In this research, gas sweetening process of the Iraq Majnoon refinery plant and its optimization scenarios were investigated using ASPEN HYSYS 8.4 and genetic algorithm optimization. First, values of optimization parameters such as the values of the population, generations and crossover for single and multi-objective optimizations were obtained. The effect of temperature and molar flow of feed gas and make-up water on concentration of CO2 and H2S in the sweet gas were studied. The result showed that with increasing the temperature and molar flow of feed gas, the concentration of CO2 and H2S in the sweet gas was increased. The single and multi-objectives’ optimizations of process were carried out with minimizing the concentration of CO2 and H2S, minimizing the consumed energy of stripper and overall consumed energy of plant including energy of stripper and cooler. It was observed that for optimization of concentration of CO2 and H2S, mole fraction of CO2 and H2S decreased to minimum amounts of 5.52 e-4 and 6.84 e-9 between optimization data sets. Also, it was found that with increasing the number of objective functions of the optimization, the ability of the algorithm to reduce the amount of the objective functions decreases, because genetic algorithm should consider more constraints with increasing the number of objective functions. The novelty of this research was a comprehensive study of gas sweetening process optimization with single to four objectives.
