WO2011118822A1

WO2011118822A1 - Method for producing sintered ore

Info

Publication number: WO2011118822A1
Application number: PCT/JP2011/057494
Authority: WO
Inventors: 友司岩見; 伸幸大山
Original assignee: Ｊｆｅスチール株式会社
Priority date: 2010-03-24
Filing date: 2011-03-18
Publication date: 2011-09-29
Also published as: JP5585503B2; KR101475130B1; JP2012207236A; TW201134946A; CN102822360A; CN102822360B; TWI449795B; KR20120130260A

Abstract

Disclosed is a method for producing a sintered ore, which involves: forming a charged layer by charging a sintering starting material comprising fine ore and a carbon material on a circulating pallet; igniting the carbon material on the surface of the charged layer; introducing air, which contains gas fuel that is diluted to the lower combustion limit concentration or less and which is above the charged layer, into the charged layer by sucking the aforementioned air by means of a wind box disposed below the pallet; and burning the aforementioned gas fuel and the carbon material within the charged layer. The aforementioned method for producing a sintered ore also involves: supplying the abovementioned gas fuel to a region, in which the high-temperature retention period during which the temperature is retained at 1200°C to 1400°C inclusive lasts for less than 150 seconds, when sintering at the heat of combustion of the carbon material; setting the high-temperature retention period to 150 seconds or more; and enriching the oxygen within the air in the gas fuel supplying region.

Description

Method for producing sintered ore

The present invention relates to a method for producing a high-quality blast furnace raw material sintered ore that is high in strength and excellent in reducibility using a downward suction type dwytroid sintering machine.

Sinter ore, which is the main raw material for the blast furnace ironmaking method, is generally manufactured through a process as shown in FIG. The raw materials for sintered ore are iron ore powder, sintered ore sieving powder, recovered powder generated in steelworks, CaO-containing auxiliary materials such as limestone and dolomite, granulation aids such as quick lime, coke powder and anthracite Yes, these raw materials are cut out from each of the hoppers 1. The cut out raw material is added with an appropriate amount of water by the

drum mixers

2 and 3 and the like, mixed and granulated to obtain a sintered raw material which is pseudo particles having an average diameter of 3 to 6 mm. The sintered raw material is then transferred to 400 to 800 mm on an endless moving type sintering machine pallet 8 from the

surge hoppers

4 and 5 arranged on the sintering machine through the drum feeder 6 and the cutting chute 7. The charge layer 9 is charged with a thickness and is also referred to as a sintered bed. Thereafter, the carbon material on the surface of the charging layer is ignited by an ignition furnace 10 installed above the charging layer 9, and the air above the charging layer is passed through a wind box 11 disposed immediately below the pallet 8. By sucking downward, the carbonaceous material in the charging layer is sequentially burned, and the sintered raw material is melted by the combustion heat generated at this time to obtain a sintered cake. The sintered cake thus obtained is then crushed and sized, and an agglomerate of about 5 mm or more is recovered as a product sintered ore and supplied to a blast furnace.

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

FIG. 2 shows that in the charging layer when the combustion zone moving in the 600 mm thick charging layer is at a position of about 400 mm on the pallet in the charging layer (200 mm below the charging layer surface). This shows the distribution of pressure loss and temperature, and the pressure loss distribution at this time shows that about 60% is in the wet zone and about 40% is in the combustion zone.

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

Fig. 3 shows the change in temperature and time at a certain point in the charging layer when the sintered ore productivity is high and low, that is, when the pallet moving speed of the sintering machine is fast and slow. It is. The time for which the sintering raw material particles start to melt is maintained at a temperature of 1200 ° C. or higher is represented by T ₁ when the productivity is low and T ₂ when the productivity is high. Because at high productivity faster moving speed of the pallet, the high temperature zone holding time T _2, is shorter than the T ₁ of the at low productivity. However, if the holding time at a high temperature of 1200 ° C. or more is shortened, the firing becomes insufficient, the cold strength of the sintered ore is lowered, and the yield is lowered. Therefore, in order to produce a high-strength sintered ore in a short time with a high yield and high productivity, some measures are taken to extend the time for which the high-temperature sintered ore is held at a high temperature of 1200 ° C. or higher. It is necessary to increase the cold strength. In general, SI (shutter index) and TI (tumbler index) are used as indices representing the cold strength of sintered ore.

FIG. 4 shows that the carbon material in the surface of the charging layer ignited in the ignition furnace is continuously burned by the sucked air to form a combustion zone, which sequentially moves from the upper layer to the lower layer of the charging layer. It is the figure which showed typically the process in which is formed. FIG. 5A shows the temperature distribution when the combustion zone is present in each of the upper layer portion, middle layer portion, and lower layer portion of the charging layer shown in the thick frame shown in FIG. It is shown schematically. The strength of the sintered ore is influenced by the product of the temperature and time maintained at a temperature of 1200 ° C. or higher, and the greater the value, the higher the strength of the sintered ore. Therefore, the middle layer and lower layer in the charging layer are preheated by being transported by the air sucked by the combustion heat of the carbon material in the upper charging layer, so that it can be held at a high temperature for a long time. On the other hand, the upper portion of the charge layer is not preheated, and therefore the combustion heat is insufficient, and the combustion melting reaction (sintering reaction) necessary for sintering tends to be insufficient. As a result, the yield distribution of the sintered ore in the cross section in the width direction of the charging layer becomes lower in the upper layer portion of the charging layer as shown in FIG. In addition, the pallet width ends also have a low yield due to heat dissipation from the pallet side walls and supercooling due to the large amount of air passing through, so that sufficient holding time in the high temperature range necessary for sintering cannot be secured. Become.

In response to these problems, conventionally, the amount of carbonaceous material (powder coke) added to the sintering raw material has been increased. However, by increasing the amount of coke added, as shown in FIG. 6, the temperature in the sintered layer can be increased and the time for maintaining the temperature at 1200 ° C. or more can be extended. The maximum reached temperature exceeds 1400 ° C., and for the reasons explained below, the reducibility of the sintered ore and the cold strength are reduced.

