JP2020007577A - Sinter production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a sinter that reduces the generation of NOx in a two-stage charging two-stage ignition sinter method. SOLUTION: A lower layer 10 is formed on a pallet constituting a Dwightroid (DL) type sintering machine, ignited from the upper part of the lower layer 10, and air is sucked from below to sinter the lower layer 10. The upper layer 20 is formed on the lower layer 10 after ignition, the upper layer 20 is ignited, air is sucked from below to start sintering of the upper layer 20, and then air is blown from below. This is a method for producing a sintered ore by a two-stage charging two-stage ignition sintering method in which the upper layer 20 and the lower layer 10 are sintered by suction, and iron-containing raw materials, auxiliary raw materials, and carbon-based coagulants are mixed. After being collectively granulated and used as a compounding raw material, the compounding material is distributed so that the lower layer thickness h1 / upper layer thickness h2 = 0.7 to 0.9 to form the lower layer 10 and the upper layer 20. do. [Selection diagram] Fig. 2

Description

  The present invention relates to a method for producing a sintered ore.

  Currently, the main raw material for blast furnace ironmaking is sinter. This sintered ore is usually produced as follows. First, iron ore (powder) as raw material, iron ore, iron-containing raw material such as steelmaking dust, flux containing silicon oxide, auxiliary material such as lime containing CaO, and sinter are sintered by combustion heat as fuel ( A carbon material as a coagulant to be coagulated) is mixed at a predetermined ratio, and the mixture is granulated to obtain a blended raw material. Next, the granulated compounded raw material is placed on a pallet of a Dwydroid (DL) type sintering machine that is suctioned downward from a hopper so as to form a raw material packed layer, and the raw material packed layer is placed on the placed raw material packed layer. From the (surface layer), the carbon material in the raw material packed layer is ignited. Then, oxygen is supplied by sucking air from below the pallet while continuously moving the pallet, and combustion of the carbon material in the raw material packed bed proceeds from the upper part to the lower part, thereby burning the carbon material. Sintered by heat sequentially. The obtained sintered part (sinter cake) is pulverized to a predetermined particle size, sieved and the like, and sized to obtain a sintered ore, which is a raw material for blast furnace iron making.

In such a method for producing a sinter using a DL-type sintering machine, a multi-stage charging multi-stage ignition sintering method in which the formation and ignition of a raw material packed layer are performed in two or more stages has been proposed.
In the multi-stage charging, multi-stage ignition sintering method, the compounded raw materials are sequentially loaded in the height direction of the sintering machine to form a multi-stage raw material packed layer, and the surface of each raw material layer is ignited by sucking air from below. This is a method in which the sintering reaction of each layer is made to progress frequently to perform sintering.

A two-stage charging two-stage ignition sintering method in which charging is performed in two stages and ignition is performed in two stages will be described with reference to FIG.
First, in order to granulate the compounded raw material for sinter ore production, in a separate system, a carbon-based coagulant such as coke breeze or the like is added to the iron-containing raw material, and water is added. Granulation is carried out by the first drum mixer 1A and the second drum mixer 2A, respectively.
Although not shown, the first compounded raw material granulated by the first drum mixer 1A is charged by a first hopper 1B onto a pallet laid with bedding ore to form a lower layer 10. .
The lower layer 10 formed on the pallet moves to a position below the first igniter 1C by moving the pallet in the downstream direction 5, and ignites the carbon-based aggregate of fuel by the first igniter 1C from above. Then, using a wind box below the pallet (not shown), the lower-layer combustion zone 10A is formed by the downward suction 6 that sucks air from below, and sintering of the lower layer 10 is started.
The sintering of the lower layer 10 is started, the sintering proceeds while the lower layer combustion zone 10A is lowered, and further moves to a position below the second hopper 2B. Then, the second compounded raw material granulated by the second drum mixer 2A is charged onto the lower layer 10 after ignition by the second hopper 2B to form the upper layer 20.
The carbon-based condensed material of the fuel is ignited from the upper portion of the formed upper layer 20 by the second igniter 2C, and the upper layer combustion zone 20A is formed by the downward suction 6, and the sintering of the upper layer 20 is started. . The lowermost portions of the lower combustion zone 10A and the upper combustion zone 20A that descend as sintering progresses are called the combustion fronts of the respective combustion zones.
Thereafter, lower suction 6 is performed to lower the lower combustion zone 10A and upper combustion zone 20A of the lower combustion layer 10 and the upper combustion layer 20, respectively, so that sintering proceeds, and the lower combustion zone 10A and the upper combustion zone 10A. When 20A reaches the lowermost portion of each layer, sintering by combustion of the carbon-based coagulant ends, and the sintered portion 3 is formed. The sintering of the sintered part 3 proceeds by the residual heat even after the combustion of the carbon-based coagulant, but the sintered part 3 which has been finally sintered is discharged from the end of the pallet.

