JP2014105277A - Dusting suppression method for coal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dusting suppression method for a coal pile in which the increase of cost is suppressed, and dusting can be effectively suppressed.SOLUTION: Provided is a dusting generation method for coal, comprising a step of contacting the fine grains of the coal with water; and a step of mixing the fine grains and the other grains of the coal. It is preferable that the coal is made of modified coal obtained from porous coal. It is preferable that the grain size of the fine grains is 500 μm or lower. The mass ratio between the fine grains and the other fine grains in the mixing step is (1:99) to (1:3).

Description

  The present invention relates to a method for suppressing coal dust generation.

  Coal used in thermal power generation and steelworks is usually stored as piles piled up in an outdoor yard. In such a coal pile, it is necessary to prevent dust from being scattered in order to prevent environmental pollution and influence on the human body due to the scattering of coal powder.

  As a means for suppressing the dust generation of the coal pile, a watering method of spraying water or a surfactant aqueous solution on the surface of the pile is generally used. In order to further enhance the dust generation suppression effect, a method using a spray liquid containing wax emulsion or algae for spraying has been proposed (see Japanese Patent Laid-Open Nos. 2000-080355 and 2011-251882). However, in these conventional watering methods, if the amount of water spray is increased in order to suppress dust generation, the combustion efficiency decreases due to the increase in water content, and the cost increases due to an increase in the amount used of surfactants, wax emulsions, etc. It has the inconvenience.

  On the other hand, a production method for obtaining modified coal from porous coal having a high moisture content and a low calorific value has been developed (see JP-A-7-233383). This manufacturing method is as follows. First, porous charcoal (raw coal) is pulverized and granulated, and then mixed with a mixed oil containing heavy oil and solvent oil to obtain a raw slurry. Next, the raw slurry is preheated and then heated to advance the dehydration of the porous coal, and the mixed oil is impregnated into the pores of the porous coal to obtain a dehydrated slurry. Thereafter, the modified porous charcoal and the mixed oil are separated from the dewatered slurry, and then the modified porous charcoal is dried (drained). The dried modified porous coal is cooled and shaped as desired. According to this production method, it is said that, along with a decrease in the moisture content of the porous coal, heavy oil adheres in the pores of the porous coal, and a modified coal having a high calorific value can be obtained.

  The modified coal obtained by the above production method has high hydrophobicity due to adhesion of heavy oil and the like. Therefore, even if water is sprinkled on the pile of modified coal to prevent dust generation as described above, it is difficult for water to penetrate into the pile, and a large amount of water is required. Therefore, in the pile of modified coal, reduction of the amount of water used in the watering is more important.

JP 2000-080355 A JP 2011-251782 A JP 7-233383 A

  The present invention has been made based on the circumstances as described above, and can suppress the amount of water used, can effectively suppress dust generation, and thus can suppress the decrease in combustion efficiency, and thus can suppress the decrease in combustion efficiency. It aims to provide a method.

The invention made to solve the above problems is
A method for suppressing coal dust generation,
The method includes a step of bringing the fine particles of coal into contact with water, and a step of mixing the fine particles with other particles of the coal.

  In the coal dust generation suppressing method, among the many granular coals forming a pile or the like, fine particles that are easily scattered are brought into contact with water by watering or the like. For this reason, according to the said dust generation suppression method, the quantity of the water to be used can be reduced and dust generation can be suppressed effectively.

  The coal is preferably modified coal obtained from porous coal. Since the modified coal obtained from the porous coal has high hydrophobicity as described above, there is a great advantage in adopting the present invention in which the fine particles causing dust generation are brought into contact with water mainly. Moreover, since the said modified coal is porous, once water is absorbed, the water retention ability is high, and the dust generation suppressing effect can be maintained.

  The particle diameter of the fine particles is preferably 500 μm or less. Usually, the particle size of particles that generate dust is about 100 μm or less. However, by bringing water into contact with fine particles including particles having a relatively large particle size of 500 μm or less as described above, workability can be improved, for example, scattering of fine particles during work can be suppressed. In addition, when such relatively large particles are brought into contact with water, the relatively large particles tend to form nuclei with the relatively large particles as nuclei. Therefore, by doing in this way, dust generation can be suppressed more effectively.

  The mass ratio between the fine particles and other particles in the mixing step is preferably 1:99 or more and 1: 3 or less. By setting it as such a mass ratio, the reduction of water usage and effective suppression of dust generation can be made compatible.

