Open hearth furnace

Open hearth furnaces are one of a number of kinds of electric arc furnace.

Technically perhaps, the first primitive open hearth furnace was the puddling furnaces from its application.

The Siemens regenerative furnace

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.

The regenerators are the distinctive feature of the furnace and consist of fire-brick flues filled with bricks set on edge and arranged in such a way as to have a great number of small passages between them. The bricks absorb most of the heat from the outgoing waste gases and return it later to the incoming cold gases for combustion.

Open Hearth steelmaking

  In 1865, Emile Martin and Pierre Martin took out a licence from Siemens and first applied his furnace for making Bessemer process. It is slower and thus easier to control.

LD process replaced the open hearth furnace. In the US, steel production using the inefficient open hearth furnaces had stopped by 1992. The highest share of steel produced with open hearth furnaces (almost 50%) still retained in Ukraine. (http://www.energystar.gov/ia/business/industry/41724.pdf).

Further reading

• K. Barraclough, Steelmaking 1850-1900 (Institute of Metals, London 1990), 137-203.
• W. K. V. Gale, Iron and Steel (Longmans, London 1969), 74-77.