JP2014019814A - Strength estimation method of formed coke - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method in which when poor quality bony coal is used to produce formed coke, coke strength of the formed coke can be estimated beforehand to obtain stable quality formed coke.SOLUTION: In a method, expansion testings by at least two temperature raising conditions are executed beforehand to two or more kinds of testing bony coals, correlation between expansion specific volumes of the testing bony coals and coke strengths of testing formed cokes obtained from respective testing bony coals is obtained, and coke strength of a formed coke obtained using a bony coal is estimated from an expansion specific volume of the bony coal used for actual production on the basis of a correlation equation thereof.

Description

  The present invention relates to a method for estimating the strength of a formed coke, and more particularly to a method for estimating the coke strength of a formed coke obtained using coal called inferior coal.

One of the important qualities in producing coke necessary for blast furnace operation is coke strength. Many methods have been reported so far for estimating the strength of coke produced in a chamber-type coke oven. For example, using the degree of void filling during coal softening defined by the following formula, the relationship between the degree of void filling during coal softening and the surface fracture strength of coke is obtained, and the coal softening of coal used in actual production A method for estimating the surface fracture strength of coke from the specific volume at the time and the bulk density of the coal when charged in the coke oven is known (see Patent Document 1).
Void filling degree during coal softening (-) = specific volume during coal softening (cm ³ / g) × coal bulk density of the coke RoSo Nyutoki (g / cm ³⁾

However, the method for estimating the coke strength as described above is based on the premise of using non-caking coal (non-caking coal and caking coal) or coal having a higher degree of coalification. That is, in the method of Patent Document 1, the maximum expansion volume (cm ³ ) of coal based on the coefficient of expansion (%) of coal measured by the expansibility test method (dilatometer method) of JIS M 8801 The so-called inferior coal, whose specific volume at the time of softening the coal is calculated from the ratio with the amount of coal charged (g) and does not show expansibility in the expansibility test specified in JIS M8801 When using, it is not applicable.

JP 2002-121565 A

  Due to the recent increase in steel demand at the world level, the price of raw coal for coke has soared. In particular, the price increase of good quality coal will continue for some time, and the price difference with inferior quality coal is expected to increase further. Therefore, it is urgent to establish a technology for producing coke using relatively inexpensive coal. One of them is a method of producing carbonized coke by carbonizing carbonized coal. According to this method, raw material coal is formed in advance, so that coal having relatively poor caking properties can be used.

  Molded coke, which has been studied in the past, is aimed exclusively at preventing cracks and cracks so that air permeability in the blast furnace can be ensured. Coal that has caking properties such as caking is blended at a certain ratio or more, but considering the recent rise in the price of raw coal, the use of good quality coal in the production of molded coke is to be suppressed as much as possible. It is desirable to make it. However, it cannot be said that the production of formed coke using inferior coal, which has been considered to have no expansibility, has been well established, and almost no consideration has been given to methods for estimating the coke strength in advance. Has not been made.

  Accordingly, an object of the present invention is a method capable of estimating the coke strength of a formed coke in advance so as to obtain a formed coke having a stable quality when producing formed coke using inferior quality coal having inferior quality. Is to provide.

  As a result of intensive studies to solve these problems, the present inventors have increased the rate of temperature rise from 3.0 ± 0.1 ° C./min specified by the dilatometer method of JIS M8801. It was newly found that the expansibility of the inferior coal can be detected by the expansibility test, and there is a correlation between the expansion specific volume for each brand of the inferior coal and the coke strength. Based on this correlation, the coke strength of the formed coke can be estimated, and the present invention has been completed.

