JP2016056405A - Method for enriching oxygen in heat insulating furnace of sintering machine, and the heat insulating furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for enriching oxygen in a heat insulating furnace, which is used in a sintering machine having the heat insulating furnace and in which gaseous fuel can be supplied and simultaneously oxygen can be enriched without removing the heat insulating furnace, and to provide the heat insulating furnace.SOLUTION: The method for enriching oxygen in the heat insulating furnace of the sintering machine comprises a step of supplying high-temperature gas containing gaseous fuel diluted to the concentration, which is equal to or lower than the combustion lower limit concentration, to the inside of a sintering raw material charging layer which is installed on the downstream of an ignition furnace. An oxygen supply pipeline for supplying oxygen to the high-temperature gas is connected to the upstream side of a connection position of a high-temperature gas supply pipeline used for supplying the high-temperature gas to the heat insulating furnace, with the heat insulating furnace so that the high-temperature gas having the oxygen concentration exceeding 21 vol% can be supplied to the inside of the heat insulating furnace.SELECTED DRAWING: Figure 15

Description

  The present invention relates to oxygen enrichment in a heat-retaining furnace in a downward suction type Dwytroid (DL) sintering machine that produces a high-quality sintered ore for blast furnace raw material by supplying gaseous fuel in addition to carbonaceous materials as a sintering heat source. The present invention relates to a crystallization method and a heat insulation furnace.

  In general, sintered ore, which is a main raw material for the blast furnace ironmaking method, is 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 at a predetermined ratio on a conveyor. The cut out raw material is added with an appropriate amount of water by the drum mixers 2 and 3 and the like, mixed and granulated to obtain a sintered raw material which is pseudo particles having an average diameter of 3 to 6 mm. This sintered raw material is then transferred to 400 to 800 mm on an endless moving type sintering machine pallet 8 from the surge hoppers 4 and 5 arranged on the sintering machine through the drum feeder 6 and the cutting chute 7. A sintered raw material charging layer (hereinafter also simply referred to as “charging layer”) 9, which is charged with a thickness and is also referred to as a sintering bed, is formed. Thereafter, the carbon material on the surface of the charging layer is ignited by the ignition furnace 10 installed above the charging layer 9, and the air above the charging layer is passed through the window box 11 disposed immediately below the pallet 8. Is sucked downward to sequentially burn the carbonaceous material in the charging layer, 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 continues to be combusted by the air that is sucked by the wind box 11 and flows in the charging layer from the upper layer toward the lower layer in the thickness direction. A combustion / melting zone having a width (hereinafter simply referred to as “combustion zone”) is formed. This combustion zone gradually moves from the upper layer to the lower layer of the charging layer as the pallet 8 moves to the downstream side, and after the combustion zone has passed, the sintered cake (hereinafter simply referred to as a sintered cake). Also referred to as “sintered layer”).
FIG. 2 shows that the carbon material of the charging layer surface ignited in the ignition furnace is sucked by the wind box and continuously burned by the air introduced into the charging layer to form a combustion zone. It is the figure which showed typically the process in which it moves sequentially from an upper layer to a lower layer, and a sintered cake is formed.

In general, the strength of sintered ore depends on the product of temperature and time when the sintering raw material particles melt and the sintering reaction begins to occur, that is, when the temperature is maintained at a temperature of 1200 ° C. or higher. It is known that the larger the value, the higher the value. Therefore, the longer the time of holding at a temperature of 1200 ° C. or higher (hereinafter referred to as “high temperature region holding time”), the higher the yield of sintered ore and the higher the productivity.
FIG. 3 shows the temperature distribution in the charging layer when the combustion zone exists in the middle part in the thickness direction of the charging layer when the moving speed of the pallet of the sintering machine is high (corresponding to high productivity). And a slow case (equivalent when productivity is low). In the figure, the time held in 1200 ° C. or more temperature (high temperature zone holding time), T ₁ if the moving speed of the pallet is _high, but when the moving speed of the pallet is low is indicated by T _2, T ₁ It is shorter than the _{T 2} is. When the high temperature region holding time is shortened, the sintering is insufficient, the cold strength of the sintered ore is lowered, and the yield is lowered. Therefore, in order to produce high-strength sintered ore in a short time with a high yield and high productivity, some measures are taken to extend the holding time in the high temperature range and increase the cold strength of the sintered ore. I need to do it.