Non-Patent Document 1 shows the tensile strength (cold strength) and reducibility of various minerals generated in the sintered ore during the sintering process, as shown in Table 1. In the sintering process, as shown in FIG. 7, a melt starts to be generated at 1200 ° C., and calcium ferrite having the highest strength among the constituent minerals of sintered ore and relatively high reducibility is generated. To do. This is the reason why a sintering temperature of 1200 ° C. or higher is required. However, when the temperature rises further and exceeds 1400 ° C., more precisely, 1380 ° C., calcium ferrite is reduced to amorphous silicate (calcium silicate) having the lowest cold strength and reducibility, and reduced. It begins to decompose into skeletal secondary hematite that is easy to powder. In addition, secondary hematite, which is the starting point for reducing powderization of sintered ore, is obtained from Mag. As shown in the phase diagram of FIG. ss + Liq. Since it precipitates when it is heated up to the zone and cooled, it is possible to suppress the reduction powdering by producing sintered ore through the path (2) instead of the path (1) shown on the phase diagram. It is important to do.

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

Incidentally, several techniques have been proposed in the past for improving the yield reduction in the upper layer of the charging layer and improving the productivity. For example, in Patent Document 1, when producing sintered ore, in addition to coke added to the sintering raw material, an exothermic gas is added to the air sucked into the sintering raw material, A technique for improving the strength, production rate, and product yield of sintered ore has been proposed. However, since the technique of this patent document 1 raises the highest reached temperature at the time of sintering by burning coke and gaseous fuel, and aims at the improvement of the intensity | strength of a sintered ore, a production rate, and a yield, product sintering There is a problem that the reducibility (RI) of the ore is deteriorated.

Further, in Patent Document 2, when the charging layer upper layer part is sufficiently fired, the mass flow rate of the oxygen-containing gas supplied to the charging layer is set within the range in which the charging layer upper layer part is fired. The mass flow rate is 1.01 to 2.6 times greater, the differential pressure in the charging layer is increased, the transition speed of the combustion melting zone is extremely accelerated, the production rate is increased, and the product yield and quality are excellent. A method for obtaining a new product has been proposed. However, the technique of Patent Document 2 can increase the layer thickness of the charging layer and increase the pallet moving speed, and can improve the production rate of the sintering machine. However, there is a problem that the reducibility of the product sintered ore is deteriorated.

Patent Document 3 discloses that the oxygen concentration in the combustion air sucked into the charging layer is enriched to 35% or more while the upper layer portion of the charging layer on the pallet is sintered. Has proposed an oxygen-enriched operation method that improves productivity and product yield. However, the technology of Patent Document 3 improves the combustibility of coke by increasing the oxygen concentration in the combustion air to 35% or more, and increases the maximum temperature, but the combustibility is improved. As a result, there is a problem that the high temperature region holding time of 1200 ° C. or higher necessary for sintering becomes insufficient.

Therefore, as a technique for solving the above-mentioned problems, the inventors reduced the amount of carbonaceous material added to the sintering raw material, and then variously diluted below the lower combustion limit concentration downstream of the ignition furnace of the sintering machine. By introducing gaseous fuel into the charging layer from above the pallet and combusting the gaseous fuel in the charging layer, both the maximum temperature reached in the charging layer and the holding time in the high temperature range are controlled within an appropriate range. Techniques are proposed in Patent Documents 4 to 6 and the like.

Japanese Examined Patent Publication No. 46-027126 WO98 / 077891 Japanese Patent Laid-Open No. 02-073924 JP 2008-095170 A JP 2010-047801 A JP 2008-291354 A

Applying the techniques of Patent Documents 4 to 6 to the method for producing sintered ore using a downward suction type sintering machine, reducing the amount of carbonaceous material added to the sintered raw material, and lowering the concentration below the lower limit of combustion. When the diluted gaseous fuel is introduced into the charging layer and the gaseous fuel is burned in the charging layer, as shown in FIG. Since it burns in the charging layer (in the sintered layer), the width of the combustion / melting zone can be expanded in the thickness direction without exceeding the maximum temperature of the combustion / melting zone exceeding 1400 ° C. In particular, it is possible to extend the high temperature range holding time.

However, in the prior arts of Patent Documents 4 to 6, in order to obtain a high-quality sintered ore having high strength and excellent reducibility, how long it is kept in a high temperature range of 1200 ° C. to 1400 ° C. It has not been fully clarified whether it is necessary to do this, and to which region the diluted gaseous fuel should be supplied.

In addition, it should be noted in the techniques of Patent Documents 4 to 6 that a combustion-supporting gas that burns carbonaceous material or gaseous fuel when determining the range of the maximum temperature and the high-temperature range holding time that are preferable for sintering. As described above, air containing 21 vol% oxygen is used as it is. This is because the charging layer during actual sintering should have an atmosphere different from the atmosphere due to the combustion reaction of carbonaceous materials and gaseous fuel, and the composition and composition of the combustion-supporting gas. If this changes, the gas atmosphere in the charging layer also changes, and naturally, the maximum temperature reached during sintering and the high temperature region holding time should also change. Therefore, it is necessary to change the operating conditions of the sintering machine according to the characteristics of the combustion-supporting gas. However, in the prior art, the actual situation is that little consideration has been given to the influence of the characteristics of the combustion-supporting gas, particularly the amount of oxygen contained in the air, on the sinterability and the quality of the sinter.

The present invention has been made in view of the above-described problems of the prior art, and its purpose is to sinter by burning a carbonaceous material and a gaseous fuel in a charging layer using a lower suction type sintering machine. In the method of manufacturing ore, the high temperature region holding time required for sintering is clarified, the appropriate region to be supplied with gaseous fuel is determined, and the combustion-supporting gas for the highest temperature reached during sintering and the high temperature region holding time is determined. Based on the results, we propose a method for producing high-quality sintered ore with high strength and excellent reducibility at a high yield based on the results. There is to do.

The inventors have intensively studied to solve the above problems. As a result, in order to obtain a high-quality sintered ore with high strength and excellent reducibility, the time to be maintained in the temperature range of 1200 to 1400 ° C., that is, the high temperature region retention time is approximately 150 seconds or more. Therefore, the gaseous fuel should be supplied to the region where the high-temperature region holding time is less than 150 seconds, and conventionally, the air containing 21 vol% of oxygen, which is a combustion-supporting gas, is further enriched with oxygen. If it is, the gas atmosphere during sintering shifts to the oxidation direction, the combustion start temperature of the carbonaceous material and gaseous fuel in the sintering raw material can be shifted to the low temperature side, without causing an increase in the maximum reached temperature, The retention time in the high temperature range can be greatly extended. As a result, the amount of calcium ferrite produced in the sinter increases, and a sinter with high strength and excellent reducibility can be obtained. Maximize the effect of enrichment In order to achieve this, it has been found that it is effective to enrich oxygen in a region where the gaseous fuel is to be supplied, preferably in a region within 1/2 of the upstream side of the region where the gaseous fuel is to be supplied. The present invention has been completed.

