The effect of disintegrated iron-ore pellet dust on deposit formation in a pilot-scale pulverized coal combustion furnace. Part II: Thermochemical equilibrium calculations and viscosity estimations

Sefidari, Hamid; Lindblom, Bo; Wiinikka, Henrik; Nordin, Lars Olof; Lennartsson, Andreas; Mouzon, Johanne; Bhuiyan, Iftekhar Uddin; Öhman, Marcus

doi:10.1016/j.fuproc.2018.05.005

Cited by 13 publications

(8 citation statements)

References 30 publications

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“…The foregoing suggests that the resulting melt (owing to the interaction of fuel ash and pellet dust) has a lower viscosity in the case of the raw stem wood compared to coal. The presence of low viscosity molten slags in rotary-kilns (as verified in the previous publications [6,7]) results in the formation of sturdier deposits, which ultimately complicates the cleaning procedures intended to remove the deposited ash.…”

Section: The Effect Of Ash Composition On Slagging/depositionmentioning

confidence: 76%

“…The foregoing is particularly helpful when coupled with viscosity estimations made based on the predicted molten phases. The applicability of TECs in making reliable predictions concerning deposition/slagging has been experimentally verified in the authors' previous studies [6,7,20,29]. Thermochemical equilibrium calculations were extensively used by others pertaining to other technologies, e.g., biomass gasification [30][31][32][33].…”

Section: Thermochemical Equilibrium Calculations (Tecs) and Viscosity Estimationsmentioning

confidence: 90%

“…The reason for the above-mentioned anomalies is because Equation (2) was initially developed for high-rank coals with similar ash contents, whereas in this study the investigated biochars have a considerably higher ash content than their raw-biomass counterparts. However, as extensively discussed in the authors' previous publications [6,7,20,21], the strength of the deposited matter (the degree of sintering) is also a deciding factor that could readily complicate/facilitate the process of deposit removal. The degree of sintering is inversely correlated to the viscosity (Watt [60,61], Mackenzie and Shuttleworth [62], and Boow [63]).…”

Section: Quantification Of the Absolute Deposition Tendency Across The Studied Domainmentioning

confidence: 99%

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The Feasibility of Replacing Coal with Biomass in Iron-Ore Pelletizing Plants with Respect to Melt-Induced Slagging

et al. 2020

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Combustion-generated fly ash particles in combination with the particles arising from the disintegration of iron-ore pellets, could give rise to the build-up of deposits on the refractory linings of the induration facility. Due to climate change and other environmental issues, there is a desire to cut down on use of fossil fuels. Therefore, it is of interest to investigate the feasibility of replacing coal with less carbon-intensive alternatives such as upgraded biomass, e.g., biochar and pyrolysis bio-oil. While the combustion of biomass can be carbon-neutral, the effects of biomass ash upon slagging during the iron-ore pelletizing process in a grate-kiln setup is unknown. In the present study, the effect of the interaction between the pellet dust and biomass-ash upon melt formation and the viscosity of the resulting melt, which can collectively affect melt-induced slagging, was theoretically assessed. The slagging potential of 15 different biomass fuels, suitable for the pelletizing process, was quantified and compared with one another and a reference high-rank coal using a thermodynamically derived slagging index. The replacement of coal with biomass in the pelletizing process is a cumbersome and challenging task which requires extensive and costly field measurements. Therefore, given the wide-ranging nature of the biomasses investigated in this study, a prescreening theoretical approach, such as the one employed in the present work, could narrow down the list, facilitate the choice of fuel/s, and help reduce the costs of the subsequent experimental investigations.

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Section: The Effect Of Ash Composition On Slagging/depositionmentioning

confidence: 76%

Section: Thermochemical Equilibrium Calculations (Tecs) and Viscosity Estimationsmentioning

confidence: 90%

Section: Quantification Of the Absolute Deposition Tendency Across The Studied Domainmentioning

confidence: 99%

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The Feasibility of Replacing Coal with Biomass in Iron-Ore Pelletizing Plants with Respect to Melt-Induced Slagging

et al. 2020

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“…However, the temperature measurements from this campaign were deemed to be unreliable because a sufficiently high suction flow through the suction pyrometer could not be sustained. Four papers have been published on the results from this campaign: one regarding radiative heat transfer and three on deposit formation. − The combustion of Coal 2 was tested in full-scale in FlexiFuel 5.…”