  Here, the “particle diameter” of fine particles and the like refers to a value measured in accordance with the dry screening in JIS Z 8815 (1994) General Screening Test Law. Further, the “mass” of the fine particles and the like is a mass including water and the like attached to the fine particles.

  As described above, according to the coal dust generation suppressing method of the present invention, it is possible to suppress an increase in cost due to a large amount of water spray, etc., to effectively suppress dust generation, and to suppress a decrease in combustion efficiency. it can.

Schematic which shows an example of the apparatus used for the dust generation suppression method of coal of the present invention.

  Hereinafter, embodiments of the coal pile dusting suppression method of the present invention will be described in detail.

The coal dust suppression method is:
The step of bringing the coal fine particles into contact with water (contacting step), and the step of mixing the fine particles with other particles of the coal (mixing step)
Have

  In this way, the coal dusting suppression method, in the above-described contact step, makes the fine particles that are likely to scatter among the many granular coals forming the coal pile or the like contact with water by watering or the like. For this reason, according to the said dust generation suppression method, the quantity of the water to be used can be reduced, cost increase can be suppressed, and dust generation can be suppressed effectively.

  Further, in the dust generation suppression method, after bringing the fine particles into contact with water, the fine particles are mixed with other particles. For example, when piled up, the coal inside the pile is also in a state of containing water equally. ing. Therefore, according to the method, since the temperature rise inside the pile can be reduced, the spontaneous ignition of the pile can also be suppressed.

  The coal is not particularly limited, and anthracite, semi-anthracite, bituminous coal, subbituminous coal, lignite, lignite, peat, or coal (modified coal) obtained by modifying these coals can be used. In addition, in the said dust generation suppression method, it is preferable to use the modified coal obtained from the coal (porous coal) which has a porous shape. Examples of the porous coal include subbituminous coal, lignite, lignite, and peat. Since the modified coal obtained from porous coal has high hydrophobicity, there is a great advantage in adopting the present invention in which fine particles that cause dust generation are mainly brought into contact with water. Moreover, since the said modified coal is porous, once water is absorbed, the water retention ability is high, and the dusting suppression effect and the ignition suppression effect can be maintained.

  The modification of the porous coal can be performed, for example, by the following method. First, the porous charcoal containing water is pulverized and granulated, and then mixed with a mixed oil containing a heavy oil and a solvent oil to obtain a raw material slurry. Next, the raw slurry is preheated as necessary, and heated to advance dehydration of the porous coal, and the pores of the porous coal are impregnated with the mixed oil to obtain a dehydrated slurry. Thereafter, the modified porous charcoal and the mixed oil are separated from the dewatered slurry, and then the modified porous charcoal is dried (drained). The dried modified porous coal is cooled and shaped as desired. Usually, the modified porous charcoal is molded into a briquette shape and stored as a pile of piled briquettes.

(Separation process)
The dust generation suppressing method usually includes a step of separating granular coal into fine particles and other particles prior to the contacting step.

  The separation means is not particularly limited, and can be performed using a known device such as a sieve. Also, fine particles can be appropriately separated during the reforming step. For example, when the modified porous charcoal is dried using a steam tube dryer in which a carrier gas is circulated in a cylinder, the fine particles are collected by collecting dust (fine particles) accompanying the carrier gas with a filter. Can be separated (collected).

  The above-mentioned fine particles are a relative concept indicating a part having a small particle diameter among many granular materials constituting the coal. The specific particle diameter of the fine particles is not particularly limited, but is, for example, 1 mm or less, and preferably 500 μm or less. Usually, the particle size of particles that generate dust is about 100 μm or less. However, by bringing water into contact with fine particles having a relatively large particle diameter of 500 μm or less as described above, workability can be improved, for example, scattering of fine particles during work can be suppressed. In addition, fine particles having a size of 100 μm or less tend to be clayy when containing water. Such a clay-like substance is not preferable in terms of workability including mixing with other particles. Therefore, the workability of fine particles in a water-containing state can be improved by bringing them into contact with water, including fine particles having a relatively large particle size. Furthermore, when the relatively large fine particles are brought into contact with water, the relatively large fine particles serve as nuclei and the fine particles easily form aggregates. Therefore, by doing in this way, dust generation can be suppressed more effectively.

(Contact process)
In this contact step, the fine coal particles are brought into contact with water. The contact method is not particularly limited, and may be a method of adding the fine particles to a tank in which water is stored, and then separating the water in addition to watering using a spray or the like. Among these, it is preferable to make it contact with water by watering. By doing in this way, it can contact with water efficiently with respect to a lot of fine particles. For example, as shown in FIG. 1, the watering can be performed by using a spray 3 on the fine particles 2 deposited on the belt conveyor 1. By doing in this way, continuous watering work becomes possible.

