JP5359011B2 - Sintering machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To propose a technology capable of manufacturing a sintered ore of high strength with a high yield, without deteriorating ventilation performance of the whole placing layer, by supplying diluted gas fuel in the placing layer even in the presence of a cross wind, in operation of a lower suction type sintering machine. <P>SOLUTION: This sintering machine has a circularly moving pallet, a raw material supply device for forming the placing layer by placing a sintered raw material including a powder ore and a charcoal material on its pallet, an ignition furnace for igniting the charcoal material in its sintered raw material, and a wind box under the pallet. The sintering machine is characterized in that a gas fuel supply device is arranged on the downstream side of the ignition furnace, and the gas fuel supply device is provided with a cross wind preventive hood having an atmospheric suction opening part in its upper part. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a downward suction type Dwydroid (DL) sintering machine used for producing sintered ore for blast furnace raw material, and more particularly to a cross wind prevention technique when supplying gaseous fuel to the sintering machine. .

  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 are iron ore powder, iron mill recovered powder, sintered ore sieve powder, CaO-containing auxiliary raw materials such as limestone and dolomite, granulation aids such as quick lime, coke powder and anthracite. 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 using a drum mixer 2 and the like, mixed and granulated to obtain a sintered raw material which is a pseudo particle having an average diameter of 3.0 to 6.0 mm. This sintering raw material is 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 sintered bed A so-called charging layer 9 is formed. The thickness (height) of the charging layer is about 400 to 800 mm. Then, the ignition furnace 10 installed above the charging layer 9 ignites the carbon material in the surface layer of the charging layer, and lowers the air through the wind box 11 disposed under the pallet 8. In this way, the carbonaceous material in the charging layer is sequentially combusted, and the sintering raw material is combusted and melted by the combustion heat generated at this time to produce a sintered cake. The obtained sintered cake is then crushed and sized and recovered as a product sintered ore consisting of agglomerates of 5.0 mm or more.

  In the manufacturing process, first, the ignition layer 10 is ignited by the ignition furnace 10. The ignited carbon material in the charging layer continues to be burned by the air sucked from the upper layer portion to the lower layer portion of the charging layer by the windbox, and the combustion zone gradually moves to the lower layer and forward as the pallet 8 moves. Proceed (downstream). As the combustion progresses, the moisture contained in the sintering raw material particles in the charging layer is vaporized by the heat generated by the combustion of the carbonaceous material, sucked downward, and the lower layer where the temperature has not yet risen. Concentrate in the sintering raw material to form a wet zone. If the moisture concentration exceeds a certain level, moisture fills the gaps between the raw material particles, which are the flow paths of the suction gas, and the ventilation resistance is increased. Note that the melted portion necessary for the sintering reaction that occurs in the combustion zone is also a factor that increases the ventilation resistance.

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 volume of the sintering machine includes 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. It depends on. In order to increase the production of sintered ore, the air permeability (pressure loss) of the charging layer is improved to shorten the sintering time, or the cold strength of the sintered cake before crushing is increased. It is considered effective to improve the retention.

  FIG. 2 shows the inside of the charging layer when the combustion (flame) front moving through the charging layer having a thickness of 600 mm is at a position of about 400 mm (200 mm from the surface of the charging layer) on the pallet of the charging layer. 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 / melt zone.

FIG. 3 shows the temperature distribution in the charging layer during high production and low production of sintered ore. The time during which the raw material particles begin to melt is maintained at a temperature of 1200 ° C. or higher (hereinafter referred to as “high temperature region holding time”) is t _{1 in} the case of low production, and in the case of high production with an emphasis on productivity. It is represented by t _2. For high productivity, to increase the movement speed of the pallet, the high temperature zone holding time t ₂ is shorter than the t ₁ when low production. When the high temperature region holding time is shortened, firing becomes insufficient, resulting in a decrease in the cold strength of the sintered ore and a decrease in yield. Therefore, in order to increase the production amount of high-strength sintered ore, the yield strength is maintained and improved by increasing the strength of the sintered cake, that is, the cold strength of the sintered ore, even in the short-time sintering. It is necessary to take some measures that can be done. In general, SI (shutter index) and TI (tumbler index) are used as indices representing the cold strength of sintered ore.

  FIG. 4A shows the progress of sintering in the charging layer on the sintering machine pallet, FIG. 4B shows the temperature distribution (heat pattern) in the sintering process in the charging layer, and FIG. ) Shows the yield distribution of the sintered cake. As can be seen from FIG. 4B, the temperature of the upper portion of the charging layer is less likely to rise than the lower layer portion, and the high temperature region holding time is also shortened. Therefore, in the upper part of the charging layer, the combustion and melting reaction (sintering reaction) becomes insufficient, and the strength of the sintered cake is lowered. Therefore, as shown in FIG. It is a factor that causes a decline in

  In view of these problems, a method for imparting high temperature retention to the upper portion of the charging layer has been conventionally proposed. For example, Patent Document 1 discloses a technique for injecting gaseous fuel onto a charging layer after ignition of the charging layer. However, although the kind of gaseous fuel (flammable gas) is unknown in the above technique, even if it is propane gas (LPG) or natural gas (LNG), a high concentration gas is used. Moreover, since the amount of the carbon material is not reduced when the combustible gas is blown, the inside of the sintered layer becomes a high temperature exceeding 1380 ° C. For this reason, this technique has not been able to enjoy sufficient cold strength improvement and yield improvement effects. Moreover, when inflammable gas is injected immediately after the ignition furnace, there is a high risk of fire in the upper space of the sintering bed due to combustion of the combustible gas, and this is a technology that is not realistic and has not yet been put into practical use. .

  Patent Document 2 also discloses a technique of adding a combustible gas to the air sucked into the charging layer after the charging layer is ignited. It is said that about 1 to 10 minutes of supply after ignition is preferable, but the surface layer portion immediately after ignition in the ignition furnace has red-hot sintered ore remaining, and depending on the supply method, combustible gas There is a high risk of fire due to combustion, and there are few specific descriptions, but there is no effect even if combustible gas is burned in a sintered sintered zone. Since the air permeability is deteriorated due to thermal expansion, the productivity tends to be reduced, so that it has not been put into practical use.

  In Patent Document 3, a hood is disposed on the charging layer in order to make the inside of the charging layer of the sintering raw material high temperature, and a mixed gas with air and coke oven gas is passed through the hood immediately after the ignition furnace. It is disclosed to blow in position. However, this technique also has a high temperature exceeding 1380 ° C. in the combustion melting zone in the sintered layer, so that the effect of coke oven gas blowing cannot be enjoyed, and the combustible mixed gas is ignited in the upper space of the sintering bed. There is a risk of fire and is not put into practical use.

  Further, Patent Document 4 discloses a method in which a low-melting-point solvent, a carbon material, and a combustible gas are simultaneously blown at a position immediately after the ignition furnace. However, this method also has a high risk of fire in the upper space of the sintering bed because the flammable gas is blown in a state where a flame remains on the surface, and the width of the sintering zone cannot be made sufficiently thick (approximately (Less than 15 mm), the effect of inflammable gas blowing cannot be fully exhibited. In addition, since there are many low-melting solvents, excessive melting phenomenon is caused in the upper layer portion, and the pores that become air flow paths are blocked, resulting in deterioration of air permeability and reduction of productivity. This technology has not been put into practical use until now.

As described above, none of the conventional techniques proposed so far has been put into practical use, and the development of a combustible gas blowing technique that can be implemented has been eagerly desired.
Japanese Patent Laid-Open No. 48-18102 Japanese Patent Publication No.46-27126 JP-A-55-18585 Japanese Patent Laid-Open No. 5-311257

  By the way, the quality of the sintered ore is determined by the maximum temperature reached during combustion, the high temperature region holding time, and the like. Therefore, it is important to control the maximum temperature reached and the high temperature region holding time. In this regard, the method described in Patent Document 1 is a technique for increasing the temperature of the upper part of the charging layer in the first half of the sintering means by burning gaseous fuel on the surface of the charging layer. However, in this method, the concentration of gaseous fuel is high, so the amount of air (oxygen) that supports combustion is insufficient, and there is a risk of reducing the combustion of the carbonaceous material (coke) of the sintering raw material. There is a problem that improvement cannot be achieved.

  Further, even in Patent Document 2, there is a lack of concreteness, depending on the supply method, there is a high risk of fire, and there is no effect even if combustible gas is burned at the sintered zone position after sintering. It has not been put to practical use.

  Furthermore, in the method described in Patent Document 3, a hood is disposed on the charging layer in order to increase the temperature inside the charging layer of the sintering raw material, and air and coke oven gas are mixed through the hood. This is a technique for blowing gas at a position immediately after the ignition furnace. However, if the mixed gas is blown with the coke ratio as it is, the high temperature retention time is extended and the maximum temperature is increased, so that a lot of vitreous low-strength minerals are generated and the mixed gas blowing effect cannot be enjoyed. . In addition, there is a risk that a combustible mixed gas may ignite and cause a fire, and it has not been put into practical use.

  In addition, the method described in Patent Document 4 increases the amount of air (oxygen) and mixes a low-melting-point melt or carbonaceous material, so that the burning rate of combustible gas and coke increases, but the low-melting-point Since the melt and powder are blown together, there is a problem that the air permeability of the combustion air is lowered.

  An object of the present invention is a downward suction type sintering machine, in which gaseous fuel is supplied even in the presence of a cross wind, and this is burned in the charging layer, thereby deteriorating the air permeability of the entire charging layer. Therefore, it is providing the sintering machine which can manufacture a high intensity | strength sintered ore with a high yield.

In order to achieve the above object, the present invention comprises a pallet that circulates and moves, a raw material supply device that forms a charging layer by charging a sintered raw material containing fine ore and carbonaceous material on the pallet, In a sintering machine provided with an ignition furnace for igniting the carbonaceous material in the raw material and a wind box below the pallet, on the downstream side of the ignition furnace, on the downstream side of the ignition furnace, there is an air suction opening upward. A gaseous fuel supply device provided with a cross wind preventing hood having a portion is disposed , and a cross wind attenuating fence having a transmittance is installed around the top of the cross wind preventing hood. This is a characteristic sintering machine.

In the present invention, the cross wind preventing hood is
(1) be installed close contact type seal structure between its lower end and the pallet sidewalls,
(2) formed by installing a windbreak cover on the outside of its lower end and the pallet side wall,
(3) along the width direction on both sides of that pallet, it is installed crosswinds preventing shielding plates, characterized.

Further, the crosswind preventing hood in the present invention is characterized by formed by providing a gap between the lower end and the sintering bed surface of it. Further, it is preferable that a sealing material is disposed in the gap or that an air curtain is further installed.

Moreover, the hood for cross wind prevention in the present invention,
(1) sidewall upper portion is one having an inclined structure, characterized by.

In the inside of the hood for preventing cross wind in the present invention,
(1) Install a current plate,
(2) A baffle plate is provided.

  In addition to the above, the gaseous fuel supply device according to the present invention is (a) on the downstream side of the pallet moving direction of the ignition furnace, discharging gaseous fuel into the upper atmosphere of the charging layer at high speed, mixing with air, and burning (B) At least one or more disposed on the downstream side of the ignition furnace in the longitudinal direction of the sintering machine, (c) Combustion in the pallet traveling direction It is preferable that the front line is disposed at a position between the stage where the front line has progressed below the surface layer of the charging layer and the completion of the sintering, and (d) it is disposed near the sidewall.

  In the gaseous fuel supply apparatus according to the present invention, (a) a plurality of gaseous fuel supply pipes are provided along the width direction of the pallet, and a slit or an opening for discharging the gaseous fuel is provided on the pipes. Or (b) a plurality of gaseous fuel supply pipes are arranged along the direction of travel of the pallet, and the pipes are provided with slits for discharging gaseous fuel or It has a structure in which an opening is provided or a nozzle is provided, (c) it controls the amount of gaseous fuel supplied in the pallet width direction, and (d) in the vicinity of the side wall in the pallet width direction. It is preferable to supply a large amount of gaseous fuel.

