JP6327082B2 - Pretreatment method for sintered aggregates - Google Patents

Description

  The present invention relates to a pretreatment method for a sintered coagulant which suppresses the generation of nitrogen oxides in the production of sintered ore used for steel production.

Sintered ore used for iron and steel production is obtained by firing, with a sintering machine, pseudo particles obtained by mixing and granulating a sintered coagulant (hereinafter simply referred to as a coagulant) and lime, etc., with iron ore as a raw material. Manufactured. At this time, a part of nitrogen contained in the coagulation material becomes nitrogen oxide (hereinafter also referred to as NOx) and is mixed into the exhaust gas.
Since NOx is an air pollutant, there are restrictions on the concentration and amount of NOx emission to the atmosphere, and restrictions such as adjustment of operating conditions occur. Moreover, although installation of the exhaust gas processing apparatus which removes NOx is also performed, a great capital investment is required.

Therefore, for the purpose of reducing operation restrictions and capital investment, methods for suppressing the generation of NOx by pretreatment of the aggregate have been studied.
The aggregating material is a material mainly containing carbon, including a material that becomes a NOx source, and generates heat by oxidation. For example, it refers to coal and coke.

One method of suppressing the generation of NOx by pretreatment of the aggregate is to coat the surface of the aggregate with a substance that reduces the generated NOx.
For example, Patent Document 1 discloses a technique in which a fine powder catalyst containing calcium ferrite and a coagulant (fuel coke) are present side by side, and the generated NOx is reduced and suppressed.

  However, since the invention described in Patent Document 1 uses calcium ferrite, the granulation property is poor, and the effect of covering the aggregate with calcium ferrite cannot be sufficiently enhanced. For this reason, the surface of the coagulation material is exposed, and the NOx conversion rate indicating the ratio of the nitrogen content in the coagulation material converted to NOx is 30% or more, and there is a need for further reduction. The NOx conversion rate is the ratio of nitrogen content converted to NOx with respect to the total amount (100%) of nitrogen content contained in the coagulation material.

Therefore, as another method for suppressing the generation of NOx by pretreatment of the coagulation material, a method of covering the coagulation material with quick lime or slaked lime and burning the coagulation material in a high temperature region where the NOx conversion rate is low is disclosed.
For example, the invention described in Patent Document 2 is a technique using quicklime, and it is shown that the NOx conversion rate can be reduced to the 20% level.
In addition, the invention described in Patent Document 3 classifies the aggregate (carbonaceous material) for the production of sintered ore, mixes the lime source with the aggregate of 1 mm or less and granulates, It is a technology that exhibits high productivity and NOx reduction effect by suppressing contact with other raw materials used in the process.

JP-A-8-60257 JP 2012-172067 A JP 2013-216938 A

However, the conventional technique still has the following problems to be solved.
In paragraph [0005] of Patent Document 2, it is described that the fine powdered agglomerate is easily oxidized at a low temperature to generate NOx. For this reason, Patent Document 2 describes that the amount of adhesion of Ca is controlled according to the particle size of the agglomerated material (for example, claim 1), and mainly uses a agglomerated material of 0.25 mm or more to suppress NOx generation. (For example, paragraph [0023]).

Since the agglomerate is generally produced by pulverizing coal or coke, the fine agglomerate is constantly produced. For this reason, as described above, when a condensing material of 0.25 mm or more is mainly used, there is a problem that the fine condensing material becomes excessive.
Further, although the amount of fine powder of the coagulation material is described as 17% by mass or less (for example, paragraph [0023]), the coagulation material produced by pulverization generally has an amount of fine powder larger than this amount, The reduction effect is limited.

When the invention described in Patent Document 3 is granulated by mixing a lime source having a content of 1 mm or less to 70% by mass or more with a coagulating material having a content of 1 mm or less of 73.0% by mass or more, The blending amount is 5 to 50% in Ca with respect to the total amount of the coagulant and the lime source. The amount of the lime source is 7 to 70% by mass when converted by the amount of quick lime, and 7 to 230% by mass when converted by the amount of the outer coating with respect to the condensed material, so that the range is too wide.
According to the knowledge of the inventors of the present application, for example, when the amount of the lime source is too large, the hydrated lime source aggregates, and the condensed material adheres around the aggregated lime source. Granulated material may be generated, and the NOx reduction effect is limited.

