Luossavaara-Kiirunavaara Aktiebolag (Sweden)

Modeling heat transfer in packed bed processes such as iron ore pelletization is essential for optimizing process operation and furnace design. In these systems, materials like magnetite iron ore undergo thermal and chemical transformations, where heat and mass transfer are often coupled with heat effects from multiple processes — including both exothermic chemical reactions (e.g., oxidation) and endothermic physical changes (e.g., drying and sintering). As the industry moves towards fossil-free ironmaking, it becomes increasingly important to isolate pure heat transfer behavior, independent of chemical reactions, to support the development of sustainable process schemes. This study investigates convective heat transfer in a packed bed by evaluating several established correlations against the conventionally used modified Ranz–Marshall correlation. Pilot pot-scale experiments were performed by isothermally heating 120 kg of already indurated iron ore pellets at 300 °C to avoid chemical reactions, with additional experiments at 500 °C and 700 °C to assess performance at elevated temperatures typical of industrial pelletization. Results show that the modified Ranz–Marshall correlation underpredicts heat transfer rates under conditions isolating convective heat transfer, reinforcing the need for this investigation. The Wakao–Funazkri and Rowe–Claxton correlations provided the best agreement with experimental data, particularly at 300 °C. Minor deviations at higher temperatures suggest the influence of unaccounted variables, warranting further study. Sensitivity analysis identified gas velocity as the most significant parameter affecting heat transfer. The results suggest that adopting the Wakao–Funazkri and Rowe–Claxton correlations can provide a stronger basis for predictive pellet heat transfer modeling in future process design and simulation work. • Heat transfer models validated for packed beds at 300, 500 and 700 °C. • Rowe–Claxton and Wakao–Funazkri models provide the most accurate predictions. • Modified Ranz–Marshall model deviates more due to simplified porosity scaling. • Gas velocity strongly affects heat transfer; a 10% reduction improves model accuracy. • Temperature-dependent heat capacity enhances agreement between simulations and experiments. • Discrepancies at high temperatures suggest heat losses and non-uniform porosity effects.

<strong class="journal-contentHeaderColor">Abstract.</strong> LKAB currently runs an intense exploration program focused on the Per Geijer (PG) iron oxide-apatite mineralization, close to the active Kiruna mine, in northern Sweden. The mineralization and the hosting volcanic units dip at an angle of 50&ndash;60 degrees and are overlain by quartzite. Greenstones are also present in the area. The iron mineralization is associated with high levels of phosphorus and REEs. As a major part of the mineralization occurs at depths &gt;500 m, various geophysical surveys have been used to assist the exploration throughout the years, recently also including seismic measurements. An initial pilot reflection profile in 2021 showed promising results, and three additional profiles were acquired shortly afterwards, all with Vibroseis as a source. These were followed by downhole seismics (VSP) in two drill holes. During 2024 a 3D survey covering the Per Geijer mineralization was also acquired. Clear P-wave reflections are visible in the shot records from the surface seismics as well as in the downhole seismics, and the latter also show interpreted P-S reflections. The steeply dipping structures in the area complicate the data processing, and out-of-the-plane reflections are present in some of the 2D profiles, the latter confirmed via cross-dip analysis. The resulting migrated sections and volumes show prominent reflections, some of which correlate with the Per Geijer mineralization or units close to it and suggest some extensions of the known mineralization. Reflections are also observed from the northern end of the nearby Kiirunavaara ore. Sonic and density logs are available to support the interpretation. These indicate that the main cause of the reflections from the iron mineralization is the density contrast, rather than the velocity contrasts. The downhole seismics also allow a closer link to the drilling information. Further notable in both our 2D and 3D surface data is a high-amplitude reflection originating from a steeply dipping structure outside the survey area, which if projected to the surface correlates with older greenstones on the western side of the Kiirunavaara orebody.

Abstract We investigate seismic velocity changes in the rock mass related to mining induced seismic events and ore exploitation by computing a one-month long 4D elastic model of Kiirunavaara mine (Sweden). We focus on a specific mine sector, where a single $$\varvec{M_W}$$ M W =2.0 event occurred on May 22 (02:31 local time), damaging the infrastructure. We make use of P- and S-first-arrival times obtained from the permanent seismic system for computing the full 4D (continuous 3D volume in time) seismic velocity model of Kiruna mine using a trans-dimensional Monte Carlo sampling. The trans-dimensional approach guarantees that the resolution, both in space and in time, is strictly data-driven. Our results give the following insights into the velocity differences at the mining levels and at different time-length scales. (a) We observe a striking correlation between spatial variations of $$\varvec{V_P}$$ V P and ore-body geometry, confirming the robustness of the velocity model. Clay zones appear as a low $$\varvec{V_P/V_S}$$ V P / V S ratio zones, as seen in previous tomographic studies. (b) High-frequency (hourly) fluctuations of the rock mass $$\varvec{V_P}$$ V P around the ore-passes are highly correlated with seismic sequences in the same rock volumes. In particular, $$\varvec{V_P}$$ V P increases rapidly when ore-passes are seismically active and $$\varvec{V_P}$$ V P values keep a high value for few (1-4) hours after the end of the seismic sequence. (c) The smoothed velocity model, computed as averaged model over a 2-days moving window, suggests that low-frequency $$\varvec{V_P}$$ V P fluctuations can be compared to stress cell measurements located closely.

