JPH08277392A - Estimation of gas permeability of softened coal - Google Patents

Abstract

PURPOSE: To reduce the maintenance cost of a coke oven and prolong the life of the oven by measuring the gas permeability of coal in softened and molten state and efficiently estimating the gas permeability of softened coal at an arbitrary position in the coke oven from a relational diagram between the gas permeability and a compression ratio. CONSTITUTION: The gas permeability of softened and molten coal to be charged to a coke oven is measured to prepare a relational diagram between the gas permeability and a compression ratio of the coal expressed by formula, C=Vo /V [C is compression ratio (-); Vo is specific volume of coal (cm<3> /g-coal) in freely expanded state; V is specific volume of coal (cm<3> /g-coal) at the time of measuring the gas permeability]. The gas permeability of softened coal at an arbitrary position in the coke oven in carbonization is estimated from the density of the charged coal at the above position and the relational diagram. Preferably, the relationship between the coal nature and the gradient K of the straight line of the relational diagram of the gas permeability of the coal and the compression ratio is determined beforehand and the gas permeability of the softened coal is estimated from the nature of the coal to be charged into the coke oven and the relationship between the gradient K and the coal nature.

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 gas permeation coefficient of softened coal in the coal carbonization process in a coke oven.

[0002]

During the process of producing coke from coal, heated coal expands and exerts pressure on the wall of the coke oven. This pressure is called expansion pressure, but if the expansion pressure is high, there is a risk of damaging the coke oven. Therefore, controlling the expansion pressure to be equal to or less than the limit value based on the strength of the coke oven body is an important issue in coke oven operation.

It has been conventionally known that many coals having a high degree of coalification represented by volatile matter, carbon content, average reflectance, etc. have a high expansion pressure. Therefore, by setting an upper limit on the degree of coalification of the coal used in the coke oven, it has been attempted to control the expansion pressure to be equal to or lower than the limit value based on the strength of the furnace body of the coke oven. However, some coals with a high degree of coalification have a relatively low expansion pressure, and the expansion pressure cannot be determined only by the degree of coalification.

In addition, there is an example in which the expansion pressure is tried to be organized by the caking parameters such as the total expansion coefficient and the maximum fluidity.
Not well related.

As described above, since the expansion pressure cannot be predicted from the properties of coal, in order to avoid damage to the coke oven, the coal is actually carbonized in the test furnace before use in the coke oven to adjust the expansion pressure. Need to measure. For the expansion pressure measurement, it is necessary to use a movable wall furnace whose one side wall is movable, but this movable wall furnace is expensive. In addition, the amount of dry distillation of coal is relatively large (about 300 kg to 400 kg), the measuring method is not simple, and it is not possible to quickly cope with the blending of raw coal and the change of dry distillation conditions.

Therefore, as a method of predicting the expansion pressure from the coal properties and carbonization conditions, the expansion pressure in the coal carbonization process is determined by using the gas permeability coefficient of softened coal, the thickness of the softened coal layer and the gas generation rate from the softened coal layer. A method of predicting the change over time has been devised, and is disclosed in, for example, Japanese Unexamined Patent Publication No. 5-340937. The gas permeability coefficient is an index of the ease of passage of gas in the coal bed, and the ventilation resistance of the softened coal bed is determined from this and the thickness of the softened coal bed. The gas pressure in the softened coal bed is determined by the balance between the ventilation resistance and the gas generation rate. This gas pressure is transferred to the furnace wall of the coke oven through the coke and becomes an expansion pressure. The gas permeability coefficient of softened coal varies greatly with the density of the same coal. Therefore, in this expansion pressure prediction method, the density of the softened coal bed at each time is calculated by considering the mass transfer in the carbonization process, and the gas permeation coefficient and the softened coal bed density obtained by measurement in advance are calculated. The relationship is used to obtain the gas permeability coefficient. The gas permeability coefficient can be measured, for example, by Nomura et al.
Page, 1992 issued by the Iron and Steel Institute of Japan), by measuring the pressure loss in the softened coal bed.

Therefore, in this inflation pressure estimation method,
It is necessary to measure the gas permeability coefficient of the softened coal and determine the relationship with the softened coal layer density, but the mode of change of the gas permeability coefficient with the density does not have a linear relationship and differs depending on the coal. Therefore, it is necessary to measure the change in the gas permeation coefficient depending on the density for all the coals used.

