Note: Descriptions are shown in the official language in which they were submitted.
METHOD FOR DECARBURIZATION OF HIGH-CARBON
COPPER-CONTAINING MOLTEN IRON BY BLOWING CO2
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The invention belongs to the metallurgical field, and particularly
relates
to a method for decarburization of high-carbon copper-containing molten iron
by
blowing CO2.
2. The Prior Arts
[0002] China's blister copper production increases rapidly as the copper
smelting
technology develops quickly. At the same time, the volume of copper slag in
storage
rises greatly. By 2017, China's volume of copper slag in storage has reached
270
million tons or above. Such a massive storage amount of waste occupies a lot
of land
and pollutes environment. The copper slag contains massive valuable metallic
elements, the content of copper and iron is even higher than ore, and waste of
the
copper slag is also the waste of resources.
[0003] However, at the current time, the copper slag is mainly used in
the
respects of separately extracting copper or iron, and the recovery value is
low. In
order to extract copper and iron elements, the carbonaceous reducing agent is
generally used to reduce oxides and sulfides in the copper slag. To ensure the
good
reduction effect, the carbonaceous reducing agent is added excessively in most
cases,
so that copper-iron alloys obtained contain a large amount of carbon, which
makes the
utilization value of the alloys be lowered. Making the copper-containing
antibacterial
stainless steel with the copper-containing molten iron requires
decarburization.
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Date Recue/Date Received 2020-04-24
[0004] Industrial decarburization methods include the general oxygen-
blowing
decarburization method and the vacuum decarburization method. Both of the
methods
are performed by blowing oxygen to react with carbon in alloys for
decarburization,
and methods are widely used in steel making with molten iron. For the
copper-containing molten iron, the oxygen can cause the burning loss of copper
elements.
02 [CUl = CU20
[0005] The relative-low copper content is further reduced. However,
application
of the copper-containing molten iron requires a certain copper content.
Copper-containing antibacterial martensitic stainless steel requires a copper
content of
2.5-4.0%; and if the copper content is too low, the addition of copper alloys
in the
follow-up process is needed, which is not economic.
[0006] Chinese patent publication No. 104099445A provides an RH
(Ruhrstahl
Heraeus) fast decarburization method. The carbon content is reduced to 0.02-
0.045%
through the terminal control of a converter and oxygen blowing control.
However, the
method only relates to oxygen-blowing decarburization. Chinese patent
publication
No. 105316451A provides an RH forced oxygen-blowing decarburization method,
and according to the method, the carbon content can be reduced to 9 ppm under
the
vacuum condition. However, this patent application does not relate to the
decarburization of copper-containing molten iron but only the decarburization
of
molten iron. Chinese patent publication No. 105039649A provides a method for
smelting low-carbon high-manganese molten iron in an argon oxygen
decarburization
furnace. However, the method does not relate to copper-containing molten iron
decarburization either. Chinese patent publication No. 102146493A provides a
method
for smelting clean steel in an electromagnetic induction furnace by blowing
CO2.
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Date Recue/Date Received 2020-04-24
CO2 is blown for decarburization and the decarburization amount is controlled
by a
furnace gas analysis system. However, the method relates to neither an
application of
valuable metallic elements nor copper protection by decarburization.
SUMMARY OF THE INVENTION
[0007] In accordance with the defects existing in oxygen decarburization,
the
invention provides a method for decarburization of high-carbon copper-
containing
molten iron by blowing CO2. CO2 reacts with the carbon in melt to produce CO,
and CO escapes and burns to reproduce CO2. Moreover, CO2 is weak oxidizing gas
and does not react with copper, while also has the dephosphorization and
desiliconization functions. Reproduced CO2 is reused after being output.
[0008] The method is simple in process. A stirring system is arranged in
the
induction furnace, and the induction furnace is energy-saving, environmental-
friendly,
and low in cost. CO2 is adopted, and the method has high economic value and
the
function of environmental protection. The method not only can realize the
purpose of
decarburization, but also can protect the copper element from burning loss.
