JP2024031801A - Method for evaluating dust prevention agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for evaluating a dust prevention agent which can properly evaluate the performance of a dust prevention agent.

SOLUTION: The method for evaluating a dust prevention agent includes: Step A of preparing a dust prevention agent as an evaluation target; Step B of measuring the film strengh of a film obtained from the dust prevention agent as a tension test machine; Step C of determining a wetting work from the surface tension of the dust prevention agent measured from a surface tension meter and a contact angle obtained by dropping the dust prevention agent to a mirror-surface polished coal; and Step D of determining whether the film strength obtained in Step B is at least a first predetermined value and the wetting work obtained in Step C is at least a second predetermined value.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a method for evaluating dustproofing agents.

Conventionally, in coal storage areas called coal yards, a liquid containing resin (dust control agent) is sprayed to suppress dust generation, and a resin film is formed on the coal pile (for example, (See Patent Document 1).

Conventionally, the performance evaluation of such dustproofing agents has generally involved spraying a dustproofing agent liquid onto a mini-pile of coal for performance evaluation, and after drying, measuring the soil hardness of the area where the dustproofing agent has been sprayed using a Yamanaka hardness tester. This is done by measuring the thickness of the part where the dustproofing agent is sprayed. Specifically, the strength of the dustproof agent is evaluated by measuring the soil hardness of the area where the dustproof agent is sprayed using a Yamanaka hardness tester, and the permeability of the dustproof agent is evaluated by measuring the thickness of the area where the dustproof agent is sprayed. .

JP2022-27532A

However, measurements using the Yamanaka soil hardness tester show that the values are influenced by the moisture content, particle size, packing density, etc. of the Mini Mountain coal, and the strength of the resin film itself obtained from the dustproof agent is measured. It's hard to say. Furthermore, the thickness of the resin film is influenced by the particle size of the coal, etc., and has a value that varies widely depending on the measurement location. Therefore, there is a problem in that the performance of dustproofing agents cannot be evaluated appropriately.

The present invention has been made in view of the above-mentioned problems, and an object thereof is to provide a method for evaluating a dustproof agent that can appropriately evaluate the performance of the dustproof agent itself.

The present inventors conducted extensive research on evaluation methods for dustproofing agents. As a result, the performance of the dustproofing agent itself can be appropriately evaluated by using the film strength obtained from the dustproofing agent and the wetting work obtained from the contact angle obtained by dropping the dustproofing agent onto mirror-polished coal. The present inventors have discovered that this is possible, and have completed the present invention.

That is, the present invention provides the following.
[1] Step A of preparing the dustproofing agent to be evaluated;
Step B of measuring the film strength of the film obtained from the dustproofing agent using a tensile tester;
step C of calculating the wetting work from the surface tension of the dustproofing agent measured by a surface tension meter and the contact angle obtained by dropping the dustproofing agent onto mirror-polished coal;
Step D of determining whether the film strength obtained in the step B is at least a first predetermined value and the wetting work obtained in the step C is at least a second predetermined value.
A method for evaluating a dustproof agent characterized by having the following.

According to the configuration, the film strength of the film obtained from the dustproofing agent is measured using a tensile tester (Step B). The film strength obtained in this way is a value of the strength of the film itself.
Further, according to the configuration, the wetting work is determined from the surface tension of the dustproofing agent measured by a surface tension meter and the contact angle obtained by dropping the dustproofing agent onto mirror-polished coal (step C). The wetting work obtained in this way is the value of wetting work for mirror-polished coal, and there is little variation in the measured values. Moreover, the value of wetting work is also a value that can directly evaluate the permeability to coal.
In step D, it is determined whether the film strength obtained in step B is greater than or equal to a first predetermined value, and the wetting work obtained in step C is greater than or equal to a second predetermined value. do.
If the film strength obtained in step B is greater than or equal to the first predetermined value, it can be determined that the film has sufficient strength. Furthermore, if the wetting work obtained in step C is equal to or greater than the second predetermined value, it can be determined that the material has appropriate permeability.
That is, in the case where it is determined in step D that the film strength obtained in step B is greater than or equal to the first predetermined value, and that the wetting work obtained in step C is greater than or equal to the second predetermined value. Because it has sufficient strength and appropriate permeability, it can be appropriately evaluated as usable as a dustproofing agent.
The film strength measured in step B is a value measured in place of the soil hardness measured using a conventional Yamanaka soil hardness meter, and the wet work determined in step C is a value measured in place of the soil hardness measured using a conventional Yamanaka soil hardness meter. This is a value measured in place of measuring the thickness of the area where the agent is sprayed.
Soil hardness measured using the conventional Yamanaka soil hardness meter is a value that is affected by the moisture content, particle size, packing density, etc. of the mini mountain coal, so the strength of the membrane itself cannot be measured properly. In addition, the thickness of the resin film was affected by the particle size of the coal, and the value varied widely depending on the measurement location, so although the performance of the dust control agent itself could not be properly evaluated. There wasn't. On the other hand, the membrane strength obtained in step B is a value of the strength of the film itself, and the wetting work obtained in step C is a value that has little variation in measured values and allows direct evaluation of permeability. , it becomes possible to appropriately evaluate whether it can be used as a dustproof agent.

