APPARATUS FOR MANUFACTURING MOLTEN IRON AND
METHOD FOR MANUFACTURING THE SAME
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for manufacturing molten iron
and a method for manufacturing the same, and more particularly, to an apparatus
for manufacturing molten irons by charging carbonaceous materials and iron
carriers into a melter-gasifier and injecting fine carbonaceous materials into the
melter-gasifier and a method for manufacturing molten irons using the same.
2. Description of the Related Art
The iron and steel industry is a core industry that supplies the basic
materials needed in construction and in the manufacture of automobiles, ships,
home appliances, etc. Further, it is an industry which has the longest history
having advanced since the dawn of human history. Iron works, which play a
pivotal roll in the iron and steel industry, produce steel from molten iron, and then
supply it to customers, after first producing the molten iron (i.e., pig iron in a
molten state) using iron ores and coals as raw materials.
Nowadays, approximately 60% of the world's iron production is produced
using a blast furnace method that has been developed since the 14th century.
According to the blast furnace method, irons ores, which have gone through a
sintering process, and cokes, which are produced using bituminous coals as raw
materials, are charged into a blast furnace together and oxygen is supplied to the
blast furnace to reduce the iron ores to irons, thereby manufacturing molten irons.
The blast furnace method, which is the most popular in plants for manufacturing
molten irons, requires that raw materials have strength of at least a predetermined
level and have grain sizes that can ensure permeability in the furnace, taking into
account reaction characteristics. For that reason, cokes that are obtained by
processing specific raw coals are needed as carbon sources to be used as a fuel and
as a reducing agent. Also, sintered ores that have gone through a successive
agglomerating process are needed as iron sources. Accordingly, the modern blast
furnace method requires rav material preliminary processing equipment, such as
coke manufacturing equipment and sintering equipment. Namely, it is necessary
to be equipped with subsidiary facilities in addition to the blast furnace, and also
equipment for preventing ar d minimizing pollution generated by the subsidiary
facilities. Therefore, the heavy investment in the additional facilities and
equipment leads to increased manufacturing costs.
In order to solve these problems with the blast furnace method, significant
effort is made in iron works all over the world to develop a smelting reduction
process that produces molten irons in the melter-gasifier by directly using general
coals as a fuel and as a reducing agent and by directly using iron ores as iron
sources.
Since a coal packed bed consisting of coals is formed in the melter-gasifier,
iron carriers and additives are melted and slagged in the coal packed bed, and are
discharged as molten irons and slags. The oxygen is injected into the
melter-gasifier through a plurality of tuyeres installed on the outer wall of the
melter-gasifier, and burns the coal packed bed. Therefore, the oxygen is converted
into a hot reducing gas and the hot reducing gas is supplied to the fluidized bed
reactor. The hot reducing gas reduces and sinters iron carriers and additives and is
discharged outside.
The lumped coals charged into the upper portion of the melter-gasifier are
differentiated due to the sudden thermal shock while falling in a dome portion of
the melter-gasifier that is mainlained at a hot temperature of about 1000°C. In this
case, a large amount of dust containing a large amount of carbon components is
generated. Therefore, the permeability of the melter-gasifier is deteriorated due to
the large amount of dust. For solving this problem, a dust burner is installed in
the upper portion of the melter- gasifier and burns the dust while oxygen is injected
to the melter-gasifier by the dust burner. By burning the dust, the combustion
heat of the carbon components contained in the dust can be used.
Meanwhile, lumped coals are charged into the melter-gasifier and are
rapidly heated in the dome portion thereof. The volatile matters contained in the
lumped coals are firstly pyrolyzed as a pyrolysis gas having a chain structure of
CnHm or as a tar phase having a ring structure. The volatile matters are first
pyrolyzed and are then re pyrolyzed into a reducing gas, such as a CO gas and a
H2 gas. The heat, which is necessary for the pyrolyzing process, is absorbed
during the process, and thereby the temperature of the dome portion is lowered.
Therefore, extra oxygen, in addition to the oxygen which is necessary for burning
the dust, is supplied by a dust burner or an oxygen burner in order to prevent a
lowering of the temperature. A portion of the reducing gas formed in the dome
portion of the melter-gasifier is burned by supplying the extra oxygen, and so
prevents a lowering of the temperature thereof. However, in spite of such
combustion, a portion of the coal pyrolysis gas or the tar is not completely
pyrolyzed into CO2 and H2. Therefore, a portion of gas containing depyrolyzed
hydrocarbon, such as CH4, is contained in the reducing gas discharged from the
melter-gasifier.