  The present invention has been made in view of such circumstances, and provides a pretreatment method for a sintered coagulant capable of suppressing the generation of NOx as compared with the prior art without making a fine powder coagulant surplus. For the purpose.

A pretreatment method for a sintered coagulant according to the present invention that meets the above-described object is a pretreatment method for a sintered coagulant that is granulated with quicklime for use in a sintering step.
The amount of particles of 2 mm or more in the sintered aggregate is 10% by mass or less, and the particle of 1 mm or less in the quicklime is 80% by mass or more. Is 10% by mass or more and 27% by mass or less.
In addition, the numerical value of the above-mentioned particle diameter is the size of the sieve mesh, and the sieve top when sieving (sieving selection) using the sieve equipped with the sieve mesh is described as “above”. The following is described as “below” (hereinafter the same).

  In the pretreatment method for a sintered coagulant according to the present invention, it is preferable to use a vibration granulator in which a plurality of compacted media are housed in a horizontal cylindrical container for the granulation of the sintered coagulant and the quicklime.

The pre-treatment method for a sintered coagulant according to the present invention includes a sintered coagulant in which particles having a particle size of 2 mm or more are reduced to 10% by mass or less, and quicklime having 80% by mass or more of particles having a particle size of 1 mm or less. In addition, the amount of quick lime with respect to the sintered condensate is 10% by mass to 27% by mass, so that the sintered condensate is covered with fine powder quick lime and the fine powder is peeled off. It is possible to selectively produce a granulated product that is not easily generated (that is, a P-type granulated product), and a dense granulated product is obtained.
As a result, when the granulated product is transported, it can be charged into the sintering machine while maintaining its shape while suppressing the generation of fine powder. Generation of NOx can be suppressed.

  In addition, when a vibration granulator is used for granulating the sintered coagulant and quick lime, the granulated product has a denser structure, so that the NOx reduction effect can be further improved.

It is sectional drawing of the vibration granulator used for the pre-processing method of the aggregate for sintering which concerns on one embodiment of this invention. It is a graph which shows the influence which the particle size of coke has on the reduction rate of NOx. It is a graph which shows the influence which the particle size of quicklime has on the reduction rate of NOx. It is a graph which shows the influence which the compounding quantity of quicklime has on the reduction rate of NOx. It is a graph which shows the influence which the granulation method has on the reduction rate of NOx.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
First, the background that has been conceived of the pretreatment method for a sintered coagulant of the present invention will be described.

When using the granulated product obtained by mixing and granulating the sintered coagulant and quick lime, the following events occur when the granulated product is conveyed to the sintering machine. For the first time.
A granulated product with a coarse aggregate having a particle size of 2 mm or more (hereinafter also referred to as a C-type granulated product) has a NOx reduction effect because the fine aggregate present in the surface layer is peeled off. Become limited. On the other hand, a granulated product composed of a coagulant having a particle size of 2 mm or less (hereinafter also referred to as a P-type granulated product) is maintained until it is charged into a sintering machine.
This is because the coarse-grained condensate described above has a complicated surface layer portion and a large number of irregularities, so that voids are generated between the coarse particles and the fine powder adhering to the surface, This is because it is considered that fine particles are separated from the surface of the coarse particles starting from the pores.

  Moreover, about quicklime, when the particle size became coarse or when it became large quantity, since the hydrated quicklime became dama, it discovered that NOx could not be reduced appropriately by coke adhering to the circumference | surroundings.

Therefore, the present inventors reduce the coarse particles having a particle size of 2 mm or more in the coagulation material containing fine powder, and the quick lime granulated together with the coagulation material has an appropriate particle size and blending amount so that peeling does not occur. A P-type granulated product was selectively produced, resulting in a dense granulated product, which led to a pretreatment method for preventing the generation of fine powder during transportation.
That is, in the pretreatment method for a sintered coagulant according to an embodiment of the present invention, when the coagulant used in the sintering process is granulated with quick lime, the particle size in the coagulant is 2 mm or more (2 mm sieve mesh). The particle size of the sieving of the sifter is 10% by mass or less, the particle size in the quicklime is 1 mm or less (under the sieving of the 1 mm sieve, the same shall apply hereinafter) and 80% by mass or more of the particles. The blending amount of quicklime is 10% by mass or more and 27% by mass or less as an outer shell.

