## 2 Textural Segmentation in OIA of Coke  
Metallurgical coke is one of the major components of the blast furnace load, and its qualities, such as strength, abrasion resistance and reactivity, which are strongly dependent on coke structure/texture, are critical for stable blast furnace operation. OIA enables an improved understanding of the relationships between coke quality, parent coal blend composition and coke structure/texture. This allows for the improvement and optimization of the processes involved in coke production, such as parent coal blending, sizing, cooking, etc.  
In this section we essentially discuss coke \"structure\", defining it as the spatial distribution of porosity and the coke matrix, which consists of different cooked/reacted macroals. In many disciplines within mineral processing, the term \"texture\" means approximately the same as \"structure\". However, when applied to coke characterization, \"texture\" is understood to mean the spatial distribution of different isotropic and anisotropic carbon types within the coke, typically determined during optical imaging by differences in bi-reflectance [18; 19].  
During coking of parent coal blends, some macroals, such as different types of vitrinite, are significantly fluidized and thus subject to a stronger reaction. The parts of the coke matrix resulting from such reactions are called Reacted Maceral Derived Components (RMDC). The non-reacted or significantly less reacted types of macroals (inerts) form Inert Maceral Derived Components (IMDC). One of the major tasks during the characterization of coke structure is to determine the relative amounts of carbonaceous materials with different degrees of reaction. The relative abundance and corresponding size distributions of these coke phases show strong significant correlations with different coke strength indices and parent coal blend composition [18]. For example, a study by [PERSON] et al. [18] confirmed the earlier findings of [PERSON] et al. [22] that 1.5 mm is the critical size for IMDC affecting coke strength.  
Mineral4 segments and comprehensively characterizes three different phases in coke matrix: unreacted IMDC, partially reacted IMDC and RMDC. Figure 2a shows an image obtained using a narrow bandwidth (\(\pm\)5 nm) green filter (\(\lambda\) = 546 nm) of coke made from medium rank coal. In the image, the unreacted areas (unreacted IMDC), slightly reacted areas (partially reacted IMDC), and the very porous network connecting them together (RMDC) are clearly evident. The results of automated segmentation of these structural components are given in Figure 2b. It is clear that unreacted IMDC grains can have different structures; some are quite dense, showing almost no porosity, whereas others are quite porous. This complicates the task of properly identifying them by structure. Standard segmentation by thresholding is also of limited use here. While the coke matrix as a whole can be reliably thresholded to distinguish it from porosity, there is no critical difference in reflectivity between IMDC and RMDC.  
Mineral4 Textural Identification uses three different methods to identify various areas of unreacted IMDC and then combines the results into one unreacted IMDC map. These three methods are bulk identification of IMDC, porous IMDC identification and identification of \"washed out\" IMDC. Similar methodology is used for identification of the partially reacted IMDC. The remainder of the coke matrix is then considered to be RMDC. It is important to highlight that the understanding of RMDC structure as the one consisting of thin walls and large pores is applied in some IMDC identification methods to exclude areas that are \"not IMDC\". Generally, for successful structural segmentation, a knowledge of the individual features of all phases is critical.