VGB Workshop on Mercury Control, Berlin, Germany, 15-16 June 2017
Posted: 17 June 2016 By: Dr Lesley Sloss
This was a satisfyingly technical meeting of over 100 participants from 14 countries, including EU member states, the USA and Japan. The meeting opened with a quick summary of the state of the EU BREF (best available technology reference documents) which are being prepared under revisions of the IED (Industrial Emission Directive) which applies to emissions of pollutants, including mercury, from coal-fired power plants in Europe. The BREF is almost complete and, as it stands, the proposed limits for mercury will be challenging for many plants. A vote on the acceptance of the BREF should take place in late 2016/early 2017. VGB has set up an initiative to work on joint activities to determine appropriate compliance options for German utilities.
The BREF should be adopted in 2017 and permits for plants will have to change accordingly within 4 years of publication.
The current proposed emission limits for mercury for coal-fired plants are as follows:
<300 MW 1-9 µg/m3 for existing plants and 1-3 µg/m3 for new plants
>300 MW 1-4 f µg/m3 for existing plants and 1-2 µg/m3 for new plants
For lignite plants:
<300 MW 1-10 µg/m3 for existing and 1-5 µg/m3 for new plants
>300 MW 1-7 µg/m3 for existing and 1-4 µg/m3 for new plants
The limit for discharge water is 0.2-3 microgram/l.
Monitoring for compliance can be by continuous emission monitoring (CEM) or sorbent trap (yearly average values).
The emission limit is undeniably low and, judging by the vociferousness of the question and answer session, there is some disagreement, even within Germany, on how achievable and how affordable compliance with the new BREF will be, especially for lignite plants.
Kather from TU Hamburg gave a review of how emissions from lignite plants in Germany compared with the US MATS (Mercury and Air Toxics Standard) limits. MATS appears tighter in that it has a lower maximum value but, under the BREF, some plants may be required to comply with limits which are much lower in practice. Kather suggested that the conversion to EU units of equivalent MATS limits have been miscalculated in the past and that the MATS limits are, in fact, more lenient than quoted in many documents. Kather also expressed concern at the way data from circulating fluidised bed combustion (CFBC) plants in Germany have been included in emissions studies because they show consistently lower mercury emissions than pulverised plants. At the moment, the BREF proposes to bring all plants to meet the limits achievable by the top third performing plants in the EU but, according to Kather, the definition of “best performing” is open to interpretation. Based on current data, the top 1/3 achieve <1 µg/m3, which would be very challenging for other plants, especially lignite units. Kather argues that CFBC plants are pulling the emission values down to a level which is too challenging for lignite plants - no lignite plants in Germany can currently meet <1 µg/m3.
Kather also argued that the conversion of the MATS emission limit values (expressed in weight of emissions per energy produced in imperial units) into EU units (on a weight per volume basis, metric) has been calculated incorrectly in the past. Conversions of values in lb per BTU to µg/m3 requires taking into account the different O2 contents and standard volumes as well as considering the conversion from gross calorific value (HHV, higher heating value) used in the USA to LHV (lower heating value) for the EU. These conversions must be performed in the correct order to be meaningful and will vary with the efficiency of the plant. If the correct conversion is used, Kather suggests that the MATS limit is actually less challenging than the BREF limits. As a result, Kather suggests that 50% of the German lignite plants would already be in compliance with MATS values and that setting a lower value is too challenging - if the BREF moves forward with the lower level range of emission limit, <1 µg/m3, then this means that the German limit would be 50% of the MATS ELV – much harder to achieve.
An Okopol study cited by Kather calculated the cost of compliance with MATS and BREF. In the US the cost of MATS is equivalent to 0.25 eurocent/kWh. Okopol suggests that German plants could meet the BREF limits for 0.0167 eurocents/kWh. But Kather argued that actual costs are likely to be around 50 times higher and suggested that German politicians are promoting a limit for Germany that is too tight and that it is significantly more expensive than is being claimed. Unsurprisingly, the question and answer sessions involved quite a bit of disagreement on the data and calculations used from proponents on both sides of the argument.
I then gave a presentation on the Minamata Convention and the mercury control requirements therein which I suspect was largely light entertainment since, as it stands, the BAT/BEP within the convention is much less structured and currently significantly less stringent than the EU BREF being discussed. However, the audience appreciated a wider view of what was happening globally with respect to reducing mercury emissions from the coal sector, although it did serve as a reminder that there is a significant gap between the emission limits in many westernised countries and those, if any, in emerging coal using nations.
Reissner, from the EPPSA, discussed the predicted costs of mercury control in Europe. Dry flue gas desulphurisation (FGD) plus ACI (activated carbon injection) or bromine addition came in at <15 eurocent/MWh. This implies that the cost of mercury control in the EU would be around 50% of the cost in the USA. Wet FGD with mercury control could be <11 eurocent/MWh. Recovery on investment would be achievable within 10 years. The presentation included some very interesting cost data and the full EPPSA report is available as a free download from http://bit.ly/25Ap8lc
There was then a session on mercury behaviour and chemistry including interesting and technical papers on the importance of FGD chemistry on mercury capture and the avoidance of re-emission of mercury from FGD systems. The final session of Day 1 of the meeting concentrated on compliance monitoring under the proposed new BREF, something that has been the subject of a previous blog I published from the CEM meeting in Lisbon a few weeks ago.
Day 2 carried on with further high quality presentations on how best to maximise mercury oxidation throughout the coal plant to enhance mercury control and capture, especially in ash and gypsum. The issue of re-emission of mercury from FGD systems was mentioned often and, each time, led to much discussion over the ability to work with the existing chemistry of the system to reduce mercury emissions or whether additives were necessary.
The papers presented at the meeting are available free to registered meeting delegates although they may be available, upon request, from the conference organisers. Contact email@example.com at VGB Powertech for further details.
For those who are as fascinated with mercury emissions as I am, please do join us at MEC12 in South Africa 28 February – 3 March 2017. Check our website for details, as registration will be open soon.