JP7091902B2 - Deterioration estimation method of coking coal for coke production and coke production method - Google Patents

Description

The present invention relates to a method of estimating deterioration of coking coal for coke production and a method of producing coke using coking coal selected based on this estimation method.

It is known that if the coking coal is continuously stored in the yard, the cohesiveness of the coking coal decreases due to the oxidation of the coking coal. Therefore, in Patent Document 1, it is estimated that the cohesiveness deteriorates due to the oxidation of the coal stored in the yard. Specifically, the maximum fluidity (MF) is specified as an index of the deterioration of caking property, and the maximum fluidity of coal at the start of storage, the specific surface area of coal, the storage period of coal, and the storage period of coal are defined. The maximum fluidity of stored coal is calculated (estimated) based on the temperature and oxygen concentration of the coal seam.

Japanese Unexamined Patent Publication No. 58-142981

In Patent Document 1, in order to calculate the maximum fluidity of coal in storage, the transition of the temperature of the coal layer is grasped based on the heat balance equation, and the transition of the oxygen concentration of the coal layer is determined based on the oxygen balance equation. You have to figure it out. In the heat balance type and oxygen balance type, initial conditions and boundary conditions must be set for each type of coal, so it is necessary to grasp the transition of temperature and oxygen concentration, and by extension, the maximum fluidity of the stored coal. It is complicated to estimate.

The inventors of the present application focused on the amount of pressure decrease in the closed container when the coking coal was put into the airtight container together with the oxygen-containing gas. We have found that there is a correlation with and have completed the present invention. The definition of deterioration rate will be described later.

The present invention is a method for estimating deterioration of coking coal used for producing coke. First, a closed container filled with coking coal at the time of reference and an oxygen-containing gas having a predetermined oxygen concentration is allowed to stand at a predetermined atmospheric temperature, and the pressure inside the closed container is measured to measure the amount of pressure decrease with respect to the initial pressure. The change over time is calculated. Then, based on the change with time of the pressure drop amount, the maximum pressure drop rate at which the change amount of the pressure drop amount per unit time is maximized is calculated.

The ratio of the total expansion rate of the coking coal according to the elapsed time from the reference time to the total expansion rate of the coking coal at the reference time is defined as the deterioration rate. The amount of change in the deterioration rate per unit time is defined as the deterioration rate. The reference time is a reference time for estimating the deterioration of the coking coal (in other words, the total expansion coefficient of the coking coal when a predetermined time elapses as described later), and for example, the coking coal is used. It can be set as the reference time when it arrives in the yard.

Here, the correlation between the maximum pressure decrease rate and the deterioration rate is obtained in advance, and based on this correlation, the deterioration rate corresponding to the maximum pressure decrease rate of the coking coal to be used is calculated.

The above-mentioned correlation is represented by the following formula (I).

In the above formula (I), Vd is the deterioration rate, Vp is the maximum pressure decrease rate, and k1 and k2 are coefficients. When the above-mentioned reference time is when the coking coal arrives at the yard, it is exemplified as a typical value that the coefficient k1 is −0.1277 and the coefficient k2 is 0.2708.

If the total expansion rate of the coking coal to be used at the reference time is measured, the coking coal to be used will be determined from the reference time based on the total expansion rate and the calculated deterioration rate. The total expansion rate can be calculated when the time (time until the time when the use for coke production is considered or planned) has elapsed.

Then, based on the value of the total expansion coefficient calculated for each of the plurality of types of coking coal that are planned to be used, the priority of using the plurality of types of coking coal is determined and coke is manufactured.

According to the present invention, if the maximum pressure decrease rate of the coking coal to be used is obtained, the deterioration rate of the coking coal can be estimated, and a predetermined time elapses from the reference time based on this deterioration rate. It is possible to estimate the total expansion rate of the coking coal at that time. Therefore, by estimating the deterioration rate of the coking coal that is planned to be used without performing complicated calculations as in Patent Document 1, the coking coal that is planned to be used has a predetermined time from the reference time. The total expansion rate over time can be estimated.