  The gaseous fuel supply device according to the present invention is (a) discharging gaseous fuel above the charging layer and downward toward the charging layer, and (b) charging gaseous fuel. (C) the gas fuel is discharged toward the reflector above the charging layer, and (d) the gas fuel. The gas discharge slits, openings or nozzles provided in the supply pipe are dispersed in the range of ± 90 degrees with respect to the vertical direction toward the charge layer surface, (e) gas The fuel supply pipe is rotatable about the axis of the fuel supply pipe, and the discharge direction is swung. (F) The gaseous fuel is discharged at a height of 300 mm or more above the surface of the charging layer. preferable.

  Further, the gaseous fuel supply apparatus according to the present invention includes (a) discharging the gaseous fuel at a speed that is at least twice the burning speed of the gaseous fuel, and (b) turbulent combustion of the gaseous fuel. It is preferable to discharge at a speed twice or more the speed.

  The gaseous fuel supply device in the present invention is (a) for introducing a combustible gas into the charging layer as diluted gaseous fuel diluted to a concentration of 75% or less and 2% or more of the lower combustion limit concentration, (B) The combustible gas is introduced into the charging layer as a diluted gas fuel diluted to a concentration of 60% or less and 2% or more of the lower combustion limit concentration. (C) The combustible gas is 25 of the lower combustion limit concentration. It is preferable to introduce it into the charging layer as a diluted gas fuel diluted to a concentration of 2% or less and 2% or more.

  The gaseous fuel in the present invention is selected from (a) blast furnace gas, coke oven gas, blast furnace / coke oven mixed gas, city gas, Tennobu gas, methane gas, ethane gas, propane gas, and mixed gas thereof. It is preferably any flammable gas, (b) a CO content of 50 mass ppm or less, and (c) any one of city gas 13A and propane gas.

  Further, the gaseous fuel in the present invention is obtained by vaporizing a liquid fuel whose ignition temperature in a gaseous state is higher than the temperature of the surface layer of the sintered bed, and the liquid fuel includes alcohols, ethers, Petroleum and other hydrocarbon compounds are preferable. Furthermore, in the sintering machine of the present invention, it is preferable that the gaseous fuel supply pipe when the liquid fuel is vaporized and used is maintained at a temperature equal to or higher than the boiling point of the liquid fuel and lower than the ignition temperature.

  According to the present invention, in the operation of the downward suction type sintering machine, even in the presence of a cross wind, the gaseous fuel is discharged into the atmosphere above the charging layer and the diluted gaseous fuel diluted to a predetermined concentration is loaded. It can be supplied (introduced) into the bed and burned at a target position in the bed. In addition, in this case, by controlling the supply position of the diluted gas fuel, the maximum temperature reached during combustion, and the high temperature range holding time, if only the upper part of the charging layer where the cold strength of the sintered ore tends to be low due to insufficient combustion, It is possible to perform an operation that increases the strength of the sintered ore in any portion below the middle layer of the charge layer. Moreover, in the present invention, the reaction in the combustion / melting zone, for example, the thickness in the vertical direction of the zone or the width in the pallet traveling direction is controlled without deteriorating the air permeability of the entire charging layer. Since the strength of the sintered cake in can be controlled, it is possible to produce a product sintered ore having a high cold strength as a whole ore while ensuring a high yield and high productivity. And if the sintering machine of this invention is used, operation of such a sintering machine can be performed stably also in presence of a cross wind.

  A sintering machine according to the present invention includes a pallet that circulates, a raw material supply device that charges a sintered raw material containing fine ore and carbonaceous material on the pallet to form a charging layer, and the sintered raw material An ignition furnace for igniting a carbon material of the above and a sintering machine provided with a window box below the pallet, wherein a gaseous fuel supply device is disposed downstream of the ignition furnace It is. Here, the gaseous fuel supply device is a device for obtaining diluted gas fuel below the lower combustion limit concentration by supplying and diluting the gaseous fuel into the air above the charging layer, and a wind box disposed under the pallet. The diluted gas fuel and air are sucked into the charging layer by suction force, and the diluted gas fuel is combusted in the charging layer. At the same time, the air sucked into the charging layer causes the inside of the charging layer. In order to sinter the sintering raw material and generate a sintered cake with the combustion heat generated by burning the carbonaceous material, it plays an extremely important role in the present invention.

  Specifically, as shown in FIG. 5, a plurality of gaseous fuel supply pipes are arranged along the width direction of the pallet, and the gaseous fuel is discharged into the pipes as the gaseous fuel supply apparatus. A structure having slits or openings or nozzles or a plurality of gaseous fuel supply pipes along the direction of pallet movement as shown in FIG. It is preferable that a slit or opening for discharging gaseous fuel is provided or a nozzle is provided.

  Moreover, it is preferable that the said gaseous fuel supply apparatus can control the supply quantity of the gaseous fuel in a pallet width direction, for example by providing a flow control means in a gaseous fuel supply pipe, a nozzle, etc. In particular, in the vicinity of the side wall in the pallet width direction, there is a high risk that the gaseous fuel concentration will be dilute due to the influence of crosswinds and the supplied gaseous fuel will flow in the machine side direction or leak out of the machine. Therefore, it is preferable that a large amount of gaseous fuel can be supplied in the vicinity of the sidewall.

  Further, the gaseous fuel supply device causes the gaseous fuel to be discharged into the atmosphere at a high speed above the charging layer, thereby mixing with the surrounding air in a short time, and a concentration below the lower combustion limit concentration of the gaseous fuel. And then dilute gaseous fuel must be introduced into the charging layer.

As described above, the reason why the gaseous fuel is diluted to a concentration lower than the lower combustion limit concentration is as follows.
Table 1 shows the lower combustion limit concentration, supply concentration, and the like of typical gaseous fuels that can be used in the present invention. In order to prevent the occurrence of fire, the gas concentration when supplying gaseous fuel into the sintered raw material is safer as it is lower than the lower combustion limit concentration. In this respect, city gas has a lower combustion limit concentration that is similar to that of C gas (coke oven gas), but since the amount of heat is higher than that of C gas, the supply concentration can be lowered. Therefore, from the viewpoint of ensuring safety, city gas that can lower the supply concentration is superior to C gas. Moreover, as will be described later, city gas does not contain CO (carbon monoxide) harmful to the human body as a component, nor does it contain hydrogen.

  Table 2 shows the combustion components (hydrogen, CO, methane) contained in the gaseous fuel, the lower and upper combustion concentrations of these components, laminar flow, combustion speed during turbulent flow, and the like. In order to prevent the occurrence of fire during sintering, that is, to prevent the occurrence of fire due to gaseous fuel supplied during sintering, it is necessary to prevent backfire, but for that purpose, at least laminar combustion The gaseous fuel may be discharged at a speed higher than the speed, preferably higher than the turbulent combustion speed. For example, when methane, which is a main combustion component of city gas, is used as a gaseous fuel, there is no fear of backfire if it is discharged at a speed exceeding 3.7 m / s. On the other hand, since hydrogen gas has a higher turbulent combustion speed than CO and methane, it is necessary to discharge hydrogen gas at a higher speed in order to ensure safety. From this point, when comparing the gaseous fuel shown in Table 1, the city gas that does not contain the hydrogen component can slow down the discharge speed compared to the C gas containing 59 vol% of the hydrogen component. Is advantageous. Moreover, since city gas does not contain a CO component, it is safe without causing gas poisoning. Therefore, from the viewpoint of ensuring safety, it can be said that city gas has favorable characteristics when used as gaseous fuel. The same can be said for natural gas. Note that C gas can also be used as gaseous fuel, but in that case, it is necessary to increase (accelerate) the gas discharge speed and to separately take measures against CO.

  Table 3 shows the results of evaluating the advantages and disadvantages of the type of supplying the gaseous fuel. In the table, direct top blowing means that gas fuel such as city gas or C gas is supplied (discharged) as it is, and is diluted to a predetermined concentration by entraining the surrounding atmosphere and sucked into the charging layer (introduced) The premixed blowing is a so-called pre-mixing method in which air and gaseous fuel are mixed in advance and diluted to a predetermined concentration and supplied to the charging layer and sucked (introduced) into the charging layer. Refers to the mix format. In the direct injection type, it is easy to prevent backfire if gaseous fuel is discharged at a speed higher than the turbulent combustion rate described above, but in the premixed injection type, when a concentration deviation occurs, backfire is caused. there is a possibility. On the other hand, in the direct-injection type, when the gaseous fuel is mixed with the surrounding atmosphere and diluted, concentration unevenness is likely to occur. Therefore, the possibility of abnormal combustion is greater than in the premixed injection type. However, in the case of comprehensive evaluation including equipment costs, direct injection of city gas is the most advantageous.

  Further, in the present invention, the gaseous fuel supply device causes the gaseous fuel to be discharged into the atmosphere at a high speed above the charging layer, thereby mixing with the surrounding air in a short time, and the combustion possessed by the gaseous fuel. The reason why it is necessary to dilute to a concentration below the lower limit concentration and then introduce the diluted gaseous fuel into the charge layer is as follows.

  As shown in FIG. 7 (a), a sintered pan having an inner diameter of 300 mmφ × a height of 400 mm is filled with a sintered cake, and a nozzle is embedded at a position 90 mm deep from the top of the center of the sintered cake. Table 4 shows the results of measuring the methane gas concentration in the circumferential direction and the depth direction in the sintered cake by blowing 100% methane gas to 1 vol% against air. On the other hand, as shown in FIG. 7B, the results of measuring the distribution of methane gas concentration in the same manner as described above for the case where methane gas is supplied from the position 350 mm above the sintered cake using the same nozzle are shown. This is shown in FIG. From these results, when methane gas was directly introduced 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 and diffuses sufficiently in the lateral direction. From the above results, it is understood that the gaseous fuel is preferably diluted uniformly before being introduced into the charging layer by supplying it into the air above the sintered cake.

  Next, in the present invention, the discharge speed of the gaseous fuel from the slits and nozzles provided in the gaseous fuel supply pipe of the gaseous fuel supply apparatus needs to be discharged at a high speed from the viewpoint of preventing backfire. In this case, it is desirable to discharge at a speed that is at least twice the combustion speed of the gaseous fuel, more preferably at a speed that is at least twice the turbulent combustion speed of the gaseous fuel. That is, in the sintering operation of the present invention, in the sintering pallet, forming a combustion / melting zone, or there is a sintered layer that is being formed, always in the state of having a fire type, above the charging layer, A discharge operation of the gaseous fuel is performed. The gaseous fuel is diluted by the stage of being sucked / introduced into the surface layer of the charging layer to be below the lower combustion limit concentration in the atmosphere, but the possibility of flashback always follows. Therefore, in order to prevent backfire even when the gas fuel is ignited, the discharge speed of the gas fuel is at least twice the combustion speed of the gas fuel, more preferably twice the turbulent combustion speed. It is desirable to discharge at the above speed.

  In order to obtain the discharge speed of the gaseous fuel, it is preferable that the discharge pressure of the gaseous fuel from the nozzle, opening or slit is 300 mmAq or more and less than 40000 mmAq with respect to the atmospheric pressure.

  Moreover, it is preferable that the magnitude | size of the opening part which discharges gaseous fuel from gaseous fuel piping shall be the range of 3-0.5 mmphi. The reason for this is that, as described above, in order to prevent backfire to the gaseous fuel, it is preferable to set the discharge speed of the gaseous fuel to a speed exceeding the combustion speed, but if the opening area of the discharge section is large, the ignition will occur. In this case, it is difficult to extinguish the fire and there is a possibility of causing a backfire. However, if the nozzle diameter is about 3 mmφ or less, it has been found that the backfire does not occur even if ignited. Preferably, it is 2 mmφ or less. On the other hand, from the viewpoint of preventing backfire, the smaller the hole diameter, the better. However, considering the prevention of clogging of the opening and workability, the lower limit of the hole diameter is preferably about 0.5 mmφ.

