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~; ~ ~ ~ ~•~ <br />Paga 19 <br />-~ <br />TABLE 18 <br />OPERATING EXPENSES <br /> <br />Item --. <br />~' ltst oer Tone of Ore <br />:,-: ; , _ <br />' •, H,SO~t't ~ S 0.20 <br />CaOnt 5 0.07 <br />. - NaOHt't S 0.40 <br />Electricait~t ; 0,03 <br />Operator'6' ~ 0.03 <br /> S 0.73 <br />r'i Based on 50.05/Ib for 93% H,SO.. <br />m Based on 50.04/Ib CaO. <br />°1 Based on 48% NaOH sdtfon of 50.18/Ib. <br />t'i Based on the currant mine price of 50,04fkw-hr. <br />t6t Based on 535,000 per year. <br />Based on the estimated operating costs for the two mines, an average cost of about 50.50/ton of ore <br />processed was obtained. There was an economy of scale for capital costs which ranged from about <br />5575jion for the 3,500 tonJday mine to about 5250/ton for the 15,000 ton/day mine. <br />These examples clearly demonstrate the economic and environmental viability of the cyanl•~e recovery <br />process. The economic advantages when coupled wfth the environmental advantages yield an efficient pre- <br />treatment alternative for slurries or sdutions containing cyanide. <br />THE FUTURE OF CYANIDE RECOVERY <br />~_~ As mentioned previously, the real advantage of cyanide recovery from slurries includes the lowering of <br />~ ~ cyanide and metals levels entering a tailings impoundment, thereby minimizing downstream treatment and <br />the potential for surface and groundwater and groundwater contamination. <br />Cyanide recovery Is not well suited as a primary treatment process, when very low levels of residual cyanide <br />_ are required Q.e. < t.0 mg/I), although In many Instances these levels are achievable. However, 6y lowering <br />" ~ the Inftial cyanide level entering an Impoundment and eriharicirig natural attenuation, downstream cyanide <br />values are lowered, allowing for more eHectNe and reliable treatment. By lowering the downstream cyanide <br />level, conventional chemical or bidogical treatment processes can be employed to reduce the residual <br />concentrations, which In most instances are not achievable when treating the higher influent cyanide and <br />metals levels. <br />With Increasing concern over groundwater and wlldl'rfe Issues, there will be Increasing presst.re to more <br />closely regulate cyanide entering callings Impoundments. Cyanide recovery processes sdve the problem <br />In an economically and environmentally acceptable manner. in addition, cyanide recovery allcws the use <br />of higher cyanide levels during metals recovery, thereby Increasing the flexibility of existing or proposed <br />metallurgical clrcuRs <br />