Demonstration Bio-reactor plant with the collaboration of Department of Bio-technology, Government of India has been set up to maximize recoveries from the refractory ores since the recourses of free gold ore are limited.
Due to the limitations of processing of refractory ore through the concentrated smelting route, alternative recovery route such as bioleaching need to be pursued vigorously.
A major initiative has been taken by HGML through the setting up of demonstration bioreactor plant, being the first of its kind in India. Gold ore occurs in native form and is disseminated in a quartz matrix such ores, referred to as free milling ores, are treated in a conventional process with a cyanide to solubililse gold-cyanide complex. Whereas, in case gold ores are found to be refractory in nature, i.e. gold is associated with sulphides such as pyrite and arsenopyrite. In the absence of prior bio-treatment, direct cyanidation of a refractory gold bearing sulphides will yield only 30-40%, while after bio-liberation the gold recovery can be enhanced to more than 80-90%. It is being planned to upstage the demonstrator plant to a large-scale plant for GR halli & Ajjana halli refractory ores.