JP6680163B2 - Coke particle size estimation method - Google Patents

Description

  The present invention relates to a method for estimating the particle size of coke formed by carbonizing carbon in a coke oven.

  When manufacturing coke for a blast furnace with a chamber furnace type coke oven, it is necessary to keep the produced coke particle size (average particle size) at a certain value or more at all times in order to ensure air permeability of the blast furnace and realize stable operation. It is essential. Therefore, various methods for estimating the particle size of the coke produced in the chamber-type coke oven have been studied.

For example, in Patent Document 1 by the present inventors, a temperature T is set in a range of not less than the resolidification temperature of coal and not more than 1000 ° C., and coal for charging a coke oven is heated to a temperature T in a container to obtain a resolidification temperature. The value obtained by dividing the volume difference or length difference of the contents at temperature and temperature T by the volume or length at the resolidification temperature is obtained as the shrinkage rate of the coke generated from the coal, and the obtained coke shrinkage rate of the plain coal. Is calculated by weighted averaging with the blending ratio to obtain the coke shrinkage of the blended coal, and the relationship between the coke particle size of various blended coals and the coke shrinkage of the blended coal is determined in advance as a linear function, and the candidate blended coal is obtained. The method for estimating the coke particle size, which is characterized in that the coke particle size of the candidate coal blend is estimated by substituting the coke shrinkage ratio of No. 1 into the above function.
In this estimation method, coal is continuously heated to a temperature above the resolidification temperature to 1000 ° C., the coke shrinkage is measured from the change in the volume at the resolidification temperature and 1000 ° C., and a high correlation is found between the shrinkage and the coke particle size. Since the relationship is obtained, the coke particle size can be estimated with high accuracy using the obtained relationship.

JP, 2005-232349, A

However, in recent years, against the backdrop of soaring coal prices, the use of non-slightly coking coal, which has not been used as a raw material for producing coke, has been required.
Therefore, it was examined whether the method for estimating the coke particle size described in Patent Document 1 can be applied to a blended coal containing a large amount of non-fine coking coal.
Here, non-slightly caking coal means coal having a volatile content of 35% by mass or more, coal having a total expansion coefficient of 10% or less measured by the JIS M 8801 expansion test method, and volatile content of 35% by mass or more. And a coal having a total expansion coefficient of 10% or less measured by the JIS M 8801 expansion test method, and one or two or more of these coals are used as non-fine coking coal.

  Patent Literature 1 describes a plain coal that forms coke by producing coke using coke containing 30% by mass or more of non-caking coal and measuring the average particle size of the coke. As described above, the shrinkage rate of plain coal is obtained from the change in the volume of the contents at the time of re-solidification and the volume of the contents at the time of 1000 ° C. by heating to 1000 ° C. The weighted average was calculated to obtain the shrinkage ratio of the blended coal.

Fig. 1 shows the relationship between the shrinkage ratio of the coal blend obtained this time and the measured coke particle size of the coke produced from the coal blend. Further, in FIG. 1, a straight line which is an estimation formula for estimating the coke particle size from the shrinkage ratio of the blended coal shown in FIG. 6 of Patent Document 1 is also shown.
In the blended coal that uses 30% or more of non-slightly caking coal, the corresponding points of the shrinkage rate of the blended coal and the coke particle size come to be located outside the conventional estimation formula, and obtained in Patent Document 1. There is a case where sufficient estimation accuracy cannot be obtained with the estimated formula.

For stable operation of the blast furnace, it is necessary to maintain the target coke particle size. Therefore, it is necessary to accurately estimate the coke particle size so that the target coke particle size can be secured even if 30% or more of non-slightly caking coal is used as the blended coal. Therefore, there is a demand for a method of estimating the coke particle size more accurately than ever, regardless of the conditions of the coal blend.
Therefore, an object of the present invention is to make it possible to more accurately estimate the coke particle size even when non-slightly caking coal is used as a part of blended coal.

  The present inventor examined factors that determine the coke particle size under the condition where a large amount of non-caking coal is used. As a result, under the condition that a large amount of non-caking coal is used, the coke particle size is governed by the shrinkage ratio in the region of resolidification temperature to (600 ± 30) ° C. during coal carbonization, and heating the coal. It was found that the coke particle size can be accurately estimated by using the shrinkage ratio calculated from the change in volume measured at that temperature.

