CZ20032954A3 - Process for producing liquid steel from solid charge and apparatus for making the same - Google Patents

Abstract

In the present invention, there is disclosed a process for producing molten steel from a solid charge using fossil fuels and in conditions of intensified heat transfer wherein the process is characterized in that the solid charge, such as scrap, pig iron, direct reduction products and optionally iron oxides of natural origin or waste of preceding iron manufacture, is first melted by means of fossil fuel oxygen burner (13) within a set (1) of rotary furnaces (2). The melt is controlled according to method of dephosphorization and tapped with the required carbon content and oxygen activity. Carbon content in the metal is controlled during the process course by one of the below specified methods: pouring onto the metal surface, injecting into the metal volume and injecting gaseous or liquid hydrocarbons into the metal volume. For ensuring dephosphorization of the molten metal outside the melting set, the carbon content should be above 0.15 percent by weight and oxygen activity below 0.02 percent by weight. In case the dephosphorization is carried out within the rotary furnace (2), the slag formed during the dephosphorization process is separated from the metal prior another, usually reduction operation. In all variants, the finish of the melt treatment is carried out outside the melting sets within a converter (5) or in secondary metallurgy (6). Disclosed is also apparatus for making the process wherein such apparatus comprises at least two rotary furnaces (2) arranged to form a set (1). The rotary furnace (2) consists of a vessel (11) with a jacket (26), two convex faces (12, 19) and an internal refractory lining (27). At its ends, in the direction of its longitudinal axis (30), the furnace (2) is provided with openings. The first opening serves for inserting therein a fossil fuel oxygen burner (13) being either fixed and excludes so the control of the flame direction or movable enabling flame direction control. Equipment for injecting, such as injecting nozzle (14) of carbon or other additives particularly slag forming additives, is added to the burner opening. This additional equipment is either stationary or movable enabling so change of tilting angle. The additional injecting equipment construction is either integral with the burner (13) or independent equipment enabling quick exchange. The other opening is connected with venting, whereby one of the openings is at the same time the solid charge charging opening. Further, the rotary furnace (2) is provided with at least one eccentric metal or slag tap hole, whereby the whole vessel (11) is inclined in transverse direction to the axis (30) of rotation. Tapping of the furnaces (2) arranged to a set (1) is carried out in accordance with required melting period successively from one or several rotary furnaces (2) in a single ladle (4) either directly or through the mediation of a system of pouring spouts (25).

Description

Technical field

The present invention relates to a method and apparatus for producing liquid steel from solid feed by means of fossil fuels under conditions of intensified heat transfer. It addresses an increase in the overall thermal efficiency of the melting of metal-bearing raw materials while reducing the investment cost of the process and, in some cases, reducing greenhouse gas emissions.

BACKGROUND OF THE INVENTION

There is a known method for producing liquid steel from a solid charge, the so-called Siemens Martin process, which uses a regenerative method of utilizing the heat of the flue gas to heat the blown air, thereby helping to raise the flame temperature. This process allows the production of steel independently of the supply of molten pig iron.

The disadvantage of this method is the relatively low rate of physico-chemical processes. Another disadvantage is the adverse impact on the environment.

Furthermore, the process of melting solid charge in electric arc furnaces (EOP) is known. The processes in electric arc furnaces were gradually intensified, especially in two directions, both in increasing the electric power of the furnace and in the introduction of oxygen and fossil fuels. Further shortening of the melting time was made possible by the introduction of secondary metallurgy and the transfer of part of the metallurgical operations outside the melting aggregate.

As the share of recycled material in total steel production increases, so does the share of electric arc furnaces. The main trend in the development of these furnaces is the replacement of electricity by fossil fuels. The current situation is in the range of 20 to 50% of energy in the form of fossil fuels and the rest in the form of electricity.

