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

Abstract

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 .

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

“…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].…”

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

“…For entrained-flow gasifiers, it is important that the models describe the viscosity of fully liquid slag in multi-component slag systems and also predict the viscosity of partly crystallized liquid slag. For predicting the viscosity of homogeneous liquid slag, the models of Urbain, Fereday, and the silica percentage model are used, as well as modified versions of those models (such as Kalmanovitch-Urbain, Watt and Fereday, and S 2 ) [68,75,76]. The main challenge of all these models is their validity over a limited composition and temperature range, and their accuracy for different slag systems (e.g., Kalmanovitch model best predicts western coal slag above 1350 °C [77]).…”

“…The main challenge of all these models is their validity over a limited composition and temperature range, and their accuracy for different slag systems (e.g., Kalmanovitch model best predicts western coal slag above 1350 °C [77]). To predict the viscosity of the crystalline phase slags, Annen's or Einstein's models were used [68,76]. Most viscosity models are based on particular viscosity datasets and, therefore, can predict slag viscosity only for the specific compositions and temperatures.…”

Slag properties of blending coal in an industrial OMB coal water slurry entrained-flow gasifier

“…Thus slag properties, especially the viscosity and flow behavior of the slag in the gasifier under high temperature as well as the char-slag transition process play important roles in the gasification process [4,5]. Several mechanical models have been proposed to predict slag formation and deposition characteristics in entrained-flow gasifiers [6,7] [8][9][10]. It has been identified that the viscosity of slag that can ensure a smooth tapping is lower than 25 Pa s. Further investigations are needed on the ash slag flow characteristics because they are widely recognized as the main potential area of concern in relation to the suitability of coals for use in entrained-flow coal gasifiers [11,12].…”