JP5888482B2 - Method for producing sintered ore - Google Patents

Description

  The present invention relates to a method for producing a high-quality sintered ore for a blast furnace raw material having a high strength and excellent reducibility using a downward suction type dweroid sinter.

  Sinter ore, which is the main raw material of the blast furnace ironmaking method, is generally manufactured through a process as shown in FIG. The raw materials for sintered ore are iron ore powder, sintered ore sieving powder, recovered powder generated in steelworks, CaO-containing auxiliary materials such as limestone and dolomite, granulation aids such as quick lime, coke powder and anthracite Yes, these raw materials are cut out from each of the hoppers 1. The cut out raw material is added with an appropriate amount of water by the drum mixers 2 and 3 and the like, mixed and granulated to obtain a sintered raw material which is pseudo particles having an average diameter of 3 to 6 mm. This sintered raw material is then transferred to 400 to 800 mm on an endless moving type sintering machine pallet 8 from the surge hoppers 4 and 5 arranged on the sintering machine through the drum feeder 6 and the cutting chute 7. The charge layer 9 is charged with a thickness and is also referred to as a sintered bed. Thereafter, the carbon material on the surface of the charging layer is ignited by an ignition furnace 10 installed above the charging layer 9, and the air above the charging layer is passed through a wind box 11 disposed immediately below the pallet 8. By sucking downward, the carbonaceous material in the charging layer is sequentially burned, and the sintered raw material is melted by the combustion heat generated at this time to obtain a sintered cake. The sintered cake thus obtained is then crushed and sized, and an agglomerate of about 5 mm or more is recovered as a product sintered ore and supplied to a blast furnace.

  In the above manufacturing process, the carbonaceous material in the charging layer ignited by the ignition furnace 10 is continuously burned by the air sucked from the upper layer toward the lower layer in the charging layer, and has a width in the thickness direction. A combustion / melting zone (hereinafter also simply referred to as “combustion zone”) is formed. The melted portion of the combustion zone obstructs the flow of the air that is sucked in, so that the sintering time is extended and productivity is lowered. The combustion zone gradually moves from the upper layer to the lower layer as the pallet 8 moves downstream, and after the combustion zone has passed, the sintered cake layer ( Hereinafter, simply referred to as “sintered layer”) is generated. In addition, as the combustion zone moves from the upper layer to the lower layer, the moisture contained in the sintering material is evaporated by the combustion heat of the carbon material and concentrated in the lower sintering material that has not yet risen in temperature. To form a wet zone. If this moisture concentration exceeds a certain level, the voids between the sintered raw material particles that become the flow path of the suction gas are filled with moisture, which becomes a factor that increases the airflow resistance as in the melting zone.

By the way, the production amount (t / hr) of the sintering machine is generally determined by the production rate (t / hr · m ² ) × sintering machine area (m ² ). That is, the production amount of the sintering machine varies depending on the width and length of the sintering machine, the thickness of the raw material charging layer, the bulk density of the sintering raw material, the sintering (combustion) time, the yield, and the like. Therefore, to increase the production of sintered ore, the permeability (pressure loss) of the charge layer is improved to shorten the sintering time, or the yield is increased by increasing the cold strength of the sintered cake before crushing. It is considered effective to improve the above.

Fig. 2 shows the change in temperature and time at a certain point in the charging layer when the sinter productivity is high and low, that is, when the pallet moving speed of the sintering machine is fast and slow. It is. The time for which the sintering raw material particles start to melt is maintained at a temperature of 1200 ° C. or higher is represented by T ₁ when the productivity is low and T ₂ when the productivity is high. Because at high productivity faster moving speed of the pallet, the high temperature zone holding time T _2, is shorter than the T ₁ of the at low productivity. However, if the holding time at a high temperature of 1200 ° C. or more is shortened, the firing becomes insufficient, the cold strength of the sintered ore is lowered, and the yield is lowered. Therefore, in order to produce a high-strength sintered ore in a short time with a high yield and high productivity, some measures are taken to extend the time for which the high-temperature sintered ore is held at a high temperature of 1200 ° C. or higher. It is necessary to increase the cold strength. In general, SI (shutter index) and TI (tumbler index) are used as indices representing the cold strength of sintered ore.

