JP5454503B2 - Carbon material reforming equipment - Google Patents

Description

The present invention relates to a carbonaceous material reforming treatment facility that can suppress generation of NOx.

In the production of sintered ore, nitrogen oxides (NOx) are generated in the exhaust gas due to combustion of carbonaceous materials used as fuel. This reduction of NOx is an important issue in improving air pollution.
As a means for reducing NOx, for example, Patent Document 1 discloses a technique for removing NOx using a catalyst mainly composed of a CaO—FexO-based composite oxide having a CaO content of 5 to 50 mass%.
However, since the CaO-FexO-based composite oxide described above is manufactured by melt-molding a lime-based material and iron ore, it is more expensive than a lime-based material used as an auxiliary material in normal sintering.

Therefore, without using an expensive oxide as described above, a lime-based raw material used as a normal sintering auxiliary material is used, and the lime-based raw material and coke are mixed and granulated to form a lime-based surface of the coke. Covering with raw materials to reduce NOx during combustion of carbonaceous materials has been studied.
Here, as a method of granulating the lime-based raw material and coke, for example, a technique described in Patent Document 2 is disclosed. Specifically, one or two types of quick lime and slaked lime (hereinafter simply referred to as lime) are blended with coke having a particle size of 0.3 mm or less and 50% by mass or more, and then granulated and cured. Is the method. In addition, the average particle size of the lime to mix | blend is 0.5-3 mm.

JP-A-6-15174 JP 2006-290925 A

However, in the technique described in Patent Document 2, since the particle size of coke is smaller than the particle size of lime, when this is granulated, coke adheres around the lime. For this reason, coke burns in a low temperature region, a large amount of NOx is generated, and NOx cannot be reduced.

The present invention has been made in view of such circumstances, and an object thereof is to provide a carbonaceous material reforming treatment facility that can economically suppress the generation of NOx in a low temperature region.

The gist of the present invention made to solve the above problems is as follows.
(1) The surface of the carbonaceous material used for the sintered raw material is coated with a coating containing 36% by mass or more of Ca derived from the lime-based raw material at a rate of 2% by mass to less than 30% by mass with respect to the carbonaceous material. A carbonaceous material reforming treatment facility for producing the surface coated carbonaceous material, mixing the surface coated carbonaceous material and the sintered blended raw material with a mixer to obtain the sintered raw material,
Adding water equal to or more than the number of moles of quick lime in the lime-based material to the kneading machine supplied with the lime-based material and the carbon material as the raw material for the surface-coated carbon material, The carbonaceous material reforming treatment facility is adjusted so that the water content of 9.5 mass% or more and less than 19 mass%.

(2) The said quicklime has an average particle size of less than 10 mm and an activity of 210 milliliters or more.

(3) A dust collector is provided in an upper part of the kneader, and dust generated by a hydration reaction in the kneader is collected, and the collected dust is supplied again to the kneader ( Carbonaceous material reforming treatment facility according to 1) or (2).

(4) Any one of (1) to (3), wherein the stirring blade of the kneader is a uniaxial or multiaxial screw blade or a uniaxial or multiaxial spiral paddle blade. The carbonaceous material reforming treatment facility according to claim 1.

(5) The carbonaceous material reforming treatment facility according to (4), wherein the rotation speed of the stirring blade is 5 rpm or more and less than 80 rpm.

(6) The carbonaceous material reforming treatment facility according to any one of (1) to (5), wherein a residence time of the kneader is 2.5 minutes or more and less than 30 minutes.

(7) The water addition amount in the kneader is an amount corresponding to a molar ratio of 1.5 times or more and less than 7.3 times the quicklime in the lime-based raw material (1) to (6) The carbonaceous material reforming treatment facility according to any one of (6).

(8) Any one of (1) to (7), wherein a granulator is provided between the kneader and the mixer to improve the adhesion strength of the covering to the carbonaceous material. Equipment for reforming carbonaceous materials as described in 1.

(9) The amount of water added in the granulator is set to 5% by mass or less of the total amount of water added to produce the surface-coated carbonaceous material. Carbonaceous material reforming equipment.

(10) The carbonaceous material reforming treatment facility according to (8) or (9), wherein a residence time of the granulator is 1 minute or more and less than 10 minutes.

(11) The carbonaceous material improvement according to any one of (1) to (10), wherein a storage tank capable of storing the produced surface-coated carbonaceous material is provided upstream of the mixer. Quality processing equipment.

The carbonaceous material reforming treatment facility according to the present invention adds a predetermined amount of water to a kneading machine to which a lime-based raw material and carbonaceous material as a raw material for the surface-coated carbonaceous material are supplied, Since it adjusts so that quantity may be 9.5 mass% or more and less than 19 mass%, the coating efficiency of the coating | cover of the optimal thickness to the surface of a carbonaceous material can be improved. This is because the slaked lime crystals produced from quick lime in the lime-based raw material are easily crystallized selectively on the surface of the carbonaceous material with a kneader, and the adhesion strength of the coating on the surface of the carbonaceous material can be improved.
Therefore, NOx generation can be suppressed economically.

Here, when a dust collector is provided in the upper part of the kneader and the dust collected by the dust collector is supplied again to the kneader, the amount of slaked lime generated increases, so the effect of the present invention becomes more remarkable. Most of the dust trapped by the dust collector is slaked lime after the hydration reaction. Therefore, by circulating and supplying the dust to the kneading machine, this dust plays the role of seed crystal in the water added to the kneading machine and promotes crystallization of slaked lime, which is the rate limiting condition for the hydration reaction. The effects described above can be obtained.

Moreover, when the stirring blade of the kneading machine is a screw blade or a paddle blade, the coating efficiency of the coating on the surface of the carbonaceous material can be increased as compared with a kneading machine without the stirring blade.

