Gas treatment for H2S and CO2 removal has been representing for more than SO years an important industrial application; nowadays these processes are becoming increasingly important as environmental tools also for controlling the composition of the flue gas streams. Natural gas, exhaust gases from power plants, and refinery gases are all sources of carbon dioxide and/or hydrogen sulfide, two components whose presence is strictly limited by the commercial specifications of the final product (i.e., natural gas or syngas) and/or by environmental regulations. In addition, especially H2S is a poison for many catalysts, thus the necessity for removal in order to obtain the best performance in some processes. In this paper, a new model is proposed, where Eddy diffusivity theory instead of film theory is taken into account. The new model is used to develop an external subroutine for ASPEN Plus, a commercial simulation software, that is used as a framework. The use of this tool on different case studies taken from operating plants shows an improvement in the representation of the absorption phenomenon, in comparison with the experimental data.