That is, the present invention is to charge a sintered raw material containing fine ore and carbonaceous material on a circulating pallet to form a charging layer, ignite the carbonaceous material on the surface of the charging layer, and lower combustion lower concentration The air above the charging layer containing the diluted gaseous fuel is sucked in the wind box arranged under the pallet and introduced into the charging layer, and the gaseous fuel and the carbonaceous material are burned in the charging layer. In the method for producing sintered ore, the gaseous fuel is supplied to the region where the high temperature region retention time is maintained at 1200 ° C. or higher and 1400 ° C. or lower when sintering with the combustion heat of the carbonaceous material is less than 150 seconds. A method for producing a sintered ore characterized in that a high temperature region holding time is set to 150 seconds or more and oxygen in the air is enriched in the gaseous fuel supply region.

The method for producing a sintered ore of the present invention is a region in which the amount of carbonaceous material in the sintered raw material is changed to maintain the maximum temperature within the range of 1200 to 1400 ° C. and the high temperature region retention time is less than 150 seconds. The amount of gaseous fuel supplied to is changed, and the high temperature region holding time is 150 seconds.

In the method for producing sintered ore of the present invention, oxygen is enriched in a region within 1/2 of the upstream side of the gaseous fuel supply region, or upstream of the gaseous fuel supply region (1/4 to 1). / 2) It is characterized by enriching oxygen in a region within.

Further, the method for producing a sintered ore according to the present invention is characterized in that the oxygen concentration in the air is more than 21 vol% and less than 35 vol% by the oxygen enrichment.

In the method for producing a sintered ore of the present invention, the O ₂ concentration in the gas atmosphere in the charging layer in the oxygen-enriched region is set to 12.5 vol% or more by the oxygen enrichment, and the highest temperature reached In a temperature range of 1275 to 1375 ° C.

Further, in the method for producing a sintered ore of the present invention, the high temperature region retention time in the region where the high temperature region retention time is less than 150 seconds due to the supply of the gaseous fuel and the enrichment of oxygen is 150 seconds to 300 seconds. It is characterized by doing.

Also, the method for producing sintered ore according to the present invention is characterized in that the amount of carbon material equivalent to or greater than the calorific value of the gaseous fuel to be supplied is reduced.

Further, in the method for producing sintered ore according to the present invention, the air to which the gaseous fuel is added is obtained by adding gaseous fuel previously diluted below the lower combustion limit concentration to the air, or gaseous fuel in the atmosphere above the charging layer. Is injected at high speed and diluted to below the lower combustion limit concentration.

In the method for producing sintered ore according to the present invention, the gaseous fuel is arranged in one or more stages with a gap in the middle in the height direction in the hood installed above the charging layer in the region where the gaseous fuel is supplied. The oxygen which is supplied below the baffle plate provided and enriched is supplied toward the gap between the baffle plates above the baffle plate in the hood.

According to the present invention, the following effects can be obtained.
(1) High temperature region holding time during sintering in all regions in the charging layer by supplying gaseous fuel only to the region where the time for maintaining the temperature at 1200 ° C. or higher and 1400 ° C. or lower is insufficient. For 150 seconds or more.
(2) The amount of calcium ferrite produced in the sintered ore can be increased by enriching the combustion-supporting gas (air) with oxygen and shifting the gas atmosphere during sintering in the oxidation direction.
(3) Furthermore, by supplying gaseous fuel and enriching oxygen in a limited range, the combustion position of the carbonaceous material in the gaseous fuel and sintered raw material can be shifted to the low temperature side, so it reaches the highest level. The high temperature range retention time can be extended without increasing the temperature.
(4) Therefore, according to the present invention, a high-quality sintered ore having high strength and excellent reducibility can be produced with high productivity.

It is a schematic diagram explaining a sintering process. It is a graph explaining the temperature distribution and pressure loss distribution in a sintered layer. It is a figure explaining the temperature distribution in the charging layer at the time of high production and low production. It is a schematic diagram explaining the change in the charging layer accompanying sintering progress. It is a figure explaining the temperature distribution when a combustion zone exists in each position of the upper layer part of the charging layer, the middle layer part, and the lower layer part, and the yield distribution of the sintered ore in the width direction cross section of the charging layer. . It is a figure explaining the temperature change in the charging layer by the change (increase) of the amount of carbon materials. It is a figure explaining a sintering reaction. It is a figure explaining the process in which a skeleton-like secondary hematite produces | generates. It is a schematic diagram explaining the horizontal electric furnace used for experiment. It is a graph which shows the influence which the high temperature range holding time has on the cold intensity | strength of a sintered ore, and the amount of calcium ferrite production. O ₂ concentration in the gas atmosphere during sintering is a graph showing the effect on the rate of formation of calcium ferrite. In the gas atmosphere during sintering CO / (CO + CO ₂₎ is a graph showing the effect on the rate of formation of calcium ferrite. O ₂ concentration in the gas atmosphere during sintering is a graph showing the effect on the rate of formation of calcium silicate. In the gas atmosphere during sintering CO / (CO + CO ₂₎ is a graph showing the effect on the rate of formation of calcium silicate. O ₂ concentration and sintering temperature in the gas atmosphere during sintering is a graph showing the effect on the rate of formation of calcium ferrite. It is a figure explaining the change of the temperature distribution in the sintered layer by gaseous fuel supply. It is a figure explaining the change of the temperature distribution in a sintered layer when oxygen is enriched simultaneously with gaseous fuel supply. It is a figure explaining the sintering test pot used for experiment. It is a graph which shows the effect of gaseous fuel supply which acts on the quality, production rate, etc. of a sintered ore. It is a graph which shows the influence which sintering conditions exert on the cold strength SI and production rate of a sintered ore. It is a figure explaining the experimental conditions which enrich oxygen simultaneously with supply of gaseous fuel. It is a graph which shows the influence which supply of gaseous fuel and oxygen enrichment has on the quality, production rate, etc. of a sintered ore. It is a figure explaining an example of the gaseous fuel supply apparatus which supplies gaseous fuel and oxygen simultaneously. In an Example, it is a figure explaining the experimental condition which performs oxygen enrichment simultaneously with supply of gaseous fuel. It is a graph which shows the influence which the supply of gaseous fuel and oxygen enrichment have on the high temperature range holding time and the highest attained temperature. It is a graph which shows the influence which supply of gaseous fuel and oxygen enrichment has on the quality, production rate, etc. of a sintered ore.