That is, the gist of the present invention is as follows.
(1) When producing formed coke using inferior coal, the correlation between the expansion specific volume of multiple types of test inferior coal and the coke strength of test formed coke obtained from each of the inferior coals for testing is obtained. A method for estimating the coke strength of the formed coke obtained using the inferior coal from the expansion specific volume of the inferior coal used for actual production based on the correlation equation,
The expansion specific volume is obtained by an inferior coal fine powder sample obtained by an expansibility test in which a piston is placed on a fine powder sample of inferior coal filled in a thin tube and heated at a predetermined temperature rise rate to obtain the highest point of piston displacement. Is the ratio (V / W) between the maximum expansion volume V and the filling mass W of the inferior quality coal fine powder sample,
First, the expansion under the first temperature rise condition in which the average temperature rise rate HR _400-500 is over 3 ° C./min from when the test inferior coal reaches at least 400 ° C. to 500 ° C. The expansion specific volume is measured in the property test, and the correlation equation of the first test poor coal group in which the expansion specific volume has a correlation with the coke strength is obtained,
Subsequently, the expansion specific volume was measured by an expansion test under a second temperature increase condition in which the average temperature increase rate HR _400-500 was made faster than the first temperature increase condition, and the first test poor coal group A method for estimating the strength of a formed coke, wherein a correlation equation of the second test poor coal group is obtained from the correlation between the expansion specific volume of the test poor coal other than the above and the coke strength.
(2) The expansion specific volume of the inferior coal used in the actual production is measured by the expansion test under the first temperature rise condition, and the expansion specific volume becomes the reference expansion specific volume a ₁ when the piston displacement is zero. If it is 1.1 times or more (≧ 1.1 × a ₁ ), the coke strength is estimated using the correlation equation obtained from the first test poor coal group,
If the expansion specific volume is less than 1.1 times (<1.1 × a ₁ ) with respect to the reference expansion specific volume a ₁ , the expansion specific volume is measured by an expansion test under the second temperature rise condition, and the expansion When the specific volume is 1.1 times or more (≧ 1.1 × a ₂ ) with respect to the reference expansion specific volume a ₂ when the piston displacement is zero, the correlation formula obtained from the second test poor coal group The coke strength estimation method according to (1), wherein the coke strength is estimated using

  According to the present invention, based on the expansibility of inferior coal that could not be detected by the conventional dilatometer method, the ability to develop coke strength can be differentiated for each brand of inferior coal, and the coke strength of the formed coke is estimated in advance. It becomes possible to do. Therefore, when producing formed coke using inferior quality coal, it is possible to select the inferior quality coal so that the coke strength of the obtained shaped coke becomes a desired value, so that stable quality shaped coke can be obtained. Become. In addition, the efficiency of operations in the production of formed coke can be improved, and coke that contributes to blast furnace operation can be produced using relatively inexpensive inferior coal. Can be solved at the same time.

FIG. 1 is an explanatory diagram showing an outline of an apparatus used for an expansibility test according to the present invention. FIG. 2 is a graph showing the expansion specific volume and the coke strength of the test poor coal obtained in the expansibility test at an average heating rate of HR _400-500 = 12 ° C./min. FIG. 3 is a graph showing the expansion specific volume of test poor coal obtained in the expansibility test at an average heating rate of HR _400-500 = 100 ° C./min and its coke strength.

Hereinafter, the present invention will be described in detail.
First, the inferior coal used in the present invention is an extremely low expansion rate coal that has less caking properties than non-slightly caking coal and the like, and is classified as inferior coal among bituminous coals. Specifically, coal having a total expansion rate of 5% or less, preferably coal having a total expansion rate of approximately 0%, measured by the expansibility test method of JIS M8801, The target is coal that does not turn into coke. Although it is not expected to obtain coke strength at the same level as blast furnace coke from such inferior coal, if it is a small coke that is charged around the blast furnace and mainly serves as a reductant, it will The strength of is not required.

Here, Table 1 shows an example in which the surface fracture strength DI ¹⁵⁰ ₆ of the formed coke obtained by pressure-molding inferior coal to produce formed coal and dry-distilling in a test furnace is shown. The dry distillation conditions in the test furnace were as follows. For all the inferior coals of Coal A to Coal I, the average temperature increase rate at the center temperature of the formed coal was increased to 1000 ° C. at 6 ° C./min to obtain formed coke. .

  When carbonized coal produced by pressure-molding inferior coal is obtained by dry distillation, the average temperature rising rate of the center temperature of the coal in the temperature range of 400-500 ° C is in the range of 6-30 ° C / min. It is preferable to heat to about 1000 ° C. by setting the predetermined temperature increase rate. The reason is that it is a condition that can be carried out when coke is produced with an actual machine using a coal obtained by pressure-molding inferior coal.

