JPH0469749B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD This invention relates to a method for measuring caking property, which is important for quality evaluation of raw material coal for coke production. Prior art and its problems One of the important issues in the coke manufacturing industry in recent years is to simultaneously achieve stabilization of coke quality for stable operation of large blast furnaces and efficient operation of coke ovens. To address this issue, for example, in Japan, automation of combustion management is being promoted with the aim of uniformly carbonizing coke and reducing the amount of heat of carbonization, while automation of coal and coke property analysis is also being progressively promoted to stabilize coke quality. is reflected in. By the way, as is well known, the factors that control coke quality include coal properties and carbonization conditions, and among them, the caking property of coal is cited as a major factor. Therefore, in order to stabilize the quality of coke, it is effective to quickly and accurately grasp the caking properties of coal, and to reflect this in adjusting the quality of coal charged in a coke oven. There are various methods for measuring the caking properties of coal, but the methods that are widely used worldwide and are in practical use are a. crucible expansion test method (button method, CSN), b.
Method based on fluidity (Gieserer plastometer method), method based on c-expansion (dilatometer method)
The three common measurement methods commonly used in Japan are the dilatometer method and the Gieseler plastometer method specified in JISM8801. However, both the dilatometer method and the Gieseler plastometer method require a heating rate of 3.
C./min and the measurement procedure is complicated, so the time required for measurement is long and it is not suitable for measurements that require speed, such as coke quality control. On the other hand, in the button method, a sample is placed in a predetermined crucible and rapidly heated at a high temperature of 820°C ± 5°C.
This method compares the shape and size of the produced coke with a standard ring and displays it using the Button index, and is widely used because measurements can be made easily and quickly. However, in the case of this button method, the button index is a rough value in 1/2 increments, so it is rarely used for actual operational management, and is usually used as a reference value. In addition to the above-mentioned button method, as a method for rapidly measuring the caking property of coal, there are known methods such as the Lessing method and the Nenko method, which is a slightly improved version of the Lessing method.
For example, in the Nenken method, 1 g of coal crushed to a particle size of 250 μm or less is filled into a quartz tube with a length of 100 mm, an inner diameter of 13 mm, and an outer diameter of 15 mm. Approximately 6.5 g of quartz weight was loaded on the sample surface and charged into a vertical annular electric furnace maintained at a temperature of 600°C. After being held for 7 minutes, it was taken out and the heating expansion relative to the filling height of the unheated coal was measured. The ratio of the height of the coal afterward is determined and used as an index of caking property. However, with this method, because the diameter of the thin tube is large, the heating of the coal becomes uneven between the part near the tube wall and the center, causing variations in the expansion of the coal, and furthermore, the packing density of the sample is not specified. Similarly, variations occur. Additionally, due to the high holding temperature of the electric furnace, depending on the type of coal, the sudden generation of steam and pyrolysis gas during heating may cause a type of bumping phenomenon in the coal sample, causing the coal to scatter and impairing measurement accuracy. etc., the reproducibility of measured values was lacking.
Furthermore, there were many deficiencies as a measurement method, such as the loaded quartz weight sometimes solidifying with the molten and expanded coal, making post-processing work after measurement difficult.
For this reason, the Lessing method and the Burning method are hardly put to practical use. Purpose of the Invention The present invention has been made in view of the above-mentioned conventional situation, and an object of the present invention is to propose a method for quickly and accurately grasping the caking property of coal. Structure of the Invention The method for measuring the caking property of coal according to the present invention is to
A bottomed tube made of metal or glass with an inner diameter of 5 to 12 mm is filled with a charging density of 1.0 g/cm ³ or less, and the coal is heated at a heating rate of at least 10 °C/min or more and 250 °C/min or less to 470 to 550 °C. After heating the coal to a temperature of It is characterized by being used as an index. In other words, this invention applies the knowledge that the expansion of coal is highly dependent on the heating rate to the rapid measurement of the degree of expansion, which is an indicator of the caking property of coal. Fill the sample directly into a tube without molding it and heat it at 10℃/
