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The use of an electric arc furnace to treat nickel iron , which is simple and complex in composition, has certain advantages over other methods. However, it also has disadvantages: smelting consumes high electric energy, complicated process of removing impurities, and long process cycle.
The National Nickel Industry Institute of Science and the Babus Nickel Plant jointly developed and commissioned a method for treating nickel-containing waste, which was treated with a converter.
The company's process stipulates that nickel and iron are extracted from oxidized ore into ferronickel in a thermal furnace. In this case to obtain a nickel-depleted iron alloy. It is characterized by high impurity content. The approximate composition of the ferronickel is: Ni4 to 5%, Co 0.2% to 0.3%, Si4 to 6%, Cr 1.5% or less, C2% or less, S0.25% or less, and P0.15%. This kind of ferronickel cannot be a commodity and needs to be refined. The sulfur is first removed by an external furnace method, and then the impurities are removed in the converter. Impurities are melted into the melt by means of oxygen blowing. When processing ferronickel containing 2% silicon, a one-time refining is required.
High silicon nickel iron is continuously refined in two converters. The chromium and some of the cobalt are removed from the furnace with an acid lining and transferred to the slag; the sulfur remaining after the phosphorus and the depleted sulfur outside the furnace are removed in a furnace with a basic lining.
The first phase of refining is characterized by the release of large amounts of heat due to oxidation of silicon, carbon and local oxidation of iron:
Si+O 2 = SiO 2 + 875.71 kJ/mol ↘
C+O 2 =CO 2 +393.13 kJ/mol (1)
Fe+1/2 O 2 =FeO+268.77 kJ/mol ↗
In order to maintain a standard temperature of 1500 to 1600 ° C, a dedicated coolant must be used. The Babus Nickel plant uses limestone , oxidized nickel ore and water as this special coolant.
The cooling effect of limestone is based on its thermal dissociation:
CaCO 3 =CaO+CO 2 -205.65 kJ/mol (2)
At the temperature conditions of the converter smelting, an endothermic reaction occurs:
Fe (liquid) + CO 2 = FeO + CO - 13.93 kJ / mol (3)
The water entering the melt with the blast requires 6562 kJ/kg of heat for heating and gasification, so that the steam is heated to 1480 °C.
The treatment of recycled non-ferrous metals with the first batch of crude nickel iron in the converter has a problem associated with the thermal equilibrium of the converter. When the cold material of the nickel-iron alloy is added, heat is required to be heated and melted. In this case, the heat balance acts as a cold feed. When processing the more complex waste materials, they act as cold materials, and then start to oxidize and slag. The temperature in the converter began to rise. A near-value of the heat released during the oxidation of the metal-impurities can be determined according to the following reactions:
2Cr+1 1/2 O 2 =Cr 2 O 3 +1123.6 kJ/mol ↘
W+1 1/2 O 2 =WO 3 +858.15 kJ/mol (4)
Mo+1 1/2 O 2 =MoO 3 +326.8 kJ/mol
Co+1 1/2 O 2 =CoO+216.0 kJ/mol ↗
The listed thermal effect values ​​demonstrate that in the duplex process, it is desirable to place the regrind in an alkaline converter, i.e., the second refining stage. Because there is a lot of excess heat released during the first refining stage.
The properties of chromium, tungsten and molybdenum in an alkaline lining converter are similar to those described above, with the difference being the nature of the oxidant. When smelting ferronickel in an electric furnace, the power of impurity oxidation depends on the interaction in the solid-solid system, liquid-solid system. In converters, solid-gas systems, liquid-gase systems are the primary systems. These systems are more advantageous in terms of dynamics. If it takes a few hours to remove impurities in the furnace, it takes only a few minutes in the converter. [next]
When making ferronickel, special attention should be paid to copper when observing the condition of impurities in the converter. Copper is one of the least desirable and one of the most difficult to separate elements, especially at high temperatures. According to Eliot's data, in the Fe-Cu system, the activity coefficient of copper is equal to 10.1 in the low concentration range at 1600 °C. Under the same conditions, the activity coefficient of iron is only close to 1.
C, Si, Cr and W increase the activity of copper dissolved in iron. Nevertheless, it is still impossible for copper to be transferred to the slag according to the exchange reaction, ie in the system, there is no such metal oxide capable of transferring oxygen to copper.
The equilibrium smelting carried out by the Babus Nickel Plant indicates that the copper in the slag transferred to the refined acid stage is not more than 1% of its content; the copper in the slag transferred to the refined alkaline stage is slightly more, accounting for 6~ of its content. 10%. The content of copper in the slag was 0.007%.
Therefore, before the recycled metal enters the furnace, it is necessary to first expand the preparation of copper and not to incorporate commercial copper.
The obtained slag in a converter with an alkali lining contains CaO of 20 to 30%, Ni of 0.7 to 0.3%, and Co of 0.02 to 0.8%. Tungsten and molybdenum usually contain 0. n%, sometimes slightly more. The chromium content is about an order of magnitude higher.
Recycled nickel-containing waste entering the Babush Nickel Plant is generally a riser, slab, trimming, and scraping. The nickel content is 60% and the cobalt is 40%. Waste also contains a small number of other non-ferrous metals.