  The amount of water sprayed is preferably 5% by mass to 30% by mass, and more preferably 15% by mass to 25% by mass with respect to the mass of the fine particles before water spraying. When the amount of water spray is less than the above lower limit, there is a possibility that a sufficient dust generation suppressing effect cannot be obtained. On the other hand, when the amount of water spray exceeds the above upper limit, the amount used is increased, resulting in an increase in cost.

  The water may be pure water or an aqueous solution in which other components are dissolved or dispersed. Examples of the other components include surfactants, waxes, water-soluble resins, and the like. By using the surfactant aqueous solution, affinity with coal (fine particles) is increased, and dust generation can be more effectively suppressed.

  The content (concentration) of the surfactant in the aqueous solution is not particularly limited, but is preferably 0.1% by mass or more and 5% by mass or less. By setting it as the content rate of the said range, the increase in cost by a large amount of use can be suppressed, expressing the effect of using surfactant.

  In the present contact step, coal other than fine particles (for example, coal having a particle diameter exceeding 500 μm) may be included in the coal in contact with water as long as the effects of the present invention are not impaired.

(Mixing process)
In this mixing step, the fine particles that have been subjected to the contact step are mixed with other particles of coal. The size of the other particles is not particularly limited as long as it is relatively large with respect to the fine particles. For example, the particle size is about several mm to several cm. The other particles may contain fine coal particles that are not in contact with water.

  The particle size distribution of the entire mixed coal (mixture of fine particles and other particles) is not particularly limited, but 10 mm or less is 30% by mass to 97% by mass, 1 mm or less is 5% by mass to 40% by mass, It is preferable that 0.15 mm or less is 20 mass% or less, 10 mm or less is 50 to 95 mass%, 1 mm or less is 10 to 30 mass%, and 0.15 mm or less is 2 to 10 mass. % Or less is more preferable.

  Since the entire mixed coal is made of such a granular material having a broad particle size distribution, the fine particles can be dispersed uniformly throughout the mixing step. Moreover, when the granular materials having such a broad particle size distribution are piled up, a pile having a small gap and a high filling rate can be formed. Generation of dust generation can be further reduced by forming a pile having such a high filling structure. Moreover, by doing in this way, it becomes difficult to ventilate oxygen inside and generation | occurrence | production of spontaneous combustion can also be reduced. On the other hand, the mixed coal as a whole may be a mixture composed only of briquettes (for example, relatively large particles having a particle size of 10 mm or more) and fine particles. Even in the case of a granular material having such a particle size distribution, the effect of the present invention can be sufficiently obtained by watering only the fine particles.

  The mixing method is not particularly limited, but as shown in FIG. 1, a belt conveyor 1 that conveys the fine particles 2, a belt conveyor 5 that conveys the other particles 4, and a coal 6 in which these are mixed is conveyed. The method using the belt conveyor 7 is mentioned. According to such an apparatus, the fine particles 2 conveyed by the belt conveyor 1 and the other particles 4 conveyed by the belt conveyor 5 are deposited on the belt conveyor 7, whereby the fine particles 2 and the other particles 4 are accumulated. Are mixed on the belt conveyor 7. By using such a method and apparatus, the contacting step and the mixing step can be performed continuously. Moreover, the pile 8 can be formed by conveying the coal 6 mixed by the belt conveyor 7 and depositing it.

  In addition, as a mixing method, it can also mix using a screw conveyor, a mixer, etc. other than the method of using the said apparatus.

  The mass ratio of the fine particles to other coal in this mixing step is preferably 1:99 or more and 1: 3 or less, and more preferably 1:19 or more and 1: 4 or less. By setting it as such a mass ratio, the reduction of water usage and effective suppression of dust generation can be made compatible. When this mass ratio is less than the above lower limit, the amount of fine particles in contact with water is small, and there is a possibility that dust generation cannot be sufficiently suppressed. On the contrary, when this mass ratio exceeds the upper limit, the amount of water used increases and the effect of the present invention is reduced.

  In addition, although this mixing process may be performed by one time of mixing, it is preferable to perform in multiple times. For example, the other particles are divided into a particle A having a relatively small particle size and a particle B having a relatively large particle size. First, as the first mixing step, the fine particles and the particle A are mixed. A mixture of fine particles and particles A and particles B are mixed. In this way, the fine particles having a large amount of water can be uniformly mixed by mixing in a plurality of times. At this time, the particle diameter of the particle A can be set to, for example, 500 μm or more and 1 cm or less. Further, the amount of the particles A with respect to the fine particles can be 1 to 10 times on a mass basis.

