KR100286655B1 - Smelting reduction process of fine iron ore using ladle gas and apparatus used in the method - Google Patents

Abstract

PURPOSE: A method is provided to enable fluidized bed reduction of the fine iron ore by carbon coating the surface of fine iron ore in which fluidized bed reduction has been impossible using a ladle gas, and an apparatus is provided which is capable of smelting reducing the fine iron ore using the ladle gas. CONSTITUTION: In a smelting reduction process using a smelting reduction system comprising a pre-reduction furnace reducing iron ore and a smelting reduction furnace recovering iron by smelting the pre-reduced iron, the smelting reduction process of fine iron ore using ladle gas comprises the steps of drying and preheating fine iron ore charged from a hopper as forming bubbling fluidized bed using an exhaust gas flown into the lower side from a first fluidized bed furnace(20); preheating a ladle gas which is supplied from a ladle gas supplying device(1), and from which CO2 is removed using a flue gas heated by heating a flue gas of the first fluidized bed furnace(20) with a flue gas heating device(2); carbon coating the surface of the dried and preheated fine iron ore supplied from the first fluidized bed furnace(20) as forming bubbling fluidized bed through the second fluidized bed furnace(30) by flowing the CO2 removed preheated ladle gas into the lower side of a second fluidized bed furnace(30); and supplying the coated fine iron ore to an existing pre-reduction furnace, and circulating a flue gas generated after coating reaction in the second fluidized bed furnace(30) to the lower side of the first fluidized bed furnace(20) for using.

Description

Melt reduction method of ground iron ore using converter flue gas and apparatus used therein

The present invention relates to a melt reduction method and a reduction apparatus used therein, and more particularly, a method for reducing a distribution layer by carbon coating a surface of a fine iron ore that has been impossible for fluidized bed reduction using a furnace exhaust gas, and It relates to the apparatus used.

Up to now, iron ore fluid filling reduction has been used with a particle size of about 8 mm, but in the case of fine iron ore, sticking phenomenon occurred during fluidized bed reduction, making it impossible to use.

On the other hand, the conventional ladle gas (ladle gas) has been used as a fuel, such as a boiler or heating furnace for thermal power generation, but the main exhaust gas is about 65% CO, CO ₂ is about 15%, H ₂ is less than 2%. Since the rest is inert N ₂ , CO ₂ is a very good source of CO2 removal. In recent years, the CO component is separated from the converter exhaust gas for the purpose of improving the added value of the converter exhaust gas. _In addition, research on the development of acid processes to synthesize industrial raw materials such as olefins and oxygen-containing chemicals such as alcohol or acetic acid is in full swing. However, in order to develop these new processes, high-purity CO recovery must be possible, and high selectivity and high activity adsorbents or catalysts are required for this purpose. Therefore, there are many technical and economic problems.

Accordingly, an object of the present invention is to provide a melt reduction method capable of utilizing 100% of fine iron ore, which was not previously available by carbon coating a surface of fine iron ore using a converter exhaust gas during the melt reduction of iron ore.

Another object of the present invention is to provide a device capable of melt reduction of fine iron ore using the converter exhaust gas.

1 is an example of a melt reduction apparatus according to the present invention

<Explanation of symbols for main parts of drawing>

1: converter exhaust gas supply device 2: exhaust gas preheating device

10: hopper 20: the first fluidized bed

30: second distribution layer 40: first cyclone

50: second cyclone 60: heat exchanger

70: absorption tower 80: converter exhaust gas pressurizer

90 gas cooler 100 bag filter

ll0: Air compressor 120: Existing melt reduction equipment

130: flarestack

The present invention for achieving the above object is in the melt reduction method using a melt reduction apparatus comprising a preliminary reduction path for reducing iron ore and a molten reduction path for recovering iron by dissolving pre-reduced reduced iron, fine powder charged from the hopper Drying and preheating iron ore while forming a bubble fluidized bed by exhaust gas flowing downward from the first fluidized bed furnace; The gonggup is in a converter exhaust gas supply by the heat to heat the exhaust gas to the first fluidized bed by the exhaust gas heating device exhaust gas preheating the converter exhaust gas to remove the CO _2; Carbon coating the surface of the dried, preheated fine iron ore supplied from the first fluidized bed while forming a bubble fluidized layer through the preheated exhaust gas from which the CO ₂ has been removed; And supplying the coated fine iron ore to the existing preliminary reduction reactor and using the exhaust gas generated after the coating reaction in the second fluidized bed to circulate downwardly to the first fluidized bed. It relates to a melt reduction method of fine iron ore using a converter exhaust gas comprising a.

