Sustainable Metal Production: Use of Biocarbon and the Concern of Dusting

The silicon and ferroalloy industries in Norway have traditionally relied on fossil carbon products as reductants for their respective process. Efforts to reduce fossil CO2 emissions by introducing biocarbon have already begun, and targets of 25–40% biocarbon use by 2030 have been set by various producers in Norway. An understanding of the effects of the physical properties of the carbon on the process must be obtained so that the transition can take place with minimal process interruptions. It is well documented that charcoal is more friable than traditional fossil carbons, particularly during transportation and handling. Major issues related to the fines generation are concerning material loss, effect of furnace performance, personal health and safety concerns by inhalation of particles, and possibility of dust explosions. The strength of unreacted material, the cold strength, can give good information about the dusting potential of a material; however, many methods exist for these evaluations. In this work, an overview of the raised issues concerning dusting, and methods to evaluate cold strength in relation to dusting, is included, as is some relevant comparisons between charcoals and traditional carbon sources with respect to tumbling strength.acceptedVersio

SIGNAL SENSING BY THE ARCHITECTURE OF EMBEDDED I/O PAD CIRCUITS

Despite the rigorous emission control measures in the ferroalloy industry, there are still emissions of dust during the production of various alloys. Dust particles were collected from laboratory scale processes where oxide particulate matter was formed from liquid silicon (metallurgical grade). The dust was produced in a dry air atmosphere to mimic industrial conditions. To investigate possible effects of ultrafine dust on the central nervous system, a human astrocytic cell line was employed to investigate inflammatory effects of particles as astrocytes play a number of active and neuron supporting roles in the brain. Toxicity on the astrocytes by amorphous silica generated in laboratory scale was compared to crystalline macro-sized silica using several doses to determine toxicological dose response curves. The cell viability experiments indicated that low particle doses of amorphous silica induced a small nonsignificant reduction in cell viability compared to crystalline silica which led to increased levels of toxicity. The gene expression of amyloid precursor protein (APP), a biomarker of neurodegenerative disease, was affected by particle exposure. Furthermore, particle exposure, in a dose-and time-dependent manner, affected the ability of the cells to communicate through gap junction channels. In conclusion, in vitro studies using low doses of particles are important to understand mechanisms of toxicity of occupational exposure to silica particles. However, these studies cannot be extrapolated to real exposure scenarios at work place, therefore, controlling and keeping the particle exposure levels low at the work place, would prevent potential negative health effects

Real-Time Measurements and Characterization of Airborne Particulate matter from a Primary Silicon Carbide Productin Plant

Airborne particulate matter in the silicon carbide (SiC) industry is a known health hazard. The aims of this study were to elucidate whether the particulate matter generated inside the Acheson furnace during active operation is representative of the overall particulate matter in the furnace hall, and whether the Acheson furnaces are the main sources of ultrafine particles (UFP) in primary SiC production. The number concentration of ultrafine particles was evaluated using an Electrical Low Pressure Impactor (ELPITM, Dekati Ltd., Tampere, Finland), a Fast Mobility Particle Sizer (FMPSTM, TSI, Shoreview, MN, USA) and a Condensation Particle Counter (CPC, TSI, Shoreview, MN, USA). The results are discussed in terms of particle number concentration, particle size distribution and are also characterized by means of electron microscopy (TEM/SEM). Two locations were investigated; the industrial Acheson process furnace hall and a pilot furnace hall; both of which represent an active operating furnace. The geometric mean of the particle number concentration in the Acheson process furnace hall was 7.7 × 104 particles/cm3 for the UFP fraction and 1.0 × 105 particles/cm3 for the submicrometre fraction. Particulate matter collected at the two sites was analysed by electron microscopy. The PM from the Acheson process furnace hall is dominated by carbonaceous particles while the samples collected near the pilot furnace are primarily rich in siliconpublishedVersio

