Sloss..worth a visit.

So, you find yourself driving I-65, I-59, or I-20 in Alabama, maybe somewhere near Birmingham. May I recommend a side-trip to the Sloss Furnaces National Historic Landmark.

First, a little background on the relatively new city of Birmingham. By design, the city was located at the intersection of two railroad lines and on top of a massive mineral deposit in the Jones Valley, at the southern end of the Appalachian mountain chain. The growing railroads and heavy industry needed iron, and lots of it. A group of investors founded the Elyton Land Company in 1870 to capitalize on this trend. They quickly purchased land in the valley and planned the development. After six months of selling lots and attracting residents, the city was chartered by the state in 1871. Everything seemed to be going well, until the influx of new residents overwhelmed the water and sewage resources in the valley. A cholera epidemic took hold in valley and temporarily slowed the city’s growth. This was followed by an economic panic in 1873. The plan got back on track in 1878 when the Pratt Coal and Coke Company got coal mines into production. This was followed by the opening of several blast furnaces.

Between 1880 and 1890, the production of iron sky-rocketed and helped the rapidly growing Birmingham earn the moniker “Magic City.” By the turn of the century, Birmingham became the leading industrial and transportation city in the region. Of course, that couldn’t last forever, and through the tumult of the 20th century, the city had valleys and peaks in its fortunes. Iron is no longer the sole financial backbone of Birmingham, but the remains of its legacy industry are still visible all over the city. Just east of downtown, a major remnant of the glory days are the Sloss Furnaces, which closed down in 1970.

Originally built in 1881 by James Withers Sloss as the City Furnaces, it was one of many blast furnaces built to exploit the iron, limestone and coal deposits underfoot. It started production in 1882. In 1886, Sloss, an original investor in the land company, sold out and retired. Under the new management, Sloss-Sheffield Steel and Iron, began expanding production. By the time World War One broke out in Europe, the company was a leading producer of pig iron.

The Number 2 furnace and cast shed at Sloss.

By the way, what on earth is pig iron? Basically, it is an intermediate form of the iron, on its way to becoming something else, most commonly steel.

The central fixture of Sloss, or any other furnace operation is the blast furnace. It’s an up-right cylinrical vessel made of a heat resistant material such a steel and lined with bricks. Sloss currently preserves two 400 ton furnaces dating to the late 1920s. They were supported by steam boilers driving massive reciprocating “blowing engines” from the first decade of the 1900s. These were replaced with two steam turbine driven cetrifugal blowers in the middle 1900s. There are a number of other structures that provided support for the furnaces, including cast sheds, stock tunnel, railroad sidings, pyrometer house, and a power house.

From overhead, it makes more sense than seeing it at ground level. The “blowing engines” are in the large central building. Below that are the boilers. On either side of the central building are the hot blast stoves. Then forming left and right wings are the blast furnaces and cast sheds. Above each cast shed are slag pits, and running the length of the complex on the other side is the stock tunnel.

Input and output from the blast furnace.

Iron ore, coal, and limestone were first dumped into the stock tunnel from a rail car. Coal was used to feed the boilers and to make “coke,” a high carbon fuel with very few impurities. Waste gas was directed into the hot blast stoves to pre-heat the air that would be sent into the blast furnaces. Skip hoists, running continuously from the stock tunnels, loaded iron ore, limestone and coke into the top of the blast furnaces while 1400 degree Fahrenheit high pressure air was directed in from the bottom. The furnace maintained an internal temperature of 3800 degrees Fahrenheit. About every four hours, molten iron and the byproduct slag were released from the bottom of the furnace. The molten iron was directed into the cast shed where it was cooled in the form of pig iron ingots.

Fire boxes under the boilers with air handling equipment to feed in more oxygen for an efficient burn.

The hot blast stoves turned heat from waste gases from the boilers into preheated air for the blast furnace.

Until 1949, Four reciprocating blowing engines used steam to compress air for the blast furnaces.

After 1949, the steam from the boilers was directed to turbines that spun high-speed blowers. Here the covers are lifted to show the internal workings. The upper photo is the turbine and the lower is the centrifugal blower.

Blast furnace number one as seen from inside the cast shed. The channel leading away from the furnace carried the molten iron out onto the sand floor for casting or into a ladle car outside the shed.

The sand floor would be prepared with trenches for the molten metal to follow after being poured out.

The ladle car carried the molten iron to a conveyor belt-style pig iron casting system. This method cast the pigs faster by cooling them with a water spray and automatically dumping them into a waiting rail car.

I hope this has sparked your imagination and got you wondering about the cool stuff happening inside the massive industrial facilities you pass every day. Speaking of everyday, this technology is pretty old, but still essential to modernity. A nation without blast furnaces is doomed to third world status. Read more about iron making here.

Thanks for visiting, and don’t forget the gift shop on your way out!