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

Abstract

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.