FINEX PCI fuel diversification for techno-economical operations: Impact of high-volatile coal agglomeration on combustion

•The applicability of pulverized high volatile coal in ironmaking PCI was evaluated.•As the amount of agglomeration increases, unburned carbon increases.•Agglomeration occurs between coals due to tar the devolatilization process.•When agglomeration occurs, the specific surface area structurally decreases.•Tar plays bridging role within devolatilization agglomeration process. Large-scale (volume > 2000 m3) blast furnaces (BFs) requiring expensive, high-grade coal are currently used in the iron and steel industry. High-volatile coal (HVC) must provide a substitute for high-grade coal to facilitate economical operations. This study determines the applicability of HVC and thermal coal within the fine particle extraction (FINEX) and conventional BF steelmaking processes using a drop-tube furnace. Furthermore, the characteristics of single- and blending-coal-carbon conversions are analyzed using unburned carbon (UBC). In the BF, an increase in agglomeration leads to an increase in UBC, where approximately 20 % agglomeration can be achieved. However, under FINEX conditions, due to the high oxygen concentration approximately 50 % agglomeration can be achieved. To determine the principle of the agglomeration phenomenon, a chemical-percolation-devolatilization model is used to analyze the amount of tar, light gas, and char generated during the devolatilization process. Using HVC achieves 89.7 % agglomeration which generates a 30 % tar volume during devolatilization. Tar has a significant effect on agglomeration and facilitates bridging, causing agglomeration into a large particle as identified from the structural agglomeration of a scanning electron microscopy image. This phenomenon affects raceway formation and the combustion stability of pulverized coal injections.