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

FIG. 10 shows the results of the above-described experiment, and the following was found from this figure.
(A) The longer the time of holding at a temperature of 1200 ° C. to 1400 ° C. (high temperature region holding time), the more calcium ferrite is generated in the sintered ore, and the strength of the sintered ore is accordingly increased. To rise.
(B) When the high temperature region holding time is secured for 150 seconds or more, the amount of calcium ferrite produced increases greatly, and at the same time, the crushing strength in the crushing strength test also increases greatly. In this example, the crushing strength of the sintered ore is 4. It becomes 60 kN or more, and sufficient strength is obtained as a blast furnace raw material.
(C) When the high temperature region holding time exceeds 300 seconds, the amount of calcium ferrite in the sintered ore approaches the theoretical value (45.7 mass%) and becomes saturated. An improvement in the cold strength of the sintered ore cannot be expected, but is not preferable from the viewpoint of fuel cost.

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

Next, the inventors examined the influence on the sintering reaction when oxygen was enriched with respect to air containing 21 vol% oxygen.
As shown in Table 1 above, calcium ferrite produced in sintered ore during the sintering process has high strength and good reducibility, whereas calcium silicate has low strength and reducibility. Is also inferior. Therefore, what is important in producing a high-quality sintered ore is how to produce a large amount of calcium ferrite in the sintered ore and not to produce calcium silicate. Moreover, the mineral produced | generated in a sintered ore changes with the highest ultimate temperature at the time of sintering, and high temperature range holding time, as shown in FIG.7 and FIG.8. However, it is considered that the maximum temperature reached and the high temperature range holding time will also change depending on the components and composition of the gas atmosphere during sintering.

Therefore, the inventors first investigated the influence of the gas atmosphere during sintering on the maximum temperature reached and the high temperature holding time by the following experiment.
In the experiment, using a pelletizer, iron ore having a particle size of 0.5 mm or more is used as a core particle, and iron ore having a particle size of less than 0.5 mm and auxiliary materials such as calcium carbonate and silicon dioxide are added as exterior materials. Granulation was performed to obtain a sintered raw material of about 2 to 5 mmφ.
This sintered raw material was placed on an alumina boat, charged near the center of the soaking zone of the horizontal electric furnace shown in FIG. 9, and sintered in a temperature range of 1200 to 1400 ° C. The calcined sample was then rapidly cooled and collected, and the mineral species produced by sintering and their production ratio (mass%) were measured using a powder X-ray diffraction method.
The gas atmosphere at the time of sintering in the above sintering experiment was predicted from the component composition of the exhaust gas from the actual machine, and the O ₂ concentration and CO / (CO + CO ₂ ) that were largely dispersed therein were predicted. Focusing on the ratio, these were varied as operating factors.

FIG. 11 shows the relationship between the O ₂ concentration in the atmosphere and the generation ratio of calcium ferrite, and FIG. 12 shows the relationship between CO / (CO + CO ₂ ) and the generation ratio of calcium ferrite. From these figures, it can be seen that the generation ratio of calcium ferrite increases as the O ₂ concentration increases and as CO / (CO + CO ₂ ) decreases.

Similarly, FIG. 13 shows the relationship between the O ₂ concentration in the atmosphere and the production rate of calcium silicate, and FIG. 14 shows the relationship between CO / (CO + CO ₂ ) and the production rate of calcium silicate. From these figures, it can be seen that as the O ₂ concentration increases and as CO / (CO + CO ₂ ) decreases, the production rate of calcium silicate decreases.

These results show that as the O ₂ concentration in the gas atmosphere during sintering increases, that is, as the gas atmosphere during sintering shifts in the oxidation direction, the generation rate of calcium ferrite increases, and the calcium silicate A reduction in the production rate, and thus an increase in the O ₂ concentration in the gas atmosphere during sintering, is extremely effective for improving the quality of the sintered ore.

These changes in mineral structure due to the O ₂ concentration and CO / (CO + CO ₂ ) are explained as follows. About 70% by weight of calcium ferrite is composed of hematite. Hematite is trivalent iron oxide, and is stabilized when the gas atmosphere during sintering moves in the oxidation direction. Therefore, it is considered that when the O ₂ concentration in the gas atmosphere at the time of sintering increases and shifts in the oxidation direction, the hematite is stabilized and the generation ratio of calcium ferrite is increased.

On the other hand, calcium silicate is composed of wustite at about 15% by weight. Wustite is a divalent iron oxide and is lost by an oxidation reaction when the gas atmosphere during sintering moves in the oxidation direction. Therefore, it is considered that the O ₂ concentration in the gas atmosphere at the time of sintering was increased and moved in the oxidation direction, whereby wustite disappeared and the generation rate of calcium silicate decreased.

FIG. 15 shows the results obtained by performing a number of sintering experiments as described above as the relationship between the O ₂ concentration and the sintering temperature and the generation ratio of calcium ferrite. According to FIG. 15, the holding temperature during sintering is controlled to 1250 to 1375 ° C., preferably 1275 to 1375 ° C., and the O ₂ concentration in the gas atmosphere during sintering is set to 12.5 vol% or more. It can be seen that the generation ratio of calcium ferrite can be remarkably increased by increasing the gas atmosphere, that is, shifting the gas atmosphere during sintering in the oxidation direction.

In addition, when gaseous fuel is supplied at the same time as enriching oxygen in the air, which is a combustion-supporting gas, in addition to the influence on the mineral structure generated in the sintered ore, the sintering described below is performed. A favorable influence on the sintering reaction rate and sintering temperature distribution is also expected.
In general, the reaction rate is expressed by the following equation.
r = A × k × C ⁿ
Where r: reaction rate (mol / m ² · s)
A: Constant independent of temperature (frequency factor)
k: Reaction rate constant (m / s)
C: Gas component concentration used in the reaction (mol / m ³ )
n: Number of molecules of gas component necessary for a single molecule reaction to proceed (-)
However, this reaction rate equation does not consider the reverse reaction.

