JP5439982B2 - Method for producing sintered ore - Google Patents

Description

  The present invention relates to a method for producing sintered ore by a downward suction type sintering machine capable of producing high strength and high quality sintered ore with high yield and safety.

  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 charged onto an endless moving type sintering machine pallet 8 from a surge hopper 4, 5 arranged on the sintering machine via a drum feeder 6 and a cutting chute 7, and baked. A charging layer 9, also referred to as a binding bed, is formed. The thickness (height) of the charging layer is usually around 400 to 800 mm. The surface position of the charging layer is controlled to be constant by the cut-off plate 12 installed on the sintering pallet, and the thickness of the charging layer corresponds to the distance from the upper end of the pallet 8 to the lower end of the cut-off plate 12. To do. Thereafter, the ignition furnace 10 installed above the charging layer 9 ignites the carbon material on the surface of the charging layer, and sucks the atmosphere downward through the wind box 11 disposed immediately below the pallet 8. By doing so, 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 having a predetermined particle size (for example, about 5 mm) or more is recovered as a product sintered ore.

  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 to the lower layer by the windbox, and has a wide combustion. -A melting zone (hereinafter, simply referred to as "combustion zone") is formed. This combustion zone gradually moves from the upper layer to the lower layer of the charging layer as the pallet 8 moves downstream, and after passing through the combustion zone, a 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. When the moisture concentration exceeds a certain level, the voids between the sintered raw material particles serving as suction gas flow paths are filled with moisture, thereby increasing the ventilation resistance. Further, the melted portion generated in the combustion zone necessary for the sintering reaction also becomes a factor for increasing the airflow resistance.

  FIG. 2 shows the inside of the charging layer when the combustion zone moving in the charging layer having a thickness of 600 mm is located approximately 400 mm above the pallet of the charging layer (200 mm below the charging layer surface). This shows the pressure loss and temperature distribution. The pressure loss distribution at this time is about 60% in the wet zone and about 40% in the combustion zone.

The production amount (t / hr) of the sintering machine is generally determined by the sintering production rate (t / hr · m ² ) × sintering machine area (m ² ). That is, the production amount of the sintering machine depends on the machine width and length of the sintering machine, the thickness of the raw material deposition layer (charge layer thickness), the bulk density of the sintering raw material, the sintering (combustion) time, the yield, etc. Change. Therefore, to increase the production of sintered ore, improve the air permeability (pressure loss) of the charge layer and shorten the sintering time, or increase the cold strength of the sintered cake before crushing and increase the yield. It is considered effective to improve the above.

Fig. 3 shows the change in temperature and time at a certain point in the charging layer when the sintered ore productivity is high and low, that is, when the pallet moving speed of the sintering machine is fast and slow. It is. The time at which the sintered raw material particles start to melt is maintained at a temperature of 1200 ° C. or higher (hereinafter referred to as “high temperature region holding time”) is t ₁ when productivity is low, and t ₂ when productivity is high. It is represented by Because at high productivity faster moving speed of the pallet, the high temperature zone holding time t _2, is shorter than the t ₁ when the productivity is low. If the high temperature region holding time is shortened, firing is likely to be insufficient, the cold strength of the sintered ore is lowered, and the yield is lowered. Therefore, in order to produce high-strength sintered ore in a short time and with high yield and good productivity, some measures should be taken to extend the “high temperature range holding time” and the strength of the sintered cake, 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. 4 shows that the carbon material in the surface of the charged layer ignited by the ignition furnace continues to burn by the sucked air to form a combustion zone, which moves sequentially from the upper layer to the lower layer of the charged layer, It is the figure which showed typically the process in which is formed. FIG. 5A shows the temperature distribution when the combustion zone is present 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 sintered ore is affected by the time of holding at a temperature of 1200 ° C. or higher, more precisely the product of temperature and time held at a temperature of 1200 ° C. or higher. Becomes higher. The middle layer portion and the lower layer portion of the charging layer are preheated by being transported together with the air by which the combustion heat generated by the combustion of the carbon material in the upper layer of the charging layer is sucked. Therefore, while the middle layer and lower layer of the charging layer are kept at a high temperature for a long time, the upper layer of the charging layer lacks the heat of combustion, and the combustion melting reaction (sintering) required for sintering. The chemical reaction) tends to be insufficient. As a result, as shown in FIG. 5B, the yield distribution of the sintered ore in the cross section in the width direction of the sintering machine in the charging layer becomes lower in the upper layer portion of the charging layer.

  For this problem, several techniques have been proposed for the purpose of keeping 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. The temperature is 1400 ° C or higher, and the temperature is higher than 1380 ° C from a strict chemical reaction point of view. Calcium ferrite produced in the sintering process decomposes, resulting in a sintered ore with low reducibility and low cold strength. The yield improvement effect is not obtained, the gas permeability increases due to the temperature rise and thermal expansion caused by the combustion of the gaseous fuel, the productivity decreases, and further, the use of the gaseous fuel reduces the productivity of the sintered bed ( There is a risk of fire in the upper space), so none have been put to practical use.

  Therefore, as a technique for solving the above-mentioned problems, the applicant, in the downstream of the ignition furnace of the sintering machine, various gaseous fuels diluted below the lower combustion limit concentration are used for the sintering raw material layer (charging layer) on the pallet. Patent Document 5 proposes a method of adjusting either one or both of the highest temperature reached in the charging layer and the high temperature region holding time by supplying from above, introducing into the charging layer, and burning. .