  In Table 1, simple coking coal is obtained for each brand of inferior quality coal to produce formed coke. That is, it can be seen that the coke strength of the inferior coal molded coke varies greatly from brand to brand. The total expansion rate (%) in Table 1 is a value determined by the expansibility test method specified in JIS M 8801, and the inferior quality coal charged in the expansion rate measuring device (dilatometer) is 300 to 550 ° C. In this temperature range, the temperature was raised at a heating rate of 3.0 ± 0.1 ° C./min. However, all of them have a total expansion rate of 0%, and the ability to develop coke strength cannot be evaluated (differentiated) for each brand of inferior coal.

In general, it is believed that coal begins to soften at temperatures around 400 ° C., then expands and resolidifies at temperatures around 500 ° C. Therefore, if the average heating rate HR _400-500 from the time when the inferior coal reaches 400 ° C to the time when it reaches 500 ° C is increased faster than in the case of the dilatometer method, the expansibility of the inferior coal is confirmed. I understood that I could do it. About the expansibility which such inferior charcoal shows, the present inventors evaluated by the expansibility test different from the dilatometer method of JISM8801.

That is, instead of using a rod-shaped sample body (pencil) as in the dilatometer method, as shown in FIG. 1, a fine powder sample of inferior coal is filled into a thin tube, and the inferior coal fine in the thin tube is filled. A piston is inserted on the powder sample, heated at a predetermined temperature increase rate, and the vertical displacement of the piston at that time is measured. Then, by reading the highest point of the piston displacement, the maximum expansion volume V of the inferior coal fine powder sample is obtained, and the expansion specific volume of the inferior coal is obtained from the ratio (V / W) with the filling mass W of the inferior coal fine powder sample. Like that. Such a method is described in Japanese Patent Application Laid-Open No. 5-60707. In this document, the expansion specific volume of coal is measured at a temperature rising rate of 3.0 ± 0.1 ° C./min as in the case of the dilatometer method. However, in the present invention, at least the average temperature rising rate HR _400-500 from the time when the inferior coal reaches 400 ° C. to the time when it reaches 500 ° C. is set to be higher (3 ° C. / The difference is that the expansibility of inferior coal is evaluated. In the expansibility test apparatus shown in FIG. 1, the expansion specific volume is calculated from the following equation (Z), assuming that the piston height when the filled inferior carbon powder sample expands to the maximum is h _1. can do.
Expansion specific volume (cm ³ / g) = maximum expansion volume (cm ³ ) / filling mass of inferior coal fine powder sample (g) = {π × (0.8 / 2) ² × h ₁ } /2.413 ...... (Z)

Table 1 shows an example in which the expansion specific volume for each grade of inferior coal was measured in an expansibility test heated from 300 ° C. to 550 ° C. with an average heating rate HR _400-500 = 12 ° C./min, and the average It shows an example in which the expansion specific volume was measured in an expansibility test heated from 300 ° C. to 550 ° C. at a rate of temperature increase HR _400-500 = 100 ° C./min. Then, for these results, summarized the relation between the expansion ratio volume of the low-quality coal (x) and the coke strength of a molded coke obtained from each low-quality coal (y), the average heating rate H. R. _{400- When} heating from 300 ° C. to 550 ° C. with ₅₀₀ = 12 ° C./min, the graph shown in FIG. 2 is obtained, and the average heating rate HR _400-500 = 100 ° C./min with 300 ° C. to 550 ° C. When heated up to, the graph shown in FIG. 3 is obtained.

  That is, according to the graph of FIG. 2, the group (A charcoal to D charcoal) showing the relationship in which the coke strength improves as the expansion specific volume increases, and the xy linear function has no inclination and the expansion specific volume. Then, it turns out that it classify | categorizes into the group (E coal-I coal) which cannot differentiate the coke strength expression power of inferior quality coal. Moreover, in the graph of FIG. 3, it turns out that the inferior quality coal (E charcoal-I charcoal) classified into the latter group in FIG. 2 shows the relationship which coke intensity | strength improves with the increase in expansion specific volume. On the other hand, for the former group of inferior coals (A coal to D coal), the difference in the expansion specific volume was reduced, and it was difficult to differentiate the inferior coal by the expansion specific volume.