  By the way, in the production of sintered ore, NOx generated by a reaction between nitrogen contained in coke as a carbonaceous material and oxygen in air sucked downward is included in exhaust gas after sintering. Since NOx is a cause of air pollution, it is necessary to remove NOx from the exhaust gas before releasing it to the atmosphere or to suppress the residual NOx after sintering so as not to be contained in the exhaust gas.

  Conventionally, as a means for reducing NOx in exhaust gas after sintering, there has been known a method of coating coke breeze with quick lime or slaked lime before sintering (Patent Document 1). However, quick lime and slaked lime are expensive, and there are restrictions on the mixing amount depending on the steelworks.

According to Patent Document 2, the multi-stage charging and multi-stage ignition sintering method can change the supply ratio of the raw material of each layer, and therefore the sintering yield due to impaired air permeability caused by a difference in particle size between the upper layer 20 and the lower layer 10. It is described that it is possible to cover the decrease in the amount of exhaust gas, to improve the yield, and to have the advantage of reducing the amount of exhaust gas.
However, Patent Document 2 does not describe or suggest production or reduction of NOx.

Patent Document 3 states that the sintering exhaust gas NOx can be reduced by a multi-stage charging multi-stage ignition sintering method. The NOx reduction mechanism is as follows.
1. Since the sintering of the lower layer 10 burns the carbon material at a low oxygen concentration, the NOx conversion rate (the rate at which nitrogen contained in the carbon material is released as NOx during combustion) decreases.
2. NOx generated during sintering of the upper layer 20 is decomposed in the lower layer combustion zone 10A.

JP 2012-172067 A JP-A-47-26304 JP-A-53-48904

  As described in Patent Document 3, according to the multi-stage charging / multi-stage ignition sintering method, NOx in the final exhaust gas discharged from the lower layer 10 is reduced to some extent by itself. However, in order to reduce the environmental load, it is desired to further reduce NOx in the exhaust gas and reduce the processing steps and energy required for the exhaust gas treatment.

  The present invention provides a method for producing a sintered ore by a two-stage charging and two-stage ignition sintering method, which does not apply a special treatment such as coating to a carbon-based aggregate and can further reduce the amount of NOx emitted from the sintering exhaust gas. The purpose is to provide.

  The present invention solves the above-mentioned problems, and the gist thereof is as follows.

Pallets that make up the Dwyroid (DL) sintering machine
The lower layer is formed by supplying the first compounded raw material obtained by mixing and granulating the iron-containing raw material, the auxiliary raw material, and the carbon-based coagulant,
Ignition from the upper part of the lower layer, start sintering of the lower layer by sucking air from below,
On the lower layer after ignition, an iron-containing raw material, an auxiliary material, and a second blended raw material obtained by mixing and granulating a carbon-based coagulant are further supplied to form an upper layer,
Ignition the upper layer and start sintering the upper layer by sucking air from below,
A method for producing a sintered ore by a two-stage charging two-stage ignition sintering method of thereafter sintering the upper layer and the lower layer by sucking air from below,
The lower layer and the upper layer are obtained by mixing the iron-containing raw material, the auxiliary raw material, and the carbon-based coagulant, granulating them at once, and forming a compounded raw material, and then mixing the compounded raw material with the first compounded raw material. A method for producing a sintered ore, wherein the method is distributed to the second compounding raw material and the lower layer thickness h1 / the upper layer thickness h2 is set to 0.7 to 0.9.

