Four dust samples were collected from a blast furnace (BF) for this investigation, two at all coke and two at Pulverized Coal Injection (PCI) operations. Samples of solid carbonaceous fuels (coals and coke) used in the evaluated BF were utilized. Char samples were produced in the laboratory from the pulverized coals used in PCI. The atomic structure of raw coke, chars and its parent coals used in PCI were investigated. This study utilized the X-ray diffraction technique (XRD) as a standard procedure to identify and differentiate the char and coke structures. This technique was used to quantify the proportions of fines of these carbonaceous materials in the BF flue dust samples. A simplified quantification was proposed. XRD of demineralized dust samples showed the unexpected presence of coke fines in quantities smaller than 63 mu m. The quantification of the carbonaceous material present in the BF off-gas samples is important information in order to evaluate the efficiency of the PCI process and the PCI coal combustibility, and it could be used to improve PCI performance in operating blast furnaces. (C) 2012 Elsevier Ltd. All rights reserved.