Due to increasing price and economic pressures, there is a need to minimise coke consumption. The lesser amount of coke used has indirectly set higher standards for coke quality and led to a wish for even more knowledge about its function in the blast furnace. Over the last 20 years, coke quality has been strongly dictated by the so- called CSR value because it was believed that a higher CSR leads to improvement in productivity and more stable operation. Due to lack of suitable coals, often cokes are made from coals with relatively inferior coals leading to coke with lower values of the so-called CRI indicia. Because of this, there was an indirect focus on cokes with lower CRI values. Therefore, this thesis will address some of the important issues of coke strength and focus on changes occurring with coke when it passes through a blast furnace. The main aim of this study is to understand the degradation mechanisms and reactivity changes of coke in order to investigate the factors that affect coke quality. Cokes excavated from LKAB's Experimental Blast Furnace (EBF) are used as a basis for the research. Two campaigns with similar coke (low CRI/high CSR) but different blast furnace injection material have been studied. The coke is supplied from SSAB Tunnplåt Luleå AB. Physical and chemical properties of cokes samples from the EBF were measured. Evolution of coke properties particularly carbon structure and alkali uptake were related to CO2 reactivity as well as coke behaviour (e.g. CSR/abrasion). In addition to this, a trial with very high CRI coke was studied. On the basis of this study, following conclusions were made. The order of carbon structure and concentration of alkali species were increased and these were the most notable changes in the coke properties as it passed through shaft to the cohesive zone of the EBF. The degree of graphitisation was increased while amorphous carbon content was decreased in the hotter zones of the EBF. A linear correlation between the height of the carbon crystallite (Lc) values and the coke bed temperature was established to demonstrate the strong effect of temperature on the carbon crystallite value (Lc) of coke in the EBF. The alkali concentration of coke increased with increasing temperature of the coke bed such that most of the alkali content was evenly distributed in the bulk of the coke rather than in the periphery of the coke matrix. The CO2 reactivity of coke was found to increase during progressive movement of the coke from shaft to cohesive zone of the EBF, and was related to the catalytic effect of increased alkali concentration in coke. The deterioration of coke quality in the EBF, particularly coke strength (CSR) and abrasion propensity (I drum test), was related to coke graphitisation, alkalization and reactivity to demonstrate the strong effect of the coke graphitisation on the propensity of coke degradation. Differential Thermal Analysis indicated that reactions with CO2 are enhanced as coke descends through the EBF.In addition, a trial period with poor coke quality was studied by extensive sampling. The results from this study gave the following additional conclusions: Comparison between high and poor quality coke indicate structure to be connected with alkali uptake, reaction with CO2 and degradation. Isotropic coke carbon components are more resistant than anisotropic components when passing through the EBF. Both cokes develop a more ordered structure as they descend through the EBF. / Godkänd; 2005; 20070102 (haneit)

In Sweden, concrete has traditionally been manufactured with glaciofluvial deposits as fine aggregate. In 2004 the production of this aggregate was approximately 21 million tons. Due to environmental reasons and local shortage of this natural resource there exists a goal to reduce the production to 12 million tons in year 2010. In order to compensate for the reduced production an alternative material which can be used as replacement has to be found. Aggregate from crushed bedrock is an alternative which is locally available and found in sufficient amounts. However, the characteristics of this type of aggregate generally differ from the ones of glaciofluvial fine aggregate and are known to generate concrete with higher water demand and lower workability. In order to facilitate a changeover to crushed fine aggregate, it is important to achieve a better understanding of the influence of crushed fine aggregate characteristics on the workability of concrete. The properties of the mortar phase of concrete influence the workability of concrete. The study of the mortar phase of concrete with crushed fine aggregate can therefore be valuable in predicting the influence of the fine aggregate characteristics on concrete workability. The aim of this licentiate thesis was to clarify the influence of the characteristics of crushed fine aggregate (0-2 mm) on the rheological properties of mortars. This included studies of the effect of aggregate shape, quality and amount of fines, washed fine aggregate and superplasticizer addition. The experimental work was divided into three different parts, i.e., zeta potential study, micromortar and mortar rheology. In the zeta potential part, the interaction between different fines and a common type of superplasticizer was studied. The results indicate that the superplasticizer is preferentially adsorbed on biotite rich fines. In the micromortar part, the fines fraction of different fine aggregates was studied separately in order to evaluate the influence of their particle shape, specific surface area and mineral composition. The results from this part showed that the quality of the fines has a large influence on the rheological properties of micromortars. Furthermore, the yield stress and plastic viscosity were shown to increase with the specific surface area of the fines. The results also suggest that the shape of the fines mainly influences the plastic viscosity, i.e., the viscosity of the micromortars with elongated fines was higher than the corresponding micromortars with cubic shaped fines. In the mortar part, different fine aggregates were studied both with their original and with standardized grading curves. The evaluation was done both with and without addition of superplasticizer and at different paste volumes. The effect of washed fine aggregate was also evaluated. The results show that the shape of the fine aggregate particles mainly influences the plastic viscosity of the mortar. The fines content was shown to increase the yield stress and, thus, the water demand of the mortar. Furthermore, the results showed that washing and the use of superplasticizer are two potential ways to reduce the water demand of mortars with fine aggregates from crushed rock. Finally, the results from this work suggests that the higher yield stress and plastic viscosity often shown by mortars containing crushed fine aggregate can be related to two main characteristics of the aggregate. The high yield stress is believed to mainly originate from the high amounts of fines often seen in crushed fine aggregates, while the higher plastic viscosity can be related to the more elongated particle shape of the fine aggregate. / Godkänd; 2006; 20070109 (haneit)

