Document ID: EPA-HQ-OAR-2017-0664-0137
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2019-09-25T04:00Z

September 3, 2019
SUBJECT: 	Trip report for site visit to ArcelorMittal Minorca Mine, Virginia, MN, October 12, 2018
FROM:	Michael Laney, RTI International
TO:		David Putney, U.S. Environmental Protection Agency (EPA)
       BACKGROUND
As part of the risk and technology review (RTR) project for the national emission standards for hazardous air pollutants (NESHAP) for taconite iron ore processing, site visits were conducted to three taconite iron ore processing facilities located along the Mesabi Range in Minnesota. This trip report summarizes the October 12, 2018 visit to the ArcelorMittal Minorca processing facility in Virginia, MN.
       PARTICIPANTS
ArcelorMittal Minorca
Jaime Johnson, Manager - Environmental
Robb Peterson, Operations Manager
Nate Holmes, Process Engineer
U.S. EPA
David Putney, Office of Air Quality Planning and Standards
RTI International
Michael Laney
       SUMMARY
 Preliminary Discussions
Prior to touring the facility, participants met to discuss the agenda for the day.
Background. David Putney provided information on the purpose of the site visits and the RTR project. He described the different tiers of analyses done to assess risks.
Minnesota Pollution Control Agency (MPCA) mercury initiative. ArcelorMittal Minorca is currently evaluating control options for meeting the 72 percent reduction in mercury emissions that will be required by MPCA.
Mercury concentration in raw ore. David Putney described the process that would be use for setting emission limits for mercury if the EPA decides to propose numerical MACT standards for mercury emissions. He explained that, in addition to emissions data, information on the variability of mercury concentrations in raw ore could be important information for EPA to consider in developing emission standards that accurately reflect variability in mercury emissions. He noted that there is precedence for using information on mercury variability in raw ore to set emission standards. He requested that ArcelorMittal Minorca provide the EPA with any such mercury data they may have, or can get, to assist EPA in the event they set mercury emission standards for the industry.
ArcelorMittal personnel noted that mercury concentrations vary across the Mesabi Range, with concentrations lowest in the east and higher to the west. They stated that facility personnel do not do coring and have no mercury data from core samples. They stated they would look for information on mercury concentration data and provide any data they find to EPA. An email providing this information was provided to David Putney from Paul Balserak of AISI on September 12, 2018 at 4:54 pm.
David Putney described changes to the NESHAP that are being planned beyond any that might be made as a result of the RTR. Among the revisions currently planned are the following:
Once in always in. This refers to a provision of the rule (i.e., 40 CFR 63.9581), and has been EPA policy, whereby if a source was subject to the rule as a result of being a major source for purposes of title III of the CAA (greater than 10 tons of a single HAP or 25 tons of all HAP combined), it would always be subject to the rule even if they reduce their HAP emissions to less than major source status. As a result of a change in EPA policy, this provision in the NESHAP will be modified.
Electronic reporting. Compliance test results will be required to be submitted to EPA through EPA's electronic reporting tool (ERT).
Startup, shutdown, and malfunction (SSM). As a result of a court ruling, the exemption from the emission standards during periods of SSM will be removed. Sources will be subject to an emissions standard, but it may be a work practice standard if it is not possible to demonstrate compliance with the emission limits. David Putney stated that to set work practice standards, EPA would need information from the industry that defines startups and shutdowns as well as work practices that facilities could implement during startup and shutdown to ensure compliance or minimize emissions. In other rules, work practices such as the use of clean fuels and operating control devices during a startup or shutdown have been required.
Burden reduction. David Putney explained the EPA is interested in industry's experience with any requirements of the current rule that they consider to be burdensome that could be revised to be less burdensome while not comprising environmental protection.
Jaime Johnson stated that the 60-day notice requirement before being able to conduct emissions testing can be burdensome. She explained that when there is an equipment failure, the plant's goal is to get the operation up and running as soon as possible. The 60-day notification requirement can cause costly delays in operations. This is particularly important to the Minorca facility given that it only uses one indurating furnace and is unable to operate while that device is down for maintenance or repair.
Technology Review. David Putney explained that the technology review aspects of the RTR project and requested information regarding the development of any new controls or processes in the taconite industry that have become available that could reduce HAP emissions.
ArcelorMittal stated that they have not developed any new controls or processes in their taconite iron ore processing facility and were not aware of any such developments in the industry sector.
Facility operations. Nate Holmes gave the following overview of facility operations
The Minorca operations are situated on about 16,000 acres. There are three active mining pits. Blasting is typically conducted one to two times per week. They are managing their raw ore in order to maintain proper levels of silica and magnetite iron. Most of the water needed for the process (about 75 percent) is from water recovered from their tailings settling basins.
The blasted material is fed to a primary crusher to produce a coarse ore and then fed to a fine crushing plant. The fine crushed ore is conveyed to a fine ore stockpile. From there, the material is conveyed to surge bins that continuously feed the concentrator processes.
In the concentration process, the fine ore and water are fed to rod mills to further reduce the particle size. The material is then fed into magnetic separator drums called cobbers where the iron-bearing material is separated from gangue material. The gangue material goes to clarifiers where the large tailings are separated out. The larger tailings are removed from the process and are used for building and maintaining facility roadways. Smaller tailings are partially dewatered and sent to a tailings basin where they are further dewatered. The concentrate from the magnetic separators is fed to ball mills where the material is further reduced in size. The material passes through additional magnetic separation steps. The fine concentrate is subjected to additional sizing and separation, additional ball milling, and to final finishing magnetic separators. The concentrate is sent to flotation tanks where more silica is separated from the iron concentrate. The iron concentrate is mixed with the fluxing agents, mainly limestone and dolomite. The fluxed concentrate is dewatered using vacuum disc filters. The dewatered filter cake is mixed with bentonite and then rolled into balls on rotating discs.
The unfired ("green") pellets are conveyed to a straight grate indurating furnace. The furnace is primarily fired using natural gas with fuel oil as a backup. In the furnace, the green pellets pass through different temperature zones to dry and harden the pellets. In straight grate furnaces, the green pellets are deposited on a hearth layer of fired, or finished, pellets to protect the grate bars. At the end of the furnace, the hardened pellets pass through a cooling zone. Exhaust gases from cooling are recirculated to the furnace to dry, pre-heat and fire the green pellets. Emissions from the furnace are controlled using wet scrubbers.
The furnace is taken off line once per year for maintenance. This outage lasts about 20 days.
Critical process parameters as well as control device parameters are monitored from a control room.
 Site Tour
Mine Operation. The tour did not include the mine operation.
Processing. Nate Holmes and Jaime Johnson conducted the tour of the facility. The tour included the fine crushing, concentrator operations, and the pellet plant. The details of the process were described during the preliminary discussions at the beginning of the site visit.
 Wrap Up
During startup and shutdown of the furnace, control devices are turned on before startup and remain on during shutdown. During startup, the pressure differential is usually lower due to cooler furnace conditions.
David Putney explained that a draft trip report would be sent to Jaime Johnson to review for accuracy and for confidential business information.
Following up on earlier discussions regarding mercury concentrations of taconite ore, parts of the rule that ArcelorMittal considered particularly burdensome, and developments in processes, controls and work practices (as part of the technology review), David Putney requested that any information or input that ArcelorMittal could provide on these and other topics be provided by the middle of November 2018.