[0009] The method for decarburizing high-carbon copper-containing molten
iron
by blowing CO2, comprises the following steps of:
[0010] (1) Introducing the high-carbon copper-containing molten iron into
an
induction furnace, and ensuring a temperature of the high-carbon copper-
containing
molten iron to be greater than or equal to 1450 C,
[0011] (2) Blowing CO2 into the high-carbon copper-containing molten
iron, and
performing stirring, wherein a molar ratio of the CO2 to C in the high-carbon
copper-containing molten iron is (1.2 to 1) - (1.5 to 1), and a blowing time
is 20-80
min;
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Date Recue/Date Received 2020-04-24
[0012] (3) Stopping performing spraying and blowing CO2 when a percentage
by mass of carbon in the high-carbon copper-containing molten iron is smaller
than or
equal to 0.2%. Copper-containing molten iron and molten slag is obtained, and
gas
is collected, wherein the gas is produced CO and unreacted CO2;
[0013] (4) Performing a post-treatment on the CO, so that CO2 is
produced,
returning the CO2 to the induction furnace for reuse, and separating the
copper-containing molten iron from the molten slag.
[0014] In the step (1), the high-carbon copper-containing molten iron is
reduced
molten high-carbon copper-containing molten iron obtained by adding a reducing
agent to molten copper slag, and the temperature of the high-carbon
copper-containing molten iron is 1450-1650 C;
[0015] In the step (1), the induction furnace comprises a slag discharge
opening,
a molten iron discharge opening and a gas blowing-in opening, wherein the gas
blowing-in opening is a bottom blowing opening or a side blowing opening; the
molten iron discharge opening is formed in a lower part on one side of the
induction
furnace, the slag discharge opening is formed in an upper part on the other
side of the
induction furnace, the bottom blowing opening is formed in a bottom of the
induction
furnace, and the side blowing opening is formed in the lower part on one side
of the
induction furnace;
[0016] The induction furnace is provided with a stirring paddle, an air
hood and
a flue gas purifying system, wherein the stirring paddle is eccentrically
mounted at a
top of the induction furnace; the air hood is arranged above the induction
furnace, an
inlet of the flue gas purifying system is connected with the air hood through
a pipeline,
and an outlet of the flue gas purifying system is connected with a gas blowing-
in
opening of the induction furnace through a pipeline;
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Date Recue/Date Received 2020-04-24
[0017] The stirring system comprises the stirring paddle and a stirring
paddle
lifting system;
[0018] In the step (1), the launder is used for introducing the reduced
molten
high-carbon copper-containing molten iron into the induction furnace;
[0019] In the step (1), a method for ensuring the temperature of the high-
carbon
copper-containing molten iron to be greater than or equal to 1450 C is that
the
induction furnace is used for heating;
[0020] In the step (2), the CO2 is blown thereinto from the bottom of the
induction furnace or the side of the induction furnace;
[0021] In the step (2), the stirring is performed by inserting the
stirring paddle to
1/3-1/2 of the liquid level of copper-containing molten iron for eccentric
stirring with
an eccentricity of 0.1-0.8 and a stirring speed of 50-200 r/min, so that the
CO2 is
dispersed, and the CO2 and the melt can be thoroughly mixed;
[0022] In the step (4), the generated CO and the unreacted CO2 enter the
flue gas
purifying system through the air hood, the treated gas and 02 are mixed and
burnt to
generate CO2, and the CO2 is reused;
[0023] In the step (4), molten slag is placed in an upper layer of the
induction
furnace, and the copper-containing molten iron is placed in a lower layer of
the
induction furnace; and the molten slag is discharged from a slag discharge
opening of
the induction furnace, and the copper-containing molten iron is poured out of
a molten
iron discharge opening of the induction furnace.
[0024] Through the method disclosed by the invention, the carbon content
in the
copper-containing molten iron can be effectively reduced, so that the carbon
mass
content in the copper-containing molten iron is smaller than or equal to 0.2%.
Furthermore, the content of phosphorus and silicon can be reduced to a certain
extent,
Date Recue/Date Received 2020-04-24
and the copper content in molten iron is not reduced. Therefore, molten iron
meets the
requirements for steel making.
