The mining area stretches 5km in the E-W direction and 2.5km in the N-S direction (Lund, 2013). The ore is composed of magnetite (95%) and hematite (5%), and the grade for the different ore bodies varies from 49% to 63% (Lund, 2013). The width of the ore bodies varies from 20 to 100m, and the tonnage varies from 5MT to 250MT (Savilahti and Jonsson, 2013). The mine is divided into two parts: the western and eastern fields. The ore bodies in the eastern fields are composed of massive magnetite ores with a current known depth of 1600m and provide 80% of the total production (Lund, 2013). The western fields consist of small magnetite-hematite deposits with a current known depth of 950m (Lund, 2013). The ore bodies in the eastern field are Alliansen (Al), Fabian (Fa), Kapten (Ka), Dennewitz (De), Parta (Pa), Printzsköld (Pr), Östergruvan (Og) and Vitåfors-Riddarstolpe (Vi-Ri). The western field includes the Välkomman (Vä), Baron (Ba), Johannes (Jh), Hens (Hn) and Josefina (Js) ore bodies.

The Malmberget mine has scattered ore bodies with varying mine design parameters.

The mine design and layout at the Malmberget mine vary from one ore body to another. The Malmberget mine uses both transverse and longitudinal layouts for production, depending on the width of the ore body. This provides the mine with the flexibility to employ different mine layouts to reduce ore loss. The layout at one level can be longitudinal and the level below can be transverse, making the layout more complicated than a typical SLC operation. In most cases, levels up to 780m (below surface) have a longitudinal SLC layout, while levels from 805m and below have a transverse layout (Kristina Jonsson, personal communications, 2015).

A drift´s orientation is guided by ore geometry and ore geology. The production drifts are planned to avoid weak zones and zones with major waste intrusions (Sven-Erik Wennebjörk, personal communications, 2015). Longitudinal SLC accounts for 10% of the production and transverse SLC accounts for 90% (Sven-Erik Wennebjörk, Personal communications, 2016). The sublevel interval varies from 20 to 30m (floor to floor) depending on the ore body. The drift spacing stays constant at 22.5m (centre to centre) for all ore bodies. The overall orientation of the production drifts is optimized to minimize ore loss, as the ore body shape and size varies. But this variation results in a complex network of production drifts, and drifts at the upper levels are not parallel to those at the lower levels.

Malmberget’s underground mine consists of around 20 orebodies, of which around 10 are currently mined.

Before the iron ore, in the form of green pellet is entering the straight grate induration furnace, it has been processed in different stages. In the sorting-plant, the crude ore that has been extracted from the mine is separated from gangue and crushed down to smaller fractions. Further on the crushed iron ore is entering the concentrating plant.

At the facility in Malmberget there are today two pelletising plants. The first plant (BUV) was started up in the early 70’s. The pelletising plant consists of a number of different operation units, where the main unit is the straight grate induration furnace. Both plants are constructed more or less in the same way. The main difference between the two pelletising induration furnaces is that the newest induration furnace has an additional exhaust gas fan connected to the hot part of the furnace, and there are also a waste heat boiler installed in the newer induration furnace.

As the picture shows, the pelletising plant is divided into different zones where the main task is to dry, fire and cool the iron ore pellets.

Additives, such as olivine, limestone, quartzite, bentonite and water is added to form a slurry that later on will be rolled into centimetre sized spheres, these spheres, or green pellet, is then loaded onto a 90 meter long travelling grate and form a ........