KR20010032730A - Method for reducing iron oxides and smelting iron and installations therefor - Google Patents

Abstract

The present invention provides for at least two successive steps, namely a first conventional step of reducing the degree of metallization to 80-94%, preferably 85-90%, heating to a temperature of at least 1000 ° C., up to a temperature close to melting point, and A second step in which the iron metallization, the rod, the fluidizer and the surplus carbon mixture are fed into a melting furnace containing a molten cast iron phase and then the metal and slag are preferably continuously removed by overflow It relates to iron oxide and molten iron reduction method comprising a.

Description

Iron oxide reduction and iron melting method and equipment {METHOD FOR REDUCING IRON OXIDES AND SMELTING IRON AND INSTALLATIONS THEREFOR}

As the production of steel by electricity increases, the need for scrap is increasing because of the lack of adequate quality scrap.

Similarly, pressure from environmental groups has increased, competition among producers and falling prices have forced steel producers to develop new production methods that pollute the environment at low cost.

To this end, several methods have been developed to reduce iron oxide to produce steel known as direct-reduece iron (DRI). Direct reduced iron can be, for example, gas reduction (HYL process, Midrex) or reduction from carbon containing sources such as in SL-RN, Fastmet, Inmetco or Circofer and Comet methods, or filed January 28, 1998 by the same applicant Obtained mainly by the method according to European Patent Application No. 98200242.0. The main disadvantage of most of the methods is the fact that the product obtained is a reduced state product which is very low in density, usually described as sponge iron, and has a high specific surface area, which promotes iron reoxidation. For this reason, storage and transportation are difficult, and in most cases, it must be costly and compact to carry out subsequent processing. As an example, sponge iron has a bulk density of 1.5 to 2 kg / dm ³ and is generally compacted to 5 to 5.5 kg / dm ³ .

In addition, a large amount of latent heat present in the reducing material before cooling is eliminated.

Some of the proposed reduction methods use solid carbon containing sources, such as coal, in which the amount is excessively added to ensure sufficient reduction. Such excess carbon-containing sources are included in other surplus products containing ash to be treated.

All of these disadvantages can be solved by the step-down reduction / melting method according to the invention. Unprocessed pig iron produced in the molten state can be used in all common applications, for example in the casting of small ingots in electric steel plants or oxygen converters or in refining operations in steel production.

The present invention relates to a novel method for producing molten metal from iron ore, such as ore or recycled products, and coal and / or gas by reducing iron oxide to produce molten steel. It is an object of the present invention to achieve various economic advantages as described below over known methods.

The invention also relates to a plant capable of carrying out the method.

1 is a block diagram of a facility for performing the method.

2 is a schematic diagram of a plant having a feed pipe, a gas discharge pipe and a submerged arc furnace according to a first embodiment of the present invention;

3 is a cross-sectional schematic view of a plant according to a second embodiment of the present invention connected to a DRI supply chute and to a plant for discharging treated material and a gas exhaust plant;

4 is a schematic view of a fixed disk mounted on a feed end of a rotary furnace;

5 is a schematic view of a device for separating liquid pig iron and slag with a sealing joint capable of rotating the furnace relative to the non-rotating member of the present invention.

6 is a schematic view of a first form in which the furnace narrows conically in an upstream to a downstream direction;

7 is a schematic view of a second form in which the step is narrowed from upstream to downstream;

8 is a longitudinal sectional view of certain additional equipment in the rotary furnace.

9 is a sectional view of the supply end along line A-A.

It is an object of the present invention to continuously convert reduced iron oxide, in particular immediately after production, to obtain economically more desirable liquid pig iron in a more compact technical installation that is improved over current installations.

In particular, it is an object of the present invention to consume less and more economically through the recovery of energy by fuel selection and direct recycling of combustion gases flowing upstream of the plant, thus producing continuously pig iron which is preferably sulfur removed and separated from slag. It is.

The process according to the invention comprises at least two successive steps, in which the first step achieves approximately 80 to 94%, preferably 85 to 90% degree of metallization while standardizing the slag to be produced in the second step by adding a solvent. Is the standard reduction step until. The second step is just after the first step of producing pig iron.

