Pickling sludge generated in the stainless steel industries contains large amounts of calcium fluoride and water and relatively small amounts of metals. Therefore, such sludge is difficult to be directly recycled back to the EAF process and would be harmful to the environment if deposited as landfill for a long term. The main objective of the present thesis work is to find out proper ways to treat the pickling sludge and to recover useful metals from it. For this, characterisations, solid-state reduction and smelting reduction tests on the pickling sludge were carried out in the laboratory. Likewise, comparison studies on solid-state reduction of pure metal oxides with graphite and on pickling sludge with p-coke were conducted using TGA. In addition, the off-gas generated by smelting reduction of pickling sludge was monitored by measurements with a mass spectrometer. Through the present thesis study it can be concluded that it is possible to treat and recycle pickling sludge by using both solid-state reduction and smelting reduction methods. In order to completely separate the reduced metals from the sludge, the smelting reduction method would be preferred. / Godkänd; 2001; 20070313 (ysko)

This work is based on experiences from industrial blast furnaces. Process irregularities when testing self-fluxed pellets Process disturbances when charging increased proportions of coarse pellets Laboratory tests to evaluate the effect of basic fluxes on the slag formation in the bosh and in the raceway have been carried out. Pilot scale tests have been performed to verify the effect of coarse pellets. The effect of reduction degree and the reduction behaviour on the slag formation and blast furnace performance have been evaluated It was found that decreased degree of reduction of pellets or lowly reduced core of coarse pellets decrease the melting temperature and increase the softening and melting temperature interval. Basic fluxes have a negative effect on the melting properties of the self-fluxed pellets and a positive effect on the melting properties of the olivine pellets. Basic fluxes have a positive effect on the melting properties of tuyere slags. / Godkänd; 2001; 20070313 (ysko)

No description available.

Godkänd; 1997; 20070418 (ysko)

To meet the increasing demand for raw materials, higher throughput of mineral separation through froth flotation is becoming important. This higher throughput can be achieved by increasing the size of flotation equipment termed scaling up. Flotation performance is greatly affected by the size of flotation machines and remains an important research area to correlate flotation behavior between small and larger flotation machines. The Outotec GTK LabCell®, a mechanical flotation machine, has been used as a benchmark for many industrial pre-feasibility studies around the world for the past decade. This study deals with the scale-up assessment in terms of flotation rate constant between 2 L and 7.5 L flotation cells of the Outotec GTK LabCell®, machine. The design of these lab scale flotation machines is comparable to other Outotec industrial scale flotation equipment considering rotor and impeller design, and the main difference is in scale. The influence of the hydrodynamic parameters on the flotation performance in both the cells was investigated by varying the impeller tip speed and superficial gas velocity. Particle size distribution analysis indicated concentrate product was finer at smaller cell size at all combinations of impeller tip speed and superficial gas velocity. The results showed for both cells, mass and water recovery increased with an increase in the impeller tip speed and superficial gas velocity until a certain value, after which they decreased. Maximum mass and water recovery were achieved using an impeller tip speed of 3.1 m/s and superficial gas velocity of 0.21 cm/s. Flotation kinetic analysis indicated scaling up of flotation cells was possible at different impeller tip speed by keeping the superficial gas velocity at 0.21 cm/s.

This thesis describes optimization of die temperature in high pressure die-casting (HPDC) of A380 alloy by experimental observation and numerical simulation with the use of statistical tools. The goal of this research is to determine the optimum die temperature to minimize incidence of these defects and thus maximize production of parts without defects.   In HPDC, molten metal is injected into the die at high speed (40-60 m/s for aluminum alloys). Die temperature plays an important role on the rate of rejected parts. Therefore, flow patterns of molten metal in HPDC of an automotive component with very complex geometry (the ladder frame from the EF7 motor) were examined to determine the optimal die temperature. Defects in the production process fall into three categories, including surface, internal and dimensional defects. Samples produced in the experiments were classified according to any present defects. Another important parameter that influences casting defects is the cooling rate. Die temperatures were measured at the initial step and final filling positions. Experiments were performed with die temperatures ranging from 150 °C to 250 °C. The results show that the melt temperature difference in the die between the initial step and the final filling position was between 20 and 25 °C. Statistical tools such as regressions, relationships, max, min, correlations, ANOVA, T-test, Principal Component Analysis (PCA) and descriptive statistics were used to facilitate interpretation of data from the die-cast experiments. Perform some case studies in order to study the process behavior, take a better knowledge of effective parameters, and measure the required parameters. The collected data are utilized to: Set the model Validate/ verify the model ProCast software was used to simulate the fluid flow and solidification step, and the results were verified by experimental measurements. The optimal die temperature for this alloy was found to be above 200 oC. Statistical analysis of the experimental results found that defects were minimized and confirmed parts were maximized in HPDC of the ladder frame within a die temperature range of 210° C to 215° C.

