JP7207147B2 - Method for producing sintered ore - Google Patents

Description

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

Currently, the main raw material for blast furnace ironmaking is sintered ore. This sintered ore is usually produced as follows. First, iron ore (powder) as a raw material, iron-containing miscellaneous raw materials such as steelmaking dust, MgO-containing auxiliary raw materials such as peridotite, CaO-containing auxiliary raw materials such as limestone, return ore, and sintered ore are sintered (coagulated) by combustion heat. ) is mixed with a carbonaceous material (also referred to as a coagulant) to be used as a fuel in a predetermined ratio, and the mixture is granulated to obtain a blended raw material. Next, the granulated blended raw material is loaded from the hopper onto a pallet of a downward suction type Dwight Lloyd (DL) type sintering machine to form a raw material packed bed. The carbon material in the raw material packed bed is ignited from above (surface layer) of the formed raw material packed bed. Then, by continuously moving the pallet, air is sucked from below the pallet to supply oxygen, and the carbonaceous material in the raw material packed bed is burned from the top to the bottom, so that the combustion heat of the carbonaceous material Sinter in sequence. The obtained sintered part (sinter cake) is pulverized to a predetermined particle size, sieved, or the like to obtain sintered ore, which is a raw material for a blast furnace.

Coke and anthracite are mainly used as carbon materials for sintering.
Coke for sintering is obtained by pulverizing coke, which is not suitable for blast furnace use (usually 40 mm or less), to 3 mm or less, which is suitable for sintering use, in the process of producing blast furnace coke. In contrast to lump coke for blast furnaces, coke for sintering is also called fine coke.
Anthracite is one of the classifications (brown coal, bituminous coal, anthracite) given to coal, and is the most carbonized coal. Coal with a fuel ratio (fixed carbon/volatile matter (mass ratio)) of 4 or more, simply coal with a carbon content of 90% by mass or more is classified as anthracite coal. Anthracite used in sintering is also required to have a low nitrogen content.

Among methods for producing sintered ore using such a DL type sintering machine, a multistage charging multistage ignition sintering method has been proposed in which the formation of a raw material packed bed and ignition are performed in two or more stages.
In the multi-stage charging multi-stage ignition sintering method, the mixed raw materials are sequentially loaded in the layer height direction of the sintering machine to form multi-stage raw material packed layers, and the surface of each raw material layer is ignited to suck air from below. In this method, the sintering reaction of each layer is allowed to proceed in parallel by sintering.

A two-stage charging and two-stage ignition sintering method, in which the material is charged in two stages and ignited in two stages, will be described with reference to FIG.
First, in order to granulate the blended raw material for producing sintered ore, water is added to the raw material obtained by blending the iron-containing raw material, the auxiliary raw material, the carbonaceous material, etc., and the first drum mixer 1A and the second drum are mixed. Each is granulated by the mixer 2A.
The first mixed raw material granulated by the first drum mixer 1A is charged from the first hopper 1B onto a pallet (not shown) covered with bedding ore to form the lower layer 10. .
The lower layer 10 formed on the pallet moves below the first igniter 1C by moving the pallet in the pallet advancing direction 5, where the raw material layer (lower layer 10) is caused by the first igniter 1C. The carbon material on the surface is ignited. After ignition, sintering of the lower layer 10 is initiated by downward suction 6 for sucking air from below through a wind box (not shown) below the pallet, and the subsequent downward suction 6 advances it downward to lower the lower layer. A stratified combustion zone 10A is formed.
When the lower layer 10 where sintering has started moves below the second hopper 2B, the second blended raw material granulated by the second drum mixer 2A is discharged from the second hopper 2B to the lower layer after ignition. 10 to form the top layer 20 .
The carbonaceous material on the surface of the raw material layer (upper layer 20) is ignited by the second igniter 2C from above the formed upper layer 20, and the upper layer combustion zone 20A is formed by downward suction 6, and the upper layer 20 is burned. Knotting begins. The front surfaces (lowermost portions) of the lower-layer combustion zone 10A and the upper-layer combustion zone 20A, which descend as sintering progresses, are called combustion fronts of the respective combustion zones.
By the subsequent downward suction 6, the lower layer combustion zone 10A and the upper layer combustion zone 20A of the lower layer 10 and the upper layer 20 descend simultaneously and sintering progresses. When the lower layer combustion zone 10A and the upper layer combustion zone 20A reach the bottom of each layer, sintering by combustion of the carbonaceous material is completed, and the sintering zone 3 is formed. Finally, the sintered portion 3 that has completed sintering is discharged from the end of the pallet.