The second stage of producing pig iron is carried out in two successive sub-stages. First, the iron oxide is substantially reduced by 100%. It uses a small reactor with a core or injection lance through which gas can pass to feed the preheated coal from the top, almost completely metallized iron, gangue, solvent and This can be achieved by transferring the mixture of surplus coal directly into the blast furnace containing molten pig iron, and then draining the metal and slag, for example, preferably continuously.

Iron oxide reduced from the first reduction step can be carried out in a rotating-hearth furnace, shaft furnace, rotary furnace or fluidized bed furnace, among other types of equipment. It can be obtained by any reduction method present. The process according to the invention becomes economically more advantageous when the temperature of the reduced product rises, ie it further contains latent heat.

In the first embodiment, the energy required for melting may be supplied by induction or possibly by an electric arc, for example a submerged arc.

In the second embodiment, further reduction and continuous melting can also be carried out in a single plant which essentially comprises a unit for feeding into the material to be treated which is preferably generated directly at the high temperatures possible from the first stage. The supply unit is open at the opposite end, first of which is funnel-shaped for discharging pig iron and slag, first connected to the preferred unit and then to the gas discharge unit. A burner located parallel to the supply unit supplies the heat necessary for melting the material to be treated, while an injection lance located at the other end of the blast furnace removes sulfur from the bath. The burners may be located on the same side as the discharge unit or may overlap if required by the melting method.

In this case, the above-mentioned constituent members of the installation are preferably mounted on the common chassis such that the entire assembly is inclined. Conventionally, the blast furnace is preferably mounted on a ring located on a roller driven by a motor and a suitable transmission system.

In particular, the inclination of the chassis supporting the rotary furnace can be controlled so that the blast furnace continuously tilts, as a result of which hot pig iron from the discharge end of the blast furnace is intermittently transferred to its feed end, thereby making the pig iron not continuous. It will pulsate to the exit continuously or better with pulsating motion. This ensures good melting of the charged ore by selecting the hot melt mass from the outlet, which mixes with the cooling solution of the bath located at the feed end. At the same time, this homogenizes the increasing carbon concentration during movement from the feed end to the discharge end.

The homogenization increases the melting capacity and the reducing capacity, thereby improving the properties of the molten bath. Increasing the carbon concentration lowers the temperature at which pig iron is cured, which also has a very desirable effect on the process.

In addition, the general configuration of the furnace is an important factor influencing the melting of sponge iron. It is evident that making the inner diameter of the feed end larger than the inner diameter of the discharge end is particularly effective by increasing the pig iron volume, increasing the pumping effect and increasing the melt capacity, especially in conjunction with the above described tilting effect.

The main feature of the present invention is that all the transfer from the DRI production unit to the unit from which pig iron is produced is achieved under the influence of gravity, taking care to reduce heat loss.

The process of the present invention is of course different from the methods used in the present technology because of the fact that the first iron oxide is almost completely reduced and the second obtained material flows directly into the melting bath comprising liquid pig iron without interruption, in particular without distinct cooling between steps. Note that they are different.

It should be noted that the liquid pig iron produced has a precisely measured carbon concentration of at least 3% and preferably from about 4.5 to 5.5%, thereby generally obtaining molten pig iron with satisfactory fluidity for most iron oxides.

Other details relating to the method according to the invention are described in more detail below.

In the first embodiment described above, the method is carried out so that the gas produced in the lower furnace is supplied directly to the first stage through the gas discharge pipe to assist through its latent heat and reducing capacity.

The pipe for supplying the metal mixture flowing from the first stage is provided with a regulating flap valve to form a buffer zone with sufficient weight and sufficient descent height when the metal mixture is discharged, As a result, the mixture is forced through the liquid side of the lower furnace, which allows for significant progress in melting.

The lower blast furnace is provided in the form of a trap in which the pig iron and slag are separated in a known manner, in order to intermittently discharge the liquid pig iron, preferably for simplicity. The slag may preferably be granulated or solidified in a basin provided for this purpose. Two types of slag are known as commercially available byproducts. Liquid pig iron forms a particularly useful product in refining processes using, for example, electric furnaces (RAFs) or oxygen converters (BOFs).

Although a method for reducing iron oxide has been disclosed, it can also be applied to the reduction of other metal oxides or mixtures of metal oxides and iron oxides, especially metals used in combination with iron to produce alloys such as stainless steel. It also applies to recovering dust from blast furnaces, conversion furnaces and electric furnaces.

