News

Ultra-Fine Lime: Pilot Plant Construction and Commissioning

Background

Acid mine drainage (AMD) is produced by the oxidation of sulphide minerals, mainly iron pyrite or iron disulphide (FeS₂). This is a natural chemical reaction which can proceed when minerals are exposed to air and water. Acidic drainage is found around the world both as a result of naturally occurring processes and activities associated with land disturbances, such as highway construction and mining where acid-forming minerals are exposed at the surface of the earth. These acidic conditions can cause metals in geologic materials to dissolve, which can lead to impairment of water quality when acidic and metal laden discharges enter waters used by terrestrial or aquatic organisms.

Considering the vast number of publications on Acid Mine Drainage (AMD) and the treatment thereof, the long-term impact on the local ecological area must be understood as well as how to treat the problem in a sustainable manner.

There are two main treatment processes available:

• Active Treatment: Dosing of limestone is performed in a water treatment plant, designed especially for Acid Mine Drainage (AMD).
• Passive Systems: Contaminated water from mine drainage is treated by exposing it to limestone and other vegetation that form carefully designed components of ponds, neutralizing ditches, buried channels, and wetlands.

Calmasil Development

Calmasil has been supplying limestone to the gold mining industry for a number of years to be used in their water treatment process. The limestone is milled by the clients to < 106 µm to ensure rapid reaction. In order to add value for our clients, Calmasil embarked on a project to classify the limestone to < 106 µm, thereby eliminating the expensive milling process. Phase one (1) of the project was to develop a small scale test plant, which was successfully commissioned and showed excellent results.

Based on the performance of the product and ability to classify < 106 µm product, Calmasil has completed the basic design of a full scale plant that will yield ±4000mt per month of ultra-fine limestone.

Calmasil Prima with a pH >12 and a C.C.E of ±100 % on its own is an extreme cost effective alternative to CaO (Unslaked lime) and CaOH (Slaked lime). The increased reactivity due to particle size reduction is set to result in vast performance improvements compare to the standard product, assisting in stabilizing the pH levels in the AMD ensuring that the pH level is at the required level.

Calmasil projects that the full scale plant will be constructed and commissioned by end March 2012. We intend to keep everyone up to date as we reach our various milestones in this project.