  Based on these findings, in the present invention, a plurality of types of test inferior coals are prepared in advance, and their expansion specific volumes are measured according to two or more temperature rise conditions in the above-described expansion test. When selecting the test inferior coal, it is preferable to measure the coke strength of a simple formed coke in advance and prepare various brands of inferior coal with varying coke strength. In that case, in the expansibility test under at least one temperature rise condition, there are 2 or more, preferably 3 or more, each of the inferior coals belonging to the group that can differentiate the inferior coals from the expansion specific volume and the group that is not. It should be included. Of course, if the number of them increases, the accuracy of the strength estimation value will improve, so there is no particular limitation. However, if any group contains five types of test inferior coal, It is enough to grasp the strength in advance. The coke strength is generally the drum strength index DI according to the drum test method defined in JIS K 2151. In addition to the drum strength index defined by JIS, the tumbler strength index defined by ASTM and JIS, ISO You may make it use the Mycom strength index of regulation, NF regulation and DIN standard, the irsid strength index of NF regulation and ISO regulation, etc.

First, the expansion specific volume was measured in the expansibility test under the first temperature rising condition in which the average heating rate HR _400-500 of the test poor coal was over 3 ° C./min. The correlation equation of the first test poor coal group (group in which the test poor coal can be differentiated by the expansion specific volume) showing a correlation with the coke strength is obtained. The average heating rate HR _400-500 employed in the first heating condition is higher than the heating rate of the dilatometer method of JIS M 8801, so that the expansion specific volume from a part of the test poor coal is increased. As long as a correlation is recognized between the coke strength and the coke strength. The specific HR _400-500 may be set as appropriate depending on the type (brand) and number of the inferior coal constituting the test inferior coal, but preferably 6 ° C / min or more as a guideline for the setting. It is good to make it within a range of less than 100 ° C./min, more preferably within a range of 12 ° C./min to 50 ° C./min. If H.R. _400-500 is 6 ° C / min or more, it is preferable because two or more brands of poor quality coal can sufficiently exhibit expansibility that can be classified into the first test poor quality coal group. It is. By the way, when H.R. _400-500 is 100 ° C / min or higher, it may be difficult to significantly derive the correlation classified into the first test inferior coal group for these brands of inferior coals. Since it becomes high, it is suitable to set it within the range of less than 100 ° C./min, more preferably 50 ° C./min or less.

Next, the expansion specific volume of the test inferior coal was measured in the expansibility test under the second temperature rise condition in which the average temperature rise rate HR _400-500 was made faster than the first temperature rise condition. From the correlation between the expansion specific volume of test poor coals other than those classified into the test poor coal group of 1 and the coke strength, the second test poor coal group (the test poor coal differentiated by the expansion specific volume) The correlation formula of the group that can do this is obtained. The average heating rate HR _400-500 employed in the second temperature _raising condition is a test in which the correlation between the expansion specific volume and the coke strength was not obtained in the expansion test under the first temperature raising condition. Since it is necessary for the inferior quality coal to be differentiated by the expansion specific volume, it is faster than the first temperature raising condition. Specific HR _400-500 may be set as appropriate as in the case of the first temperature rise condition, but as an indication of the setting, preferably the average temperature rise rate of the first temperature rise condition 2 times or more, more preferably 5 times or more of the temperature increase condition of the first average temperature increase rate. Further, the upper limit value of the average temperature rising rate is not particularly defined because it depends on the first temperature raising condition, but the actual practicable range is preferably 100 times or less, more preferably 10 times. The following can be illustrated. By the way, when HR _400-500 is more than 8 times the average rate of temperature increase under the first temperature rise condition, the correlation with HR _400-500 , which is relatively slow like the first temperature rise condition, is correlated. It is confirmed that a significant relationship between the expansion specific volume and the coke strength can be sufficiently recognized for the test inferior coal that did not show the it can.

In the example shown in Table 1 above, inferior coal that showed a relatively high expansion specific volume in the expansion test under the first temperature rise condition of HR _400-500 = 12 ° C./min is the expansion specific volume. And is classified into the first test poor coal group, and the correlation equation (1) can be calculated from the first test poor coal group. On the other hand, for the remaining inferior coal whose expansion specific volume showed a relatively low value, the expansion specific volume determined by the expansion test under the second temperature rise condition of HR _400-500 = 100 ° C./min. The correlation equation (2) can be calculated from the second test poor coal group. Therefore, if the correlation equations (1) and (2) obtained by these are used, the coke strength of the formed coke obtained using the inferior coal can be estimated from the expansion specific volume of the inferior coal used in actual production. it can. When there is a further need in the example of Table 1 or when the differentiation by the expansion specific volume is not sufficient for all the test poor coals in the expansibility test under the first and second heating conditions, Of course, an expansibility test is carried out under the third temperature rise condition, which is HR _400-500 faster than the second temperature rise condition, and an expansibility test is carried out under the fourth and subsequent temperature rise conditions. It may be.