Further, the change of the gas permeation coefficient with the density is not linear, and it is difficult to estimate the gas permeation coefficient at an arbitrary density by making a regression equation from several measured values.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a simple method for estimating the gas permeation coefficient of softened coal in order to solve the problems in the prior art as described above.

[0010]

In order to solve the above-mentioned problems, the present invention relates to a coal charged into a coke oven,
Measuring the gas permeability coefficient of coal in the softened and molten state,
A relational diagram with the compression ratio shown in the equation (1) is created in advance, and from the density of the coal charged in the coke oven and the relational diagram, the softened coal of the softened coal in the coke oven at the time of carbonization is shown. It is a method of estimating a gas permeability coefficient of softened coal, which is characterized by estimating a gas permeability coefficient.

C = V ₀ / V (1) where C: compression ratio [−], V ₀ : coal specific volume at free expansion [cm ³ / g-coal], V: at gas permeability measurement Is the specific volume of coal [cm ³ / g-coal].

Further, the relationship between the straight line gradient k in the relational diagram of the gas permeation coefficient of the coal and the compression ratio and the coal property is obtained in advance, and the coal property of the coal charged into the coke oven and the above-mentioned slope are obtained. Using the relationship between k and coal properties, the gas permeation coefficient of the softened coal at the location in the coke oven during carbonization is estimated from the density of the arbitrary location of the coal charged in the coke oven. This is a method for estimating the gas permeability coefficient of coal.

Here, the coal property indicates the degree of coalification such as average reflectance and the caking property.

[0014]

[Operation] When coal is charged into the coke oven and the carbonization starts,
A coal softened layer is formed near the furnace wall, and this softened layer apparently moves from the furnace wall side to the center of the carbonization chamber, and carbonization proceeds. Although gas is generated in the softened layer, the softened layer has a low gas permeation coefficient, so that the gas cannot easily escape to the outside of the layer and a gas pressure is generated. This gas pressure is the cause of the expansion pressure of coal. Therefore, it is necessary to accurately know the gas permeability coefficient of the softening layer in order to predict the expansion pressure.

The present inventor has studied the gas permeation coefficient of softened coal and clarified the cause of the low gas permeation coefficient of softened coal. As a result, the reciprocal of the gas permeation coefficient of softened coal (corresponding to ventilation resistance) is calculated as the compression ratio. It was found that a straight line was obtained for all coals when plotting against, and the estimation method was invented.

When the coal particles are softened, they are expanded by the gas generated by thermal decomposition. The gas permeability coefficient is high when the coal is expanded freely. However, in the coke oven, the volume of the softened coal bed is limited to a certain amount and the bed as a whole cannot expand. Therefore, coal particles have no choice but to expand into voids between the particles. Therefore, the volume of voids between particles is reduced. This reduction in porosity reduces the gas permeability coefficient of the softened layer.

As described above, when the expansion of the coal softening layer is restricted, the gas permeability coefficient becomes low. Based on this idea, Nomura et al. (Materials and Process, Vol. 5, p. 92, 1992)
The gas permeation coefficient was measured using the method of measuring the pressure loss in the softened coal bed (published by the Iron and Steel Institute of Japan), and the relationship between the gas permeation coefficient and the density of the softened coal bed was examined. For some coals, the gas permeation coefficient was measured while varying the specific volume (reciprocal of density) of the coal, and the relationship between the compression ratio and the gas permeation coefficient defined by the following equation (1) was investigated.

C = V ₀ / V (1) where C is the compression ratio [−], V ₀ is the specific volume of coal in free expansion [cm ³ / g-coal], and V is the gas permeability coefficient. The specific volume of coal [cm ³ / g-coal] at the time of measurement is shown. The compression ratio is a value indicating how much the coal is compressed when the gas permeation coefficient is measured, as compared with the case where the gas can freely expand. Specific volume of coal during free expansion V ₀
Can be determined by the following equation (2) from the expansion rate b [%] measured by the expansion test method described in JIS M8801.

V ₀ = πd ² L (100 + b) / 400W (2) Here, π is the circular constant, d is the inner diameter [cm] of the expansion coefficient measuring thin tube, and L is the coal filling height [cm]. ], W represents the amount of coal charged [g], respectively. V is the reciprocal of the density of the coal based on the weight of the charged coal when the coal is softened and expanded, that is, the reciprocal of the coal density of the softened layer.

