulates and acid gas emissions, and mercury control is a lower priority. Case studies should be available which will maximise Hg reduction under these restrictions

B – coal type

C – combustion type (pulverised, fluidised bed etc)

D – control technologies in place (particulate controls, flue gas desulphurisation etc)

This will produce a matrix of case studies which it is hoped would be relevant to all. It is likely that some areas of the matrix will have numerous case studies to choose from. For example, the US will soon be able to produce numerous case studies relevant to over 90% mercury control on plants firing typical US coals. However, further projects may be required to populate areas of the matrix which represent more unique situations (such as fluidised bed plants, plants with older particulate scrubbers, plants with high ash coals).

The iPOG (the interactive computer model of mercury behaviour in coal plants, available as a free download from both the IEA CCC and UNEP) could be an extremely useful tool with respect to both the BAT/BEP guidance and the case studies. However, to be relevant to all coals and plants, and to include cost data, further development of the iPOG will be necessary.

The initial call for case studies demonstrating Hg reduction from coal combustion went out, via the IEA CCC, last month. The final call will go out within the next few months, following a revision of the template. This will be available from the CCC and UNEP upon completion.

The MEC group worked through some draft case studies which had been requested to test the template and this raised several issues:

1- The format of the case studies is generally okay but may work better in the form of an excel spreadsheet. This would mean that case studies could be collated in a single file and would be easier to search.

2 – More information should be provided on the final fate of the mercury (concentration in ash, waste water etc)

3 – Information should be provided on the location of the case study (geographically) and the host site, if possible. In some situations, specific details may be omitted if they are commercially sensitive.

4 – Information should be provided on the duration of the case study. Although long-term studies will provide better quality data, short-term pilot studies are likely to be required to be relevant to more unique fuel types or plant conditions. For example, the UNEP Coal Partnership project on mercury capture in wet particulate scrubbers in Russia was only carried out over a few months, but may be the only full-scale data available for plants of this type.

5 – Recommendations should be made on the units used (such as lb Btu vs Mg/GJ). This may be challenging.

The collation and dissemination of case study information was discussed. The official UNEP WG will need to select a steering review committee and this is likely to include several delegates from MEC as well as partners from the UNEP Coal Partnership. A system will need to be established which will allow the distribution and review of case studies as they are received in order to select the most appropriate. Several organisations have offered websites and facilities to host the case studies. However, it was agreed that the commercial nature of some of this data may mean that UNEP or a similar body would have to be the host.

A report from discussions at the MEC meeting will be provided to the UNEP working group and it is expected that the WG will call on MEC delegates, as well as other experts, to assist with the review of the BAT/BEP guidance and the case studies. IEA CCC will keep its members at the forefront of this discussion.