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First, the smelting product
Heteroaryl copper smelting blast furnace black product of copper or copper black times, slag, furnace gas and dust.
(1) Black copper or secondary black copper When smelting yellow copper, white copper and ore copper refining slag, black copper is produced, and its chemical composition is shown in Table 1.
The product obtained by smelting other copper-containing slags other than ore-bearing copper refining slag is called secondary black copper, and its chemical composition is shown in Table 2.
Table 2 chemical composition of black copper
Black copper is generally directly fed into the reverberatory furnace to produce anode copper or refined copper; the secondary black copper is generally refined by converter and then enters the reverberatory furnace for refining.
(2) slag
a, slag composition and properties of the slag and the fuel charge is co-melt various metals and non-metal oxides formed in the smelting process. These oxides form a compound, a solid solution, a liquid solution, and the like with each other.
The properties of the blast furnace slag have a significant impact on the fuel consumption, furnace temperature, bed energy rate, and metal recovery rate of the smelting process. The purpose of the slag formation is to mix an appropriate amount of flux according to the production requirements, so that the impurity components of the charge and the various oxides formed during the smelting form slag.
The slag of the copper blast furnace is a co-melt of oxides such as SiO 2 , CaO, FeO, MgO, Al 2 O 3 , Fe 3 O 4 , ZnO, PbO, and SnO 2 . The sum of SiO 2 , CaO and FeO is 75% to 80%. Therefore, the nature of the slag is largely determined by these three components.
At high temperatures, various slag oxidation behaviors are different. Among them, SiO 2 is an acidic oxide and can be combined with various basic oxides to form a silicate; Al 2 O 3 is an amphoteric oxide, and most other metal oxides are alkaline. [next]
The degree of acidity of the slag is usually expressed by the degree of silicic acid. The degree of silicic acid is the ratio of the oxygen content of SiO2 in the slag to the sum of the oxygen content of the basic oxide. It is expressed by K and can be calculated by the following formula:
K=Osio 2 /ΣOMe O
The slag having a K value of less than 1 is an alkaline slag, and the K value is less than 1.5 as an acidic slag, and the K value is between 1 and 1.5 as a neutral slag. The K value of the copper blast furnace slag is between 1 and 1.5.
b. Melting point of slag The melting point of slag is not a fixed value, but a temperature interval, which increases with the increase of SiO 2 content. Generally, the temperature at which the slag is completely liquid is referred to as the melting point of the slag.
The slag formed by different slag components has different melting points. The melting points of the components in the slag are shown in Table 3.
Table 3 Melting point of each component in the slag
As can be seen from the above table, when each oxide is present alone, its melting point is high and it is impossible to melt at the blast furnace melting temperature. However, when a plurality of oxides are mixed and heated, they interact into a low melting point compound, a solid solution, and a fusible eutectic, so that the melting point is much lower than the melting point of each individual oxide.
The CaO content in the blast furnace slag is relatively high, ranging from 25% to 32%, so the melting point is also high, generally around 1473K.
c. Viscosity of slag Viscosity is one of the important properties of slag. The release of slag, the separation of slag from copper, the reaction between slag and metal melt, and the heat transfer process in the furnace are all related to viscosity.
Generally, the viscosity of the easily flowable slag is less than 0.5 Pa·s, the fluidity slag is 0.5 to 1 Pa·s, the viscous slag is 1 to 2 Pa·s, and more than 2 Pa·s is a very viscous slag. The viscosity of the copper blast furnace slag is about 1 Pa·s.
The viscosity of the slag changes as its composition changes. SiO 2 can increase the viscosity of the slag, while FeO can lower the viscosity, and CaO can also lower the viscosity, but the high calcium slag has a high melting point.
d. Density of slag The greater the difference in density between slag and copper, the more favorable it is for clarification separation, and the less copper is lost with slag. The solid density of each component of the slag is shown in Table 4.
Table 4 Solid density of each component of slag
When the oxide content is increased, the density is increased. The replacement of FeO by CaO in production can reduce the density of the slag and improve the sedimentation conditions.
In addition, other compositions in the slag, such as Al 2 O 3 , MgO, ZnO, PbO, SnO 2 , etc., also have a certain influence on the properties of the slag.
e. Loss of copper in slag Copper in slag is the main channel for copper loss during smelting. The copper blast furnace smelting belongs to the flux, and the loss of copper in the slag includes chemical loss, physical loss and mechanical loss.
The chemical loss is the loss caused by the oxide, silicate and ferrite of copper entering the slag; the physical loss is the loss of copper dissolved in the slag at high temperature; the mechanical loss is the loss taken by the slag with the metal copper inclusions.