In the above equation, the influence of temperature is included in k, and the reaction rate r including k increases as the temperature increases. Further, the reaction rate r increases as the gas component concentration C used for the reaction increases. That is, the reaction rate r increases with an increase in the reaction rate constant k accompanying the temperature increase and the gas component concentration C used for the reaction. This means that the reaction rate at a certain temperature can be increased by increasing the gas component concentration used in the reaction, and the gas component concentration used in the reaction can be increased. This means that the reaction rate can be achieved even at low temperatures.

Therefore, if the reaction rate is considered as the combustion rate of the carbonaceous material and the gaseous fuel and the gas component used for the reaction is replaced with oxygen, the combustion rate of the carbonaceous material and the gaseous fuel will enrich oxygen in the air. In addition, by enriching oxygen in the air, the same burning rate as that of the high temperature can be achieved even at a low temperature.

FIG. 16 is a diagram for explaining the combustion state inside the sintered layer shown in Patent Document 4 that discloses a technique for adding gaseous fuel to air, and (a) is the spread (size) of the combustion zone. (B) schematically shows the temperature distribution curve at that time. According to Patent Document 4, the gaseous fuel blown into the air burns at a position farther from the combustion position of the carbonaceous material, that is, at a lower temperature side above the charging layer, so that the combustion of the carbonaceous material is performed. Two temperature peaks are formed, the temperature peak accompanying combustion of gaseous fuel and the temperature peak accompanying combustion of gaseous fuel, and the temperature distribution curve synthesized from these two temperature peaks shows a wide distribution of the bottom, resulting in an extended high temperature region retention time. It is explained.

On the other hand, in the case of adding gaseous fuel at the same time as enriching oxygen in the air, as described above, the effect of increasing the combustion speed of the gaseous fuel and the carbonaceous material or shifting the combustion temperature to a lower temperature side. Is obtained. Here, the position on the low temperature side where the gaseous fuel burns is the upper side of the charging layer where the sintering is completed and the sintered ore (sintered cake) is generated, while the low temperature where the carbonaceous material burns. The position on the side refers to the lower side of the charging layer where there is a raw material that has not yet been burned with charcoal.

FIG. 17 shows the change in the combustion position in comparison with FIG. 16, where (a) shows the spread (size) of the combustion zone, and (b) shows the temperature distribution curve at that time. This is shown schematically. As can be seen from the comparison between FIG. 16B and FIG. 17B, when gaseous fuel is blown simultaneously with oxygen enrichment, the interval between the combustion position of the carbonaceous material and the combustion position of the gaseous fuel is only gaseous fuel. It will have a wider base than when blowing in. As a result, if the addition amount of carbonaceous material and gaseous fuel is properly controlled, oxygen enrichment and simultaneous blowing of gaseous fuel can be used to maintain the higher temperature range than the conventional technology without increasing the maximum temperature. It shows that the time can be extended.

In order to confirm the above-described effect of oxygen enrichment, the following experiment was conducted using a sintering test pot.
First, a sintered raw material in which iron ore, a solvent, powder coke, etc. are mixed so that the blending ratio excluding the powder coke becomes the value shown in Table 2 is put into a drum mixer, and the size is about 5 mmφ. Granulated. At this time, the silica in the obtained sintered ore was adjusted to be 4.9 mass% and the basicity was 2.0. Next, the granulated particles are filled into a cylindrical iron sintering pot having a size of 290 mmφ × 400 mmH shown in FIG. 18 to form a charging layer, and an ignition furnace disposed above the charging layer is used. Sintering was performed by igniting and using a blower disposed below the sintering pan to suck air from above the charging layer to burn the carbonaceous material (powder coke) in the sintering raw material.

In the above-described sintering experiment, as shown in Table 3, the conventional sintering conditions (T1) in which only air (O ₂ : 21 vol%) is introduced into the charge layer as a combustion-supporting gas, and the O ₂ concentration Sintering conditions (T2) in which oxygen-enriched air is introduced into the charging layer so that the amount of oxygen is 28 vol%, air in which LNG is diluted to a concentration of 0.4 vol% is introduced into the charging layer, and the like Sintering conditions (T3) described in Patent Document 4 in which the amount of carbon material of heat is reduced, and when air with LNG diluted to a concentration of 0.4 vol% is introduced into the charging layer, and the amount of carbon material with the same amount of heat is reduced At the same time, sintering conditions (T4) for enriching oxygen so that the O ₂ concentration becomes 28 vol%, and air in which LNG is diluted to a concentration of 0.4 vol% are introduced into the charging layer, while reducing 1.5 times the carbonaceous material, acid _{to O 2} concentration of 28 vol% It was subjected to five levels of the experimental sintering conditions to enrich (T5).

In the above sintering experiment, the time required for sintering was measured, and the shutter strength of the obtained sintered ore was measured in accordance with JIS M8711, and the product yield was obtained. Asked.

The results of the above test are shown in FIG. From this result, in the sintering method (No. T2) in which only oxygen is enriched in the air, the cold strength (SI) and product yield of the sintered ore are slightly higher than those in the conventional technique (No. T1). As a result, the sintering time is greatly shortened, resulting in an improved production rate. On the other hand, in the sintering method (No. T3) described in Patent Document 4 in which LNG is blown into the air as gaseous fuel, the cold strength is improved more than the sintering method only with oxygen enrichment, and the product yield is also greatly improved. In addition, as a result of the sintering time being slightly shortened compared to the prior art, the production rate is improved. In addition, LNG as a gaseous fuel is blown into the air, and at the same time, in the sintering method enriched with oxygen (No. T4, T5), the cold strength is further improved, and a product yield equivalent to LNG blowing can be obtained. Moreover, as a result of the sintering time being shortened to the same extent as oxygen enrichment alone, a significant increase in production rate has been achieved.

FIG. 20 shows the above experimental results as the effect of oxygen and LNG blowing on the cold strength (SI) and production rate of the sintered ore. As is clear from this figure, by adding gaseous fuel to the air or enriching air with oxygen, both the cold strength and production rate of the sintered ore can be improved, but the gaseous fuel is added. At the same time, when sintering was performed with oxygen enrichment, both the cold strength and the production rate were significantly improved compared to the case of oxygen enrichment alone and LNG addition alone. Can be confirmed. Moreover, no. It can be seen that at T5, the shutter strength and the production rate are greatly improved despite the reduction of the amount of coke that exceeds the calorific value of the injected gaseous fuel.

