Coal used in metallurgical processes can participate in reduction reactions to produce metals and alloys from oxides. Base metals production leads to generation of slag, which contains valuable metals that can be recovered and recycled. There are several options to treat the slag, depending on the metal content in the slag. One is slag fuming, which is a well-established process that is traditionally used to vaporize zinc from zinc containing slags, mainly lead blast furnace slag, but is applied in a few plants for copper smelting slags. In this process reduction is achieved using pulverized coal, lump coal or natural gas. Conventionally pulverized coal injected to the furnace is utilized both to participate in reduction reactions and also to supply heat. On the other hand, the amount of possible alternative reducing agents such as residue plastic material is increasing steadily and the issue of sustainable disposal management of these materials has arisen. As carbon and hydrogen are major constituents of the residue plastic-containing materials, they have the potential to be an auxiliary source of reducing agents, to partially replace conventional sources such as coal. Shredder Residue Material (SRM) is a plastic-containing residue material after separation of main metals. Utilization of SRM as an alternative reducing agent, would lead to not only decreased dependency on primary sources such as coal but also to an increase in the efficiency of utilization of secondary sources. This calls for systematic scientific investigations, wherein these secondary sources are compared with primary sources with respect to e.g., devolatilization characteristics, gasification characteristics and reactivity. As a first step, devolatilization characteristics of SRM are compared with those of coal using thermogravimetric analysis. To study the reduction potential of the evolved materials, composition of evolved off-gas was continuously monitored using quadrupole mass spectroscopy. To gain a better understanding of possible interaction of plastics in a mixture, the devolatilization mechanisms and the volatile composition of three common plastics; polyethylene, polyurethane and polyvinylchloride and their mixture have been studied. Furthermore, gasification characteristics and reactivity of char produced from SRM is compared with coal char. The effect of devolatilization heating rate on gasification rate of char was investigated. Proximate analysis has shown that SRM mainly decomposes by release of volatiles, while coal shows high fixed carbon content, which is reported to contribute to reduction reactions. The composition of volatiles shows H2, CO and hydrocarbons which are known to have reduction potential. Therefore, it is essential that SRM be used in a process that could utilize the evolved volatiles for reduction. The results confirm the interaction between the plastics within the binary and ternary mixtures, which suggests that similar phenomenon may occur during devolatilization of SRM. Although the char produced from SRM contains lower amounts of fixed carbon compared to coal char, it has a porous structure and high surface area, which makes it highly reactive during gasification experiments. In addition to physiochemical properties, the catalytic effect of ash content of SRM char contributes to its higher reactivity and lower activation energy value compared to coal char. Moreover, the gasification reactivity of char produced at fast devolatilization heating rate was highest, due to less crystalline structure of produced char.

New technologies are continuously considered for the handling and deposition of tailings. With thickened tailings only a fraction of water used conventionally reaches the disposal area, thus limiting sizes of water holding dam facilities and areas to be rehabilitated. Heat may also be recovered with direct water circulation from the thickening. Technical-economical feasibility considerations are here coupled to the Svappavaara iron ore operations by the Luossavaara-Kiirunavaara AB (LKAB) Company in northern Sweden. Local conditions here favour placement with an elevated thickener location close to the disposal area.The thickened tailings studied here have typically average particle sizes of 20 to 100 µm with maximum sizes of up to about 500 µm. The corresponding slurries cover an intermediate area between homogeneously and heterogeneously flowing mixtures. Various design features are often refereed to in rheological terms, i.e. homogeneous flow. Here, these terms are considered with some caution due to the notable amount of particles larger than about 40 µm.The objective is to form a background for feasibility considerations based on laboratory and pilot-scale experiments in pipelines and flumes together with viscometric measurements and depositional slope observations. Pipeline diameters covered the full-scale range, up to 0.15 m.It was found that a solids concentration by volume of about 48 % characterizes the pipeline pumping, here estimated to be on the conservative side with respect to thickened product quality requirement. The overall pipeline loop results were evaluated in terms of a representative pipe wall stress of about 200 Pa. Approximate values of the Bingham yield stress and plastic viscosity were estimated to 185 Pa and 0.03 Pas, respectively. Depositional slopes have been estimated to about 4 % for slurry properties that gives a conceptually