New Experimental Evaluation Strategies Regarding Slag Prediction of Solid Biofuels in Pellet Boilers

Document identifier: oai:DiVA.org:ltu-76878
Access full text here:10.1021/acs.energyfuels.9b03098
Keyword: Engineering and Technology, Mechanical Engineering, Energy Engineering, Teknik och teknologier, Maskinteknik, Energiteknik
Publication year: 2019
Relevant Sustainable Development Goals (SDGs):
SDG 12 Responsible consumption and productionSDG 7 Affordable and clean energy
The SDG label(s) above have been assigned by OSDG.ai

Abstract:

Pellet boilers and pellet stoves are widely used for heat production. But in most cases, only specific wood pellets with a low ash content are approved due to the increased risk of slagging and limited deashing capacity. The ash fusion test (AFT), according to prCEN/TS 15370-1, is currently the only standard method for the prediction of slagging. This method is not feasible for all biomass fuel types, since sometimes the characteristic temperatures cannot be determined or the characteristic shapes do not occur for temperature determination. Furthermore, the method is costly and requires complex instrumental infrastructure. Hence, a demand for more expressive or more rapid methods to characterize slag formation potential of fuels is often claimed. Based on a literature study, four such laboratory test methods were chosen, partly adapted, and then experimentally investigated. These methods included thermal treatment of the fuel itself or the ashes of the fuel and were the rapid slag test, CIEMAT, the slag analyzer, and the newly developed pellet ash and slag sieving assessment (PASSA) method. Method performance was practically assessed using 14 different biomass fuel pellets, which were mainly from different assortments of wood, but also herbaceous or other nonwoody fuels. The results from the tests with these four alternative methods were evaluated by comparing to both results from standard AFT and results from full-scale combustion tests performed over a maximum of 24 h. Seven different pellet boilers were assessed, of which one boiler was used to apply all 14 test fuels. According to the granulometric ash analysis (i.e., the ratio of >1 mm-fraction toward total ash formed), the sensitivity of the new test methods to depict slagging phenomena at a suitable level of differentiation was assessed. Satisfactory conformity of the boiler ash assessment (reference) was found for both, the slag analyzer and the PASSA method. The latter may, in particular, be seen as a promising and relatively simple low-input procedure, which can provide more real-life oriented test results for fixedbed combustion. The standardized AFT could, however, not sufficiently predict the degree of slag actually formed in the reference boiler, particularly when only wood fuels are regarded.

Authors

Claudia Schön

Solid Biofuels, Technology and Support Centre in the Centre of Excellence for Renewable Resources, Straubing, Germany
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Sabine Feldmeier

Bioenergy 2020+, Austria
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Hans Hartmann

Solid Biofuels, Technology and Support Centre in the Centre of Excellence for Renewable Resources, Straubing, Germany
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Manuel Schwabl

Bioenergy 2020+, Austria
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Jonas Dahl

Danish Technological Institute, Denmark
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Josef Rathbauer

FJ-BLT-Biomass, Logistics, Technology, Austria
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Daniel Jose Vega-Nieva

Escola de Enxeñería Forestal da Universidade de Vigo,Pontevedra, Spain
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Christoffer Boman

Department of Applied Physics and Electronics, Umeå University, Umeå, Sweden
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Marcus Öhman

Luleå tekniska universitet; Energivetenskap
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Jan Burval

Skellefteå Kraft AB,Skellefteå, Sweden
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