Architect 2014-02.pdf

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ARCHITECT the AiA mAgAzine February 2014 WWW.arCHITeCTMaGaZINe.COM
mind & matter
Iron Man
Steel iS the world’S moSt widely recycled material, but itS high
embodied energy iS roughly equivalent to that of concrete.
a new method to extract iron from virgin reSourceS might
give the metal alloy the environmental edge after all.
Text by Blaine Brownell, aia
Illustration by Jameson simpson
With a manufacturing process responsible
for 7 percent of the world’s carbon-dioxide emissions,
concrete often gets a bad rap. But steel,
frankly, is no better. Steel production is the
second-largest industrial consumer of energy.
To improve steel’s track record in this area,
researchers at the University of Utah have developed
a flash-forming reduction technique that
produces iron—the primary component of steel—
in a more efficient manner. Typically, liquid iron
is smelted from a mixture of iron ore, limestone,
and coke (a high-carbon fuel made from coal) in
a blast furnace, requiring a lot of heat and forced
air. Instead of using coke, the Utah researchers’
flash iron-making process uses hydrogen or
natural gas to extract the iron particles through
reduction. “These gases … have a greater affinity to
oxygen than iron,” says Hong Yong Sohn, a professor
of metallurgical engineering and an adjunct
professor of chemical engineering at the university.
“Thus, they remove oxygen from iron oxide
in iron ore, leaving iron in the metallic state.”
This approach can leverage the large quantity
of iron ore concentrate—particles smaller
than 0.1 millimeter—that is produced in the
United States and other countries, and bypass
the intermediate step of forming the particles
into ½-inch pellets before ironmaking. Steel producers
could streamline the process further by
making steel in the same vessel as the molten
iron and foregoing the blast furnace altogether.
The technology, which may require another
three to five years to reach commercialization,
would slash the energy requirements needed to
make iron by half, Sohn says. It would also emit
only 0.04 metric tons of CO 2 per metric ton of
iron—a 97.5 percent improvement over using the
conventional blast furnace.
experimental
flash reactor
1. power feeder
Using a rotating disk and
blade, this device feeds
iron ore concentrate at
a constant rate along
with the process gas,
namely hydrogen.
2. preheater
The experimental reactor
preheats the hydrogen. A
commercial reactor will be
lined with bricks to reduce
heat loss, eliminating the
need for this component.
3. flash reactor
In an environment heated
to temperatures between
1300 C and 1600 C, the
hydrogen reacts with iron
ore in seconds, producing
iron and water vapor.
3
4
4. collection chamber
This gas-tight chamber
collects iron particles in
a controlled atmosphere
to prevent re-oxidization.
The particles can be
briquetted for further use.
5
5. off-Gas scrubber
The off-gas—which has
unreacted hydrogen,
water vapor, and fine
dusts—is bubbled
through water to cool it
and remove the dusts.