[0025] The principle of decarburization is as follows:
CO2 + [C] = 2C0(g)
[0026] Compared with conventional oxygen-blowing decarburization, the
method for decarburization of high-carbon copper-containing molten iron by
blowing
CO2, disclosed by the invention has the following characteristics and
beneficial
effects:
[0027] 1. CO2 gas can be recycled. Produced CO2 has a certain
temperature,
and reacts with [C] in the melt for decarburization without preheating. During
decarburization, copper is not oxidized, the effect of decarburization can be
achieved,
and burning loss of the copper can also be avoided. CO2 has an excellent
effect when
being used for treating molten iron containing valuable metallic elements;
[0028] 2. The method adopted by the invention can effectively utilize
copper
slag, so that waste is reduced;
[0029] 3. The method adopted by the invention can reduce emission of
smoke
and dust and is favorable for increment of yield, and environmental
protection; and
[0030] 4. CO2 spraying and blowing adopted by the invention achieves the
purpose of decarburization, and the sprayed and blown gas can also achieve the
stirring function, so that the CO2 comes into full contact with high-carbon
copper-containing molten iron to reach sufficient decarburization.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 shows a structure diagram of the induction furnace system
in the
method of the invention, wherein 1 indicates slag discharge opening, 2
indicates
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Date Recue/Date Received 2020-04-24
molten iron discharge opening, 3 indicates bottom blowing opening, 5 indicates
air
hood, 6 indicates flue gas purifying system, and 7 indicates stirring paddle;
[0032] FIG. 2 shows a structure diagram of the induction furnace system
in the
method of the invention, wherein 1 indicates slag discharge opening, 2
indicates
molten iron discharge opening, 4 indicates side blowing opening, 5 indicates
air hood,
6 indicates flue gas purifying system, and 7 indicates stirring paddle.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0033] The invention will be further detailed below in combination with
embodiments.
Embodiment 1
[0034] High-carbon copper-containing molten iron is used in the
embodiment of
the invention. Table 1 shows the analysis results of elements in high-carbon
copper-containing molten iron.
[0035] FIG. 1 shows the structure diagram of the induction furnace system
in the
embodiment.
[0036] The method for decarburization of high-carbon copper-containing
molten
iron by blowing CO2 comprises the following steps of:
[0037] (1) Introducing 20t reduced molten high-carbon copper-containing
molten iron through the launder into the induction furnace as shown in Fig. 1,
and
heating the high-carbon copper-containing molten iron through the induction
furnace
to 1500 C;
[0038] (2) Inserting the stirring paddle 7 to 1/3 of the liquid level of
the
copper-containing molten iron through the stirring paddle lifting system for
eccentric
stirring with an eccentricity of 0.1 and a stirring speed of 50 r/min; and
besides,
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Date Recue/Date Received 2020-04-24
blowing CO2 into the high-carbon copper-containing molten iron through the
bottom
blowing opening 3 in the bottom of the induction furnace, wherein the molar
ratio of
the CO2 to C in high-carbon copper-containing molten iron is 1.2: 1, and the
spraying
and the blowing time is 60 min;
[0039] (3) Stopping blowing CO2 when the carbon mass content in the
high-carbon copper-containing molten iron is 0.2%, (at this time, the total
CO2
blowing amount is 1000 m3), and obtaining copper-containing molten iron and
molten
slag, wherein the Cu mass content in the copper-containing molten iron is
5.25%, the
C content is 0.2%, the P content is 0.05% and the Si content is 0.122%;
[0040] (4) Placing molten slag in the upper layer of the induction
furnace,
placing the copper-containing molten iron in the lower layer of the induction
furnace,
and discharging the molten slag from a slag discharge opening 1 of the
induction
furnace, and pouring out the copper-containing molten iron from a molten iron
discharge opening 2 of the induction furnace; and
[0041] (5) Sending the generated CO and the unreacted CO2 to the flue gas
purifying system 6 through the air hood 5, performing mixing and burning on
the gas
treated with CO and 02 to generate CO2, and performing reusing;
[0042] It can be seen that by adopting the method disclosed by the
embodiments,
the C content in the high-carbon copper-containing molten iron is remarkably
reduced
and the Cu content is basically unchanged, indicating that the method
effectively
achieves the purposes of decarburization and copper protection.
Embodiment 2
[0043] High-carbon copper-containing molten iron is used in the
embodiment of
the invention. Table 1 shows the analysis results of elements in high-carbon
copper-containing molten iron.
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Date Recue/Date Received 2020-04-24
[0044] FIG. 2 shows the structure diagram of the induction furnace system
in the
embodiment.
