JP5561146B2 - Method for producing blast furnace coke - Google Patents

Description

  The present invention relates to a method for producing coke for blast furnace by charging pulverized coal, in particular, blended coal containing a large amount of low-grade coal such as non-slightly caking coal into a coke oven.

  Blast furnace coke is generally manufactured by blending and pulverizing multiple brands of coal, or pulverizing and blending multiple brands of coal, and then charging them into a coking oven carbonization chamber and subjecting them to dry distillation for a predetermined time. The On the other hand, in blast furnace operation, high-strength coke is necessary to ensure air permeability in the blast furnace and maintain stable operation.

  In order to produce high-strength coke for blast furnace, the coal particle size after blending is, for example, a mass ratio of 3 mm or less (hereinafter sometimes simply referred to as “−3 mm%”) of 70 to 90 for the entire blended coal. % (See Patent Document 2).

  In recent years, the demand for highly caking coal suitable for the production of high-strength coke is in a state of tightness worldwide, raising the cost of producing coke. Therefore, many methods have been proposed so far for producing high-strength coke by using a large amount of inexpensive non-slightly caking coal having low caking properties (difficult to coke).

  For example, coal rich in active ingredients is coarsely crushed, coal that is not rich in active ingredients such as non-slightly caking coal is finely pulverized, and inert ingredients in coal are finely divided and uniformly dispersed (patented) Reference 4), and for good quality caking coal, -3 mm% is set to 50 to 70%, while for non-fine caking coal, -3 mm% is set to 80 to 95% (Patent Document 1, Have been proposed).

  Also, not only caking coal and non-slightly caking coal, but if there is a coarse inert component in the coal, it will cause a reduction in coke strength, so the coarse inert component of 1.5 mm or more is finely ground by strong pulverization. Has been proposed (see Patent Documents 2 and 3).

  As described above, when producing high-strength coke using a large amount of non-slightly caking coal, a technique of strongly pulverizing coal is often employed. However, when coal is strongly pulverized, a large amount of pulverized coal having a particle size of 0.3 mm or less is generated (see Patent Document 3).

  When the fine powder component increases in the pulverized coal, dust generation in the coal conveyance process and carry-over at the time of charging the carbonization chamber increase. In particular, an increase in carry-over increases tar sludge to deteriorate tar quality, and also increases carbon adhering in the carbonization chamber, thereby hindering stable operation of the coke oven (see Patent Document 5).

  In particular, excessive production of attached carbon at the riser base of the carbonization chamber clogs the riser base and, as a result, causes troubles such as dry distillation product gas leaking from the carbonization chamber. In addition, if carbon adhering to the furnace wall or ceiling is excessively generated, the extrusion resistance of the coke cake is increased, and in the worst case, it leads to major troubles such as clogging and furnace wall damage.

  Further, when it is desired to increase the coke strength, one means is to increase the furnace temperature (dry distillation temperature) of the coke oven, but naturally the amount of adhered carbon increases as the furnace temperature is increased.

  Thus, from the viewpoint of improving coke strength, it is desirable to pulverize coal and raise the furnace temperature. On the other hand, strong pulverization of coal and an increase in furnace temperature are the cause of operational troubles. This leads to an increase in the amount of attached carbon.

  Therefore, an industrial production method capable of stably producing high-strength blast furnace coke by blending a large amount of various grades or brands of low-grade coal is strongly demanded.

JP-A-10-183136 JP 2004-339503 A JP 2008-297385 A Japanese Unexamined Patent Publication No. 56-032587 Japanese Patent No. 4173952

  In view of the above situation, the present invention is capable of stably producing coke for blast furnace having a required coke strength (DI) from a coal blended with a large amount of low-grade coal having low caking properties such as non-slightly caking coal. It aims at providing the industrial manufacturing method which can be manufactured efficiently.

  As described above, coal pulverization (hereinafter, simply referred to as “strong pulverization”), which is a means for increasing the coke strength, and furnace temperature of the coke oven (hereinafter simply referred to as “furnace temperature”). )), On the other hand, increases the amount of carbon adhering to the riser base of the carbonization chamber and the carbonization chamber (including the ceiling), which causes operational troubles.

