JP6565642B2 - Coke shrinkage estimation method - Google Patents

Description

  The present invention relates to a method for estimating the coke shrinkage when coal is carbonized under predetermined conditions, and more specifically, for example, predicting the particle size of coke obtained by carbonizing coal, or coke strength. It is related with the method of estimating the coke shrinkage rate used in the case of predicting.

  In order to further improve the efficiency of blast furnace operation, the strength and particle size of coke obtained by carbonizing coal must be stable, that is, coke having the target strength and particle size can be produced. It has been demanded. In addition, in order to reduce the production cost of coke, it is necessary to use as much low-priced low-grade coal as non-slightly caking coal as much as possible. Predicting the particle size and strength of the obtained coke in advance is becoming more important because the diameter decreases and the volume fracture powder rate increases.

Among these, in estimating the strength of coke, it is known that the drum strength index DI ¹⁵⁰ ₁₅ which is one of the indexes of coke strength can be expressed as follows (see, for example, Patent Document 1).
DI ¹⁵⁰ ₁₅ = DI ¹⁵⁰ ₆ -DI ¹⁵⁰ _6-15
That is, in Patent Document 1, when coke is obtained from a coal blended with a high-coalized coal and a low-coalized coal, the drum strength index DI ¹⁵⁰ ₁₅ is used as the surface fracture strength DI ¹⁵⁰ ₆ and the volume fracture powder. The ratio DI ¹⁵⁰ _6-15 is estimated separately, and the volume fracture powder rate is estimated by adding the vitrinite average reflectance Ro of the high-carbonized coal to be blended and the blending ratio of the low-carbonized coal. Is used. Here, the drum strength index DI ¹⁵⁰ ₁₅ indicates a lump ratio of 15 mm or more after impact specified in JISK2151.

Also, the volume fracture powder rate DI ¹⁵⁰ _6-15 is estimated from the solidification temperature of the blended coal, and the surface fracture strength DI ¹⁵⁰ ₆ is calculated from the value obtained by weighted average of the expansion rate or specific volume of each coal constituting the blended coal. A method of estimating and estimating the strength of coke based on these (see Patent Document 2) is also known.

On the other hand, it is known that the particle size of coke can be estimated based on, for example, the following equation (see Patent Document 3).
Coke particle size of blended coal = a + b × coke shrinkage ratio of blended coal In Patent Document 3, coke is produced using blended coals in various blends and the coke particle size is measured. The coke shrinkage is measured for each coal contained in the coal, and the coke shrinkage in each blended coal is calculated by weighted averaging according to the blending ratio of each coal. It is assumed that the coefficients a and b are determined by a method such as regression analysis based on the measured diameter value and the calculated coke shrinkage rate.

  Here, the particle size and volume fracture powder rate of coke are determined due to the macro cracks in the order of cm in the coke mass. Generally, when coal is carbonized, thermal decomposition or thermal polymerization reaction of an organic polymer structure occurs, and various physical phenomena are manifested accordingly. That is, coal softens and melts from around 400 ° C., particles adhere to form a porous mass, resolidifies at around 500 ° C., and thereafter contracts to form a coke with a denser structure. At this time, since there is a temperature distribution in the width direction of the carbonization chamber, it is considered that a thermal stress is generated due to the strain of shrinkage and a macro crack is formed, so in accurately estimating the strength and particle size of coke, It is necessary to grasp the coke shrinkage rate in the shrinkage process after coal resolidification.

  Regarding the coke shrinkage rate, the above-mentioned Patent Document 3 discloses a measuring method thereof. That is, in patent document 3, it heats to temperature T (degreeC) more than the resolidification temperature of coal, and the volume difference or length difference of the contents in resolidification temperature and temperature T is the volume or length in resolidification temperature. The value divided by the above is defined as the coke shrinkage at the temperature T of coke produced from the coal. Specifically, coal is charged into an internal thin tube of a sample tube having a double structure of an internal thin tube and an external thin tube provided with a plurality of vent holes, and a piston is placed thereon, and a predetermined heating rate Then, the vertical displacement of the piston with respect to the heating temperature is measured, and the coke contraction rate is obtained based on the piston height at the resolidification temperature and the piston height at the temperature T.

