Usually, there are
two smelting types of iron ore:
1. Acid sinter
It mainly
consists of iron concentrates and rich iron powder mixing with agents of fusion.
The iron ore contained are mainly magnetite and hematite, and main binding
minerals are fayalite (2FeO•SiO2) and kirschsteinite (CaO•FeO•SiO2).
The sintered acid
iron ore does not pulverize naturally during the cooling process. It has high
mechanical strength, and contains much ferric oxide (FeO), resulting in poor reducibility
and bad temperature resistance.
A large amount of
limestone is required to smelting this kind of iron ore and concentrates.
2. Iron ore concentrates
Poor
iron ore can be ground and separated to obtain an iron powder with high grade. Iron ore concentrates is the raw material to produce artificial rich iron ore.
Iron
ore concentrate can be divided into magnetic concentrate, hematite concentrate,
and limonite concentrate according to different iron ore components. It can
also be divided into weakly magnetic concentrate, strongly magnetic concentrate,
flotation concentrate, and gravity concentrate.
In general, magnetite concentrate is obtained from magnetic ores by the method
of magnetic separation.
Hematite concentrate is obtained by gravity separation, flotation
separation, high-intensity magnetic separation, and magnetizing
calcination –
magnetic separation or a combined separation process.
Limonite concentrate is obtained by gravity separation, high-intensity
magnetic separation, or magnetizing calcination – magnetic separation.
There are 4
details of iron concentrates required by smelting plant:
1High iron content
The iron content of
magnetite concentrate should be more than 65%, iron in hematite concentrate
should be more than 60％ and in limonite concentrate
should be more than 50%. The fluctuation of iron content should be in the range
of 0.5%.
2Low water content
The humidity
contained in the concentrate has large effects on storage, transportation,
mixture, and briquette. Commonly, the humidity of magnetite concentrate should
be no more than 10%, and no more than 12% in limonite concentrate and hematite
concentrate.
3Uniform size
The iron
concentrate used for producing pellets should be uniform. There should be more
than 70% of particles under the size of 0.074 mm, and the specific surface area
should be better to be in the range of 1200 to 2000 cm2/g.
4Low impurities
The fewer impurities
(such as sulfur, phosphorus, lead, arsenic, zinc and copper), the better iron
concentrates. It is usually required:
Impurity
Content range
Sulfur
0.10%-0.19%
Phosphorus
0.05%-0.09%
Lead
No more than 0.1%
Arsenic
0.04%-0.07%
Zinc
0.1%-0.2%
Copper
0.1%-0.2%
9 elements in iron ore badly effected on
its smelting
The minerals badly effected
on the iron ore smelting are usually sulfur, phosphorus, potassium, sodium,
lead, arsenic, zinc, titanium and copper. Generally, they have the following
bad effects on smelting:
Elements that bad for iron ore smelting
1Sulfur (S): it is the most harmful
element to iron ore smelting. It will make the steel with hot brittleness. More
sulfur contained in iron ore, more cost in the following blast furnace
desulfurization will spend.
2Phosphorus (P): it is also the
common harmful element for steel material. It will bring the steel with cold
brittleness. Phosphorus in iron ore will be sintered into the cast iron during
the smelting process.
And during the
following steelmaking process, the dephosphorization will be getting more
complex and the cost will be increased.
3Alkali metals (K & Na): alkali metals
mainly include potassium and sodium.
The effect of
potassium and sodium on the blast furnace is not proportional, and the blast
furnace itself has a certain capacity of discharging alkali, and the alkali
metal has little influence on the blast furnace within the control range.
However, if there is
too much alkali metals remained in the iron ore, exceeding the alkali discharge
capacity of the blast furnace, the alkali metals will be concentrated, causing
the alkali metal content of the charge in the middle and upper part of the
blast furnace to exceed the original level of the charge greatly.
More alkali metals
contained in iron ore are inclined to reduce the softening temperature and move
up the soft melt zone, which is not conducive to the development of indirect
reduction.
4Lead (Pb): almost all lead is
reduced in the blast furnace. As the density of lead is as high as 11.34 t/m3,
which is easy to destroy and burn though the brick joints of the furnace
bottom.
5Zinc (Zn): zinc is easy to gasify,
and the vaporized zinc vapor easily enters the brick joint. The zinc will
become zinc oxide after oxidation, and its volume will expand, thereby
destroying the refractory brick lining on the upper body of the furnace, and harming
the smelting effect.
6Arsenic (As): arsenic is also one of
the harmful elements for steel, which makes the steel cold brittleness and poor
welding performance.
In addition,
arsenic volatilizes in the sintering process, which has a great impact on the
environment.
7Copper (Cu): copper will bring the
steel with hot brittleness, which will make steel hard to roll and welding. However,
a small amount of copper can improve the corrosion resistance of steel.
In blast furnace smelting, all the
copper is reduced into cast iron.
8Titanium (Ti): it can improve the
wear resistance and corrosion resistance of steel.
However, during the
smelting of the blast furnace, the slag will deteriorate, and about 90% of the
titanium will enter into the slag.
The low content of
titanium has little effect on the slags and smelting process. But when the
content is high, it will thicken slag and cause poor fluidity, which has a
great influence on the smelting process and is easy to form furnace nodules.
For the smelting of iron ore, better
control of the above harmful elements in the content of iron ore, not only can
control the smelting effect, but also can improve the performance of the
product, achieving good iron ore utilization rate, and bringing more profits
for the enterprise.
