JP3131121B2 - Method for estimating fluidity of blended coal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for estimating the fluidity of a coal blend as a raw material for coke.

[0002]

2. Description of the Related Art Metallurgical coke must have characteristics suitable for blast furnace operation, such as robustness to withstand use in a blast furnace. Therefore, as the raw material, coal having appropriate caking property and degree of coalification is required, but since there are few natural coals, it is common to mix and adjust coals with different properties. . In particular, Japan lacks coal resources and has to rely on coal imported from various regions, so it is inevitable to use blended coal consisting of various types of coal for the production of coke.

[0003] Usually, ten or more types of plain coals are used as blended coal, and the coal used and its blending ratio are determined according to the conditions under which coke suitable for blast furnace operation is produced. In particular, the fluidity of coal has a large effect on coke strength. Since the fluidity of coal has a very close relationship with the properties of coke to be produced, it is very important to know the fluidity of blended coal blended with plain coal.

[0004] This fluidity is measured in accordance with JIS M 8801 (1).
997), which is measured by a Giesler plastometer and shows the relationship between the temperature and the flow rate, which is the rotation speed of the stirring rod (usually expressed by logarithmic value logddpm), under a certain condition. It can be represented by a curve.

However, in order to determine the brand and blending ratio of the plain coal to be used, it is necessary to actually produce blended coal for all combinations and blending ratios which are candidates, and measure the fluidity of each blended coal. Is almost impossible. Therefore,
It is common practice to estimate the fluidity of blended coal from the properties of each blended plain coal.

That is, a weighted average value of the highest fluidity of each single coal used in blending is generally adopted as the highest fluidity of blended coal. However, in this method, the flow rate curve cannot be known, and the maximum flow rate obtained is about 0.2 to 0.3 larger than the actually measured value.

Japanese Patent Application Laid-Open No. Sho 62-217141 discloses a method for estimating a fluidity curve of blended coal by using the reflectance distribution of vitrinite, the amount of inactive components and the blending ratio of each plain coal ( Hereinafter, referred to as an overlapping method). In the case of this superposition method, if the overlapping of the melting temperature ranges of the individual coals used for blending is small, the difference from the measured value cannot be avoided, and the influence of the overlapping of the melting temperature ranges is fully reflected. There is a problem that can not be done. Furthermore, in coal blends, the effect of coal with a low melting temperature range is more pronounced, so the actual solidification temperature of coal blends is lower than the value estimated by this superposition method, and the phenomenon of the solidification process Is not fully reflected.

[0008]

SUMMARY OF THE INVENTION Therefore, the present invention
In order to solve the above-mentioned problems of the prior art, and propose a method for accurately estimating the fluidity curve of the blended coal in consideration of the overlapping of the softening and melting temperature ranges between the single coals and the influence of solidification of the coal. The purpose is to:

[0009]

SUMMARY OF THE INVENTION The present invention relates to a blended coal obtained by blending a plurality of types of plain coals, based on a viscosity calculated by regarding the blended coal charged into a coke oven as a suspension. This is a method for estimating the fluidity of blended coal, characterized in that a fluidity curve of blended coal is obtained by using the method.

Here, the viscosity is calculated from a solvent viscosity and a solid fraction calculated by considering the blended coal as a suspension;
Further, it is advantageous to carry out that the solvent viscosity is calculated from the solvent viscosity of each plain coal, the melting rate and the blending rate, and the solid phase rate is calculated from the solid phase rate and the blending rate of each plain coal. .

[0011]

[Function] Coal in the softened and molten state in the coke oven
It is a gas-solid mixed layer in which a melt, an unmelt, a solid, and a generated gas are mixed. Therefore, the present inventors focused on coal particles in particular, and blended coal in a softened and molten state in a coke oven with a suspension in which particles having different particle sizes are mixed in a mixture of solvents having different viscosities. Considered modeling.

That is, the blended coal is regarded as a suspension, its viscosity is calculated, and the fluidity corresponding to the calculated viscosity is determined from the relationship between the viscosity and the fluidity determined in advance. By performing this operation at various temperatures, the fluidity at each temperature is obtained, and the fluidity curve of the blended coal can be estimated based on the obtained results.

