RU2193605C1 - Method of processing iron-manganese concretions containing phosphorus - Google Patents

Abstract

FIELD: ferrous and non-ferrous metallurgy; electric furnace reduction of high-phosphorous ironmanganese concretions containing non-ferrous metals. SUBSTANCE: proposed method includes high-temperature treatment of iron-manganese concretions at temperature of 800 to 1000 C and reduction electric smelting; reductant is fed to surface of melt at definite amount and is kept in this state during preset period of time. Conversion slag of electric smelting process is delivered for extraction of manganese and alloy is delivered for utilization of valuable components. Provision is also made for separation of iron-manganese concretions into +5mm and 5mm fractions at separate processing. EFFECT: reduced power requirements; facilitated procedure. 3 cl, 3 tbl

Description

 The invention relates to the field of ferrous and non-ferrous metallurgy, in particular to the process of electric furnace recovery of high phosphorous ferromanganese nodules containing non-ferrous metals, and can be used to extract manganese, non-ferrous and related noble metals.

 A known method of processing manganese raw materials with a high phosphorus content (0.2-0.25%), low iron content and a very low content of non-ferrous metals, in particular enriched manganese concentrate for the conversion of manganese slag by reduction smelting in ferroalloy ore-thermal furnaces with feed charge of a small amount of a solid reducing agent, for example, coke ("Production of Low Phosphorous Manganese Ferroalloys," Overview. Central Information Research Institute and feasibility studies of ferrous metallurgy, issue 3, M., 1987, p.2-3). The essence of the dephosphorization of the concentrate consists in the selective reduction of the phosphorus and iron contained in the manganese concentrate with carbon, converting them to the associated metal. At the same time, a small amount of reduced manganese (up to 10%) also passes into the metal-containing melting product.

 Before smelting, the initial manganese-containing raw material (ore) with a high content of gangue is subjected to enrichment (washing, magnetic separation, etc.). In this case, 20-25% of Mn contained in raw ore is lost with washing sludge. If necessary (fine particle size distribution), the enriched manganese concentrate is subjected to agglomeration, for example, by agglomeration.

 The resulting metal, as a rule, is sent for recycling to blast furnace production to produce special cast iron or to steel production for the smelting of automatic steels with a high phosphorus content.

 The disadvantage of this method is its bulkiness (a large number of redistributions), as well as the limitation of the allowable phosphorus content in the processed raw materials, which does not allow processing of high-phosphorous types of raw materials, including non-ferrous metals, in particular ferromanganese nodules, by this method. In addition, the co-loading of the reducing agent in a mixture with the raw material leads to an over-expenditure of the reducing agent due to its longer residence time in the furnace and a greater degree of “burn-out”.

Closest to the claimed method for processing ferromanganese nodules, the technical solution is the US patent 4162916 "Method for processing complex metal-containing ore, such as nodules," adopted for the prototype. According to this method, nodules containing, along with valuable metals (manganese, iron, non-ferrous metals) and impurities such as phosphorus, sulfur, etc., are subjected to high-temperature processing by drying at temperatures above 500 ^o C (mainly 650 ^o C), then nodules or the briquettes obtained from them are loaded with the amount of carbon-containing reducing agent required for separating copper from manganese into an electric furnace. (5 kg of coke are added per 100 kg of nodules). Processing of nodules is also possible using a liquid reducing agent, for example fuel oil, which is introduced at the stage of obtaining briquettes. At the first stage of electric melting, two intermediate products are obtained: primary manganese-containing slag, including a smaller part of copper, and a primary metal alloy containing the bulk of copper, as well as nickel and cobalt. The obtained primary metal alloy is sent for processing in order to extract non-ferrous metals. At the next stage of the process, primary manganese-containing slag is decontaminated by ferrosilicon to obtain a converted manganese slag and a secondary metal alloy containing, in addition to Cu and Fe, up to 15% Mn. Converted manganese slag is processed to produce marketable manganese-containing products, for example ferromanganese, and the secondary alloy is sent to the process head using available Fe as a non-ferrous metal reducing agent.

 The disadvantages of the prototype include the impossibility of obtaining this method of slags suitable for the production of ferromanganese and other manganese-containing products from high phosphorus nodules (phosphorus content of more than 0.25%) due to the transition of phosphorus to the manganese slag, as well as the complexity of the process and high energy consumption.