[Composition of condensate]
When agglomerated material containing coarse particles is granulated, it becomes a granulated product in a form in which a mixture of quicklime and fine powder agglomerated around the coarse agglomerated material (ie, C-type agglomerated material). . However, as described above, since such a granulated product has a complicated shape (unevenness) on the coarse-grained coke surface, voids are likely to be generated inside. The fine powder on the surface of the coarse particles is peeled off, and it is considered that the amount of NOx generated increases due to low temperature combustion.
On the other hand, a granulated product of a coagulation material that does not contain coarse particles or has a low ratio (that is, P-type granulated product) is less likely to cause the above-described pores, and is thus supplied to a sintering machine while suppressing separation of the granulated product. Since it can be charged, the amount of NOx generated can be efficiently reduced, and the fine powder condensate does not become excessive as described in Patent Document 2 described above.

From the above, the particles having a particle diameter of 2 mm or more in the coagulant were set to 10 mass% or less. However, in order to produce the P-type granulated material, the amount of particles having a particle diameter of 2 mm or more should be smaller. Therefore, it is preferably 5% by mass or less, more preferably 2% by mass or less, or 0% by mass.
In addition, the particle size adjustment of the coagulant can adjust the amount of coarse particles having a particle size of 2 mm or more by pulverizing the coagulant (for example, pulverized coal or coke breeze), but is not limited thereto. It can also be adjusted by removing the coarse particles by classification or the like. The removed coarse particles can be used by further grinding.

[Reasons for specifying the condensate and raw material to be granulated]
By granulating the coagulating material and quick lime and coating the coagulating material with quick lime, the oxidation of the coagulating material is difficult to proceed up to about 1000 to 1200 ° C. in the sintering machine pallet. On the other hand, when the temperature exceeds 1000 to 1200 ° C., the quick lime on the surface of the granulated product and the iron ore around the granulated product form a low melting point compound, and the quick lime melts and flows out sequentially from the surface of the granulated product. In response to this, the aggregate is exposed to a high temperature atmosphere, and the oxidation of the aggregate progresses remarkably. In addition, the melting point of quicklime exceeds 2000 ° C, and as a low melting point compound (complex oxide of quicklime and iron ore) generated by the reaction with iron ore around the granulated product, until quicklime is consumed and flows out, Since the coating effect of the aggregate is effective, the oxidation of the aggregate progresses only at a high temperature. For this reason, the coating of the condensate with quicklime has a more favorable effect than the coating of the condensate with a complex oxide of quicklime and iron oxide (melting point is 800 to 1000 ° C., depending on the composition).
Thus, for example, in a high temperature atmosphere exceeding 1000 to 1200 ° C., it becomes possible to advance the oxidation of the coagulation material, and therefore, the coagulation material and quick lime are preferably granulated.
In addition, quick lime is partly digested to form fine calcium hydroxide fine particles (particle size is significantly reduced compared to quick lime particles, mainly having a particle size of 1 μm or less), and dispersion is promoted. Dispersion is improved because a part of it is dissolved and re-precipitated between the coagulant particles as calcium hydroxide fine particles. In addition, it generates heat during digestion and promotes evaporation of moisture. As a result, the presence of the coagulant particles, quicklime particles, and the calcium hydroxide fine particles that bind them, mainly makes use of the effect of covering the coagulant by the quicklime particles, resulting in a strong and dense granulated product. It is preferable to use it as a binder at the time of granulation.
From the above, quick lime was used as the raw material to be granulated with the coagulant.

[Reason for prescribing the particle size and amount of quicklime]
Since the surface of the agglomerated material to be granulated is hydrophobic, it has poor affinity with water. On the other hand, in the granulation of the agglomerated material to which quicklime has been added, the quicklime as a binder is arranged around the agglomerated material in a state of affinity with water, and the particles of the agglomerated material are linked together.
Therefore, the coagulant is not suitable for granulation using a water-soluble binder, and in order to enhance the granulation function of the coagulant, it is necessary to increase the concentration of quick lime arranged around the aggregate.
A portion of quicklime is digested to form calcium hydroxide, and the fine particles of calcium hydroxide (mainly having a particle size of 1 μm or less) contribute to the formation of dense granules, but also from the viewpoint of promoting the formation of calcium hydroxide. It is preferable to use a lot of quick lime of 1 mm or less. This action is peculiar to quicklime, and the above-mentioned action cannot be expected from limestone or a composite oxide of quicklime and iron oxide.
On the other hand, quick lime with a particle size of more than 1 mm has low reactivity with water at the time of granulation, and part of the quick lime is not used as a binder during granulation, and fine aggregates are arranged on the surface of unreacted quick lime. , NOx reduction effect may not be exhibited.
Therefore, it is necessary to use quick lime to be used with a high fine powder amount.

