Coke manufacturing method
By adding sludge to coal and then simultaneously or subsequently adding a bulk density improver in the transport line, the method addresses the challenge of sludge disposal and improves the bulk density of the coal-sludge mixture, ensuring high-quality coke production.
Patent Information
- Application Number
- JP2022067747
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2022-04-15
- Publication Date
- 2026-05-18
- Estimated Expiration
- 2042-04-15
AI Technical Summary
The disposal of sludge in a coke oven is costly, and existing methods of adding bulk density improvers to coal before sludge do not sufficiently improve the bulk density of the resulting mixture.
A method involving the addition of sludge to coal at a designated position downstream in the transport line, followed by the simultaneous or subsequent addition of a bulk density improver, either at the same time or at a further downstream position, to enhance the bulk density of the coal-sludge mixture before charging it into the coke oven.
This method effectively improves the bulk density of the coal-sludge mixture, allowing for efficient disposal of sludge while maintaining or enhancing the quality of the produced coke.
Smart Images
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Abstract
Description
Technical Field
[0001] The present disclosure relates to a method for producing coke.
Background Art
[0002] Coke is produced by charging coal as a raw material into a coke oven and carbonizing the coal at a high temperature. In the production of coke, the bulk density of coal greatly affects the quality of coke such as strength and productivity. Therefore, it is required to improve the bulk density of the coal used as the raw material for coke.
[0003] As a method for improving the bulk density of coal, a method of adding a bulk density improver (surfactant) to coal in a transfer line for transferring coal to a coke oven is known (for example, Patent Document 1). Patent Document 1 describes that in the coal transfer line, an excellent bulk density improving effect can be obtained by adding a bulk density improver to the coal after pulverization by a pulverizer as compared with the case of adding the bulk density improver to the coal before pulverization.
Prior Art Documents
Patent Documents
[0004]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0005] By the way, in a steelworks including a coke oven, waste is generated, and the treatment of this waste becomes a problem. A typical waste is surplus sludge. Hereinafter, hydrous substances such as sludge are simply referred to as "sludge". For example, a coke oven is provided with a purification facility as its auxiliary equipment. In the purification facility, wastewater treatment is performed using activated sludge, and sludge is generated by this wastewater treatment. Since it is costly to dispose of the sludge, it is required to dispose of the sludge in the coke oven.
[0006] The purpose of this disclosure is to provide a method for producing coke that can improve the bulk density of coal, even when sludge is disposed of in a coke oven. [Means for solving the problem]
[0007] The coke manufacturing method according to this disclosure comprises a coal supply step, a sludge addition step, and a chemical addition step. In the coal supply step, coal is supplied to a first position designated on a transport line that transports coal to a coke oven. In the sludge addition step, sludge is added to the coal at a second position designated downstream of the first position on the transport line. In the chemical addition step, a bulk density improver is added to the coal at the same time as the sludge is added at the second position, or a bulk density improver is added to the coal and sludge at a third position designated downstream of the second position on the transport line. [Effects of the Invention]
[0008] According to the coke manufacturing method described herein, sludge can be disposed of in the coke oven, and even in this case, the bulk density of the coal can be improved. [Brief explanation of the drawing]
[0009] [Figure 1] Figure 1 is a flow chart showing a method for producing coke according to an embodiment. [Figure 2] Figure 2 is a schematic diagram showing an example of a coal transport line configuration. [Figure 3] Figure 3 shows the verification results of the first embodiment. [Figure 4] Figure 4 shows the verification results of the first embodiment. [Figure 5] Figure 5 shows the verification results of the second embodiment. [Modes for carrying out the invention]
[0010] To solve the above problems, the inventors conducted extensive research. First, they discovered that in order to dispose of sludge in a coke oven, it is sufficient to add the sludge to the coal in the transport line that carries the coal to the coke oven. After adding the sludge to the coal, the resulting mixture is charged into the coke oven. The sludge added to the coal is carbonized together with the coal in the coke oven and becomes a component of coke.