The process according to the invention, which transfers two successive steps in gravity, can treat the renewable by-products from the steel plant.

The pig iron produced can be used not only directly in molten state but also in ingot form.

The almost complete absence of iron oxide at the end of the second stage ensures a long refractory lining at the outlet of the reactor and a long service life of the inlet.

The process of the invention is characterized by very high productivity in the steel production process since the starting materials used are in the liquid state, in particular in place of the solid state materials produced by the DRI method.

The selection of the DRI method for the first step is guided by some local situation taking into account the most economical conditions and incorporated into the second step of the method.

In addition, the method has several advantages in terms of required energy.

Continuous casting of both stages prevents any energy loss. In addition, the useful gas released in the second step can be reused. The surplus fuel (coal) in the first stage is preferably used in the second stage. The surplus coal is distributed to the feed pipe upon final reduction of the unreduced iron oxide, and the surplus coal of the second stage serves as pig iron fractionation.

Due to the supply pipe connecting the first and second stages, the equipment can be constructed in a particularly compact shape and the material costs can be reduced. The melting unit of the second stage is quite small in volume.

Finally, the method can optimally use recycled materials.

In terms of quality, pig iron is much more stable than scrap (not reoxidized) and forms a desirable raw material, which is key to quality problems because of the impurities present. Pig iron includes additional energy sources in the form of carbon present. Desulfurization of pig iron is carried out in the blast furnace.

As mentioned above, in the second embodiment of the present invention, two sub-steps forming the second step of the present invention may also be executed in one facility.

In this case, the feed unit of the plant may be a feed chute, or any other suitable feed system, such as an Archimedean screw, mounted on a disc and into which a universal burner is also inserted. It is preferred to be configured. A pulverized coal charging device may also be mounted on the disc to prevent the regeneration of the first charge, the final reduction of the sponge iron and the addition of coal to the melting tank to obtain high quality pig iron.

The disk is fixedly connected to one end of the rotary furnace, for example by a double sealed joint mounted on the expansion joint, the intermediate chamber of the joint is compressible with an inert gas, preferably nitrogen, and the entire assembly is fixed Relative movement between the disk and the rotary furnace can absorb the thermal expansion.

Similarly, at the other end of the rotary furnace a similar device can absorb the expansion and rotate the other end of the rotary furnace relative to the unit to discharge pig iron and slag.

The supply unit is connected to the chute, which itself is connected to a pipe, or to the DRI production unit of the first stage. The support point of the chassis used to adjust the inclination of the furnace shaft is ideally located in the center of the connection surface of the feed pipe. By arranging in this way, the flow rate of pig iron to be discharged can be adjusted or the flow can be stopped, for example, the liquid pig iron can be discharged by changing the apparatus.

It is desirable to provide a flap valve, preferably a double flap valve upstream of the rotation point, which allows solid material to pass through the DRI production furnace but prevents gas reflux.

Likewise, the gas discharge unit is connected to the pipe fixed to the outside by the same type of expansion joint.

Of course, fire-resistant linings are provided throughout the plant.

Other details and features of the invention will become apparent from the following detailed description of embodiments of the invention.

The pig iron produced can be used in the initial production of steel, for example electric furnaces or BOF-type converters, to reduce the time taken for the production cycle compared to the DRI charging cycle.

The present invention implements a simple, compact and low cost structural design.

In addition, the structure is not only an energy source, such as natural gas, coke oven gas and / or pulverized coal, but also oils, plastics, etc. which are prepared for the purpose and cheaper than fuel used in conventional electric furnaces, in particular induction furnaces or arc furnaces. Use fuels from renewable wastes with high exothermic value.

Another object of the installation according to the invention is that, for example, the corrosion and chemical breakdown of the general phenomena appearing in the slag level of the electric furnace are agitated, and in particular in the second embodiment of the invention the melting furnaces centered on their horizontal axis of rotation The life of the refractory lining is increased because it is prevented due to continuous rotation.

In addition, it may not use a separate dust-extractor and may recover almost latent heat from the fuel gas of the plant located upstream of the furnace.