In addition, the present invention is a molten reduction apparatus comprising a preliminary reduction path for reducing iron ore and a molten reduction path for recovering iron by dissolving the pre-reduced reduced iron, the fine iron ore supplied from the hopper to the exhaust gas introduced from the bottom A first fluidized bed furnace for drying and preheating the bubble fluidized bed by forming a bubble fluidized bed; A first cyclone for collecting particulate iron ore contained in the flue gas generated in the first fluidized bed furnace and recycling it to one side of the first fluidized bed furnace; A second fluidized bed furnace for coating the surface of the ground iron ore supplied from the first fluidized bed furnace in a bubble flow state by the converter exhaust gas introduced from the lower part thereof and supplying the coated fine iron ore to the existing preliminary reduction reactor; The fine iron ore collected by collecting the fine iron ore contained in the exhaust gas discharged after the coating reaction is recycled to one side of the lower side of the second fluidized bed, and the exhaust gas discharged to the lower side of the first fluidized bed and ; A converter exhaust gas supply device for supplying converter exhaust gas to the lower portion of the second fluidized bed furnace; It relates to a pulverized iron ore melt reduction apparatus using a converter exhaust gas comprising a; pre-heating device for preheating the exhaust gas discharged from the first cyclone.

First, a preferred example of the melt reduction apparatus according to the present invention will be described with reference to FIG.

The fine iron ore melt reduction apparatus of the present invention is an improvement of the conventional melt reduction facility comprising a preliminary reduction path for reducing iron ore and a molten reduction path for recovering iron by dissolving pre-reduced reduced iron. Prior to the preliminary reduction of the melt reduction facility, a fine iron ore surface coating apparatus is provided and configured.

That is, the molten reduction apparatus including the fine iron ore surface coating apparatus of the present invention, as shown in FIG. 1, forms a bubble flow layer by the exhaust gas introduced from the bottom of the fine iron ore supplied from the hopper 10 A first fluidized bed furnace 20 for drying while preheating; A first cyclone 40 for collecting the fine iron ore contained in the flue gas generated in the first fluidized bed furnace 20 and recycling it to one lower side of the first fluidized bed furnace 20; The fine iron ore supplied from the first fluidized bed furnace 20 is coated with its surface in a bubble flow state by the converter exhaust gas introduced from the lower portion thereof, and the coated fine iron ore is added to an existing preliminary reduction reactor (not shown). A second fluidized bed furnace 30 for supplying; The fine iron ore collected by collecting the fine iron ore contained in the exhaust gas discharged after the coating reaction is recycled to one side of the lower side of the second fluidized bed furnace 30 and the exhaust gas is supplied to the lower part of the first fluidized bed furnace 20. A second cyclone 50; A converter exhaust gas supply device (1) for supplying converter exhaust gas to the lower portion of the second fluidized bed furnace (30); It is configured to include an exhaust gas preheater (2) for preheating the exhaust gas discharged from the first cyclone (40).

The first fluidized bed passage 20 has an exhaust gas supply port 21 of a second cyclone 50 formed at a lower end thereof, and a gas distribution plate 22 is mounted therein, and the first conduit 11 is formed at one side thereof. A supply port 25 of iron ore flowing from the hopper 10 is installed, and the first outlet 23 at one lower side is connected to the lower one side of the second flow passage 30 via the fifth conduit 24. The upper one side is connected to the upper one side of the first cyclone 40 through the third conduit 26. In addition, the connection portion between the first conduit 11 and the lower one side of the first fluidized bed 20 and the connection between the fifth conduit 24 and the lower one side of the second fluidized bed 30 is provided with a small amount of gas supply port. (P) is installed to prevent clogging of fine iron ore.

