EP1956101B1 - Procede de production de minerai fritte - Google Patents

Procede de production de minerai fritte Download PDF

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Publication number
EP1956101B1
EP1956101B1 EP06822967A EP06822967A EP1956101B1 EP 1956101 B1 EP1956101 B1 EP 1956101B1 EP 06822967 A EP06822967 A EP 06822967A EP 06822967 A EP06822967 A EP 06822967A EP 1956101 B1 EP1956101 B1 EP 1956101B1
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EP
European Patent Office
Prior art keywords
gaseous fuel
combustion
sintering bed
sintering
concentration
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EP06822967A
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German (de)
English (en)
Japanese (ja)
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EP1956101A1 (fr
EP1956101A4 (fr
Inventor
Nobuyuki c/o Intellectual Property Dept. OYAMA
Hideaki c/o Intellectual Property Dept SATO
Satoshi c/o Intellectual Property Dept. MACHIDA
Kanji c/o Intellectual Property Dept. TAKEDA
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JFE Steel Corp
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JFE Steel Corp
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B1/00—Preliminary treatment of ores or scrap
    • C22B1/14—Agglomerating; Briquetting; Binding; Granulating
    • C22B1/16—Sintering; Agglomerating
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B1/00—Preliminary treatment of ores or scrap
    • C22B1/14—Agglomerating; Briquetting; Binding; Granulating
    • C22B1/16—Sintering; Agglomerating
    • C22B1/20—Sintering; Agglomerating in sintering machines with movable grates
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B1/00—Preliminary treatment of ores or scrap
    • C22B1/14—Agglomerating; Briquetting; Binding; Granulating
    • C22B1/16—Sintering; Agglomerating
    • C22B1/20—Sintering; Agglomerating in sintering machines with movable grates
    • C22B1/205—Sintering; Agglomerating in sintering machines with movable grates regulation of the sintering process
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B21/00—Open or uncovered sintering apparatus; Other heat-treatment apparatus of like construction
    • F27B21/06—Endless-strand sintering machines
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D3/00—Charging; Discharging; Manipulation of charge
    • F27D3/10—Charging directly from hoppers or shoots

Definitions

  • the present invention relates to a method for producing sintered ore as a raw material for blast furnace using a downward suction type Dwight Lloyd (DL) sintering machine, and to a
  • Sintered ore which is the main raw material of the blast furnace iron making process is manufactured generally by the process illustrated in FIG. 1 .
  • the raw materials include fine iron ore, recovered fine in iron works, under-sieve fine of sintered ore, CaO-containing raw material such as limestone and dolomite, agglomeration assistant such as burnt lime, coke fine, and anthracite.
  • the CaO-containing raw material such as limestone and dolomite is hereinafter referred to as the "CaO-based auxiliary raw material".
  • the supplied raw materials are blended together and agglomerated in a drum mixer 2 or the like with the addition of adequate amount of water, thus forming a sintering raw material which is quasi-particles having a mean particle size between 3.0 and 6.0 mm.
  • a sintering raw material is dried in a rotary kiln 3.
  • the dried sintering raw material is charged onto an endless traveling moving pallet 8 of the sintering machine from surge hoppers 4 and 5 located above the sintering machine via a drum feeder 6 and a charge chute 7, thereby forming a charged bed 9 which is also called the sintering bed.
  • the thickness (height) of the sintering bed is approximately in a range from 400 to 800 mm.
  • the carbonaceous material in the sintering bed is ignited by an ignition furnace 10 positioned above the sintering bed 9.
  • an ignition furnace 10 positioned above the sintering bed 9.
  • the carbonaceous material in the sintering bed successively combusts downward.
  • the generated combustion heat brings the sintering raw material combust to melt, thus forming a sintered cake.
  • the sintered cake is crushed and regulated in size, thereby being collected as the product sintered ore composed of 5.0 mm or coarse agglomerates.
  • the ignition furnace 10 ignites the surface of the sintering bed.
  • the carbonaceous material in the sintering bed is combusted by the suction gas sucked from the top of the sintering bed down to the lower layer portion thereof, and the combustion propagates to downward layer and front side with the travel of the pallet 8.
  • water content in the sintering raw material particles in the sintering bed is vaporized by the heat generated from the combustion of carbonaceous material, which vapor and water are then sucked downward, thus the water is enriched in the sintering raw material in a wet zone in lower layer where the temperature is not increased yet.
  • the production of sintered ore, (t/hr), is generally determined by [the productivity of sinter (t/hr ⁇ m 2 ) x the area of sintering machine (m 2 )].
  • the production varies with the width and length of the sintering machine, the thickness of the raw material packed bed (the thickness of sintering bed), the bulk density of sintering raw material, the sintering (combustion) time, the yield, and other variables.
  • there are expectedly effective methods such as the one to improve the gas permeability (pressure loss) of the sintering bed to shorten the sintering time, and the one to improve the cold strength of the sintered cake before crushing to improve the yield.
  • FIG. 2 is a graph showing the pressure loss and the temperature distribution in the sintering bed.
  • the temperature distribution curve in FIG. 2 shows that the moving combustion (flame) front comes at about 400 mm above the pallet in the sintering bed in the thickness direction thereof.
  • the pressure loss distribution at that moment is about 60% in the wet zone and about 40% in the combustion and melting zone.
  • FIG. 3 shows the temperature distribution in the sintering bed at high productivity of sintered ore and at low productivity thereof, respectively.
  • the holding time in high temperature zone where the temperature is kept at or above 1200°C of beginning the melt of raw material particles is expressed by t 1 for the case of low productivity and by t 2 for the case of high productivity which emphasizes the productivity.
  • the pallet moving speed has to be increased, thus the holding time t 2 in high temperature zone becomes short compared with the holding time t 1 in high temperature zone for low productivity. Since the time kept at high temperature becomes short, sintering becomes insufficient, and the cold strength of sintered ore decreases, thus deteriorating the yield.
  • the cold strength of sintered ore is represented by shutter index (SI) and tumbler index (TI).
  • FIG. 4(a) illustrates the principle of the progress of sintering in the sintering bed on the pallet of sintering machine
  • FIG. 4 (b) shows the temperature distribution (heat pattern) in the sintering process in the sintering bed
  • FIG. 4 (c) shows the yield distribution of the sintered cake.
  • the upper portion of the sintering bed is difficult to increase the temperature compared with the lower layer portion thereof, thus the holding time in high temperature zone becomes short.
  • the combustion and melting reaction sintering reaction
  • the strength of the sintered cake decreases to suppress the increase in the yield, thereby likely deteriorating the productivity.
  • JP-A-48-18102 discloses the injection of a high concentration flammable gas directly after the ignition furnace. Since the amount of carbonaceous material is not decreased on injecting the flammable gas, the sintering layer becomes a high temperature of exceeding 1380°C, which fails to fully improve the cold strength and to attain improvement in the yield.
  • the injection of flammable gas directly after the ignition furnace for a period of 0 to 2 minutes has a possibility of igniting the flammable gas to raise serious fire accident, thus the technology is not realistic, and has not been practically applied.
  • JP-A-55-18585 discloses, for attaining high temperature in the sintering bed of the sintering raw material, the installation of a hood above the sintering bed, and injection of a mixed gas of air and coke oven gas through the hood at a position directly after the ignition furnace.
  • the temperature in the sintering layer becomes as high as above 1350°C, which fails to attain the effect of the injection, and has a possibility of ignition of the mixed flammable gas to lead to serious fire accident. Therefore, the technology is not brought into practical application.
  • JP-A-5-311257 discloses a method of injecting a low-melting point flux, carbonaceous material, and flammable gas, at a time, at directly after the ignition furnace. Since the method also injects the flammable gas in a state that flame remains on the surface, the method has high possibility of inducing serious fire accident, and since the thickness of the sintering zone is not fully increased, (about 15 mm or less), the effect cannot fully be attained. In addition, since a large amount of low melting point flux exists, excessive melting phenomenon occurs at upper layer portion, and the pores as the air flow passage are plugged, which deteriorates the gas permeability to decrease the productivity. Consequently, the technology is also not practically applied at present.
  • JP-A-48-18102 is a technology to increase the temperature at upper portion of the sintering bed in the first half period of the sintering - process by bringing a gaseous fuel combust on the surface of the sintering bed.
