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Influence of Peat Ash Composition on Particle Emissions and Slag Formation in Biomass Grate Co-combustion
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
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2014 (English)In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 28, no 5, 3403-3411 p.Article in journal (Refereed) Published
Abstract [en]

Co-combustion by fuel blending of peat and biomass has shown positive effects on operational problems. However, peat ash compositions vary considerably, and this has been shown to affect the potential for operational problems in different fuel-blending situations. The present work used three different peat types with the objective to elucidate how the variation in peat ash composition influences both particle emissions and slag formation during co-combustion with three different biomasses in a small-scale pellet boiler. Estimations of potassium release and slag formation were performed and discussed in relation to fuel composition in the (K2O + Na2O) (CaO + MgO) (SiO2) system. All tested peat types reduced the fine particle emissions by capturing potassium into the bottom ash as one or several of the following forms: slag, sulfates, chlorides, and alumina silicates. However, there were considerable differences between the peat types, presumably depending upon both their content and mineral composition of silicon, calcium, aluminum, and sulfur. Some general important and beneficial properties of peat type in co-combustion situations with biomass are defined here, but the specific blending proportion of peat should be decided on an individual basis for each scenario based on the relative contents in the fuel mixture of the most relevant ash-forming elements.

Place, publisher, year, edition, pages
2014. Vol. 28, no 5, 3403-3411 p.
National Category
Bio Materials
Identifiers
URN: urn:nbn:se:umu:diva-90439DOI: 10.1021/ef4023543ISI: 000336199300063OAI: oai:DiVA.org:umu-90439DiVA: diva2:733451
Available from: 2014-07-09 Created: 2014-06-23 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Fine particle emissions and slag formation in fixed-bed biomass combustion: aspects of fuel engineering
Open this publication in new window or tab >>Fine particle emissions and slag formation in fixed-bed biomass combustion: aspects of fuel engineering
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

There is a consensus worldwide that the share of renewable energy sources should be increased to mitigate climate change. The strive to increase the renewable energy fraction can partly be met by an increased utilization of different biomass feedstocks. Many of the "new" feedstocks puts stress on certain challenges such as air pollution emissions and operation stability of the combustion process. The overall objective was to investigate, evaluate, and explain the effects of fuel design and combustion control - fuel engineering - as primary measures for control of slag formation, deposit formation, and fine particle emissions during biomass combustion in small and medium scale fixed-bed appliances. The work in this thesis can be outlined as having two main focus areas, one more applied regarding fuel engineering measures and one more fundamental regarding the time-resolved release of ash forming elements, with particular focus on potassium.

The overall conclusion related to the abatement of particle emissions and slag formation, is that the release of fine particle and deposit forming matter can be controlled simultaneously as the slag formation during fixed-bed biomass combustion. The methodology is in this perspective denoted “fuel engineering” and is based on a combined approach including both fuel design and process control measures. The studies on time-resolved potassium release showed that a Macro-TG reactor with single pellet experiments was a valuable tool for studying ash transformation along the fuel conversion. The combination of dedicated release determinations based on accurate mass balance considerations and ICP analysis, with phase composition characterization by XRD, is important for the understanding of potassium release in general and time-resolved data in particular. For wood, the results presented in this work supports the potassium release mechanism from "char-K" but questions the previously suggested release mechanism from decomposition of K-carbonates. For straw, the present data support the idea that the major part of the potassium release is attributed to volatilization of KCl. To further explore the detailed mechanisms, the novel approach developed and applied in this work should be complemented with other experimental and analytical techniques.

The research in this thesis has explored some of the challenges related to the combined phenomena of fuel conversion and ash transformation during thermochemical conversion of biomass, and has contributed with novel methods and approaches that have gained new knowledge to be used for the development of more effective bioenergy systems.

Place, publisher, year, edition, pages
Umeå: Umeå Universitet, 2015. 73 p.
Keyword
Renewable energy, biomass, thermochemical fuel conversion, combustion, fine particle emissions, slag formation, fixed-bed, ash chemistry, fuel engineering, release
National Category
Chemical Process Engineering Energy Engineering Environmental Engineering
Identifiers
urn:nbn:se:umu:diva-102687 (URN)978-91-7601-274-1 (ISBN)
Public defence
2015-05-25, KBC-huset, sal KB3A9, Umeå Universitet, Umeå, 13:00 (Swedish)
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Available from: 2015-05-04 Created: 2015-04-30 Last updated: 2015-05-08Bibliographically approved

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Fagerström, JonathanNäzelius, Ida-LinnBoström, DanBoman, Christoffer
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