The traditional agglo,-coke,-blast furnace cycle possesses well known essential and unavoidable drawbacks.

The extremely specific intermediate product-coke produced from peculiar coals-is needed for blast furnace smelting. The resources of such coals are restricted. Only 10% of the world ones are suitable for the production of coke. There are 6% of them in China along with the full absence of natural gas, 6-8% in South Africa. The similar situation exists in Korea, Australia, India. The Japan metallurgy employs only imported raw materials.

In CIS 1) the coking coals are not deficient. Their resource amounts to 58% of total.

Because of the natural discrepancy between a brand of any coal deposit and that one necessary to prepare a coking charge, an interbasin charging is widely employed. It includes contrary trans- portations of coals which do not possess selfcoking properties. In the case of lengthy communi- cations stipulated by big size of a territory, overloading and wearing out of railroad transport the situation is aggravated, becomes to be ruinous.

The rate of energy consumption and economic indices of production depend upon its scheme-relative quantity of iron reduced"by solid carbon"with CO formation,-"direct reduction degree"rd. At rd=l, complete combustion of CO with oxygen and transmitting of the evolved heat to the reduction zone the heat excess in system is equal to 3.41 GJ, or 116 kg of conventional fuel per 1 t Fe. Because of the unavoidable heat losses practically all schemes of reduction are in need of energy from outside (are"allothermic", from Greek"allos"-another one), for example, in the form of electric energy. The amount of necessary external heat compensation depends upon a scheme, and is minimal at rd=l [l].

The post-combustion of gas with the free oxygen in carbonless systems is feasible, has been undertaken repeatedly and employed in shaft (Viberg's process) and in some rotary kiln furnaces (Accar). In cupolas the blast is introduced above the level of the coke bed charge.

In the presence of free carbon in reducing aggregates it is impossible to achieve the Commonwealth of Independent States (late USSR).

complete oxydation of carbon. Failures in pertinent. attempts in low-shaft furnaces are known (in Mulheim, Ruhr; Calcutta, India).

The complete combustion of gas in the blast-furnace smelting is hindered not only by the presence of coke, which fills 3/4 of the furnace volume, but also by the equilibrium ratios in metal-oxides systems. Here rd=0, 5-0, 6, but the lack of heat is covered by the least profitable way - by the combustion of additional amount of coke in the hot zone of the hearth, where carbon oxidizes only to CO. The scheme of the process does not take into account the unique property of carbon as an energy source: despite the general rule, the cohesion with it of the first atom of oxygen gives less heat than of the second one 2). Less than 40% of carbon caloricity is realized therefore. It explains the similarity of energy consumption in agglo,-coke,-blast furnace cycle and in processes with electric energy application: the efficiency of transformation of primary fuel heat content into electric energy is 0.31 in CIS and 0.37 as an average in Europe.

The energy consumption in agglo,-coke,-blast furnace cycle is 23.4 GJ/t. With the return of 7,6 GJ with the waste gas for external employment taken into account the transparent consumption is equal to 16.1 GJ/t [2]. Quite near from it is the result 17.5 GJ/t in the paper [3].

Estimation [4] for the one of the best producers gave the value 23.4 GJ/t of cast iron, the expenditures for the production of sinter, pellets and coke included.

The rise of ore-carbon materials (pellets and briquettes made of finely dispersed components) permits to realize rational schemes of iron production to use completely the reducing and heat production possibilities of carbon in a single aggregate. Purely quantitative distinctions of these materials and ore-carbon stocks (degree of dispersion and area of contact interface between the components) commit to a system new qualities. The intensive reduction inside lump's volumes is compatible with the high oxidation potential in cavities between the lumps. Zones of reduction and oxidation here are separated by the protective gaseous film around a lump, which is forming and continuously renewing on heating.

The production of iron-carbon materials is now well-familiarized, so the processes with their employment are quite realizable. Their production is simplifying in the last years. Cellular rolls are suggested [5] instead of pelletizing dishes: a powder-like mixture after rolling between them transforms to flat grains.

The employment of iron-carbon materials has the additional advantage-the possibility of 2) Attempts were undertaken [2] to explain this phenomenon, but a generally adopted opinion is absent.

more precise dosing in their production than in the case of charging of their components into an aggregate separately.

