JP6540359B2 - Modified carbon material for producing sintered ore and method for producing sintered ore using the same - Google Patents

Description

  The present invention relates to a modified carbon material for producing sintered ore and a method for producing sintered ore using the same.

Sintered ore is a main iron source for producing pig iron, and occupies most of it as a blast furnace raw material. The manufacturing method is as follows.
First, a compounding raw material obtained by mixing sintered raw materials such as iron ore, limestone and carbon material in a particle size of 10 mm or less is granulated and then charged into a sintering pallet, so that the layer thickness is about 500 mm. Form a packed bed. Then, the solid fuel on the surface of the packed bed is ignited by an ignition burner, and the air in the atmosphere is sucked from below the packed bed to start sintering. Sintering is performed by burning and heating the carbonaceous material in the compounding material, and partially melting iron ore and limestone with this heat. Finally, the obtained sinter is crushed to obtain a sintered ore of about 20 mm.

  The above-mentioned method of producing sintered ore is an excellent method which is capable of agglomerating powdery and granular sintered raw materials inexpensively and easily in large quantities. On the other hand, a large amount of air is consumed to discharge the exhaust gas to the atmosphere because the carbon material is burned at the time of sintering. The exhaust gas released to the atmosphere contains a large amount of air pollutants, particularly nitrogen oxides (NOx), the reduction of which is a major issue, and many technological developments have been made.

Methods of reducing NOx in a sintering machine are roughly classified into a method of decomposing and removing the generated NOx in the exhaust gas with a denitrification facility and a method of suppressing the generation of NOx itself in the sintering process. The former requires enormous and complicated processing equipment, and has problems in terms of volume and economy.
The latter methods of NOx suppression in the sintering process include a method by pretreatment of the raw material and a method of allowing the exhaust gas to be drawn to the surface layer of the packed bed represented by the exhaust gas circulation and the like. In any of the methods, when the generation of NOx is suppressed, the combustion of the carbon material is delayed, and the productivity of the sintered ore is significantly reduced. Therefore, the NOx reduction effect can not be sufficiently obtained, and the NOx reduction effect remains at around 20% at present.

Generally as a method by pretreatment of a raw material, particle size control of carbon material is mentioned. The formation of NOx during the sintering process is the carbon material in the packed bed, mainly coke, but the air (O ₂ , this coke (mainly containing carbon, partially containing nitrogen)) passes through the packed bed. When N ₂ ) causes a combustion reaction (C + O ₂ → CO ₂ ), it is explained that nitrogen oxidation reaction (N + 1/2 O ₂ → NO) is also caused at the same time.
However, when the supply of O ₂ is bad in the above combustion reaction and the O ₂ potential is low, the nitrogen oxidation reaction does not occur and NOx is not generated. In this case, a reaction to generate nitrogen molecules occurs (2N → N ₂ ). That is, although the basic factor for generating NOx is nitrogen in the carbonaceous material, whether this nitrogen becomes NOx or N ₂ (NOx conversion rate) is affected by the O ₂ potential around the combustion site .
At this time, when the particle size of the carbonaceous material is small, the contact between the carbonaceous material and the air becomes good, the combustion speed is fast, and the NOx conversion rate also becomes high. Conversely, if the particle size of the carbonaceous material is large, the contact between the carbonaceous material and air will be poor, the combustion rate will be slow, and the NOx conversion rate will also be low. For this reason, as for the particle size of the suitable carbonaceous material in sintering, 0.5 to 3 mm except coarse particles and powdery materials is considered to be good. Then, the carbonaceous material is crushed and classified, or granulated with a binder added so that the particle size of the carbonaceous material falls within the above range as much as possible. However, in the control method of the combustion rate and NOx conversion rate assuming the above-mentioned particle size change, the medium combustion rate and the medium NOx conversion rate can be eventually achieved only by performing simple adaptation. It is only a technology aimed at, and it is impossible to achieve both a high combustion rate and a low NOx conversion rate, and a significant reduction in NOx at a high production rate.

The following techniques are disclosed regarding sinter ore.
Patent Literatures 1 and 2 disclose a technique for forming a coating layer having a thickness of several hundreds of microns around granular coke, and reducing NOx by melting and cracking catalysis of the coating layer.
Further, Patent Document 3 discloses a method for producing granular fuel obtained by granulating and curing cement, blast furnace granulated slag, and the like to fine-grained coke and coarse-grained coal.
Further, Patent Document 4 discloses a technology for producing a partially reduced sintered ore by utilizing a molded product produced by mixing iron ore, a carbonaceous material and limestone as a part of a sintering raw material.

Patent Document 5 discloses that a predetermined amount of coarse-grained coke is contained when powdery coke is blended with a coagulant and subjected to rolling granulation.
In Patent Document 6, a strength developing agent such as Portland cement and water are added to pulverized coke, and pregranulation is performed to granulate into fine particles by rolling and fine particles into small spherical particles. Further, it is disclosed to produce small pellets by curing.
Patent Document 7 discloses that a particulate carbon source and a binder are mixed and granulated to form a binder-coated non-combustible bulk carbon source, and this is added to a sintering material.

International Publication No. 2011/129388 JP, 2012-172067, A Japanese Patent Application Laid-Open No. 62-220590 Japanese Patent Application Laid-Open No. 2002-226920 JP-A-59-39333 JP-A-54-127902 JP 2001-262241 A

However, the techniques of Patent Documents 1 and 2 reduce NOx generated from granular coke, and are not intended for powdered coke.
Further, the above-mentioned Patent Document 3 only clarifies the conditions for producing the granular fuel which does not cause a problem in transportation, and the purpose of improving the sintering operation, more specifically, the reduction of NOx at the sintering operation. The condition was not designed consciously.
Further, Patent Document 4 described above is a reduction-sintering technology using a high-carbon material for producing a special reduction-sintered ore with high FeO content containing m-Fe, which is usually used in a blast furnace. It is not intended for reducing high-quality sinter.
Moreover, in order to achieve efficient granulation of fine powdered coke, the above-mentioned patent document 5 only contains a predetermined amount of coarse-grained powdered coke, and the condition is conscious of NOx reduction at the time of sintering operation. It is not designed.
In addition, Patent Document 6 mentioned above is intended to substitute unused coke dust powder for powder coke for sintered fuels, and conditions were designed with consideration for NOx reduction during sintering operation. is not.
Moreover, the said patent document 7 is for manufacturing a carbon-containing sintered ore containing a large amount of carbon sources, and does not consider NOx reduction.

