Wyniki wyszukiwania dla: Bengt-Johan Skrifvars

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artykuł

Applicability of ToF-SIMS and stable oxygen isotopes in KCl-induced corrosion studies at high temperatures

Juho Lehmusto, Mikael Bergelin, Jingxin Sui, Jyrki Juhanoja, więcej

Corrosion Science > 2017 > 125 > C > 1-11

The applicability of Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) in combination with the use of stable oxygen isotopes (¹⁶O and ¹⁸O) in high-temperature corrosion research was addressed in this study. In terms of the corrosion reaction timescale, the focus was on the initiation of KCl-induced high-temperature corrosion and on the behaviour of three commercial alloys under conditions...

artykuł

Novel insight to aluminum compounds in the outermost layers of hot dip galvanized steel and how they affect the reactivity of the zinc surface

Ville Saarimaa, Antti Markkula, Jyrki Juhanoja, Bengt-Johan Skrifvars

Surface and Coatings Technology > 2016 > 306 > PB > 506-511

Hot dip galvanized zinc coatings (containing about 0.2% of aluminum) were studied with surface analytical techniques. A few nanometer thick aluminum oxide (Al₂O₃) layer dominated the very outermost surface of such zinc coatings. The inert Al₂O₃ layer formed a continuous impermeable barrier on zinc, providing short term humidity resistance. However, this barrier effect was largely lost during temper...

artykuł

Improvement of barrier properties of Cr-free pretreatments for coil-coated products

Ville Saarimaa, Antti Markkula, Jyrki Juhanoja, Bengt-Johan Skrifvars

Journal of Coatings Technology and Research > 2015 > 12 > 4 > 721-730

Humidity resistance of pretreated and coil-coated panels was evaluated with a special emphasis on the process parameters that govern the uniformity and barrier properties of hexafluorotitanic acid-based pretreatment layers. Humidity resistance tests showed that good barrier effect was obtained with pretreatments in the coating weight range of about 2–17 mg Ti/m². It was further verified by rinsing...

artykuł

Cross‐sectional high‐resolution microscopy of thin pretreatment layers on hot dip galvanized steel

Ville Saarimaa, Jere Manni, Esko Kauppinen, Antti Markkula, więcej

Surface and Interface Analysis > 46 > 9 > 620 - 624

Hexavalent chromium containing pretreatments and primers for coil coating are soon to be entirely prohibited, which sets new demands for Cr‐free alternatives. Most of the presently used Cr‐free pretreatment layers operate predominantly via barrier formation and adhesion promotion mechanisms and lack the self‐healing effect typical for Cr⁶⁺‐pretreatments. This sets new demands also for the formation...

artykuł

Ash-forming elements in four Scandinavian wood species part 3: Combustion of five spruce samples

Johan Werkelin, Daniel Lindberg, Dan Boström, Bengt-Johan Skrifvars, więcej

Biomass and Bioenergy > 2011 > 35 > 1 > 725-733

Forest residue is the remaining fraction after the outtake of timber, which comprises the tree tops and branches. It may as fuel cause damage to the combustion device through ash slagging and fouling. The objective of this work was to model the ash composition from well-specified samples of a spruce tree: wood, bark, twigs, needles, and shoots. Their ash at 1000 °C was modelled using global chemical...

artykuł

Chemical forms of ash-forming elements in woody biomass fuels

Johan Werkelin, Bengt-Johan Skrifvars, Maria Zevenhoven, Bjarne Holmbom, więcej

Fuel > 2010 > 89 > 2 > 481-493

Advanced fuel characterization helps to predict ash fouling and slagging. Chemical fractionation analysis, i.e. sequential leaching in H ₂ O, NH ₄ Ac(aq), and HCl(aq), was applied to the biomass of spruce, pine, birch, and aspen. All of the Cl in the samples and most of the K, Na, and P were water-soluble; most of the Mg and Mn, and some of the Ca were leached in NH ₄ Ac; most...

artykuł

Fouling tendency of ash resulting from burning mixtures of biofuels. Part 3. Influence of probe surface temperature

Mischa Theis, Bengt-Johan Skrifvars, Maria Zevenhoven, Mikko Hupa, więcej

Fuel > 2006 > 85 > 14-15 > 2002-2011

Mixtures of peat with bark and peat with straw were burned in a large lab-scale entrained flow reactor under controlled conditions, and deposits were collected on an air-cooled probe controlled at four to six different probe surface temperatures between 475 and 625 °C. The results show that the probe surface temperature has no effect on the deposition rate when peat is burned. When burning bark, either...

artykuł

Deposition behaviour of model biofuel ash in mixtures with quartz sand. Part 1: Experimental data

Mischa Theis, Christian Mueller, Bengt-Johan Skrifvars, Mikko Hupa, więcej

Fuel > 2006 > 85 > 14-15 > 1970-1978

Model biofuel ash of well-defined size and melting properties was fed into an entrained flow reactor (EFR) to simulate the deposition behaviour of commercially applied biofuel mixtures in large-scale boilers. The aim was to obtain consistent experimental data that can be used for validation of computational fluid dynamics (CFD)-based deposition models. The results showed that while up to 80wt% of...

artykuł

Fouling tendency of ash resulting from burning mixtures of biofuels. Part 2: Deposit chemistry