  In order to achieve the above-mentioned object, the present inventors firstly set the particle size (mass%) after pulverization of coal (hereinafter sometimes simply referred to as “pulverized particle size”), furnace temperature (° C.), and We believe that it is necessary to quantitatively elucidate the relationship between the cold strength (DI) of manufactured coke (hereinafter sometimes simply referred to as “coke strength” or “strength”) and I tried hard.

  As a result, the inventors have found that a predetermined correlation is established among the pulverized particle size (mass%), the furnace temperature (° C.), and the coke strength (DI), and have reached the present invention.

  This invention was made | formed based on the said knowledge, The summary is as follows.

(1) In a method of pulverizing coal and charging it into a coke oven to produce blast furnace coke,
In order to obtain the target coke strength DIz by measuring the coke strength of coke obtained by pulverizing coal at various ratios of -3 mm and carbonizing different coal at different ratios of -3 mm at various furnace temperatures. The required lower limit value Z of -3 mm is obtained for each furnace temperature Tz
The relationship between DIz and Tz with respect to the obtained lower limit value Z is obtained in advance as the following formula (1),
In the actual operation of the coke oven, the target coke strength DIz and the furnace temperature Tz are set, and the lower limit value Z (mass%) of the ratio of −3 mm after pulverization of coal to obtain the target coke strength is expressed by the following formula: obtained in (1), and percentage of -3mm after pulverization is pulverized coal so that the above Z, method of manufacturing blast furnace coke, which comprises charging the coke oven.

Z (mass%) = C1 × DIz + C2 × Tz + C3 × Tz × DIz + C4 (1)
here,
C1 to C4: obtained by performing multiple regression analysis with the lower limit value Z determined for each furnace temperature Tz as a dependent variable, and the target coke strength DIz, the furnace temperature Tz, and [DIz × Tz] as independent variables. coefficients that are

(2) In the above formula (1), Tz: 1000 to 1300 ° C. and DIz: DI ¹⁵⁰ ₁₅ are 84.0 to 87.0. Production method.

(3) The method for producing coke for blast furnace as described in (1) or (2) above, wherein the coal is blended coal in which low-grade coal is blended at less than 40% by mass .

  According to the present invention, coal is pulverized to a pulverized particle size determined by the relationship between the target coke strength and the furnace temperature of the coke oven and charged into the coke oven. It can be manufactured stably and efficiently.

It is a figure which shows the relationship between a grinding | pulverization particle size (mass%), furnace temperature (degreeC), and coke strength (DI). It is a figure which shows the relationship between the furnace temperature of a coke oven, and the lower limit of -3 mm%. It is a figure which shows the relationship between target coke intensity | strength (DI management value) and the inclination of each straight line shown in FIG. It is a figure which shows the relationship between target coke intensity | strength (DI management value) and the Y intercept of each straight line shown in FIG. It is a figure which shows the correlation of the lower limit (estimated value) of -3mm% calculated | required by Formula (1), and an actual value.

  The present invention will be described below with reference to the drawings.

  In the method of pulverizing coal and charging it into a coke oven to produce coke for blast furnace, the present invention is such that -3 mm% after pulverization of coal is equal to or greater than Z (mass%) defined by the following formula (1) It grind | pulverizes so that it may become, It is characterized by charging with a coke oven.

Z (%) = C1 × DIz + C2 × Tz + C3 × DIz × Tz + C4 (1)
Where Tz: furnace temperature (° C)
DIz: Target coke strength (DI ¹⁵⁰ ₁₅ )
C1 to C4: Coefficients determined by multiple regression analysis

  The present inventors have intensively investigated the relationship between the pulverized particle size (mass%), the furnace temperature (° C.), and the coke strength (DI). The result is shown in FIG.

  Incidentally, the furnace temperature in the present invention means the average temperature of the combustion chamber during coal carbonization. The method for obtaining the average temperature is not particularly limited. For example, a plurality of thermometers (thermocouples) embedded in bricks at the top of the combustion chamber at a certain interval in the furnace group direction (direction in which the carbonization chambers are arranged). It is recommended to use the average of the values measured in

In order to maintain the stable operation of the blast furnace, the coke strength needs to be controlled to, for example, DI ¹⁵⁰ ₁₅ at 85.3 or more (see the dotted line in FIG. 1). Here, DI ¹⁵⁰ ₁₅ is a mass ratio (−) of coke on a 15 mm sieve after 150 rotations by a drum tester defined in JIS K 2151, and is an index representing coke strength (also referred to as drum strength). It is.

