Potash Solution Mining
The element potassium is an important constituent of fertilisers, and therefore makes a major contribution to feeding the world. Potassium is also used in various forms by the chemical industry, for the manufacture of glass, and many other industrial sectors.
Potassium is currently mainly extracted using conventional mining techniques used to develop salt deposits. However, the conventional mining of potash seams is increasingly associated with technical problems and additional costs when exploiting deposits which either lie at considerable depths, or which are not very thick, or which only have low potash concentrations. In addition, it is also becoming increasingly inacceptable to dispose of the conventional salt – produced as a by-product of the physical mining methods – in large unsightly mine tips on the surface.
Extracting potash using solution mining technology is therefore becoming increasingly interesting. One of the positive effects is that potash is particularly soluble in water. The following characteristics make solution mining more beneficial compared to conventional mining:
- Lower footprint for the operating facilities on the surface
- Lower technical risks
- Avoidance of underground mining risks
- Considerable reduction in mining losses thanks to the improved cavern/pillar ratio
- Continuous hydraulic and solid backfilling in the caverns
- Lower investment costs because a shaft and underground workings are not required
- Usually a faster lead time before production starts.
There are various extraction concepts used for solution mining which have to be adapted to the particular characteristics of each salt deposit. These include the geometry and the mineralogical composition of the potash deposit. The potash is usually located within silvinite deposits (so-called hard salt) or within carnallite deposits.
Planning a potash solution mining project first requires an assessment of the suitability of the deposit for solution mining extraction, and the economics of the project. This economic assessment is undertaken based on a precise description of the conditions within the deposit, and the reserves, as part of the geological exploration, as well as the results of laboratory solution mining tests undertaken on core samples.
Depending on the properties and the production objectives, the solution mining extraction of potash can be optimised by using cold and/or hot solution mining methods.
In addition to the main potash exploited by solution mining which is in the form of potassium chloride (KCl), it is also possible to produce other by-products such as rock salt or table salt (NaCl), and possibly also magnesium chloride (MgCl2), and then to process the salts for subsequent sale.