Therefore, when coke is manufactured, coking coal can be prioritized and used, and it is possible to prevent coking coal that has deteriorated too much from remaining in inventory. When coke is produced using coking coal that has deteriorated too much, the amount of high-quality coking coal used increases in order to secure the strength of coke (for example, drum strength index DI). If coke is produced before the deterioration of the coking coal progresses too much, the amount of high-quality coking coal used can be reduced.

It is a schematic diagram which shows the structure of the pressure measuring apparatus for measuring the pressure change by oxygen consumption of coking coal. It is a figure which shows the relationship between the pressure drop amount and the elapsed time about three kinds of coking coals (A coal-C coal). It is a figure which shows the relationship between the deterioration rate and the elapsed months about A coal. It is a figure which shows the relationship between the deterioration rate and the elapsed months about B coal. It is a figure which shows the relationship between the deterioration rate and the elapsed months about C coal. It is a figure which shows the relationship between the maximum pressure drop rate and the deterioration rate about the coking coal.

In this embodiment, the total expansion coefficient of coking coal scheduled to be used in the production of coke is estimated when a predetermined time has elapsed from the reference time. Specifically, first, the deterioration rate Vd of the coking coal at the reference time is estimated. This coking coal is used for the production of coke, and generally, coke is obtained by charging the coking coal into a coke oven and carbonizing it.

The deterioration rate Vd described above is the amount of change ΔDR of the deterioration rate DR of the coking coal per unit time. The deterioration ratio DR is the ratio of the total expansion coefficient TD _t of the coking coal according to the elapsed time t from the reference time to the total expansion coefficient TD _ref of the coking coal at the reference time. The total expansion coefficient TD is a value measured by the expansion test method of JIS M8801.

That is, the deterioration rate DR is represented by the following formula (1), and the deterioration rate Vd is represented by the following formula (2).

According to the above formula (1) and the above formula (2), if the total expansion coefficient TD _ref of the coking coal at the reference time is measured, the predetermined time t elapses from the reference time by estimating the deterioration rate Vd. The total expansion coefficient TD _t of the coking coal can be estimated. Specifically, since the deterioration rate Vd and the time interval Δt (that is, the predetermined time t) represented by the above formula (2) can be specified by estimating the deterioration rate Vd, the deterioration rate is based on the above formula (2). The amount of change in DR ΔDR can be calculated. Here, if the difference between the deterioration rate DR (DR = 1) of the coking coal at the reference time and the deterioration rate DR of the coking coal when a predetermined time t has elapsed from the reference time is the change amount ΔDR, the change amount ΔDR is used. By measuring the total expansion rate TD _ref of the coking coal, the total expansion rate TD _t of the coking coal when a predetermined time t has elapsed from the reference time can be obtained based on the above formula (1).

Hereinafter, a method of estimating the deterioration rate Vd of the coking coal will be described.

It was found that there is a predetermined correlation between the deterioration rate Vd and the maximum pressure decrease rate Vp described later, and this correlation holds regardless of the type of coking coal. Therefore, if the correlation between the deterioration rate Vd and the maximum pressure decrease rate Vp is obtained in advance and the maximum pressure decrease rate Vp is obtained for the coking coal for which the deterioration rate Vd is to be estimated, the deterioration rate Vd is estimated. Can be done.

The maximum pressure decrease rate Vp is the maximum value of the rate at which the pressure decreases when the pressure in the closed container decreases as the coking coal consumes the oxygen gas in the closed container in the closed container. .. If a closed container filled with coking coal at the reference time and an oxygen-containing gas adjusted to a predetermined oxygen concentration is allowed to stand at a predetermined atmospheric temperature and the pressure inside the closed container is continuously measured, the change in pressure over time can be observed. Can be grasped. The maximum pressure decrease rate Vp can be calculated based on this change with time. Here, the initial pressure in the closed container is a predetermined pressure (for example, atmospheric pressure).