Today, the main raw material for vanadium production is vanadium containing steelmaking slags. The yield of the vanadium extraction process is affected by the composition of the slag, which in turn determines the phases present, the fractions of the phases and the distribution of the elements between the phases. The aim of this thesis was to experimentally investigate the effect of Al2O3, CaO and SiO2 on the phase relations in vanadium containing slags at 1673 K. Synthetic slags, in which the contents of Al2O3, CaO and SiO2 were varied individually, were equilibrated at 1673 K in a vertical resistance furnace. Closed molybdenum crucibles were used to set the oxygen potential of the individual samples.  The phases present, the phase compositions and the phase fractions of the samples were studied using SEM-EDS and LOM combined with an image analysis software. The results indicate that the samples consisted of a mixture of a vanadium and iron rich spinel phase and an iron and silicon rich liquid phase at 1673 K. Practically all the vanadium was concentrated into the spinel phase while no free silica or solid phases into which both calcium and vanadium concentrate to a significant extent were observed. The effect of Al2O3 on the phase compositions and the phase fractions was seen to be limited in the range studied. CaO primarily affected the composition of the liquid phases, while the effect on the phase fractions was small. SiO2 affected both the composition and fraction of the phases. The main effect was a decreased fraction of spinel phase, with an increasing vanadium content in the spinel phase as consequence.

Electric arc furnace (EAF) slags are basic characteristic slags that include approximately 40 % iron oxide compounds. Iron oxide can be recycled and re-used in the process to decrease amount of waste product besides reducing loss of raw materials. According to result of survey performed by The European Association Representing Metallurgical Slag Producers and Processors (EUROSLAG) in 2010, 8.5 million tons of EAF slag is produced in Europe. High percentage of EAF slag is re-used in road construction as aggregate. However it can be re-cycled in the internal use for metallurgical processes as well. In order to re-use EAF slag in the process as a raw material, direct reduction is a new approach. Direct reduction is reduction of iron containing raw materials with gas or solid reductants without melting of charge. In this study, reduction conditions of 39 % Fe2O3 containing EAF slag in tube furnace was examined. As the reducing agent, metallurgical coke was used. EAF slag was milled and pelletized in raw material preparation step. Pellets were charged to fixed bed type tube furnace in a graphite boat at 1050, 1100 and 1150°C respectively with 150 and 200% of stoichiometrically required amount of metallurgical coke. 5, 10, 15, 30, 60, 90 and 120 minutes process durations were performed. Direct reduced pellets were milled to be characterized by using X-Ray Diffraction (XRD) and chemical analysis methods. Results indicate that increased temperature, process duration and stoichiometry have a positive impact on direct reduction of EAF slag in terms of iron metallization. 90 % metallization degree has been achieved as the result of the study with the process conditions of 200 % stoichiometry and 90 minutes process duration at 1150 °C.

Trough the following pages a comprehensive study of open structures will be shown, including mono-vacancy calculations and open surfaces. These are electronic structure calculations using density functional theory within the exact muffin tin method. First we investigate the accuracy of five common density functional approximations for the theoretical description of the formation energy of mono-vacancies in three closepacked metals. Besides the local density approximation (LDA), we consider two generalized gradient approximation developed by Perdew and co-workers (PBE and PBEsol) and two gradient-level functionals obtained within the subsystem functional approach (AM05 and LAG). As test cases, we select aluminium, nickel and copper, all of them adopting the face centered cubic crystallographic structure. This investigation is followed by a performance comparison of the three common gradientlevel exchange-correlation functionals for metallic bulk, surface and vacancy systems. We find that approximations which by construction give similar results for the jellium surface, show large deviations for realistic systems. The particular charge density and density gradient dependence of the exchange-correlation energy densities is shown to be the reason behind the obtained differences. Our findings confirm that both the global (total energy) and the local (energy density) behavior of the exchange-correlation functional should be monitored for a consistent functional design. Last we show the vacancy formation energies of paramagnetic Fe-Cr-Ni alloys as a function of chemical composition. The theoretical predictions obtained for homogeneous chemistry and relaxed nearest-neighbors are in line with the experimental observation. In particular, Ni is found to decrease and Cr increase the vacancy formation energy of the ternary system. / QC 20110929

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