From the point of view of comprehensive utilization of resources, the complex alloy scraps sent to enterprises mainly have trimming and chipping, which is the most advantageous. The ingredients of this material are listed below:
Steel grade Ni Fe
Б-66 14.5 62
H29K18 ※ 29 33
ÐИ929 ※1 28 4.5
ÐИ598 64 4.5
ÐИ602 73 2.5
ÐИ617 65 4.5
ÐИ699 70 4.5
ÐИ703 37 32
ÐИ783 35 41
ÐИ481 8 67
ÐИ437 28 42
ÐИ126 27.5 40
The complex alloy raw material is charged into a converter and blown by oxygen. Carbon and phosphorus are removed from the ilmenite to remove tungsten, molybdenum and chromium from the recycled feedstock.
The product is nickel iron фH-07, containing Ni4～6%, C1.2～2.0%, Cu0.1%, Si3～5%. The user of ferronickel is the automotive tractor industry.
In domestic practice, a converter with a capacity of 50 tons is used. The converters with capacities of 250 tons and 300 tons have been designed, these are vertical furnaces. The main dimensions of the above-mentioned capacity converter are as follows:
Capacity (tons) 50 250 and 300
Furnace height (mm)
Overall high — 9485
Work space 6335 8490
Diameter (mm)
Outer diameter 5200 8350
Inner diameter 3600 6500
Furnace 1080 2600
Molten pool depth (mm) 1050 1500
Capacity ( m3 ) 55 217
The outer casing of the converter is welded with a calendered and molded steel plate of 35 to 100 mm thickness. The conical portion of the so-called "top cover" is often made in a removable form because it wears out quickly. The bottom of the furnace is also detachable. Converter with a basic lining in the furnace wall has two layers, an inner layer with magnesium chrome brick build from the insert, close to the housing by a layer of chromium magnesite brick.
A refractory powder (magnesia) is filled between the refractory brick layer and the metal casing. In order to prevent the converter from drying and expanding, every 12 to 15 bricks have a 3 mm thick expansion joint. The belt seam is lined with chrome-magnesia brick (Fig. 1). The average life of the converter is 150 to 200 furnaces. The burning speed of the lining was 0.3 mm/min. [next]
The smelting temperature and slagging system, the charging method and composition of the flux and recycled materials, and the duration of smelting are the basic reasons for the lining burn.
Figure 1 Vertical blown furnace (unit is mm)
The turning mechanism of the converter consists of a transmission system (reducer) connected to the lug with the transmission. The rotation is driven by two DC motors that can operate at the same time with a power of 75 to 200 kW. The oxygen blaster is made of three seamless concentric tubes. Oxygen is passed through the central pipe, passing water along the intermediate pipe, and the water is discharged along the external pipe. The connecting pipe at the upper part of the tuyere is connected with the oxygen pipe and the water pipe by a hose, and the copper joint is connected with the nozzle by screwing or welding at the lower part of the tuyere to supply oxygen to the converter.
The shape of the nozzle has an important influence on the process specifications. It can be made into a cylindrical shape with a wide outlet and contraction, with a rotating guide piece to ensure that the airflow reaches the speed of sound in the cylindrical retractable tuyere. This speed, as proven by practice, certainly has an effect on the kinetics of carbon oxidation, which can reduce the oxidizing property of the slag and reduce the spatter of the molten pool, which helps to absorb oxygen more fully.
The oxygen vents with Laval nozzles have an average life of 600 to 800 furnaces (Fig. 2). The length of the tuyere depends on the size of the converter, ranging from 7 meters to 15 meters; the diameter of the nozzle opening depends on the oxygen consumption, between 28 mm and 100 mm.
Figure 2 Laval nozzle (unit is mm)
Multi-flow nozzles are promising, ensuring oxygen supply to multiple locations in the converter, thereby reducing the swirling strength of the working chamber wall and reducing the vortex energy of the entire splash.
The practice of vertical blow furnace operation for many years shows the relationship between the furnace wall, the amount of charge, the oxygen flow force and the composition of the metal being drawn. The working volume of the vertical blown furnace should accommodate the two-phase molten pool (the volume of the two static cells) and the slag splashing area when the maximum amount of gas is separated.
(Former) The Soviet Union used a capacity of 0.8 to 1.0 m 2 /ton when designing the converter. The ratio of free working space to metal pool volume should be greater than 4, and the optimum ratio is V furnace : V metal = 5.
The depth of the static molten pool is 1 to 1.75 meters, and the ratio of the working space to the depth of the pool is equal to 5; the ratio of the diameter of the molten pool to the depth should be 3.0 to 3.6.
The furnace mouth is made inclined, and the diameter of the furnace lining should ensure that the nickel-iron is extracted, the flux and the recycled non-ferrous metal waste are loaded. In a medium volume converter, the diameter of the furnace mouth should be equal to one-half of the inner diameter of the converter.
The above information is usually used to verify the correctness of the selected converter. These converters are produced by machinery factories according to current standards. 11:21:25We are manufacturer of Check Valve in China, if you want to buy Air Check Valve,Brass Check Valve,One Way Check Valve please contact us.
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