And when a granulator is provided between a kneader and a mixer, the adhesion strength of the coating to the carbonaceous material can be further improved.

Furthermore, when the storage tank which can store the manufactured surface covering carbon material is provided in the upstream of the mixer, the surface coating carbon material can be temporarily stored before supplying the surface coating carbon material to the mixer. Thereby, for example, even when the operation of the kneading machine for producing the surface-coated carbon material has to be stopped, the surface-coated carbon material stored in the storage tank can be stably supplied to the mixer.

It is a graph which shows the relationship between NOx conversion rate and temperature. It is explanatory drawing of the modification | reformation processing equipment of the carbonaceous material which concerns on one embodiment of this invention. It is explanatory drawing of the reforming equipment of the carbonaceous material which concerns on a 1st modification. It is explanatory drawing of the modification | reformation processing equipment of the carbonaceous material which concerns on a 2nd modification. (A), (B) is a photograph which shows the microscope observation result of a surface covering carbon material, respectively. It is a graph which shows the influence which a coating body has on NOx conversion rate. It is a graph which shows the relationship between the coating amount in a combustion test, and NOx conversion rate.

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 carbonaceous material reforming equipment of the present invention will be described.
NOx generated (generated) by sintering is obtained by oxidizing nitrogen in the carbonaceous material, and as shown in FIG. 1, it is confirmed that the amount of generation increases as the combustion temperature decreases at 1100 ° C. or lower. Has been. The NOx conversion rate on the vertical axis in FIG. 1 is calculated by the equation (1).
{NOx conversion rate (mol%)}
= 100 × {NOx generation amount (mol)} / {Nitrogen amount in carbonaceous material (mol)} (1)
Therefore, in order to suppress NOx production, it is important to burn the carbonaceous material as high as possible.

In the above-mentioned Patent Document 1, a carbon material having a surface coated with a CaO-FexO-based composite oxide having a CaO content of 5 to 50% by mass is obtained by the catalytic action of the CaO-FexO-based composite oxide. NOx produced during combustion is reduced or decomposed and removed. Since the CaO-FexO-based composite oxide whose CaO content is limited to 50% by mass or less has a low melting point and melts in a high temperature range of 1200 ° C. or higher, a certain amount of NOx can be obtained by coating the surface of the carbon material. A reduction effect is expected.
However, the CaO-FexO-based composite oxide is manufactured by melt-molding a lime-based raw material and iron ore, and is therefore more expensive than a lime-based raw material used as an auxiliary material in normal sintering.

Therefore, the present inventors use a lime-based raw material, which is used as a normal sintering auxiliary material, as a covering (coating material) on the surface of a carbon material without using the above-described expensive oxide. NOx reduction during combustion is possible.
As shown in FIG. 2, a carbonaceous material reforming treatment facility (hereinafter also simply referred to as a reforming processing facility) 10 according to an embodiment of the present invention is a carbonaceous material (for example, powder coke) used as a sintering raw material. A surface-coated carbon material is produced by coating a coating containing 36% by mass or more of Ca derived from a lime-based raw material on the surface at a ratio of 2% by mass to less than 30% by mass with respect to the carbonaceous material. A facility for mixing a coated carbon material and a sintered blending raw material with a mixer 11 to form a sintered raw material, which has a kneader 12 for producing a coating and coating the coating on the surface of the carbon material ing. This will be described in detail below.

The kneader 12 adds moisture to quick lime (calcium oxide: CaO) in the lime-based raw material to promote slaked calcification (digestion) by a hydration reaction, and from slaked lime (calcium hydroxide: Ca (OH) ₂ ). Or a device for producing a coating containing slaked lime and coating the coating on the surface of the carbonaceous material.
The kneading machine 12 is not particularly limited as long as it can produce a coating by digesting quick lime and coat the coating on the surface of the carbonaceous material. For example, a dow mixer, a redige mixer, etc. A general-purpose kneader such as an Eirich mixer or a cement mixer can be used, and in particular, a mixer equipped with a biaxial screw type stirring blade such as a Dow mixer is preferable.
As a result, quick lime and charcoal are charged into the kneader 12, further moisture is added, and this is stirred with a stirring blade to digest the quick lime into slaked lime, and the coating containing the slaked lime is further converted into charcoal. The surface of the material can be coated.

In addition, as the stirring blade of the kneader 12, a single-shaft or multiple-axis (for example, biaxial) screw blade or a single-shaft or multiple-axis (for example, 2-axis) spiral paddle blade can be used. . The number of revolutions of the stirring blade is preferably 5 rpm (times / minute, the same applies hereinafter) or more and less than 80 rpm.
Here, when the rotation speed of the stirring blade is less than 5 rpm, the rotation speed is too slow and insufficient kneading occurs, resulting in insufficient mixing of the carbonaceous material and the coating. On the other hand, when the rotational speed is 80 rpm or more, the rotational speed is too fast, the shearing force of the stirring blade is increased, and the action of peeling the coating from the carbonaceous material surface works.
Therefore, although the rotation speed of the stirring blade is 5 rpm or more and less than 80 rpm, it is preferable to adjust the lower limit within the range of 15 rpm and the upper limit within the range of 30 rpm.

Further, in this kneader, since a large amount of water vapor and dust are generated, as shown in FIG. 3, it is possible to use a kneader 14 (kneader having a dust collecting function) provided with a dust collector 13 in the upper part. preferable.
The dust collector 13 is a dry dust collector (preferably a bag filter) that is provided with a dust collecting filter 15 and collects dust generated by a hydration reaction in the kneader 14. It can also be made into the wet type dust collector which sprinkles and collects. The dust collector 13 is configured to supply the dust collected and collected by the dust collector 13 to the kneader 14 again (circulation supply). You may make it the structure to carry out.
When the dust collected by the dust collector 13 is returned to the kneader 14, the dust can be reused as a seed crystal of slaked lime in the kneader 14, so that resources can be effectively used (recycled) and the kneader 14 Since it can be dispersed and supplied into the interior, the kneading property with the carbonaceous material and the covering property of the coating are improved.