  FIG. 3 shows that the charcoal material in the surface of the charging layer ignited in the ignition furnace continues to burn by the sucked air to form a combustion zone, which sequentially moves from the upper layer to the lower layer of the charging layer. It is the figure which showed typically the process in which is formed. FIG. 4A shows the temperature distribution when the combustion zone exists in each of the upper layer portion, middle layer portion and lower layer portion of the charging layer shown in the thick frame shown in FIG. It is shown schematically. The strength of the sintered ore is influenced by the product of the temperature and time maintained at a temperature of 1200 ° C. or higher, and the greater the value, the higher the strength of the sintered ore. Therefore, the middle layer and lower layer in the charging layer are preheated by being transported by the air sucked by the combustion heat of the carbon material in the upper charging layer, so that it can be held at a high temperature for a long time. On the other hand, the upper portion of the charge layer is not preheated, and therefore the combustion heat is insufficient, and the combustion melting reaction (sintering reaction) necessary for sintering tends to be insufficient. As a result, the yield distribution of the sintered ore in the cross section in the width direction of the charging layer becomes lower in the upper layer portion of the charging layer as shown in FIG. In addition, the pallet width ends also have a low yield due to heat dissipation from the pallet side walls and supercooling due to the large amount of air passing through, so that sufficient holding time in the high temperature range necessary for sintering cannot be secured. Become.

  In order to cope with these problems, conventionally, the amount of carbonaceous material (powder coke) added to the sintered raw material has been increased. However, by increasing the amount of coke added, as shown in FIG. 5, the temperature in the sintered layer can be increased and the time maintained at 1200 ° C. or higher can be extended. The maximum reached temperature exceeds 1400 ° C., and for the reasons explained below, the reducibility of the sintered ore and the cold strength are reduced.

  Non-Patent Document 1 shows the tensile strength (cold strength) and reducibility of various minerals produced in the sintered ore during the sintering process, as shown in Table 1. In the sintering process, as shown in FIG. 6, a melt starts to be generated at 1200 ° C., and calcium ferrite having the highest strength among the constituent minerals of sintered ore and relatively high reducibility is generated. To do. This is the reason why a sintering temperature of 1200 ° C. or higher is required. However, when the temperature rises further and exceeds 1400 ° C., more precisely, 1380 ° C., calcium ferrite is reduced to amorphous silicate (calcium silicate) having the lowest cold strength and reducibility, and reduced. It begins to decompose into skeletal secondary hematite that is easy to powder. Further, secondary hematite, which is the starting point for reducing powderization of sintered ore, was obtained from Mag. As shown in the phase diagram of FIG. ss + Liq. Since it precipitates when it is heated up to the zone and cooled, it is possible to suppress the reduction powdering by producing sintered ore through the path (2) instead of the path (1) shown on the phase diagram. It is important to do.

  That is, in Non-Patent Document 1, in order to ensure the quality of sintered ore, the control of the maximum temperature reached during combustion and the holding time in the high temperature range are very important management items. It is disclosed that the quality of the ore is almost determined. Therefore, in order to obtain a sintered ore that is excellent in reduced powder (RDI), high strength, and excellent reducibility, the calcium ferrite produced at a temperature of 1200 ° C. or higher is decomposed into calcium silicate and secondary hematite. Therefore, it is important that the temperature in the charging layer is 1200 ° C. (calcium ferrite) without exceeding the maximum reached temperature in the charging layer during sintering of over 1400 ° C., preferably over 1380 ° C. It is necessary to keep the temperature above (solidus temperature) for a long time. Hereinafter, in the present invention, the time maintained in the temperature range of 1200 ° C. to 1400 ° C. will be referred to as “high temperature range retention time”.

  Conventionally, several techniques have been proposed for the purpose of maintaining the upper portion of the charging layer at a high temperature for a long time. For example, Patent Document 1 discloses a technique for injecting gaseous fuel onto a charging layer after the charging layer is ignited. Patent Document 2 discloses a technique in which air is sucked into the charging layer after the charging layer is ignited. In addition, in Patent Document 3, a hood is disposed on the charging layer so that the inside of the charging layer of the sintering raw material is heated, and air or coke is discharged from the hood. A technique for blowing a mixed gas with a furnace gas at a position immediately after the ignition furnace, and Patent Document 4 propose a technique for simultaneously blowing a low-melting-point solvent and a carbonaceous material or a combustible gas at a position immediately after the ignition furnace. .

