Michigan agency slammed for new SO2 plan that covers some coal retirements

The Michigan Department of Environmental Quality (DEQ) on May 31 submitted its plan to reduce SO2 emissions in heavily-industrialized southern Wayne County to the U.S. Environmental Protection Agency for final approval.

The agency said this State Implementation Plan (SIP) ensures the air in Detroit and surrounding communities meets a health-based National Ambient Air Quality Standard (NAAQS) for SO2. It requires four industrial sources in the area to make substantial reductions in SO2 emissions during the next 2.5 years. The industrial sources are achieving these reductions in a variety of ways, DEQ noted:

  • DTE Electric‘s coal-fired River Rouge Power Plant is required to permanently shut down one of its two coal boilers by the end of the year.
  • DTE’s Trenton Channel Power Plant permanently shut down four of its five coal-fired boilers in April 2016.
  • The Carmeuse Lime kilns in River Rouge will vent SO2 emissions to a new 120-foot smokestack by October 2018 to better disperse the emissions and limit their impact.
  • U.S. Steel is required to make SO2 emission reductions via a new state rule, which is in draft form as a placeholder in the SIP. The rule will be finalized within the next few weeks, and the emission reductions are required to be in effect by the end of this year.

The SIP contains legally enforceable air permits for the changes at both DTE plants and at Carmeuse Lime.

The DEQ compiled the SIP after the EPA’s standard for sulfur dioxide dropped in 2010 and air monitors near Southwestern High School in Detroit showed levels of SO2 that violated the new standard. DEQ noted that the air monitor near Southwestern High School has shown air quality that meets the one-hour SO2 standard for the past two years. Despite these improvements, the SIP is required to ensure continued progress in air quality, including in areas where the DEQ does not have a monitor.

The Sierra Club on June 1 slammed the DEQ plan, saying it once again fails to require modern pollution controls on any existing coal-powered generating units. “This revised plan comes nearly 14 months late, and only after EPA informed MDEQ that their initial plan failed to protect public health and adequately lower sulfur dioxide emissions levels,” said the club. 

In 2013, the U.S. Environmental Protection Agency (EPA) designated a portion of Wayne County as failing to meet federal minimal air quality standards for SO2, which are established to protect public health. The club said that MDEQ proposed a plan last summer that would have allowed increases in actual emissions from the area’s largest sources of SO2: the DTE Trenton Channel and River Rouge coal plants, which produce 80% of the area’s sulfur dioxide pollution. 

Regina Strong, Director of the Michigan Beyond Coal Campaign for the Sierra Club, said: “This draft plan leaves coal plants online with no modern pollution controls in an area that has been overburdened by pollution for far too long. The citizens of Wayne County deserve a plan that reduces the emissions of each facility by way of modern pollution controls or by completely transitioning current coal fired units to clean energy.”

Said the Michigan agency’s May 31 SIP filing with EPA about its process to arrive at this plan: “The process included the development of an initial draft strategy that was included in a proposed SIP in August of 2015. The proposed SIP received public comment from August 20 through October 5, 2015, with a public hearing on September 23, 2015. Many comments were received stating that the proposed SIP strategy was not adequate to maintain attainment. The USEPA commented that the proposed SIP did not meet the requirement that compliance with the standard was to be achieved at all modeled receptors.

“Based on these comments, the MDEQ undertook additional modeling analysis, applying additional controls and reductions to achieve compliance at all modeled receptors. The subsequent analysis also updated the meteorological data used and demonstrated the background SO2 concentration should be reduced from 15 ppb to 12 ppb. The MDEQ worked with DTE and Carmeuse Lime to achieve additional SO2 reductions and reduced SO2 impacts, with the modeled results showing NAAQS attainment throughout the nonattainment area. Permits for the DTE power plants and Carmeuse Lime were revised to incorporate the changes.”