[0045] The method for decarburization of high-carbon copper-containing
molten
iron by blowing CO2, comprises the following steps of:
[0046] (1) Introducing 30t reduced molten high-carbon copper-containing
molten iron through the launder into the induction furnace as shown in fig. 2,
and
heating the high-carbon copper-containing molten iron through the induction
furnace
to 1500 C;
[0047] (2) Inserting the stirring paddle 7 to 1/2 of the liquid level of
the
copper-containing molten iron through the stirring paddle lifting system for
eccentric
stirring with an eccentricity of 0.4 and a stirring speed of 100 r/min; and
besides,
blowing CO2 into the high-carbon copper-containing molten iron through the
side
blowing opening 4 in the bottom of the induction furnace, wherein the molar
ratio of
the CO2 to C in high-carbon copper-containing molten iron is 1.5 : 1, and the
blowing
time is 80 min;
[0048] (3) Stopping blowing CO2 when the carbon mass content in the
high-carbon copper-containing molten iron is 0.09% (at this time, the total
CO2
spraying and blowing amount is 1600 m3), and obtaining copper-containing
molten
iron and molten slag, wherein the Cu content in the copper-containing molten
iron is
4.89 wt%, the C content is 0.09 wt%, the P content is 0.07 wt% and the Si
content is
0.136 wt%;
[0049] (4) Placing molten slag in the upper layer of the induction
furnace,
placing the copper-containing molten iron in the lower layer of the induction
furnace,
and discharging the molten slag from a slag discharge opening 1 of the
induction
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Date Recue/Date Received 2020-04-24
furnace, and pouring out the copper-containing molten iron from a molten iron
discharge opening 2 of the induction furnace; and
[0050] (5) Sending the generated CO and the unreacted CO2 to the flue gas
purifying system 6 through the air hood 5, performing mixing and burning on
the gas
treated with CO and 02 to generate CO2, and performing reusing;
Embodiment 3
[0051] High-carbon copper-containing molten iron is used in the
embodiment of
the invention. Table 1 shows the analysis results of elements in high-carbon
copper-containing molten iron.
[0052] FIG. 2 shows the structure diagram of the induction furnace system
in the
embodiment.
[0053] The method for decarburization of high-carbon copper-containing
molten
iron by blowing CO2, comprises the following steps of:
[0054] (1) Introducing 30t reduced molten high-carbon copper-containing
molten iron through the launder into the induction furnace as shown in fig. 2,
and
heating the high-carbon copper-containing molten iron through the induction
furnace
to 1450 C;
[0055] (2) Inserting the stirring paddle 7 to 1/2 of the liquid level of
the
copper-containing molten iron through the stirring paddle lifting system for
eccentric
stirring an eccentricity of 0.5 and a stirring speed of 100 r/min; and
besides, blowing
CO2 into the high-carbon copper-containing molten iron through the side
blowing
opening 4 in the bottom of the induction furnace, wherein the molar ratio of
the CO2
to C in high-carbon copper-containing molten iron is 1.3 : 1, and the blowing
time is
40 min;
Date Recue/Date Received 2020-04-24
[0056] (3) Stopping blowing CO2 when the carbon mass content in the
high-carbon copper-containing molten iron is 0.15% (at this time, the total
CO2
spraying and blowing amount is 1600 m3), and obtaining copper-containing
molten
iron and molten slag, wherein the Cu content in the copper-containing molten
iron is
4.89 wt%, the C content is 0.15 wt%, the P content is 0.09 wt% and the Si
content is
0.155 wt%;
[0057] (4) Placing molten slag in the upper layer of the induction
furnace,
placing the copper-containing molten iron in the lower layer of the induction
furnace,
and discharging the molten slag from a slag discharge opening 1 of the
induction
furnace, and pouring out the copper-containing molten iron from a molten iron
discharge opening 2 of the induction furnace; and
[0058] (5) Sending the generated CO and the unreacted CO2 to the flue gas
purifying system 6 through the air hood 5, performing mixing and burning on
the gas
treated with CO and 02 to generate CO2, and performing reusing.
Embodiment 4
[0059] High-carbon copper-containing molten iron is used in the
embodiment of
the invention. Table 1 shows the analysis results of elements in high-carbon
copper-containing molten iron.
[0060] FIG. 2 shows the structure diagram of the induction furnace system
in the
embodiment.
