Abstract: A functional industrial ammonia plant has been simulated using the plant data. All the unit operations, including definition and formation of reactions set have been performed in Aspen HYSYS V8.8. The simulated results compared with the plant data indicate reasonable agreement. The process optimization was performed using the optimization techniques such as BOX, Mixed and Sequential Quadratic Programming in Aspen HYSYSV8.8. The SQP, Mixed and BOX optimization algorithms gave optimum variables at quick convergence with reasonable iterative numbers. It was therefore deduced that the SQP, Mixed and BOX algorithms were more appropriate for the multi-step ammonia process. From the algorithms, the optimum operating conditions that increased the yield of ammonia production are 43.97oC, 4839kPa and 25670kg/hr for natural gas and 280.6oC 21490.0kPa for the ammonia production respectively given the percentage of ammonia to increase from 24.37 to 41.04 mole percent. The performance criterion which was Energy consumption was the objective function which was minimized in the reforming sections. The results showed that there was reduction of energy from 125.36Gcal/hr to 75.095Gcal/hr in the primary reformer and from 43.021Gcal/hr to 34.37Gcal/hr in the secondary reformer respectively. The effect of process parameters on the component performance was performed. It was observed that temperature, pressure and mass flow rate of the natural gas greatly influenced the yield of ammonia. Comparison of the plant, simulated and optimized results were done in terms of operating process parameters and compositions of sour gas, desulfurized gas and ammonia synthesis converter products.