A disadvantage of EOP steel production is that the high process intensity in a modern electric arc furnace requires protection of the furnace walls with water-cooled panels that reduce the energy efficiency of the furnace. A disadvantage is also the relatively short retention time of the combustion products in the furnace, the interaction of the combustion products with the arc and the inadequate sealing of the furnace, resulting in a further reduction in the efficiency of the electric arc furnace. The energy efficiency of converting electrical energy to thermal energy for melting in an electric arc furnace is relatively high. However, the efficiency of fossil fuel power generation, which varies from 30 to 55% depending on the method of electricity generation, must also be included in the overall energy balance.

The last method used for melting iron-based alloys is the rotary kiln used in foundries. This process uses fossil fuel as a source of melting and intensifies the heat transfer by mixing and combining several mechanisms. However, this process is limited to low hourly performance. Another limitation is the high carbon and silicon content of the melt and the resulting different linings not applicable to the steel process.

A very fast and very heat-efficient process is the production of steel from liquid batches in converters. This process is very demanding in terms of investment, especially in terms of liquid batch production.

Rotary kilns are known as aggregates with wide application. They are used for drying, preheating, reducing oxides and melting low-melting metals and alloys such as aluminum. For iron-carbon alloys, they are used up to 1550 ° C and in extreme cases up to 1600 ° C. The manufacturer of these furnaces is for example the Italian company SOGEMI. These furnaces are used in foundry industry. Their share in foundry production is constantly growing.

Rotary kilns are not yet used in the steel industry. Attention is given to possible use by W. L. Sherwood and Ρ. V. Barr in articles published at 59th Electric Furmnation Conference, Phoenix, 2001. The articles describe the necessary requirements for the design of existing foundry furnaces. Attention is paid to constructional and technological requirements and also a change of the lining concept is described. The conditions of heat transfer and how to influence them are described in detail.

The industrial application of the rotary kiln in the steel industry is known from the sixties of the twentieth century when the KALDO process was used industrially. A detailed comparison of the KALDO processes and the dominant LD process is made, for example, in the Journal of The Iron and Steel Institute, October 1966, pp. 997-1006. The paper confirms the achievement of a higher degree of equilibrium compared to the classical LD converter. This drawback of the LD converter was overcome by the introduction of bottom mixing. Overall, simpler design and lower production costs have decided to unequivocally implement LD converter technology.

However, rotary kilns have not disappeared in the iron and steel industry, and many of their advantages have led to the emergence of a number of technical and technology and patents.

The following writings are known in the steel industry:

EP 0 134 336 discloses the use of a rotary kiln in conjunction with secondary metallurgy and continuous steel casting.

EP 0 933 436 discloses the use of a rotary furnace for melting, preheating and desulphurization of direct reduced iron.

WO 94/11536 describes a continuous rotary kiln divided into two sections. The first section serves for preheating and melting and the second section for heating the melt to the desired temperature. The apparatus is equipped with carbon injection into the melt in the second section.

WO 95/29137 discloses a device for removing slag from metallurgical aggregates, for example rotary kilns.

WO 99/60172 discloses a continuous rotary kiln divided into two sections. The first section serves for preheating and melting and the second section for heating the melt to the desired temperature. The apparatus is equipped with carbon injection into the melt in the second section. At the end of the second section a vacuum device is connected with which molten steel can be pumped from the rotary kiln.

U.S. Pat. No. 4,105,438 discloses a rotary kiln apparatus and method for evacuating molten metal by vacuum.

US 3 991 987 describes the connection of a rotary kiln to an electric arc furnace. In the rotary furnace, the melt itself is heated to the desired temperature.

U.S. Pat. No. 3,514,280 discloses an apparatus for the continuous production of steel by melting in a rotary kiln. This rotary kiln is equipped with a pair of burners located on opposite sides of the kiln. The metal flows from the furnace continuously through a siphon device.

U.S. Pat. No. 4,062,674 describes the use of a high-speed rotary kiln for the production of iron and steel. The speed of rotation of this furnace is such that the centrifugal force holds the charge on the inside of the shell.