As a method for measuring the pressure in the closed container, a known measuring method can be appropriately adopted. For example, BOD (Biochemical Oxygen Demand), which is a method for measuring the oxygen consumption of microorganisms, can be adopted. Pressure measurement can be performed using the OxiTop method.

Hereinafter, a method for calculating the maximum pressure drop rate Vp will be specifically described. The pressure measurement conditions described below are examples.

First, the coking coal (predetermined mass) for which the deterioration rate Vd is to be estimated is placed in the container 10 of the pressure measuring device 1 shown in FIG. As this coking coal, the coking coal at the time of reference is used. Specifically, when the coking coal arrives at the yard (reference time), it is preferable to use the coking coal sampled at the same timing as the coking coal sampled in order to measure the total expansion coefficient.

If the timing for calculating the maximum pressure decrease rate Vp is different from the timing when the above-mentioned coking coal arrives at the yard, the coking coal is set to the timing for calculating the maximum pressure decrease rate Vp as a reference time. The total expansion coefficient TD _t of the coking coal may be estimated by measuring the total expansion coefficient of TD _ref .

Further, it is preferable that the coking coal is in a state of being stored in the yard, in other words, the particle size distribution is almost the same. It is preferable to dry the coking coal in order to grasp the change of the pressure in the closed container with time.

In FIG. 1, the container 10 has two branch portions 11 and 12, and the two branch portions 11 and 12 are sealed by septums 13 and 14, respectively. Further, the container 10 has a charging unit 15 for putting the coking coal into the inside of the container 10. A pressure recording head 16 for detecting the pressure in the container 10 is attached to the charging unit 15, and the charging unit 15 is sealed by the pressure recording head 16. By attaching the septums 13 and 14 and the pressure recording head 16 to the container 10, the inside of the container 10 can be sealed.

Next, the inside of the container 10 containing the coking coal is filled with a non-oxidizing gas (for example, nitrogen gas), and the same volume of non-oxidizing gas as the oxygen gas to be injected into the container 10 later is added to Septam. Aspirate from 13 or 14 with a syringe or the like. Then, the same volume of oxygen gas as the sucked non-oxidizing gas is injected into the container 10 from the septum 13 or 14 with a syringe or the like, and then the pressure measuring device 1 is allowed to stand at a predetermined atmospheric temperature. By preparing a syringe filled with oxygen gas and inserting the syringe needle into the septum 13 (or septum 14), oxygen gas can be injected from the syringe into the inside of the container 10, so that oxygen in the container 10 can be injected. The concentration can be adjusted arbitrarily. In the present embodiment, the pressure drop due to the consumption of oxygen gas in the closed container 10 due to the coking coal is measured. The oxygen gas injected into the container 10 may be pure oxygen gas or oxygen gas having an oxygen concentration of less than 100%. Further, the pressure in the container 10 immediately after the oxygen gas is injected into the container 10 is a predetermined pressure (for example, atmospheric pressure).

The reason why the pressure measuring device 1 is allowed to stand at a predetermined atmospheric temperature is to simulate the environment of the yard where the coking coal is stored. Therefore, the predetermined atmospheric temperature is appropriately determined in consideration of the environmental temperature of the yard. For example, the average value of the environmental temperature of the yard within the predetermined storage period of the coking coal can be set as the predetermined atmospheric temperature. Further, when considering that the environmental temperature of the yard changes according to the season, a plurality of storage periods can be set according to the season, and the average value of the environmental temperature in each storage period can be set as a predetermined atmospheric temperature. .. In this case, a plurality of atmospheric temperatures are set, but one atmospheric temperature may be determined in consideration of the period in which the coking coal for which the deterioration rate Vd is to be estimated is actually stored.

