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• '~ <br />SECTION 2.0 <br />PROCESS DESCRIPTION <br />The function of the Tailings pH Adjustment System is t reduce the <br />pH of the tailings slurry from 11.1 to the 8.5 to 8.9 r nge, by the <br />addition of concentrated sulfuric acid. At the to er pH, the <br />residual sodium cyanide (and certain other cyanides) i the slurry <br />I are partially decomposed to form hydrogen cyanide (HC ). Some of <br />this HCN is stripped from the slurry as a gas by igorous air <br />sparging and mechanical agitation, and recovered from t e resulting <br />I air stream by contact with sodium hydroxide (NaOH) so ution, in a <br />scrubber. <br />Slurry discharged from the final CIL tank (04-TK-OS) lows to the <br />agitated, air-sparged pH Adjustment Tank (04-TK-09). oncentrated <br />sulfuric acid is metered into the tank to reduce 'the pH and <br />decompose cyanide. The tank is covered, and the sparge air, <br />r containing the HCN evolved, is ducted to a packed tow r absorber, <br />L Fume Scrubber 04-SR-01. The HCN is absorbed in a circulating <br />solution of sodium hydroxide, to reform sodium cyanid . <br />t Bleed solution from the scrubber is discharged to eithe Leach Tank <br />04-TK-O1 or 04-TK-02, to recycle the regenerated so ium cyanide <br />I contained in this stream. Scrubbed air drawn through he scrubber <br />by Fan 04-FA-O1 is vented to atmosphere via a sta k. Slurry <br />discharged from the pH Adjustment Tank flows to the C rbon Safety <br />Screen 04-SC-10. Both this screen, and Tailings Hopp r 04-HP-02, <br />r are covered and vented to the Fume Scrubber. <br />L, <br />L. <br />pj/1473rp 012591 2-1 <br /> <br />