The ecological advantages of iron-carbon materials before sinter are stipulated by the elimination of bursts. Sulphur is removed here on the stage of ore concentration. The evolution of sulphureous substances can be excluded at the employment of certain binders.

Economics of any production depends on its intensity. Rate of iron reduction differs for various combinations of aggregate states of oxide and reductant. Most slowly iron is reduced from solid oxides by gas, and it is of no importance by what method the gas was obtained: either by gasification of a solid fuel (processes Corex, Purofex, HyL-111) or with the help of natural gas reforming (Midrex). In the last case (shaft furnace of Orsk-Khalilov metallurgical plant) the intensity is only 0.04 kg Fe/m3 sec [6]. The specific productivity of a blast furnace (at the usual smelting rate of 0. 5t of pig iron daily per 1 m3 of the volume) is equal to 0.05 kg Fe/m3 sec. The gaseous metallurgy is perspective only if the intensity of a process is of no significance.

Carbon dissolved in liquid iron reduces iron of solid oxide most quickly: 22 kg Fe/m3sec, i. e. 440 times as quick than by gas, and 5-10 times more rapidly than by free carbon. Rate of the process falls with the increase of carbon activity ac in the melt up till the saturation (ac = 1) [7,8] (see the figure). Apparantly the phenomenon is linked with iron embryos formation and their dissolution in the bath. The dissolution of even compact iron in a bath proceeds with the rate of 3 order higher than that one following from the theory of convective diffusion, as has been settled by the method with a disk of equally accessible surface [9]. The anomaly remains to be unexplained, but it does not hinder the use of it in processes including the pertinent stage, for example-in the claimed one.

The intensive interaction of dissolved carbon with iron oxides in blast furnaces is excluded. Here the reduced iron melts at the content of about 1.7 % C [10], rapidly drops to the metal acceptor dissolving carbon of coke lumps up to the saturation.

In the view of the strong inverse dependence of the rate of the process upon the carbon activity in the liquid metal phase it is unexpedient to bring the carbon content in the product up to saturation, what takes place in all the analogs of the proposing method. Initial components of the ore-carbon materials must be dosed aiming to a final content of 2-3 % C in the bath. This task becomes to be attainable by the use of low carbon metal additions, such as broken amortizational scrap. Melting of it is in our case compatible with the main process.

Simultaneously can be solved the problem of utilization of secondary metal. Neither blast furnaces, nor converters, are fit for the purpose. The scale of open hearth steel production can

: hus be lowered essentially. 3) The development of the proposed method will not abolish chemical industry of its main raw material-coke oven gas if pyrolisis of not coking coals in coking ovens will be familiarized. The employment of gaseous coals will even increase the output of volatiles.

The solid product of such technology (powder-like carbon) can be used as a component for ore- carbon materials, [11].

Analogs of the invented method can be divided into two categories. One of them is characterized with employment of a proper material (in our case-ore-carbon briquettes or pellets) in unsuitable aggregate. In other ones a perspective aggregate is employed for another destination. Raw material and an aggregate for its working over are rationally combinated in the prototype, but its indexes can be substantially improved, and it is the aim of the present claim.

At Zhu Zhe plant briquettes of 24-120 mm size prepared from iron ore concentrate (66% Fe) bituminous and anthracite coals and the binder were melted in cupola equipped with the front furnace. It served also as a storing and combustion chamber furnished with tap holes and dust coal burner. So the ore-carbon material was heated in the volume of cupola by gas from the front furnace. During 5 melts 10 tons of briquettes were worked over obtaining 3.85 tons of metal containing 1.5-2. 9 % C spending 514 kg C and 80 kWh/t. The cost of this product was lower than the blast furnace one by 30 % [12].

At Elwood-sity plant (USA) iron is produced by heating of ore-coal pellets in a"rotary hearth"furnace (a ring furnace of the roundabout type) -with subsequent melting of semiproduct in electric furnace. The layer of pellets on the pallets is heated to 1250-1550°C from above with gas stream from burners, removing 90-95% 02 [13].

Similar installations are used somewhere else (methods Fastmet and Comet).