  However, since these technologies use high-concentration gaseous fuel and do not reduce the amount of carbonaceous material when fuel gas is injected, the maximum temperature reached during sintering in the charged layer is the upper limit for operation management. When the temperature exceeds 1400 ° C, the calcium ferrite produced during the sintering process decomposes, producing a sintered ore with low reducibility and low cold strength, and the yield improvement effect cannot be obtained. Increased temperature and thermal expansion due to fuel combustion may deteriorate air permeability, reduce productivity, and use of gaseous fuel may cause a fire in the upper space of the sintering bed (charging layer). Therefore, none of them has been put into practical use.

  Therefore, as a technique for solving the above problems, the inventors reduced various amounts of gas diluted in the sintering furnace downstream of the ignition furnace after reducing the amount of carbonaceous material added in the sintering raw material. Patent Document 5 discloses a technique for controlling both the maximum temperature reached in the charging layer and the high temperature region holding time to an appropriate range by introducing fuel into the charging layer from above the pallet and combusting in the charging layer. It is proposed to ~ 7.

Japanese Patent Laid-Open No. 48-018102 Japanese Examined Patent Publication No. 46-027126 Japanese Patent Application Laid-Open No. 55-018585 JP 05-311257 A WO2007-052776 JP 2010-047801 A JP 2008-291354 A

“Mineral Engineering”; Hideki Imai, Toshihisa Takeuchi, Yoshiki Fujiki, (1976), p. 175, Asakura Shoten

Applying the techniques of Patent Documents 5 to 7 to a method for producing sintered ore using a downward suction type sintering machine, reducing the amount of carbonaceous material added to the sintered raw material, and lowering the concentration below the lower limit of combustion When the diluted gaseous fuel is introduced into the charging layer and the gaseous fuel is burned in the charging layer, as shown in FIG. 8, the gaseous fuel is charged after the charcoal is burned. Because it burns in the layer (in the sintered layer), the width of the combustion / melting zone can be expanded in the thickness direction without making the maximum temperature of the combustion / melting zone exceed 1400 ° C, effectively It is possible to extend the high temperature range holding time.
However, in the prior arts of the above Patent Documents 5 to 7, in order to obtain a high-quality sintered ore having high strength and excellent reducibility, how long it is held in a high temperature range of 1200 ° C. or higher and 1400 ° C. or lower. It has not been fully clarified whether it is necessary to do this, and to which area the diluted gaseous fuel should be supplied.

  Accordingly, an object of the present invention is to provide a holding time (high temperature holding time) to be held in a high temperature range of 1200 ° C. or higher and 1400 ° C. or lower in order to obtain a high-quality sintered ore having high strength and excellent reducibility. The purpose of the present invention is to propose a method for producing a sintered ore that can determine the high temperature region holding time at all positions in the charging layer.

  The inventors have intensively studied to solve the above problems. As a result, in order to obtain high-quality sintered ore with high strength and excellent reducibility, the maximum temperature reached in the charging layer during sintering is set to a temperature range of 1200 ° C. or higher and 1400 ° C. or lower for 150 seconds or longer. That is, it is necessary to set the high temperature region holding time to 150 seconds, and for that purpose, the temperature change during sintering at each position in the charging layer is measured, and only the combustion heat of the carbon material is high. The inventors have found that it is effective to supply diluted gas fuel to a region where the region holding time is less than 150 seconds, and have developed the present invention.

