Formcoke production from char fines of hard brown coals by air curing

Abstract

The purpose of the present study was to explore the technical feasibility of formcoke production from non-coking bright hard brown coals and pitch as a binder by air curing. The briquettes obtained from the chars of Soma coals carbonised at 500, 600, 700, 800 and 900°C with 12% pitch were air cured in a streaming gas containing 16%O₂(air + N₂) for 120 min at 270°C and the formcoke strength was found to be 10–40% higher than that of raw briquettes. Under the prevailing conditions, the formcoke strength and the apparent specific gravity of the green and formcoke briquettes increased as the carbonisation temperature increased, reaching a maximum at the optimum carbonisation temperature of 800°C. M₄₀ and M₁₀ values and the compressive strength of SK800 formcokes were determined to be 92·3, 7·7% and 23·5 MPa respectively being similar to those of conventional cokes produced at coke ovens. The optimum curing conditions (pitch content, curing time and temperature) were determined using TK800 char. The optimum curing time for TK800 briquettes at 220°C was determined to be 90 min. The formcoke strength of TK800 briquettes subjected to a thermal treatment at 220°C was lower than that of the briquettes air cured at the same temperature. The optimum curing temperature for TK800 briquettes with 10% pitch and cured in a gas stream containing 16%O₂ in terms of formcoke strength was determined to be 285°C. M₄₀ and M₁₀ values and the compressive strength of TK800 formcokes were determined to be 91, 8·1% and 19·6 MPa respectively. The experimental results reveal the advantages of the method because the formcokes produced possess suitable properties for various metallurgical processes and smokeless fuel consumption. The gas and tar obtained during the carbonisation of raw coal are the added benefits.