  • the method uses high concentration of gaseous fuel, which may lack the quantity of air (oxygen) supporting the combustion of the gaseous fuel, thereby deteriorating the combustion of the carbonaceous material (coke) of the sintering raw material in some cases, thus raising a problem of failing to improve the quality of sintered ore.
  • the method described in JP-A-55-18585 is a method to attain further high temperature by feeding a flammable gas together with the combustion air utilizing a hood.
  • the method also lacks the heat. That is, the method also consumes oxygen, necessary for the combustion of coke, in the combustion of the injected flammable gas in the high temperature zone, which raises a problem of delayed combustion of coke and of elongation of sintering period.
  • JP-A-5-311257 increases the quantity of air (oxygen), and mixes a low melting point flux and a carbonaceous material. Accordingly, although the combustion rate of flammable gas and coke increases, the simultaneous injection of the low melting point flux and the powder raises a problem of decreasing the permeability of combustion air.
  • EP 0 079 264 discloses a method for producing sintering ore and apparatus, in which predrying and post-ignition are carried out prior to and after ignition of a charged raw material, respectively, by means of hot gaseous flow passing through the charged raw material, the post-ignition gaseous flow being oxidizing.
  • JP S46-27126 discloses a method for producing a sintered ore, the method includes igniting a raw material to be sintered, adding thermogenic gas at room temperature into the air to be sucked by the raw material so that the heat value is 500 to 9000 Kcal/m2 ⁇ min, and performing sintering while burning the thermogenic gas of room temperature in a sintering zone.
  • JP 2000-192153 discloses a blast furnace operation method in which sintered ore produced in a sintering machine is charged in a blast furnace, wherein heat generated from blast furnace gas is controlled.
  • the present invention provides a method for producing sintered ore, comprising the steps of:
  • the gaseous fuel combusting step preferably comprises:
  • the ultimate maximum temperature in the sintering bed is preferably adjusted by the following modes.
  • the ultimate maximum temperature is preferably adjusted to a range from 1205°C to 1350°C.
  • the holding time in high temperature zone in the sintering bed is preferably adjusted by the following modes.
  • the gaseous fuel combusting step preferably comprises adjusting a shape of the combustion and melting zone in the following modes.
  • the gaseous fuel combusting step is conducted in the following modes in relation to the feed position of the gaseous fuel.
  • the gaseous fuel is preferably a flammable gas which is diluted to 75% or less and 2% or more of the lower limit concentration of combustion, and more preferably a flammable gas diluted to 60% or less and 2% or more of the lower limit concentration of combustion, and most preferably a flammable gas diluted to 25% or less and 2% or more of the lower limit concentration of combustion.
  • the gaseous fuel is preferably at least a gas selected from the group consisting of blast furnace gas, coke oven gas, a mixed gas of blast furnace gas and coke oven gas, propane gas, natural gas, and methane gas.
  • the method for producing sintered ore comprises the steps of charging, igniting, sintering, and gaseous fuel combusting.
  • the charging step charges the sintering raw material containing a fine iron ore and a carbonaceous material onto the pallets moving in circulation, thereby forming the sintering bed containing the carbonaceous material on the pallet.
  • the igniting step ignites the carbonaceous material on the surface of the sintering bed at the ignition furnace.
  • the sinter step sucks air via the wind boxes located under the pallet to combust the carbonaceous material in the sintering bed, and forms the sintered cake utilizing the generated combustion heat.
  • the gaseous fuel combustion step feeds the gaseous fuel diluted to below the lower limit concentration of combustion from above the sintering bed at a position after the ignition furnace, thereby combusting the gaseous fuel in the sintering bed.
  • the gaseous fuel combustion step is a feature of the present invention.
  • a flammable gas as the gaseous fuel, which dilutes the firing component to 75% or less of the lower limit concentration of combustion in air at normal temperature, more preferably to 60% or less, and most preferably that diluted to 25% or less.
  • the flammable gas diluted to 75% or less of the lower limit concentration of combustion is preferred.
  • the concentration of the gaseous fuel has to be diluted so as to avoid lack of air (oxygen) necessary for the combustion of the entire carbonaceous material (solid fuel + gaseous fuel) in the sintering raw material, thus to avoid insufficient combustion.
  • the gaseous fuel is preferably a flammable gas diluted to 2% or more of the lower limit concentration of combustion. If the concentration is 2% or more, the strength and the yield of sintered ore are further improved.
  • the gaseous fuel is adjusted in terms of concentration depending on the amount of carbonaceous material (solid fuel). Furthermore, as described later, the gaseous fuel can adjust the combustion at a specified position in the region in the sintering bed by diluting the gaseous fuel.
  • the diluted gaseous fuel is fed to the sintering bed after igniting the carbonaceous material in the sintering bed. At the position immediately after the ignition, even if the diluted gaseous fuel is fed, combustion occurs only on the surface layer, and the sintering layer is not affected. It is preferable that the feed of the diluted gaseous fuel to the sintering bed is done after firing the sintering raw material in the upper portion of the sintering bed and after forming the sintered cake layer. The feed of the diluted gaseous fuel can be done at an arbitrary position if only the sintered cake layer is formed. The reasons of feeding the diluted gaseous fuel after forming the sintered cake are the following.
  • the diluted gaseous fuel under the condition of the thickness of the combustion and melting zone at least 15 mm or more, more preferably 20 mm or more, and most preferably 30 mm or more. If the thickness thereof is less than 15 mm, owing to the cooling by air (a mixed gas of air and gaseous fuel) sucked through the sintered layer (sintered cake), the feed of gaseous fuel does not accompany the increase in the thickness of combustion and melting zone, which results in insufficient effect of the gaseous fuel feed.
  • the thickness of the combustion and melting zone significantly increases, thus increasing the holding time in high temperature zone.
  • the confirmation of thickness of the combustion and melting zone can be given by, for example, using a transparent quartz window or a vertical tubular test pot.
  • the confirmation contributes to the determination of charge position of the diluted as fuel.
  • the diluted gaseous fuel is preferably fed at a position where the combustion front propagates below the surface layer, and at a position where the combustion and melting zone becomes deep by 100 mm or more, more preferably 200 mm or more, from the surface layer. That is, the feed of the diluted gaseous fuel is preferably given targeting the intermediate to low layer regions. For instance, the diluted gaseous fuel is fed so as to begin the combustion at a stage of intermediate to low layer portions in the sintering bed after forming the sintered cake in the sintering bed, or at the stage that the combustion front propagates to 100 mm depth from the surface layer, (so as the diluted gaseous fuel to reach the region in unburned state).
  • the reason is that, at the position of 100 mm or more of depth, the effect of cooling by air sucked through the sintered layer becomes weak, and the increase in the thickness of the combustion and melting layer is induced. More preferably, a depth of 200 mm or more eliminates the effect of cooling by air, and the thickness of the combustion and melting layer increases to 30 mm or more.
  • the feed is more preferably done at both ends in the width direction (the direction perpendicular to the pallet moving direction) near the side wall where the deterioration of yield is significant.
  • a preferable positioning of the gaseous fuel feed apparatus varies with the scale of the sintering machine. For example, at a scale of the sintering machine of 90 m of length, and at a gaseous fuel feed capacity from 1,000 to 5,000 m 3 (normal)/hr and a production of about 15 thousand tons a day, a preferable position thereof is about 5 m or more at downstream - side from the ignition furnace.
  • the feed position of the diluted gaseous fuel is preferably at one or more arbitrary points after forming the sintered cake at exit side of the ignition furnace in the pallet moving direction, between the position where the combustion front propagates to below the surface layer, (for example, 100 mm or more of depth below the surface layer, preferably about 200 mm or less of depth where the combustion of the gaseous fuel begins), and the position of completion of the combustion.
  • gaseous fuel feed begins at a stage when the combustion front moves to below the surface layer in the sintering bed, as described above, which means that the combustion of the gaseous fuel propagates inside the sintering bed and that the combustion successively moves to lower layer, which suggests that the danger of explosion is eliminated and that safe operation is available.
  • the feed of diluted gaseous fuel into the sintering bed also means to enhance the reheating of the formed sintered cake. That is, the sintered cake with low cold strength of sintered ore tends to become insufficient heat under the inherent condition of short holding time in high temperature zone.
  • the gaseous fuel fed from above the sintering bed after ignition is sucked (introduced) down to the combustion and melting zone in the unburned state, then letting the fuel combust at the target position.
