RJM in Power Engineering International, December 2008
Controlling a Hungarian NOx uprising
PEi visits AES Tisza II, near Budapest, Hungary, home to a 900 MWe gas and light oil ired power plant. RJM International has developed and installed burner modiications, which reduced NOx emissions by over 70 per cent.
In the European Union, the Large Combustion Plant Directive (LCPD) ? one of the main pieces of legislation covering the power sector and the ever- tightening limits of Nitrogen Oxide (NOx) into atmosphere, is particularly challenging for some of the older power plants that resided on the "wrong side of the border" during the Cold War.
AES Tisza is a 900 MW oil/gas ired power plant in Tiszaujvaros, Hungary, some 200 kilometres east of Budapest situated relatively close to the eastern borders with Ukraine and Romania. The power plant is an oil and gas ired plant originally commissioned in 1978 and built by a Czechoslovakian company utilizing West German technology and origi- nally operated by the Hungarian state power irm MVM.
Times have changed somewhat since then. In 1996, US power com- pany AES acquired the power plant (together with two nearby coal-ired power plants and a local coal mine, now closed). AES Tisza underwent a major refurbishment between 2002 and 2004. The irst phase of the refurbishment was the replacement of the original Deutsche Babcock burn- ers of units 2 and 3, replaced with Alstom low-NOx, dual fuel burners and an OFA system.
These Alstom burners have now been replaced by burners made by UK NOx control specialists RJM International, which was the subject of a management buy-out from its US owners in 2005, in order to help the plant comply with the limits set out in the LCPD.
AES Tisza needed to reduce the original NOx level for gas iring for two of these boilers by almost two-thirds. For oil iring, RJM International was faced with reducing the original NOx level by more than half.
The basic fuel mix at AES Tisza is primarily natural gas, representing approximately 70 per cent of the overall total. The remaining parts of the mix are C9 and crack oil.
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Optimization and performance testing was completed for units 2 and 3 on 27 June 2008. To limit the optimization process in June to just three days (and in so doing saving AES a great deal of money in lost output), RJM concentrated on getting the NOx levels right with crack oil irst, as this is the most problematic fuel, before natural gas. Later, by basing the optimized burner settings RJM International used for crack oil to burn C9 oil, RJM International achieved a C9 NOx level of 3 at full load during the performance test. 186 mg/Nm
Goldring said: "We had some experience on unit 2 in February. We knew that crack oil was the most dificult, so when we came back to do unit 3 in June we made sure we got that right irst before moving on to C9. The basic difference between C9 and crack oil is that the C9 has no nitrogen, whereas the crack oil has 0.2 per cent, very similar to a normal heavy fuel oil."
"We provided the same equipment that we did for units 1 and 4 in 2004, but the 2008 emissions targets were harder to meet than then, so the settings had to be adjusted."
Final NOx levels achieved on units 2 and 3 following a short 3 on natural gas and less optimization period are less than 150 mg/Nm 3 on C9 oil. The same performance can be realized on than 200 mg/Nm units 1 and 4 by applying the same settings.
Since the new burner installations, AES Tisza II's four 215 MW units has been re-rated to 225 MW. Future work at the plant may include a repower- ing of unit 1 and there are also some expansion plans for new units.