Background

In LKAB’s iron ore mines in Kiruna and Malmberget, the ore is extracted deep underground and transported to the surface by hoists. During further processing at the process plants, a number of different products are produced, including iron ore fines and sintered iron-ore pellets.

Water is a critical component in the processing plants, as the iron ore must be screened, concentrated, and pelletized. After the raw ore has been crushed and ground in the mills, it is transported (pumped) further (by adding water to the fine grinded iron ore) to the final treatment stage, where the particles are separated from the water, which is then reused in the process. A large portion of the tailing (waste) materials from the processing plants is also transported using water. From both an energy use and environmental impact perspective, it is extremely important to reuse as much of the water as possible. At some of process plants, LKAB has faced recurring issues where the process water has not reached a sufficient level of clarity, which has at times forced a reduction in production rates.

The Assignment

In this project, Alteco was responsible for project management, design coordination, sizing, and construction of two thickeners for wastewater. The delivery included all necessary equipment and instrumentation for flocculation, particle sedimentation, flow distribution, and sludge handling. Advanced simulation technology (CFD-DEM) was applied in the project to predict particle, distribution, and flocculation behavior.

The North American technology company Westech Inc. was early on appointed as one of the main suppliers for large parts of the process equipment, including the feedwell and drive systems for the rake mechanism. The main contractor, Vinab, carried out the complex and highly extensive site erection work in record time. Alteco maintained a very good and mutually beneficial collaboration with Vinab throughout the entire project. Alteco participated all the way through to the construction and commissioning phases at the end customer, LKAB.

During the course of the project, it was discovered that the water flow and the amount of (feed) waste differed somewhat from initial expectations. Therefore, certain modifications had to be made to the feedwell, distribution tank, and intake screens. After adjustments and modifications, the final performance far exceeded expectations: the purification level was a full 30 percentage points better than the specified requirement. Efficiently reusing process water is one of the keys to a sustainable production chain in the future, and Alteco’s project managers, process engineers, and mechanical engineers — through their application expertise and attentiveness to the customer’s needs — helped bring the project successfully to completion.