even inclination with no segregation of particles and virtually no drainage of water.With an elevated thickener location close to the disposal area a new high pressure pumping system for about 10 MPa is avoided while the thickener underflow slurry is delivered with a centrifugal pump a short distance during the first years of operation. In order to meet the most effective long-term solution for pipeline distribution and placement, continued use of centrifugal pumps in series installations is considered as the discharge point advances during the 20-year life.The performance of a centrifugal pump is affected when handling highly concentrated slurries which shows up as reductions of the clear water head and efficiency curves. It was found that maximum reductions in head and efficiency were about 10 and 15 %, respectively, when operating at the design flow rate, QBEP, in the best efficiency region. As opposed to Newtonian fluids, a diverging tendency from the water head curve for decreasing flow rates has sometimes been reported below about 0.5QBEP for slurries that show a highly non-Newtonian behaviour. Various mechanisms related to the diverging tendency are discussed. The suction side pressure requirement is normally fulfilled with a large margin for a thickener underflow pump. It was observed in an installation how a standard pump operating at 0.5QBEP under a thickener showed no unstable head tendencies for a tailings slurry with an yield stress of nearly 200 Pa. However, pumps in series installation should be arranged with sufficient margins for an increased suction side pressure requirement.Keywords: Tailings slurry, highly concentrated, non-Newtonian behaviour, centrifugal pump performance, tailings depositional conditions.

In blast furnace ironmaking, efforts are made to decrease the coke consumption mainly by increasing the pulverized coal injection rate. This will cause changes in in-furnace reduction conditions, burden distribution and demands on raw material strength, etc. In order to maintain stable operation and minimize material losses through the off-gas, it is important to understand fines generation and behaviour in the blast furnace. The strength and reactivity of coke at high temperature, measured by the Coke Strength after Reaction (CSR) and Coke Reactivity Index (CRI), have been studied. Mechanisms of disintegration were evaluated using basket samples charged into the LKAB Experimental Blast Furnace (EBF) prior to quenching and dissection. Coke charged into basket samples was analysed with CSR/CRI tests and compared with treated coke from the blast furnace. Results from tumbling tests, chemical analyses of coarse and fine material, as well as Light Optical Microscope (LOM) studies of original and treated coke have been combined and evaluated. The results indicate a correlation between the ash composition and CSR values. Differences in the texture of the coke were determined with LOM, and a change in the coke texture during the CSR/CRI test conditions was found. The results suggest that the main reaction between coke and CO2 during the solution loss reaction took place in isotropic areas, which was especially pronounced in coke with a low CSR. Signs of degradation were apparent throughout the coke pieces that have undergone CSR/CRI testing, but were less observable in coke reacted in the blast furnace. The results indicate that the solution loss reaction was generally limited by the chemical reaction rate in the CSR/CRI test, while in the blast furnace the reaction is limited by the diffusion rate. Coke degradation is therefore mostly restricted to the coke surface in the blast furnace. At a later EBF campaign, off-gas dust and shaft fines were sampled during operation with different iron-bearing materials. EBF process data were used to evaluate the relationship between off-gas dust amounts and furnace conditions. Characterization was focused on fines from coke, iron-bearing materials and slag formers. The graphitization degree (Lc value) of coke taken out of the EBF shaft and coke in flue dust was determined in order to trace the fines generation position. The results showed that flue dust, mainly <0.5 mm, was mechanically formed and created in the same manner for all investigated samples. Carbon-containing particles dominated in the fractions >0.075 mm and consisted mainly of coke particles originating from the shaft. Solution loss in the shaft had a negligible effect on coke degradation and the coke particles which ended up in the flue dust were mainly derived from abrasion at low temperatures. Sludge consisted mainly of chemically formed spherical particles <1μm formed in the blast furnace high-temperature area and then precipitated from the ascending gas as the temperature decreased. The amount of alkali and SiO2 in sludge increased with higher pulverized coal injection rates and flame temperatures, which confirmed that submicron spherical particles in sludge originated from the high-temperature area around the raceway. Theoretical critical particle diameters of materials, which could be blown out with the off-gas, were estimated. Flow conditions in the top of the shaft as well as the properties of fine particles in terms of size and density are important when outflow of mechanical dust, such as flue dust, is concerned. Low off-gas temperatures, and thus lower off-gas velocities, are desirable for blast furnace operation with low amounts of flue dust.