At Novotulskiy metallurgical plant ore-coal pellets were charged into a 10-tons open hearth furnace. CO evolved was combusted by the grazing flame and the heat of combustion was transmitted to the bath by dome radiation. Assimilation of the heat by the bath was promoted by the slag barbotage. ("BSL", method of the Boiling Slag Layer). Rate of heating of pellets by slag was higher than by gas. Iron reduced practically completely before melting the pellets. In such a way one succeeded to increase the bath contents by 30-44 %. The employment of an oxidizing 3) Accumulated amount of secondary metal stock in countries of CIS, for example, exceeds 2 billions of tons and is sufficient to work over yearly 60-70 millions of tons. Though the development of LD-process softened the requirements to the conversion pig iron composition, in CIS about 40% of steel is still produced in open hearths. aggregate led to the overoxidizing of the slag (10-15% FeO) and compelled to cease the process periodically to finish, deoxidize and desulphurate the metal [14]. The offering method provides the application of induction electric furnaces of industrial frequency for the working over of ore-carbon materials. The heating them in a bath here thanks to circulation of metal under the 125 influence of vortical Foucault currents proceeds with a density of heat flow towards the briquette surface up to 2 GW/m2. Here the most profitable combination of aggregate states of reagents is realized. The reduction of iron from solid oxides by carbon dissolved in liquid metal has the greatest velocity, as well as the solution of reduced iron in bath precedes unusually quickly.

From smelting reduction this method distinguishes in that the carbothermic reduction proceeds 130 the melting of oxide phase.

Comparison of the parameters and production indexes of arc and induction furnaces is in many cases in behalf of the latter ones. Their work is accompanied with less oscillations of electric regime. At a given electric power the temperature of metal can be easily regulated by charging rate of raw materials. Here are absent the high temperature zones inherent in 135 electric arcs, so an overheating and metal burning are easier to avoid. In arc furnaces there is no circulation of metal which in the induction ones provides the intensive heating of the charge.

Electric and thermal efficiency of powerful induction furnaces are compatible with those of arc furnaces: 0.87 and 0.81 correspondingly which gives the transparent efficiency 0.7 [15].

140 The expenditures for erection and exploitation of both types of furnaces are alike, but at a continuous of process those for the induction furnaces are less owing to the simplification of buildings and gas cleaning, obviation of the expenses for noise weakening, for refractories and service. The expenditures diminish additionally at the presence of two aggregates, one of which is at work and the other one-in repair. In this case the high degree of utilization of the power 145 settled is attainable [16,17].

The additional advantages as compared with the crucible induction furnaces possess the channel (horizontal) ones. Their electric efficiency at the melting of pig iron reaches 95 % and the power efficiency coefficient 0.8. Tapping from such furnaces without their inclination insures the stability of temperature regime of refractories work and excludes the mechanical strains at 150 taps. The continuous smelting of pig iron has been tested in the horizontal furnaces.

The charge here can be continuously loaded through the input opening and metal continuously poured through the taphole. Such a process is energetically profitable as here there is no the loss of power in periods of charging and tapping. High-alumina and mullite firebrick remain fit to further work even after 8,5 months of exploitations [18].

155 To diminish heat losses and energy consumption is useful to apply aggregates of a big capacity, for example such as the channel induction furnace of 6000 kW power, 1500 t capacity, and the productivity of 57 tons of scrap per hour. Taking into account the successful exploitation of such furnace at ISCOR plant (South Africa) the furnace has been constructed by Ajax Magnethermic Corp. (USA) for the Fukuoke plant of the Nippon Steel (Japan) intended for metal 160 scrap melting and keeping the pig iron at 1300-1500°C [19]. Being employed for carboelectrothermal process such aggregate can work in the mixer regime spending electroenergy only to compensate heat losses, as the process with post-combustion of gas is energetically self- sufficient.

Crucible unduction furnaces were employed for the production of synthetic pig iron from 165 oxidized charge without burning of alloying elements [20-22]. These furnaces are essentially melting, not metallurgical aggregates as they are not used for the production of metal from primary raw materials.

