Effect of reaction conditions on coke tumbling strength, carbon structure and mineralogy

An experimental study was carried out to examine the effect of different reaction conditions on the changes in the tumbling strength of coke samples from two types of pilot-scale coke ovens. Cokes were reacted with different CO2 concentration and different duration at the CSR test temperature of 1373 K and 1573 K. Tumbling strength of the reacted cokes was measured using a typical CSR test routine. Carbon structure and mineralogy of cokes was measured using X-ray diffraction. Under the test conditions, temperature is shown to have the most significant impact on the modification of coke properties when compared to CO2 concentration or the reaction duration. The tumbling strength of cokes reacted at 1573 K were found to be higher than the CSR value of the original cokes. With increasing temperature of the tests, low CSR cokes indicated a greater improvement of the tumbling strength. High tumbling strength cokes indicated high ordering of carbon structure and lesser amounts of reactive iron-bearing minerals. The effect of temperature on the improvement of tumbling strength can be related to the adverse effect of increased ordering of carbon structure and decreased proportion of iron-bearing phases on the coke reactivity, both being more notable in case of low CSR cokes. The study has implications on the efficient utilization of low premium coal resources and for the true assessment of coke performance in a blast furnace.