Blue sky thinking in Shenzhen, China

24 May 2019

Ultra-low-NOx combustion upgrade completed on nine 9E gas turbines in China, providing a benchmark for other operators of mature fleets.

GE has reported successful completion of the first installation of its ‘DLN1.0+ with Ultra Low NOx’ combustion upgrade, on nine GE 9E gas turbines at five power generation enterprises in Shenzhen, China (Shenzhen Nanshan Power Corporation, Shenzhen New Power Corporation, Shenzhen Datang Baochang Gas Power Generation Co Ltd, Shenzhen Yuhu Power Co Ltd, and CNOOC Shenzhen Power Co Ltd).

GE announced completion in April during the “Shenzhen Blue Sky” DLN1.0+ retrofit completion celebration event it co-hosted with Shenzhen Municipal Ecology and Environment Bureau and Shenzhen Nanshan Power Corporation. More than 100 power plant operators attended the event.

“Power generation companies are currently facing dual pressure from environmental indicators and economic performance,” said Liang Jianqiang, head of Shenzhen Nanshan power plant. “We continue to search for a two- way solution to help contribute to local blue skies while improving asset performance.”

The combustion upgrade has reduced NOx emissions from 50 mg/m3 (about 25 ppm) to 15 mg/m3 (about 7.5 ppm), thus contributing to Shenzhen municipal government’s “Blue Sky” campaign, which required all gas-fired power plants in the city to reduce emissions to below 15 mg/m3 in six months. Power plants that fail to comply with the requirements will be taken offline.

“The successful modernisation of nine gas turbines – in a record time of less than six months – provides a reference for many 9E units to repower and adapt to the needs of the new era”, said Yang Dan, CEO of GE Power China.

The project mobilised more than 200 experts from China and around the world to carry out factory modifications to meet specific timeframe requirements and exceeded performance expectations, serving as a model for operators of more mature gas turbine fleets in China and around the world, GE believes.

The improved combustion system, which can reduce NOx to as low as 5 ppm, includes:

  • more robust materials and improved thermal barrier coatings to extend maintenance interval and parts life;
  • new combustion hardware – fuel nozzle, liner and transition piece – improving the mixing of air with fuel and enhancing the hot gas temperature profile;
  • installation of a combustion dynamics monitoring system and improved control system using “Corrected Parameter Control (CPC)”, which employs real time information (eg, ambient humidity, ambient temperature, inlet and exhaust pressure losses) to adjust the split between the primary and secondary fuel circuit, helping maintain emissions below target.

In addition, the upgrade allows wider Wobbe index fluctuations to be accommodated, expanding gas source choices and helping the units to operate flexibly.

The upgrade can also potentially extend combustion system maintenance intervals to 32 000 hours or 1300 starts and stops, reducing maintenance costs and increasing operational flexibility.

GE notes that the upgrade is applicable not only to the nearly 700 9E turbines operating around the world but also to the global fleet of some 1000 operating 6B gas turbines, representing a total installed capacity of about 120 GW. 

CNOOC Shenzhen power plant
A principle aim of the ‘DLN1.0+ with Ultra Low NOx’ retrofit is to optimise the air-to-fuel ratio. Combustion hardware modifications include improving the distribution of air passing through the holes located at the head end of the liner, which feeds natural gas into the front end of the combustor, and the addition of a venturi shape to the same liner. The venturi is dual purpose: it tightly regulates the gas flow into the air–fuel mix, and also prevents flame blow-back into the front end. Downstream, in the transition piece leading to the gas turbine hot gas path, dilution holes have been inserted to enable introduction of additional air to achieve a leaner fuel mix. This enables ‘last-second’ addition of air to tailor the temperature profile inside the combustor and to further mix the hot gases to ensure a uniform combustor exit temperature
Shenzhen Datang Baochang power plant

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