Viscosity measurements and empirical predictions for fluxed Australian bituminous coal ashes

Hurst, H.J.; Novak, F.; Patterson, Joshua T.

doi:10.1016/s0016-2361(99)00094-0

Cited by 84 publications

(63 citation statements)

References 2 publications

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“…These mixed SCA samples were molded into a 4 × 4 × 12 mm cuboid sample before sending the sample for further analysis. This preparation of SCA samples is deemed satisfactory, since the properties of coal ashes at high temperatures might be similar to the properties of synthetic ashes composed of primary oxides [22]. …”

Section: Synthetic Coal Ash Samples Preparationmentioning

confidence: 99%

“…Earlier studies have explored the influence of components on ash fusibility or viscosity [20][21][22], but not much data is available on sintering characteristics. It has been concluded that high SiO 2 /Al 2 O 3 ratios (S/As) and low concentrations of basic oxides account for the high ash fusion temperatures of most Australian bituminous coal ashes [23].…”

Section: Introductionmentioning

confidence: 99%

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Effects of SiO2/Al2O3 Ratios on Sintering Characteristics of Synthetic Coal Ash

Zhou

Meng

et al. 2017

Energies

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This article explores the effects of SiO 2 /Al 2 O 3 ratios (S/A) on sintering characteristics and provides guidance for alleviating ash depositions in a large-scale circulation fluidized bed. Five synthetic coal ash (SCA) samples with different S/As were treated in a muffle furnace for 12 h at different temperatures (from 773 K to 1373 K, in 100 K intervals). The morphological and chemical results of the volume shrinkage ratio (VSR), thermal deformation analysis by dilatometer (DIL), scanning electron microscope (SEM), X-ray photoelectron spectrometer (XPS), and X-ray diffraction (XRD) were combined to describe the sintering characteristics of different samples. The results showed that the sintering procedure mainly occurred in the third sintering stage when the temperature was over 1273 K, accompanied with significant decreases in the VSR curve. Excess SiO 2 (S/A = 4.5) resulted in a porous structure while excess Al 2 O 3 (S/A = 0.5) brought out large aggregations. The other three samples (S/A = 1.5, 2.5, 3.5) are made up of an amorphous compacted structure and are composed of low fusion temperature materials (e.g., augite and wadsleysite.). Sintering temperatures first dramatically decrease to a low level and then gradually rise to a high level as S/A increases, suggesting that Al 2 O 3 -enriched additives are more effective than SiO 2 -enriched additives in alleviating depositions.

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Section: Synthetic Coal Ash Samples Preparationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effects of SiO2/Al2O3 Ratios on Sintering Characteristics of Synthetic Coal Ash

Zhou

Meng

et al. 2017

Energies

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“…Jak et al 27,28 modified the Weymann-Frenkel equation to be able to predict the viscosities of fully liquid phase slag for all compositions in the Al 2 O 3 -CaO-''FeO''-SiO 2 system in equilibrium with metallic iron and coal ash slag samples. Hurst et al 29 fitted the [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com. ]…”

Section: Introductionmentioning

confidence: 99%

Measurement and simulation of flow properties of coal ash slag in coal gasification

Song

Sun

et al. 2011

AIChE Journal

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The viscosities of 45 coal ash slag samples at high temperature have been measured under different temperatures and shear rates. The computer thermodynamic software package FactSage has been used to predict liquidus temperatures, volume fractions of crystallized solid particles (/), and the compositions of remaining liquid phase for 45 coal ash slag samples. The flow properties of completely liquid and partly crystallized coal ash slag samples have been predicted by three viscosity models. The Urbain formalism has been modified to describe the viscosities of fully liquid slag and homogeneous remaining liquid phase in coal ash slag samples. The modified Einstein equation and Einstein-Roscoe equation have been used to describe the viscosities of heterogeneous coal ash slag samples of / \ 10.00 vol % and / ! 10.00 vol %, respectively. These three models provided a good description of the experimental data of fully liquid and heterogeneous coal ash slag samples. The new models also predicted flow properties of mixtures of coal ash slags with CaO, Fe 2 O 3 , MgO, SiO 2 , and Al 2 O 3 .

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“…To reduce flux cost, coal with <3% flux requirement by weight may be blended with other coal possessing low ash fusion characteristics, thus reducing or eliminating the need for flux [26]. The viscosity contour as a function of composition or viscosity models could be used to calculate the amount of flux required to obtain a proper viscosity for smooth slag flow in an entrained-flow gasifier [27]. In addition, adding a flux agent increases ash content; therefore, the amount of added agent should be considered.…”

Section: Viscosity With Flux Agents and In Reducing Gas Environmentsmentioning

confidence: 99%

“…Because slag viscosity strongly depends on temperature and chemical composition, it could be optimized by raising/reducing the gasifier operating temperature or adding a flux or blend coals with low fusibility [22,26]. The viscosity model can be used as a guide for designing the gasifier, as well as determining the operation temperature, the amount of flux, and suitable coals for the gasifier [27,28]. Changes in coal result in changes in the composition of ash, which causes changes in the flow of slag within an existing gasifier and affects downstream processing.…”

Section: Introductionmentioning

confidence: 99%

Slag Behavior in Gasifiers. Part I: Influence of Coal Properties and Gasification Conditions

2013

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Abstract:In the entrained-flow gasifiers used in integrated gasification combined cycle (IGCC) plants, the majority of mineral matter transforms to liquid slag on the wall of the gasifier and flows out the bottom. However, a small fraction of the mineral matter is entrained (as fly ash) with the raw syngas out of the gasifier to downstream processing. This molten/sticky fly ash could cause fouling of the syngas cooler. To improve gasification availability through better design and operation of the gasification process, a better understanding of slag behavior and the characteristics of the slagging process is needed. Char/ash properties, gas compositions in the gasifier, the gasifier wall structure, fluid dynamics, and plant operating conditions (mainly temperature and oxygen/carbon ratio) all affect slagging behavior. Because coal has varying ash content and composition, different operating conditions are required to maintain the slag flow and limit problems downstream. In Part I, we review the main types and the operating conditions of entrained-flow gasifiers and coal properties used in IGCC plants; we identify and discuss the key coal ash properties and the operating conditions impacting slag behavior; finally, we summarize the coal quality criteria and the operating conditions in entrained-flow gasifiers. In Part II, we discuss the constitutive modeling related to the rheological studies of slag flow.

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Viscosity measurements and empirical predictions for fluxed Australian bituminous coal ashes

Cited by 84 publications

References 2 publications

Effects of SiO2/Al2O3 Ratios on Sintering Characteristics of Synthetic Coal Ash

Effects of SiO2/Al2O3 Ratios on Sintering Characteristics of Synthetic Coal Ash

Measurement and simulation of flow properties of coal ash slag in coal gasification

Slag Behavior in Gasifiers. Part I: Influence of Coal Properties and Gasification Conditions

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