This method expands coal by rapidly heating it at a heating rate of 250°C/min or more. When measuring the degree of expansion of coal under such rapid heating conditions, it is necessary to heat the coal uniformly and to suppress the scattering of coal particles due to the deviation of water vapor and pyrolysis gas generated during heating. is extremely important. In order to solve these problems, the inventors conducted many experiments and found conditions under which reproducible measurement values could be obtained. First, in order to uniformly heat the coal, the inner diameter of the thin tube filled with the coal sample should be 5 to 12 mm. The reason for this is that when the inner diameter of the tube becomes larger than 12 mm, the heating of the coal becomes uneven between the part near the wall and the center, causing variations in the expansion of the coal. Furthermore, if the diameter is extremely small, less than 5 mm, smooth expansion of the coal will not be achieved, resulting in variations in measured values. On the other hand, in order to suppress the scattering of coal particles, it is necessary to facilitate the escape of generated gas and to adjust the pulverized particle size of coal. For this reason, in this invention, the pulverized particle size of coal is limited to a maximum particle size of 840 μm or less and 250 μm or more. That is, if the diameter is less than 250 μm, the scattering of coal particles increases, which causes variations in measured values. On the other hand, even if the coal particle size is too large,
This is because it has been found that the influence of sample quality deviations is large, and that measurements exceeding 840 μm will cause variations in measurement values. In addition, in this invention, when filling a thin tube with coal of the above particle size, the charging density was adjusted to 1.0 g/cm ³ or less because a high charging density would inhibit the smooth escape of the generated gas. , it is not possible to obtain reproducible measurement values because it causes bumping phenomenon and scatters coal particles. Therefore, in this invention, the charging density of coal is limited to 1.0 g/cm ³ or less.
In addition, the heating rate at this time should be set to 250℃ at 10℃/min or more.
The reason why the heating rate was set to below C/min was that it was confirmed that the detection sensitivity of the expansion coefficient was high at the heating rate in this range. Note that the heating temperature is 470 to 550°C, at which the expansion of the coal is completed. This invention relates to the height of coal after expansion obtained by expanding coal under measurement conditions set within a range that satisfies the above conditions, or the expansion height of coal after heating relative to the filling height of coal before heating. The ratio is measured and this measured value is used as an index of caking property. In other words, the ratio of the expansion height of the heated coal to the coal height after expansion or the coal filling height before heating has high repeatability and also has a high correlation with the expansion rate measured by the conventional dilatometer method. This is because it was found that it can be fully used as an indicator of the caking property of coal. The method of this invention will be explained based on FIGS. 1 and 2. In a bottomed thin tube 1 made of metal or glass with an inner diameter of 5 to 12 mm, a particle size of 250 μm with a maximum particle diameter of 840 μm or less is placed.
Charging density of coal 2 pulverized to 1.0 g/m or more
Fill to a specified density of cm ³ or less. Let the height of the coal filling at that time be l _p . Then, the above capillary is heated for at least 10 minutes to a temperature of 470-550℃, where the expansion of the coal is completed.
Rapid heating at a heating rate of ℃/min or more and 250℃/min or less. As a method for rapidly heating the coal, an annular electric furnace or a metal bath heated to a predetermined temperature can be used, an infrared image furnace, a microwave heating furnace, etc. can be used. Figure 2 shows the state after the coal is rapidly heated to a predetermined temperature and allowed to expand freely.The coal that was at the filling height l _p before heating is the expanded coal that has the height added to the expansion height l _d . It becomes 3. In this invention, the ratio of the expansion height l d of the coal after heating to the height of the coal after expansion (l _p +l _{d )} or the filling height l _p of the coal before heating is measured, and the ratio is determined as an index of the caking property of the coal. shall be. In addition, the heating temperature of the coal in the thin tube 1 can be measured by inserting a thermocouple into the thin tube in advance. Example 1 Among the three types of coal shown in Table 1, a coal blend used for coke production for blast furnaces was used, and 20 pieces of pulverized coal were placed in a heat-resistant glass thin tube with an inner diameter of 10 mm and a length of 120 mm.
Filled to a height of mm with a charging density of 0.7 g/ ^cm3 , and
The coal is immersed in a metal bath with an electric capacity of 1kW set at 500℃ to a height of 100mm from the bottom of the tube, heated at a heating rate of approximately 100℃/min, and taken out after 4 minutes to measure the expansion height of the coal. At the same time, the ratio of the expansion height of the coal after heating to the filling height (20 mm) of the coal before heating was determined. By the above method, the blended coal shown in Table 1 is pulverized to a particle size of
1680μm or less, 840μm or less, 250μm or less, 149μm
Each coal was pulverized and adjusted as follows, and the degree of expansion was measured five times, and the average value () and variation range (R) of these measurement results are shown in Table 2. As is clear from the results in Table 2, the pulverized particle size
In the case of 1680 μm or less, the average value ( ) of the expansion height and expansion ratio is not significantly different from the crushed particle size of 840 μm or less and 250 μm or less, but the variation range (R) is large. This is presumed to be because when the pulverized particle size is coarse, the influence of the difference in properties of each coal particle size becomes noticeable. On the other hand, when the pulverized particle size is 149 μm or less, the average value () of the expansion height and expansion ratio is low, and the fluctuation range (R) is smaller than the pulverized particle size. This is larger than the cases of 840 μm or less and 250 μm or less. Therefore, the maximum particle size of crushed coal during rapid heating is 840 to 250 μm.
It can be seen that the range of is appropriate.

