METHOD FOR INJECTING FINE IRON ORE IN SMELTING REDUCING PROCESS

Abstract: A method for injecting fine iron ore in a smelting reducing process is disclosed, in which the carrier gas for the iron ore is the discharge gas from a melter without the need of separate carrier gas. It includes the steps of prereducing iron ore in a prereduction furnace (12), melting and reducing it in the melter gasifier; spouting the cooled and cleaned fine iron ore through a recycling system (15) and a melting burner (16) into the melter gasifier (11). A part of the discharge gas is supplied through a venturi scrubber (17), a first compressor (18) and a tube (19) into tube (13). A part of the compressed gas circulating through tube (19) is recompressed by means of a second compressor (21) and the fine iron ore is recirculated into the tube (13) by the recompressed gas by means of a pneumatic fine iron or conveying system (22).

Description: METHOD FOR INJECTING FINE IRON ORE IN SMELTING REDUCING PROCESS FIELD OF THE INVENTION The present invention relates to a method for injecting fine iron ore in a smelting-reducing process. More specifically, the present invention relates to a method for injecting fine iron ore, in which in order to lower the temperature of discharge gas (reducing gas) from a melter gasifier, a fine iron ore is injected by utilizing a part of a circulating cooling gas as carrying gas. DESCRIPTION OF THE PRIOR ART A typical smelting-reducing method is disclosed in U.S. Patent 4,978,387, in which iron ore and coal are directly used without carrying out a pre-treating process so as to produce hot metal. In the method of U.S. Patent 4,978,387, the iron ore and the ordinary coal are directly used, and the pre- treating processes such as sintering process and the coking process are omitted. Therefore, compared with other pig iron manufacturing process such as blast furnace process, the process and facilities are simplified. That iε, as shown in FIG. 1, the facility for carrying out the method includes: a melter gasifier 11 for converting the coal into a gas and for melting the reduced iron ore; a pre- reduction furnace 12 for indirectly reducing the iron ore by using the reducing gas generated in the melter gasifier 11; and other auxiliary facilities. The operating temperature of the melter gasifier is 1050°C which is the condition of the complete decomposition of the tar component of the coal. The pre-reduction furnace is maintained at an operating temperature of 850°C which is the optimum condition for the indirect reduction of the iron ore. Therefore, in order to lower the high temperature of the gas of the melter gasifier to 850°C, a part of the gas which is produced in the melter gasifier is cooled down and cleaned by a venturi scrubber 17, and is subjected to a pressure stepup, before being sent to an ascending tube 13. Meanwhile, the dust which iε produced in the melter gasifier is separated by a cyclone 14, and passes through a dust recycling system 15. Then the dust is reinjected by a melting burner 16 into the melter gasifier so as to be molten and fallen-down, thereby minimizing the losseε of the fuel and the raw material. However, the above deεcribed method haε the disadvantage that only sized ore and sized coal of the optimum size (8-35 mm) can be used. The present inventor has developed a method for alleviating the restriction of the size, and filed a patent application under Korean Patent Application No. 93- 8750. In this technique, a fine iron ore is injected into an ascending tube 13 of the melter gasifier 11 or into the recycling system 15. Then the fine iron ore together with the dust from the cyclone 14 is injected into the melter gasifier 11 by means of the melting burner 16, thereby melting and agglomerating them. Thus the redustification is prevented, and the fine iron ore can be directly used. However, in this technique, only the conception of injecting the fine iron ore into the melter gasifier is provided, but no descriptions are presented as to how the fine iron ore can be injected. SUMMARY OF THE INVENTION The present invention is intended to overcome the above described disadvantages of the conventional techniques. Therefore it is an object of the present invention to provide a method for injecting a fine iron ore in a smelting reducing process for manufacturing a hot metal by using a fine iron ore, in which the fine iron ore is carried by utilizing a discharge gas from a melter gasifier, so that a separate gas for carrying and injecting the fine iron ore would not be required, and that the fine iron ore can be injected without any variation in the amount and composition of the process gas. In achieving the object, the method for injecting a fine iron ore in a smelting reducing procesε according to the preεent invention includes the steps of: pre-reducing an iron ore by utilizing a discharge gas generated in a melter gasifier; smelting and reducing the pre-reduced iron ore in the melter gasifier; supplying the discharge gas of the melter gasifier through an ascending tube and a cyclone to a pre-reduction furnace; spouting the fine iron ore (cooled down and cleaned by the cyclone) through a recycling system and a melting burner into the melter gasifier; and supplying a part of the