In addition, a lower end portion of the first cyclone 40 is connected to a lower portion of the first fluidized bed passage 20 through a second plate 41, and a gas outlet 42 is provided at an upper end portion of the first cyclone 40. The outlet 42 is connected to the upper side of the gas cooler 90 of the exhaust gas preheater 2 via the fourth conduit 43.

The second fluidized bed furnace 30 has a converter exhaust gas supply port 31 heated at a lower end thereof, a gas distribution plate 32 is mounted therein, and an outlet 23 of the first fluidized bed furnace 20 is installed at one lower side thereof. ) And the fifth conduit 24 are connected. And, the third outlet 33 of the other lower portion is connected to the preliminary reduction path of the existing fluidized-bed reduction facility 120 which is the next process. In addition, a seventh conduit 35 is connected to the upper one side of the second fluidized bed 30 and connected to the upper one side of the second cyclone 50. In addition, the lower end of the second cycle comb 50 is connected to the lower portion of the second flow passage 30 through the eighth conduit 51.

In this case, the first and second flow passages 20 and 30 are preferably such that the lower height thereof is 7-12 times the lower inner diameter and the upper height is about 2-4 times the upper inner diameter. That is, the first fluidized bed furnace 20 and the second fluidized bed furnace 30 should increase the gas utilization rate by activating the bubble flow of fine iron ore at the bottom of the furnace, wherein the first and second fluidized bed furnaces 20 and 30 are used. If each lower height is less than seven times the lower inner diameter and each upper height is less than two times the upper inner diameter, there is a large amount of scattering losses. On the contrary, if the lower height is higher than 12 times the lower inner diameter and the upper height is four times the upper inner diameter. There is a lot of heat loss. On the other hand, it is preferable to form an expanded furnace body that can reduce the gas flow rate of the upper part of the furnace by increasing the inner diameter of the upper part of the furnace lower than the inner diameter of the furnace so that scattering of the ultrafine iron ore is suppressed.

The converter exhaust gas supply device 1 includes: a converter exhaust gas pressurizer 80 which pressurizes and sends the converter exhaust gas supplied from the converter; The converter exhaust gas pressurizer 80 is configured to include an absorption tower 70 for adsorption and removal of the CO ₂ gas in the converter exhaust gas passed through the twelfth conduit 81. In addition, the exhaust gas preheater (2), the cooler 90 for cooling the exhaust gas discharged from the first cyclone (40); A bag filter 100 for filtering and cooling the cooled exhaust gas and recycling the filtered fine iron ore to the first fluidized bed furnace 20; A burner is mounted therein to burn the clean exhaust gas with air blown from the supply pressurizer 110 to remove CO ₂ from the absorption tower 70 to preheat the converter exhaust gas supplied to the second fluidized bed furnace 30. And a heat exchanger 60 for discharging the exhaust gas after preheating to the flare stack 130.

One lower side of the gas cooler 90 is connected to an upper side of the bag filter 100 through a thirteenth conduit 91, and the other side of the upper portion of the bag filter 100 is connected to a heat exchanger 60 through a fifteenth conduit 102. ) And the lower center is connected to the second conduit 41 through the 14th conduit 101.

The exhaust gas circulated through the fifteenth conduit 102 is combusted by the burner of the heat exchanger 60 together with the air supplied from the sixteenth conduit 111 connected to the air pressurizer 110, wherein the exhaust gas circulates through the preheated exhaust gas. The converter exhaust gas from which the CO ₂ gas is desorbed is configured to be preheated in the heat exchanger 60 before being supplied to the lower portion of the second fluidized bed furnace 30.

Hereinafter, the method for melt-reducing fine iron ore using the converter exhaust gas in the above-described melt reduction apparatus will be described in detail.