  • the reason is that it should be more effective for the feed of gaseous fuel, or of injection into the sintering bed, to extend not only to the upper portion of the sintering bed but also to the combustion and melting zone at the center portion in the thickness direction.
  • the feed of a diluted gaseous fuel has the first characteristic of adjusting the position of feeding the diluted gaseous fuel from the viewpoint that the selection of the position of the action and effect of the feed thereof, and has the second characteristic of degree of adjustment of the ultimate maximum temperature and the holding time in high temperature zone in the sintering bed, together with the feed of the fuel, responding to the amount of the solid fuel under the scheme of constant heat.
  • the present invention therefore, on feeding the diluted gaseous fuel into the sintering bed, it is preferable not only to adjust the feed position but also to adjust the form of the combustion and melting zone itself, and further to adjust the ultimate maximum temperature and/or the holding time in high temperature zone in the combustion and melting zone.
  • the position of the combustion and melting zone varies with the propagation of combustion (flame) front to downward and frontward (to downstream side) accompanied with the pallet movement, as shown in FIG. 4(a) .
  • the heat history subjected in the sintering process in the sintering layer differs among upper layer, intermediate layer, and lower layer, and as shown in the figure, the holding time in high temperature zone largely differs between the upper layer and the lower layer, (about 1200°C or more).
  • the sintering layer gives a yield distribution as shown in Fig. 4 (c) .
  • the yield in the surface layer portion is low, and that in the intermediate layer and the lower layer increases.
  • the combustion and melting zone varies to increase the thickness and the range in the vertical direction, which reflects the improvement in the quality of the product sintered ore. Since the intermediate layer and the lower layer which give high yield distribution can further adjust the holding time in high temperature zone, the yield can further be increased.
  • the adjustment of feed position of the gaseous fuel allows the adjustment of the form of the combustion and melting zone, or the thickness of the zone in the height direction and/or the width in the pallet moving direction, and also allows the adjustment of the ultimate maximum temperature and the holding time in high temperature zone. Those adjustments further increase the effect of the present invention, and achieve the sustained and sufficient firing through the increase in the thickness of the combustion and melting zone in the vertical direction and through the adjustments of the ultimate maximum temperature and the holding time in high temperature zone, thereby effectively contributing to the increase in the cold strength of the product sintered ore.
  • the feed of the gaseous fuel to the sintering bed can also perform the adjustment of cold strength of entire product sintered ore. That is, the object of the injection of the gaseous fuel is to improve the cold strength of the sintered cake and further of the sintered ore. Specifically the object is to bring the cold strength (shutter index SI) of the sintered ore 75% or more to about 85%, preferably 80% or more, and more preferably 90% or more, through the adjustment of the feed position of gaseous fuel, the adjustment of the holding time in high temperature zone such as the retention time of the sintering raw material in the combustion and melting zone, and the adjustment of the ultimate maximum temperature.
  • SI cold strength
  • that strength level can be attained at low cost through the adjustment of specifically the concentration, the feed amount, the injection position, and the injection range of the gaseous fuel, preferably considering the amount of carbonaceous material in the sintering raw material (under a condition of keeping the entering heat to a constant level).
  • the improvement of the cold strength of the sintered ore may lead to the increase in the gas flow resistance and to the deterioration in the productivity.
  • the present invention solves the problems by adjusting the ultimate maximum temperature and the holding time in high temperature zone, and increases the cold strength of the sintered ore. For the above cold strength, or SI value, the sintered ore manufactured by a commercial sintering machine gives higher SI value (by 10 to 15%) than that of the pot test.
  • the adjustment of feed position of the gaseous fuel in the pallet moving direction is determined on the basis of the target cold strength of the sintered ore in an arbitrary zone between the zone of sintered cake formed in the sintering bed and the wet zone.
  • the present invention adjusts the scale (size), the amount, and the position (distance from the ignition furnace) of the gaseous fuel charge apparatus, and the gas concentration, preferably responding to the amount of carbonaceous material (solid fuel) in the sintering raw material, thus adjusting not only mainly the size of the combustion and melting zone (in the vertical direction and width in the pallet moving direction) but also the ultimate maximum temperature and the holding time in high temperature zone, thereby adjusting the strength of the sintered cake formed in the sintering bed.
  • the gaseous fuel preferably adopts blast furnace gas, coke oven gas, a mixed gas of blast furnace gas and coke oven gas, propane gas, natural gas, methane, or a mixed gas of them.
  • Each of those gases contains combustion component, and the gas is diluted by air or the like to prepare a gaseous fuel having a concentration of 75% or less of the lower limit concentration of combustion.
  • the dilution of the gaseous fuel may be done by, other than air, an inert gas, inert gas and oxygen, inert gas and air, or air and oxygen.
  • the applied sintering machine is a downward suction type DL sintering machine having a pallet on which the sintering bed of sintering raw material is formed to move in circulation, a suction wind box located below the pallet, a raw material charge apparatus on the pallet, an ignition furnace on the pallet at downstream side in the pallet moving direction, wherein a gaseous fuel feed apparatus is located at downstream side of the ignition furnace to inject the gaseous fuel diluted to a concentration of below the lower limit concentration of combustion into the sintering bed from above thereof.
  • the gaseous fuel feed apparatus is located so as to extend over both side walls of the pallet along the width direction of the sintering machine.
  • the gaseous fuel feed apparatus is preferably structured by an injection hood which feeds the diluted gaseous fuel, or an injection hood which also has rows of injection pipes in slit shape or in plane pattern for the gaseous fuel or the diluted gaseous fuel.
  • the gaseous fuel feed apparatus is preferably arranged one or more at a position of downstream side of the ignition furnace and in the pallet moving direction in the progress of the combustion and melting zone through the sintering bed, thus the feed of the gaseous fuel into the sintering bed is preferably given at a position after the ignition of the carbonaceous material in the sintering bed. That is, the apparatus is placed by one or more at an arbitrary position of downstream side of the ignition furnace and of propagation of the combustion front below the surface layer. The size, the position, and the quantity of the apparatus are adjusted from the viewpoint of adjusting the target cold strength of the product sintered ore.
  • the gaseous fuel feed apparatus is preferably located at a position in the low yield portion near both side walls, and the gaseous fuel preferably uses a flammable gas diluted to 75% or less and 2% or more of the lower limit concentration of combustion, and more preferably uses a flammable gas diluted to 60% or less and 2% or more of the lower limit concentration of combustion.
  • operation of the downward suction type sintering machine allows the combustion at a target position in the sintering bed by feeding a diluted gaseous fuel from above the sintering bed, and further the operation allows increasing the strength of sintered ore not only in the upper portion of the sintering bed where combustion likely becomes insufficient and the cold strength of the sintered ore likely decreases but also in an arbitrary portion at or below the intermediate layer of the sintering bed by adjusting the feed position of the diluted gaseous fuel, the ultimate maximum temperature during combustion, and the holding time in high temperature zone.
  • the present invention allows adjusting the strength of sintered cake at an arbitrary position through specifically the reaction in the combustion and melting zone, for instance the adjustment of thickness of the zone in the vertical direction and the adjustment of width in the pallet moving direction, without deteriorating the gas permeability of entire sintering bed. Consequently, the product sintered ore having high cold strength can be manufactured over the entire sintered ore while assuring good yield and high productivity. With the use of the sintering machine, the operation of the sintering machine can be stably attained.
  • FIG. 5 illustrates an embodiment of the apparatus for producing sintered ore according to the method of the present invention.
  • a gaseous fuel feed apparatus (hood) 12 for injecting gaseous fuel such as a mixed gas (M gas) of blast furnace gas and coke oven gas is positioned by only one unit at upper side of the sintering bed at downstream side of an ignition furnace 10 in the pallet moving direction.
  • the gaseous fuel feed apparatus 12 is composed of pluralities of pipe-shaped gas injection nozzles 12a facing downward in pluralities of rows in the machine width direction.
  • the pluralities of pipe-shaped gas injection nozzles 12a are arranged to cover the sintering bed above the side walls (not shown) via the gaseous fuel feed apparatus 12.
  • the M gas which is fed from the gaseous fuel feed apparatus 12 is sucked down to a deep portion (lower layer) of the sintering bed from above thereof via the sintered cake formed at the surface layer by the suction force of the wind box 11 below the pallet 8.