  And, when estimating the coke strength of the formed coke for the inferior coal used in actual production, an expansibility test is performed in advance under two or more temperature rising conditions as described above, and At least correlation equations (1) and (2) are obtained from the correlation between the expansion specific volume and the coke strength of the test molded coke obtained from the respective test inferior coals.

Next, about the inferior quality coal used for an actual manufacture, the expansion specific volume is measured by the expansibility test by the 1st temperature rising condition similar to the case where said correlation Formula (1) is calculated | required. If the obtained expansion specific volume I satisfies the following condition <1-i>, using the correlation equation (1) obtained from the first test poor coal group based on the expansion specific volume, The coke strength of the formed coke obtained by molding the inferior coal is estimated. If the obtained expansion specific volume I corresponds to the following condition <1-ii>, the expansibility test under the second temperature rise condition similar to the case of obtaining the above correlation equation (2) To measure the expansion specific volume II.
Expansion specific volume I ≧ 1.1 × a ₁ ...... <1-i>
Expansion specific volume I <1.1 × a ₁ ...... <1-ii>
(Here, a ₁ represents the reference expansion specific volume when the piston displacement in the narrow tube filled with the fine powder sample of inferior coal is zero in the expansion test under the first temperature rise condition.)

If the expansion specific volume II obtained again satisfies the following condition <2-i>, the correlation equation (2) obtained from the second test poor coal group is obtained based on the expansion specific volume II. To estimate the coke strength. If the expansion specific volume II obtained again satisfies the following condition <2-ii>, an expansibility test is performed in advance under the third and subsequent temperature rise conditions, and correlation equations (3), (4 ),..., (N), and conditions <3-i>, <4-i>,... Obtained in the same manner as <1-i> and <2-i> above. This is repeated until <ni> is satisfied. Alternatively, if the coke strength expected to some extent is estimated from the expansion specific volume in the most recent expansibility test, for example, it is expected that the surface fracture strength DI ¹⁵⁰ ₆ is not expected to reach a predetermined quality control value. When the condition <n-ii> is satisfied, it may be determined that the poor quality coal is not suitable for the production of formed coke.
Expansion specific volume II ≧ 1.1 × a ₂ ...... <2-i>
Expansion specific volume II <1.1 × a ₂ ...... <2-ii>
Expansion specific volume n ≧ 1.1 × a _n ...... <ni>
Expansion ratio volume _{n <1.1 × a n ...... <} n-ii>
[Here, a ₂ represents the reference expansion specific volume when the piston displacement in the narrow tube filled with the fine powder sample of inferior coal is zero in the expansion test under the second temperature rise condition. Further, the expansion ratio volume n is an expansion ratio volume measured by the expansion test according to the temperature-raising condition of the n, a _n, the piston in the tubules filled with fine powder sample of low-quality coal in its expanded test The reference expansion specific volume when the displacement is zero is represented (n is a natural number). ]

In obtaining these conditions <ni> and <n-ii>, the present inventors used the expansibility test apparatus shown in FIG. The expansion specific volume was measured by conducting an expansibility test at HR _400-500 = 12 ° C./min. When the number of samples was set to 5 and the standard deviation σ of the expansion specific volume was determined, it was 3σ = 0.123. If it is 3σ, it is considered that it is surely expanded rather than in the range of variation. Incidentally, in the case of this expansibility test, according to the conditions in Table 2, when the piston displacement in the narrow tube is zero, that is, the initial height h instead of h _{1 in} the equation (Z) for obtaining the expansion specific volume shown above. _{If 0} = 60 mm is substituted, the standard expansion ratio volume when coal X is not expanded at all is 1.25. Therefore, taking this 3σ into consideration, the expansion specific volume after the expansibility test is 1.250 + 0.123 = 1.375, but this value is approximately 1 with respect to the reference expansion specific volume of 1.250. It turns out that it is 1 time. This tendency was almost the same for various inferior coals.