That is, when the coal blend is regarded as a suspension in which particles having a particle diameter d are suspended in a solvent having a viscosity η _L , the apparent viscosity η of this suspension is expressed by the following equation (1). Can be represented by η = η _L ｛1+ (d · S _r / 2φ)｝ --- (1) where S _r is the surface area of all particles, while φ is the ultimate solid fraction g _scr and solid fraction S It can be expressed by the following equation (2). φ = 1 / S-1 / g _scr ---- (2) In the case of spherical particles, the relationship shown in the following formula (3) is obtained between the volume and the average surface area regardless of the particle size distribution. To establish. (D · S _r ) / 2 = 3 (3) Therefore, the above equation (1) is as follows: η = η _L (1 + 3 / φ) --- (4)

Here, assuming that the diameters of all particles are equal in the blended coal in the softened and molten state, the ultimate solid fraction g _scr is as follows:
Since it can be approximated to 0.52, the above equation (2) becomes φ = 1 / S−1 / 0.52 = 1 / S−1.92 ---- (5), and this equation (5) is substituted into the above equation (4). Then, η = ηL ｛1 + 3 / (1 / S−1.92)｝ --- (6). Therefore, the viscosity η can be calculated from the solvent viscosity η _L and the solid fraction S.

The relationship between the viscosity η and the fluidity F is determined by the method of measuring the flow of the fuel cell, see the Journal of the Fuel Association, 53 569 (197
4) Equations of various wealth described on pages 779 to 790｝ log F = kη log η + aη Here, kη: −0.98 aη: 7.08 can be used to arrange as shown in FIG. ) The fluidity corresponding to the viscosity calculated by the formula is obtained.

The solvent viscosity η _L and the solid fraction S, which are necessary for calculating the viscosity of the blended coal, are calculated based on the solvent viscosity η _L
Can be determined from the solvent viscosity, the melting rate, and the blending ratio of each plain coal, and the solid phase ratio S can be determined from the solid phase ratio and the blending ratio of each plain coal, respectively. These data are measured or calculated for each plain coal used.

Further, the procedure for estimating the flow rate curve of the blended coal by a computer will be described more specifically with reference to the flowchart of FIG. First,
The softening temperature, maximum fluidity and its temperature, solidification temperature, inert (inactive component) content,
In addition, enter the blending ratio of plain coal. Here, the softening temperature, the maximum fluidity, its temperature, and the solidification temperature may be measured when each plain coal is received.

Then, based on the input data of each single coal, the properties of each single coal at the temperature T, that is, the particle diameter,
Calculate the solid fraction and the solvent viscosity. Here, the solid fraction is
At the highest fluidity temperature, the particles are calculated as a function of temperature based on the assumption that everything but the inert melts and that the softening and solidification points have a critical solid fraction.
Similarly, the solvent viscosity is calculated as a function of temperature based on the assumption that the solvent viscosity is at a minimum at the highest flow rate.

That is, the particle diameter d _i is: d _i = AT + B The solid fraction S _i is S _i = (d _i / d ₀ ) ³ where d ₀ is the initial particle diameter, the solvent viscosity η _Li is η _Li = Aexp (B / T) Here, A and B can be obtained by using constant expressions.

Next, the solid fraction S in the blended coal is determined by the following equation (7) from the solid fraction S _i and the blend R _{i of} each plain coal. S = ΣR _i · S _i ---- (7) Also, the solid fraction of each plain coal S _i , the solvent viscosity η _Li , and the melting rate L
_i and the mixing ratio R _i, the solvent viscosity η in the coal blend
_{L is obtained} by the following equation (8). _{log η L = {Σ (L} i · R i) · log η Li} / (1-S i) ---- (8) Incidentally, the melt index L _i is determined by L _i = 1-S _i .

From the solvent viscosity ηL and the solid fraction S thus obtained, the viscosity η is calculated using the above equation (6). Then, based on the relationship shown in FIG. 1, the calculated viscosity η is converted into a fluidity.

