Thermal conductivity of coal ash and slags and models used

Rezaei, Hamid; Gupta, Rajender; Bryant, Glenn; Hart, James T.; Liu, G.S; Bailey, C. W.; Wall, Terry; Miyamae, S.; Makino, Koya; Endo, Yoshihiro

doi:10.1016/s0016-2361(00)00033-8

Cited by 116 publications

(38 citation statements)

References 5 publications

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“…the particle size distribution, the porosity and the sintering conditions [31]. Chemical composition was found to have little effect on the thermal conductivity, apart from influencing the extent of sintering [32].…”

Section: Fouling Factormentioning

confidence: 90%

“…As explained in previous section, the effective ther mal conductivity varies with the deposit physical structure. Rezaei et al [32] measured the thermal conductivity of unsintered ash samples concluding that in general, thermal conductivity increases with decreasing porosity and increasing particle size. According to Zbogar et al [31] the thermal conductivity of a fused deposit is higher than of a particulate structured deposit.…”

Section: Dp M Dep M Ash ð4þmentioning

confidence: 99%

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Study of ash deposition during coal combustion under oxyfuel conditions

Fryda

Sobrino

Glazer

et al. 2012

Fuel

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a b s t r a c tThis paper presents a comparative study on ash deposition of two selected coals, Russian coal and lignite, under oxyfuel (O 2 /CO 2 ) and air combustion conditions. The comparison is based on experimental results and subsequent evaluation of the data and observed trends. Deposited as well as remaining filter ash (fine ash) samples were subjected to XRD and ICP analyses in order to study the chemical composition and mineral transformations undergone in the ash under the combustion conditions. The experimental results show higher deposition propensities under oxyfuel conditions; the possible reasons for this are investigated by analyzing the parameters affecting the ash deposition phenomena. Particle size seems to be larger for the Russian coal oxy fired ash, leading to increased impaction on the deposition surfaces. The chemical and mineralogical compositions do not seem to differ significantly between air and oxyfuel conditions.The differences in the physical properties of the flue gas between air combustion and oxyfuel combus tion, e.g. density, viscosity, molar heat capacity, lead to changes in the flow field (velocities, particle tra jectory and temperature) that together with the ash particle size shift seem to play a role in the observed ash deposition phenomena.

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Section: Fouling Factormentioning

confidence: 90%

Section: Dp M Dep M Ash ð4þmentioning

confidence: 99%

Study of ash deposition during coal combustion under oxyfuel conditions

Fryda

Sobrino

Glazer

et al. 2012

Fuel

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show abstract

“…It has been recognized that the viscosity of slag and the thermal conductivity of ash deposits are two of the most important constitutive parameters that must be studied. As Rezaei et al [39] state, the latter depends on the porosity, chemical composition, temperature of the deposit, etc. They observed that the thermal conductivity of ash increases with increasing temperature, but decreases with increasing porosity.…”

Section: Introductionmentioning

confidence: 95%

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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“…It has been recognized that the viscosity of slag and the thermal conductivity of ash deposits are two of the most important constitutive parameters that must be studied. As Rezaei et al (2000) state, the latter depends on the porosity, chemical composition, temperature of the deposit, etc. They observed that the thermal conductivity of ash increases with increasing temperature, but decreases with increasing porosity.…”

Section: Computational Fluid Dynamics (Cfd) and Multiphase Issuesmentioning

confidence: 99%

A Brief Review of Viscosity Models for Slag in Coal Gasification

Massoudi¹,

Wang²

2011

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Thermal conductivity of coal ash and slags and models used

Cited by 116 publications

References 5 publications

Study of ash deposition during coal combustion under oxyfuel conditions

Study of ash deposition during coal combustion under oxyfuel conditions

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

A Brief Review of Viscosity Models for Slag in Coal Gasification

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