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Abstract

During iron ore sintering the moisture content of the lower bed increases because of condensation. It is commonly assumed that the solids, gases and water there are at the equilibrium dew-point condition, giving a constant steady-state waste-gas temperature of between 50 and 60°C for a large part of the sintering period. Gas flow and waste-gas temperature results obtained from laboratory pot tests were examined as the starting-point of an attempt to elucidate the condensation mechanism. Measurements of moisture were also taken for sinter tests terminated before burnthrough. Simple heat and mass calculations show that the proposed equilibrium conditions are most probably not achieved in practice. An alternative hypothesis is offered that affords an explanation of why condensation occurs even when the gases appear capable of carrying the evaporated water and of why steady-state waste-gas temperatures are within such a narrow range—and increase in value slightly during a test. With an increased quantity of porous ores the moisture of the wet zone increases and the waste-gas temperatures could also drop. It is concluded that condensation of water, regardless of the level of moisture, should not be a problem if the bed permeability is high and uniform. Countermeasures to raise waste-gas temperatures are also discussed.

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Changes in water distribution when sintering porous goethitic iron ores

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