Hydrated lime is a key industrial chemical used for pH control or regulation in a variety of processes. In the mining industry it finds use in pH regulation in gold cyanidation, stabilizing the cyanide complex by prevent formation of hydrogen cyanide. It is also a very good pH regulator in the flotation of a variety of minerals.
Because we are aware of the demand different processes place on the active component in lime, calcium oxide, we ensure that our lime is of the right specification. We offer various grades of lime, with different CaO, which can be quite safely interchanged with ease.
The specifications of our lime are such that there is no addition of undesirable elements in your reaction. This reaction is translated by the Elsner Equation. This chemical equation occurs at an optimum pH of 10-12, which prevents the formation of HCN and thus optimises cyanide usage in leaching. To maintain an alkaline solution, hydrated lime is normally added to the leach tanks.
Method of Application
Dosage rates for lime are determined by:
- pH of feed material
- Alkalinity of recycled water or material – use of more recycled water tends to result in a build up of alkaline material in the system, resulting in reduced need for addition of of lime to maintain optimum pH. Effective water balancing systems have to be incorporated at the design stage of the plant.
Ore preparation in heap leaching involves mixing it with lime before putting it on the leach pads. Added lime is determined by pH of feed and return water.
For ores that are difficult to cyanide leach, lime and sodium cyanide can be introduced in the ball mill to ensure increased times of contact between the lime cyanide and ore. Lime additions in processing dump material are high to counter the effect of increased cyanide demand for complete dissolution of the gold in them. In all these methods, lime addition is done to maintain an alkaline reaction environment optimum for cyanidation.
The pH in the leach tanks is monitored by using pH meters.
Other Uses of Hydrated Lime
- Hydrated lime is also used in water treatment plants also for pH correction.
- Oil and detergent manufacturing set ups also use lime in their effluent treatment plants to neutralize sulphuric acid added to effluent.
- Lime can also be used as a pH modifier in froth flotation