JP7227042B2 - Evaluation method and evaluation device - Google Patents

Description

The present invention relates to an evaluation method and an evaluation device.

For example, Patent Literature 1 discloses an evaluation method for evaluating heat transfer tube surface adhesion by measuring the degree of adhesion of combustion ash of coal. The degree of adhesion is a type of index of adhesion obtained by rotating sintered ash using a rattra tester and comparing the weight before rotation and the weight after rotation. Such a method for evaluating heat transfer tube surface adhesion in Patent Document 1 is generally applied to bituminous coal.

Japanese Patent Application Laid-Open No. 2004-361368

By the way, it is currently considered to use sub-bituminous coal as a fuel in boilers and the like. Compared to bituminous coal, sub-bituminous coal has a higher moisture content and tends to have higher adhesion to combustion ash, so it is necessary to evaluate adhesion during selection. However, conventional adhesion evaluation methods require the use of complicated procedures and special equipment. It takes time and effort to select

SUMMARY OF THE INVENTION The present invention has been made in view of the problems described above, and an object of the present invention is to easily evaluate the adhesion of sub-bituminous coal.

The present invention, as a first means related to an evaluation method for solving the above problems, is an evaluation method for evaluating the adhesion of combustion ash to a heat transfer tube surface in a pulverized coal boiler using pulverized coal as fuel, wherein the fine powder A configuration is adopted in which the coal contains subbituminous coal, and the heat transfer tube surface adhesion is evaluated based on the correlation between the volume of the solid sample of pulverized coal before heating and the volume of the solid sample after heating.

As a second means related to the evaluation method, in the first means, the correlation is a volume ratio between the volume of the solid sample before heating and the volume of the solid sample after heating. do.

As a third means related to the evaluation method, in the second means, the volume ratio calculation step of calculating the volume ratio and the agglutination estimation step of estimating the agglutination of the pulverized coal based on the volume ratio Adopt the configuration of preparing.

As a fourth means relating to the evaluation method, in the second or third means, a configuration is adopted in which a stickiness measurement step is provided to measure the stickiness when the volume ratio is out of a predetermined range.

As a fifth means related to the evaluation method, in the first or second means, the correlation of the comparative coal, which is a pulverized coal with a known correlation and a known heat transfer tube surface adhesion, and the pulverized coal to be evaluated. A configuration is adopted in which the adhesion to the heat transfer tube surface is evaluated by comparing with the correlation of .

As a first means related to the evaluation device, an evaluation device for evaluating the adhesion of combustion ash to a heat transfer tube surface in a pulverized coal boiler using pulverized coal as a fuel, wherein the pulverized coal contains subbituminous coal, and the pulverized coal A configuration is adopted in which the adhesion to the heat transfer tube surface is evaluated based on the correlation between the volume of the solid sample before heating and the volume of the solid sample after heating.

According to the present invention, it is possible to evaluate the adhesion of a solid sample of subbituminous coal based on the amount of change in volume between before and after heating. Therefore, when selecting sub-bituminous coal, it is possible to easily evaluate adhesion without conducting complicated tests or tests using specialized equipment.

4 is a graph showing changes in volume ratio and degree of agglutination according to the present invention for each temperature. 1 is a block diagram showing the functional configuration of an evaluation device according to a first embodiment of the present invention; FIG. It is a flow chart which shows the evaluation method concerning a 1st embodiment of the present invention. It is a flow chart which shows the evaluation method concerning a 2nd embodiment of the present invention.

An embodiment of the evaluation method according to the present invention will be described below with reference to the drawings.

In the evaluation method according to the present invention, in a pulverized coal boiler that burns pulverized coal, the ease of adhesion of combustion ash generated during combustion to the heat transfer tube surface in the boiler (heat transfer tube surface adhesion) is preliminarily evaluated. . Such an evaluation method is used as a criterion when selecting sub-bituminous coal, which is the raw material of pulverized coal.

