a period of time. Simulation can be done by hand or on a computer, simulation involves the generation of artificial history of the system and the observation of artificial history to draw inferences concerning of the operating characteristic of the real system. Thus, simulation modelling can be used both as an analysis tool for predicating the effect of changes to existing system and as a design tool to predict the performance of new system under the varying set of circumstances. Process simulation describes processes flow diagram where various unit operations are present and connected by product streams. It is extensively used both in educational arena and industry to predicate the behavior of a process using material balance equations, equilibrium relationship, reaction kinetics, etc. Batch distillation In batch distillation, the feed is charged to the still pot to which heat is supplied continuously through a steam jacket or a steam coil. As the mixture boils, it generates a vapour richer in the more volatile. But as boiling continue, concentration of more volatile in the liquid decrease. It is generally assumed that equilibrium vaporization occurs in the still. The vapour is led to a condenser and the condensate or the top product is collected in the receiver. At the beginning, the condensate will be pretty rich in the more volatiles, but the concentrations of the more volatiles in it decrease as the condensate keep on accumulating in the receiver. The condensate is usually withdrawn intermittently having products or cuts of different concentrations. Batch distillation is used when the feed rate is not large enough to justify installation of a continuous distillation unit. It may also be used when the constituents greatly differ in volatility. Figure 1 show the batch distillation setup. Batch distillation of binary mixture Let L be the moles of material in the still and x be the concentration of the volatile component (i.e. A) and let the moles of accumulated condensate be D. Concentration of the equilibrium vapour is Over a small time, the change in the amount of liquid in the still is and the amount of vapour withdrawn is . The following differential mass balance equation may be written as:Let L be the moles of material in the still and x be the concentration of the volatile component (i.e. A) and let the moles of accumulated condensate be D. Concentration of the equilibrium vapour is Over a