  • the nozzles 12a are arranged so as to feed a large amount of gaseous fuel to a position near both side walls of the pallet.
  • Applicable gaseous fuel being fed from the gaseous fuel feed apparatus 12 includes blast furnace gas (B gas), coke oven gas (C gas), a mixed gas (M gas) of blast furnace gas and coke oven gas, propane gas, natural gas (LNG), methane, and a diluted mixture of them.
  • B gas blast furnace gas
  • C gas coke oven gas
  • M gas mixed gas
  • propane gas propane gas
  • natural gas LNG
  • methane methane
  • a diluted mixture of them may be fed by a separate piping system, independent from the ignition furnace 10.
  • they may be fed by a common pipe to the fuel pipe for ignition furnace, specifically along with the diluted gas introduction pipe, thus connecting to the extended gas feed pipe (not shown) for the ignition furnace 10 after diluted and adjusted the concentration of the gaseous fuel to below the lower limit concentration of combustion.
  • TABLE 1 shows examples of gas concentration for varieties of gaseous fuels applied to the present invention, in terms of lower limit concentration of combustion and upper limit concentration for injection, (75%, 60%, and 25%).
  • the lower limit concentration of combustion is 2.2% by volume
  • the upper limit concentration of injection gas diluted to 75% is 1.7% by volume
  • the upper limit concentration of injection gas diluted to 60% is 1.3% by volume
  • the concentration of injection gas diluted to 25% is 0.4% by volume.
  • the concentration begins to show the injection effect, or the lower limit concentration of diluted injection gas is 0.05% by volume. Therefore, the respective preferable ranges are the following.
  • the lower limit concentration of combustion is 5.0% by volume
  • the upper limit concentration of injection gas diluted to 75% is 3.8% by volume
  • the upper limit concentration of injection gas diluted to 60% is 3.0% by volume
  • the concentration of injection gas diluted to 25% is 0.9% by volume.
  • the concentration begins to show the injection effect, or the lower limit concentration of diluted injection gas is 0.24% by volume. Therefore, the preferable ranges are the following.
  • the lower limit concentration of combustion is 4.8% by volume
  • the upper limit concentration of injection gas diluted to 75% is 3.6% by volume
  • the upper limit concentration of injection gas diluted to 60% is 2.9% by volume
  • the concentration of injection gas diluted to 25% is 0.9% by volume.
  • the lower limit concentration of diluted injection gas is 0.1% by volume. Therefore, the preferable ranges are the following.
  • the lower limit concentration of combustion is 40.0% by volume
  • the upper limit concentration of injection gas diluted to 75% is 30.0% by volume
  • the upper limit concentration of injection gas diluted to 60% is 24.0% by volume
  • the concentration of injection gas diluted to 25% is 7.6% by volume.
  • the lower limit concentration of diluted injection gas is 0.24% by volume. Therefore, the preferable ranges are the following.
  • TABLE 2 shows the content and calorific value of hydrogen, CO, methane, ethane, and propane as the combustion components of C gas, LNG, and B gas.
  • TABLE 1 Gas Lower limit concentration of combustion %, to Air (lower limit of explosion) Upper limit concentration for injection %, to Air (75%) Upper limit concentration for injection %, to Air (60%) Upper limit concentration for injection %, to Air (25%) Ignition temperature in Air, °C Propane 2.2 1.7 1.3 0.4 528-588 Hydrogen 4.0 3.0 2.4 0.8 580-590 Methane 5.0 3.8 3.0 0.9 650-750 CO gas 12.5 9.4 7.5 2.3 658-674 Coke oven gas 5.0 3.8 3.0 0.9 about 630 LNG 4.8 3.6 2.9 0.9 about 680 Blast furnace gas 40.0 30.0 24.0 7.5 about 680 TABLE 2 Hydro gen (vol%) Nitrogen (vol%) CO (vol%) CO (vol%) Methane (vol%) Ethane (vol%) Propane (vol%)
  • the experiment is an example of operation of the following.
  • An experimental apparatus is the one shown in FIG. 6 , or a test pot in vertical tubular shape (150 mm in diameter and 400 mm in height) equipped with a transparent quartz window.
  • the gaseous fuel is a mixed gas (M gas) of blast furnace gas and coke oven gas.
  • the applied sintering raw material is the same to that used in a sintering plant of the inventors of the present invention, or the sintering raw material given in TABLE 3.
  • the downward suction pressure is constant level of 11.8 KPa.
  • the concentration of the combustion component in the M gas is diluted by air to vary in a range from 0.5 to 15% by volume.
  • the lower limit concentration of combustion of the M gas is 12% by volume.
  • FIG. 6 also shows the condition observed through the transparent quartz window by video, specifically the descending behavior accompanied with the propagation of combustion front.
  • a gaseous fuel containing 15% by volume of M gas, exceeding the lower limit concentration of combustion (12% by volume) was injected into the raw material packed layer in the test pot, the gaseous fuel immediately began combustion at the surface of the sintering bed, thus failing to reach the lower layer of the sintering bed, and attaining only a small effect of injection.
  • the descending speed of the combustion zone (the inverse value thereof is the sintering time), corresponding to the propagation of the combustion front accompanied with the travel of the pallet in the commercial sintering machine, increased with the feed of the diluted gaseous fuel, and increased the thickness of the combustion zone in the vertical direction similar to the case of increased amount of coke and to the case of injection of hot air.
  • Figs 7(a) to (d) summarize the results of sintering pot tests in the above experiment.
  • the yield increased to some extent ( FIG. 7(a) ) and the sinter productivity also increased ( FIG. 7(b) ), though the sintering time changed very little.
  • the shutter strength (SI) which is a control index of the cold strength largely affecting the operation performance of blast furnace also increased by more than 10% ( FIG. 7(c) ), and the reduction degradation index (RDI) increased by as large as 8% ( FIG. 7(d) ).
  • the present invention uses a diluted gas as the gaseous fuel being fed to the sintering bed.
  • the degree of dilution is described below.
  • TABLE 4 shows the lower limit of combustion and the upper limit of combustion for blast furnace gas, coke oven gas, a mixed gas (M gas) of blast furnace gas and coke oven gas, propane, methane, and natural gas, respectively.
  • M gas mixed gas
  • propane, methane, and natural gas propane, methane, and natural gas
  • the inventors of the present invention made trial and error experiments, and adopted a gaseous fuel which was diluted to a limit of not inducing the above possibility, or diluted to below the lower limit of combustion, and used a gaseous fuel having 75% or below the lower limit concentration of combustion to further increase the safety, and confirmed that no problem occurred in many experimental runs.
  • the range of combustion of blast furnace gas is, as shown in TABLE 4, 40% by volume as the lower limit of combustion (that is, below 40% by volume does not induce combustion) in air at normal temperature, and 71% by volume as the upper limit of combustion. This means that, higher than 71% by volume gives excessively high concentration of the blast furnace gas, which case is also the not-combusting state.
  • TABLE 4 (vol%) Lower limit of combustion Upper limit of combustion Blast furnace gas 40.0 71 Coke oven gas 5.0 22 Mixed gas (M gas) 12.0 42
  • FIG. 8 shows an example of the method to determine the combustion limits of blast furnace gas.
  • the combination of H 2 and CO 2 , and CO and N 2 gives the following.
  • the upper limit of combustion can be determined. With the procedure, the lower limit of combustion and the upper limit of combustion can be derived for the blast furnace gas.
  • FIG. 9 shows the relation between the concentration of combustion component (combustion gas) of the gaseous fuel, in air at normal temperature, and the temperature, (refer to the "Combustion Handbook" of CORONA PUBLISHING CO., LTD.).
  • combustion limits can be determined as above, the combustion limits have a temperature dependency. For example, even when the lower limit of combustion at normal temperature (equivalent to the concentration of combustion gas in FIG.
  • 9 is about 40% by volume, it varies in a range from 26 to 27% by volume in a 200°C region, and several percentages in a 1000°C region, and further it can combust even at less than 1% by volume in a 1200°C region.
  • the findings showed that safety is assured if the concentration of gaseous fuel (content of the combustion component) fed to the sintering bed is diluted to a safe region, or lower than the lower limit of combustion at normal temperature, and that the freedom of adjustment of the combustion position in the thickness direction (temperature distribution) in the sintering bed increases if only the concentration of the diluted gas is adjusted.
