Numerical analysis of fuel-flexible FINEX PCI raceway: Natural gas co-firing with advanced coal fragmentation model

FINEX process is an energy-intensive ironmaking process in which improving the fuel consumption efficiency is crucial for economic viability and greenhouse gas reduction. The melter-gasifier generates the heat through pulverized coal burning. However, particles inside the reactor undergo a structural change, fragmentation, in high-temperature and high-pressure, which significantly affects combustibility. In this study, the fragmentation of approximately seven pulverized coal particles was derived using a laminar flow reactor, and an advanced char fragmentation model reflecting this phenomenon was developed and applied to the pulverized coal injection (PCI) system of the FINEX and raceway computational fluid dynamics (CFD) model. The effect of increasing the combustion rate while considering char fragmentation was confirmed, and the possibility of optimizing the injection rate of the pulverized coal was suggested. In addition, an operating method was presented to optimize the natural gas injection in the FINEX melter-gasifier and minimize the impact on the combustibility of the pulverized coal when partially replacing the carrier gas. The 3D computerized analysis model developed in this study can be used to ensure economic efficiency and reduce exhaust emissions by optimizing the operating conditions based on the fuel characteristics. Thus, CO2 emissions can be reduced and the fuel combustion efficiency improved.