An overview of the coal ash transition process from solid to slag

Shi, Wenju; Bai, Jin; Kong, Lingxue; Li, Huaizhu; Bai, Zongqing; Vassilev, Stanislav V.; Li, Wen

doi:10.1016/j.fuel.2020.119537

Cited by 39 publications

(14 citation statements)

References 95 publications

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“…The main mechanism of the ash sintering process is the melting of the surface of individual ash particles. The ash particles with melted surface coalescent as a result of minimization of the surface tension [6,9,10]. The formation of ash deposits-slagging in the radiative region and fouling in the convection region of the combustion system can cause consequences such as deterioration of heat transfer, damage of boiler surfaces, and even shutdown of the boiler [11,12].…”

Section: Introductionmentioning

confidence: 99%

“…To detect the shrinkage behavior of the ash sample during the sintering process, the Thermomechanical Analysis (TMA) method can be implemented. That is originally applied in metallurgy [10]. The other interesting methods are thermal conductivity analysis [21], compressing strength analysis [22][23][24], electrical resistivity measurements [23], thermogravimetric analysis (TGA) [18,25], thermodynamic FactSage analysis [18], optical heating stage microscopy (OSHM) [26], pressure drop test [9,10,27,28], and other techniques presented in detail [29].…”

Section: Introductionmentioning

confidence: 99%

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Application of the Mechanical and Pressure Drop Tests to Determine the Sintering Temperature of Coal and Biomass Ash

Król

Nowak-Woźny

2021

Energies

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The aim of this paper is to investigate the mechanical properties of coal and biomass ash during the sintering process. For this study, bituminous coal, lignite, wheat straw, barley straw, and rye straw were selected. The proximate, ultimate, and oxide analyses were performed. The ash from these fuels was prepared in a special way that ensured the physicochemical invariability of the initial state of the mineral matter of coal and biomass. The purpose of this selection was to obtain widely available and clearly diversified materials. Based on the results of ash composition and ultimate analysis the most common ash deposition, indices were determined. Certain conflict of index indications was observed. Then, the mechanical test and pressure drop test were performed. During the mechanical test, the fracture stress as a function of sintering temperature was measured. During the pressure drop test, the pressure before and behind the sample was measured as a function of sintering temperature. Both tests showed that the characteristic changes (the occurrence of a maximum on the pressure drop curve and the inflection point at the mechanical curve) dependencies were at nearly the same temperatures. These results were compared with the initial deformation temperature (IDT) from the standard Leitz method. A linear relationship between sintering temperatures determined by the mechanical test, pressure drop test, and IDT Leitz test was obtained. The obtained results are promising in terms of the application of the mechanical methods (fracture stress test and pressure drop test) as methods of the early stage prediction of slagging/fouling risks.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Application of the Mechanical and Pressure Drop Tests to Determine the Sintering Temperature of Coal and Biomass Ash

Król

Nowak-Woźny

2021

Energies

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“…The influence of the chemical composition of fly ash on the vaporization of heavy metals is mainly achieved by changing the melting characteristics of fly ash [ 17 , 18 , 19 ]. SiO 2 reacts with Al 2 O 3 and CaO to form eutectic with a low-melting point, improving the ability of glass melts to capture heavy metals and limiting their volatilization [ 20 , 21 ]. Jiao et al [ 22 ] investigated the vaporization of cesium during thermal treatment of the simulated fly ash by adding CaCl 2 .…”

Section: Introductionmentioning

confidence: 99%

Effect of Atmospheres on Transformation of Heavy Metals during Thermal Treatment of MSWI Fly Ash: By Thermodynamic Equilibrium Calculation

Jiao

Liu

et al. 2021

Molecules

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The vaporization behaviors of eight heavy metals (Pb, Zn, Cu, Cd, Cr, Co, Mn, and Ni) in municipal solid wastes incineration (MSWI) fly ash during thermal treatment under air atmosphere (21% O2/79% N2), an inert atmosphere (100% N2), and a reducing atmosphere (50% CO/50% N2) were evaluated based on a thermodynamic equilibrium calculation by FactSage 8.1. The results show that the reducing atmosphere promotes the melting of MSWI fly ash, resulting in a more liquid phase than in air or an inert atmosphere. Except for Cd, the formation of liquids can dissolve heavy metals and reduce their vaporization ratio. In the air and inert atmospheres, Pb, Zn, Cu, Co, Mn, and Ni vaporize mainly in the form of metallic chlorides, while Cd volatilizes in the form of metallic Cd (g) and CdO (g). In the reducing atmosphere, Co, Mn, and Ni still vaporize as chlorides. Zn and Cd mainly vaporize in the form of Zn (g) and Cd (g), respectively. In terms of Pb, in addition to its chlorides, the volatiles of Pb contain some Pb (g) and PbS (g). Cr has a low vaporization ratio, accounting for 2.4% of the air atmosphere. Cr, on the other hand, readily reacts with Ca to form water-soluble CrCaO4, potentially increasing Cr leaching. Except for Cd, the results of this study suggest that the reducing atmosphere is used for the thermal treatment of MSWI fly ash because it promotes the melting of fly ash and thus prevents heavy metal vaporization.

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“…Due to its remote location and late development, there are few literatures on the pyrolysis mechanism of HSW coal. This study focuses on the influence of heating rate on the pyrolysis behavior of HSW coal, and then expounds the mechanism of coal pyrolysis through kinetic analysis [12,13] .…”

Section: Introductionmentioning

confidence: 99%

Pyrolysis Reactive Behaviors and Kinetic Characteristics of HSW Vitrinite Coal based on Coats-Redfern and DAEM Models

Wang¹,

Wang²,

Li³

et al. 2021

Preprint

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In this work, the weight loss behavior of vitrinite in hongshiwan coal at different heating rates was investigated by thermogravimetric mass spectrometry (TG-MS). Then Coats-Redfern and DAEM models were established to analyze the kinetics of coal pyrolysis. The results show that the weight loss rate of pyrolysis decreased with the increase of heating rate. When the pyrolysis temperature reaches 400–500°C, the weight loss rate reaches the maximum, which is 0.1593, 0.1539, 0.1478 and 0.1414%/°C respectively at the heating rates of 5, 10, 15 and 20°C/min, With the increase of heating rate, the corresponding temperature peaks of the five pyrolysis gases are shifted to the high temperature direction, and the amount of gas escaping is increasing. The trend of higher heating rate delayed the release of volatile compounds was consistent with TG-DTG results. Two kinetic models both prove that the activation energy of coal pyrolysis increases with the increase of temperature. The maximum activation energy occurs between 600 ℃ and 900 ℃, because the multi condensation of coal tar and the re solidification of semi coke will occur in this temperature range.

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An overview of the coal ash transition process from solid to slag

Cited by 39 publications

References 95 publications

Application of the Mechanical and Pressure Drop Tests to Determine the Sintering Temperature of Coal and Biomass Ash

Application of the Mechanical and Pressure Drop Tests to Determine the Sintering Temperature of Coal and Biomass Ash

Effect of Atmospheres on Transformation of Heavy Metals during Thermal Treatment of MSWI Fly Ash: By Thermodynamic Equilibrium Calculation

Pyrolysis Reactive Behaviors and Kinetic Characteristics of HSW Vitrinite Coal based on Coats-Redfern and DAEM Models

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