JPS6339637B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing high-quality metallurgical coke used in iron manufacturing etc. from raw material pulverized coal. In recent years, as a method for producing metallurgical coke, a so-called method for producing coke blended with briquette coal has been widely adopted. This briquette blended coke manufacturing method is
After adding a binder to the pulverized coal for briquette coal and heat-treating it, or without heat treatment, it is pressure-molded, and a portion of the resulting briquette coal is blended with raw material pulverized coal to make coke oven charging coal. It is carbonized in a furnace to produce metallurgical coke. In this way, when some briquette coal is blended into raw coal powder, the briquetting effect and the bulk density of the charged coal are improved, and the strength of the coke is also improved accordingly. It is generally known that non-slightly caking inferior quality coal can be blended into charged coal. However, in the conventional coke production method with briquette charcoal, the bulk density of the coal charged into the coke oven increases as the briquette ratio increases up to a predetermined briquette ratio. The strength of the coke obtained by carbonization improves, but if the blending ratio of briquette coal exceeds a certain level, the space formed between the briquette coals will not be sufficiently filled with raw coal powder, and the charging bulk density will decrease. However, the strength of the coke produced deteriorates or does not improve. In other words, when charging coal with a briquette mixture is charged into a coke oven from a certain height, the relationship between the two is investigated using the charging bulk density on the vertical axis and the briquette blending ratio on the horizontal axis. If you look, there is a maximum value. The maximum value of this charging bulk density varies depending on the dimensions of the coke oven, the particle size distribution of the briquette coal, the particle size and particle size distribution of the pulverized coking coal, the proportion of moisture contained in the briquette coal and the pulverized coking coal, etc. , is measured and determined as a unique value by setting these fluctuation values constant.For example, if the particle size of briquette coal is 20
~100mm, powdered raw coal particle size of 3mm or less70~
When charged into a normal coke oven with a moisture content of approximately 3 to 15 wt%, the blending ratio of briquette coal is approximately 90 wt%.
The charging bulk density reaches its maximum value within the range of 50 to 85 wt%, and even if the blending ratio of briquette coal is increased beyond this point, the charging bulk density will not increase, but will decrease. It is clearly observed that the strength of the coke also decreases. Therefore, if the blending ratio of non-slightly caking poor quality coal contained in raw coal powder is constant, there is a limit to the strength of the coke produced even if the blending ratio of briquette coal is increased, and there is a limit to the strength of the coke produced from the coke oven. Due to the load involved when extruding the produced coke using an extruder, it was previously believed that the blending ratio of briquette coal was limited to about 30 wt%. By the way, as a method to prevent a decrease in the charging bulk density when the blending ratio of briquette coal is 35 wt% or more, a method of blending briquette coal having multiple types of particle sizes has been proposed (Japanese Patent Application Laid-Open No. 1983-1983). −133301). However, since this method uses briquette coal having multiple types of particle sizes, the manufacturing process becomes complicated, such as requiring multiple types of pressure molding machines and molds of different shapes. There is a problem in that the particle size of the briquette coal is discontinuous and the particle size ratio is small, so that it is difficult to expect much improvement in the charging bulk density such as closest packing. Therefore, in this method, even if the blending ratio of briquette coal is increased, the charging bulk density cannot be expected to improve and is slightly decreased, and the coke strength is also lower than that of 20 to 85wt% when the blending ratio of briquette coal is 20 to 85wt%. It is explained that it remains almost constant within the range of , and that no significant improvement can be obtained. Therefore, when charging coal with a briquette blend into a coke oven from a certain height, the present inventors charged the coal at a charging bulk density higher than the expected maximum charging bulk density. Various methods for charging coal into a coke oven were investigated. As a result, when blending briquette coal into powdered raw coal, if part or all of the powdered raw coal is replaced with briquette coal that has been heat-treated with a binder added in advance, or kneaded without heat treatment, it is surprisingly possible. What should be noted is that not only is there no decrease in the charged bulk density due to a high blend of molten coal as in the case without substitution, but on the contrary, the charged bulk density is greatly improved, and the drum of coke obtained The strength and strength CSR (%) after small-scale reaction were also significantly improved, and more importantly, an unexpected particle size adjustment effect was obtained, with a higher proportion of intermediate particle size distribution between 25 and 75 mm. This knowledge led to the completion of the present invention. That is, the present invention produces briquette coal by adding a binder to pulverized coal for briquette coal and pressurizing it to a predetermined particle size, distributing the briquette coal to raw pulverized coal to prepare coke oven charging coal, and In a method of manufacturing coke by carbonizing inserted coal in a coke oven, the blending ratio of the briquette coal is in the range of 40% by weight or more and 85% by weight or less, and part or all of the raw material pulverized coal is preliminarily reduced to an amount equivalent to soft pitch or less. This method is characterized in that it is replaced with a mixed coal briquette formed by adding a binder having a softening point of . In a particularly preferred specific embodiment of the present invention, briquette coal is blended up to the blending ratio of briquette coal at which the bulk density of the charged coal reaches its maximum value when only briquette coal is blended with the powdered raw coal. , replacing part or all of the remaining raw material pulverized coal with briquette coal, which reduces the expected charging volume when charging coal with a blend of briquettes into a coke oven from a certain height. Charging coal can be charged into a coke oven with a bulk density higher than the maximum value of the density, and the coke strength is improved and the grain size adjustment effect becomes remarkable. The pulverized coal for briquettes, pulverized coking coal, and pulverized coal for briquettes as used in the present invention are ordinary charging coal for coke ovens, or ordinary charging coal for coke ovens that is not suitable for producing coke for blast furnaces. 10wt% or more of suitable non-slightly caking inferior quality coal and/or coke powder, pitch coke, petroleum coke, tar slag, etc., each alone or in combination.