  An object of the present invention is to provide a modified carbon material for producing a sintered ore and a method for producing a sintered ore using the same, which can suppress the generation amount of NOx in exhaust gas at a high production rate.

As described above, NOx in the sintering process is generally referred to as Fuel-NOx, and the generation origin is said to be nitrogen in the carbonaceous material. For this reason, if the amount of nitrogen in the carbonaceous material is low, or if the NOx conversion rate is low, the amount of NOx produced will decrease.
The carbon material used for the sintering raw material has a particle diameter of 8 mm or less, but a powder (a particle diameter of 0.25 mm or less) and a granular material (a particle diameter of 0.25 to 8 mm) are mixed. It is about 35/65 in mass ratio.
With regard to the form of the granulated material which is a sintering material, as shown in FIG. 1 (A), in the granular carbon material particle 1, it becomes a nucleus of the granulated material, and the powdery ore 2 is coated around it. Structure (S type). The NOx conversion rate of the S-shaped structure 3 is affected by the layer thickness and composition of the coating layer.
On the other hand, in the case of powdery carbonaceous material particles, a coating layer is formed when it is mixed with powdery ore, but in the case of granulation of only the powdery raw material in which no granular material is present, FIG. As shown, it becomes P type structure 4 of the structure which does not have a nucleus called P type.
The present inventor aimed at the improvement of the burning rate of the carbonaceous material and the significant reduction of the NOx conversion rate, and clarified the suitable conditions in the P-type granulated particle based on the particulate carbonaceous material having a particle size of 0.25 mm or less. And a method for producing the same, and the present invention has been completed.

The gist of the present invention is as follows.
[1] A granulated material of a raw material containing a carbon material, iron ore, and a lime hydraulic binder, and satisfying the following A) to D), a modified carbon material for producing a sintered ore.
A) The ratio of the water washing particle size of 0.25 mm or less of the particles constituting the granulated matter is 85% by mass or more B) The carbon content of the granulated matter is 21% by mass or more and 68% by mass or less C) of the granulated matter CaO content is 4% by mass or more and 15% by mass or less D) The particle size of the granulated product is 10 mm or less
However, about 500 g of the above-mentioned granulated product immediately after granulation formation is collected by condensation, put into a water washing disintegrator, and sieved for 10 minutes while supplying a water stream, and then the drier After drying at 105 ° C. for 2 hours or more, the particle size distribution is measured and calculated using a low-tap sieve shaker with a JIS standard sieve (diameter 200 mm).
[2] The modified coal for producing a sintered ore according to [1], wherein the modified carbonaceous material for producing a sintered ore contains calcium ferrite composed of oxides of Ca and Fe. Material.
[3] The modified carbon material for producing sintered ore according to [1] or [2], which contains sintered return ore in the modified carbon material for producing sintered ore.
[4] The modified carbon material for producing sintered ore according to any one of [1] to [3], wherein the water content of the granulated product is 10% by mass or more.
[5] The modified carbon material for producing sintered ore according to any one of [1] to [4], wherein the raw material constituting the granulated product is mixed and pulverized in advance.
[6] A sintered ore characterized by using the modified carbon for producing sintered ore according to any one of [1] to [5] as a part or all of the carbonaceous material for sintering. Production method.
[7] A portion or all of the portion of 0.25 mm or less is separated from the carbon material of the raw material for sintering, and the separated carbon material of 0.25 mm or less is used in any of [1] to [5] A method for producing a sintered ore, comprising producing the modified carbon material for producing a sintered ore described above, and using the modified carbon material for producing the sintered ore and the remaining carbon material.
[8] In the granulation of the raw material for sintering with a drum mixer, the above-mentioned granulation time after the addition of water, which is the granulation time from the time when water is added to the drum mixer until the end thereof is reached The modified carbon material for producing sintered ore is to be fed to the drum mixer such that the granulation time to reach the end is within 20.8% of the granulation time after the addition of water. The method for producing sintered ore according to [6] or [7] characterized by the above.

  According to the present invention, the generation of NOx is suppressed without reducing the burning speed of the carbonaceous material by adjusting the water washing particle size, the carbon content, the CaO content, and the particle size of the granulated material constituting the granulated material. Thus, a modified carbon material for producing sintered ore is obtained. By using such a modified carbon material for producing a sintered ore as a carbon material of a raw material for sintering, high quality of low FeO component can be obtained without reducing the sintering productivity and suppressing the generation amount of NOx. Sinter can be produced.

BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic which shows the structure of a sintering carbon-material granulated material, (A) shows S type structure and (B) shows P type structure. Schematic of a small sintering reaction experiment apparatus. The figure which shows the relationship between the coating composition and the coverage in the sintering experiment which used S type | mold granulated material for the carbonaceous material, NOx conversion, and the largest burning rate. The figure which shows the relationship between the carbon material compounding ratio in the sintering experiment which used P-type granulated material for the carbon material, NOx conversion, and the largest burning rate. The figure which shows the relationship between the CaO density | concentration in a P-type granulated material, NOx conversion, and the largest burning rate. The figure which shows the relationship between the lime hydraulic binder kind in P-type granulated material, NOx conversion, and the largest burning rate. Diagram showing changes in burn rate and NOx conversion rate of changing the type of iron ore hematite iron ore, the CaO · Fe ₂ O ₃ and sintering return ores.

In the following, particle size means diameter. Powdery, powder refers to particles having a particle size of less than 0.25 mm. Granular, core means particles having a particle size of 0.25 mm or more and 8 mm or less. Percentage means mass%. Further, FeOx represents an Fe oxide, x represents an oxidation degree represented by 1.0 to 1.5, and represents FeO, Fe ₃ O ₄ , Fe ₂ O ₃ or the like.