U.S. Pat. No. 3,689,251 discloses a rotary kiln system for direct reduction and subsequent melting and processing of a steel melt.

US 5 163 997 discloses an apparatus for the continuous production of steel by melting in a rotary kiln. This rotary kiln is divided into two zones and is equipped with a pair of burners located on opposite sides of the rotary kiln. The burner on the planting side is used to set up and preheat the solid charge.

WO 91/07127 discloses a rotary kiln for the incineration of hazardous waste followed by melting the resulting slag.

EP 0 442 040 discloses a pellet reduction device.

EP 0 982 407 discloses an apparatus for melting inorganic substances with their injection under flame.

The following publications are known for use in the foundry industry:

U.S. Pat. No. 5,141,208 discloses joining two furnaces in series, one serving as a melting aggregate and the other for preheating.

U.S. Pat. No. 0 673 887 describes furnaces which are commonly used in foundry industry.

After 2000, interest in rotary kilns in the USA continues.

US 2001/6012 discloses an apparatus for continuously melting metal in a rotary kiln.

The machine is equipped with a series of nozzles, burners and a batch conveyor that allows continuous production. The device uses the flue gas heat from the melting zone in the charge preheating zone.

US2002 / 130448 discloses a very complicated apparatus associated with a single rotary kiln for the direct production of pig iron or steel of a freak. The equipment consists of a reduction reactor in which the reduction of oxides in the gas phase takes place. The reduction reactor may be, for example, a shaft furnace, the author admitting all known methods of direct reduction in the gas phase. The partially reduced product is in the hot state transferred to a long rotary kiln in which the reduction and melting are completed. Decarburization is also possible in this apparatus. It is therefore a universal device of the continuous type, in which the individual phases of the process are clearly separated in individual zones.

The main difference to the proposed process is the continuous character of the production with respect to batch. Further differences arise from the versatility of the apparatus of US 2001/6012 and US 2002/130448, in which several physicochemical processes take place simultaneously. The equipment is divided into individual zones in which conditions are optimized to optimize the fuel potential.

In the present invention, the rotary kiln is made up of only one zone and the physicochemical processes take place gradually. The productivity of the device is achieved by counting the individual aggregates connected in the battery, in contrast to the required size of one device according to the documents 2001/6012 and US 2002/130448. Another advantage is the batch production process, which better corresponds to the current state of the subsequent metal processing, i.e. secondary metallurgy and continuous casting.

All publications assume individual rotary kilns or aggregate arrangements in which the rotary kiln is connected to a continuous device. In the papers, and in particular in the aforementioned articles from the 59th Electric Furmation Conference, Phoenix, 2001, the furnace performance is increased, in particular, by increasing the furnace volume and increasing the temperature of the flame and flue gas. To achieve a performance comparable to an electric arc furnace (EOP), a 2200 ° C flame temperature should be used, reducing the flame temperature by 200 ° C reduces the rotary kiln performance by 50%. The high temperature of the flame and the flue gas leads to an increase in the load on the linings and other technical complications such as a loss of thermal efficiency and in particular an increase in the complexity of the device. The high flue gas temperature makes it necessary to use this heat, which entails technical and environmental problems.

The present invention does not utilize high process intensities, but pursues process optimization. This is achieved by lowering the flame temperature and reducing specific production, this deficiency being solved by increasing the number of rotary kilns. Emphasis is placed on the simplicity of production equipment. The main difference from the other processes lies in the battery arrangement and the gradual tapping of molten metal from the furnaces according to the needs of post-processing, for example continuous casting. Another significant difference is that large melts are provided by simultaneous tapping from several furnaces into one pan. Another significant difference is the frequent effort to use the rotary kiln as a continuous device, which is technically correct, but the industrial application of the continuous device in steel metallurgy is technologically and organizationally complicated, so it is better to maintain existing steel production processes, especially secondary metallurgy and continuous casting and use the rotary furnace only as a source of melt.