[2] The first predetermined value is 0.14 N/mm ² , and when charcoal A having the following properties <Properties of charcoal A> is used as the evaluation charcoal, the second predetermined value is 25 mN/m, the method for evaluating a dustproof agent according to [1].
<Properties of Charcoal A>
ASH: 9.1%
VM: 21.8%
TS: 0.49%
Gieseler IST: 420℃
Gieseler MFT: 468℃
Gieseler MFD: 314ddpm
Gieseler logMF: 2.50logddpm
Gieseler ST: 500℃
Ro: 1.210%
TI: 24.8%
ASH, VM, TS, Gieseler IST, Gieseler MFT, Gieseler MFD, Gieseler logMF, Gieseler ST, Ro, and TI have the following meanings.
ASH: Mass percentage of the ash remaining after heating coal in air to the entire coal (specified in JIS M8812)
VM: Value obtained by subtracting moisture from the mass loss rate when a sample is heated under specified conditions without contact with air (can be measured according to JIS M 8812).
TS: Mass of the entire coal when heated to approximately 1350°C in an oxygen stream to oxidize and gasify all sulfur, collect this in a hydrogen peroxide solution, and titrate with a standard sodium hydroxide solution. Percentage (can be measured according to JISM8813)
Gieseler IST: Softening onset temperature by Gieseler plastometer method. Temperature when stirring rod starts moving continuously and reaches 1.0 ddpm. (Can be measured according to JISM8801.)
Gieseler MFT: Maximum fluidity temperature of Gieseler plastometer method. The temperature at which the stirrer reaches its maximum movement. (Can be measured according to JISM8801.)
Gieseler MFD: Maximum flow rate of Gieseler plastometer method. The flow rate when the stirring rod reaches its maximum movement. (Can be measured according to JISM8801.)
Gieseler log MF: Logarithm of the value at which the rotor impeller rotates at its highest speed in a test using a Gieseler plastometer (test of heating softening and melting properties of coal whose details are specified in JIS M8801). Raw material. An index that represents the caking property of coal.) Common logarithm of Gieseler MFD.
Gieseler ST: Solidification temperature of Gieseler plastometer method. The temperature when the stirring rod slows down and stops. (Can be measured according to JISM8801.)
Ro: Average value of maximum reflectance of 50 or more points of one polished sample in reflectance measurement of vitrinite (microstructure mainly derived from woody parts of plants). A parameter that indicates the degree of coalification of raw coal. )
TI: Volume ratio of the total amount of inert structure to the entire coal (can be measured according to JIS M 8816)

If the first predetermined value is 0.14 N/mm ² and the second predetermined value is 25 mN/m, is it possible to use it as a dustproof agent to prevent dust generation in a coal yard? It becomes possible to suitably determine.

According to the present invention, it is possible to provide a method for evaluating a dustproof agent that can appropriately evaluate the performance of the dustproof agent itself.

This is a graph plotting dustproofing agents A to D with film strength on the vertical axis and wet work on the horizontal axis. 1 is a graph showing wetting work measured using charcoal A to charcoal D for dustproofing agent A and dustproofing agent C.

Embodiments of the present invention will be described below.

