Chemistry Model

The chemistry model used herein to simulate the in situ reheat is a two-step, global, finite rate combustion model for methane and combustion gases [West­brook and Dryer, 1981, Hautman et al., 1981]

CH4 + 1.5O2 ^ CO + 2H2O

CO + 0.502 ^ CO2. (2)

The rate of progress (or Arrhenius-like reaction rate) for methane oxidation is given by:

qi = Ai exp (Ei/Rm/T) [CHJ-0’3 [O2j1’3 , (3)

where A1 = 2.8 ■ 109 s-1, E1/Rm = 24360 K. The reaction rate for the CO/CO2 equilibrium is:

q2 = A2 exp (E2/Rm/T) [COj [O2]0’25 [H2Oj0’5

with A2 = 2.249 ■ 1012 (m3/kmol)°’75 s-1 and E2/RM = 20130 K. The symbols in the square brackets represent local molar concentrations of various species. The net formation/destruction rate of each species due to all reactions is:


Wi = ^2 MiVikqk, k=i

where vik are the generalized stoichiometric coefficients. Note that the gen­eralized stoichiometric coefficient is vik = vik — vik where v’ik and v"k are stoichiometric coefficients for species i in reaction k appearing as reactant or as a product. Additional details on the implementation of the chemistry model can be found in [Isvoranu and Cizmas, 2002].