  For the direction in which the gaseous fuel is discharged into the air, various forms can be adopted. For example, as shown in FIG. 8, the gaseous fuel is discharged downward (vertically downward) toward the charging layer. In this way, a part of it is reflected on the surface of the charging layer and diluted, and as shown in FIG. 9, gaseous fuel is introduced into the charging layer by discharging it parallel (horizontal direction) to the surface of the charging layer. Make the path to reach longer and mix with air. A method of promoting dilution, or a method of promoting dilution by discharging gaseous fuel toward a baffle plate (reflecting plate) as shown in FIG. 10, and a gaseous fuel supply pipe as shown in FIG. Adopting a method that promotes dilution by dispersing the gas discharge slit, opening or nozzle provided on the surface of the charging layer in multiple directions within the range of ± 90 degrees with respect to the vertical direction. can do. Furthermore, as a modification of the above FIG. 11, a structure can be adopted in which the gas fuel supply pipe can be rotated around the axis and the discharge direction can be swung.

  In addition, it is preferable to perform discharge of the gaseous fuel in the said gaseous fuel supply apparatus at the height of 300 mm or more above the charging layer surface. Fig. 12 shows the expansion of methane gas when methane gas (concentration: 100%) is discharged from two types of nozzles with a nozzle diameter of 2 mmφ and 1 mmφ in a flow rate range of 20 to 300 m / s and discharged vertically downward. This shows the spread at positions 0.2 m, 0.4 m, 0.6 m and 0.8 m from the nozzle tip. From these figures, the smaller the nozzle diameter and the higher the speed of the gaseous fuel to be discharged, the easier the mixing with the surrounding air occurs, and the dilution is promoted. It can be seen that the distance from the nozzle tip increases at 0.4 m. Therefore, the present invention considers this result and the rebound of the discharged gaseous fuel on the charged layer surface, and the gaseous fuel is supplied to the atmosphere at a height of 300 mm or more above the charged layer surface. To do.

  Further, as described above, the faster the discharge speed is, the higher the speed of the gaseous fuel to be discharged, since the more easily mixing with the surrounding air occurs and the dilution is promoted. Furthermore, when the gaseous fuel supplied from the gaseous fuel supply device is ignited by some kind of fire, if the flow rate of the gaseous fuel discharged from the nozzle or the like is slow, backfire occurs, and the gaseous fuel supply device or the gaseous fuel supply pipe May cause explosion or combustion. In order to avoid this danger, it is preferable to discharge at a rate twice or more the combustion rate of the gaseous fuel used. More preferably, the speed is twice or more the turbulent combustion speed of the gaseous fuel. Incidentally, the laminar combustion speed of methane gas is about 0.4 m / s, and the turbulent combustion speed is about 4 m / s.

Next, countermeasures for cross wind in the gaseous fuel supply apparatus of the present invention will be described.
As described above, the gaseous fuel supplied to the atmosphere above the charging layer from the gaseous fuel supply device is diluted and then sucked in by the wind box disposed below the pallet, and the entire amount is usually ambient. However, when the wind speed is increased, especially when the wind speed increases, the supplied gaseous fuel is caused to flow in the machine side direction. End up. FIG. 13 shows the result of analyzing the influence of crosswind on the concentration distribution of gaseous fuel in the case of wind speeds of 2 m / s and 5 m / s. From this result, it can be seen that when no measures are taken, even if the cross wind is 2 m / s, the gaseous fuel is dissipated and the concentration distribution of the gaseous fuel introduced into the charging layer is adversely affected. .

  Therefore, in order to reduce the influence of the cross wind, the effect of installing the vertical 2m-height on both sides of the gaseous fuel supply device was analyzed, and the result is shown in FIG. 14 for the wind speed of 5 m / s. It was. Fig. 14 (a) shows the result when a 2m high vertical plate is installed. At a wind speed of 5m / s, a vortex flow is formed inside the vertical frame and the gas fuel is dissipated. I can't understand. FIG. 14 (b) shows the result when the upper part 1m with a height of 2m is made of a material with a porosity of 30%. By providing the gap, the formation of air vortices is suppressed, and the gas It can be seen that fuel dissipation can be prevented.

  From the above analysis results, in order to prevent the dissipation of gaseous fuel due to crosswind, it is effective to install on the both sides of the gas fuel supply device what has a vertical wind prevention effect. It has been clarified that the formation of vortices due to the installation of can be reduced by providing a gap of about 30% in terms of area ratio.

  Furthermore, the inventors examined the suppression of the influence of cross wind by providing a hood above the gaseous fuel supply device. As a result, it was found that the installation of the hood is more effective than a fresh wind as a measure against crosswinds. However, this hood must have an opening in the upper central portion or a structure having a suitable transmittance (voidage) and can take in air from this portion. Thereby, it is for mixing with the gaseous fuel discharged from the gaseous fuel supply piping inside the hood, and making it a diluted gaseous fuel. In the case of a sintering machine having a pallet width of 5 m, if the opening is about 1 m, the pressure loss of the hood can be almost ignored. Moreover, when providing a space | gap in an opening part, if the transmittance | permeability was about 80%, it turned out that it can suppress to the pressure loss of about several mmAq. In addition, by installing a baffle plate in the hood, it has the effect of suppressing vortex flow in the hood, and the void ratio in the upper part of the hood (periphery) is most effective in the range of 30-40%. It was found from the results of the analysis.

  Further, a gap is inevitably generated between the lower end of the hood and the surface of the sintered bed (sintered layer surface), but if the gap is not sufficiently sealed, for example, the transmittance is 20 to 30%. In some cases, it was found that air was engulfed into the hood from this part, and the concentration distribution of the gaseous fuel was increased. Therefore, it is important to prevent intrusion of air from the lower end of the hood, between the lower end of the hood and the sintered bed surface, or between the lower end of the hood and the pallet sidewall, as shown in FIG. It is preferable to install a sealing material such as a wiper seal or a seal brush, to install a close seal, or to install an air curtain as shown in FIG. The sealing material is preferably heat-resistant and flexible or has a high degree of freedom of deformation and does not damage the surface of the sintered layer.

  The result of analyzing the effect of the hood using a numerical fluid analysis code (program) by the finite volume method in the case where there is a cross wind of 5 m / s will be described. FIG. 17 shows the gaseous fuel supply apparatus used for the calculation and the hood provided above it. The pallet width of the sintering machine is 5 m, and the gas blowing pipes for discharging gaseous fuel are arranged at a height of 500 mm above the sintered ore bed (charging layer) at intervals of 600 mm and parallel to the pallet traveling direction. The gas blowing pipe and the upper part thereof are provided with a rectifying plate, the upper part thereof is provided with a hood, and the upper central part has an opening having a width of 1000 mm (the porosity is 100% and 80%). The structure is provided with calculation for the case. Further, the side of the hood has a transmittance for attenuating the crosswind (where a non-permeability fence is used, a vortex is formed downstream of the fence, which is undesirable. For the purpose of suppressing the formation of the film, the transmittance is preferably 30 to 40%.) A fence is provided, and the transmittance at the lower end of the hood is set to 20% on the assumption that a chain curtain is installed.

  FIG. 18 shows an analysis result of the concentration distribution of the gaseous fuel. From this result, the concentration distribution of the gaseous fuel is improved by making the upper part of the side wall of the hood an inclined structure and narrowing the upper part of the hood, and the difference between the case where the porosity of the opening is 100% and that of 80% is small It can be seen that the generation of the vortex is suppressed by the installation of the current plate. FIG. 19 shows the analysis result of the pressure distribution. It can be seen that the pressure loss due to the inclined structure above the hood is small, and the generation of vortex is suppressed by the installation of the rectifying plate. FIG. 20 shows the analysis result of the gas flow velocity distribution. From this, it can be seen that if there is a permeability at the lower end of the hood, a drift occurs due to the inflow of air. Further, FIG. 21 shows a vector diagram of the gas flow velocity, and it can be seen that the vortex is suppressed by the inclined structure of the upper portion of the hood and the installation of the current plate.

  Further, what can be said in common from FIGS. 18 to 21 is that even if a hood is installed, there is a difference in the amount of air involved between the windward and leeward, and it is necessary to take another means to solve this problem. I found out that As this means, it is effective to change the discharge amount of the gaseous fuel on the upstream side and the downstream side, or to further increase the throttle above the hood than the above calculation model.

  Next, based on the above knowledge, an application example of the cross wind prevention measure provided in the gaseous fuel supply device of the actual sintering machine will be described. FIG. 22 shows an example thereof, a hood having an opening on the top is installed above the gas supply device, and a fence with a transmittance of 30% for preventing vortex formation is installed on the top, This shows an example in which a chain curtain (wipe seal) for preventing cross wind intrusion from the gap between the hood and the pallet is suspended at the lower end of the hood, and further, a rectifying plate is installed on the gas blowing pipes at both ends. FIG. 23 is a modified example of FIG. 22 and shows an example in which a rectifying plate is installed along the gaseous fuel supply pipe in the hood. FIG. 24 shows an example in which the upper part of the hood of FIG. 23 is opened and a current plate is installed instead. In addition, it is preferable to change suitably the installation space | interval of the said baffle plate. FIG. 25 is an example in which the upper part of the hood of FIG. 24 is completely opened and only the current plate is installed upward, and FIG. 26 is for promoting the mixing of the current plate and the gaseous fuel in the hood. Shows an example of using a baffle plate together. Further, the above-described cross wind prevention measure of FIG. 17 may be applied. All of the hoods exemplified above have an effect of suppressing the influence of crosswind.

In the present invention, as the gaseous fuel, it is preferable to use the gaseous fuel diluted to 75% or less of the lower limit concentration of combustion at normal temperature in the atmosphere, and more preferably as the gaseous fuel. A product diluted to a concentration of 60% or less of the lower limit of combustion and more preferably 25% or less of the lower limit of combustion is used. There are two reasons for using the combustible gas diluted to 75% or less below the lower combustion limit concentration.
(A) The supply of the combustible gas as it is to the upper part of the charging layer may sometimes cause explosive combustion, and at least at room temperature, it is necessary to make it not burnable even if there is a fire type.
(B) Even if it reaches an electric precipitator or the like downstream of the wind box without being completely burned in the charging layer, there is no need to be burned by the discharge of the electric precipitator. It is.

In addition, as will be described later, the concentration of the diluted gas fuel is such that the shortage of air (oxygen) necessary for the combustion of the total carbonaceous material (solid fuel + gas fuel) in the sintering raw material does not cause shortage of combustion. It is necessary to use a diluted product.
However, the diluted gas fuel preferably has a concentration of 2% or more of the lower combustion limit concentration. This is because when the concentration is less than 2%, the strength of the sintered ore and the yield cannot be improved even by heat generated by combustion. Moreover, it is preferable to adjust the density | concentration of diluted gas fuel according to the amount of carbonaceous materials (solid fuel). Furthermore, the diluted gas fuel can cause combustion at a predetermined position in the charging layer by adjusting the concentration.

In the method for producing a sintered ore according to the present invention, after the carbon material in the charging layer is ignited, diluted gaseous fuel is supplied (introduced) into the charging layer. The reason is that even if the diluted gas fuel is supplied at a position immediately after ignition, it only burns on the surface layer of the charging layer, and does not affect the sintered layer. Therefore, it is necessary to supply diluted gas fuel to the charging layer after the sintering raw material at the upper part of the charging layer is fired to form a sintered cake layer. The diluted gas fuel can be supplied at an arbitrary position until the sintering is completed as long as the sintered cake layer is formed on the surface of the charging layer. The reasons other than the above, in which the diluted gas fuel is supplied after the sintered cake layer is formed, are as follows.
(A) If the diluted gas fuel is supplied in a state where no sintered cake is formed on the top of the charging layer, there is a risk of causing explosive combustion on the charging layer.
(B) It is preferable to supply the diluted gas fuel to a portion where it is necessary to improve the yield of the sintered ore, that is, to supply combustion in a portion where the strength of the sintered ore is desired to be increased.