Due to the special design of the members constituting the installation, the unit requiring replacement of the lining can be simply replaced with a spare unit without noticeably disrupting production.

The installation of the casting zone is particularly simple and reliable, and a plugging machine or a drilling machine for casting is not necessary because it is for the casting floor of the blast furnace.

Accordingly, the present invention relates to a method for producing pig iron economically in terms of material costs and operating costs, which method is advantageous for small units producing only 250 kt, for example.

In general, since the equipment and its usage are simple and reliable, it can be operated with a small number of people, and much less than the known equipment in terms of risk level, that is, accident rate.

The method produces slag having characteristics close to that of slag produced in the blast furnace, which is readily available for commercial use, and is not slag produced by direct DRI charging of the steel production process.

Explanation of References in FIG. 1

1 iron oxide reduction furnace

2 Pipes for feeding iron metallization to the furnace

3 melting furnace

4 Pipes to discharge combustion gases from the melting furnace

5 pig iron refining plant

6 slag treatment equipment

After the DRI production 1 of the first standard stage, the metallization mixture (DRI) is transported through the pipe 2 and prepared to be supplied to the melting furnace 3. The combustion gas is discharged from the melting furnace through the pipe 4 to the DRI furnace, while pig iron is discharged to the refinery 5 and slag is discharged to the slag treatment facility 6.

Explanation of References in FIG. 2

11 submerged arc furnace

13 electrodes

13 slag

14 pig iron

15 slag discharge chute

16 pig iron exhaust chute

17 Pipe to discharge combustion gas from melting furnace

18 Rotary Furnace Iron Oxide Reduction Furnace

19 reduction furnace

20 Pipes charging metallized mixtures

21 Flap valve to control the flow rate

a. Pig iron discharge direction

b. Discharge direction of slag

c. Combustion direction of exhaust gas

d. Discharge direction of metallized mixture

The plant comprises an iron oxide reduction furnace 18, a DRI feed pipe 20, a submerged-arc electromelting furnace in which the DRI is charged and melted in a first stage, and a gas discharge pipe 17.

The DRI mixed with excess coal, lime and other solvents at temperatures of 1000 ° C. or higher is discharged from the hearth 19 to one of the four discharge pipes 20. The flow regulating flap valve 21 intermittently releases the metallized mixture that penetrates the slag and permeates the molten pig iron. The electrode 12 of the melting furnace is immersed in the slag 13 in which the electric arc is formed. The produced pig iron is discharged through the chute 16, the slag is discharged through the chute 15, the combustion gas is discharged through the chute 17 and re-injected into the reduction furnace 18.

Molten pig iron can be used in any conventional application.

The slag can be granulated and can be used in the general application of slag, in particular furnace slag.

3 to 9 show a second embodiment of the present invention. The following references have been used.

Explanation of reference numerals of FIGS. 3 to 9

101 rotary furnace

102 DRI

103 Supply Section

104 downstream opening

105 supply pipe

106 supply chute

107 pig iron outlet

131 DRI Mass

132 Flooding of the Melt Charge

133 gas

134 Support Point

135 funnel

137 traps

139 pig iron

141 slag

The equipment shown in FIG. 3 is provided with a supply 103 for supplying a DRI 102 at one end (upstream end in the direction of movement of the material) and a liquid pig iron and slag outlet 107 and a gas at the other end (downstream). It is essential that the rotary furnace 101 is provided with an opening 104 connected to the outlet 109.

4 shows a supply 103, in particular consisting of a disk 103, which forms a buffer provided with an inclined supply chute 106. Burner 113 penetrates into the furnace through the disc. By adjusting the burner length penetrating into the furnace, it is possible to optimally melt the DRI mass at the inlet of the furnace 101. This burner can be mounted on the opposite side and can also be arranged in duplicate by mounting the burners on both sides. The disc 103 may also be provided with pulverized coal injection device 114. The sealing joint 119 of the outer circumference allows the furnace to rotate relative to the stationary disk.

The other end of the furnace is opened and penetrates toward the primary unit 135 and through the secondary unit 109.

Suitable joints 120 may also be provided to rotate the furnace.

