I have simulated combustion of char in CFX 11.0 However, when the particles are injected into the domain, they burn before reaching the oxidizer region, that is, the combustion process occurs too fast in regions where the oxygen concentration is zero.

Could someone help me with this problem ? Thankou!

are you sure that there is no initial nonzero oxygen concentration?

Yes, yes, yes. The concentration at the inlet is zero. After several investigations, I have discovered that CFX has a very broad difficulty in treating multiphase reactions, when there's more than one simultaneous reaction occuring (in my problem, the formation of methane from char and hyrdogen is also important).