By the way, the above-described sintering experiment shows the effect of supplying gaseous fuel and enriching oxygen in all the time from the start of sintering (ignition) to the end of sintering. However, as described above, the gaseous fuel may be supplied in a region where the time (high temperature region retention time) maintained in the temperature range of 1200 ° C. or higher and 1400 ° C. or lower is less than 150 seconds. Even if fuel is supplied, it is not preferable in terms of fuel cost. In addition, it is not preferable from the viewpoint of running cost and equipment cost to perform oxygen enrichment beyond the gaseous fuel supply region. Further, the amount of oxygen to be enriched is preferably as small as possible.

In view of this, the inventors supply a range of oxygen to be supplied under a condition where the amount of oxygen to be enriched is constant, that is, supply a high concentration of oxygen in a narrow range. An experiment was conducted to investigate whether it is better to enrich oxygen thinly over a wide range.
In the experiment, similar to the above-described experiment, the sintering raw materials shown in Table 2 were put into a drum mixer and granulated to a size of about 5 mmφ. At this time, the silica in the obtained sintered ore was adjusted to be 4.9 mass% and the basicity was 2.0.
Next, the granulated particles are filled into a cylindrical iron sintering pot having a size of 290 mmφ × 400 mmH shown in FIG. 18 to form a charging layer, and an ignition furnace disposed above the charging layer is used. A blower placed under the sintering pan is ignited and air is sucked from the upper part of the charging layer downward to burn the carbonaceous material (powder coke) in the sintering raw material. Production volume is 312,000 tons / month A sintering experiment simulating an actual sintering machine was conducted.

In the above-mentioned sintering experiment, the effective machine length (ignition furnace exit side to the ore excavation part) is a sintering machine having a 58 m carbon material amount of 5.0 mass% based on sintering conditions without LNG supply ( T1), and the sintering conditions in which the supply range of gaseous fuel (LNG), the concentration of oxygen to be enriched, and the supply length were changed as shown in Table 4 were simulated. Specifically, without oxygen enrichment, LNG diluted to 0.4 vol% is supplied as gaseous fuel over the upstream side of the effective pilot length of 17 m, that is, diluted to the range of 29% of the upper layer portion of the charging layer. In the conditions (T2) and T2 for supplying gaseous fuel, oxygen is enriched over the entire length (17 m) of the LNG supply range (T3), and in the condition for T2, 1/2 on the upstream side of the LNG supply range. 5 levels of the condition (T5) for enriching oxygen at (8.5 m) and the condition (T5) for enriching oxygen at 1/4 (4.25 m) upstream of the LNG supply range in the condition of T2 A sintering experiment was conducted. In the case of supplying LNG, the amount of carbon material in the sintered raw material is set to 4.7 mass%. In the case of supplying LNG and enriching oxygen, the amount of carbon material in the sintered raw material is set to 4%. Reduced to 5 mass%. An image of the above experimental conditions is shown in FIG.

In the above sintering experiment, the time required for sintering was measured, and the shutter strength of the obtained sintered ore was measured in accordance with JIS M8711, and the product yield was obtained, and the production rate was obtained from these results. The results are shown in FIG. From this result, with respect to the base condition (T1) in which neither LNG supply nor oxygen enrichment is performed, in the condition (T2) in which LNG is supplied, the strength of the sintered ore is increased and the yield is improved. The production rate is greatly improved because the sintering time is also shortened. However, under the conditions (T3 to T5) in which oxygen is enriched together with the supply of LNG, the strength of the sintered ore is further increased and the yield is improved. However, under the condition (T3) in which oxygen is thin and long and enriched in the same range as the supply of LNG, the sintering time is extended and the production rate tends to decrease. However, the production rate is improved over the base condition (T1).
From the results of the above sintering experiment, it is effective to enrich oxygen in conjunction with the supply of gaseous fuel, but preferably the region within 1/2 of the upstream side of the region for supplying gaseous fuel, more preferably upstream It was found that it is effective to intensively enrich the gaseous fuel in the region within the side (1/4 to 1/2).

The reason why the sintering time is increased by enriching oxygen in a thin and long range as described above is considered as follows.
As described above, when gaseous fuel is supplied into the charging layer and burned, the gas in the charging layer (sintering layer) where the sintering temperature is decreasing after passing through the sintering zone due to the combustion of the carbonaceous material. Since the fuel burns, the temperature in that portion can be increased to expand the width of the combustion zone in the thickness direction, and the high temperature region holding time can be extended. Further, since enrichment of oxygen has an effect of lowering the combustion temperature of the gaseous fuel, the gaseous fuel is combusted in a lower temperature range, that is, in the upper part of the charging layer than when oxygen is not enriched. However, as described with reference to FIG. 2, the combustion zone has an effect of increasing the ventilation resistance. Therefore, the expansion of the width of the combustion zone leads to a decrease in the amount of air flow and an extension of the sintering time. The effect becomes larger as the time for enriching oxygen becomes longer. Therefore, it is considered that the sintering time is particularly extended under the condition where oxygen is enriched in the same range as the LNG supply region.

Next, the manufacturing method of the sintered ore of this invention is demonstrated concretely.
The method for producing a sintered ore according to the present invention uses a downward suction type sintering machine to charge a sintered raw material containing fine ore and carbonaceous material on a circulating pallet to form a charging layer. While igniting the charcoal on the surface of the charging layer, the air above the charging layer containing gaseous fuel diluted below the lower combustion limit concentration is sucked into the charging layer and introduced into the charging layer. This is the same as the techniques of the conventional patent documents 4 to 6 in that it is a method for producing sintered ore by burning the gaseous fuel and the carbonaceous material in the charging layer. Therefore, when supplying gaseous fuel, in order to keep the highest temperature in the charging layer during sintering, particularly in the middle layer to the lower layer of the charging layer in the range of 1200 to 1400 ° C., It is preferable to reduce the amount of carbon material to be added.

However, a feature of the method for producing a sintered ore of the present invention is that the gaseous fuel is held at a temperature of 1200 ° C. or higher and 1400 ° C. or lower when the gaseous fuel is sintered with combustion heat of only a carbonaceous material, and the high temperature region holding time is less than 150 seconds (First feature), and oxygen enrichment in a region within 1/2 of the upstream side of the region that supplies the gaseous fuel (second feature) It is in.

