ANSYS FLUENT 12.0 Theory Guide - 13.2.2 Governing Equations for SOx Transport

13.2.2 Governing Equations for SOx Transport

ANSYS FLUENT solves the mass transport equations for the species, taking into account convection, diffusion, production and consumption of and related species. This approach is completely general, being derived from the fundamental principle of mass conservation. The effect of residence time in SOx mechanisms, a Lagrangian reference frame concept, is included through the convection terms in the governing equations written in the Eulerian reference frame. If all fuel sulfur is assumed to convert directly to and the other product and intermediate species are assumed negligible, then only the species transport equation is needed:

$\frac{\partial}{\partial t}(\rho Y_{\rm SO_2}) + \nabla \cdo... ...nabla \cdot (\rho {\cal D} \nabla Y_{\rm SO_2}) + S_{\rm SO_2}$

(13.2-1)

As discussed in Section 13.2.3, SOx formation mechanisms involve multiple reactions among multiple species, and tracking sulfur-containing intermediate species is important. ANSYS FLUENT solves transport equations for the $H{_2}S$ , , SO, and SH species in addition to the species:

$\frac{\partial}{\partial t} (\rho Y_{\rm H{_2}S})+ \nabla \c... ...= \nabla \cdot (\rho {\cal D} Y_{\rm H{_2}S}) + S_{\rm H{_2}S}$

(13.2-2)

$\frac{\partial}{\partial t} (\rho Y_{\rm SO_3})+ \nabla \cdo... ...3}) = \nabla \cdot (\rho {\cal D} Y_{\rm SO_3}) + S_{\rm SO_3}$

(13.2-3)

$\frac{\partial}{\partial t} (\rho Y_{\rm SO})+ \nabla \cdot ... ...rm SO}) = \nabla \cdot (\rho {\cal D} Y_{\rm SO}) + S_{\rm SO}$

(13.2-4)

$\frac{\partial}{\partial t} (\rho Y_{\rm SH})+ \nabla \cdot ... ...rm SH}) = \nabla \cdot (\rho {\cal D} Y_{\rm SH}) + S_{\rm SH}$

(13.2-5)

where $Y_{\rm SO_2}$ , $Y_{\rm H{_2}S}$ , $Y_{\rm SO_3}$ , $Y_{\rm SO}$ , and $Y_{\rm SH}$ are mass fractions of , $H{_2}S$ , , SO, and SH in the gas phase. The source terms $S_{\rm SO_2}$ , $S_{\rm H{_2}S}$ , $S_{\rm SO_3}$ , $S_{\rm SO}$ , and $S_{\rm SH}$ are to be determined depending on the form of fuel sulfur release ( and/or $H{_2}S$ ) and inclusion of , SO and SH in the SOx mechanism.

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