First, the correlation between the adherence of combustion ash of pulverized coal and the degree of stickiness and volume ratio will be described. Table 1 below is a table showing the correlation between adhesiveness, degree of agglutination and volume ratio.

Adhesion is generally classified into four grades, as shown in Table 1. Not has the lowest adhesion, and in an actual boiler, it hardly adheres to the surface of heat transfer tubes and has the property of becoming powdery ash with fine particles. The next lowest adhesiveness is Low, and in an actual boiler, although it adheres to the heat transfer tube surface, it has the property of being easily peeled off. Medium has the next lowest adhesiveness, and in an actual boiler, it has a property that it adheres to the heat transfer tube surface and can be broken by an operator's hand. High is the one with the highest adhesiveness, and in an actual boiler, it has the property of being difficult to remove when it adheres to the heat transfer tube surface. Among these, pulverized coal with adhesion of medium or less is suitable for use as a boiler fuel. In other words, pulverized coal with High adhesion is not suitable as boiler fuel. Pulverized coal ash tends to increase in adhesion as the combustion temperature increases.

Adhesion is applied to Ratra test to quantify the hardness of sintered ash (a sample formed by sintering coal ash at a predetermined temperature (1000, 1050, 1100, 1150, 1200°C, etc.)). is a dimensionless number. Specifically, the sintered ash is rotated by a rattra tester, and the weight of the sintered ash remaining in the rattra tester is measured. Then, the degree of adhesion is calculated by dividing the residual weight of the sintered ash after rotation by the weight of the sintered ash before rotation. As disclosed in detail in Japanese Patent No. 4244713, etc., adhesion has a correlation with the degree of adhesion, and increases as the residual weight of the sintered ash after rotation increases. That is, the degree of agglutination is an index indicating that the larger the value, the higher the adhesion, and the smaller the value, the lower the adhesion. Such adhesion is, for example, less than 0.2 is Not in adhesion, 0.2 to 0.4 is Low in adhesion, 0.4 to 0.8 is Medium in adhesion, and more than 0.8 is Corresponds to High in adhesiveness.

The volume ratio (correlation) indicates the ratio between the volume of the sintered ash before heating and the volume after heating, and is a dimensionless number whose value decreases as the volume after heating decreases. As shown in FIG. 1, such a volume ratio tends to decrease as the temperature rises, that is, as the degree of adhesion increases. Then, as shown in Table 1, the average volume ratio of a plurality of samples with a known degree of agglutination is 0.98 when the degree of agglutination is 0.2, 0.96 when the degree of agglutination is 0.4, and When the degree of agglutination is 0.6, it becomes 0.94, and when the degree of agglutination is 0.8, it becomes approximately 0.91. That is, by measuring the volume ratio, it is possible to estimate the tendency of stickiness.

[First embodiment]
Next, the evaluation device 1 that executes the evaluation method according to the first embodiment of the present invention will be described.
The evaluation device 1 includes an image recognition unit 2, a volume calculation unit 3, a volume ratio calculation unit 4, an adhesion degree estimation unit 5, and an adhesion determination unit 6, as shown in FIG. Note that the evaluation device 1 is implemented as one function of a computer, for example, and functions by linking a CPU, a memory, a storage medium, a display, an input device, and the like.

The image recognition unit 2 acquires images of the cube-shaped solid sample of coal ash captured before and after heating, and performs image processing such as binarization to recognize the outline of the solid sample of coal ash. .

The volume calculation unit 3 measures the length of each side of the cube from the contour of the solid sample of coal ash acquired by the image recognition unit 2, and calculates the length of the solid sample of coal ash before and after heating. Calculate the volume.

The volume ratio calculator 4 calculates the volume ratio from the volumes of coal ash before and after heating calculated by the volume calculator 3 . The volume ratio is calculated by dividing the volume after heating by the volume before heating.

