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Combustion and fuel characterisation of wheat distillers dried grain with solubles (DDGS) and possible combustion applications
Swedish Univ Agr Sci, Dept Forest Resource Management, S-90183 Umea, Sweden.
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.ORCID iD: 0000-0002-5777-9241
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
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2012 (English)In: Fuel, ISSN 0016-2361, Vol. 102, 208-220 p.Article in journal (Refereed) Published
Abstract [en]

The present transition to a sustainable global energy system requires that biomass is increasingly combusted for heat and power production. Agricultural fuels considered include alkali-rich fuels with high phosphorus content. One such fuel is wheat distiller’s dried grain with solubles (wheat DDGS) from wheat-based ethanol production. Further increases in ethanol production may saturate the current market for wheat DDGS as livestock feed, and fuel uses are therefore considered. Fuel properties of wheat DDGS have been determined. The ash content (5.4 ± 1.6 %wt d.s.) is similar to many agricultural fuels. In comparison to most other biomass fuels the sulphur content is high (0.538 ± 0.232 %wt d.s.), and so are the contents of nitrogen (5.1 ± 0.6 %wt d.s.), phosphorus (0.960. ± 0.073 %wt d.s.) and potassium (1.30 ± 0.35 %wt d.s.). To determine fuel-specific combustion properties, wheat DDGS and mixes between wheat DDGS and logging residues (LR 60 %wt d.s. and DDGS 40 %wt d.s.), and wheat straw (wheat straw 50 %wt d.s., DDGS 50 %wt d.s.) were pelletized and combusted in a bubbling fluidised bed combustor (5 kW) and in a pellets burner combustor (20 kW). Pure wheat DDGS powder was also combusted in a powder burner (150 kW). Wheat DDGS had a high bed agglomeration and slagging tendency compared to other biomass fuels, although these tendencies were significantly lower for the mixture with the Ca-rich LR, probably reflecting the higher first melting temperatures of K–Ca/Mg-phosphates compared to K-phosphates. Combustion and co-combustion of wheat DDGS resulted in relatively large emissions of fine particles (<1 μm) for all combustion appliances. For powder combustion PMtot was sixteen times higher than from softwood stem wood. While the Cl concentrations of the fine particles from the the mixture of LR and wheat DDGS in fluidised bed combustion were lower than from combustion of pure LR, the Cl- and P-concentrations were considerably higher from the wheat DDGS mixtures combusted in the other appliances at higher fuel particle temperature. The particles from powder combustion of wheat DDGS contained mainly K, P, Cl, Na and S, and as KPO3 (i.e. the main phase identified with XRD) is known to have a low melting temperature, this suggests that powder combustion of wheat DDGS should be used with caution. The high slagging and bed agglomeration tendency of wheat DDGS, and the high emissions of fine particles rich in K, P and Cl from combustion at high temperature, mean that it is best used mixed with other fuels, preferably with high Ca and Mg contents, and in equipment where fuel particle temperatures during combustion are moderate, i.e. fluidised beds and possibly grate combustors rather than powder combustors.

Place, publisher, year, edition, pages
2012. Vol. 102, 208-220 p.
Keyword [en]
Biofuel, Combustion, Ash transformations, Alkali, Phosphorus
National Category
Natural Sciences Chemical Engineering
URN: urn:nbn:se:umu:diva-60959DOI: 10.1016/j.fuel.2012.05.019ISI: 000308804500025OAI: diva2:564964
Available from: 2012-11-05 Created: 2012-11-05 Last updated: 2014-05-14Bibliographically approved
In thesis
1. Ash chemistry and fuel design focusing on combustion of phosphorus-rich biomass
Open this publication in new window or tab >>Ash chemistry and fuel design focusing on combustion of phosphorus-rich biomass
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Biomass is increasingly used as a feedstock in global energy production. This may present operational challenges in energy conversion processes which are related to the inorganic content of these biomasses. As a larger variety of biomass is used the need for a basic understanding of ash transformation reactions becomes increasingly important. This is not only to reduce operational problems but also to facilitate the use of ash as a nutrient source for new biomass production.

Ash transformation reactions were examined in the present work using the Lewis acid-base concept. The model presented in Paper I was further extended and discussed, including the definition of tertiary ash transformation reactions as reaction steps where negatively charged molecular ions, Lewis bases, other than hydroxides are present in the reactants. The effect of such reactions for bonding of various metal ions, Lewis acids, were discussed. It was found that the formation of various phosphates through secondary and tertiary ash transformation reactions is important for the behaviour of biomass ash in combustion. The suggested model was supported by findings in Papers II-VIII.

The experimental findings in Papers II-VIII were discussed in terms of ash transformation reactions. The fuel design choices made to investigate the effect of phosphorus in particular on ash transformation reactions were high-lighted. Addition of phosphoric acid to woody-type and agricultural biomasses showed that phosphate formation has a large influence on the speciation of Si, S, and Cl. Co-combustion of a problematic agricultural residue with other biomasses showed that the relation between phosphorus, alkali and alkaline earth metal content is important. Co-combustion of biosolids with wheat straw was shown to greatly improve the combustion properties of wheat straw.

It was suggested that fuel analyses should be presented using molar concentration (mole/kg) in diagrams based on ash transformation reactions and elements forming Lewis acids or bases. This may facilitate the assessment of the combustion behaviour of a fuel. Some comments were made on fuel design and additives, specifically pointing out that phosphorus content should always be carefully considered in relation to alkali and alkaline earth metals in fuels and fuel blends.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2014. 50 p.
phosphorus, biomass, combustion, ash chemistry, fuel design, ash transformation, phosphorus-rich, ash-forming elements, fuel fingerprint, ash transformation reactions, Lewis base, Lewis acid
National Category
Inorganic Chemistry Energy Engineering
Research subject
Inorganic Chemistry
urn:nbn:se:umu:diva-88505 (URN)978-91-7601-070-9 (ISBN)
Public defence
2014-06-05, N430, Naturvetarhuset, Umeå universitet, Umeå, 10:00 (English)
Available from: 2014-05-15 Created: 2014-05-08 Last updated: 2014-05-15Bibliographically approved

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Skoglund, NilsBoström, Dan
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