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Due to the increased focus on exhaust gas emissionsa BWSC succeeded in achieving the necessary experience and know how for construction of new power plants with special emission requirements and for retrofitting abatement processes in existing plants.
Depending on the actual emission requirement different abatement technologies can be applied.
Nitrogen-oxides (NOx):
Diesel engines with high thermal efficiency emit a relatively large amount of NOx.
The normal NOx emission level dictated by e.g. IMO and World Bank can normally be achieved by adjustment of the diesel engine and/or use of special NOx optimized fuel injection valves. Compared to an engine optimized for lowest possible fuel consumption slightly increased fuel consumption will be a consequence of such adjustments/modifications.
For NOx abatement in the area of 30 - 40% of fuel optimized NOx emission, water-fuel emulsion can be used with a slight fuel penalty of 1 - 2%. The water injected with the fuel will reduce the peak temperatures during combustion, which otherwise cause formation of NOx. Such system has recently been installed at the 85 MW Guam Piti Power Station built by BWSC.
In case further NOx reduction is required, a Selective Catalytic Reduction (SCR) system needs to be applied. Such system will remove 90% or more of the NOx contained in the exhaust gas.
In the SCR process ammonia (NH3) is added, which in a catalytic converter reacts with the nitrogen-oxides and reduces these to water vapour and harmless nitrogen, which already constitutes the main part of atmospheric air.
Such system has been retrofitted by BWSC on the 6 units that constitute the 232 MW Coloane Power Station in Macau.
Particle Matter (PM):
Recent years’ development of diesel engines include improved fuel injection valves and electronically controlled high efficient cylinder lubrication systems. The improved fuel injection and the reduction of cylinder oil consumption have made it possible to fulfil the strict World Bank requirements for PM emission without additional filtration of the exhaust gas.
New plants will normally be fitted with such features from day one, but BWSC has now retrofitted several older plants with these features, e.g. the 232 MW Coloane Power Station in Macau, the two 100 MW power barges moored on the coasts of Mindanao in the Philippines, and a 60 MW power barge located in the Port of Colombo in Sri Lanka. Not only does the equipment improve the ambient environment, it is also a sound investment for the power plant operator, as it contributes to a reduction of the cylinder oil consumption.
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