NOx (Fuel NOx) resulting from nitrogen contained in the carbonaceous material is generated with the combustion of the carbonaceous material in the production process of the sintered ore. This is contained in the sintering exhaust gas at a concentration of several hundred ppm. Since NOx is one of the causes of air pollution, it is necessary to either remove it from the exhaust gas before it is released into the atmosphere, or suppress the production of NOx during the sintering process so that it is not included in the exhaust gas in the first place. .

Conventionally, as a means for reducing NOx in the exhaust gas after sintering, a method of coating coke fine with quicklime/slaked lime before sintering is known (Patent Document 1). However, quicklime and slaked lime are expensive, and there are restrictions on the blending amount depending on the ironworks.

In Patent Document 2, since the multi-stage charging multi-stage ignition sintering method can change the supply ratio of the raw materials of each layer, the sintering yield is reduced due to the impediment of air permeability caused by the difference in particle size between the upper layer 20 and the lower layer 10. It is described that it has the advantage of being able to compensate for the decrease in , improving the yield, and reducing the amount of exhaust gas.
However, Patent Document 2 does not describe or suggest any generation or reduction of NOx.

Patent Literature 3 states that NOx in the sintering exhaust gas can be reduced by the multistage charging and multistage ignition sintering method. The NOx reduction mechanism is as follows.
1. The sintering of the lower layer 10 reduces the NOx conversion rate (ratio of nitrogen contained in the carbonaceous material to be released as NOx during combustion) because the carbonaceous material is burned at a low oxygen concentration.
2. NOx generated during sintering of the upper layer 20 is decomposed in the lower layer combustion zone 10A.

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

As described in Patent Document 3, according to the multistage charging multistage ignition sintering method, NOx in the final exhaust gas discharged from the lower layer 10 can be reduced to some extent. However, in order to reduce the environmental load, it is desired to further reduce NOx in the exhaust gas and to reduce the processing steps and energy required for treating the exhaust gas.

The present invention provides a method for producing sintered ore by a two-stage charging two-stage ignition sintering method, which does not apply any special treatment such as coating to the carbonaceous material and can further reduce NOx emissions in the sintering exhaust gas. for the purpose.

The present invention is intended to solve the above problems, and the gist thereof is as follows.

(1) A step of charging a lower raw material mixture into a sintering machine to form a lower raw material packed layer; and igniting the surface of the lower raw material packed bed and the surface of the upper raw material packed bed, respectively, and sucking the air in the lower raw material packed bed and the upper raw material packed bed downward. In the two-stage ignition sintering method having
A method for producing sintered ore, wherein the lower-stage blended raw material contains coke and/or anthracite, and a highly combustible carbonaceous material having an ignition temperature lower than that of coke and anthracite.
(2) The sintered ore according to (1), wherein the upper-stage blending raw material uses coke and/or anthracite having a higher nitrogen content than the coke or anthracite used as the lower-stage blending raw material. manufacturing method.
(3) According to (1) or (2), the blending ratio of the highly combustible carbonaceous material is 30% by mass or more and 70% by mass or less with respect to the total amount of carbonaceous material contained in the lower stage blending raw material. method for producing sintered ore.
(4) Any one of (1) to (3), wherein the lower-stage blended raw material contains, as the highly combustible carbonaceous material, char obtained by carbonizing low-fluidity coal having a Loga index of less than 10 as raw coal. Or the manufacturing method of the sintered ore as described in one.
(5) The lower-stage blending raw material contains, as the highly combustible carbon material, oil palm kernel shell coal, which is a solid carbide produced by heat-treating oil palm kernel shells (1) to ( 3) The method for producing a sintered ore according to any one of items.

