Small Scale Modular Gold Batch Cyanide Leaching Plant
Application
The modular batch leaching plant recovers gold from concentrate and high-grade ore. Concentrate produced by flotation and/or gravity concentration and high-grade ore are collected to process together.
Main Flowchart
Processing Characteristics
The materials, steel balls and cyanide solution are loaded into the ball mill to grind and leach at same time. Also, oxygen is fed into the drum of the ball mill intermittently to offset oxygen consumption of chemical reaction which greatly improves the leaching efficiency. The suitable grinding fineness is obtained by controlling grinding time which ensures gold is liberated fully and dissolved by cyanide.
The slurry after grinding is discharged from the ball mill to the leaching tank for continue leaching during agitation. The slurry settles naturally after hours of leaching. The clarified pregnant solution is discharged out of the leaching tank and flows into the pregnant solution pond, the barren solution is fed into the leaching tank to continue leaching and decantation. The gold extraction rate can be greatly improved by controlling the duration of leaching and decantation for repeating the cycle several times.
The depurated pregnant solution is pumped to Merrill-Crowe system to replace the dissolved gold with zinc powder. The vacuum pumps removes oxygen out of the sealed Merrill-Crowe system to minimize zinc loss and improve replacement efficiency. After the replacement reaction is completed, the gold sludge naturally settles and the barren solution is discharged into the barren solution pond. After enough accumulation of gold sludge, it is discharged out of the displacement agitation tank with conical bottom. Zinc is removed out gold sludge by sulfuric acid and the remainder is sent to smelt the bullion bars.
Specific Equipment
Batch Grinding Ball Mill
The ball mill is designed as a sealed structure specially for batch leaching. The materials, cyanide, water and grinding balls are fed into the ball mill arbitrarily as required. The ball mill is equipped with a special inflatable tube which periodically supply air into the drum of the ball mill during grinding to keep enough oxygen content in the grinding drum for ensuring that gold exposed during grinding reacts with cyanide in time. It enhances the leaching ability and improves the leaching efficiency.
Leaching and Decantation Agitation Tank
An agitator is assembled in the tank with drainage outlets of different height. The tank has the dual functions of agitating leaching and decantation. Slurry settles naturally after each leaching action. It is decided which height outlet discharges solution according to the content of gold in the solution. Then the barren solution is filled to continue leaching and decantation.
The leaching efficiency is increased much because the gold bearing solution is discharged out of the leaching tank in time and the tank is filled by barren solution.
Because of batch operation, a battery of tanks work by turns.
Merrill-Crowe Process Equipment
The depurate pregnant solution enters the closed circular tank with the agitator and cone bottom. The vacuum pump discharges air from the tank and the zinc powders are fed into the cylinder to replace superfine gold powders out which settle in the cone bottom of the tank. The sampling valve is installed on the tank body for measuring the gold content in the solution at any time to decide whether zinc powders are added more or not. Natural sedimentation occurs and the barren solution is discharged after the reaction is completed.
This process equipment has the advantages of simple structure, convenient operation, more than 99% replacement efficiency, low zinc consumption, and reducing the workload and acid consumption of acid pickling in the next process.
Specifications
Per batch grinding capacity: 650kg
Total leaching time: 24-48 hours
Leaching particle size: 325 mesh
Cycle times of leaching-decantation: 3-4