  FIG. 4A shows the inside of the charging layer when the combustion zone exists at 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. The temperature distribution in the thickness direction is schematically shown. The middle layer and lower layer of the charging layer are preheated by the combustion heat of the carbon material in the upper layer of the charging layer being carried by the air sucked into the charging layer. However, since the upper layer portion of the charging layer does not have the preheating effect, the high temperature region holding time is short, and the combustion melting reaction (sintering reaction) tends to be insufficient. As a result, the yield distribution of the sintered ore in the cross section in the pallet width direction of the charge layer becomes lower as the charge layer upper layer part as shown in FIG. In addition, in FIG.4 (b), although the yield has also reduced significantly also in the both width | variety edge part side of the pallet width direction cross section of a charging layer, this is due to the heat dissipation from a pallet side wall or the overcooling by the air which passes. This is because the high temperature region holding time cannot be secured sufficiently.

  As a countermeasure against the above-mentioned problem, in particular, the yield non-uniformity problem in the charge layer thickness direction, conventionally, increasing the amount of carbonaceous material (powder coke) added to the sintered raw material as a heat source has been performed. It was. However, when the amount of coke in the sintered raw material is increased, as shown in FIG. 5, although the high temperature range holding time maintained at a temperature of 1200 ° C. or higher can be extended, Calcium ferrite, which has the highest ultimate temperature of over 1400 ° C and has the highest strength among the minerals constituting the sintered ore and is also excellent in reducibility, is an amorphous silicate inferior in cold strength and reducibility. Calcium silicate) and skeletal secondary hematite, which is easily reduced to powder, are decomposed, and conversely, the reducibility and cold strength of the sintered ore are lowered, and the yield is lowered.

Accordingly, the inventors have reduced the amount of carbonaceous material added to the sintering raw material as a technique for solving the above problems, and then installed a hood of a gaseous fuel supply device installed immediately downstream of the ignition furnace of the sintering machine. By supplying gaseous fuel into the gas, introducing the gaseous fuel diluted below the lower combustion limit concentration into the charging layer and burning it, both the maximum reachable temperature and the high temperature range retention time in the charging layer are in the proper range. A technology for controlling the frequency is developed (see, for example, Patent Documents 1 and 2).
When these techniques are applied, as shown in FIG. 6, the supplied gaseous fuel is located away from the position where the carbonaceous material in the charging layer burns, that is, the combustion of the carbonaceous material is completed, Since it burns at the position being cooled, the width of the combustion zone can be expanded in the thickness direction of the charging layer without exceeding the maximum temperature of the combustion zone exceeding 1400 ° C. The holding time can be extended.

  In the downward suction type DL sintering machine, conventionally, the cooler used for cooling the combustion exhaust gas generated from the sintering machine and sucked and discharged by the wind box and the sintered ore discharged from the exhaust section. In many cases, the exhaust gas is discharged at a high temperature after being subjected to exhaust gas treatment such as dust removal. Therefore, in order to effectively use the sensible heat of the exhaust gas, a heat insulation furnace (heat insulation furnace) is provided downstream of the ignition furnace, and instead of the air sucked into the charging layer as combustion support gas, A technology for supplying a high-temperature gas in which a part of the cooler exhaust gas is circulated and reusing it for preheating the sintered raw material charging layer has been put into practical use (see, for example, Patent Document 3).

  However, if the gaseous fuel supply technology disclosed in Patent Documents 1 and 2 described above is applied to a sintering machine having a thermal insulation furnace, the thermal insulation furnace becomes an obstacle to the installation of the gaseous fuel supply apparatus. In addition, when trying to remove the heat-retaining furnace, the heat-retaining furnace, like the ignition furnace, has a solid structure in which the inside is attached with refractory bricks. It is inevitable to stop the operation. Therefore, Patent Document 4 proposes a technique in which a heat-retaining furnace is left as it is, and the furnace is used as a hood for a gaseous fuel supply facility.

  By the way, in order to increase the productivity of sintered ore, it is effective to promote the sintering reaction by enriching the oxygen introduced into the charging layer as combustion support gas and shorten the sintering time. Is known (see, for example, Patent Documents 5 and 6). Therefore, the applicants have proposed a technique for producing sintered ore in which the oxygen enrichment technique described above and the gas fuel supply technique disclosed in Patent Documents 1 and 2 described above are combined. For example, in Patent Document 7 and Patent Document 8, the inside of the hood of the gaseous fuel supply apparatus installed at the position immediately downstream of the ignition furnace in which the sintering reaction proceeds in the upper part of the charging layer where the high temperature region holding time is insufficient Proposes a technique for producing sintered ore that supplies gaseous fuel and enriches oxygen at the same time.

JP 2008-095170 A JP 2008-291354 A JP 50-015702 A JP 2010-132946 A WO98 / 077891 Japanese Patent Laid-Open No. 02-073924 JP 2012-207236 A JP 2014-031580 A

  However, when the apparatus for simultaneously supplying gaseous fuel and enriching oxygen proposed in Patent Document 7 and Patent Document 8 is applied to a sintering machine having a heat-retaining furnace described in Patent Document 4, It is necessary to remove the heat-retaining furnace, which is not realistic as described above.