discharge gas (passed through the cyclone) through a venturi scrubber, a compressor and a compressed gas circulating tube into the ascending tube, and the method further includes the steps of: recompresεing a part of the compressed gas which circulates through the compressed gas circulating tube; and injecting the fine iron ore into the ascending tube by utilizing the recompressed gas. BRIEF DESCRIPTION OF THE DRAWINGS The above object and other advantages of the present invention will become more apparent by describing in detail the preferred embodiment of the present invention with reference to the attached drawings in which: FIG. 1 is a schematic illustration showing the conventional smelting reduction system for manufacturing a hot metal from an iron ore; FIG. 2 is a schematic illustration showing the smelting reduction system according to the present invention; and FIG. 3 is a detailed illustration of the pneumatic fine iron ore conveying system of the smelting reduction system of FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 2 illustrates an embodiment of the smelting reduction system according to the present invention. As shown in FIG. 2, the smelting reduction system to which the method of the present invention is applied includeε: a melter gasifier 11 for gasifying the coal and for melting the reduced ore; a pre-reduction furnace 12 for indirectly reducing an iron ore by utilizing the discharge gas of the melter gasifier 11; a cyclone 14 for receiving the discharge gas from the melter gasifier 11 through an ascending tube 13 to capture the fine iron ore from the discharge gas so as to send it to a recycling system 15, and for supplying the fine iron ore and the separated discharge gas to the pre-reduction furnace 12; a melting burner 16 installed on the melter gasifier 11, for spouting the fine iron ore of the recycling system 15 into the melter gasifier 11; a venturi scrubber 17 for receiving a part of the discharge gas of the cyclone 14, to collect dust and cool it; a compresεor 18 for compressing the cooled gas of the venturi scrubber 17 so as to supply the compressed gas through a compressed gas circulating tube 19 to the ascending tube 13; a second compressor 21 for reco pressing a part of the compressed gas; and a pneumatic fine ore conveying system 22 for supplying the fine iron ore to the ascending tube 13 by utilizing the recompressed gas of the second compreεsor 21. The melter gasifier 11 and the pre-reduction furnace 12 communicate together through a reduced ore discharge tube 5. The pre-reduction furnace 12 is connected to a discharge gas discharging tube 8, and to an iron ore supplying tube 2 for supplying a fine iron ore. The pre-reduction furnace 12 communicates with the cyclone 14 through a first discharge gas circulating tube 3a. The venturi scrubber 17 communicates with the cyclone 14 through a εecond discharge gas circulating tube 3b. The venturi scrubber 17 communicates with the compressor 18 through a cooling gas circulating tube 17a. The compressor 18 communicates with the ascending tube 13 and the second compressor 21 through a compressed gas circulating tube 19 and a second compressed gas circulating tube 19a respectively. The second compressor 21 communicates with the pneumatic fine ore conveying system 22 through a third compresεed gas circulating tube 21a. The pneumatic fine ore conveying system 22 communicates with the ascending tube 13 through a fine ore supplying tube 22a. The recycling system 15 communicates with the cyclone 14 through a firεt fine iron ore circulating tube 14a, and iε connected through a εecond fine iron ore circulating tube 15a to the melting burner 16. FIG. 3 iε a detailed illustration of the pneumatic fine ore conveying system of the smelting reduction syεte . Aε shown in FIG. 3, the pneumatic fine iron ore conveying system includes a raw material storing vessel 221, a lock vessel 222, a dispenεing vessel 223, a raw material dispensing feeder 224 and an injector 225. In the present invention, the pneumatic fine iron ore conveying system iε constituted as follows. That is, the gaε which iε recompressed by the second compreεsor 21 is supplied through the third gas circulating tube 21a to the injector 225, and is supplied through a fourth compressed gas circulating tube 227 to the lock vessel 222. In the present invention, the pre-reduction furnace 12 pre-reduces the iron ore by utilizing the discharge gaε of the melter gaεifier 11. The iron ore which has been pre-reduced iε smelt-reduced by the melter gasifier 11. The discharge gas of the melter gasifier 11 iε supplied through the ascending tube 13 and the cyclone 14 to the pre-reduction furnace 12. The ore fines which are collected by the cyclone 14 are spouted through the recycling syεtem 15 and the melting burner 16 into the melter gaεifier 11. A part of the gaε which haε passed through the cyclone 14 is supplied through the venturi scrubber 17, the compresεor 18 and the compreεεed gaε circulating tube 19 to the ascending tube 13. Thus the method can be applied to the smelting reduction for manufacturing a hot metal. For injecting the fine iron ore according to the present invention, a part of the gas which has passed through the compressed gas circulating tube 19 is recompressed