In the two-stage charging and two-stage ignition sintering method, the amount of NOx emissions in the sintering exhaust gas can be reduced by using carbonaceous materials with different combustibility in the lower stage blending raw materials.

It is a schematic diagram of a DL type sintering machine used for a two-stage charging two-stage ignition sintering method. It is a figure which shows an example of the raw material processing process in the two-stage charge two-stage ignition sintering method of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing explaining the outline of this embodiment. FIG. 3 is a diagram showing the relationship between the blending ratio of PKS coal in all carbonaceous materials and the NOx conversion rate.

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the present specification and drawings, constituent elements having substantially the same functional configuration are denoted by the same reference numerals, thereby omitting redundant description.

In the sintering process for the production of sintered ore, NOx in the exhaust gas is considered to be Fuel-NOx generated during the combustion process of the carbonaceous material in the raw material for sintering, and the source of its generation is nitrogen contained in the carbonaceous material. It is This is explained by the nitrogen oxidation reaction (N(in fuel) + 1/ _2O2 →NO) occurring at the same time when the carbon material causes the combustion reaction (C+ _O2 → _CO2 ) by the air passing through the raw material packed bed. .

In the two-stage charging and two-stage ignition sintering method, NOx is generated by the combustion of the carbonaceous material in the upper combustion zone 20A and the carbonaceous material in the lower combustion zone 10A, respectively, and the upper combustion zone 20A and the lower combustion zone 10A The NOx generated in 1 moves downward in each layer due to the suction of air. Of the NOx that has moved downward, the NOx generated in the lower combustion zone 10A transfers directly to the exhaust gas. On the other hand, it is believed that the NOx generated in the upper combustion zone 20A is partially decomposed in the lower combustion zone 10A when passing through the lower combustion zone 10A.

In order to reduce the NOx emissions in the sintering exhaust gas, the present inventors used the two-stage charging two-stage ignition sintering method in which the width of the lower combustion zone 10A (the moving direction of the pallet (horizontal direction in FIG. 2) ), the NOx generated in the upper combustion zone 20A can be efficiently decomposed. Then, as a measure to ensure a wide width of the lower combustion zone 10A, the inventors came up with the idea of using two or more types of carbonaceous materials with different combustibility as the carbonaceous materials in the lower-stage compounding raw material. The embodiment will be described below.

FIG. 2 is a diagram showing an example of raw material processing steps for carrying out the method for producing sintered ore by the two-stage charging and two-stage ignition sintering method of the present invention. As shown in FIG. 2, the raw material processing step includes a first raw material tank group 1D (hereinafter also referred to as a lower raw material tank group) and a second raw material tank group 2D (hereinafter also referred to as an upper raw material tank group). , to supply raw materials of the required type and quantity. The first blended raw material (hereinafter also referred to as the lower stage blended raw material) is supplied from the first raw material tank group 1D to the first drum mixer 1A and granulated, and is granulated in the first hopper 1B of the sintering machine. transferred to In addition, the second compounded raw material (hereinafter also referred to as the upper-stage compounded raw material) is supplied from the second raw material tank group 2D to the second drum mixer 2A and granulated, and is granulated in the second stage of the sintering machine. It is transferred to the hopper 2B. The sintering process after transferring the lower-stage compounding raw material and the upper-stage compounding raw material to the Dwight Lloyd (DL) type sintering machine is the same as the production of the sintered ore described above with reference to FIG.

