FEATURE BATTERIES, GENERATORS & BACK UP POWER
MCPD AND THE ROLE OF THE DIESEL GENERATOR
TECHNOLOGY INNOVATIONS Diesel engine technology combines high thermal efficiencies with good fuel efficiency, resulting in low carbon dioxide emissions. High temperatures in the combustion chamber also increase the levels of nitric oxide (NO), which when released in to the atmosphere, oxides rapidly to create nitrogen dioxide. The trade-off is typically to lower the temperature in the combustion chamber to reduce the amount of NO produced, but this increases the likelihood of soot formation. It is this area where suppliers, such as Finning and Caterpillar are making significant engineering advances. Finning offers a range of air-to-air after
The Medium Combustion Plant Directive (MCPD), passed in to UK law in December 2017 and bought with it an array of stringent emissions’ legislation affecting new and existing combustion plant such as electricity generators, boilers and turbines rated between 1 MW and 50 MW thermal input
D
esigned to reduce harmful sulphur dioxide (SO2), nitrogen oxides
(NOX) and particulates in exhaust gases, the legislation is thought to affect around 150,000 sites in Europe. Headline-grabbing commentary
suggests that this could spell danger for existing diesel generator plants as achieving the new limits on nitrogen oxide emissions of 190mg/Nm3 is not feasible for a typical four-stroke engine process. However, with diesel-fired generators
playing such an integral part in on-site electric power generation, operators will want reassurances that their existing installation will remain unaffected and that manufacturers can continue to supply, and support, new and existing fleets. Jason Harryman, sales and business
development manager, Electric Power- Diesel for Finning (UK and Ireland), the UK’s sole distributor of Cat power generation equipment, discusses how by taking an engineering-led approach, operators can continue to invest in new diesel generator plants.
38 FEBRUARY 2019 | FACTORY EQUIPMENT
REDUCING NOX LEVELS The first area to consider is the application of the diesel generator, specifically the number of operating hours. The regulations set strict NOx limits ranging between 190-205 mg of NOx per Nm3 for power generation equipment up to the 50 MW threshold, which may limit, but not exclude, the potential of diesel to continue to be used as a power source 24/7. Reducing NOx emissions in a
conventional four-stroke engine to the levels required for continuous operation is problematic and both operators and regulators need to be mindful of the engineering limitations. However, the vast majority of diesel generators are commissioned on a standby basis, and therefore will fall below this threshold, with a caveat that operating hours should not exceed 50 hours per annum. This means there is already a vast,
installed estate of existing diesel generators in the UK and the challenge for manufacturers is to offer engineered solutions that can reduce NOx emissions while still continuing to offer engines with a high-power output.
Finning
www.finning.com T: +44 0800 028 7778
By taking an engineering-led approach, operators can contine to invest in new diesel generator plants
cooled, or charge-air cooled engines from the Cat 3516 range. This cools the engine air after it has passed through a turbocharger but before it enters the combustion chamber, effectively returning the air to a lower temperature for optimum power. The decrease in air intake temperature enables a denser intake charge to the engine and allows more air and fuel to be combusted per engine cycle, increasing engine output while lowering combustion temperatures to limit NOx production.
SELECTIVE CATALYTIC REDUCTION (SCR) Another area to consider is the introduction of selective catalytic reduction (SCR). SCR uses a urea-based diesel exhaust fluid (DEF) and a catalytic converter to reduce harmful NOx emissions. DEF is injected into the exhaust air stream where the energy contained in hot exhaust gas causes the NOx to evaporate into ammonia. Once the ammonia and exhaust gas reach the SCR catalyst it decomposes, breaking down into nitrogen gas and water vapour. Most operators expect fuel consumption
to increase if emissions are lowered. Engine-out NOx and fuel consumption are inversely proportional, meaning the greater the engine-out NOx, the lower the volume of fuel consumed. There is much work being carried out in
the stand-by market to ensure ongoing compliance below the 50 MW threshold. The future for diesel continues to look promising – especially for operators balancing their power demand with cost implications of investing in new plant and equipment.
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