JP7598021B2 - Dust generation rate evaluation device and dust generation rate evaluation method - Google Patents

Description

This disclosure relates to a dust generation rate evaluation device and a dust generation rate evaluation method.

The molten iron obtained from the blast furnace is refined in a converter. In the refining process in the converter, processes such as decarburization and desiliconization are carried out, and the height of the main lance, the oxygen supply rate, the amount of auxiliary materials added, etc. are controlled according to the progress of these processes. In controlling such converters, a technology that utilizes the emission spectrum of the converter combustion flame has been known for some time.

Patent documents 1 and 2 disclose a method for analyzing converter exhaust gas in which light emission is analyzed in the converter exhaust gas flue and the component concentrations of the exhaust gas and dust in the flue are calculated in order to estimate decarburization and other processes during the refining process with high accuracy.

Patent Document 3 discloses a spectroscopic characteristic measuring device that includes an imaging spectroscopic device that acquires the light emitted by an object as spectroscopic information, a two-dimensional imaging device that captures an image of a two-dimensional area of the object, and a calculation device that determines the range from which the imaging spectroscopic device acquires spectroscopic information based on the image captured by the two-dimensional imaging device. Patent Document 3 also describes using this technology to measure the spectroscopic characteristics of a flame generated from a refining furnace and to control the refining furnace.

Patent documents 4 and 5 disclose a technique for measuring the emission spectrum of the furnace-mouth combustion flame blowing out from the furnace mouth of a converter, calculating the change over time in emission intensity at wavelengths in the measured range of 580 to 620 nm, estimating changes in conditions inside the furnace based on the calculated changes over time in emission intensity, and estimating the end point of the desiliconization reaction and the carbon concentration of molten iron based on the estimated changes in conditions inside the furnace.

Patent Document 6 discloses a technique for estimating the carbon concentration in molten metal based on performance information, including information about the optical characteristics of the throat of a converter.

Japanese Patent Application Publication No. 62-90524 Japanese Unexamined Patent Publication No. 62-90525 International Publication No. 2019/168141 JP 2020-105610 A JP 2020-105611 A WO 2019/220800

Incidentally, the amount of dust generated during converter blowing amounts to 1% to several percent of the total molten iron, so reducing the amount of dust generated during converter operation directly leads to cost reduction. However, the dust generation rate evaluation methods proposed so far have been methods that involve manual sampling of the dust amount or continuous measurement of the dust amount using dust collection water or exhaust gas piping, and require maintenance including periodic replacement of parts and removal and cleaning of parts in areas that are infrequently visited during normal operation. For this reason, it is difficult to constantly carry out such labor-intensive methods in a converter that is constantly in operation. In addition, the techniques in Patent Documents 1 to 6 do not estimate the dust amount (dust generation rate).

In view of the above, the objective of the present disclosure is to provide a dust generation rate evaluation device and a dust generation rate evaluation method that can operate continuously, have a small maintenance load, and can evaluate the dust generation rate with high accuracy.

As one means for solving the above problem, the present disclosure provides a dust generation rate evaluation device that evaluates the generation rate of dust generated during the operation of a refining furnace, the dust generation rate evaluation device including a spectral radiance acquisition unit that acquires the spectral radiance of the radiation spectrum at a wavelength of interest from a combustion flame generated at the opening of the refining furnace, a combustion flame temperature estimation unit that estimates the temperature of the combustion flame when the spectral radiance acquisition unit acquires the spectral radiance, a blackbody radiation radiance calculation unit that calculates the blackbody radiance at the wavelength of interest at the estimated combustion flame temperature, a spectral emissivity calculation unit that calculates the spectral emissivity from the ratio of the spectral radiance acquired by the spectral radiance acquisition unit and the blackbody radiance calculated by the blackbody radiation radiance calculation unit, and a time-change recording unit that records the change over time in the calculated spectral emissivity.

The dust generation rate evaluation device may include a dust generation rate estimation unit that estimates the dust generation rate based on the change over time of the spectral emissivity recorded by the time-varying change recording unit. The dust generation rate estimation unit may estimate the dust generation rate based on a relational expression between the spectral emissivity and the dust generation rate that has been determined in advance.

