Thermodynamic Equilibrium Study on the Melting Tendency of the K-Ca-Mg-P-Si-O System with Relevance to Woody and Agricultural Biomass Ash CompositionsShow others and affiliations
2022 (English)In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 36, no 13, p. 7035-7051Article in journal (Refereed) Published
Abstract [en]
A major challenge in the combustion of biomass fuels is the heterogeneity of ash-forming elements, which may cause a wide range of ash-related problems. Understanding the melting tendency of the coarse ash fractions is necessary to mitigate agglomeration and slagging. This work aims to evaluate the melting tendency of the K-Ca-Mg-Si-P-O system by use of thermodynamic equilibrium calculations. The formation of condensed phases were systematically assessed in a combustion atmosphere, varying temperatures, and composition. Compositional ranges were based on fuel ash data extracted from the Phyllis 2 database. The speciation and degree of polymerization of phosphates, silicates, and melts were evaluated and indicated a systematic variation in composition. The melt fraction was predicted as a function of temperature and composition. The melting tendency was modeled for three systems, i.e., a P-dominated, a Si-dominated, and a mixed Si-P system. Four ratios between K2O, CaO, MgO, SiO2, and P2O5 were found to have a large effect on the melting tendency of the ash mixtures: the ratio between network formers (SiO2, P2O5), K2O to total network modifiers, CaO to CaO + MgO, and the ratio of network formers to total ash oxides. This modeling approach showed qualitative agreement with ash-related issues seen in previous lab-scale experiments in bubbling fluidized bed and fixed bed combustion. Practical implications of the results are discussed from the perspective of fuel design with the aim of preventing ash-related problems. This study presents a novel method of applying thermodynamic equilibrium calculations for a broad range of compositions and shows potential for predicting ash-related issues related to the melting of coarse ash fractions.
Place, publisher, year, edition, pages
American Chemical Society (ACS), 2022. Vol. 36, no 13, p. 7035-7051
National Category
Energy Engineering
Identifiers
URN: urn:nbn:se:umu:diva-198618DOI: 10.1021/acs.energyfuels.2c00785ISI: 000819242300001Scopus ID: 2-s2.0-85135443894OAI: oai:DiVA.org:umu-198618DiVA, id: diva2:1689905
2022-08-242022-08-242023-09-05Bibliographically approved