The gist of the present invention made as a result is as follows.
( I ) A non-fine coking coal which satisfies at least one of a volatile content of 35% by mass or more and a total expansion coefficient of 10% or less measured by an expansion test method defined by JIS M 8801 is A weighted average shrinkage of a coal blend obtained by weighted averaging the shrinkage rates of the plain coals that make up the coal blend, which is a method of estimating the coke particle size when coke is produced using the blended coal blended in an amount of more than mass%. The relationship between the rate and the coke particle size is obtained in advance, the weighted average shrinkage of the blended coal to be estimated is obtained, and the coke particle size estimation method for obtaining the coke particle size of the blended coal to be estimated from the relationship is given.
The shrinkage rate of the plain coal constituting the blended coal was changed by changing the volume of the plain coal at the resolidification temperature and the temperature within the range of (600 ± 30) ° C. when the plain coal was heated in a container. A method for estimating the coke particle size, which is characterized in that it is obtained from the amount.

( II ) As a relationship between the weighted average shrinkage rate of the above blended coal and the coke particle size,
When the non-caking coal ratio to be blended is 60% or less, the relationship represented by the following formula (1) is obtained in advance, and when the non-caking coal ratio exceeds 60%, the following (2) is used. The coke particle size estimating method as described in (I) above, wherein the relationship represented by the formula is obtained in advance.
Coke particle size of blended coal = a + b x coke shrinkage of blended coal (1)
Coke particle size of blended coal = a + b x coke shrinkage of blended coal
+ Cx (Non-lightly caking coal ratio-60) (2)
Here, a and b are coefficients determined by regression analysis from measured values of coke particle diameter and coke shrinkage, and c is a coefficient similarly determined by further considering the non-caking coal ratio.

  The coke particle size refers to the average particle size obtained from the particle size distribution measured by JIS K2151 "Cokes Testing Method". In the case of coke produced in a test furnace, the particle size distribution of the coke after carbonization was measured without shuttering, and a sample for drum test was sampled. The diameter is used.

  According to the present invention, the coke particle size can be more accurately predicted even when non-slightly caking coal is used as a part of blended coal, which can contribute to stable operation of the blast furnace.

It is a figure which shows the relationship between the shrinkage rate weighted average and the coke particle diameter of the blended coal calculated | required according to patent document 1 about the blended coal containing 30 mass% or more of non-caking coal. It is a figure which shows the relationship between the shrinkage-weighted average of the blended coal and the coke particle diameter which were calculated | required according to this invention. It is a figure which shows the change of the shrinkage coefficient above the re-solidification temperature at the time of heating coal to 1000 degreeC.

The present inventor examined factors that determine the coke particle size under the condition where a large amount of non-caking coal is used.
Coal softens and melts at around 400 ° C. in the temperature rising process and then resolidifies, but contracts after softening and melting.
Regarding this shrinkage, when looking at the transition of the shrinkage coefficient (1 / K) of the coke which represents the change in shrinkage rate per unit temperature change, the shrinkage coefficient is the largest immediately after the re-solidification temperature, as shown in FIG. It exhibits a minimum value at around 600 ° C and a maximum value at about 700 ° C.

The grain size of coke is considered to be determined by cracks generated in the coke, and the cracks are generated by thermal stress caused by strain difference (nonuniform shrinkage) in the coke block. The strain that causes such thermal stress is considered to be caused by shrinkage behavior that differs depending on the temperature difference in the coke mass.
Therefore, it is considered that the difference in the shrinkage coefficient in the coke mass immediately after the re-solidification temperature, which has a large shrinkage coefficient, has a great influence on the crack of the coke, that is, the coke grain size.

In Patent Document 1, the shrinkage ratio in the region of 1000 ° C. from the resolidification temperature is obtained, and the shrinkage ratio in the region of temperature lower than 1000 ° C. from the resolidification temperature (for example, 600 ° C. or 800 ° C.) is Not considered at all.
Therefore, the shrinkage ratio was measured in the range of various temperatures below the re-solidification temperature to 1000 ° C under the condition that a large amount of non-caking coal was used, and the relationship with the coke particle size was obtained. Was newly found to be strongly controlled by the shrinkage ratio at the resolidification temperature to (600 ± 30) ° C.

The results obtained by the examples described below are shown in FIG. 2. The coke of each of the obtained plain coals was obtained by obtaining the shrinkage ratio between the resolidification temperature and 600 ° C. of the plain coals constituting the blended coal. The shrinkage rate is weighted averaged according to the blending ratio of the blended coal to obtain the weighted average shrinkage rate of the blended coal, and the coke particle size when the blended coal is subjected to carbonization to form coke.
It has been shown that there is a good relationship between the weighted average shrinkage rate (%) of the blended coal and the coke particle size (mm), which is represented by a linear function of the following equation (1).
Coke particle size of blended coal = a + b x coke shrinkage of blended coal (1)

As described above, the non-fine coking coal is a coal that satisfies at least one of the conditions that the volatile content is 35% by mass or more, or the total expansion coefficient is 10% or less. , The re-solidification temperature decreases. Therefore, in particular, the shrinkage rate at a temperature near 600 ° C. at which the shrinkage coefficient has a minimum value from the resolidification temperature has a large difference depending on the coal type. On the other hand, the difference in the shrinkage ratio from around 600 ° C to 1000 ° C depending on the type of coal is not large.
Further, in the case of non-slightly caking coal having a total expansion coefficient of 10% or less, the difference in resolidification temperature depending on the type of coal becomes larger than that of coal having a total expansion coefficient of more than 10%. This is probably because the melting of coal ends at a low temperature and, as a result, resolidification starts at a low temperature.

