EPA issues revised regional haze air limits for taconite plants in Minnesota, Michigan

The U.S. Environmental Protection Agency is proposing revisions to its 2013 Federal implementation Plan (FIP) addressing the requirement for best available retrofit technology (BART) for taconite (iron ore) processing plants in Minnesota and Michigan.

In response to petitions for reconsideration, the agency in the Oct. 22 Federal Register will propose to revise the NOX limits for taconite furnaces at facilities owned and operated by Cliffs Natural Resources and ArcelorMittal USA LLC. It is also proposing to revise the SO2 requirements at two of Cliffs’ facilities. EPA is proposing these changes because new information has come to light that was not available when it originally promulgated the FIP in February 2013. Also, it agreed to revisions in settling legal cases brought against the FIP.

Comments on the proposed revisons must be received within 30 days after the date of publication in the Federal Register.

In February 2013, EPA promulgated a FIP that included BART limits for certain taconite furnaces in Minnesota and Michigan (referred to as the 2013 Taconite FIP). The new revisions cover the following taconite plants: United Taconite, Hibbing Taconite, Tilden Mining, and ArcelorMittal Minorca Mine. Cliffs is the owner and operator of the United Taconite and Tilden Mining facilities and part owner and operator of Hibbing Taconite. ArcelorMittal is the owner and operator of the Minorca Mine facility and a part owner of the Hibbing Taconite facility. Specifically, EPA is proposing to revise the NOX limits and compliance schedules for these four facilities and is also proposing to revise the SO2 requirements for Tilden Mining and United Taconite.

EPA took the 2013 action because Minnesota and Michigan had failed to meet a statutory deadline to submit their Regional Haze State Implementation Plans (SIPs) and subsequently failed to require BART at the taconite facilities. Cliffs, ArcelorMittal, and the State of Michigan petitioned the U.S, Eighth Circuit Court of Appeals for review of the FIP, and Cliffs and ArcelorMittal filed a joint motion for stay of the final rule, which was granted by the Eighth Circuit in June 2013 and is still in effect.

EPA received petitions for reconsideration of the 2013 Taconite FIP from the National Mining Association, the State of Michigan, Cliffs, Congressman Richard M. Nolan, the State of Minnesota and United States Steel Corp.

In a related action, EPA published a final partial disapproval of the Michigan and Minnesota Regional Haze SIPs in September 2013. Cliffs and U.S. Steel petitioned EPA for reconsideration of EPA’s partial disapproval of the Michigan and Minnesota Regional Haze SIPs. Further, Cliffs, ArcelorMittal, Michigan and U.S. Steel petitioned the Eight Circuit Court of Appeals for review of the final rule partially disapproving the Michigan and Minnesota Regional Haze SIPs.

EPA subsequently reached a settlement agreement with Cliffs, ArcelorMittal, and Michigan regarding issues raised by these parties in their petitions for review and reconsideration. The settlement agreement was fully executed on April 9, 2015. Pursuant to the settlement agreement, EPA granted partial reconsideration of the 2013 Taconite FIP on July 2, 2015, based on new information raised in Cliffs, ArcelorMittal, and Michigan’s petitions for reconsideration. EPA did not grant reconsideration of the 2013 SIP disapprovals because EPA continues to believe that BART for taconite plants involves significant reductions of NOX and SO2 emissions that were not required in the Michigan and Minnesota SIPs.

Devil is in the details when it comes to taconite processing facilities

The U.S. taconite iron ore industry uses two types of pelletizing machines or processes: straight-grate kilns and grate-kilns.

  • In a straight-grate kiln, a continuous bed of agglomerated green pellets is carried through different temperature zones with upward draft or downward draft blown through the pellets on the metal grate.
  • The grate-kiln system consists of a traveling grate, a rotary kiln, and an annular cooler.

A significant difference between these designs is that straight-grate kilns do not burn coal and therefore have a much lower potential for emitting SO2. The differences between these kilns and processes form a key basis for the changes to the emissions limits proposed in this action, EPA noted.

The 2013 Taconite FIP established BART NOx limits for all straight-grate and grate-kiln taconite furnaces. The limits are 1.2 lbs NOX/MMBtu when burning natural gas and 1.5 lbs/MMBtu when burning a gas/coal mix. These limits were based upon the performance of high stoichiometric (high-stoich) Low-NOx Burners (LNBs) at two of U.S. Steel Minntac’s grate-kilns. EPA granted reconsideration of the NOX limits for the United Taconite and Tilden grate-kilns, as well as for the Hibbing and ArcelorMittal straight-grate kilns, because information that became available after the close of the public comment period on the 2013 FIP suggests that the installation of high-stoich LNBs at these furnaces could lead to serious technical hurdles.

In addition, it granted reconsideration of the SO2 limits for the United Taconite and Tilden grate-kilns because of information that became available after the close of the public comment period regarding the inability of United Taconite to handle and burn very low sulfur coal and Tilden’s intent to burn mixed fuels.

The 2013 FIP contains SO2 and NOX limits for U.S. Steel’s Minntac and Keetac taconite furnaces in Minnesota. EPA has not granted U.S. Steel’s petition and is not proposing any revisions of the BART limits for these U.S. Steel facilities at this time. Also, EPA is not reconsidering the NOX limits at Cliffs’ Northshore taconite plant because this facility is already complying with the 1.2 pounds per million Btu (lb/mmBtu) NOX limit in the 2013 FIP. Finally, EPA is not reconsidering the SO2 limits at the Hibbing, ArcelorMittal, or Northshore straight-grate furnaces.