  In order to adjust either or both of the maximum reached temperature of the charging layer and the high temperature region holding time, the thickness of the combustion / melting zone is at least 15 mm or more, preferably 20 mm or more, more preferably 30 mm or more, It is preferable to supply the diluted gas fuel. When the thickness of the combustion / melting zone is less than 15 mm, the cooling effect by the air sucked through the sintered layer (sintered cake) and the diluted gas fuel makes the effect insufficient even if the gas fuel is burned, and combustion / melting. This is because the thickness of the belt cannot be increased. On the other hand, if the diluted gas fuel is supplied at a stage where the thickness of the combustion / melting zone is 15 mm or more, preferably 20 mm or more, more preferably 30 mm or more, the thickness of the combustion / melting zone is greatly expanded, and the high temperature region holding time is increased. It can be extended, and as a result, a sintered ore with high cold strength can be obtained.

  The thickness of the combustion / melting zone can be confirmed using, for example, a vertical tubular test pan with a transparent quartz window. This test pan is an effective means for determining the supply position of the diluted gas fuel.

  Further, the introduction of the diluted gas fuel into the charging layer is performed at a position where the combustion front is lowered below the surface layer and the combustion / melting zone is lowered by 100 mm or more, preferably 200 mm or more from the surface layer, that is, the middle / lower layer region of the charging layer. It is preferable to carry out for the target. That is, the diluted gas fuel passes through the sintered cake region (sintered layer) generated in the surface layer of the charging layer without burning, and is supplied so as to burn when the combustion front moves 100 mm or more from the surface layer. Is preferred. The reason is that if the combustion front is at a position lower than the surface layer by 100 mm or more, the adverse effect of cooling by the air sucked through the sintered layer is reduced, and the thickness of the combustion / melting zone can be increased. . Furthermore, if it is a position 200 mm or more lower than the surface layer, the influence of cooling by air is almost eliminated, and the thickness of the combustion / melting zone can be expanded to 30 mm or more. Further, it is more preferable to supply the diluted gas fuel in the vicinity of the sidewalls at both ends in the pallet width direction where the yield is greatly reduced.

In addition, although the diluted gaseous fuel production | generation apparatus changes with scales of a sintering machine, for example, gaseous fuel supply amount is 1000-5000m < ³ > (standard) / h, and a production amount is about 15,000 t / day, In a sintering machine having a length of 90 m, it is preferable that the sintering machine is disposed at a position about 5 m or less downstream of the ignition furnace.
In the manufacturing apparatus according to the present invention, the supply position of the diluted gas fuel (introduction position to the charging layer) is the ignition furnace exit side in the pallet traveling direction, and the so-called combustion front after the sintered cake is formed is below the surface layer. It is preferable to carry out at one or more arbitrary positions from the advanced position (for example, the position where combustion of gaseous fuel occurs below 100 mm, preferably about 200 mm or less below the surface layer) to the completion of sintering. This means that, as described above, the introduction of the gaseous fuel starts when the combustion front moves below the surface of the charging layer, and as a result, the combustion of the gaseous fuel is started in the charging layer. Since it occurs inside and gradually moves to the lower layer, it means that there is no risk of explosion and a safe sintering operation becomes possible.

  In the production method according to the present invention, the introduction of the diluted gas fuel into the charging layer also means that the reheating of the produced sintered cake is promoted. That is, this diluted gaseous fuel is originally supplied with a highly reactive gaseous fuel compared to the solid fuel to the portion where the cold strength of the sintered ore is low and the cold strength of the sintered ore is likely to be short of heat. This is because the heat of combustion in this portion that is likely to be deficient is compensated for, and the regeneration / expansion of the combustion / melting zone is assumed.

  In the method for producing sintered ore according to the present invention, the supply of the diluted gaseous fuel from the upper part of the charged layer after ignition is such that at least a part of the introduced diluted gaseous fuel in the charged layer remains unburned. It is preferable to reach the combustion / melting zone and burn at a target position where combustion heat is to be compensated. It is considered that it is more effective to supply the diluted gas fuel, that is, to introduce the effect into the charging layer not only to the upper part of the charging layer but also to the combustion / melting zone which is the central part in the thickness direction. Because. In other words, if the supply of gaseous fuel is performed in the upper layer of the charging layer, which tends to be short of heat (insufficient holding time in the high temperature range), sufficient combustion heat will be provided. The quality can be improved, and further, if the supply operation of the diluted gas fuel is extended to the zone below the middle layer, the recombustion / melting zone with the diluted gas fuel is added to the combustion / melting zone with the original carbonaceous material. This results in equal expansion of the combustion / melting zone in the vertical direction, so it is possible to extend the holding time of the high temperature range without increasing the maximum temperature, so the pallet movement speed can be increased. This is because sufficient sintering can be realized without dropping. As a result, the quality of the sintered cake of the entire charged layer is improved (improving the cold strength), and consequently the quality (cold strength) and productivity of the product sintered ore are improved.

  The present invention has a first feature in that the supply position of the diluted gas fuel is determined from the viewpoint of where in the charging layer the operation / effect of the supply is exerted. The second characteristic is in how much the maximum reachable temperature and the high temperature region holding time in the charging layer are controlled in accordance with the amount of the solid fuel under the constant heat quantity as well as the supply.

  Therefore, in the present invention, when the diluted gas fuel is introduced (supplied) into the charging layer, not only the supply position is adjusted, but also the form of the combustion / melting zone itself is controlled, and thus It is preferable to control the maximum temperature reached in the melting zone and / or the high temperature region holding time.

  In general, in the charged layer after ignition, the combustion (flame) front gradually expands downward and forward (downstream) as the pallet moves, and the position of the combustion / melting zone is shown in FIG. ). And as shown in FIG.4 (b), the thermal history received in the sintering process in a sintered layer differs in an upper layer, a middle layer, and a lower layer, and it is high temperature range holding time (about 1200 degreeC or more with an upper layer-a lower layer). Time) is very different. As a result, the yield of sintered ore by position in the pallet shows a distribution as shown in FIG. That is, the yield of the surface layer portion (upper layer portion) is low, and the yield distribution is high in the middle layer and the lower layer portion. Therefore, when the gaseous fuel is supplied according to the method of the present invention, the combustion / melting zone has an increased thickness in the vertical direction, a width in the pallet traveling direction, and the like, which are reflected in improving the quality of the product sintered ore. And since the intermediate | middle layer part and lower layer part which become high yield distribution can control high temperature range holding time, it can raise a yield more.

  By adjusting the supply (introduction) position of the gaseous fuel, it is possible to control the form of the combustion / melting zone, that is, the thickness in the height direction of the combustion / melting zone and / or the width in the pallet traveling direction, and reach the maximum. The temperature and the high temperature range holding time can be controlled. These controls make the effects of the present invention stand out more and are always sufficient through expansion of the vertical thickness of the combustion / melting zone and the width of the pallet traveling direction, and control of the maximum temperature reached and the high temperature range holding time. Performs firing and contributes effectively to improving the cold strength of the sintered product ore.

  In the present invention, it can also be said that the supply (introduction) of the diluted gas fuel into the charging layer is for controlling the cold strength of the entire product sintered ore. In other words, the original purpose of supplying diluted gaseous fuel is to improve the cold strength of the sintered cake, and thus the sintered ore. Through the control of the high temperature range holding time, which is the time to stay in, and the control of the maximum temperature, the cold strength (shutter index SI) of the sintered ore is about 75 to 85%, preferably 80% or more, more preferably 90% or more Is to do.

  In the present invention, this strength level is particularly determined in consideration of the concentration of the diluted gas fuel, the supply amount, the supply position, and the supply range of the carbonaceous material in the sintered raw material (under the condition that the input heat amount is constant). By adjusting above, it can be achieved inexpensively. On the other hand, the improvement of the cold strength of sintered ore may lead to an increase in ventilation resistance and a decrease in productivity. In the present invention, such problems are also controlled by controlling the maximum temperature and holding time in the high temperature range. In order to solve this problem, the cold strength of the sintered ore is improved. In addition, the cold strength SI value of the sintered ore manufactured by the real machine sintering machine shows a value 10-15% higher than the value obtained by a pan test.

  In the production method of the present invention, the introduction position of the diluted gas fuel into the charging layer in the pallet traveling direction is a sintered ore in an arbitrary zone between the sintered cake formed in the charging layer and the wet zone. It is based on how to make the cold strength of. For this control, in the present invention, the scale (size), number, position (distance from the ignition furnace), gas concentration of the gaseous fuel supply device, preferably the amount of carbonaceous material (solid fuel) in the sintered raw material By adjusting according to the above, not only the size of the combustion / melting zone (the thickness in the vertical direction and the width in the pallet traveling direction) but also the high temperature reached temperature and the high temperature range holding time are controlled. Controls the strength of the sintered cake formed in the charge layer.

  In the above production method of the present invention, the gaseous fuel supplied into the charging layer is blast furnace gas, coke oven gas, blast furnace / coke oven mixed gas, city gas, natural gas or methane gas, ethane gas, propane gas, butane gas, or It is preferable to use one of these mixed gases. Each of these contains a combustion component, and any one of these gaseous fuels is discharged into the air at high speed, mixed with air and diluted to obtain a diluted gaseous fuel having a combustion lower limit concentration of about 75% or less. Supply (introduction) into the charging layer.

  Furthermore, in the present invention, as the gaseous fuel supplied into the charging layer, in addition to the gaseous fuel, the ignition temperature in the gaseous state is higher than the temperature of the surface layer of the sintered bed, alcohols, ethers, petroleums, etc. It is also possible to use a vaporized liquid fuel such as hydrocarbon compounds. Table 6 shows liquid fuels that can be used in the present invention and their characteristics. Since the gas fuel vaporized from such a liquid fuel has an ignition temperature higher than that of the gas fuel described above, it burns inside the charging layer, which is higher than the temperature of the sintered bed surface layer, It is effective for expanding the temperature of the burning / melting zone at the blowing position. In particular, the effect is large when the ignition temperature is close to 500 ° C. 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 the present invention, among the gaseous fuels, those having a CO content of 50 massppm or less are preferably used. That is, CO gas is harmful to the human body, and if gaseous fuel supplied onto the charging layer is not introduced into the charging layer in its entirety, it may cause human injury if it leaks out of the machine. Because there is. Specifically, the use of city gas 13A or propane gas is preferable from the viewpoint of cost as well as safety.

  Further, in producing sintered ore by the method of the present invention, a pallet that circulates and a raw material supply device that forms a charged layer by charging a sintered raw material containing fine ore and carbonaceous material onto the pallet. And an ignition furnace for igniting the carbonaceous material in the sintering raw material, and a sintering machine provided with a wind box below the pallet, the gaseous fuel is placed on the downstream side of the ignition furnace and the gaseous fuel is air above the charging layer. A sintering machine is used, which is provided with a gaseous fuel supply device that is supplied into the dilute gaseous fuel below the lower combustion limit concentration and then introduced into the charging layer.

  The gaseous fuel supply device in the sintering machine of the present invention is preferably disposed so as to straddle both side walls of the pallet along the width direction of the sintering machine. The gaseous fuel supply apparatus has a plurality of, preferably 3 to 15, pipes for supplying gaseous fuel arranged in parallel or perpendicular to the pallet traveling direction, and each pipe has a gas It is preferable to be configured by a plurality of slits, ejection holes, or nozzles for supplying fuel at high speed to the atmosphere.

  One or more of the gaseous fuel supply devices are disposed downstream of the ignition furnace and at any position in the pallet moving direction in the process in which the combustion / melting zone advances in the charging layer, and enters the charging layer. It is preferable that the gaseous fuel is supplied at a position after ignition of the carbonaceous material in the charging layer. In other words, one or more devices are installed at any position after the combustion front advances below the surface layer on the downstream side of the ignition furnace. From the viewpoint of adjusting the strength, the size, position, and number are determined. In addition, this gaseous fuel supply device is disposed at a low yield position near both sidewalls, and the gaseous fuel is 75% or less and 2% or more of the lower combustion limit concentration, or 60% or less of the lower combustion limit concentration. Further, it is preferable to use a combustible gas diluted to a concentration of 2% or more, or 25% or less of the lower combustion limit concentration and 2% or more.