  The present invention has been made in view of the above-mentioned problems in the prior art, and its purpose is to enrich oxygen simultaneously with the supply of gaseous fuel without removing the heat retention furnace in a sintering machine having a heat retention furnace. The present invention proposes an oxygen enrichment method for a heat-retaining furnace and provides the heat-retaining furnace.

  The inventors have intensively studied to solve the above problems. As a result, in order to realize the supply of gaseous fuel and enrichment of oxygen while leaving the thermal insulation furnace that supplies the high temperature gas, the high temperature gas supplied to the thermal insulation furnace is not supplied directly to the thermal insulation furnace. It has been found that it is effective to increase the oxygen concentration in the reactor in advance and then supply it to the heat-retaining furnace, leading to the development of the present invention.

  That is, the present invention is a method for enriching oxygen in a heat retaining furnace of a sintering machine that is installed downstream of an ignition furnace and supplies a high-temperature gas containing gaseous fuel diluted below a lower combustion limit concentration into a sintering material charging layer. Then, the oxygen enrichment method to the heat retention furnace of the sintering machine characterized by supplying the high temperature gas which increased oxygen concentration beforehand in a heat retention furnace is proposed.

  The oxygen enrichment method of the above-mentioned sintering machine of the present invention to the heat-retaining furnace is performed by connecting an oxygen supply pipe for supplying oxygen to a high-temperature gas supply pipe for supplying high-temperature gas to the heat-retaining furnace. It is characterized by increasing.

  Moreover, the oxygen enrichment method to the heat retention furnace of the said sintering machine of this invention is characterized by raising oxygen concentration in the high temperature gas supplied to the said heat retention furnace over 21 vol%.

  Further, the high-temperature gas used in the method for enriching oxygen in a heat retaining furnace of the sintering machine of the present invention is a combustion exhaust gas generated from the sintering machine and / or a cooler exhaust gas used for cooling the sintered ore. Features.

  The present invention is also a heat retention furnace of a sintering machine installed downstream of the ignition furnace and supplying a high temperature gas containing gaseous fuel diluted below the lower combustion limit concentration into the sintering material charging layer, A high-temperature gas supply pipe for supplying a high-temperature gas is connected to the upper surface of the furnace, and a gaseous fuel is supplied to the high-temperature gas flow supplied from the high-temperature gas supply pipe to the inside of the heat insulation furnace at the connection position of the high-temperature gas supply pipe. A gas fuel supply nozzle for ejecting gas is disposed, and an oxygen supply pipe for supplying oxygen to the high-temperature gas is connected upstream of the connection position of the high-temperature gas supply pipe with the heat-retaining furnace. It is a heat retention furnace of the sintering machine.

  In the heat retention furnace of the sintering machine according to the present invention, an oxygen concentration meter is installed between a connection position of the high temperature gas supply pipe with the heat retention furnace and a connection position of the oxygen supply pipe, The oxygen supply amount to the hot gas is controlled based on the measured concentration value.

  Further, the heat retaining furnace of the above-described sintering machine according to the present invention is a gas fuel supply device for supplying air containing gaseous fuel diluted below the lower combustion limit concentration into the sintered raw material charging layer, or combustion on the downstream side. It is characterized by having a gaseous fuel supply device for supplying air enriched with oxygen containing gaseous fuel diluted below the lower limit concentration into the sintering raw material charging layer.

  According to the present invention, since oxygen can be enriched at the same time as supplying gaseous fuel even in a heat retaining furnace of a downward suction type Dwytroid sintering machine, it is of high quality and excellent in reducibility. Stable ore for blast furnace raw material can be produced stably.

It is a figure explaining the outline | summary of the manufacturing process of a sintered ore. It is a figure explaining the change accompanying progress of sintering in an insertion layer. It is the figure which showed the temperature distribution in the charging layer at the time of sintering compared with the time of high production and the time of low production. Temperature distribution in the charging layer when the combustion zone exists in the upper layer, middle layer and lower layer of the charging layer, and yield distribution of sintered ore in the pallet width direction cross section of the charging layer FIG. It is a figure explaining the change of the temperature distribution in a charging layer when increasing carbon material addition amount. It is a figure explaining the change of the temperature distribution in a sintered layer when gaseous fuel is supplied. It is a figure explaining the test pan used for a sintering experiment. It is a graph which shows the influence which the position which enriches oxygen has on the productivity of a sintered ore. It is a graph which shows the influence which the density | concentration which enriches oxygen has on the productivity of a sintered ore. It is a figure explaining the influence which the position which enriches oxygen has on the temperature pattern at the time of sintering. It is a graph which shows the influence which the position which enriches oxygen has on the high temperature range holding time and the highest ultimate temperature. It is a figure explaining the conventional heat retention furnace which supplies gaseous fuel and high temperature gas. It is a figure explaining the gaseous fuel supply apparatus of the prior art which enriches oxygen. It is a figure explaining the heat retention furnace of this invention which supplies the high temperature gas which enriched gaseous fuel and oxygen. It is a graph which shows the effect which it has on the productivity of a sintered ore when oxygen is enriched in addition to gaseous fuel supply with a thermal insulation furnace.

