Iron ores, salt and sandstones . t, the bosh or work-ing part of the furnace. Above the bosh is the stack or heatintercepting part gradually increasing in diameter to the bosh contracts downward so that the materials whichhave descended to this part, may be held up until the fuelis burned away at or near the top of the bosh; and the thenmelted pig iron and slag gradually drop to the hearth or reason of difference in density, the slag and pig ironseparate from each other and are tapped out in a fluid con-dition from the furnace. The inner lining of the furnace is composed of fir
Iron ores, salt and sandstones . t, the bosh or work-ing part of the furnace. Above the bosh is the stack or heatintercepting part gradually increasing in diameter to the bosh contracts downward so that the materials whichhave descended to this part, may be held up until the fuelis burned away at or near the top of the bosh; and the thenmelted pig iron and slag gradually drop to the hearth or reason of difference in density, the slag and pig ironseparate from each other and are tapped out in a fluid con-dition from the furnace. The inner lining of the furnace is composed of fire brickor blocks backed by brick of lower grade and separated fromthe metal sheeting by a narrow space filled with granulatedslag. The bosh is usually lined with water-cooled metalplates. The top of the furnace has a cup and bell arrange-ment which closes the mouth except at the moment of charg-ing. The hot furnace gases can thus be collected below the s Iron and Steel Manufacture, p. 188 and ff. 84 METALLURGY OE IRON AND Fig. 2. Section of one of the Duquesne Blast Furnaces (Henry in Bng. & Min. Journal). GG, flanges on the ore bucket; HH, fixed flanges on top of thefurnace; J, counterweighted false bell; K, main bell; O, tuyere; P,cinder ratch; RR, water cooled boxes; S, blast pipe. WEST VIRGINIA GEOLOGICAL SURVEY. 85 bell and conveyed in pipes to be used for heating the ainblast. The cup is shaped like the wider portion of an invertedhollow cone, while the bell is made to fit the lower edge ofthe cup and is suspended from a balanced and weightedbeam. The charge of materials is dumped into the circular-tapered trough thus formed, and over-balancing the weightedbell beam, the bell descends and the materials slip into thefurnace. After the load is thus removed, the bell automati-cally rises and closes the mouth of the furnace. A hydraulicpiston arrangement prevents any sudden downward orupward movement, giving a smooth and uniform size and design of th
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