Moreover, when the compounding quantity of quick lime with respect to a setting material is low, the force which connects the setting materials of a fine powder will become weak, and collapse of a granulated material will arise. Furthermore, the effect of covering the coagulant with high melting point quicklime particles cannot be obtained.
In addition, when the same amount of limestone is used in terms of the amount of quicklime, the effect of covering the coagulant is obtained by quicklime produced by decomposition at over 800 ° C, but the effect of linking the particles of the coagulant without digesting limestone Is low, the NOx reduction effect is poor. In addition, when the same amount of complex oxide (complex oxide of quicklime and iron oxide) is used in terms of the amount of quicklime, the composite oxide starts melting at about 800 ° C., so the coating effect of the coagulant cannot be obtained. In addition, the effect of digestion (dense granulated product utilizing calcium hydroxide fine particles) cannot be expected, so the NOx reduction effect is greatly inferior.
On the other hand, when the amount of quicklime is excessive, the hydrated quicklime is agglomerated and becomes lumps, and the above-mentioned fine aggregates are arranged around the quicklime agglomerates. Does not demonstrate.
Therefore, it is necessary to appropriately set the blending amount of quicklime with respect to the setting material.

From the above, particles with a particle size of 1 mm or less in quicklime were set to 80% by mass or more. For the reasons described above, the amount of particles with a particle size of 1 mm or less is preferably larger because the amount of NOx generated can be reduced. Is 90% by mass or more, more preferably 95% by mass or more, or 100% by mass.
Moreover, although the compounding quantity of the quick lime with respect to the coagulating material was 10 mass% or more and 27 mass% or less with the amount of the coagulating material as 100 mass%, the addition effect of quick lime was acquired more notably from the reason mentioned above. The lower limit is preferably 12% by mass, more preferably 15% by mass, and the upper limit is preferably 26% by mass, more preferably 25% by mass.

[Mechanism to suppress NOx generation]
The inventors of the present invention investigated the relationship between the granulated material containing the fine-coagulated material described in Patent Document 2 and the generation of NOx.
Specifically, a drum mixer which is a granulating apparatus having a relatively small acceleration and / or pressing force in order to investigate the effect of the acceleration and pressing force (pressure density) applied to the granulated product, particularly the granulation method of the aggregate. In addition, a vibration granulator and a briquette making machine, which are granulators with a large applied pressure, and a malmerizer, which is a granulator with a large acceleration, were compared with the pan pelletizer.
The above-mentioned granulated material containing the coagulant is added to a drum mixer for granulating a sintering raw material containing iron ore to produce pseudo particles, and the sintered ore is fired in a pan test, and NOx at the time of firing is calculated. investigated.

As a result, it was confirmed that the granulated product granulated with a drum mixer or a pan pelletizer had a high NOx conversion rate of over 30% and contributed little to the suppression of NOx generation. In addition, it was confirmed that the Malmerizer with a large acceleration also has a low NOx reduction effect with a NOx conversion rate exceeding 30%.
The granulated product granulated with a drum mixer or pan pelletizer has an acceleration applied to the granulated product at the time of granulation of about 1G (G is the gravitational acceleration, the same applies hereinafter), whereas in the Malmerizer it is 20G. However, since the NOx reduction effect is equally low, it has been found that it is not always possible to sufficiently reduce NOx by increasing the acceleration.

On the other hand, the present inventors used a granulator manufactured using a vibration granulator having an acceleration of, for example, 1.5 G or more and a briquette manufacturing machine having a linear pressure of 1 ton / cm. The amount of NOx generated was investigated.
As a result, compared with the granulated product granulated with a drum mixer, pan pelletizer, and mulmerizer, the NOx conversion rate is 20% when firing using the granulated product manufactured using a vibration granulator or briquette manufacturing machine. It has been found that the amount of NOx generated can be greatly reduced.

  In addition, we compared the case where the granulated product granulated with a drum mixer was cured in the atmosphere for several days to improve the strength of the granulated product, but the strength of the granulated product increased. Nevertheless, the NOx reduction effect was not sufficient.

