Enhancing the Production Rate of Mobarakeh MIDREX Direct Reduction Mega Module Unit Using Numerical Simulation and Geometric Parameter Study of its Ejector Stack

This study uses the numerical simulation to successfully improve the performance of a subsonic ejector stack, which is used for the expulsion of flue gas in a Direct Reduction Iron unit located in Esfahan’s Mobarakeh Steel Company. The current extended computational fluid dynamics (CFD) software uses the finite-volume method to solve the governing equations representing the incompressible turbulent flow through the ejector stack. The study specifically focuses on evaluating the influence of key geometric parameters, such as the mixing chamber length, diffuser length, and the nozzle ejector and diffuser angles, on enhancing the deteriorated performance of the ejector. The performed simulations show that the mixing chamber length cannot be treated as a good geometry parameter to enhance the present performance. As another important parameter, it is shown that the diffuser length can reliably enhance the ejector performance. It needs about 38% increases in this length to achieve an optimum performance value. Examining the convergence and divergence angles of the nozzle and diffuser of the ejector, respectively, it is shown that the optimal angles are 4.9 degrees for the divergence part and 12.5 degrees for the convergence part. Indeed, this study provides a novel and fundamental approach, which helps the industry people to improve the efficiency of their defective ejector stack systems.