2008 Volume 48 Issue 5 Pages 563-571
In order to improve coke strength by the technique of coal size control, it is essential to understand the relationship between inertinite size and coke strength. The size and area of the inertinite in coke was measured with a microscope and an image analysis technique and the effect of the inertinite size on coke strength was investigated. Moreover the reason why DI150–6 leveled off at an inertinite size of 1.5 mm was investigated.
The results are follows.
(1) When the inertinite size is between about 1.5 mm and 5 mm, the surface breakage product (DI150–6) decreases as the size of inertinite in coke diminishes. When the inertinite size is over about 5.0 mm, volume breakage product (DI1506–15) decreases as the inertinite size diminishes.
(2) Effects of 1% increase/decrease of different size groups of inertinite on DI150–6 and DI1506–15 were clarified.
(3) According to Hertzian contact theory and Griffith equation, it is estimated that cracks under 0.5 mm do not grow by fall of coke in the drum tester. The critical inertinite size (1.5 mm) is an appropriate value for this critical crack size (0.5 mm), because the size of the crack around the inertinite grain is equal to or smaller than the size of the inertinite grain.