JP5668287B2 - Method for producing metallurgical coke - Google Patents

Description

  The present invention relates to a method for producing metallurgical coke using inert highly dispersed coal.

  As a raw material for coke used as an iron-making raw material, blended coal obtained by mixing several to a dozen types of coal is used. Coal not only has different properties depending on the production area and brand, but the properties of the same brand also vary from lot to lot.Therefore, there is no blending theory for blending various types of coal to produce coke with the desired quality. Has been built. In particular, since coke plays an important role of ensuring air permeability in the blast furnace, a blending technique has been developed for the purpose of producing high-strength coke that is difficult to be pulverized in the blast furnace.

  When determining the composition of coal, specific coalescence parameters such as volatile content (VM), vitrinite maximum average reflectance (Ro) or strength index (SI), and coalescer maximum flow Two types of parameters such as “caking parameter” such as degree (MF), total expansion rate (TD), and tissue equilibrium index (CBI) are used in combination. In addition, the amount of chemical components such as the amount of ash is also considered, but unlike the strength, it is easily calculated by the weighted average of the amount of chemical components for each coal (for example, see Non-Patent Document 1).

  In addition to the above blending parameters, blending technology that takes into account the gas pressure during dry distillation (see, for example, Patent Document 1), or blended coal as a set of combinations of two types of each coal, the average of actual measurements and each two coals A blending technique (for example, see Patent Document 2) using a deviation (interaction coefficient) from the average value of coke characteristics of the seed combination as a scale has been proposed.

  Moreover, when using a specific coal conventionally, it could not respond | correspond enough with the conventional mixing | blending theory, and there existed a case where it was difficult to use. For some of such coals, for example, Canadian coals are individually evaluated for blending effects (see, for example, Non-Patent Document 2).

Japanese Patent Laid-Open No. 9-228771 Japanese Patent No. 3550862

Miura Yoshiaki “Coke Production” Fuel Association, Vol. 58, 1979, p. 902-913 Atsushi Dobashi, Yutaka Suzuki, Koichi Ikeda, Takashi Arima, Kenji Kato, W. Ross Leeder, C.T. 147-148

  The conventional blending design is based on a method of managing the blended coal so that the average quality is constant. However, as described above, the conventional blending theory that combines the two parameters of coalification parameter and cohesiveness parameter cannot be fully explained, and it has been pointed out that some coals are difficult to use empirically. Some have been considered the representative coal.

  Therefore, various new control factors have been developed to complement the conventional compounding theory. For example, gas pressure, which is complementary to the caking parameter, is considered an important factor controlling coke quality. However, the impact on coal that is difficult to use empirically has not been fully verified.

  In addition, in the case of general blending conditions, the interaction coefficient quantifying the coal combination effect can be estimated and used, but for coal that is difficult to use empirically, At the same time that it has not been fully verified, many experiments are required if it is obtained experimentally.

  Therefore, the object of the present invention is to empirically use a kind that has been considered difficult to be used in combination with other coal so that its performance can be fully demonstrated using conventional blending theory. It is an object to provide a method for producing high-quality metallurgical coke by using coal.

The features of the present invention for solving such problems are as follows.
(1) A method for producing metallurgical coke, characterized in that inert high-dispersion coal is used when blending coal, which is a raw material for producing coke, and the blending ratio of the inert high-dispersion coal exceeds 40 mass%.
(2) When adjusting the Gieseler maximum fluidity (logMF) of the blended coal, the arithmetic average value of the Gieseeller maximum fluidity is about coal having a Gieseler maximum fluidity of 3.0 or more among the coals constituting the blended coal. The method for producing metallurgical coke according to (1), wherein the compounding is performed so as to be less than 4.0.
(3) The number density of the inert component is 2.0 × 10 ¹⁰ when the coal in which the inert high-dispersion coal is pulverized to a particle size distribution of 6 mm or less and 100 mass% is packed to a packing density of 750 kg / m ^3. The method for producing metallurgical coke according to (1) or (2), characterized in that the coal is coal of not less than / m ³ .

  According to the present invention, it is easy to use inert high-dispersion coal such as Canadian coal, which has been considered difficult to use as a raw material for coke. As a result, the choice of coal to be used is widened, resource constraints are reduced, and stable quality coke can be supplied. Therefore, blast furnace operation can be stably continued.