The fine iron ore melt reduction method of the present invention forms a two-stage fluidized bed to dry and preheat fine iron ore in the first step, and the second step is to dry and preheat the surface of the fine iron ore coated with carbon and then coated fine iron ore Proceeds to melt reduction in a conventional manner.

That is, the present invention comprises drying and preheating the fine iron ore charged from the hopper in the melt reduction apparatus while forming a bubble flow layer by exhaust gas flowing downward from the first fluidized bed furnace 20; Preheating the converter exhaust gas from which the exhaust gas of the first flow passage 20 is heated by the exhaust heating apparatus 2 and supplied from the converter exhaust gas supply device 1 by the heated exhaust gas to remove CO ₂ ; The surface of the dry, preheated fine iron ore supplied from the first fluidized bed furnace 20 while forming a bubble fluidized bed through the preheated exhaust gas from which the CO ₂ has been removed is introduced into the lower side of the second fluidized bed furnace 30. Carbon coating; And the coated fine iron ore is supplied to the preliminary reduction reactor of the existing molten reduction facility 120 and the exhaust gas generated after the coating reaction in the second fluidized bed furnace 30 is used by circulating below the first fluidized bed furnace 20. Doing; It is configured to include.

In detail, according to the present invention, the fine iron ore supplied from the hopper 10 to the middle portion of the first flow passage 20 is dried / heated in the bubble flow state by using the exhaust gas of the second cyclone 50, and thus 2 is supplied to the fluidized bed 30, and this fine iron ore is pressurized by the converter flue gas pressurizer 80 and CO ₂ is removed from the CO ₂ absorption tower 70, and the CO component of the converter flue gas heated by the heat exchanger 60 is removed. Carbon coating is performed on the surface of the bubble fluidized bed by a carbon deposit reaction and then supplied to the fluidized bed reduction facility 120 which is the next process. In the present invention, after the CO ₂ in the converter flue gas is removed, the fine iron ore is carbon coated on the surface of the fine iron ore before the fluidized bed reduction. In this way, sticking phenomenon can be prevented during spectral fluidized bed reduction. 100% of the ultrafine iron ore (200㎛ or less) is impossible. This does not require high-purity CO gas, and can reduce the amount of gas emitted by the carbon deposition reaction as described below, and fuel is saved as much as the precipitated carbon is eventually charged into the melting furnace.

2 CO = CO ₂ + C

At this time, the ultrafine iron ore entrained with the converter flue gas supplied to the first flow passage 20 is folded into the first cyclone 40 and recycled to the first fluidized bed furnace 20, and the exhaust gas is cooled again. ) Is cooled and supplied to the bag filter 100, wherein the collected fine particles are circulated in the first fluidized bed furnace 20 via the 14th conduit 101 and the second conduit 41 and the exhaust gas is 15th. It is supplied to the burner of the heat exchanger 60 via the conduit 102 and burned with the air to be used to preheat the exhaust gas to be supplied to the second fluidized bed furnace 30. The ultrafine iron ore entrained together with the converter exhaust gas supplied to the second fluidized bed furnace 30 is collected by the second cyclone 50 and recycled to the second fluidized bed furnace 30.

In addition, the flow rate of the flue gas flowing in the lower side of the first and second fluidized bed furnaces 20 and 30 is 1.5-3.0 times the minimum flow rate of the fine iron ore staying in each fluidized bed furnace, The flue-gas flow rate of is preferably less than or equal to the final velocity of fine iron ore. The reason is that if the flow rate of the flue gas is less than 1.5 times the minimum fluidization rate of the fine iron ore staying in each fluidized bed furnace, the flow is not smooth. On the contrary, if the flow rate is more than 3.0 times, the microparticles are not collected in the cyclone. This is because scattering loss increases.

In addition, the preheating converter exhaust gas supplied to the second fluidized bed furnace 30 is preferably carried out at 2-5 atm. The reason is that if the preheating converter exhaust gas is less than 2 atm, the reaction rate is slowed, the gas unit increases, and if it is at least 5 atm, the reaction efficiency is good, but it is dangerous and expensive.