(Modified carbon material for producing sintered ore)
According to a first aspect of the present invention, a modified carbonaceous material for production of sintered ore (hereinafter sometimes simply referred to as "modified carbonaceous material") contains a carbonaceous material, iron ore, and a lime hydraulic binder. Granulated material which is a raw material, and is characterized by satisfying the following A) to D): A) The ratio of the water washing particle size of 0.25 mm or less of the particles constituting the granulated product is 85% by mass or more B) Carbon content of the granulated product is 21% by mass to 68% by mass C) CaO content of the granulated product is 4% by mass to 15% by mass D) particle size of the granulated product is 10 mm or less Other than the auxiliary materials such as dolomite and miscellaneous materials such as scale may be added as long as the effects of the present invention are not impaired.

  In searching for the conditions from the above A) to D), a small sintering reaction test apparatus 10 shown in FIG. 2 capable of measuring the carbon burning rate and the NOx conversion rate was used. The small-sized sintering reaction experimental apparatus 10 includes a reaction cell 11, a heater 12 provided around the reaction cell 11, and a gas composition analyzer 13. The reaction cell 11 is cylindrical, and on the lower side of the inside, a tray 14 is installed. The reaction cell 11 used in the present embodiment has an inner diameter of 36 mm. Further, an air introduction hole 15 is provided on the upper end side of the reaction cell 11, and a gas discharge hole 16 is provided on the lower end side. Further, the gas discharge hole 16 and the gas composition analyzer 13 are connected via a pipe, and the exhaust gas discharged from the gas discharge hole 16 is configured to be introduced into the gas composition analyzer 13.

In the experiment using the small-sized sintering reaction test apparatus 10, first, alumina spheres are filled from above the reaction cell 11 to form the alumina sphere heat exchange layer 17. Next, 50 g of the blended material is filled, and the loaded material layer 18 is formed on the alumina sphere heat exchange layer 17 at a height of about 20 mm. Then, alumina spheres are filled, and an alumina sphere preheating layer 19 is formed on the blended raw material packed bed 18.
Next, the reaction cell 11 is heated and held at 900 ° C. by the heater 12 and air is introduced into the reaction cell 11 from the air introduction hole 15 at a flow rate of 20 NL / min, and the carbonaceous material in the blended raw material packed bed 18 Burn the Then, the exhaust gas discharged by this combustion is sent from the gas discharge hole 16 to the gas composition analyzer 13 to measure the concentration change of the exhaust gas (CO, CO ₂ , NOx).
From this measurement result, calculate the maximum burning rate (% / s) and NOx conversion rate (mol%) = (gas (NOx)-raw material [C]) / (gas (CO + CO ₂ )-raw material [N]) It can be evaluated. However, CO ₂ generated from limestone is deducted.

Using the above-described small-sized sintering reaction test apparatus 10, sintering experiments were carried out with respect to compounding materials in which hematite iron ore, limestone and carbonaceous material granules were mixed. The proportions of hematite iron ore, limestone and carbonaceous material granulates are shown in Table 1 below. The carbonaceous material granulate used in the sintering experiment is S-type granulate and P-type granulate. The composition of S-type granules and P-type granules used is shown in Table 2 below.
The evaluation result of the sintering experiment which used S type | mold granulated material for carbonaceous material in FIG. 3 is shown. FIGS. 3A and 3B show the relationship between the coating composition and the NOx conversion rate and the maximum burning rate when the coverage rate is 10%. FIGS. 3C and 3D show the relationship between the coverage, the NOx conversion, and the maximum burning rate when the coating composition CaO / Fe ₂ O ₃ is 40/60 in mass ratio. In addition, in FIG. 3 (A)-(D), the white circle mark has shown the result of the granular coke (non-coated coke) of a coating rate which is 0%.
It can be seen from FIG. 3 that in the case of non-coated coke with a coverage of 0%, the NOx conversion is about 30%, but it tends to be slightly reduced if a coating layer is formed around granular coke. In particular, tended to NOx conversion decreases in _CaO-Fe 2 _{O 3} based coating layer, the NOx conversion rate at the maximum was reduced to 20%. On the other hand, the maximum burning rate is only about 1.8% / s, and is not greatly affected by the layer thickness and composition of the coating layer.

Next, the evaluation result of the sintering experiment which used P type granulated material for the carbon material is shown in FIG. FIGS. 4 (A) and 4 (B) are diagrams showing the relationship between the blending ratio of carbonaceous material, and the NOx conversion rate and the maximum burning rate. In FIG. 4, evaluation results of 8 mm size compression molded product (10 mm diameter, 5 mm thick tablet) and granulated product (3 mm diameter spherical pellet) by 3 mm size plate pelletizer as P type granulated material Is shown.
From FIG. 4, when the blending ratio of the carbonaceous material (powdery coke) is 25% by mass or less, the NOx conversion ratio is high. On the other hand, when the blending ratio of the carbonaceous material (powdery coke) is in the range of 25% by mass to 80% by mass, the NOx conversion rate is significantly reduced, and the maximum burning rate is also about 1.8% / min. , The improvement effect is clearer than S type granulate. Here, for P-type granulated products, spherical pellets manufactured using a small pan pelletizer and tablets manufactured by compression molding in a cylindrical shape are shown. Among these, the NOx conversion rate of the tablets has been reduced to 10% or less, and the more finely and strongly granulated tablets show a larger improvement effect.