The graph which shows the relationship between the compounding rate of the coal O in blended coal, and the drum 150 rotation 15mm index | exponent of the obtained coke. Inert high-dispersion coal with respect to the arithmetic average value of Gieseller fluidity in coal with a Gieseler maximum fluidity log MF of 3.0 or more among the coals constituting the blended coal and the drum 150 rpm 15 mm index of 0 mass% inert high-dispersion coal The graph which shows the relationship with the increase amount of the drum 150 rotation 15mm index | exponent of 50 mass% compounding coke. The graph which shows the effect of the present invention in a real furnace.

  The present inventors have studied about coal such as Canadian coal, which cannot be adequately handled by conventional compounding theory, and are difficult to use, and found that some of these coals have high dispersibility of inert components, We focused on the difference in the dispersibility of the inert components of coal. And the inert high dispersion charcoal with high dispersibility of the inert component was extracted, and the relationship between the blending condition of the inert high dispersion charcoal and the coke properties was investigated, and the optimum blending method of the inert high dispersion charcoal was found.

  Since the dispersibility of the inert component differs depending on the type of coal, quantitative evaluation is required. The dispersibility of the inert component represents a state indicating the height of dispersion of the inert component contained in the coal, and can be defined using the number density of the inert component. The number density of the inert component is affected by the amount of the inert component and the coal particle size. The amount of the inert component is almost constant for each type of coal, whereas the coal particle size varies greatly depending on the coal pulverization conditions. . Therefore, it is preferable to evaluate the premise of the pulverization condition as being constant, and a condition close to pulverization in actual operation is most desirable. For example, the pulverization particle size of coal in actual operation is generally about 3 mm or less and about 80 mass%, so particle size distribution such as 3 mm or less, 80 mass%, 3 mm or less, 100 mass%, or 6 mm or less, 100 mass% is the condition of actual operation. It is considered close and easy to manage.

  In addition, since the pulverization method such as the pulverizer to be used also affects the coal particle size, it is desirable to make the pulverization method constant when adjusting the coal particle size. Since there was no change in the size relationship between the different dispersibility brands, fluctuations in the grinding conditions are relatively acceptable.

  Coal structure analysis is a typical technique for identifying inert components. For example, by dividing the pulverized coal into predetermined particle size categories and identifying the amount of the inert component in each category, the dispersibility of the inert components such as the existence ratio distribution and number density of the inert components for each particle size can be evaluated. Note that it is not always necessary to perform identification using a microscope, and any method may be adopted as long as similar information can be obtained.

Although it is difficult to uniquely define inert high-dispersion coal with a high dispersibility of inert components, inert high-dispersion coal is a coal with a higher dispersibility of inert components than coal to which conventional blending theory can be applied. In the present invention, the number density of the inert component when the packing density is 750 kg / m ³ of coal in a state of being pulverized to a particle size distribution of 6 mm or less and 100 mass% is 2.0 × 10 ¹⁰ pieces / m ³ or more. Is defined as inert high dispersion coal. In addition to this, the number density of inert components when coal in a state of being pulverized to a particle size distribution of 3 mm or less and 80 mass% is filled to a packing density of 750 kg / m ³ is 2.0 × 10 ¹⁰ pieces / m ³ or more. The number density of inert components is 2.0 × 10 ¹⁰ pieces / m ³ or more when the packing density is 750 kg / m ³ and the coal is pulverized to a particle size distribution of 3 mm or less and 100 mass%. Can be defined as coal.

  Coal exhibits expansion in the softening and melting temperature range by generating bubbles in the active ingredient that exhibits softening and melting and growing it. In the homogeneous component system, bubbles are generated at the same probability at every position, but in the coal softened and melted state, it is a heterogeneous system due to the presence of inert components. In that case, bubble nucleation with homogeneous components is performed. Compared with free energy, bubble nucleation free energy in non-uniform portions such as around inert components is small, and bubbles are likely to be generated. In inert high-dispersion coal, the inert component is fine and there are many, so that many bubbles are generated and at the same time the inert component suppresses the bonding of the bubbles. As a result, since the growth of pores is suppressed, the amount of expansion is reduced.