by the second compresεor 21, and the fine iron ore iε injected into the ascending tube 13 by means of the pneumatic fine iron ore conveying system 22 by utilizing the recompressed gas. The fine iron ore which has been injected into the ascending tube 13 iε spouted through the cyclone 14, the recycling system 15 and the melting burner 16 into the melter gasifier 11. In the case where the pneumatic fine iron ore conveying system of FIG. 3 is used, the cooling reducing gas is subjected to a presεure stepup, and then, the gaε is supplied to the lock vessel 222 and to the injector 225 installed beneath the pneumatic fine iron ore conveying εystem 22. By utilizing the cooling reducing gaε aε the carrying medium, the fine iron ore iε injected into the aεcending tube 13 of the melter gasifier 11 under operation with a presεure of 3.0 - 3.5 Kg/cm 2 . The fine iron ore thus injected undergoes a heating and a partial reduction by being raised by the rising gas. The fine iron ore and the dust are separated by the cyclone 14, and then, are supplied through the recycling syεtem 15 and the melting burner 16 into the melter gasifier 11. Then carbon reacts with oxygen which is injected by a dust burner, so as to be burned. Owing to the combuεtion heat, the pre-reduced fine iron ore is melted and agglomerated, so as to be fallen down to below the melter gasifier, with the result that it undergoes a smelting reduction, thereby producing a hot metal. The presεure within the aεcending tube εhould be preferably 3.0 - 3.5 Kg/cm 2 . Further, it is desirable that the compresεor 18 εhould compreεs the gas to a pressure of 3.7 - 4.2 Kg/cm 2 . Further, it iε desirable that the second compressor 22 should compress the gas to a presεure of 5 - 10 Kg/cm 2 . For example, the diεcharge gas of the melter gasifier 11 is composed of 60-65% of CO, 25-30% of H 2 , 3-5% of C0 2 and 2-4% of N 2 . Now the action and effect of the present invention will be described. The gas which is produced by the melter gasifier 11 has a high temperature of 1000-1100°C, and thiε is produced through the complete decomposition of a large amount of the tar which is the volatile material contained in the coal. However, the optimum temperature in the pre- reduction furnace 12 is 850°C, and therefore, about 20% of the produced reducing gas is collected by the venturi scrubber 17 so as to cool it. Then the cooled gas iε compressed by the compresεor 18, and then, the co preεsed gaε iε recirculated into the lower portion of the ascending tube 13 of the melter gasifier 11, thereby adjusting the temperature of the gas. In the present invention, in order to inject the fine iron ore in the smelting reducing process, a part of the recirculated gaε is collected so as to reco presε it. Then the recompressed gas is supplied to the pneumatic fine ore conveying εyεtem 22, so that the recompressed gas can be used for carrying the fine iron ore into the ascending tube 13 of the smelting reducing furnace. The carrying gas which carries the fine iron ore should be an inert or reducing gas, so that the carrying gas would not react with the reducing gas or the fine particles, and that no influence would be given to the thermal or material balance during the process. In view of this, nitrogen may be used, but when nitrogen is used, a separate nitrogen supplying device is required, and the nitrogen gas is mixed with the reducing gaε. If the nitrogen content within the reducing gaε exceedε about 10%, the reducing εpeed iε slowed in the reducing furnace. Further, if the inert gas is used, a separate expense is incurred aε much as the gas cost. If the present invention is applied to injecting the fine iron ore in the smelting reducing process, that is, if a part of the conventional circulating gas (which is composed of about 65% of CO, 25% of H 2 , 5% of C0 2 and 3% of N 2 ) is used as the carrying gas, not only there iε no variation in the amount of the total carried gas in the ascending tube, but alεo there iε no change in the composition of the reducing gas supplied to the reducing furnace. Therefore the iron ore reducing operation is poεsible in a state with the existing conditions unchanged. Further, an additional expense is not incurred. Now the present invention will be described based on an actual example. A testing facility was prepared in the COREX C-2000 plant, for testing the fine iron ore operation. In the existing COREX c-2000 tower, there is no space for installation of a pneumatic fine ore conveying system, and therefore, at a distance of 10 m from the COREX main tower, there was installed a fine iron ore carrying tower which included a fine iron ore storing facility and a pneumatic fine iron ore conveying system. The pneumatic fine iron ore conveying distance consisted of a horizontal distance of 45 and a vertical diεtance of 40 m. The pneumatic conveying condition for the fine iron ore was a minimum presεure of 9 Kg/cm 2 , and thiε was determined in accordance with the conveying distance. As to the carrying gas for pneumatically carrying the fine iron ore to the ascending tube of the melter gasifier, nitrogen having a presεure of 11 Kg/cm 2 waε εupplied so as to reduce its pressure to 10 Kg/cm 2 . Thus the fine iron ore could be injected into the aεcending tube.