Differences between coals became a key issue

The 2013 Taconite FIP set a 0.60% sulfur limit on coal combusted at United Taconite. EPA promulgated this limit in response to a proposal by Cliffs to use low sulfur fuel at United Taconite to decrease baseline SO2 emissions. However, Cliffs did not have an opportunity to comment on the specific numeric stringency of the limit. In other words, it was impracticable for Cliffs to comment on the final sulfur limit prior to the close of the public comment period.

In its petition for reconsideration, Cliffs also presented new information directly pertaining to the criteria for determining BART limits. Cliffs stated that the United Taconite facility had been designed to handle and burn eastern bituminous coal, not the low-sulfur, western subbituminous coals from the Powder River Basin (PRB) that Cliffs would be required to use to meet the 0.60% sulfur content limit. For example, PRB coal is more prone to explosion and fire and has a lower heat value than eastern bituminous coal. These differences, among others, would require Cliffs to expend significant costs to change operations, address safety issues, and increase the amount of coal required to be burned to meet furnace and pellet temperature requirements.

The 2013 Taconite FIP required the Tilden grate-kiln Line 1 to burn 100% natural gas. However, although mentioned in discussions with Cliffs, this requirement had not been proposed before the final rule. Therefore, it was impracticable for Cliffs to comment on the final BART requirement to burn solely natural gas. Cliffs more recent intent to burn mixed fuels at Tilden is new information that EPA did not consider in determining BART for Tilden. The burning of mixed fuels will significantly increase SO2 emissions, resulting in Cliffs’ inability to meet the BART limit. Therefore, the new information is of central relevance to the outcome of the 2013 Taconite FIP. On this basis, EPA granted reconsideration to the 2013 Taconite FIP requirement to burn only natural gas at the Tilden grate-kiln Line 1.

According to modeling and engineering reports provided by the burner manufacturer, a low-stoich burner can be designed to meet 2.8 lbs/MMBtu when burning natural gas and 1.5 lbs/MMBtu when burning a gas/coal mix. BART requires that the burners be designed to meet these limits and EPA said it expects that these limits will be met. However, because of the lack of experience with these low-stoich burners, including their impact on pellet quality, it is proposing to increase the final limits up to 3.0 lbs/MMBtu when burning natural gas only, and up to 2.5 lbs/MMBtu when burning a gas/coal mix if a rigorous demonstration is made that 2.8 lbs/MMBtu and 1.5 lbs/MMBtu limits cannot be met.

Based upon the engineering report prepared for ArcelorMittal in which the use of water and steam injection and pre-combustion technologies is described, EPA is confident that ArcelorMittal Minorca Mine and Hibbing Taconite can meet a limit of 1.2 lbs NOX/MMBtu. BART requires that these technologies be designed to meet a limit of 1.2 lbs/MMBtu and EPA expects that these limits will be met. However, because the particular combination of water and steam injection and pre-combustion technologies being considered has not previously been used on straight-grate kilns, and there is some uncertainty with respect to their effect on pellet quality, EPA is proposing to increase the final limit up to 1.8 lbs/MMBtu if a rigorous demonstration is made that the 1.2 lbs/MMBtu limit cannot be met.

For United Taconite, the proposed BART is based on burning low sulfur fuels, including increased use of natural gas, sufficient to meet a federally enforceable aggregate emission limit of 529 lbs SO2/hr, based on a 30-day rolling average. This alternative will result in about 1,900 tons per year of SO2 reductions. In addition to the emission limit proposed by Cliffs, to ensure the use of low-sulfur fuels and SO2 reductions resulting from the use of low-sulfur fuels at United Taconite, EPA is also establishing a limitation on the coal to be used by requiring that it have a sulfur content no greater than 1.5% sulfur by weight based on a monthly block average. The 529 lbs SO2/hour and 1.5% sulfur limit constitute BART because of the economic infeasibility of FGD controls and also because the facility is not designed to handle lower sulfur coal.

At Tilden, BART for SO2 at Tilden’s Grate Kiln Line 1 furnace is proposed to be met by the use of low-sulfur coal and natural gas. Beginning six months after the effective date of the rule, any coal burned on Tilden Grate Kiln Line 1 shall have no more than 0.6% sulfur by weight based on a monthly block average. This furnace shall also meet an initial emission limit of 500 lbs SO2/hr based on a 30-day rolling average beginning six months after the effective date of the rule. The owner or operator must subsequently calculate a permanent lbs SO2/hr mass emission limit based on 12 continuous months of emissions monitoring data.

These are the dates following the effective date of the final action on reconsideration by which EPA plans to publish notices making the NOX emission limits effective:

  • Tilden – 60 months
  • Hibbing Line 1 – 37 months
  • Hibbing Line 2 – 55 months
  • Hibbing Line 3 – 60 months
  • United Taconite Line 2 – 55 months
  • United Taconite Line 1 – 37 months
  • ArcelorMittal – 55 months

The staggered schedule is necessary because there is a limited downtime each year for each furnace during which the low NOX burner(s) can be installed without interfering with production, experience gained on the earlier installations can be applied to the ones installed later, and installation costs may be spread out.

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.