 The technical result of the invention is to increase the ratio Mn / P in the slag to the required (not less than 350) for its further processing into commercial manganese-containing alloys, as well as simplifying the method and reducing energy consumption.

The technical result is achieved by the fact that the processing of ferromanganese nodules containing, in addition to manganese and iron, non-ferrous metals and phosphorus, is carried out as follows: ferromanganese nodules are sent to the high-temperature processing operation at a temperature of 800-1000 ^o C, the prepared material is melted in an electric furnace without a reducing agent, into a melt load a solid reducing agent in an amount of 2.5-6% based on carbon from the weight of the loaded nodules, withstand the melt with a reducing agent in an oven for 0.5-3 hours owls and produce the resulting slag, which is sent for processing to obtain marketable manganese-containing products, and the resulting metal alloy is released and sent for the disposal of useful components.

 In a particular case, to increase the total extraction of manganese from ferromanganese nodules before firing, the nodules are separated into fractions of +5 mm and -5 mm, the -5 mm fraction is separated and processed separately, and the +5 mm fraction is sent to the electric melting with the loading of a solid carbon-containing reducing agent on the surface melt. The -5 mm ferromanganese nodule fraction can also be processed according to the scheme adopted for the +5 mm fraction, and the tailings slag obtained from the electric melts of both fractions are processed together.

 The electrofusion of high-temperature treated nodules with the loading of a solid carbon-containing reducing agent on the melt surface with subsequent melt holding allows one stage to provide the necessary degree of separation of phosphorus from manganese with the transfer of the required part of phosphorus to a metal alloy and thereby to obtain products suitable for further processing of high-phosphorus ferromanganese nodules processing: a metal alloy containing the bulk of non-ferrous metals, iron and phosphorus and conversion manganese slag containing manganese and iron, with a ratio of Mn / P> 350 in it, which can be used in the production of ferromanganese.

 Electric melting with the supply of a solid reducing agent to the melt surface and holding the melt with the reducing agent for a certain time leads to the fact that the reducing agent interacts with a constantly updated surface of the melt, which is in a strong convective motion in the immersion region of the electrodes located up to the slag-metal alloy interface. The resulting smallest particles of a metal solid solution based on reduced iron, which is the extracting phase for phosphorus, and non-ferrous metals coagulate with each other, coarsen and fall into the bottom phase formed on the bottom of the furnace. Thus, due to the constant contact of the upper layer of the melt with a reducing agent, it is depleted in iron, non-ferrous metals, and phosphorus, which transform into the alloy, and its enrichment with manganese. The alloy accumulating on the bottom contains, by weight. %: Mn ~ 9-11; Cu ~ 0.2; Ni ~ 0.5; Co ~ 0.1; P ~ 5; Fe ~ 78-83 and can be disposed of in blast furnace production. The claimed amount of carbon-containing reducing agent (2.5-6%) is sufficient for the development of the process of recovering the amount of iron necessary for the conversion of non-ferrous metals and phosphorus into an alloy without reducing manganese, which mainly remains in the slag at the required Mn / P ratios. The amount of reducing agent less than 2.5% does not provide the necessary degree of recovery of phosphorus and non-ferrous metals. Exposure of the melt with a reducing agent for 0.5-3 hours allows you to achieve the required degree of recovery of phosphorus and non-ferrous metals, a longer exposure is associated with increased energy consumption.

The conditions for preparing nodules for electric melting (roasting or calcining at a temperature of 800-1000 ^o C) allows you to completely remove the volatile components of nodules and carry out electric melting with the reductant loaded onto the melt, avoiding the foaming of the melt, which can lead to process shutdown. A temperature of less than 800 ^o C does not allow the complete removal of volatile components. Raising the temperature above 1000 ^o With impractical, since the necessary degree of removal of volatile components has already been achieved and a further increase in temperature only leads to overheating of nodules and increased energy consumption.

 The proposed method, compared with the prototype, allows for one stage of electric melting to obtain products from high phosphorus nodules that can be used to obtain marketable products containing valuable components, this simplifies the processing method and reduces energy consumption by eliminating the second stage of electric melting, and processing the working alloy obtained at this stage.