As shown in FIG. 2, the lower raw material tank group includes five raw material tanks 1D1 to 1D5. The upper stage raw material tank group includes four raw material tanks 2D1 to 2D4. Raw material tanks 1D1 and 2D1 contain iron ore, raw material tanks 1D2 and 2D2 contain MgO-containing auxiliary raw materials, and raw material tanks 1D3 and 2D3 contain CaO-containing auxiliary raw materials. The raw material tank 1D4 and the raw material tank 2D4 are first carbon material tanks containing the first carbon material. Also, the raw material tank 1D5 is a second carbonaceous material tank containing a second carbonaceous material. Thus, the lower raw material tank group includes two carbon material tanks (raw material tank 1D4 and raw material tank 1D5). The first carbonaceous material stored in the raw material tank 1D4 and the second carbonaceous material stored in the raw material tank 1D5 have different combustibility. is blended and used.

In this embodiment shown in FIG. 2, raw material tanks 1D4 (first carbon material tank) of the lower raw material tank group and raw material tanks 2D4 (first carbon material tank) of the upper raw material tank group contain carbon materials other than highly combustible carbonaceous materials. Carbonaceous material (for example, coke and/or anthracite) is stored, and highly combustible carbonaceous material (for example, coal char, biomass coal, etc.) is stored in raw material tank 1D5 (second carbonaceous material tank). Here, the highly combustible carbonaceous material is a highly combustible carbonaceous material, that is, a carbonaceous material having a high burning rate. Regarding the burning rate of carbonaceous material, various measurement methods and measurement results have already been published, but there is a problem that the obtained measurement results vary greatly unless well-controlled measurements are performed. Therefore, in the present invention, the ignition temperature, which has a substantially corresponding relationship with the burning speed, is used as an index representing the burning speed. That is, the highly combustible carbonaceous material refers to a carbonaceous material having a lower ignition temperature than coke and anthracite.

Table 1 is a table showing the ignition temperature of various carbonaceous materials. As exemplified in Table 1, highly combustible charcoal includes coal char and biomass charcoal (oil coconut shell charcoal, charcoal char produced by dry distillation of wood, etc.).

Coal char is, for example, carbonaceous material for sintering (char) produced by dry distillation of low-fluidity coal having a loga index of less than 10 as raw coal. This carbonaceous material for sintering is produced by dry distillation of raw material coal (including blended coal) in a pyrolysis furnace (for example, rotary kiln). Here, the Loga index is calculated by the Loga test method specified in JIS-M8801. In the Loga test method, standard anthracite coal is added to a sample, carbonized under certain conditions, and the resulting crucible coke is subjected to a small drum test, and its mechanical strength is expressed as the Loga index (abbreviation: RI). By using low-fluidity coal with a Loga index of less than 10 as raw coal, highly combustible coal char can be produced. The fluidity of coal is a property resulting from the degree of molecular weight reduction during heating.

Biomass coal is, for example, carbonaceous material produced from biological resources such as oil palm kernel shell coal and charcoal char. Palm kernel shell charcoal (PKS charcoal) is a solid char produced by heat-treating (carbonizing) palm kernel shell. The method for producing PKS coal is described in Japanese Unexamined Patent Application Publication No. 2014-218713 (Hara et al.) and the like, so the details are omitted.

FIG. 3 is an explanatory diagram for explaining the outline of this embodiment, and is an enlarged view of part of the lower layer 10 in FIG. In FIG. 3, the front surface (the end surface of the combustion zone on the descending direction side) and the rear surface of the lower-stage combustion zone 10A when a highly combustible carbonaceous material is used as part of the carbonaceous material in the lower-stage blending raw material are represented by the straight line X and the rear surface, respectively. A straight line Y indicates the front surface and rear surface of the lower layer combustion zone 10A when no highly combustible carbonaceous material is used as the lower-stage blending raw material, and dashed lines X1 and Y1 indicate the front and rear surfaces, respectively. For convenience, hatching in FIG. 1 is omitted.