As one means for solving the above problem, the present disclosure provides a refining furnace that controls the refining furnace based on the dust generation rate evaluated by the above dust generation rate evaluation device.

As one means for solving the above problem, the present disclosure provides a dust generation rate evaluation method for evaluating the generation rate of dust generated during the operation of a refining furnace, the dust generation rate evaluation method comprising a spectral radiance acquisition process for acquiring the spectral radiance of a radiation spectrum at a wavelength of interest from a combustion flame generated at the opening of the refining furnace, a combustion flame temperature estimation process for estimating the temperature of the combustion flame when the spectral radiance is acquired in the spectral radiance acquisition process, a blackbody radiance calculation process for calculating the blackbody radiance at the wavelength of interest at the estimated combustion flame temperature, a spectral emissivity calculation process for calculating the spectral emissivity from the ratio of the spectral radiance acquired in the spectral radiance acquisition process and the blackbody radiance calculated in the blackbody radiance calculation process, a time-varying change recording process for recording the time-varying change in the calculated spectral emissivity, and a dust generation rate estimation process for estimating the dust generation rate based on the time-varying change in the spectral emissivity recorded in the time-varying change recording process.

In the above dust generation rate evaluation method, the dust generation rate estimation step may estimate the dust generation rate based on a relational expression between the spectral emissivity and the dust generation rate that has been determined in advance.

As one means for solving the above problem, the present disclosure provides a method for controlling a refining furnace, which controls the refining furnace based on the dust generation rate evaluated by the above dust generation rate evaluation method.

According to the present disclosure, continuous operation is possible, the maintenance load is small, and the dust generation rate can be evaluated with high accuracy.

FIG. 1 is a schematic diagram of a dust generation rate evaluation device 100. The relationship between the spectral emissivity and the amount of filter collected per unit time and the elapsed time in Example 1 is shown. The relationship between the estimated filter collection amount per unit time in Example 1 and the actual filter collection amount per unit time is shown. The relationship between the dust generation rate (index value) and the elapsed time in Example 2 is shown.

The inventors of the present invention measured the combustion flame generated at the opening (furnace mouth frame) of the refining furnace with a spectroscope and confirmed that the radiation spectrum was the main component. The spectral emissivity can be calculated from the ratio of the measured brightness at the wavelength of interest of this radiation spectrum to the blackbody radiation brightness calculated by Planck's law. If no luminous material is included in the measurement area, the measured value of the spectral emissivity is 0, while if the measurement area is seemingly filled with luminous materials, it is equivalent to surface emission, and the measured value of the spectral emissivity coincides with the spectral emissivity as a property of the luminous material. In this way, since the measured spectral emissivity depends on the concentration of the luminous material (dust in the case of the furnace mouth combustion flame) in the measurement area, the inventors of the present invention came up with the idea that the generation rate of dust in a refining furnace can be evaluated based on the spectral emissivity. In order to confirm the success of this idea, the inventors used a test converter to evaluate the relationship between the spectral emissivity calculated from the radiation spectrum of the combustion flame and the amount of dust generated collected from a filter, and confirmed that there is a good correlation between the spectral emissivity and the amount of dust generated. The dust generation rate evaluation device and dust generation rate evaluation method disclosed herein were invented based on this knowledge. The dust generation rate evaluation device and dust generation rate evaluation method disclosed herein will be described below.

[Dust generation rate evaluation device]
The dust generation rate evaluation device of the present disclosure will be described using a dust generation rate evaluation device 100 (hereinafter, sometimes referred to as "device 100") as one embodiment. A schematic diagram of the device 100 is shown in FIG.

The device 100 is an apparatus for evaluating the dust generation rate generated during the operation of the refining furnace 1, and includes a spectral radiance acquisition unit 10 that acquires the spectral radiance of the radiation spectrum at a wavelength of interest from the combustion flame generated at the opening 2 of the refining furnace 1, and a calculation unit 20 that performs calculations to evaluate the dust generation rate.

