Aspen Plus, Aspen HYSYS, ChemCad and MATLAB, PRO are the commonly used process simulators for modeling, simulation and optimization of a distillation process in the chemical industries. Distillation is the technique of preferential separation of the more volatile components from the less volatile ones in a feed followed by condensation. The vapor produced is richer in the more volatile components. The distribution of the component in the two phase is governed by the vapour-liquid equilibrium relationship. In practice, distillation may be carried out by either two principal methods. The first method is based on the production of vapor boiling the liquid mixture to be separated and condensing the vapors without allowing any liquid to return to the still. There is no reflux. The second method is based on the return of part of the condensate to still under such conditions that this returning liquid is brought into intimate contact with the vapors on their way to condenser. Chemical process modeling Chemical Process modeling is a technique used in chemical engineering process design. Process modeling is defined as the physical, mathematical or logical representation of the real process, system or phenomena using model library present in the process simulator software. In this technique by using process simulator software we define a system of interconnected components. A system is defined as group of object that are joined together in some regular order or interdependence toward the accomplishment of some purpose. Which system are then solved so that the steady-state or dynamic behavior of the system can be predicted. Components of the system and connections are represented as a process flow diagram. A flow diagram for the ammonia process (Finlayson, 2006) is shown in figure 1 below using aspen plus software. The most important result of developing of mathematical model of chemical engineering system is the understanding that is gained what really make the process tick. Mathematical models can be useful in all phase of chemical engineering from research and development to plant operations and even in business and economics studies. The basis for the mathematical models are the fundamentals physical and chemical law, such as the laws of conservation of mass, energy and momentum, degree of freedom. Mathematical modeling is very much an art. It takes experience, practice and brain power to be a good mathematical modeler. Process simulation A simulation is the representation of the real world process or system over