The effects of these results are considered as follows.
When the blending ratio of coke in P-type granules exceeds 80% by mass, the combustion reaction is similar to that of granular coke, that is, S-type granules. On the other hand, when the blending ratio of coke is less than 25% by mass, the NOx conversion rate is high, and even if the carbon in the carbonaceous material is burned by the oxygen in the air and generates heat, the carbonaceous material ratio in the granulated material Is absorbed by the surrounding iron ore and heat accumulation does not proceed, resulting in slow combustion at low temperature. The carbon material blending ratio of a general sinter compounding raw material is about 4% by mass, which is the same as the reason why the NOx conversion ratio of carbon material particles having a particle size of 0.25 mm or less is high here.
However, in the case where the content ratio of coke is 25% by mass to 80% by mass and coke, iron ore and binder are appropriately present in the granulated material, around the granulated material in the granulated material Poor contact with the air present.
In this case, the combustion reaction of the carbonaceous material takes a complicated form. For example, when iron ore is Fe ₂ O ₃ , the combustion reaction of the carbonaceous material takes the form shown in the following reaction formulas (1) and (2).
C + Fe ₂ O ₃ → CO + 2 FeO, 2N → N ₂ (Inside granulated material: carbon reduction reaction) (1)
CO + 1/2 O ₂ → CO ₂ (area around granulated material: CO combustion reaction) ... (2)

That is, since the inside of the P-type granulated material is dense, the carbon in the powdery coke inside the granulated material is not burned by the oxygen in the air present around the granulated material, but the inside of the granulated material Cause the carbon reduction reaction of the above reaction formula (1) with Fe ₂ O ₃ in iron ore. This reaction produces CO and maintains low O ₂ potential, so the nitrogen coexisting with carbon in the carbonaceous material produces N ₂ rather than NOx, and the NOx conversion rate is significantly reduced. Then, the generated CO is released from the inside to the outside of the granulated product, and the CO combustion reaction of the above-mentioned formula (2) proceeds in the space around the granulated product to obtain a large calorific value.
As described above, the two-stage reaction can be progressed by the appropriate blending ratio of iron ore and carbonaceous material, and a high burning rate and a low NOx conversion can be obtained. However, since the reaction of the above reaction formula (1) is a near contact reaction between powders, the particle size of iron ore and carbonaceous material is preferably a powder (a particle size of 0.25 mm or less), so that powder can be well contacted. It is important that they are compact granules mixed between the bodies.

There is also a restriction on the reaction formula (2). The refusal of the contact between the air present around the granules and the carbonaceous material in the fine granules means that there is no escape of CO generated inside the granules. Therefore, there is no gas path inside the granulated material at the combustion temperature (about 600 ° C.) of the carbon material and air, but after the reaction start (about 800 ° C.) of the above reaction formula (2), the inside of the granulated material It is important that the gas path be formed in the For this purpose, at about 800 ° C., it is necessary to provide a mechanism for changing the interparticle space inside the granulated material. The lime hydraulic binder has the function of filling the powder space with a hydrated gel to bind the powder particles, but this hydrated gel is characterized by being thermally decomposed at about 800 ° C. to form a crack. Therefore, if a lime hydraulic binder is added to the inside of the P-type granulated material, CO generated by the reaction of the above reaction formula (1) is obtained from the gas passage formed by the crack due to the thermal decomposition of the hydrated gel. And without delay, the granulated material is released to the outside and burned. For this reason, a high burning rate can be held.
FIGS. 5A and 5B show the relationship between the CaO concentration in the P-type granulated product, the NOx conversion rate, and the maximum burning rate.
As shown in FIG. 5, when the blending ratio of slaked lime (Ca (OH) ₂ ) increases and the CaO concentration of the granulated material exceeds 15% by mass, the NOx conversion ratio increases, and the maximum burning rate also increases. There is a tendency for the improvement effect to decrease. In addition, if the CaO concentration is less than 4% by mass, the binder is insufficient and a strong granulated product can not be produced, and the granulated product is disintegrated by mixing with other raw materials, and the object can not be achieved.
Based on the above search results, the appropriate conditions from the above A) to D) were set as follows.

The particle diameter of the constituent particles is extremely important because the contact state between the powder particles constituting the P-type granules is important. Therefore, in the condition A), the ratio of the washing water particle size of 0.25 mm or less of the particles constituting the granulated material is specified as 85 mass% or more. The water washing particle size of the particles constituting the granulated product of the condition A) is the water washing particle size of the particles constituting the granulated material immediately after the granulation formation. The reason for this is that, as will be described later, in the method of producing a modified carbon material, there is a step of mixing and crushing the carbon material, iron ore, and lime hydraulic binder, followed by granulation, and hydration and solidification after granulation. It is because it is difficult to measure the particle size of the carbonaceous material or iron ore by a simple method because there is an expected aspect. Therefore, in order to accurately grasp the particle size of the particles constituting the granulated product immediately after granulation, it was specified by a method of crushing the particles constituting the granulated product using a water washing apparatus and measuring the particle size.
The method for measuring the water washing particle size distribution of the particles constituting the granulated material is as follows.
First, about 500 g of a granulated material immediately after granulation formation is collected by a fraction, and this is used as a measurement sample. The measurement sample is then placed in a water washing and disintegrating apparatus and sieved for 10 minutes while supplying a water stream. Next, the sample is dried in a drier (105 ° C., 2 h or more), and the particle size distribution is measured and calculated with a JIS standard sieve (diameter 200 mm) using a low tap sieve shaker.
In addition, since the solidification reaction of the hydraulic binder is slow, immediately after granulation formation, specifically, within 6 hours after granulation, it is possible to easily granulate even to the constituent particles by the shower by the water flow of the water washing disintegration device It can crush things.
The water washing particle size of the particles constituting the granulated product desirably has a total particle size of 0.25 mm or less. However, industrially, even if the particle size of 0.25 mm or less is 85 mass% or more, sufficient effects can be exhibited. .

Condition B) is that the carbon content of the granulated material is 21% by mass or more and 68% by mass or less.
This condition B) is based on the fact that both the NOx conversion rate and the maximum burning rate are good results within the range of 25 mass% or more and 80 mass% or less of the carbon material blending ratio shown in FIG. 4. As the carbonaceous material, anthracite containing a small amount of nitrogen may be used besides coke. Therefore, under the condition B), the carbon content of the coke was regarded as 85.5 mass%, and the carbon content of the granulated material was specified as 21 mass% or more and 68 mass% or less.