  In order to determine the optimum position and the optimum oxygen concentration when enriching oxygen in a sintering machine having a heat retaining furnace and a gaseous fuel supply device, such as the sintering machine disclosed in Patent Document 4, A sintering experiment using a sintering test pot simulating a sintering machine was performed. Here, as shown in FIG. 7, the test pan has a cylindrical shape with an inner diameter of 300 mmφ × a height of 400 mm, a bottom portion in a lattice shape and a breathable quartz-made sintered raw material charging container (pot portion). After charging the sintered raw material added with the carbon material to form the charging layer, the upper surface of the charging layer is ignited by an ignition device (not shown) and exhausted by a blower disposed below the container. Then, the air above the charging layer is sucked and introduced into the charging layer, and the carbonaceous material in the sintering raw material is burned so that the sintering can be performed.

<Experiment 1>
As shown in Table 1, city gas as a gaseous fuel is added to the air supplied to the sintering test pan to a concentration of 0.25 vol% (constant), and 320 seconds after ignition (about the total sintering time) Sintering experiment was conducted, in which oxygen was enriched to 24 vol% and the enrichment time was changed to three levels between 80 sec, 160 sec and 320 sec after ignition. The time and the yield of the sintered ore were measured, and the production rate (unit time, the amount of sintered ore production per unit hearth area (t / h · m ² )) was determined from the results.
Here, the oxygen enrichment time of 80 sec is the condition for oxygen enrichment only in the above-described sintering furnace, and the supply time of 160 sec is oxygen enrichment in the insulation furnace and the hood of the # 1 gas fuel supply device. The conditions and the supply time of 320 seconds correspond to the conditions for oxygen enrichment in all the hoods of the warming furnace to the # 3 gaseous fuel supply apparatus.

  The results of the experiment are shown together in Table 1 and shown in FIG. The yield change amount in Table 1 is a change amount based on the case where oxygen is not enriched (oxygen concentration 21 vol%). From this result, the effect of improving the production rate by enriching oxygen is the largest at the level T1, that is, the condition for enriching oxygen only in the heat-retaining furnace, and the gas after the heat-retaining furnace as in the levels T2 and T3. It was found that the effect of improving the production rate was small under the condition of enriching oxygen with the fuel supply device, and the reverse effect was obtained in terms of the yield of sintered ore.

<Experiment 2>
Next, based on the result of the above <Experiment 1>, a sintering experiment was conducted in which the preferred range of the oxygen concentration to be enriched was investigated under the condition that the time for enriching oxygen was limited to only a heat-retaining furnace.
In the experiment, as shown in Table 2, city gas was diluted to 0.25 vol% and added to the air supplied to the sintering test pot, and supplied for 320 seconds after ignition, and the oxygen concentration in the air Was changed to 5 levels of 21 vol% (no oxygen enrichment), 24 vol%, 27 vol%, 30 vol% and 33 vol%, and supplied for 80 seconds after ignition, and then switched to normal air for sintering, Similar to <Experiment 1>, the sintering time and the yield of sintered ore were measured, and the production rate (the production rate of sintered ore per unit time and unit hearth area (t / h · m ²⁾ was determined from the results. )).

  The results of the experiment are shown in Table 2 and FIG. 9 shows the relationship between the oxygen concentration, the sintering time, and the yield of the sintered ore. From these results, the higher the oxygen concentration, the shorter the sintering time, but the yield of sintered ore becomes maximum at 27-30 vol%, and it decreases below that. As a result, the effect of increasing the production rate is It was found that when the oxygen concentration was 27 vol% or higher, the saturation state was reached, and at 33 vol%, the oxygen concentration decreased.

As described above, the inventors consider the reason why the heat insulation furnace immediately downstream of the ignition furnace is most effective as a position to enrich oxygen as follows.
As described above, oxygen enrichment to an appropriate concentration is effective for extending the high temperature range retention time. This is because, as can be seen from FIG. 4, the position in the thickness direction of the charging layer where the high temperature region holding time necessary for sintering is insufficient is the upper layer portion of the charging layer. Therefore, enriching oxygen in the region where the sintering reaction is proceeding in the above-mentioned part, that is, enriching oxygen immediately downstream of the ignition furnace, extends the high temperature region holding time of the upper part of the charging layer. It is considered effective against this.