In addition, the converter exhaust gas supplied to the second fluidized bed furnace 30 is preferably used to be preheated to a temperature range of 500-700 ℃. If the temperature is below 500 ° C. or higher than 700 ° C., the reaction does not occur well. That is, the best temperature for preheating the converter flue gas is in the range of 500-700 ° C.

Further, the pressure drop in the first fluidized bed furnace 20 or the second fluidized bed furnace 30 is 0.3-0.6 atm, the temperature drop in the furnace is 30-80 ° C., and the residence time of fine iron ore is 20-40 minutes. It is preferable to. If the pressure drop is less than 0.3 atm, the flow velocity in the reactor is not uniform. On the contrary, if the pressure is more than 0.6 atm, the pressure loss is high, resulting in clogging of the dispersion plate. In addition, if the residence time is less than 20 minutes, the reaction is not made completely, if the length is longer than 40 minutes, there is a problem that only the gas source unit is increased because the reaction continues to remain in the finished state.

The molten reduction method for fine iron ore is preferably applied to fine iron ore having a particle size of about 1 mn or less. In other words, if the particle size is larger than 1 mm, the reaction rate is slow, and the reaction is not possible in a short time, and there is a problem in that it is not economical.

Hereinafter, the present invention will be specifically named through examples.

EXAMPLE

Has a particle size distribution as shown in Table 1, the composition is by weight, T.Fe: 62.36%, SiO ₂ : 5.65%, Al ₂ O ₃ : 2.91%, S: 0.OOO7%, p: 0. Iron ore of OO65% was used as a raw material, and charged into a melt reduction apparatus of FIG. 1 having the specifications as shown in Table 2 at a rate of 5 kg / min to carry out a fluidized bed reduction operation.

The converter flue gas used in this experiment was composed of CO: 64%, H ₂ : 2%, CO ₂ : 18%, M: 16%, and DEA (Diethanolamine) for adsorption of CO _{2 in} the converter flue gas. A CO ₂ absorption solution was used, which maintained the aqueous solution containing about 25-30% at about 40 ° C.

Under the above conditions, it could be discharged from the second fluidized bed within 60 minutes after the start of operation. The discharged iron ore had a carbon content of 10-15%, and the degree of metallization ion was 25-35%. This carbon-coated iron ore was confirmed to be completely reduced to iron without sticking.

As described above, according to the present invention, the iron ore carbon coating operation is carried out in two stages, while maintaining the bubble flow in the first fluidized bed furnace 20 and the second fluidized bed furnace 30 to obtain uniform carbon coated iron ore by preheating and carbon coating, respectively. It is possible to utilize all the fine iron ore of less than 1mm, and to maximize the gas utilization rate, as well as to use the waste gas from the exhaust gas again to preheat the telegraph flue gas, which makes it nearly 100%.

In particular, it is possible to increase the added value by removing only CO _{2 of the} converter exhaust gas, and to reduce the amount of gas released by the carbon deposition reaction, and to prevent the sticking phenomenon from occurring because the deposited carbon completely covers the surface of the spectroscopy. This carbon can eventually be charged into the furnace, thus saving fuel.

In view of these aspects, the present invention is more economical in terms of efficiency and energy saving than simple addition of oxides or carbonates such as Ca and Mg, which are known from US Pat. No. 3,615,352 (October 26, 1971). Can be.

Claims (11)