Condition C) is that the CaO content of the granulated material is 4% by mass or more and 15% by mass or less.
This condition C) is based on the result shown in FIG. Here, as the lime hydraulic binder, not only Ca (OH) ₂ but also Portland cement, granulated blast furnace slag, quick lime, etc. may be used. FIG. 6 shows the results of evaluating various types of lime hydraulic binders. 6 (A) and 6 (B) are diagrams showing the relationship between the type of lime hydraulic binder in P-type granules, the NOx conversion rate, and the maximum burning rate. The types used are CaO, Ca (OH) ₂ , Portland cement, blast furnace granulated slag and steelmaking KR slag. Moreover, it is a P-type granulated product (compression molded product), and the CaO content of the granulated product is 15% by mass.
From FIG. 6, low NOx conversion and high maximum burning rate as shown in FIG. 3 and FIG. 4 were confirmed for any type.

The condition D) is that the particle size of the granulated product is 10 mm or less.
This is because although the powder of carbonaceous material is densely packed at a high concentration inside the granulated product, the granulated product is also a fuel source compounded with the carbonaceous material, so that even uniform dispersion in the packed bed is also possible. It is a necessary condition. That is, it is necessary to aim at a uniform uniform dispersion throughout the layer in a proper accumulation unit. From this point of view, the particle size of the granulated product is important, and under the condition D), the particle size of the granulated product is specified to be 10 mm or less. In addition, when the particle size of the granulated material is too large, it becomes an inhomogeneous state and an adverse effect that the burning rate is lowered appears.

A second aspect according to the present invention is characterized in that the modified carbonaceous material contains a calcium ferrite mineral represented by CaO · FeOx instead of iron ore.
The carbonaceous material for producing sintered ore is composed of carbonaceous material, iron ore containing CaO · FeOx, and lime hydraulic binder, but unlike iron ore, unlike the first aspect which is not particularly specified, Fe ₂ represented by FeO x It is preferable to use iron ore containing calcium ferrite mineral represented by CaO · FeOx, not iron ore mainly composed of iron oxide such as O ₃ , Fe ₃ O ₄ or FeO. This is because the reaction between CaO / FeOx and carbonaceous material C is more active than the catalytic reaction between FeOx and carbonaceous material C in iron ore due to the acceleration effect of Ca electrons, and the burning rate improvement and conversion ratio This is because the reduction is effectively achieved. In this case, for example, in CaO · Fe ₂ O ₃ , the above-mentioned equation (1) is as follows.
C + CaO · Fe ₂ O ₃ → CO + 2CaO · FeO, 2N → N ₂
(Inside granulated material: carbon reduction reaction) ... (1) '
CO + 1/2 O ₂ → CO ₂ (area around granulated material: CO combustion reaction) ... (2)

A third aspect according to the present invention is characterized in that the modified carbon material contains sintered return ore instead of iron ore.
The carbonaceous material for producing sintered ore is composed of carbonaceous material, sintered return ore, lime hydraulic binder, but different from the first aspect which is not particularly specified for iron ore, Fe ₂ O ₃ represented by FeO x, It is preferable not to be a simple iron oxide-based iron ore such as Fe ₃ O ₄ or FeO, but a sintered return ore containing a calcium ferrite mineral represented by CaO · FeO x. In this way, in order to obtain the effect of CaO · FeOx shown in the second aspect, it is possible to utilize the sinter return produced as a product undersize in the sinter production process. The main minerals of the sinter cake are roughly classified into calcium ferrite represented by CaO · FeOx and hematite and magnetite represented by FeOx. The sinter cake is crushed and sieved, and separated into product sinter ore and sinter return and recovered. Therefore, the sintered ore contains a large amount of CaO · FeOx, and its use satisfies the second aspect. CaO · FeOx is not a naturally occurring mineral, but is a substance that can be produced by high temperature contact treatment of iron ore and CaO-containing matter in advance. By utilizing sinter return, it is an aspect that can be achieved without providing a new production process of CaO · FeOx.
FIG. 7 shows the effect on NOx conversion and burning rate when the type of iron ore is changed to hematite iron ore, CaO · Fe ₂ O ₃ and sinter return. Carbonized material granulated using CaO · Fe ₂ O ₃ (a kind of CaO · FeOx) or sintered return (containing CaO · FeOx) as iron ore to be added to carbon material and lime hydraulic binder is Fe ₂ It is a preferred embodiment with a lower NOx conversion than that with O ₃ (normal iron ore).

(Method of manufacturing modified carbon material)
Production of the modified carbon material is made by blending iron ore, carbon material and lime-based hydraulic binder to desired carbon content and CaO content, adding water, and using a mixer / granulator. Granulate.
According to a fourth aspect of the present invention, the water content of the granulated material is 10% by mass or more. In order to reduce the NOx conversion rate, it is necessary to suppress the combustion reaction between the carbon inside the granules and the air present around the granules as much as possible, and the temperature rise outside the P-type granules is As it is, in order to slow the temperature rise in the P-type granulated product particles, a high water content of 10% by mass or more is used to suppress the temperature rise.
Part of coke and iron ore may be replaced with dust or pellet iron ore. Since these usually have a particle size of 0.25 mm or less, the next grinding step can be omitted. Granulation can use a plate-type granulator. In the granulation operation, in order to make the particle size of the granulated product 10 mm or less, it is possible to adjust by appropriately adjusting the production speed and the granulated water. The particle size of the granulated material can be increased by reducing the production rate and increasing the granulated water content.

  The 5th aspect concerning this invention mixes and grinds the raw material which comprises granular material beforehand. A ball mill etc. are used for grinding. At the time of grinding, it is preferable to mix and grind the raw materials. This is because the NOx conversion rate is lowered and the combustion efficiency is high by reducing the particle size and enhancing the contact between the particles to actively perform the reaction of the reaction formula (1). In addition, it may replace with the combination of a ball mill and a dish-type granulator, and can also use the high speed stirring mixer which combined the role of mixing, crushing, and granulation with one stand, a vibro mixer, a vibration mill etc.

