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Östermalm, Sweden

Johansson M.H.,AF Industry AB
Nordic Pulp and Paper Research Journal | Year: 2016

Filtration to separate dregs from the green liquor is efficient but expensive. A low-cost alternative could be hydrocyclones which also might be used to split the dregs in various fractions where non-process components are removed and the process related components are recycled to the process. A single cyclone was installed after the outlet pump of the homogenization tank at the causticizing plant at a kraft pulp mill. Trials were conducted using one cyclone with 55 g-force and one with 150 g-force. No flocculating agent was added to the hydrocylone. It was found that the particle size from the homogenization tank to the hydrocyclone was smaller than expected which reduced the separation effect. The shear forces on the dregs in a cyclone appeared to split them to smaller particles which reduced the separation when a cyclone with higher g-force was used. Particles containing Ca and Mg settled well and were likely present as dense crystals since a cyclone with high gforce improves the separation slightly. The separation effect of dregs from green liquor in hydrocyclones was low compared to modern equipment. Source

Wilde M.W.,AF Industry AB | Johansson F.,KTH Royal Institute of Technology
Journal of Geotechnical and Geoenvironmental Engineering | Year: 2013

Structural reliability analysis is not widely used for the design and assessment of concrete dams. In this paper, the system reliability of a spillway structure consisting of two monoliths is calculated. Limit state functions are defined from the failure modes sliding in the concrete rock contact, sliding in the rock mass, and adjusted overturning. Random variables in the limit state functions are defined by stochastic distributions. These are defined based on site investigations and laboratory tests from samples taken at the dam. Simulations and information from the literature are used for the remaining variables. The safety index is calculated by the first-order reliability method for each failure mode and monolith, and the system reliability is approximated by direct integration of the bivariate normal distribution. The output is the safety index including associated sensitivity values at the single failure mode, monolith, and system levels. The results show that the system safety is governed by a persistent rock joint beneath one monolith. A system reliability analysis is found to be a useful tool in the dam risk management process as it can be used to calculate the probability of failure and to identify important failure modes and variables. © 2013 American Society of Civil Engineers. Source

Abbasi S.,KTH Royal Institute of Technology | Abbasi S.,Golpayegan University of Technology | Teimourimanesh S.,Chalmers Applied Mechanics CHARMEC | Vernersson T.,Chalmers Applied Mechanics CHARMEC | And 4 more authors.
Wear | Year: 2014

Braking events in railway traffic often induce high frictional heating and thermoelastic instability (TEI) at the interfacing surfaces. In the present paper, two approaches are adopted to analyse the thermomechanical interaction in a pin-on-disc experimental study of railway braking materials. In a first part, the thermal problem is studied to find the heat partitioning between pin and disc motivated by the fact that wear mechanisms can be explained with a better understanding of the prevailing thermal conditions. The numerical model is calibrated using the experimental results. In a second part, the frictionally induced thermoelastic instabilities at the pin-disc contact are studied using a numerical method and comparing them with the phenomena observed in the experiments. The effects of temperature on material properties and on material wear are considered. It is found from the thermal analysis that the pin temperature and the heat flux to the pin increase with increasing disc temperatures up to a transition stage. This agrees with the behaviour found in the experiments. Furthermore, the thermoelastic analysis displays calculated pressure and the temperature distributions at the contact interface that are in agreement with the hot spot behaviour observed in the experiments. © 2013 Elsevier B.V. Source

Bjurstrom H.,AF Industry AB | Lind B.B.,Swedish Geotechnical Institute | Lagerkvist A.,Lulea University of Technology
Fuel | Year: 2014

Unburned carbon (UC) in 21 combustion residues from solid biofuels has been examined using several methods of analysis (including LOI and TOC) as well as micro-Raman spectroscopy. The concentration of unburned carbon in the residues varied over an order of magnitude and in several samples accounted for about 10% of the ash mass. It was observed that TOC had a poor correlation to organic carbon, especially for fly ashes. LOI at all tested temperatures showed a better correlation than TOC to the organic carbon content, whereas the TOC is better correlated to elemental carbon. LOI550 gave a larger variation and a less complete mobilisation of unburned carbon than LOI at 750 or 975 C did, but at the highest temperature metal oxidation was notably affecting the mass balance to the extent that some samples gained mass. For this reason, and of the temperatures tested, LOI750 seem to be the most stable indicator for organic remains in the incineration residuals. Most of the unburned carbon is elemental, and only slowly degradable, so the potential emissions of organic compounds from ashes should not be assessed by using a TOC test. The structure of the detected elemental carbon in UC is similar to that of activated carbon, which indicates a potentially large specific surface. This should be borne in mind when assessing the environmental impact of using ash for different purposes, including use as a construction material. Field studies are needed to verify the actual impact as it may depend on environmental conditions. © 2013 Elsevier Ltd. All rights reserved. Source

Vernersson T.,Chalmers University of Technology | Vernersson T.,AF Industry AB | Lunden R.,Chalmers University of Technology
Wear | Year: 2014

Wear of brake blocks at tread braking of railway wheels is one of the key factors that control the time period between scheduled train maintenance and hence has a substantial impact on the life cycle cost of the vehicle. Wear simulations using two different numerical models, one thermal model and one thermoelastic model, are presented implementing wear rates for some brake block materials exploiting results from previously performed temperature-controlled pin-on-disc tests. It is found that the thermal model and the thermoelastic model give the same wear for cases when thermoelastic instability effects are small. However, for cases when the thermoelastic effects increase the local contact pressures and surface temperatures, large differences are found. © 2013 Elsevier B.V. Source

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