When the pressure measuring device 1 is allowed to stand at a predetermined atmospheric temperature, the pressure in the closed container 10 decreases due to the consumption of oxygen gas in the closed container 10 by the coking coal (that is, oxidation of the coking coal). Since the pressure recording head 16 can measure the pressure in the container 10, the pressure drop amount ΔP in the container 10 can be obtained based on the measurement result. The pressure drop amount ΔP is based on the pressure when the oxygen gas in the container 10 is not consumed, and is represented by the difference between this reference pressure and the pressure in the container 10 when an arbitrary time elapses. .. Specifically, the pressure drop amount ΔP is the pressure [hPa] in the container 10 when the oxygen gas is injected into the container 10 and an arbitrary time elapses, and the pressure immediately after the oxygen gas is injected into the container 10 [hPa]. hPa] is subtracted. When the oxygen gas in the closed container 10 is consumed by the coking coal, the pressure drop amount ΔP becomes a negative value.

By obtaining the pressure drop amount ΔP for each elapsed time t after injecting oxygen gas into the container 10, a transition curve of the pressure drop amount ΔP with respect to the elapsed time t can be obtained. The maximum pressure drop rate Vp can be calculated based on this transition curve. Specifically, among the slopes of the plurality of tangents in the transition curve, the largest slope is the maximum pressure drop rate Vp.

Under the same temperature condition, immediately after injecting oxygen gas into the container 10, the consumption of oxygen gas by the coking coal becomes maximum, and the pressure drop amount ΔP becomes the largest. Therefore, in the coordinate system of the pressure drop amount ΔP and the elapsed time t, the slope ΔP / Δt of the tangent line of the transition curve at the origin is the maximum pressure drop rate Vp. The origin referred to here is that the pressure drop amount ΔP is 0 [hPa] and the elapsed time t is 0 [hr].

Next, the correlation between the deterioration rate Vd and the maximum pressure decrease rate Vp will be described.

The correlation between the deterioration rate Vd and the maximum pressure decrease rate Vp is expressed by the following equation (3).

In the above equation (3), k1 and k2 are coefficients. Under the conditions of the examples described later, the coefficient k1 is −0.1277 and the coefficient k2 is 0.2708.

The correlation between the deterioration rate Vd and the maximum pressure decrease rate Vp can be obtained in advance using a plurality of types of coking coal. Here, it is preferable that the particle size distributions of the plurality of types of coking coal are the same. For example, the cumulative ratio of particles having a particle size of 3 mm or less for each coking coal can be set within the range of 70 to 80%.

When determining the correlation between the deterioration rate Vd and the maximum pressure decrease rate Vp, the maximum pressure decrease rate Vp is obtained for each of the plurality of types of coking coal based on the above-mentioned measurement of the pressure decrease amount ΔP.

Further, for each of the plurality of types of coking coal, the total expansion coefficient TD _ref at the reference time is measured, and the total expansion coefficient TD _t is measured for each elapsed time t from the reference time to obtain the deterioration rate DR. Grasp the change over time in the deterioration rate DR. Here, regardless of the type of coking coal, the deterioration ratio DR decreases as the elapsed time t increases, and the relationship between the deterioration ratio DR and the elapsed time t is represented by a linear function (negative correlation). As described above, since the deterioration rate Vd is the amount of change in the deterioration rate DR per unit time, the slope of the linear function is the deterioration rate Vd. Since the linear function has a negative correlation, the slope of the linear function has a negative value, but in the present embodiment, the deterioration rate Vd is set as the absolute value of the slope of the linear function.

In the coordinate system of the maximum pressure decrease rate Vp and the deterioration rate Vd, if the relationship between the maximum pressure decrease rate Vp and the deterioration rate Vd of each coking coal is plotted to obtain a regression curve, this regression curve is expressed by the above equation (3). Will be done. Here, when the maximum pressure decrease rate Vp is 0, the deterioration rate Vd becomes 0, so that the regression curve is a curve that passes through the origin of the coordinate system of the maximum pressure decrease rate Vp and the deterioration rate Vd.