After injection of calcium carbide and magnesium during desulphurisation of hot metal, the slag is normally solid and contains large amounts of iron. Besides the enclosed iron droplets in the slag, drawn-off hot metal during slag skimming also accounts for iron losses during desulphurisation of hot metal. Iron losses during hot metal desulphurisation using both calcium carbide (mono-injection), and calcium carbide and magnesium (co-injection), have been studied by large-scale investigations of slag from the slag pit as well as slag sampling during the desulphurisation process at SSAB EMEA in Luleå.An alkali-containing mineral, nepheline syenite, was mixed together with thecalcium carbide to facilitate slag formation during desulphurisation and to enhance the separation of iron from the slag. Even though the addition of nepheline syenite resulted in a more fine-grained slag, no reduction in the iron content in the slag before slag skimming was observed. The addition of 5 wt-% of nepheline syenite to the calcium carbide during mono-injection decreased the magnetic fraction of the slag from the slag pit from 2.5 wt-% to 1.9 wt-%. The decrease in the larger magnetic fractions combined with the improved iron yield may arise from a more effective slag skimming due to the change in slag consistency.During co-injection with magnesium and calcium carbide, the magnetic fraction of the slag from the slag pit decreased from 3.2 wt-% to 3.1 wt-% with the addition of 10 wt-% of nepheline syenite. Even though nepheline syenite has a positive effect on the slag skimming, due to a decrease in larger magnetic fractions, the total magnetic iron losses have not decreased significantly. A plausible explanation for the lack of improved iron yield during co-injection in the present study could be that the increased turbulence during injection of magnesium counteracts any positive effect from addition of nepheline syenite on the slag properties. Finally, no negative effect on the reagent efficiency was observed during the trials with addition of nepheline syenite.

Copper was one of the first metals ever extracted and used by mankind. It is used for its unique properties, like corrosion resistance, good workability, high thermal conductivity and attractive appearance. New mines are opened to maintain a supply of primary feedstock to copper smelters. These new deposits are in many instances found to have a more complex mineralogy with several minor elements. Besides treating primary material, copper smelters also show an increasing interest in treating secondary material, such as copper containing scrap from waste electric and electronic equipment, which also have a complex composition.Waste electric and electronic equipment are first disassembled and upgraded by mechanical processing, generating a product stream called e-scrap, that can be added directly to the smelting processes as cold material or melted in a separate furnace producing a metallic alloy (referred to as black copper) and a slag phase. The black copper can be refined in different ways, whereof one is by using it as a secondary feed material for input to Peirce-Smith converters. Consequently the load of minor elements to the converter can be expected to increase with an increased treatment of e-scrap.This increased complexity of the raw material can potentially lead to smelter plants having to deal with a feedstock containing several minor elements such as; antimony, bismuth, arsenic, gold, silver, etc. in levels that can influence the ability to, in a cost effective way, maintain the final grade of the copper cathode. Process simulations can be an important tool for understanding the impact of process parameters on the product quality and for the purpose of process optimisation. In the present work a dynamic, non-equilibrium model based on thermodynamics over the Peirce-Smith converter has been developed. The non-equilibrium conditions have been simulated by introducing individual but linked segments. The purpose of using segments was to consider different reaction zones which yield different conditions within the converter. The model was validated using plant data and showed good agreement for the major elements. The agreement between plant and calculated data for Pb, and Zn was not as good and more work is required regarding this aspect. The model was used to investigate the influence on the distribution of Bi and Sb during addition of black copper with or without slag. When black copper is added to a blow, the removal of Bi and Sb becomes lower compared to a blow without addition of black copper. Similar result is obtained during addition of black copper with slag. To maintain a total removal of Bi and Sb in similar levels as a blow without black copper, the black copper should be added as early as possible during the converting operation.

