JP5454501B2 - 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,
A digester for adding moisture to quick lime to produce the coating containing slaked lime, and a kneader for adding moisture to the coating and the carbonaceous material to knead and coat the coating on the surface of the carbonaceous material A carbonaceous material reforming treatment facility characterized by comprising:

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

(3) The digester is provided with a dust collector, and the collected material collected by the dust collector is supplied to the digester. (1) or (2) .

(4) The water addition amount in the digester is set to a molar ratio of 1.5 to 2.2 times that of the quicklime, according to any one of (1) to (3) Carbonaceous material reforming equipment.

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

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

(7) The residence time from the entry side of the digester to the exit side of the kneader is 2.5 minutes or more and less than 30 minutes, (1) to (6), Carbonaceous material reforming equipment.

(8) The water addition amount in the kneader is adjusted so that the water content of the surface-coated carbon material is 9.5 mass% or more and less than 19 mass% (1) to (7) The carbonaceous material reforming treatment facility according to any one of the above.

(9) Any one of (1) to (8), wherein a granulator is provided between the kneader and the mixer to improve the adhesion strength of the coating to the carbonaceous material. The carbonaceous material reforming equipment described in 1.

(10) 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 carbon material, according to (9) Carbonaceous material reforming equipment.

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

(12) A reforming of the carbon material according to any one of (1) to (11), wherein a storage tank capable of storing the produced surface-coated carbon material is provided upstream of the mixer. Quality processing equipment.

The carbonaceous material reforming treatment facility according to the present invention has a digester that adds moisture to quick lime to produce a coating containing slaked lime, and a kneader that coats the surface of the carbonaceous material with this coating. The coating efficiency of the coating on the surface of the carbonaceous material can be improved. This is because the slaked lime crystals produced by the digester are easily selectively crystallized on the surface of the carbonaceous material, 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 digester and the collected matter collected by the dust collector is supplied to the digester, the amount of slaked lime generated increases, so the effect of the present invention becomes more remarkable. Most of the fine collected matter captured by the dust collector is slaked lime after the hydration reaction. Therefore, by circulating the collected product to the digester, this collected product plays the role of seed crystal in the moisture added to the digester, and crystallization of slaked lime, which is the rate limiting condition of the hydration reaction, is achieved. Since it is promoted, the above-described effects 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 if a state where operation of a digester or a kneading machine for producing a surface-coated carbon material must 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. It is explanatory drawing of the modification | reformation processing equipment of the carbonaceous material which concerns on a 3rd 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. The equipment for mixing the coated carbonaceous material and the sintered blended raw material with the mixer 11 to make the sintered raw material, the digester 12 for producing the coating, and the kneader 13 for coating the surface of the carbonaceous material with the coating. And have. This will be described in detail below.

The digester 12 adds moisture to quick lime (calcium oxide: CaO) to promote slaked calcification (digestion) by a hydration reaction, and consists of slaked lime (calcium hydroxide: Ca (OH) ₂ ) or slaked lime. It is an apparatus for producing a covering comprising.
The digester 12 includes a casing 14, a single-shaft or multi-shaft stirring blade 15 that is rotatably provided inside the casing 14, and a water supply pipe (not shown) that adds (sprinkles) moisture into the casing 14. Have. In addition, the structure of this digester may be a structure in which a water supply pipe is provided in a general-purpose kneader such as a Dow mixer, a Redige mixer, or a cement mixer.
Thereby, quick lime can be digested into slaked lime by charging quick lime into the casing 14 and sprinkling it with a water supply pipe while stirring it with the stirring blade 15.

In this digester 12, since a large amount of water vapor and dust are generated, it is preferable to provide a dust collector 16 as shown in FIG.
The dust collector 16 is a wet type dust collector that collects the collected matter by sprinkling water on the collected matter (dust) that is sucked, but may be a dry dust collector (bag filter). The dust collector 16 is configured to supply the collected material collected by the dust collector 16 to the digester 12 again (circulation supply). It may be configured.
By circulating and supplying the collected material, the fine collected material generated in the digester 12 can be prevented from scattering to the outside, and the collected material collected by the dust collector 16 is reused as a slaked lime seed crystal. it can.

As shown in FIG. 2, the kneader 13 disposed on the downstream side of the digester 12 is a device that adds moisture to the covering and the carbonaceous material, kneads them, and coats the surface of the carbonaceous material with the coating.
The kneading machine 13 is not particularly limited as long as it can cover the surface of the carbonaceous material. Although a machine can be used, a dow mixer (two-screw type) is particularly preferable. The stirring blades of the kneader 13 are uniaxial or multi-axial (for example, biaxial) screw wings, or uniaxial or multi-axial (for example, biaxial) paddle blades. it can.

The rotation speed of the stirring blade of the kneading machine 13 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.

