Tests of post combustion of CO gas in 15 t pilot converter and 160 t and 250 t commercial combined blowing converter were carried out for aiming to improve heat balance.
And also coal injection test through top lance with post combustion system was carried out in 15 t pilot converter with bottom gas stirring.
Following results were obtained.
(1) The optimum amount of oxygen for post combustion was about 20% of total oxygen rate, and the jet angle of 3035° was desirable for obtaining the good condition of post combustion.
(2) The heat transfer efficiency of post combustion to metal bath was 70 to 100%.
Accordingly around 10% increase of scrap ratio was obtained.
(3) In the case of blasting of pulverized coal on metal surface, the heat transfer was nearly equal to the theoretical value and the scrap ratio increased in proportion to the amount of coal added.

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