JP2007063350A - Method for producing coke - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing coke, comprising compounding coal with a caking material, thereby enabling to improve the strength of the coke, prevent the enhancement of expansion pressure as much as possible, when the coke is softened and melted, and simultaneously improve the contraction of the coke in the oven width direction. <P>SOLUTION: This method for producing the coke, comprising compounding coal with a caking material, is characterized by controlling the average particle diameter of the caking material to a prescribed value or less to enhance the contraction coefficient of the coke in the oven width direction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing coke, and more particularly, to a method for producing coke, which is produced by blending a caking additive with coal.

  When producing coke, it is known that the strength (drum index) of coke is improved by adding an appropriate amount of caking additive to coal (for example, Non-Patent Document 1 below). In addition, coke strength (CSR) after gasification reaction with carbon dioxide, which is one of the quality evaluations of coke, taking into account the condition that coke is exposed in the blast furnace, by adding an appropriate amount of caking additive to coal. Is known to improve (for example, Non-Patent Document 1 below).

  Non-Patent Document 1 shows the quality improvement effect (improved coke cold and hot strength) when SRC (solvent refined coal), which is a heavy component by-product during coal liquefaction, is added to coal. Has been. The reason for this is that the addition of a low softening point material reduces the inter-particle friction of the charged coal, improves the charging density in the carbonization chamber, and increases the expansibility during the softening and melting process due to the compatibility of SRC with the coal. In other words, the development of an optically anisotropic structure of the produced coke increases the coke structure corresponding to the high-rank coal.

  Non-Patent Document 2 describes that when coke is produced by blending a caking additive with coal, the expansion coefficient and expansion pressure increase.

"Coal and coke" issued in 2002, issued by: Japan Iron and Steel Association, 4.4 blending, carbonization, post-treatment coke quality control technology p119-120 “Iron and Steel” Vol. 63, S87, published in 1977, Japan Iron and Steel Institute, “Comparison of properties of various coking binders” p87

  As described above, it is known from the above document that coke strength is improved by blending a caking additive into coal. However, when various caking materials are blended with the charging coal to the coke oven, the expansion pressure when the charging coal is softened and melted increases (for example, Non-Patent Document 2), so that coke due to excessive expansion pressure is obtained. Since the pressure on the furnace carbonization chamber furnace wall also leads to collapse due to deformation of the coke oven furnace wall, excessive expansion pressure is not preferable in terms of maintenance of the furnace. Further, when the expansion pressure increases, the shrinkage rate of the coke tends to decrease, and the gap between the furnace wall and the coke cake becomes narrower. As a result, when the coke after dry distillation is extruded and discharged from the carbonization chamber, the frictional resistance between the coke cake and the furnace wall increases, which hinders smooth coke cake extrusion. Thus, the excessive expansion pressure and the decrease in the coke shrinkage in the furnace width direction impose an excessive burden on the furnace wall of the coking chamber of the coke oven, which is not preferable from the viewpoint of the furnace life.

  Therefore, the inventors of the present invention have intensively studied the influence of the pulverized particle size of the binder mixed with coal on the shrinkage of coke, and the expansion pressure is increased by adjusting the pulverized particle size of the binder. It was found that coke having a high shrinkage rate can be obtained, and the present invention was completed.

  That is, in view of the above-described problems of the prior art, the object of the present invention is to suppress the increase in coke strength by adding a caking additive to coal and still increase the expansion pressure during softening and melting. It is another object of the present invention to provide a coke production method capable of improving the coke shrinkage in the furnace width direction.

  The above-mentioned subject is achieved by the invention described in each claim. That is, the characteristic configuration of the coke production method according to the present invention is a method for producing coke by adding a caking additive to coal, and adjusting the average particle diameter of the caking agent to a predetermined value or less, and the coke oven width direction. The purpose is to increase the shrinkage rate.

  According to this configuration, the caking strength (drum index) can be effectively improved by adding a caking additive to coal, and when the coal is softened and melted due to the caking additive being added. At the same time, the expansion coefficient and expansion pressure of the steel can be suppressed, and at the same time, the reduction of the coke shrinkage in the furnace width direction can be suppressed, and the adverse effect on the furnace life due to the addition of the binder can be effectively reduced. .

  As a result, a coke production method that can improve coke strength by adding caking additive to coal, yet suppresses the expansion pressure during softening and melting as much as possible, and at the same time, improves coke shrinkage in the furnace width direction. Could be provided.

  It is preferable that the binder has an average particle diameter of 4.6 mm or less.

  When the average particle size of the binder is 4.6 mm or less, the strength (drum index) of the coke is reliably improved, and the expansion pressure when the coal is softened and melted is increased, and the coke oven width direction It is possible to suppress the shrinkage rate of the resin from decreasing to an extent that does not hinder actual production. More preferably, the average particle diameter of a caking additive is 2.4 mm or less, More preferably, it is 0.8 mm or less.

  The blending ratio of the caking additive to the coal is preferably 5% or less.