  According to such a method, it is possible to directly measure the coke shrinkage, which is a cause of generation of cracks that control volume fracture and coke particle size. However, in this method, depending on the type of coal, the piston may be fixed due to molten coal or tar, and measurement may not be possible. Further, since the apparatus itself is special, there is a problem that the coke shrinkage rate cannot be measured at any time.

  On the other hand, there is a report focusing on the relationship between coal properties and coke shrinkage (see Non-Patent Document 1). In this Non-Patent Document 1, the coke shrinkage rate is obtained by the method described in Patent Document 3 above, and it is confirmed that the coke shrinkage rate and the coke particle size have a correlation. In addition, we are investigating the relationship between the coke shrinkage rate and the volatile matter (VM) of coal and the degree of coalification, but no significant results were found. Is not decided. For reference, the relationship between the coke shrinkage (1000 ° C.) described in Non-Patent Document 1 and the particle size of coke is shown in FIG. 5 (see FIG. 9 of Non-Patent Document 1). Figure 6 shows the relationship between the volatile matter of coal and the coke shrinkage (1000 ° C) (Fig. 6 is shown).

  By the way, regarding the contraction of coke, there are some which are defined with different physical quantities of interest. For example, in Japanese Patent Application Laid-Open No. 2013-216913 (Patent Document 4), the coke after dry distillation and the furnace wall of the coke oven The clearance (clearance) formed between the bricks is defined as the amount of contraction of coke. In addition to the coke shrinkage described above, this shrinkage is affected by at least various factors such as temperature distribution and expansion pressure, and is different from the coke shrinkage targeted in the present invention. It is.

JP 2005-194358 A JP-A-9-263964 JP-A-2005-232349 JP 2013-216814 A

Seiji Nomura and Takashi Arima (2013) .Effect of coke contraction on mean coke size.Fuel, 105, 176-183.

  As described above, in order to further improve the estimation accuracy of the strength and particle size of coke, it is extremely important to grasp the coke shrinkage rate in the shrinkage process after resolidification of coal. According to the method described in Patent Document 3, coke shrinkage can be measured directly, but a special device must be used, and measurement may be difficult depending on the type of coal. On the other hand, a technique for estimating the coke shrinkage from the properties of coal by industrial analysis has not yet been established.

  Therefore, as a result of intensive studies to solve these problems, the present inventors have found that the coke shrinkage rate at a temperature T equal to or higher than the resolidification temperature of coal is from the resolidification temperature of the coal to the temperature T. It was newly found that there is a correlation with the weight loss rate. And if this correlation is utilized, since a coke shrinkage rate can be estimated with sufficient accuracy, the present invention was completed.

  Therefore, an object of the present invention is to provide a method capable of estimating the coke shrinkage rate more easily and accurately regardless of the type of coal.

That is, the gist of the present invention is as follows.
(1) Put coal in a container and heat it to a temperature T equal to or higher than the resolidification temperature of the coal. The volume difference or length difference of the contents between the resolidification temperature and temperature T is the volume or length at the resolidification temperature. A method for estimating a coke shrinkage at a temperature T of coke generated from the coal, expressed by a value obtained by dividing the coke,
For a plurality of test coals whose coke shrinkage at temperature T is known in advance, the weight loss curve is measured by thermogravimetric analysis, and the resolidification temperature is measured by the Gieseler plastometer method specified in JIS M8801, For each coal used, the weight reduction rate from the resolidification temperature to the temperature T is obtained from the weight reduction curve, and a correlation equation between the coke shrinkage rate at the temperature T of each test coal and the weight reduction rate is obtained,
A method for estimating a coke shrinkage rate, wherein a coke shrinkage rate at a temperature T is unknown, and a coke shrinkage rate is estimated from an obtained correlation equation based on a weight reduction rate from a resolidification temperature to a temperature T.
(2) The coke shrinkage ratio is measured using a sample tube having a double structure of an internal thin tube and an external thin tube provided with a plurality of vent holes as a container for coal. While charging coal into the pipe, placing the piston and heating it at a specified rate of temperature rise, the piston's vertical displacement relative to the heating temperature is measured, and the piston height at the coal resolidification temperature and the piston height at temperature T are measured. The coke shrinkage rate estimation method according to (1), which is calculated based on the above.
(3) The method for estimating the coke shrinkage rate according to (1) or (2), wherein the temperature T is 800 ° C. or higher and 1300 ° C. or lower.

