SINTERING REACTIONS BETWEEN A COMPLEX CHINESE IRON-ORE CONCENTRATE AND AUSTRALIAN ORES

A study has been undertaken of the sintering behaviour of the complex domestic iron ore concentrate that is used by the Shanghai Meishan Met allurgical Corporation, Nanjing, People's Republic of China. The ore c ontains significant siderite, magnetite and hematite, and studies carr ied out with an infrared-image furnace showed that the siderite has a very significant influence on its sintering behaviour. On the basis of the experimental findings and published information it is proposed th at decomposition of the siderite starts at around 400 degrees C and re sults in the formation of carbon monoxide (and/or hydrogen via the wat er-gas shift reaction), which then reduces the hematite present in the ore to magnetite prior to the initiation of high-temperature sinterin g reactions. This gaseous reduction process is extremely effective and particles of Australian hematite and pisolite ores, when mixed with t he concentrate, also undergo significant reduction. A consideration of the calcination and reduction equations indicates that carbon monoxid e is probably not the only gaseous reductant to be generated during th e calcination of siderite. As the reduction process is so effective, t he subsequent high-temperature sintering reactions essentially involve magnetite and the fluxes, Consequently, the low-temperature forms of the bonding phase silico-ferrite of calcium and aluminium (SFCA) canno t form, even at high sinter basicity. The results obtained with the be nch-scale furnace were confirmed on a pilot-scale sintering facility. The pilot-plant sinters consisted mainly of magnetite, high-temperatur e SFCA and glass, which is typical of sinters formed from mixes that-c ontain high levels of magnetite ore.