Multi-objective optimization of iron ore induration process using optimal neural networks

Induration in steel industries is the process of pelletizing iron ore particles. It is an important unit operation which produces raw materials for a subsequent chemical reduction in Blast Furnace. Of the enormous amount of energy consumed by Blast Furnace, a large portion is utilized in processing the raw materials. High-quality raw materials, therefore, ensure less consumption of energy in the Blast Furnace. Thus, optimization of induration process is necessary for conservation of a significant amount of energy in steelmaking industries. To realize this, a highly non-linear, industrially validated, 22 dimensional first principles based model for induration is created and a multi-objective optimization problem is designed. However, the physics-based model being computationally expensive, Multi-layered Perceptron Networks (MLPs) are trained to emulate the induration process. Novelty in this work lies with the optimal architecture design of MLPs through a multi-objective integer non-linear programming (MO-INLP) problem and with simultaneous training size estimation through four different Sobol sampling-based algorithms. Successful emulation of induration process resulted in 10-fold speed increment in optimization through surrogate models. To justify the parsimonious behavior of resultant MLPs, five different tests are performed for checking whether they are over-fitted. Comparison with Kriging adds to other highlights.