Setting Material Properties

Since the composition of different types of coal varies, it is important to define the correct composition of the type of coal that is used in the combustor.

The raw coal devolatilizes into char in the particle phase and CoalVolatile in the gas phase. The composition of the coal volatile species is not fixed, but depends on the properties of the coal type being simulated. The proximate and ultimate analysis of the coal sample determines the coal volatile composition. In addition to the proximate and ultimate analysis, the calorific value of the coal type is needed to estimate the heat of formation of the coal volatile.

The proximate analysis is given by:
Component Mass Fraction (-)
Volatile Matter 0.5502
Fixed Carbon 0.3668
Ash 0.083
H2O 0.0
The ultimate analysis (dry ash free) is given by:
Component Mass Fraction(%)
C 80.36
H 5.08
N 1.45
S 0.94
O 12.17

The proximate analysis gives us a yield of 0.6, the low calorific value of coal is 7.1 ⁢     kcal / g and the specific heat of coal is 1100 ⁢     J / kg ⁢   ⁢ K .

To set the material properties:
  1. For the Coal Combustion continuum, select the Models > Multi-Component Gas > Material Properties > Thermal Conductivity node and set Method to Mass Weighted Mixture.
  2. Expand the Multi-Component Gas > Gas Components node.
  3. Multi-select all of the [Gas Component] > Material Properties > Molecular Weight nodes and set Method to Elemental Composition.
  4. Define the composition of the CoalVolatile.
    1. Expand the Gas Components > CoalVolatile > Material Properties > Elemental Composition node.
    2. Right-click the Elemental Composition > Elemental Composition Method > Atoms node and select New Atom.
    3. In the Add atom to elemental composition dialog, set Choose atom to S and click OK.
    4. Expand the Atoms node and set the following properties:
      Node Property Setting
      C Value 2.8029
      H Value 4.2329
      N Value 0.0860
      O Value 0.6340
      S Value 0.0240
  5. Expand the Gas Components > CoalVolatile > Material Properties node and set properties:
    Node Property Value
    Specific Heat Method Constant
    Constant 1100.0 J/kg-K
    Heat of Formation
    Constant -4725729.0 J/kg
  6. Expand the Multi-Component Gas > Material Properties node and set the following properties:
    Node Property Setting
    Absorption Coefficient Method Weighted Sum of Gray Gases
    Weighted Sum of Gray Gases Optical Path Length 1.8 m
  7. Define the surface materials and specify radiation properties:
    1. Select the Coal Combustion > Models > Surface Materials > Surface Materials > Default node and rename it to Cooling Loops.
    2. Select the Cooling Loops > Material Properties > Emissivity > Constant node and set Value to 0.4.
    3. Right-click the Surface Materials > Surface Materials node and select Select Surface Materials.
    4. In the Select Surface Materials dialog, select Cast Iron (Cast Iron).
    5. Click Apply twice, then click Close.
    6. Rename the Cast Iron node to Furnace and the Cast Iron 1 node to Inlet Ducts.
    7. Set the following properties:
      Node Property Setting
      Furnace > Material Properties > Emissivity > Constant Value 0.5
      Inlet Ducts > Material Properties > Emissivity > Constant 0.6
  8. Save the simulation.