[0011] When a bulk density improver is added to coal, the improver adheres to moisture and covers the surface of the coal, thereby lowering the surface tension of the coal. Conventionally, bulk density improvers were added early in the coal transport line (for example, immediately after the coal was supplied to the transport line). This is because adding the bulk density improver to the coal early increases the time between the addition of the bulk density improver and the charging of the coal into the coke oven, allowing the bulk density improver to spread uniformly across the surface of the coal. For this reason, the inventors tried adding sludge to the mixture of coal and bulk density improver after adding the bulk density improver to the coal. However, when the bulk density improver and sludge were added to the coal at this timing, the bulk density of the resulting mixture did not improve sufficiently, despite the addition of the bulk density improver to the coal. Hereinafter, a mixture in which at least one of sludge and a bulk density improver has been added to coal will simply be referred to as a "mixture".
[0012] Therefore, the inventors investigated the timing of adding a bulk density improver and sludge to coal. As a result, they found that the timing of adding the bulk density improver and sludge to the coal greatly affects the effect of improving the bulk density of the resulting mixture. Specifically, when adding sludge to coal, it was found that adding the bulk density improver to the mixture after adding the sludge to the coal resulted in a more easily improved bulk density of the resulting mixture compared to adding the bulk density improver to the mixture before adding the sludge. The reason for this is thought to be that when sludge is added after the bulk density improver, the bulk density improver covering the surface of the coal is washed away or locally diluted by the water contained in the sludge, causing the surface tension of the coal surface to increase.
[0013] Therefore, when adding sludge to coal, the bulk density of the resulting mixture is likely to improve unless the bulk density improver is added before the sludge is added. In other words, when adding sludge to coal, the bulk density of the resulting mixture is likely to improve if the bulk density improver is added to the coal at the same time as the sludge, or if the bulk density improver is added to both the coal and the sludge after the sludge has been added.
[0014] The coke production method according to the embodiments of this disclosure has been completed based on the above findings.
[0015] The coke manufacturing method according to this embodiment comprises a coal supply step, a sludge addition step, and a chemical addition step. In the coal supply step, coal is supplied to a first position designated on a transport line that transports coal to a coke oven. In the sludge addition step, sludge is added to the coal at a second position designated downstream of the first position on the transport line. In the chemical addition step, a bulk density improver is added to the coal at the same time as the sludge is added at the second position, or a bulk density improver is added to the coal and sludge at a third position designated downstream of the second position on the transport line (first configuration).
[0016] In the first method of manufacturing the composition, in the sludge addition step, sludge is added to the coal at a second position downstream from the first position where the coal was supplied in the coal supply step. In the chemical addition step, a bulk density improver is added to the coal at the second position simultaneously with the sludge, or the bulk density improver is added to the coal and sludge at a third position downstream from the second position. In short, in the first method of manufacturing the composition, the timing of adding the bulk density improver to the coal is either at the same time as adding the sludge to the coal, or after adding the sludge. As described above, adding the bulk density improver to the coal at such a timing improves the bulk density of the resulting mixture. Thus, according to the first method of manufacturing the composition, the bulk density of the mixture obtained by adding the bulk density improver and sludge to the coal being transported in the coal transport line for charging into the coke oven can be improved.
[0017] The method for manufacturing coke of the first configuration may have the following configuration. The conveying line includes a kneading machine for kneading coal. Each of the first position, the second position, and the third position is located inside the kneading machine (second configuration).
[0018] In the manufacturing method of the second configuration, each of the first position, the second position, and the third position is located inside the kneading machine. In short, in the coal supply step, coal is supplied into the kneading machine, and the sludge addition step and the chemical addition step are carried out inside the kneading machine. Thereby, the mixture obtained by adding sludge and a bulk density improver to coal can be kneaded by the kneading machine. Therefore, the mixture is uniformly mixed, and the bulk density of the obtained mixture is further improved.
[0019] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each figure, the same or corresponding components are denoted by the same reference numerals, and the same description will not be repeated.
[0020] FIG. 1 is a flowchart showing a method for manufacturing coke according to the present embodiment. As shown in FIG. 1, the manufacturing method of the present embodiment includes a coal supply step (#5), a sludge addition step (#10), and a chemical addition step (#15). In the manufacturing method of the present embodiment, sludge and a bulk density improver are added to the coal after being pulverized by a pulverizer. The obtained mixture is charged into a coke oven. The mixture (coal, sludge, and bulk density improver) is carbonized in the coke oven, thereby producing coke. In short, the addition of sludge and the bulk density improver is carried out on the conveying line for conveying coal to the coke oven. Hereinafter, each step shown in FIG. 1 will be specifically described.