  According to the present invention, the coke shrinkage rate can be estimated more easily and accurately with any coal. By establishing a method for estimating the coke shrinkage in this way, it is possible to further improve the accuracy of predicting the particle size and strength of coke obtained by carbonizing coal, and relatively inexpensive coal such as non-slightly caking coal This is extremely useful in the production of blast furnace coke.

FIG. 1A is an overall schematic explanatory view of an apparatus (high temperature dilatometer) for measuring coke shrinkage, and FIG. 1B is an explanatory view showing a state in which a sample (coal) is charged into a sample tube. FIG. 1 (c) is a plan sectional view of the internal thin tube. FIG. 2 shows weight reduction curves of various coals (coal C, D, H, O) measured with a thermobalance. FIG. 3 shows an example of measurement using a coal Geseller plastometer used in the examples [(a) is Coal H, (b) is Coal O]. FIG. 4 is a correlation equation obtained in the example and is a graph showing the relationship between the weight reduction rate from the resolidification temperature of coal to 1000 ° C. and the coke shrinkage rate at 1000 ° C. FIG. 5 is a graph showing the relationship between coke shrinkage and coke particle size (quoting FIG. 9 of Non-Patent Document 1). FIG. 6 is a graph showing the relationship between the volatile matter of coal and the coke shrinkage (quoting FIG. 6 of Non-Patent Document 1).

The present invention will be described in detail below.
First, the coke shrinkage targeted in the present invention is measured by the method described in Patent Document 3. Coal is put in a container and heated to a temperature T equal to or higher than the coal resolidification temperature, It is represented by a value obtained by dividing the volume difference or length difference between the contents at the solidification temperature and the temperature T by the volume or length at the resolidification temperature. Specifically, the coke shrinkage can be measured as follows using the apparatus (high temperature dilatometer) shown in FIG.

  This device can raise the temperature to a higher temperature than normal dilatometers (heating up to 550 ° C) for testing the expansibility of coal (heating up to 1300 ° C). Sample tube 4 having a double structure of 2 and external thin tube 3 is used. That is, the apparatus (high temperature dilatometer) used here heats the sample tube 4, the piston 6 placed on the coal 1 charged in the sample tube 4, and the coal in the sample tube 4 at a predetermined temperature rising rate. An electric furnace 8 having a heater 7 that can be used, and a laser displacement meter 9 that measures the vertical displacement of the piston are provided. Among these, the internal thin tube 2 has a plurality of vent holes 5 on the surface thereof, so that gas generated by coal can escape to the outside of the internal thin tube 2. This is because if coal generates a pyrolysis gas during softening and melting and expands greatly, molten coal or tar enters the gap between the piston 6 and the internal thin tube 2 and the movement of the piston is restricted after re-solidification. By providing the vent hole 5 in the internal thin tube 2, the gas at the time of softening and melting is discharged, the expansion is suppressed, and the shrinkage after resolidification can be measured. The upper end of the external pipe 3 is covered with a lid 10 and acts as a guide for preventing the axis deviation of the piston 6.

When charging the coal 1 into the sample tube 4, a thin sheet 11 such as paper through which pyrolysis gas can pass is placed along the inside of the internal thin tube 2, and the coal pulverized to a predetermined particle size is loaded. The coal is prevented from spilling from the vent hole 5 of the internal thin tube 2, and the coal in the sample tube 4 is heated at a predetermined temperature increase rate. Then, while measuring the vertical displacement of the piston with respect to the heating temperature, from the piston height h at the resolidification temperature and the piston height h ′ at the temperature T, the coke shrinkage ratio R (− ). At this time, in consideration of the thermal expansion of the piston 6 due to the temperature rise, the influence of the piston expansion is obtained in advance as a function of temperature based on the actual value in the blank, and the coke shrinkage rate according to the equation (1) is obtained. Corrections may be made when calculating.
R = (h−h ′) / h (1)

