DAQ-2024-005108

Mr. Bryce Bird - Director
Department of Environmental Quality
Division of Air Quality
P.O. Box 144820
Salt Lake City, Utah 841144820
February 08,2024
Rio Tinto Kennecott
4700 Daybreak Parkway
South Jordan, Utah 84009
UTAH OEPAFtrMENT OF
ENVIRONMENIAL OUAI.JTV
FEB - B )n)4
DIVISION OF AIR QUALIN'
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Subject: R307-107 and l.S.2.c: Smelter Main Stack Particulate Breakdown
Kennecott Utah Copper - Smelter Facilitv Title V operatino Permit
3500030004
Dear Mr. Bird,
This letter provides a report of a breakdown event that occurred on January sth, 2024 at the
Kennecott Utah Copper, LLC (Kennecott) Smelter. This report is intended to satisfy the
requirements of Permit Condition 1.S.2.c, deviation reporting, including deviations due to
breakdowns in accordance with R307-107.
Background
The Main Stack (SME011) is the exhaust stack for gases from the acid plant, secondary gas
system, rotary dryer, powerhouse superheater, matte grinding plant, anodes area, and
hydrometallurgical plant. To monitor particulate emissions, Kennecott operates a continuous
particulate sampler (CPS) to collect a daily sample which provides a calendar-day average for
particulate emissions in pounds per hour (lbs/hr). The sample is a filter installed in the CPS,
operated for between 20 - 28 hours. Samples are then removed from the CPS and desiccated in
the Smelter laboratory for 24 hours or more. For this reason, Main Stack particulate emission
results are available to Kennecott personnel between 25 - 30 hours after the sample has
completed.
Description of Incident
On January 251h,2024, the Smelter laboratory results indicated that the Main Stack particulate
emissions measured on January 5 were 94.13 lbs/hr exceeding the particulate matter less than
1 0 microns (PM 1 0) permit limit of 89.5 lbs/hr. Mr. Sean Daly called Mr. Joseph Randolph of the
Utah Division of Air Quality at 2:30pm on January 261h,2024 to provide initial notification of the
breakdown event.
Rio Tinto Kennecott Utah Copper, LLC.4700 Daybreak Parkway, South Jordan, Utah 84009
REVIEWED
Initials JBR Date 3/6/2024
Comp Status Meets
File # 10346 Blue 2
NFA bag failure. No recurrance
Analysis of Events
On January 4th, the CPS result was 43.1 lb/hr which would be considered a normal result. The
following day, on January Sth, Smelter Operations personnel noticed leading indicators of a
potential problem with the Matte Baghouse. During the following day shift, on January 6th,
Smelter personnel scheduled time to inspect the Matte Baghouse. Once inside, maintenance
personnel found broken bags in one of the four baghouse cells, and replaced them. Once the
process was brought back online, all indications were that the emissions from the Matte
Baghouse had returned to normal. A timeline of the particulate emissions sample results and
corrective action is provided in the table below:
Data Evaluation
As discussed above, the CPS is the permitted monitoring toolfor daily compliance with the
PM10 emissions limit. However, the CPS operation is based on an Environmental Protection
Agency Method 5 procedure and for that reason; it measures all Total Suspended Particulate
(TSP) rather than the PM10 fraction. For comparison with the permitted PM10 emissions limit,
Kennecott also performs an annual PM10 stack test. Historically, the PM10 value from the
stack test is less than the CPS result for the same day, as expected. ln the past five years, the
comparison of the CPS data and the stack test results have indicated that the PM10 fraction of
the CPS measured value is 44.2o/o.lf we apply this historic PM10 fraction to the CPS result for
January Sth, the result would be 41.6 lbs/hr, which is below the permitted limit.
Additionally, as outlined in the permit, Kennecott monitors differential pressure (dP) on the
Matte Grinding baghouse. During the days preceding and following the event, baghouse dP
remained within the permitted range.
Representative of typical operations; No actions
taken
Operations notices sustained elevated opacity
readings and dust indicators.
Matte Baghouse determine to be likely cause
Operations shuts down Matte Grinding during day
shift and enters baghouse
Broken bags found and replaced
Representative of typical operations; No actions
taken
Page 2 of 3
Corrective Action Summary
Kennecott believes the Matte Grinding baghouse and related process equipment are maintained
and operated in a manner consistent with good practices for minimizing emissions. To the
maximum extent possible, air pollution control equipment and process equipment are
maintained and were operated per standard procedures and in a manner consistent with good
practice for minimizing emissions, including minimizing bypass emissions. Kennecott
conducts monthly maintenance inspections and dye testing on the baghouses to try to minimize
breakdowns and catch issues that could affect performance of the pollution control systems.
All practicable steps were taken to minimize potential impacts on ambient air quality.
Kennecott responded to indicators that there may be excessive PM from the Matte Baghouse by
scheduling offline time to perform additional corrective actions. Review of events suggests that
corrective actions on January 6th reduced emissions below the PM10 emissions limit. Once the
equipment was restarted on January 6th, Kennecott used available process data to ensure that no
additionalexcess emissions were emitted from the Matte Grinding baghouse.
Based on information and belief formed after reasonable inquiry, the statements and information
in this document are true, accurate, and complete (R307-415-5d).
Should you have any questions regarding this report or need further information regarding the
event, please contact me or Sean Daly at 801-204-2563.
Yours sincerely,z2
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Jerome Dozol
General Manager - Metals
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