Japanese Patent Laid-Open No. 48-18102 Japanese Patent Publication No.46-27126 JP-A-55-18585 Japanese Patent Laid-Open No. 5-311257 WO2007-052776

  According to the technique of the above-mentioned Patent Document 5, gaseous fuel diluted to a predetermined concentration can be introduced into the charging layer of the downward suction type sintering machine and burned at a target position in the charging layer. Therefore, by appropriately controlling the maximum temperature reached during combustion of the sintering raw material and the holding time in the high temperature range, the strength of the sintered ore in the upper part of the charge layer that tends to decrease the cold strength of the sintered ore due to insufficient heat quantity And the strength of sintered ore in the middle and lower layers of the charging layer can be increased.

  However, when the gaseous fuel diluted to the predetermined concentration is supplied downstream of the ignition furnace, the gaseous fuel is still in a high concentration in the vicinity of the nozzle opening to which the gaseous fuel is supplied. If ignition and combustion cannot be prevented, the supplied gaseous fuel burns on the sintering bed, and the original gaseous fuel supply effect cannot be obtained. If the supplied gaseous fuel is ignited, temporarily stop supplying gaseous fuel, purge with nitrogen gas to extinguish the flame, expel gaseous fuel from the supply pipe, and then blow gaseous fuel again. In the meantime, the effect of supplying the gaseous fuel cannot be obtained. Further, in the sintering operation for supplying the gaseous fuel, the carbonaceous material (coke) in the sintering raw material filled in the pallet has been reduced in advance in consideration of the gaseous fuel supply effect. However, there is a problem that the quality of the sintered ore during the time period when the supply of ceases is insufficient due to insufficient heat.

  Accordingly, an object of the present invention is to ignite gaseous fuel in the vicinity of a jet outlet in a method for producing high-strength, high-quality sintered ore by supplying gaseous fuel downstream of an ignition furnace of a downward suction type sintering machine. In addition to effectively preventing gas and combustion, the sintering operation can be continued without stopping the supply of gaseous fuel even when ignition or combustion occurs, and the gas fuel supply effect can be maximized. The purpose of this is to propose a method for producing sintered ore.

  In order to solve the above-mentioned problems, the inventors have made extensive studies on a method for supplying gaseous fuel. As a result, the combustion concentration range of gaseous fuel can be changed by mixing the gaseous fuel with an extinguishing gas such as nitrogen gas, carbon dioxide, water vapor, etc. If the concentration is increased, not only can the concentration of the diluted gaseous fuel supplied be increased, but even if the gaseous fuel ignites and causes combustion, the gaseous fuel continues to be supplied and ignition combustion is prevented. The present invention has been developed in view of the fact that it is possible.

That is, the present invention includes a charging step of forming a charging layer by charging a sintered raw material containing fine ore and carbonaceous material on a circulating pallet, and an ignition furnace for the carbonaceous material on the surface of the charging layer. An ignition process for igniting, a gaseous fuel supply process for supplying gaseous fuel to the atmosphere in the hood above the charging layer, and a gas box disposed under the pallet to bring the gaseous fuel and air into the charging layer. Suction is performed to burn the carbonaceous material in the charging layer and to sinter the raw material by burning the gaseous fuel in the upper layer of the combustion / melting zone formed by the carbonaceous material combustion. In the method for producing sintered ore , the gaseous fuel and the extinguishing gas are expressed by the following formula (1) from a height of 30 mm or more above the charged layer surface in the gaseous fuel supply step :
h ≧ 2.5d (200 / C + 1) +50 (1-cos β) (1)
Here, h: nozzle height from the charging layer surface (mm) (however, h ≧ 30 mm)
d: Nozzle diameter (mm)
β: Nozzle blowing angle from vertically below (degrees)
C: Combustion lower limit concentration (vol%) of gaseous fuel
By filling and supplying the above, an extinguishing gas is mixed with the gaseous fuel and diluted to produce a sintered ore.

  In the method for producing sintered ore according to the present invention, the flame extinguishing gas is a gas in which one or more selected from nitrogen gas, carbon dioxide gas, argon gas and water vapor are mixed. .

  Further, in the method for producing a sintered ore according to the present invention, the extinguishing gas is obtained when the concentration of the diluted gas fuel becomes ¼ or more of the lower combustion limit concentration at any position in the hood, and / or It mixes when the gaseous fuel in a hood ignites.

  According to the present invention, not only the concentration of gaseous fuel to be supplied can be increased by mixing a gaseous fuel with an extinguishing gas such as nitrogen, carbon dioxide, water vapor, etc., and raising the lower combustion limit concentration, but also the supplied gas Since ignition and combustion of the fuel can be surely prevented, it becomes possible to manufacture the sintered ore safely. Even if gaseous fuel is ignited or burned, mixing the gaseous fuel with an extinguishing gas can prevent ignition and combustion, and supply of gaseous fuel can be continued, so high quality firing is possible. A stable ore can be produced.

