Indianapolis gets air permit for Harding Street coal-to-gas conversions

The Indiana Department of Environmental Management’s Office of Air Quality on Sept. 20 issued a final air permit revision that allows Indianapolis Power & Light to perform two coal-to-gas conversions at the Harding Street power plant.

IPL on April 30 filed the application with the department relating to conversion of Boilers 50 and 60 (Emission Units 5 and 6) from coal with a fuel oil backup to natural gas combustion only. The following is a list of the modified emission units as covered by the permit revision:

  • One 1,162 MMBtu/hr Combustion Engineering Boiler number 50, identified as Unit 5, constructed in 1958, approved for modification in 2013 from coal to natural gas combustion only, and exhausting at Stack/Vent ID 5-1. Unit 5 is a pulverized coal tangentially fired unit with a design heat input capacity rated at 1017.0 million Btu per hour.
  • One 1,162 MMBtu/hr Combustion Engineering Boiler number 60, identified as Unit 6, constructed in 1961, approved for modification in 2013 from coal to natural gas combustion only, and exhausting at Stack/Vent ID 6-1. Unit 6 is a pulverized coal tangentially fired unit with a design heat input capacity rated at 1017.0 million Btu per hour.
  • One activated carbon storage silo identified as EU-7 ACI, approved for construction in 2013, with a maximum hourly throughput of 1,337 lbs/hour, controlled by a fabric filter dust collector identified as ACI-1 and exhausting to stack S-ACI1.

The Indiana Utility Regulatory Commission on Aug. 14 approved $511m worth of new air controls for the “Big Five” coal units of IPL to meet air rules like the Mercury and Air Toxics Standards (MATS). Its Big Five consists of Petersburg Units 1-4 and Harding Street Unit 7. The Big Five comprise 65% of IPL’s total generating capacity and more than 82% of its coal-fired capacity.

The Big Five are fully scrubbed and have fewer years of service compared to the other primarily coal-fired units in IPL’s fleet, which are due for retirement. IPL was approved to construct a Pulse Air Fabric Filter System on Units 2 and 3 at Petersburg, and, on all Petersburg units, other environmental controls and monitoring equipment, including activated carbon injection (ACI), sorbent injection, FGD upgrade (Units 1 and 2) and electrostatic precipitator (ESP) enhancements (Units 1, 3 and 4) and continuous emission monitoring at Petersburg. IPL also requested approval for environmental controls on Harding Street 7 including ACI, FGD upgrade, ESP and Sodium Based Solution System (SBS) upgrades and continuous emission monitoring.

IPL said during that case that current analysis indicates that it is likely that the Eagle Valley coal plant will be fully retired ahead of MATS implementation, and that the coal-fired Harding Street Units 5 and 6 may be retired or repowered as gas-fired peakers. These units represent 472 MW of net capacity in total.

To replace this generation, in April IPL filed a petition with the IURC seeking a certificate to build a 550 MW to 725 MW combined cycle gas turbine (CCGT) project at its Eagle Valley site and to refuel Harding Street Units 5 and 6 from coal to natural gas (106 MW net capacity each).

If approved, the CCGT is expected to be placed into service in April 2017 and the refueling project is expected to be complete by April 2016. If Harding Street Units 5 and 6 are not refueled, they will likely need to be retired because it is currently not economical to install controls on those units to comply with MATS.

The Indiana Department of Environmental Management is in the meantime taking comment until Oct. 3 on a draft air permit that would allow IPL to shut the coal-fired capacity at the Eagle Valley plant and build a new gas-fired facility at the site.

“IPL Eagle Valley Generating Station is proposing to replace the current coal and oil fired electric generating units at Indianapolis Power and Light’s (IPL’s) Eagle Valley Generating Station (EVGS) with a state-of-the-art, highly efficient combined cycle combustion turbine generation facility,” said an agency notice. “The proposed combined cycle facility would include two nominal 192.5 Mega Watt (MW) combustion turbines with steam waste heat recovery to drive a nominal 271 MW steam turbine generator. The new facility would have a total nominal capacity of 656 MW (net). The exclusive fuel for the new combustion turbines will be natural gas.”

About Barry Cassell 20414 Articles
Barry Cassell is Chief Analyst for GenerationHub covering coal and emission controls issues, projects and policy. He has covered the coal and power generation industry for more than 24 years, beginning in November 2011 at GenerationHub and prior to that as editor of SNL Energy’s Coal Report. He was formerly with Coal Outlook for 15 years as the publication’s editor and contributing writer, and prior to that he was editor of Coal & Synfuels Technology and associate editor of The Energy Report. He has a bachelor’s degree from Central Michigan University.