  By optimizing the thickness ratio of the upper layer 20 and the lower layer 10, during the sintering in the two-stage charging two-stage ignition sintering method, the upper and lower two combustion zones (almost in the machine length direction of the sintering machine) The lower-layer combustion zone 10A and the upper-layer combustion zone 20A) can be present at the same time, and the amount of NOx emission in the sintering exhaust gas can be reduced.

FIG. 1 is a schematic diagram of a DL-type sintering machine used in a two-stage charging two-stage ignition sintering method. BRIEF DESCRIPTION OF THE DRAWINGS The figure which shows the two-stage charge two-stage ignition sintering method of this invention which presupposes one-piece granulation. The figure which shows the transition of the exhaust gas composition of the single-stage charging and the single-stage ignition. The figure which shows the transition of the exhaust gas composition of two-stage charging two-stage ignition. The figure which shows the time-dependent change of a combustion front.

  According to the present invention, a lower layer 10 is formed by supplying a first blended raw material obtained by mixing and granulating an iron-containing raw material, an auxiliary raw material, and a carbon-based coagulant material to a pallet constituting a Dwyroid (DL) type sintering machine. Then, sintering of the lower layer 10 is started by igniting from the upper part of the lower layer 10 and sucking air from below, and the iron-containing raw material, the auxiliary material, and the carbon-based coagulant are mixed on the lower layer 10 after ignition. The second compounded raw material thus granulated is further supplied to form the upper layer 20, the upper layer 20 is ignited, and the air is sucked from below to start sintering of the upper layer, and thereafter from below, This is a method for producing a sintered ore by a two-stage charging two-stage ignition sintering method in which the upper layer 20 and the lower layer 10 are sintered by sucking air.

In the two-stage charging two-stage ignition sintering method of the present invention, as shown in FIG. 2, the lower layer 10 and the upper layer 20 are formed by first mixing an iron-containing raw material, an auxiliary raw material, and a carbon-based coagulant. The whole is granulated by the drum mixer 1 to obtain a granulated product. After that, the same granulated material, which has been granulated collectively, is divided and distributed to the first and second blended raw materials such that the lower layer thickness h1 and the upper layer thickness h2 have a predetermined ratio. That is, the first compounding material forming the lower layer 10 and the second compounding material forming the upper layer 20 are substantially homogeneous and the same compounding material.
As a raw material for forming the lower layer 10 and the upper layer 20, the same raw material, which has been granulated in a lump, is distributed to each of them, so that the first drum mixer 1A and the second drum mixer 2A as shown in FIG. There is no need to perform granulation in the two systems. That is, as shown in FIG. 2, a granulator such as the drum mixer 1 can be a single system or a single granulator. In addition, as will be described in detail later, the ratio between the lower layer thickness h1 and the upper layer thickness h2 is set to a predetermined value, and the lower layer combustion zone 10A and the upper layer combustion zone 20A are simultaneously present so that the lower layer 10 and the upper layer combustion zone 20A are simultaneously present. It is necessary that the raw materials for forming the upper layer 20 are the same.

  In the two-stage charging two-stage ignition sintering method of the present invention, the first compounding raw material for forming the lower layer 10 and the second compounding material for forming the upper layer 20 are made of the same material as described above. It is divided into individual amounts and distributed to form each layer. The first and second blended raw materials are iron-containing raw materials such as iron ore, returned ore, and steelmaking dust, as well as auxiliary raw materials such as lime and flux, and carbon-based coagulants such as coke breeze and anthracite as carbon materials for combustion. It was added and granulated. As the iron-containing raw material, in addition to oxide ores such as hematite and magnetite, any iron ore such as iron ore containing hydroxide such as goethite can be used.

  As a result of various studies, the inventors have found conditions that can maximize the NOx reduction effect in the two-stage charging two-stage ignition sintering method. Next, how the ratio between the lower layer thickness h1 and the upper layer thickness h2 is set to a predetermined value as shown in FIG. 2 will be described in detail.