If the above operation is performed until the temperature T exceeds 500 ° C. and the fluidity at various temperatures is obtained, a fluidity curve can be drawn, and at the same time, the maximum fluidity is determined. The reason for estimating the fluidity in the temperature range up to 500 ° C. is that most coal blends have a fluidity of 0 below 500 ° C. because few coals exhibit fluidity above 500 ° C.

[0023]

【Example】

Example 1 Two brands selected from a plurality of types of plain coals shown in Table 1 at a ratio of 1: 1
The flowability curve was estimated according to the procedure shown in FIG. For comparison, a flowability curve was also estimated for the same blended coal by the above-described superposition method. The flow rate curve obtained in this way, together with the result of actual measurement with a Giesler plastometer,
As shown in FIGS. Further, Table 2 shows a comparison between the actually measured value of the maximum flow rate and the estimated value obtained by the above-described weighted average method, superposition method and the present invention method.

[0024]

[Table 1]

[0025]

[Table 2]

Table 2 shows that the weighted average method is compared with the actually measured value, and the estimated value is higher than the actually measured value in all the coal blends. In addition, in the superposition method, particularly as in the case of blended coal (c), the flowability curve approaches the actually measured value as the overlapping of the melting temperature ranges of blended plain coals increases. Therefore, it can be seen that this superposition method is effective when the overlapping of the melting temperature ranges is large. In addition, the solidification point of the blended coal is higher than the actually measured value, and the flow behavior in the solidification process cannot be reflected.

On the other hand, in the method according to the present invention,
Both the flow rate curve and the maximum flow rate agree well with the measured values,
It was confirmed that the two brands of coal blends could be accurately estimated.

Example 2 A fluidity curve was estimated for blended coal obtained by mixing 10-13 brands of plain coal shown in Table 3 according to the procedure shown in FIG. FIGS. 7 and 8 show the thus obtained flowability curves together with the results of actual measurement using a Giesler plastometer.
As shown in the figure, the measured flow rate curve and the estimated flow rate curve were in good agreement, and it was confirmed that the method of the present invention was effective even in the case of multi-brand blended coal.

[0029]

[Table 3]

[0030]

According to the present invention, since the fluidity of the blended coal charged into the coke oven can be accurately estimated, the quality of the produced coke and the precision of clearance management can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between viscosity and fluidity.

FIG. 2 is a flowchart showing a flow rate estimation procedure according to the present invention.

FIG. 3 is a diagram showing a flow rate curve of blended coal.

FIG. 4 is a diagram showing a flow rate curve of blended coal.

FIG. 5 is a diagram showing a fluidity curve of blended coal.

FIG. 6 is a diagram showing a fluidity curve of blended coal.

FIG. 7 is a view showing a flow rate curve of blended coal.

FIG. 8 is a diagram showing a fluidity curve of blended coal.

Continuation of the front page (72) Inventor Kenichi Sorimachi 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Engineering Co., Ltd. (56) References JP-A-62-217141 (JP, A) JP-A-56-163439 (JP, A) Takashi Matsui, Masaru Igawa, Kenichi Sorimachi, "Model for Estimating the Fluidity of Coal Blends Using the Viscosity Evaluation Method for Solid-Liquid Coexisting Phases", Materials and Processes, The Iron and Steel Institute of Japan, November 3, 1995 , Vol. 8, No. 4, pp. 918 (58) Field surveyed (Int.Cl. ⁷ , DB name) G01N 11/00 G01N 33/22 JICST file (JOIS)

Claims (3)

(57) [Claims] 1. A method for determining a fluidity curve of a blended coal based on a viscosity calculated by regarding a blended coal in a molten state as a suspension for a blended coal obtained by blending a plurality of types of plain coals. Characteristic method of estimating fluidity of blended coal. 2. The method for estimating fluidity of a blended coal according to claim 1, wherein the viscosity is calculated from a solvent viscosity and a solid fraction calculated by considering the blended coal as a suspension. 3. The method according to claim 2, wherein the solvent viscosity is calculated from the solvent viscosity, the melting rate, and the mixing ratio of each of the single coals, and the solid phase ratio is calculated from the solid phase ratio and the mixing ratio of each of the single coals. Method for estimating fluidity of blended coal.