When the reciprocal of the measured gas permeation coefficient (corresponding to ventilation resistance) is taken on the vertical axis and plotted against the compression ratio,
For both coals, it became a straight line. Further, all of these straight lines passed through the point (1,0).

From these results, it can be considered that when the compression ratio is 1, that is, when the coal can freely expand, the gas easily escapes and the gas permeability coefficient is very large, but the ventilation resistance increases due to the restriction of expansion. .

Therefore, the change of the gas permeation coefficient due to the compression ratio is expressed by the following equation (3), where k is a constant.

1 / P = k (C−1) (3) Here, P represents a gas permeability coefficient [m ² ] and C represents a compression ratio [−].

From the above results, the gas permeation coefficient of coal was measured by changing the specific volume for several kinds, and the obtained gas permeation coefficient was plotted against the compression ratio defined by the equation (1). The gas permeation coefficient at an arbitrary compression ratio can be estimated from the straight line of the equation (3). Therefore, it is possible to estimate the gas permeation coefficient at an arbitrary density. Therefore, using this, for example, the expansion pressure can be estimated by the expansion pressure estimation method disclosed in Japanese Unexamined Patent Publication No. 5-340937.

Further, the difference depending on the coal type can be summarized in two, namely, the straight line gradient k of the equation (3) when plotted as described above and V ₀ (coal specific volume during free expansion). V ₀ can be obtained from the expansion coefficient b [%] measured by the expansion test method described in JIS M 8801 by the above formula (2). It was found that the slope k has a correlation with properties such as the average reflectance of coal and the degree of coalification such as volatile matter. Therefore, if the relationship between k and these coal properties is obtained, k can also be estimated only from the coal properties. That is, it is possible to estimate the gas permeability coefficient at an arbitrary density only from the coal properties without actually measuring the gas permeability coefficient. Using this, for example, the expansion pressure can be predicted by the expansion pressure measuring method disclosed in the above-mentioned JP-A-5-340937.

[0026]

【Example】

Example 1 Nomura et al. (Materials and Process, Vol. 5, p. 92, issued by the Iron and Steel Institute of Japan, 1992) measure the pressure loss in a softened coal seam, while varying the specific volume of coal for some coals. The gas permeability coefficient was measured and the relationship between the compression ratio and the gas permeability coefficient was investigated.

As a result, in FIG. 1, coal A (average reflectance 1.65), coal B (average reflectance 1.32), coal C
As shown in the example of (average reflectance 1.12), when the reciprocal of the gas permeation coefficient (corresponding to ventilation resistance) was taken on the vertical axis and plotted against the compression ratio, a straight line was obtained for all coals. Further, all of these straight lines pass through the point (1,0).

Therefore, the gas permeation coefficient at an arbitrary compression ratio can be estimated from this straight line. The compression ratio is
There is a relation of V, which is the reciprocal of the coal density of the softening layer, with the equation (1). Therefore, the gas permeation coefficient at an arbitrary density can be estimated. Therefore, using this, for example, by the expansion pressure estimation method disclosed in Japanese Patent Laid-Open No. 5-340937, the density of the softened coal layer at each time is calculated by considering the mass transfer in the carbonization process. The expansion pressure can be accurately estimated by estimating the gas permeation coefficient at the calculated density by the method of the present invention.

For example, in the case of coal A, the relationship between the gas permeation coefficient P and the compression ratio C is expressed by the following equation (4) from FIG.

1 / P = 12.0 × 10 ¹⁵ × (C-1) (4) Further, the coal specific volume V ₀ at the time of free expansion of the coal A is 2.25.
It was [cm ³ / g-coal]. When this coal A is charged into a coke oven at a density of 0.8 [g-coal / cm ³ ], a softened coal layer near the furnace wall is obtained by the expansion pressure estimation method disclosed in Japanese Patent Laid-Open No. 5-340937. Is calculated to be 1.25 [cm ³ / g-coal], and therefore the gas permeation coefficient is 1.04 × 10 ⁻¹⁶ [m ^2] using the equations (1) and (3). ] Is calculated. Similarly, in the center of the carbonization chamber, the specific volume V of the softened coal layer is calculated to be 1.65 [cm ³ / g-coal],
Therefore, the gas permeability coefficient is calculated as 2.29 × 10 ⁻¹⁶ [m ² ] by using the equations (1) and (4).