(Method of producing sintered ore)
A sixth aspect according to the present invention uses a modified carbon material for part or all of the carbon material of the raw material for sintering in the production of sintered ore. Here, the reduction effect of NOx becomes large in proportion to the ratio of transferring the carbon material of the raw material for sintering to the modified carbon material.
The method for producing sintered ore according to the present invention is a sintering method using a dwightroid type (DL type) sintering machine, and the FeO component of the sintered ore product is preferably 15% by mass or less, and 10% by mass. % Or less is more preferable. Sinter with high FeO content has an adverse effect of increasing the reducing material ratio in blast furnace operation, and it is desirable that FeO content be as low as possible.
In this embodiment, reduction of the NOx conversion rate and formation of FeO can be achieved by reducing the O ₂ potential by direct reduction action between the carbonaceous material and iron ore, but it is formed after the carbon in the carbonaceous material has reacted. It is desirable that FeO be oxidized to return to FeOx and generate heat. Then, the function of the gas path by the thermal decomposition of the lime hydraulic binder mentioned above is calculated | required. That is, this gas passage serves as an exhaust passage for CO in the first half of production, but functions as an air passage for oxidizing FeO in the second half of production and works to reduce the FeO component of sintered ore. Thus, lime hydraulic binders are also important for reducing the FeO concentration.

  A seventh aspect according to the present invention is a modified carbonaceous material obtained by separating a part or the whole of a portion of 0.25 mm or less from the carbonaceous material for sintering and using the separated carbon material of 0.25 mm or less The modified carbon material and the remaining carbon material are used as a sintering carbon material. In this aspect, since the ratio of the pulverized carbon material in the carbon material decreases, a larger NOx reduction effect can be obtained.

In the eighth aspect according to the present invention, in granulation of the raw material for sintering by a drum mixer, after the addition of water, which is the granulation time from the time when the water is added to the drum mixer to the end thereof With respect to the grain time, the modified carbon material for producing a sintered ore has the drum such that the granulation time to reach the end is within 20.8% of the granulation time after the water addition. It is put into the mixer . For example, at the time of granulation of the sintering raw material, the place where the modified carbon material is charged is within 5 m from the end of the drum mixer granulation facility. This is because the granulated matter contains a carbon material and serves as a heat source for the sinter-blended raw material, so minimal mixing operation is required, but if the strength of the granulated matter is weak, the mixing process with other raw materials Collapse and there is a part that can not fulfill its function. In the examination in the example described later, mixing of the granulated material is good if mixing within 25 seconds with the drum mixer, and if it is calculated back, if it is inserted within 5 m from the end of the drum mixer, good construction Granules can be maintained. Then, it is desirable to employ | adopt the method of suppressing disintegration of a granulated material as much as possible, and mixing with another raw material, and processing of light mixing is desirable.

Next, the present invention will be described in more detail by way of examples. The present invention is not limited to the contents described in these Examples.
The effect of the present invention was confirmed by the sintering pot test.
(Preparation of raw materials)
The particle size distribution of each grade of the sintering raw material used for the sintering pot test is shown in Table 3 below. The coke having a carbon content of 85.5 mass% was selected as the carbonaceous material, and six types of cokes A to F having different particle sizes were used. The coke D and the coke E are obtained by sieving the coke B with a 0.25 mm sieve, the coke on the sieve is coke D, and the coke on the sieve is coke E. Also for iron ore, two types of iron ore A with a particle size of 0.25 mm or less of 88% and iron ore B in which a powder and particles were mixed were used. Also, instead of iron ore, CaO · Fe ₂ O ₃ and sintered return were also prepared. As the lime hydraulic binder, Ca (OH) ₂ of 100% or less in particle diameter of 0.25 mm or less obtained by hydration treatment of quick lime was used.

  Table 4 shows the breakdown of the blending of the granulated material. Table 5 shows the blending of the granulated material and other raw materials used in the sintering pot test. In Table 5, the granulated material is a modified carbonaceous material, and the coke alone is a coke blended as a single material without being granulated in the modified carbonaceous material.

(Manufacturing method of granulated material)
With respect to the combination numbers 1 to 3 and 17 shown in Table 4, no granulation treatment is performed. That is, no granulated material is produced. The average particle size of cokes A to C prepared in combination numbers 1 to 3 is 10 mm or less, and the average particle size of coke F prepared on combination number 17 is 12.3 mm.
For Formulation Nos. 4 to 16, each raw material is blended at a ratio shown in the breakdown of the granulated product in Table 4 above, and the blend and 7 to 11.2% by mass of water are mixed for 60 seconds with a high-speed stirring mixer, Subsequently, granulation was carried out with a pan pelletizer, and coarse granules were removed with a 10 mm sieve to produce granules having a particle size of 10 mm or less. The water washing particle size of the granulate-constituting particles, the carbon content of the granulate, and the CaO content of the granulate are as shown in the respective columns on the right side of Table 4 above.
The water washing particle size of the particles constituting the granulated product was measured as follows.
First, the granulated material immediately after granulation formation was fractionated and about 500 g was collected to obtain a measurement sample. Next, the measurement sample was placed in a water washing and disintegrating apparatus (manufactured by Fritsch Japan, electromagnetic sieve shaker A-3 PRO), and sieved for 10 minutes while supplying a water flow. Next, the sample is dried in a drier (105 ° C., 2 h or more), and then using a low-tap sieve shaker (manufactured by TANAKA TEC Co., Ltd .: RS2 type, shaking number 246 rpm, hammer number 123 number) The particle size distribution was measured and calculated using a JIS standard sieve (diameter 200 mm).
The carbon content of the granulated material is a value obtained by multiplying the carbon material ratio (numerical value in parentheses) in the granulated material breakdown column of Table 4 above by 0.855.

(The granulation method of the compounding material
Table 6 shows the characteristics of the formulations used in the experiment.

