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Figure 2 Blast furnace for smelting recycled lead materials (unit is mm)
The best technical and economic indicators can be achieved by smelting with hot air at 240-300 °C. The hot air can accelerate the smelting process under the condition of reducing 15-20% coke at the same time, and regulate the heat exchange between the furnace gas and the charge. After reducing the ferrous oxide content in the slag, the refractory calcium slag can be utilized. As a result, the loss of lead with slag is reduced.
Blast furnace smelting and recycling lead raw materials
(Former) Soviet Union about 80% recycled material is lead in the blast furnace process. The amount of recycled lead raw materials used in blast furnaces abroad is similar.
The blast furnace refining and recycling lead material is a typical reduction process. Its mission is to make the lead and antimony concentrated In one metal, and all the rest is converted into slag. May get some amount of matte (1 to 2% of the sulfur content is higher than when the charge).
The treated regenerated feedstock is characterized by two different charge components in the feedstock - components having a high saturated vapor pressure at elevated temperatures and components having a low drink and saturated vapor pressure.
The first category belongs to the first compound of bismuth and lead. The second category is broader. It includes other compounds of non-ferrous metals (such as copper), iron compounds, and mineral-free rocks.
The most easily transferred to the gas phase is a ruthenium compound. The vapor pressure (Psb 2 O 3 ) at 772 ° C was 7.98 kPa.
Lead sulfides have high volatility.
The interaction between the high-valent oxide and sulfate dissociation processes, the solid-phase and gas-phase components, and the solid-phase and liquid-phase components should be attributed to the interaction in the blast furnace. For example, lead sulfate is clearly dissociated at temperatures above 707 ° C, and PbO 2 is actually completely decomposed into PbO at 627 ° C. The undecomposed lead sulfate interacts with the sulfide in the following reactions:
PbSO 4 +Pb S =2Pb+2SO 2 (1)
The equilibrium pressure of SO 2 was 3.99 kPa at 597 ° C and 100.4 kPa at 673 ° C.
The solid charge of the furnace body is penetrated by the rising gas stream, and one of the components of the gas stream is a product of incomplete combustion of the coke in the CO-duct region. As noted earlier, non-ferrous metal oxides are readily reduced. The reduction process is essentially carried out in a solid-state process in a solid phase.
Lead oxide is reduced at 177 ° C by the following reaction:
PbO+CO=Pb+CO 2 (2)
The ruthenium chloride (Sb2O3) is reduced by the following reaction:
Sb 2 O 3 +CO=2Sb+CO 2 (3)
The temperature range is from 400 to 700 °C.
The reaction formulas (191) and (192) are desirable because the purpose of the smelting is to prepare a lead-bismuth alloy.
As the charge moves closer to the tuyere zone (the highest temperature zone), both the reaction between the solid and liquid components and the interaction in the liquid phase are developing.
In this regard, the PbO-Sb 2 O 3 system listed in Figure 1 is most meaningful. As can be seen from the figure, Sb 2 O 3 greatly reduces the melting point of PbO. Establish a balance between the oxide phase and the metal phase:
3PbO+2Sbâ†â†’Sb 2 O 3 +3Pb (4)
The equilibrium constant of the reaction can be reflected by the activity:
K=apbasb 2 o 3 /a 3 pboa 2 sb (5)
Figure 1 PbO-Sb 2 O 3 system state diagram
The correlation between the equilibrium concentration of lead in the lead and the Sb 2 O 3 content in the slag at a temperature of 802 ° C is as follows:
Sb 2 O 3 (%) 20 24 30 36 40
Sb(%) 0.018 0.04 0.13 0.40 1.0
The data listed demonstrates that PbO is an oxidant of hydrazine. Therefore, in order to transfer the crucible to the metal lead in the greatest amount, it is necessary to create a condition in the furnace for reducing lead and antimony oxide with a gaseous reducing agent (CO). [next]
Metallic iron can also act as a reduction in smelting. Iron is fed into the furnace as a charge component, and sometimes it is specifically charged with a flux. Iron oxide is necessary for slagging, and metallic iron is used for the interaction of the following reactions:
PbO+Fe=FeO+Pb (6)
PbS+Fe=FeS+Pb (7)
Liquid smelting products, slag and metal accumulate in the hearth and are layered there according to density. Lead is continuously discharged from the lower part of the hearth (through the flow cell), and the slag is periodically discharged through the discharge port placed in the upper part of the hearth, which creates favorable conditions for the process at the interface of "metal and slag" and makes the system Close to equilibrium.
