The Indiana Department of Environmental Management on Sept. 15 approved air permit revision application submitted on Feb. 26 by Indianapolis Power & Light for its Harding Street Station.
The approved change is a modification to Boiler 70 (Unit 7) to enable the unit to use natural gas as its only fuel and discontinue the use of coal and fuel oil. The rated capacity of the unit will increase slightly from 4,123 MMBtu/hour to 4,346 MMBtu/hour as a result of the fuel change. This modification to Boiler 70 will also allow for the removal of the recently permitted storage silo for activated carbon, which will not be constructed and the source is also proposing to install a new 100 MMBtu/hr natural gas-fired auxiliary boiler.
Unit 7 is a Combustion Engineering boiler that is equipped with low NOX burners, neural net controls, separated over fire air (SOFA), and selective catalytic reduction technology (SCR). These technologies were voluntarily installed. Construction was completed on the boiler in 1973.
In 2013, the utility had permitted at Harding Street:
- the 1,162 MMBtu/hr Combustion Engineering Boiler 50 (also referred to identified as Unit 5), constructed in 1958, for modification from coal to natural gas combustion only;
- the 1,162 MMBtu/hr Combustion Engineering Boiler 60 (also referred to identified as Unit 6), constructed in 1961, from coal to natural gas combustion only.
The Indiana Utility Regulatory Commission on July 29 approved an October 2014 application from Indianapolis Power & Light for certificates of public convenience and necessity related to this coal-to-gas conversion project at Harding Street Unit 7. The commission had previously approved coal-to-gas conversions at Harding Street Units 5 and 6.
The Unit 7 conversion is needed to comply with federally-mandated requirements, including the National Pollutant Discharge Elimination System (NPDES) and the Mercury and Air Toxics Standards (MATS). IPL’s “Compliance Plan” approved July 29 includes the construction of wastewater treatment technologies, operational changes, and use of modified stormwater management practices at its coal-fired Petersburg and Harding Street plants, and refueling of Harding Street Unit 7.
IPL is a unit of AES Corp. (NYSE: AES).