BLAST FURNACE PROCEDURE

The objectives in Blast Furnace operation are two-fold. The first objective is to reduce the iron ore to liquid metallic iron. The second is to control as far as possible the quantities of impurities which find their way into the iron either wholly or in part.

The first intentional attempt to extract iron from iron ore in a furnace-type of container was in Catalonia, Spain (circa.1300 A.D.) where a 'Catalan' forge (basically,a scaled-up blacksmith's forge) was used to produce iron. The Catalan forge was anywhere from 20 inches square and 16 inches deep to around 30 inches by 40 inches square and something over 2 feet deep. The nozzle (or tuyere), through which the blast was blown into the furnace, was placed about 9 inches from the bottom in the smaller hearths and about 15 inches from the bottom in the larger hearths.

The hearth was filled to the level of the tuyere with charcoal, on which was piled lumps of iron ore mixed with charcoal. These materials were placed so as to form two separate columns, the charcoal against the tuyere side of the hearth, and the ore against the other side. A gentle blast of air was applied at first and the carbon monoxide, formed by combustion of the charcoal, passed through the open pile of iron ore. The ore was reduced to metallic iron when the oxygen in the iron oxide of the ore combined with the carbon monoxide to form carbon dioxide.

The waste gases escaped at the top of the charge. The metallic iron resulting from the reduction of the ore became pasty enough to form a coherent 'bloom'. After as much as possible of the ore had been reduced, the bloom was pried out of the hearth and hammered into bar form. Thus began the series of developments from the small stone-built structure capable of producing 50 tons of pig iron a year to the modern 100-foot tower with a capacity of more than 2,000 tons a day.

Les Forges Saint-Maurice in Quebec was Canada's historic first ironworks, producing castings and wrought iron bars from a charcoal-fired blast furnace in 1738. Care must be taken to distinguish between the French term 'Les Forges' and the English word 'Forge' (blacksmithing). In French historical writings, 'Les Forges' has a very broad meaning. It signifies a complete ironworks establishment. This included the blast furnace as well as the foundry, pattern shop and all the facilities for re-heating pig iron and hammering out wrought iron bars.

Usually the term also included the associated ore collection, charcoal burning, storehouses, workmen's quarters, etc., i.e. the whole pioneer industrial community. All the necessary raw materials for the manufacture of iron were found in abundance within a few miles of the blast furnace at Saint-Maurice. The blast furnace at Les Forge Saint-Maurice is known to have been thirty feet in height. It can be described briefly as a cold blast, charcoal-fired furnace employing water power for the air blast and the associated forge hammer, for making wrought iron bars. The blast furnace was eventually abandoned in 1883.

 

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Last updated February 1, 2006