TRIALS TO INJECT PULVERIZED COAL IN COMBI NATION WITH FINE-GRAINED IRON-ORES INTO BLAST-FURNACES

Objective. In view of the increasing share of fines accruing worldwide in the mining and dressing of iron ores, it was investigated and disc ussed whether a direct use of fine-grained iron oxides in blast furnac es is realisable without any agglomeration. The combined injection of pulverised coal and are fines was researched by basic experiments to d etermine the reaction mechanism, by calculations of the name temperatu re, and by means of pilot trials at a char coal blast furnace. Summ. T he findings of the laboratory experiments confirm the evaluations reac hed in previous work, namely that fine-grained iron ores can be reduce d,within a matter of milliseconds, to the state of metallic iron. Coal grades with a high proportion of volatile constituents displayed a lo wer reduction potential than low-volatile coal grades, which can be at tributed mainly to the differing devolatisation, ignition and combusti on behaviour. The calculations of the adiabatic name temperature revea led that a fall in the flame temperature can be counteracted by oxygen enrichment. In the pilot trials a facility was developed with which i t was possible to achieve continuous injection rates of up to 500 kg o re fines/h through an experimental tuyere over several hours. No incre ase in pressure to indicate a loss of permeability in the raceway was observed at the experimental tuyere.