A mixture of 1wt% or more with a particle size of 3mm or less from 70 to
It is used after being crushed to about 90wt%. Each of these can be used alone, but it is also possible to use a mixture thereof in a predetermined ratio. The above-mentioned normal charging coal for coke ovens has a volatile content of 25 to 35%, a CSN (JIS M8801, 4 crucible expansion test method) range of 3 to 9, and cannot be used to coke in a practical coke oven. Charging coal for coke production for blast furnaces obtained by blending and preparing any coal so that the drum strength (JISK2151, 6.2 Drum test method) DI ¹⁵⁰ ₁₅ 80 or higher is obtained when the coal is used in blast furnace coke production and has a property range conventionally known. That's fine. In addition, non-slightly caking inferior quality coal has a CSN of 0 to 2, a fluidity index [JISM8801,
5 Fluidity test method (Gieseler plastometer method): 0 to 10, total expansion index (Audaiber-Arneux method): 0, and this coal is considered unsuitable for producing coke for blast furnaces. Further, in the present invention, a coal-based or petroleum-based bituminous material is used as the binder used when producing the mixed coal briquette. Suitable coal-based bituminous materials include, for example, coal-based pitch, road tar, coal solvent extracts or their residues, coal-based heavy oil, etc.; Pitch, asphalt, petroleum heavy oil, or those obtained by heat treatment or solvent extraction treatment of these oils are suitable. Whichever of the bituminous materials mentioned above is used, it is a heavy material with a softening point equivalent to that of soft pitch or lower, that is, a softening point of 70° C. or lower. However, those with low boiling points that are liquid at room temperature are not effective as binders and also cause problems in charging operations. Furthermore, heavy materials with a softening point of over 70°C and a medium pitch or higher must be cooled after being kneaded into pulverized coal, but the coal particles will strongly bond to each other and form lumps, so they must be crushed again when blended into briquette coal. There is a need. On the other hand, in the case of a binder having a softening point lower than that of soft pitch, the cohesive strength of the coal particles is appropriate, and the pulverization step is not necessary because only pseudo particles are formed. Because of this difference in particle size of briquette coal, in the case of a binder with a high softening point, the bulk density cannot be increased simply by blending it with briquette coal. Molded coal in the present invention is obtained by adding a binder to powdered coal for molding, mixing it, and then applying appropriate heat treatment or pressure-molding it to a predetermined particle size using a molding machine without heat treatment. Yes, and although there is no particular limitation, the particle size of briquette coal should be 20
It is advantageous to set it to about 100 mm. Molded coal may be partially crushed during transfer to a coke oven or during coal charging, but these are treated as molten coal. Furthermore, the briquette coal in the present invention is made from ordinary coke oven charging coal, or normal coke oven charging coal mixed with 10 wt% or more of non-slightly caking poor quality coal, This is coal in which a binder is added and heat treated as appropriate, or the binder is kneaded without heat treatment, so that the binder is coated on the surface of the coal particles. In the present invention, the powdered raw coal, the powdered coal for molded coal, and the powdered coal for mixed coal briquettes may each have the same composition of coal blend, or may be different.