FIG. 10 shows a high temperature region holding at a depth of 100 mm from the upper surface of the raw material charging layer charged in the test pan when the oxygen enrichment range was changed in the above-described <Experiment 1> sintering experiment. The measurement result of time (time hold | maintained at 1200 degreeC or more) and the highest attained temperature is shown.
From this result, compared with the condition (level 1) enriched with oxygen only by the heat-retaining furnace, the gas fuel supply device downstream thereof is maintained at 1200 ° C. or higher under the condition (level 2 and 3) enriched with oxygen. Time (high temperature range holding time) decreases, and the maximum temperature reached during sintering also decreases.

The reason for the change is estimated as follows.
As shown in FIG. 11, under the condition (level 1) enriched with oxygen only in the heat-retaining furnace, as shown in FIG. 11 (b), when only city gas is supplied (FIG. 11 (a)). Because the combustion position of the gaseous fuel shifts to the upper layer side of the charging layer, the maximum temperature is slightly lowered, but the width of the combustion zone in the charging layer thickness direction is expanded, and the high temperature region holding time is extended. . However, under the conditions (levels 2 and 3) in which the gaseous fuel supply apparatus enriches oxygen in addition to the thermal insulation furnace, the combustion position of the gaseous fuel is further above the charging layer as shown in FIG. Moving. As a result, the difference between the combustion positions of the coke and the gaseous fuel becomes too large, and not only the effect of extending the high temperature region holding time cannot be obtained, but also the maximum temperature reached is lowered.

Further, the inventors consider the reason why there is an optimum range of the oxygen concentration as described above as follows.
The combustion reaction of coke C is represented by the following formula:
C + O ₂ → CO ₂
The reaction rate equation is represented by the following formula:
r _C = A × αexp (−Ea / RT) × [O ₂ ]
The combustion reaction of methane CH ₄ , which is the main component of city gas, is represented by the following formula:
CH ₄ + 2O ₂ → CO ₂ + 2H ₂ O
The reaction rate equation is represented by the following formula:
r _CH4 = A × αexp (−Ea / RT) × [O ₂ ] ²
It is represented by

That is, while the combustion rate of coke is proportional to the first power of the oxygen concentration, the combustion speed of gaseous fuel (city gas) is proportional to the second power of the oxygen concentration. In some cases, gaseous fuel burns relatively quickly. Further, when the oxygen concentration increases, the combustion start temperature of the gaseous fuel also decreases. As a result, the same phenomenon as in FIG. 11 (b) occurs, the gap between the position where the coke burns and the position where the gaseous fuel burns increases, and the high temperature range holding time is extended. However, if the oxygen concentration becomes too high, the combustion position of the gaseous fuel further moves upward in the charging layer, so that the same phenomenon as in FIG. 11C occurs, and the deviation width between the combustion position of the coke and the gaseous fuel. Becomes too large, and the effect of extending the holding time in the high temperature range cannot be obtained.
In addition, oxygen enrichment increases the combustion rate of coke and gaseous fuel and shortens the combustion time, so the high temperature region retention time is further shortened and the yield of sintered ore is reduced.
Furthermore, when supplying gaseous fuel, since the amount of carbonaceous material added to the sintering raw material is reduced in order to suppress an increase in the maximum temperature reached, the negative effect is further increased.

  From the results of <Experiment 1> and <Experiment 2>, in the sintering machine having a heat-retaining furnace, when supplying gaseous fuel and enriching oxygen to produce sintered ore, an ignition furnace and gaseous fuel supply It has been found that it is effective to enrich oxygen to a concentration exceeding 21 vol% in a heat retaining furnace between apparatuses, and that the oxygen concentration after enrichment in that case is preferably in the range of 27 to 30 vol%.

  In addition, when performing a sintering operation enriched with oxygen in an actual sintering machine, since a large amount of oxygen is required, it is necessary to consider the cost, and the oxygen enrichment shown in Table 2 above is required. In the case of the production rate improvement effect by the above, the optimum value of the oxygen concentration is about 27 vol% (depending on the cost of oxygen) from the viewpoint of cost effectiveness.

Next, the inventors examined a method for enriching oxygen in a heat-retaining furnace having a function of supplying gaseous fuel disclosed in Patent Document 4.
FIG. 12 schematically shows an upstream portion of a sintering machine having a heat retaining furnace described in Patent Document 4 described above. An ignition furnace is installed downstream of the feed section, and one heat retention furnace and three gaseous fuel supply devices are arranged downstream from the ignition furnace from upstream to downstream.
Here, in the gaseous fuel supply apparatus, the gaseous fuel is supplied into the air in the hood from a plurality of rows of gaseous fuel supply pipes arranged in the pallet width direction at the lower part in the height direction of the hood, and instantly. Diluted to a concentration below the lower combustion limit concentration. Also, above the gaseous fuel supply pipe (in the middle of the hood height direction), baffle-shaped baffles are arranged in multiple rows in the pallet width direction and in multiple rows in a staggered manner in the hood height direction. The flow of air sucked and introduced into the charging layer is controlled by a wind box (not shown) disposed below the pallet, and the gaseous fuel supplied from the gaseous fuel supply pipe is out of the apparatus. To prevent leakage.

