2014 Volume 54 Issue 11 Pages 2503-2511
The strength of coke largely depends on the thermoplastic and dilatation behavior of its coal constituents. Therefore, understanding the behaviors that ensure high-strength coke is important. In this study, the combination of blended coal was varied and (in a separate experiment) asphalt pitch (ASP) was added to the blended coal. The resulting changes in coke pore structure were investigated by image analysis of a cross-section of coke. The main findings are summarized below.
(1) When the thermoplastic temperature of low- and high-rank coal was very different, the proportion of low-circularity pores increased in the textures of both the grades of coal. It was concluded that when the particles of high-rank coal did not dilate, those of the low-rank coal freely expanded. Meanwhile, the dilatation of high-rank coal decreased the extent of dilatation in the neighboring low-rank coal. Consequently, high-rank coal not adjacent to low-rank coal achieved free expansion, and its texture became characterized by increased low-circularity pore areas.
(2) The addition of ASP to blended coal decreased the number of low-circularity pores in the texture of high-rank coal. ASP appears to lower the softening temperature of high-rank coal, enabling it to fill the voids between coal particles before the low-rank coal solidifies.
The abovementioned investigation of coke pore structure assists our understanding of the thermoplastic and dilatation behavior of coal.