The product of this converter is acid steel produced as in the Bessemer process except that the Tropenas converter directs its blast against the surface and not through the metal. Fig. 137 shows a Tropenas converter in cross-section. The lining is the same as that for an acid Bessemer converter, and the tuyeres, arranged in two horizontal rows in the side of the converter, are formed of lining-bricks with holes through them. The lower tuyeres, used throughout the blow, are called the reaction tuyeres and they open into the main wind box C. The upper tuyeres, used during the latter part of the blow, are called the combustion tuyeres, and open into the auxiliary wind box D. The advantages claimed for this converter are (1) the blast pressure is very low (not over 5 lbs.) as it is not forced through the metal, and therefore requires a less powerful blower; (2) the surface impact agitates the metal less, causing it to take up less gas than the through blow; and (3) the combustible impurities in the metal are more completely burned.

Fig. 137. - Converter for Steel Foundries.

The converter is charged with very hot metal from the cupola, the blast is admitted through the lower tuyeres, and the burning out of the impurities proceeds as in the acid Bessemer process. As the blast enters through the tuyeres, it strikes the surface of the metal at an angle, agitating it slightly, and when the flame from the mouth of the converter begins to die down, air is admitted through the upper tuyeres for a greater supply and better distribution of oxygen. The blow lasts but a few minutes, and when the flame dies out, the recarburizer is poured in and stirred. The steel is then poured into ladles and taken to the moulds.