The evaluation method of the dustproof agent according to this embodiment is as follows:
Step A of preparing a dustproof agent to be evaluated;
Step B of measuring the film strength of the film obtained from the dustproofing agent using a tensile tester;
step C of calculating the wetting work from the surface tension of the dustproofing agent measured by a surface tension meter and the contact angle obtained by dropping the dustproofing agent onto mirror-polished coal;
Step D of determining whether the film strength obtained in the step B is at least a first predetermined value and the wetting work obtained in the step C is at least a second predetermined value.
has.

<Process A>
In the dustproofing agent evaluation method according to the present embodiment, first, a dustproofing agent to be evaluated is prepared. The dustproof agent to be evaluated may be obtained, for example, by purchasing a commercially available dustproofing agent. Generally, dustproofing agents contain a resin and a solvent (dispersion). The solvent (dispersion liquid) is usually water.

<Process B>
Next, the film strength of the film obtained from the dustproofing agent prepared in step A is measured using a tensile tester.
Specifically, the membrane strength is obtained by the following procedure.
First, a dustproof agent with a resin concentration of 20% is spread thinly in a container and dried at room temperature for 72 hours to obtain a resin film with a thickness of 1 to 2 mm. Next, it is cut into pieces 1 cm wide and 4 to 6 cm long to obtain samples for tensile strength measurement. Next, measure the thickness of the sample. Next, the tensile stress of the sample is measured using a tensile tester. Thereafter, the obtained tensile stress is divided by the cross-sectional area, and the tensile stress per unit area is defined as the film strength. A more specific method for measuring membrane strength using a tensile tester is as described in Examples.

<Process C>
Further, wetting work is determined from the surface tension of the dustproofing agent measured by a surface tension meter and the contact angle obtained by dropping the dustproofing agent onto mirror-polished coal. The specific method for determining the wet work is according to the method described in Examples.

The order in which the steps B and C are performed is not particularly limited. The step B may be performed first, and then the step C may be performed, or the step C may be performed first, and then the step B may be performed. Further, the step B and the step C may be performed separately and simultaneously.

<Process D>
After the step B and the step C, the film strength obtained in the step B is at least a first predetermined value, and the wetting work obtained in the step C is at least a second predetermined value. Determine whether it exists or not.
In step D, if it is determined that the film strength obtained in step B is greater than or equal to the first predetermined value, and the wetting work obtained in step C is greater than or equal to the second predetermined value; , has sufficient strength and appropriate permeability, so it can be appropriately evaluated as usable as a dustproofing agent.
Soil hardness measured using the conventional Yamanaka soil hardness meter is a value that is affected by the moisture content, particle size, packing density, etc. of the mini mountain coal, so the strength of the membrane itself cannot be measured properly. In addition, the thickness of the resin film was affected by the particle size of the coal, and the value varied widely depending on the measurement location, so although the performance of the dust control agent itself could not be properly evaluated. There wasn't. On the other hand, the film strength obtained in step B is a value of the strength of the film itself, and the wet work obtained in step C has little variation in measured values, so it is necessary to appropriately determine whether it can be used as a dustproof agent. It becomes possible to evaluate.

Applications of the dustproof agent include prevention of dust generation in coal yards. The use of coal that is subject to dust generation prevention is not particularly limited, and examples thereof include coke production, power generation, and the like.
However, the use of the dustproofing agent is not limited to preventing dust generation in coal yards, but includes, for example, preventing dust generation in sports fields and construction sites.

The first predetermined value and the second predetermined value may be appropriately set according to the required dustproof performance.
The first predetermined value is preferably 0.14 N/mm ² , more preferably 0.19 N/mm ² .
The second predetermined value is preferably 25 mN/m, more preferably 26 mN/m when charcoal A having the following properties <Properties of charcoal A> is used as the evaluation charcoal.

<Properties of Charcoal A>
ASH: 9.1%
VM: 21.8%
TS: 0.49%
Gieseler IST: 420℃
Gieseler MFT: 468℃
Gieseler MFD: 314ddpm
Gieseler logMF: 2.50logddpm
Gieseler ST: 500℃
Ro: 1.210%
TI: 24.8%