  Here, in specifying the resolidification temperature when the coal is heated by this measurement, as shown in Patent Document 3, the behavior of the piston displacement greatly changes as the temperature rises, and the piston height suddenly increases. The decreasing temperature can be used as the resolidification temperature. Specifically, using the above-described apparatus, the length of the coal 1 being heated is continuously measured based on the position of the piston 6, and the change in the coal length per unit temperature change is calculated during the temperature rising. Then, when observing the relationship with temperature as the rate of change in length, it is possible to find a temperature where the rate of change in length decreases and then increases rapidly in the region of 400 to 550 ° C. It may be temperature. Also, when the shrinkage coefficient per unit temperature change is defined as the shrinkage coefficient (-/ K) and the relationship between the shrinkage coefficient and temperature is observed, the shrinkage coefficient decreases in the temperature range immediately before the coal resolidification temperature. Since the shrinkage coefficient increases rapidly in the temperature region immediately after the resolidification temperature, the change in the shrinkage coefficient may be observed and the temperature at which the shrinkage coefficient increased rapidly may be specified as the resolidification temperature of coal.

  On the other hand, the temperature T can be arbitrarily set as long as the temperature is equal to or higher than the resolidification temperature, but considering that the obtained coke shrinkage is used for estimating the particle size and strength of the coke, etc. It is good to set it as the carbonization temperature at the time of obtaining coke from coal, Preferably it is 800 degreeC or more and 1300 degrees C or less, Most preferably, it is 1000 degreeC.

  In the present invention, such a coke shrinkage rate is obtained (estimated) without using the apparatus shown in FIG. That is, the present inventors have assumed that the shrinkage phenomenon of coke occurs after resolidification of softened and melted coal, and further occurs when part of semi-coke is desorbed as gas after resolidification by heating. The resolidification temperature was measured with a Gisseler plastometer specified in JISM8801, and the desorption of the gas after resolidification of the coal was obtained from the weight loss curve by thermogravimetric analysis to enable estimation of the coke shrinkage.

  Specifically, for a plurality of test coals having a known coke shrinkage at temperature T, measurement of a weight loss curve by thermogravimetric analysis and measurement of a resolidification temperature by the Gieseler plastometer method defined in JIS M8801 are performed. Like that. Here, when measuring the weight loss curve of coal by thermogravimetric analysis, it is preferable that the conditions be similar to those in a coke oven. For example, the coal is heated in a nitrogen atmosphere by a thermobalance. Then, the temperature increase rate at that time is set to 1 to 10 ° C./min, and the ultimate temperature is set to 800 to 1300 ° C., and the weight reduction curve is measured. As an example, FIG. 2 shows a weight reduction curve of coals C, D, H, and O used in examples described later.

  The re-solidification temperature is measured by the Gieseler plastometer method defined in JIS M8801, as described above, and the solidification temperature, which is the temperature at which the stirring rod stops and stops, is obtained. In the present invention, this solidification temperature is called a resolidification temperature. Similarly, FIG. 3 shows a measurement example of the coal H [FIG. 3 (a)] and the coal O [FIG.

  Then, for each test coal, the weight reduction rate from the resolidification temperature to temperature T is calculated from the weight reduction curve obtained above, and a correlation equation between the coke shrinkage rate of each test coal and this weight reduction rate is obtained. Just do it. FIG. 4 shows the relationship between the coke shrinkage of the test coal obtained in the examples described later and the weight reduction rate, and it can be seen that a good correlation is exhibited. Therefore, for coal with unknown coke shrinkage at temperature T, the weight loss curve is measured in the same manner as for the test coal, the resolidification temperature is obtained, and the weight loss rate from the resolidification temperature to temperature T is calculated. Then, the coke shrinkage rate can be estimated from the obtained correlation equation. The thermogravimetric analysis and measurement using a Gisela plastometer used at that time are both general-purpose, and according to the present invention, the coke shrinkage can be easily estimated without using a special device, and any charcoal can be estimated. The estimation method of the present invention can also be applied to seeds.