It is a figure explaining the manufacturing process of a sintered ore. It is a figure explaining the pressure loss and temperature distribution in the charging layer at the time of sintering. It is the figure which compared and showed the time transition of the temperature in a charging layer when the productivity of a sintered ore is high and low. It is a figure which illustrates typically the progress process of the sintering of a charging layer. It is a figure explaining the temperature distribution at the time of sintering in a charging layer upper layer part, an intermediate | middle layer part, and a lower layer part, and the yield distribution of the sintered ore in the charging layer width direction cross section. 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 figure explaining the test apparatus used for the comparison of the supply method of dilution gas fuel. It is a figure explaining an example of the gaseous fuel supply apparatus in this invention. It is a figure explaining the other example of the gaseous fuel supply apparatus in this invention. It is a graph which shows the influence which it has on the combustible range when an extinguishing gas is mixed with gaseous fuel. It is another graph which shows the influence which it has on the combustible range when flame-extinguishing gas is mixed with gaseous fuel. It is a figure explaining an example of the method of mixing flame-extinguishing gas with gaseous fuel. It is a figure explaining the operation method of the present invention when gas fuel is ignited. It is a top view explaining the example of arrangement | positioning of gaseous fuel supply piping. It is a figure explaining the jet direction of the gaseous fuel from a gaseous fuel blowing nozzle. It is a figure explaining the relationship between the gas blowing angle (beta) from a nozzle, and gas flow path length.

  The manufacturing method of the sintered ore of this invention is comprised from each process of a charging process, an ignition process, a gaseous fuel supply process, and a sintering process. Here, the above charging step is a step of charging a sintered raw material including fine ore and carbonaceous material on a circulating pallet to form a charging layer, and the ignition step is charged by an ignition furnace. It is a step of igniting the carbon material on the surface layer. In the gas fuel supply process, high-concentration gas fuel is discharged from the gas fuel supply device into the atmosphere above the charging layer at a high speed on the downstream side in the pallet moving direction of the ignition furnace, and instantaneously mixed with air. The diluted gas fuel having a predetermined concentration below the lower combustion limit concentration, and this diluted gas fuel is sucked together with air by a wind box placed under the pallet and introduced into the charging layer, and the sintering step is The carbon material in the charging layer is combusted by the air sucked into the charging layer, the sintered raw material is melted and sintered by the generated combustion heat, and the diluted gas fuel is passed through the combustion zone. Is a step of generating a sintered cake by burning at a predetermined position and further promoting melting and sintering.

First, the reason why gaseous fuel is supplied into the charging layer in the method for producing sintered ore of the present invention will be described.
According to “Mineral Engineering” (Hideki Imai, Toshihisa Takeuchi, Yoshiki Fujiki, 1976, 175, Asakura Shoten), the sintering reaction is summarized as shown in the schematic diagram of FIG. Table 1 shows the tensile strength (cold strength) and reducibility values of various minerals produced during the sintering process. As can be seen from FIG. 6, in the sintering process, a melt starts to be generated at 1200 ° C., and calcium ferrite having the highest strength and relatively high reducibility among the constituent minerals of the sintered ore is generated. When the temperature rises further and exceeds about 1380 ° C., it begins to decompose into amorphous silicate (calcium silicate) having the lowest cold strength and reducibility and secondary hematite that is easily reduced to powder. Therefore, in order to stably obtain a sintered ore excellent in both cold strength and reducibility of the sintered ore, calcium ferrite obtained at a temperature of 1200 ° C. or higher in the sintering process is used as calcium silicate. It is an important point not to decompose into secondary hematite.

Further, according to the above-mentioned publication “Mineral Engineering”, the precipitation behavior of secondary hematite, which is the starting point for reducing powdering of sintered ore, is explained from the result of the mineral synthesis test with the state diagram of FIG. According to the explanation, the skeletal secondary hematite used as the starting point of reduced powdering is Mag. ss + Liq. Since it precipitates after heating up to the zone and cooling, reducing powdering can be suppressed by producing sintered ore via the path (2) instead of the path (1) on the phase diagram. It is said.
Therefore, in order to obtain a sintered ore excellent in reduced powdering property (RDI) and having high strength and excellent reducibility, the maximum reached temperature in the charging layer during sintering does not exceed 1380 ° C., It is necessary to control the temperature in the charging layer in the range of 1200 ° C. (solidus temperature of calcium ferrite) to 1380 ° C. (transition temperature).

  In addition, as described above, the formation of calcium ferrite is performed for a period of time during which the temperature is maintained at a temperature of 1200 ° C. or higher and 1400 ° C. or lower in actual operation. Depends on product. Therefore, in order to obtain a sintered ore with high strength, good reducibility, and low RDI, how should a heat pattern be maintained for a long time in the temperature range of 1200 to 1400 ° C. during the sintering? It will be a challenge whether to realize it. Therefore, the present invention secures a heat source necessary for sintering and further dilutes in addition to the carbonaceous material in order to extend the time for maintaining the temperature in the charging layer during sintering in the temperature range of 1200 to 1400 ° C. A sintering method is employed in which gaseous fuel is supplied into the charging layer.

  However, when supplying gaseous fuel, it should be noted that, in the past, when only coke was used as a carbonaceous material, the above sintering temperature was secured by the combustion heat of coke, but the same amount as before When carbon dioxide is included and diluted gas fuel is supplied into the charging layer, the highest temperature reached during sintering is increased by the combustion heat of the gaseous fuel, and the above-mentioned appropriate temperature range (1200 to 1400 ° C.) is reached. This means that the temperature in the charging layer cannot be maintained, and calcium ferrite having a low sintering strength is generated, resulting in a decrease in yield and reducibility. Therefore, it is preferable to reduce the amount of carbonaceous material blended in the sintered raw material according to the gaseous fuel to be supplied. If the amount of carbon material can be reduced, not only the carbon material cost can be reduced, but also the amount of carbon dioxide generated in the sintering process can be reduced.

