Effect of coal tar pitch on highly reactive coke properties and microstructure

ABSTRACT

Highly reactive and high-strength cokes are important for developing and producing hydrogen-rich blast furnaces. The work aimed to produce cokes with high reactivity and high post-reaction strength. The coal tar pitch (CP) was added to improve the post-reaction strength of cokes on the premise of adding alkali metals or alkaline earth metals to improve the reactivity of cokes. The chemical reactivity index of coke samples generally decreases by about 1%, while the post reaction strength of coke samples shows a significant improvement after the addition of coal tar pitch, with coke rich in CaO increasing by about 6% and coke rich in K₂CO₃ and Na₂CO₃ increasing by about 3% after adding the CP. Besides, the structural strength and micro strength of coke samples from the composite CP were improved. The microstructure analysis of the coke samples before and after the composite CP showed that the addition of the CP could weaken the originally developed pore structure of the coke samples and reduce the surface area of the gasification reaction of coke samples. Therefore, the gasification reaction of coke samples was inhibited. Moreover, the CP reduced the damage of alkali or alkaline earth metals to the dense aromatic-ring structure in the carbon matrix during the carbonization process of coking coal. It increased the amount of qualitative carbon in the coke samples and the order of carbon microcrystals. The effect of the CP on coke samples varied due to differences in coking coal and catalyst types.

KEYWORDS:

• Alkali metal
• alkaline-earth metal
• coal tar pitches
• coke properties
• microstructures

Acknowledgements

The work was supported by Minmetals Science and Technology Special Program Green Low Carbon Hydrogen Metallurgy Technology and Key Equipment, China (Grant No. 2020ZXA01)

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by the Minmetals Science and Technology Special Program Green Low Carbon Hydrogen Metallurgy Technology and Key Equipment, China [Grant No. 2020ZXA01].