Technical Market Support » Metallurgical Coal
The Surface Breakage Rate Constant (SBRC) is an index of coal quality derived from tumbling coke in a conventional drum but with continuous removal of the fines. SBRC has been thought to be related to the tensile strength of the coke and as such, should provide a cheap and statistically reliable measure of coke quality compared with tensile strength measurement.
The main factors that control SBRC are found to be coal rank, coal type (limited) and bulk density of the coking charge.
Similar factors are known to control other coke quality indices, including Mean Tensile Strength. The relationship with rank is generally quasi-parabolic which in each case implies an optimum coal rank for maximum coke quality. However, the optimum for SBRC differs significantly from most of the other coke quality indices including Mean Tensile Strength. This means that at both high rank and low rank the apparent relationship of SBRC to Mean Tensile Strength is quite diverse. It also suggests that for the lower rank range of coking coal blends used in manufacture, the relationship is one of parallelism and association, not correlation in the strict sense. It also means that the relationship between SBRC and Tensile Strength breaks down in the very area of most interest which is between the rank defined optima of Rv,max 1.15% and 1.35%.
Hence in striving to optimise SBRC, it is unlikely to also optimise Mean Tensile Strength.
An associated finding is that the forms of the relationships between the conventional drum indices are also explained.