SUMMARY OF THE INVENTION

The proposed process consists in melting the solid charge with fossil fuels in conditions of intensified heat transfer. Such conditions can be created in a rotary kiln. The production of the device is ensured by the battery arrangement. Good heat transfer is ensured by mixing the charge not only in the liquid state but also in the solid state.

The produced liquid metal is subsequently processed depending on the carbon content of the converter and secondary metallurgy or only secondary metallurgy.

The present invention provides a process for producing liquid steel from a solid charge using fossil fuels and oxygen or oxygen-enriched preheated air in a rotary kiln, and further arranging the proposed melting devices so as to achieve the desired tapping time and melting size.

The metallurgical process in a rotary kiln is limited to melting. Other metallurgical processes are carried out only to a limited extent in the melting aggregate. The necessary metal refining is carried out outside the melting unit. The proposed process is a duplex melting aggregate - secondary metallurgy or triplex melting aggregate - converter or a special ladle - secondary metallurgy.

The method of the invention, which is based on the fact that the heat of the fossil fuel is directly used in the battery of rotary kilns, largely eliminates the drawbacks of the existing process for producing steel from solid charge in an electric arc furnace.

The present invention describes a method and apparatus for producing liquid steel from a solid charge, characterized in that the solid charge such as scrap, pig iron, HBI (briquetted directly reduced iron), DRI (directly reduced iron) is first melted using an oxy-fuel burner in a fossil fuel. a rotary kiln battery, the process of melting the metal-bearing raw materials with additives provides a controlled content of FeO in the slag. The metal is tapped from the furnace with the desired carbon content and oxygen activity, for the phosphorus deposition of the molten metal outside the melting aggregate, the carbon content is above 0.15% and the oxygen activity is below 0.02%. 15% and an oxygen activity above 0.02% by weight. The slag from the de-phosphorizing process is separated from the metal before the next, typically, reduction operation. The carbon content of the metal during the process is controlled in one of three ways specified below:

• pouring onto the metal surface and slag; • injection into the metal volume _/ • injection of gaseous or liquid hydrocarbons into the metal volume;

the casting of the liquid metal from the rotary kiln is followed by treatment outside the melting aggregate depending on the carbon content.

At a carbon content above 1%, the metal is treated in a converter followed by secondary metallurgy or only in a ladle with a high free height above the metal level of at least 1.25 m. using a reduced pressure, in the triplex process (rotary kiln - converter - secondary metallurgy), the liquid metal in the converter is treated with a minimum amount of slag since the feed liquid feedstock contains a minimum amount of silicon and aluminum.

When the metal is tapped with a carbon content below 1%, the metal is further processed in a secondary metallurgy plant, also using a device using reduced pressure.

The device according to the invention consists of a number of rotary furnaces arranged in a battery to achieve a suitable tapping frequency and a melt size for subsequent operations, in particular continuous casting operations. Each rotary kiln consists of a vessel consisting of a central cylindrical part with two convex faces and an internal refractory lining and provided with openings at its ends along the longitudinal axis, where the fossil fuel oxy-fuel burner is fixed in the first opening; or it is movable to control the direction of the flame, furthermore, it is possible to add to the burner opening a device for injecting carbon or other additives, in particular slag-forming, and these additional devices also allow the angle of inclination to be varied. The additional injection device may be integrated into the burner or may be self-contained, with a quick changeover capability, the second orifice being connected to the flue gas outlet, one of the orifices being the fixed orifice charging hole; furthermore, the vessel is provided with at least one eccentrically located metal or slag tap hole, the entire vessel being hinged transversely to the axis of rotation. Tapping of furnaces arranged in a battery is solved as a common tapping of several furnaces into one pan, either directly or by means of a set of troughs.

The main advantage of the method according to the invention is the direct exploitation of the chemical potential of fossil fuels for melting metal-bearing raw materials, i.e. an increase in the overall thermal efficiency of the smelting compared to melting by means of an electric current that was previously produced in a fossil fuel power plant. For this solution, it is necessary to ensure a high flame temperature and intensive heat transfer to the molten metal and later to the bath. Both of these requirements can be achieved in a rotary kiln.

