<Original Paper>Relative Ignition Temperatures of Copper Sulfide Concentrates and Other Flash Smelting Feed Materials

The oxidation of copper sulfide concentrate and other flash smelting feed materials like pyrite, coke and coal has been studied using the Differential Thermogravimetric Analyzer (DTGA). The relative ignition temperature of the different materials under ignition conditions with a particle size ranging from 37 to 45 microns are 326 to 390℃ for copper concentrates (with varying tendencies to ignite), 410℃ for the calcined Lepanto copper concentrate, 457℃ for pyrite, 433℃ for metallurgical coke and 498℃ for coal. Decreasing the particle size for all materials resulted in increased reactivity. It is also observed that some copper concentrates are more susceptible to the effect of particle size than others. The variation of oxygen concentration from 33 to 100% in the reaction gas did not have a significant shift but rather tends to vary the steepness of the DTA curve. Low oxygen concentration showed tendencies for stepwise reaction. Several copper concentrates tested under conditions of 20mg sample weight with the same particle size, heated at a rate of 30℃/min in oxygen flowing at 30ml/min showed differing tendencies to ignite. Mixing the most reactive copper concentrate with a less reactive one significantly lowered the ignition temperature of the resulting blend. The differing levels of reactivity can be explained by the mineral phases present in the copper concentrates. From the results of x-ray diffraction, the presence of covellite (CuS) mineral could have initiated the ignition reactions for the Erzteast copper concentrate. Copper concentrates that are predominantly composed of chalcopyrite (CuFeS_2) with bornite (Cu_5FeS_4) and pyrite (FeS_2) ignited at a higher temperature. These results were supported by conducting ignition temperature experiments using synthetically prepared covellite, chalcopyrite and bornite