The reduction of NOx in the exhaust gas by the multi-stage charging / multistage ignition sintering method is based on the fact that the NOx in the exhaust gas generated in the upper combustion zone 20A is decomposed in the lower combustion zone 10A. For this reason, at each position in the machine length direction of the DL type sintering machine, two combustion zones (lower combustion zone 10A and upper combustion zone 20A) are formed simultaneously in time and spatially at different heights in the height direction. If they exist in the same direction, NOx in the exhaust gas discharged from the lower layer 10 is reduced. In other words, it is sufficient that the lower combustion zone 10A exists immediately below the upper combustion zone 20A.
Therefore, attention was paid to the importance of expanding the region in the machine length direction where the lower combustion zone 10A and the upper combustion zone 20A overlap in the height direction of the DL sintering machine in the machine height direction.

In order to examine the sintering conditions in which the lower combustion zone 10A and the upper combustion zone 20A overlap in the layer height direction, in the constant wind speed pot test (1.3 Nm ³ / min), one-stage charging one-stage ignition And the time course of the exhaust gas composition when two-stage charging and two-stage ignition were measured. In the single-stage charging single-stage ignition, the layer thickness is 480 mm. In the two-stage charging two-stage ignition, the lower layer thickness h1 is 480 mm, which is the same as the layer thickness of the single-stage charging single-stage ignition, and the upper layer thickness h2 is 360 mm. did. That is, in FIG. 4, the total layer thickness of the lower layer 10 and the upper layer 20 is 840 mm. Here, when the lower layer 10 and the upper layer 20 are formed, the first compounding material forming the lower layer 10 and the second compounding material forming the upper layer 20 are granulated collectively and collectively. The same uniform raw materials granulated in the above were distributed and used in required amounts. The results are shown in FIGS.

  FIG. 3 shows the transition of the exhaust gas composition of the single-stage charging single-stage ignition, and FIG. 4 shows the transition of the exhaust gas composition of the two-stage charging two-stage ignition. The dashed line (auxiliary line) at the elapsed time 0 in FIG. 3 indicates the timing of ignition of the raw material packed bed. On the other hand, the broken line (auxiliary line) at the elapsed time 0 in FIG. 4 indicates the timing at which the lower layer 10 was ignited, and the broken line (auxiliary line) at the elapsed time of less than 12 min indicates the timing at which the upper layer 20 was ignited. Is shown.

Focusing on the change in the NOx concentration, the single-stage charging and single-stage ignition shown in FIG. 3 changes at a substantially constant value until the elapsed time of about 30 min after the completion of the combustion of the coke breeze as the carbonaceous material. Completion of the combustion of the coke breeze can be determined by a drop in the CO ₂ concentration in the exhaust gas composition.

On the other hand, in the two-stage charging two-stage ignition shown in FIG. 4, after the lower layer 10 is first ignited, the same level as the one-stage charging one-stage ignition (emission time of CO _{2 in} the exhaust gas composition) is maintained for about 0 to 12 min. (The concentration is about 14 to 16%), the CO ₂ concentration in the exhaust gas composition changes. Thereafter, when igniting the upper layer 20 to the time of the elapsed time 12min weak, the CO ₂ concentration increases sharply immediately after the elapsed time up to the point of about 32Min, levels (exhaust gas composition of CO ₂ to the upper layer 20 before ignition The CO ₂ concentration in the exhaust gas composition has changed at a level higher by at least 10% than the CO ₂ concentration in the exhaust gas composition (about 14 to 16%).

After the upper layer 20 is ignited, the CO ₂ concentration in the exhaust gas composition increases because sintering of the lower layer 10 progresses and sintering of the upper layer 20 progresses at the same time. This is because CO ₂ is added up. In other words, the sintering of the lower layer 10 and the sintering of the upper layer 20 proceed simultaneously from the time of about 12 minutes to the time of 32 minutes when the upper layer 20 is ignited. The zone 10A and the upper-layer combustion zone 20A are present at the same time.

In the exhaust gas composition after the ignition time (in terms of elapsed time, less than 12 minutes from the ignition time 0 of the lower layer 10) to the upper layer 20, the lower layer combustion zone 10A and the upper layer combustion zone 20A begin to exist simultaneously. NOx concentration rapidly decreases. That is, the simultaneous existence of the lower combustion zone 10A and the upper combustion zone 20A reduces the NOx concentration in the gas composition.
Therefore, it is important that two combustion zones exist in the height direction of the bed.

