CFD Online Discussion Forums - Heterogeneous reaction converge problem

Hi, I have a heterogeneous convergence problem.

I'm using Fluent12. I recently learned UDF, and I put just simple number as a

reaction rate in my UDF ex) rr = 0.005

my reaction is not that complex CaO + S -> CaS + O, I'm using VOF model

(2 Phases) and geometry is quite simple (no flow, just upper and lower phase)

BUT result didn't go well, especially product residual didn't converge (CaO..)

Usually, residual line is going up or going down regardless of convergence, but

my product residual line is just straight line (---------)

How can I solve this problem?