The stickiness estimation unit 5 estimates the stickiness from the calculated volume ratio. Specifically, based on a pre-stored correlation map of temperature, volume ratio, and agglutination, the agglutination estimating unit 5 determines, for example, if the volume ratio at 1150° C. is 0.98, the agglutination is Estimate a cohesion range that corresponds to the volume ratio, such as the range 0.1 to 0.3.

The stickiness determination unit 6 determines stickiness based on the stickiness estimated by the stickiness estimation unit 5 . The adhesiveness determination unit 6 determines the adhesiveness corresponding to the estimated degree of agglutination based on a map stored in advance, and displays it on the monitor.

An evaluation method using such an evaluation apparatus 1 will be described with reference to FIG.
First, an operator captures an image of coal ash formed into a cube (step S1). Then, the operator heats coal ash in a heating furnace (step S2), and takes an image of the coal ash after heating (step S3).

Subsequently, the contour of coal ash before heating is extracted from the captured image by the image recognition unit 2 . Further, the volume calculator 3 calculates the volume of the coal ash before heating from the extracted outline of the coal ash (step S4).
Then, the image recognition section 2 extracts the outline of the coal ash after heating, and the volume calculation section 3 calculates the volume of the coal ash after heating (step S5).

Next, the volume ratio calculation unit 4 calculates the volume ratio between the calculated volume before heating and the calculated volume after heating (volume ratio calculation step) (step S6). Then, the stickiness estimation unit 5 estimates the stickiness range based on the volume ratio (stickiness estimation step) (step S7). Next, the adhesiveness determination unit 6 determines the adhesiveness based on the estimated degree of agglutination, and displays it on the monitor (step S8).

At this time, the adhesion determination unit 6 determines whether or not the estimated range of adhesion is within the High or Medium range (predetermined range) (step S9). If the adhesiveness is within the predetermined range, that is, if the determination in step S9 is YES, the adhesiveness determination section 6 causes the monitor to display an instruction to measure the degree of agglutination (step S10). In this case, the operator actually measures the degree of adhesion of the sintered ash according to instructions, and re-evaluates the degree of adhesion based on the degree of adhesion (adhesion measurement step). Note that step S10 is not performed when the adhesiveness is outside the predetermined range.

According to such an evaluation method according to the present embodiment, the adhesion can be determined by calculating the volume ratio. Therefore, it is not necessary to measure the degree of agglutination each time when sub-bituminous coal is selected, and it is possible to evaluate adhesion by a simple method.

Further, according to the evaluation method according to the present embodiment, when the adhesion is poorly evaluated (the adhesion is High or Medium), the adhesion test is performed to more accurately evaluate the adhesion of sub-bituminous coal. is possible.

[Second embodiment]
A modification of the first embodiment will be described as a second embodiment. It should be noted that the same reference numerals are used for the same configuration as in the first embodiment, and the description thereof is omitted.

The evaluation device 1 according to this embodiment does not have the stickiness estimation unit 5 . In addition, the volume ratio of sub-bituminous coal (comparative coal) having a degree of cohesion of about 0.6 and medium adhesion is stored in advance in the evaluation device 1 . Then, the adhesion determination unit 6 acquires the volume ratio and compares it with the volume ratio of the comparative coal.

An evaluation method according to this embodiment will be described with reference to FIG.
First, an operator captures an image of coal ash formed into a cube (step S11). Then, the operator heats the coal ash in the heating furnace (step S12), and takes an image of the coal ash after heating (step S13).

Subsequently, the contour of coal ash before heating is extracted from the captured image by the image recognition unit 2 . Further, the volume calculator 3 calculates the volume of the sintered ash before heating from the extracted outline of the coal ash (step S14).

Then, the image recognition section 2 extracts the outline of the coal ash after heating, and the volume calculation section 3 calculates the volume of the coal ash after heating (step S15). Next, the volume ratio calculation unit 4 calculates the volume ratio between the calculated volume before heating and the volume after heating (step S16).