【table】

[Table] Example 2 When the coal blend shown in Table 1 was pulverized to a pulverized particle size of 250 μm or less and the expansion degree was measured in the same manner as in Example 1, the coal charging density of the thin tube was 0.50, 0.70, 1.00,
Table 3 shows the results of measuring the degree of expansion five times for each charging density, with each charging density being changed to 1.10 g/cm ³ . The height of coal filling was kept constant at 20 mm. As is clear from the results in Table 3, the filling height is
Since the charging density is constant at 20 mm, the larger the charging density, the larger the amount of charging coal, and the average value of the expansion height and expansion ratio () increases sequentially, but the charging density
In the case of 1.10g/ ^cm3 , the variation range (R) is the charging density
This is significantly increased compared to the case of 1.00 g/cm ³ or less. This is because when the charging density is higher than 1.00 g/ ^cm3 , the escape of the generated gas is inhibited, the gas pressure inside the packed sample becomes high, the bumping phenomenon occurs and the sample is lifted irregularly, and the fluctuation range ( It is presumed that R) becomes larger. Therefore, the coal charging density is
It can be seen that 1.0 g/cm ³ or less is appropriate.

[Table] Example 3 The coal blend shown in Table 1 was pulverized to a particle size of 250 μm or less, and the coal charging density in the tube was 0.70 g/
cm ³ and filling height of 20 mm, when measuring the degree of expansion using the same method as in Example 1, the inner diameter of the heat-resistant glass capillary tubes used was changed to 4, 6, 10, 12, and 13 mm, and each capillary was Table 4 shows the results of measuring the degree of expansion five times. As is clear from the results in Table 4, the tube diameter is 4.
In the case of mm and 13 mm, the expansion degree is abnormally large or small compared to other tubule diameters. This is because if the tube diameter is too small, such as 4 mm, the smooth escape of the generated gas is inhibited, and the gas pressure inside the filled sample increases and is abnormally lifted, resulting in a large degree of expansion. Ru. On the other hand, if the tube diameter is too large, such as 13 mm, there will be a large temperature difference between the tube wall and the center of the sample inside the tube during rapid heating, and uniform coal expansion will not occur, resulting in a large variation range (R). It is assumed that this indicates the degree of expansion. From these results, it can be said that a diameter of 5 to 12 mm is appropriate for measuring the expansion degree of coal with good reproducibility.

[Table] Example 4 The coal blend shown in Table 1 was pulverized to a particle size of 250 μm or less and packed into a heat-resistant glass tube with an inner diameter of 10 mm and a length of 120 mm at a charging density of 0.70 g/cm ³ to a height of 20 mm. Using an infrared image furnace with an electric capacity of 1 kW, the heating rate was varied, and after reaching 500°C, it was held for 3 minutes, cooled to room temperature, and the expansion degree of the coal was measured after taking it out of the furnace. Table 5 shows the results. Shown below. As is clear from the results in Table 5, the tendency is that the higher the heating rate, the higher the degree of expansion;
Only a small degree of expansion in °C/min was detected. On the other hand, it can be seen that a heating rate of 10° C./min or more and 250° C./min or less shows a large degree of expansion, and that both detection sensitivity and accuracy are good. but,
Although the degree of expansion increases at a heating rate of 250° C./min or more, the fluctuation range (R) becomes large and measurement accuracy deteriorates. This is thought to be because if the heating rate becomes too high, the amount of gas generated per unit time becomes too large, the gas pressure within the sample becomes high, a bumping phenomenon occurs, and the sample is lifted irregularly. Therefore, the heating rate is 250 °C/min or more.
It is judged that a temperature of ℃/min or less is desirable.

[Table] Example 5 Using three types of samples containing the coal blends shown in Table 1,
Table 6 shows the results of measuring the degree of expansion using the same method as in Example 4. The heating rate of the infrared image furnace was kept constant at 100°C/min. From the results in Table 6, the variation range of expansion degree is small for all coal types and has good reproducibility, and the total expansion coefficient measured according to JISM8801 and this invention method among the coal properties shown in Table 1. It can be seen that the trend agrees well with the values measured in .

[Table] Effects of the Invention As is clear from the above examples, according to the method of this invention, scattering of coal particles can be suppressed under rapid heating conditions and reproducible measurement values can be obtained.
Moreover, since it can be measured simply and quickly, it is far more useful than the caking property measurement method specified in the current JIS method, and it greatly contributes to stabilizing coke quality.

[Brief explanation of drawings]

Figures 1 and 2 are explanatory diagrams showing the method for measuring coal caking properties according to the present invention. Figure 1 is a vertical cross-sectional view of a thin tube showing the state before coal heating, and Figure 2 is a longitudinal cross-sectional view of a thin tube showing the state before coal heating. It is a longitudinal cross-sectional view of a thin tube showing a state. 1... Thin tube, 2... Coal before heating, 3... Expanded coal.

Claims (1)

[Claims] 1. Fill coal pulverized to a maximum particle size of 840 μm or less and 250 μm or more into a metal or glass bottomed tube with an inner diameter of 5 to 12 mm to a charging density of 1.0 g/cm ³ or less,
After heating the coal to a temperature of 470 to 550°C at a heating rate of at least 10°C/min to 250°C/min to cause free expansion, the height of the coal after expansion or the filling height of the coal before heating. 1. A method for rapidly measuring the caking property of coal, which comprises: measuring the ratio of the expansion height of the coal after heating, and using the measured value as an index of the caking property.