Based on this finding, the present invention, as long as 1.1 times or more with respect to the measured expansion ratio volume of the reference expansion ratio volume a _n in the expansion test, it is determined that the expansion of the low-quality coal can be confirmed Thus, the coke strength was estimated using the correlation equation obtained in the expansibility test. If it is less than 1.1 times, it is judged that the inferiority of the inferior coal cannot be confirmed, and the coke strength is estimated from another expansibility test having a high average heating rate.

  The strength estimation method according to the present invention is used to estimate the coke strength when molding inferior quality coal to produce shaped coke, and also to produce shaped coke by blending multiple types of inferior quality coal. be able to. When blending multiple types of inferior charcoal, the coke strength of the resulting coke is estimated by measuring the expansion specific volume for each inferior coal in the expansibility test according to the present invention and weighted average with the blending ratio. can do. Moreover, it can apply also when manufacturing a shaping | molding coke including the other coal which shows non-caking coal and caking property other than inferior coal. In that case, what is necessary is just to make it combine the well-known intensity | strength estimation method regarding non-slightly caking coal.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not restrict | limited to the content of the following Examples.

  Nine types of inferior charcoal (A charcoal to I charcoal) having the properties shown in Table 1 were prepared and used as test inferior charcoal. As for these, the total expansion rate calculated | required by the expansibility test method prescribed | regulated to JISM8801 was 0%. With respect to these nine types of test poor coals, plain coals were prepared as follows.

  First, each inferior coal is pulverized so that 1.5 mm or less becomes 100%, and hot water is added to the pulverized inferior coal in an amount of 1000 cc / 30 kg-coal and heated in order to prevent uneven distribution of the binder added later. Then, SOP (soft pitch) was added in an external number of 8% by mass as a binder and kneaded for 180 seconds with a kneading machine (Laidge mixer, 550 mmφ × 670 mmL) to make each inferior charcoal a kneaded charcoal. Next, the obtained kneaded charcoal was molded at a linear pressure of 3 t / cm using a double roll press molding machine having a cup size of 65 mm in length, 45 mm in width, and 30 mm in thickness. Charcoal was used.

Next, each of the obtained coals was heated to 1000 ° C. using a direct distillation furnace to obtain a test molded coke. At that time, in order to dry-distill in a temperature rising pattern in which the average temperature rising rate from the time when the temperature of the central part of the forming coal reaches 400 ° C. to 500 ° C. is 6 ° C./min, The sample was heated to 1000 ° C. at an average rate of temperature increase of 6 ° C./min. About 500 g of each of the obtained test molded cokes, about 500 g is screened by a hand sieve with a sieve having an opening diameter of 25 mm, and the surface fracture strength of each test molded coke is measured by a drum tester based on JIS K2151 using the sieve top as a measurement sample. DI ¹⁵⁰ ₆ (−) was measured. The results are as shown in Table 1.

Moreover, the expansion specific volume was measured as follows using the expansibility test apparatus shown in FIG.
First, pulverize so that 1.5 mm or less becomes 100%, prepare a fine powder sample of inferior charcoal for each test, and insert into a measuring tube (fine tube) made of SUS310S having an inner diameter of 8 mm × height of 372 mm. A piston was placed on the upper side in the tube so that the height of the test inferior coal fine powder sample was 60 mm. In addition, each of the test inferior coal fine powder samples charged in the measuring tube had a mass of anhydrous base of 2.413 g, and the packing density (bulk density) at that time was 0.8 g / cm ³ . did.