A mixer 11 is disposed on the downstream side of the kneader 12 (or kneader 14).
This mixer 11 includes a sintered ore blended raw material (that is, a sintered blended raw material) excluding a part or all of the raw material used for the production of the surface-coated carbon material, and the produced surface-coated carbon material. It is an apparatus for mixing and granulating, and for example, a drum mixer or other mixer can be used. A conveyor (charging device) 16 for charging the surface-coated carbon material into the mixer 11 is attached to the downstream side of the mixer 11 to supply the surface-coated carbon material to the sintered blending raw material in the middle of granulation. It can be configured.
In general sintering machines, there are many examples in which two or more mixers are arranged in series or in parallel, or in a configuration in which series and parallel are combined in order to increase the degree of mixing of the sintered blending raw materials. In this case, the conveyor 16 is installed in a mixer located on the most downstream side, and a surface-coated carbon material is charged into the mixer to perform a mixing process.

Here, as shown in FIG. 4, a granulator 17 may be provided between the kneader 12 and the mixer 11 (conveyor 16). The granulator 17 is a device that improves the adhesion strength of the coating to the carbonaceous material. For example, a rolling granulator such as a pan pelletizer or a drum mixer can be used.
2 and 3, for example, between the kneaders 12 and 14 and the mixer 11 (conveyor 16), and in FIG. 4, the granulator 17 and the mixer 11 ( A storage tank (not shown) can also be provided between the conveyors 16). This storage tank is a tank capable of temporarily storing the surface-coated carbon material produced by the kneaders 12 and 14 and the granulator 17. The storage tank is also a buffer for supplying a raw material of a stable component to the sintering machine when the kneaders 12 and 14 or the granulator 17 are stopped due to a trouble.

Next, a method for producing sintered ore using the above-described carbonaceous material reforming treatment facility 10 (carbonaceous material reforming method) will be described.
In this invention, after performing the process which coat | covers the coating material derived from a lime-type raw material to all or one part of the carbonaceous material used by sintering using the modification processing equipment 10, using the mixer 11, The surface-coated carbon material and other sintered blending raw materials are mixed. And this mixed raw material is baked in a sintering machine, and a sintered ore is manufactured.

A surface covering carbon material is manufactured in the procedure shown below.
As shown in FIG. 2, quick lime (CaO) is supplied from the storage hopper 18 and carbon material is supplied from the storage hopper 19 to the kneader 12, and moisture is added to the kneader 12 to add slaked lime (Ca ( A coating comprising OH) ₂ ) is produced and this coating is applied to the surface of the carbonaceous material.
Although the kind of this quicklime is not specifically limited, For the following reasons, an average particle size of less than 10 mm and an activity of 210 ml (hereinafter also referred to as mL) or more should be used. Is preferred. In addition, activity is the quantity which neutralizes and consumes 4N-HCl in 40 minutes in 50 ± 1 (degreeC) water in 10 minutes.

Here, when the average particle size of quicklime is 10 mm or more, it takes a long time to digest (for example, less than 50% by mass in 30 minutes), and a sufficient amount of slaked lime (with a particle size of 10 μm or less for coating). Product particles) cannot be obtained. Further, even if the average particle size is less than 10 mm, quick lime having an activity of less than 210 mL, such as low-purity quick lime or hard-burned quick lime, has poor hydration reactivity and requires a long time for digestion.
For quicklime, the smaller the particle size and the higher the activity, the higher the hydration reactivity, and the shorter the digestion time, the lower the particle size and the upper limit of the activity. However, the minimum particle size of commercially available quicklime is 0.1 mm, and the upper limit is 400 mL for activity.

From the above, the average particle size of quicklime is less than 10 mm and the activity is 210 mL or more, but the average particle size is preferably 5.0 mm or less and the activity is 300 mL or more (target digestibility: for example, 30 50% by mass or more per minute).
In addition, although the purity of quicklime is preferable high purity, it is good to set it as 85 mass% or more, for example, Preferably it is 90 mass% or more, More preferably, it is 93 mass% or more. The upper limit may be 100% by mass for the reason described above.

Moreover, the fuel used for coke (powder coke), anthracite, and other sintered ore manufacture can be used for a carbon material, for example.
This carbonaceous material may have a particle size of 5 mm or less, which is usually used as a sintering raw material, but coarse particles in which the cumulative mass of fine carbonaceous material having a particle size of less than 0.5 mm is 20% by mass or less. It is preferable to use a carbonaceous material, and more preferably 11.0% by mass or less. On the other hand, the lower limit value of the cumulative mass of the carbonaceous material having a particle size of less than 0.5 mm is not particularly defined for the above-described reason, but it is 5% by mass considering the sieving limit by the sieve mesh.
Furthermore, the cumulative mass of the carbonaceous material having a particle size of 0.5 mm or more and 5 mm or less is preferably 40% by mass or more, and particularly preferably 70% by mass or more.

When producing a surface-coated carbon material in which a lime-based raw material containing quick lime and a carbon material are kneaded with a kneader 12 and the surface of the carbon material is coated with a coating, the amount of water added in the kneader 12 is determined by the lime-based material. It is necessary to add water equal to or more than the number of moles of quicklime contained in the inside, and further prepare the amount of water corresponding to the number of moles of 1.5 times or more and less than 7.3 times the number of moles of quicklime. Is preferred.
1 mol of quicklime consumes 1 mol of water equal to the number of moles of quicklime due to the hydration reaction. In addition, at least 0.5 mol of water is lost by evaporation due to heat generated by the hydration reaction.

