Metallurgy of Key Minerals - Thanatia: The Destiny of the Earth's Mineral Resources - page 183

primary production is 1.67 t CO 2 (only BOF route) and 0.7 t CO 2 (direct reduced
iron + EAF route) respectively. For scrap production the CO 2 emissions reported
also stand at 0.7 t (only EAF route). Additional energy requirement values from
earlier studies are reported in Table 8.3.
With respect to environmental issues, the steel industry ranks as one of greatest
contributors of CO 2 emissions in the world, despite efforts to take increasing care
of all the solid residues, fumes and gases generated in all the processes through
flue-gas treatment plants. Its large quantity of emissions derives from the need of
huge amounts of coal to reduce the ore, the application of heat for melting the
metal, the fuels burnt in transporting materials and the electricity used in oxygen
production, not to mention direct consumption. Also as coal is the key feedstock for
the reduction process, the industry is traditionally located in areas with coal and/or
iron ore mines and electricity is typically coal generated. This practice increases
CO 2 emissions further, compared to other less emitting technologies such as natural
gas combined cycles or hydropower. Many believe that the industry must begin,
given the level of carbon emissions emitted, to invest in CO 2 capture and storage
technologies (IPPC, 2001; EPA, 2010).
GHG and GWP are not the only concerns relating to atmospheric emissions.
Indeed sinter plants of an integrated steelworks account for up to 50% of the total
dust released. Their off-gas emissions can contain heavy metals, including SO 2 ,
HCl, HF and persistent organic pollutants. In the coke oven plants, the flue-gases
originating from the under-firing of coal and mixed in with other process gases in
order to take advantage of their exergy, contain CO 2 , SO 2 , tar, naphthalene, light
oil and various other dust particles. The blast furnace meanwhile principally emits
CO 2 because ore reduction is done with coke. Dust, wastewater from gas scrubbers
and sulphur emissions from slag treatment are also important considerations that
require additional abatement processes.
The basic oxygen furnace plants meanwhile are responsible for the induced emis-
sions relating to oxygen production as well as dust emissions, should the collecting
systems become insu cient, wastewater when wet de-dusting occurs and solid pro-
cess residues from hot metal treatments. In the EAF the key environmental issues
revolve around the off-gas. Such issues include dust emissions, slag production, cool-
ing water demand and those effects associated with the production of electricity and
pure oxygen.
8.3 Aluminium
8.3.1 Process
Aluminium oxide or alumina is the raw material required in aluminium production.
Alumina is obtained in the Bayer process from bauxite ore, which is a mixture
of various aluminium hydroxides with impurities of iron oxides, quartz and clay