Abstract
This study developed a theoretical model for the determination of the Coke Anisotropy Quotient (CAQ) of semi-coke from the properties of its precursor coal. This is an useful parameter to define the resistance and reactivity of semi-coke in the blast furnace. For 36 semi-coke samples, a textural analysis was performed alongside a fluidity test to determine the real CAQ. The main textures observed were: isotropic and circular for high volatile bituminous coals (HVB); lenticular and fine ribbons for the medium volatile bituminous coals (MVB); and medium and thick ribbons for the low volatile bituminous coals (LVB). The CAQ varied in a range from 1 to 11. A principal component analysis (PCA) and multiple regression allowed to discriminated the importance of certain coal properties, in determining the CAQ to be recognized and to estimate parameters of the mathematical model. The statistical analysis suggested that CAQ can be best predicted from the fluidity, volatile matter, and Ro of the parent coals. The veracity of this model result was then tested using a second dataset from Poland. This work optimizes the usefulness of standard datasets in the prediction of CAQ's offering a means of quality control that could be implemented in Colombian coke production.
Highlights
Coke is the main product of the thermal treatment of bituminous coals, brought about by the destructive distillation or pyrolysis of organic matter in an oven or in some specific natural geological conditions [1],[2]
The studied coals varied from high volatile bituminous (HVB) coals to low volatile bituminous (LVB) coals according to the ASTM D388-19a standard
The presence of significant amounts of macerals of the inertinite group could be related to the generation of a coke with maximum strength and stability [4], the Coke Anisotropy Quotient (CAQ) value depends only on the textures formed from the reactive macerals
Summary
Coke is the main product of the thermal treatment (heat flow) of bituminous coals, brought about by the destructive distillation or pyrolysis of organic matter in an oven or in some specific natural geological conditions [1],[2]. Steel manufacturing requires coke with high-quality standards, for example, in order to provide heat, a reducing environment and a permeable agent in the blast furnace during the steel production, coke with a Resistance after Reaction with CO2 (CSR) values > 65% [5],[6], and a Reactivity Index (CRI) between 20 and 30%, is required [7]. According to [7] these coke quality indexes are dependent on the precursor coal (on 70%), the preparation of the sample and the furnace operating conditions during coke production (the remaining 30%). In Colombia, the value of coal and coke exports in the second quarter of 2017 contributed 1,549.81 million dollars FOB (Free On Board) to the country’s budget, according to the Ministry of Mines and Energy, it is necessary to carry out studies to improve the quality of Colombian coke and so that international standards can be met
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