  FIG. 27 shows one embodiment of the sintered ore manufacturing apparatus according to the present invention, but the present invention is not limited to this illustrated embodiment. In the example shown in FIG. 27, gaseous fuel such as a mixed gas (M gas) of blast furnace gas and coke oven gas is discharged into the atmosphere on the upper side of the charging layer corresponding to the downstream side in the pallet traveling direction of the ignition furnace 10. In addition, only one gaseous fuel supply device 12 for providing a diluted gaseous fuel having a desired concentration is disposed. The gaseous fuel supply device 12 is provided with a plurality of gaseous fuel supply pipes 12a along the width direction of the pallet, and a nozzle 12b that discharges gaseous fuel into the atmosphere at a high speed is directed downward in the pipe and the pallet width. A plurality of elements arranged in the direction are arranged so as to cover the charging layer from above a sidewall (not shown). The M gas supplied from the gaseous fuel supply device 12 is mixed with surrounding air to become diluted gaseous fuel, and then, using the suction force of a wind box (not shown) under the pallet 8, the M gas is supplied. It is introduced into the deep part (lower layer) of the charging layer through the sintered cake generated on the surface layer from the upper part of the layer. This gaseous fuel supply device 12 can supply a large amount of gaseous fuel near both side walls of the pallet, particularly when it is desired to improve the yield at both ends of the pallet (region of 60% yield in FIG. 4 (c)). As described above, it is preferable to place the nozzle 12a in a focused manner.

  Examples of the gaseous fuel supplied from the gaseous fuel supply device 12 include blast furnace gas (B gas), coke oven gas (C gas), mixed gas of blast furnace gas and coke oven gas (M gas), city gas, natural gas Gas (LNG), methane, ethane, propane, butane gas, or a mixed gas thereof is used. These gaseous fuels may be supplied under a piping system that is independent from the ignition furnace 10, and as the same type as the fuel pipe for the ignition furnace, a gas supply pipe (not shown) to the ignition furnace 10. ) May be connected on the extension.

Table 7 below shows the lower combustion limit concentrations of various gaseous fuels used in the present invention and the upper blowing concentration of the gaseous fuel (75%, 60%, 25% of the lower combustion limit concentration).
For example, since propane gas has a lower combustion limit concentration of 2.2 vol%, the gas concentration upper limit diluted to 75% is 1.7 vol%, and the gas concentration upper limit diluted to 60% is 1.3 vol%, diluted to 25%. The gas concentration used is 0.6 vol%. Accordingly, the preferred range is as follows. Note that the lower limit of the diluted gas concentration, that is, the lower limit concentration at which the effect of supplying gaseous fuel is manifested is 0.05 vol% in the case of propane gas.
Preferred range (1): 2.2 vol% to 0.05 vol%
Preferred range (2): 1.7 vol% to 0.05 vol%
Preferred range (3): 1.3 vol% to 0.05 vol%
Preferred range (4): 0.6 vol% to 0.05 vol%

In addition, since the lower limit concentration of combustion for C gas is 5.0 vol%, the upper limit of gas concentration diluted to 75% is 3.8 vol%, and the upper limit of gas concentration diluted to 60% is 3.0 vol%, diluted to 25%. The gas concentration used is 1.3 vol%. Accordingly, the preferred range is as follows. In the case of C gas, the lower limit concentration at which the effect of supplying gaseous fuel is manifested is 0.24 vol%.
Preferred range (1): 5.0 vol% to 0.24 vol%
Preferred range (2): 3.8 vol% to 0.24 vol%
Preferred range (3): 3.0 vol% to 0.24 vol%
Preferred range (4): 1.3 vol% to 0.24 vol%

LNG gas has a combustion lower limit concentration of 4.8 vol%, so the upper limit of gas concentration diluted to 75% is 3.6 vol%, and the upper limit of gas concentration diluted to 60% is 2.9 vol%, diluted to 25%. The gas concentration is 1.2 vol%. Accordingly, the preferred range is as follows. The lower limit concentration at which the effect of supplying the gaseous fuel of LNG gas is 0.1 vol%.
Preferred range (1): 4.8 vol% to 0.1 vol%
Preferred range (2): 3.6 vol% to 0.1 vol%
Preferred range (3): 2.9 vol% to 0.1 vol%
Preferred range (4): 1.2 vol% to 0.1 vol%

In addition, since the lower limit concentration of blast furnace gas is 40.0 vol%, the upper limit of gas concentration diluted to 75% is 30.0 vol%, and the upper limit of gas concentration diluted to 60% is 24.0 vol%, diluted to 25%. The gas concentration used is 10.0 vol%. Accordingly, the preferred range is as follows. Note that the lower limit concentration at which the effect of supplying the gaseous fuel of the blast furnace gas is 0.24 vol%.
Preferred range (1): 40.0 vol% to 1.25 vol%
Preferred range (2): 30.0 vol% to 1.25 vol%
Preferred range (3): 24.0 vol% to 1.25 vol%
Preferred range (4): 10.0 vol% to 1.25 vol%

  Next, Table 8 shows the contents and heat values of hydrogen, CO, methane, ethane, and propane contained as combustion components in C gas, LNG, and B gas.

Hereinafter, an experiment that has become an opportunity to develop a method for producing a sintered ore according to the present invention will be described.
This experiment uses the experimental apparatus shown in FIG. 28, that is, a bowl-shaped tubular test pan (150 mmφ × 400 mmH) with a transparent quartz window, and a mixed gas of blast furnace gas and coke oven gas (M gas) ), And using the same sintering raw material as used in the applicant's company's sintering factory, that is, the sintering raw material shown in Table 9, a sintering pot test at a constant downward suction pressure of 11.8 kPa This is an example. Here, the concentration of the combustion component of the M gas was diluted with air and varied within the range of 0.5 vol-15 vol%. In addition, the combustion minimum concentration of M gas used for this experiment is 12 vol%.

  FIG. 28 also shows a video observation of the combustion melting zone from the transparent quartz window of the test pan, and particularly shows the descending state of the combustion zone accompanying the movement of the combustion front. As can be seen from this figure, when gaseous fuel containing 15 vol% M gas exceeding the lower combustion limit concentration (12 vol%) is blown into the raw material deposit layer in the test pan, the gaseous fuel burns immediately on the charged layer surface. The effect of blowing was not obtained because it did not reach the lower layer of the charging layer. On the other hand, according to the present invention, when gaseous fuel diluted with air to 3 vol%, which is 75% or less of the lower limit concentration of combustion (12 vol%) of the gaseous fuel, is used, it does not burn on the surface of the raw material deposition layer. , It reached the combustion layer and reached the region corresponding to the combustion / melting zone and burned. As a result, the thickness of the combustion zone (also called the combustion / melting zone) when sintered with only air was 70 mm, whereas the thickness width of the combustion zone when diluted with M gas was used. Can be enlarged to 150 mm, that is, twice or more. This increase in the thickness of the combustion zone also means that an extension of the high temperature region holding time is achieved.

  In addition, in the experiment using this test pan, the descent rate of the combustion zone corresponding to the traveling speed of the combustion front accompanying the movement of the pallet in the actual sintering machine (the reciprocal is the sintering time) is the supply of diluted gas fuel. In addition, the thickness of the combustion zone in the vertical direction could be increased in the same way as when coke was increased or hot air was blown. In this way, when the appropriately diluted gaseous fuel is injected into the charging layer of the sintering raw material, the combustion band width is smaller than when using solid fuel, liquid fuel, and undiluted combustible gas. It has been found that the expansion effect of is increased, and the rate of descending the combustion front is not reduced as in the case of increasing the amount of coke, and the speed is almost the same as in the case of atmospheric sintering.

  FIGS. 29A to 29D summarize the results of the sintering pot test. According to this result, when appropriately diluted M gas was blown into the raw material charging layer according to the present invention, the yield was slightly improved although the sintering time hardly changed (FIG. 29 (a )), And the sintering productivity is also increasing (FIG. 29 (b)). In addition, the shutter strength (SI), which is a cold strength management index that greatly affects the operating results of the blast furnace, has improved by 10% or more (Fig. 29 (c)), and the reduction powdering property (RDI) has improved by 8%. (FIG. 29 (d)).

  In the present invention, a diluted combustible gas is used as the gaseous fuel introduced into the charging layer. The degree of dilution will be described below. Table 10 shows the combustion lower limit concentration and the combustion upper limit concentration of blast furnace gas, coke oven gas, and a mixed gas (M gas), propane, methane, and natural gas. For example, when a gas having such a combustion limit goes to the exhaust fan without burning in the charging layer, there is a risk of explosion or combustion in an electric dust collector on the way. Therefore, as a result of trial and error, the inventors decided to introduce gaseous fuel diluted to a concentration at which there is no danger, that is, a concentration below the lower limit of combustion, into the charging layer, and to further improve safety, As a result of many experiments using diluted gas fuel having a concentration of 75% or less of the lower combustion limit concentration, it was confirmed that no problem occurred.

  For example, as shown in Table 10, the concentration range in which the blast furnace gas burns at room temperature in the atmosphere has a combustion lower limit of 40 vol% (that is, combustion does not occur below 40 vol%), and the upper combustion limit is 71 vol%. . This means that if it exceeds 71 vol%, the blast furnace gas concentration becomes too high, and in this case also, no combustion occurs. Below, the basis of this numerical value is demonstrated based on drawing.

FIG. 30 shows an example of a method for obtaining the combustion limit of blast furnace gas. The ratio of the combustion component (combustible gas) and other (inert: inert gas) contained in the blast furnace gas in the figure is as follows when examined in combination with H ₂ and CO ₂ and CO and N _2. .
(1) The ratio of (inert gas) / (combustible gas) for the combination of the “H ₂ and CO ₂ ” portions is 20.0 / 3.5 = 5.7.
Therefore, a portion where the H ₂ + CO ₂ curve intersects the 5.7 axis (flammability limit) on the horizontal axis indicating the ratio of (inert gas) / (combustible gas) in this combustion limit diagram was obtained. The lower limit is 32 vol%, and the upper limit is 64 vol%. That is, the lower limit of the combustion limit of H ₂ + CO ₂ is 32 vol%, and the upper limit is 64 vol%.
(2) On the other hand, the ratio of (inert gas) / (combustible gas) in the case of the combination of the remaining combustion components “CO and N ₂ ” is 53.5 / 23.0 = 2.3. Similarly, the lower limit: 44 vol% and the upper limit: 74 vol% are obtained from the point where the horizontal axis 2.3 intersects with the curve of CO + N ₂ from FIG. Therefore, the lower limit of the combustion limit in this case is 44 vol%, and the upper limit is 74 vol%.
(3) Furthermore, the lower limit of combustion of the blast furnace gas containing both combustion components can be obtained by the lowermost expression in the left side of FIG. Further, the upper limit of combustion can be obtained by applying the upper limit values of (1) and (2) in the same equation. In this way, the lower limit of combustion and the upper limit of combustion of the blast furnace gas can be obtained.

  In the present invention, another reason for focusing on the lower limit of combustion of gaseous fuel is that the combustion limit has temperature dependence. In the Fuel Handbook (edited by the Japan Fuel Association), as the effect of temperature, the heat dissipation rate slows down when the temperature is high, so the intersection of both the heat generation and dissipation velocity curves becomes deeper and the explosion range ( Explains that the (combustion range) extends to the left and right. That is, although the combustion limit is obtained as described above, the combustion limit has temperature dependence, and as an influence of the temperature of the combustion range of methane gas, Table 11 The example described in is shown. If this is plotted as the temperature dependency of the lower combustion limit concentration, it is as shown in FIG. The mark ● in the figure is an example of methane gas described in Table 11.