Next, in the method for producing sintered ore according to the present invention, any method may be used for supplying gaseous fuel to the atmosphere in the hood above the charging layer. For example, the gaseous fuel is previously mixed with air. You can also. The concentration of the gaseous fuel in the hood is preferably below the lower combustion limit concentration, and in particular, high-concentration gaseous fuel is discharged (spouted) into the atmosphere at a high speed above the charging layer, and the ambient air and the surrounding air for a short time. It is preferable that the gas fuel is mixed and diluted to a concentration lower than the lower combustion limit concentration of the gaseous fuel, and then the diluted gaseous fuel is introduced into the charging layer. The reason is as follows.
An experimental apparatus was fabricated in which a sintered cake having an inner diameter of 300 mmφ and a height of 400 mm was filled with a sintered cake, and air could be sucked through the sintered cake below the sintered cake. Next, as shown in FIG. 8A, a nozzle is embedded at a depth of 90 mm from the top of the central portion of the sintered cake, and 100% concentration methane gas in an amount of 1 vol% with respect to the sucked air is added. The distribution of methane gas concentration in the circumferential direction and depth direction in the sintered cake was measured, and the results are shown in Table 2. Further, as shown in FIG. 8B, the same nozzle is used to dilute the same amount of methane gas from the position 350 mm above the sintered cake by supplying it into the atmosphere. The distribution of methane gas concentration in the sintered cake was measured, and the results are shown in Table 3. From these results, when methane gas was introduced directly into the sintered cake, the lateral diffusion of methane gas was insufficient, whereas when methane gas was supplied above the sintered cake, It can be seen that the methane gas concentration in the cake is almost uniform. As can be seen from this result, it is preferable that the gaseous fuel is supplied to the atmosphere above the sintered cake and diluted uniformly before being introduced into the charging layer.

  In addition, as a method of supplying the diluted gaseous fuel having the above-mentioned concentration into the charging layer, a gaseous fuel such as city gas, LNG, or C gas is discharged into the atmosphere at a high concentration and mixed with the surrounding air. Directly-injecting method that introduces into the charging layer after diluting to a predetermined concentration, and premixing blowing method that supplies air and gaseous fuel mixed in advance and diluted to a predetermined concentration from above the charging layer (So-called premix format). Table 4 evaluates the pros and cons of both types. In the direct injection method, it is easy to prevent backfire if the gaseous fuel is discharged at a speed higher than the turbulent combustion speed, but concentration unevenness is likely to occur when the gaseous fuel is mixed with the surrounding atmosphere and diluted. The possibility of abnormal combustion is high compared to the premixed blowing method. However, when comprehensively evaluated including the equipment cost, the direct injection method of city gas (LNG) is the best.

  As an apparatus for supplying gaseous fuel, for example, as shown in FIG. 9, a plurality of gaseous fuel supply pipes are arranged along the width direction of the pallet, and slits or openings for discharging gaseous fuel are provided in the pipes. Or having a gaseous fuel supply means provided with a nozzle, or, as shown in FIG. 10, a plurality of gaseous fuel supply pipes are arranged along the direction of travel of the pallet, and gaseous fuel is supplied to the pipes. It is preferable to have a gaseous fuel supply means that is provided with slits or openings for discharging or has nozzles attached.

Next, in the method for producing sintered ore of the present invention, the type of diluted gas fuel supplied into the charging layer will be described.
Table 5 shows the lower limit concentration of combustion, supply concentration, etc. of gaseous fuel (city gas, coke oven gas (C gas), blast furnace gas (B gas)) used in the steel industry. From the viewpoint of preventing explosion and fire (ignition), it is safer that the concentration of the gaseous fuel at the time of feeding into the sintered raw material is lower than the lower combustion limit concentration. In this respect, the city gas uses natural gas (LNG) mainly composed of methane, and the lower limit concentration of combustion is similar to that of C gas, but since the amount of heat is higher than that of C gas, the supply concentration is reduced. Can be lowered. Moreover, since city gas does not contain CO, there is no risk of gas poisoning. Therefore, in order to ensure safety, city gas that can lower the supply concentration is superior to C gas. In addition, the main raw material of city gas is LNG, and the main component of LNG is methane.

  Table 6 shows the combustion components (hydrogen, CO, methane) contained in the gaseous fuel, the lower and upper combustion concentrations of these components, the laminar flow, the combustion speed during turbulent flow, and the like. In order to prevent ignition of the gaseous fuel supplied from the gaseous fuel supply device during sintering, it is necessary to prevent backfire. For that purpose, it is considered that the gaseous fuel may be discharged at a high speed at least equal to or higher than the laminar combustion speed, preferably equal to or higher than the turbulent combustion speed. For example, in the case of city gas mainly composed of methane, there is no fear of backfire if it is discharged at a speed exceeding 3.7 m / sec. On the other hand, hydrogen gas has a turbulent combustion speed that is faster than that of CO or methane. Therefore, in order to prevent backfire, it is necessary to discharge hydrogen gas at a higher speed. In this regard, city gas (LNG) that does not contain hydrogen can make the discharge speed slower as compared with C gas containing 59 vol% hydrogen. Therefore, it can be said that city gas (LNG) has preferable characteristics as a gaseous fuel used in the present invention.