Section: Descriptions Of Kilns Burners Fuels and Measurement Campaignsmentioning

confidence: 99%

Evaluation of NO_x-Reduction Measures for Iron-Ore Rotary Kilns

et al. 2020

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The grate-kiln process is employed for sintering and oxidation of iron-ore pellets. In this process, a fuel (typically coal) is combusted with a large amount of excess air in a rotary kiln, and the high air-to-fuel ratio leads to significant NO x formation. The current Article is an assessment of NO x reduction measures that have been tested in pilot-scale and in full-scale by the Swedish iron-ore company Luossavaara-Kiirunavaara Aktiebolag (LKAB). The results show that the scaling between the full-scale kiln and the pilot-scale kiln is crucial, and several primary measures that reduce NO x significantly in pilot-scale achieve negligible reduction in full-scale. In the investigated full-scale kiln, thermal NO x formation is efficiently suppressed and low compared with the NO formation from the fuel-bound nitrogen (especially char-bound nitrogen). Suppressing the NO formation from the char-bound nitrogen is difficult due to the high amounts of excess air, and all measures tested to alter mixing patterns have shown limited effect. Switching to a fuel with a lower nitrogen content is efficient and probably necessary to achieve low NO x emissions without secondary measures. Simulations show that replacing the reference coal with a biomass that contains 0.1% nitrogen can reduce NO x emissions by 90%.

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“…Experiments were performed in a down-scaled combustion facility simulating either one of the combustion chambers in SG plants or the whole kiln in GK plants. In addition to the general combustion performance such as process temperature, flame radiation, and gaseous emissions, we also focus on ash related operational problems for the GK process since this is a well-known industrial problem. − The renewable fuels considered as a replacement for fuel oil (FO) in the SG process were H 2 and pyrolysis oil (PO). H 2 can be considered as a renewable fuel if it is produced from wind, water, or solar (WWS) powered water electrolysis or biomass gasification.…”

Section: Introductionmentioning

confidence: 99%

Combustion Evaluation of Renewable Fuels for Iron-Ore Pellet Induration

et al. 2019

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Induration (or sintering) of iron-ore pellets requires high temperature (∼1300 °C), which today is generated by burning fuel oil in the firing zone of the straight-grate plant (SG) or coal in the rotary kiln of grate-kiln (GK) plants. In this study, ∼150 kW th combustion experiments were used to investigate the opportunity of totally replacing fuel oil with H 2 or pyrolysis oil and replacing coal with wood pellets or black pellets powder. For SG plants, the fuel oil can probably be replaced with either H 2 or pyrolysis oil without any major concerns, except for slightly or much higher NO x emissions in the case of pyrolysis oil and H 2 , respectively. For GK induration machines, it is probably challenging to replace coal entirely with biomass since the temperature profile will be different, and there is a risk for increased ash related operational problems. For both SG and GK plants, the slightly lower O 2 concentration in the flue gas observed during biomass combustion (pyrolysis oil, wood pellets, and black pellets) may, however, be negative for the induration process, and this needs to be clarified in future research.

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The effect of disintegrated iron-ore pellet dust on deposit formation in a pilot-scale pulverized coal combustion furnace. Part II: Thermochemical equilibrium calculations and viscosity estimations

Cited by 13 publications

References 30 publications

The Feasibility of Replacing Coal with Biomass in Iron-Ore Pelletizing Plants with Respect to Melt-Induced Slagging

The Feasibility of Replacing Coal with Biomass in Iron-Ore Pelletizing Plants with Respect to Melt-Induced Slagging

Evaluation of NO_x-Reduction Measures for Iron-Ore Rotary Kilns

Combustion Evaluation of Renewable Fuels for Iron-Ore Pellet Induration

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The effect of disintegrated iron-ore pellet dust on deposit formation in a pilot-scale pulverized coal combustion furnace. Part II: Thermochemical equilibrium calculations and viscosity estimations

Cited by 13 publications

References 30 publications

The Feasibility of Replacing Coal with Biomass in Iron-Ore Pelletizing Plants with Respect to Melt-Induced Slagging

The Feasibility of Replacing Coal with Biomass in Iron-Ore Pelletizing Plants with Respect to Melt-Induced Slagging

Evaluation of NOx-Reduction Measures for Iron-Ore Rotary Kilns

Combustion Evaluation of Renewable Fuels for Iron-Ore Pellet Induration

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Evaluation of NO_x-Reduction Measures for Iron-Ore Rotary Kilns