Therefore, the lower limit of the amount of water added is preferably 1.5 times or more the number of moles of quicklime supplied. When the molar ratio is less than 1.5 times, all the quicklime cannot be digested due to insufficient moisture, and the adhesion strength of the coating to the carbonaceous material tends to decrease.
On the other hand, the upper limit of the amount of water added is preferably less than 7.3 times the number of moles of quicklime supplied. Here, when the water addition amount is set to a molar ratio of 7.3 times or more, the raw material adheres to the stirring blade inside the kneading machine, and the kneading machine is overloaded and clogged, resulting in a significant reduction in productivity. .
In setting a specific water addition amount, the moisture content of the carbonized material before the reforming treatment, that is, the moisture content of the surface-coated carbonaceous material (hereinafter also referred to as product moisture content) is taken into consideration. ) Needs to be prepared by supplying an insufficient amount of water so that the target value is set in a range of 9.5 mass% or more and less than 19 mass%.

Here, the moisture content of the carbonaceous material before the reforming treatment is moisture originally contained in the carbonaceous material, and is a mass% (outer coating) with respect to the carbonaceous material 100 in a dry state.
The product moisture content is the moisture content of the final product (surface-coated carbon material before being charged into the mixer 11), the moisture content of the lime-based raw material and the carbon material, digestion, kneading, And the total amount excluding the amount of water consumed in the digestion reaction and the amount of water lost due to evaporation or the like with respect to the amount of water added, which is the total amount of added water during granulation. This product water content is mass% (outer coating) with respect to the surface-coated carbon material (slaked lime and carbon material) 100 in a dry state.
When the product moisture content is less than 9.5% by mass, the moisture content is too small and the adhesion strength of the coating to the carbonaceous material becomes weak, and the coating easily peels off from the carbonaceous material. . On the other hand, when the product moisture content is 19% by mass or more, the moisture content is too large and the coatings tend to be agglomerated, making it difficult to uniformly coat the coating on the carbonaceous material, and the NOx reduction effect is reduced.
From the above, the product moisture content of the surface-coated carbon material is set to 9.5 mass% or more and less than 19 mass%, but the lower limit is preferably 12.0 mass% and the upper limit is preferably 16.0 mass%.

Thereby, all or most of quicklime can be made into slaked lime.
In addition, the manufactured slaked lime contains 70% by mass or more (or 100% by mass) of which particle size is 10 μm or less, and most of the slaked lime is, for example, 70% by mass or more, preferably 80% by mass or more. It is finer than that.
Then, the kneading machine 12 further kneads the covering mainly composed of slaked lime (for example, 80% by mass or more) and the carbonaceous material, and coats the surface of the carbonaceous material with this coating.

Further, as described above, when the product moisture content of the surface-coated carbon material is 9.5 mass% or more and less than 19 mass%, the layer thickness of the coating (coating layer thickness) is an appropriate thickness, that is, 5 μm or more and 500 μm or less. The yield of the surface-coated carbon material can be improved (60% by mass or more).
Here, FIG. 5 (A), (B) shows an example of the result of microscopic observation of the surface-coated carbonaceous material. Since FIG. 5 (A) is a surface-coated carbon material whose product moisture content is adjusted within the above-described range, it has been found that the layer thickness of the coating is the appropriate thickness described above. On the other hand, in FIG. 5B, it was found that the product moisture content exceeded the upper limit value of the above-described range, so that the layer thickness of the coating exceeded the above-described upper limit value of the appropriate thickness.

Moreover, an example of the result which showed the influence which a coating body has on NOx conversion rate is shown in FIG.
As shown in FIG. 6, when a coating was not formed on the surface of coke (carbonaceous material) (no coating), the NOx conversion rate was about 30 mol%, but by covering the coke surface with a coating of 500 μm It was found that the NOx conversion rate can be reduced to about 28.6 mol% or less.
From the above, it is preferable that the product moisture content of the surface-coated carbon material is 9.5 mass% or more and less than 19 mass%.

In addition, it is good for the rotation speed of the stirring blade of the kneader 12 to be 5 rpm or more and less than 80 rpm for the reason described above.
The residence time of the kneader 12 is preferably 2.5 minutes or more and less than 30 minutes.
Here, when the residence time is less than 2.5 minutes, the residence time is too short and the hydration reaction of quick lime becomes insufficient, the digestibility does not reach the target value of 50%, and a sufficient covering effect is obtained. I can't. On the other hand, the digestibility improves as the residence time increases. However, since the hydration reaction reaches a saturated state in 30 minutes or longer, it is not necessary to increase the residence time any longer, so the upper limit was set to less than 30 minutes. In addition, it is not preferable to lengthen the residence time because it directly leads to an increase in equipment cost and operating power.
Therefore, although the residence time of the kneader 12 is 2.5 minutes or more and less than 30 minutes, the lower limit is preferably 5 minutes and the upper limit is preferably 25 minutes.

Thus, for example, a surface-coated carbon material in which a coarse carbon material having a particle size of less than 0.5 mm and having a particle size of 20% by mass or less is used as a core particle and the surface is coated with a coating is formed.
The covering is preferably composed only of slaked lime, for example, any one or two of lime-based raw materials such as undigested quicklime, lime milk (slaked lime suspension), finely pulverized limestone, and the like. The above may be further included. In addition, since slaked lime becomes a binder and forms a coating that adheres closely to the surface of the carbonaceous material, for example, during mixing with the sintered blending raw material or in the conveying process until the raw material is charged into the sintering machine, Desorption of the coating on the surface of the material can be suppressed.

