Recovery of Economic Minerals from Graphite Float of Rajpura Dariba mines

Abstract

A 3000 tpd lead-zinc ore beneficiation plant was commissioned in 1983 to produce lead and zinc concentrates suitable for Indian smelters. The problems encountered in the production of individual concentrates are mainly high graphite and lower lead grade in lead concentrate and high silica in zinc concentrate. Due to variable nature of ore quality, Graphite mica - schist, the incidence of high graphite and lower grade of lead in lead concentrates can be explained and taken care by use of pre flotation of graphite and by gravity techniques. It has been observed during extensive laboratory scale testing by in-house R&D of HZL and by the National Laboratories in India and plant operations for over a decade that incidence of graphite mica -schist in the ore affects zinc flotation only to a limited extent whereas lead metallurgy is adversely affected. Hence one of the methods tried was pre-flotation of graphite ahead of lead-zinc selective flotation. In this paper, efforts made towards recovery of lead and zinc minerals present in the pre-graphite float are discussed. The studies include lead and zinc depressionduring reverse flotation, graphite depression and lead flotation and use of gravity techniques. The results indicate that gravity techniques are effective in removing most of the liberated graphite,thereby ensuring enrichment of lead and zinc minerals present in the higher specific gravity fractions, which can be recirculated and recovered in the plant.