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Construction undertaken by Titaco at Hernic Ferrochrome’s No. 3 furnace
where a section of the raw materials conveyor is being lifted into position.
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Technology gives Hernic Ferrochrome
the edge
Titaco Projects, a BATEMAN subsidiary, is currently engineering,
supplying and constructing one of the most sophisticated charge chrome
producing plants in the world for Hernic Ferrochrome (Pty) Ltd. The
process technology used combines Outokumpu’s ore sintering and
furnace charge preheating processes with a large closed type submerged
ore smelter designed by Titaco in collaboration with Hernic, Outokumpu
and Tanabe Corporation. It will be the largest furnace of this type
in South Africa.
Hernic, currently the third largest producer of ferro-chrome in South
Africa, is expanding its operations to become not only one of the global
players but one of the lowest-cost producers of charge chrome in the
world. This state-of-the-art technology, together with the benefits
of large scale production, will result in Hernic further improving its
competitive advantage through improved stability of the furnace operation,
increased chrome recovery and overall energy saving.
The technology for the pretreatment and agglomeration of the ore ensures
improved furnace stability and ease of operation during smelting. Pellets
of the correct strength and size are sent to sintering where proper
conditions in the furnace ensure a hard but porous structure important
for improved rate and efficiency of reduction. The high specific surface
of the finely ground chromite increases the reduction rate in the smelting
furnace and avoids non-uniform reduction. The pretreated pellets contain
iron in its more easily reducible ferric form and their porous structure
and high temperature strength improves solid state reduction. The volatile
hydroxides and carbonates decompose during sintering, reducing the demand
for electrical energy in the smelting phase. Pelletising and sintering
thus produce energy savings in smelting as the costs incurred are quickly
recovered in more rapid smelting and a high chromium yield. In the furnace
the hot gases from the cooling compartments are recycled to the drying,
preheating and sintering compartments, thus improving energy efficiency.
The process gas from the closed smelting furnace is cleaned by two wet
scrubber units, rendering it suitable as a heating fuel. Some of this
gas is used in the sintering process and for preheating the smelter
feed. The rest of the gas can be used for general heating or drying
purposes or flared if not used.
A major reduction in electrical energy consumption results from preheating
with gas instead of using electricity for this purpose as in the normal
smelting process. Charge preheating also significantly increases smelting
capacity and reduces electrode consumption. The absence of moisture
and other volatiles in the smelting furnace together with better gas
permeability of the burden (from the use of pellets instead of fines)
reduces eruptions and hence furnace downtime.
These features combine to yield improved availabilities, optimum furnace
performance and increased production
volumes for the overall plant.
The fact that Hernic adopted this process as part of its long term strategy
will certainly put it in a very strong competitive position. Given current
market conditions when the plant is commissioned, Hernic will be amongst
the few producers equipped to weather the storm.
For more information, please contact Jurgens van Tonder, General Manager,
AC Furnaces, on +27-11-899-2363 or
email acfurnaces@batemanengineering.com.
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