This is the case of CO2 stripper modeling on Aspen plus.
Ammonia & CO2 containing aqueous solution (AKA ammonium carbonate liquor, AC liquor)is the feed to the stripper as sketched in file attached.Actual plant operation shows erratic behaviour of CO2 vent with high temperature ( >100deg_C / Specified= 45 deg_C)& high ammonia content. This erratic condition can be corrected with low temperature AC feed liquor at 112~115 deg_C(Specified is 140 deg_C).
Actual operation simulation gets converged in the temperature range of 112 ~120 deg_C but on higher temperature,It indicates "not converged try better temperature & composition" but there is no more further clarification.
Can you please elaborate the reasons for "Non convergence" at higher temperature? for stripper model.
The following are further points which are not confirmed on simulation run(i.e. simulation shows reverse than mentioned below):
1] More ammonia loss from top bed (Top bed is washer bed to remove traces of NH3)
2] Heavy CO2 slip from tower sump to system.
Thanks in advance.
D R Dave