  Further, in the heat insulation furnace disposed between the ignition furnace and the gaseous fuel supply device, the combustion exhaust gas sucked and discharged by the wind box of the sintering machine and the sintered ore discharged from the ore discharge section are cooled. The high-temperature gas reusing the cooler exhaust gas used in the process is supplied into the furnace from a plurality of high-temperature gas supply pipes connected to the upper surface of the heat insulation furnace, and the gaseous fuel is connected to the high-temperature gas supply pipe. It is ejected from the ring-shaped gaseous fuel supply nozzle disposed in the lower part (inside the heat-retaining furnace) toward the high-temperature gas flow, instantaneously mixed with the high-temperature gas, and diluted below the lower combustion limit concentration.

  FIG. 13 shows a gaseous fuel supply apparatus capable of enriching oxygen simultaneously with the supply of the gaseous fuel disclosed in Patent Documents 7 and 8 described above. In this gaseous fuel supply apparatus, an oxygen supply pipe is arranged above a baffle plate arranged in a plurality of rows and a plurality of stages in the middle in the height direction in the hood of the gaseous fuel supply apparatus, and the baffle plate is connected to the baffle plate from the pipe. By blowing out oxygen toward the gap, oxygen is prevented from leaking to the outside, while enriching oxygen and making the concentration uniform.

  However, the gaseous fuel supply device cannot be applied to the sintering machine disclosed in Patent Document 4 as it is. This is because in a thermal insulation furnace, a pressure gauge is installed to prevent the supplied hot gas from leaking to the outside, and the flow rate of the hot gas is controlled so as to be always negative with respect to the outside. ing. However, when oxygen is newly supplied here, it is necessary to control not only the flow rate of the high-temperature gas but also the flow rate of oxygen, which makes it difficult to control the pressure inside the heat insulation furnace.

  Further, in the heat insulation furnace disclosed in Patent Document 4, in order to dispose a nozzle for newly supplying oxygen in addition to the ring-shaped nozzle for supplying gaseous fuel, from the viewpoint of preventing fire and explosion, an oxygen supply nozzle The location where the gas fuel is surely diluted to below the lower combustion limit concentration, where it is sufficiently away from the gas fuel supply nozzle, and the oxygen supplied into the heat insulation furnace is mixed and homogenized with the hot gas Although it is necessary to be a place where time can be secured, there is no position satisfying such a condition in a limited space in the heat insulation furnace. Furthermore, in order to measure the oxygen concentration supplied into the heat insulation furnace, it is necessary to measure at a plurality of locations in the heat insulation furnace.

  In addition, the said problem can be solved by removing a heat retention furnace and newly providing the gaseous fuel supply apparatus disclosed by patent document 7 or 8. FIG. However, the above method requires a large amount of cost for removing the heat-retaining furnace and newly installing a gaseous fuel supply device, and is not practical in view of a decrease in the production of sintered ore during the construction period.

  Therefore, in the present invention, the oxygen enrichment to the heat insulation furnace is not performed by directly supplying oxygen to the heat insulation furnace, but the oxygen concentration of the high-temperature gas supplied to the heat insulation furnace is increased in advance. 14, specifically, as shown in FIG. 14, oxygen is supplied to the high-temperature gas upstream from the connection position of the high-temperature gas supply pipe for supplying the high-temperature gas to the heat-retaining furnace. We decided to adopt a method of connecting oxygen supply piping to supply oxygen to high temperature gas, supplying and mixing oxygen, and supplying it to the heat insulation furnace after homogenization.

  If this method is used, oxygen enrichment can be realized without removing the heat-retaining furnace or performing a large remodeling of the heat-retaining furnace. Further, the oxygen concentration can be controlled only by controlling the flow ratio of the high-temperature gas and the oxygen gas, and the oxygen concentration needs to be measured only at one location of the high-temperature gas supply pipe. Can be easily controlled and managed. Furthermore, since oxygen is supplied to the high-temperature gas supply pipe, the supply nozzle such as gaseous fuel is not clogged and maintenance is facilitated.