When high-combustibility carbonaceous material is used as part of the carbonaceous material of the lower-stage blending raw material, as shown in Fig. 3, compared to the case where no high-combustibility carbonaceous material is used, the lower layer combustion The width of the band 10A can be expanded. This widening of the width is due to the fact that the start of combustion is hastened by using a highly combustible carbonaceous material with a low ignition temperature in the lower stage blending raw material for the front side. In addition, for the rear surface, by using two types of carbonaceous materials with different combustibility (highly combustible carbonaceous and carbonaceous materials other than highly combustible carbonaceous), as a result of the difference in the burning time of each carbonaceous material, This is because a long combustion time is ensured for the entire carbonaceous material. By widening the width of the lower combustion zone 10A, the time for NOx generated by combustion in the _upper combustion zone 20A to pass through the lower combustion zone 10A is lengthened from t1 to t. Therefore, NOx generated by combustion in the upper combustion zone 20A can be efficiently decomposed in the lower combustion zone 10A. In addition, since the highly combustible carbonaceous material leaves less unburned residue even under low oxygen concentration compared to coke or anthracite, under the low oxygen concentration in the lower layer combustion zone 10A, which was a problem in the two-stage ignition sintering method, The problem of poor combustion of carbonaceous materials can also be solved at the same time.

In the present embodiment, the above-described lower stage raw material tank group and upper stage raw material tank group are provided, and the upper stage system mixed material and the lower stage system mixed material are provided on the pallet as separate systems. It is not limited to this, and it is sufficient that two or more types of carbon materials having different combustibility are blended with the lower system blending raw material. For example, the raw material tanks for storing the iron ore, the MgO-containing auxiliary raw material, the CaO-containing auxiliary raw material, and the first carbonaceous material are divided into the raw material tanks 2D1 to 2D4 of the upper raw material tank group and the raw material tanks of the lower raw material tank group 1D1 to 1D4. Although they are separated, they may be stored in the same raw material tank and supplied to the first drum mixer 1A and the second drum mixer 2A.

The raw materials to be mixed are not limited to those described above, and two or more types of carbonaceous materials with different combustibility may be mixed in the raw materials to be mixed in the lower stage. The raw material is appropriately selected and used so that the zone 20A and the lower combustion zone 10A are at approximately the same position (for example, part or all of the upper combustion zone 20A overlaps with the lower combustion zone 10A). can be done. In this embodiment, by using two types of carbonaceous materials with different combustibility (a highly combustible carbonaceous material and a carbonaceous material other than the highly combustible carbonaceous material) as the carbonaceous material of the lower stage blending raw material, the lower layer combustion zone Although the width of 10A is widened, three or more kinds of carbonaceous materials including at least one highly combustible carbonaceous material and at least one highly combustible carbonaceous material may be used. In the case where a highly combustible carbonaceous material is not used as the carbonaceous material for the lower-stage blending material, it is conceivable to use two or more types of coke and/or anthracite with different combustibility as the lower-stage blending material.

In this embodiment, the raw material tank 1D4 and the raw material tank 2D4, which are the first carbon material tanks, store the same carbonaceous materials other than the highly combustible carbonaceous materials, but different carbonaceous materials may be stored. If there are two or more different types of coke or anthracite coal, it is desirable to use coke or anthracite with a lower nitrogen content than the upper-stage blending material for the lower-stage blending material in order to reduce NOx emissions. . As described above, the NOx generated in the upper combustion zone 20A is partially decomposed when passing through the lower combustion zone 10A, while the NOx generated in the lower combustion zone 10A is directly transferred to the exhaust gas. It is from.

The effect of the two-stage charging two-stage ignition sintering method of the present invention was verified. A sintering pot test with single-stage ignition and double-ignition under the following conditions, simulating the method of producing sintered ore by single-stage charging, single-stage ignition and double-charging, two-stage ignition with a Dwight Lloyd (DL) type sintering machine. went.

(Raw material composition)
Table 2 shows the raw material mixing conditions.
Regardless of the test case, the composition of new raw materials (raw materials other than carbonaceous material) is the same. The ratio of the carbonaceous material was set to 5.0% by mass, with the new raw material in which iron ore, limestone, peridotite, and quicklime were mixed as 100% by mass. Iron ores A to E in Table 2 were from different production areas.