ASH, VM, TS, Gieseler IST, Gieseler MFT, Gieseler MFD, Gieseler logMF, Gieseler ST, Ro, and TI have the following meanings.
ASH: Mass percentage of the ash remaining after heating coal in air to the entire coal (specified in JIS M8812)
VM: Value obtained by subtracting moisture from the mass loss rate when a sample is heated under specified conditions without contact with air (can be measured according to JIS M 8812).
TS: Mass of the entire coal when heated to approximately 1350°C in an oxygen stream to oxidize and gasify all sulfur, collect this in a hydrogen peroxide solution, and titrate with a standard sodium hydroxide solution. Percentage (can be measured according to JISM8813)
Gieseler IST: Softening onset temperature by Gieseler plastometer method. Temperature when stirring rod starts moving continuously and reaches 1.0 ddpm. (Can be measured according to JISM8801.)
Gieseler MFT: Maximum fluidity temperature of Gieseler plastometer method. The temperature at which the stirrer reaches its maximum movement. (Can be measured according to JISM8801.)
Gieseler MFD: Maximum flow rate of Gieseler plastometer method. The flow rate when the stirring rod reaches its maximum movement. (Can be measured according to JISM8801.)
Gieseler log MF: Logarithm of the value at which the rotor impeller rotates at its highest speed in a test using a Gieseler plastometer (test of heating softening and melting properties of coal whose details are specified in JIS M8801). Raw material. An index that represents the caking property of coal.) Common logarithm of Gieseler MFD.
Gieseler ST: Solidification temperature of Gieseler plastometer method. The temperature when the stirring rod slows down and stops. (Can be measured according to JISM8801.)
Ro: Average value of maximum reflectance of 50 or more points of one polished sample in reflectance measurement of vitrinite (microstructure mainly derived from woody parts of plants). A parameter that indicates the degree of coalification of raw coal. )
TI: Volume ratio of the total amount of inert structure to the entire coal (can be measured according to JIS M 8816)

If the first predetermined value is 0.14 N/mm ² and the second predetermined value is 25 mN/m, is it possible to use it as a dustproof agent to prevent dust generation in a coal yard? It becomes possible to suitably determine.

When the first predetermined value is 0.14 N/mm ² and the second predetermined value is 25 mN/m, the amount of dust generated is suppressed to a certain level or less. Specifically, in the measurement of the amount of dust generated below, the amount of dust generated can be 0.01 g or less, which can withstand actual use.

Here, the reason why it is preferable that the first predetermined value is 0.14 N/mm ² will be explained.
Generally, coal piles are stacked so that the stacking angle is 40° regardless of the type of coal.
A resin film of the dustproofing agent is formed on the slope of the coal pile along the slope. In the resin film of the dustproofing agent, there is a frictional force between the coal pile and the resin film, and an adhesive force between the coal pile and the resin film, so that the entire resin film does not slide down along the slope. Therefore, if the resin film of the dustproofing agent is not torn off by external force, the coal will not be exposed between the resin films and dust generation can be prevented.
Here, based on the past empirical results and assumptions of the present inventors and the applicant, the present inventors have determined that the maximum value of the external force that is expected to be applied to the resin membrane of the coal pile placed in the storage facility is: A force was set equal to the force of gravity (3 kg x 9.8 m/s ² =29.4 N) acting on an object with a mass of 3 kg on a cross section of a resin film with a width of 1 m. In other words, a resin film having a tensile strength greater than this force can withstand the expected load.
Generally, when forming a resin film of a dustproof agent on a coal pile, it is generally done by spraying 2.5L of a dustproof agent with a resin concentration of 10% per ^square meter of the surface of the pile. . Therefore, in this embodiment, the first predetermined value was determined as follows, using the resin film formed in this manner as a reference.
Assuming that the density of the dustproof agent is 1.0 kg/L, which is the same as water, the weight of the resin per 1 m ² of the pile surface is 250 g (2.5 L x 1.0 kg/L x 10% = 250 g).
Here, since the density of the resin used for the dustproofing agent is generally about 1.1 g/cm ³ empirically, the density of the resin film was assumed to be 1.1 g/cm ³ . Then, the volume of the resin is 227cm ³ (250g÷1.1g/cm ³ =227cm ³ ), which is the weight divided by the density.
Since 227 cm ³ of resin is spread over 1 m ² (10000 cm ² ), the thickness of the resin film is calculated to be 0.0227 cm (0.227 mm). If a force equal to the force of gravity (29.4N) acting on an object with a mass of 3kg is applied to this cross section, that is, a portion of width 100cm x thickness 0.227mm, the force applied per unit area is (29.4N÷ 227 mm ² ), it becomes approximately 0.13 N/mm ² .
From the above, in this embodiment, 0.14 N/mm ² is determined as a preferable value for the first predetermined value. As mentioned above, when the first predetermined value is 0.14 N/mm ² , there is a very low possibility that the resin film of the dustproof agent will be torn off by the assumed external force, so coal will not be exposed between the resin films. Therefore, dust generation can be prevented.
The reason why it is preferable that the first predetermined value is 0.14 N/mm ² has been explained above.

