Predicting coal ash slag flow characteristics (viscosity model for the Al 2 O 3 –CaO–‘FeO’–SiO 2 system)

Jak, Evgueni

doi:10.1016/s0016-2361(01)00083-7

Cited by 105 publications

(71 citation statements)

References 9 publications

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“…The presence of iron decreases the glass transition temperature (Tg) of the geopolymers, causing densification and shrinkage. This role of iron, as a flux, was reported in the formation of coal ash slag (Al2O3-CaO-'FeO'-SiO2) [45], in which a completely liquid phase was formed at lower temperature as FeO concentration increased. The previous study [38] also proposed that the crystallization at high temperature (700-800°C) may lead to the thermal expansion of fly ash geopolymers.…”

Section: Thermal Resistancesupporting

confidence: 54%

Mechanical, thermal insulation, thermal resistance and acoustic absorption properties of geopolymer foam concrete

Zhang

Provis

Reid³

et al. 2015

Cement and Concrete Composites

423

160

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This study reports the synthesis and characterization of geopolymer foam concrete (GFC). A Class F fly ash with partial slag substitution was used for GFC synthesis by mechanical mixing of preformed foam. The GFCs exhibited 28 day compressive strengths ranging from 3 to 48 MPa with demolded densities from 720 to 1600 kg/m 3 (105°C oven-dried densities from 585 to 1370 kg/m 3 ), with the different densities achieved through alteration of the foam content.The thermal conductivity of GFCs was in the range 0.15 to 0.48 W/m·K, showing better thermal insulation properties than normal Portland cement foam concrete at the same density and/or at the same strength. The GFC derived from alkali activation of fly ash as a sole precursor showed excellent strength retention after heating to temperatures from 100 to 800°C, and the post-cooling compressive strength increased by as much as 100% after exposure at 800°C due to densification and phase transformations. Partial substitution of slag for fly ash increased the strength of GFC at room temperature, but led to notable shrinkage and strength Preprint of: Z Zhang, JL Provis, A Reid, H Wang, Mechanical, thermal insulation, thermal resistance and acoustic absorption properties of geopolymer foam concrete (GFC), Cement and Concrete Composites, 62(2015): 97-105. Final published version is at: http://dx.doi.org/10.1016/j.cemconcomp.2015.03.013 2 loss at high temperature. Thin GFC panels (20 -25 mm) exhibited acoustic absorption coefficients of 0.7-1.0 at 40 to 150 Hz, and 0.1-0.3 at 800 to 1600 Hz.

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Section: Thermal Resistancesupporting

confidence: 54%

Mechanical, thermal insulation, thermal resistance and acoustic absorption properties of geopolymer foam concrete

Zhang

Provis

Reid³

et al. 2015

Cement and Concrete Composites

423

160

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“…The kinetics of crystalline behavior is directly linked to degree of polymerization of melt (or viscosity) and is not well understood [95]. Despite limited theoretical understanding, heterogeneous slag viscosity can be predicted using thermodynamic models in conjunction with empirical viscosity models and/or combination of thermodynamic models and tools like HT-XRD [19,39,[96][97][98].…”

Section: Slag Mobilitymentioning

confidence: 99%

A Critical Review of Mineral Matter Related Issues during Gasification of Coal in Fixed, Fluidized, and Entrained Flow Gasifiers

Krishnamoorthy

Pisupati

2015

Energies

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Gasification of coal is gaining more popularity due to its clean operation, and its ability to generate products for various markets. However, these technologies are not widely commercialized due to reliability and economic issues. Mineral matter in coal plays an important role in affecting the availability/reliability of a gasifier. Agglomeration in the bed, slag mobility and blockage of the syngas exit section are some of the operations related concerns in fixed-bed gasifiers, while ash deposition and sudden defluidization are the major concerns in fluidized bed gasifiers. In the case of entrained flow gasifiers, syngas cooler fouling and blockage, corrosion and erosion of refractory, and slag mobility are some of the major issues affecting the operations and the reliability of the gasifier. This review is aimed at critically examining various mineral matter related issues contributing to the operation and reliability problems in three types of generic gasifiers (fixed bed, fluidized bed and entrained flow gasifiers). Based on the review, some strategies to counter the potential mineral matter related issues are presented.

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“…Riboud and Lareecq [71] suggested that parameters A and B in the Urbain model should be polynomial functions of the composition. Kondratiev and Jak [72] used a similar argument and suggested that parameters m and n should also be functions of composition in the following manner:…”

Section: A Brief Review Of Various Viscosity Modelsmentioning

confidence: 99%

“…However, in many cases, the IGCC processes operate at conditions where there are still some solid particles in the liquid phase, and therefore, a complete understanding of the rheological behavior of slag should allow for the case of "partly crystallized slag," which contains some solid particles. Kondratiev and Jak [72,73] developed a viscosity model for the cases of completely liquid and heterogeneous and partly crystallized, using a semi-empirical model originally introduced by Urbain et al [86] for Al 2 O 3 -CaO-FeO-SiO 2 systems in equilibrium with metallic iron. Here, the viscosity of the liquid slag was described by the Weymann-Frenkel equation:…”

Section: A Brief Review Of Various Viscosity Modelsmentioning

confidence: 99%

“…They represent B as a polynomial function depending on the slag composition, composed of the three groups: G-glass formation (SiO 2 ) Amphamphoteric oxides (Al 2 O 3 ), and Mod-modifier oxides (CaO-FeO, MgO), such that: where X G , X Mod , and X Amph are the mole fractions of glass formers, modifiers, and amphoteric oxides, respectively. Kondratiev and Jak [72,73] also tested a number of viscosity correlations for the heterogeneous liquids and found that the Roscoe equation [87] is suitable for the cases studied. This equation is appropriate for a colloidal fluid with suspension of rigid spheres of diverse sizes:…”

Section: A Brief Review Of Various Viscosity Modelsmentioning

confidence: 99%

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Slag Behavior in Gasifiers. Part II: Constitutive Modeling of Slag

Massoudi

Wang

2013

Energies

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Abstract:The viscosity of slag and the thermal conductivity of ash deposits are among two of the most important constitutive parameters that need to be studied. The accurate formulation or representations of the (transport) properties of coal present a special challenge of modeling efforts in computational fluid dynamics applications. Studies have indicated that slag viscosity must be within a certain range of temperatures for tapping and the membrane wall to be accessible, for example, between 1,300 °C and 1,500 °C, the viscosity is approximately 25 Pa·s. As the operating temperature decreases, the slag cools and solid crystals begin to form. Since slag behaves as a non-linear fluid, we discuss the constitutive modeling of slag and the important parameters that must be studied. We propose a new constitutive model, where the stress tensor not only has a yield stress part, but it also has a viscous part with a shear rate dependency of the viscosity, along with temperature and concentration dependency, while allowing for the possibility of the normal stress effects. In Part I, we reviewed, identify and discuss the key coal ash properties and the operating conditions impacting slag behavior.

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Predicting coal ash slag flow characteristics (viscosity model for the Al 2 O 3 –CaO–‘FeO’–SiO 2 system)

Cited by 105 publications

References 9 publications

Mechanical, thermal insulation, thermal resistance and acoustic absorption properties of geopolymer foam concrete

Mechanical, thermal insulation, thermal resistance and acoustic absorption properties of geopolymer foam concrete

A Critical Review of Mineral Matter Related Issues during Gasification of Coal in Fixed, Fluidized, and Entrained Flow Gasifiers

Slag Behavior in Gasifiers. Part II: Constitutive Modeling of Slag

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