Vol 7, No 3 (2016) > Metalurgy and Material Engineering >

The Effect of Reduction Time and Size Distribution of Mixed Iron Ore with Coconut Shell Charcoal on the Percentage of Metallization by using a Rotary Kiln

Soesaptri Oediyani, Kustiarana Willyandhika, Suharto Suharto



Steel is an important material
that is widely used and its development has
occurred in
conjunction with the history of mankind over the last two centuries. In general, the steelmaking process has been
done through a combination of a direct
reduction process and an Electric Arc Furnace (EAF) or
an indirect reduction process and a
Basic Oxygen Furnace (BOF).
The combination of the steelmaking processes
can be adapted to the specific conditions of Indonesian
local iron ore. In Indonesia, the raw material reserves of iron and steel making are
quite large, but spread over several islands. UPT BPML LIPI in cooperation with
the Department of Metallurgical Engineering UNTIRTA conducted research to
improve the economic value of the local iron ore in South Lampung Regency. The total amount of primary iron
ore resources in South Lampung is
estimated to be in the region of 11 million tons. South Lampung Regency iron
ore is primary iron ore with a content of pure magnetite and
magnetite-containing impurity silica levels ranging from 40-65% Fe in total.  South
Lampung Regency low-grade iron ore has the potential to
be reduced by using a rotary kiln. A rotary kiln is a tool used to reduce
low-grade iron ore and produce sponge iron with a high metallization. This process is in accordance with the
Indonesian government policies that regulate the minimum value of percentage of
sponge iron metallization for export, i.e. 85%. In this research, sponge iron is made of a mixture of Lampung iron ore pellets with coconut shell charcoal as a
reduction agent. The composition of coconut
shell charcoal is about 20%, which will determine the optimum amount of South Lampung iron ore pellets in the mixture. In addition, during the reduction process, the residence time of pellets
in the rotary kiln is observed in order to obtain the optimal
percentage of metallization. The method used in this research was the direct
reduction process using a pilot-scale rotary kiln with the variables related to residence time (1, 2 and 3
hours) for
the pellets and to the diameter of the pellets
(-12+8mm and  -20+12mm). Meanwhile, the reduction temperature was
fixed, i.e. 1100oC. The maximum metallization of sponge iron achieved
at a residence time of 3 hours was 99.50% for the average pellet diameter of (-12+8mm).

Keywords: Coconut shell charcoal; Direct reduction; Percent metallization; Rotary kiln; Sponge iron

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