Effect of Coke Strength after Reaction (CSR) on Blast Furnace Performance

摘要

This paper is divided into two parts: a) Review of factors affecting CSR and the influence of CSR on blast furnace performance and b) Relationship of CSR to cold strength properties and incorporation of coke properties for development of a new CSR prediction model. With regard to a), the general consensus is that the blast furnace will continue to play a dominant role in the production of ironmaking worldwide. Evidence showing a strong correlation between increased CSR and reduced degradation has been reported by a number of furnace operators. Some operators also reported the need for increased cold strength as well, particularly as furnace size increased. However, it is difficult to determine exact specifications for cold and high-temperature coke strength. It is possible that individual furnaces will have different coke quality requirements, depending upon their size, quality of other burden materials, burden distribution control and alternative fuel injection. It is also difficult to obtain coke samples that accurately represent all coke produced at a battery, since coke mechanical and high-temperature strength can be extremely variable within an oven, due to differences in coal bulk density and coke temperature. Overall, controversy surrounds current tests for cold and high-temperature coke strength, as questions exist regarding their ability to represent the environment in the lower part of a blast furnace. With regard to b), a plot of coke quality data from 40 adjustable wall oven (AWO) tests conducted at U.S. Steel indicate a stronger correlation between CSR and hardness and a weaker correlation between CSR and stability. Based on statistical analysis, a CSR prediction model was developed that takes into account three parameters, namely hardness (abrasion index), carbon form (gasification reactivity), and coke ash chemistry (catalysts for gasification). This model for the first time correlates CSR to abrasion resistance properties.