  • combustion of gaseous fuel has above-described temperature dependency, for example, the combustion range widens when the environmental temperature increases, that combustion proceeds in a temperature field near the combustion and melting zone of the sintering machine, and that combustion does not occur at a concentration given in the preferable examples of the present invention in a temperature field at about 200°C such as the position within the electric precipitator located at downstream side of the sintering machine.
  • the gaseous fuel which is fed into the sintering bed of the sintering raw material is sucked by the wind box below the pallet, and is combusted in a high temperature region in the combustion and melting zone formed by the combustion of solid fuel (coke) in the sintering bed. Accordingly, when the feed of gaseous fuel is adjusted in terms of concentration and feed amount thereof under a condition to keep the heat entering the sintering bed constant, the amount of coke fine in the sintering raw material can be adjusted (decreased).
  • concentration of gaseous fuel means to adjust the combustion of the gaseous fuel to begin at an expected position (in a concentration region) in the sintering bed.
  • the combustion and melting zone in the sintering bed indicates the zone of combusting only the solid fuel (coke fine).
  • the zone is the one to combust further gaseous fuel adding to the coke fine. Consequently, according to the present invention, when the conditions of concentration and feed amount of the gaseous fuel and of other feeding conditions are adequately varied in relation to the presumption of existence of coke fine as a part of the fuel, the ultimate maximum temperature and/or the holding time in high temperature zone can be adjusted to a desired state, thereby achieving the increase in the strength of sintered cake.
  • Another reason of using a diluted gaseous fuel in the present invention is to adjust the strength and the yield of the sintered cake through the above-described adjustment of form of the sintering and melting zone. That is, the role of the diluted gaseous fuel effectively functions to adjust the holding time and the ultimate temperature of the sintered cake in the high temperature zone (combustion and melting zone).
  • the use of the gaseous fuel means the adjustment so as the sintering raw material to elongate the holding time in high temperature zone and to increase the ultimate maximum temperature to an adequate level.
  • That adjustment means to use the gaseous fuel which is diluted and adjusted so as to assure a proper amount of the combustion support gas (air or oxygen) in the combustion atmosphere responding to the amount of solid fuel (coke fine) in the sintering raw material.
  • the conventional technologies inject the combustion support gas without adjusting the concentration and independent of the amount of the solid fuel in the sintering raw material, thus induces insufficient amount of the combustion support gas (oxygen) for the amount of solid fuel and of flammable gas, thereby resulting in insufficient combustion, or inversely induces over-combustion locally to result in non-uniform strength.
  • the present invention can avoid those problems by using the gaseous fuel after adjusting the dilution degree.
  • FIG. 10 shows the conditions and the results of comparison experiments between the conventional sintering method (without injection of gaseous fuel) and the sintering method of the present invention using a gaseous fuel diluted to below the lower limit of combustion.
  • the conventional sintering method not injecting diluted gaseous fuel is an example of use of coke fine by 5%.
  • the amount of added coke fine is 4.2% by mass to keep the total heat constant by injecting the diluted gaseous fuel equivalent to 0.8% of coke fine.
  • the example of use of diluted gaseous fuel showed improvement in the shutter strength, the product yield, and the productivity.
  • the improvement in the shutter strength, the product yield, and the like presumably came from the widening of the combustion and melting zone indicated as the combustion state, and is given as the result of extended holding time in high temperature zone.
  • FIG. 11 shows the effect of concentration of injection gas when propane gas and C gas are used as the gaseous fuel, giving the relation of the concentration of diluted gaseous fuel and each of the shutter strength (a), the yield (b), the sintering time (c), and the productivity (d).
  • the improvement in the shutter strength appears at the addition of 0. 05% by volume, and the yield shows almost equal effect.
  • Distinctive effect appears for the propane gas from 0.1% by volume, preferably from 0.2% by volume.
  • the C gas conversion the effect appears from 0.24% by volume of addition, preferably from 0.5% by volume, and distinctive improvement effect appears from 1.0% by volume.
  • the necessary addition is at least 0.05% by volume, preferably 0.1% by volume or more, and more preferably 0.2% by volume or more.
  • the necessary addition is at least 0.24% by volume, preferably 0.5% by volume, and most preferably 1.0% by volume, and the upper limit is 75% or less of the lower limit concentration of combustion.
  • propane gas addition by 0.4% by volume almost saturates the effect, and the gas concentration at that moment corresponds to 25% of the lower limit concentration of combustion.
  • the sintering process begins the formation of melt at 1200°C, thus forming Calcium-ferrite which has the highest strength among the ores structuring the sintered ore and has relatively high reducing property.
  • the calcium-ferrite decomposes to an amorphous silicic compound (calcium-silicate) which has the lowest cold strength and reducing property among the structuring minerals, and to a secondary hemantite which is likely reduced and powdered. Therefore, to improve the cold strength and RDI of sintered ore, there is an issue that the calcium-ferrite is to be stably and sustainably formed without decomposing thereof.
  • the ultimate maximum temperature in the sintering bed in which the amount of adding carbonaceous material is adjusted by the feed of the gaseous fuel, is regulated to a range from above 1200°C to below 1380°C, and preferably from 1205°C to 1350°C.
  • the inventors of the present invention conducted an experiment, using a vertical tubular test pot equipped with a transparent quartz window, of injecting propane gas which was diluted by flue gas of the sintering machine cooler into the sintering bed of the sintering raw material from above the pot.
  • the applied sintering raw material was an ordinary one used by the company of the inventors of the present invention.
  • the suction pressure was kept constant at 1200 mmH 2 O.
  • the concentration of the injected propane gas was diluted to 0.5% by volume and 2.5% by volume, respectively.
  • the entered heat at the injection of 0.5% by volume of propane gas nearly corresponded to 1% by mass of coke fine.
  • FIG.14 shows photographs of observed combustion zone on injecting propane gas in the experiment.
  • the propane gas which was diluted to 2.5% by volume combusted immediately after the injection on the raw material sintering bed, and the gaseous fuel did not enter into the sintering bed, thus no effect was attained.
  • the propane gas With the propane gas of 0.5% by volume of diluted concentration to air, the gas did not combust in upper portion of the sintering bed, and entered into the sintering bed, and then combusted within the sintering bed at a high combustion rate.
  • the injection of that diluted propane gas widened the vertical width of the combustion zone (corresponding to the holding time in high temperature zone) to 150 mm, or more than two times.
  • the experiment investigated the descending speed of the combustion zone, (inverse thereof is the holding time in high temperature zone).
  • the descending speed significantly decreased to deteriorate the productivity.
  • the combustion rate remarkably increased compared with the example of using a solid fuel, thus the descending speed of the combustion zone gave almost the same to that of the case of atmospheric air sintering.
  • the inventors of the present invention investigated the effect of the injection position of diluted gaseous fuel.
  • Test No. 1 is under the condition of 5% by mass of coke in the sintering raw material, or current base condition.
  • Test No. 2 is under the condition of 4% by mass of coke fine therein, decreasing the content of coke fine by 1% by mass, while injecting 0.5% by volume of propane gas to keep the entering heat constant.
  • Test No. 3 is under the condition of 10% by mass of coke fine.
  • Test No. 4 is under the condition of injecting 450°C hot gas in order to verify the difference from the soaking furnace ( JP-A-60-155626 ).
  • Test No. No.1 No.2 No.3 No. 4 Coke fine ratio (to raw material, mass%) 5 4 10 5 Propane concentration (to Air, vol%) 0 0.5 0 0 Soaking furnace (injection of 450°C hot air) OFF OFF OFF ON
  • FIG. 15 shows the results, giving an example of using coke oven gas (C gas) diluted to 2% as the gaseous fuel.
  • FIG. 15 gives the results of investigation on the gaseous fuel injection in terms of the relation of the injection position, the shutter strength of the product sintered ore, and the product yield.
  • the injection position of the diluted gaseous fuel was selected to the position of "100 to 200 mm" from the surface of the sintering bed, the position of "200 to 300 mm” therefrom, and the position of "300 to 400 mm” therefrom, respectively.
  • the diluted gaseous fuel was fed from above the test pot after the combustion and melting zone (bright (white) indication) moved to the 100 mm position, thereby combusting the diluted gaseous fuel in the combustion and melting zone while the injection position remained at the "100 to 200 mm" position.
