Effect of Gold Grade on Cyanidation
During the Feasibility study is important to study the possible behavior of the gold ore in the cyanidation circuit. It has been noted in several projects that the gold grade has an effect on the performance of recovery process such as Carbon-in-Pulp or Carbon-in Leach. Considering the fact that gold grade changes are beyond operational control, operators must not be held accountable for reduction in gold recovery produced by lower head grades. On the other hand, the ore must take credit for a gold recovery increase. For this reason, detailed metallurgical testing programs, feasibility studies, production planning and budgets must consider variations in recovery due to changes in gold grade. Some metallurgists think that the problem is a reflection of ore geology and mineralogy that are specific for some ores. Also, comparison of recoveries at different sites is not important without a detailed knowledge of the problems associated to gold liberation.
Many metallurgists are used to consider a regression analysis of cyanidation plants in order to develop a modeling tool to apply the results to the first years of operations. These results are a first approximation of the full scale results of the new project. This alternative has been employed with high success to estimate and project gold recoveries and produce additional incomes at several gold operations in Canada, Peru, the States, Australia and South Africa. This tool provides economic optimization by quantifying the potential effects of the parameters responsible for gold losses into tails. The information obtained in this kind of study show the important role of the gold grade in the estimated metallurgical performance of the plant. Basically, the influence of the gold grade is a truly aspect many times overlooked in the study of the new project or gold operation.
Essentially, the regression analysis tries to separate statistically the most meaningful variables or parameters in a plant that are the reason of gold losses. In this way a through interpretation of the gold cyanidation and recovery process are important when employing the procedure to improve the metallurgical performance and economy of the project. It has been noted that the most important parameters that affect the recovery process are classified in two groups. The first group comprises all parameters or variables that are responsibility of the operator such as gold grade and mineralogy variation. The second group includes all the typical parameters that are normally controlled in a cyanidation plant such as percent solids, fineness of primary grind, cyanide dosage, pH value or any pre-treatment before leaching.