From a constructional point of view, the advantage of providing a relatively small compact aggregate for melting solid charge while reducing the investment cost of the device and simplifying the process compared to a modern intensified electric arc furnace. It is also an advantage that the battery arrangement of the melting units makes it possible to optimally utilize the capacities of the waste gas treatment plant, typesetting equipment and the like. The multi-unit concept allows a tandem arrangement suitable for preheating.

From the technological point of view, the advantage of the proposed process is the direct exploitation of the chemical potential of fossil fuels for melting metal-bearing raw materials, ie increasing the overall thermal efficiency of melting compared to electric melting, and that the process small amounts of slag.

From a logistical point of view, it is an advantage that if several units are side by side, simple production control is possible without losing process efficiency by simply influencing the number of units working while minimizing downtime.

In terms of maintenance, only one spare container is needed. The vessel replacement time is shorter compared to the intensified electric arc furnace because of the simpler design, it is not necessary to connect the bottom blowing gases, cooling water and individual burners.

BRIEF DESCRIPTION OF THE DRAWINGS

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be explained in more detail by means of the drawings, in which FIG. 1a and FIG. Fig. 2 shows a diagram of a rotary kiln. Fig. 3a shows a section through a rotary kiln in the plane of tap holes. Fig. 3b shows a section through the rotary kiln in a plane outside the tap holes.

DETAILED DESCRIPTION OF THE INVENTION

The invention is illustrated in more detail in the accompanying drawings, in which Fig. 1a and Fig. 1b show a diagram of both a battery and rotary kiln steel plant 2. Fig. 1a is a triplex process suitable for treating liquid metal with a carbon content above 1%; from the rotary kilns 2. The liquid metal is tapped from the rotary kilns 2 into the ladle 4, which stands on the transfer car 3. The ladle 4 is transported from the car 3 and the liquid metal with a carbon content greater than 1% is poured into the converter 5 or in a special pan 4 with large free space. Decarburization in the converter 5 or in the special ladle 4 is followed by treatment in the secondary metallurgy 6, which may consist, for example, of a LF (Ladle Furnace) station for correcting the temperature and chemical composition, and alternatively in a vacuum apparatus. The final production stage is, for example, continuous casting in a device consisting of a turntable 7, a tundish 8 and individual streams 9 of continuous castings. Casting is also possible on slab casting or in ingots.

An example of a melt treatment plant made from a solid feedstock with a carbon content after melting below 1% is shown in Fig. Ib - this process can be referred to as a duplex process. The liquid metal is tapped from the rotary kilns 2 into the ladle 4, which stands on the transfer car 3. From the car 3, the ladle 4 is transported for processing in secondary metallurgy 6, which may consist for example of a LF (Ladle Furnace) temperature and chemical composition, and alternatively in an oxygen blowing vacuum device.

The final stage of production is, for example, continuous casting, wherein the apparatus consists of a rotary stand 7, a tundish 8 and individual streams 9 of continuous castings. Casting is also possible on slab casting or in ingots.

A diagram of the rotary kiln 2 is shown in Fig. 2. The rotary kiln 2 standing on the substrate 10 is formed by a rotary vessel 11 with a face 12 with tap holes. A burner 13 with an injection nozzle 14 is inserted into the tap hole face 12, which is inserted into the face 12 by various easy-to-fit mechanisms. In this example, the device is a rotary mechanism 15 allowing easy opening of the burner 13 and the injection device 14. The vessel 11 of the rotary kiln 2 is mounted in a tilting stand 16. The rotation of the rotary kiln 2 is provided by gripping rotary rollers 17 enabling rotation in any rotational position care

2. The tilting stand 16 of the rotary kiln 2 is mounted on the base plate 18. The rear face 19 is provided with a flue gas outlet which is guided by the flue gas duct 20. The rotary kiln 2 is planted in the folded state 1 lb from the magazine 21 by a conveyor 22. is also possible using troughs transported by crane. The rotary kiln 2 can be folded to a vertical position 11a suitable for repairing the lining, for example. Liquid metal is tapped from the furnace 2 into a ladle 4, which can be placed on a transport car 3 or suspended on a crane or laid on the ground. In some cases, especially when casting two or more melts, a casting trough 25 may be used.

