JP3129166B2 - Particle Size Estimation Method for Room Coke Oven - 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 particle size of coke produced in a coke oven furnace by numerical calculation.

[0002]

2. Description of the Related Art Conventionally, the production of coke having a large particle size and high strength is indispensable for securing the permeability of a blast furnace and realizing a stable operation. Therefore, various methods for estimating the particle size of coke produced in a coke oven furnace have been studied, and a technology for controlling the particle size of coke has been developed.

[0003] Regarding the estimation of coke particle size, for example, FIG.
As shown in the figure, it was common to empirically create the correlation between the operating rate of the coke oven and the average coke particle size from the analysis of the actual operation during normal heating, and to estimate from this empirical formula. . In addition, coke particle size change was estimated by program heating and changing the mixing conditions.

[0004]

However, in the conventional method of estimating the coke particle diameter based on the operation rate, since the calculation is performed from the actual operation data having a small fluctuation range, when the heating conditions and the blending conditions are largely changed, There is a problem that the estimation accuracy becomes extremely low.

As means for producing large-grain coke in the current coke oven operation, there are a method of lowering the operation rate and a method of blending coal for producing high-strength coke. However, the former has a problem that coke production is reduced, and the latter has a problem that raw material costs are increased.

[0006] In order to solve such a problem, development of a program heating method has been advanced. However, since the conventional particle size estimation method is an operation analysis result during normal heating, there is a problem that the particle size cannot be estimated with the programmed heating method in which the heat history applied to coal and coke changes greatly in a complicated manner. ing.

The problem to be solved by the present invention is that the crack initiation mechanism in the coke lump which determines the particle size of the coke is based on two physical factors: the tensile stress generated in the coke lump, which is a basic phenomenon, and the tensile strength at that time. The purpose is to estimate the coke particle size by analyzing with the dynamic parameters.

[0008]

Means for Solving the Problems The inventors assumed that the particle size of coke is due to the fracture mechanism of coke, and found that the tensile stress generated in the coke mass of the coke oven of the coke oven and the coke Attention was paid to the relationship between the two physical quantities of the tensile strength.

[0009] Then, it was presumed that a crack was generated when the stress generated in the coke mass exceeded the coke strength of the stress generating portion, and that the coke was broken. That is, paying attention to the initial crack generation and the crack propagation, the initial crack generation appears when the balance between the tensile stress and the tensile strength at that position becomes tensile stress> tensile strength.

[0010] As the initial cracks develop, the coke becomes finer and the grain size is determined. The growth of the initial crack depends on the balance between the coke tensile strength and the tensile stress around the crack, and the growth of the crack is promoted as the ratio of the tensile stress to the tensile strength increases.

Accordingly, the inventors have found that the average coke particle size can be estimated from the initial crack initiation temperature and the ratio of the tensile stress to the tensile strength at each position in the furnace, and have reached the following invention.

(1) The invention of claim 1 provides a method for estimating the particle size of coke, comprising the following steps. (A) a step of dividing the cross section of the carbonization chamber of the coke oven of the furnace type in the furnace width direction into a plurality of elements having a predetermined size; and (b) for each of the elements, the coking blended coal in the element. A step of obtaining a ratio of a tensile strength (S) to a tensile stress (F) applied to the coked coal blend in the element with respect to a position in the cross section in the furnace width direction and a predetermined temperature range accompanying a rise in the temperature of the carbonization chamber; And (c) the coke particle diameter (D) from the minimum value ((S / F) _MIN ) of the ratio determined for a predetermined range and a predetermined temperature range in the furnace width direction cross section according to the following equation.
Estimating. D = α × (S / F) _MIN + β (1) where, D: average particle size of coke, S: tensile strength of coked blended coal, F: tensile stress applied to coked blended coal, α, β: constant

(2) The invention according to claim 2 is that the predetermined range in the cross section in the furnace width direction is within a range of 35% of the distance from one heating surface of the carbonization chamber to the center of the furnace width. And the predetermined temperature range is a range from the re-solidification temperature of the coked blended coal to the secondary peak temperature of the linear shrinkage ratio, An estimation method is provided.

(3) The invention according to claim 3 is that the tensile stress (F) applied to the coked coal blend in the element is obtained by combining an unsteady two-dimensional heat transfer equation and a strain equation, And a method for estimating the particle size of coke according to claim 1 or claim 2.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION

[Overview] As shown in FIG. 1, the present invention divides a cross section (thickness is T) of a coke oven into elements of a predetermined size, and mixes the coke blended coal in this element during the coking process. The ratio between the tensile strength and the stress acting on the coked coal blend is determined, and the ratio is determined spatially for each element within a predetermined range in the coke oven width direction and also determined temporally. This is a method of obtaining the coke particle size from the minimum value using the following equation.

D = α × (S / F) _MIN + β (1) where, D: average particle size of coke, S: tensile strength of coked blended coal, F: tensile stress applied to coked blended coal , (S / F) _MIN : minimum value of S / F ratio, α,
β: a constant peculiar to a specific coke making furnace.

