The
Coal Calculator dialog box automates calculation and setting of the relevant input parameters for the Species, Discrete-Phase (DPM) and Pollutant models associated with coal combustion. It is available in the
Species dialog box for the
Species Transport model when the
Eddy-Dissipation or
Finite-Rate/Eddy-Dissipation turbulence-chemistry option is selected.
The inputs to the
Coal Calculator dialog box are:
1.
Coal
Proximate Analysis, which is the mass fraction of
Volatile, Fixed Carbon, Ash and
Moisture in the coal.
ANSYS FLUENT will normalize the mass fractions so that they sum to unity.
2.
Coal
Ultimate Anaysis, which is the mass fraction of atomic
C, H, O, N and optionally
S, in the Dry-Ash-Free (DAF) coal.
ANSYS FLUENT will normalize the mass fractions so that they sum to unity.
3.
A choice of
One-step or
Two-step chemical mechanism. The one-step mechanism is,
(15.1-3)
The two-step mechanism involves oxidation of volatiles to
in the first reaction and oxidation of
to
in the second reaction:
(15.1-4)
The stochiometric co-efficients in Equations
15.1-3 and
15.1-4 are calculated from the ultimate and proximate analyses.
4.
An option to
Include SO2. When this is enabled, an input for the atomic mass fraction of sulphur,
S, appears in the ultimate analysis frame.
5.
Wet Combustion, which will enable the DPM Wet Combustion option by default in all injections created after the
OK button is clicked in the Coal Calculator dialog box.
6.
The
Coal Particle Material Name. A DPM combusting-particle material will be created with this name. The default name is
coal-particle.
7.
The
Coal As-Received HCV, where HCV denotes the Higher Calorific Value.
8.
Volatile Molecular Weight is the molecular weight of pure volatiles.
9.
The
CO/CO2 Split in Reaction 1 Products can be used to specify the molar fraction of
to
in the first reaction of Equation
15.1-4. The default value of 1 implies that all carbon is reacted to
, with no
produced.
10.
The
High Temperature Volatile Yield. Enhanced devolatization at higher temperatures can cause the volatile yield to exceed the proximate analysis fraction. To model this, the actual Volatile fraction used is calculated as that specified in the
Proximate Analysis input multiplied by the
High Temperature Volatile Yield. The actual Fixed Carbon fraction is then calculated as one minus the sum of the actual Volatile, Ash and Moisture fractions.
11.
Fraction of N in Char (DAF). This input is used in calculating the split of atomic nitrogen for the Fuel NOx model.
12.
Coal Dry Density is used to calculate the Volume Fraction of liquid-water for the
Wet Combustion option in the
Injections dialog box.
When
OK is clicked,
ANSYS FLUENT makes the following changes:
1.
A Mixture material is created, named
coal-volatiles-air, with a one or two step reaction mechanism as specified in the
Mechanism option. If the Fluid material species (
etc.) do not exist, they are created. A Fluid material called
coal-volatiles, is also created with a Standard State Enthalpy calculated from the ultimate and proximate analyses, as-received HCV and volatile molecular weight.
2.
A combusting-particle material is created with
Volatile Component Fraction and
Combustible Fraction calculated from the ultimate and proximate analyses. The Discrete Phase Model (DPM) is enabled.
3.
For the Fuel NOx model, the default fuel specie is set to
vol, the char N conversion is set to
NO, and the Fuel NOx
Volatile and
Char mass fractions are set according to the ultimate and proximate compositions. Note that even though some of the default Fuel NOx parameters are changed, the Fuel NOx model itself is not enabled.
4.
If
Wet Combustion is selected, all subsequent injections that are created will have Wet Combustion enabled. The evaporation material will be set to
water-liquid, and the volume fraction of water will be calculated from the
Moisture mass fraction specified in the proximate analysis, and the
Coal Dry Density. The
Density for the combusting-particle in the
Create/Edit Materials dialog box will also be set to
Coal Dry Density.
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in the first reaction and oxidation of
to
in the second reaction:
to
in the first reaction of Equation
15.1-4. The default value of 1 implies that all carbon is reacted to
, with no
produced.
etc.) do not exist, they are created. A Fluid material called
coal-volatiles, is also created with a Standard State Enthalpy calculated from the ultimate and proximate analyses, as-received HCV and volatile molecular weight.
