Weathering study of an industrial coal blend used in cokemaking

Weathering studies were carried out on a coking coal blend prepared and ground at industrial scale and stored in the open yard. This typical and complex blend, composed of 13 different coals was used by the Spanish Steel Company. Several methods were applied for detecting weathering in the blend. Gieseler maximum fluidity was the most sensitive indicator of the loss of thermoplastic properties. Carbonization tests were carried out in a movable-wall oven and a semi-industrial oven of 6 t capacity. In addition to the measurements of internal gas pressure and coking pressure, laboratory tests were performed to measure expansion/contraction behaviour of the coal blend. A clear decrease in internal gas pressure with weathering was observed in the semi-industrial oven. As regards coke quality, no significant changes were produced in a storage period of ten months, however after this date impairment was observed.