The assembly formed of the furnace 101 and the units 103, 107, 135 (or 137) is supported by the chassis 115. A roller 125 supporting the rotary furnace 101 is mounted on the chassis. The furnace itself is provided with a ring 123 positioned on the roller, which is driven directly or indirectly by a motor (not shown).

The end of the chute 106 is connected to the pipe 105 by a compressible member 121.

The entire chassis with the rotating installation 101 and the fixing installations 103, 107 and 135 (or 137) supporting it can be tilted horizontally about a support point 134 located at the same level as the connection.

Provides two working states. In the first state, the furnace is in production and its axis of rotation is slightly inclined.

In this case, due to the compressibility in the chute 106 and the pipe 105 of the joint 121, the imperviousness of the link is maintained during the rotation.

Because of the length of the rotary furnace 101, even if slightly inclined, the downstream end of the furnace can be displaced vertically by about 10 to 20 cm.

The gas discharge unit 107 is connected to the recirculation pipe 109 for supplying the DRI to the furnace by the expansion joint 129 which seals against infiltration.

The second working state is a state in which the actual furnace inspection should be carried out.

In this case, only chute 106 may be detached from pipe 105 to move the chassis with integral unit. In addition, the installation can be disassembled by detaching the furnace 101 from one end of the unit 103 and the other end of the unit 107, 135 (or 137) (of course, several expansion joints and other joints are also disassembled).

Next, if a complete overhaul of the furnace 101 refractory lining is required, for example, suitable handling means provided for this purpose can be fixed vertically.

Indeed, the plant of the present invention is designed so that it can be dismantled very quickly and replaced with a complete spare plant, or partially disassembled so that one of its components can be replaced.

For example, the DRI supply of the furnace can be very quickly disconnected and replaced with a preheated spare.

Various plant parts may be provided to the plant.

Both the furnace 101 and the units 103, 105, 107, 109, and 135 (or 137) are provided with suitable refractory linings that can withstand temperature and charges.

The liquid pig iron discharge unit with a preferred funnel 135 shape as shown in FIG. 3 may be provided with a trap 137 as shown for example in FIG. 5.

Likewise, an observation window 127 may be provided in the wall facing the opening 104, for example.

In the wall, desulfurization lances 111 and oxygen lances located at the top may be provided at the ends of the openings 104 to remove any pig iron and slag deposits that may be formed at these locations.

The outer shape of the disk 103 and the outer shape of the furnace 101 lining at the position to be joined together are selected so that the installation can function optimally.

Since the shape of the furnace, in particular as shown, is inclined, it is necessary to gradually displace the material (from left to right in FIG. 3) while keeping the molten material 131 in the bath. The feed material to be treated is generally lighter than the material in the bath and partially floats on its surface.

It should be noted that the material to be treated, as well as the material to be melted, is subjected to final reduction in the furnace and carbonized to 4% carbon by pulverized coal injection.

The heat required for melting is mainly provided by radiation from the burner flame above the charge and radiation from the furnace walls. In addition, the hot refractory lining of the rotary furnace heats the bath by direct contact.

Rapid melting of linings due to slag corrosion is observed and, unlike melting furnaces and electric furnaces that cause local wear, local wear is not observed in the installation of the present invention, which greatly improves its lifespan.

It may be desirable for the burners mounted on the disc 103 to move longitudinally with respect to the axis of rotation of the furnace, in particular so as to prevent reoxidation of the feed material. The same applies to burner 112 which may be located at the outlet side.

It is preferred that the feed pipe 105 is provided with a double non-return flap valve 117 through which solid material can pass and be fed into the furnace. The non-return flap valve prevents combustion gas from flowing backward from the burner.

6 and 7 illustrate two types of other equipment equivalent to the equipment 101. In the case of FIG. 6 the shape is tapered towards the outlet, and in FIG. 7 the shape has a "step" from one end to the other end.

As shown, the furnace diameter is larger than the diameter of the discharge end.

In addition, as illustrated by the arrow 160, the furnace may perform a tilting motion.

The generally disc-shaped supply unit, indicated at 103, may be provided with an apparatus 114 for injecting pulverized coal, an oxygen lance and burner 113 which is preferably submerged in the molten mass (as described above in the application). It is also desirable to be able to recycle some of the pig iron produced via feed chute 106 or additional pipes by trap 162.

