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- Broström, Markus, 1977-, et al.
(författare)
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Sulfation of corrosive alkali chlorides by ammonium sulfate in a biomass fired CFB boiler
- 2007
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Ingår i: Fuel processing technology. - Amsterdam : Elsevier Bv. - 0378-3820 .- 1873-7188. ; 88:11-12, s. 1171-1177
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Tidskriftsartikel (refereegranskat)abstract
- Biomass and waste derived fuels contain relatively high amounts of alkali and chlorine, but contain very little sulfur. Combustion of such fuels can result in increased deposit formation and superheater corrosion. These problems can be reduced by using a sulfur containing additive, such as ammonium sulfate, which reacts with the alkali chlorides and forms less corrosive sulfates. Ammonium sulfate injection together with a so-called in situ alkali chloride monitor (IACM) is patented and known as "ChlorOut". IACM measures the concentrations of alkali chlorides (mainly KCl in biomass combustion) at superheater temperatures. Tests with and without spraying ammonium sulfate into the flue gases have been performed in a 96MW(th)/25MW(e) circulating fluidized bed (CFB) boiler. The boiler was fired mainly with bark and a chlorine containing waste. KCl concentration was reduced from more than 15 ppm to approximately 2 ppm. during injection of ammonium sulfate. Corrosion probe measurements indicated that both deposit formation and material loss due to corrosion were decreased using the additive. Analysis of the deposits showed significantly higher concentration of sulfur and almost no chlorine in the case with ammonium sulfate. Results from impactor measurements supported that KCl was sulfated to potassium sulfate by the additive. (C) 2007 Elsevier B.V. All rights reserved.
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| 5. |
- Eriksson, Maria, 1969-, et al.
(författare)
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Violence capital : On the framing and construction of a policy problem
- 2022
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Ingår i: Violence: An International Journal. - : Sage Publications. - 2633-0024 .- 2633-0032. ; 3:2, s. 179-198
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Tidskriftsartikel (refereegranskat)abstract
- Criminal law is directed at distinct individual actions and is therefore less suited for combating patterned, repeated, and collective actions. In an attempt to overcome such problems, the concept of violence capital was introduced in an amendment to the Swedish Criminal Code in 2016. The current study aims at initiating an academic debate and theory development regarding violence capital, through critical engagement with the empirical case of how the concept of violence capital was constructed when it was introduced in Swedish criminal policy and criminal law. The legal reform seems to mainly rest on the work of a specific group within the Swedish Council of Crime Prevention. Furthermore, violence capital comes across as a somewhat “slippery” concept without links to wider academic debates. The study highlights the fact that such a fundamental form of social action as violence has been absent in the academic line of thought regarding different forms of capital. Also, there is a gap between common sense ways of understanding patterns of violence and their cumulative effects and researcher models. As the concept seems to be largely unknown outside of the Swedish language media and policy debates, to be relevant to wider academic debates, the concept needs to be more clearly defined and theorized. Further developed, the concept of violence capital has the potential to shed light upon the process whereby individual acts may accumulate collective, transferable resources.
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| 7. |
- Gavelin, Karin, et al.
(författare)
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Om idéburna organisationers särart och mervärde : en forskningskartläggning
- 2010
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- I den här rapporten redovisas en kartläggning av forskning om idéburna organisationers särart och mervärde. Detta tema är högaktuellt i dagens diskussioner kring idéburna organisationer inom det sociala området. Har idéburna organisationer någon särart? Har de något mervärde?