Optimering av glödgningsparametrar för kromstål

Validerat; 20101217 (root

Ti3SiC2 synthesis from TiC and Si powders

The aim of this work was to produce Ti3SiC2 from TiC and Si powders and to investigate process parameters with respect to optimised Ti3SiC2 yield. The reaction pathway of Ti3SiC2 formation and the thermochemical degradation reactions were examined. Various material characterization and analysis methods have been applied, including x-ray diffractometry, dilatometry, calorimetry, scanning electron microscopy, energy dispersive spectroscopy and mass spectroscopy. Through the work performed it has been found that Ti3SiC2 may be produced in relatively large quantities (96.8 vol%) from TiC and Si powders. Short holding times (0-3 hours) and relatively high temperatures (1350-1400°C) produce the largest amounts of Ti3SiC2 when pressureless sintering is applied.The effect of varying the silicon contents on yield was investigated; excess silicon may be beneficial for the Ti3SiC2 yield if combined with appropriate heat treatments. TiSi2 is found to play a key role in the formation of Ti3SiC2 from TiC and Si powders. TiSi2 is present in samples heat treated at relatively low temperatures with short holding times. It is consumed in the formation of Ti3SiC2. Decomposition of Ti3SiC2 may occur at relatively low temperatures (1300°C) when there is oxygen present in the furnace atmosphere. The effect becomes more significant with long holding times (&gt; 5 hours) and is also significant at very high temperatures (1500°C). When the partial pressure of oxygen is limited, no decomposition has been observed below 1450°C. At these temperatures, the presence of carbon in the furnace atmosphere induced no detrimental effect on the thermochemical stability of Ti3SiC2.Godkänd; 2010; 20100310 (idaker); DISPUTATION Ämnesområde: Konstruktionsmaterial/Engineering Materials Opponent: Professor Marc Anglada, Department of Materials Science and Engineering, ETSEIB, Barcelona, Spain Ordförande: Doktor Marta-Lena Antti, Luleå tekniska universitet Tid: Torsdag den 10 juni 2010, kl 09.00 Plats: E243, Luleå tekniska universitet</p

Ti3SiC2 synthesis by powder metallurgical methods

The MAX phases constitute a group of ternary ceramics which has received intense attention over the last decade due to their unique combination of properties. The Ti3SiC2 is the most well studied MAX phase to date and it has turned out to be a promising candidate for high temperature applications. It is oxidation resistant, refractory and not susceptible to thermal shock, while at the same time it can be machined with conventional tools which is of great technological importance. Most attempts to synthesize bulk Ti3SiC2 have involved pure titanium in the starting powder mixtures, but Ti powder is oxidising and requires an inert atmosphere throughout the synthesis process which makes the procedures unsuitable for large scale production. The aim of the first part of this study was to delineate the influence of sintering time and temperature on the formation of Ti3SiC2 from a starting powder which does not contain pure titanium. Titanium silicon carbide MAX phase was synthesised from ball milled TiC/Si powders, sintered under vacuum for different times and temperatures. After heat treatment the samples were evaluated using scanning electron microscopy (SEM) and x-ray diffraction (XRD). This study showed that TiC was always present in the final products whereas TiSi2 was an intermediate phase to the Ti3SiC2 formation. The highest amount of Ti3SiC2 was achieved for short holding times of 2-4 hours, at high temperatures, 1350-1400¢ªC. More elevated temperatures or extended times resulted in silicon loss and decomposition of Ti3SiC2. In the second part of this study the sintering reactions and the mechanisms of formation of Ti3SiC2 were investigated by x-ray diffractometry, thermodilatometry, thermogravimetry, differential scanning calorimetry and mass spectrometry. TiC/Si powders of the different ratios; 3:2 and 3:2.2, were heated to different temperatures under flowing argon gas in a dilatometer and examined by XRD. The TiC/Si powder samples of the ratio 3:2 were further investigated by the other thermal analysis methods. The results confirmed the presence of the intermediate phase TiSi2. From 1500¢ªC silicon evaporation and MAX phase decomposition were observed, and the results show that the MAX phase formation may be concurrent with the melting of silicon. TiC was always present in the final products, either as a reactant or as a decomposition product. The extra silicon of the 3:2.2 TiC/Si powder significantly increased the Ti3SiC2 conversion and no intermediate phases were observed for this powder mixture. The Si of these samples did not melt or evaporate, and only minor decomposition was observed even at 1700¢ªC. These results indicate that the silicon content of the initial powder mixture is decisive to the reaction mechanisms of the sintering process.Godkänd; 2007; 20070523 (ysko)</p

Energy Distribution in HC FeMn and SiMn - Energy vs Exergy Analyses

The metal producing industry is a high consumer of energy and large amounts of excess heat are produced. Increasing the energy efficiency would be beneficial, both in terms of the environment and also from an economical point of view. In order to do this, it is crucial to know how the energy is distributed throughout process operation. Energy (enthalpy) and exergy analyses were used to discuss the production of high-carbon ferromanganese (HC FeMn) and silicomanganese (SiMn). The two different analysis methods were compared to decide if exergy analyses provide a better understanding of the distribution and recovery potentials for the production process of HC FeMn and SiMn. It was found that the distribution of energy and exergy between the different material streams is highly similar and key potential recovery sites are the same regardless of the analysis method utilized. The additional information provided by the exergy analysis compared to enthalpy is the reduction in energy quality (exergy destruction) due to irreversible processes within the furnace. These values were found to be 13.7% for HC FeMn and 10.8% for SiMn.publishedVersio