Therefore, in the non-lightly caking coal, since there is a large difference between the resolidification temperature and the vicinity of 600 ° C. depending on the kind of the coal, the blending coal containing the non-lightly caking coal in an amount of 30% by mass or more, It is considered that the estimation accuracy of the coke grain size is improved by using the shrinkage ratio at the temperature at which the shrinkage coefficient shows the minimum value from the resolidification temperature.
Then, since the temperature at which the shrinkage coefficient exhibits a minimum value varies depending on the brand of coal, it was found by experiments that it is appropriate to measure the shrinkage ratio in the range of (600 ± 30) ° C. from the resolidification temperature.

Furthermore, as a result of investigating the influence of the non-lightly cohesive coal ratio, up to 60% by mass, good results are obtained in the relationship of the above formula (1), but the non-lightly cohesive coal ratio exceeds 60 mass%. Then, the deviation from the measured value will occur.
To this end, it was also confirmed that it is effective to use the following equation (2), which is obtained by adding a correction term based on the non-slightly caking coal ratio (mass%) to the above equation (1).
Coke particle size of blended coal = a + b x coke shrinkage of blended coal
+ Cx (Non-lightly caking coal ratio-60) (2)

The method described in Patent Document 1 can be used to measure the shrinkage ratio.
That is, the coal to be measured is charged into a cylindrical container whose upper side is open, and the piston is arranged in contact with the upper end of the charged coal. This piston is supported so that it can rise and fall as the coal expands and contracts. In the measurement, the container is heated by a heater, and the position of the upper end of the piston in the temperature rising process is measured to measure the volume change of the content in the container, and the shrinkage rate is calculated.

In the calculation of the shrinkage rate, the change in the length L of the coal is obtained from the position of the piston, the length of the content at the resolidification temperature is LR, the length of the content at the temperature T is LT, and the shrinkage rate R is It can be calculated by the following formula.
R = (LR-LT) / LR
Further, by converting the change in length into a change in volume, the volume of the contents at the re-solidification temperature is VR, and the volume of the contents at the temperature T is VT, which can be obtained by the following formula.
R = (VR-VT) / VR

A procedure for estimating the coke particle size using the shrinkage obtained by the above-described method for measuring the shrinkage of coal will be described.
(A) The coke shrinkage rate of each plain coal used as the blended coal is determined. At that time, as described above, the plain coal is put into a container and heated, and the shrinkage rate is obtained from the amount of change in the volume of the content in the container from the resolidification temperature to (600 ± 30) ° C.

(B) Various coal blends are subjected to dry distillation to measure the coke particle size. At the same time, the shrinkage ratios of various blended coals are determined by weighted averaging the shrinkage percentages of the plain coals with the blending ratios.
(C) The relationship between the weighted average shrinkage of the coal blend and the coke particle size is determined.
The coke particle size of the blended coal can be determined as a function of the obtained weighted average shrinkage of the blended coal. For example, it is expressed as a linear function of the weighted average shrinkage ratio of the blended coal as in the following formula (1).
Coke particle size of blended coal = a + b × weighted average shrinkage of blended coal (1)
The coefficients a and b of the equation can be determined by using a method such as regression analysis using the coke particle diameter and the coke shrinkage ratio data obtained in the step (b).
(D) The weighted average shrinkage rate of the blended coal is calculated by obtaining the shrinkage rate in the same manner as in (a) for each of the plain coals constituting the blended coal whose coke particle size is to be estimated, and performing the weighted average by the blending ratio. To calculate.
(E) From the calculated weighted average shrinkage ratio of the blended coal, the coke particle size of the blended coal is determined using the relationship determined in the step (c).
Although the coke particle size can be accurately estimated by the above procedure, when the non-fine coking coal ratio exceeds 60%, the gap between the measured value and the estimated value tends to increase. In that case, the following equation (2) is used in the step (c).
Coke particle size of blended coal = a + b x coke shrinkage of blended coal
+ Cx (Non-lightly caking coal ratio-60) (2)
The coefficient c of the equation is also a coefficient determined in the same manner as a and b by taking into account the data of the coke particle size and the coke shrinkage ratio and the data of the non-slightly caking coal ratio.

  The present invention is configured as described above. Next, the present invention will be described in more detail with reference to examples. The present invention is not limited to the contents described in these examples.