  The time during which the lower-layer combustion zone 10A and the upper-layer combustion zone 20A exist are determined by the lower-layer thickness h1 / the lower-front combustion speed of the lower layer 10 and the upper-layer thickness h2 / the lower-front combustion speed of the upper layer 20, respectively. , The combustion front descent speed is referred to as “FFS (Frame Front Speed)”). In order for the two combustion zones to overlap in the upper and lower layers in all the sintering strands, the FFS of the upper layer 20 and the lower layer 10 is grasped, and the upper layer thickness h2 and the lower layer thickness h1 are determined based on the FFS. It has been concluded that optimizing the ratio is important.

There is no prior art that considers the FFS of the upper layer 20 and the lower layer 10, and this was found for the first time.
FIG. 5 shows the change over time of the combustion front in a pot test under a constant wind speed (1.3 Nm ³ / min). The sintering conditions such as the layer thickness of each layer are the same as in FIGS. Case 1 indicates a one-stage charging single-stage ignition, and Cases 2 and 3 indicate a two-stage charging two-stage ignition sintering method. In FIG. 5, in Case 1, the ignition time is set to elapsed time 0, and in Cases 2 and 3, the time at which the lower layer 10 is ignited is set to elapsed time 0. The broken lines (auxiliary lines) of Cases 2 and 3 indicate the ignition timing of the upper combustion zone 20A. The inclination of each straight line in FIG. 5 corresponds to the FFS of each raw material packed layer.

  Thus, Table 1 shows the FFS obtained from FIG. The FFS of the lower layer 10 after the ignition of the upper layer 20 was lower than the FFS of the lower layer 10 before the ignition of the upper layer 20, and the result was 75-80% of the FFS of the upper layer 20.

  Thereafter, the raw material particle size and the carbon material blending ratio were changed to examine the FFS. However, under the condition that the first and second blended raw materials were uniform and the same as those obtained by the batch granulation, the upper layer 20 was ignited. It has been found that the FFS of the lower layer 10 falls within 70-90% of the FFS of the upper layer 20. Therefore, in order to make the time zone in which the lower combustion zone 10A and the upper combustion zone 20A are simultaneously present (= combustion front descent time zone) equal, the lower layer thickness h1 is compared with the upper layer thickness h2 in accordance with each FFS. The thickness may be set to 70 to 90% of the upper layer thickness h2. Therefore, in the present invention, the lower layer thickness h1 / upper layer thickness h2 was set to 0.7 to 0.9 based on the findings of FIGS.

  In the usual two-stage charging two-stage ignition sintering method, it is assumed that the upper layer thickness h2 and the lower layer thickness h1 are equal. As a prior art which discloses a layer thickness ratio between the upper layer thickness h2 and the lower layer thickness h1, Japanese Patent Application Laid-Open No. Sho 62-109932 discloses that the ratio of the lower layer thickness h1 is slightly increased and the upper layer thickness h2: It is only described that the ratio of the lower layer thickness h1 is 1: 1 to 1: 1.2.

If the raw materials forming the upper layer 20 and the lower layer 10 are different, each FFS changes even if the lower layer thickness h1 is 70-90% of the upper layer thickness h2, and the lower layer combustion zone 10A and the upper layer combustion zone The time zone in which 20A exists is not equal.
Of course, it is desirable to charge and ignite the second compounding material forming the upper layer 20 immediately after the lower layer 10 is ignited. However, it is practically impossible to set the time lag of the ignition time of the lower layer 10 and the upper layer 20 (the time interval from the completion of the ignition of the lower layer 10 to the start of the ignition of the upper layer 20) to 0. If the time lag is within 2 minutes, the effect of the present invention is not impaired. More preferably, the time lag is within 1 minute. The time from the start of ignition to the completion of ignition for each layer is preferably 0.4 to 1 min as usual.
The present invention has been completed based on such findings.

  The batch granulation by the drum mixer 1 shown in FIG. 2 is replaced by batch granulation by a high-speed stirring mixer such as an Erich mixer (trade name) or batch granulation by a dish-type granulator such as a pan pelletizer. be able to. Alternatively, a high-speed stirring mixer and a dish-type granulator may be arranged in series and granulated sequentially, and the uniformed compounded raw material may be distributed to the lower layer 10 and the upper layer 20. In that case, the order of the high-speed stirring mixer and the dish-type granulator may be either. If a high-speed stirring mixer and / or a dish-type granulator is employed, the stirring power is high and the granulation strength is improved.