The spectral radiance acquisition unit 10 includes a light acquisition unit 11 and a spectroscope 12, and the light acquisition unit 11 and the spectroscope 12 are connected by an optical fiber or the like. The light acquisition unit 11 may be disposed in a position where it can acquire the light emitted by the combustion flame generated at the opening 2 of the refining furnace. In addition, by using a focusing lens in the light acquisition unit 11 to clarify the measurement range, it is possible to improve the accuracy of acquiring the spectral radiance. Such a spectral radiance acquisition unit 10 has a known configuration.

The spectral radiance acquisition unit 10 acquires the spectral radiance of the radiation spectrum at a wavelength of interest from the combustion flame generated at the opening 2 of the refining furnace 1, and typically acquires a spectral spectrum that includes this information. The spectral radiance acquisition unit 10 then transmits the spectral radiance information to the calculation unit 20. The wavelength range of the acquired spectral spectrum is, for example, 350 nm to 1000 nm.

Here, the radiation spectrum at the wavelength of interest will be explained. The spectroscopic spectrum obtained from the emission of a combustion flame includes the radiation spectrum, molecular emission spectrum, atomic emission spectrum, etc. Among these, a wavelength that includes the radiation spectrum but does not include the molecular emission spectrum or atomic emission spectrum is selected. For example, a wavelength that includes only the radiation spectrum is selected. The wavelength selected in this way is the wavelength of interest. For example, the molecular emission spectrum of 580 nm to 620 nm caused by the production and disappearance of FeO, the atomic emission spectrum of 589 nm of Na, and the atomic emission spectrum of 767 nm to 770 nm of K are not preferable wavelengths of interest. However, if the wavelength resolution of the spectrometer is high, it is possible to eliminate the effects of molecular emission and atomic emission even in the above ranges.

In this disclosure, the spectral luminance acquisition unit 10 is not limited to the form shown in FIG. 1. For example, a light sensor that can acquire the spectral luminance of a specific wavelength using an optical element such as a bandpass filter may be used.

The spectral radiance acquisition unit 10 may acquire the spectral radiance of only one point, or may acquire the spectral radiance of two or more points. In other words, the spectral radiance acquisition unit 10 may measure multiple points. This can improve the accuracy of the evaluation of the dust generation rate.

The calculation unit 20 evaluates the dust generation rate generated during the operation of the refining furnace based on the spectral brightness of the wavelength of interest transmitted from the spectral brightness acquisition unit 10. The calculation unit 20 is a known computer equipped with a CPU, RAM, ROM, a specified interface, etc.

The calculation unit 20 includes a combustion flame temperature estimation unit that estimates the temperature of the combustion flame when the spectral radiance acquisition unit 10 acquires the spectral radiance, a blackbody radiation radiance calculation unit that calculates the blackbody radiance of the wavelength of interest at the estimated combustion flame temperature, a spectral emissivity calculation unit that calculates the spectral emissivity from the ratio of the spectral radiance acquired by the spectral radiance acquisition unit and the blackbody radiance calculated by the blackbody radiation radiance calculation unit, and a time-varying recorder that records the time-varying change in the calculated spectral emissivity. The calculation unit 20 may also include a dust generation rate estimation unit that evaluates the dust generation rate based on the time-varying change in the spectral emissivity recorded by the time-varying recorder.

The combustion flame temperature estimation unit estimates the temperature of the combustion flame when the spectral luminance acquisition unit 10 acquires the spectral luminance. When the spectral luminance acquisition unit 10 acquires a spectral spectrum, the temperature of the combustion flame can be estimated from the spectral spectrum using the principle of a two-color thermometer. The temperature of the combustion flame may also be measured separately using a radiation thermometer. In this case, it is necessary to measure the temperature of the combustion flame simultaneously with the acquisition of the spectral luminance by the spectral luminance acquisition unit 10. Simultaneous does not have to be completely simultaneous. For example, an error of one second or less is acceptable. Preferably, the temperature of the combustion flame is estimated from the spectral spectrum using the principle of a two-color thermometer.