Table 3 shows the composition of the 5.0% by mass (outside number) carbonaceous material.
In single-stage ignition, test case 1 uses only coke breeze, test case 3 is a case in which 32% of the coke breeze in test case 1 is replaced with oil palm kernel shell coal (hereinafter also referred to as PKS coal), test case 5 is a case in which 56% of coke fine in test case 1 is replaced with PKS coal. In the two-stage ignition, coke breeze was used in all cases as the carbonaceous material for the upper stage system. As the carbonaceous material for the lower stage blending raw material, test case 2 used only coke breeze, and test cases 4, 6 to 9 used both coke breeze and PKS coal. Here, a case in which only coke dust is used as the carbon material is used as a reference example, and a case in which both coke dust and PKS coal are used as the carbon material is used as a comparative example. A case in which powdered coke and PKS coal are used as the carbon material was used as an invention example. In Examples 1 to 5, the blending ratio of PKS coal in the carbonaceous material of the lower system blending raw material was changed, 50% (2.5% by mass of new raw material (outside number)), 10% (0.5 mass of new raw material) % (external number)), 30% (relative to new raw material 1.5 mass% (external number)), 70% (relative to new raw material 3.5 mass% (external number)), 90% (relative to new raw material 4.5 % by mass (outside number)). The coke fines and PKS coal blends of Comparative Examples 1 and 2, which are single-stage charging, are the total carbon materials (upper and lower) of Invention Examples 1 and 5, which are two-stage charging, respectively. It was set to be substantially the same as the blending ratio (% by mass) of PKS coal (see Tables 4 and 5). That is, in Comparative Example 1 and Inventive Example 1, and in Comparative Example 2 and Inventive Example 5, the mixing ratios of coke fine and PKS charcoal with respect to the total raw materials to be mixed were substantially the same.

(Granulation method)
In the case of single-stage ignition, the blended raw materials were granulated together, and in the case of two-stage ignition, the upper-stage blended raw material and the lower-stage blended raw material were granulated separately. For granulation, after mixing for 4 minutes (min) with a drum mixer (diameter 600 mm, rotation speed 25 rpm), 7.0% by mass of water is added to 100% by mass of the blended raw materials, and further 4 minutes with a drum mixer ( min) treated.

(Charging/ignition method)
Two pans were prepared: a cylindrical lower pan (φ300 mm) with a height of 500 mm and a cylindrical upper pan (φ300 mm) with a height of 300 mm. In the case of single-stage ignition, two pots were stacked so that the lower pot was on the bottom, and the blended raw material (layer thickness: 800 mm) was charged and ignited at 1100 ° C. for 1 minute (min). In the case of two-stage ignition, the lower-level compounding material (layer thickness: 500 mm) was charged into the lower-level pan, and the upper-level compounding material (layer thickness: 300 mm) was charged into the upper-level pan. Then, first, the pot for the lower stage charged with the raw materials for the lower stage was set and ignited at 1100° C. for 1 minute (min). After the ignition was completed, the upper pot was immediately placed on the lower pot and ignited at 1100°C for 1 minute (min). The suction pressure was kept constant at 14.7 kPa from the start of ignition. It took 30 seconds from the end of the ignition of the lower-stage blended raw material to the start of ignition of the upper-stage blended raw material.

(Sintering time)
Sintering time was measured as follows. Thermocouples were set at positions 60 mm, 150 mm, 300 mm, and 450 mm from the upper surface of the pan for the lower stage. In the case of single-stage ignition, the sintering time was defined as the time required until the peak time of the thermocouple at the 450 mm position. On the other hand, in the case of two-stage ignition, the later of the completion of sintering in the upper stage and the completion of sintering in the lower stage is regarded as the completion of sintering for the entire upper and lower stages, so the second peak time of the thermocouple at the 60 mm position (upper The sintering time was defined as the longer of the required time until sintering completion) and the required time until the first peak time of the thermocouple at the 450 mm position (sintering completion in the lower row). After 3 minutes from the time when the sintering was completed, the suction was stopped to complete the sintering.