A mixer 11 is disposed on the downstream side of the kneader 13 described above.
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) 17 for charging the surface-coated carbon material into the mixer 11 is attached to the downstream side of the mixer 11, and the surface-coated carbon material is supplied 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 17 is installed in a mixer located on the most downstream side, and the surface-coated carbon material is charged into the mixer to perform a mixing process.

Here, a granulator 18 may be provided between the kneader 13 and the mixer 11 (conveyor 17) as shown in FIGS. The granulator 18 is a device that improves the adhesion strength of the coating to the carbonaceous material, and for example, a rolling granulator such as a pan pelletizer or a drum mixer can be used.
Further, on the upstream side of the mixer 11, for example, between the kneader 13 and the mixer 11 (conveyor 17) in FIGS. 2 and 3, and in FIG. 4 and FIG. 5, the granulator 18 and the mixer 11. A storage tank (not shown) may be provided between (conveyor 17). This storage tank is a tank capable of temporarily storing the surface-coated carbon material produced by the digester 12, the kneading machine 13, and the granulator 18. The storage tank is also a buffer for supplying a raw material having a stable component to the sintering machine when the digester 12, the kneading machine 13, or the granulator 18 is 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 19 to the digester 12, and water is supplied into the digester 12 to produce a coating containing slaked lime (Ca (OH) ₂ ). .
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.

When this quicklime is digested with the digester 12 to produce slaked lime, the amount of water added in the digester 12 is preferably 1.5 to 2.2 times that of quicklime.
Here, when the amount of water added is less than 1.5 times that of quick lime, the amount of water added is too small, so that the amount of water is evaporated by the heat generated during the hydration reaction of quick lime to make slaked lime. And the amount of water retained by slaked lime is insufficient. On the other hand, when the amount of water added is more than 2.2 times that of quick lime, the amount of water added is too large, so that slaked lime tends to flow down from the carbonaceous material surface.
Therefore, the amount of water added in the digester 12 is 1.5 to 2.2 times the molar ratio of quicklime, but it is preferable that the lower limit is 1.6 times and the upper limit is 2.0 times.

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.
The slaked lime produced by the above method (partly including undigested quicklime) is supplied to the kneader 13. At this time, the carbon material is supplied from the storage hopper 20 to the kneading machine 13, and moisture is also added to the kneading machine 13.

Here, as the carbon material, for example, coke (powder coke), anthracite, and other fuels used for manufacturing sintered ore can be used.
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 this carbon material and the above-mentioned slaked lime are kneaded in the kneader 13 and the surface of the carbon material is coated with a coating, the amount of water added in the kneader 13 is determined by the amount of water in the surface-coated carbon material to be produced (hereinafter referred to as It is preferable to adjust so that the product water content is 9.5 mass% or more and less than 19 mass%.
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.

Here, when the product moisture content of the surface-coated carbon material is less than 9.5% by mass, the moisture content is too small and the adhesion strength of the coating to the carbon material becomes weak, and the coating easily peels from the carbon material. Therefore, the NOx reduction effect is reduced. 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%.

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, an example of the result of microscopic observation of the surface-coated carbonaceous material is shown in FIGS. Since FIG. 6 (A) is a surface-coated carbon material in which the product moisture content is adjusted within the above-described range, it was found that the layer thickness of the coating is the appropriate thickness described above. On the other hand, in FIG. 6B, it was found that the product moisture content exceeded the upper limit value of the above-described range, and thus 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 | cover has on a NOx conversion rate is shown in FIG.
As shown in FIG. 7, 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 coating the coating on the coke surface with 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 kneading machine 13 at the time of coat | covering a coating | covering material on the surface of carbonaceous material to be 5 rpm or more and less than 80 rpm from the reason mentioned above.
The residence time from the entry side of the digester 12 to the exit side of the kneader 13 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, the residence time from the entry side of the digester 12 to the exit side of the kneader 13 is 2.5 minutes or more and less than 30 minutes, but the lower limit is preferably 5 minutes and the upper limit is preferably 25 minutes.
In addition, the above-mentioned residence time is determined in consideration of a state (for example, 1 minute or less) in which there is almost no transport time from when the slaked lime leaves the digester 12 to enter the kneader 13. That is, the residence time described above is the total residence time of the digester 12 and the kneader 13. In addition, although the hydration reaction of quicklime progresses also at the time of conveyance of slaked lime, since the advancing speed is slow compared with the case where it is agitated with the digester 12 or the kneader 13, it can be considered that it can be almost ignored.

