Interstate seeks Iowa approval related to end of coal use at Prairie Creek Unit 4

The 116-MW Unit 4 will end its coal use by the end of 2017

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Interstate Power and Light on Dec. 15 asked the Iowa Utilities Board for a declaratory order saying that its planned cessation by the end of 2017 of coal-fired generation at Unit 4 of its Prairie Creek Generating Station is not a “significant alteration” that would require a full board proceeding.

The utility wrote: "On or before the end of calendar year 2017, IPL will cease using coal as an electric generating fuel at Prairie Creek Unit 4 and will operate that unit solely on natural gas. For the reasons discussed below, IPL does not believe that this action qualifies as a “significant alteration” that is subject to the Board’s jurisdiction under Chapter 476A."

The Prairie Creek Generating Station in Cedar Rapids, Iowa, consists of three electric generating units (1A, 3, and 4) that have a collective net summer and winter capacity of approximately 163 MW. Prairie Creek Unit 4 was originally placed into service in 1968 and has a net summer and winter capacity of approximately 116 MW. This unit is currently capable of combusting coal or natural gas to produce electricity. Historically, the unit has operated as a baseload facility, but will likely operate as an intermediate or peaking facility once it begins running exclusively on natural gas.

In 2015, to resolve allegations that IPL violated provisions of the Prevention of Significant Deterioration program under the federal Clean Air Act at various power plants, IPL entered into a Consent Decree with the United States government, the State of Iowa, Linn County, Iowa, and the Sierra Club. The Consent Decree, which has been entered by the U.S. District Court for the Northern District of Iowa, is federally enforceable. The Consent Decree did not significantly change IPL’s emissions control plans; rather, it just memorialized them and made them concrete requirements.

The Consent Decree requires IPL to refuel or retire several of its coal-fired units. Refueled units must cease burning coal and can only burn natural gas to generate electricity. Retired units must be shut down and cannot—physically or legally—burn any fossil fuels. Under the Consent Decree, IPL must refuel or retire Prairie Creek Unit 4 no later than June 1, 2018. Even before entering into the Consent Decree, IPL was considering converting or refueling Prairie Creek Unit 4 to run on natural gas.

IPL said it will not have to incur any capital expenses or make any physical modifications to facilitate the exclusive use of natural gas at Prairie Creek Unit 4.

Interstate also pursuing air permit change related to Unit 4

In the meantime, the Iowa Department of Natural Resources is out for comment until Dec. 31 on an air permit revision that covers the end of any coal or oil use at Prairie Creek Unit 4 by the end of 2017.

The DNR noted that the Prairie Creek Generating Station operates four coal-fired natural gas-fired boilers.

  • Boiler 1 is a spreader stoker unit which was constructed in 1949 with a rated heat input capacity of 304 MMBtu/hr. However, it is limited to a heat input capacity of 245 MMBtu/hr. Boiler 2 is also a spreader stoker unit constructed in 1949 with a heat input capacity of 304 MMBtu/hr. These two boilers serve a single 14 MW generating unit.
  • Unit 3 is a dry bottom pulverized coal unit which was constructed in 1957. It has a heat input capacity of 611 MMBtu/hr which serves a 50-MW turbine. Unit 4 is a dry bottom pulverized coal unit which was constructed in 1965. It has a heat input capacity of 1,370 MMBtu/hr which is used to power a 149-MW turbine. These units are utility boilers operated for electricity generating purposes and are subject to the EGU-MATS regulation.
  • Boiler 5 is a natural gas-fired boiler constructed in 1996. It has a heat input capacity of 278 MMBtu/hr. Boiler 6 is a natural gas-fired package boiler which was constructed in 2014. It has a heat input capacity of 99.9 MMBtu/hr. These boilers sole operating purpose is to provide steam to industrial customers.

The DNR said the legal settlement entered into by Interstate included the following:

  • 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 30-day rolling average emission rate for NOx of no greater than 0.090 lb/mmBTU by Jan. 31, 2015; and 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 July 2010.
  • Continuous operation of a low NOx combustion system at Ottumwa Unit 1 and compliance with: a 30-day rolling average emission rate for NOx of no greater than 0.210 lb/mmBTU; and 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 began operation in June 2014. The FGD system for Ottumwa Unit 1 began operation in November 2014.
  • Compliance with annual system-wide tonnage limitations for NOx and SO2.
  • Compliance with annual tonnage limitations for NOx and SO2 for Prairie Creek.
  • Annual surrender of any excess SO2 and NOx allowances resulting from actions taken under the Consent Decree.
Barry Cassell
About the Author

Barry Cassell

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 26 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.

Barry can be reached at barryc@pennwell.com.

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