Competition is picking up in the electric-arc
furnace (EF) zinc dust recovery business. The frontrunner in
the industry, Monaca, Pa.-based Horsehead Corp., scored a coup
late last year, when it signed a long-term agreement to handle
all of the baghouse dust from Nucor Corp.'s three steel mills
in the Carolinas its Darlington, S.C., bar mill; its Berkeley
County sheet mill; and the Nucor Steel-Hertford plate mill in
Cofield, N.C. (AMM, Dec. 27).
Horsehead, which gathers spent zinc dust from
mini-mill melt shops and skimmings and drosses from hot-dip
galvanizers to refine into reusable zinc oxides and Prime
Western Grade zinc metal, plans to build new regional EF dust
recycling facilities near Nucor's Carolina steel mills and have
them on-stream by 2009.
Horsehead now has four facilities that handle
baghouse dust its Palmerton, Pa., plant north of Allentown in
eastern Pennsylvania, a plant in Chicago, another in Rockwood,
Tenn., and a fourth in Beaumont, Texas. It started up a second
Waelz kiln at its Rockwood plant late last year, doubling the
EF dust-processing capacity there.
Three of its plants use the Waelz kiln
process to winnow away other metals and materials and enrich
its zinc content. Baghouse dust from mini-mills typically
contains about 20-percent zinc until processed in Horsehead's
kilns, which raise the zinc content to about
Ali Alavi, Horsehead's vice president of
corporate administration, said that while the company uses
Waelz kilns at three of its facilities, at Beaumont it uses its
own flame-reactor technology developed at its Monaca plant.
"It takes the EF dust and produces the same
product at the end of the day. It is just a slightly different
process," he said.
Horsehead ships some reclaimed zinc to its
zinc calcinators to further refine the zinc to the
upper-60-percent level and yield a by-product called
polymetallic concentrate. This is shipped to its Bartlesville,
Okla., facility, where a hydrometallurgical process makes zinc
calcine to serve as feedstock to produce zinc metal and zinc
Horsehead's Waelz kilns produce two distinct
products, Alavi said. One is a crude zinc oxide product that is
shipped to Monaca for further refining. The other is an
iron-rich material called IRM, which Horsehead sells primarily
for use as an aggregate in the asphalt industry and as an iron
source in the cement-making process.
"The crude zinc oxide affords the company
more opportunities," Alavi said. "We can do a couple of things
with it. Some we take to our Monaca facilities, where it is
refined into Prime Western Grade zinc. Some of its metal output
is sold to hot-dip galvanizers." Horsehead then takes back the
skimmings and drosses and once again reclaims the material.
The zinc metal and zinc oxides that come from
Horsehead's Monaca plant are derived from recycled metals. "The
company does not use zinc concentrate or zinc ore. Clearly that
has been our model, so I certainly think our business model is
one that promotes the principles of sustainable development,"
Horsehead's newest competitor is Steel Dust
Recycling LLC (SDR), led by veteran zinc industry executive
Russ Robinson. His company has built a Waelz kiln facility in
northwestern Alabama to recycle 110,000 tons of EF dust
annually, much of it from SeverCorr LLC's new steel mill in
Columbus, Miss. Robinson, former president of Houston-based
U.S. Zinc Corp., and Tom Knepper, a Waelz expert, formed SDR a
little more than a year ago.
The Waelz kiln is the preferred technology
for treating EF dust, Robinson said. A lot of money has been
spent over the years on other technologies to process and treat
EF dust, but most of them haven't worked as well as the Waelz
kiln, he said.
About 25 percent of SDR's feedstock will come
from SeverCorr's 1.5-million-ton-a-year sheet steel mill. If
SeverCorr expands as planned to 3 million tons, it would supply
up to 50 percent of the material fed into the kiln, Robinson
In addition to the SeverCorr mill, SDR is
looking to pick up material from other EF mills in the southern
United States. At its opening ceremonies in mid-July, Robinson
noted that steel mills in the region are busier these days and
that his company was already thinking about expansion.
SDR will recover zinc from the dust and
supply it to zinc smelters and refiners in North America and
around the world. The remaining steel-based slag will be
available to cement producers or for road aggregate.
"You are taking electric furnace dust that
has approximately 20-percent zinc and you are upgrading to
60-percent zinc," he said. "At 60-percent zinc, it can be sold
to zinc smelters around the world as a substitute for zinc
concentrate. The smelters will further refine the zinc and sell
it back to the galvanizing industry. It's sort of a full-circle
When dust arrives at the SDR plant, it is
pelletized with water and coke, then charged into the kiln. In
the kiln's reaction zone, the metal oxides are reduced at about
1,100 degrees Celsius so that zinc and lead emerge from the
charge as metal vapors. The hot, dust-laden gas is then cooled
and the zinc oxide is collected in a precipitator.
Most of the zinc trapped in the EF melt
shop's baghouse comes from automotive shredded scrap because
all auto bodies are galvanized before they are painted. Basic
oxygen furnace steel mills don't generate this zinc-rich dust;
it is solely a by-product of the mini-mills' melt shops.