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Home My WebLink AboutDAQ-2024-004075Mr. Bryce Bird - Director Department of Environmental Quality Division of Air Quality P.O. Box 144820 Salt Lake City, Utah 84114-4820 December 06,2023 Rio Tinto Kennecott 4700 Daybreak Parkway South Jordan, Utah 84009 I,TAH DEPARTMENT OF ENVIBONMENTAL QUAIJTY D[0 1 1 2i23 iland \elid"r4 DIVISION OF AIR QUALTTY Subject: R307-107 and l.S.2.c: Smelter Main Stack Particulate Breakdown Kennecott Utah Copper - Smelter Facilitv Title V operatinq Permit 3500030004 Dear Mr. Bird, This letter provides a report of a breakdown event that occurred on November 25,2023, and November 26, 2023, 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 provided to Kennecott personnel between 25-30 hours after the sample has completed. Description of lncident On November 28, 2023, the Smelter laboratory results indicated that the Main Stack particulate emissions measured on November 25,2023 were 99.8 lbs/hr exceeding the particulate matter less than 10 microns (PM10) 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 November 29,2023 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 1/9/2023 Comp Status Meets File # 10346 Blue 2 Baghouse fail post shutdown. No further fails, NFA Analysis of Events On November 27th, the particulate emissions sample result for November 24th was 68.5 lbs/hr. Kennecott classified the emissions ftom this sample asl 'elevated" compared to normal operations and teams began to investigate what equipment could be contributing to the increased particulate emissions. Kennecott identified that the Matte Grinding baghouse (SME011g) was the most likely source of emissions and executed corrective actions including dye testing, bag changes and cleaning system repairs in one of the four Matte Grinding baghouse cells. Once the final bags were replaced, the baghouse was returned to service. On November 28th, the particulate emissions sample result for November 25th was 99.8 lbs/hr and the results for November 26th was 115.6 lb/hr. On November 29th, the particulate emissions sample result for November 27th was 28.5 lbs/hr. 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. The 2020 stack test performed on November 9-10,2020, measured 5.4 lbs/hr of PM10 compared to the CPS result of 27.6lbs/hr for the same day. The 2021 stack test performed on November 17th 2021, measured 6.7lbs/hr of PM10 compared to the CPS results of 23.4lbs/hr for the same day. Based on this Representative of typical operations; No actions taken29.6lbs/hr (November 23rd data) 68.Slbs/hr (November 24th data) - Elevated particulate emissions- lnvestigation identified Matte Grinding baghouse as suspect 99.8lbs/hr (November 25th data) - Process scheduled offline - Dye tested all four baghouse cells changing 6 bags 115.61bs/hr (November 26th data) Process Brought back online and monitored opacity to determine that no other actions need to be taken. 28.Slbs/hr (November 27th data) - Data review indicates corrective actions on November 28th reduced emissions Page 2 of 3 comparison, approximately 24 percent of the emissions measured by the CPS were PM10 emissions. lf this same comparison is applied to the sample from November 28th and 29th, the actual PM10 emissions would be 23.9 lbs/hr and 27.8lbs/hr which is less than the PM10 emission limit. 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 ranges from 24-59 percent, all of which would suggest that the PM10 emissions from the Main Stack during the breakdown event were below the 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. 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 minim2ing 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 the elevated particulate emissions on November 27th by scheduling offline time to perform additional corrective actions. The emissions increase between samples on November 27th and November 28th was about 39 lbs/hr which is an unexpected increased compared to the historical data related to these types of events. Review of events suggests that corrective actions on November 27th and November 28th reduced emissions below the PM10 emissions limit. Once the equipment was restarted on November 29th, Kennecott used available process data to ensure that no additional excess 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 at801-204-2563. be.Q- Jerome Dozol General Manager - Metals 4, l%+<futten+( Yours sincergJy &"lefe*r-6 zzt*'t'<<e Page 3 of 3