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FINEX® Technology
Finex is an innovative
ironmaking process developed by Posco and
Siemens VAI for the production of hot-metal
based on the direct use of iron-ore fines
and non-coking coal.
The production of hot metal is simplified
because the sintering and coking steps,
necessary in the blast-furnace route, are
eliminated. |
View of Finex Plant (left: Melter
Gasifier Tower, right: Fluidized Bed Reactor
Tower), Pohang, Korea |
The Process
Fine iron ore is charged into a series of
fluidized-bed reactors together with fluxes such as
limestone or dolomite. The iron-ore fines pass in a
downward direction through four reactors where they
are heated and reduced to direct-reduced iron (DRI)
by means of a reduction gas – derived from the
gasification of the coal – that flows in the
counter-current direction to the ore.
After exiting the final reactor, the DRI fines are
hot-compacted to HCI (hot-compacted iron),
transferred to a charging bin positioned above the
melter gasifier and then charged by gravity into the
melter gasifier where smelting takes place. The
tapped product, liquid hot metal, is equivalent in
quality to the hot metal produced in a blast furnace
or Corex plant.
Briquetted coal fines and/or lump coal are charged
into the dome of the melter-gasifier, while
pulverized coal is injected into the vessel together
with oxygen. The coal is gasified and a reducing gas
is generated which is comprised mainly of CO and H2.
After exiting the top of the melter gasifier, this
gas is ducted to the fluidized-bed reactor system to
reduce the iron ore fines. A portion of the consumed
reducing gas which exits from the top of the
fluidized-bed reactor train is recycled back into
the system after CO2 removal in order to
achieve a higher gas-utilization rate. The heat
generated from the gasification of the coal with
oxygen also serves as the energy source for the
melting of the HCI to hot metal as well as for the
formation of liquid slag. Both hot metal and slag
are tapped exactly as in standard blast furnace
procedure.
The excess gas from the Finex Process is a valuable
by-product which can be used for a variety of
industrial applications such as for heating purposes
within a steel works, power generation or for
additional DRI/HBI (hot-briquetted iron) production.
Economic Considerations
The unique characteristics of the Finex process
and its ability to use low-cost raw materials means
that both capital investment and production costs
are much lower than in the blast furnace route. A
1.5-million-ton-per-year Finex plant can produce hot
metal more cost effectively than a modern
three-million-ton-per-year blast furnace. When
oxygen and power plants are included in the
comparison, the capital and operating costs of a
Finex plant will be approximately 20% and 15% lower,
respectively, than in the blast furnace route.
Environmental Aspects
The environmentally friendly nature of the Finex
process ensures that it will be even more attractive
in the future. SOx, NOx and
dust emissions are significantly lower in the Finex
Process compared to blast furnace route. This is due
to the elimination of the coke oven and sinter
plants – both major sources of emissions. The sulfur
contained mostly in the coal reacts with limestone
to form CaS, which is bound in the slag. Therefore,
there is almost no opportunity for SOx to
escape to the environment. NOx emissions
hardly occur in the Finex Process because the
metallurgical reactions take place in a reducing
atmosphere, unlike the oxidizing atmosphere inherent
in the sinter plant, coking plant and hot-stoves of
the blast-furnace route. Dust emissions are low as
well, due to the integrated and closed nature of the
Finex Process. It has also been verified that no
dioxins are generated in Finex operations.
Outlook
The further development and optimization of
Finex technology by Posco and Siemens VAI continues
with the goal to further improve the feasibility of
the process and its overall competitiveness. The
Finex Process is thus an outstanding example of a
highly successful cooperation between a plant
operator and plant builder, which allows hot metal
to be produced in a highly cost-effective and
environmentally friendly manner.
See
video of first tapping of hot metal from the
new Finex Commercial Plant at Posco's Pohang Works,
Korea (under 'More Infomation').
Simplified Flow Sheet of the Finex Process
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