That is, the present invention is to charge a sintered raw material containing fine ore and carbonaceous material on a circulating pallet to form a charging layer, ignite the carbonaceous material on the surface of the charging layer, and lower combustion lower concentration The air above the charging layer containing the diluted gaseous fuel is sucked in the wind box arranged under the pallet and introduced into the charging layer, and the gaseous fuel and the carbonaceous material are burned in the charging layer. In the method of manufacturing sintered ore, the pallet from the ignition furnace exit side to the ore discharge part is divided into a plurality of sections in the traveling direction and the width direction, and the gaseous fuel is supplied in the unit of the pallet traveling direction and the width direction. ON / OFF of the high temperature region holding time in the section in which the high temperature region holding time maintained at 1200 ° C. or higher and 1400 ° C. or lower when sintering with the combustion heat of only the carbonaceous material is less than 150 seconds is 150 seconds. and 300 seconds or less or more A method for producing sintered ore according to claim and.

  The air containing the diluted gaseous fuel in the method for producing sintered ore according to the present invention is a mixture of gaseous fuel previously diluted below the lower combustion limit concentration in the air above the charging layer, or gaseous fuel. It is characterized in that it is either one injected at high speed into the air on the charging layer, mixed and diluted to a concentration below the lower limit of combustion.

  According to the present invention, in all regions in the charging layer, it is possible to maintain the maximum temperature during sintering in a high temperature range of 1200 ° C. or higher and 1400 ° C. or lower for 150 seconds or more. It becomes possible to produce a high-quality sintered ore with excellent productivity and high productivity. In addition, according to the present invention, the amount of carbonaceous material added to the sintered raw material can be reduced, which can contribute to the reduction of carbon dioxide emission.

It is a schematic diagram explaining a sintering process. It is a graph explaining the temperature distribution in the charging layer at the time of high production and low production. It is a schematic diagram explaining the change in the charging layer accompanying progress of sintering. It is a figure explaining the temperature distribution when a combustion zone exists in each position of the upper layer part of the charging layer, the middle layer part, and the lower layer part, and the yield distribution of the sintered ore in the width direction cross section of the charging layer. . It is a figure explaining the temperature change in the charging layer by the change (increase) of the amount of carbon materials. It is a figure explaining a sintering reaction. It is a state figure explaining the process in which skeletal secondary hematite is produced. It is a schematic diagram explaining the influence which dilution gas fuel supply has on high temperature range holding time. It is a schematic diagram explaining the horizontal electric furnace used for experiment. It is a graph which shows the influence which high temperature range holding time has on the production amount and cold strength of calcium ferrite. It is a figure explaining the method to measure the high temperature range holding time in a charging layer. It is a graph which shows the example of a measurement of distribution of the high temperature range retention time in the charge layer thickness direction of a real machine sintering machine.

The inventors first have to maintain a high temperature range at a temperature of 1200 ° C. or higher and 1400 ° C. or lower, which is necessary for producing a high-quality sintered ore having high strength and excellent reducibility with high productivity. Time), a sintering experiment using an electric furnace was performed.
In this experiment, using a pelletizer, iron ore with a particle size of 0.5 mm or more was used as the core particle, and iron ore with a particle size of less than 0.5 mm and auxiliary materials such as calcium carbonate and silicon dioxide were added as raw materials. Granulated and used as a sintering raw material of about 2 to 5 mmφ. Next, the sintered raw material is placed on an alumina boat and charged in the vicinity of the soaking zone in the horizontal electric furnace shown in FIG. 9, and the holding time is in the temperature range of 1200 to 1400 ° C. in the range of 0 to 350 seconds. Sintering was carried out by changing. In the above experiment, the actual sintering conditions were simulated by flowing an atmospheric gas having the same composition as the exhaust gas of the actual sintering machine during the sintering experiment. The sintered ore obtained as described above was then rapidly cooled and recovered, and the cold strength and the amount of calcium ferrite produced were measured. The strength of the sintered ore is determined by crushing the sintered ore obtained in the above process to a predetermined particle size by using a crushing strength tester and crushing the sintered ore. The load was determined. The amount of calcium ferrite was measured using a powder X-ray diffraction method.