In Experiment cases 1 to 3 and 19 shown in Table 6, sintering experiments were carried out using compounding materials obtained by simply blending cokes A to C and F as a carbon material without producing a granulated material. . That is, as shown in Table 5 above, predetermined amounts of 63% by mass of iron ore B, 13% by mass of limestone, 20% by mass of returned ore and 4.0% by mass of carbonaceous material were weighed as standard compounding materials. After these materials were mixed for 60 seconds using a drum mixer, water was added to a final 7% water content, and then granulated for 120 seconds using a drum mixer. The difference between the test cases 1 to 3 and 19 is the particle size of the used coke.
In Experiment cases 4 to 18, sintering experiments were performed using compounding materials obtained by compounding the granulated material. That is, as shown in Table 5 above, 56 to 63% by mass of iron ore B, 10 to 13% by mass of limestone, 20% by mass of returned mineral B and 4.0 to 11.6% by mass as standard compounding materials A predetermined amount of carbon material (including granulated material) is weighed out, and these raw materials are mixed using a drum mixer for 60 seconds, and then water is added so as to obtain a final 7 to 11.2% water content. Granulated for 25 to 120 seconds.

(Sintering apparatus and method)
A sintering pot having an inner diameter of 300 mm and a layer height of 500 mm was prepared as a sintering experimental device.
The sintering pot is formed in a tubular shape, and an inner bottom portion thereof is provided with a gas-permeable grate. A wind box is installed at the bottom of the sintering pot. A suction fan is connected to the air box via an exhaust gas pipe for exhausting the exhaust gas, and the exhaust gas can be sucked through the air box. Inside the air box, a temperature sensor for measuring the temperature of the sintering exhaust gas is provided. In addition, an exhaust gas collection pipe is installed between the wind box and the suction fan.
Then, 2.0 kg of 10 to 15 mm sintered ore was laid on the grate, and 65 kg of the blended material was loaded thereon to form a packed bed. Next, the pressure in the lower part of the sintering pot was adjusted to about 9.8 kPa (1000 mm Aq conversion) to ignite the upper part of the packed bed. The ignition time was 1 minute. After the end of ignition, the sintering reaction was advanced by suctioning air from the upper part of the packed bed under a constant negative pressure of about 9.8 kPa (converted to 1000 mm Aq) under the pan. Moreover, exhaust gas temperature was measured by the temperature sensor installed in the wind box under the pan. The time when the exhaust gas temperature became maximum was taken as the sintering completion time. That is, the sintering time was from the start of ignition to the reaching of the exhaust gas temperature.
During the sintering reaction, the exhaust gas was collected from the exhaust gas collecting pipe, and the gas composition analysis was continuously performed, and the flow rate of the exhaust gas was measured by an orifice to calculate the NOx generation amount. Moreover, the sintered production rate and the product yield were evaluated according to JIS-M 8700.

(Test results)
The evaluation test results are summarized in Table 6 and shown.
Of the experimental cases 1 to 19, the experimental case 4 and the experimental cases 101 to 103 and the experimental cases 11 to 18 are inventive examples satisfying the conditions A) to D).
Experimental cases 1 to 3 are examples in which the carbonaceous material granulate is not used. In experimental cases 1 to 3 in which coke was simply added, the amount of NOx generated was as high as 8.8 to 11.4 mol / raw material t. When the experimental cases 1 to 3 are compared, as the coke particle size becomes finer, the NOx generation amount increases, and the decrease in the production rate becomes remarkable. On the other hand, when coarse-grained, the amount of NOx generation decreases, but the amount of FeO increases.

  Experimental cases 4 to 6 are examples in which the granulated material of S-type and P-type was evaluated by changing the particle size of the carbonaceous material. In the experimental case 4 using the fine-grained coke, the amount of NOx generation was significantly reduced to 3.2 mol / raw material t. In the experimental cases 5 and 6 in which the particle size of the carbon material used was coarse, the NOx generation amount increased to 6.3 mol / raw material t and 6.8 mol / raw material t, respectively, and the improvement effect was reduced. In addition, the sintering production rate was also the highest in Experiment Case 4, and it was confirmed that the method of the present invention is excellent.

Experiment case 7 is an example which produced a granulated material, without adding coke, and added the carbonaceous material simply like experiment cases 1-3. In the experimental case 7, as in the experimental cases 1 to 3, the amount of NOx generation was high.
Experimental case 8 is an example in which iron ore B having a coarse particle size is added to the granulated material. The ratio of the water washing particle size immediately after granulation was 0.25 mm or less was rough at 65 mass%, and the NOx generation amount did not decrease significantly at 8 mol / raw material t.

In Experimental Case 9 and Experimental Case 101, the addition amount of Ca (OH) ₂ which is a lime hydraulic binder of the granulated material is changed, and the influence of the CaO concentration in the granulated material is evaluated. Even in the experimental case 9 where the CaO concentration is 0 mass%, the amount of NOx generation decreases to 6.8 mol / raw material t, but the improvement effect is small. On the other hand, in the experimental case 101 in which the CaO concentration is 15% by mass, the NOx generation amount is greatly reduced to 4 mol / raw material t.

In Case 101, Case 102, and Case 103, the type of iron ore is changed using iron ore A, powder of CaO · Fe ₂ O ₃ prepared by electric furnace firing and sintered return metal A, and the effect is evaluated. The total amount of NOx is greatly reduced to 4 mol / raw material t in the use of iron ore A in case 101, but 2.7 mol / raw material t in case 102 and the use of sinter return metal in case 103 in the use of CaO · Fe ₂ O ₃ The use of the compound significantly decreased to 3.1 mol / raw material t, and the effects of the embodiment 2 and the embodiment 3 could be confirmed.
Experimental cases 11 to 13 are examples in which portland cement is used as the lime hydraulic binder of the granulated product, and the blending ratio of coke powder / (iron ore powder + binder) is changed. In any case, it was confirmed that the amount of NOx generation was significantly reduced to 4 to 5 mol / t of the raw material.