In this project the internal material transport processes of wet low-intensity magnetic separation (LIMS) is studied. The aim is to use results from experiments combined with published results to create a base for further research and development. During the initial work, presented here, the focus has been to develop an experimental platform and verify that ultrasound is a viable tool for flow measurement in suspensions with solids concentrations realistic for wet magnetic separation processes. The experiments have been carried out in a purpose built flow cell equipped with ultrasonic transducers and supported by a pump, mixer and necessary data accusation electronics. In the first conference paper, ultrasonic velocity profiling is used to estimate flow velocity profiles, and initial results are presented. When applied to flows of mineral suspensions of high solids concentration, similar to those in wet LIMS, the method is unique in combining:* Non-intrusive measurements.* Operation by a single transducer element.* Relatively good spatial resolution.* Operation in opaque suspensions.* Fast sampling rate.In a second conference paper the signal processing behind the measurement method is investigated more thoroughly and focus is on robust profile estimation. The connection between solids concentration, ultrasonic transducer centre frequency and penetration depth is also investigated. In a publication the measurements are put in relation to the application of interest. It is shown that the methods are generally applicable and can be used in situations where variations in suspension flow velocity through narrow geometries are of interest.The novelty shown is that it is possible to measure flow velocity profiles through suspensions carrying at least 10 vol% solids. For solids concentrations of 5 vol% or less it is possible to get a velocity profile through at least 50 mm of suspension. Results from measurements in suspensions of such high solids concentration combined with such long penetration depth have not been published before. The measurement method has gained attention from industry since it is generally applicable to narrow channel flows reachable from only one access point. / Wet LlMS - Measurements and models

The demands for more effective utilization of ore bodies and proper risk management in the mining industry have resulted in a new cross discipline called geometallurgy. Geometallurgy connects geological, mineral processing and subsequent downstream processing information together to provide a comprehensive model to be used in production planning and management. A geometallurgical program is the industrial application of geometallurgy. It provides a way to map the variation in the ore body, to handling the data and giving metallurgical forecast on spatial level.Three different approaches are used in geometallurgical programs. These include the traditional way, which uses chemical elements, the proxy method, which applies geometallurgical tests, and the mineralogical approach using mineralogy. The mineralogical approach provides the most comprehensive and versatile way to treat geometallurgical data. Therefore it was selected as a basis for this study. For the mineralogical method, quantitative mineralogical information is needed both on deposit and for the process. The geological model must describe the minerals present, give their chemical composition, report their mass proportions (modal composition) in the ore body and describe the texture. The process model must be capable of using mineralogical information provided by the geological model to forecast the metallurgical performance of different geological volumes (samples, ore blocks, geometallurgical domains or blends prepared for the plant) and periods (from minutes via hourly and daily scale to week, monthly and annual production). A literature survey showed that areas, where more development is needed for using the mineralogical approach, are: 1) quick and inexpensive techniques for reliable modal analysis of the ore samples; 2) textural classification of the ore capable to forecast the liberation distribution of the ore when crushed and ground; 3) unit operation models based on particle properties (at mineral liberation level) and 4) a system capable to handle all this information and transfer it to production model. This study focuses on solving the first and the third problem. A number of methods for obtaining mineral grades were evaluated with a focus on geometallurgical applicability, precision and trueness. The method survey included scanning electron microscopy based automated mineralogy, quantitative X-ray powder diffraction with Rietveld refinement, and element-to-mineral conversion. A new technique called combined method uses both quantitative X-ray diffraction with Rietveld refinement and the element-to-mineral conversion method. The method not only delivers the required turnover for geometallurgy, but also overcomes the shortcomings if X-ray powder diffraction or element-to-mineral conversion when used alone. Furthermore, various methods of obtaining modal mineralogy were compared and a model for evaluating precision and closeness of the methods was developed.Different levels of processing models can be classified in geometallurgy based on in which level the ore, i.e. the feed stream to the processing plant, is defined and what information subsequent streams carry. For mineral processing models the following five levels can be distinguished: particle size only level, elemental level, element by particle size level, mineral level, mineral by particle size level and mineral liberation (particle) level. The most comprehensive level of mineral processing models is the particle-based one which includes all necessary information for modeling unit operations. Within this study, as the first step, a unit operation model is built on particle level for wet low-intensity magnetic separation. The experimental data was gathered through a survey of the KA3 iron ore concentrator plant of Luossavaara-Kiirunavaara AB (LKAB) in Kiruna. The first wet magnetic separator of the process was used as the basis for the model development since the degree of liberation is important at this stage. Corresponding feed, concentrate and tailings streams were mass balanced on a mineral by size and liberation level. The mass balanced data showed that the behavior of individual particles in the magnetic separation is depending on their size and composition. The model, which has a size dependent by-pass parameter and a separation parameter dependent of the magnetic volume of the particle, is capable of forecasting the behavior of particles in magnetic separation. Modeling and simulation show the benefits that particle-based simulation provides compared to lower level process models which take into account only elemental or mineral grades.