  In FIG. 1, the lower limit value of the pulverized particle size (−3 mm%) when pulverizing coal is obtained from the intersection of the control value (target coke strength) 85.3 and the coke strength-ground particle size curve for each furnace temperature. .

  In the pulverization example shown in FIG. 1, the lower limit value of −3 mm% is (a) 75.2 mass% at a furnace temperature of 1250 ° C., (b) 76.4 mass% at a furnace temperature of 1200 ° C., and (c) furnace temperature 1150. 78.8% by mass at ℃, (d) 82.2% by mass at 1100 ° C furnace temperature, 84.1% by mass at 1050 ° C furnace temperature. -3mm% needs to be increased.

The management value is not limited to 85.3, and is set as appropriate based on the blast furnace operating conditions. If the control value is set appropriately, the lower limit value of the pulverized particle size (-3 mm%) necessary to achieve the target coke strength (DI ¹⁵⁰ ₁₅ , hereinafter referred to as “target DI”) can be seen from FIG. Can be obtained for each furnace temperature of the coke oven. Table 1 shows an example.

  FIG. 2 shows the result of plotting the relationship between the lower limit of −3 mm% for achieving the coke target DI shown in Table 1 and the furnace temperature of the coke oven for each target DI (DI management value). It can be seen that the lower limit of −3 mm% and the furnace temperature of the coke oven have a good correspondence.

The correspondence relationship shown in FIG. 2 is approximated for each target DI by a linear expression represented by the following expression (3), and a straight line inclination “a” and a Y intercept “b” are obtained. The results are shown in Table 2.
-3 mm% lower limit (%) = a × [furnace temperature (° C.)] + B (3)

FIG. 3 shows the relationship between the slope “a” of the straight line shown in Table 2 and the DI management value, and FIG. 4 shows the relationship between the Y intercept “b” of the straight line and the DI management value. The relationship between “a” and the DI management value, and the relationship between “b” and the DI management value, respectively, are determined by using a linear function represented by the following equation (4) and the following equation (5). ² can be expressed.

a (slope) = 0.0286 × (DI management value) −2.4925 (4)
b (Y intercept) = (− 27.626) × (DI management value) +2493.6 (5)
In the formula (4), R ² = 0.9851 and in the formula (5), R ² = 0.9856.

  When the above formulas (4) and (5) are applied to the formula (3) and rearranged, the following formula is obtained.

-3 mm% lower limit (% by mass) = [0.0286 × (DI management value) −2.4925]
X [furnace temperature (° C)] + [(-27.626) x (DI management value) + 2493.6]
= C1 x DIz + C2 x Tz + C3 x DIz x Tz + C4 (6)
C1 to C4: Coefficient
DIz: DI management value (target coke strength: DI ¹⁵⁰ ₁₅ )
Tz: Furnace temperature (° C)

(6) In order to obtain the coefficients C1 to C4 of the equation, the lower limit value of -3 mm% is subordinate (objective) variable, DI control value, furnace temperature ° C, and [DI management value x furnace temperature (° C)] independent (explanation) Multiple regression analysis with variables was performed. As a result, the following formula (2) was obtained.
Z (mass%) = (− 22.0855) × DIz + (− 2.0548) × Tz
+ 0.02354 × Tz × DIz + 20166.9 (2)

  Here, the relationship between the lower limit value (estimated value) of −3 mm% obtained by the above formula (2) and the actually measured value is shown in FIG. From FIG. 5, it can be seen that there is a very good correspondence between the estimated value and the actually measured value. From this, it can be said that the lower limit (estimated value) of −3 mm% obtained by the above formula (1) is a significant numerical value that defines the particle size (mass%) after pulverization when the coal is actually pulverized.

  The temperature of the coke oven is determined by the amount of coke demand in the blast furnace. That is, if the demand for coke in the blast furnace increases, the furnace temperature is set higher to increase the operating rate. Conversely, if the demand volume decreases, the furnace temperature is set lower to lower the operating rate. The temperature Tz is set as appropriate according to the amount of coke demand.

Usually, in the operation of a coke oven, the furnace temperature is set in the range of 1000 to 1300 ° C, and therefore, in the above formulas (1) and (2), Tz is preferably a temperature in the range of 1000 to 1300 ° C. The target DI is usually Since DI ^0.99 ₁₅ is 84.0 to 87.0, the above formula (1) and (2), Diz is in the range of 84.0 to 87.0 in DI ^0.99 ₁₅ Values within are preferred.

