Blown smelting of raw and recycled raw materials
In recent years, due to the limited raw materials, blasting of glacial copper has become more and more significant. Copper sulfide ores, frit and renewable raw materials (waste televisions, double metal bulk, thin pasteboard, etc.) are copper-containing material (such as waste materials containing copper reproducing television, such as a bimetal composition and properties Previously listed).
The Karabash Copper Smelting Company uses the process developed by the Ural Copper Scientific Research and Design Institute to mix the raw and recycled raw materials with a blast furnace. The process flow for processing raw ore and recycled raw materials for the preparation of blister copper is shown in Figure 1.
Figure 1 is a process flow diagram for processing raw ore and recycled raw materials for preparing crude copper.
The composition of the raw material in the copper-containing charge provided by the sulphide ore of the Guyi deposit is: copper 4 to 6%, iron 17 to 18%, sulfur 20 to 21%, zinc 1.6 to 2.4%, and silica 32 to 50%. . Among them, nonferrous metals and iron exist in the form of sulfides (CuFeS 2 , Zns, FeS 2 , etc.).
The frit is formed when the zinc slag is treated by a rotary kiln method. This is a heterogeneous material, including sulfide, silicate, metal, and carbonaceous compositions. The sulfide component of the frit is a copper wall, iron, zinc, lead sulfide, the silicate component is an oxide of silicon, calcium and aluminum , the metal component is a carburized iron alloy, and the carbon component is Blocky coke.
The chemical composition of the frit is: copper 2 to 3%, zinc 1.5 to 3.5%, lead 0.2 to 1.5%, iron 27 to 35%, silica 11 to 15%, calcium oxide 3.3 to 4.0%, aluminum oxide 4 to 5%, sulfur 5 to 6%, and carbon about 20%. The amount of copper plating is 22 to 32%, and the amount of iron plating is 80 to 90%. The fine fraction (-10 mm) in the frit accounts for a large proportion (60 to 70%), resulting in an increase in the amount of soot during smelting and uneven blasting into the charge.
The Karabash Copper Smelting Company will layer the copper-containing charge in 20,000 to 30,000 tons per pile. Limestone , converter slag and coke are separately charged into the blast furnace. Quartz is not used as a charge component because there is enough quartz in the ore and in the solution to make slag, no need to add.
Depending on the nature of the physicochemical action carried out, this type of blast melting belongs to semi-self-heating smelting. The heat required for the smelting process is derived from the oxidative exothermic reaction of sulphide and slagging and coke combustion. Semi-autothermal smelting is carried out according to the composition of the raw materials, and the coke consumption is 6 to 14%. According to the height of the furnace, it is divided into three areas: a preliminary area, an oxidized melting area and a hearth area.
In the above preparation zone, the charge temperature is 280-880 °C. The environment in this area is an oxidizing environment, so the oxidization of the sulfide and charge metal components is basically carried out because most of the sulfides have a lower ignition temperature than coke. The ignition temperature of coke is 580 to 880 °C.
The biggest feature of the preparation area is the interaction:
2FeS 2 + 5.5O 2 = Fe 2 O 3 + 4SO 2
3FeS 2 +8O 2 = Fe 3 O 4 +6SO 2
FeS 2 =FeS+0.5S 2
2CuFeS 2 +6.5O 2 =CuO·Fe 2 O 3 +CuO+4SO 2 (1)
2CuFeS 2 =Cu 2 S+2FeS+0.5S 2
2Me+O 2 =2MeO
S 2 +2O 2 = 2SO 2
CaCO 3 = CaO + CO 2 and the like.
In the oxidative melting zone (temperature 880 ~ 1380 ° C), according to the degree of heating of the charge, the fusible components of the charge (copper, iron, lead, nickel and recycled metal raw materials) are melted, in this zone, from the rock-forming component Perform slagging. When the liquid phase flows into the lower portion of the furnace, the refractory component of the charge is simultaneously melted. In the sulfide melt (copper), non-ferrous metals, precious metals and metallic irons are dissolved. The result is a sulfide-metal melt. In the slag solution containing 2FeO·SiO 2 as an essential component, oxides of calcium, aluminum, magnesium and other metals are dissolved.