  As the gaseous fuel that can be supplied into the charging layer in the present invention, in addition to the above-mentioned city gas (LNG), B gas, C gas, CO gas, ethane gas, propane gas, butane gas, and a mixed gas thereof Either of these can be used. However, when B gas or C gas is used, it is necessary to increase the gas discharge rate and to take CO countermeasures separately.

  Furthermore, in the production method of the present invention, in addition to the gaseous fuel, alcohols, ethers, petroleums, and other hydrocarbon-based liquid fuels whose ignition temperature in the gaseous state is higher than the temperature of the surface layer of the sintered bed are used. A vaporized product can also be used. Table 7 shows liquid fuels that can be used in the present invention and their characteristics. Since the gas fuel obtained by vaporizing such liquid fuel has a relatively low ignition temperature compared to the gas fuel described above, it burns at a higher temperature than the surface layer of the sintered bed, and burns in the upper part of the charging layer, so that the blowing position It is effective for expanding the temperature of the combustion / melting zone at the bottom. In particular, when the ignition temperature is around 300 ° C., the effect is great. In addition, when using the gaseous fuel which vaporized liquid fuel, it is preferable to hold | maintain gas supply piping to the temperature more than the boiling point of this liquid fuel and less than ignition temperature so that the vaporized fuel may not re-liquefy.

  In addition, since waste oil etc. may contain the component which is easy to ignite, and the component with low ignition temperature, it is unpreferable for using by this invention. When liquid fuel such as waste oil containing components with low ignition temperature and flash point is vaporized in advance and supplied onto the sintering material bed, the upper part of the material bed surface before reaching the vicinity of the combustion zone in the material bed This is because it burns in the space or in the vicinity of the surface layer of the raw material bed, so that the effect of extending the high temperature holding time by burning in the vicinity of the combustion zone of the sintered raw material bed intended by the present invention cannot be obtained.

Next, the density | concentration of the dilution gas fuel supplied with the manufacturing method of the sintered ore of this invention is demonstrated.
In the manufacturing method of the present invention, the diluted gas fuel introduced into the charging layer has a flammable gas (combustion component) concentration of ¼ (25%) of the lower combustion limit concentration at normal temperature in the atmosphere. It is preferable that it is diluted below. The reason for this is that the supply of high-concentration combustible gas to the upper part of the charge layer may sometimes lead to explosive combustion, and at least at room temperature, it must be in a state that does not burn even if there is a fire type. Even if it reaches the electrostatic precipitator or the like downstream of the windbox without burning completely in the charging layer, it is necessary that there is no risk of burning due to the discharge of the electrostatic precipitator. Furthermore, due to the consumption of oxygen due to the combustion of diluted gaseous fuel, it is diluted to such an extent that the shortage of oxygen required for the combustion of the total fuel (carbon material + gaseous fuel) contained in the sintering raw material will not be caused. This is because it is necessary to be made.

  On the other hand, the lower limit concentration of the diluted gas fuel is preferably 1/25 (4%) or more of the lower limit concentration of combustion. This is because if it is less than 4% of the lower limit of combustion concentration, the calorific value due to combustion is insufficient, and the effect of improving the strength and yield of sintered ore cannot be obtained.

  From the above, it is preferable that the concentration of the diluted gas fuel supplied to the charging layer in the present invention is in the range of 4 to 25% of the lower combustion limit concentration. Looking at this for natural gas (LNG), the lower combustion concentration of LNG is 4.8 vol% (see Table 4), so the concentration of diluted gas fuel is preferably in the range of 0.2 to 1.2 vol%. It will be.

  However, the lower combustion concentration of the gaseous fuel is a value when mixed with air. Therefore, if the lower combustion limit concentration can be increased by mixing with an extinguishing gas by some means, for example, the concentration of the diluted gaseous fuel is increased to ¼, so that a higher concentration of gaseous fuel is supplied accordingly. In addition, the gas fuel can be prevented from being ignited and burned, so that safety can be further improved. Furthermore, if the ignition and combustion of the gaseous fuel can be easily prevented, it is not necessary to stop the supply of the gaseous fuel at the time of abnormality, so that the gaseous fuel supply operation can be performed stably.

FIG. 11 shows a mixture ratio (extinguishing gas / carbon dioxide) when hydrogen (H ₂ ) and carbon monoxide (CO), which are gaseous fuels, are mixed with nitrogen (N ₂ ) and carbon dioxide (CO ₂ ) as an extinguishing gas. It is the figure which showed the relationship between the combustible range of gaseous fuel) and gaseous fuel, and the range enclosed by the line in a figure is a combustion range. From this figure, it can be seen that the lower the combustion limit concentration is, the higher the mixing ratio of the extinguishing gas is. For example, when hydrogen is used as the gaseous fuel and nitrogen is used as the extinguishing gas, the lower combustion limit concentration of hydrogen in the air is 4.0 vol%, but when nitrogen is mixed with hydrogen and the mixing ratio is set to 10. It can be seen that the lower limit concentration of combustion of the mixed fuel is 48 vol%. Then, hydrogen in the mixed fuel becomes 4.4 vol% at 48 / (1 + 11), and the hydrogen concentration can be substantially increased by 4.4-4.0 = 0.4 vol%. In the case of methane (LNG), the lower limit concentration of combustion in air is 5.0 vol%, and the lower limit concentration of combustion of the mixed fuel when 1 × ₂ CO ₂ is mixed with methane is 17.5 vol%. Is 5.8 vol%. When gaseous fuel is used with the lower limit of combustion as a constraint by mixing CO ₂ twice the volume of methane, the methane concentration can be substantially increased by 5.8−5.0 = 0.8 vol%. it can.