The blackbody radiation luminance calculation unit calculates the blackbody radiation luminance of the wavelength of interest at the temperature of the combustion flame estimated by the combustion flame temperature estimation unit. The blackbody radiation luminance of the wavelength of interest can be calculated using Planck's law.

The spectral emissivity calculation unit calculates the spectral emissivity (M 0 /M B ) from the ratio between the spectral radiance (M ₀ ) acquired by the spectral radiance acquisition unit 10 and the blackbody radiance (M _{B )} calculated by the _blackbody radiance calculation unit.

Here, the term "spectral emissivity" refers to a concept that includes both the absolute value of the spectral emissivity and a value proportional to the spectral emissivity. The value proportional to the spectral emissivity is the product of the absolute value of the spectral emissivity and a predetermined coefficient that depends on the measurement system. Specifically, the theoretical formula of the temperature-dependent coefficient (relative value) of the "spectral luminance of blackbody radiation" at the wavelength of interest is calculated according to Planck's law, and the "spectral luminance obtained by measurement" is divided by the temperature-dependent coefficient obtained by substituting the "measured radiation temperature (combustion flame temperature)" into the theoretical formula, thereby obtaining a value proportional to the spectral emissivity. This is because even if a value proportional to the spectral emissivity is used, it has little effect on the evaluation of the dust generation rate. However, the evaluation accuracy is improved by obtaining the coefficient that depends on the measurement system in advance using a blackbody furnace and obtaining the absolute value of the spectral emissivity. For example, the absolute value of the spectral emissivity can be obtained by previously obtaining the attenuation rate in a standard blackbody furnace using an apparatus with the same configuration as the apparatus 100.

The time-varying change recording unit records the time-varying change in the spectral emissivity calculated by the spectral emissivity calculation unit. The recorded time-varying change may be output to a display or the like so that it can be visually seen by the operator of the device.

The spectral emissivity calculated by the spectral emissivity calculation unit is the average spectral emissivity within the collection range. The spectral emissivity indicates the amount of illuminant (dust) occupying the collection range when the spectral luminance of the wavelength of interest is acquired by the spectral luminance acquisition unit 10; if the amount of dust is large, the spectral emissivity is large, and if the amount of dust is small, the spectral emissivity is small. In this way, the spectral emissivity and the dust amount are correlated, so the change over time in the amount of dust in space (dust generation rate) can be evaluated from the change over time in the spectral emissivity.

For example, the operator of the refining furnace can visually observe the change over time in the spectral emissivity output on a display or the like, and evaluate the amount of dust generation from the up and down movement of the spectral emissivity. In addition, if the spectral emissivity exceeds a predetermined threshold, the amount of dust generation may be deemed excessive.

However, when the volumetric proportion of dust in the space is small, the measured spectral emissivity is proportional to the dust generation rate, but when the volumetric proportion of dust becomes large, the overlap of dust particles cannot be ignored, and the measured spectral emissivity is no longer proportional to the dust generation rate. Therefore, the spectral emissivity is preferably in the range of 0.01 to 0.9, and more preferably in the range of 0.01 to 0.7.

On the other hand, by determining the relational equation between the spectral emissivity and the dust generation rate in advance, it is possible to evaluate the dust generation rate even in a range where the spectral emissivity and the dust generation rate are not proportional to each other. This process is performed by the dust generation rate estimation unit.

The dust generation speed estimation unit estimates the dust generation speed based on the change over time in the spectral emissivity recorded by the time-varying change recording unit, and estimates the dust generation speed based on a relational equation between the spectral emissivity and the dust generation speed that has been determined in advance.

The above spectral emissivity is a value related to the instantaneous amount of dust within the focusing range, so in order to convert the spectral emissivity to the dust generation rate, it is necessary to obtain an empirical formula in advance with the spectral emissivity and the gas passing speed near the furnace diameter and the furnace mouth of the refining furnace 1 as variables. Here, since the gas passing speed is equivalent to the gas generation rate (gas generation amount) based on the amount of oxygen blown from the top and bottom, the gas generation rate may be used in the empirical formula. Such an empirical formula (relationship) can be obtained experimentally or by simulation.

