Abstract
The failure strength of metallurgical coke is examined on the basis of materials mechanics and fracture mechanics. A novel concept of the "rule of scaling" is addressed for the macro-, meso-, and the micro/nano-structures of coke that comprises complex pores and cracks embedded in a carbonaceous matrix. It is emphasized that the failure strength of coke grains having the dimension of meso-scale (scale from about 5 to about 30 mm) is essential for mechanically qualifying the grade of metallurgical coke.
Through instrumented spherical indentation testing, the mechanical characterization in mm-scale is conducted for the cokes made from various types of coals encompassing from caking to non-caking coals (strongly coking to poorly coking coals). The indentation test results confirm that the discrepancy in the mechanical properties (elastic modulus, yielding strength, and work-of-indentation) of these cokes in mm-scale is insignificant, whereas there exists a crucial discrepancy in the values of their drum indices (DI). The Weibull statistic is applied to the compressive failure load of coke grains with mm-scales (6 to 15 mm grains and 15 to 25 mm grains). The results of Weibull statistics for the compressive failure loads are successfully related in a quantitative manner to the DI-values.