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| 9. |
- Gåård, Anders, 1977-
(författare)
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Wear in sheet metal forming
- 2008
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The general trend in the car body manufacturing industry is towards low-series production and reduction of press lubricants and car weight. The limited use of press lubricants, in combination with the introduction of high and ultra-high strength sheet materials, continuously increases the demands of the forming tools. To provide the means of forming new generations of sheet material, development of new tool materials with improved galling resistance is required, which may include tailored microstructures, introducing of specific(MC, M(C,N))carbides and nitrides, coatings and improved surface finish. In the present work, the wear mechanisms in real forming operations have been studied and emulated on a laboratory scale by developing a test equipment. The wear mechanisms identified in the real forming process, were distinguished into a sequence of events consisting of initial local adhesive wear of the sheets resulting in transfer of sheet material to the tool surfaces. Successive forming operations led to growth of the transfer layer and initiation of scratching of the sheets. Finally, scratching changed into severe adhesive wear, associated with gross macroscopic damage. The wear process was repeated in the laboratory test-equipment in sliding between several tool materials, ranging from cast iron to conventional ingot cast tool steels to advanced powder metallurgy tool steel, against dual-phase carbon steel sheets. By use of the test-equipment, selected tool materials were ranked regarding wear resistance in sliding against ferritic-martensitic steel sheets at different contact pressures. Wear in sheet metal forming is mainly determined by adhesion; initially between the tool and sheet surface interaction and subsequently, after initiation of material transfer, between a sheet to sheet contact. Atomic force microscopy force curves showed that adhesion is sensitive to both chemical composition and temperature. By alloying of iron with 18wt.% Cr and 8wt.% Ni, alloying in itself, or changes in crystal structure, led to an increase of 3 times in adhesion at room temperature. Hence, alloying may be assumed a promising way for control of adhesive properties. Additionally, frictional heating should be controlled to avoid high adhesion as, generally, adhesion was found to increase with increasing temperature for all investigated materials.
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| 10. |
- Holmberg, Anders
(författare)
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Contact fatigue and crack propagation studies of sintered PM steel
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Gears made of PM steel are of interest for the automotive industry because from the press/sinter route, complex geometries can be produced to near net shape with only a few processing steps while keeping the material and energy usage at a minimum. However, the PM steels of today have significant performance limitations caused by the inherent porosity which impairs the mechanical properties by acting as stress raisers in the material. The teeth of automotive gears are subjected to pure rolling and sliding as well as a mixture between the two, leading to different mechanisms of wear at different parts of the gear surface. Pure rolling occurs only at the pitch line and the sliding to rolling ratio increases with distance from it. At the vicinity of the pitch line, the force acting on the gear teeth is at its maximum and the repeated cyclic loading leads to fatigue wear. For PM steels, which due to the porosity are highly sensitive to cyclic loads, this results in crack initiation at pores underneath the surface, eventually causing failure of the gear teeth as these cracks propagate to the surface. The SSF project Nanotechnology Enhanced Sintering Steel Processing aims to reduce the gap in performance between PM steels and wrought steels by using nanopowders as a compliment to the standard microsized powder to increase the performance of the material. This thesis aims to increase the knowledge of how different manufacturing parameters, such as sintering temperature, initial powder particles size distribution and addition of nanopowder affect the fatigue properties of the materials. This was done by developing new test equipment for rolling contact fatigue which simulates the contact at the pitch line in a spur gear contact. Utilizing extensive image analysis enables coupling of the different input parameters and their respective pore and microstructure to the fatigue properties. Furthermore, I have investigated how cracks propagate in PM steels using a novel setup which can propagate short cracks in the material. Extensive EBSD studies were performed on the materials after sintering, after case hardening and on cracks after testing. From the rolling contact fatigue tests and image analysis, it was found that materials manufactured using a finer powder fraction together with a higher sintering temperature results in a material well suited for handling cyclic fatigue despite the inherent porosity. Also, by adding a relatively small amount of nanopowder to the standard fraction the fatigue properties were improved considerably. The improved fatigue properties are probably attributed to the reduction of pores with a size in the range of 200 – 400 µm2. These pores are probably the cause of early crack initiation as they are large enough in size as well as in numbers. Smaller pores, although many in numbers do not appear to promote early crack initiation and larger pores, although critical in terms of size, are too few to statistically affect the outcome of the fatigue tests. From the crack propagation studies, it was found that cracks appear to propagate along prior austenite grain boundaries, which for sintered steels are highly related to the particle boundaries after sintering. A finding which helps to explain the deflective pattern of crack propagation found in the rolling contact fatigue studies.
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