I am trying to validate and simulate fluidized bed gasification of rice husk and air...

I have added UDF for devolatization and char combustion which are given by fluent.

My mesh is fine, my mass flow rate is 0.3 kg per hour of rice husk, which is 1.32e-5 m per second, mass flow rate of air is 0.00276 meter per second.

i have taken 4 phases

one mixture gas

other is mixture biomass

othere for sand, finally nitrogen for superficial velocty

I am getting error after 1000 iteration like

divergence detected in amg solver: phase-1-species-0..

I tried reducing under relaxation factor, changing to F cycles, decreasing time steps But nothing is working

I have attachted my case file please help me