  • the diluted gaseous fuel was fed from above the test pot at a stage that the combustion and melting zone reached the 200 mm position, and similarly at the position of "300 to 400 mm", the diluted gaseous fuel was fed at a stage that the combustion and melting zone reached the position of 300 mm.
  • FIG. 15 also gives the combustion and melting zone in the conventional method in terms of the above respective positions of layer without injecting the diluted gaseous fuel.
  • the combustion air fed to the test pot flows downward from top, similar to the case of ordinary sintering operation.
  • the gaseous fuel is added to the combustion air to a specified concentration before charging.
  • the combustion and melting zone is shown in bright (white).
  • the combustion and melting zone was slightly thicker than that in the conventional method.
  • the thickness of the combustion and melting zone distinctively increased compared with the conventional method.
  • the region from 300 to 400 mm there gave distinctive difference from the conventional method.
  • the charge of gaseous fuel is given to the combustion and melting zone portion on the pallet of the sintering machine, which portion is at or deeper than 200 mm below the surface of the sintering bed. That injection also decreases the cost of applied gaseous fuel.
  • the yield of the product sintered ore can be totally improved because the shutter strength of the sintered ore significantly increases by charging the diluted gaseous fuel to the region of 200 mm or deeper without forcefully feeding the gaseous fuel to the region shallower than 200 mm.
  • FIG. 16 shows sketches of combustion state at upper layer portion between the surface and less than 200 mm depth of the sintering bed, at intermediate and lower layer portions at or deeper than 200 mm.
  • the arrow A in the figure indicates the propagation direction of the sintering (fuel direction).
  • FIG. 16(a) shows the combustion position of coke fine and gaseous fuel in the upper layer portion ( ⁇ 200 mm).
  • the combustion zone being formed by the coke fine fuel is inherently narrow at upper portion of the sintering bed, and the combustion zone of the coke fine and the combustion point of gaseous fuel which combusts in the combustion zone are close to each other, thus the temperature pattern given at right side of the figure is established.
  • the combustion zone of coke fine (solid fuel) is expressed by hatched area, and the temperature zone of gaseous fuel combusting above therefrom is expressed by not-hatched area.
  • the combustion of coke and the combustion of gaseous fuel occur at the same time (both combust at close position with each other) so that the holding time in high temperature zone (corresponding to about 1200°C), given between T 1 and T 2 , becomes short as shown in the figure. That is, the temperature distribution allows only slightly widened coke combustion zone shown by the hatched area.
  • FIG. 16(b) shows the case of feeding the gaseous fuel into intermediate and lower layer portions.
  • the combustion zone width increases with the propagation of combustion zone from upper layer downward, also supported by the increase in the temperature of sintering bed, thus the combustion occurs at a position more distant from the case of FIG. 16(a) .
  • the temperature distribution becomes that given at right side of FIG. 16(b) .
  • the combustion point of gaseous fuel is distant from the combustion point of solid fuel (coke) expressed by hatched area, thus the synthesized temperature distribution curve becomes a wide-base distribution.
  • the holding time in high temperature zone based on the combustion of solid fuel and of gaseous fuel, given by T 3 and T 4 , respectively, extends to increase the shutter strength of the obtained sintered ore.
  • the ignition temperature of the gaseous fuel for adjusting the holding time in high temperature zone is preferably in a range from 400°C to 800°C, and more preferably from 500°C to 700°C. If the ignition temperature is below 400°C, the high temperature zone does not widen, and simply the distribution of low temperature zone widens. If the ignition temperature exceeds 800°C, the holding time becomes too close to the holding time in high temperature zone of the combustion of solid fuel, thus giving small effect of extending the holding time in high temperature zone.
  • FIG.17 is a schematic drawing of the temperature distribution during sintering.
  • the figure illustrates the sintering method according to the present invention, on the basis of the conventional sintering method with a temperature distribution example of addition of 5% by mass of solid fuel (coke fine).
  • the conventional sintering method is given by the curve "a".
  • increase in the quantity of coke fine is effective.
  • the case of the addition of 10% by mass of coke fine is expressed by the broken line "a'".
  • the maximum temperature also increases from about 1300°C to about 1370°C to 1380°C, which fails to attain the low RDI sintered ore and the high strength sintered ore.
  • the sintering operation method according to the present invention can suppress the ultimate maximum temperature to 1270°C and widens the holding time in high temperature zone to (0 - C) owing to the injection of diluted C gas while suppressing the use amount of coke fine to 4.2% by mass, the object of producing low RDI and high strength sintered ore, which cannot be achieved by the conventional method, is fully attained.
  • the conventional sintering method is an operational method focusing on either of the holding time in high temperature zone or the adjustment of maximum temperature.
  • the method according to the present invention is an operational method that adjusts the ultimate maximum temperature (1205°C to 1350°C) by adjusting the amount of coke fine (for example, suppressing to 4.2% by mass), and that adjusts also the holding time in high temperature zone by the injection of diluted gaseous fuel.
  • the curve "d" in FIG. 16 is an example of simply decreasing the amount of solid fuel to 4.2% by mass, thus giving low ultimate maximum temperature and short holding time in high temperature zone.
  • FIG. 18 is an example of conventional sintering method, using 5% by mass of coke fine, and an example compatible to the present invention, using 4.2% by mass of coke fine and injecting a C gas diluted to 2.0% by volume.
  • the conventional method generated a combustion state exceeding 1400°C to maintain the holding time in high temperature zone.
  • the amount of coke fine was limited to 4.2% by mass and that the C gas of 2% by volume was injected, the 1400°C region disappeared, the ultimate maximum temperature was regulated to 1350°C or below, and the holding time in high temperature zone could be extended.
  • FIG. 19 shows the variations of internal temperature of sintering bed (a), flue gas temperature (b), gas flow rate (c), and flue gas composition (d) with time resulting from the injection of diluted propane gas under a condition of constant entering heat.
  • the internal temperature of sintering bed is an observed value in the test pot using a thermocouple inserted at a position of 200 mm above the grate bar, (thickness of sintering bed: 600 mm). The measurement was given at two points in the circumferential direction of the test pot, namely at the center and at 5 mm from the wall.
  • FIG. 20 compares the variations of internal temperatures of the sintering bed with time, (a) and (a'), and of flue gas concentrations with time, (b) and (b'), resulting from the injection of diluted propane (0.5% by volume) and from the increase only the coke (10% by mass).
  • FIG. 21 summarizes the results of various characteristics in above tests. As clearly shown in FIG. 21 , although the injection of diluted propane gas increased the sintering time to some extent, the yield, the shutter strength, and the productivity improved, and also the reduction degradation index (RDI) and the reducing property significantly improved.Consequently, it was confirmed that, by optimizing the injection of diluted gaseous fuel, the high quality of sintered ore can be attained together with the improvement of productivity and yield.
  • RDI reduction degradation index
  • the gas when a diluted gaseous fuel is applied, the gas combusts in the sintering bed to widen the combustion zone in the layer and also to form a wide combustion zone owing to a synergy effect of the combustion heat of coke in the sintering raw material and the combustion heat of the diluted propane gas.
  • the ultimate maximum temperature did not excessively increase, while the holding time in high temperature zone was extended by the combustion of charged diluted gas.
  • the inventors of the present invention investigated the effect of the injection of diluted gaseous fuel on the reducing property, the cold strength, and other characteristics of the product sintered ore, comparing with those in the conventional method (5% by mass and 10% by mass of coke; injection of hot air).
  • the measured items are the composition of minerals in the product sintered ore, (affecting the cold strength and the reducing property), the apparent specific gravity (affecting the cold strength), and the distribution of pore size of 0.5 mm or smaller (affecting the reducing property).
  • FIG. 22 shows the result of determined composition of the mineral phase in the product sintered ore, quantified by the powder X-ray diffractometry.
  • FIG. 22 suggests that, when the entered heat is constant (coke 4% by mass + propane 0.5% by volume), using both the solid fuel and the diluted propane gas, the calcium-ferrite is stably formed, which then improves the reducing property and increases the cold strength.
  • FIG. 23 gives the observed result of apparent specific gravity of product sintered ore
  • FIG. 24 gives the observed result of distribution of pore size of 0.5 mm or smaller using a mercury intrusion porosity meter.
  • FIG. 22 suggests that the injection of diluted propane gas conducts heating from outside of the granulated particles, thus the melt flow is enhanced, which decreases the porosity of 0.5 mm or larger, (apparent specific gravity), and the decreased porosity causes the increase in the cold strength.