[Calculation Procedure] S: The tensile strength of coked coal blend can be obtained as a function of temperature as shown in FIG. 2 by performing the indirect strength test method (JIS A1113) on coke produced from blend coal. it can. Note that S also has a relationship with the reflectance (R ₀ ) of coal (JIS M8816), and the reflectance of blended coal can be obtained by weighted average of the reflectance of each blended coal type.

A specific method for measuring the tensile strength of coke when the blended raw coal becomes coke is described below. Disk-shaped samples (14φ × 8mm) were prepared from coke lump with clear heat treatment conditions (coal brand, maximum heat treatment temperature, etc.) subjected to various heat treatments, and subjected to indirect tensile strength test (JI
SA1113) and calculated by the following equation (2).

[0019] _{σ t (= S) = 2W} / πD o t (2) where, σ _t: indirect tensile strength, W: sample圧裂during load, D
_o : Sample diameter t: Sample thickness

F: The tensile stress applied to the coke blended coal when the coal is carbonized into coke is determined by assuming that the coke cake formed by resolidification of the blended coal in the cross section in the width direction of the coke oven is an elastic body. Incremental strain theory for large deformation thermoelastic materials (thermal stress and thermal fatigue, page 28 and below, Shuji Hira, Nikkan Kogyo Shimbun,
It can be calculated by the finite element method based on (Showa 49). S
Since F and F are functions of the temperature and the position (x, y) in the coke oven, S / F is also a function of the temperature and the position (x, y) in the coke oven.

The specific method of calculating the coke tensile stress will be described below. As a calculation target, the same phenomenon in the coke oven length direction was assumed, and the cross section in the coke oven width direction was considered. The calculation was based on the unsteady two-dimensional heat transfer equation (3) and the strain equation (4). The heat transfer calculation is formulated by the Galerkin method and calculated by the finite element method.The strain calculation assumes that the coke after resolidification is an elastic body, derives the basic formula based on the strain increment theory of the large deformation thermoelastic problem, Analysis was performed by the element method.

Cpρ (∂θ / ∂t) = (∂ / ∂x) (λ (∂θ / ∂x)) + (∂ / ∂y) (λ (∂θ / ∂y)) −−−− ( 3) σ = Eε (4) where Cp: heat capacity, ρ: density, t: time, λ: thermal conductivity, θ: temperature σ: stress, E: Young's modulus, ε: strain amount

Here, Cp (J / kg / K) = 1170.4 (θ ≦ 100 ° C.) 1588.4 (θ = 350 ° C.) 2717.0 (θ = 570 ° C.) 836.0 (θ: 750 ° C.) ) Linear interpolated value of 1755.6 (θ ≧ 1000 ° C.)

Ρ (kg / m ³ ) = 725 (θ ≦ 300 ° C.) 610 (θ = 500 ° C.) Linear interpolation value of 565 (θ ≧ 800 ° C.) λ (W / m / K) = λ ₀ exp ( α (θ−θc)) θc = 70.3 × r + 668.0 (r: average reflectance) λ ₀ = 0.0311 × r + 0.147 α = 5.88 × 10 ⁻⁴ × r + 6.88 × 10 ⁻⁴ (Θ <θc) 5.53 × 10 ⁻⁴ × r + 3.32 × 10 ⁻⁴ (θ ≧ θc) In the above, λ ₀ is the thermal conductivity at the transition temperature, θc is the transition temperature, and α is the temperature coefficient. The calculation of S / F was executed for each time mesh and position mesh.

Next, a desirable range for calculating the S / F will be described. A desirable range is a range where the distance from the furnace wall is up to 35% when the distance between the center line of the cross section of the coke oven in the width direction and the furnace wall is 100%. The reason for this is that the inventors of the present invention investigated coke carbonized under various conditions, and found that the location of the initial cracks in coke was up to 35% of the thickness from the furnace wall to the center line of the furnace. .

Next, a desirable temperature range for calculating the S / F will be described. This temperature range is from the re-solidification temperature of the blended coal to the temperature at which the linear shrinkage shows a secondary peak.
The reason is as follows. FIG. 3 shows the linear shrinkage during the coking process of coal. The linear shrinkage increases from the re-solidification temperature (around 500 ° C.) and increases at the secondary peak (around 750 ° C.).

Therefore, although the growth of the initial crack depends on the generated maximum tensile stress, there is a relation that this maximum tensile stress increases as the linear shrinkage rate increases. Therefore, the desirable temperature range to be calculated is the re-solidification temperature (500 °
This is a temperature range that shows a secondary peak from around (C).

Next, the reason why the coke particle size can be determined from the minimum value of the S / F determined above will be described. S is the tensile strength of the coked coal blend, and F is the tensile stress generated in the coked coal blend within the element.
Theoretically, if S / F ≦ 1, a crack is considered to occur.

However, coke is usually porous, and after cracking, the stress is released. Therefore, in the present invention, the S / F ratio was determined for each element and for each temperature in the furnace, and the relationship between the S / F ratio and the coke particle size was determined based on the minimum value, and a good correlation was found. FIG. 4 illustrates this relationship.