  From the above results, it is presumed that it is effective for reducing NOx to apply a strong pressure to the granulated material to form a dense granulated material. In particular, the NOx is not sufficiently reduced despite securing the strength of the granulated product by curing, but NOx is reduced when a forced pressurizing force by a compacting medium or roll is applied to the granulated product. Since the reduction effect was expressed, it is presumed that the granulated material was densified by pressurization and the NOx conversion rate was suppressed.

The difference in the generation amount of NOx described above is that, in the oxidation of the fine aggregated material in the granulated product, the granulated product having a small pressure density allows the air to pass between the constituent particles. While the fine powder condensate in the product oxidizes, the granulated product produced by a vibration granulator or briquette production machine consolidates the particles and suppresses air permeability between the particles. It is thought that the oxidation of the fine powder coagulant did not progress at the stage.
Furthermore, when the temperature reaches 1000 ° C. or higher in the sintering machine, quick lime and slaked lime constituting the granulated material melt and flow out, and the exposed fine powder aggregate is oxidized at a high temperature of 1000 ° C. or higher, thereby generating NOx. Is considered to be suppressed.

From the above, it is preferable to use a vibration granulator equipped with a plurality of compaction media for the granulation treatment of the coagulant and quicklime. This is because the granulated product is pressed by the compacting medium at the time of granulation, and the compacted granulated product can be produced.
Moreover, the vibration granulator is preferable because it has a function of kneading the coagulating material and quicklime.
Furthermore, it is preferable that the vibration granulator uses a horizontal cylindrical container in which a plurality of compaction media are stored. This is because the vibration granulator is excellent in the kneading function of the coagulating material and quick lime, can produce a granulated product in which the coagulating material and quick lime are more uniformly dispersed, and can be expected to improve the NOx reduction effect. .
In the vibration granulator, it is preferable to use a compacted medium having a density higher than that of the granulated product.

Here, an example of the vibration granulator described above is shown in FIG.
The vibration granulator 10 includes a horizontal cylindrical container 11, a plurality of compacting media 12 accommodated in the horizontal cylindrical container 11, and a pair of weight rotary vibration motors 13 disposed on both sides of the horizontal cylindrical container 11. It is roughly structured.

In the upper part of the horizontal cylindrical container 11, there are provided an opening 14 for introducing the raw material into the horizontal cylindrical container 11 and a water injection port 15 for injecting water into the horizontal cylindrical container 11.
A cylindrical steel rod (a steel ball may be used) is used as the compacting medium 12, and the pair of weight rotary vibration motors 13 are synchronously rotated in the same direction.

When the pair of weight rotating vibration motors 13 rotate to the right, for example, the horizontal cylindrical container 11 vibrates circularly so as to draw a loop in the vertical plane. Thereby, each compaction medium 12 accommodated in the horizontal cylindrical container 11 rotates to the right, and rotates in the left direction as a whole by contacting the horizontal cylindrical container 11. That is, each compaction medium 12 rotates while rotating in the horizontal cylindrical container 11 like a planetary gear.
Along with the vibration, the condensed material, quicklime, and moisture enter between the compacted medium 12 and the compacted medium 12 and between the compacted medium 12 and the horizontal cylindrical container 11, and are impacted, sheared, mixed, kneaded, and flaky. A granulated product is formed.

  In order to prevent the vibration of the vibration granulator 10 from being propagated elsewhere, the vibration granulator 10 is supported on the base 16 via an air spring 17 in an anti-vibration manner.

  When producing a granulated product using this vibratory granulator, for example, the moisture is adjusted so that the moisture during granulation is 10% by mass or more (upper limit is about 20% by mass). It is preferable to set the granule time at an acceleration of 1.5 G or more for 60 seconds or more (the upper limit is about 600 seconds from the viewpoint of suppressing the destruction of the granulated product).

The granulated material described above is charged into a pan pelletizer (may be a drum mixer or a Redige mixer) as necessary, and further granulated, and then stored in a storage tank. Thereby, the density of the granulated product and the coating layer is improved, and the NOx reduction effect is expanded.
And an artificial particle can be manufactured by granulating the above-mentioned granulated material with a drum mixer with other sintering raw materials (for example, iron ore and anthracite).
The pseudo particles produced by this drum mixer are charged into a sintering machine and fired to form a sintered ore. In addition, the exhaust gas generated at the time of sintering is sucked from the sintering machine by a blower, and dust and the like are removed by an electric dust collector, and then discharged from the chimney to the atmosphere.

