UNITED STATES DEPARTMENT OF LABOR Mine Safety and Health Administration Investigative Report March 1999 A Study of the Fire and Explosion Hazards Associated with the Electrowinning of Copper in Arizona Surface Mine Plants By Derrick M. Tjernlund Fire Protection Engineer Engineering Support Branch -Originating Office- Approval and Certification Center Steven J. Luzik, Chief Engineering and Testing Division David C. Chirdon, Chief RR #1, Box 251 Industrial Park Road Triadelphia, West Virginia 26059 (304) 547-0400 PART I. INTRODUCTION ........................................................................................................................1 A. PURPOSE OF STUDY .....................................................................................................................................1 B. SCOPE ..........................................................................................................................................................1 C. STUDY METHODOLOGY ...............................................................................................................................2 PART II. GENERAL MINE INFORMATION ........................................................................................2 A. APPLICABILITY.............................................................................................................................................2 B. MINE LIST AND LOCATION MAP ...................................................................................................................3 C. MADSS DATABASE SEARCH RESULTS........................................................................................................3 PART III. SXEW PROCESS......................................................................................................................3 A. OVERVIEW ...................................................................................................................................................3 1. Description of process.............................................................................................................................3 2. Ore types .................................................................................................................................................5 3. Leaching..................................................................................................................................................5 B. SX PROCESS ................................................................................................................................................6 1. General....................................................................................................................................................6 2. Mixing and Separation............................................................................................................................6 3. Chemical Reactions.................................................................................................................................7 4. multi-stage extraction..............................................................................................................................9 5. multi-stage stripping ...............................................................................................................................9 6. wash stage .............................................................................................................................................10 C. EW PROCESS.............................................................................................................................................10 1. General..................................................................................................................................................10 2. Cathodes................................................................................................................................................11 3. Anodes...................................................................................................................................................11 4. Tankhouse .............................................................................................................................................11 5. Cell operation........................................................................................................................................12 6. Normal electrochemical process ...........................................................................................................12 7. Abnormal electrochemical process .......................................................................................................13 8. acid misting from electrowinning..........................................................................................................14 D. RECOVERY OF FUGITIVE ORGANIC SOLUTION............................................................................................17 1. Fugitive organic....................................................................................................................................17 2. Economic benefit...................................................................................................................................17 3. Hazard reduction ..................................................................................................................................17 PART IV. FIELD OBSERVATION.........................................................................................................18 A. FIELD SURVEY PROCEDURES .....................................................................................................................18 B. FIELD SURVEY FORMS................................................................................................................................18 C. SX .............................................................................................................................................................18 D. EW............................................................................................................................................................20 PART V. HAZARDS ANALYSIS ............................................................................................................23 A. INTRODUCTION ..........................................................................................................................................23 B. LABORATORY INVESTIGATION OF HAZARDS OF FUGITIVE ORGANIC ..........................................................23 1. Goal.......................................................................................................................................................23 2. Methodology..........................................................................................................................................24 3. Results ...................................................................................................................................................25 C. LABORATORY INVESTIGATION OF HAZARDS OF CELL DEPLETION..............................................................27 1. Goal.......................................................................................................................................................27 2. Methodology..........................................................................................................................................28 3. Results ...................................................................................................................................................30 i PART VI. CONCLUSIONS AND RECOMMENDATIONS.................................................................32 A. TANKHOUSE HAZARD MITIGATION STRATEGIES........................................................................................32 1. Fugitive Organic Hazards.....................................................................................................................32 2. Cell Depletion Hazards.........................................................................................................................36 B. SOLVENT EXTRACTION HAZARD MITIGATION STRATEGIES.......................................................................39 C. LEACH PAD HAZARD MITIGATION STRATEGIES .........................................................................................39 PART VII. ACKNOWLEDGMENTS .....................................................................................................40 PART VIII. REFERENCES .....................................................................................................................40 PART IX. LIST OF ATTACHMENTS ...................................................................................................41 A. ATTACHMENT 1: MINES SITES VISIT FOR STUDY ......................................................................................41 B. ATTACHMENT 2: MINE SITE LOCATION MAP .............................................................................................41 C. ATTACHMENT 3: FIELD SURVEY FORM......................................................................................................41 D. ATTACHMENT 4: TABLES ..........................................................................................................................41 E. ATTACHMENT 5: FIGURES..........................................................................................................................41