Example 2 In the same manner as in Example 1, the gas permeation coefficient was measured for various coals with various specific volumes, and the relationship between the compression ratio defined by the equation (1) and the gas permeation coefficient was investigated. . When the reciprocal of the gas permeation coefficient (corresponding to ventilation resistance) was taken on the vertical axis and plotted against the compression ratio, a straight line was obtained for all coals.

As shown in FIG. 2, it was found that the slope of this straight line has a certain relationship with the degree of coalification of coal (the average reflectance Ro was used in FIG. 2). Therefore, without measuring the gas permeation coefficient, it is possible to estimate the gas permeation coefficient at an arbitrary density based only on the coal properties. Therefore,
Using this, for example, by the expansion pressure estimation method disclosed in Japanese Patent Laid-Open No. 5-340937, the density of the softened coal layer at each time is calculated by considering the mass transfer in the carbonization process, and calculated. The expansion pressure can be accurately estimated by estimating the gas permeation coefficient at the obtained density by the method of the present invention.

For example, referring to FIG. 2, the relationship between k and the average reflectance Ro of coal is expressed by the following equation (5).

Logk = 3.350 × Ro + 11.22 (5) By using this formula, the k of an arbitrary coal can be estimated by measuring the average reflectance Ro of the coal. For example,
The average reflectance of Coal D was 1.35 [%]. Therefore, k of this coal is calculated as 5.52 × 10 ¹⁵ from the equation (5). The specific volume V ₀ of the coal D when it was freely expanded was 2.48 [cm ³ / g-coal]. Therefore,
This coal D was placed in a coke oven at a density of 0.7 [g-coal /
[cm ³ ], the specific volume V of the softened coal layer near the furnace wall is 1.43 [cm ³ / g-co] according to the expansion pressure estimation method disclosed in JP-A-5-340937.
Therefore, the gas permeation coefficient is calculated as 2.47 × 10 ⁻¹⁶ [m ² ] using the equations (1) and (3). Similarly, in the center of the carbonization chamber, the specific volume V of the softened coal layer is 1.95 [cm ³ / g-coal].
Therefore, the gas permeation coefficient is calculated by the equations (1) and (3).
It is calculated as 6.67 × 10 ⁻¹⁶ [m ² ] by using the equation and.

[0035]

According to the present invention, the gas permeation coefficient of softened coal can be accurately and quickly estimated. This made it possible to accurately estimate the expansion pressure before charging coal into the coke oven.

As a result, the damage of the coke oven can be avoided, the repair cost of the coke oven can be reduced and the life of the coke oven can be extended, and its economic effect is great.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the compression ratio of coal and the reciprocal of the gas permeation coefficient.

FIG. 2 is a diagram showing the relationship between the degree of coalification (average reflectance Ro) of coal, the compression ratio of coal, and the slope k of the straight line of the reciprocal of the gas permeation coefficient.

Claims (2)

[Claims] 1. The gas permeation coefficient of coal in a softened and molten state is measured for coal charged into a coke oven, and (1)
A relationship diagram with the compression ratio shown in the formula is created in advance, and from the relationship diagram and the density of an arbitrary portion of the coal charged in the coke oven,
Method for estimating gas permeation coefficient of softened coal characterized by estimating gas permeation coefficient of softened coal at the above-mentioned location in coke oven during carbonization C = V ₀ / V (1) where C: compression ratio [−] V ₀ : Specific volume of coal at free expansion [cm ³ / g-coa
l] V: Specific volume of coal when measuring gas permeation coefficient [cm ³ / g-c
oal] 2. The coal property of the coal to be charged into the coke oven is obtained in advance by previously obtaining the relationship between the straight line gradient k in the relationship diagram between the gas permeability coefficient and the compression ratio of the coal according to claim 1 and the coal property. And the gradient k and the coal properties, the gas permeability coefficient of the softened coal at the location in the coke oven during carbonization is estimated from the density of the arbitrary location of the coal charged in the coke oven. Method for estimating gas permeation coefficient of softened coal.