Indianapolis permits coal-to-gas conversions at Harding Street

Indianapolis Power & Light, a unit of AES Corp. (NYSE: AES), is pursuing a revised Title V air permit for its Harding Street plant that would allow the conversion of two coal units to firing natural gas.

The Indiana Department of Environmental Management is taking public comment until Sept. 16 on the draft version of the revised permit.

The planned conversions involve:

  • One Combustion Engineering boiler number 50 identified as Unit 5. Unit 5 is a pulverized coal tangentially fired unit with a design heat input capacity rated at 1017.0 million Btu per hour. Emissions are directed to one cold side electrostatic precipitator (ESP). SO3 injection is utilized as a flue gas conditioning agent for the ESP but the source is not required to perform gas conditioning. It is also equipped with low NOX burners, neural net controls, separated overfire air (SOFA), and selective non-catalytic reduction technology (SNCR). These technologies were voluntarily installed. Distillate fuel oil is used as supplemental fuel and for firing during startup of Unit 5. The installation date for Unit 5 is 1958.
  • One Combustion Engineering boiler number 60 identified as Unit 6. Unit 6 is a pulverized coal tangentially fired unit with a design heat input capacity rated at 1017.0 million Btu per hour. Emissions are directed to one ESP, with SO3 injection is utilized as a flue gas conditioning agent for the ESP but the source is not required to perform gas conditioning. Also equipped with low NOX burners, neural net controls, SOFA and SNCR. These technologies were voluntarily installed. Distillate fuel oil is used as supplemental fuel and for firing during startup of Unit 6. The installation date for Unit 6 is 1961.

Not to be converted to firing natural gas is the other coal unit at Harding Street. It consists of one Combustion Engineering boiler number 70 identified as Unit 7. Unit 7 is a pulverized coal tangentially fired unit with a design heat input capacity rated at 4123.0 million Btu per hour. Emissions are directed to one cold side ESP, with SO3 injection utilized as a flue gas conditioning agent for the ESP, though the source is not required to perform gas conditioning. Unit 7 is equipped with low NOX burners, neural net controls, SOFA, selective catalytic reduction technology (SCR) and a flue gas desulfurization (FGD) scrubber. These technologies were voluntarily installed. When the FGD is in operation, Unit 7 exhausts to a separate wet stack. Distillate fuel oil and used oil are used as supplemental fuel and for firing during startup of Unit 7. Unit construction was completed in 1973.

Indianapolis has offered coal-to-gas conversions within broader air plan

The Indiana Utility Regulatory Commission on Aug. 14 approved $511m worth of new air controls for the “Big Five” coal units of Indianapolis Power & Light (IPL) to meet air rules like the Mercury and Air Toxics Standards (MATS). IPL owns and operates 3,353 MW of nameplate capacity. Its Big Five consists of Petersburg Units 1-4 and Harding Street Station Unit 7 (HSS 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 requested approval to construct, install and operate 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, flue gas desulfurization (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 HSS 7 including ACI, FGD upgrade, ESP and Sodium Based Solution System (SBS) upgrades and continuous emission monitoring.

IPL in that case did not request approval of a control plan for its Small Six coal-fired units. These units are being evaluated separately and IPL is broadly looking at all options on a remaining life cycle basis. IPL said during the case that current analysis indicates that it is likely that the Eagle Valley coal plant will be fully retired ahead of MATS rule implementation, and that the coal-fired Harding Street Units 5 and 6 may be retired or repowered as gas-fired peakers.

These units are primarily coal-fired and represent 472 MW of net capacity in total. To replace this generation, in April 2013, IPL filed a petition and case-in-chief 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.

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.