[0021] 〔Coal supply step (#5)〕 In the coal supply process (#5), coal is supplied to the coal conveying line. The coal supplied in the coal supply process (#5) is the coal after being pulverized by a pulverizer. The coal to be supplied is pulverized so that, for example, the ratio of the fraction with a particle size of 3 mm or less in the whole coal is 80 to 90%. When the moisture content in the coal is low, it is easier to improve the bulk density of the mixture obtained using the coal compared with the case where the moisture content in the coal is high. This is because when the moisture content in the coal is low, the slipperiness between particles becomes good and the bulk density is improved. Therefore, it is preferable that the moisture content of the supplied coal is as low as possible. The moisture content of the coal is, for example, 10.0% or less.
[0022] FIG. 2 is a schematic diagram showing a configuration example of the coal conveying line. The conveying line includes a kneader 2. In the conveying line, the coal pulverized by the pulverizer 1 is conveyed to the coke oven 3 while passing through the kneader 2. The coal is conveyed, for example, by a belt conveyor. The kneader 2 has a drum shape and is rotatable about an axis along the conveying direction of the coal in the conveying line. The kneader 2 kneads the coal inside the kneader 2.
[0023] Referring to FIG. 2, in the coal supply process (#5), coal is supplied to the first position A of the conveying line. The first position A is located inside the kneader 2. In short, in the coal supply process (#5), coal is supplied into the kneader 2.
[0024] 〔Sludge addition process (#10)〕 In the sludge addition process (#10), sludge is added to the coal at the second position B. The second position B is defined downstream of the first position A in the conveying line. That is, in the sludge addition process (#10), sludge is added to the coal after being supplied to the first position A in the coal supply process (#5).
[0025] The sludge added to the coal in the sludge addition process (#10) is, for example, surplus sludge generated from a purification facility using activated sludge. This purification facility is an auxiliary facility of the coke oven 3 and treats wastewater. The moisture content of the sludge is, for example, 80 to 95%.
[0026] 〔Chemical addition process (#15)〕 In the chemical addition process (#15), a bulk density improver is added to the coal and sludge at the third position C. The third position C is located downstream of the second position B in the conveying line. In other words, in the chemical addition process (#15), after sludge has been added to the coal in the sludge addition process (#10), a bulk density improver is added to the resulting mixture of coal and sludge.
[0027] The bulk density improvers added to the coal in the chemical addition step (#15) are typically surfactants. Examples of bulk density improvers include dialkyl sulfosuccinic acid or its salts (e.g., sodium salt, ammonium salt, potassium salt, triethanolamine salt), anionic surfactants (e.g., polyoxyethylene alkyl ether sulfate), and nonionic surfactants (e.g., polyoxyethylene (POE) addition polymer or its salt). In the chemical addition step (#15), one type of bulk density improver may be added to the coal, or a mixture of multiple types of bulk density improvers may be added. The mass % concentration of the bulk density improver added to the coal is, for example, 0.05 to 0.30%.
[0028] In this embodiment, the bulk density improver is added at the third position C during the chemical addition step (#15). However, the timing of adding the bulk density improver is not limited to this; it just needs to be before the sludge is added. In other words, the third position C, where the bulk density improver is added, does not need to be located upstream of the second position B, where the sludge is added. That is, the second position B and the third position C may be at the same location. In this case, during the chemical addition step, the bulk density improver is added to the coal at the same time as the sludge at the second position B. When adding the bulk density improver at the same time as the sludge, the sludge and bulk density improver may be added via separate routes, or the sludge and bulk density improver may be mixed in advance, and the mixed sludge and bulk density improver may be added.
[0029] In this embodiment, the first position A, the second position B, and the third position C are located inside the mixer 2. However, the second position B and the third position C may be located downstream of the mixer 2. In short, sludge and a bulk density improver may be added to the coal after it has been mixed in the mixer 2. However, in that case, it is preferable that the sludge and bulk density improver be added to the coal as far upstream as possible (for example, immediately after the first position A). This is because the resulting mixture is thoroughly mixed in the mixer 2 and at the transfer points of the conveyor belt in the transport line, and the bulk density improver is spread uniformly on the surface of the coal.