Next, a method of estimating the total expansion coefficient TD _t of the coking coal when a predetermined time t has elapsed from the reference time will be described.

If the maximum pressure drop rate Vp of the coking coal is obtained as described above, the deterioration rate Vd can be estimated. According to the above formula (1) and the above formula (2), if the deterioration rate Vd is estimated and the total expansion coefficient TD _ref at the reference time is measured, the coking coal when a predetermined time t has elapsed from the reference time. The total expansion coefficient TD _t of can be calculated.

According to the present embodiment, if the maximum pressure decrease rate Vp of the coking coal at the reference time is obtained, the deterioration rate Vd can be estimated based on the correlation between the deterioration rate Vd and the maximum pressure decrease rate Vp. Therefore, the deterioration rate Vd of the coking coal can be estimated without performing a complicated calculation as in Patent Document 1.

Further, by measuring the total expansion coefficient TD _ref of the coking coal at the reference time, the total expansion rate of the coking coal when a predetermined time t has elapsed from the reference time based on the estimated deterioration rate Vd of the coking coal. The TD _t can be estimated. This makes it possible to estimate the future total expansion coefficient TD _t of the coking coal stored in the yard without performing complicated calculations as in Patent Document 1.

Further, by estimating the total expansion coefficient TD _t for each of the plurality of types of coking coal stored in the yard, the coking coal having a low total expansion coefficient TD _t is preferentially used when producing coke. Can be done. In this way, by prioritizing the order of use of the plurality of types of coking coal based on the total expansion coefficient TD _t estimated for each of the plurality of types of coking coal, the coking coal whose deterioration has progressed (in other words, all). It is possible to prevent the coking coal having a reduced expansion coefficient TD) from remaining in inventory. When coke is produced using the deteriorated coking coal, the amount of high-quality coking coal used increases in order to secure the strength of the coke (for example, the drum strength index DI). However, if coke is produced before the deterioration of the coking coal progresses too much, the amount of high-quality coking coal used can be reduced.

Three types of coking coal (coal A to C) shown in Table 1 below were prepared, and the correlation between the deterioration rate Vd and the maximum pressure decrease rate Vp was determined. As the coking coal (A charcoal to C charcoal), the coking coal when it arrived at the yard was used.

In Table 1 above, water (IM), ash (Ash) and volatile content (VM) were measured by the industrial analysis method specified in JIS M8812. The mass% of carbon (C), hydrogen (H), sulfur (S) and nitrogen (N) was measured by the elemental analysis method specified in JIS M8819. The mass% of oxygen (O) was defined as the balance obtained by subtracting the total value of mass% of carbon (C), hydrogen (H), sulfur (S) and nitrogen (N) from 100 mass%. The total expansion coefficient TD was measured by the expansion test method of JIS M8801.

Dry samples (charcoal A to charcoal C) were prepared by the treatment described below. The sample was prepared in a glove box in which dry nitrogen gas (concentration 100% by volume) was circulated.

First, a magnetic crucible (outer diameter 39 mm, height 29 mm, internal volume 15 mL) containing a sample (charcoal A to C) is installed in an electric furnace, and then the ambient temperature inside the electric furnace is raised to 130 ° C. The sample was dried. In this drying operation, the sample was stirred in a magnetic crucible so that uneven drying of the sample did not occur. The drying operation was carried out until the temperature of the sample was maintained at 100 ° C. or higher and the mass change of the sample due to the evaporation of water converged. By drying the sample, it is possible to suppress the influence of the variation in the pressure drop amount ΔP due to the difference in the water content contained in the sample when obtaining the pressure drop amount ΔP described later.

After the drying operation was completed, 10.0 g of the sample was placed in the container 10 of the pressure measuring device 1 shown in FIG. The container 10 is made of glass, and the internal volume of the container 10 is 320 mL. Since nitrogen gas is circulating in the glove box, the inside of the container 10 is filled with nitrogen gas.