  Coal resolidifies after softening and melting, and shrinks while releasing gas such as hydrogen as the temperature rises. In this process, the contraction amount is different between the tissue derived from the active component and the inert component, so that cracks are likely to be generated at a portion where the tissue having a different contraction amount exists. As a result, the volume of the crack occupies the coke, and the amount of shrinkage as a coke mass decreases. In inert high-dispersion coal, since there are many inerts that are the starting points of cracks, shrinkage as a coke mass is suppressed.

  Therefore, the present inventors consider that the blending ratio of the inert highly dispersed coal having the characteristic that the amount of expansion after softening and melting is small, while the amount of shrinkage after resolidification is small has an influence on the coking process. By conducting a thorough investigation into the effect of inert high-dispersion coal and the effect of coke properties, the composition of the mixture was controlled, leading to the establishment of high-quality coke production technology based on the use of inert high-dispersion coal.

  Inert high dispersion charcoal, including average high reflectivity (Ro), maximum Gieseller fluidity (log MF) and total inert ratio (TI), which are typical physical properties of blended coal properties, including inert high dispersion charcoal It has been found that the blending ratio and the composition of the blended coal have an influence on the coke quality. Specifically, when the blending ratio of inert high-dispersion coal, which is coal with high dispersibility of the inert component contained in the coal, is about 25 mass% to about 30 mass%, the coke quality tends to deteriorate as the blending ratio increases. From about 30 mass% to about 50 mass%, the coke quality tends to improve as the blending ratio increases. In order to obtain coke with higher quality than when inert high dispersion coal is not used, it is desirable to mix inert high dispersion coal in a proportion higher than 40 mass% with respect to the coal charged into the coke oven. A rate of 45 mass% to 55 mass% is most desirable.

  In addition, also from the result of the thermal stress analysis in the case where the large and small particles are mixed in a predetermined ratio, when the ratio of the large and small particles is 75 mass% and 25 mass%, Compared to the case where the ratio of large and small particles of expansion and contraction is 0 mass% and 100 mass%, and 50 mass% and 50 mass%, the thermal stress generated during the dry distillation is larger, three particles with large expansion and contraction, and small expansion and contraction. It is verified that the maximum thermal stress is generated at the part where one particle is fused.

  Inert high-dispersion coal has many coals with poor caking properties, such as those with low Guesser fluidity, and therefore, using coal with high caking properties, the caking properties of the blended coal as a whole, for example, the maximum Gieseler fluidity is constant. It will be necessary to manage. There are many types of coal in the highest Gieseller fluidity, but in order to further improve coke quality, one of the coals that make up the blended coal has a Gieseller maximum fluidity log MF of 3.0 or higher. About the above coal, it is preferable that the Gieseler maximum fluidity log MF is less than 4.0 in terms of arithmetic average value, and most desirably 3.5 or more and less than 3.7.

  The inert dispersibility was evaluated for each coal brand (coal A to U), and inert high-dispersion coal was selected.

  First, coal is pulverized to a particle size distribution of 6 mm or less and 100 mass%, then 0.1 mm or less, 0.1 to 0.3 mm, 0.3 to 0.5 mm, 0.5 to 1.0 mm, 1.0 to 3. It classify | categorized into 6 particle size of 0 mm and 3.0-6.0 mm, the structure | tissue analysis was performed with respect to the coal of each division, and the volume ratio of the inert component was measured for every particle size division.

Next, assuming that the inert component is spherical, the average volume of one inert component is obtained for each particle size category, and the volume of the inert component for each particle size category obtained by the above-described structure analysis is divided by the average volume of one inert component. Thus, the number of inert components for each particle size category was determined. The sum of the number of inert components in each particle size category was defined as the number density of inert components (pieces / m ³ ). In addition, when converting into the number per unit volume, it was calculated on the assumption that the packing density of coal was 750 kg / m ³ and the specific gravity of coal was constant 1300 kg / m ³ .

  Table 1 shows the evaluation results of inert dispersibility for each coal brand. Table 1 also shows the number density of inert components, the average maximum reflectance (Ro) for each coal brand, the Gieseler maximum fluidity (logMF), and the total inert rate (TI). Note that Ro and TI were measured according to JIS M8816, and log MF was measured according to JIS M8801.

