Energy Saving Opportunities in an Air Separation Process

The process of a large-scale air separation unit is simulated based on the industrial process and operational parameter of a petrochemical company by using ASPEN PLUS. The actual operating performance is analyzed for the total site. According to the simulation results, exergy efficiency of major equipment is analyzed. The optimization problem can be solved by a new algorithm, which combines genetic algorithm with linear programming. Accordingly a modified air separation process is proposed. The equipment deficiency is overcome in the new process. Also the nitrogen expansion and the structure packing column are added. Meanwhile the pinch analysis is done for the new process. The results of the pinch analysis considering the impact of phase transition agree better with industrial data than those without doing so. The energy consumption can be 7.55MW lower than the original process. The total energy efficiency can be raised by 27.21%. Finally seven unified principles for energy saving, which can be widely used in air separation process, are summarized.