The CaO content in the charge is too low, and the loss reduction atmosphere is insufficient, which is easy to cause chemical loss of copper in the slag; the slag temperature is too high, the FeO content in the slag is too high, and physical loss is easy to make; the slag has large viscosity, high melting point, high density, and clarification. When the separation is incomplete, it is easy to cause mechanical loss. [next]
When the blast furnace is used to smelt copper, the slag generally contains 0.50% to 0.07% of copper. Slag containing more than 0.5% copper should not be discarded.
The main components of the copper blast furnace slag are shown in Table 5.
(3) Furnace gas and soot The composition of the furnace gas of the copper blast furnace is shown in Table 6.
Table 6 furnace gas composition
The amount of furnace gas produced per minute per square meter of the tuyere area is about 500 m 3 , and the temperature at which the furnace gas is discharged is between 1073 and 1273 K.
The dust content of the furnace gas is related to the raw materials processed. Melting containing zinc, lead, tin Copper high furnace gas dust in an amount of 30 ~ 50g / m, recovery of zinc, lead and tin oxide by a dust collection system wherein.
Second, the main technical and economic indicators
The main technical and economic indicators for the melting of copper blast furnace are as follows.
(1) Bed energy rate The bed energy rate refers to the amount of charge that is smelted every day on the cross section of the furnace vent area of ​​the blast furnace. The bed energy rate of the copper blast furnace is related to the nature of the treated charge. The bed energy rate is about 100t when smelting high zinc mixed copper, and 70~80t when smelting copper containing slag.
(2) Focal rate The focal rate refers to the percentage of consumed carbon and total processing. The heat in the smelting process of the copper blast furnace is almost entirely dependent on the combustion supply of coke , and the reducing atmosphere in the furnace is maintained by the combustion reaction of coke, so the coke rate is higher than that of the general copper blast furnace. When treating high zinc mixed copper, the coke rate is generally 25% to 28%; when treating copper-containing slag, it is 28% to 30%.
Preheating the blast can strengthen the smelting process. Preheating the air temperature to above 473K, the bed energy rate of the furnace can be increased by about 10%, the coke rate can be reduced by 3% to 4%, and other technical and economic indicators are also improved to varying degrees.
(3) Recovery rate The recovery rate refers to the copper content of black copper or secondary black copper produced by the blast furnace, which is a percentage of the copper content of the consumed materials. The recovery rate depends mainly on the nature of the charge. When smelting high-zinc copper, the mechanical loss is small, the slag contains low copper, and the recovery rate of copper is high, generally up to 99% to 99.8%. When smelting copper-containing slag, the recovery rate is low, generally 96% to 98. %between.
(4) Flux rate The flux rate refers to the percentage of the melted amount consumed and the amount of copper-containing material charged. When the copper blast furnace smelts high-zinc copper, the slag rate is low, so the flux rate is also low, generally 5% to 6%. When smelting copper-containing slag, the slag formation rate is high, and the flux rate is as high as 25% to 30%. .
Blast furnace smelting and reclaiming copper (4)
Products of blast furnace smelting and main technical and economic indicators
Table 1 Chemical composition of black copper /%
Raw material
Black copper chemical composition
Cu
Pb
Ni
Zn
As
Sb
Sn
Fe
Yellow copper
White copper
85～90
About 90
2 to 4
1 to 3
0.3 to 0.5
6 to 14
3 to 6
3~7
0.07~0.1
0.4 to 0.6
2 to 3
0.5 to 1
0.5 to 8
Raw material
Secondary black copper chemical composition
Cu
Pb
Ni
Zn
As
Sb
Sn
Copper-containing slag
60～70
8~9
0.4 to 1.0
1.0 to 1.5
0.08~0.2
0.6 to 0.9
10~12
Oxide
SiO 2
FeO
CaO
MgO
Al 2 O 3
Fe 2 O 3
Melting point / K
1983
1633
2483
3073
2323
2123
Component
FeO
SiO 2
CaO
Fe 2 O 4
MgO
Al 2 O 3
Density / g · cm -3
5.00
2.51
2.30
5.18
3.40
3.20
Table 5 Main components of slag
Raw material
Slag composition
SiO 2
CaO
FeO
Al 2 O 3
MgO
Copper
Copper-containing slag
25~32
25~32
25~32
25~30
6 to 15
<20
<27
6 to 17
<4
<12
Furnace gas composition
CO 2
O 2
CO
Me
content
3 to 5
8~10
11~14
69～75