  According to Table 1, the dispersibility of the inert component differs depending on the coal brand, and the tendency is that the number density of the inert component tends to increase as the Ro or TI increases.

  In particular, coals M, O, Q, R, and S have a larger number density of inert components than other coals, and are found to be representative brands of inert highly dispersed coal.

Of the coals that were identified as representatives of inert high-dispersion coals, coal O or M was blended at varying blending ratios in order to evaluate the effect of blending conditions of coals O and M of approximately equal number density on coke quality. The coal blend was dry-distilled, and the properties of the obtained coke were tested. The blended coal was adjusted so that Ro was a constant value of 1.1 and logMF was 2.3. Moreover, the filling conditions of coal were set to a constant of 6 mass% moisture and a charged bulk density of 775 kg / m ³ .

  A small electric furnace capable of simulating an actual furnace was used for the dry distillation test, and the drum strength of the drum 150 rotation 15 mm index defined in JIS K2151 was used for property evaluation of the obtained coke.

  FIG. 1 shows the relationship between the inert high dispersion charcoal content and the drum strength for the produced coke. In FIG. 1, the horizontal axis represents the blending ratio of coal O, and the vertical axis represents the coke drum 150 rotation 15 mm index. According to FIG. 1, it can be confirmed that the blending ratio of the inert highly dispersed coal affects the coke strength. Specifically, although 0% and 10 mass% where the blending ratio of coal O is low, almost no effect is recognized, the blending ratio of 25 mass% to 30 mass% decreases the drum strength, and further increases the blending ratio to 40, 50 mass%. When increasing, the strength tends to improve contrary to the previous one. In addition, the same result as coal O was obtained also in coal M.

Next, the horizontal axis represents the arithmetic average value of the Gieseler maximum fluidity in coal with a Gieseler maximum fluidity log MF of 3.0 or more among the coals constituting the blended coal. FIG. 2 shows the result of plotting the increase amount (ΔDI ¹⁵⁰ ₁₅ ) of the drum 150 rotation 15 mm index of the coke containing 50 mass% of the inert highly dispersed coal against the drum 150 rotation 15 mm index (base).

  According to FIG. 2, 0% mass of inert high dispersion coal is included when the arithmetic average value of the highest Gieseller fluidity is 4.0 or higher for coal having a Gieseller maximum fluidity log MF of 3.0 or higher among the coals constituting the blended coal. It is clear that the strength decreases with respect to coke.

  A confirmation test of the effect of the present invention was performed in a coke oven (actual furnace).

  Coal blending was designed such that Ro, which is a general coke strength factor, was 1.0 and logMF was 2.7. The coal O used in Example 1 is adopted as coal with high dispersibility of the inert component, and the blending ratio of the coal and the coke strength of the inert high-dispersion coal is determined by performing the blending ratio of the coal O in two levels of 3 mass% and 50 mass% on average. The relationship was investigated. The operation was performed so that other operating factors such as coal moisture, particle size, combustion temperature, and carbonization time were almost constant.

  The drum strength of the produced coke was measured when the blending ratio of coal O was an average of 3 mass% (comparative example) and 50 mass% (invention example). The drum strength was a drum 150 rotation 15 mm index similar to that in Example 1, and an average value for about one week was obtained. The results are shown in FIG. In addition, the straight line shown on each bar graph of FIG. 3 shows the dispersion | variation in drum intensity | strength.

  According to FIG. 3, it was confirmed that the coke strength is improved by using the method of the present invention in which the blending ratio of the inert highly dispersed coal exceeds 40 mass%.

Claims (1)

When blending coal, which is a raw material for producing coke, the number density of the inert component when the packing density is 750 kg / m ³ when the coal is pulverized to a particle size distribution of 6 mm or less and 100 mass% is 2.0. a × 10 ¹⁰ atoms / m ³ or more and becomes coal being defined inert high manufacturing method of dispersing coal metallurgical coke Ru with,
The blending ratio of the inert high dispersion coal and less 40 mass% greater than 55 mass%,
Manufacture of metallurgical coke characterized by blending so that the arithmetic average value of Gieseller maximum fluidity is less than 4.0 for coal with a maximum Gieseller fluidity of 3.0 or more among the coal composing the blended coal Method.

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