[0030] [effect] In the manufacturing method of this embodiment, in the sludge addition step (#10), sludge is added to the coal at a second position B downstream of the first position A where the coal was supplied in the coal supply step (#5). In the chemical addition step (#15), the bulk density improver is added to the coal at the same time as the sludge at the second position B, or the bulk density improver is added to the coal and sludge at a third position C downstream of the second position B. In short, in the manufacturing method of this embodiment, the timing of adding the bulk density improver to the coal is either at the same time as adding the sludge to the coal, or after adding the sludge. Adding the bulk density improver to the coal at such a timing improves the bulk density of the resulting mixture. As a result, according to the manufacturing method of this embodiment, the bulk density of the mixture obtained by adding the bulk density improver and sludge to the coal being transported in the coal transport line to be charged into the coke oven 3 can be improved.
[0031] In the manufacturing method of this embodiment, the first position A, the second position B, and the third position C are each located inside the kneader 2. In short, in the coal supply step (#5), coal is supplied into the kneader 2, and the sludge addition step (#10) and the chemical addition step (#15) are carried out inside the kneader 2. This allows the mixture obtained by adding sludge and a bulk density improver to the coal to be kneaded in the kneader 2. As a result, the bulk density of the resulting mixture is further improved. [Examples]
[0032] [First Embodiment] To confirm the effectiveness of the coke manufacturing method of this embodiment, the difference in the effect of improving the bulk density of the mixture depending on the timing of adding the bulk density improver to the coal was verified using the coal transport line of an actual coke oven. In this embodiment, the bulk density of the mixture obtained when sludge was added after the bulk density improver was added to the coal (Case 1) was compared with the bulk density of the mixture obtained when the bulk density improver was added after the sludge was added to the coal (Case 2).
[0033] In this example, verification was performed using multiple coals with different -0.3 mm ratios in each of Case 1 and Case 2. The "-0.3 mm ratio" refers to the proportion of particles with a particle size of 0.3 mm or less in the total coal, and hereafter, the "-0.3 mm ratio" may be referred to as the "fine-grain ratio". In this example, first, the actual bulk density of the obtained mixture was plotted on a graph for each fine-grain ratio of the coal used. Next, for Case 1, an approximate straight line of the plot was found, and the bulk density value when the fine-grain ratio on that approximate straight line was 20% was calculated, and this value was set as the reference value a.
[0034] Figure 3 shows the verification results of this embodiment. In Figure 3, the horizontal axis represents the -0.3 mm ratio of the coal used, and the vertical axis represents the relative bulk density of the mixture. Figure 3 plots the relationship between the -0.3 mm ratio of the coal used and the relative bulk density of the obtained mixture. Relative bulk density is the value obtained by dividing the bulk density of the mixture by a reference value. In Figure 3, each plot for Case 1 and Case 2 is shown as a relative value to the reference value a.
[0035] For the plot in Case 1 shown in Figure 3, we found the approximate line S1. Referring to Figure 3, the approximate line S1 for the plot in Case 1 can be expressed as y = -0.0024x + 1.0474, where the horizontal axis is x and the vertical axis is y. Furthermore, for Case 2, we found the approximate line S2 for the plot. The approximate line S2 for the plot in Case 2 can be expressed as y = -0.0024x + 1.0651.
[0036] Figure 4 shows the verification results of this embodiment. In Figure 4, the relative bulk density when the fine particle ratio (-0.3 mm ratio) of coal is 20% and when the fine particle ratio is 25% are shown as bar graphs for Case 1 and Case 2, respectively.
[0037] In Figure 4, the reference value for relative bulk density when the fine particle ratio is 25% differs from the reference value for relative bulk density when the fine particle ratio is 20%. When the fine particle ratio is 20%, the relative bulk density is the value obtained by dividing the actual bulk density of the mixture by the reference value a. In short, the reference value in Figure 4 when the fine particle ratio is 20% is the same as the reference value in the graph in Figure 3. When the fine particle ratio is 20%, the relative bulk density in Case 1 is the value calculated by the approximation line S1 in Figure 3, i.e., shown as 1, and the relative bulk density in Case 2 is the value calculated by the approximation line S2 in Figure 3.