(Post-process)
Coal (mixture of fine particles and other particles) that has undergone the mixing process is usually piled up and stored as a pile. The method for stacking is not particularly limited, and a known method can be used. Usually, it is performed using a belt conveyor or the like.

  According to the dust generation suppression method, as described above, it is possible to effectively suppress dust generation while suppressing the amount of water used. Further, according to the dust generation suppression method, the amount of water used can be suppressed, so that a decrease in combustion efficiency and an increase in cost can be suppressed.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

[Example 1]
A granular modified coal obtained through a process of mixing and heating with a mixed oil of heavy oil and solvent oil using sub-bituminous coal as a raw material was prepared. This granular modified coal was molded to obtain briquettes (size: 47 mm × 47 mm × 28 mm). The briquette under-sieving powder was screened into 500 μm over and 500 μm under (fine particles) by dry sieving. The 500 μm over was 79% by mass, and the 500 μm under was 21% by mass. Further, the under-sieving powder had a particle size distribution in which 2 mm under 6 mm over was 26.5 mass%, 2 mm over 6 mm under, and 2 mm under 36.4 mass%. A surfactant aqueous solution was sprayed at a ratio of 5% by mass on the fine particles obtained by the above sieving. As the surfactant, NOF manufactured by NOF Corporation was used. The concentration of this aqueous surfactant solution was adjusted to 0.7% by mass and used.

  After spraying, first, the fine particles were mixed with the sieved powder over 500 μm obtained by sieving so as to be uniform. Thereafter, the mixture (under sieve powder) and the briquette were further uniformly mixed at a mass ratio of 8: 2. The particle size distribution of the obtained mixture was 10 mm or less, 60 mass%, 1 mm or less, 25 mass%, 500 μm or less, 16 mass%, or 150 μm or less, 7 mass%. In addition, this particle size distribution is a value measured by a method according to JIS Z 8815 using a shake screen manufactured by FRITSCH.

[Examples 2 to 5]
The same operation as in Example 1 was performed except that the amount of water sprayed in the surfactant aqueous solution was changed to the amount shown in Table 1.

[Comparative Example 1]
The same operation as in Example 1 was performed, except that the sieving powder and briquette were uniformly mixed at a mass ratio of 8: 2 without sieving and sprinkling the above sieving powder.

[Comparative Examples 2 to 5]
Without sieving and sprinkling the above sieving powder, the sieving powder and briquette were uniformly mixed at a mass ratio of 8: 2, and the amount of water shown in Table 1 was sprinkled on this mixture. The same operation as in Example 1 was performed.

[Evaluation]
The obtained mixture was dropped from a height of 1.5 m, the dust generation state was confirmed, and evaluated according to the following criteria. The evaluation results are shown in Table 1.
A: Dust generation was sufficiently suppressed.
B: Slight dust generation was observed, but almost suppressed.
C: An effect of suppressing dust generation is seen to some extent, but is insufficient.
D: Although the effect of watering was seen slightly, it was outside an allowable range.
E: Considerable dust generation was observed.

  Table 1 shows the water content in each of the obtained mixtures. This water content was measured by an industrial analysis method based on JIS-M 8812.

  As shown in Table 1, in the comparative example, an aqueous solution of 4% by mass with respect to the total coal was required to suppress dust generation (Comparative Example 4). On the other hand, in the example, the generation of dust could be suppressed with a 2.63% by mass aqueous solution with respect to the total coal (Example 3).

  As described above, the method for suppressing dust generation of a coal pile according to the present invention can suppress an increase in cost due to a large amount of water spray or the like and can effectively suppress dust generation. Therefore, the dust generation suppression method can be suitably used in, for example, a coal-fired power plant or a steelworks.

1 Belt conveyor 2 Fine particles 3 Spray 4 Other particles 5 Belt conveyor 6 Coal 7 Belt conveyor 8 Pile

Claims (4)

A method for suppressing coal dust generation,
A method for suppressing coal dusting, comprising: bringing the fine particles of coal into contact with water; and mixing the fine particles with other particles of the coal.   The method for suppressing dust generation according to claim 1, wherein the coal is a modified coal obtained from porous coal.   The method for suppressing dust generation according to claim 1 or 2, wherein a particle diameter of the fine particles is 500 µm or less. The method for suppressing dust generation according to claim 1, wherein the mass ratio of the fine particles to other particles in the mixing step is 1:99 or more and 1: 3 or less.

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