Driven by the rotation of the furnace, it illustrates a portion of a partial separation panel 163 provided with a central opening 165 and a peripheral opening 164 as illustrated. The panel 163 is capable of evacuating gas and transporting pig iron to the discharge end upstream of the furnace but retaining bubbles produced by active action in the bath during oxygen injection through the discarded clinker and oxygen lance 161.

While preferred embodiments of the invention have been described, it should be understood that various modifications can be made without departing from the scope of the invention, particularly the following claims.

Claims (16)

In the iron oxide reduction method, At least two successive steps, A first basic step of reducing the initial oxide until metallization is achieved at 80-94%, preferably 85-90%, heating to a temperature of at least 1000 ° C., up to a temperature close to melting point, and A second step in which the mixture of iron metallization, gangue, flux and surplus coal is fed directly by gravity into the melting furnace containing molten pig iron and then the metal and slag are preferably removed continuously, in particular by overflow Iron oxide reduction method comprising a. 2. The method of claim 1, wherein there is no intermediate cooling step to completely recover excess energy in the iron metallization mixture. The iron oxide reduction method according to claim 1 or 2, wherein the combustion gas from the melting furnace is supplied directly to the step of reducing the iron oxide to assist in latent heat and reducing capacity. In the reduction facility which implements the reduction method of any one of Claims 1-3, Iron oxide reduction furnace for the first stage (1) and melting furnace for the second stage (3) Including, One or more pipes provided with a flap valve for feeding the metallization mixture from the first stage to the melting furnace 3 by gravity transfer, and one or more pipes for discharging the combustion gas from the melting furnace 3 to the iron oxide reduction furnace 1. Connected by (4), Unit for discharging pig iron to pig iron refining facility (5) and unit for discharging slag to slag processing facility (6) Reduction equipment comprising a. 5. The reduction apparatus according to claim 4, wherein the melting furnace (3) is an induction furnace in which stirring of the melting tank does not fluctuate excessively due to an induction current. Reduction plant according to claim 4, wherein the melting furnace (3) is an electric arc furnace, in particular a submerged-arc furnace. 5. The melting furnace (3) according to claim 4, wherein the melting furnace (3) feeds the material to be treated, and is first connected to a unit having a funnel type which discharges molten iron and slag at one end from an open tubular rotary furnace with an opposite end and then discharges gas A unit, essentially comprising a unit connected to a combined fuel burner that supplies the heat required for melting the material to be treated. The method of claim 7, wherein the members constituting the melting furnace can be mounted on a common chassis to cause the first rotary furnace and auxiliary equipment to be tilted without disruption to production, and the second assembly or any of its constituent members quickly. Replaceable reduction facility. 9. An expansion bellows according to claim 7 or 8, wherein the supply unit is connected to a chute mounted on a pipe or a DRI unit and the support point of the chassis provided for tilting the installation is preferably located at the level of the connection line. Reduction plant in which the level is reliably gas-tight connected by a telescopic joint such as a bellow. 10. The reduction plant according to any one of claims 7 to 9, wherein the gas exhaust unit is primarily connected directly to an upstream plant which takes in hot combustion gases and supplies the plant with the substance to be treated. 11. The supply unit upstream of the furnace according to any one of claims 7 to 10, wherein the supply unit upstream of the furnace is mounted on a supply chute, or any other suitable supply such as an Archimedean screw mounted on the disk and through which the burner penetrates therein. Reduction plant comprising a system. 2. A reduction plant as set forth in claim 1, wherein said disk comprises a pulverized coal input device, which adds coal to the bath to prevent regeneration of the first charge and finally reduce the sponge iron to obtain high quality pig iron. 13. A reduction plant as claimed in any of claims 7 to 12, comprising a flap valve capable of preventing gaseous reflux while allowing the solid material to pass therethrough. 14. A lance, monitoring window, and possibly an inverted burner or second burner for desulfurizing pig iron on a wall facing the outlet opening. Reduction equipment provided. The reduction installation according to any one of claims 7 to 14, wherein the furnace is inclined and because of its shape, molten material is maintained in the bath while gradual movement of the material is ensured. The reduction apparatus according to any one of claims 7 to 15, wherein a tilting chassis can interfere with combustion casting, so that a transfer device filled with liquid pig iron can be replaced.