<Measurement of dust generation amount>
200 g of coal sample (moisture 10%) crushed under a 0.15 mm sieve was formed into a mountain shape with a packing density of 0.666 g/cm ³ , and a dustproof agent liquid (aqueous solution or aqueous dispersion) with a resin concentration of 5% was added. Spray 30g using a sprayer and dry to obtain a test sample. Thereafter, the test sample is exposed to wind at a wind speed of 10 m/s for 5 minutes, and the weight of the dust collected in a water vat placed behind the test sample is measured.

In the step D, it is first determined whether the film strength obtained in the step B is greater than or equal to a first predetermined value, and then it is determined whether the wetting work obtained in the step C is greater than or equal to a second predetermined value. It may be determined whether or not the wetting work obtained in the step C is equal to or higher than the second predetermined value, and then the wetting work obtained in the step B is determined. It may be determined whether the intensity is greater than or equal to a first predetermined value. Also, determining whether the film strength obtained in the step B is greater than or equal to a first predetermined value, and determining whether or not the wetting work obtained in the step C is greater than or equal to a second predetermined value. You may do both at the same time.
In particular, in the step D, it is first determined whether the film strength obtained in the step B is equal to or higher than a first predetermined value, and then the wetting work obtained in the step C is determined as a second predetermined value. It is preferable to determine whether it is equal to or greater than a predetermined value. If the film strength is less than the first predetermined value, it is usually impossible to withstand actual use even if the wet work is high. Therefore, first, it is determined whether the film strength is greater than or equal to the first predetermined value, and if it is determined that the film strength is greater than or equal to the first predetermined value, the wetting work is greater than or equal to the second predetermined value. It is preferable to determine whether or not there is.

<Process E>
Thereafter, if necessary, it is determined that the film strength obtained in step B is greater than or equal to a first predetermined value, and that the wetting work obtained in step C is greater than or equal to a second predetermined value. A step (step E) of dispersing a dustproof agent in the coal yard is performed. In step D, the dustproofing agent is determined to have a film strength obtained in step B that is equal to or greater than a first predetermined value, and a wet work obtained in step C that is equal to or greater than a second predetermined value. , has sufficient strength and appropriate permeability, so if the dustproofing agent is actually used in a coal yard, it can reliably reduce the amount of dust generated.

The method for evaluating the dustproofing agent according to the present embodiment has been described above.

Hereinafter, the present invention will be described in detail using examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

Four types of dustproofing agents (dustproofing agent A to dustproofing agent D) were prepared. Dustproofing agents A to D are commercially available products, but other than the fact that they contain resin, other details such as composition have not been disclosed.

As charcoal for evaluation, charcoal A having the following properties was prepared. Note that the following wetting work was measured using Charcoal A.
<Properties of Charcoal A>
ASH: 9.1%
VM: 21.8%
TS: 0.49%
Gieseler IST: 420℃
Gieseler MFT: 468℃
Gieseler MFD: 314ddpm
Gieseler logMF: 2.50logddpm
Gieseler ST: 500℃
Ro: 1.210%
TI: 24.8%

<Measurement of film strength>
The film strength of Dustproof Agents A to D was measured.
Specifically, the membrane strength was obtained using the following procedure.
First, a dustproof agent with a resin concentration of 20% was spread thinly in a container and dried at room temperature for 72 hours to obtain a resin film with a thickness of 1 to 2 mm. Next, it was cut into pieces 1 cm wide and 4 to 6 cm long to obtain samples for tensile strength measurement. Next, the thickness of the sample was measured using a digital caliper manufactured by Mitutoyo. Next, the tensile stress of the sample was measured using a tensile testing machine (Tensilon Universal Testing Machine (RTC-1325A) manufactured by Orientech Co., Ltd.). Thereafter, the obtained tensile stress was divided by the cross-sectional area, and the tensile stress per unit area was defined as the film strength. The average value of five measurements was taken as the value of film strength. The results are shown in Table 1.