  In other words, it is indicated that mixing the extinguishing gas with the gaseous fuel increases the lower combustion limit concentration of the gaseous fuel and makes it difficult to burn. In addition, from FIG. 11, when gaseous fuel is blown in the vicinity of the lower combustion limit concentration in the air, even if ignition occurs, if the gaseous fuel is diluted with an extinguishing gas and the lower combustion limit concentration is increased, It shows that combustion of gaseous fuel can be easily prevented.

Further, FIG. 12 shows ethane (C ₂ H ₄ ), ethylene (C ₂ H ₆ ) and benzene (C ₆ H ₆ ), which are hydrocarbon-based gaseous fuels, and nitrogen (N ₂ ) and dioxide as an extinguishing gas. FIG. 10 is a diagram showing the relationship between the mixing ratio (extinguishing gas / gas fuel) and the combustible range of gaseous fuel when carbon (CO ₂ ) is mixed, and the same thing as FIG. 9 can be seen. Although not shown in FIGS. 11 and 12, since the flame-extinguishing effect of water vapor (H ₂ O) is higher than that of CO ₂ , it is suitable as a flame-extinguishing gas in an environment where low-pressure steam can be easily used. Can be used. Incidentally, the anti-inflammatory effect is in the order of H ₂ O, CO ₂ and N ₂ from the highest effect.

  As a means for mixing the extinguishing gas with the gaseous fuel, as shown in FIG. 13, an extinguishing gas supply pipe is arranged near, for example, directly below the gaseous fuel supply pipe arranged on the charging layer. A simple method is to provide an extinguishing gas to a place where gaseous fuel is discharged. Of course, a method of previously mixing the gaseous fuel and the extinguishing gas may be used.

Next, the manufacturing method of the sintered ore of the present invention when the gaseous fuel is ignited will be described.
In a conventional method for producing sintered ore that supplies gaseous fuel, for example, when the ignition to the gaseous fuel is detected by an ultraviolet fire detector or the like, the gaseous fuel supply is temporarily shut off and the fuel in the pipe is purged. Then, after the fire was extinguished, the fuel supply was started again, so the supply of gaseous fuel was cut off for at least a few minutes, and in the case of a long period of time, nearly 10 minutes. The quality could be adversely affected.

  Therefore, in the present invention, as shown in FIG. 14 (a), after the ignition is detected, the extinguishing gas is immediately increased to easily extinguish the combustion of the gaseous fuel without stopping the supply of the gaseous fuel. it can. Therefore, high-quality sintered ore can be produced safely without causing deterioration of the quality of the sintered ore and the productivity due to the stop of the blowing of the gaseous fuel.

  In the above description, the mixing of the flame-extinguishing gas into the gaseous fuel was premised to be always performed during the sintering operation. For example, as shown in FIG. Is the operation of mixing gaseous fuel with gaseous fuel only when gaseous fuel is ignited without gas supply, and only when gaseous fuel ignition or abnormal distribution of gaseous fuel concentration is detected. The method can also be adopted.

Next, preferable gaseous fuel supply conditions (nozzle ejection conditions) for mixing gaseous fuel and / or extinguishing gas with ambient air and diluting them uniformly to a predetermined concentration below the lower combustion limit concentration will be described.
FIG. 15 is a layout view (plan view) of the gaseous fuel supply pipe arranged on the sintered pallet. By arranging the gaseous fuel supply pipe in parallel with the pallet traveling direction, the gaseous fuel is arranged in the pallet width direction. The supply concentration can be adjusted.

  The amount of gaseous fuel blown from the nozzle attached to the gaseous fuel supply pipe into the atmosphere is a predetermined concentration with respect to the flow rate of air sucked by the windbox (area of the gaseous fuel supply area × flux). It is necessary to blow in the gaseous fuel. The ejection speed from the nozzle at this time needs to be ejected at a high speed of 70 m / sec or more in order to prevent ignition of the gaseous fuel.

  FIG. 16 is a view showing an example of the ejection direction of the gaseous fuel or the extinguishing gas from the nozzle in the present invention. By blowing a gaseous fuel or an extinguishing gas in a horizontal direction from a nozzle installed in the pipe, it is quickly mixed with the surrounding air sucked into the sintered layer.

The inventors further examined the conditions for diluting the gaseous fuel uniformly near the nozzle to a level sufficient for operation. The following formula (1);
h ≧ 2.5d (200 / C + 1) +50 (1-cos β) (1)
Here, h: nozzle height from the charging layer surface (mm) (however, h ≧ 30 mm)
d: Nozzle diameter (mm)
β: Nozzle blowing angle from vertically below (degrees)
C: Combustion lower limit concentration (vol%) of gaseous fuel
It was found that it is important to satisfy. The height of the nozzle outlet is set to 30 mm or more from the surface of the insertion layer in order to avoid contact with the surface of the charging layer.