(production rate)
The production rate was obtained by the following formula (1) based on the sintering time measured as described above.
Production rate = product amount (t) / sintered area (0.07 m ² ) / sintered time (days) (1)

(NOx evaluation method)
Exhaust gas NOx concentration was measured by sampling the sintering exhaust gas and supplying it to an analyzer.
The NOx conversion rate calculated by the formulas (2) and (3) was used as an evaluation index for exhaust gas NOx emissions. Here, the NOx conversion rate is the molar ratio of the amount of NOx generated to the amount of nitrogen in the carbonaceous material, but it is necessary to consider the carbon combustion rate of the carbonaceous material.
On the other hand, the CO and _CO2 contained in the exhaust gas are considered to be derived from carbonaceous material, ignition gas and limestone, but the amount of carbonaceous combustion carbon is calculated by subtracting the amount of carbon derived from ignition gas and limestone from the amount of CO and CO produced. asked. Here, it was assumed that all the carbon in the ignition gas was burned and all the limestone was decarboxylated.

ηNO=100×[NOx/N _COKE ]×[C _COKE /C _{COKE Comb} ]
(2)
C _{COKE Comb} = (CO + CO ₂ - C _LPG - C _CLS ) (3)
ηNO: NOx conversion rate (%)
NOx: Exhaust gas NOx integrated amount from start to finish of sintering (mol)
CO: Total amount of exhaust gas CO (mol) from start to finish of sintering
CO ₂ : integrated amount of exhaust gas CO ₂ from the start to the end of sintering (mol)
N _COKE : Nitrogen input amount derived from carbon material (mol)
C _COKE : Amount of carbon derived from carbon material (mol)
C _{COKE Comb} : Combustion carbon amount (mol) derived from carbon material
C _LPG : amount of carbon input (mol) derived from ignition gas
C _CLS : Limestone-derived carbon content (mol)

(Test results)
The results of test cases 1-4 are shown in the lower part of Table 4. As shown in Table 4, Comparative Example 1 and Invention Example 1 have substantially the same mixing ratio of PKS coal to all carbon materials (upper and lower). That is, the same amount of PKS coal is distributed throughout the layer thickness direction in Comparative Example 1 (one-stage charging, one-stage ignition), whereas in Invention Example 1 (two-stage charging, two-stage ignition), only the lower layer 10 are distributed over Inventive Example 1, in which PKS coal is used only in the lower layer 10, the NOx conversion rate is 15% lower than in Comparative Example 1, in which PKS coal is distributed throughout.

In addition, as shown in Table 4, in the one-stage charging and one-stage ignition, Comparative Example 1 using coke breeze and PKS coal as the carbon material has a higher NOx The conversion is reduced by 10%. When only coke fine was used as the carbon material, the NOx conversion rate was reduced by 8% in Reference Example 2 with two-stage charging and two-stage ignition compared to Reference Example 1 with one-stage charging and one-stage ignition. there is In Invention Example 1, which uses only coke breeze in the upper stage and coke breeze and PKS coal in the lower stage, the NOx conversion rate is reduced by 25% compared to Reference Example 1. Thus, in Invention Example 1, the effect of NOx decomposition in the lower combustion zone by two-stage charging two-stage ignition (reduction rate 8%; Reference Example 2 against Reference Example 1) and the NOx generation reduction effect of PKS coal itself (reduction rate 10%; the NOx conversion rate decreased more than the synergistic value (17%) with Comparative Example 1) with respect to Reference Example 1. In addition, among test cases 1 to 4, the production rate of invention example 1 was the highest.

