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An experimental and numerical study on the combustion of lignites from different geographic origins

Özer, B, and Debiagi, P. and Hasse, C. and Faravelli, T. and Kazanç, F. (2020):
An experimental and numerical study on the combustion of lignites from different geographic origins.
In: Fuel, 278, p. 118320. ISSN 0016-2361,
DOI: 10.1016/j.fuel.2020.118320,
[Article]

Abstract

Coal combustion involves multi-scale, multi-phase and multi-component aspects, in a process where both transport phenomena and reaction kinetics must be considered. The aim of the work is to investigate the differences between the combustion characteristics of Turkish (Soma lignite, Tunçbilek lignite, Afşin-Elbistan lignite) and German (Rhenish lignite) lignites. Combustion characteristics of these lignites were investigated experimentally and numerically. Experiments were conducted using a high temperature (1000 °C) and high heating rate (~104 °C/s) drop tube furnace (DTF), along with a thermogravimetric analyzer (TGA) at non-isothermal conditions (5, 10, 15, 20 °C/min). Both experimental trials were done in a dry air environment and atmospheric pressure. Additionally, DTF and TGA are the experimental setups used to validate the numerical model used in this work. The numerical part of the study includes the computational fluid dynamic analysis of DTF and the predictive multi-step kinetic model analysis of the fuel particle. TGA experiments showed that fuel ratio has an effect on the ignition times. Moreover, maximum reaction rates obtained by TGA experiments were inversely proportional to the ash contents of the fuels used. High heating rate DTF experiments showed similar combustion behaviours with TGA experiments. According to DTF experiments, RL has the highest reactivity (RL: 7.8 s−1) among all fuels (AEL: 5.3, SL: 4.7, TL: 2.9 s−1). In comparison to experimental data, PoliMi model predictions on high-temperature volatile yields are satisfactory with 5–7 errors. PoliMi model overpredicted the devolatilization rates whereas char oxidation rate predictions seem to be lower than the experimental results.

Item Type: Article
Erschienen: 2020
Creators: Özer, B, and Debiagi, P. and Hasse, C. and Faravelli, T. and Kazanç, F.
Title: An experimental and numerical study on the combustion of lignites from different geographic origins
Language: English
Abstract:

Coal combustion involves multi-scale, multi-phase and multi-component aspects, in a process where both transport phenomena and reaction kinetics must be considered. The aim of the work is to investigate the differences between the combustion characteristics of Turkish (Soma lignite, Tunçbilek lignite, Afşin-Elbistan lignite) and German (Rhenish lignite) lignites. Combustion characteristics of these lignites were investigated experimentally and numerically. Experiments were conducted using a high temperature (1000 °C) and high heating rate (~104 °C/s) drop tube furnace (DTF), along with a thermogravimetric analyzer (TGA) at non-isothermal conditions (5, 10, 15, 20 °C/min). Both experimental trials were done in a dry air environment and atmospheric pressure. Additionally, DTF and TGA are the experimental setups used to validate the numerical model used in this work. The numerical part of the study includes the computational fluid dynamic analysis of DTF and the predictive multi-step kinetic model analysis of the fuel particle. TGA experiments showed that fuel ratio has an effect on the ignition times. Moreover, maximum reaction rates obtained by TGA experiments were inversely proportional to the ash contents of the fuels used. High heating rate DTF experiments showed similar combustion behaviours with TGA experiments. According to DTF experiments, RL has the highest reactivity (RL: 7.8 s−1) among all fuels (AEL: 5.3, SL: 4.7, TL: 2.9 s−1). In comparison to experimental data, PoliMi model predictions on high-temperature volatile yields are satisfactory with 5–7 errors. PoliMi model overpredicted the devolatilization rates whereas char oxidation rate predictions seem to be lower than the experimental results.

Journal or Publication Title: Fuel
Journal volume: 278
Uncontrolled Keywords: Char reactivity, Drop tube furnace, TGA, PoliMi model
Divisions: 16 Department of Mechanical Engineering
16 Department of Mechanical Engineering > Simulation of reactive Thermo-Fluid Systems (STFS)
Date Deposited: 22 Jun 2020 05:44
DOI: 10.1016/j.fuel.2020.118320
Official URL: https://doi.org/10.1016/j.fuel.2020.118320
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