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Predicting fuel properties of biomass using thermogravimetry and multivariate data analysis
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.ORCID iD: 0000-0003-1095-9154
2017 (English)In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 156, p. 107-112Article in journal (Refereed) Published
Abstract [en]

Simple and reliable characterization methods for determining fuel properties of biomass are needed for several different applications. This paper describes and demonstrates such a method combining thermogravimetric analysis with multivariate data analysis, based on the thermal decomposition behavior of the fuel. Materials used for the tests were milled samples of wood chips thermally pretreated under different conditions in a torrefaction pilot plant. The predictions using the multivariate model were compared to those from a conventional curve deconvolution approach. The multivariate approach showed better and more flexible performance, with error of prediction of 2.7% for Mass Yield prediction, compared to the reference method that resulted in 29.4% error. This multivariate method could handle samples pretreated under more severe conditions compared to the curve deconvolution methods. Elemental composition, heating value and volatile content were also predicted with even higher accuracies. The results highlight the usefulness of the method and also the importance of using calibration data of good quality. (C) 2016 Elsevier B.V. All rights reserved.

Place, publisher, year, edition, pages
2017. Vol. 156, p. 107-112
Keywords [en]
Thermogravimetric analysis, Multivariate data analysis, Fuel characterization, Fuel composition, Torrefaction
National Category
Bioenergy Chemical Engineering
Identifiers
URN: urn:nbn:se:umu:diva-130216DOI: 10.1016/j.fuproc.2016.10.021ISI: 000390078200014OAI: oai:DiVA.org:umu-130216DiVA, id: diva2:1070986
Available from: 2017-02-02 Created: 2017-01-14 Last updated: 2018-06-09Bibliographically approved
In thesis
1. Fuel conversion and ash formation interactions: a thermochemical study on lignocellulosic biomass
Open this publication in new window or tab >>Fuel conversion and ash formation interactions: a thermochemical study on lignocellulosic biomass
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Biomass is considered to be CO2 neutral, and to be able to reduce the dependency on fossil fuels the need for expanded and sustainable biomass feedstock is increasing. Ash-related problems are some of the most important aspects of this increasing use of new biomass assortments in thermal energy conversion systems. An improved basic understanding of fuel conversion, ash formation, ash transformation and ash interactions with the converting fuel is therefore important.

In the present thesis, the main objective was to provide new knowledge on thermochemical fuel conversion, specifically on how ash formation interacts with fuel conversion for lignocellulosic biomasses. The main methods used were experimental characterization of decomposition behavior and analysis of morphology and elemental composition of samples, using different appliances, analytical methods and fuels. Multivariate data analysis was successfully used on thermogravimetric data for prediction of compositional data and fuel properties.

New, detailed explanations of structural changes in char morphology and ash properties during conversion were provided including descriptions of the influences of ash formation on fuel conversion rates under different conditions. The influences were found different depending on both particle size and ash composition. One implication of these findings is that for fuels with low temperature melting ash, the diffusion barrier formed causes difficulties for typical thermogravimetric experiments aiming at determination of reactivity in the kinetically controlled regime. This is recommended to carefully consider for future studies. On a single pellet level, char encapsulation was not found to dominate and limit gas transport and conversion for any of the fuels tested. In practical applications, however, the situation may be different with thick ash layers accumulating on a fuel bed surface. Another important finding was the extensive formation of cracks and internal cavities during combustion of pellets, providing new insights in the fundamentals of fuel conversion.

Clean woody fuels, rich in calcium, formed a porous ash layer with no sign of limiting char conversion rates. The phase chemical transformations involving carbonate and oxide formation from poplar pellets was studied in detail. For grassy fuels, on the other hand, low melting point silicates are expected to form. The physical properties of K-Ca-silicates from silicon rich straw fuels were also characterized, providing new insights on ash formation on micrometer scale resolution; at high temperature, the silicate melt formed bubbles on the surface that partially covered the char, while for lower temperature a more rigid net structure was formed.

Place, publisher, year, edition, pages
Umeå: Umeå Universitet, 2018. p. 66
Keywords
Char conversion, pyrolysis, devolatilization, ash transformation, biomass, fuel characterization, fuel composition, ash composition, silicate formation, carbonate formation, thermogravimetric analysis, micro-tomography
National Category
Energy Systems Chemical Process Engineering Inorganic Chemistry
Identifiers
urn:nbn:se:umu:diva-147532 (URN)978-91-7601-871-2 (ISBN)
Public defence
2018-06-01, Carl Kempe salen (KBE 303), KBC-huset, Umeå, 10:00 (Swedish)
Opponent
Supervisors
Available from: 2018-05-09 Created: 2018-05-07 Last updated: 2018-06-09Bibliographically approved

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Strandberg, AnnaHolmgren, PerBroström, Markus

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