  The effect of the two-stage charging two-stage ignition sintering method of the present invention was verified by simulating a method for producing a sintered ore using a Dwyroid (DL) type sintering machine and performing a sintering pot test of φ300 mm under the following conditions. .

1) Raw material blending Table 2 shows the raw material blending conditions.
The test case is a case in which two-stage charging and two-stage ignition are performed by batch granulation, and after granulation, the mixture is divided in proportion to the layer thickness, and the first compounding material (for the lower layer 10) and the second compounding This was used as a raw material (for the upper layer 20). In addition, the difference of brand of hematites A and D and the difference of brand of limonites B and C in Table 2 depend on the difference of the production place. Also, peridotite forms flux. Hematite concentrate is fine ore with a particle size of 0.125 mm or less.

2) Granulation method After mixing for 4 minutes (min) using a drum mixer (diameter 600 mm, rotation number 25 rpm), water was added, and the mixture was further processed with a drum mixer for 4 minutes (min). The water content was 7.0%.

3) Charging / Ignition Method For the two-stage charging and two-stage ignition, two cylindrical pans having a diameter of 300 mm and a height of 300 mm, namely, a lower pan and an upper pan were prepared. A first compounding material (for the lower layer 10) and a second compounding material (for the upper layer 20) are charged to a predetermined layer thickness. First, the lower pot was set on the lower row, and the ignition was performed at 1100 ° C. for 1 minute (min). Immediately after the completion of the ignition, the upper pan was set on the lower pan and ignited at 1100 ° C. for 1 minute (min). Here, it took 30 seconds from the end of ignition of the lower layer 10 to the start of ignition of the upper layer 20.

In addition, although the layer thickness of the lower layer 10 and the upper layer 20 differs in each case, ignition was performed as follows.
First, the first compounded raw material (for the lower layer 10) was adjusted so that a position lower than the upper surface of the lower pot by a predetermined amount was the upper surface of the raw material filling layer, and the lower layer 10 was ignited. After the lower layer 10 is ignited, the raw materials are immediately added to the upper surface of the lower pan, and then the upper pan, into which the second compounding material (for the upper layer 20) has been previously charged, is placed on the upper pan. Ignition 20. That is, the lower layer thickness h1 is the layer thickness charged in the lower pot before the lower layer 10 is ignited, and the upper layer thickness h2 is the amount added to the lower pot after the lower layer 10 is ignited. It is the sum of the amount charged in the pot.
The suction air volume was kept constant at 1.3 Nm ³ / min from the start of ignition.

4) Sintering end timing and sintering time Three minutes (min) from the time when the temperature of the exhaust gas from the lower layer 10 peaked, the blowing was stopped, and the sintering was ended. The sintering time was the time required from the time when the lower layer 10 was ignited to the time when the temperature of the exhaust gas from the lower layer 10 peaked.

5) NOx evaluation method The exhaust gas NOx concentration was measured by separating a sintered exhaust gas and providing it to an analyzer.
NOx conversion rate is calculated by equation (1) as an evaluation index of the exhaust gas NOx emissions (ηNO: 100 × [NOx generation amount in the exhaust gas / (CO and CO ₂ generation amount in the exhaust gas)] / [nitrogen Iriryou / (Carbon content)]) was used.
Here, CO and CO ₂ contained in the exhaust gas were regarded as being derived from ignition gas, coke breeze and limestone, and the calculation was performed on the assumption that all NOx was derived from coke breeze.