Here, the reason for using quick lime digested as the slaked lime in the coating is shown below.
Calcium oxide (CaO) in quicklime becomes calcium hydroxide (Ca (OH) ₂ ) by an explosive hydration reaction. However, since the generated calcium hydroxide has low solubility, it is crystallized once as a submicron crystal through a supersaturated aqueous solution of calcium hydroxide. At this time, since the calcium hydroxide crystals have the property of being easily crystallized selectively at the active sites on the particle surface of the carbonaceous material, the coating efficiency on the carbonaceous material is less than the condition of using solid slaked lime as the lime source. improves.

In this calcium hydroxide production reaction, nucleation from a supersaturated aqueous solution is one rate-limiting process, and the reaction rate can be improved by supplying calcium hydroxide seed crystals.
Therefore, most of the dust recovered by the dust collector 13 shown in FIG. 3 is calcium hydroxide crystals after the hydration reaction, and this dust is circulated and used in the kneader 14 from the viewpoint of promoting nucleation. Is considered effective. Thereby, the dust in the added water plays the role of a seed crystal, and the precipitation of calcium hydroxide, which is a bottleneck of the hydration reaction, is promoted.

The above-mentioned coating contains 36 mass% or more of Ca derived from lime-based raw materials.
Here, when the Ca content of the coating is less than 36% by mass, the amount of the solvent is too small, and the surrounding is in a state of high iron ore concentration. The effect of promoting combustion is reduced.
Moreover, when using only slaked lime for a lime-type raw material, it is desirable to make content of slaked lime in a coating into 67 mass% or more, and it is especially desirable to set it as 100 mass%. Furthermore, when quick lime, lime milk, finely pulverized limestone or the like is included as a lime-based raw material, it is particularly desirable that the content thereof in the coating is 100% by mass.

This covering needs to be coated on the carbon material at a ratio of 2% by mass or more and less than 30% by mass with respect to the carbon material.
Here, when the mass% of the covering with respect to the carbonaceous material is less than 2 mass%, it becomes difficult to form a sufficient covering (covering layer) surrounding the entire carbonaceous material surface, and a part of the carbonaceous material surface is exposed. In addition, the coating layer thickness becomes too thin, and the NOx reduction effect due to blocking of oxygen in the atmosphere at low temperatures cannot be obtained. On the other hand, when the coating amount on the surface of the carbonaceous material is 30% by mass or more, the coating layer thickness becomes too thick, the combustibility of the powder coke is deteriorated, and the strength of the sintered ore and the yield of the sintered product are reduced.
For this reason, the coating on the surface of the carbon material is 2% by mass or more and less than 30% by mass with respect to the carbon material, but it is desirable that the lower limit is 5% by mass and the upper limit is 20% by mass.

Here, in the combustion test, the results showing the influence of the coating amount (= (coating amount) / (coke) × 100) on the coke (carbon material) on the NOx conversion rate are shown in FIG. FIG. 7 also shows the influence of the Ca concentration in the coating on the NOx conversion rate.
As is apparent from FIG. 7, it was confirmed that the NOx conversion rate can be reduced with the increase in the amount of the coating by setting the amount of the coating on the coke to 2% by mass or more. Although the NOx conversion rate can be reduced even when the coating amount is 30% by mass or more, as described above, it is not preferable because the strength of the sintered ore and the yield of the sintered product are lowered.
Moreover, it was also confirmed that the NOx conversion rate can be reduced by increasing the amount of Ca derived from the lime-based material in the coating from 36% by mass to 54% by mass (36% by mass or more).

The surface-coated carbon material produced by the above method is supplied via the conveyor 16 into the mixer 11 in which the sintered blending raw material in the middle of granulation is charged.
When the surface-coated carbon material is added before mixing and granulating the sintered blending raw material, the coating on the surface of the carbonaceous material is collapsed and peeled when the sintered blending raw material is mixed or granulated. Therefore, in order to avoid this peeling, it is preferable to supply the surface-coated carbon material to the sintered blending raw material in the middle of granulation (the final stage).
In order to further suppress the peeling of the coating from the surface of the carbon material, it is preferable to supply the surface-coated carbon material to the sintered blended raw material after granulation.
The supply amount of the surface-coated carbon material is, for example, about 0.5 mass% to 4.5 mass% of the total sintering raw material charged into the sintering machine, and can be adjusted according to the amount of NOx to be reduced. it can.

Further, the surface-coated carbon material produced by the kneader 12 is preferably further granulated by a granulator 17 as shown in FIG. 4 in order to improve the adhesion strength of the coating to the carbon material.
In this granulator 17, finishing granulated water is supplied. In addition, this moisture addition amount is 5 mass% of the moisture content of the total moisture added by the modification processing equipment (that is, the total moisture added by the kneader 12 and the granulator 17 to produce the surface-coated carbon material). It is preferable to adjust by the following amounts.
Here, when the amount of water exceeds 5% by mass, it is not preferable because a portion where water is locally distributed in the granulator is formed, and a lump of 10 mm or more that is too large as a carbon material for sintering is easily generated. . On the other hand, the lower limit of the amount of water is not particularly specified because the granulating effect by the granulator can be obtained even if it is 0% by mass, but it is not enough to compensate for the amount of water lost by natural evaporation during granulation. By adjusting the moisture content (5% by mass or less), the adhesion of the coating can be further improved.