<Wet work>
Wet work was determined for dustproofing agents A to D.
Specifically, first, the surface tension was determined by the following procedure, and then the contact angle was determined.

<Measurement of surface tension>
1. Calibration First, pure water and ethanol (manufactured by Kishida Chemical, purity 99.5%) were measured using a surface tension meter (Dunoy method surface tension meter) in the usual manner. Specifically, the torsional angle of the arm suspending the platinum ring when it was separated from the liquid surface was measured. Next, a calibration curve was created using the angle obtained from the measurement and the surface tension of pure water and ethanol (literature values). The surface tensions (literature values) of pure water and ethanol were 72.8 mN/m (20°C) and 22.5 mN/m (20°C), respectively.
2. Measurement 1 above. Using the surface tension meter used in 1. above for each dustproofing agent A to D. The twist angle was measured in the same way. Next, the surface tension of each dustproofing agent was determined from the obtained angle and the above-mentioned calibration curve. Each dustproofing agent was measured five times, and the average value was taken as the surface tension value.

<Measurement of contact angle>
The samples were prepared by polishing coal with a size of 20 to 38 mm to a mirror finish. Specifically, polishing was performed for 30 seconds with a No. 240 abrasive, 30 seconds with a No. 600 abrasive, 30 seconds with a No. 1000 abrasive, and 1 minute with a No. 2000 abrasive. At this time, additional polishing was performed if necessary while checking the state of the polished surface at each step. The polished surface was then polished to a mirror finish using an alumina polisher and buff.
3 μL of a dustproof agent solution with a resin concentration of 5% was dropped onto the mirror-finished coal sample as described above. The contact angle θ was calculated from the base x and height y of an image taken from the horizontal direction of the formed droplet as part of a sphere using the formula 2*arctan(2*y/x)=θ.

Next, wetting work was determined using the formula: wetting work (W/ΔS)=γLGcosθ. Here, W means the energy change when a liquid wets the solid surface, ΔS means the wetted area, and γLG means the gas-liquid interfacial tension.
The equation of wetting work (W/ΔS)=γLGcosθ was derived as follows.
The osmosis phenomenon is thought to occur when a liquid moves through the gaps in a solid. As the liquid wets the surface of the solid, the liquid level advances. The energy change W when a liquid wets a solid surface is the product of the difference between solid-gas interfacial tension (γSG) and solid-liquid interfacial tension (γSL) and the wetted area. Therefore, it can be expressed by the following formula (a).
W=(γSG−γSL)ΔS Formula (a)
Here, since the solid-gas interfacial tension (γSG) and the solid-liquid interfacial tension (γSL) cannot be directly measured, they are derived indirectly. In a droplet on a solid plane, three interfacial tensions (energy), namely solid-gas interfacial tension (γSG), solid-liquid interfacial tension (γSL), and gas-liquid interfacial tension (γLG), are balanced at the edge. Therefore, it can be expressed by the following equation (b).
γSG=γSL+γLGcosθ Formula (b)
From equations (a) and (b), W/ΔS=γLGcosθ is derived.
Using the value obtained in the section for measuring the surface tension as the gas-liquid interfacial tension (γLG), and using the value obtained in the section for measuring the contact angle as θ, from the formula (W/ΔS) = γLG cos θ, wetting The work was calculated five times, and the average value of the five times was taken as the wet work value. The results are shown in Table 1.

<Measurement of dust generation amount>
200 g of coal sample (moisture 10%) crushed under a 0.15 mm sieve was formed into a mountain shape at a packing density of 0.666 g/cm ³ , and dustproofing agents (dustproofing agents A to D) with a resin concentration of 5% were applied. 30g was sprayed using a sprayer and dried to obtain a test sample. Thereafter, the test sample was exposed to wind at a wind speed of 10 m/s for 5 minutes, and the weight of the dust collected in a water vat placed behind the test sample was measured. Commercially available Charcoal A was used as the coal sample. The results are shown in Table 1.

FIG. 1 is a graph plotting the film strength on the vertical axis and the wet work on the horizontal axis for dustproof agents A to D. From Table 1 and FIG. 1, dustproof agents A, B, and D, which have a film strength of 0.14 N/mm ² or more and a wet work of 25 mN/m or more, have a dust generation amount of 0. It can be said that the dust resistance is excellent.

