Lead-Smelting Processes The major smelting processes to
recycle lead scrap involve the use of blast furnaces, short
rotary furnaces, long rotary kilns, reverberatory furnaces,
electric furnaces, and top-blown rotary furnaces.
Blast Furnaces
For many years blast furnaces were the primary furnace for
recycling lead. Blast furnaces are used to recycle slag,
dross, and residues from other processes. Blast furnaces
require metallurgical coke, produce large volumes of gas
that must be filtered, require a special charge, require
afterburners to burn carbon monoxide contained in off-gases,
and produce slag and matte that, in some cases, may be
considered hazardous materials. Blast furnaces produce a
bullion that is high in antimony; this bullion can be
readily refined into lead-antimony alloys.
Rotary Furnaces
In most of the world other than the U.S., rotary furnaces
(long, short, and top blown) have replaced blast furnaces as
the major smelting vessels for lead recycling. Rotary
furnaces are very versatile. They can accept virtually any
type of lead-bearing feed material, including battery scrap,
dust, dross, scrap lead, and sludge. Rotary furnaces can use
any carbon source such as coal, coke, or ebonite as reducing
agent, and they can use a variety of fuels, such as oil,
coal, or gas. Because they are batch furnaces, rotary
furnaces can be operated in stages to produce low-impurity
bullion for refining to pure lead, or they can completely
reduce the charge to recover all metal values for production
of lead-antimony alloys. Rotary furnaces generally use
Na2CO3 and iron as fluxes, which produce a fluid,
low-melting slag.