ηNO = 100 × [NOx / (CO + CO ₂ )] / [N _COKE / (C _LPG + C _COKE + C _CLS )] (1)

here,
ηNO: NOx conversion rate (%)
NOx: Exhaust gas NOx (%)
CO: Exhaust gas CO (%)
CO ₂ : exhaust gas CO ₂ (%)
N _COKE : Nitrogen input from coke breeze per unit time (mol)
C _LPG : Carbon input from ignition gas per unit time (mol)
C _COKE : Input amount of carbon derived from coke breeze per unit time (mol)
C _CLS : Limestone-derived carbon input per unit time (mol)

6) Test level Table 3 shows the test cases. In all cases, two-stage charging and two-stage ignition were performed after the granulation was performed at once, divided, and distributed to form each layer (FIG. 2).
The difference between the cases is the ratio of the lower layer thickness h1 / the upper layer thickness h2,
Comparative Example 1 Lower layer thickness h1 / upper layer thickness h2 = 1.0
Inventive Examples 1-3 Lower layer thickness h1 / upper layer thickness h2 = 0.9, 0.8, 0.7
Comparative Example 2 Lower layer thickness h1 / upper layer thickness h2 = 0.6
The suction air volume at the time of sintering was kept constant at 1.3 Nm ³ / min from the start of ignition.
Blowing was stopped 3 minutes after the time when the temperature of the exhaust gas from the lower layer 10 reached a peak, and sintering was completed.

7) Test results The test results are shown in the lower part of Table 3.

  In Comparative Example 1, since the lower layer thickness h1 / upper layer thickness h2 exceeded 0.9, the combustion front descent time zone of the lower layer 10 was too long, and overlapped with the combustion front descent time zone of the upper layer 20. The time (the length of time (a) during which the combustion front is falling in both the upper and lower stages) is short. As a result, the time during which the lower-layer combustion zone 10A and the upper-layer combustion zone 20A were simultaneously present in the layer height direction was shortened, and the NOx conversion rate was increased.

  In Comparative Example 2, since the lower layer thickness h1 / upper layer thickness h2 was less than 0.7, the combustion front descent time zone of the upper layer 20 was too long, and overlapped with the combustion front descent time zone of the lower layer 10. The time (the length of time (a) during which the combustion front is falling in both the upper and lower stages) is short. As a result, the time during which the lower-layer combustion zone 10A and the upper-layer combustion zone 20A were simultaneously present in the layer height direction was shortened, and the NOx conversion rate was increased.

On the other hand, in Invention Examples 1 to 3, the time length (a) (min) in which the combustion front is falling in both the upper and lower stages is long, and the time length in which at least one of the upper and lower combustion fronts is falling. The ratio with respect to (b) (min) is high. As a result, the NOx conversion rate decreased.
As described above, by optimizing the layer thickness ratio of the upper and lower stages, it is possible to reduce the NOx conversion rate by increasing the time length (a) (min) during which the combustion front is falling in both the upper and lower stages.

  According to the present invention, in the two-stage charging two-stage ignition sintering method, the generation of NOx can be reduced, so that it is environmentally friendly and the burden of NOx treatment can be reduced. It has special industrial applicability that makes it possible.

DESCRIPTION OF SYMBOLS 1 ... Drum mixer, 1A ... 1st drum mixer, 1B ... 1st hopper, 1C ... 1st igniter, 10 ... Lower layer, 10A ... Lower layer combustion zone, 2A ... 2nd drum mixer, 2B ... 2nd hopper, 2C: second igniter, 20: upper layer, 20A: upper layer combustion zone, 3: sintered part, 5: downstream direction, 6: downward suction

Claims (1)

Pallets that make up the Dwyroid (DL) sintering machine
The lower layer is formed by supplying the first compounded raw material obtained by mixing and granulating the iron-containing raw material, the auxiliary raw material, and the carbon-based coagulant,
Ignition from the upper part of the lower layer, start sintering of the lower layer by sucking air from below,
On the lower layer after ignition, an iron-containing raw material, an auxiliary material, and a second blended raw material obtained by mixing and granulating a carbon-based coagulant are further supplied to form an upper layer,
Ignition the upper layer and start sintering the upper layer by sucking air from below,
A method for producing a sintered ore by a two-stage charging two-stage ignition sintering method of thereafter sintering the upper layer and the lower layer by sucking air from below,
The lower layer and the upper layer are obtained by mixing the iron-containing raw material, the auxiliary raw material, and the carbon-based coagulant, granulating them at once, and forming a compounded raw material, and then mixing the compounded raw material with the first compounded raw material. A method for producing a sintered ore, wherein the method is distributed to the second compounding raw material and the lower layer thickness h1 / the upper layer thickness h2 is set to 0.7 to 0.9.

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