  FIG. 32 shows the relationship between the temperature of the combustion component (combustion gas) concentration of gaseous fuel at normal temperature in the atmosphere and the temperature. Although the combustion limit is obtained as described above, the combustion limit is temperature-dependent, and the temperature-dependent tendency is exemplified by the lower limit of combustion at room temperature (corresponding to the combustion gas concentration in the figure). Even if it is approximately 40 vol%, it varies from 26 to 27 vol% in the 200 ° C. region, and it burns even if it is several percent in the 1000 ° C. region and less than 1 vol% in the 1200 ° C. region.

  From this, the concentration of gaseous fuel (combustion component content) supplied to the charging layer is safer if the concentration is lower than the lower limit of combustion at room temperature, and even the concentration of the dilution gas is adjusted to an appropriate range. If it did, it turned out that the freedom degree of the combustion position control of the gaseous fuel in the thickness direction in the charging layer becomes high.

  In this way, combustion of gaseous fuel has temperature dependence, for example, the combustion range becomes wider as the ambient temperature becomes higher, and burns well in the temperature field near the combustion / melting zone of the sintering machine. However, it has also been found that in a temperature field of about 200 ° C., such as in an electrostatic precipitator on the downstream side of the sintering machine, combustion does not occur at the gaseous fuel concentration as shown in the preferred embodiment of the present invention.

  By the way, in the production of sintered ore, the diluted gaseous fuel supplied into the charging layer of the sintering raw material is sucked by the wind box under the pallet, and the solid fuel (powder coke) in the charging layer is burned. It burns in the high temperature region of the combustion / melting zone formed by Accordingly, the supply of the diluted gas fuel can be adjusted by adjusting the amount of the diluted gas fuel, the supply amount, etc. under the condition that the amount of heat input to the charging layer is constant ( Decrease). Further, the adjustment of the concentration of the diluted gaseous fuel means that the combustion of the gaseous fuel is controlled so as to occur at an expected position (concentration region) in the charging layer.

  In this sense, the combustion / melting zone in the charge layer under the prior art is a zone where only solid fuel (powder coke) burns. In the present invention, in addition to the powder coke, further gas It can be said that the fuel is also burned in parallel. Therefore, in the present invention, if the concentration, supply amount, and other supply conditions of the diluted gas fuel are premised on that there is coke breeze as part of the fuel, if it is suitably changed in relation to this, the maximum temperature reached And / or desirable control of the high temperature holding time is possible, leading to improved strength of the sintered cake.

  In the method of the present invention, yet another reason for using the diluted gaseous fuel is to control the strength and yield of the sintered cake through the above-described shape control of the sintering / melting zone. The role of this diluted gas fuel functions effectively in controlling how long the sintered cake is kept in the high temperature zone (combustion / melting zone) and how much temperature is reached. Because it does. In other words, the use of the diluted gas fuel means that the high temperature range holding time of the sintered raw material is long and the maximum attained temperature is controlled to be appropriately high. And such control is diluted according to the amount of solid fuel (powder coke amount) in the sintering raw material so that the amount of supporting gas (air or oxygen) does not become excessive or insufficient in the combustion atmosphere. This means that the adjusted gaseous fuel is used. In this regard, in the prior art, in order to inject the flammable gas without adjusting the concentration of the solid fuel of the sintering raw material, the amount of the flammable gas corresponding to the amount of the solid fuel or the flammable gas ( Since (oxygen) was not supplied, combustion failure occurred, or conversely partial combustion occurred, resulting in variations in strength. That is, the present invention avoids such a problem by diluting the gas fuel and adjusting the concentration.

  Next, the influence of diluted gaseous fuel depending on the type of gaseous fuel will be described. FIG. 33 shows experimental results comparing the sintering method of the present invention using diluted gaseous fuel obtained by diluting several types of gaseous fuels to below the lower combustion limit concentration and the conventional sintering method without blowing gaseous fuel. . In the conventional sintering example in which the diluted gas fuel is not injected, the amount of powder coke added is 5 mass%. On the other hand, in the present invention example in which the diluted gas fuel is injected, the diluted gas fuel equivalent to 0.8 mass% is injected. In order to keep the total heat amount constant, the amount of powder coke added was set to 4.2 mass%. As can be seen from this figure, when diluted gas fuel was used, in any of the examples, improvements in shutter strength, product yield, and productivity were recognized. As described above, in the use example of diluted gas fuel, the reason why the shutter strength, product yield, and the like are improved is considered to be due to the expansion of the combustion / melting zone shown as the combustion state and the extension of the high temperature region holding time. .

  FIG. 34 is a diagram showing the influence of the blown gas concentration when propane gas is used as the gaseous fuel. The concentration of the diluted gaseous fuel, the shutter strength (a), the yield (b), and the sintering time ( c) shows the relationship with the production rate (d). As can be seen from this figure, in the case of propane gas, when this is used as a diluted gas fuel, an effect is produced by adding 0.05 vol% to improve the shutter strength, and the yield is also substantially the same. . A clear effect is obtained from 0.1 vol%, preferably 0.2 vol%, with propane gas. When this result is converted into the case where C gas is used as the blown gas, the effect of C gas is obtained by adding 0.24 vol%, preferably 0.5 vol% or more, and the clear improvement effect is 1.0 vol% or more. Will occur. Therefore, in propane gas, it becomes at least 0.05 vol% or more, preferably 0.1 vol% or more, more preferably 0.2 vol% or more. On the other hand, in C gas, it is at least 0.24 vol% or more, preferably 0.5 vol% or more, more preferably 1.0 vol% or more, and the upper limit is 75% of the lower combustion limit concentration. In the case of propane gas, the effect is almost saturated with the addition of 0.4 vol%, and the gas concentration at this time corresponds to 25% of the lower combustion limit concentration.

  Next, the cold strength and reduced powdering characteristics (RDI) of sintered ore produced by supplying the gaseous fuel in consideration of the amount of carbonaceous material in the sintered raw material according to the method 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 12 shows the values of tensile strength (cold strength) and reducibility of various minerals generated during the sintering process. As is apparent from FIG. 35, in the sintering process, a melt starts to be generated at 1200 ° C., and calcium ferrite having the highest strength among the constituent minerals of the sintered ore and relatively high reducibility is generated. . When the temperature rises further and exceeds about 1380 ° C., it is decomposed 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 improve the cold strength of sintered ore and to improve RDI, it becomes a problem whether calcium ferrite can be stably generated without being decomposed.

  In addition, according to the above-mentioned publication “Mineral Engineering”, the precipitation behavior of secondary hematite, which is the starting point for reducing powderization of sintered ore, is described with reference to FIG. According to the explanation, in the result of the mineral synthesis test, the skeletal secondary hematite that is the starting point of the reduction powdering is Mag. ss + Liq. Since it precipitates after being heated up to the zone and cooled, on the phase diagram, the reduced powdering property can be suppressed by producing the sintered ore through the path (2) instead of the path (1). It is said. Therefore, in order to produce a sintered ore having both a low RDI sintered ore and a high-strength sintered ore, the range is 1200 ° C. (solidus temperature of calcium ferrite) and about 1380 ° C. (transition temperature). It is important how to realize a heat pattern held for a long time in the charging layer. Therefore, it is important to adjust the amount of carbon material to be added by supplying gaseous fuel so that the maximum temperature reached in the charging layer is in the range of 1200 ° C. to less than 1380 ° C., preferably in the range of 1205-1350 ° C. It turns out that it is desirable to do.

  Next, in order to know the relationship between the vertical thickness (width) of the combustion zone and the diluted fuel gas, the inventors used a vertical tubular test pan with a window made of transparent quartz, and the exhaust gas from the sintering machine cooler. An experiment was conducted in which the propane gas diluted in step 1 was blown into the charging layer of the sintering raw material from above the pan. The sintering raw material used in this experiment is a general one used by the applicant company, and the suction pressure is set at a constant 1200 mmAq. In this experiment, the propane gas to be blown was diluted to a concentration of 0.5 vol% and 2.5 vol%. In terms of the amount of heat input, 0.5 vol% propane gas blowing substantially corresponds to 1 mass% compounding of powder coke.

  FIG. 37 is a photograph showing the result of observing the form of the combustion zone when propane gas was injected in this experiment. As shown in this figure, with propane gas diluted to 2.5 vol%, which is close to the lower combustion limit concentration (theoretical value, against air), the propane gas burns on the raw material charge layer immediately after being blown, and the gaseous fuel enters the charge layer. The effect of gas fuel supply was not obtained. On the other hand, when the propane gas dilution concentration is 0.5 vol% with respect to air, the propane gas enters the charging layer without burning at the upper part of the charging layer, and in the charging layer. Burned at high speed. As a result, the vertical width (thickness) of the combustion zone when sintered under atmospheric conditions was about 70 mm, whereas the width of the combustion zone when such diluted propane gas was injected was 150 mm. More than doubled. This is equivalent to extending the high temperature region holding time.

  Therefore, it has been found that the effect of increasing the thickness of the combustion zone is exhibited even at 0.5 vol%, which is 1/5 of the lower combustion limit concentration of propane. On the contrary, in the gas fuel injection technique according to the present invention, it can be seen that it is difficult to control the combustion in the charging layer unless the gas fuel is diluted.

  Further, in this experiment, the descent rate of the combustion zone (the reciprocal is the high temperature region holding time) was also examined. As a result, when the coke is simply increased or when high-temperature air is blown in, the descent rate is greatly reduced and the productivity is reduced. However, when diluted gaseous fuel is used, the solid fuel is increased. Since the burning rate can be increased as compared with the above example, the descent rate of the burning zone was hardly different from that in the case of atmospheric sintering.

  Next, in order to investigate the influence of the supply position of the diluted gaseous fuel into the charging layer, the inventors used coke oven gas (C gas) diluted to 2% as the gaseous fuel. A sintering pot experiment was performed by changing the blowing position from a surface of the charging layer to a position of 100 to 200 mm, a position of 200 to 300 mm, and a position of 300 to 400 mm, and the result is shown in FIG.

  Here, the blowing position 100 to 200 mm on the horizontal axis in FIG. 38 means that the combustion / melting zone shown brightly (white) in the figure moves from the charged layer surface to the 100 mm position, and above the test pan. This is an example in which dilute gas fuel is blown and burned until the supply of the diluted gas fuel is started and the combustion / melting zone reaches the position of 200 mm. In this case, the combustion / melting zone (in the figure, The result of observing the progress of the combustion / melting zone is bright (white) is shown on the vertical axis. Similarly, the blowing position 200 to 300 mm is an example in which the diluted gas fuel is supplied and burned from the stage where the combustion / melting zone reaches the 200 mm position until it reaches 300 mm, and the blowing position 300 to 300 mm. 400 mm indicates an example in which the diluted gas fuel is supplied and burned from the stage when the combustion / melting zone reaches the 300 mm position until it reaches 400 mm. For comparison, the progress of the combustion / melting zone was also investigated in the case of the conventional method in which the diluted gas fuel was not injected. In addition, since the supply of combustion air in the test pan flows from the top to the bottom in the same manner as in a normal sintering operation, when adding gaseous fuel, gaseous fuel is added to the combustion air to a predetermined concentration, Supplied.

  As can be seen from FIG. 38, when the diluted gas fuel is supplied in the region of 100 to 200 mm from the surface of the charging layer, the thickness of the combustion / melting zone becomes slightly larger than that of the conventional method. It stays. On the other hand, when the diluted gas fuel is supplied in the combustion / melting zone of 200 to 300 mm, the thickness of the combustion / melting zone is clearly increased compared to the conventional method, and the 300 to 400 mm region is also used in the conventional method. It can be seen that there is a clear difference.

  In view of the above, it is preferable that the dilution gas fuel is blown into the portion where the position of the combustion / melting zone is 200 mm or less from the charged layer surface. And about the area | region less than 200 mm from the charging layer surface, even if it does not supply gas fuel forcibly, by supplying gas fuel in the area below 200 mm, the shutter intensity | strength of the sintered ore of this area | region is greatly increased. Since it can improve, the yield of a product sintered ore can be improved as a whole. Therefore, the gas fuel cost can be reduced.

