The predicted increase in steel demand in Asia
will provide opportunities for the establishment of newer steel
making technologies in preference to the traditional technology of
the integrated blast furnace. The two new processing routes will be
direct reduction of the iron ore (DRI) to produce a feedstock, as
an alternative to scrap, for the Electric Arc Furnace (EAF), and
direct smelting processes. The smelting reduction processes do not
require the use of coking coal or scrap iron, rather they are able
to use iron ore or DRI and thermal coals
directly.
A number of Direct Smelting processes for the
direct production of hot metal from iron ore or DRI are being
developed around the world. This is being driven by the desire
for:
-
the
ability to utilise cheaper and more abundant raw materials such as
non-coking coals and non-agglomerated ores,
-
smaller
economic plant sizes and,
-
reduced
capital costs and environmental problems through the elimination of
coke ovens and sinter/pellet plants.
The benefits are:
-
competitive hot metal,
-
flexibility of operation, and
-
the
product can be fed to an EAF for steelmaking.
The metal produced from such processes is a
premium grade product which has a high value in use to an EAF
steelmaker compared to alternative DRI
materials.
At this stage the only direct smelting process
that is in commercial operation is the COREX process with
plants operating in South Africa, Korea, India and the USA. The
COREXprocess is a two-stage process. In the first
step the iron ore is reduced in a shaft furnace. In second step
the reduced iron ore is melted in the melter gasifier using the
energy generated from the gasification (and partial combustion)
of coal. The reducing gas produced in this second stage is used
in the shaft furnace.
The coal used in the COREXprocess must supply
heat for the devolatilisation of the coal, the gasification of the
char and the melting of the reduced iron from the reduction shaft.
It must also provide sufficient gas to the reduction shaft to
reduce the iron ore feed. Coals most suited for use with the
COREXprocess have an air
dried fixed carbon content from 55 to 70%. Many coals from the
Bowen Basin within Queensland are suited to the COREXprocess and several
mines currently supply POSCO’s plants in
Korea.
This is to ensure good gas flow within the melter
gasifier and to reduce the carry over of coal and/or char. The
amount of fine coal (minus 5 mm material) that is fed to the
COREXprocess must be
minimised. Therefore all coals must be sized or agglomerated before
use.
There are many alternatives to achieve minimum
fines content depending on the facilities at the loading port,
discharge port and COREX®
plant.
The flexibility of Queensland coal export terminals allows the
sizing and blending of coals at the loading port to meet the needs
of COREX®
operators.