Slag formation plays a decisive role in all steelmaking processes. In top-blowing Basic Oxygen Steelmaking (BOS), i.e. in the LD process, an emulsion consisting of liquid slag, dispersed metal droplets and solid particles will, together with process gases, form an expanding foam. Extensive research has defined the parameters that govern the foaming characteristics of BOS slag emulsions. It is a well known fact that certain process conditions will lead to an excessive foam growth, forcing the foam out through the vessel opening (mouth). This process event is commonly known as slopping. Slopping results in loss of valuable metal, equipment damage, lost production time and pollution. A literature survey covering the slopping phenomena has been carried out, as well as a deeper investigation into the causes behind slopping on the BOS vessels, type LD/LBE, at SSAB EMEA Metallurgy Luleå, equipped with an automatic system for slopping registration using image analysis. Good slag formation and foam-growth control in order to avoid slopping is primarily accomplished by taking preventive "static" measures. Improved slopping control has been achieved by developing a new oxygen lance control scheme, featuring adjustment of the distance between the lance tip and the metal bath according to scrap quality and ore additions. If "static" measures cannot be effectuated, in-blow control measures are needed. For such "dynamic" measures to be effective, it is necessary to have a system for slopping prediction. In the early-1980s a system for foam level and slopping control, based on BOS vessel vibration, was temporarily installed and tested on one of the vessels in Luleå. Based on the experiences from these tests it was decided to re-investigate the vessel vibration measurement technique. Trials on industrial scale BOS vessels of type LD/LBE have been carried out. FFT spectrum analysis has been applied in order to find the frequency band with best correlation to an estimated foam height. The results show that there is a correlation between vessel vibration and foam height which can be used for dynamic foam level and slopping control. The vessel vibration results have been tested against perhaps the most common implemented technique for dynamic foam height estimation and slopping control, the audiometric system. Parallel vibration and audio measurements have been carried out on a 130-tonne as well as on 300-tonne BOS vessels. The results show that during stable process conditions there is good agreement between the two methods with regard to foam height estimation and that combining the two methods will provide a powerful slopping prediction and control system.

The success of mineral flotation processes depends on the hydrophobization of the surface for the desired mineral particles whilst keeping, or making, all other minerals hydrophilic. This is achieved by adding several reagents to the flotation pulp to adsorb selectively at the mineral/water interface. The reagents (surface active agents) which selectively adsorbs on minerals to be floated are called collectors. It is realized that many of these commonly used reagents are highly toxic and often potential threats to the environment. Use of many of theseconventional chemicals will therefore be restricted soon and must eventually be stopped. An immediate effort is necessary to develop alternative eco-friendly reagents in order to continue to extract valuable minerals from ores. In addition, with the steady depletion of high grade, relatively easy to process ores, the mineral industry is confronted with a challenging task of finding more efficient techniques so as to exploit low grade, complex and disseminated typeof ore deposits and old tailing dumps. The development of new selective and environmentally acceptable substances containing almost tailor-made reagents is thus inevitable for sustainability. Several known chelating agents have been appropriately modified to make those behave as selective flotation collectors with some degree of success. The problem is that almost all of the chelating groups form complexes with almost all of the transition and many non-transition metals. As a consequence, absolute selectivity does not exist. Besides beingunsatisfactory from a scientific viewpoint, it assumes that the metal ion specificity observed for a functional group in bulk aqueous system would remain valid during surface chelation at the interface, while in actual practice, the specificity based on metal ion is neither valid nor useful where the cations participating in the complexation reactions are the same, for example separation among the calcium minerals.It is clear that a selective reagent should be based on the reagent interactions not merely with the metal ion on the surface, but with the whole surface. It is more appropriate to design reagents having functional groups so spaced that those are compatible with the relative positions of the metal ion sites available on the surface, that is, to design not just metalspecificbut structure-specific reagents. The understandings of molecular interactions involved in the recognition of surfaces by organic molecules in biomineralization process suggest the possibility of reagents specific to