Next, examples carried out for confirming the effects of the present invention will be described.
Here, the NOx reduction effect was confirmed by the pot test using the granulated material manufactured by changing the particle size of coke used as a coagulation material, the particle size of quicklime, and the compounding quantity (concentration) of quicklime.
Tables 1 to 3 show the particle size of the coke used, the particle size of quicklime, and the blending conditions of the sintering raw materials, respectively. The blending conditions shown in Table 3 are blending conditions for pseudo particles after the coke and quicklime granulated product and other sintered raw materials are treated with a drum mixer.

The granulated product was obtained by granulating coke and quicklime using a drum mixer or a vibratory granulator. In addition, the compounding quantity of the quick lime to coke was adjusted in the range of 5-40 mass% on the outside with respect to coke.
The drum mixer used is a 1 m diameter tester. In use, granulation was performed at a rotation speed of 20 rpm for 5 minutes.
Moreover, the vibration granulator is one in which six 50φ steel rods (consolidation medium) are housed in a horizontal cylindrical container having a diameter of 300 mm. In use, granulation was performed for 5 minutes at a vibration acceleration of 6G.
Table 4 shows test conditions and test results.

Of the types (granularity) described in Table 4, symbols A to D in the coke column correspond to symbols A to D in Table 1, respectively, and symbols a to c in the quick lime column respectively Corresponds to symbols a to c.
Moreover, the concentration of NOx shown in Table 4 is the concentration of NOx obtained in the pan test, and in this example, the NOx reduction effect appeared at 150 ppm or less.
The NOx reduction rate described in Table 4 indicates the reduction ratio with respect to the NOx concentration (180 ppm) of the base conditions described in Table 4. Here, the base is a non-granulated coagulant to which quicklime is not added.
The formula for calculating the NOx reduction rate is shown below.
{(NOx concentration of base condition) − (NOx concentration of each condition)} / (NOx concentration of base) × 100 (%)

In Examples 1 to 4 shown in Table 4, the coke particle size, the quick lime particle size, and the quick lime compounding amount are respectively in appropriate ranges (coke particle size: 2 mm or more, 10 mass% or less, quick lime particle size: 1 mm or less. 80 mass% or more, quick lime blending amount: 10 to 27 mass%, the same applies hereinafter), and a coke and quick lime having a relatively low particle size. Under these conditions, the NOx reduction effect was great (NOx concentration: 150 ppm or less).
In addition, Examples 5 to 8 are the results of adjusting the coke particle size, the quick lime particle size, and the quick lime blending amount to appropriate ranges, and particularly adjusting the quick lime blending amount to the lower limit and the upper limit of the proper range. Even under these conditions, a high NOx reduction effect was obtained.
Furthermore, Example 9 is the result of setting the coke particle size, the quick lime particle size, and the quick lime compounding amount to appropriate ranges, respectively, and using a vibrating granulator. Under these conditions, the highest NOx reduction effect was obtained (NOx concentration: 132 ppm).

On the other hand, Comparative Examples 1 to 3 are the results of increasing the coarse particles in the coke by setting the coke particle size outside the proper range (2 mm or more exceeding 10 mass%). Under these conditions, the NOx reduction effect was limited (NOx concentration: over 150 ppm).
Moreover, the comparative examples 3 and 4 are the results of making the particle size of quick lime out of an appropriate range (1 mm or less is less than 80 mass%) and reducing the fine powder in quick lime. Under these conditions, quick lime is poor in reactivity, so the NOx reduction effect was limited.
And the comparative example 5 is the result which made the compounding quantity of quick lime less than the lower limit of an appropriate range (less than 10 mass%), and decreased the compounding quantity of quick lime, but since it cannot granulate a fine coke on these conditions. The NOx reduction effect was limited. On the other hand, Comparative Example 6 is the result of setting the amount of quick lime to exceed the upper limit (over 27% by mass) of the appropriate range and increasing the amount of quick lime, but quick lime aggregates and fine coke is arranged around it. Therefore, the NOx reduction effect was limited.