  When the blending ratio of the binder to the coal is within this range, the drum index can be suitably increased, and the expansion pressure when the coal is softened and melted is increased, and the contraction rate of the coke in the furnace width direction. Can be suppressed to such an extent that there is no problem in actual production. If the blending ratio of the binder exceeds 5%, the expansion pressure when the coal is softened and melted tends to be high. More preferably, the content of the binder is 2 to 5%. When the blending ratio of the binder is less than 2%, the drum index of coke is hardly increased.

  As the binder, a pitch obtained by thermally decomposing asphalt can be preferably used.

  Embodiments of the present invention will be described in detail with reference to the drawings. First, the manufacturing process of metallurgical coke will be briefly described with reference to FIG.

<Coke production process>
Coal is landed from the coal carrier 1 berthed at the quay and stored in the coal storage 2 for each property (brand) of the coal. The amount of coal stored in the coal storage 2 is dispensed by the reclaimer for each brand and sent to the blending tank 3 by the belt conveyor. The blending tank 3 has a plurality of tanks, and one brand of coal is stored in one blending tank. Coal has high and low costs due to its properties, and in order to produce high-quality coke at low cost, coal with different properties is cut out from a plurality of blending tanks 3 at an optimum blending ratio, and raw coal for coke production. Is completed.

  That is, for coke production, various types (brands) of coal are imported from overseas and stored in the coal storage 2 for each brand. This is because coal mined in each coal mine has different properties for each coal mine, and the properties of coke produced differ depending on the properties. Therefore, by combining multiple coals, it is requested by the user at the cheapest cost. This is because it is necessary to satisfy the coke properties (quality).

  The pulverization equipment 4 is provided with a known pulverizer, and pulverizes the blended coal. The coal pulverized in the pulverization facility 4 is transferred to the coke oven 6 by a belt conveyor or the like. The transferred coal is temporarily stored in a coal bin (coal tower) 6a, and then charged into the coke oven 6 by a charging vehicle 6b, and is dry-distilled (steamed) for about 20 hours. The dry-distilled coal becomes coke and is pushed out of the coke oven by the extruder 6c. The obtained product coke is finally fed into the blast furnace.

  If the pressure (side pressure) on the coking chamber furnace wall is too high during coke extrusion by the extruder 6c, a considerable load is applied to the coking chamber furnace wall, causing a clogging phenomenon of the furnace (clogging or depressing), Causing damage and reducing furnace life. Therefore, it is desirable that the shrinkage rate of coke in the carbonization chamber furnace width direction is large.

<Experimental result>
In the present invention, asphalt pyrolysis pitch (ASP) can be pulverized by the pulverization equipment 4 for pulverizing coal. It is known to improve coke strength by blending coal with asphalt pyrolysis pitch.

  However, as described above, it is known that when various caking materials are added to the coke oven charging coal, the expansion rate and the expansion pressure when the charging coal is softened and melted are increased (Non-patent Document 2). As the expansion pressure increases, the contraction rate of coke tends to decrease. As a result, an excessive burden is applied to the carbonization chamber wall of the coke oven, which adversely affects the furnace life.

  Therefore, by controlling the pulverized particle size of the asphalt pyrolysis pitch, the expansion pressure when the coal is softened and melted can be suppressed, and the shrinkage rate of the coke in the furnace width direction can be suppressed. This was confirmed experimentally.

As shown in Table 1, asphalt pyrolysis pitches having different particle sizes were adjusted (three types). That is, asphalt pyrolysis pitch was obtained and pulverized so as to change the particle size distribution, and three types of asphalt pyrolysis pitch samples (pitch _4.6 , pitch _2.4 , pitch _0.8 ) were obtained. Table 1 shows the average particle diameter of each sample and the particle size ratio of 3 mm or less. The average particle diameter was sieved with a sieve according to JIS Z8801-1, and was calculated as a weighted average value from the intermediate value for each fraction and the particle size ratio. As the sample name, the average particle diameter is shown in the lower right as a subscript.

  Table 2 shows a blended coal not containing asphalt pyrolysis pitch (comparative example) and a sample in which 2.0% of the asphalt pyrolysis pitch sample shown in Table 1 above was blended with the blended coal (Example 1, 2, 3) and 5.0% mixed samples (Examples 4, 5, 6) were prepared.

Using a medium-scale test furnace having a carbonization chamber having a width of 430 mm, a height of 900 mm (effective height of 800 mm), and a length of 1200 mm, the sample in Table 2 was adjusted so that the sample moisture was 7.5%. It was packed at a density of 735 kg / m ³ , and carbonized at a furnace temperature of 1010 ° C. for about 18 hours. After leaving the kiln, wet cooling was performed to obtain coke.