In the melt reduction method using a molten reduction apparatus comprising a preliminary reduction path for reducing iron ore and a molten reduction path for dissolving pre-reduced reduced iron to recover iron, the fine iron ore charged from the hopper to the first fluidized bed furnace (20) Drying and preheating while forming a bubble flow layer by the exhaust gas flowing downward from the; Heating the exhaust gas of the first fluidized bed furnace 20 with the exhaust gas heater ₂ to preheat the converter exhaust gas from which the CO ₂ is removed by being supplied from the converter exhaust gas supply device 1 by the heated exhaust gas; The preheated converter exhaust gas from which the CO ₂ has been removed is introduced into the lower side of the second fluidized bed furnace 30 to form a bubble fluidized bed through which the surface of the dried, preheated fine iron ore supplied from the first fluidized bed furnace 20 is formed. Carbon coating; And supplying the coated fine iron ore to the existing preliminary reduction reactor and circulating the exhaust gas generated after the coating reaction in the second fluidized bed 30 to the lower side of the first fluidized bed 20. Melt reduction method of fine iron ore using converter exhaust gas, characterized in that comprises a. According to claim 1, wherein the flow rate of the flue-gas flowing in the lower side of the first and second fluidized bed furnace (20, 30) is 1.5-3.0 times the minimum fluidization rate of fine iron ore staying in each fluidized bed furnace, the top of the fluidized bed furnace The exhaust gas flow rate of the method characterized in that less than the terminal speed of fine iron ore. The method according to claim 1, wherein the preheating converter exhaust gas supplied to the second fluidized bed furnace (30) is performed at 2-5 atmospheres. The method of claim 1, wherein the converter flue gas supplied to the second fluidized bed (30) is preheated to a temperature range of 500-700 ℃. The pressure drop in the first fluidized bed furnace 20 is 0.3-0.6 atm, the temperature drop in the furnace is 30-80 ° C., and the residence time of fine iron ore is 20-40 minutes. Way. The pressure drop of the second fluidized bed furnace 30 is 0.3-0.6 atm, the temperature drop in the furnace is 30-80 ° C., and the residence time of fine iron ore is 20-40 minutes. Way. The method according to any one of claims 1 to 6, wherein the fine iron ore has a particle size of 1 mm or less. In the melt reduction apparatus including a preliminary reduction path for reducing iron ore and a molten reduction path for dissolving pre-reduced reduced iron to recover iron, the fine iron ore supplied from the hopper 10 is bubbled by the exhaust gas introduced from the bottom A first fluidized bed furnace 20 for drying and preheating while forming a fluidized bed; A first cyclone 40 for collecting the fine iron ore contained in the flue gas generated in the first fluidized bed furnace 20 and recycling it to one lower side of the first fluidized bed furnace 20; A second fluidized bed furnace which coats the surface of the fine iron ore supplied from the first fluidized bed furnace 20 in the bubble flow state by the converter exhaust gas introduced from the lower part thereof and supplies the coated fine iron ore to the existing preliminary reduction reactor. 30; The fine iron ore collected by collecting the fine iron ore contained in the exhaust gas discharged after the coating reaction is recycled to one side of the lower side of the second fluidized bed 30 and the exhaust gas is supplied to the lower part of the first fluidized bed 20. A second cyclone 50; A converter exhaust gas supply device (1) for supplying converter exhaust gas to the lower portion of the second fluidized bed furnace (30); The exhaust iron preheating device for preheating the exhaust gas discharged from the first cyclone (40); fine iron ore melt reduction apparatus using a converter exhaust gas, characterized in that it comprises a. The converter exhaust gas supply device (1) according to claim 8, further comprising: a converter exhaust gas pressurizer (80) for pressurizing and sending the converter exhaust gas supplied from the electric furnace; Apparatus characterized in that it comprises an absorption tower 70 for adsorption and removal of the CO ₂ gas in the converter exhaust gas from the converter exhaust gas pressurizer (80). 10. The exhaust gas preheater (2) according to claim 9, further comprising: a cooler (90) for cooling the exhaust gas discharged from the first cyclone (40); A bag filter 100 for filtering and cooling the cooled exhaust gas and recycling the filtered fine iron ore to the first fluidized bed furnace 20; A burner is mounted therein to burn the clean exhaust gas with the air blown from the air pressurizer 110 to remove CO ₂ from the absorption tower 70 to preheat the converter exhaust gas supplied to the second fluidized bed furnace 30. And a heat exchanger (60) for discharging the exhaust gas after preheating to the flare stack (130). 10. The apparatus according to claim 9, wherein the first and second fluidized bed passages (20) (30) each have a lower height of 7-12 times the lower inner diameter and an upper height of 2-4 times the upper inner diameter.