As described above, when the lumped coals are charged into the
melter-gasifier, the combustion heat of the carbon contained in the volatile matters
is mainly used in pyrolysis of the gas generated from the volatile matters
themselves and raises he temperature of the pyrolysis gas. Carbonaceous
materials are partly discharged out of the melter-gasifier without generating
combustion heat. Therefore, only the amount of carbonaceous materials
excepting the amount of carbon contained in the volatile matters among the entire
amount of carbonaceous materials contained in the lumped coals is burned in the
lower portion of the melter-gasifier. Accordingly, carbonaceous materials in an
amount more than actually necessary should be used in order to supply a
sufficient heat source for manufacturing molten irons. Meanwhile, depyrolyzed
hydrocarbon gas, such a: a CH4, is discharged from the melter-gasifier while partly
existing in the reducing gas. In addition, the reducing gas containing CO2 and
H2O is partly discharged since the excessive oxygen is injected through the dust
burner. Therefore, there s a problem in that a reduction power of the reducing
gas supplied to the reduction reactor is deteriorated.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above-mentioned
problems, and is contrived to minimize a fuel rate when manufacturing molten
irons by injecting fine carbonaceous materials into the melter-gasifier and
supplying a reducing gas laving enhanced reduction power.
In addition, the present invention provides an apparatus for manufacturing
molten irons having enhanced utilization efficiency of the combustion heat of coals
by injecting fine carbonaceous mate rials.
For solving the abcve described problems, the present invention provides a
method for manufacturing molten irons including the steps of reducing mixtures
containing iron ores in a reduction reactor and converting the mixtures containing
iron ores into reduced materials, preparing lumped carbonaceous materials
containing volatile matters as a heating source for melting the reduced materials,
charging the lumped carbonaceous materials into a dome-shaped upper portion of
a melter-gasifier and forming a coal packed bed, preparing fine carbonaceous
materials containing volatile matters as a heating source for melting the reduced
materials, injecting oxygen and the fine carbonaceous materials into the coal
packed bed through a tuyere installed in the melter-gasifier, charging the reduced
materials into the melter-gasifier connected to the reduction reactor and
manufacturing molten irons, and supplying the reducing gas in the melter-gasifier
made from volatile matters contained both in the lumped carbonaceous materials
and the fine carbonaceous materials to the reduction reactor.
The fine carbonaceous materials may contain volatile matters in the range
from 8.0 wt% to 35.0 wt%, and the volatile matters may contain carbon and
hydrogen in the step of preparing fine carbonaceous materials containing volatile
matters as a heating source for melting the reduced materials.
The free swelling index (FSI) of the fine carbonaceous materials is preferably
not more than 6.0.
The lumped carboraceous materials may contain volatile matters in the
range from 20.0 wt% to 35 0 wt%, and the volatile matters may contain carbon and
hydrogen in the step of preparing lumped carbonaceous materials containing
volatile matters as a heating source for melting the reduced materials.
It is preferable that the grain size of the lumped carbonaceous materials is in
the range from 8mm to 35mm.
The step of preparing lumped carbonaceous materials preferably includes
the steps of dividing raw coals into fine coals and lumped coals, and preparing
lumped carbonaceous materials in which the lumped coals come in contact with
hot gas and are then dried
The method for manufacturing molten irons may further include a step of
injecting the divided fine coals as the fine carbonaceous materials into the coal
packed bed.
The method for manufacturing molten irons may further include a step of
transferring fine coals, which are collected when the lumped coals come in contact
with hot gas, and injecting the fine coals as the fine carbonaceous materials.
The lumped carbonaceous materials may include coal briquettes and the
step of preparing lumped carbonaceous materials may include the steps of
dividing the raw coals into fine coals and lumped coals and molding the fine coals
and then manufacturing coal briquettes.
The step of manuiacturing the coal briquettes may include the steps of
drying the fine coals, adding a binder to the fine coals and mixing together, and
molding the fine coals in which the binder is added and mixed together, and
manufacturing coal briquettes.
The above described step of manufacturing the coal briquettes may further
include a step of transferr ng fine coals collected in the step of drying the fine coals
and injecting the fine coals as the fire carbonaceous materials.
It is preferable that the fine carbonaceous materials are made by crushing
raw coals and a grain size of the crushed fine carbonaceous materials is not more
than 3mm in the step of injecting fine carbonaceous materials into the coal packed
bed.
It is preferable that an oxidization ratio of the reducing gas decreases to be in
the range of above 0% to 11.432% as an injecting amount of the fine carbonaceous
materials increases in the step of supplying reducing gas to the reduction reactor.
It is preferable that an amount of CH4 gas in the melter-gasifier decreases as
an injecting amount of the fine carbonaceous materials increases and an
oxidization ratio of the reducing gas decreases as the amount of the CH4 gas
decreases.
It is preferable that y = 0.0001x is substantially satisfied when x denotes an
injecting amount of the fine carbonaceous materials and y denotes a reducing
amount of CH4 gas in thr melter-gasifier. Here, the unit of x is kg/t-p, the unit of
y is %, and the unit of 0.0301 is %/(kg/t-p).
It is preferable that -3.4718