The pressure measuring device 1 containing the sample was taken out from the glove box, and oxygen gas was injected into the container 10 using a syringe. The oxygen gas injection work was performed according to the following procedure.

First, the manometer was stabbed in the septum 13, and the syringe needle was stabbed in the septum 14. While monitoring the pressure value in the container 10 detected by the manometer, 20% by volume of nitrogen gas was sucked from the container 10 using a syringe. Next, after removing the syringe that sucked the nitrogen gas, 20% by volume of oxygen gas was injected into the container 10 by inserting the syringe needle of the syringe filled with oxygen gas into the septum 14. Here, 20% by volume of nitrogen gas was replaced with 20% by volume of oxygen gas under the condition of simulating the oxygen concentration in the atmosphere.

Further, the timing immediately after injecting 20% by volume of oxygen gas into the container 10 was set as the timing for starting the pressure measurement. Immediately after injecting oxygen gas into the container 10, the pressure measuring device 1 was allowed to stand in a blower-type incubator whose atmospheric temperature was set to 40 ° C. In this embodiment, the atmospheric temperature in the blower type incubator was set to 40 ° C. so that the conditions were close to the average value of the environmental temperature of the yard in which the coking coal was stored. Immediately after injecting oxygen gas into the container 10, the pressure inside the container 10 was continuously measured using the pressure recording head 16.

FIG. 2 shows the results of pressure measurement in each sample (charcoal A to charcoal C). FIG. 2 shows the relationship between the elapsed time [hr] and the pressure drop amount ΔP [hPa]. As described above, the pressure drop amount ΔP has a negative value. As can be seen from FIG. 2, for all the samples, the pressure in the container 10 continued to decrease due to the consumption of oxygen gas by the samples immediately after the pressure measurement was started. The transition of the pressure decrease (pressure decrease curves L11 to L13) was different depending on the sample (charcoal A to coal C).

The maximum pressure drop rate Vp was calculated based on the pressure drop curves L11 to L13 of each sample. As can be seen from FIG. 2, since the pressure dropped the most immediately after the pressure measurement was started, the slope of the tangents of the pressure drop curves L11 to L13 at the origin of FIG. 2 is the maximum pressure drop rate Vp. At the origin of FIG. 2, the elapsed time t is 0 [hr], and the pressure drop amount ΔP is 0. The maximum pressure decrease rate Vp of A charcoal is 0.5577 [hPa / hr], the maximum pressure decrease rate Vp of B charcoal is 0.4623 [hPa / hr], and the maximum pressure decrease rate Vp of C charcoal is 1. It was .1143 [hPa / hr].

On the other hand, the total expansion rate TD of each coking coal (A coal to C coal) was measured for each number of months elapsed from the arrival of the coking coal (A coal to C coal) in the yard. In this embodiment, the above-mentioned reference time is set when the coking coal arrives at the yard. Then, for each coking coal, the relationship between the deterioration rate DR of the coking coal and the number of elapsed months was investigated. FIG. 3 shows the relationship between the deterioration rate DR and the number of elapsed months in the A coal. FIG. 4 shows the relationship between the deterioration rate DR and the number of elapsed months in B coal. FIG. 5 shows the relationship between the deterioration rate DR and the number of elapsed months in C coal.

As can be seen from FIGS. 3 to 5, the deterioration ratio DR changes linearly for all coking coals (coal A to coal C). As shown in FIG. 3, if the regression line L21 is obtained, the slope (absolute value) of the regression line L21 becomes the deterioration rate Vd of the A coal. In this example, the deterioration rate Vd of the A coal was 0.1159 [− / month]. In FIG. 3, the correlation coefficient ^R2 was 0.9531.