FIG. 3a shows a section through the rotary kiln 2 in the plane of tap holes. The rotary kiln 2 is formed by a jacket 26 with faces 12 and 19. The rotary kiln 2 is internally equipped with a refractory lining 27 consisting of several layers of material including a thermal insulation layer. In one of the faces 12, 19, tap holes 28 and a burner hole 29 are located. The rotary kiln 2 rotates about the axis of rotation 30. The cells 12, 19 are attached to the housing 30 of the rotary kiln 2 by means of flanges 31. The housing 26 is reinforced by means of stiffeners 24 which simultaneously serve as a support for rotating the rotary kiln 2. The working space 23 of the rotary kiln 2 is internal.

FIG. 3b shows a section through the rotary kiln 2 in a plane outside the tap holes.

Example 1 - Melting Phase

The equipment and technology are designed so that the process achieves optimum thermal efficiency and limits the oxidation of the charge to the minimum necessary. For this solution, it is necessary to ensure a high flame temperature and intensive heat transfer to the molten metal and later to the bath. Both of these requirements are achieved in the proposed plant. High flame temperatures are achieved by burning fuel with oxygen or with preheated oxygen enriched air. Intense heat transfer is achieved by a combination of several heat transfer mechanisms.

These include:

• Direct heating of the metal at its low surface temperature • After reaching the surface temperature of the batch 900 ° C, the dominant heat transfer mechanism is changed to direct heating of the primary slag and the flame radiation to the metal and the lining 27.

• When the charge surface temperature exceeds 800 ° C, the rotary kiln 2 begins to rotate, creating conditions for other heat transfer mechanisms. In particular, the mixing of the charge ensures the transfer of the relatively cold charge to the surface and the heated charge from the surface to the charge volume. The heated charge is brought into the volume by stirring, where it transfers heat to the surrounding cooler charge. In parallel with this mechanism, heat is transferred from the heated lining 27 to the charge by conduction when the lining 27 contacts the charge.

• Slag is heated simultaneously with the metal. After reaching a temperature higher than 1300 ° C, the process is conducted in such a way that the combustion products do not come into contact with the metal and the heat transfer is mainly indirect.

Thus, the proposed process consists in melting the solid charge with fossil fuels in conditions of intensified heat transfer. Such conditions are created in a cylindrical rotary kiln 2. Good heat transfer is ensured by mixing the charge not only in a liquid state but also in a solid, and a large heat transfer area - the charge is heated not only from above but also from below.

Melting in a new type of melting furnace is conducted to avoid unnecessary metal oxidation. The metal is protected against oxidation by slag on the metal surface and by carbon dissolved in the liquid metal. Unnecessary oxidation of the metal is further prevented by limiting the direct contact of the flue gases with the metal, which is achieved by controlling the direction and length of the flame. The degree of metal oxidation is determined by the need for de-phosphorization in the rotary kiln 2.

Carbon is supplied to the metal during betting and continuously through one of the three methods specified below or a combination thereof:

• By adding carbon to the surface of the slag and metal.

• By injecting carbon below the metal level.

• By injecting a gaseous or liquid hydrocarbon below the metal level.

When injecting liquid or gaseous hydrocarbons, the injection device is subsequently inerted with an inert gas.

// Addition of carbon allows control of the carbon content of the melt and thus control of tapping temperatures.

