Biomass Pellet Combustion - problem with CO
 

I modell Biomass pellet combustion in domestic furnace with ANSYS Fluent v12.1 using species transport (Finite Rate/Eddy dissipation) and Discrete Phase Model (DPM). Combustible particles (biomass pellets) are injected as a group of particles in model domain, and combustion model is defined with three reactions (two volumetric: 1. CxHyOz + kO2 = xCO + y/2H2O + jN2; 2. CO + 0,5O2 = CO2; and one particle surface reaction: 3. C(s) + 0,5O2 = CO).

My problem is small mole fraction of CO in outflow of domain, although experimental results show oposite. It seems that all CO burn to CO2 in my model. I try to change Preexponential Factor and Activation Energy for reaction 2, but nothing happens. Any ideas, where I'm wrong? :confused:

Tnx in advance!