As shown in FIG. 2, the shrinkage rate in the furnace width direction of the coke is measured by measuring the length (L ₁ + L ₂ ) of the longest portion of the coke lump 11 in the furnace width direction with calipers, and then coke after dry distillation. The shrinkage rate of coke in the furnace width direction was calculated from the following equation with respect to the coal bed width (W _coal ) before dry distillation, with the length in the furnace width direction (W _coke ). Here, the reference numeral 12 is the furnace wall of the carbonization chamber, S is the burn-out of the central portion generated after the dry distillation, and p indicates the gap between the furnace wall of the carbonization chamber and the coke lump 11. This measurement was performed for all the obtained cokes.

Coke shrinkage rate in the furnace width direction [%] = (W _coal −W _coke ) × 100 / W _coal
W _coal : Coal bed width before dry distillation [mm]
W _coke : Length of coke after dry distillation in the furnace width direction [mm] = W _coal −S−2p
The drum index was measured as follows. The resulting coke, after dropped 2 times from a height 2m, the coke strength in accordance with JIS K2151, was measured (ratio of more particle size 15 mm (mass%) after the rotary 150) drum index DI ¹⁵⁰ ₁₅ . Samples were taken and measured 8 times from each experimental example. The drum index average value was calculated from the measurement results.

Next, about the said coal sample, the expansion pressure was measured by the method shown below. As the measurement method, after adjusting the sample moisture of each coal sample shown in Table 2 to 7.5% with a test tube 14 having a diameter of 14 mm and a length of 150 mm, the sample height is set to 35 mm. The test was carried out by filling a coal sample (about 4.6 g) 16 at a density of 780 kg / m ³ .

  That is, as shown in FIG. 3, a test tube 14 is placed in an electric furnace 13 that has been heated to 150 ° C. in advance, each coal sample 16 is filled in the test tube 14, and a piston 15 is inserted into the test tube 14. Then, a load M of 700 g was applied to the upper part of the piston, and a load cell C was further installed thereon. Thereafter, each coal sample 16 was heated from 150 ° C. to 600 ° C. at a rate of temperature increase of about 3 ° C./min, and the expansion pressure of the coal sample 16 during that time was recorded with a recorder (not shown) connected to the load cell C. did. The results are shown in Table 3. In Table 3, the shrinkage ratio in the furnace width direction represents the average value of each experimental example. In FIG. 3, the reference numeral 17 schematically represents the asphalt pyrolysis pitch contained in the coal sample 16.

  From Table 3, the shrinkage ratio in the furnace width direction is smaller when blended with asphalt pyrolysis pitch than when not blended, but when compared with the same blending ratio, the average particle size of asphalt pyrolysis pitch was reduced. It can be seen that coke with a larger shrinkage rate in the furnace width direction of coke can be obtained. If it is the contraction rate of the furnace width direction shown in Examples 1-6, there will be no trouble in actual production.

  The drum index is higher when blended with asphalt pyrolysis pitch than when it is not blended. When compared with the same blending ratio, the coke with higher drum index is better when the average particle size of the asphalt pyrolysis pitch is smaller. can get.

  Therefore, it can be seen that even if the blending ratio of the asphalt pyrolysis pitch is the same, reducing the average particle diameter increases the shrinkage ratio in the furnace width direction and provides coke with a high drum index.

  As shown in Table 3, the maximum expansion pressure is higher when blended with asphalt pyrolysis pitch than when not blended, but the maximum expansion pressure is increased by reducing the average particle size of the asphalt pyrolysis pitch. It can be seen that this can be suppressed. If it is about the maximum expansion pressure shown in Examples 1 to 6, there is no particular problem in actual production.

  As described above, according to the present embodiment, the maximum expansion pressure is increased by adjusting the pulverization particle size of the caking additive without incurring significant costs such as introducing new equipment. It can be seen that coke that can be suppressed and has a large shrinkage ratio in the furnace width direction can be obtained.

[Another embodiment]
In the said embodiment, although demonstrated as a manufacturing process of the metallurgical coke, this invention is applicable also in the case of coke manufacture other than metallurgical. Further, asphalt pyrolysis pitch has been described as an example of the binder, but the binder is not limited to this as long as the binder has a softening point of up to 200 ° C.

The figure explaining the schematic process of the coke manufacturing method which concerns on this invention Schematic diagram explaining the method of measuring the shrinkage rate of coke oven width direction Schematic explanatory diagram of expansion pressure test equipment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Coal carrier 2 Coal storage yard 3 Mixing tank 6 Coke oven 6a Coalbin 6b Charging vehicle 6c Extruder 11 Coke lump 13 Electric furnace 14 Test tube 15 Piston 16 Coal sample 17 Caking material (asphalt pyrolysis pitch)

Claims (4)

A method for producing coke by blending a binder with coal, and adjusting the average particle diameter of the binder to a predetermined value or less to increase the shrinkage rate of the coke in the furnace width direction. . The coke manufacturing method according to claim 1, wherein an average particle diameter of the binder is 4.6 mm or less. The coke manufacturing method according to claim 1 or 2, wherein a blending ratio of the binder to the coal is 5% or less. The coke manufacturing method according to any one of claims 1 to 3, wherein the binder is a pitch obtained by thermally decomposing asphalt.

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