Effect of micro-pores on cracks formation in metallurgical coke

Abstract

The relationships of micro-pores and cracks in metallurgical coke have been investigated by optical microscope and FESEM, using surface section samples. The pores have circular, elliptical and irregular shapes with smooth outlines, formed during the thermoplastic stage of the coking process. They often associate with connecting cracks between neighbouring pores. In case of elliptical pores, the connecting cracks are usually oriented along the longer axis of the pore. The connecting cracks can be developed between the pores, depending on their size and the distance between them. The coke with a large number of small pores rather than with a small number of larger pores will have lower strength due to the increased amount of connecting cracks. When compared to circular pores, elliptical and flattened pores have a lower ability to resist load pressure. Nano-sized pores have polygonal outlines, indicating an "explosion"-type formation in the solidified matrix.

A Comprehensive Review of Characterization Methods for Metallurgical Coke Structures

“…He found that slight roundness and large distorted pores might cause stress concentration and significantly reduce the strength of coke. Gornostayev et al [ 24 ] found a similar result by directly observing the coke using a scanning electron microscope. The elliptical, elongated, and flattened pores, compared with circular pores, showed a lower ability to resist load pressure.…”

“…In this process, the structures of the coke change significantly [ 18 ]. It is well known that the reactivity [ 19 , 20 ] and the strength of coke [ 21 , 22 , 23 , 24 ] are closely related to its structures. Therefore, it is essential to characterize the coke structures comprehensively.…”