Effects of Atmosphere on Viscosity of Selected Bituminous and Low-Rank Coal Ash Slags

and, Bruce C. Folkedahl†; Schobert, Harold H.

doi:10.1021/ef040013o

Cited by 36 publications

(15 citation statements)

References 18 publications

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“…The oxygen partial pressure inside a coal gasifier is typically on the order of 10 −8 to 10 −9 atm (1 to 0.1 mPa), sufficient to reduce most of the iron present in slags to a Fe 2+ state. A decrease in slag viscosity was observed by Folkedahl and Schobert in their study on the effect of reducing atmospheres on the viscosity of coal ash slags [30]. The effect of oxygen partial pressure on coal ash slag viscosity highlights the importance of matching experimental parameters to gasifier operating conditions in data collection.…”

Section: Viscosity Of Fully Molten Silicatesmentioning

confidence: 82%

Correlation between the critical viscosity and ash fusion temperatures of coal gasifier ashes

Hsieh

Kwong

Bennett

2016

Fuel Processing Technology

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Coal gasification yields synthesis gas, an important intermediate in chemical manufacturing. It is also vital to the production of liquid fuels through the Fischer-Tropsch process and electricity in Integrated Gasification Combined Cycle power generation. Minerals naturally present in coal become molten in entrained-flow slagging gasifiers. Molten coal ash slag penetrates and dissolves refractory bricks, leading to costly plant shutdowns. The extent of coal ash slag penetration and refractory brick dissolution depends on the slag viscosity, the gasification temperature, and the composition of slag and bricks. We measured the viscosity of several synthetic coal ash slags with a high-temperature rotary viscometer and their ash fusion temperatures through optical image analysis. All measurements were made in a carbon monoxide-carbon dioxide reducing atmosphere that approximates coal gasification conditions. Empirical correlation models based on ash fusion temperatures were used to calculate critical viscosity temperatures based on the coal ash compositions. These values were then compared with those obtained from thermodynamic phase-transition models. An understanding of slag viscosity as a function of ash composition is important to reducing refractory wear in slagging coal gasifiers, which would help to reduce the cost and environmental impact of coal for chemical and electricity production.Published by Elsevier B.V.

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Section: Viscosity Of Fully Molten Silicatesmentioning

confidence: 82%

Correlation between the critical viscosity and ash fusion temperatures of coal gasifier ashes

Hsieh

Kwong

Bennett

2016

Fuel Processing Technology

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“…Slag viscosities greatly impact the rate and ease with which they can be tapped out of the gasifier. A viscosity in the range of 5-25 Pa-s is considered ideal for the operation of slagging gasifiers [3,4]. Higher viscosities result in solidification of the slag before tapping, thus clogging the tapping valves.…”

Section: Introductionmentioning

confidence: 99%

A FactsSage Simulation Study on the Interaction of Synthetic Petcoke Slags with Alumina Crucibles

Karri

Banik

Pisupati

2021

Fuels

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In entrained flow gasifiers, inorganic species in solid fuels are converted to slag, which flows continuously along the gasifier’s refractory lining. Slag viscosity is critical for its continuous flow and, consequently, reliable operation of the gasifier. Viscosity of synthetic petcoke ash was measured in a high temperature viscometer (up to 1500 °C) using high alumina crucibles. Crucible material was found to dissolve in slag, causing thinning and leading to formation of holes on the walls. To explain this dissolution, thermodynamic equilibrium calculations were performed in FactSage™ (Thermfact/CRCT, Montreal, QC, Canada and GTT-Technologies, Aachen, Germany) using different synthetic petcoke ash compositions in 100% H2, 5% H2/ 95% N2, 69.5% CO/30.5% CO2, and 100% O2 atmospheres. An inverse correlation was found between crucible dissolution and alumina content in the slag. Rates of dissolution of alumina from crucible into slag varied significantly in the different atmospheres. The correlation was validated experimentally by heating six synthetic slags with varying compositions to 1500 °C in 5% H2/N2 (to simulate viscometer’s atmosphere) gas. SEM-EDS analysis of the samples confirmed that the sample with lower initial content of alumina in the slag showed higher amounts of aluminum at the slag–crucible interface. Additions of alumina in the synthetic petcoke ash (containing up to 49.74% V2O5) mitigated crucible dissolution.

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“…Nowok et al [16,17] investigated the effects of atmosphere and local structure of a lignitic coal slag on viscosity. Schobert et al [18,19] reported the fluidity of slag under different atmospheres and flow properties of laboratory ash in a reducing atmosphere. However, little work has been investigated on the rheology of slag, except the studies reported by Tomukayakul et al [20] and Song et al [21].…”

Section: Introductionmentioning

confidence: 99%

Rheology and Viscosity Prediction of Bituminous Coal Slag in Reducing Atmosphere

Zhao¹,

Xu²,

Huo³

et al. 2015

J Chem Eng Process Technol

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The high-temperature rheology of bituminous coal slag in the reducing atmosphere was investigated in this study. The characteristics of slag sample were analyzed by multi-techniques. The rheological measurement of the slag was carried out by a high-temperature rheometer at temperatures of 1360-1460℃. The effects of the shear rate and temperature on the rheological property of the slag were studied. The volume fractions of crystallize particles and mineral matters variation were predicted by thermodynamic software FactSage. The results show that the viscosity and shear stress of the slag increase with decreasing temperature at the constant shear rate. When the volume fraction of the crystallize particles is less than 10%, the slag behaves as a Newtonian fluid. When the volume fraction of the crystallize particles is more than 15%, the slag viscosity decreases with increasing shear rate. The non-Newtonian fluid behavior of slag is illustrated by shear thinning behavior and thixotropic behavior. With decreasing temperature, the shear thinning behavior becomes increasingly significant. In addition, the viscosity prediction model basing on S2 model and Einstein-Roscoe model was established.

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Effects of Atmosphere on Viscosity of Selected Bituminous and Low-Rank Coal Ash Slags

Cited by 36 publications

References 18 publications

Correlation between the critical viscosity and ash fusion temperatures of coal gasifier ashes

Correlation between the critical viscosity and ash fusion temperatures of coal gasifier ashes

A FactsSage Simulation Study on the Interaction of Synthetic Petcoke Slags with Alumina Crucibles

Rheology and Viscosity Prediction of Bituminous Coal Slag in Reducing Atmosphere

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