  FIG. 10 shows the results of the above-described experiment. From this figure, the longer the time of holding at a temperature of 1200 ° C. or higher and 1400 ° C. or lower (high temperature region holding time) is, the more it is produced in the sintered ore. If the amount of calcium ferrite increases, the strength of the sintered ore increases accordingly, and if the high temperature range holding time is secured for 150 seconds or more, the amount of calcium ferrite produced also increases greatly, and at the same time the crushing strength in the crushing strength test The strength also greatly increases, and in this example, the crushing strength of the sintered ore becomes 4.60 kN or more, and sufficient strength can be obtained as a raw material for a blast furnace. However, when the high temperature region holding time exceeds 300 seconds. Since the amount of calcium ferrite in the sintered ore approaches the theoretical value (45.7 mass%) and saturates, the cold strength of the sintered ore is improved even if the holding time of the high temperature region is further extended. Expected no longer, but rather, it was found that undesirable from the viewpoint of fuel cost.

  As described above, in order to obtain a high-quality sintered ore, it is necessary to set the high temperature region holding time at 1200 ° C. or higher and 1400 ° C. or lower to 150 seconds or longer. In the manufacturing method of the sintered ore used, it is necessary to supply the diluted gas fuel to the region in the charging layer where the high temperature region holding time cannot be secured for 150 seconds or more only with the combustion heat of the carbonaceous material. It became clear. However, even if the high temperature region holding time exceeds 300 seconds, the effect of adding gaseous fuel is saturated and rather disadvantageous in terms of cost. Therefore, the upper limit is preferably about 300 seconds.

It should be noted that the region of the charging layer in which the holding time of the high temperature region cannot be secured for 150 seconds or more with only the combustion heat of the carbonaceous material is sintered at the position by inserting a thermocouple into the charging layer of the actual sintering machine. It can be specified by actually measuring a change with time in the temperature and obtaining a high temperature region holding time at which the temperature is maintained at 1200 ° C. or higher and 1400 ° C. or lower at each position.
For example, the region in the thickness direction of the charging layer in which the high temperature region holding time of the central upper layer portion in the pallet width direction shown in FIG. 4B is less than 150 seconds is from the charging layer surface layer in the central portion in the pallet width direction. A thermocouple is inserted into the inside, and a temperature change during sintering is measured, and a distribution of the high temperature region holding time at each position in the thickness direction of the charging layer is obtained and can be obtained from the distribution.

  In order to extend the high temperature region holding time in the region where the high temperature region holding time is less than 150 seconds, it is necessary to supply the diluted gas fuel at the stage where the sintering reaction is proceeding. For example, in the region of the upper layer portion 20% in the thickness direction of the charging layer, when the high temperature region holding time is less than 150 seconds, the ignition furnace exit side to the ore discharge where the sintering reaction of that portion is proceeding It is necessary to supply the diluted gas fuel within the range of 20% upstream of the part (hereinafter also referred to as “effective captain”).

  In the actual machine sintering machine, it is not realistic in terms of equipment to change the supply range of the diluted gas fuel by the pallet progression method in units of%. Therefore, the effective machine length part of the sintering machine from the ignition furnace exit side to the exhausting part is divided into a plurality of sections in the traveling direction so that the diluted gas fuel can be supplied in the divided units, and the entire range of the effective machine length Therefore, it is preferable that the diluted gas fuel supply can be turned on and off in units of sections so that the high temperature region holding time is 150 seconds or longer. However, since the surface layer of the charging layer immediately after leaving the ignition furnace is still hot and there is a concern about ignition of the gaseous fuel, supply of gaseous fuel should be avoided for about 3 m from the ignition furnace exit side. Is preferred.

Further, in order to improve the yield at the end portion in the pallet width direction shown in FIG. 4B, in the same manner as described above, the high temperature region holding time in the charging layer thickness direction at each position in the pallet width direction is obtained. The distribution in the width direction of the region in the thickness direction of the charging layer where the high temperature region holding time is less than 150 seconds is specified, and gaseous fuel may be supplied at the stage where the sintering reaction is in progress.
For example, the region where the high temperature region holding time is less than 150 seconds is the region of the upper layer portion 20% in the thickness direction of the charging layer in the center of the pallet width direction, while the upper layer portion width direction both ends, When the area is 40% of the upper layer part in the thickness direction of the charging layer, gas fuel is supplied to the section at both ends in the width direction in the range of 40% upstream of the effective machine length from the ignition furnace to the ore removal part. Just do it.

