REV14706 - Laserfiche WebLink

Home Browse Search

successfully employ the INCO SO,/Air process at the San Luis stte. INCO's conceptual design crkeria were developed using data du g from laboratory-scale treatability studies. The system has been designed to reduce cyanide concentrations in the tailings slurry to meet permk limitations for the tailings impoundment sdutlons as set forth In MLRD Pennk No. M-88-112. \ , ~ (INCO Exploration and Technical Services, Incorporated, 1992). The INCO S0,/Air treatment ~ ~ a ,~.r~ system will consist of one reactor. The design capacity of the system will be approximately fi0 ~ ~ ~ ~,r, percent greater than the average cyanide load. Audide alarms will notify operating personnel of ya` ~~~ upset condkions. Inmost situations, there will be sufficient storage capacity available in the reactor ~,;f to batch treat the tailings slurry, as necessary, prior to discharge to the fallings impourxJment. 2~ However, o ratin pe g personnel will stop the reactor feed 'rf upset conditions persist, to allow sufficient storage capacity for adequate tailings treatment The INCO SOz/Air process for the San Luis ske Is designed to handle a maximum WAD cyanide load of 73 kg/hour and a maximum slurry throughput of 1,330 gallons per minute (gpm). Based current operating condkions, the typical cyanide load Is expected to be approximately 47 kg/hour and slurry flow rates average 1,270 gpm. Under normal condkions, the INCO SOZ/Air system will operate on a continuous basis. Under upset condklons, BMR will have the ability to batch treat the tailings slurry, as necessary to meet effluent cyanide limitations. INCO's treatabiliry test work was pertormed using a reactor residence time of approximately 45 minutes. According to INCO, a residence time of approximately 60 minutes is generally recommended for operations such as San Luis. However, at the request of BMR, INCO has designed for addttional reactor capacity resulting in an average residence time of 75 minutes, neady 170 percent of that required under laboratory conditions. A process flow diagram for the proposed INCO SO,/Air process is included es Figure 1. As the tailings slurry exks the last of six CIL tanks, tt will gravity flow into a reactor. The reactor will be constructed of mild steel, wkh a concrete bottom. The reactor will have a maximum capacity (brimming) of approximately 122,780 gallons. Suffur dioxide will be added to the reactor using asingle-point sparger terminating near the bottom and center of the reactor. The amount of sulfur dioxide fed to the system will be measured as a liquid, allowed to flash, and then added to the reactor. If the pH of the reactor drops below 7.5, the 25302/RN0610.RPT INCO SOz/Air Technical Reviaon Page 6 June 16, 1992 San Wis Mine