Saturday, October 11, 2014

Bay Furnace: One of only Two Blast Furnaces Remaining in the U.P.

On the way back to Grand Marais last weekend, my sister and I stopped by the Bay Furnace, located in Christmas, MI.  Originally there were 29 blast furnaces in the Upper Peninsula of Michigan that were used to melt down and purify iron ore.  Only two sites remain including the Bay Furnace and Fayette.  Iron ore was first discovered in the U.P. in the 1840s.  Although the iron ore rock mined in the Upper Peninsula has up to 72 percent iron, it was necessary to remove the impurities and extract the iron.

Iron is purified from iron ore in a huge container called a blast furnace. Beginning in the 1840s in Michigan's Upper Peninsula, iron ores such as hematite and magnetite were mined and then transported to blast furnaces.  To purify the ore, the rock was added to the blast furnace along with limestone and charcoal.  The mixture was heated  to around 2282°F (1250°C) almost 300 degrees below iron's melting point of 2786°F (1538°C).

In this reduction reaction, the charcoal was used to heat the mixture and add carbon to the chemical reaction.  The limestone served as a flux that helped to catalyze the desired reaction and chemically bind to and remove impurities, such as silica.  In this reaction, the iron oxide was reduced to iron, the carbon was oxidised to carbon dioxide, and the impurities were formed into slag, which was separated and removed.

The Bay Furnace site has several interpretive signs.  To read the information in the photos below, click on the individual pictures.


Below are photos of pig iron bars and slag impurities.


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