  In an actual sintering machine, it is still impractical for the facility to change the supply range of the diluted gas fuel in the pallet width direction in units of%. Therefore, after dividing the effective machine length of the sintering machine from the ignition furnace exit side to the exhausting section into a plurality of sections in the traveling direction, the sections are further divided in the width direction, and the diluted gas is divided into sections in the width direction. It is preferable to be able to supply the fuel, and to enable ON / OFF of the diluted gas fuel in the width direction division unit so that the high temperature region holding time is 150 seconds or more in the entire range of the effective length.

  In addition, it is preferable that the said dilution gaseous fuel is the density | concentration below the combustion minimum density | concentration of the gaseous fuel. If the concentration of the diluted gas fuel is equal to or higher than the lower combustion limit concentration, combustion may occur above the charging layer, and the effect of supplying the gaseous fuel may be lost, or an explosion may occur. In addition, if the diluted gas fuel has a high concentration, it is burned in a low temperature range, so that it may not be able to effectively contribute to the extension of the high temperature range holding time. Accordingly, the concentration of the diluted gas fuel is preferably 3/4 (75%) or less of the lower limit of combustion at normal temperature in the atmosphere, more preferably 1/5 (20%) or less of the lower limit of combustion, and more preferably the lower limit of combustion. It is 1/10 (10%) or less of the concentration. However, if the concentration of the diluted gas fuel is less than 1/100 (1%) of the lower combustion limit concentration, the calorific value due to combustion is insufficient, and the effect of improving the strength and yield of sintered ore cannot be obtained. Set to 1% of the lower combustion limit concentration. Looking at this for natural gas (LNG), the lower limit concentration of LNG at room temperature is 4.8 vol%, so the concentration of diluted gas fuel is preferably in the range of 0.05 to 3.6 vol%.

  Note that the air containing gaseous fuel diluted below the lower combustion limit concentration is a mixture of gaseous fuel previously diluted below the lower combustion limit concentration in the air above the charging layer, or high-concentration gaseous fuel. It may be one that is instantaneously diluted below the lower combustion limit concentration by being injected into the air on the charging layer at a high speed and mixed with air.

  Further, it is preferable that the amount of carbon material added to the sintering raw material is reduced by an amount equal to or more than the amount corresponding to the calorific value of the gaseous fuel added to the air. The reason is that when gaseous fuel is added with the amount of carbon material as it is, the total calorific value becomes excessive, the maximum temperature reached exceeds the upper limit (1400 ° C) of the appropriate temperature range, and calcium ferrite is generated. This is because the ratio decreases and the calcium silicate increases, resulting in a sintered ore having low strength and poor reducibility. Therefore, in the present invention, the amount of carbonaceous material in the sintering raw material is a temperature range of 1200 to 1400 ° C., which is the highest temperature during sintering, depending on the amount of gaseous fuel added to the air (combustion heat). Desirably, it is necessary to adjust so that it may become a temperature range of 1200-1380 degreeC.

  The raw material sintering machine with a pallet width of 5m and an effective machine length (ignition furnace exit side to pallet length from the ore discharge section) of 82m was charged with a sintering material with powdered coke added as a charcoal at a layer thickness of 730mm. As shown in FIG. 11, the thermocouple was placed in an alumina protective tube at a depth of 50 mm, 210 mm, 370 mm, 530 mm, and 700 mm from the surface of the charging layer at the center in the pallet width direction. Was inserted, and the time-dependent change in temperature at each position in the thickness direction during sintering was measured to determine the high temperature region holding time at each position. The maximum temperature reached during the sintering was maintained at a temperature of 1400 ° C. or lower at all positions.

  The measurement result of the high temperature region holding time is shown in FIG. From this figure, it was found that the region where the maximum temperature reached in the central part in the pallet width direction of the actual sintering machine was less than 150 seconds was the 185 mm portion of the upper layer part. This region corresponds to about 25.3% of the total thickness of the charging layer (730 mm), and indicates that the high temperature region holding time is insufficient at 20.8 m upstream of the effective machine length (82 m).

