Last week’s ‘EXPPERTS’ conference in Krakow was dominated by discussion of the incoming EU legislation on power plant emissions, known as the LCP BREF*. Currently in draft and likely to take effect from 2020, this is a revised reference document on the ‘best available techniques’ (BAT) for emissions control in large combustion plants, which will now also dictate binding emissions limits under the industrial emissions directive. The new document will have a huge impact on the fossil fuel power industry as it proposes SO2, NOx and particulate limits that are significantly stricter than the existing values, whilst adding new species such as mercury and HCl. Consequently, most of the conference presentations were either from utilities alarmed by the new ruling or pollutant control technology providers offering possible solutions.
Despite the European Commission’s presentation outlining the painstaking discussions with industry that led to the current draft, there seemed to be general agreement that the proposed limits would be crippling for the coal power industry and had not sufficiently accounted for costs. A presentation from power industry representative Eurelectric warned that the legislation should not dictate the power mix in Europe, whilst emphasising the importance of thermal power plant to grid stability and flexibility. We heard repeatedly that fossil fuel plants are caught in a perfect storm where low power prices and running hours are making it impossible to invest in the necessary flue gas cleaning equipment. Power plants in some countries, including the UK and Poland, will already struggle to meet the limits in place from next year until 2020, and have applied for more lenient ‘transitional national plans’ for this period. In particular, Polish utility Tauron asserted that the HCl limits set by the new BREF would be simply unattainable given the composition of Polish coal, whilst several others highlighted the difficulty of controlling mercury emissions in FGD wastewater. Exemptions from the new legislation, known as derogations, will only be possible where the plant can prove that the environmental cost will be less than the cost of BAT installation.
With this strained environment in mind, many of the technologies discussed were aimed at obtaining effective emissions reductions at a reduced cost. For NOx control, this is generally a case of avoiding installation of an expensive SCR system at all costs, instead applying advanced primary measures and better targeted SNCR. Mobotec presented their rotating overfire system ‘ROFA’, which can halve NOx reductions by introducing turbulence and increasing combustion residence time. Advanced SNCR systems generally involve more adaptive injection of ammonia or urea using adjustable nozzles and furnace temperature modelling, and can now even be applied to boilers larger than 600 MW. The catalyst sellers were undeterred however, presenting some more economical new concepts such as particulate filter bags with catalyst embedded in the fibres, or meeting SNCR halfway by installing only a single catalyst layer in the flue gas duct. Advanced catalyst compositions have also been developed to deal with mercury whilst avoiding the formation of the troublesome by-product ammonium bisulphate.
In flue gas desulphurisation there was less innovation on show, but again a clear move towards less capital intensive options such as dry sorbent injection, particularly for plants with not much time left to run. A Greek power company even related how they had opted for lime injection over installation of wet FGD at 300 MW lignite units with 15 years remaining, generating huge quantities of solid waste. Another analysis by Valmet demonstrated how, in certain cases, semi-dry FGD could be more economical than wet FGD even for large coal plants.
An informative talk from IFK Stuttgart outlined the fate of mercury in coal flue gas, which is ideally oxidised to a charged, soluble form in an SCR before dissolving in a wet FGD. In the absence of these scrubbers, elemental mercury can stick to fly ash and be captured by particulate filters, but this is less effective with the low-carbon ash produced by an efficiently run boiler. Injection of sorbents such as activated carbon is one solution now being widely adopted in the US, where mercury limits have been recently introduced, although these techniques were not really featured. Of course, the mercury captured by the FGD water also needs to be dealt with, probably by a precipitation and filtration process.
The new BREF legislation still has to go through some final stages of the Brussels machine, and it will be interesting to see if the issues raised at this event have any impact on the proposed limits. In its current form it seems likely to deal a serious blow to the already struggling coal power industry in Europe, with coal-dependent countries like Poland set to lose significant proportions of their generating capacity. By implementing technologies like the ones on show at EXPPERTS, coal plants can, in fact, meet almost any emissions limits. Unfortunately, such investment is unlikely unless European energy markets move away from an ‘energy only’ model to one which better values the necessary capacity and flexibility provided by these power plants.
*LCP = large combustion plant
BREF = Best Available Techniques (BAT) reference documents