  • FIG. 22 suggests that the injection of diluted propane gas conducts heating from outside of the granulated particles, thus the melt flow is enhanced, which decreases the porosity of 0.5 mm or larger, (apparent specific gravity), and the decreased porosity causes the increase in the cold strength.
  • FIG. 22 suggests that the injection of diluted propane gas conducts heating from outside of the granulated particles, thus the melt flow is enhanced, which decreases the porosity of 0.5 mm or larger, (apparent specific gravity), and the decreased porosity causes the increase in
  • FIG. 25 shows the schematic drawings of sintering behavior for the case that sole coke is used, (a) and the case that diluted gaseous fuel is simultaneously injected, (b).
  • the conventional sintering using only coke conducts heating from inside of pseudo-particles by the combustion of coke fine, while the simultaneous use of coke and gaseous fuel, in accordance with the method of the present invention, conducts heating from outside of the pseudo-particles by the combustion of gaseous fuel, which latter case presumably makes easily keep remaining the micropores in the ore, thus the JIS-RI also moves to relatively high position, though the RDI is at a low level.
  • FIG. 26 shows a schematic diagram of pore structure in the sintered ore under the injection of a diluted gaseous fuel.
  • it is effective for improving the productivity of sintered ore to enhance the joining of pores of 0.5 to 5 mm in size, which sizes affecting the yield and the cold strength, and to decrease the number of these pores, thus increasing the percentage of the pores of 5 mm or larger size, which sizes affecting the gas permeability.
  • the improvement in the reducing property of the sintered ore is attained preferably by forming a pore structure retaining a large quantity of micropores of 0.5 mm or smaller in size existing mainly in the iron ore.
  • injection of diluted gaseous fuel presumably attains a pore structure very close to that in the ideal sintered ore.
  • FIG. 27 shows the result of tests to grasp the limit coke ratio that can keep the necessary cold strength, (which limit coke ratio is a coke ratio equivalent to 73% of the shutter strength, which is the maximum value on not-using diluted propane gas).
  • the coke ratio to obtain the same cold strength to that of current state, (73% of shutter strength), by injecting diluted propane gas (0.5% by volume) can be decreased from 5% by mass to 3% by mass, (about 20 kg/t), as shown in FIG. 27 (a) .
  • the coke ratio to attain 73% yield and 1.86 productivity decreases from 5% by mass to 3.5% by mass.
  • the present invention provides an action to strengthen the functions of combustion and melting zone in the sintering bed by charging a diluted gaseous fuel responding to the amount of carbonaceous material to an adequately selected position during the transition of the combustion and melting zone from surface layer to lower layer of the sintering bed accompanied with the travel of pallet, thereby improving the quality of sintered ore and increasing the productivity.
  • the sintering layer contained 4.8 to 5.0% by mass (outside value) of coke fine.
  • a C gas of 1.0 to 2.0% by volume (to air) was injected to a position of "100 to 400 mm" below the surface of the sintering bed (total thickness of 600 mm, containing 200 mm of return fine at the lowest layer), under a suction pressure of 1200 mmAq (1000 Aq of pressure difference).
  • TABLE 8 shows the results of Example 3 (Nos. 1 to 7).
  • SI strength cold strength
  • yield of the sintered ore increased in No. 2 to No. 7 which are compatible examples to the present invention, compared with No. 1 which is a comparative example.
  • examples Nos. 3, 4, 6, and 7 which positioned the injection point to an intermediate stage of the sintering bed showed significant improvement.
  • productivity increases by adjusting the injection gas concentration to 1% by volume under a condition of constant coke amount (4.8% by mass) rather than decreasing the coke amount and increasing the injection gas concentration.
  • RI reducing property
  • RDI reduction degradation index
  • the operation of the sintering machine totally increased the tumbler strength by about 3% from that of the ordinary operation, improved the RDI by about 3% therefrom, improved RI by about 4% therefrom, and further improved the productivity by 0.03 t/hr ⁇ m 3 .

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Abstract

La présente invention concerne un procédé de production d’un minerai fritté selon lequel différents combustibles gazeux sont introduits par la partie supérieure d’une couche de charge d’un matériau de frittage déposé sur un plateau de chargement, dans un four de frittage. Pendant la production de minerai fritté, un combustible gazeux dilué jusqu’à une concentration de limite inférieure d’inflammabilité ou moins est utilisé en tant que combustible gazeux introduit à partir de la partie supérieure de la couche de charge sur le plateau de chargement ; de plus, pendant l’introduction dudit combustible gazeux pour le frittage, au moins un paramètre choisi parmi la position d’introduction, la plus haute température pouvant être atteinte par la couche de charge, ou la durée de maintien dans une plage de température élevée est régulé afin de produire un minerai fritté. L'invention concerne également un four de frittage caractérisé en ce qu’il comprend un appareil d'introduction de combustible gazeux.

Claims (23)

  1. Procédé de production de minerai fritté, comprenant :
    une étape de chargement consistant à charger une matière première de frittage contenant un minerai de fer fin et un matériau carboné sur une palette en déplacement, formant ainsi un lit de frittage contenant le matériau carboné sur la palette ;
    une étape d'inflammation consistant à enflammer le matériau carboné sur la surface du lit de frittage dans un four de calcination ;
    une étape de frittage consistant à mettre en combustion le matériau carboné dans le lit de frittage en aspirant l'air à travers des boîtes à vent positionnées sous la palette, formant ainsi un gâteau fritté utilisant la chaleur de combustion générée ; et
    une étape de combustion de combustible gazeux consistant à envoyer un combustible gazeux dilué ayant une concentration inférieure à la limite inférieure de la concentration de combustion dans le lit de frittage depuis le dessus du lit de frittage au niveau d'un emplacement situé après le four de calcination, et à mettre le combustible gazeux en combustion dans le lit de frittage.
  2. Procédé de production de minerai fritté selon la revendication 1, dans lequel l'étape de combustion du combustible gazeux consiste à :
    envoyer un combustible gazeux dilué ayant une concentration inférieure à la limite inférieure de la concentration de combustion dans le lit de frittage depuis le dessus du lit de frittage au niveau d'un emplacement situé après le four de calcination, et à mettre le combustible gazeux en combustion dans le lit de frittage ; et
    ajuster une température maximale finale du lit de frittage ou un temps de maintien dans la zone de haute température du lit de frittage, ou une température maximale finale du lit de frittage et un temps de maintien dans la zone de haute température du lit de frittage.
  3. Procédé de production de minerai fritté selon la revendication 2, dans lequel l'étape de combustion du combustible gazeux consiste à :
    envoyer un combustible gazeux dilué ayant une concentration inférieure à la limite inférieure de la concentration de combustion dans le lit de frittage depuis le dessus du lit de frittage au niveau d'un emplacement situé après le four de calcination, et à mettre le combustible gazeux en combustion dans le lit de frittage ; et
    ajuster une température maximale finale du lit de frittage.
  4. Procédé de production de minerai fritté selon la revendication 3, dans lequel l'étape de combustion du combustible gazeux consiste à :
    envoyer un combustible gazeux dilué ayant une concentration inférieure à la limite inférieure de la concentration de combustion dans le lit de frittage depuis le dessus du lit de frittage au niveau d'un emplacement situé après le four de calcination, et à mettre le combustible gazeux en combustion dans le lit de frittage ; et
    ajuster la température maximale finale du lit de frittage en ajustant une quantité du matériau carboné dans la matière première de frittage.
  5. Procédé de production de minerai fritté selon la revendication 4, dans lequel l'étape de combustion du combustible gazeux consiste à :
    envoyer un combustible gazeux dilué ayant une concentration inférieure à la limite inférieure de concentration de combustion dans le lit de frittage depuis le dessus du lit de frittage au niveau d'un emplacement situé après le four de calcination, et à mettre le combustible gazeux en combustion dans le lit de frittage ; et
    ajuster la température maximale finale du lit de frittage à une température allant de 1205 °C à 1350 °C en ajustant une quantité du matériau carboné dans la matière première de frittage.
  6. Procédé de production de minerai fritté selon la revendication 3, dans lequel l'étape de combustion du combustible gazeux consiste à :
    envoyer un combustible gazeux dilué ayant une concentration inférieure à la limite inférieure de la concentration de combustion dans le lit de frittage depuis le dessus du lit de frittage au niveau d'un emplacement situé après le four de calcination, et à mettre le combustible gazeux en combustion dans le lit de frittage ; et
    ajuster une température maximale finale du lit de frittage à une température allant de 1205 °C à 1350 °C en ajustant une quantité du combustible gazeux.
