The effect of bituminous additives on the carbonization of oxidized coals

- Oxidation had a detrimental effect on the coking properties of the bituminous coals.
- The addition of bituminous additives enhanced the fluidity of oxidized coals.
- The effect of oxidation was not reflected in a clear impairment of coke quality.
- The use of coal tar led to an increase in the coking pressure of the high rank coal.

Two bituminous coals of different rank and coking characteristics were oxidized at low temperature for two months. Bituminous additives obtained in-situ in the coking plant were used to improve the thermoplastic properties of the oxidized coals. The Gieseler fluidity test was applied to evaluate their coking properties. A thermogravimetric analysis (TGA) of the fresh, oxidized coals and their blends with the bituminous additives was carried in order to evaluate the interaction between the blend components. In addition, carbonization tests of the fresh and oxidized coals and the blends with the additives were carried out in a movable wall oven of 17 kg capacity and the quality of the cokes tested by means of standardized methods generally used by the steel industry. The additives increased coal fluidity but the original fluidity values could not be recovered. From TGA it was concluded that the blend components behave independently of one another during co-carbonization. The oxidation of coal leads to an increase in the dangerousness of the low volatile coal which was related to the porous texture of the cokes. In addition, it was found that the decrease in the quality of the coke produced from low rank oxidized coal can be partially recovered by using bituminous additives.