Water jacket furnace (metallurgy)

[3] Water jacket furnaces began to be common in the later part of the century, from the 1880s, particularly for smelting sulphide ores.

[8] A water jacket furnace can be used to reduce non-ferrous oxide ores mixed with coke, to produce metal and slag.

The conventional blast furnace process produces molten metal by reducing the ore, and separating out the silica as slag.

The smelting of sulphide copper ores in a water jacket furnace can be viewed as concentrating the non-ferrous metallic portion of the ore, as matte, and separating out some impurities, such as silica and iron, in the mainly iron silicate slag, and much of the sulphur, as sulphur dioxide in the off-gas.

Sulphide copper ores could be smelted without first roasting the ore. Production per furnace was generally higher.

Low grade ore could be smelted, because the water jacket furnace could more readily discharge large amounts of molten slag.

It could not use the cheaper fuels such as firewood or fine raw coal that could be used to fire a reverberatory furnace.

However, they were also more versatile, being a readily scalable technology; large or small furnaces could be made, and would operate effectively.

However, this was in one way an advantage over reverberatory furnaces that operated as a batch process with around 24 hours typical duration.

The associated cycles of heating and cooling of a reverberatory furnace led, over time, to damage of its masonry and higher maintenance and downtime as a result.

[17] In contrast, a well-operated water jacket furnace might achieve years of operation before needing new fire bricks.

[21] to ensure that the noxious gases from smelting, largely sulphur dioxide, were carried far from the smelter and any nearby settlement.

In contrast to a conventional blast furnace used to make iron, lead metal or copper matte and slag were run off more or less continuously.

The molten copper matte run from such a furnace, under this arrangement, still contained a proportion of slag.

The copper matte was run first into a vessel known as a 'settler' to allow any slag to accumulate on the surface, from where it could overflow from the settler.

In that case, the furnace was completely sealed, to allow the zinc to be recovered, from flue gases, in its vapour phase.

Smelters such as the Great Cobar mine were struggling to achieve economic operation, as early as 1912, despite buoyant copper prices.