Modern process logging systems for electric arc furnaces have the capability of storing large quantities of data, both in terms of variables and number of heats. The objective of this research is to evaluate how this data can be used for improvement of operating practices and optimisation of energy and scrap utilisation. In previous research projects, a process visualisation and monitoring system was developed and installed on four meltshops in Scandinavia. The system consists of a real-time database, a historical database, operator screens and a report generation system. By showing relevant information to the operators during the melting operation and generating reports based on the performance of the different operating teams, reduction of energy consumption, increase of productivity and reduced production costs could be achieved. Further analysis of data from the historical database led to the development of process optimisation tools for post combustion, hot heel practice, slag foaming and charging of scrap baskets. With the use of these tools, energy consumption and power-on time could be decreased further. However, steel scrap is the most important raw-material in electric steelmaking, contributing between 60% and 80% of the total production costs. Today the degree of which the scrap mix can be optimised, and also the degree of which the melting operation can be controlled and automated, is limited by the knowledge of the properties of the scrap and other raw- materials in the charge mix. In this thesis, multivariate regression methods have been used to develop prediction models for final chemical analysis of the steel, total electric energy consumption and metallic yield. The predictions are based on composition of the raw-material mix, total consumption of injected materials (like oxygen, oil, coal, slagformers) and initial condition of the furnace (hot heel composition). A prediction model for total energy consumption for melting of the first scrap basket based on continuous measurements of electrical parameters and wall panel temperatures was also developed. The models have been used to estimate some scrap properties (chemical composition, specific electrical energy consumption, yield coefficients), evaluate the efficiency of post-combustion and to estimate the optimal time to charge the second scrap basket. The results show that it is possible to provide estimates of the levels of tramp elements (Cu, Sn, As, etc.) and alloy elements (Cr, Ni, Mo, etc.) in commonly used scrap grades based on evaluation of commonly logged process data. To ensure that the estimates remain consistent with scrap quality, it is suggested that they be updated on a regular basis. It is also discussed how the estimates of scrap properties can be used for improved process control and monitoring of scrap quality. / <p>Godkänd; 2005; 20070102 (haneit)</p>

Valmet AB has ha foundry located I Karlstad, Sweden. The foundry has specialized in large components in ductile and gray iron. This report is a part of an evaluation of a new alloy that Valmet has produced. The alloy is called S550 where 550 is the expected tensile strength in a cast on sample. S550 is a ferritic ductile alloy with 4,15-4,25% silicone. In this experiment the alloy is casted in very large sections to better match the intended final product. The purpose of the report is to promote a better understanding of how silicon works in large castings. Ultimate tensile strength, yield strength and elongation will be measured. The microstructure will be mapped and described. This as a step to ensure that the material is ready to use to produce castings in large dimensions. In the experiment, the microstructure is examined from 3 charges. Mechanical properties are collected from the 3 charges by widened specimens from 3 details of 2785 kg/piece and 4 drilled samples from 4 details about 600 kg/piece. The samples are processed to test bars according to standard SS-EN1563: 2012. Thereafter the rods are dragged in a tensile testing machine to collect data. The microstructure is mapped through light optic microscopy. The samples where machined according to SS-EN1563:2012. Tensile testing machine was used to record the mechanical values. Microstructure was mapped using a light-optic microscope. The material achieved a tensile strength of 544 MPa on average which is below the expected value. The yield strength was 436 MPa in average. The material shows low dispersion, mainly in fracture limit and yield limit. The elongation in average 12.8% varied in the different geometries but with lower variations within the same geometry. The alloy got better mechanical values on Detail B that had a shorter cooling time. In Detail A, micro porosity and slag were found which adversely affected their mechanical properties. The ground mass is considered as ferritic. The graphite nodes had a size of 82μm and a nodule density of 75 nodules / mm2. Most nodules had graphite form VI, small amount of graphite V and III have been found. No degenerated graphite forms as chunky or exploded graphite has been found.

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.