METHOD OF HEAT TREATMENT OF WASTES CONTAINING HEAVY METALS AND FERRIC OXIDES Russian patent published in 2003 - IPC

FIELD: heat treatment of wastes containing heavy metals and ferric oxides, such as dusty wastes of electric steel melting processes or sludge of converters for production of steel. SUBSTANCE: for this method multiple-hearth furnace is used with several hearths located one above the other. Method contains steps of continuous charging of wastes to the uppermost hearth of furnace, their progressive movement to underlying hearths, supply of reducing agents to the uppermost and/or to the underlying hearths, interaction of reducing agents with wastes with generation of directly reduced iron and heavy metals, evaporation of heavy metals, separate suction of gases containing heavy metals at the level of those hearths whereon evaporation of these heavy metals takes place, unloading of directly reduced iron along with the remains of reducing agents in zone of the lowermost hearth and suction of gases from multiple-hearth furnace below those hearths whereon evaporation of heavy metals takes place. In so doing, gases being sucked off below hearths on which evaporation of heavy metals takes place are totally or partially injected again to multiple- hearth furnace above the level of these hearths. EFFECT: utilization of wastes, such as dusty wastes of electric steel melting processes or sludge of converters for production of steel. 21 cl, 1 dwg, 1 tbl