Mischa Theis, Bengt-Johan Skrifvars, Maria Zevenhoven, Mikko Hupa, więcej

Fuel > 2006 > 85 > 14-15 > 1992-2001

Mixtures of peat with bark and peat with straw were burned in a lab-scale entrained flow reactor under controlled conditions, and deposits were collected on an air-cooled probe at a temperature of 550°C. The fuel and deposit compositions were compared using chemical fractionation analysis and SEM/EDX. Chemical fractionation analysis was capable of explaining the relative fouling tendency of peat,...

artykuł

Fouling tendency of ash resulting from burning mixtures of biofuels. Part 1: Deposition rates

Mischa Theis, Bengt-Johan Skrifvars, Mikko Hupa, Honghi Tran

Fuel > 2006 > 85 > 7-8 > 1125-1130

Specified mixtures of peat with bark and peat with straw were burned in a lab-scale entrained flow reactor that simulates conditions in the superheater region of a conventional biomass-fired boiler. The deposition rates were recorded on an air-cooled probe that was inserted into the reactor at the outlet. For both mixtures, the deposition behaviour followed a non-linear pattern, which suggests that...

artykuł

Bed Agglomeration Characteristics of Wood-Derived Fuels in FBC

Maria Zevenhoven-Onderwater, Marcus Öhman, Bengt-Johan Skrifvars, Rainer Backman, więcej

Energy & Fuels > 2006 > 20 > 2 > 818 - 824

artykuł

Ash-forming elements in four Scandinavian wood species. Part 1: Summer harvest

Johan Werkelin, Bengt-Johan Skrifvars, Mikko Hupa

Biomass and Bioenergy > 2005 > 29 > 6 > 451-466

Woody biomass in Finland and Sweden comprises mainly four wood species: spruce, pine, birch and aspen. To study the ash, which may cause problems for the combustion device, one tree of each species were cut down and prepared for comparisons with fuel samples. Well-defined samples of wood, bark and foliage were analyzed on 11 ash-forming elements: Si, Al, Fe, Ca, Mg, Mn, Na, K, P, S and Cl. The ash...

artykuł

The Fouling Behavior of Rice Husk Ash in Fluidized-Bed Combustion. 2. Pilot-Scale and Full-Scale Measurements

Bengt-Johan Skrifvars, Patrik Yrjas, Tor Laurén, Jouni Kinni, więcej

Energy & Fuels > 2005 > 19 > 4 > 1512 - 1519

artykuł

The Fouling Behavior of Rice Husk Ash in Fluidized-Bed Combustion. 1. Fuel Characteristics

Bengt-Johan Skrifvars, Patrik Yrjas, Jouni Kinni, Peter Siefen, więcej

Energy & Fuels > 2005 > 19 > 4 > 1503 - 1511

artykuł

Deposition behaviour of molten alkali-rich fly ashes—development of a submodel for CFD applications

Christian Mueller, Maria Selenius, Mischa Theis, Bengt-Johan Skrifvars, więcej

Proceedings of the Combustion Institute > 2005 > 30 > 2 > 2991-2998

In this work, an advanced CFD-based ash deposition model is presented that allows for the quantitative prediction of the transport of fly ash particles near furnace walls and heat exchanger surfaces, combined with a detailed description of the thermochemical properties of the particles that consist of salt mixtures melting over a wide temperature range rather than at one specific melting point. The...

artykuł

Ash behaviour in a pulverized wood fired boiler-a case study

Bengt-Johan Skrifvars, Tor Laurén, Mikko Hupa, Rob Korbee, więcej

Fuel > 2004 > 83 > 10 > 1371-1379

The behaviour of the mineral matter in a fuel may crucially affect the availability of a boiler when the fuel is fired. The ash may cause severe problems in the flue gas channel in forms of fireside deposits on heat exchangers. These deposits lower the efficiency of the boiler and cause in the most severe cases an unscheduled shutdown.In this paper we report results from a study where the ash behaviour...

artykuł

The ash chemistry in fluidised bed gasification of biomass fuels. Part I: predicting the chemistry of melting ashes and ash-bed material interaction

Maria Zevenhoven-Onderwater, Rainer Backman, Bengt-Johan Skrifvars, Mikko Hupa

Fuel > 2001 > 80 > 10 > 1489-1502

This paper is part I in a series of two describing the modelling of the ash-chemistry of seven biomass fuels under reducing, pressurised conditions in fluidised bed gasification by means of thermodynamic multi-phase multi-component equilibrium (TPCE) calculations. The fuels considered were Salix, a Scandinavian forest residue, Miscanthus, Reed Canary Grass, Eucalyptus, Arundo Donax and Lucerne.The...

artykuł

Ash behaviour in a CFB boiler during combustion of coal, peat or wood

Bengt-Johan Skrifvars, Rainer Backman, Mikko Hupa, George Sfiris, więcej

Fuel > 1998 > 77 > 1-2 > 65-70

This paper presents selected results from an extensive on-site measurement campaign where the ash behaviour in a 12 MW CFB boiler was studied during firing of coal, peat and wood. Samples were taken from all in-going (bed material, fuel) and out-going solid material streams (secondary cyclone and bag filter) as well as from the bed and the return leg. Deposit samples were further collected from...

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