The residence time of the granulator 17 is preferably 1 minute or more and less than 10 minutes.
Here, when the residence time is less than 1 minute, the granulating action of adhering the fine powder coke (carbon material) of 0.5 mm or less to the surface of the coarse powder coke (carbon material) of 1 mm or more becomes insufficient, and the coating The object is easily peeled off, and the NOx reduction effect is reduced. On the other hand, when the residence time is 10 minutes or more, the above-described granulation treatment effect of fine-grained coke is saturated, so the upper limit was set to 10 minutes. In addition, it is not preferable to lengthen the residence time because it directly leads to an increase in equipment cost and operating power.
Therefore, although the residence time of the granulator 17 is 1 minute or more and less than 10 minutes, it is preferable that the lower limit is 3 minutes and the upper limit is 7 minutes.

Further, the surface-coated carbon material manufactured by the kneaders 12 and 14 and further manufactured by the granulator 17 is supplied to the mixer 11, but before being supplied to the mixer 11, it is supplied to the storage tank. Can also be stored. Thereby, for example, even if a state where the operation of the kneaders 12 and 14 for producing the surface-coated carbon material must be stopped occurs, the surface-coated carbon supplied to the mixer 11 according to the amount of NOx to be reduced Even if the amount of material fluctuates, the surface-coated carbon material can be stably supplied to the mixer 11.

As described above, a large amount of NOx produced by sintering is produced by low-temperature combustion of a carbonaceous material at 1100 ° C. or lower. Therefore, in order to suppress the generation of NOx, it is necessary to suppress the low temperature combustion of the carbonaceous material and to perform the high temperature combustion as much as possible.
Since the above-described surface-coated carbon material is covered with a coating in the low temperature region at the initial stage of combustion of the carbon material, combustion of the carbon material in the coating is suppressed and generation of NOx is suppressed.

On the other hand, when reaching a high temperature region of 1200 ° C. or higher, CaO derived from the lime-based raw material in the coating reacts with the surrounding ore and melts as a low melting point calcium ferrite and melts down. As a result, the surface of the carbonaceous material becomes bare with the covering disappeared, but even in the bare state, the carbonaceous material is burned in a high temperature region of 1200 ° C. or higher, and therefore NOx generation is small. There is no loss of productivity due to active combustion.
Therefore, generation of NOx in the low temperature region can be economically suppressed by using the carbonaceous material reforming treatment facility of the present invention.

Next, examples carried out for confirming the effects of the present invention will be described.
The prepared sintering raw materials are iron ore, limestone, quicklime, serpentine, return mineral, and fine coke. Iron ore is 82.85% by mass, limestone is 13.1% by mass, quicklime is 1.00% by mass, and serpentine is 3.05% by mass. 15.0 mass% and powdered coke 4.2 mass%, respectively.
Here, in producing the surface-coated carbonaceous material, 2.5 to 4.2% by mass of 4.2% by mass of the powder coke in the above-described sintered raw material was used. Moreover, about the quicklime in the coating coat | covered on the surface of carbon | charcoal material, it changed in the range of 50 mass% over 0 or 0 by the outer frame mixing | blending (outer coating) with respect to carbon mass. In addition, as a coating material other than quick lime, sintered dust is used in Comparative Example 4, fine limestone is used in Example 2, slaked lime is used in Examples 12 to 14, and environmental dust collectors of sintering machines are used in Examples 29 to 31. Each of the captured sintered dusts was blended.

Using this sintered raw material, a sintering pot test was conducted to investigate the influence of the preparation conditions of the surface-coated carbon material on the generation of NOx.
The sintering pot test apparatus used has a pot shape with a diameter of 300φ and a bed height of 600 mm. The sintering raw material is charged into the pot, and the carbonaceous material in the sintering raw material is ignited for 90 seconds in an ignition furnace, A set test was performed. At this time, exhaust was performed at a constant negative pressure of 15 kPa with a suction blower from an air box installed below the pan, and components of exhaust gas accompanying sintering combustion were analyzed.
Moreover, mixing of the sintering compounding raw material was performed for 6 minutes using a drum mixer having a diameter of 1000 mm. On the other hand, the surface-coated carbon material produced under various adjustment conditions is added to the above-described sintered blended raw material after mixing for 5 minutes and 45 seconds from the start of mixing in the drum mixer, and the mixing process is performed for 15 seconds. It was decided.
The production conditions for the surface-coated carbon material are shown in Tables 1 to 3, respectively. Table 4 shows the sintering production rate, product yield, and NOx conversion rate in the sintering test in which the manufactured surface-coated carbon material was mixed with the sintering blended raw material.

Comparative Example 1 is a result of sintering a granulated sintered raw material without using a carbonaceous material reforming treatment equipment, that is, without producing a surface-coated carbonaceous material.
Moreover, Comparative Examples 2 and 3 produce a surface-coated carbon material in which the amount of the coating (quick lime) is outside the appropriate range (less than 2% by mass or 30% by mass or more), and Comparative Example 4 is a Ca in the coating. This is a result of manufacturing surface-coated carbon materials whose amount is out of the proper range (less than 36% by mass), and mixing and sintering these together with the sintered blending raw materials.
In Comparative Examples 5 and 6, the surface-coated carbon material was added by adding water with a kneader so that the moisture content of the surface-coated carbon material was outside the proper range (less than 9.5 mass% and 19 mass% or more). This is the result of manufacturing, mixing and sintering together with the raw material for sintering.
On the other hand, Examples 1-31 use a part of powder coke of a sintering raw material, the amount of coating is within an appropriate range (2 mass% or more and less than 30 mass%), and the amount of Ca in the coating is within an appropriate range. (36% by mass or more), and further, water is added by a kneader so that the moisture content of the surface-coated carbon material is 9.5% by mass or more and less than 19% by mass to produce a surface-coated carbon material, It is the result of having mixed and sintered with the sintering compounding raw material.