Experiment case 14 is an example using the carbon material granulated material of the combination number 4, and raising the moisture of the granulated material to 10.4 mass%. In the experimental case 14, the NOx generation amount was lower than that in the experimental case 4, and the effect of the mode 4 could be confirmed.
Experiment case 15 is an example which used the carbon material granulated material of the combination number 4, and reduced the granulation time of the carbon material granulated material and other compounding materials to 25 seconds. It was confirmed that the experimental case 15 has a lower amount of NOx generation than the experimental case 4 and is more effective.
The experimental case 16 is an example in which the carbonaceous material granulated material having the formulation number 14 is used, and the granulated material raw material is charged into a ball mill and subjected to a mixing and pulverizing process before the material is kneaded and processed by a high speed stirring mixer. The amount of generated NOx was lower in experimental case 16 than in experimental case 4 of the same blending ratio, and it was confirmed that the fifth embodiment of the above-mentioned modified carbon material production is more effective.

  Experiment case 17 uses the carbon material granulated material of combination number 15 for a part (34 mass%) of the carbon material in the raw material for sintering, and the remaining part (66 mass%) of the carbon material in the raw material for sintering This is an example using coke B. As in the case of the above-mentioned formulation No. 13, when partially using the carbon material granulated material, the amount of NOx generation is reduced compared to the experimental case where the carbon material granulated material is used for the whole amount of carbon material of sintering raw material. The effect is small. However, the generation amount of NOx has decreased to 7.4 mol / feed material t, and even in the partial use shown in the sixth embodiment, the reduction effect corresponding to the usage rate was sufficiently confirmed.

  In experimental case 18, coke B was classified in advance with a sieve of 0.25 mm, and a carbonaceous material granulated product was produced using coke E under the sieve, and the above-mentioned production was performed on a part of the carbonaceous material (34 mass%) It is an example using the coke D on a sieve (66 mass%) for the remainder of the carbonaceous material using the granulated carbonaceous material. As in the case of the test case 17 described above, the carbon material granulated product is partially used, but the NOx generation amount is reduced to 6.6 mol / raw material t as compared with the test case 17 in which the sieve classification is not performed. The effectiveness of Embodiment 7 was confirmed.

The experimental case 19 is an example using coarse-grained coke containing coarse grains of 10 mm or more without using carbonaceous material granulate. The sintering production rate decreased to 14.3 s-t / d / m ^2, and the product yield significantly decreased to 38.2%.

In the above Test Case 4, Test Cases 101 to 103 and Test Cases 11 to 18, the sintering production rate is also recorded at 30 s / t / d / m ^2, and it is confirmed that a high sintering production rate is secured. did it. Moreover, the sintered ore FeO component can secure 10 mass% or less.
As described above, the modified carbon material of the present invention is characterized in that the amount of NOx generated is extremely low and the sintering production rate is high, and by using this modified carbon material, the amount of NOx generation can be significantly reduced at a high production rate. .

  By adjusting the water washing particle size, carbon content, CaO content, and granulated particle size of the particles constituting the granulated material, it is possible to improve the combustion speed of the carbonaceous material and significantly reduce the NOx conversion rate. It is a quality carbon material, and the method for producing sintered ore using this modified carbon material can suppress the amount of NOx generated in the exhaust gas at a high production rate.

  DESCRIPTION OF SYMBOLS 1 ... Carbon material particle | grains 2. Powdered ore 3. S type structure 4 ... P type structure 10 Small sintering reaction experiment apparatus 11 Reaction cell 12 heater 13 Gas composition analyzer , 14: tray, 15: air introduction hole, 16: gas discharge hole, 17: alumina sphere heat exchange layer, 18: blended raw material filling layer, 19: alumina sphere preheating layer.

Claims (8)

It is a granulated material of the raw material containing a carbon material, iron ore, and a lime hydraulic binder, Comprising: The following A)-D) are satisfy | filled, The modified carbon material for sintered ore manufacture characterized by the above-mentioned.
A) The ratio of the water washing particle size of 0.25 mm or less of the particles constituting the granulated matter is 85% by mass or more B) The carbon content of the granulated matter is 21% by mass or more and 68% by mass or less C) of the granulated matter CaO content is 4% by mass or more and 15% by mass or less D) The particle size of the granulated product is 10 mm or less
However, about 500 g of the above-mentioned granulated product immediately after granulation formation is collected by condensation, put into a water washing disintegrator, and sieved for 10 minutes while supplying a water stream, and then the drier After drying at 105 ° C. for 2 hours or more, the particle size distribution is measured and calculated using a low-tap sieve shaker with a JIS standard sieve (diameter 200 mm). The modified carbon material for producing sintered ore according to claim 1, wherein the modified carbon material for producing sintered ore contains calcium ferrite composed of oxides of Ca and Fe .   The modified carbon material for producing sintered ore according to claim 1 or 2, wherein the modified carbon material for producing sintered ore contains a sinter return.   The moisture content of the said granulated material is 10 mass% or more, The modification carbon material for sintered ore manufacture as described in any one of the Claims 1 thru | or 3 characterized by the above-mentioned.   The raw material which comprises the said granulated material has been mixed and ground beforehand, The modification carbon material for sintered ore manufacture as described in any one of the Claims 1 thru | or 4 characterized by the above-mentioned.   A sintered ore according to any one of claims 1 to 5, wherein the modified carbon for producing sintered ore is used for a part or all of the carbonaceous material for sintering. Method.   The carbon material according to any one of claims 1 to 5, wherein a carbon material of 0.25 mm or less separated from the carbon material of the raw material for sintering is used. A method for producing a sintered ore, comprising producing a modified carbon material for producing a sintered ore, and using the modified carbon material for producing the sintered ore and the remaining carbon material. In the granulation of the raw material for sintering with a drum mixer, the sinter ore is used relative to a granulation time after water addition which is a granulation time from the time when water is added to the drum mixer until the end thereof is reached. The modified carbon material for production is characterized in that it is introduced into the drum mixer such that the granulation time to reach the end is within 20.8% of the granulation time after the addition of water. The manufacturing method of the sintered ore of Claim 6 or Claim 7.

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