The furnace had two ducts leading each to a chamber of brick checkerwork. In use, the hot exhaust fumes were passed out through one duct, heating the brick to high temperature, while air intake was through the other. Periodically the streams were reversed, so that the incoming air was preheated by the hot brick before passing the burners, thus greatly increasing the flame temperature. Some furnaces were liquid-fueled, but if the fuel was gaseous it might have been fed in with the air.
In the basic process, the charge was of iron ore, scrap steel, and limestone. The impurities in the ore combined with the limestone to form a basic slag. In the less important acid process, refractories of silica resulted in an acid slag.
Related category INDUSTRIAL CHEMISTRY
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