  For the test coal having a known coke shrinkage at the temperature T prepared to obtain such a correlation equation, it is sufficient to prepare a plurality of coals having different coke shrinkage, with different origins and brands. It is good to prepare 5 or more, more preferably 10 or more. At that time, since the coke shrinkage is generally about 10 to 18%, it is preferable to include the upper limit side and the lower limit side of this numerical range.

  Further, the coke shrinkage of each single coal used for blending by the method of the present invention is determined, and the coke shrinkage of each coal obtained is weighted average according to the blending ratio to obtain the coke shrinkage of the blended coal. Can be estimated. Therefore, based on the coke shrinkage of the blended coal thus obtained, for example, the particle size of coke is estimated by the method described in Patent Document 3 described above, or the strength of coke is determined by a known method. If estimated, a more accurate estimated value can be obtained.

  EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not restrict | limited to these contents.

Example 1
Coal A to O having the properties shown in Table 1 were prepared. Here, Ash (% db) is the mass fraction (namely, ash) of the amount of ash remaining when heat ashing under the conditions specified in the industrial analysis method of JIS M8812, and VM (% db) is Similarly, volatile content defined in the industrial analysis method of JIS M8812, log (MF / ddpm) is the maximum fluidity required by the JIS M8801 Guiseller Plastometer method, and TD (%) is JIS M8812 And Ro (%) represents the average maximum reflectance of vitrinite measured by the method described in JIS M8816 Coal Microstructure Component and Reflectance Measurement Method.

First, using the apparatus shown in FIG. 1, the coke shrinkage rate at a temperature T = 1000 ° C. was measured for each of the coals A to O as follows.
The internal thin tube 2 of the apparatus used for the measurement is composed of a SUS cylindrical container having an inner diameter of 8 mm and an outer diameter of 14.5 mm. There are a total of 368 holes 5 having a diameter of 1 mm in 8 circumferential directions at intervals of 2 mm in the height direction. Is provided. The outer tubule 3 is arranged concentrically with the inner tubule 2, and the material of the outer tubule 3 is SUS, the inner diameter is 16 mm, and the outer diameter is 24 mm. The piston 6 can be inserted into the internal thin tube from above, and the lower end of the piston 6 has a diameter of 7.5 mm and is arranged so as to contact the upper end of the coal 1 charged in the internal thin tube 2. . Further, the vertical position of the piston 6 can be measured by a laser displacement meter 9, and the outside of the outer thin tube 3 of the coal 1 charged into the inner thin tube 2 by an electric furnace equipped with a heater 7. The temperature can be heated up to 1300 ° C.

  Then, a paper (thin sheet) 11 having a thickness of about 50 μm is inserted along the inner periphery of the internal thin tube 2, and 1.25 g of coal pulverized to −3 mm (3 mm or less) is charged therein, and the piston 6 Then, the temperature was raised to 1000 ° C. by the heater 7 at a rate of 3 ° C./min. At that time, the length of the coal 1 being heated was continuously measured based on the position of the piston 6. Further, during the temperature increase, the change in the coal length per unit temperature change was calculated to obtain the length change rate, and when the relationship with the temperature was observed, the length change rate was found in the temperature range of 400 to 550 ° C. A temperature that decreased and then increased rapidly was found, and this temperature was defined as the resolidification temperature of coal. Such measurement was performed on each of the coals A to O, and the coke shrinkage rate at 1000 ° C. was obtained based on the previous equation (1). The results are as shown in Table 2.

  Moreover, about coal A-O, the weight reduction | decrease curve was measured by thermogravimetric analysis as follows. For the measurement, using a thermobalance (TGA51H, manufactured by Shimadzu Corporation), 20 mg of coal pulverized to 150 μm or less was heated in a nitrogen atmosphere with a flow rate of 200 mL / min at a temperature rising condition of 3 ° C./min, and the ultimate temperature was 1000 ° C. The mass change was measured. Among these, the weight reduction curves of coal C, D, H, and O are shown in FIG.

