U

. S. Steel Co rporation Minnesota Ore Operations P.O. Box 4 1 7 Mt. Iron, MN 55768

CERTIFIED MAIL 7006 0100 0006 4747 9599 August 17, 2009 Hongming Jiang Minnesota Pollution Control Agency 520 Lafayette Road N. St. Paul, MN 55155-4194 Re: U. S. Steel Minntac updated pilot testing schedule Dear Mr. Jiang, In the NOx pilot testing schedule submitted by U. S. Steel Minntac (Minntac) on February 27, 2009, Minntac committed to submitting an updated pilot testing schedule related to pilot testing opportunities based on additional research and evaluation. The original due date was July 31, 2009, but was adjusted due to the schedule approval not being received after March 31, 2009

. Over the last several months Minntac has been aggressively pursuing different avenues towards NOx reduction/control technologies. In addition to making progress on pilot testing ofthe low NOx main burner and Selective Non-Catalytic Reduction (SNCR), the U. S. Steel Engineering group solicited vendors to review our process and propose the best NOx teclmology for our application. Several Selective Catalytic Reduction (SCR) vendors were included in the process, and they ultimately declined to bid. According to Mitsubishi Power Systems: "The temperature and layoutpose significant challenges for SCR. Andthe same challenges are likely non-issues for other technologies. An e xample of this is how to best extract 100% of the flue gas and treat them in the optimal SCR operating range of600**~** 750F" Other SCR vendors we spoke with had similar comments as to teclmical difficulties in using a SCR system on our furnaces, including potential catalyst poisons after r eviewing a stack test from November 2000 on Line 7. A lot ofdiscussion has occmTed in the past as to LKAB KK4 and the installation ofSCR on that pelletizing line

. Very little information has been available on this application other than a brochure that the equipment vendor Alstom produced. Alstom was contacted by U. S. Steel Engineering and requested to bid on a NOx reduction/control strategy for Minntac

. Alstom declined to bid. U. S. Steel contacted Alstom and requested they reconsider. Alstom declined to bid again

. After Alstom declined to bid Minntac had the opportunity to sit down with several employees from LKAB on June 25, 2009 including their General Manager, Engineering Manager, Manager ofKK4 and several Metso employees who assisted in the construction ofthe KK4 line and SCR system. According to the KK4 personnel they had been experiencing issues since startup in October. Amajor difficulty is the very nan·ow temperature range in which the equipment can operate. However the KK4 personnel said they have no catalyst poisons in their process gas stream. Due to the difficulties they have encountered with the SCR system they are cun·ently looking at process optimization and better burners as ways to reduce NOx in the future, rather than installing another SCR system. After several SCR vendors, most notably Alstom, declining to bid and discussions with personnel from LKAB familiar with the SCR system installed at KK4, we believe that SCR presents numerous technical difficulties and therefore we will not be pursuing a pilot ofa SCR system. Another technology Minntac has looked at is LoTOx. Minntac previously identified a number ofissues related to this technology including cross-media impacts and severe energy demands. We also understand that the MPCA feels actual data from a taconite operation utilizing LoTOx would be beneficial. 

### It is Miillltac's understanding that Minnesota Steel will be gathering that infonnation as required by their Title V operating pem1it. Since the MPCA will be receiving the data from Minnesota Steel, Minntac does not plan on testing LoTOx. Minntac continues to make progress on the SNCR and low NOx main burner pilot tests. Nalco-Mobotec has been onsite with equipment and personnel to conduct the SNCR test. We are working with a burner manufacturer on designing a low NOx main burner which would be a technology that would reduce the generation ofNOx. In addition to the eff01ts on the specific pilot tests, resources have been committed to looking at ways to reduce NOx generation through process optimization. We feel reducing the generation of NOx is a very promising way to limit NOx emissions in an environmentally responsible manner. Ifyou have any questions related to this submittal please contact Chrissy Bmtovich at (218) 749-7364 or clbmtovich@uss.com.
Sincerely,

# ~ol:.::o**{J_;,~** General Manager

- Minnesota Ore Operations

cc: Cill'is Nelson- MPCA Suzmme Baumann

- MPCA Tishie Woodwell- U. S. Steel Mike Dzurinko- U. S. Steel Clll'issy Bartovich- U. S. Steel Ryan Siats- U. S. Steel