The reason for supplying the gaseous fuel in a region where the high temperature region holding time maintained at 1200 ° C. or higher and 1380 ° C. or lower when the gaseous fuel is sintered with the combustion heat of the carbon material is less than 150 seconds is the first feature. By supplying gaseous fuel to the region of the charging layer where combustion temperature of the material alone cannot secure a high temperature region holding time of 150 seconds or more, and burning it, the high temperature region holding time is provided at all positions in the charging layer. This is to secure 150 seconds or more to obtain a high-quality sintered ore. That is, the present invention is a technique for setting the high temperature region holding time to 150 seconds or more by mainly changing the supply amount of the gaseous fuel in the method for producing sintered ore with the combustion heat of the carbonaceous material.

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

And, in order to extend the high temperature region holding time in the region where the high temperature region holding time is less than 150 seconds, it is necessary to supply gaseous fuel in the stage where the sintering reaction is proceeding. For example, in the region of the upper layer portion 20% in the thickness direction of the charge layer, when the high temperature region holding time is less than 150 seconds, the ignition furnace exit side to the ore discharge where the sintering reaction of that portion is proceeding It is necessary to supply gaseous fuel in the region of 20% upstream of the part (effective machine length).

In an actual sintering machine, it is not realistic in terms of equipment to change the supply range of gaseous fuel by the pallet progression method in units of%. Therefore, the effective machine length part from the ignition furnace exit side to the discharge section is divided into multiple parts in the direction of travel, so that diluted gas fuel can be supplied in each division unit, and the high temperature range is maintained over the entire range of the effective machine length It is preferable to be able to turn ON / OFF dilution gas fuel on a segment basis so that the time is 150 seconds or more. However, since the surface layer of the charging layer immediately after leaving the ignition furnace is still hot and there is a concern about ignition of the gaseous fuel, supply of gaseous fuel should be avoided for about 3 m from the ignition furnace exit side. Is preferred.

However, in the region where the high temperature region retention time is less than 30 seconds, it is substantially difficult to extend the high temperature region retention time to 150 seconds or more even if gaseous fuel is supplied. Therefore, in reality, a thermocouple is inserted from the surface of the charging layer in the center in the pallet width direction, and the temperature change during sintering at each position in the thickness direction of the charging layer is measured, It is preferable to supply the gaseous fuel to a region where the holding time is 30 seconds or more and less than 150 seconds.

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

The air containing the gaseous fuel diluted below the lower combustion limit concentration is a mixture of gaseous fuel previously diluted below the lower combustion limit concentration in the air above the charging layer, or in the air above the charging layer. Alternatively, it may be diluted instantly below the lower combustion limit concentration by injecting (raw) gaseous fuel with high concentration at high speed and mixing it with air.

Moreover, it is preferable to reduce the amount of carbonaceous material added to the sintering raw material (coke amount) equal to or more than the amount corresponding to the calorific value of the gaseous fuel added to the air. The reason is that when gaseous fuel is added without changing the amount of carbon material, the total calorific value is excessive and the maximum temperature exceeds the upper limit (1400 ° C) of the appropriate temperature range, producing calcium ferrite. This is because the ratio decreases and the calcium silicate increases, resulting in a sintered ore having low strength and poor reducibility. Therefore, in the present invention, the amount of carbonaceous material in the sintering raw material is a temperature range of 1200 to 1400 ° C. with the highest temperature during sintering depending on the amount of gaseous fuel added to the air (combustion heat amount), Desirably, it is necessary to appropriately adjust the temperature range of 1200 to 1380 ° C.
Incidentally, when viewed in terms of calorific value, the gaseous fuel corresponding to 1 mass% of the amount of carbon material is about 1 vol% for LNG (liquefied natural gas) and about 0.5 vol% for propane gas.

Next, the reason for enriching oxygen in the region where the gaseous fuel is supplied, which is the second feature, is that the gas atmosphere at the time of sintering shifts to the oxidation direction due to the oxygen enrichment, and as a result, sintering is performed by sintering. This is because the production rate of calcium ferrite in the ore is increased and the production rate of calcium silicate is reduced, so that a sintered ore having high strength and excellent reducibility can be obtained.
Further, the reason why it is preferable to limit the oxygen-enriched region to within 1/2 of the upstream side of the region where the gaseous fuel is supplied is that, as shown in FIG. This is because, when supplied, a high-strength sintered ore can be obtained, and the sintering time becomes long, so that the production rate decreases.

The oxygen enrichment effect can be obtained even if the oxygen concentration contained in the air to be sucked in the charging layer exceeds the oxygen concentration (21 vol%) in the atmosphere, but is preferably sintered. It is preferable that the amount of oxygen is such that the O ₂ concentration at that time can be 12.5 vol% or more. From this viewpoint, it is preferable to enrich the oxygen concentration in the air to 24.5 vol% or more. On the other hand, when the oxygen concentration in the air is 35 vol% or more, the cost required for oxygen enrichment exceeds the benefits to be enjoyed. Therefore, the amount of oxygen enriched in air is preferably added so that the oxygen concentration in the air is in the range of more than 21 vol% and less than 35 vol%, more preferably in the range of 24.5 to 30 vol%, and still more preferably, It is in the range of 24.5 to 28 vol%.

The method for enriching oxygen is not particularly limited. For example, a method of adding pure oxygen to air sucked through a charging layer in a windbox, or a method of adding high-concentration oxygen together with a gaseous fuel described later A method of adding a high concentration of oxygen to the atmosphere to which the fuel is added to obtain a predetermined oxygen concentration in advance can be suitably used.
As an example of the former, FIG. 23 shows a schematic diagram of an apparatus for supplying oxygen in a gaseous fuel supply apparatus using raw gas as the gaseous fuel. In this apparatus, one or more baffle plates are provided with a gap in the middle in the height direction in the hood installed above the charging layer in the region where the gaseous fuel is supplied, and below the baffle plate A gas fuel supply pipe is installed at the high-speed horizontal method where the raw gas fuel is blown off and instantly used as a diluted gas fuel having a concentration lower than the lower limit of combustion, and oxygen above the baffle plate. A supply pipe is provided to supply enriched oxygen toward the gap between the baffle plates. Accordingly, the oxygen supplied from the oxygen supply pipe once reaches a concentration that is enriched until it passes over the baffle plate or the gap between the baffle plates, and then merges with the gaseous fuel. Can be prevented from touching. Note that the oxygen supplied from the pipe may not be pure oxygen. Here, the baffle plate disposed above the gaseous fuel supply pipe is for preventing the LNG and other gaseous fuels from being lighter than the air, and thus preventing leakage and scattering above the hood. In addition, since oxygen has a specific gravity heavier than that of gaseous fuel, there is little risk of diffusion outside the hood.