 When dividing the initial ferromanganese nodules into fractions of +5 mm and -5 mm, a significant part of non-ferrous metals is concentrated in a smaller fraction, a significant part of phosphorus also passes here, therefore, its separation will already allow phosphorus and non-ferrous metals to be further separated from manganese in the process head. The ratio of manganese, phosphorus, and non-ferrous metals in the fraction (+5 mm) extracted during mechanical separation is such (Table 1) that, upon subsequent electric melting, the slag practically does not contain non-ferrous metals and is suitable for processing to ferromanganese (Table 1). The -5 mm fraction can be processed in a separate branch, for example, according to the roasting-reduction electric melting scheme, and when restoring this fraction in the furnace, taking into account the use of the entire combination of the claimed parameters, non-ferrous metals are mainly converted to a metal alloy. The resulting slag has a composition similar to that of perdelnogo slag from the electric smelting fraction +5 mm, which makes it possible to process them together.

 The parameters of the proposed method for processing ferromanganese nodules were established in the research process on a large-laboratory three-electrode electric furnace. Ferromanganese nodules were calcined in an enlarged laboratory tube rotary drum furnace.

 The implementation of the proposed method is illustrated on a representative batch of ferromanganese nodules deposits of the Baltic Sea. In the table. 1 shows the average compositions of ferromanganese nodules, including initial sample (without separation into fractions), fractions +5 mm and fractions -5 mm.

 As a reducing agent used coke with a carbon content of 85 wt.%.

An electric furnace (EPU) with a capacity of 225 kVA was a pilot enlarged laboratory three-electrode rectangular furnace with an electrode diameter of 125 mm, designed for melting metals, ores or concentrates, slags, and other materials. The slag capacity of the unit is 30 t / day • m ² .

 The melt bath level in the electric furnace was 500-550 mm, the metal level was 100-150 mm.

 Before loading into the receiving hopper of the installation, each portion of ferromanganese nodules was previously weighed and tested. Nodules were loaded into the furnace through a rectangular slit (loading window), available in the arch of the furnace, using a vibrating feeder. Here, after the melting of the metal, coke was also served. After each smelting, the products obtained (slag and metal alloy) were discharged into the ladle from the notch located near the bottom. At first, metal was produced, then slag. Frozen in the ladle melting products after weighing were tested.

 The conditions under which the experimental swimming trunks were carried out are given in table.2.

Melting 1 was carried out with pre-calcined at 900 ^o With the original ferromanganese nodules; nodules were first loaded and melted into the furnace, then coke was added to the molten bath in an amount of 4% based on carbon based on the mass of nodules; the melt was kept in an oven for 1.5 hours.

When conducting melting 2 ferromanganese nodules, previously calcined at 900 ^o C, were loaded into the furnace together with coke; other parameters: amount of reducing agent, melt holding time in the furnace, remained the same as in the first heat.

 In all subsequent swimming trunks 3-18 coke was also fed to the melt. In all melts, only one process parameter was selectively changed, including the calcination temperature or the amount of reducing agent supplied to the melt per carbon from the mass of nodules loaded into the furnace, or the exposure time of the melt with the reducing agent in the furnace. Moreover, all other parameters were kept the same, declared in the middle of the range.

Swimming trunks 3-8 were carried out in order to determine the temperature necessary for the calcination of ferromanganese nodules necessary for the process, while in melting 3, non-calcined nodules were used, and in melting 4-8 the calcination temperature was changed in the range 750-1050 ^o C.

 In melts 9-13, the amount of reducing agent supplied to the melt was varied from 2 to 6.5 wt.% Calculated on carbon from the mass of nodules loaded into the furnace.

 In swimming trunks 14-18, the exposure time of the melt with the reducing agent in the furnace was changed from 20 minutes to 3 hours 15 minutes.

 In the table. Figure 3 shows the results obtained from experimental melts of ferromanganese nodules.

 When melting 1, the Mn / P ratio in the slag is 350 and a relatively low specific energy consumption of 3250 kWh per 1 ton of manganese in the slag is obtained.