Archives
Recent Posts
Categories
Calendar
Meta
Adverse Effects of 9 Elements in Iron Ore on Its Smelting
Usually, there are
two smelting types of iron ore:
1. Acid sinter
It mainly
consists of iron concentrates and rich iron powder mixing with agents of fusion.
The iron ore contained are mainly magnetite and hematite, and main binding
minerals are fayalite (2FeO•SiO2) and kirschsteinite (CaO•FeO•SiO2).
The sintered acid
iron ore does not pulverize naturally during the cooling process. It has high
mechanical strength, and contains much ferric oxide (FeO), resulting in poor reducibility
and bad temperature resistance.
A large amount of
limestone is required to smelting this kind of iron ore and concentrates.
2. Iron ore concentrates
Poor
iron ore can be ground and separated to obtain an iron powder with high grade. Iron ore concentrates is the raw material to produce artificial rich iron ore.
Iron
ore concentrate can be divided into magnetic concentrate, hematite concentrate,
and limonite concentrate according to different iron ore components. It can
also be divided into weakly magnetic concentrate, strongly magnetic concentrate,
flotation concentrate, and gravity concentrate.
In general, magnetite concentrate is obtained from magnetic ores by the method
of magnetic separation.
Hematite concentrate is obtained by gravity separation, flotation
separation, high-intensity magnetic separation, and magnetizing
calcination –
magnetic separation or a combined separation process.
Limonite concentrate is obtained by gravity separation, high-intensity
magnetic separation, or magnetizing calcination – magnetic separation.
There are 4
details of iron concentrates required by smelting plant:
1 High iron content
The iron content of
magnetite concentrate should be more than 65%, iron in hematite concentrate
should be more than 60％ and in limonite concentrate
should be more than 50%. The fluctuation of iron content should be in the range
of 0.5%.
2 Low water content
The humidity
contained in the concentrate has large effects on storage, transportation,
mixture, and briquette. Commonly, the humidity of magnetite concentrate should
be no more than 10%, and no more than 12% in limonite concentrate and hematite
concentrate.
3 Uniform size
The iron
concentrate used for producing pellets should be uniform. There should be more
than 70% of particles under the size of 0.074 mm, and the specific surface area
should be better to be in the range of 1200 to 2000 cm2/g.
4 Low impurities
The fewer impurities
(such as sulfur, phosphorus, lead, arsenic, zinc and copper), the better iron
concentrates. It is usually required:
9 elements in iron ore badly effected on
its smelting
The minerals badly effected
on the iron ore smelting are usually sulfur, phosphorus, potassium, sodium,
lead, arsenic, zinc, titanium and copper. Generally, they have the following
bad effects on smelting:
Elements that bad for iron ore smelting
1 Sulfur (S): it is the most harmful
element to iron ore smelting. It will make the steel with hot brittleness. More
sulfur contained in iron ore, more cost in the following blast furnace
desulfurization will spend.
2 Phosphorus (P): it is also the
common harmful element for steel material. It will bring the steel with cold
brittleness. Phosphorus in iron ore will be sintered into the cast iron during
the smelting process.
And during the
following steelmaking process, the dephosphorization will be getting more
complex and the cost will be increased.
3 Alkali metals (K & Na): alkali metals
mainly include potassium and sodium.
The effect of
potassium and sodium on the blast furnace is not proportional, and the blast
furnace itself has a certain capacity of discharging alkali, and the alkali
metal has little influence on the blast furnace within the control range.
However, if there is
too much alkali metals remained in the iron ore, exceeding the alkali discharge
capacity of the blast furnace, the alkali metals will be concentrated, causing
the alkali metal content of the charge in the middle and upper part of the
blast furnace to exceed the original level of the charge greatly.
More alkali metals
contained in iron ore are inclined to reduce the softening temperature and move
up the soft melt zone, which is not conducive to the development of indirect
reduction.
4 Lead (Pb): almost all lead is
reduced in the blast furnace. As the density of lead is as high as 11.34 t/m3,
which is easy to destroy and burn though the brick joints of the furnace
bottom.
5 Zinc (Zn): zinc is easy to gasify,
and the vaporized zinc vapor easily enters the brick joint. The zinc will
become zinc oxide after oxidation, and its volume will expand, thereby
destroying the refractory brick lining on the upper body of the furnace, and harming
the smelting effect.
6 Arsenic (As): arsenic is also one of
the harmful elements for steel, which makes the steel cold brittleness and poor
welding performance.
In addition,
arsenic volatilizes in the sintering process, which has a great impact on the
environment.
7 Copper (Cu): copper will bring the
steel with hot brittleness, which will make steel hard to roll and welding. However,
a small amount of copper can improve the corrosion resistance of steel.
In blast furnace smelting, all the
copper is reduced into cast iron.
8 Titanium (Ti): it can improve the
wear resistance and corrosion resistance of steel.
However, during the
smelting of the blast furnace, the slag will deteriorate, and about 90% of the
titanium will enter into the slag.
The low content of
titanium has little effect on the slags and smelting process. But when the
content is high, it will thicken slag and cause poor fluidity, which has a
great influence on the smelting process and is easy to form furnace nodules.
For the smelting of iron ore, better
control of the above harmful elements in the content of iron ore, not only can
control the smelting effect, but also can improve the performance of the
product, achieving good iron ore utilization rate, and bringing more profits
for the enterprise.