The present invention is characterized in that oxygen is enriched at the same time as the supply of the gaseous fuel. However, this not only enhances the sintering reaction and shortens the time required for sintering, but also enhances the combustion with the gaseous fuel. The combustion position of the carbonaceous material in the raw material is shifted to a lower temperature side, making the temperature distribution curve in the charging layer very wide and the holding time at the high temperature range can be further extended. It is possible to improve the quality of the sintered ore while increasing the rate.

Furthermore, when gaseous fuel is supplied at the same time as oxygen enrichment, the retention time in the high temperature range can be greatly extended, so that it is possible to reduce the amount of carbon material equivalent to the calorific value of the gaseous fuel. Become. This reduction in the amount of charcoal contributes to the reduction of carbon dioxide generated by combustion, and is therefore preferable for the global environment.

The sintering raw materials shown in Table 2 were put into a drum mixer and granulated to a size of about 5 mmφ. At this time, the silica in the obtained sintered ore was adjusted to be 4.9 mass% and the basicity was 2.0. Next, the above granulated particles were filled in a cylindrical iron sintering pot having a size of 290 mmφ × 400 mmH shown in FIG. 18 with carbon material addition amounts of 4.7 mass% and 4.5 mass%, and a charging layer. The carbon material in the sintering raw material is ignited by an ignition furnace disposed above the charging layer and sucked from the charging layer to the lower side by a blower disposed below the sintering pan. A sintering experiment simulating an actual sintering machine for burning (powder coke) was conducted.

In the above-described sintering experiment, an effective machine length (ignition furnace exit side to exhausting section) is 58 m, and as shown in FIG. 24, gaseous fuel is supplied over the upstream side 17 m. Table 5 shows the regions where the LNG diluted to 0.4 vol% is supplied to the region of the upper layer portion 29% of the charging layer and the oxygen concentration is enriched to 25.4 vol% in the gaseous fuel supply region. Simulating changing as shown. Specifically, the base (T1) is based on the condition of adding only LNG as the gaseous fuel, and the condition (T2) for enriching oxygen in the same region as the gaseous fuel supply region is added to this condition. Sintering was performed at three levels of the condition (T3) for enriching oxygen in the upstream half region.

Moreover, in the above-mentioned sintering simulation experiment, a thermocouple was inserted into each position of 100 mm, 200 mm and 300 mm from the surface layer in the sintering test pot, and the high temperature region holding time at each position during sintering was measured, and the result was obtained. This is shown in FIG. In addition to measuring the time required for sintering, the shutter strength of the obtained sintered ore is measured according to JIS M8711, the product yield is further determined, the production rate is determined from those results, and the result is obtained. This is shown in FIG.

From the result of the above test, in the condition (T2) in which oxygen is enriched in the gaseous fuel supply region in addition to the supply of the gaseous fuel, only the gaseous fuel is supplied and compared with the condition (T1) in which oxygen is not enriched. As a result, the cold strength SI and product yield of the sintered ore can be greatly increased, and the production rate is also greatly improved. Further, in the condition (T3) in which oxygen is enriched in the upstream half region of the gaseous fuel supply region, only the gaseous fuel is supplied and sintering is performed in comparison with the condition (T1) in which oxygen is not enriched. The cold strength SI and product yield of the ore can be greatly increased, and the production rate has also been greatly improved. Also, productivity is greatly improved in comparison with the condition (T2) in which oxygen is enriched over the entire length of the gaseous fuel supply region.

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

1: Raw material hopper 2: 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: Cut-off plate

Claims

A gaseous fuel diluted with a sintered raw material containing fine ore and charcoal on a circulating moving pallet to form a charging layer, igniting the charcoal on the surface of the charging layer and diluting below the lower combustion limit concentration Suction ore is produced by sucking the air above the charging layer, including the slag, into the charging layer by sucking it with a wind box placed under the pallet, and burning the gaseous fuel and carbonaceous material in the charging layer. In the way to
The gas fuel is supplied to a region where the high temperature region holding time maintained at 1200 ° C. or higher and 1400 ° C. or lower when sintering with the combustion heat of the carbonaceous material is less than 150 seconds, so that the high temperature region holding time is 150 seconds or longer. A method for producing a sintered ore characterized by enriching oxygen in the air in the gaseous fuel supply region.
The amount of carbon material in the sintered raw material is changed to keep the maximum temperature within the range of 1200 to 1400 ° C., and the amount of gaseous fuel supplied to the region where the high temperature region retention time is less than 150 seconds is varied. The method for producing a sintered ore according to claim 1, wherein the high temperature region holding time is 150 seconds.
The method for producing a sintered ore according to claim 1 or 2, wherein oxygen is enriched in a region within 1/2 of the upstream side of the gaseous fuel supply region.
The method for producing sintered ore according to claim 1 or 2, wherein oxygen is enriched in a region within an upstream side (1/4 to 1/2) of the gaseous fuel supply region.
The method for producing a sintered ore according to any one of claims 1 to 4, wherein the oxygen concentration in the air is more than 21 vol% and less than 35 vol% by the enrichment of oxygen.
By the oxygen enrichment, the O 2 concentration in the gas atmosphere in the charging layer in the oxygen enriched region is set to 12.5 vol% or more, and the maximum temperature reached is a temperature range of 1275 to 1375 ° C. The method for producing a sintered ore according to any one of claims 1 to 5.
7. The high temperature region holding time in the region where the high temperature region holding time is less than 150 seconds is set to 150 seconds or more and 300 seconds or less by supplying the gaseous fuel and enriching oxygen. A method for producing a sintered ore according to claim 1.
The method for producing a sintered ore according to any one of claims 1 to 7, wherein the amount of the carbonaceous material equivalent to the calorific value of the gaseous fuel to be supplied is reduced.
The air to which the gaseous fuel is added is obtained by adding gaseous fuel previously diluted below the lower combustion limit concentration to the air, or diluted to below the lower combustion limit concentration by injecting the gaseous fuel into the atmosphere above the charging layer at high speed. The method for producing a sintered ore according to any one of claims 1 to 8, wherein the method is any one of the above.
The gaseous fuel is supplied below a baffle plate having one or more stages with a gap in the middle in the height direction in the hood installed above the charging layer in the region where the gaseous fuel is supplied, The method for producing a sintered ore according to any one of claims 1 to 9, wherein the enriched oxygen is supplied toward a gap between the baffle plates above the baffle plate in the hood.