Here, the above equation (1) will be described.
J. et al. M.M. Bear, N.C. A. Calculation of the amount of ambient gas entrained by a jet described in Cigar "Aerodynamics of Combustion" (translated by Ryoichi Tanaka, Japan Thermal Energy Technology Association, issued June 30, 1976) Based on the technique, the gaseous fuel is burned when the gaseous fuel is ejected vertically downward from a nozzle installed at a height h from the charging layer surface of the sintering machine as shown in FIG. When the amount of air to be entrained before reaching the surface of the stratification is determined as 100% city gas (main component is methane), the gas to be ejected is expressed by the following equation (i).
V _e / V _o ≈0.4 (h / d) -1 (i)
Here, V _e : volume of ambient air involved in the city gas to be ejected
V _o : City gas volume to be ejected
d: Nozzle diameter (mm)
h: Distance from nozzle tip (nozzle height) (mm)
If another gaseous fuel is used instead of city gas, the gas density is different and correction is necessary. However, if the degree of dilution is large, a large error may occur even if equation (i) is used. Does not occur.

From the above formula (i), is ejected from a height of h, the city gas concentration C _h reaching the sintering bed surface, when being diluted to lean by involving air, is V _e> V _o So
C _h (vol%) = 100 · V _o / (V _e + V _o ) ≈100 · V _o / V _e (ii)
Here, since _Ch (vol%) is expressed as a concentration fraction, it is _Ch / 100.
C _h / 100≈V _o / V _e ≈1 / (0.4 · (h / d) −1) (iii)
It becomes.
When this equation is converted into an equation for obtaining h,
h = 2.5 (100 / C _h +1) d (iv)
Is obtained.

Next, when the dilution of the gaseous fuel to the target is C, the actual uniformly it is diluted to exist variations of no small difficulty concentration, (iv) expression of C _h is C 1/2 Assuming that it is determined that the gaseous fuel is uniformly diluted to C when the concentration becomes the nozzle height h for diluting to the concentration C / 2 (which can be determined to be uniformly diluted to C), Since C _h = C / 2,
h = 2.5 (200 / C + 1) d (v)
It becomes.
Therefore, in the case of the target dilution concentration C of the gaseous fuel, the height h of the nozzle that ejects the gaseous fuel is
h ≧ 2.5 (200 / C + 1) d
When satisfying, if the nozzle interval is appropriate, it can be determined that the gaseous fuel is sufficiently uniformly diluted,
h <2.5 (C / 200 + 1) d
If so, it can be determined that the entrainment of air into the gaseous fuel is insufficient.

The above equation (v) is a calculation formula when gaseous fuel (city gas) is ejected vertically downward. Next, the ejection direction of the city gas from the nozzle is as shown in FIGS. Thus, the case where it has the angle of (beta) from the perpendicular downward direction is considered.
In this case, the gaseous fuel ejected from the nozzle travels a longer distance than the case of ejecting vertically downward until it reaches the charged layer surface. Need to be corrected.
According to the knowledge from numerical thermal fluid analysis and experimental results regarding numerous gaseous fuel injections conducted by the inventors, the gaseous fuel ejected from the nozzle is about 50 mm away from the nozzle tip, as shown in FIG. Then, it is the flow which goes to the perpendicular downward direction along the flow of the air attracted | sucked by the wind box.

Therefore, when β ≦ 90 degrees is considered (FIGS. 17B and 17C), the flow path length until the gaseous fuel reaches the charged layer surface increases by +50 mm and decreases by 50 cos β (mm). So, if that amount is corrected for h,
h = 2.5 (200 / C + 1) d + 50 (1-cosβ) (vi)
Is obtained.
Similarly, when β> 90 degrees (FIG. 17D) is considered, the flow length of the gaseous fuel increases by +50 mm, and further increases by 50 cos β (mm). However, when β> 90 degrees, the sign of cos β is −, so that the same equation as the equation (vi) is obtained.

Therefore, the height h of the gaseous fuel injection nozzle is expressed by the following equation (1);
h ≧ 2.5 (200 / C + 1) d + 50 (1-cos β) (1)
If it is installed so as to satisfy the conditions, until the gaseous fuel supplied from the gaseous fuel injection nozzle reaches the charging layer surface (until it is sucked into the charging layer), it will be at a sufficient level with no operational problems. Diluted uniformly. In the case of an extinguishing gas, if the lower combustion limit concentration in the case of only gaseous fuel is used as C, the dilution condition can be similarly determined.

  As described above, according to the present invention, by mixing the gaseous fuel with the extinguishing gas, the lower limit concentration of the diluted gaseous fuel can be increased, so that a high concentration gaseous fuel can be supplied. Therefore, the amount of carbonaceous material blended in the sintered raw material can be reduced. In addition, according to the present invention, by mixing an extinguishing gas with the gaseous fuel, it is possible to prevent the gaseous fuel from being ignited and burned, and thus it is possible to further improve safety. Furthermore, since the ignition and combustion of the gaseous fuel can be easily prevented, it is not necessary to stop the supply of the gaseous fuel at the time of abnormality, and the gaseous fuel supply operation can be performed stably.

  In the above description, the technology for mixing the flame-extinguishing gas into the gaseous fuel has been introduced in the direct blowing method in which the gaseous fuel is discharged into the atmosphere at a high concentration, diluted, and introduced into the charging layer. It was. However, the technology for mixing the flame-extinguishing gas into the gaseous fuel of the present invention is not limited to the above-described direct blowing method, but a premixing blowing method (mixing and supplying the gaseous fuel and the quenching gas in advance) The same applies to the so-called premix format.

