Open-hearth furnace

[1] Because steel is difficult to manufacture owing to its high melting point, normal fuels and furnaces were insufficient for mass production of steel, and the open-hearth type of furnace was one of several technologies developed in the nineteenth century to overcome this difficulty.

In 1865, the European engineer Pierre-Émile Martin took out a licence from Siemens and first applied his regenerative furnace for making steel.

Preparing a heat usually takes eight to eight and a half hours, and longer to finish the conversion into steel.

[4] 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.

Through this method, an open-hearth furnace can reach temperatures high enough to melt steel, but Siemens did not initially use it for that.

[5] 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.

This was an advantage in the early 20th century, 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 idea is to burn away excess carbon and impurities with oxygen blast instead of free flame formation.

[7] This is similar as the AJAX furnace, which also uses oxygen blow instead of free flame formation and regenerator chambers.

India's SAIL shut it down in April 2020 with the advent of COVID19 because of nonavailability of manpower to run the labor intensive process.