While he also prevents interruption of the operation by means of water-jackets, he uses hot-blast, and produces, besides metallic lead, large volumes of lead fumes which are drawn off by fans through long cooling tubes, and then forced through suspended bags which filter off the dust, called "blue powder."
When, however, a hot blast is used on highly sulphuretted copper ores, a concentration of 8 of ore into i of matte is obtained, with a consumption of less than one-third the fuel which would be consumed in smelting the charge had the ore been previously calcined.
It is smelted raw with hot blast in cupola furnaces, the largest being 2 10 in.
This is reconcentrated raw in hot-blast cupolas to 55%, and blown directly into copper in converters.
James Beaumont Neilson Open Each hot blast furnace gave work to 400 men.