(Creation of relationship between shrinkage-weighted average value and coke average particle size)
The coal was placed in a container and heated, and the shrinkage ratio from the resolidification temperature to 600 ° C. was measured for each brand of coal. Coke was prepared from blended coal containing blended coal whose shrinkage was measured, and the coke particle size was measured. In addition, for the blended coal, the weighted average shrinkage was calculated by weighting the shrinkage according to the blending ratio. The relationship between the weighted average shrinkage ratio and the average coke particle size of the obtained blended coal is shown in FIG. It should be noted that, in the blended coal, blended coal containing non-fine coking coal having a volatile content of 35% by mass or more or total expansion rate of 10% or less and 30% or more and 60% or less, and non-fine coking coal is less than 30%. A blended coal (including 0%) was used.

As shown in FIG. 2, a strong correlation was obtained between the weighted average shrinkage of the coal blend and the average coke particle size. Further, the following relational expression (1) ′ based on the above expression (1) was obtained.
Coke particle size = 123.12-16.14 x weighted average shrinkage of blended coal (1) '
The correlation coefficient R2 of this function was 0.98, and the accuracy was remarkably improved in the case of the present invention for blended coal containing 30% or more of non-slightly caking coal. Further, in the data of FIG. 6 of Patent Document 1, since the correlation coefficient R2 can be calculated as 0.86, when the shrinkage ratio is obtained by the method of the present invention, when the non-slightly caking coal content is low. However, the result is that the accuracy is improved.
Further, in the case where the above-mentioned blended coal contains non-fine coking coal having a volatile content of 35 mass% or more or a total expansion coefficient of 10% or less in excess of 60%, the above formula (2) is used. The following relational expression (2) ′ based on the above is obtained.
Coke particle size = 123.12-16.14 x weighted average shrinkage rate of blended coal +
[−0.1 × (non-caking coal ratio-60)] ... (2) '

(Estimation of average particle size of coke)
Next, the average coke grain size estimated using the above relationship was compared with the actual measurement value.
Using coals A to E shown in Table 1, blended coals TZ shown in Table 2 were obtained. Coal D is non-caking coal having a total expansion rate of 10% or less, and coal E is a non-caking coal having a volatile content of 35 mass% or more. Table 2 shows the shrinkage rates of the coals A to E from the solidification temperature to 600 ° C.

The blended coals TZ were subjected to carbonization to prepare coke, and the coke particle size was measured. In addition, the shrinkage ratios of the respective coals shown in Table 2 were used, and the weighted average shrinkage ratios of the blended coals TZ were calculated by weighted averaging based on the blending ratio (mass%) of Table 2.
The coke particle size was estimated using the relational expression (1) ′ from the weighted average shrinkage rates of the obtained blended coals TZ.

  Table 2 shows the measured and estimated values of the coke particle size for the blended coals TZ, and good agreement was obtained in all cases. However, in the blended coals Y and Z having a non-caking coal ratio of more than 60%, the difference between the actually measured value and the estimated value of the coke particle size is slightly large. By using the formula) ′, an estimated value of 33.5 mm was obtained for the blended coal Y and 33.0 mm for the blended coal Z, and a result in agreement with the actual measurement value was obtained.

Claims (2)

30% by mass or more of volatile matter content is 35% by mass or more, or total non-caking coal satisfying at least one of 10% or less in total expansion coefficient measured by the expansivity test method specified in JIS M8801 A method for estimating the coke particle size in the case of producing coke using blended coal, which is a weighted average shrinkage ratio and coke of the blended coal obtained by performing a weighted average of the shrinkage percentages of the plain coal constituting the blended coal. The relationship between the particle sizes is obtained in advance, the weighted average shrinkage of the blended coal to be estimated is obtained, and the coke particle size estimation method for obtaining the coke particle size of the blended coal to be estimated from the relationship is given.
The shrinkage rate of the plain coal constituting the blended coal was changed by changing the volume of the plain coal at the resolidification temperature and the temperature within the range of (600 ± 30) ° C. when the plain coal was heated in a container. A method for estimating the coke particle size, which is characterized in that it is obtained from the amount. As the relationship between the weighted average shrinkage rate of the above blended coal and the coke particle size,
When the non-caking coal ratio to be blended is 60% or less, the relationship represented by the following formula (1) is obtained in advance, and when the non-caking coal ratio exceeds 60%, the following (2) is used. The coke particle size estimating method according to claim 1, wherein the relationship represented by the formula is obtained in advance.
Coke particle size of blended coal = a + b x coke shrinkage of blended coal (1)
Coke particle size of blended coal = a + b x coke shrinkage of blended coal
+ Cx (Non-lightly caking coal ratio-60) (2)
Here, a and b are coefficients determined by regression analysis from measured values of coke particle diameter and coke shrinkage, and c is a coefficient similarly determined by further considering the non-caking coal ratio.

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