The results of arranging the effects of the coke particle size, quick lime particle size, quick lime blending amount, and granulation method on the NOx reduction rate will be described using the above results.
First, the influence of the coke particle size on the NOx reduction rate will be described with reference to FIG.
FIG. 2 shows that the type of quicklime is a (particle size of 1 mm or less is 100% by mass), the amount of quicklime is 20% by mass, and the coke particle size is 2 to 30% by mass (AD). It is a graph at the time of making it change in a range. That is, A to D on the horizontal axis in FIG. 2 correspond to Example 1, Example 2, Comparative Example 1, and Comparative Example 2 in Table 4, respectively. A drum mixer was used for the granulator.
As shown in FIG. 2, by changing the coke type from B to C, coarse particles having a particle diameter of 2 mm or more exceeded 10% by mass, and thus the NOx reduction rate was greatly reduced.
Therefore, it is considered preferable to use coke in which coarse particles having a particle diameter of 2 mm or more are 10 mass% or less.

Next, the effect of the quicklime particle size on the NOx reduction rate will be described with reference to FIG.
FIG. 3 shows that the type of coke is A (particle size of 2 mm or more is 5% by mass), the amount of quick lime is 20% by mass, and the particle size of quick lime is 1 mm or less is 100 to 55.6% by mass (ac). It is a graph at the time of changing in the range. That is, a to c on the horizontal axis in FIG. 3 correspond to Example 1, Example 3, and Comparative Example 4 in Table 4, respectively. A drum mixer was used for the granulator.
As shown in FIG. 3, by changing the particle size of quicklime from b to c, the fine powder having a particle size of 1 mm or less is less than 80% by mass, so the NOx reduction rate is greatly reduced.
Therefore, it is considered preferable to use quick lime whose fine powder having a particle diameter of 1 mm or less is 80% by mass or more.

Then, the influence which the compounding quantity of quicklime has on the reduction rate of NOx is demonstrated, referring FIG.
FIG. 4 shows that the type of coke is A (particle size of 2 mm or more is 5% by mass), the type of quick lime is a (particle size of 1 mm or less is 100% by mass), and the amount of quick lime is 5 to 40% by mass. It is a graph at the time of making it change in a range. That is, the plot points in FIG. 4 correspond to Comparative Example 5, Example 5, Example 1, Example 6, and Comparative Example 6 in Table 4 from the left, respectively. A drum mixer was used for the granulator.
As shown in FIG. 4, when the amount of quicklime was 5 mass% and 40 mass%, the NOx reduction rate was low because it was outside the range of 10 to 27 mass%.
Therefore, it is considered that the amount of quicklime is 10 to 27% by mass.

Finally, the influence of the granulation method on the NOx reduction rate will be described with reference to FIG.
FIG. 5 shows that the type of coke is A (particle size of 2 mm or more is 5% by mass), the type of quick lime is a (particle size of 1 mm or less is 100% by mass), and the amount of quick lime is 20% by mass. It is a graph at the time of changing the kind of grain machine. That is, the drum mixer in FIG. 5 corresponds to Example 1 in Table 4, and the vibration granulator in FIG. 5 corresponds to Example 9 in Table 4.
As shown in FIG. 5, it was found that the vibration granulator can greatly reduce NOx as compared with the drum mixer. This is presumably because the use of the vibration granulator enabled fine granulation of the fine powder to suppress subsequent collapse due to mixing with other sintered raw materials.

  As described above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the configuration described in the above embodiment, and the matters described in the scope of claims. Other embodiments and modifications conceivable within the scope are also included. For example, a case where the pretreatment method for a sintered aggregate according to the present invention is configured by combining a part or all of the above-described embodiments and modifications is also included in the scope of the right of the present invention.

10: vibration granulator, 11: horizontal cylindrical container, 12: compaction medium, 13: weight rotary vibration motor, 14: opening, 15: water inlet, 16: base, 17: air spring

Claims (2)

In the pre-treatment method of the sintered coagulant that granulates the sintered coagulant used in the sintering process with quick lime,
The amount of particles of 2 mm or more in the sintered aggregate is 10% by mass or less, and the particle of 1 mm or less in the quicklime is 80% by mass or more. Is a pretreatment method for a sintered coagulant, characterized in that it is 10 mass% or more and 27 mass% or less.   2. A pretreatment method for a sintered coagulant according to claim 1, wherein a vibrating granulator containing a plurality of compacted media in a horizontal cylindrical container is used for granulation of the sintered coagulant and the quicklime. A pre-treatment method for a sintered aggregate.

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