For the production of steel or a liquid semiproduct two-sectional channel induction furnace was applied [23]. Coal was immersing into one of the sections with the help of a plunger and 170 dissolving in metal to the content up to 4 %. Under the influence of an axial inductor the pig iron was forced to flow into the other section where it interacted with the ore charged through a dome from tubular furnace for prereduction. The achieved productivity was 50 kg/h, electroenergy consumption-1850 kWh/t (6.7 GJ/t). The method was not broadly adopted because of its evident intricacy.

175 The patented method [24] of obtaining the carbon composite melt in induction furnace of continuous action included the separate loading of materials beneath the melt mirror. Here the metal is not protected from secondary oxidation so the combustion of CO above the bath can be only partial, not complete.

At the plant in Lulea (Sweden) was built and tested the installation for pig iron production 180 in a crucible induction furnace (Inred Boliden method [25]). The crucible has an induction coil of 3 m in diameter and 1.9 m height. The aggregate worked in a mixer regime, had a productivity of 5 t/h, and produced 98t of pig iron containing 3.4-3. 9% C and 27 t of highly basic slag containing only 1% FeO. The combustion of gas, coal and black mineral oil in the volume under the dome according to calculation covered 90% of the heat needed in process. The possibility of 185 energetically self-providing of the process has been shown. The energy demand of the process was evaluated with the help of two-zone Rist's model [26]. At the productivity of 88 t/h the carbon rate was estimated to be 400 kg/t. The erection of a demonstrative unit has been planned for the output of 39 t/h (240 thousands of tons a year) with the crucible of. 6m in diameter. The projected consumption of primary energy (16 GJ/t) is lower than in the existing cycle.

190 The realization of the Inred method could be impeded with the unsuccessful constructive- technological decision. For storing of the metal acceptor was used in the form of a ringlike deepening in the bottom, i. e. below the inductor coil and out of the zone of its action. The latter was filled with conglomerate consisted of slag, coke and iron (the latter had the apparent density of only 1.1 t/m3. This pasty viscous mass accepted the induction heating badly. Here we 195 have an obvious underestimation of the role of starting volume of metal ("swamp") which is recommended to be up to 60% of crucible capacity.

In the paper [28] some questions were discussed concerning the employment of induction furnaces as an aggregates of metallurgical destination, problems of slag removal, choice of binders for the production of iron-carbon materials etc.

200 The patented method-prototype distinguished in the employment of ore-carbon single briquette of unlimited length (produced with the help of hot extrusion or pressing by screws used in the refractories industry) and gradual immersion of it into the metal bath of the induction furnace. It apriory proceeded from the notion of the uniformity of reduction velocity everywhere in the volume of a lump because it depends upon the temperature only, and the temperature field 205 within the lump volume supposed to be uniform. The rate of reduction in this case must not depend upon a size of lamps and must be determined by the rate of charging.

Investigations [29,30] of the last years undertaken in connection with Fastmet and Comet processes have shown that the temperature field inside the volume of iron-carbon particle is not uniform. Owing to the heat consumption by the reaction 210 Fe203+3C=2Fe+3CO-4. 19MJ/tFe rate of the process in the core of a lump drops behind and is determined by the conductive heat transfer through porous semiproducts of the reaction above. Therefore this rate depends not only upon the intensity of heating, but also upon the summary specific area of the external surface of lumps. Such an area of the above mentioned single briquette is unreasonably small and it is very 215 useful to increase it by replacing the single briquette with certain adequate quantity of smaller ones.

If, for example, to replace a cylindrical briquette with spherical ones of the same density, for a given charging rate their total quantity must be equal to n= 3HD2/(2d3), 220 where H, D-length and diameter of the replacing briquette, d-diameter of the spherical briquette.

At D = 0.12 m and H = 1 m (such briquettes, of the 17 kg mass, made at Makeevsky

metallurgical plant, were smelted in crucible induction electrofurnace in the Istra Division of the Scientific Research Institute) and d = 0.05 m the necessary amount is n = 173. The area of the heat accepting surface and smelt intensity will increase more than 4 times.

The suggesting here change of technology notwithstanding of its apparent simplicity permits to improve the process indexes essentially.

To enhance the process still more substantially is possible by limitation of carbon content in the bath (see above and figure). This measure has been lost in sight in the prototype as well as in all the analogs of the claiming method.

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