The DTE plants affected are:

River Rouge

The River Rouge power plant is located in the city of River Rouge. When SIP development began, the River Rouge plant had three electric-generating units. Unit 1 is a 2,400 million British thermal units (MMBtu) per hour natural gas-fired boiler that is not part of this analysis. Units 2 and 3 were solid fuel-fired boilers rated at 2,280 and 2,670 MMBtu per hour, respectively. Units 2 and 3 had nameplate capacities of 292 MW and 358 MW, respectively. Both of these boilers were permitted to fire pulverized coal, natural gas, blast furnace gas, and COG and exhausted to separate stacks. For the SIP, Unit 2 was removed as an emissions source.

River Rouge has a capacity of 651 MW. The plant was constructed in 1957 and 1958. The plant burns coal of varying sulfur content and has been increasing its use of western low-sulfur coal over the last few years. This coal is lower in Btu value than eastern coal but is currently cheaper per Btu. The power plant primarily burns eastern coal on the days when electricity demand is the highest, typically during summer months. The SO2 is emitted from the power plant’s two 400-foot stacks.

To address the unacceptable combined hotspot impact northeast of the facility, DTE has agreed to permanently shut down Unit 2, achieving an additional 45% reduction in SO2 emissions from the River Rouge plant. This change is included in a Permit to Install which was approved on May 3, 2016. The permit retains the emission rate for Unit 3 of 2,300 pounds per hour of SO2 as contained in the original permit. Also retained from the original permit is a 720-hour rolling average for the emission limit for Unit 3.

Trenton Channel

The Trenton Channel plant is located in the City of Trenton. When SIP development began, the Trenton Channel plant consisted of five coal- and oil-fired boilers and five oil-fired Slocum peaker generating units. Boilers 16, 17, 18, and 19 were similar, tangentially fired coal-fired boilers with a combined heat input capacity of 3,023 MMBtu per hour for all four boilers. Boiler 9A is a coal-fired boiler with a rated heat input capacity of 4,530 MMBtu per hour serving an electric generator with a nameplate capacity of 520 MW. Boilers 16, 17, 18, and 19 were exhausted to a common stack and Boiler 9A is exhausted to a separate dedicated stack. Only Unit 9’s emissions are covered under the new SIP for continued operation.

Trenton Channel has a capacity of 776 MW. The existing plant was constructed in 1950, with a newer section added in 1968. The plant burns coal of varying sulfur content and has been increasing its use of western low-sulfur coal in recent few years The power plant primarily burns eastern coal on the days when electricity demand is the highest, typically during summer months. The SO2 is emitted from the power plant’s two 500-foot stacks.

DTE has agreed to permanently shut down Units 16-19 at Trenton Channel and to retain the emission limit for Unit 9 contained in the original Permit to Install. The change is included in a new Permit to Install which was approved on April 29, 2016. Also retained from the original permit is a 720-hour rolling average for the emission limit for Unit 9.

Notable is that a Permit to Install issued on April 29 allows DTE to install five permanent natural gas-fired package boilers which will replace four existing coal-fired boilers (Units 16-19) at Trenton Channel. Boilers 16, 17, 18, and 19 have a combined heat input capacity of 3,023 million British Thermal Units (MMBTU’s) per hour. These four boilers are collectively referred to as the “High Side” boilers.

Effective April 16, 2016, the existing coal-fired boilers at DTE became subject to the federal Mercury and Air Toxics Standards (MATS) for coal- and oil-fired electric utility steam generating units. Previously, DTE has undertaken a MATS Compliance Project involving modifications to Boiler 9A allowing it to meet these requirements. As they currently exist, the High Side boilers cannot be operated in compliance with MATS. Therefore, DTE shut them down around April 15, 2016.

Each of the five natural gas-fired package boilers will be rated at a steam delivery rate of 75,000 pounds per hour and have a nominal heat release capacity of 99.9 MMBTU’s per hour. Only three of the five boilers are proposed to operate simultaneously.

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.