A process for intensifying the roasting of ores in superposed hearth furnaces by recycling the combustion gases

摘要

PICT:0863001/III/1 In a superposed hearth furnace for roasting sulphides or arsenic ores throughput is increased and even heating obtained by recirculating a proportion of the effluent gases after passing through a waste heat boiler c, through a pipe e, dust separator f, fan g and pipe h back to several of the lower hearths under control of valves h1, h2, h3. The ore is fed into the furnace by a hopper k, preferably on to the top drying hearth j. Thereafter it traverses the remaining hearths j1-j4 &c. either successively or alternately through part of the furnace. Certain middle hearths may be overfed by part of the dried ore or by ore from the upper hearths.