  Furthermore, when oxygen is supplied in the heat insulation furnace, it is necessary to supply high concentration oxygen to the heat insulation furnace. However, since the heat insulation furnace is adjacent to the ignition furnace, the upper surface of the raw material charging layer is a gaseous fuel. There is a high possibility that there is a residual fire that causes abnormal combustion (fire and explosion). Therefore, in order to prevent the piping itself from burning out, it is necessary to make the oxygen supply pipe incombustible by using an expensive pipe made of copper, copper alloy, Ni alloy or the like subjected to oil prohibition treatment. However, in the above oxygen mixing method for high-temperature gas, since there is no fire type, the use of expensive piping becomes unnecessary.

  Note that the oxygen concentration in the air supplied into the sintering raw material layer in the heat insulation furnace of the present invention is that the amount of high-temperature gas supplied to the heat insulation furnace is overwhelmingly higher than that of gaseous fuel. It is almost determined by the concentration. Therefore, the oxygen concentration in the air supplied into the sintering raw material layer may be controlled by the oxygen concentration in the high-temperature gas. For example, as shown in FIG. By installing an oxygen concentration meter between the connection position of the oxygen supply pipe and the connection position of the oxygen supply pipe, and adjusting the opening of the flow rate adjustment valve installed in the oxygen supply pipe based on the measured value of this oxygen concentration meter The oxygen concentration can be easily controlled.

Next, the high temperature gas supplied to the heat retention furnace of the present invention will be described.
In the present invention, the high-temperature gas supplied to the heat-retaining furnace is not particularly limited, but high-temperature exhaust gas generated from the sintering machine, for example, combustion exhaust gas sucked / exhausted by a wind box disposed below the pallet, or sintering machine If it is a cooler exhaust gas used for cooling of the sintered ore discharged | emitted from the exhaust part of this, it can use suitably. Moreover, you may use both combustion exhaust gas and cooler exhaust gas, and in that case, combustion exhaust gas and cooler exhaust gas may be supplied separately, and may be supplied after mixing beforehand. Further, the supply position of the combustion exhaust gas and the cooler exhaust gas may be different. In addition, when using combustion exhaust gas, it is preferable to use gas with little oxygen consumption and high oxygen concentration.

  The high temperature gas preferably has a temperature in the range of 130 to 300 ° C. If the temperature is lower than 130 ° C., the effect of preheating the sintered raw material is small. On the other hand, if the temperature exceeds 300 ° C., the sintered raw material that is the granulated particles collapses due to rapid drying.

Next, the gaseous fuel supplied to the heat retaining furnace and the gaseous fuel supply device in the present invention will be described.
Gas fuels used in the present invention include city gas, LNG, methane gas, ethane gas, propane gas, butane gas, or a mixed gas thereof, as well as blast furnace gas (B gas) and (coke oven gas) C gas generated at steelworks. CO gas or a mixed gas thereof can be used. However, when B gas, C gas, or CO gas is used, it is necessary to take measures against CO gas leakage. Further, in the present invention, in addition to the gaseous fuel, alcohols, ethers, petroleums, and other hydrocarbon-based liquid fuels that are vaporized can also be used. However, in this case, it is preferable to maintain the gas supply pipe at a temperature not less than the boiling point of the liquid fuel and less than the ignition temperature so that the vaporized fuel does not re-liquefy.

It should be noted that the concentration of the gaseous fuel contained in the air supplied into the sintered raw material charging layer by the heat retaining furnace or the gaseous fuel supply device (concentration after dilution) needs to be lower than the lower combustion limit concentration at normal temperature. If the concentration of the diluted gaseous fuel is higher than the lower combustion limit concentration, it may burn above the charging layer, and the effect of supplying the gaseous fuel may be lost, or a fire or explosion may occur. Further, when the concentration of the diluted gas fuel is high, the combustion temperature is lowered, and combustion is performed in a region where the sintering reaction has already been completed, so that it may not be able to contribute effectively to extending the high temperature region holding time. The concentration of the diluted gaseous fuel is preferably 75% or less of the lower limit of combustion at normal temperature in the atmosphere, more preferably 20% or less of the lower limit of combustion, and further preferably 10% or less of the lower limit of combustion. However, if the concentration of the diluted gas fuel is less than 1% of the lower combustion limit concentration, the calorific value due to combustion is insufficient, and the quality improvement effect and productivity improvement effect of sintered ore cannot be obtained. The above is preferable. More preferably, it is 2% or more. Incidentally, since the lower combustion limit concentration of city gas and LNG mainly composed of methane CH ₄ is about 4.8 vol%, the concentration of the diluted gas fuel is preferably in the range of 0.05 to 3.6 vol%, and The range of 05-1.0 vol% is more preferable, and the range of 0.05-0.5 vol% is more preferable.