The results of test cases 5-9 are shown at the bottom of Table 5. As shown in Table 5, Comparative Example 2 and Invention Example 5 have substantially the same mixing ratio of PKS coal to all carbon materials (upper and lower). As in the case of Comparative Example 1 and Invention Example 1 described above, Invention Example 5, which uses PKS coal only in the lower layer 10, has a lower NOx conversion rate than Comparative Example 2, which uses PKS coal in the entire layer, a reduction of 4%. are doing.

FIG. 4 is a diagram showing the relationship between the mixing ratio of PKS coal to the total carbonaceous material and the NOx conversion rate in the test results of test cases 1 to 9. As shown in FIG. 4, the NOx conversion rate was lower in the two-stage ignition case than in the one -stage ignition case at the same PKS coal blending ratio. In particular, the blending ratio of PKS coal in the carbonaceous material in the lower system was low when it was 30% or more and 70% or less. If the blending ratio of PKS coal in the lower system carbonaceous material is less than 30%, the effect of using PKS coal is difficult to appear, and if it exceeds 70%, the burning speed of the carbonaceous material becomes too fast, resulting in the lower layer combustion zone 10A. It is considered that this is because the width cannot be widened and NOx cannot be sufficiently decomposed.

Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention belongs can conceive of various modifications or modifications within the scope of the technical idea described in the claims. It is understood that these also naturally belong to the technical scope of the present invention.

1A first drum mixer, 1B first hopper, 1C first igniter, 1D first raw material tank group (lower raw material tank group), first raw material tank 1D1 to 1D4, 2A first 2 drum mixer, 2B... second hopper, 2C... second igniter, 2D... second raw material tank group (upper raw material tank group), second raw material tank 2D1 to 2D5, 10... lower layer, 10A ... lower layer combustion zone 20 ... upper layer 20A ... upper layer combustion zone 3 ... sintering section 5 ... pallet traveling direction 6 ... downward suction

Claims (5)

A step of forming a lower raw material filling layer by charging a lower raw material mixture into a sintering machine, and a step of charging an upper raw material mixture onto the lower raw material packed layer to form an upper raw material packed layer. and a step of igniting the surface of the lower raw material packed bed and the surface of the upper raw material packed bed, respectively, and sucking downward the air in the lower raw material packed bed and the upper raw material packed bed. In the ignition sintering method,
The lower-stage blended raw material contains coke and/or anthracite, and a highly combustible carbonaceous material having a lower ignition temperature than the coke and anthracite in the lower-stage blended raw material ,
A method for producing sintered ore, wherein the upper-stage compounding raw material contains only coke and/or anthracite as a carbonaceous material . A step of forming a lower raw material filling layer by charging a lower raw material mixture into a sintering machine, and a step of charging an upper raw material mixture onto the lower raw material packed layer to form an upper raw material packed layer. and a step of igniting the surface of the lower raw material packed bed and the surface of the upper raw material packed bed, respectively, and sucking downward the air in the lower raw material packed bed and the upper raw material packed bed. In the ignition sintering method,
The lower-stage blended raw material contains coke and/or anthracite, and a highly combustible carbonaceous material having a lower ignition temperature than the coke and anthracite in the lower-stage blended raw material,
A method for producing sintered ore, wherein coke and/or anthracite having a higher nitrogen content than the coke or anthracite used as the lower-stage compounding material is used as the upper-stage compounding material. The sintering according to claim 1 or 2, wherein the blending ratio of the highly combustible carbonaceous material is 30 mass% or more and 70 mass% or less with respect to the total amount of carbonaceous material contained in the lower stage blending raw material. Ore production method. 4. Any one of claims 1 to 3, wherein the lower-stage blended raw material contains, as the highly combustible carbonaceous material, char obtained by dry-distilling low-fluidity coal having a Loga index of less than 10 as raw coal. The manufacturing method of the sintered ore as described in . 4. The method according to any one of claims 1 to 3, wherein the lower-stage blending raw material contains, as the highly combustible carbon material, oil palm kernel shell coal, which is a solid carbide produced by heat-treating oil palm kernel shells. A method for producing a sintered ore according to any one of the items.

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