File:Annual report of the State Mineralogist for the year ending (1883) (p. 822).png

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LEAD SMELTING IN SPAIN THE CASTILIAN BLAST FURNACE. This blast furnace is quite small in comparison to those used in this country, its dimensions being only about eight feet high and three feet internal diameter.

It is represented in Figs. 21 and 22, and constructed of firebricks molded into the shape required. The shaft thus constructed is surmounted by a box-shaped hood, in the sides of which the feeding door and flue are fitted.

This is closed on top by an arch or dome of brickwork laid tightly in clay.

The breast is formed by an iron pan, having on its upper edge a lip to allow the slag to flow off, and on one side a long narrow slot for tapping or drawing off the reduced metal. The bottom of this furnace is made in the following way: A mixture of fire clay and coke dust is slightly moistened and stamped or beaten into the hearth bottom until it reaches the top of the breast pan. This is hollowed out in the usual way to form a cavity for the collection of the reduced metal and allowed to dry thoroughly before the apparatus is used.

The blast is applied by three tuyeres having a diameter of five and one half inches at the receiving ends and three inches at the nozzles.

The blast is conducted to them through brick channels placed under the floor of the furnace house.

The structure is well secured by several iron bands encircling it, and the hood is supported by four iron columns as shown in Figs. 21 and 22.

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In working this furnace the charge should never contain over a third of its volume in lead. If richer ore is to be treated, it must be reduced to this proportion by the addition of poor slags.

To prevent the walls from getting too hot, and preserve the bricks from burning or melting, care has to be taken in charging to throw the fuel towards the center and the ore towards the walls. Attention has to be paid to the proper regulation of the temperature, as a too high degree of heat will cause loss of lead by volatilization. As long as the slag flows liquid and readily, the cooler the furnace is kept the better.

Some ferruginous ore is usually added at intervals during the operation.

The slag flows continuously into cast-iron wagons, from which it is dumped after having cooled down.

The advantage of this is that if at any time the furnace should run lead or matte, it can easily be recovered.