[0038] On the other hand, when the fine particle ratio in Figure 4 is 25%, the relative bulk density value for a fine particle ratio of 25% on the approximate straight line S1 in Figure 3 is calculated, and this value is set as the reference value b. In this case, the relative bulk density is the value obtained by dividing the relative bulk densities of Case 1 and Case 2 shown in Figure 3 by the reference value b. Specifically, when the fine particle ratio is 25%, the relative bulk density of Case 1 is the value obtained by dividing the value calculated by the approximate straight line S1 in Figure 3 by the reference value b, i.e., 1, and the relative bulk density of Case 2 is the value obtained by dividing the value calculated by the approximate straight line S2 in Figure 3 by the reference value b.
[0039] Furthermore, Figure 4 shows the bulk density improvement rate for coal with a -0.3 mm ratio of 20% and 25%. The bulk density improvement rate is an index that represents the degree to which the bulk density of the mixture in Case 2 has improved compared to the bulk density of the mixture in Case 1. The bulk density improvement rate R1 satisfies the following equation (1), where ρ1 is the bulk density of the mixture in Case 1 and ρ2 is the bulk density of the mixture in Case 2.
[0040]
number
[0041] Referring to Figures 3 and 4, when comparing the results of Case 1 and Case 2 under the same conditions for the -0.3 mm ratio of coal used, the bulk density of Case 2 was greater than that of Case 1. For example, when the -0.3 mm ratio of coal is 20%, the bulk density improvement rate R1 is approximately 1.75, and when the -0.3 mm ratio of coal is 25%, the bulk density improvement rate R1 is approximately 1.71. From this, it can be seen that adding a bulk density improver to coal and sludge after adding sludge improves the bulk density of the mixture more than adding the bulk density improver before adding sludge.
[0042] [Second Example] Next, using the coal transport line of an actual coke oven, we verified the difference in the effect of coal moisture content on improving the bulk density of the mixture. In this example, we used multiple types of coal for the verification. First, we plotted the relationship between the moisture content of the coal used and the bulk density of the resulting mixture. Next, we found an approximate straight line for each plot and calculated the bulk density value when the coal moisture content on that approximate straight line was 10.0%. This value was used as the reference value, and each plot was expressed as a relative value to the reference value.
[0043] Figure 5 shows the verification results of this embodiment. In Figure 5, the horizontal axis represents the moisture content of the coal used, and the vertical axis represents the relative bulk density of the mixture. Figure 5 plots the relationship between the moisture content of the coal used and the relative bulk density of the obtained mixture. In this embodiment, the relative bulk density of the mixture is the value obtained by dividing the bulk density of the mixture by the reference value described above.
[0044] For the plots shown in Figure 5, the approximate line S3 was determined. Referring to Figure 5, the approximate line S3 for each plot can be expressed as y = -0.0122x + 1.1214, where the horizontal axis is x and the vertical axis is y. From the results shown in Figure 5, it can be seen that the lower the moisture content of the coal used, the higher the bulk density of the mixture. From this, it can be seen that it is preferable to use coal with the lowest possible moisture content.
[0045] The embodiments of this disclosure have been described above. However, the embodiments described above are merely examples for implementing this disclosure. Therefore, this disclosure is not limited to the embodiments described above, and the embodiments described above can be modified as appropriate without departing from the spirit of this disclosure. [Explanation of Symbols]
[0046] 1: Crusher 2: Mixing machine 3: Coke oven A: 1st position B: 2nd position C: 3rd position
Claims
1. A coal supply process that supplies the coal to a first position designated on a transport line that transports coal to a coke oven, In the aforementioned transport line, at a second position located downstream of the first position, a sludge addition process is performed in which sludge is added to the coal, A method for producing coke, comprising: a chemical addition step of adding a surfactant to the coal at the same time as adding the sludge at the second position, or adding the surfactant to the coal and the sludge at a third position determined to be downstream of the second position in the transport line.
2. A method for producing coke according to claim 1, The transport line includes a masher for mashing the coal, A method for producing coke, wherein each of the first position, the second position, and the third position is located inside the kneader.