ENHANCED GOLD RECOVERY DURING HEAP BIO-DETOXIFICATION AT CRIPPLE CREEK AND VICTOR MINING COMPANY

摘要

Mine closure and reclamation issues have evolved over the past several years becoming further complicated by stricter standards and by the current economic climate and price of gold. Many mine permits are calling for more stringent remediation of spent ore heaps and tailings. Leachate solution water quality must meet strict discharge criteria for multiple parameters, besides cyanide at mine closure. Closure standards are more difficult to meet and most mines do not have an increased budget at the end of mine life to deal with the falling standards. These issues make additional gold recovery at the end of mine life a critical problem in financing some closure operations. Another issue is the length of time that must be budgeted for heap rinsing operations. Innovative biological processes developed and applied by Pintail Systems, Inc. at numerous mine closures have indicated that bio-processes can significantly enhance gold recovery during heap cyanide bio-detox over the recoveries expected from rinse operations. If heap rinsing can be eliminated or reduced and if gold recovery can be improved at the end of mine life, many mine closures may be possible with processes that pay for themselves or generate profit. Additional advantages of the bio-detox technology is that it can be engineered to treat multiple contaminants besides Weak Acid Dissociable (WAD) cyanide. Other contaminants treated in heap process solutions include nitrates, ammonia, heavy metals, thiocyanate and total cyanide. At the Cripple Creek and Victor Mining Company Ironclad Mine near Victor, CO, 5 million tons of rinsed, heap leached spent ore were biologically detoxified to reduce cyanide content, enhance gold recovery during bio-detox and to reduce dissolved metals in heap leachate solutions. During the bio-detox treatment period a substantial improvement in gold recovery allowed the detox operation to operate as a profit center. Final gold recovery was at least twice what was expected from a normal rinse operation.