The dust generation rate estimation unit may display the estimated dust generation rate over time on a display or the like. This allows the operator to check the estimated dust generation rate in almost real time during operations.

The dust generation rate evaluation device of the present disclosure has been described above using the device 100, which is one embodiment. The dust generation rate evaluation device of the present disclosure acquires the spectral luminance of a predetermined wavelength of the combustion flame and evaluates the dust generation rate based on the spectral luminance. Therefore, unlike the conventional dust generation rate evaluation method, it is configured to be able to operate continuously. In addition, the dust generation rate evaluation device of the present disclosure has a high degree of freedom in the installation position because it is sufficient that the measurement device is placed at a position where the light emission of the combustion flame generated at the opening of the refining furnace can be acquired, and can be installed at a position where the operator can easily access it. The dust generation rate evaluation device of the present disclosure only requires maintenance of the part that acquires the spectral luminance of the combustion flame (light acquisition part), and does not need to be removed, so the maintenance load is also small. For example, it is sufficient to blow off the dust near the light acquisition part with an air duster, etc., and the required maintenance frequency can be reduced to about once per day or less. In addition, by devising a way to prevent dust from adhering to or accumulating on the light acquisition part, it is possible to further reduce the frequency, for example, to once per month or less. Therefore, the maintenance load can be significantly reduced compared to the conventional method. Furthermore, the dust generation rate evaluation device of the present disclosure uses a spectral emissivity based on the spectral radiance of the radiation spectrum at the wavelength of interest. As described above, the inventors have found that there is a certain correlation between the spectral emissivity and the dust generation rate. Therefore, by using the spectral emissivity, the dust generation rate can be evaluated with high accuracy. As described above, the dust generation rate evaluation device of the present disclosure can operate continuously, has a small maintenance load, and can evaluate the dust generation rate with high accuracy.

[Refining furnace]
The refining furnace of the present disclosure controls the refining furnace based on the dust generation rate evaluated by the dust generation rate evaluation device of the present disclosure. The refining furnace is a furnace for refining molten iron, such as a converter or an AOD. The control of the refining furnace means, for example, controlling the refining furnace so as to reduce the dust generation rate. Specific means include, for example, changing the height of the lance of the refining furnace, changing the amount of oxygen blown from the top or bottom, and changing the timing and rate of feeding the auxiliary raw materials. According to the refining furnace of the present disclosure, it is possible to reduce the amount of dust generation.

[Dust generation rate evaluation method]
The dust generation rate evaluation method disclosed herein is a method for evaluating the generation rate of dust generated during operation of a refining furnace, and includes a spectral radiance acquisition step of acquiring the spectral radiance of a radiation spectrum at a wavelength of interest from a combustion flame generated at an opening of the refining furnace; a combustion flame temperature estimation step of estimating the temperature of the combustion flame when the spectral radiance was acquired in the spectral radiance acquisition step; a blackbody radiance calculation step of calculating a blackbody radiance at the wavelength of interest at the estimated combustion flame temperature; a spectral emissivity calculation step of calculating a spectral emissivity from the ratio of the spectral radiance acquired in the spectral radiance acquisition step and the blackbody radiance calculated in the blackbody radiance calculation step; a time-varying change recording step of recording a time-varying change in the calculated spectral emissivity; and a dust generation rate estimation step of estimating the dust generation rate based on the time-varying change in the spectral emissivity recorded in the time-varying change recording step.

The details of the dust generation rate evaluation method of the present disclosure have been explained in the dust generation rate evaluation device of the present disclosure, so explanations will be omitted here. However, the following explanation will be added regarding the dust generation rate estimation process.

The dust generation rate estimation process includes, for example, having an operator of the refining furnace visually observe the change over time in the spectral emissivity output on a display or the like, and estimating the amount of dust generation from the up and down movement of the spectral emissivity. It also includes determining that the amount of dust generation is excessive when the spectral emissivity exceeds a predetermined threshold. It also includes estimating the dust generation rate based on a previously determined relational equation between the spectral emissivity and the dust generation rate.