  Further, the resolidification temperatures of coals A to O were measured by the Gisela plastometer method defined in JISM8801. The results are as shown in Table 2. Among these, the softening and melting characteristics of coal H are shown in FIG. 3 (a), and the softening and melting characteristics of coal O are shown in FIG. 3 (b). Then, for each of the coals A to O, the weight reduction rate from the resolidification temperature to the temperature T = 1000 ° C. was calculated from the weight reduction curve obtained above. The results are shown in Table 2.

Here, when the relationship between the coke shrinkage at 1000 ° C. of the coals A to O obtained above and the weight reduction rate from the resolidification temperature of each coal to 1000 ° C. is graphed, it is as shown in FIG. . As can be seen from FIG. 4, they have a good correlation. When the weight reduction rate from the resolidification temperature to 1000 ° C. is x and the coke shrinkage at 1000 ° C. is y, y = 0.4403x + 7. It can be represented by the correlation formula of 7141 (R ² = 0.7145).

  Therefore, for coal P having the properties shown in Table 4 below and having an unknown coke shrinkage at 1000 ° C., a weight reduction curve was measured in the same manner as described above, and a resolidification temperature was measured. As a result, the resolidification temperature of this coal P is 487 ° C., and the weight reduction rate from the resolidification temperature (487 ° C.) to 1000 ° C. determined from the weight reduction curve is 14.2%. Using the above correlation equation obtained with O as the test coal, the coke shrinkage at 1000 ° C. of this coal P was estimated to be 14.0%.

And when the coke shrinkage of this coal P was actually measured using the apparatus which measured the coke shrinkage of coal AO, it was 14.1%. In addition, when Q charcoal and R charcoal shown in Table 3 were similarly confirmed, the measured values of the coke shrinkage at 1000 ° C. were 12.4% and 15.4%. The estimated values of coke shrinkage were 12.9% and 15.6%. That is, it was found that the coke shrinkage rate very close to the actually measured value can be estimated by the present invention. In addition, the volatile matter (VM) shown in FIG. 6 is assumed to be x, the coke shrinkage rate at 1000 ° C. is y, and the approximate equation at y = 0.1127x + 11.169 (R ² = 0.4225) is used at 1000 ° C. The coke shrinkage was 14.0% for P charcoal, 13.5% for Q charcoal, and 15.1% for R charcoal. It can be seen that the coke shrinkage using the present invention is more accurate.

1: coal, 2: internal thin tube, 3: external thin tube, 4: sample tube, 5: vent hole, 6: piston, 7: heater, 8: electric furnace, 9: laser displacement meter, 10: lid, 11: thin Sheet.

Claims (3)

Coal is put in a container and heated to a temperature T equal to or higher than the resolidification temperature of the coal, and the volume difference or length difference of the contents at the resolidification temperature and temperature T is divided by the volume or length at the resolidification temperature. A method for estimating the coke shrinkage at the temperature T of coke produced from the coal represented by
For a plurality of test coals whose coke shrinkage at temperature T is known in advance, the weight loss curve is measured by thermogravimetric analysis, and the resolidification temperature is measured by the Gieseler plastometer method specified in JIS M8801, For each coal used, the weight reduction rate from the resolidification temperature to the temperature T is obtained from the weight reduction curve, and a correlation equation between the coke shrinkage rate at the temperature T of each test coal and the weight reduction rate is obtained,
A method for estimating a coke shrinkage rate, wherein a coke shrinkage rate at a temperature T is unknown, and a coke shrinkage rate is estimated from an obtained correlation equation based on a weight reduction rate from a resolidification temperature to a temperature T.   The coke shrinkage rate is measured using a sample tube having a double structure of an internal thin tube and an external thin tube provided with a plurality of vent holes as a coal container, Measure the vertical displacement of the piston with respect to the heating temperature while placing it on the piston and heating it at a specified rate of temperature rise. Based on the piston height at the coal resolidification temperature and the piston height at the temperature T The coke shrinkage estimation method according to claim 1, wherein the coke shrinkage is calculated.   The coke shrinkage estimation method according to claim 1 or 2, wherein the temperature T is 800 ° C or higher and 1300 ° C or lower.

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