A leach circuit is an integrated series of processing equipment, tanks, vessels, pipelines, and associated infrastructure through which ore slurry or crushed material passes in order for valuable minerals to be dissolved into a pregnant solution using a chemical leaching agent. In hydrometallurgical processing, the leach circuit is one of the most critical operational units, dictating the overall efficiency, throughput, and economic viability of a mineral processing plant.
In gold mining, the leach circuit commonly employs a cyanide leach process (Carbon-in-Leach or Carbon-in-Pulp circuits) where gold is dissolved from crushed ore using sodium cyanide solution in the presence of oxygen. The circuit typically includes agitated tanks arranged in a cascade configuration to ensure adequate residence time. In bauxite refining (the Bayer Process), the leach circuit involves digesting bauxite ore in hot caustic soda (sodium hydroxide) under elevated pressure and temperature to dissolve alumina trihydrate from the ore matrix, leaving behind an insoluble residue known as red mud.
In iron ore and diamond mining contexts, the leach circuit may be employed for processing complex mixed ores where soluble impurities or valuable by-products require hydrometallurgical treatment. Key design parameters of a leach circuit include the slurry density, reagent concentration, temperature, pH, residence time, and agitation intensity. Proper control of these variables ensures maximum extraction of the target mineral while minimizing reagent consumption and the dissolution of gangue minerals. Monitoring and control systems including online analyzers, flow meters, and automated dosing systems are integral components of a modern leach circuit.