Melts with higher carbon content are tapped at lower temperatures. Melts with a carbon content of about 0.15% are tapped at a temperature of at least 1560 ° C. Melts with a carbon content of about 1% are tapped at a temperature of at least 1450 ° C. At higher carbon content the tapping temperature further decreases.

Example 2 - Waste disposal

The possibility of carbon addition allows the use of the proposed device to process a batch containing metal oxides (Fe, Cr, Mn) up to 50%. In this case, however, the productivity of the equipment decreases significantly. These oxidic phases may be of natural origin (ores and non-reduced metal residues after direct reduction) or may be the product of previous metal production (waste). The reduction takes place in the slag phase at the slag metal interface.

Example 3 - Phosphorus

The charge containing more phosphorus than the allowable concentration in the final product is oxidized during the process so that the resulting slag phase is able to bind the necessary amount of phosphorus to itself. The composition of the slag is approximately 20% iron oxides with a slag base of at least 2. The liquid metal in this case has a maximum of 0.15% carbon. Under these conditions, the partition coefficient of phosphorus between the slag and the metal is at least 10. To improve the removal of phosphorus, iron oxides, for example, scale, can be added to the slag. After phosphophosphation, the oxidation slag is withdrawn and subsequently the carbon content of the melt is increased.

Example 4 - Treatment of melt with higher carbon content

The melt is tapped into the ladle 4 without the need for preliminary deoxidation since the carbon content prevents the dissolution of oxygen in the melt. The melt prepared as described above is ready for post-processing either in the converter 5 or in the ladle 4 with a large free space. Decarburization is done by blowing oxygen.

The treatment in the ladle 4 can be carried out under reduced or normal pressure by bubbling the bath with inert gas. The oxygen blowing pressure is reduced to values above 10 kPa. In the final decarburization stage, when the oxygen is blown, the pressure can be reduced to below 10 kPa. After decarburization, the melt is further processed by conventional methods of secondary metallurgy 6 in the case where a VOD or RH / zařízení type blowing device is used for decarburization, further processing immediately follows the decarburization phase without manipulating the ladle 4.

Thus, the proposed process is a triplex rotary kiln 2 - decarburization equipment (converter 5 or ladle 4 with large free space) - secondary metallurgy 6. Secondary metallurgy under reduced pressure (VOD, RH-OB) is generally preferred, although oxygen blowing under normal pressure is also possible. For carbon contents in the melt below 1%, decarburization in the ladle 4 is more economical.

Example 5 - Treatment of low carbon melt below 0.5%

The melt is tapped into the ladle 4 without the need for preliminary deoxidation. Depending on the desired reduction in the carbon content, oxygen is blown to the metal level in the ladle 4. Basic decarburization is followed by deep vacuum treatment. Only after this vacuum treatment is the bath deoxidized and poured to the desired chemical composition. This proposed technological process is therefore duplex: rotary kiln 4 - secondary metallurgy 6.

Example 6 - Preparation of steel for continuous casting

The melting aggregates are arranged side by side according to the required output. At least three rotary kilns 2 are required for production to meet the needs of the current minimil, ie more than 0.5 million tons of steel per year. The desired melting weight is achieved in one or more melting aggregates. Tapping from two or more rotary kilns 2 is then performed simultaneously.

Claims (10)