In addition, the binder for briquette coal and the binder for briquette coal may have the same composition or may be different, but if they have the same blended composition and the same composition, the raw material pulverized coal As for the briquettes to be replaced with, of course, a part of the briquettes for briquettes for briquettes before being molded into briquettes can be used as is, which simplifies the work process and further improves economic efficiency. In the present invention, while making the most of the advantages of blending briquette coal as it is in terms of improved charging bulk density and coke strength, the blending ratio of briquette coal is within a certain range or above. Taking into account that the charging bulk density reaches its maximum value within the range of 100 to 100 m, and that the charging bulk density will decrease if the ratio is higher than this, it is best to replace part or all of the raw material powder coal with briquette coal. This is preferable. Hereinafter, the present invention will be explained in more detail based on examples. (1) Test furnace and operating conditions Prepared charge coal is dropped from the charging port into a gas-heated 1/4 t coke oven, and the frieux temperature is
It was carbonized at 1300℃. (2) Preparation of powdered raw coal Non-slightly caking inferior quality coal (brand name Witsbank)
16 types of coking coal containing 12.0wt% were blended and pulverized so that when sifted through a 3 mm sieve, the sieve content was 87.6wt%, and the moisture content was adjusted to approximately 10% to produce powdered coking coal. This powdered raw coal has a strong viscosity ratio of 52% and a volatile content of
At 29.4wt%, the bulk density when charged into the test furnace was
It is 629Kg/ ^m3 . (3) Preparation of briquette coal To the powdered raw coal, 6 wt% of coal-based soft pitch with a softening point of 35°C was added as a binder, mixed, and then kneaded under direct heating while blowing steam to prepare briquette coal. (4) Preparation of briquette charcoal Molded charcoal was prepared by press-molding a part of the above-mentioned briquette charcoal into a machete mold with a size of 45 mm x 45 mm x 26 mm using a double roll press at a molding pressure of 4 tons. The apparent density of this briquette coal was 1.15 g/ml. (5) Preliminary experiment using conventional method Charging coal was prepared by blending raw coal powder and briquette coal in various proportions, and this charging coal was charged into the above test furnace to produce coke. Bulk density, drum strength of produced coke (DI ¹⁵⁰ ₁₅ ), strength CSR (%) of produced coke after compact reaction, 25 to 75 mm of produced coke
The results of examining particle size yield and coke productivity ratio are the first
It was as shown in Table A group. The strength after small scale reaction was determined by the following test method. That is, 200 g of sample coke prepared to a particle size of 20 ± 1 mm was placed in a reaction tube under a CO ₂ flow of 5/min.
The reaction was carried out for 2 hours under heating at 1100℃±10℃, and the weight after the reaction was set as Ag.The entire sample after the reaction was placed in the drum (130φ x 700mm) of a mold testing machine for 20Ypm.
× After rotating for 30 minutes, the sample is sieved, and the weight of the +10 mm portion is taken as Bg, and the strength after small reaction in this case is
CSR ⁶⁰⁰ ₁₀ was calculated using the following formula: CSR ⁶⁰⁰ ₁₀ = B/A x 100%. In addition, the coke productivity ratio was determined as follows. Coke productivity ratio = Coke generation time without briquette coal / Coke generation time with briquette coal × Amount of coke remains when briquette coal is not distributed /
Amount of ^coke remains when no briquette charcoal is added.The dotted line in Figure 1 shows the relationship between the briquette charcoal blending ratio and the charging bulk _density . The dotted line in Figure 2 shows the relationship between
Each is indicated by a dotted line in the figure.

[Table] As a result of this preliminary experiment, the charging bulk density is as shown in Table 1 and Figure 1, when the blending ratio of briquette coal is 60~
It shows the maximum value at 80wt%, and when the content is higher than this, the charging bulk density clearly decreases. Further, as shown in Table 1 and FIG. 2, the drum strength (DI ¹⁵⁰ ₁₅ ) of the produced coke reaches its maximum value when the blended ratio of briquette coal is 60 to 80 wt%, and decreases above this value. In addition, 25 to 75 of the generated coke
The mm particle size yield reaches its maximum value when the blending ratio of briquette coal is 60wt%.
It shows 60.0%, and it clearly decreases when the blending ratio is higher than this. (6) Example Based on the above preliminary experiment, the present invention was implemented as follows. In other words, the maximum charging bulk density is 0.074t/
Based on the briquette coal blending ratio of 60.0wt% when it shows m ³ , part or all of the raw material powder coal is 10wt%, 20wt%, 30wt% and
Charging coal was prepared by replacing the mixture with 40wt%, and this charging coal was charged into a test furnace under the same conditions as in the preliminary experiment to produce coke. The drum strength of coke (DI ¹⁵⁰ ₁₅ ), 25-75 mm particle size yield of produced coke, the strength CSR (%) of produced coke after small size reaction, and coke productivity ratio were investigated.
The results are shown in Table 1, Group B. The solid line in Figure 1 shows the relationship between the blended coal blending ratio and the charging bulk density, and the solid line in Figure 2 shows the relationship between the blended coal blending ratio and the drum strength of the coke produced. The relationship between the blending ratio and the particle size yield of 25 to 75 mm in coke produced is shown by solid lines in FIG. 3, respectively. In this example, as shown in Table 1 and Figure 1, it can be seen that the charging bulk density increases almost linearly as the blended coal blend ratio increases,
Furthermore, as shown in Table 1 and Figure 2, the drum strength (DI ¹⁵⁰ ₁₅ ) of the coke produced depends on the mixing ratio of briquettes.