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, since most of the dust collected (collected matter) collected by the dust collector 16 shown in FIGS. 3 and 5 is calcium hydroxide crystals after hydration reaction, from the viewpoint of promoting nucleation, It is considered effective to circulate and use this dust collection dust in the digester 12. Thereby, the dust collection 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 result of showing the influence of the coating amount (= (coating amount) / (coke) × 100) on the coke (carbon material) on the NOx conversion rate is shown in FIG. FIG. 8 also shows the influence of the Ca concentration in the coating on the NOx conversion rate.
As is apparent from FIG. 8, it was confirmed that the NOx conversion rate can be reduced as the amount of the coating is increased by setting the amount of the coating to the coke to be 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 17 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 13 is further granulated by the granulator 18 as shown in FIGS. 4 and 5 in order to improve the adhesion strength of the coating to the carbon material. Good.
The granulator 18 supplies finishing granulated moisture. In addition, this water addition amount is the water | moisture content of the total water added in a modification | reformation processing equipment (namely, total water added by the digester 12, the kneader 13, and the granulator 18 in order to manufacture a surface covering carbon material). It is preferable to adjust by the quantity of 5 mass% or less of quantity.
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 18 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 18 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.

Furthermore, the surface-coated carbon material manufactured by the kneader 13 and further manufactured by the granulator 18 is supplied to the mixer 11, but is supplied to the storage tank and stored before being supplied to the mixer 11. You can also Thereby, for example, even if a state where the operation of the digester 12 or the kneading machine 13 for producing the surface-coated carbon material has to be stopped occurs, the surface supplied to the mixer 11 according to the amount of NOx to be reduced. Even if the amount of the coated carbon material varies, 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, in Comparative Example 4, sintered dust, in Example 2, fine limestone, and in Examples 29-31, sintered dust captured by an environmental dust collector of a sintering machine, respectively. 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.
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. This is a result of producing a surface-coated carbon material (36% by mass or more) and mixing and sintering it together with a sintered blending 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 4 using the surface-coated carbon material and It was high compared. However, in Comparative Examples 2 to 4, the amount of coating or the amount of Ca was out of the proper range, so the NOx conversion rate was higher than 30 mol%.
On the other hand, Examples 1-31 produced and used a surface-coated carbon material using a digester and a kneader under conditions where the amount of coating and the amount of Ca were in appropriate ranges, so the NOx conversion rate was reduced to 30 mol% or less. did it. 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 digester and kneader to be less than the lower limit of the optimal 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, by making the water content of the surface-coated carbon material within the optimum range (9.5 mass% or more and less than 19 mass%), the NOx conversion rate is up to about 27 mol%, and further 26 mol. %.

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 79% by mass or more (up to about 83% by mass), and the sintering production rate is 29 ton / day / m ² or more (up to 32 ton / etc. can be improved to day / m ² or so), it was found that secondary effect is also obtained.

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 carbon material is converted from powder coke to surface-coated carbon material under the operating conditions of a layer thickness of 730 mm and a suction negative pressure of 17.9 kPa A transfer operation evaluation test was conducted. The sintering raw materials were as follows: blended ore 64.0% by mass, limestone 11.2% 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.
Both the digester 12 and the kneading machine 13 use a biaxial dow mixer. The digester 12 performs the treatment at a rotation speed of 35 rpm and the kneading machine 13 at a rotation speed of 20 rpm. After adding the water in the molar ratio, water was also added in the kneader 13 to produce a surface-coated carbon material having a water content of 14.2% by mass. The dust collected in the digester 12 was collected by a dry bag filter (not shown), and the entire amount was circulated and supplied to the digester 12. 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 a belt conveyor 17.

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: digester, 13: kneader, 14: casing, 15: stirring blade, 16: dust collector, 17: conveyor, 18: granulator, 19, 20: Storage hopper

Claims (12)

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,
A digester for adding moisture to quick lime to produce the coating containing slaked lime, and a kneader for adding moisture to the coating and the carbonaceous material to knead and coat the coating on the surface of the carbonaceous material A carbonaceous material reforming treatment facility characterized by comprising: 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 the digester is provided with a dust collector, and the collected material collected by the dust collector is supplied to the digester. Modification processing equipment. The reforming equipment for a carbonaceous material according to any one of claims 1 to 3, wherein the water addition amount in the digester is set to a molar ratio of 1.5 to 2.2 times that of the quicklime. A charcoal material reforming treatment facility. The carbonaceous material reforming treatment facility according to any one of claims 1 to 4, 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. 6. The carbonaceous material reforming treatment facility according to claim 5, 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 6, wherein a residence time from the entry side of the digester to the exit side of the kneader is 2.5 minutes or more and less than 30 minutes. A charcoal material reforming treatment facility. In the carbonaceous material reforming treatment facility according to any one of claims 1 to 7, in the kneader, the moisture content of the surface-coated carbonaceous material is 9.5% by mass or more and less than 19% by mass. Carbonaceous material reforming equipment characterized by adjusting the amount of water added. The reforming equipment for a carbonaceous material according to any one of claims 1 to 8, 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 9, wherein the amount of water added in the granulator is an amount of 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 9 or 10, 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 11, wherein a storage tank capable of storing the produced surface-coated carbonaceous material is provided upstream of the mixer. Carbon material reforming equipment.