Michigan DEQ takes comment on new SO2 limits for two DTE coal plants

The Michigan Department of Environmental Quality (MDEQ) is taking comment until March 11 on a preliminary decision to act on two Permit to Install (PTI) applications from the DTE Electric unit of DTE Energy (NYSE: DTE).

DTE is proposing new SO2 limits in support of the 1-hour SO2 National Ambient Air Quality Standard (NAAQS) for both the Trenton Channel Power Plant and the River Rouge Power Plant.

  • The Trenton Channel plant is located in the City of Trenton, Wayne County. It consists of five boilers, tangentially fired, fueled by pulverized coal, oil, and recovered paint solids. Boilers 16, 17, 18, and 19 have a combined heat input capacity of 3,023 million Btu per hour. These four boilers are on a common steam header feeding two General Electric turbine generators with a combined output of 210 MW. Boiler 9A has a rated heat input capacity of 5,836 million Btu per hour, which serves an electric generator with a nameplate capacity of 520 MW. All five boilers are equipped with electrostatic precipitators to control particulate matter emissions.
  • The River Rouge plant is located in the City of River Rouge, Wayne County. The facility consists of two boilers fueled by pulverized coal, natural gas, blast furnace gas, coke oven gas, and recovered paint solids. The boilers have a combined heat input capacity of 4,950 million Btu per hour and each serve a turbine generator with a combined output of approximately 540 MW. Both boilers are equipped with electrostatic precipitators to control particulate emissions.

In 2013, the U.S. Environmental Protection Agency designated a portion of Wayne County as being in nonattainment with the 1-hour SO2 standard based upon registered exceedances at an air monitor operated by the MDEQ. Both DTE facilities are located in this nonattainment area. In an effort to bring the nonattainment area into compliance with the 1-hour standard, the MDEQ is following the process outlined in the Clean Air Act. This requires the MDEQ to submit to the USEPA a State Implementation Plan (SIP) within 18 months of the nonattainment designation. The SIP must include legally enforceable measures to enable the area to regain attainment of the 1-hour SO2 standard within five years. The SIP will be submitted to the USEPA in April 2015.

In support of that plan, DTE has elected to establish lower, federally enforceable SO2 emission limits and use a continuous emission monitoring system (CEMS) for SO2 emissions. The reductions in allowable emissions proposed by DTE will eliminate both the Trenton Channel and the River Rouge individual “hot spot” impacts, and reduce the SO2 impacts at the MDEQ air monitor. Over the last several years, the levels of SO2 at the monitor have been decreasing. In fact, based on the 2012-2014 monitoring data that is currently under review, the monitor is now meeting the 75 ppb 1-hour SO2 standard. While the monitor data is an encouraging sign that SO2 levels in the area are dropping, modeling continues to show that locations exist in the nonattainment area that do not yet meet the standard, the department noted.

The SIP requires that all locations in the nonattainment area meet the standard as demonstrated by existing monitors and by modeling. This means that the reductions being proposed in the two DTE permit applications continue to be necessary for purposes of the SO2 SIP.

Neither draft permit indicates any new air emissions controls will be required for these units to attain the new limits.

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.