Subsequently, the measuring tube was put in an electric furnace preheated to 300 ° C., and a fine powder sample of test poor coal filled in the measuring tube was heated from 300 ° C. to 550 ° C. At that time, the first temperature rise condition in which the average temperature rise rate HR _400-500 from the time when the fine powder sample in the measuring tube reaches 400 ° C. until it reaches 500 ° C. is 12 ° C./min. Each test inferior charcoal is heated with a temperature rising pattern and a temperature rising pattern under the second temperature rising condition where the average temperature rising rate HR _400-500 is 100 ° C./min, and each of the two expansions is expanded. A sex test was performed. During these expansibility tests, the height of the fine powder sample that expands in the measuring tube is measured by a laser displacement meter (not shown) connected to the piston, and the maximum expansion volume V is obtained when the piston displacement reaches the maximum. The expansion specific volume was calculated from the previous equation (Z). Each result is as shown in Table 1. When obtaining the temperature increase condition of HR _400-500 = 100 ° C./min, the temperature of the electric furnace is raised to 550 ° C. in advance in this embodiment for the convenience of the output of the electric furnace used. The measurement tube was put into this and held for 7 minutes.

Then, the expansion specific volume (cm ³ / g) of each test inferior coal obtained above and the coke strength DI ¹⁵⁰ ₆ (−) of the test molded coke obtained from each test inferior coal obtained previously. The relationship is summarized for each of the expansibility tests with different temperature rising conditions as shown in the graphs of FIGS. Among these, according to the expansion test of HR _400-500 = 12 ° C./min shown in FIG. 2, the expansion specific volume (x) of Coal A, Coal B, Coal C, and Coal D is As the coke strength DI ¹⁵⁰ ₆ (y) increases, the correlation of the first test inferior coal group consisting of coals A to D is “y = 12.832x + 54.175”. It can be represented by (1). On the other hand, in the expansibility test of HR _400-500 = 100 ° C./min shown in FIG. 3, in the graph of FIG. 2, the xy linear function has no inclination, and the expansion specific volume and coke strength DI ^150. E charcoal, F charcoal, G charcoal, H charcoal, and I charcoal that do not correlate with ₆ show a relationship in which the coke strength (y) increases as the expansion specific volume (x) increases. The correlation of the second test inferior coal group consisting of charcoal to I charcoal can be represented by the correlation equation (2) of “y = −7 / (x−1.15) +80”.

  According to these correlation equations (1) and (2), the correlation between the expansion specific volume and the coke strength can be grasped for all prepared test poor coals. Thus, the inferior coal used for actual production is subjected to an expansibility test in the same manner as described above to obtain an expansion specific volume, and using these correlation equations, the coke strength when formed into coke can be estimated. Therefore, as shown in Table 3, for the inferior coals j and k that are newly received and the coke strength is unknown and the total expansion rate measured by the expansion test method of JIS M 8801 is 0%, The formed coke was manufactured while estimating the coke strength.

First, inferior charcoal j is pulverized so that 1.5 mm or less becomes 100% to obtain a fine powder sample, which is charged into a measuring tube made of SUS310S in the same manner as the previous case, and the average heating rate H.R. _The expansion specific volume I was measured in the expansibility test under the first temperature raising condition where _400-500 was 12 ° C./min. Since the reference expansion specific volume a _{1 at} this time was 1.25 and the actually measured expansion specific volume I was 1.60, the condition of expansion specific volume I ≧ 1.1 × 1.25 was satisfied. Will meet. Therefore, using the above correlation equation (1), the surface fracture strength DI ¹⁵⁰ ₆ (−) = 74.71 is obtained when the coke strength when the inferior coal j is formed into formed coke from the measured expansion specific volume I. It was estimated.

Next, in the same manner as in the case of the test-formed coke described above, a pillow-type formed coal having a volume of 56 cc was produced from this inferior coal j, and the temperature of the central portion of the formed coal reached 400 ° C. using a direct carbonization furnace. In order to set the average temperature rising rate from the time to 500 ° C. to 6 ° C./min, heating is performed from the start of temperature rising to 1000 ° C. at an average temperature rising rate of 6 ° C./min. j Simple molded coke was produced. The molded coke this poor quality coal j in the same manner as in the previous step, the surface fracture strength DI ^0.99 ₆ a drum tester based on JIS K2151 method (-) was measured, the surface fracture strength of the measured DI ^0.99 ₆ (-) Was 75.0. This value was in good agreement with the estimated surface fracture strength DI ¹⁵⁰ ₆ (−).