Load-haul-dump (LHD) machines are powered by diesel, electric, battery, or hybrid systems. Diesel LHDs are efficient but produce noise and emissions. Trolley electric lines or cables are impractical for LHDs, while batteries offer high flexibility during operations but require frequent recharging. Despite the advantages of battery LHDs, studies are limited. This study used discrete event simulation to evaluate the performance of battery LHDs focusing on battery swapping stations and energy consumption in traditional and fork production layouts in a sublevel caving mine. The results showed the battery machines are more energy-efficient when working in a traditional layout than a fork layout. The daily energy consumption is 0.64% less in a traditional layout than a fork layout. The results also showed the selected battery swapping stations are optimal because productivity is not significantly affected by changing the swapping locations.

Summary Downhole geophysics is used to support the exploration drilling carried out by LKAB in the Kiruna area, both for the actively mined Kiirunavaara ore, and for the Per Geijer Deep iron mineralization. The former is almost totally consisting of magnetite, whereas the latter is a mix of magnetite and hematite, also having associated phosphorus and REE’s. These deposits are dipping 50–60 degrees, which in combination with access limitations make seismic imaging challenging. Various downhole geophysical techniques have therefore been used for exploring the surroundings of the drill holes, including magnetics, gravity, time-domain electromagnetics (TEM), pole-dipole resistivity, magnetometric resistivity, and walkaway vertical seismic profiling. The merits and drawbacks of these methods are discussed, looking also at how to build subsurface models via forward modelling or inversion. Wireline logs of physical parameters are used to support the interpretations. Downhole magnetometry is the most common method, and it can give quick guidance to the drilling. Downhole TEM has also been used in numerous holes and can be effective to localize off-hole mineralization. The remaining methods are due to logistics not used on a routine basis, although all show distinct responses from the exploration targets.

Beneficiation of the tailings from Iron Oxide Apatite (IOA) ore has become an important topic in the field of mineral processing as phosphate rock is considered as critical raw material by the European Union. Driven by the strong call for sustainability and green technology, this paper introduces the application of novel and bio-based organosolv lignin particles (OLP) as a reagent for apatite flotation. In the artificial mineral mixture flotation tests, OLP addition or replacement to tall oil fatty acid-based collector (TOFA) was shown to improve flotation kinetics and recovery. In this study, it was demonstrated that one of the widely used commercial TOFA collectors could be replaced with OLP by 70 %. The replacement led to an increase in recovery (+2%) and only a minimal decrease in P grade (−0.3 %) for the rougher-cleaner flotation tests in one of the two feed types tested. The influence of OLP and other reagents on apatite floatability has been investigated through Hallimond tube tests and laboratory scale batch flotation tests as well as zeta potential measurements and spectroscopy tests to further understand the possible mechanism and synergism of reagents in the apatite flotation system.

ABSTRACT: The Malmberget iron ore mine owned by LKAB (Sweden) is one of the largest iron underground mines in the world. At present 10 orebodies are being mined, with seismicity being a known issue for several of them. The seismic system consists of 143 geophones, of which 36% are triaxial. They are a mix of 4.5 and 14 Hz geophones installed underground and in crown pillars. On the ground surface five 1 Hz geophones have been installed to estimate seismic source parameters. The mine seismic system records on average 440 events monthly with ML &amp;gt; 0. The largest seismic event recorded until the end of 2023 is with ML 2.9. The study was carried out in order to identify some trends in seismicity as the mining goes deeper and to find a correlation with some main controlling parameters – volume and depth of the production in order to obtain information for future seismic hazard and risk analysis. Another purpose of the study was to identify trends and behaviors for different orebodies (mining areas). The seismicity correlates strongly with the production depth, but there are differences between the orebodies. 1. INTRODUCTION The Malmberget iron ore mine owned by LKAB (Sweden) is one of the largest iron underground mines in the world. Mining in the area started by the official records in the mid-18th century, but in a small scale. The railroad was finished in the 1890s, which meant an upswing in the mining activities. Already in 1914 underground mining dominated the production. The Malmberget underground mine consists of about 20 orebodies, of which 11 are mined at present (December 2023), covering a surface area of about 4 × 8 km. The orebodies vary in size, shape and dip in addition to having different rock mechanics issues related to geology and extraction sequence. Some orebodies have been mined by surface mining, while mining in others started some distance below the ground surface, leaving a crown pillar. At present the mine uses the sublevel caving mining method.

Fibre-optic based sensing technologies are becoming popular in the field of geophysics since enable long range and high spatial resolution acoustic measurements. In this work, we present preliminary results obtained using quasi-distributed Fibre-Bragg grating sensing and Distributed Acoustic Sensing (DAS) to monitor seismic activities in an operational underground mine. 12 FBGs and 800 metres of fiber optic cable was installed in the tunnel lining an operational mine and recorded mine seismicity such as production blasts and a small seismic activity of magnitude 1.41 in September 2022.

In geophysical inverse problems, the distribution of physical properties in an Earth model is inferred from a set of measured data. A necessary step is to select data that are best suited to the problem at hand. This step is performed ahead of solving the inverse problem, generally on the basis of expert knowledge. However, expert-opinion can introduce bias based on pre-conceptions. Here we apply a trans-dimensional algorithm to automatically weigh data on the basis of how consistent they are with the fundamental assumptions made to solve the inverse problem. We demonstrate this approach by inverting arrival times for the location of a seismic source in an elastic half space, under the assumptions of a point source and constant velocities. The key advantage is that the data do no longer need to be selected by an expert, but they are assigned varying weights during the inversion procedure.