FIG. 39 schematically shows the combustion state of the upper layer part from the charged layer surface to 200 mm and the lower layer part of 200 mm or less. An arrow A shown in this figure indicates the progressing direction (fuel direction) of the sintering, and FIG. 39 (a) indicates the combustion position of the powder coke and gaseous fuel in the upper layer (up to <200 mm). In this case, the combustion zone formed by the powder coke fuel is originally narrow at the top of the charging layer, and the combustion zone of this powder coke and the combustion point of the gaseous fuel combusting in this combustion zone are close to each other. The temperature pattern is as shown on the right side of the figure. In this temperature distribution, the combustion region of the powder coke (solid fuel) is shown as a hatched portion, and the temperature region of the gaseous fuel combusting above it is shown as a non-hatched portion. As can be seen from this figure, in the upper part of the charging layer, coke and gaseous fuel are combusted at the same time (both are close to each other and combust), so that T ₁ and T ₂ in the figure The high temperature range holding time (corresponding to about 1200 ° C.) during the time shown is narrow as shown in the figure. That is, the temperature distribution is such that the coke combustion zone indicated by the hatched portion is slightly expanded. This is because when the gas fuel is supplied into the charging layer preferably after the combustion / melting zone has reached a thickness of 15 mm or more, when the original high temperature region holding time is narrow, This is consistent with the low fuel injection effect.
On the other hand, FIG. 39 (b) shows a case where gaseous fuel is supplied to the middle and lower layers. In the middle and lower layers, the temperature of the charging layer rises as the combustion zone moves downward from the upper layer. The width increases and combustion occurs at a position farther away than in the case of FIG. As a result, the temperature distribution is as shown on the right side of FIG. That is, since the combustion point of the gaseous fuel is far from the solid fuel (coke) combustion point shown by hatching, the synthesized temperature distribution curve has a large temperature distribution. Therefore, the high temperature range holding time based on the combustion of the solid fuel and the gaseous fuel indicated by T ₃ and T ₄ is extended, and the shutter strength of the obtained sintered ore is improved.

  In the case of FIG. 39B, the ignition temperature of the gaseous fuel for controlling (extending) the high temperature region holding time is preferably 400 ° C. to 800 ° C., more preferably 500 ° C. to 700 ° C. The reason for this is that if the ignition temperature is less than 400 ° C., it does not lead to the expansion of the high temperature region, but merely expands the distribution of the low temperature region. This is because the effect of extending the retention time in the high temperature region is small only by causing the maximum reached temperature to rise too much.

  Next, an example of a method for supplying the diluted gas fuel and controlling the maximum temperature (in-layer temperature) in the charging layer will be described. FIG. 40 schematically shows the temperature distribution in the charging layer during sintering, and C gas is used as a reference when the solid fuel (powder coke) is added at 5 mass% corresponding to the conventional sintering method. The sintering method according to the present invention in which the amount of coke is reduced by that amount will be described. Here, the curve a shows the relationship between the in-layer temperature and time of the conventional sintering method in which 5 mass% of coke is added and sintered. Generally, in order to extend the high temperature range retention time, the amount of powder coke used is increased. For example, as shown by the broken line b in the curve when 10 mass% of powder coke is added, Although the retention time in the high temperature range is extended from (0-A) to (0'-B) by increasing the amount, the maximum temperature reached also increases from about 1300 ° C to about 1370 ° C to 1380 ° C. It becomes impossible to obtain a sintered ore with high strength.

  In this respect, in the sintering operation method (curve c) according to the present invention method, the amount of powder coke used is suppressed to 4.2 mass%, while diluting C gas is blown, so that the maximum attained temperature can be suppressed to 1270 ° C. At the same time, the high-temperature region holding time is extended to (0-C), so that the original purpose of producing a low RDI, high-strength sintered ore that could not be realized by the conventional method can be sufficiently fulfilled.

  In short, the conventional sintering method has been an operation method focusing on either the high temperature region holding time or the maximum temperature control. On the other hand, the method of the present invention adjusts the maximum temperature to (1205 to 1350 ° C.) while adjusting the amount of powder coke used (for example, suppressed to 4.2 mass%), while the diluted gas fuel is blown. This is an operation method that also adjusts the high temperature range holding time. Curve d in FIG. 40 shows an example in which the amount of solid fuel used is simply lowered to 4.2 mass%, the maximum temperature reached is low, and the high temperature range holding time is short.

  FIG. 41 shows an example in which 5 mass% of powder coke is used as a conventional sintering method, and dilution C gas is injected as a conforming example of the present invention with a powder coke consumption of 4.2 mass% and a concentration of 2.0 vol%. The combustion situation in the example which used together is shown. As can be seen from the thermovia in this figure, in the conventional method, a combustion state exceeding 1400 ° C. occurs. On the other hand, in the case of the present invention in which the amount of powdered coke used is 4.2 mass% and C gas is blown at a concentration of 2 vol%, the 1400 ° C region disappears and the maximum temperature reached can be suppressed to 1350 ° C or less. At the same time, it can be seen that extension of the high temperature range retention time can be realized.

  FIG. 42 shows changes over time in the temperature in the charging layer (a), the exhaust gas temperature (b), the passing air volume (c), and the exhaust gas composition (d) due to the injection of diluted propane gas under a constant input heat amount condition. Is shown. The temperature in the charging layer is a value measured with a thermocouple charged at a position 400 mm below the charging layer surface (charging layer thickness: 600 mm) in the test pan, and the circumference of the test pan. In the direction, the measurement was performed at two locations 5 mm from the center and the wall. From these figures, by blowing diluted propane gas, the sintering raw material is heated to 1205 ° C or higher, and the melting time (high temperature region holding time) has increased more than twice, but the highest temperature reached Was confirmed not to rise. Further, by blowing propane gas as a diluted gas fuel, the oxygen concentration in the exhaust gas is lowered, and it is assumed that oxygen is efficiently used in the combustion reaction.

FIG. 43 shows the temperature (a), (a ′) in the charge bed and the exhaust gas concentration when diluted propane gas was blown (0.5 vol%) and when the amount of coke was increased (10 mass%). It shows the time-dependent changes of (b) and (b ′). From these figures, when the usage rate of powdered coke is doubled, the high temperature range retention time of 1200 ° C. or higher is almost the same as that when propane gas diluted to a concentration of 0.5 vol% is injected, but the highest temperature reached Is over 1350 ° C. Further, by increasing the amount of powder coke, the CO ₂ concentration in the exhaust gas greatly increases from 20 vol% to 25 vol%, the CO concentration also increases, and the proportion of the powder coke contributing to combustion decreases. It was confirmed.

  Next, a sintering experiment was performed under the conditions shown in Table 13, and the influence on the operation status and the quality of the sintered ore was investigated. Experiment No. No. 1 is the current base condition in which 5 mass% of coke in the sintering raw material is blended. No. 2 reduced powder coke by 1 mass% to 4 mass%, and instead, a constant input heat amount condition in which 0.5 vol% propane gas was blown, No. 3 is a condition in which 10 mass% of powder coke is blended. No. 4 is a condition for injecting a high-temperature gas at 450 ° C. for the purpose of verifying the difference from the heat-retaining furnace (Japanese Patent Laid-Open No. 60-155626).

  FIG. 44 summarizes the results of various characteristic tests in these tests. As is clear from this figure, although the sintering time is slightly extended by dilute propane gas injection, the yield, shutter strength (SI), and production rate are all improved, and reduced powdering property (RDI). The reducibility (RI) has also been greatly improved, and it is possible to improve the production rate and yield as well as to improve the quality of sintered ore by optimizing the injection of diluted gas fuel. confirmed.

  On the other hand, if the powder coke is only increased to 10 mass%, not only will the sintering time be extended, but the maximum temperature will rise more than necessary, so there are many low-strength amorphous silicates. As a result, both the shutter strength and the yield were greatly reduced. Moreover, in the case of blowing a high temperature gas at 450 ° C., the effect of improving the shutter strength and the yield was small, which almost coincided with the results in the conventional commercial facilities.

  As can be seen from the above description, when a diluted gaseous fuel is used, this gas is burned in the charging layer, resulting in the expansion of the combustion zone in the layer, and combustion by coke in the sintering raw material. A wide combustion zone is formed by the synergistic action of heat and the combustion heat of diluted propane gas. As a result, the high temperature range retention time can be extended without excessive increase in the maximum fuel arrival temperature.

  Next, the inventors have examined the effects of dilute gaseous fuel injection on the reducibility of the sintered product ore, cold strength, etc., with the conventional method (5 mass%, 10 mass% coke, hot air injection). The comparison was investigated. The items measured were the mineral composition ratio in the sintered product ore (influence on cold strength and reducibility), apparent specific gravity (influence on cold strength), and pore size distribution of 0.5 mm or less (influence on reducibility) ).

  FIG. 45 shows the results of investigating the composition ratio of the mineral phase in the sintered product ore quantified by the powder X-ray diffraction method. From this figure, it is understood that calcium ferrite is stably generated when solid fuel and diluted propane gas are used in combination with a constant input heat amount (coke 4 mass% + propane 0.5 vol%). And this is considered to bring about an improvement in reducibility and an increase in cold strength.

  FIG. 46 shows the change in apparent specific gravity of the product sintered ore depending on whether or not propane gas was blown. FIG. 47 shows the change in pore size distribution of 0.5 mm or less by a mercury intrusion porosimeter depending on whether or not propane gas was blown. The result of having measured is shown. From FIG. 46, it can be seen that the apparent specific gravity increases due to the injection of diluted propane gas. This is thought to be due to the fact that the melt flow was accelerated as a result of heating from the outside of the granulated particles by blowing propane gas, and the porosity of 0.5 mm or more was lowered. It will contribute to improvement. Moreover, it can be seen from FIG. 47 that the pore diameter distribution of 0.5 mm or less is increased by injecting diluted propane gas with a constant input heat amount. This is because fine pores of 500 μm or less derived from ore that affect the reducibility easily remain due to a decrease in the heat source in the sintering raw material particles, and as a result, a highly reducible sintered ore. It is considered possible to manufacture

  FIG. 48 is a schematic view showing the sintering behavior when only coke is used (a) and when coke and diluted gas fuel are used together (b). As shown in this figure, in the conventional sintering using only coke, it was heated from the inside of the pseudo particles by powder coke combustion, whereas in the combined method of coke and gaseous fuel as in the present invention, gas was used. It is presumed that fine pores in the ore are likely to remain because the pseudo-particles are heated by the combustion of the fuel, and that the reduction ratio (RI) can be relatively high for a low RDI.

  FIG. 49 schematically shows changes in pore distribution of sintered ore when diluted gaseous fuel is blown. As shown in this figure, to improve the productivity of sintered ore, promoting the coalescence of 0.5-5 mm diameter pores affecting yield and cold strength, and reducing the number thereof, and It is effective to increase the proportion of pores having a diameter of 5 mm or more that affects the air permeability. Further, in order to improve the reducibility of the sintered ore, it is desirable to have a pore structure in which a large number of fine pores of 0.5 mm or less mainly existing in the iron ore remain. In this respect, according to the present invention, it is considered that it is possible to approach an ideal sintered ore pore structure by dilute gaseous fuel injection.

FIG. 50 shows the results of a test for grasping the limit coke ratio capable of maintaining a desired cold strength. Here, the limit coke ratio is defined as a coke addition amount at which the shutter intensity (SI) is equivalent to the maximum value (73%) obtained when the diluted propane gas is not used. As shown in FIG. 50, the coke ratio at which the same cold strength (shutter strength 73%) as that of the present state can be obtained by blowing 0.5% by volume of diluted propane gas is as shown in FIG. 50 (a). Furthermore, the mass is reduced from 5 mass% to 3 mass% (about 20 kg / t). Further, as shown in FIGS. 50B and 50C, the coke ratio for obtaining a yield of 74% and a production rate of 1.86 t / hr · m ² is reduced from 5 mass% to 3.5 mass%, respectively. You can see that

  As is apparent from the above description, the present invention is appropriately diluted according to the amount of carbon material contained while the combustion / melting zone moves from the surface layer to the lower layer of the charging layer as the pallet progresses. By selecting and supplying the appropriate gaseous fuel, it is possible to create an action that expands the function of the combustion / melting zone in the charging layer, improving the quality and productivity of the sintered ore. Can be planned.