Claims: WHAT IS CLAIMED IS: 1. A method for injecting a fine iron ore in a εmelting reducing process, comprising the stepε of: pre-reducing an iron ore in a pre-reduction furnace 12 by utilizing a diεcharge gas generated in a melter gasifier ii; εmelting and reducing the pre-reduced iron ore in said melter gasifier 11; supplying the discharge gaε of εaid melter gaεifier 11 through an aεcending tube 13 and a cyclone 14 to εaid pre- reduction furnace 12; εpouting the fine iron ore (cooled down and cleaned by εaid cyclone 14) through a recycling system 15 and a melting burner 16 into said melter gasifier 11; and supplying a part of the discharge gas (passed through said cyclone 14) through a venturi εcrubber 17, a firεt compreεεor 18 and a compressed gas circulating tube 19 into εaid aεcending tube 13, the method further compriεing the εtepε of: recompreεεing by means of a second compresεor 21 a part of the compreεsed gas which circulates through said compreεεed gas circulating tube 19; and injecting the fine iron ore into said ascending tube 13 by utilizing the recompressed gas by means of a pneumatic fine iron ore conveying syεtem 22. 2. The method aε claimed in claim 1, wherein εaid pneumatic fine iron ore conveying εystem 22 compriseε a raw material εtoring vessel 221, a lock vesεel 222, a diεpensing vessel 223, a raw material dispensing feeder 224 and an injector 225, and wherein the recompresεed gaε of εaid εecond compressor 21 is supplied to said lock veεεel 222 and to εaid injector 225. 3. The method as claimed in any one of claims 1 and 2, wherein the gas recompressed by said second compressor 21 has a pressure of 5-10 Kg/cm 2 . 4. The method as claimed in any one of claims 1 and 2, wherein the discharge gas discharged from said melter gasifier 11 is co poεed of: 60-65% of CO, 25-30% of H 2 , 3-5% of C0 2 , and 2-4% of N 2 ; said ascending tube 13 has an internal presεure of 3.0-3.5 Kg/cm 2 ; and the gaε compressed by said firεt compreεεor 18 has a presεure of 3.7-4.2 Kg/cm 2 . 5. The method as claimed in claim 3, wherein the discharge gas discharged from said melter gasifier 11 is composed of: 60-65% of CO, 25-30% of H 2 , 3-5% of C0 2 , and 2-4% of N 2 ; said ascending tube 13 has an internal presεure of 3.0-3.5 Kg/cm 2 ; and the gaε compreεεed by said first compressor 18 has a pressure of 3.7-4.2 Kg/cm 2 .

Inventors: JOO SANG HOON, KEPPLINGER WERNER L, LEE IL OCK, LEE SANG DEOK, WALLNER FELIX, JOO, SANG, HOON;, KEPPLINGER, WERNER, L., LEE, IL, OCK;, LEE, SANG, DEOK;, WALLNER, FELIX
Applicants: JOO SANG HOON, KEPPLINGER WERNER L, LEE IL OCK, LEE SANG DEOK, PO HANG IRON & STEEL, RES INST IND SCIENCE & TECH, VOEST ALPINE IND ANLAGEN, WALLNER FELIX, JOO, SANG, HOON;, KEPPLINGER, WERNER, L., LEE, IL, OCK;, LEE, SANG, DEOK;, POHANG IRON & STEEL CO., LTD., RESEARCH INSTITUTE OF INDUSTRIAL SCIENCE & TECHNOL, VOEST-ALPINE INDUSTRIEANLAGENBAU GMBH, WALLNER, FELIX
Application year: 1996
Main classification: C21B13
IPC codes: C21B11, C21B13