As shown in FIG. 4, if the regression line L22 is obtained, the slope (absolute value) of the regression line L22 becomes the deterioration rate Vd of the B coal. In this example, the deterioration rate Vd of the B coal was 0.0931 [− / month]. As shown in FIG. 5, if the regression line L23 is obtained, the slope (absolute value) of the regression line L23 becomes the deterioration rate Vd of the C coal. In this example, the deterioration rate Vd of the C coal was 0.1428 [− / month]. In FIG. 4, the correlation coefficient R ² was 0.9918, and in FIG. 5, the correlation coefficient R ² was 0.9815.

As described above, by obtaining the maximum pressure reduction rate Vp and the deterioration rate Vd for each coking coal (coal A to C), the relationship between the maximum pressure decrease rate Vp and the deterioration rate Vd is unique for each coking coal. It is decided to. FIG. 6 shows the relationship between the maximum pressure decrease rate Vp and the deterioration rate Vd for the coking coal (coal A to C). Here, when the maximum pressure drop rate Vp is 0, the deterioration rate Vd becomes 0. Considering the relationship between this point and the maximum pressure decrease rate Vp and the deterioration rate Vd in each coking coal, the regression curve L3 was obtained. The correlation coefficient ^R2 at this time was 0.9646.

In this embodiment, the regression curve L3 is represented by the following equation (4).

According to FIG. 6, the relationship between the maximum pressure decrease rate Vp and the deterioration rate Vd is located on the regression curve L3 for all the coking coals (A coal to C coal), and the maximum pressure decrease rate Vp and the deterioration rate Vd are located. It was confirmed that there is a correlation with.

Therefore, if the regression curve L3 (the above equation (4)) is obtained in advance and the maximum pressure decrease rate Vp of the coking coal when it arrives at the yard is measured, the deterioration rate Vd of the coking coal can be estimated. .. Then, if the total expansion coefficient TD _ref of the coking coal when it arrives at the yard is measured, the deterioration rate Vd is estimated as described above, and the total coking coal according to the elapsed time t from the time of arrival is estimated. The expansion rate TD _t can be estimated.

1: Pressure measuring device, 10: Container, 11, 12: Branch part, 13, 14: Septum,
15: Input section, 16: Pressure recording head

Claims (2)

It is a method of estimating the deterioration of coking coal used in the production of coke.
The pressure inside the closed container is measured by allowing the closed container filled with the raw coal at the reference time when the coking coal arrives at the yard and the oxygen-containing gas having a predetermined oxygen concentration to stand at a predetermined atmospheric temperature. By doing so, the change over time in the amount of pressure decrease with respect to the initial pressure is obtained.
Based on the change over time in the pressure drop, the maximum pressure drop rate at which the change in the pressure drop per unit time is maximized is calculated.
The ratio of the total expansion rate of the coking coal according to the elapsed time from the reference time to the total expansion rate of the coking coal at the reference time was defined as the deterioration rate, and the amount of change in the deterioration rate per unit time was defined as the deterioration rate. At that time, the correlation between the maximum pressure decrease rate and the deterioration rate is obtained in advance, and based on this correlation, the deterioration rate corresponding to the maximum pressure decrease rate of the coking coal to be used is calculated. death,
The total expansion coefficient of the coking coal to be used at the reference time was measured.
Based on this total expansion rate and the calculated deterioration rate, the total expansion rate of the coking coal scheduled to be used is calculated when a predetermined time has elapsed from the reference time .
The correlation is expressed by the following formula (I).

Here, a method for estimating deterioration of coking coal for coke production, characterized in that Vd is a deterioration rate, Vp is a maximum pressure decrease rate, k1 is −0.1277, and k2 is 0.2708 . Based on the deterioration estimation method according to claim 1, the total expansion coefficient of each of the plurality of types of coking coal scheduled to be used is calculated when a predetermined time has elapsed from the reference time.
A coke manufacturing method, characterized in that coke is manufactured by determining the priority of using the plurality of types of coking coal based on the calculated total expansion coefficient value.

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