Laserfiche WebLink
[. <br />ti <br /> <br /> <br />I <br />I <br />~, <br />~ ~ <br />SECTION 2.0 <br />PROCESS DESCRIPTION <br />The function of the Tailings pH Adjustment System is to reduce the <br />pH of the tailings slurry from 11.1 to the 8.5 to 8.9 range, by the <br />addition of concentrated sulfuric acid. At the lower pH, the <br />residual sodium cyanide (and certain other cyanides) ih the slurry <br />are partially decomposed to form hydrogen cyanide (HCN). Some of <br />this HCN is stripped from the slurry as a gas by vigorous air <br />sparging and mechanical agitation, and recovered from the resulting <br />air stream by contact with sodium hydroxide (NaOH) solution, in a <br />scrubber. <br />Slurry discharged from the final CIL tank (04-TK-OB) Mows to the <br />agitated, air-sparged pH Adjustment Tank (04-TK-09). Concentrated <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 />containing the HCN evolved, is ducted to a packed tower absorber, <br />Fume Scrubber 04-SR-O1. The HCN is absorbed in a circulating <br />solution of sodium hydroxide, to reform sodium cyanide. <br />BLeed solution from the scrubber is discharged to either Leach Tank <br />04-TK-O1 or 04-TK-02, to recycle the regenerated sodlium cyanide <br />contained in this stream. Scrubbed air drawn through the scrubber <br />by Fan 04-FA-O1 is vented to atmosphere via a stalk. Slurry <br />discharged from the pH Adjustment Tank flows to the Carbon Safety <br />Screen 04-SC-10. Both this screen, and Tailings Hopper 04-HP-02, <br />are covered and vented to the Fume Scrubber. <br />pj/1473rp 012591 2-1 <br />