Open Hearth Furnace - History

History

Sir Carl Wilhelm Siemens developed the Siemens regenerative furnace in the 1850s, and claimed in 1857 to be recovering enough heat to save 70–80% of the fuel. This furnace operates at a high temperature by using regenerative preheating of fuel and air for combustion. In regenerative preheating, the exhaust gases from the furnace are pumped into a chamber containing bricks, where heat is transferred from the gases to the bricks. The flow of the furnace is then reversed so that fuel and air pass through the chamber and are heated by the bricks.Through this method, an open-hearth furnace can reach temperatures high enough to melt steel, but Siemens did not initially use it for that.

In 1865, the French engineer Pierre-Émile Martin took out a license from Siemens and first applied his regenerative furnace for making steel. The most appealing characteristic of the Siemens regenerative furnace is the rapid production of large quantities of basic steel, used for example to construct high-rise buildings. The usual size of furnaces is 50 to 100 tons, but for some special processes they may have a capacity of 250 or even 500 tons.

The Siemens-Martin process complemented rather than replaced the Bessemer process. It is slower and thus easier to control. It also permits the melting and refining of large amounts of scrap steel, further lowering steel production costs and recycling an otherwise troublesome waste material. Its worst drawback is the fact that melting and refining a charge takes several hours. This was an advantage in the early 20th C.,as it gave plant chemists time to analyze the steel and decide how much longer to refine it. But by about 1975, electronic instruments such as atomic absorption spectrophotometers had made analysis of the steel much easier and faster. The work environment around an open hearth furnace is said to be extremely dangerous, although that may be even more true of the environment around a basic oxygen or electric arc furnace.

Basic oxygen steelmaking eventually replaced the open hearth furnace. It rapidly superseded both the Bessemer process and Siemens-Martin process in Western Europe by the 1950s and in Eastern Europe by the 1980s. The open hearth steelmaking had superseded Bessemer process in UK by 1900, but elsewhere in Europe, especially in Germany, the Bessemer and Thomas processes were used until the late 1960s when they were superseded by basic oxygen steelmaking. The last European open hearth furnace in the former East Germany was stopped in 1993. In the US, steel production using the Bessemer process ended in 1968 and the open hearth furnaces had stopped by 1992. The last open hearth shop in China was shut down in 2001. The nation with the highest share of steel produced with open hearth furnaces (almost 50%) is Ukraine. The process is still in use in both India and Russia.