  7. Procédé de production de minerai fritté selon la revendication 3, dans lequel l'étape de combustion du combustible gazeux consiste à :
    envoyer un combustible gazeux dilué ayant une concentration inférieure à la limite inférieure de la concentration de combustion dans le lit de frittage depuis le dessus du lit de frittage au niveau d'un emplacement situé après le four de calcination, et à mettre le combustible gazeux en combustion dans le lit de frittage ; et
    ajuster une température maximale finale du lit de frittage à une température allant de 1205 °C à 1350 °C en ajustant une quantité du matériau carboné dans la matière première de frittage et une quantité du combustible gazeux.
  8. Procédé de production de minerai fritté selon la revendication 2, dans lequel l'étape de combustion du combustible gazeux consiste à :
    envoyer un combustible gazeux dilué ayant une concentration inférieure à la limite inférieure de la concentration de combustion dans le lit de frittage depuis le dessus du lit de frittage au niveau d'un emplacement situé après le four de calcination, et à mettre le combustible gazeux en combustion dans le lit de frittage ; et
    ajuster le temps de maintien dans la zone de haute température du lit de frittage.
  9. Procédé de production de minerai fritté selon la revendication 8, dans lequel l'étape de combustion du combustible gazeux consiste à :
    envoyer un combustible gazeux dilué ayant une concentration inférieure à la limite inférieure de la concentration de combustion dans le lit de frittage depuis le dessus du lit de frittage au niveau d'un emplacement situé après le four de calcination, et à mettre le combustible gazeux en combustion dans le lit de frittage ; et
    ajuster le temps de maintien dans la zone de haute température du lit de frittage en ajustant une concentration du combustible gazeux en réponse à une quantité du matériau carboné de la matière première de frittage.
  10. Procédé de production de minerai fritté selon la revendication 1, dans lequel l'étape de combustion du combustible gazeux consiste à :
    envoyer un combustible gazeux dilué ayant une concentration inférieure à la limite inférieure de la concentration de combustion dans le lit de frittage depuis le dessus du lit de frittage au niveau d'un emplacement situé après le four de calcination ; et mettre en combustion le combustible gazeux qui est dilué à une concentration inférieure à la limite inférieure de la concentration de combustion de sorte qu'au moins une partie du combustible gazeux reste imbrûlée tant qu'il n'a pas atteint la zone de combustion et de fusion dans le lit de frittage.
  11. Procédé de production de minerai fritté selon la revendication 1, dans lequel l'étape de combustion du combustible gazeux consiste à :
    envoyer un combustible gazeux dilué ayant une concentration inférieure à la limite inférieure de la concentration de combustion dans le lit de frittage depuis le dessus du lit de frittage au niveau d'un emplacement situé après le four de calcination ; et
    mettre en combustion le combustible gazeux dans le lit de frittage pour ajuster une forme d'une zone de combustion et de fusion.
  12. Procédé de production de minerai fritté selon la revendication 11, dans lequel l'ajustement de la forme de la zone de combustion et de fusion est réalisé en ajustant une épaisseur de la zone de combustion et de fusion dans la direction de la hauteur et/ou en ajustant une largeur de la zone de combustion et de fusion dans la direction de déplacement de la palette.
  13. Procédé de production de minerai fritté selon la revendication 1, dans lequel l'étape de combustion du combustible gazeux consiste à :
    envoyer le combustible gazeux dilué ayant une concentration inférieure à la limite inférieure de la concentration de combustion depuis le dessus du lit de frittage au niveau d'un emplacement situé après le four de calcination, faisant entrer ainsi en combustion le combustible gazeux dans le lit de frittage ;
    et
    prolonger un temps de maintien dans la zone de haute température de la zone de combustion et de fusion pour ajuster la résistance au froid du minerai fritté.
  14. Procédé de production de minerai fritté selon la revendication 1, dans lequel l'étape de combustion du combustible gazeux consiste à :
    envoyer le combustible gazeux dilué ayant une concentration inférieure à la limite inférieure de la concentration de combustion depuis le dessus du lit de frittage au niveau d'un emplacement situé après le four de calcination, faisant entrer ainsi en combustion le combustible gazeux dans le lit de frittage ;
    et
    ajuster une position d'alimentation du combustible gazeux par rapport au lit de frittage.
  15. Procédé de production de minerai fritté selon la revendication 1, dans lequel l'étape de combustion du combustible gazeux consiste à :
    envoyer le combustible gazeux dilué ayant une concentration inférieure à la limite inférieure de la concentration de combustion après formation du gâteau fritté dans la partie de couche de surface du lit de frittage et avant la fin du frittage, faisant entrer ainsi en combustion le combustible gazeux dans le lit de frittage.
  16. Procédé de production de minerai fritté selon la revendication 1, dans lequel l'étape de combustion du combustible gazeux consiste à :
    envoyer le combustible gazeux dilué ayant une concentration inférieure à la limite inférieure de la concentration de combustion vers une région dont une épaisseur d'une zone de combustion et de fusion est de 15 mm ou plus, faisant entrer ainsi en combustion le combustible gazeux dans le lit de frittage.
  17. Procédé de production de minerai fritté selon la revendication 1, dans lequel l'étape de combustion du combustible gazeux consiste à :
    envoyer le combustible gazeux dilué ayant une concentration inférieure à la limite inférieure de la concentration de combustion au niveau d'un emplacement où le front de combustion atteint 100 mm de profondeur ou plus sous la couche de surface, faisant entrer ainsi en combustion le combustible gazeux dans le lit de frittage.
  18. Procédé de production de minerai fritté selon la revendication 1, dans lequel l'étape de combustion du combustible gazeux consiste à :
    envoyer le combustible gazeux dilué ayant une concentration inférieure à la limite inférieure de la concentration de combustion à proximité des deux parois latérales du lit de frittage, faisant entrer ainsi en combustion le combustible gazeux dans le lit de frittage.
  19. Procédé de production de minerai fritté selon la revendication 1, dans lequel l'étape de combustion du combustible gazeux consiste à :
    envoyer un combustible gazeux dilué ayant une concentration inférieure à la limite inférieure de la concentration de combustion depuis le dessus du lit de frittage dans la direction longitudinale de l'appareil de frittage, faisant entrer ainsi en combustion le combustible gazeux dans le lit de frittage ; et
    ajuster une résistance au froid du minerai fritté.
  20. Procédé de production de minerai fritté selon la revendication 1, dans lequel le combustible gazeux est un gaz inflammable qui est dilué à une concentration de 75 % ou moins et 2 % ou plus de la concentration de combustion de limite inférieure.
  21. Procédé de production de minerai fritté selon la revendication 10, dans lequel le combustible gazeux est un gaz inflammable qui est dilué à une concentration de 60 % ou moins et 2 % ou plus de la limite inférieure de la concentration de combustion.
  22. Procédé de production de minerai fritté selon la revendication 11, dans lequel le combustible gazeux est un gaz inflammable qui est dilué à une concentration de 25 % ou moins et 2 % ou plus de la limite inférieure de la concentration de combustion.
  23. Procédé de production de minerai fritté selon la revendication 1, dans lequel le combustible gazeux est un ou plusieurs gaz choisi(s) dans le groupe constitué par le gaz de haut fourneau, le gaz de four à coke, un gaz mixte de gaz de haut fourneau et de gaz de four à coke, le gaz propane, le gaz naturel et le gaz méthane.
EP06822967A 2005-10-31 2006-10-27 Procede de production de minerai fritte Active EP1956101B1 (fr)

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PCT/JP2006/322049 WO2007052776A1 (fr) 2005-10-31 2006-10-27 Procede de production de minerai fritte et four de frittage

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KR101074892B1 (ko) 2011-10-19
EP1956101A1 (fr) 2008-08-13
EP1956101A4 (fr) 2009-12-02
CN101300366A (zh) 2008-11-05
TW200722529A (en) 2007-06-16
KR20080050508A (ko) 2008-06-05
AU2006309650B2 (en) 2010-12-02
KR20100099350A (ko) 2010-09-10
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KR101074893B1 (ko) 2011-10-19

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