Over recent years, incorporation of unit operation in industrial process simulators remains an intriguing area of research. This is especially applicable to natural gas plant aimed for CO2 gas removal in offshore platform that is often accompanied with a number of unit operations, complicated configurations, non-standard operating conditions and high impurities content. In addition, it is highly desirable to link the natural gas purification unit with other pretreatment, dehydration and auxiliary equipments already implemented in the process simulators to constitute the entire process plant. Although research work has arisen in this area, the incorporation is particularly challenging for iCON® process simulator since it does not inherit the intrinsic capability to incorporate standalone models of additional unit operations. Nonetheless, the incorporation is of exceptional importance since the intrinsic physical property and thermodynamic databases of iCON® process simulator can be employed conveniently to determine heating value of the product streams. Therefore, in current research work, a mathematical model has been developed to describe the countercurrent hollow fiber membrane module, which has been integrated as an extension in iCON® through utilization of the export/import functions embedded within the Excel unit operation of the process simulator. Validity of the simulation model has been demonstrated through good accordance with published literature. It is found that by determining the separation mechanism via adaptation of the mathematical model, heating value of the purified product stream can be reflected directly in iCON® to evaluate feasibility of the entire process design in offshore natural gas purification platform.