Title

THE BENEFITS OF LOW VOLATILE COALS FOR THE PCI MARKET

THE BENEFITS OF LOW VOLATILE COALS FOR THE PCI MARKET

Authorship

BENNETT, P. A.

BENNETT, P. A.

I am this author

DOI

10.5151/2594-357x-28Red-31-48

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Abstract

In this paper a general overview is developed showing how the volatile content of the injected coals can impact on char formation, blast momentum and generation of coke fines in the raceway. Although, this overview was based on the idealised properties of coal and individual coals with very few properties, it does however highlight the three important aspects of how coal properties can influence blast furnace performance. These are: Coke replacement ratio increases with the dry ash free carbon content of coal i.e. comparatively dry ash free carbon content of 91% where the replacement ratio seems to level out. The blast momentum decreases with increasing carbon content of the coal where the dry ash free carbon content is greater than 85%, the blast momentum directly influences the raceway depth and coke degradation within the raceway. Blast oxygen enrichment requirements to maintain raceway gas temperatures decrease as the dry ash free carbon of the injected coal increases. With injection rates and injecting a coal with a carbon content less than 85% daf, any fluctuations in the coal rate delivered to a tuyere will result in fluctuations in the raceway depth and the generation of coke fines. Fluctuations in raceway depth and the generation of fines will reduce blast furnace stability and therefore productivity. By choosing a coal with a dry ash free carbon content greater than 85% daf, the impact of variations in coal feed rate on blast furnace stability will be reduced and furnace productivity will be maintained.

In this paper a general overview is developed showing how the volatile content of the injected coals can impact on char formation, blast momentum and generation of coke fines in the raceway. Although, this overview was based on the idealised properties of coal and individual coals with very few properties, it does however highlight the three important aspects of how coal properties can influence blast furnace performance. These are: Coke replacement ratio increases with the dry ash free carbon content of coal i.e. comparatively dry ash free carbon content of 91% where the replacement ratio seems to level out. The blast momentum decreases with increasing carbon content of the coal where the dry ash free carbon content is greater than 85%, the blast momentum directly influences the raceway depth and coke degradation within the raceway. Blast oxygen enrichment requirements to maintain raceway gas temperatures decrease as the dry ash free carbon of the injected coal increases. With injection rates and injecting a coal with a carbon content less than 85% daf, any fluctuations in the coal rate delivered to a tuyere will result in fluctuations in the raceway depth and the generation of coke fines. Fluctuations in raceway depth and the generation of fines will reduce blast furnace stability and therefore productivity. By choosing a coal with a dry ash free carbon content greater than 85% daf, the impact of variations in coal feed rate on blast furnace stability will be reduced and furnace productivity will be maintained.

Keywords

coal injection, blast furnace, volatile matter, coke replacement ratio, raceway depth

coal injection, blast furnace, volatile matter, coke replacement ratio, raceway depth