Interstate Power and Light seeks permit changes for Ottumwa coal plant

The Iowa Department of Natural Resources (IDNR) is out for comment until Dec. 18 on draft amendments to a Prevention of Significant Deterioration (PSD) Air Quality construction permit for Interstate Power and Light (IPL) for the coal-fired Ottumwa plant.

IPL submitted four requests since May 2016. Two of the requests were associated with a federal court Consent Decree between the U.S. Environmental Protection Agency (EPA), the IDNR, Linn County, and the Sierra Club . The other requests were for a change in the pressure drop range for the baghouse on the boiler and to be allowed to combust refined coal. These requests were split into Project Numbers 16-075 and 16-195. Based on the information submitted in the applications the IDNR is proposing to make the following amendments in this draft permit:

  • Addition of the Consent Decree emission limits;
  • Addition of a 3.68 lb/hr limit for sulfuric acid mist emissions;
  • Allow the use of refined coal in the boiler;
  • Amend the pressure drop range required on the boiler baghouse;
  • A requirement to install and continuously operate a selective catalytic reduction (SCR) unit to control nitrogen oxide (NOx) emissions. The IDNR has also added a minimum ammonia injection rate to demonstrate the SCR is operating;
  • A requirement to continuously operate the flue gas desulfurization (FGD) system to control sulfur dioxide (SO2) emissions. The IDNR has also added a minimum lime slurry injection rate to demonstrate the FGD is operating;
  • A requirement to continuously operate the boiler baghouse; and
  • A new permit condition was added which covers all of the system-wide Consent Decree requirements.

The Ottumwa Generating Station (OGS) is located in southeast Iowa, about 100 miles southeast of Des Moines near the Des Moines River. There is one boiler at the plant. It is a twin-furnace tangentially-fired pulverized coal boiler that typically burns Wyoming Powder River Basin (PRB) sub-bituminous coal. The unit was designed to also operate on bituminous coal. OGS is currently capable of producing electricity during a maximum cruise operating condition at a rate of 673 MWe (net). IPL operates the unit and has a 48% ownership share. MidAmerican Energy owns the other 52%. The facility began operation in 1981.

The 2015 Consent Decree covered seven coal-fired power plants located in Allamakee, Clinton, Des Moines, Dubuque, Linn, Marshall, and Wapello counties in Iowa. IPL agreed to invest more than $620 million (EPA estimate) in pollution control technology, spend $6 million on environmental mitigation projects and pay a civil penalty of $1.1 million. Highlights of the Consent Decree include:

  • Retirement of Lansing Unit 1, Lansing Unit 2, Lansing Unit 3, M.L. Kapp Unit 1, Sutherland Unit 2, Sixth Street Unit 1, Sixth Street Unit 2, Sixth Street Unit 3, Sixth Street Unit 4, and Sixth Street Unit 5 upon entry of the Consent Decree. All of these units had already ceased operation and/or were removed from the site well before the lodging of the Consent Decree.
  • Retirement or repowering of Dubuque Unit 1, Dubuque Unit 5, Dubuque Unit 6, Sutherland Unit 1 and Sutherland Unit 3 by June 1, 2019.
  • Retirement or refueling of M.L. Kapp Unit 2 by June 1, 2015, of Burlington Unit 1 and Prairie Creek Unit 4 by Dec. 31, 2020, and of Prairie Creek boiler 1, Prairie Creek boiler 2, and Prairie Creek Unit 3 by Dec. 31, 2025.
  • Continuous operation of selective catalytic reduction (SCR) at Lansing Unit 4, and compliance with (a) a 30-day rolling average emission rate for NOx of no greater than 0.090 lb/mmBTU by Jan. 31, 2015 ,and (b) a 30-day rolling average emission rate for NOx of no greater than 0.080 lb/mmBTU by Dec. 31, 2015. The SCR system for Lansing Unit 4 was permitted by the department in 2008 and began operation in 2010.
  • Continuous operation of a low NOx combustion system at Ottumwa Unit 1 and compliance with: (a) a 30-day rolling average emission rate for NOx of no greater than 0.210 lb/mmBTU, and (b) a 12-month rolling average emission rate for NOx of no greater than 0.160 lb/mmBTU by no later than 60 days upon entry of the Consent Decree.
  • Installation and continuous operation of SCR (or alternate equivalent NOx control technology approved pursuant to the consent decree) at Ottumwa Unit 1 by Dec. 31, 2019, and compliance with a 30-day rolling average emission rate for NOx of no greater than 0.080 lb/mmBTU.
  • Installation and continuous operation of dry flue gas desulfurization (FGD) at Ottumwa Unit 1 by Dec. 31, 2015, and at Lansing Unit 4 by Dec. 31, 2016, and compliance with a 30-day rolling average SO2 emission rate of no greater than 0.075 lb/mmBTU. The FGD system for Lansing Unit 4 was permitted by the department in 2013 and it began operation in 2014. The FGD for Ottumwa Unit 1 was permitted by the department in 2012 and it began operation in 2014.

There is no projected increase in emissions at Ottumwa under this permitting for any pollutant except for sulfuric acid mist (SAM; H2SO4). The SCR will be installed upstream of the existing air quality control system (AQCS) for SO2 (i.e. FGD) and PM (i.e. baghouse) emissions. Due to its location, a portion of the SO2 from the boiler exhaust will be oxidized to SO3 by the SCR catalyst. The additional SO3 can combine with water vapor in the exhaust resulting in additional SAM emissions.

Said IPL parent Alliant Energy (NYSE: LNT) in its Nov. 4 Form 10-Q financial report about the decree: “In 2015, the U.S. District Court for the Northern District of Iowa approved a Consent Decree that IPL entered into with the EPA, the Sierra Club, the State of Iowa and Linn County in Iowa, thereby resolving potential CAA issues associated with emissions from IPL’s coal-fired generating facilities in Iowa. IPL has completed various requirements under the Consent Decree. IPL’s remaining requirements include installing an SCR system or equivalent NOx reduction system at the Ottumwa Generating Station by December 31, 2019; fuel switching or retiring Prairie Creek Unit 4 by June 1, 2018, the Burlington Generating Station by December 31, 2021 and Prairie Creek Units 1 and 3 by December 31, 2025; and either installing combined cycle technology at, or retiring, the Dubuque and Sutherland Generating Stations by June 1, 2019.

“The Consent Decree also establishes SO2, NOx and particulate matter emission rate limits with varying averaging times for the Burlington, Lansing, M.L. Kapp, Ottumwa and Prairie Creek Generating Stations. In addition, the Consent Decree includes calendar-year SO2 and NOx emission caps for the Prairie Creek Generating Station, and calendar-year SO2 and NOx emission caps in aggregate for the Burlington, Dubuque, Lansing, M.L. Kapp, Ottumwa, Prairie Creek and Sutherland Generating Stations. IPL will also complete approximately $6 million in environmental mitigation projects.

“Alliant Energy and IPL currently expect to recover material costs incurred by IPL related to the environmental control systems and environmental mitigation projects from IPL’s electric customers. The recovery of such costs will be decided by IPL’s regulators in future rate cases or other proceedings.”

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.