At 10wt% or more, the strength CSR (%) after small reaction of the coke produced is significantly improved at 100wt% or more.
% improved than briquette coal. Furthermore, as shown in Table 1 and Figure 3, the particle size yield of the coke produced was significantly improved, and the productivity ratio of the coke produced was somewhat lower compared to the case of 10wt% briquette coal. There is. In addition, in the above example, the blending ratio of briquette coal was 60wt%.
This is because the charging bulk density was almost the maximum value when the molten coal particle size was 45 mm in a 1/4 t test furnace. However, even if the briquette is made using a briquette containing 50 to 85 wt%, there is no change in the effects of improving charging bulk density, coke strength, 25 to 75 mm particle size yield, etc., and the present invention can naturally be carried out advantageously. . As can be understood from the above examples, according to the method of the present invention, part or all of the raw material pulverized coal that is blended in the conventional method when the bulk density of the charged coal reaches its maximum value is mixed into briquettes. By replacing
As shown in Table 1 and FIG. 1, the bulk density of the charged coal increases linearly. This is because raw coal powder is heated and kneaded together with a binder when producing the kneading coal, and the bulk density of the produced kneaded coal becomes larger than the raw material powder coal, and this kneaded coal with a high bulk density is formed between the molded coals. This is thought to be due to the dense filling of the voids. In this way, as the bulk density of the charged coal improves, the drum strength (DI ¹⁵⁰ ₁₅ ) of the produced coke also improves almost proportionately, which makes it possible to increase the blending ratio of briquette coal. Therefore, it becomes possible to produce high quality metallurgical coke. For this reason, the drum strength (DI ¹⁵⁰ ₁₅ ) of the produced coke is improved over the drum strength of coke produced by the conventional method, and a larger amount of inexpensive non-slightly caking inferior quality coal and/or powder is used. coke, pitch coke,
Even if petroleum coke, tar slag, etc. are used, it is possible to produce metallurgical coke with the same drum strength as conventional ones. In addition, if a large amount of non-slightly caking inferior quality coal or coke powder, pitch coke, petroleum coke, tar slag, etc. are blended in this way, the expansion of the charged coal carbonized in the coke oven will be reduced. The extrusion load when extruding coke produced in a coke oven using an extruder is reduced, and the sum of the blending ratios of briquette coal and briquette coal can be dramatically increased. Furthermore, by adding briquette coal, the bulk density of the charged coal can be increased, which improves the hot properties of the produced coke and the volume balance between the charged coal and the produced coke. The productivity ratio of coke produced can also be significantly improved. Furthermore, looking at the particle size distribution of the metallurgical coke produced by the method of the present invention, the particle size yield of the produced coke of 25 to 75 mm was significantly improved compared to the preliminary experiment using the conventional method. This is an extremely advantageous aspect of blast furnace operation. This particle size yield also shows almost the same tendency as the improvement in the charging bulk density, and is considered to be a result of the improvement in the charging bulk density in the present invention. Therefore, the present invention makes it possible to produce high-quality coke with a high blend of molded coal, effectively utilizes non-slightly caking inferior quality coal, coke powder, pitch coke, petroleum coke, tar slag, etc., and produces hard-to-obtain high-quality strong coke. It is extremely useful industrially as it helps save on charcoal.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between the blending ratio of briquette coal and the charging bulk density. Figure 2 is a graph showing the relationship between the blending ratio of briquette coal and the drum strength of coke produced. Figure 3 is a graph showing the relationship between the blending ratio of briquette coal and the particle size yield of produced coke of 25 to 75 mm.

Claims (1)

[Claims] 1. A binder is added to pulverized coal for briquette coal to produce briquette coal that is pressure-molded to a predetermined particle size, and the briquette is blended with raw material pulverized coal to prepare coal for coke oven charging. In the method of producing coke by carbonizing this charged coal in a coke oven, the blending ratio of the briquette coal is set in a range of 40% by weight or more and 85% by weight or less, and part or all of the raw material powder coal is pre-soft-pitched. A method for producing high-quality coke, characterized by replacing coke with mixed coal briquettes formed by adding a binder having a softening point below a certain level. 2. Claim 1, characterized in that, when only briquette coal is blended with raw pulverized coal, briquette coal is blended up to the briquette ratio at which the bulk density of the charged coal reaches its maximum value. The method for producing high-quality coke described. 3. The method for producing high-quality coke according to claim 1, wherein the powdered coal for briquettes, the raw material powdered coal, and the powdered coal for mixed briquettes have the same blending composition.