On the other hand, for the inferior coal k, the expansion specific volume II measured in the expansibility test under the first temperature increase condition with an average temperature increase rate HR _400-500 of 12 ° C./min is 1.31; The condition of the expansion specific volume I <1.1 × 1.25 was met. Therefore, an expansion test was performed under the second temperature increase condition with an average temperature increase rate HR _400-500 of 100 ° C./min, and the expansion specific volume II of the poor quality coal k was measured to be 1.38. there were. Since this value satisfies the condition of expansion specific volume II ≧ 1.1 × 1.25, using the correlation equation (2) obtained above, the expansion specific volume II of this inferior coal k was formed into coke. When the coke strength in this case was determined, it was estimated that the surface fracture strength DI ¹⁵⁰ ₆ (−) = 49.57.

Then, for this inferior charcoal k, a pillow type coal with a volume of 56 cc was produced in the same manner as described above to obtain an inferior charcoal k simple shaped coke. When the surface fracture strength DI ¹⁵⁰ ₆ (−) of the formed coke of this inferior coal k was measured, the surface fracture strength DI ¹⁵⁰ ₆ (−) was 50, and the surface fracture strength DI ¹⁵⁰ ₆ (−) estimated above was The results were in good agreement.

The formed coke of inferior coals j and k produced while estimating the coke strength as described above has sufficient surface fracture strength DI ¹⁵⁰ ₆ (−) as a small coke charged in the periphery of the blast furnace. Is. Therefore, it is considered that the inferior quality coals j and k can be used as simple formed coke, or formed coke mixed with other coal.

In the above embodiment, the expansibility test under the first temperature rise condition is HR _400-500 = 12 ° C./min, and the expansibility test under the second temperature rise condition is HR _{400- Although 500} = 100 ° C./min, it is a matter of course that HR _400-500 other than these can be adopted. Moreover, in the said Example, although the expansibility test which employ | adopted two temperature rising conditions is performed, you may perform an expansibility test on the temperature rising conditions which changed the average temperature rising rate further. That is, depending on the type and number of test poor coals prepared, the average heating rate may be appropriately selected so that they exhibit a predetermined correlation between the expansion specific volume and coke strength. The expansibility test can be performed by setting the number of temperature raising conditions so that all the test poor coals exhibit these significant correlations.

Claims (2)

When producing formed coke using inferior coal, the correlation between the expansion specific volume of multiple types of test inferior coal and the coke strength of test formed coke obtained from each of the inferior coals for testing is obtained in advance. Based on the correlation equation, it is a method for estimating the coke strength of the formed coke obtained using the inferior coal from the expansion specific volume of the inferior coal used in actual production,
The expansion specific volume is obtained by an inferior coal fine powder sample obtained by an expansibility test in which a piston is placed on a fine powder sample of inferior coal filled in a thin tube and heated at a predetermined temperature rise rate to obtain the highest point of piston displacement. Is the ratio (V / W) between the maximum expansion volume V and the filling mass W of the inferior quality coal fine powder sample,
First, the expansion under the first temperature rise condition in which the average temperature rise rate HR _400-500 is over 3 ° C./min from when the test inferior coal reaches at least 400 ° C. to 500 ° C. The expansion specific volume is measured in the property test, and the correlation equation of the first test poor coal group in which the expansion specific volume has a correlation with the coke strength is obtained,
Subsequently, the expansion specific volume was measured by an expansion test under a second temperature increase condition in which the average temperature increase rate HR _400-500 was made faster than the first temperature increase condition, and the first test poor coal group A method for estimating the strength of a formed coke, wherein a correlation equation of the second test poor coal group is obtained from the correlation between the expansion specific volume of the test poor coal other than the above and the coke strength. The expansion specific volume of the inferior coal used in actual production is measured by an expansion test under the first temperature rise condition, and the expansion specific volume is _{1 with} respect to the reference expansion specific volume a ₁ when the piston displacement is zero. .1 or more (≧ 1.1 × a ₁ ), the coke strength is estimated using the correlation equation obtained from the first test poor coal group,
If the expansion specific volume is less than 1.1 times (<1.1 × a ₁ ) with respect to the reference expansion specific volume a ₁ , the expansion specific volume is measured by an expansion test under the second temperature rise condition, and the expansion When the specific volume is 1.1 times or more (≧ 1.1 × a ₂ ) with respect to the reference expansion specific volume a ₂ when the piston displacement is zero, the correlation formula obtained from the second test poor coal group The coke strength estimation method according to claim 1, wherein the coke strength is estimated by using.

Images