BLAST FURNACES

The Minnesota Steel Co. built two blast furnaces with each capable of producing 750 tons of hot metal per day, an output about average for the time but a pittance by today's standards. These furnaces were of quite unusual design. The furnace shafts were enclosed by lattice girder framing with corrugated siding from the mantle to the top platform, an addition rarely seen, but needed in the cold northern Minnesota winters. The downcomers were typical of the era having four downcomers coming off of four uptakes, joining to two where they entered the dustcatcher.

In 1943, US Steel dismantled the blast furnace at its Joliet Works in Illinois and moved it to Duluth. The existing south furnace was dismantled and the Joliet furnace was installed in its place. Iron tonnage increased significantly. The north furnace was mothballed.

The real outstanding, and singular, aspect of the early furnaces were the stoves. While not unusual for the time in that they were of the three-pass type, the stoves numbered five and the exhaust gases were channeled from each stove through offtakes and breeches to a single tall stack on top of the center stove. The usual practice was to have a single stack on top of each stove.

As for hot-metal transport, Kling cars, a type of hot metal car with a partially covered ladle, were most likely used, as opposed to more modern bottle cars. Slag was granulated by water in pits next to the furnace. This slag was transported to the Universal-Atlas cement plant to be made into Portland cement.

	The two blast furnaces, under construction, from the highline side. The stoves are unusual with the exhaust gas pipes brought together into a single stack on top. Note the enclosed highline trestle to cope with the cold Minnesota winter.
There were two furnaces each with a capacity of 750 tons of molten iron a day. Note the corrugated siding around the furnace shell, the four downcomers coming off the top and the unusual exhaust gas collection piping on top of the stoves.
	The highline is a trestle running in front of the furnaces where the iron ore, limestone and coke are dumped in bins underneath the tracks. The material is transferred underneath the highline by a scale car (small railroad hopper car) after weighing and dumped into a chute feeding the skip hoist which brings it to the top of the furnace. According to an early article on the works, iron ore was not stockpiled in the ore yard, but was brought directly from the mines via the DM&IR to the highline. In winter, the ore came from the underground mines on the Vermilion and Mesabi Ranges and in the spring, summer and autumn from the Mesabi open-pit mines.