The effect of co-firing coal and woody biomass upon the slagging/deposition tendency in iron-ore pelletizing grate-kiln plants

Document identifier: oai:DiVA.org:ltu-76783
Access full text here:10.1016/j.fuproc.2019.106254
Keyword: Engineering and Technology, Mechanical Engineering, Energy Engineering, Teknik och teknologier, Maskinteknik, Energiteknik, Iron-ore pelletizing, Coal-ash, Biomass-ash, Pellet dust, Deposition (slagging), Thermochemical equilibrium calculations, Viscosity estimations
Publication year: 2020
Relevant Sustainable Development Goals (SDGs):
SDG 7 Affordable and clean energy
The SDG label(s) above have been assigned by OSDG.ai

Abstract:

Woody biomass is being considered a potential co-firing fuel to reduce coal consumption in iron-ore pelletizing rotary kilns. An important consideration is the slagging inside the kiln caused by ash deposition that can lead to process disturbances or shutdowns. In terms of ash chemistry, co-firing woody biomass implies the addition of mainly Ca and K to the Si- and Al-dominated coal-ash (characteristic of high-rank coals) and Fe from the iron-ore that are both inherent to the process. An alkali-laden gaseous atmosphere is also present due to the accumulation of alkali via the recirculation of flue gas in the system. The slagging propensity of blending woody biomass with coal in the grate-kiln process was studied based on the viscosity of the molten phases predicted by global thermochemical equilibrium modeling. This was carried out for variations in temperature, gaseous KOH atmosphere, and fuel blending levels. Results were evaluated and compared using a qualitative slagging indicator previously proposed by the authors where an inverse relationship between deposition tendency and the viscosity of the molten fraction of the ash was established. The results were also compared with a set of co-firing experiments performed in a pilot-scale (0.4 MW) experimental combustion furnace. In general, the co-firing of woody biomass would likely increase the slagging tendency via the increased formation of low-viscosity melts. The fluxing behavior of biomass-ash potentially reduces the viscosity of the Fe-rich aluminosilicate melt and intensifies deposition. However, the results also revealed that there are certain conditions where deposition tendency may decrease via the formation of high-melting-point alkali-containing solid phases (e.g., leucite).© 2019 Elsevier

Authors

Hamid Sefidari

Luleå tekniska universitet; Energivetenskap; Luossavaara-Kiirunavaara Aktiebolag (LKAB), Luleå, Sweden
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C. Ma

Department of Applied Physics and Electronics, Thermochemical Energy Conversion Laboratory, Umeå University, Umeå, Sweden
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C. Fredriksson

Luossavaara-Kiirunavaara Aktiebolag (LKAB), Luleå, Sweden
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Bo Lindblom

Luleå tekniska universitet; Energivetenskap; Luossavaara-Kiirunavaara Aktiebolag (LKAB), Luleå, Sweden
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Henrik Wiinikka

Luleå tekniska universitet; Energivetenskap; RISE ETC (Energy Technology Centre) AB, Piteå, Sweden
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L.O Nordin

Luossavaara-Kiirunavaara Aktiebolag (LKAB), Luleå, Sweden
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G. Wu

GTT Technologies, Herzogenrath,Germany. Institute of Energy and Climate Research, Microstructure and Properties of Materials (IEK-2), Forschungszentrum Jülich GmbH, Germany
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E. Yazhenskikh

Institute of Energy and Climate Research, Microstructure and Properties of Materials (IEK-2), Forschungszentrum Jülich GmbH, Germany
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M. Müller

Institute of Energy and Climate Research, Microstructure and Properties of Materials (IEK-2), Forschungszentrum Jülich GmbH, Germany
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Marcus Öhman

Luleå tekniska universitet; Energivetenskap
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