588 One important parameter to highlight is the comparison between the cost of cyanidation in ore treatment for gold and silver recovery and the cost of cyanide destruction with Caro’s Acid. Figure 4 shows that during 2002 and 2003, cyanide destruction costs with Caro’s Acid were 1.22 and 0.87 $/t of ore treated, while cyanidation process costs were 0.79 $/t. Thus, in this period, destruction costs were higher than ore treatment costs. In subsequent years, the trend reversed as a result of process optimization. Figure 4 - NaCN cost ($/t) Vs Caro’s Acid ($/t). Cyanide destruction costs relative to total cyanide in the tailings dam solution recirculated to the plant show that in 2002, the average cost of Caro’s Acid was 1.22$/t of ore treated, with average total cyanide in the recirculated solution at 18ppm. By 2006, the average cost was $0.93/t, with total cyanide at 15.2 ppm; At the end of optimization, the average destruction cost was 0.30$/t with total cyanide reduced to 0.14 ppm. Figure 5 - Caro’s Acid cost ($/t) Vs Total Cyanide in tailings dam (ppm). Optimization implies process improvement, higher product quality, cost reduction, and savings in foreign currency. In this case, cyanide destruction costs with Caro’s Acid averaged 0.93$/t of ore treated between 2002 and 2006 (before optimization). After optimization, destruction costs decreased to 0.30$/t of 0.79 0.79 0.87 1.02 1.87 2.06 1.55 1.43 1.31 1.22 0.87 0.70 0.84 1.02 0.91 0.61 0.42 0.30 0 0.5 1 1.5 2 2.5 2002 2003 2004 2005 2006 2007 2008 2009 2010 ( $ /t ) NaCN ($ / t ) Caro’s Acid ( $ / t ) 1.22 0.87 0.70 0.84 1.02 0.91 0.61 0.42 0.30 18 17 16 12 13 6 1.68 0.31 0.14 0 4 8 12 16 20 0 0.4 0.8 1.2 1.6 2002 2003 2004 2005 2006 2007 2008 2009 2010 Caro’s Acid ($/t) Total NaCN (ppm) Caro’s Acid ($/t) Total NaCN (ppm)
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