In the area directly adjacent to the tuyere and slightly above the tuyere, there are quartz and coke beds through which the metallized matte and slag are filtered. In the tuyere area, the maximum temperature (1400 ~ 1450 ° C) is reached. The main heat source in the tuyere area comes from the intense reaction of the tuyere area:
C+O 2 =CO 2 +393.5 kJ (2)
2FeS+SiO 2 +3O 2 =2FeO·SiO 2 +2SO 2 +1043 kJ (3)
2Fe+SiO 2 +O 2 =2FeO·SiO 2 +336 kJ (4)
The main role of the smelting process index for the sulphide feedstock and the copper-containing waste blast furnace is the oxidation of ferrous sulfide and metallic iron and the slag formation of other oxides through the coke-quartz bed layer.
When the blast furnace processes ore and frit, a relatively fusible sulfide-metal melt is formed. The iron oxidation and slag formation of the melt are carried out according to the reaction formula: 2SnOâ†â†’SnO 2 +Sn, ZnO·Fe 2 O 3 +Fe+C(CO)→Zn+3FeO+CO(CO 2 ). The results show that the metal iron is first oxidized, and the ferrous sulfide begins to oxidize only when the metal iron concentration is reduced to a certain limit.
When the copper-containing reclaimed raw material having a high iron content (80% or more) is contained in the charge, the slagging process of the metallic iron is quite complicated. This is related to the fact that the refractory alloy steel and bulk scrap of the metal contained in the recycled raw material are not guaranteed to dissolve in the sulfide melt. When the regrind with high iron content is charged, the furnace is gradually filled with the furnace, and the process is abnormal.
By increasing the consumption of the return converter slag: Fe + Fe 3 O 4 = 4FeO can convert part of the recycled metal iron into a melt.
Therefore, it is possible in a case where a blast furnace treats copper waste having a high iron content, that is, when the condition for dissolving metallic iron is created in the furnace, the metal iron is a solution of sulfide or oxide, and exists in the presence of quartz. Under conditions, the sulfide metal-melt is subsequently oxidized.
A liquid fire smelting product, ice copper and slag, is accumulated in the hearth, and the interaction between the oxide and the sulfide ends. The temperature in the hearth is 1200 to 1300 °C.
The working practice of the blast furnace of Karabash Copper Smelting Company shows that the uniformity of the ingredients of the raw material components is destroyed, the coke consumption is excessive, and the temperature of the tuyere zone is lowered because the iron tumor is formed in the furnace and the hearth, and the non-homogeneous melt is formed. "Blocked" the outlet of the stove.
In the blast furnace with a cross-sectional area of ​​13.5 to 15.0 m 2 in the tuyere region, the mixture of the sulfide ore raw material and the copper-containing regenerated raw material is treated into matte. The blast furnace, the top of the furnace and the flue of the furnace are packaged with water with evaporative cooling. The furnace was equipped with an unheated front bed having a volume of 40 m3 , and the liquid smelting product in the front bed was separated into matte and slag. The cyclone is composed of a cyclone dust collector to collect dust from the flue gas to ensure that the dust collection rate is not less than 99.3%.
In recent years, the composition of the blast furnace charge at the Karabash Copper Smelting Company has undergone substantial changes. For example, the proportion of ore in the charge has been reduced from 40.0% to 28.5%, and the proportion of frit and recycled raw materials has increased from 14.5% to 28.5%, and from 2.0% to 4.6%. About 8% of the charge is limestone and 20% is converter slag. At the same time, due to the optimization of the process, the consumption of coke is also reduced from 12.6 to 8.9% from the total amount of charge (excluding the carbon entering with the melt).
The production capacity of the blast furnace is 42 to 45 tons / m 2 · day and night.
The composition of the matte obtained during smelting is 25 to 30% of copper, 40 to 45% of iron (4.5 to 5.5% of metallic iron), and 23% of sulfur. The copper entering the matte is 85 to 87%. The components contained in the slag are: 0.25 to 0.30% of copper, 1.0 to 1.5% of zinc, 30 to 32% of silica, 35 to 38% of iron (including 1.5 to 3.5% of metallic iron), and 10 to 15% of calcium oxide. Aluminum oxide 4 to 6%. The composition of the waste flue gas is: 0.6 to 2.5% of sulfur dioxide, 8 to 10% of carbon dioxide, and 8 to 10% of oxygen molecules. The amount of dust discharged during smelting is 8 to 9% of the total charge of the charge.
Under the conditions of the Karabash Copper Smelting Company, the content of high-iron reclaimed material in the blast furnace charge is 4.5 to 4.6%, which is the limit content, which is consistent with the theoretical concept of this smelting method.
The air preheater is started and hot air of 280-330 ° C is blown into the furnace, and the concentration of the recycled raw materials and the frit can be increased by concentrating the tuyere area and increasing the temperature thereof.
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