  Using the test pan shown in FIG. 28, coke oven gas (C gas) diluted to 1 to 2.5 vol% was used as the gaseous fuel, and other conditions were the same as the experimental conditions described above (0092 paragraph). The sintering pot test of the sintering raw material containing 5 mass% of materials (coke) was conducted. The result is shown in FIG. As shown in this figure, when C gas diluted according to the method of the present invention is used, if the concentration of C gas is increased, the width (thickness) of the combustion zone is significantly increased, and the yield and production rate are improved. It was also found that the cold strength (SI) can be improved.

  A propane gas diluted to 0.02 to 0.5 vol% is used as the diluted gas fuel, and the other conditions are the same as in Example 1, and a sintering raw material sintering pot containing 5 mass% of carbonaceous material (coke). A test was conducted. The result is shown in FIG. From this figure, when using propane gas diluted according to the method of the present invention, if the concentration of the propane gas is increased, the width (thickness) of the combustion zone is significantly increased, and the yield and production rate are improved. It was found that the cold strength (SI) can also be improved.

  Using the test pan shown in FIG. 28, as shown in Table 14, the content (external number) of the powdered coke was changed to two levels of 4.9 mass% and 4.8 mass%. Coke oven gas (C gas) diluted with two levels of 1.0 vol% and 2.0 vol% (against air) with cooler exhaust gas was blown into the bed from above the pot, and the sintering pot test (No. .2-7). In addition, as a comparative example, the sintering pot test was similarly performed on an example (No. 1) in which the content (outside number) of the powder coke was 5.0 mass% and the dilution gas was not blown. In this example, the sintering raw material charged in the test pan had a total thickness of 600 mm, and the upper layer portion of 400 mm was laminated with the sintering raw material containing the above powder coke, and the lower layer was 200 mm. Laminated return ore.

  The diluted C gas is injected when the combustion / melting zone is located at a position of 100 to 200 mm, 200 to 300 mm, or 300 to 400 mm from the surface of the charging layer. ) Was introduced into the charging layer. The dilution C gas is injected at a position where the total length of the DL sintering machine is 80 m. When the injection position is 100 to 200 mm, 80 (m) × 100 to 200/600 (mm) = 13. A gaseous fuel supply device having a length of 13.3 m is installed between 13.3 and 26.6 m from the movement starting point of the pallet toward the position of 3 to 26.6 (m), that is, in the pallet traveling direction. This corresponds to an example in which a diluted gas fuel is injected and a sintering operation is performed. Similarly, in the case of the blowing position of 200 to 300 mm, the gas fuel supply device having a length of 13.3 m was installed at the position of 26.6 to 39.9 m from the movement starting point of the pallet, and the sintering operation was performed. For example, in the case of a blowing position of 300 to 400 mm, a gas fuel supply device having a length of 13.3 m was installed at a position of 39.9 to 53.2 m from the movement starting point of the pallet, and the sintering operation was performed. It corresponds to an example.

  Table 15 shows the results of the sintering pot test. From this result, No. of the comparative example which does not blow gaseous fuel. No. 1 of the present invention in which gaseous fuel is blown compared to No. 1. 2-No. No. 7 has improved cold strength (SI strength) and yield of sintered ore, and in particular, No. 7 in which the gaseous fuel injection position is after the middle stage of the charging layer. It can be seen that the improvement is remarkable in the examples of 3, 4, 6, and 7. It was also found that the production rate was the highest under the conditions where the coke amount was 4.9 mass% and the C gas concentration was 1 vol%. As for the influence of the diluted gas fuel injection (supply) position on the quality of the sintered ore, the position of the combustion / melting zone from both the reduction rate (RI) and the reduced powdering rate (RDI) It has been found that it is most effective to supply gaseous fuel when it is in the middle position of 200 to 300 mm.

The method for producing sintered ore according to the present invention was applied to a DL type sintering machine having a daily scale of 20,000 tons. The length of the DL sintering machine used was 90 m from the ignition furnace to the discharge section, and at a position of about 30 m behind the ignition furnace of this sintering machine, the length was 500 mm above the charging layer. (Pallet traveling direction) Nine 15m gaseous fuel supply pipes are arranged in parallel along the pallet traveling direction, and 149 nozzles for ejecting gaseous fuel downward are attached to each of the pipes at intervals of 100mm. In addition, a gas fuel supply device with a structure of 1341 was installed, city gas was discharged from the nozzle as gas fuel into the atmosphere at high speed, and charged as diluted gas fuel with a city gas concentration of 0.8 vol% Feeded on layer. The total thickness of the charging layer is 600 mm (however, the upper layer 400 mm is a sintered material containing 4.2 mass% of powdered coke), and the gaseous fuel is supplied at a combustion / melting zone of 200 to 300 mm. Corresponds when present at a position. The diluted gaseous fuel supplied as described above is sucked and introduced into the charging layer by suction negative pressure control of the wind box below the sintering machine pallet, and the combustion / melting zone existing at the above position through the sintered layer. Burned in. The amount of C gas used at this time was 3000 m ³ (standard state) / hr.

As a result of operation with this actual sintering machine, the tumbler strength (TI) of the obtained sintered ore is improved by about 3% as compared with the normal operation as a whole, and the reduced dusting property (RDI) is in the normal operation. The reduction rate (RI) was improved by about 4% from the normal operation. Moreover, the production rate increased by 0.03 t / hr · m ² , confirming the effect of the present invention.

  The technique of the present invention is 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.

It is a figure explaining a sintering process. It is a figure explaining the pressure loss and temperature distribution in a sintered layer. It is explanatory drawing which compared the temperature distribution at the time of high production and low production. It is a graph of the temperature distribution and yield distribution in a sintering machine. It is a figure explaining the structural example of the gaseous fuel supply apparatus which concerns on this invention. It is a figure explaining the other structural example of the gaseous fuel supply apparatus which concerns on this invention. It is a figure explaining the experiment which investigates the influence of the gaseous fuel supply position to a sintering cake. It is a figure explaining the example of the discharge method of the gaseous fuel which concerns on this invention. It is a figure explaining the other example of the discharge method of the gaseous fuel which concerns on this invention. It is a figure explaining the other example of the discharge method of the gaseous fuel which concerns on this invention. It is a figure explaining the other example of the discharge method of the gaseous fuel which concerns on this invention. It is a graph which shows the influence which the discharge speed of gaseous fuel and the nozzle diameter have on the concentration distribution of dilution gas. It is a figure explaining the influence of the cross wind which acts on gaseous fuel supply. It is a figure explaining the effect on the side wind. It is a figure explaining the seal structure of the food | hood lower end. It is a figure explaining the seal structure of the food | hood lower end. It is a figure explaining the model of the gaseous fuel supply apparatus used for the analysis, and the food | hood provided above it. It is a figure which shows the analysis result about the density | concentration distribution of gaseous fuel. It is a figure which shows the analysis result about pressure distribution. It is a figure which shows the analysis result about gas flow velocity distribution. It is a figure which shows the vector diagram of a gas flow velocity. It is a figure explaining the example of the cross wind countermeasure which concerns on this invention. It is a figure explaining the other example of a cross wind countermeasure which concerns on this invention. It is a figure explaining the other example of a cross wind countermeasure which concerns on this invention. It is a figure explaining the other example of a cross wind countermeasure which concerns on this invention. It is a figure explaining the other example of a cross wind countermeasure which concerns on this invention. It is a figure explaining the gaseous fuel supply process which concerns on this invention. It is a figure (photograph) which shows the change of the combustion melting zone in the test pan by M gas blowing. It is a graph explaining the influence which it has on the operation condition of sintering, and the characteristic of a sintered ore when M gas blowing is performed. It is a figure explaining the method of calculating | requiring the combustion limit of blast furnace gas. It is a graph which shows the temperature dependence of the combustion minimum density | concentration of methane gas. It is a figure explaining the relationship between the combustion component (combustion gas) density | concentration and temperature of gaseous fuel in the normal temperature in air | atmosphere. It is a figure which shows the relationship between the effect of blowing dilution gas fuel, and a gas type. It is a graph which shows the relationship between the gas density | concentration at the time of blowing propane gas, shutter intensity | strength, a yield, sintering time, and production. 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 the figure (photograph) which observed the form of the combustion zone at the time of dilution propane gas blowing. It is a figure (photograph) which shows the influence which the blowing position has on a combustion condition. It is a figure explaining the influence which the blowing position has on a combustion condition. It is a schematic diagram explaining the temperature distribution in the charging layer at the time of sintering. It is explanatory drawing which compared the combustion condition in the case of using together powder coke only and the case where powder coke and dilution C gas blowing are used together. It is a graph which shows the time-dependent change of the temperature in a charging layer, exhaust gas temperature, passing air volume, and exhaust gas composition by injection of the diluted propane gas on condition of constant heat input. It is a graph which shows the time-dependent change of the temperature in a charging layer, and an exhaust gas density | concentration at the time of the time of diluted propane gas injection | pouring (0.5 vol%) and only coke increase (10 mass%). It is a graph which shows the sintering characteristic test result under various blowing conditions. It is a graph which shows the change of the composition ratio of the mineral phase in the product sintered ore under various blowing conditions. It is a graph which shows the change of the apparent specific gravity of a product sintered ore by the presence or absence of blowing of propane gas. It is a graph which shows the change of 0.5 mm or less pore diameter distribution by the mercury intrusion type porosimeter by the presence or absence of blowing of propane gas. It is the schematic diagram which showed the sintering behavior at the time of using coke only and using coke and a diluted gas fuel together. It is a schematic diagram which shows the change of the pore distribution of the sintered ore when the diluted gaseous fuel is blown. It is a graph which shows the experimental result which grasps | ascertains the limit coke ratio which can maintain cold intensity | strength. 2 is a diagram (photograph) showing the results of Example 1. FIG. 6 is a diagram (photograph) showing the results of Example 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Raw material hopper 2 Drum mixer 3 Rotary kiln 4, 5 Surge hopper 6 Drum feeder 7 Cutting chute 8 Pallet 9 Charging layer 10 Ignition furnace 11 Wind box 12 Gaseous fuel supply device

Claims (10)

A circulating pallet,
A raw material supply device for charging a sintered raw material containing fine ore and carbonaceous material on the pallet to form a charging layer;
An ignition furnace for igniting the carbonaceous material in the sintered raw material;
In a sintering machine provided with a wind box below the pallet,
On the downstream side of the ignition furnace, a gaseous fuel supply device provided with a cross wind preventing hood having an air suction opening portion above is disposed .
And the sintering machine characterized by installing the fence for a transverse wind attenuation | damping which has the transmittance | permeability around the upper part of the food | hood for a cross wind prevention . Sintering machine according to claim 1, characterized by being installed close contact type seal structure between the lower end and the pallet side walls of the upper Symbol crosswind preventing hood. Sintering machine according to claim 1 or 2, characterized in that by installing windbreak cover the outside of the lower end and the pallet side walls of the hood above Kiyoko wind prevented. Along the pallet width direction on both sides of the upper Kiyoko wind preventing hood, sintering machine according to any of claims 1 to 3, characterized by being installed crosswind preventing shield. Sintering machine according to any deviation of the claims 1 to 4, characterized by being provided with a gap between the upper Kiyoko wind preventing hood lower and the sintering bed surface. The sintering machine according to claim 5, wherein a sealing material is disposed in the gap. The sintering machine according to claim 5 or 6, wherein an air curtain is installed in the gap. The sintering machine according to any one of claims 1 to 7, wherein the cross wind preventing hood has a structure in which an upper portion of a side wall is inclined. The sintering machine according to any one of claims 1 to 8 , wherein a rectifying plate is installed inside the cross wind preventing hood. The sintering machine according to any one of claims 1 to 9 , wherein a baffle plate is installed inside the cross wind preventing hood.

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