In an actual sintering machine in contact with the same gaseous fuel supply apparatus as shown in FIG. 13, an experiment was conducted to produce sintered ore by blowing hydrogen and hexane as gaseous fuel under the conditions shown in Table 8.
At this time, the gaseous fuel was jetted into the atmosphere at a height of 500 mm from the surface of the charging layer and from a nozzle having a diameter of 1 mmφ in a horizontal horizontal blowing (β: 90 degrees) at 200 m / sec. In addition, when the gaseous fuel is hydrogen, the flame-extinguishing gas has an amount of nitrogen gas that is 10 in the mixing ratio, and hexane that is carbon dioxide that is 1.5 in the mixing ratio. At a height of 550 mm from the surface, the nozzle was blown into the atmosphere at 300 m / sec at β: 90 degrees from a nozzle having a diameter of 1 mmφ. It mixed with gaseous fuel using the apparatus similar to what was shown in FIG.
Moreover, the carbonaceous material included in the sintering raw material with the blowing of the gaseous fuel was blended by subtracting in advance the amount corresponding to the combustion heat of the blown gaseous fuel.
The hexane used in this example is normal hexane (n-hexane, molecular formula C ₆ H ₁₄ , boiling point 69 ° C.), which is abundant in kerosene and gasoline. The steam recovered from the hot exhaust gas from the cooler was vaporized and used as gaseous fuel.

The results of the sintering experiment are shown together in Table 8. In the table, No. Reference example 5 is an example of a conventional sintering method in which sintering is performed only with the combustion heat of carbonaceous material without injecting gaseous fuel or mixing with an extinguishing gas. Evaluated this example as a base.
First of all, regarding the mixing effect of the extinguishing gas on safety, the lower limit concentration of combustion in hydrogen at room temperature and in air is 4.0 vol%. To rise. The lower limit concentration of hexane in air and air is 1.2 vol%, but when diluted with CO ₂ to a mixing ratio of 1.5, the lower limit concentration of combustion increases to 4 vol%. Therefore, the concentration of the diluted gas fuel in the invention example shown in Table 8 is safer than the comparative example from the viewpoint of the lower limit concentration against combustion.
Next, when looking at the mixing effect of the extinguishing gas on productivity and quality, no. The comparative example of No. 2 is an example in which 0.80 vol% of hydrogen was blown as a gaseous fuel. Compared with the reference example of 5, the basic unit of coke can be reduced by 1 kg / t (sintered ore), and the quality and productivity are also improved. In contrast, no. In the invention example 1, since the lower combustion limit concentration is increased by diluting hydrogen with nitrogen, there is no problem in safety even if hydrogen is increased to 0.96 vol%, and the quality and productivity are adversely affected. The amount of coke reduction can be expanded to 1.2 kg / t (sintered ore) without any problems. Similarly, no. The comparative example of No. 4 is an example in which 0.21 vol% of hexane vaporized as a gaseous fuel was blown. Compared with the reference example of 5, the basic unit of coke can be reduced by 1 kg / t (sintered ore), and the quality and productivity are also improved. In contrast, no. In the invention example 3, since the lower combustion limit concentration is increased by diluting hydrogen with carbon dioxide, there is no problem in safety even if hexane is increased to 0.42 vol%, and the quality and productivity are adversely affected. The reduction amount of coke can be expanded to 2.0 kg / t (sintered ore) without affecting.
As described above, the effect of supplying the gaseous fuel can be maximized by mixing the extinguishing gas with the gaseous fuel.

  The technology of the present invention can be applied not only to a general downward suction type sintering machine but also to a rotary hearth type or packed bed structure sintering / reaction apparatus, and for granulation / agglomeration. It can also be applied to other processes and devices.

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 (3)

A charging step of charging a sintered raw material including fine ore and carbonaceous material onto a circulating pallet to form a charging layer;
An ignition step of igniting the charcoal on the surface of the charging layer using an ignition furnace;
A gaseous fuel supply process for supplying gaseous fuel to the atmosphere in the hood above the charging layer;
A combustion / melting zone formed by sucking the gaseous fuel and air into the charging layer and burning the carbonaceous material in the charging layer with a windbox placed under the pallet, and burning the gaseous fuel by burning the carbonaceous material In the method for producing a sintered ore having a sintering step of sintering the sintering raw material by burning in the upper layer portion of
In the gaseous fuel supply step , the gaseous fuel and the extinguishing gas are supplied from the height of 30 mm or more above the surface of the charging layer so as to satisfy the following formula (1), thereby mixing the extinguishing gas into the gaseous fuel. A method for producing a sintered ore characterized by diluting.
Record
h ≧ 2.5d (200 / C + 1) +50 (1-cos β) (1)
Here, h: nozzle height from the charging layer surface (mm) (however, h ≧ 30 mm)
d: Nozzle diameter (mm)
β: Nozzle blowing angle from vertically below (degrees)
C: Combustion lower limit concentration (vol%) of gaseous fuel 2. The method for producing a sintered ore according to claim 1, wherein the flame extinguishing gas is a gas in which one or more selected from nitrogen gas, carbon dioxide gas, argon gas and water vapor are mixed. . The above-mentioned flame extinguishing gas should be mixed when the concentration of the diluted gaseous fuel is ¼ or more of the lower combustion limit concentration at any position in the hood and / or when the gaseous fuel in the hood is ignited. The manufacturing method of the sintered ore of Claim 1 or 2 characterized by these.

Images