Beneficiation studies on a Copper ore sample from Shaft No.3,Khetri, Rajasthan, of the National Mineral Development Corporation Ltd.

Abstract

Comprehensive laboratory scale flotation studies have been conducted on a copper ore sample from Shaft No. 3, Khetri, Rajasthan, received from National Mineral Development Corporation Ltd. The sample, as received, assayed Cu-0.79%,Fe-20.16% S-2.85%, SiO2-52.82%, Al2O3-10.2%, CaO-Trace, MgO-5.09%,Au-0.08% dwt/T and Ag-1.7 dwt/T. The opaque minerals present in the ore in order of abundance were magnetite, chalcopyrite, pyrrhotite and pyrite and traces of mercasite. The ore was chiefly composed of siliceous gangue, such as quartz, chlorite, ferro-magnesium minerals (chiefly enstatite) and biotite in order of abundance. Fair liberation of chalcopyrite occurred below 150 mesh. During roughing, maximum recovery of copper value was obtained at natural pH in a Fagergren cell employing an optimum grind of 69.5% -200 mesh and using 0.1 lb/T of Potassium ethyl xanthate and 0.07 lb/T of pine oil. One, two and three cleanings of the rougher concentrate at the pH range of 9.5-10.5 produced final concentrates assaying between 7% and 15% Cu, with recoveries from about 88 to 63% Cu. Pyrite-Pyrrhotite flotation did not yield a concentrate high in sulphur. Settling and filtration tests were performed with (a) selective Cu concentrate (about 15% Cu) and complete tailing obtained from locked tests, (b) bulk rougher concentrate assaying 9.77% Cu, 36.97% Fe, 28.29% S,14.6% SiO2,2.8% Al2O3,0.62% CaO and 1.9%MgO with a recovery of 92% Cu, and (c) rougher tailing as obtained in (b) Filtration rates of both the concentrate and tailing were found to be high. Use of flocculants (Separan) upto about 0.02 lb/T was helpful in increasing the settling rates. The bulk concentrate after reflotation assayed 12.28% Cu, 37.39% Fe, 34.02% S, 8.58% SiO2, 1.04% Al2O3,0.33% CaO, 1.17% MgO, 0.8 dwt/T Au and 8.9 dwt/T Ag. With recovery of 90% Cu. This should be a suitable feed to be proposed flash smelter for extraction of copper at Khetri, Rajasthan.