 As follows from the data in Tables 2 and 3, in all cases when the claimed process parameters were supported (swimming trunks 1, 5-7, 10-12 and 15-17), the required Mn / P ratio of more than 350 was achieved. Moreover, in all In the indicated melts, the specific energy consumption per 1 ton of manganese in the tailing slag was low.

 In smelting 2, a lower Mn / P ratio was obtained in the slag at lower, in accordance with the feedstock, non-ferrous metal contents in the metal alloy.

Swimming trunks 3-8 showed that the set calcination temperature range of 800-1000 ^o C is very important for the reliable provision of normal conditions for the melting of the loaded nodules during the collection of the melt bath, completely eliminating the "foaming" of the melt in the practical implementation of the process. During melting 3, during the bath set-up, there was a slight “foaming” of the melt. A much smaller "foaming" was also observed during smelting 4. With an increase in the temperature of calcination of nodules to 800 ^o C (smelting 5), this phenomenon completely disappears.

When deviating from the declared range of calcination temperature (800-1000 ^o C) in the direction of lowering the temperature in smelting 4 (calcining temperature 750 ^o C) and when using non-calcined nodules (smelting 3) at high ratios Mn / P in the slag, an increase in specific consumption was observed electricity per ton of manganese in slag. This is due to the low temperature of calcination of nodules (smelting 4), and therefore an additional energy consumption was required to remove residual volatiles and the need for energy costs to completely remove volatiles (smelting 3). With an increase in the temperature of calcination above 1000 ^o C in smelting 8 (1050 ^o C) with the obtained high ratio Mn / P in the slag, the specific energy consumption per ton of manganese did not exceed the same indicators of previous melts. However, the use of the indicated calcination temperature is impractical due to unreasonable overheating of nodules during calcination after the almost complete removal of volatile substances.

 When deviating from the claimed limits, the amount of coke fed to the melt calculated on carbon from the loaded nodule mass to the side of its reduction to 2 wt.% In smelting 9, a decrease in the Mn / P ratio <350 in the slag was observed. However, due to the lack of coke, comparatively low contents and extraction of non-ferrous metals and phosphorus into the metal alloy were also obtained. With an increase in the amount of coke loaded onto the melt to 6.5 wt. % in smelting 13, the Mn / P ratio in the slag is rather high, and the specific energy consumption per ton of manganese in the slag is low. However, with such a quantity of coke, the losses of reduced manganese with a metal alloy increase, which is unacceptable.

 When deviating from the declared limits of the exposure time of the melt of ferromanganese nodules with coke in the direction of its reduction to 20 minutes in smelting, 14 specific energy consumption per ton of manganese in the slag decreased. Nevertheless, the use of the indicated exposure time of the melt with coke was clearly not enough to remove phosphorus into the metal alloy, and the content of non-ferrous metals in the slag slightly increased. With an increase in the duration of exposure of the melt of nodules with coke to 3 hours 15 minutes in smelting 18, it led to an excessive consumption of electricity and a decrease in furnace productivity, although the Mn / P ratio was quite acceptable.

Claims (3)

1. A method of processing iron-manganese nodules containing phosphorus, including high-temperature processing of nodules at a temperature of more than 800 ^o C, reducing electric smelting of nodules with a solid carbon-containing reducing agent for manganese slag and a metal alloy, processing slag for a commodity manganese-containing product and alloy with the utilization of valuable components, characterized in , which nodules after the high temperature treatment by calcination and / or calcination at a temperature of 800-1000 ^o C is reductively electric smelting with the supply of solid carbon-containing reducing agent to the melt surface in an amount of 2.5-6% based on the carbon of the mass of loaded nodules, the melt is held in the furnace for 0.5-3 hours, and the resulting slag is sent to produce manganese-containing products .  2. The method according to p. 1, characterized in that the -5 mm fraction is separated from the ferromanganese nodules before firing and processed separately. 3. The method according to p. 2, characterized in that the -5 mm fraction is processed separately according to the scheme of firing and / or calcination at a temperature of 800-1000 ^o C, reducing electric melting with a load of solid carbon-containing reducing agent supplied in an amount of 2.5-6% on the surface of the melt, and exposure to the melt for 0.5-3 hours, and the resulting manganese slag is processed into a marketable product together with the slag obtained by electrofusing a fraction of +5 mm.

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