[0061] The method for decarburization of high-carbon copper-containing
molten
iron by blowing CO2, comprises the following steps of:
[0062] (1) Introducing 30t reduced molten high-carbon copper-containing
molten iron through the launder into the induction furnace as shown in fig. 2,
and
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Date Recue/Date Received 2020-04-24
heating the high-carbon copper-containing molten iron through the induction
furnace
to 1650 C;
[0063] (2) Inserting the stirring paddle 7 to 1/2 of the liquid level of
the
copper-containing molten iron through the stirring paddle lifting system for
eccentric
stirring with an eccentricity of 0.3 and a stirring speed is 200 r/min; and
besides,
blowing CO2 into the high-carbon copper-containing molten iron through the
side
blowing opening 4 in the bottom of the induction furnace, wherein the molar
ratio of
the CO2 to C in high-carbon copper-containing molten iron is 1.5 : 1, and the
blowing
time is 20 min;
[0064] (3) Stopping blowing CO2 when the carbon mass content in the
high-carbon copper-containing molten iron is 0.18% (at this time, the total
CO2
spraying and blowing amount is 1600 m3), and obtaining copper-containing
molten
iron and molten slag, wherein the Cu content in the copper-containing molten
iron is
4.89 wt%, the C content is 0.18 wt%, the P content is 0.06 wt% and the Si
content is
0.236 wt%;
[0065] (4) Placing molten slag in the upper layer of the induction
furnace,
placing the copper-containing molten iron in the lower layer of the induction
furnace,
and discharging the molten slag from a slag discharge opening 1 of the
induction
furnace, and pouring out the copper-containing molten iron from a molten iron
discharge opening 2 of the induction furnace; and
[0066] (5) Sending the generated CO and the unreacted CO2 to the flue gas
purifying system 6 through the air hood 5, performing mixing and burning on
the gas
treated with CO and 02 to generate CO2, and performing reusing.
Embodiment 5
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Date Recue/Date Received 2020-04-24
[0067] High-carbon copper-containing molten iron is used in the
embodiment of
the invention. Table 1 shows the analysis results of elements in high-carbon
copper-containing molten iron.
[0068] FIG. 2 shows the structure diagram of the induction furnace system
in the
embodiment.
[0069] The method for decarburization of high-carbon copper-containing
molten
iron by blowing CO2, comprises the following steps of:
[0070] (1) Introducing 30t reduced molten high-carbon copper-containing
molten iron through the launder into the induction furnace as shown in fig. 2,
and
heating the high-carbon copper-containing molten iron through the induction
furnace
to 1500 C;
[0071] (2) Inserting the stirring paddle 7 to 1/2 of the liquid level of
the
copper-containing molten iron through the stirring paddle lifting system for
eccentric
stirring with an eccentricity of 0.8 and a stirring speed is 150 r/min; and
besides,
blowing CO2 into the high-carbon copper-containing molten iron through the
side
blowing opening 4 in the bottom of the induction furnace, wherein the molar
ratio of
the CO2 to C in high-carbon copper-containing molten iron is 1.5: 1, and the
blowing
time is 80 min;
[0072] (3) Stopping blowing CO2 when the carbon mass content in the
high-carbon copper-containing molten iron is 0.12% (at this time, the total
CO2
spraying and blowing amount is 1600 m3), and obtaining copper-containing
molten
iron and molten slag, wherein the Cu content in the copper-containing molten
iron is
4.89 wt%, the C content is 0.12 wt%, the P content is 0.08 wt% and the Si
content is
0.113 wt%;
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Date Recue/Date Received 2020-04-24
[0073] (4) Placing molten slag in the upper layer of the induction
furnace,
placing the copper-containing molten iron in the lower layer of the induction
furnace,
and discharging the molten slag from a slag discharge opening 4 of the
induction
furnace, and pouring out the copper-containing molten iron from a molten iron
discharge opening 2 of the induction furnace; and
[0074] (5) Sending the generated CO and the unreacted CO2 to the flue gas
purifying system 6 through the air hood 5, performing mixing and burning on
the gas
treated with CO and 02 to generate CO2, and performing reusing.
[0075] Table 1 (percentage by mass, %)
-----.4.,,.....fisõ...... miles Embodiment Embodiment Embodiment Emb.o.diment.
Einb.a.dimErtn.
Element . 1 2 3
_
C L.6.7 338 ,L52 4..56 3.3.6.
? 0.08; .11'0 0.130 0.09 0.140
S 0.011 0. Or.:1 0.010 0_007 0..i1l15
sinallier than smaller than stnaller than smaller than sitialler than
I ,. (1'.4
0_01 0_01 C .01 G. 0 1 Obi
Si 0_338 D...240 C..328 0236 0_313
snialler than smaller than small at- than smaller than smaller than
Cr
41.01 0.0 i C.:.:1 0.01 0.01
Zn 0.019 0.036.: C .C28 C.C33 D. D26.:
sinallier than smaller than small,r than s.maller than sitiallier than
1.;.
0_01 0_01 C .01 obi 0.01
1Cu 5_26 4_92 .5.66. 5_45
Fie 89..1 90_6 818; 89_3 90_2
Other Remainder Remainder. 11'. ' =alder
Remainder. Remainder.
14
Date Recue/Date Received 2020-04-24