  Therefore, based on the above investigation results, in order to supply the diluted gas fuel to the shortage region of the high temperature region holding time, a hood of width: 5 m × length: 7.5 m is provided after 3.2 m behind the ignition furnace. 4 were installed, and during this time, the supply length of gaseous fuel diluted with LNG to 0.4 vol% (1/12 of the lower combustion limit concentration) was changed as shown in Table 2 to conduct a sintering experiment. It was. Here, T1 is a conventional sintering condition (comparative example) in which sintering is performed only with the combustion heat of the carbonaceous material, T2 is one of the most upstream hoods among the above four units, and T3 is the above four Two hoods on the most upstream side of the group, T4 is an example of three hoods on the upstream side of the four groups, and T5 is an example in which gaseous fuel is supplied to all four hoods. . In the conventional sintering conditions (comparative example), the amount of carbonaceous material in the sintering raw material is 5.3 mass%, and when the diluted gas fuel is supplied, the maximum temperature reached is prevented from exceeding 1400 ° C. Therefore, the amount of the carbon material was reduced to 5.0 mass%.

  In the sintering experiment in which the diluted gas fuel was supplied, the high temperature region holding time at each position in the thickness direction of the pallet width central portion was measured by the same method as described above, and the high temperature region holding time was less than 150 seconds. The layer thickness of the upper part of the charge layer was determined. Further, for the sintered ore obtained in the above-described sintering experiment, the shutter strength SI, the yield, and the rate of occurrence of return ore were investigated, and the results are also shown in Table 2.

  From the result of Table 2, in the example of T4 in which the diluted gas fuel is supplied only to the region where the high temperature region retention time is less than 150 seconds with the three upstream hoods, the high temperature region retention time is 150 seconds in the entire charging layer thickness. As described above, both the shutter strength SI and the yield of the product sintered ore are significantly improved as compared with the conventional condition T1. On the other hand, in the examples of T2 and T3 in which the gaseous fuel is supplied only with two or less hoods on the upstream side, the supply amount of the gaseous fuel is still insufficient, and the high temperature region holding time is reduced in the entire charging layer thickness. Since it has not reached 150 seconds or more, the strength and yield of the product sintered ore are not sufficiently improved. On the other hand, in the example of T5 in which the diluted gas fuel is supplied beyond the region where the high temperature region retention time is less than 150 seconds with four hoods, the high temperature region retention time is 150 seconds or more in the total thickness of the charging layer. However, it can be seen that the strength and yield of the sintered product ore are almost the same as the T4 example.

  The sintering technique of the present invention is not only useful as a technique for producing sintered ore used as a raw material for iron making, particularly as a blast furnace, but can also be used as another ore agglomeration technique.

1: Raw material hopper 2, 3: Drum mixer 4: Floor bedding hopper 5: Surge hopper 6: Drum feeder 7: Cutting chute 8: Pallet 9: Charging layer 10: Ignition furnace 11: Wind box (wind box)
12: Cut-off plate

Claims (2)

A gaseous fuel diluted with a sintered raw material containing fine ore and charcoal on a circulating moving pallet to form a charging layer, igniting the charcoal on the surface of the charging layer and diluting below the lower combustion limit concentration Suction ore is produced by sucking the air above the charging layer, including the slag, into the charging layer by sucking it with a wind box placed under the pallet, and burning the gaseous fuel and carbonaceous material in the charging layer. In this method, the pallet from the ignition furnace exit side to the discharge section is divided into a plurality of sections in the traveling direction and the width direction, and the supply of gaseous fuel is turned ON / OFF in units of the pallet traveling direction and the width direction. By the above, the high temperature region holding time in the section in which the high temperature region holding time maintained at 1200 ° C. or higher and 1400 ° C. or lower when sintering with the combustion heat of only the carbonaceous material is less than 150 seconds is 150 seconds or longer and 300 seconds or shorter. Sintering characterized by The method of production. The air containing the diluted gaseous fuel is a mixture of gaseous fuel that has been diluted below the lower combustion limit concentration in the air above the charging layer, or the gaseous fuel is injected into the air above the charging layer at high speed. 2. The method for producing a sintered ore according to claim 1 , wherein the sinter is mixed and diluted to a concentration lower than the lower limit of combustion.

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