In this work different tools for accurate prediction of acid gas absorption are used. At first, simulation of reactive absorption is carried out using the RATEFRAC module of Aspen Plus, which is tested against pilot plant data. The limitations and disadvantages of this module are presented. In order to present a more predictive approach a rate-based model for the gas scrubbing process is developed. In this model the assumption of thermodynamic equilibrium is considered only at the gas-liquid interphase. Chemical equilibrium among the reacting species in the liquid phase is assumed just for the bulk phase. Mass transfer is modelled using mass transfer coefficients calculated from available correlations which are then improved using an enhancement factor to account for the chemical reactions. The validity of the suggested model is established by comparison of model results with published pilot plant data. The prediction results using the proposed model are improved by around 17% AAD for CO2 and around 7.5% AAD for H2S compared to simulation results using Aspen Plus.