<Verification using different types of charcoal>
In the above examples, commercially available charcoal A was used to measure the wet work and film strength to evaluate the dustproofing agent. Below, we verified that this evaluation method can be used regardless of the type of charcoal.
First, charcoal B to charcoal D having different properties from charcoal A were prepared. Charcoal B to Charcoal D are commercially available charcoals.
The properties of Charcoal A to Charcoal D are shown in Table 2.

Next, wetting work was determined for dustproofing agent A and dustproofing agent C in the same manner as above using charcoal B to charcoal D.
The results are shown in Table 3 and Figure 2. Note that Table 3 and FIG. 2 also show values for Charcoal A. In FIG. 2, the bar graph on the left side of each charcoal is the dustproof agent A, and the bar graph on the right side is the dustproof agent C.

From Table 3 and FIG. 2, in all of Charcoal A to Charcoal D, dustproofing agent A has a larger wet work value. This means that in this evaluation method, the magnitude of the wet work of the dustproofing agent is the same regardless of the type of charcoal used for evaluation. That is, in this evaluation method, if a dustproofing agent is evaluated using charcoal A, the evaluation results can be applied to the case where dustproofing agents used for other charcoals are evaluated.

Claims (2)

Step A of preparing a dustproof agent to be evaluated;
Step B of measuring the film strength of the film obtained from the dustproofing agent using a tensile tester;
step C of calculating the wetting work from the surface tension of the dustproofing agent measured by a surface tension meter and the contact angle obtained by dropping the dustproofing agent onto mirror-polished coal;
Step D of determining whether the film strength obtained in the step B is at least a first predetermined value and the wetting work obtained in the step C is at least a second predetermined value.
A method for evaluating a dustproof agent characterized by having the following. The first predetermined value is 0.14 N/mm ² ,
The dustproofing agent according to claim 1, wherein the second predetermined value is 25 mN/m when charcoal A having the following properties is used as the evaluation charcoal. evaluation method.
<Properties of Charcoal A>
ASH: 9.1%
VM: 21.8%
TS: 0.49%
Gieseler IST: 420℃
Gieseler MFT: 468℃
Gieseler MFD: 314ddpm
Gieseler logMF: 2.50logddpm
Gieseler ST: 500℃
Ro: 1.210%
TI: 24.8%
ASH, VM, TS, Gieseler IST, Gieseler MFT, Gieseler MFD, Gieseler logMF, Gieseler ST, Ro, and TI have the following meanings.
ASH: Mass percentage of the ash remaining after heating coal in air to the entire coal (specified in JIS M8812)
VM: Value obtained by subtracting moisture from the mass loss rate when a sample is heated under specified conditions without contact with air (can be measured according to JIS M 8812).
TS: Mass of the entire coal when heated to approximately 1350°C in an oxygen stream to oxidize and gasify all sulfur, collect this in a hydrogen peroxide solution, and titrate with a standard sodium hydroxide solution. Percentage (can be measured according to JISM8813)
Gieseler IST: Softening onset temperature by Gieseler plastometer method. Temperature when stirring rod starts moving continuously and reaches 1.0 ddpm. (Can be measured according to JISM8801.)
Gieseler MFT: Maximum fluidity temperature of Gieseler plastometer method. The temperature at which the stirrer reaches its maximum movement. (Can be measured according to JISM8801.)
Gieseler MFD: Maximum flow rate of Gieseler plastometer method. The flow rate when the stirring rod reaches its maximum movement. (Can be measured according to JISM8801.)
Gieseler log MF: Logarithm of the value at which the rotor impeller rotates at its highest speed in a test using a Gieseler plastometer (test of heating softening and melting properties of coal whose details are specified in JIS M8801). Raw material. An index that represents the caking property of coal.) Common logarithm of Gieseler MFD.
Gieseler ST: Solidification temperature of Gieseler plastometer method. The temperature when the stirring rod slows down and stops. (Can be measured according to JISM8801.)
Ro: Average value of maximum reflectance of 50 or more points of one polished sample in reflectance measurement of vitrinite (microstructure mainly derived from woody parts of plants). A parameter that indicates the degree of coalification of raw coal. )
TI: Volume ratio of the total amount of inert structure to the entire coal (can be measured according to JIS M 8816)