As apparent from Table 4, the NOx conversion rate of Comparative Example 1 in which the surface-coated carbon material was not used was 31.7 mol% (mol%), and Comparative Examples 2 to 6 using the surface-coated carbon material and In comparison, it was equal or higher. In Comparative Example 2, the amount of coating was less than the lower limit of the appropriate range, so the NOx conversion rate was comparable to Comparative Example 1. Further, since Comparative Example 3 exceeded the upper limit value of the appropriate range, and Comparative Example 4 had a Ca content less than the lower limit value of the appropriate range, Comparative Examples 5 and 6 had a moisture content outside the appropriate range. Therefore, the NOx conversion rate was higher than 30 mol%.
On the other hand, in Examples 1 to 31, a kneader was used so that the moisture content of the surface-coated carbonaceous material was 9.5 mass% or more and less than 19 mass% under the conditions in which the coating amount and the Ca amount were within appropriate ranges. Since the surface-coated carbon material was manufactured and used, the NOx conversion rate could be reduced to 30 mol% or less. In particular, Examples 1 to 4 are the results of making the Ca amount in the coating substantially constant and changing the coating amount within an appropriate range, but the NOx conversion rate could be reduced with the increase in the coating amount. .

Examples 5-11 are the results of changing the type of quicklime. Examples 5 to 8 change (gradually increase) the average particle size of quicklime, and Examples 9 to 11 change (gradually decrease) the activity of quicklime.
As shown in Examples 5 to 8, by reducing the average particle size of quicklime, a sufficient amount of slaked lime for coating was obtained with a digester, and the NOx conversion rate could be reduced. In addition, as shown in Examples 9 to 11, by increasing the activity of quick lime, the hydration reactivity was increased, and a sufficient amount of slaked lime was obtained for coating in the digester, thereby reducing the NOx conversion rate. I was able to.
In particular, the NOx conversion rate could be reduced to a maximum of 26.0 mol% by setting the average particle size of quicklime within the optimum range (less than 10 mm) and the activity of quicklime within the optimum range (210 mL or more).

Examples 12-14 are the results of changing the number of revolutions of the stirring blade by using a Redige mixer equipped with a single-shaft-type stirring blade in the kneader. As shown in Examples 12 and 13, by setting the rotation speed of the stirring blade within the optimum range (5 rpm or more and less than 80 rpm), it is possible to reduce the action of the coating as in Example 14 peeling from the surface of the powder coke, The NOx conversion rate could be reduced.
Moreover, Examples 15-19 are the results of using the Dow mixer provided with a twin screw type stirring blade in the kneader and changing the rotation speed of the stirring blade. As shown in Examples 16 to 19, by setting the rotation speed of the stirring blade within the optimum range (5 rpm or more and less than 80 rpm), insufficient kneading due to insufficient rotation speed as in Example 15 can be suppressed, and NOx conversion is performed. The rate could be reduced.
In addition, Example 20 is a result of using an Eirich mixer in the kneader, but the NOx conversion rate could be sufficiently reduced by setting the rotation speed of the stirring blade within the optimum range (5 rpm or more and less than 80 rpm). .

Example 21 is the result of not using a granulator.
Except that a granulator was used, the NOx conversion rate of Example 21 was higher than that of Example 3 which was substantially the same conditions. This is because the adhesion strength to the powder coke is reduced because the granulator is not used, and when the surface-coated carbonaceous material is mixed with the sintered blending raw material, a part of the coating is peeled off from the powder coke surface. It is thought that it originates in having done.
Example 22 is the result of setting the residence time in the kneader to be less than the lower limit of the optimum range (2.5 minutes to less than 30 minutes).
The NOx conversion rate of Example 22 was higher than that of Example 3, which was substantially the same conditions except for the residence time. This is considered to be because the hydration reaction of quicklime became insufficient because the residence time was too short, the digestibility decreased, and a sufficient covering effect could not be obtained.

Examples 23-25 are the results of using a granulator and changing the amount of water added in this granulator.
As shown in Examples 23 and 24, the NOx conversion rate could be reduced as compared with Example 25 by setting the amount of water addition in the granulator within the optimum range (5% by mass or less). This is considered to be due to the fact that, as in Example 25, when the amount of water is too much, there is a portion where water is locally distributed in the granulator, and a lump of 10 mm or more is easily generated.
In addition, like Example 23, although the water addition amount in a granulator may be 0 mass%, compared with Example 24, the NOx conversion rate rose slightly.

Examples 26 to 28 are the results of using a granulator and changing the residence time in this granulator.
As shown in Examples 26 to 28, as the residence time in the granulator increased, the NOx conversion rate also increased, but the increase width gradually decreased. This is considered to be due to the fact that the granulation effect by the granulator is saturated as the residence time increases.
Here, when the residence time in the granulator was 10 minutes exceeding the upper limit of the optimum range (1 minute or more and less than 10 minutes), the NOx conversion rate could be reduced most, but the facility cost and operating power In view of the increase of the above, the above-mentioned optimum range is preferable.

Examples 29-31 are the results of changing the moisture content of the surface-coated carbonaceous material.
As shown in Examples 29 to 31, the NOx conversion rate can be reduced to about 28.7 mol% by setting the moisture content of the surface-coated carbon material within an appropriate range (9.5 mass% or more and less than 19 mass%). In particular, as shown in Example 30, the NOx conversion rate is about 26.3 mol% by setting the moisture content of the surface-coated carbon material within the optimum range (12.0 mass% or more and 16.0 mass% or less). We were able to reduce to.

As shown above, in Examples 1 to 31, the NOx conversion rate could be reduced to 30 mol% or less (about 26 mol% at the maximum). At this time, the yield (product yield) of the sintered ore can be improved to about 78 mass% or more (about 82 mass% at the maximum), and the sintering production rate is about 29 tons / day / m ² or more (31 at the maximum). It has been found that a secondary effect can also be obtained, such as an improvement to about tons / day / m ² .