Further, the adhesion determination unit 6 determines whether or not the volume ratio is equal to or greater than the pre-stored shrinkage rate of the comparative coal (step S17). If the volume ratio is equal to or less than the comparison coal, that is, if the determination in step S17 is YES, the adhesion determining section 6 causes the monitor to display an instruction to measure the degree of agglutination (step S18). In this case, the operator actually measures the degree of adhesion of the sintered ash of the coal ash according to the instructions, and re-evaluates the adhesion based on the degree of adhesion. Further, when the volume ratio is larger than that of the comparative coal, the adhesion determination unit 6 determines that the sub-bituminous coal can be used (step S19).

In the evaluation apparatus 1 according to the present embodiment, the adhesion determination unit 6 evaluates the adhesion of the evaluation target sub-bituminous coal by comparison with the comparative coal. Therefore, the evaluation device 1 does not estimate the degree of agglutination, and makes a simple determination of whether the device can be used or needs to be reexamined. In other words, those with greater volumetric shrinkage than the comparative charcoal and with the possibility of higher adhesion should be re-examined, while those with smaller volumetric shrinkage and the possibility of lower adhesion than the comparative charcoal can be used. is evaluated. In this case, the processing flow becomes simple, and determination is easy.

Although the preferred embodiments of the present invention have been described above with reference to the drawings, the present invention is not limited to the above embodiments. The various shapes, combinations, and the like of the constituent members shown in the above-described embodiment are merely examples, and can be variously changed based on design requirements and the like without departing from the gist of the present invention.

In the above embodiment, evaluation is performed using the evaluation device 1, but the present invention is not limited to this. For example, the evaluation method according to the present invention may be performed manually by an operator.

In the above embodiment, the adhesion is evaluated based on the volume ratio, but the present invention is not limited to this. For example, the adhesion may be evaluated based on the correlation between the difference between the volume before heating and the volume after heating and the degree of stickiness. Also in this case, the adhesion can be evaluated based on the amount of change in volume before and after heating.

In the above embodiment, the degree of agglutination is actually measured when the adhesiveness is high, but the present invention is not limited to this. The adhesiveness determination unit 6 may only display High or Medium when the adhesiveness is high. Alternatively, the adhesion determination unit 6 may recommend using another adhesion evaluation method when the adhesion is high.

Further, in the above embodiment, the volume of coal ash is calculated by image recognition, but the present invention is not limited to this. For example, a 3D camera, a 3D scan, or the like may be used to acquire the shape of the coal ash sample and calculate the volume. In this case, it is possible to calculate a more accurate coal ash sample volume.

1 Evaluation Device 2 Image Recognition Unit 3 Volume Calculation Unit 4 Volume Ratio Calculation Unit 5 Stickiness Estimation Unit 6 Adhesion Determination Unit

Claims (3)

An evaluation method for evaluating the adhesion of combustion ash to a heat transfer tube surface in a pulverized coal boiler using pulverized coal as fuel,
the pulverized coal comprises sub-bituminous coal;
Evaluate the heat transfer tube surface adhesion based on the correlation between the volume of the solid sample of the combustion ash before heating and the volume of the solid sample after heating ,
The correlation is a volume ratio between the volume of the solid sample before heating and the volume of the solid sample after heating,
An evaluation method characterized by comprising a stickiness measuring step of measuring a stickiness when the volume ratio is outside a predetermined range . A volume ratio calculation step of calculating the volume ratio;
an agglutination estimation step of estimating the agglutination of the pulverized coal based on the volume ratio;
The evaluation method according to claim 1, characterized by comprising : Evaluating the heat transfer tube surface adhesion by comparing the correlation of the comparison coal, which is a pulverized coal of which the correlation is known and the heat transfer tube surface adhesion is known, with the correlation of the pulverized coal to be evaluated. The evaluation method according to claim 1 , characterized by:

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