An Integrated Two-Scale Numerical Model for the Direct Reduction (DR) Shaft Furnace

Abstract A one-dimensional shaft furnace process model for direct reduction (DR) of iron ore was developed in the present study by integrating both pellet scale reduction model and furnace scale gas–solid numerical model. The downward moving bed is assumed to be comprised of pellets of iron ore, whose reduction rate is primarily affected by temperature, gas composition, and pressure. The shrinking core model with three interfaces is employed to simulate the reduction of the iron ore pellet in three steps (Fe 2 O 3 → Fe 3 O 4 → FeO → Fe) by the reducing gas composed of CO, CO 2 , H 2 , H 2 O, CH 4 , and N 2 , allowing to investigate a wide range of reducing gas composition. Ten solid–gas and gas–gas reactions including all reduction reactions, carburization reaction by CH 4 to form C and Fe 3 C, water–gas shift reaction, etc. were counted in the model. It can accommodate multiple gas inlets for reducing and cooling gases, multiple gas extraction points, as well as high pressure conditions, making it a very flexible tool for investigating various furnace designs for MIDREX and HYL ENERGIRON processes. The integrated model can predict the reduction degree, carburization and temperature of iron ore pellet, and gas composition and temperature in the shaft furnace depending on the operation conditions. With no fitting parameters, the present model can accurately reproduce all available experimental data for single-pellet experiments and DR shaft furnace plant data. For the first time, HYL shaft furnace process operating above 1090 °C and 10 atm pressure is simulated and compared with plant data. Graphical Abstract