  In the above description of the present invention, the case of supplying gas fuel together with high-temperature gas and further enriching oxygen in the heat retaining furnace of the sintering machine has been described. In addition to the gaseous fuel, oxygen enrichment may be carried out also in the gaseous fuel supply device installed downstream of the thermal insulation furnace, depending on the installation position and the length in the machine length direction.

  As shown in FIG. 14, the length from the ignition furnace exit side to the discharge portion is 90 m, and one heat-retaining furnace having a length of 7.5 m downstream of the ignition furnace and a length of 7.5 m In the actual machine sintering machine having the gas fuel supply devices of # 1 to # 3, the gas fuel is supplied from the heat insulation furnace and the gas fuel supply device, and the sintering operation for enriching oxygen in the heat insulation furnace is performed. An experiment was conducted to evaluate the effect of oxygen enrichment. In the above experiment, the amount of carbonaceous material (coke) in the sintered raw material was 4 mass% (constant), and the gaseous fuel was LNG diluted to 0.25 vol% in the above-mentioned thermal insulation furnace and gaseous fuel supply device. Then, it supplied in the raw material charge layer. In addition, oxygen is connected to a high-temperature gas supply pipe to be supplied to the heat-retaining furnace, oxygen is supplied in an amount of 27 vol%, and the oxygen concentration is made uniform in the high-temperature gas supply pipe. The oxygen in the air supplied into the raw material charging layer was enriched by supplying it from the upper surface into the heat insulation furnace.

FIG. 15 shows the relationship between the rotational strength (tumbler strength TI) of the sintered ore obtained in the sintering experiment using the above-mentioned actual machine sintering machine and the production rate, with and without oxygen enrichment. Is.
From this figure, by enriching oxygen, the average rotational strength TI of the sintered ore increased by about 2% from 69.5% to 71.5%, and the production rate also increased from 1.37 t / h · m ^2. 1.43t / h · ^{m 2} to about 0.06t / h · ^{m 2} (about 4%) it can be seen that improved.

  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 an agglomeration technique for other ores.

1: Raw material hopper 2: Drum mixer 3: Rotary kiln 4, 5: Surge hopper 6: Drum feeder 7: Cutting chute 8: Pallet 9: Raw material charging layer 10: Ignition furnace 11: Wind box 12: Cut-off plate

Claims (7)

An oxygen enrichment method for a heat retaining furnace of a sintering machine installed downstream of an ignition furnace and supplying a high temperature gas containing a gaseous fuel diluted below a lower combustion limit concentration into a sintering raw material charging layer,
A method for enriching oxygen in a heat retention furnace of a sintering machine, characterized in that a high temperature gas whose oxygen concentration has been increased in advance is supplied into the heat retention furnace. 2. The heat retention furnace for a sintering machine according to claim 1, wherein an oxygen supply pipe for supplying oxygen is connected to a high temperature gas supply pipe for supplying the high temperature gas to the heat retention furnace to increase the oxygen concentration in the high temperature gas. Oxygen enrichment method. 3. The method for enriching oxygen in a warming furnace of a sintering machine according to claim 1 or 2, wherein the oxygen concentration in the high-temperature gas supplied to the warming furnace is increased to more than 21 vol%. 4. The sintering machine according to claim 1, wherein the high-temperature gas is a combustion exhaust gas generated from the sintering machine and / or a cooler exhaust gas used for cooling the sintered ore. Oxygen enrichment method for heat insulation furnace. A heat retention furnace of a sintering machine installed downstream of an ignition furnace and supplying a high-temperature gas containing gaseous fuel diluted below a lower combustion limit concentration into a sintering material charging layer,
A high temperature gas supply pipe for supplying a high temperature gas is connected to the upper surface of the heat retaining furnace,
A gaseous fuel supply nozzle that ejects gaseous fuel to the high-temperature gas flow supplied from the high-temperature gas supply pipe is disposed on the inside of the heat insulation furnace at the connection position of the high-temperature gas supply pipe.
A heat retaining furnace for a sintering machine, wherein an oxygen supply pipe for supplying oxygen to a high temperature gas is connected upstream of a position where the high temperature gas supply pipe is connected to the heat retaining furnace. An oxygen concentration meter is installed between the connection position of the high-temperature gas supply pipe with the heat-retaining furnace and the connection position of the oxygen supply pipe, and oxygen is supplied to the high-temperature gas based on the measured oxygen concentration value of the oxygen concentration meter. 6. The heat retaining furnace for a sintering machine according to claim 5, wherein the amount is controlled. On the downstream side, a gaseous fuel supply device for supplying air containing gaseous fuel diluted below the lower combustion limit concentration into the sintered raw material charging layer, or containing gaseous fuel diluted below the lower combustion limit concentration and oxygen The heat retention furnace for a sintering machine according to claim 5 or 6, further comprising a gaseous fuel supply device for supplying the enriched air into the sintering material charging layer.

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