Patent ID: 7025942
Filing Date: 2006-04-11
Classification: C22B

Abstract:
1. A method for improving the efficiency of a gold cyanidation leach process by controlling and modifying the rate of lead compound addition to a leach liquor, by adjusting the rate of addition according to the concentration of thiocyanate ion in the leach liquor, the method comprising the steps of: (a) determining a target value for the concentration of thiocyanate ion (CNS) in the leach liquor; (b) determining an acceptable range for the concentration of thiocyanate ion having a first range limit above the target value and a second range limit below the target value; (c) measuring the concentration of thiocyanate ion in the leach liquor at a known time; (d) measuring the rate of lead compound addition at the known time of (c); (e) comparing the concentration measured in (c) with the target value, and with the first and second range limits determined in (b) for the target value determined in (a); (f) adjusting the rate of lead compound addition to maintain the thiocyanate ion concentration within the range determined in (b); and (g) monitoring the process by applying (a) to (f) at regular intervals.