Chlorine it is commonly produced through the Chlor-alkali process, which is an electrochemical process – the process energy consumption dominates the production cost. Therefore, optimization of the process has become a major issue to achieve energy conservation and cost effective production. This study aims at investigating the transient and steady-state behavior of the chlorine production system through process modeling and simulation. Material balance and energy balance of the Chlor-alkali membrane process (electrolysis), brine pre-treatment, and chlorine handling are modelled and investigated using rigorous models. MOSAIC and MATLAB, are used to model and to simulate the process response when receiving dynamic input. For validation, the simulation result is compared to experimental data.