the crystal structure. These understandings have been successfully applied to the rational design and synthesis of molecules either for the control of crystal morphology or to inhibitcrystal growth processes through the recognition of specific crystal surfaces. The idea of molecules consisting of two groups having appropriate spacing between them to achieve structural compatibility during interaction with surface exhibit structure-specificity is of direct relevance to the reagents selectivity in flotation processes. The present investigation aims to develop and distinguish mineral specific reagents with two functional groups for use in flotation of calcium containing minerals. For this purpose, a series of dicarboxylate-based surfactants with varying spacing between the carboxylate groups (one, two or three methylene groups) were synthesized. As reference, a surfactant withthe same alkyl chain length but with only one carboxylate group in the polar part was synthesized. The adsorption behavior of these new reagents on pure apatite, calcite and fluorite mineral surfaces was studied using Hallimond tube flotation, ζ-potential and FTIR measurements. The relation between the adsorption behavior of a given surfactant on a specific mineral surface and its molecular structure over a range of concentration and pH values, as well as the region of maximum recovery were established. It was found that one of the reagents, with a specific distance between the carboxylate groups, was much moreselective for a particular mineral surface than the other homologues synthesized. This selective adsorption of a given surfactant to a particular mineral surface relative to other mineral surfaces as evidenced in flotation studies is substantiated by ζ-potential and infrared spectroscopy data. Our investigation revealed that it is possible to design and develop mineral specific reagents in flotation.

One of the measures of development and economy of a nation is its per capita consumption of steel, and the demand is fulfilled by iron ore. In the context of increasing environmental constraints and ores becoming leaner and leaner, recycling and utilization of ore fines becomes necessary. Pelletization, being one of the major agglomeration techniques is increasingly practiced across the world to produce agglomerates that can be fed into the metallurgical furnaces (say blast furnaces) for subsequent processing. In Europe, Sweden has the richest iron ore deposits, and mining and metals production contributes majorly to its net export. LKAB operates with magnetite ore bodies in the northern Sweden to produce magnetite pellets (26 MTPA) exports about 70 % of its product to the European Steel producers. Therefore, constant efforts are necessary to maintain and improve the quality of magnetite pellets, and it is necessary to enhance the understanding on the reaction kinetics and mechanisms responsible while producing pellets.Magnetite pellets prepared from the fines are indurated (heat hardened) to attain the quality standards in terms of strength and other metallurgical properties. The quality of magnetite pellet is primarily determined by the physico-chemical changes the pellet undergoes as it makes excursion through the gaseous and thermal environment in the induration furnace. Among these physico-chemical processes, the oxidation of magnetite phase and the sintering of oxidized magnetite (hematite) and magnetite (non-oxidized) phases are vital. Rates of these processes not only depend on the thermal and gaseous environment the pellet gets exposed in the induration reactor but are also interdependent on each other. Therefore, a doctorate project is undertaken to systematically understand these processes in isolation to the extent possible and quantify them seeking the physics. With this motivation, the current study is focused on investigating the sintering phenomena involved during induration of magnetite pellet.Experiments with single pellets were designed to understand and quantify the sintering behavior of oxidized magnetite (hematite) and magnetite independently. The kinetics of sintering can be described using power law (Ktn) and Arrhenius (ln⁡(TK^((1/n)) )=ln⁡K' - Q/RT ) equations. In the experiments, a single pellet was exposed to different thermal profiles in a controlled atmosphere, and their in-situ shrinkage was captured continuously by a novel technique using Optical Dilatometer. It was found that the sintering behavior captured by shrinkage of the pellet can be quantified using three isothermal kinetic parameters, namely – activation energy (Q), pre-exponential factor (K’) and time exponent (n). The values of activation energy and time exponent derived suggests that sintering of oxidized magnetite (hematite) is dominated by a single diffusion mechanism, whereas sintering of magnetite showed two distinct mechanisms; one operating at lower temperatures and the other at higher temperatures. The isothermal sintering kinetic equation is also extended to predict the non-isothermal sintering for both oxidized magnetite and magnetite, and validated with the laboratory experiments. This is further useful in predicting the sintering state of pellets during induration in the plant scale operations.