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' Page 13 <br />media, similar results were obtained at air to liquid ratios <500. The goal of the studies wes to reduce WAD <br />' cyanide to <10.0 mg/I, which was achieved. Pressure drops of about t00mm water gauge weie measured <br />through the 3m of SOmm mass transfer media. <br />Schematics for the layout of the lull scale Cyanisorb Process using eRher three complete mqc reactors In <br />' series or two stripping towers are presented, In Figures 6 and 7. Based on a comparison of pedormance <br />versus cost and ease of operatbn, the use of towers were selected as the preferred process aontiguratlon. <br />The preferred configuration Invdves two single pass towers about 4.Om In diameter and t0.Om in height <br />' operated In parallel, wfth a third tower as a stand-by unit. Testing continues to Identify aAy long-term <br />mechanical or physical problems with the process. Fdlowing cyankle removal, the slurry pH will ba <br />readjusted to 9.5 to preclpttate free metals, prior to disposal of the slurry In the Impoundment. <br />( <br />t <br /> <br /> <br /> <br /> <br />In conjunction wfth development and design of the Cyanlsorb process, additional experiments and <br />calculations were prepared to evaluate the impact of the cyanide recovery circuit on cyanldA and metals <br />levels In the tailings Impoundment end associated leachates. <br />The effect of cyanide recovery on cyanide concentratbns at <br />management system are summarized In Table 10. These calcul; <br />Associates, located In Melbourne, Victoria, Australia (9). The <br />cyanide levels entering and exRing the fallings Impoundment we <br />to 9.0 mg/I, respectively. In addition, the total cyanide In the <br />facility was reduced from 14.0 mg/I to about 5.0 mg/I. Pric <br />system Into the metallurgical process a fallings washing systi <br />eliminated at a substantial cost savings to the project. <br />irlou5 points In the Golden gross water <br />ms were prepared by M.P.A. Williams and <br />~sults of the analysts indicated that total <br />reduced from 186.0 to 30.0 rrrg/I and 42.0 <br />treated feed to theted feed to the wastewa r treatment <br />o Incorporation of the cyankle recovery <br />~ was required, which was subsequently <br />TABLE 10 <br />ESTIMATED CYANIDE CONCENTRATIONS WITH AND WITHOUT <br />CYANIDE RECOVERY AT THE GOLD N CROSS MINE <br /> Without Cyanide Rec <br />Solution t't Total Cif very With Cyanide Recovery <br />Total Ctd Wl~D Cff <br />' Tailings slurry to Impoundment 166 30 10 <br /> Pumped decant from pond t'^~ 42 ~~ 9 <.01 <br /> Mine backfill going underground - 11 0.7 <br />' Mine water pumped out t: d.2 0.39 <br /> Influent to water treatment plant 14 4.7 .06 <br />' "t Values taken from Golden Cross water management system oriel. <br /> t=~ Ail values 1n mgjL, unless otherwise stated. <br />' r'~ A first order decay rate was utilized In conjunction wfth dilutio to calculate cyanide values. The decay <br /> rate for total cyanide used prior to cyanide recovery was 0. 14/hr. The total cyanide values after <br /> cyanide recovery were calculated using dilution only, while a ecay rate of 0.006 jhr was used for WAD <br />' cyande. <br />~'t The residence time In the pond before arxJ after cyanide reco ery was 14.7 and 56.4 days, respectively <br /> <br />