Next, the effect of the Example in the above-mentioned pan test was confirmed with an actual sintering machine.
Using a sintering machine with a pallet width of 5.5 m, a strand length of 120 m, and a sintering area of 660 m ² , a part of the charcoal is converted from powdered coke to a surface-coated charcoal under operating conditions of a layer thickness of 720 mm and a suction negative pressure of 18.3 kPa. A transfer operation evaluation test was conducted. The sintering raw materials were as follows: blended ore 64.4% by mass, limestone 10.8% by mass, quick lime 1.2% by mass, dolomite 2.8% by mass, and return mineral 20.8% by mass Based on the above, 3.6% by mass in 3.8% by mass (blended outer frame) of the carbon material was replaced with a surface-coated carbon material coated with 8% by mass of slaked lime (% by mass of carbon material).

The surface-coated carbon material was subjected to a modification treatment continuously in the manufacturing process shown in FIG.
The kneading machine 14 is a biaxial dow mixer. While stirring at a rotation speed of 20 rpm, water of 3.5 times the number of moles of quicklime is added by the kneading machine 14, and the water content is 14.2% by mass. A surface-coated carbon material was produced. The dust collected in the kneader 14 was collected by a dry bag filter (dust collector 13), and the entire amount was circulated and supplied to the kneader 14. The manufactured surface-modified carbon material (surface-coated carbon material) is used for charging at a position 3 m from the outlet side of the subsequent drum mixer (mixer 11) among the drum mixers arranged in two series. It was supplied by the belt conveyor 16.

It was confirmed with an actual sintering machine that the NOx conversion rate can be reduced from 30.7 mol% to 28.1 mol% by changing the powder coke to the surface-coated carbon material. Further, it has been found that a secondary operation improvement effect is obtained such that the product yield is improved by 2.0% by mass and the sintering production rate is improved by about 3.1%.
From the above, it has been confirmed that the use of the carbonaceous material reforming equipment of the present invention can economically suppress the generation of NOx in a low temperature region.

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 in which the carbonaceous material reforming treatment facility of the present invention is configured by combining some or all of the above-described embodiments and modifications is also included in the scope of the right of the present invention.
Moreover, in the said embodiment, although the coating of the surface covering carbonaceous material demonstrated the case where lime-type raw materials, such as slaked lime, were contained, it is not limited to this. That is, if the coating contains 36% by mass or more of Ca derived from the lime-based material, in addition to the lime-based material, fine iron ore and other materials may be included. In addition, fine iron ore and other raw materials include fine iron ore (including dust generated in ironworks) and auxiliary raw materials (silica stone, serpentine, peridotite, etc.) other than lime-based raw materials.

10: Carbonaceous material reforming treatment equipment, 11: mixer, 12: kneader, 13: dust collector, 14: kneader, 15: filter for dust collection, 16: conveyor, 17: granulator, 18, 19: Storage hopper

Claims (11)

The surface coating which coat | covered the coating containing 36 mass% or more of Ca derived from a lime-type raw material on the surface of the carbonaceous material used for a sintering raw material in the ratio of 2 mass% or more and less than 30 mass% with respect to the said carbonaceous material. A carbonaceous material reforming treatment facility for producing a carbonaceous material and mixing the surface-coated carbonaceous material and a sintered blended raw material with a mixer to form the sintered raw material,
Adding water equal to or more than the number of moles of quick lime in the lime-based material to the kneading machine supplied with the lime-based material and the carbon material as the raw material for the surface-coated carbon material, The carbonaceous material reforming treatment facility is adjusted so that the water content of 9.5 mass% or more and less than 19 mass%. The carbonaceous material reforming treatment facility according to claim 1, wherein the quicklime has an average particle size of less than 10 mm and an activity of 210 milliliters or more. The carbonaceous material reforming treatment facility according to claim 1 or 2, wherein a dust collector is provided above the kneader to collect dust generated by a hydration reaction in the kneader and collect the collected dust. Carbonaceous material reforming equipment, which is supplied again to the kneader. The carbonaceous material reforming treatment facility according to any one of claims 1 to 3, wherein the stirring blades of the kneader are arranged in a single-shaft or multi-shaft screw blade, or a single-shaft or multi-shaft spiral. Carbonaceous material reforming treatment facility characterized by being paddle blades. The carbonaceous material reforming treatment facility according to claim 4, wherein the rotation speed of the stirring blade is 5 rpm or more and less than 80 rpm. The carbonaceous material reforming treatment facility according to any one of claims 1 to 5, wherein a residence time of the kneader is 2.5 minutes or more and less than 30 minutes. Facility. The carbonaceous material reforming treatment facility according to any one of claims 1 to 6, wherein the amount of water added in the kneading machine is 1.5 times or more and 7.3 times that of the quicklime in the lime-based raw material. Carbonaceous material reforming equipment characterized by having an amount corresponding to a molar ratio of less than The reformer for carbonaceous material according to any one of claims 1 to 7, wherein the granulator improves adhesion strength of the coating to the carbonaceous material between the kneader and the mixer. A carbonaceous material reforming treatment facility characterized by that. The carbonaceous material reforming treatment facility according to claim 8, wherein the amount of water added in the granulator is 5% by mass or less of the total amount of water added to produce the surface-coated carbonaceous material. Carbon material reforming treatment equipment characterized by The carbonaceous material reforming treatment facility according to claim 8 or 9, wherein a residence time of the granulator is 1 minute or more and less than 10 minutes. The carbonaceous material reforming treatment facility according to any one of claims 1 to 10, wherein a storage tank capable of storing the produced surface-coated carbonaceous material is provided upstream of the mixer. Carbon material reforming equipment.