  C1 to C4 are coefficients determined by multiple regression analysis. Actually, the coke strength-grinding particle size curve shown in FIG. 1 differs depending on the properties or brands of coal and / or blending conditions, and the target DI Since the pulverization particle size (-3 mm%) necessary for achieving the above also varies depending on the furnace temperature of the coke oven, it is set in consideration of the operation results.

  When the coal is a low-grade coal such as non-slightly caking coal or contains a large amount of coarse inert components, normally, as described above, the inert components in the coal are selectively finely divided and uniformly dispersed. Therefore, since a means for increasing the coke strength is adopted, the present invention is used when producing a high strength coke using a large amount of non-slightly caking coal (low grade coal) or a coal containing a large amount of coarse inert. It is particularly effective.

  However, if too much non-slightly caking coal (low-grade coal) is used, coke strength may decrease, so the blending amount of non-slightly-caking coal (low-grade coal) should be less than 40% by mass. It is preferable.

Incidentally, in the present invention, non-slightly caking coal (low-grade coal) is defined as follows using vitrinite average maximum reflectance (Ro) and maximum fluidity (MF) measured with a Geisler plastometer. .
When Ro is 0.85 or less, coal whose logarithmic value (Log) of MF is 2.5 or less.
When Ro exceeds 0.85, coal whose logarithm value (Log) of MF is 0.5 or less.

  Next, examples of the present invention will be described. The conditions in the examples are one example of conditions used for confirming the feasibility and effects of the present invention, and the present invention is based on this one example of conditions. It is not limited. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

(Example)
It is necessary to produce coke with strength DI ¹⁵⁰ ₁₅ = 85.3 as coke for blast furnace when blended with about 32% non-coking coal and operating at a coke oven temperature Tz = 1200 ° C. occured. Therefore, in the above formula (2), when Tz = 1200 ° C. and DIz (DI ¹⁵⁰ ₁₅ ) = 85.3, a lower limit value Z (mass%) of −3 mm% was obtained, and Z = 76.8 mass% was obtained. Obtained.

Therefore, the coal was pulverized so that -3 mm% of the blended coal containing non-slightly caking coal became Z = 76.8% by mass or more and charged into a coke oven to produce coke. When the coke strength DI ¹⁵⁰ ₁₅ of the obtained coke was measured, DI ¹⁵⁰ ₁₅ ≈85.3, and the coke having the target coke strength could be stably produced.

  As described above, according to the present invention, coal is pulverized to a pulverized particle size determined by the relationship between the target coke strength and the furnace temperature of the coke oven and charged into the coke oven. The coke for blast furnace which has can be manufactured stably and efficiently. Therefore, the present invention has high applicability in the coke manufacturing industry.

Claims (3)

In the method of pulverizing coal and charging it into a coke oven to produce coke for blast furnace,
In order to obtain the target coke strength DIz by measuring the coke strength of coke obtained by pulverizing coal at various ratios of -3 mm and carbonizing different coal at different ratios of -3 mm at various furnace temperatures. The required lower limit value Z of -3 mm is obtained for each furnace temperature Tz
The relationship between DIz and Tz with respect to the obtained lower limit value Z is obtained in advance as the following formula (1),
In the actual operation of the coke oven, the target coke strength DIz and the furnace temperature Tz are set, and the lower limit value Z (mass%) of the ratio of −3 mm after pulverization of coal to obtain the target coke strength is expressed by the following formula: obtained in (1), and percentage of -3mm after pulverization is pulverized coal so that the above Z, method of manufacturing blast furnace coke, which comprises charging the coke oven.
Z (mass%) = C1 × DIz + C2 × Tz + C3 × Tz × DIz + C4 (1)
here,
C1 to C4: obtained by performing multiple regression analysis with the lower limit value Z determined for each furnace temperature Tz as a dependent variable, and the target coke strength DIz, the furnace temperature Tz, and [DIz × Tz] as independent variables. coefficients that are In the formula (1), Tz: 1000~1300 ℃ , and, Diz: production method of blast furnace coke as set forth in claim 1, characterized in that in DI ^0.99 ₁₅ is 84.0 to 87.0. The method for producing coke for blast furnace according to claim 1 or 2, wherein the coal is blended coal in which low-grade coal is blended at less than 40 mass% .

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