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

Abstract

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.

Heat Transfer and Dissipation Effects in the Flow of a Drilling Fluid

“…Therefore, in general, µ " µ pt, Π, θ, φ, p, E, Bq, where t is the time, Π is some measure of the shear rate, θ is temperature, φ is concentration, p is pressure, E is the electric field, and B is the magnetic field. For some materials or some applications, the dependence of one or more of these can be dropped (see [22]). …”

Multiphase flow patterns in entrained-flow slagging gasifiers: Physical modelling of particle–wall impact at near-ambient conditions

“…Table 1 reports the mean values of the mechanical properties of the wax and of different coals [44,45], together with their standard deviation. The Young's modulus of slag calculated at high temperatures [46] has also been reported for comparison. The mechanical properties of the wax agree quite well with data reported in Table 1.…”

Effects of Shear Dependent Viscosity and Variable Thermal Conductivity on the Flow and Heat Transfer in a Slurry

“…In this paper we use the constitutive model given in [37] and advocated by Miao et al [38,39], where:…”