Changes in water distribution when sintering porous goethitic iron ores

During iron ore sintering the moisture content of the lower bed increases b ecause of condensation. It is commonly assumed that the solids, gases and w ater there are at the equilibrium dew-point condition, giving a constant st eady-state waste-gas temperature of between 50 and 60 degrees C for a large part of the sintering period. Gas now and waste-gas temperature results ob tained from laboratory pot tests were examined as the starting-point of an attempt to elucidate the condensation mechanism. Measurements of moisture w ere also taken for sinter tests terminated before burn-through. Simple heat and mass calculations show that the proposed equilibrium conditions are mo st 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 was te-gas temperatures are within such a narrow range-and increase in value sl ightly during a test. With an increased quantity of porous ores the moistur e 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 moi sture, should not be a problem if the bed permeability is high and uniform. Countermeasures to raise waste-gas temperatures are also discussed.