The furnace used in the smelting furnace smelting process to regenerate the lead-containing raw material is structurally different from the furnace for reducing the smelting of the lead agglomerate produced from the concentrate, which is only small in size. This is conditional on the treatment of rich materials. Basically, a water jacket furnace with a rectangular cross section is used. In foreign practice, circular and elliptical blast furnaces are used in some cases. The blast furnace used in domestic practice is shown in Figure 2. The cross section of the tuyere is 2 to 5 m 2 . In order to supply air to the furnace, several air nozzles having an opening diameter of 110 to 120 mm are installed. The tuyere pressure is 25 to 30 kPa. The furnace is equipped with an evaporative cooling water jacket. Evaporative cooling stabilizes the smelting process, improves maintenance intervals, and reduces nodulation. Vapor (3 to 4 tons / hour) with a pressure of 0.5 to 0.6 MPa can be produced by using renewable energy.
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The furnace top is used to charge the furnace. The agglomerate, coke, and battery waste are charged into the furnace by turning the electric handlebar. The height of the charge is maintained at 1.5 to 2.0 meters below the level of the roof platform. When the Ukrainian zinc plant processes the agglomerates and waste lead storage batteries, the following materials are used: 20 to 25% of the agglomerates, 70 to 73% of the waste lead storage batteries and scraps, and 7 to 8% of the coke.
Lead is continuously poured into the ladle from the furnace through the siphon and transported to the refining workshop. The slag (copper copper) is periodically (or continuously) placed in the front bed, and the metal beads are separated from the slag in the front bed, and then the metal slag is poured into the slag ditch and sent to the slag heap. In the production of the third product, matte, the matte is injected into the chain mold and sent for processing. The yield of slag is 35 to 45% of the total agglomerate and total lead. Adults of slag: SiO 2 30~45%, Al 2 O 3 9-11%, FeO20-30, CaO14-19%, lead 0.5-1.5%, 锑0.5-1.5%, copper 0.2-0.25%, tin 0.5 ~1.25%.
Table 1 lists the material balance of the blast furnace regenerative lead material, and Table 2 lists the distribution of the metal in the blast furnace smelting product. [next]
Table 1 Material balance of blast furnace regenerative lead raw materials
Raw materials and smelting products
%
Main metal content (%)
Pb
Sb
Sn
Cu
Incoming charge
Sintered block
39.20
20.89
0.61
0.47
0.98
Waste battery
44.20
71.50
2.42
0.13
0.20
Unsorted raw materials
4.20
68.0
2.92
0.44
0.01
scum
4.86
62.21
3.99
2.10
7.38
Return residue
7.14
0.95
0.04
0.07
0.21
Smelting product
Crude lead
46.18
93.47
3.51
0.45
1.25
Slag
46.45
0.95
0.04
0.07
0.21
Bronze
4.96
15.13
0.14
0.33
5.10
Smoke
2.40
48.44
0.58
2.38
0.35
Table 2 Distribution of metal in blast furnace smelting products ( % )
Smelting product
Pb
Sb
Sn
Cu
Crude lead
93.98
99.36
56.47
66.34
Slag
0.96
1.25
8.84
11.20
Bronze
1.62
0.43
4.43
29.10
Smoke
2.53
0.85
15.21
0.95
loss
0.63
0.21
3.06
0.25
error
-0.28
+2.10
-11.99
+7.84
The loss of non-ferrous metals with slag is directly dependent on the completeness of the reduction of the charge. At the same time as the slag is depleted, the content of metal impurities in the crude lead increases, and the unit yield is high. The impurities float on the surface of the pot.
The thermal balance of the blast furnace lead storage battery waste is shown in Table 3 (calculated as 100 kg of charge; coke consumption 12%; ash 10%, exhaust gas CO content 14%, CO 2 content 14%).
Table 3 Heat balance of smelting lead battery waste in blast furnace
Heat income item
Heat (%)
Hot expenditure item
Heat (%)
Burning from carbon to CO 2
75.1
Oxide reduction
16.8
Burning from carbon to CO
22.7
Metal and refractory dross
2.9
Physical heat:
Blast
1.0
Slag
3.0
Charge
1.2
Water jacket
41.5
Smoke
35.8
total
100
total
100
The basic term of heat income is the burning of coke and organic compounds. The heat lost is mainly driven away by the water and smoke in the water jacket.
The blast furnace smelting has the characteristics of high productivity and continuous operation of the process as compared with other methods of processing bulk regenerated raw materials. The main technical and economic indicators for blast furnace smelting are listed below:
Unit productivity (ton / meter 2 · day and night) (according to the charge) as a god 50 ~ 60
Coke consumption (%) 8~12
Blast pressure (kPa) 25~30
Temperature (°C)
Hot air 250~300
Exhaust gas 200～300
Lead content (%)
Thick lead 91~94
Bronze 35~40
Slag 4~3
Soot 2~5
The disadvantage of blast furnace smelting is that the amount of dust discharged is large, only the agglomerates can be scraped, and expensive coke is used.
The process of treating the lead agglomerate, recycled raw materials and waste lead storage batteries in the blast furnace.