2004 Volume 90 Issue 9 Pages 694-700
Medium temperature carbonization is one of the technologies to increase productivity of a coke oven. However, strength of lower temperature coke is lower than that of high temperature coke. Then technology covering the decrease of coke strength will be necessary for accompanying the medium temperature carbonization. Heating medium temperature coke further to the high temperature carbonization level after pushed off the oven is one of the methods to modify coke quality.
Medium temperature coke was made in a test coke oven and then heated further in a vessel by an electric heater passing model heating gas. The effect of heating conditions and of reactions with reactive gas on coke strength was investigated. It took coke less than one hour to be fully modified at the heating temperature. Carbonized coke below 750°C in a coke oven at oven center did not sufficiently recover its strength even in the non-reactive gas. Coke strength decreased in proportion to the weight loss by the reaction with carbon dioxide or steam similarly. However, coke strength slightly decreased in a reaction with oxygen.
Change in gas composition along with flow was measured in a coke bed of more than 1.0 m. From the behavior of reactions between coke and reactive gas, their reaction rates were analyzed. Following these results, further heating situation in coke dry quencher (CDQ) by air injection was simulated and it is confirmed that medium temperature coke can be modified in its strength to that of high temperature coke in spite of the weakening of the coke strength by the reaction loss.