FIG. 4 shows the relationship between (S / F) _MIN and the actually measured average coke particle size when various coals are carbonized into coke by a specific heating pattern, and the above-mentioned formula (1) is satisfied. Is shown. Measured value of coke tensile strength (S)
It is confirmed that the coke particle size can be estimated by finding the minimum value (S / F) of the tensile stress (F) generated in the coke mass calculated by numerical calculation based on the heat transfer equation and the strain equation as basic equations. did.

[0031]

An embodiment of the present invention will be described. Example 1 The linear shrinkage of coke generated by heat treatment varies depending on the properties of the raw coal brand. Therefore, it is expected that the thermal stress profile generated in the coke lump during carbonization greatly differs.

Therefore, first, the influence of the properties of coal on the present estimation method was examined. Coal brands listed in Table 1
Measurement of the average particle size by dry distillation and estimation of the average particle size by carbonization were carried out for five brands (e) to (e) under the conditions of pattern A in FIG. 7 as the heating pattern. The examples were performed in a test furnace capable of faithfully expressing an actual coke oven.

FIG. 5 shows the results of the above experiment. FIG. 5 shows that the coke particle size can be estimated by the method of the present invention. The above equation (1) was used as the equation for estimating the average coke particle size. Thus, for various coal properties,
This shows that the estimated value is in good agreement with the measured value.

[0034]

[Table 1]

Example 2 It is considered that the thermal stress profile generated in the coke lump is complicatedly different depending on the heating pattern during the carbonization of each coal, and the crack generation behavior is different. Therefore, the effect of the heating pattern on the estimation method was examined. Under the conditions of brand a in Table 1 as a coal brand and patterns A to C in FIG. 7 as a heating pattern, actual measurement of the average particle size by dry distillation and estimation of the average particle size by calculation were performed.

FIG. 6 shows the relationship between the actually measured value and the estimated value. The estimated values and the actually measured values of these various heating patterns are in good agreement. As described above, it was confirmed that the estimated values and the actually measured values were in good agreement in the case of various coal properties and various types of program heating.

[0037]

According to the present invention, it is possible to estimate the particle size of the produced coke, given the type of coal blend and the heating pattern in advance. As a result, large particle size coke can be easily produced. Therefore, sufficient ventilation resistance can be ensured in the blast furnace, the blast furnace operation is always stable, and the production efficiency of pig iron is greatly improved.

[Brief description of the drawings]

FIG. 1 is a view showing an example in which a cross section of a chamber coke oven is divided for calculation by a finite element method.

FIG. 2 is a diagram showing the tensile strength of coal (coke) in the process of heating the coal.

FIG. 3 is a diagram showing a change in a linear shrinkage rate in a heating process of coal.

FIG. 4 is a diagram showing a relationship between a minimum value of a ratio (S / F) to a tensile stress (F) generated in a coke lump and a mean particle size of coke in a coke oven furnace.

FIG. 5 is an example of estimating the average particle size of coke for various coal brands by the method of the present invention.

FIG. 6 is a diagram showing an example in which the average particle size of coke is estimated for various heating patterns.

FIG. 7 is a diagram illustrating an example of a program heating method of coke.

FIG. 8 is a diagram showing a correlation between a coke oven operating rate and an average particle size of coke.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-106691 (JP, A) JP-A-3-229791 (JP, A) JP-A-4-304294 (JP, A) JP-A-4- 304295 (JP, A) JP-A-5-223725 (JP, A) JP-A-5-230462 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C10B 45/00 C10B 47 / 10 C10B 57/00

Claims (3)

(57) [Claims] 1. A method for estimating a particle size of coke, comprising the following steps. (A) a step of dividing the cross section of the carbonization chamber of the coke oven of the furnace type in the furnace width direction into a plurality of elements having a predetermined size; and (b) for each of the elements, the coking blended coal in the element. A step of obtaining a ratio of a tensile strength (S) to a tensile stress (F) applied to the coked coal blend in the element with respect to a position in the cross section in the furnace width direction and a predetermined temperature range accompanying a rise in the temperature of the carbonization chamber; And (c) the coke particle diameter (D) from the minimum value ((S / F) _MIN ) of the ratio determined for a predetermined range and a predetermined temperature range in the furnace width direction cross section according to the following equation.
Estimating. D = α × (S / F) _MIN + β where D: average particle size of coke, S: tensile strength of coked coal blend, F: tensile stress applied to coked coal blend, α, β: constant 2. A predetermined range in the cross section in the furnace width direction is a range within 35% of a distance from one heating surface of the coking chamber to a center of the furnace width, and the predetermined temperature is within a range. The method according to claim 1, wherein the range is from a re-solidification temperature of the coked coal blend to a secondary peak temperature of linear shrinkage. 3. The non-stationary two-dimensional heat transfer equation and strain equation are used to determine the tensile stress (F) applied to the coked coal blend in the element by the finite element method. The method for estimating the particle size of coke described in (1).