PATENT CLAIMS 1. A method of producing liquid steel of a feedstock by means of fossil fuels under intensified heat transfer conditions, which solves an increase in the overall thermal efficiency of melting metal-bearing raw materials while reducing the investment cost of the process and in some cases also reducing greenhouse gas emissions. such as scrap, pig iron, direct reduction products, eg / reduced briquetted directly reduced iron or directly reduced iron, eventually iron oxides of natural origin or wastes from previous iron production, are first melted with an oxygen burner (13) to fossil fuel in the battery (1 ) rotary kilns (2), wherein the number of kilns (2) in the battery (1) is selected so as to achieve the desired tapping time, the melt being controlled according to the de-phosphorizing method and tapping with the desired carbon content and oxygen activity metal during the process directs By one of the three methods specified below, the carbon content is above 0.15% and the oxygen activity is below 0.02% by spraying onto the metal and slag surface, injecting into the metal volume and injecting gaseous or liquid hydrocarbons into the metal volume. in the melting aggregate, the carbon content is below 0.15% and the oxygen activity is above 0.02% by weight; in the case of de-phosphorizing in a rotary furnace (2), the slag from the de-phosphorizing process is separated from the metal before another ? For all variants, the melt processing is completed outside the melting aggregates in the converter (5) or secondary metallurgy (6). Method according to claim 1, characterized in that the liquid metal with a carbon content above 1% is treated in the converter (5) with subsequent treatment in the secondary metallurgy (6), ie it is a triplex process, ie a rotary kiln (2). - converter (5) - secondary metallurgy (6), wherein the liquid metal in the converter (5) is treated with an extraordinary amount of slag, since the molten metal after tapping from the rotary furnace is treated, it does not contain silicon above 0.1% and aluminum above 0.05%. Method according to claim 1, characterized in that the liquid metal from the rotary kiln (2) with a carbon content above 1% of silicon content below 0.1% and aluminum below 0.05% is treated in a ladle (4) with a high free height above the metal level of at least 1.25 m, in the treatment in the ladle (4) a device is used which uses oxygen blowing to the metal level, preferably using a device using a reduced pressure. Method according to claim 1, characterized in that the liquid metal with a carbon content below 1% is further processed in a secondary metallurgy plant (6), preferably using a device using reduced pressure. Method according to claim 1, characterized in that the heat of the outgoing gases is used for preheating the solid charge or oxygen-enriched air, the alternative using preheated oxygen-enriched air being used in particular for the first stage of melting, ie heating the charge to reduce consumption. of oxygen. Method according to claim 1, characterized in that the metal is protected by slag during melting or subjected to direct contact with the flue gas and that the heat transfer is ensured, on the one hand, by heat transfer through the slag, by flame radiation directly into the metal, slag and lining ), further by radiation of the lining (27) and further by direct contact of the metal and slag with the lining (27), whereby the radiation component of the heat transfer is enhanced by flame carburization. Method according to claim 1, characterized in that the reduction of the metal-bearing oxidic wastes is carried out at the slag-metal interface with carbon from the metal or slag. Apparatus for carrying out the method according to claim 1, characterized in that it consists of at least two rotary kilns (2) arranged in a battery (1) to achieve a suitable tapping frequency and melt size for subsequent operations, in particular continuous casting, (2) is formed by a container (11) with a jacket (26), two convex faces (12, 19) and an internal refractory lining (27), provided with openings at its ends in the direction of its longitudinal axis (30), an oxygen burner (13) for fossil fuels is inserted, which is either solid and does not control the flame direction or is movable to control the flame direction, an injection device such as a carbon injection nozzle (14) or other additives, especially slag-forming additives, is added to the burner opening. and even these additional devices are fixed or allow the angle of inclination to be varied, the additional grouting devices are k designed as an integral part of the burner (13) or as a separate device, with the possibility of rapid exchange, the second hole is connected to the flue gas outlet, one of the holes is also a charging hole of the fixed charge, the rotary kiln (2) is equipped with at least one eccentrically placed tapping an opening of metal or slag, wherein the entire vessel (11) is a tilting duration transverse to the axis of rotation (30), tapping is performed in one ladle (4) directly or by means of a set of casting troughs (25). Device according to claim 8, characterized in that the battery (1) of the rotary kilns (2) has a common connection to peripheral devices such as a waste gas treatment plant, a charging plant, a gas supply, and the like. Device according to claim 8, characterized in that the lining (27) is made up of several layers of material including a thermal insulating layer, and its protection against cyclic fatigue is provided by slag which is rolled onto its walls when the rotary kiln (2) is rotated. or at a suitable rotation speed of the rotary kiln (2) to prevent the lining (27) from overheating above the burner (13).