Environmental Engineering Reference
In-Depth Information
12.5
Environmental Impact of the Steel Industry
Japanese iron- and steelmaking technology is at world-leading level in terms of
energy efficiency and environmental protection. About 520 t of coke and pulver-
ized coal are used to produce 1 t of steel. Such fuels are called a 'reducing agent',
since they are used to reduce iron oxides to metallic iron. Gases formed in the coke
oven (Coke oven gas, COG) and discharged from blast furnaces (Blast-furnace gas,
BFG) are utilized as fuels in power generation and for heating various materials in
downstream processes such as rolling. In total, about 2000 kg-CO
2
per ton of steel is
formed in such a process. On the other hand, steelmaking by an electric arc furnace
(EAF) process emits about 500 kg-CO
2
/ton-steel, which is only a quarter of that
from integrated iron- and steelmaking (Birat et al.
1999
). From this point of view,
it seems better to promote EAF steelmaking using scraps. However, the amount of
steel scrap generation is limited to about 2.5 % of the steel stockpiles which exist
in Japan as steel products and social infrastructures. Thus, about 3.5 million t of
scrap are annually generated in Japan at present against the 1.4 billion t of steel
in stockpiles (see Fig.
12.12
). Japanese steel production has been a little above
100 million t/year, and therefore it is still necessary to use natural iron ore resources
to keep this production level.
Figure
12.13
shows the CO
2
emissions from different sectors in the world. Total
emissions from the industry sector are ~ 31 % and the steel industry contributes one
quarter of this. After the introduction of modern iron & steelmaking technology,
many efforts have continued to reduce the amount of reducing agents used. The
reducing agent rate in 1950 was about 1000 kg/ton-steel but has been substantially
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Fig. 12.12
Amount of socially-stored steel and scrap generation in Japan