[Method of controlling a refining furnace]
The refining furnace control method of the present disclosure controls the refining furnace based on the dust generation rate evaluated by the dust generation rate evaluation method of the present disclosure. The contents of the refining furnace control method of the present disclosure have been described in the refining furnace of the present disclosure, so description thereof will be omitted here.

The present disclosure will be further explained below using examples.

[Example 1]
The dust generation rate was evaluated using a small converter of 2 ton scale. Here, before the evaluation, the sensitivity of the measurement system was corrected using a black body furnace. In addition, a condenser lens was used in the light acquisition section to condense light from a specific part of the converter throat. The spectral radiance acquisition section acquired the spectral radiance at a wavelength of interest of 700 nm. The temperature of the combustion flame was estimated using the principle of a two-color thermometer based on the radiance ratio of wavelengths of 700 nm and 900 nm. Then, the spectral emissivity was calculated from the ratio of the calculated spectral radiance to the black body radiation radiance. Furthermore, the converter exhaust gas was sampled at regular intervals and passed through a filter to collect dust.

Figure 2 shows the relationship between the spectral emissivity and the amount of filters collected per unit time versus the elapsed time. Figure 3 also shows the relationship between the amount of filters collected per unit time estimated using a predetermined empirical formula that determines the spectral emissivity in advance, and the actual amount of filters collected per unit time.

Figure 2 confirms that there is a strong correlation between the spectral emissivity and the filter collection amount. Furthermore, Figure 3 confirms that there is a strong correlation between the filter collection amount estimated from the spectral emissivity and the actual filter collection amount. The filter collection amount per unit time correlates with the dust generation rate. Therefore, according to the present disclosure, it is possible to evaluate the dust generation rate with high accuracy.

[Example 2]
The dust generation rate was evaluated using a 300 ton converter, and the operation of the converter was controlled based on the evaluation. Here, in carrying out this, the sensitivity of the measurement system was corrected in advance using a black body furnace. In addition, a condenser lens was used in the light acquisition section to condense light from a specific part of the converter throat. The spectral radiance acquisition section acquired the spectral radiance of the wavelength of interest, 700 nm. The temperature of the combustion flame was estimated using the principle of a two-color thermometer based on the luminance ratio of wavelengths 700 nm and 900 nm. Then, the spectral emissivity was calculated from the ratio of the calculated spectral radiance to the black body radiation radiance. Furthermore, the dust generation rate (index value) was calculated from the spectral emissivity using a predetermined empirical formula obtained in advance. The actual dust generation rate (index value) was calculated from the amount of dust collected from the dust collection water.

The amount of dust collected from the dust collection water is the ratio of the weight of dust contained in the sampled dust collection water to the amount of sampled water when the dust collection water is sampled at a specified interval. This amount of dust can be obtained, for example, by a filtration analysis that improves on "JIS K 0102 14.1 Suspended solids." Normally, in the above-mentioned "JIS K 0102 14.1 Suspended solids," an appropriate amount is poured into a filter, but since representativeness cannot be obtained for dust with a wide particle size distribution, the entire sample collected is filtered to obtain the dust amount.

Figure 4 shows the relationship between the dust generation rate (index value) and elapsed time. Here, at the 5 minute mark in Figure 4, the converter operation (lance height and oxygen flow rate) was controlled to reduce the dust generation rate.

Figure 4 shows that the dust generation rate can be reduced by the operator controlling the operation of the converter while observing the change in spectral emissivity over time.

Reference Signs List 1 Refining furnace 2 Opening 10 Spectral radiance acquisition unit 11 Light acquisition unit 12 Spectrometer 20 Calculation unit 100 Dust generation rate evaluation device

Claims (6)

An apparatus for evaluating the rate of dust generation during the operation of a refining furnace,
A spectral radiance acquisition unit that acquires a spectral radiance of a radiation spectrum at a wavelength of interest from a combustion flame generated at an opening of the refining furnace;
a combustion flame temperature estimation unit that estimates a temperature of the combustion flame when the spectral radiance acquisition unit acquires the spectral radiance;
a blackbody radiation luminance calculation unit that calculates a blackbody radiation luminance of the wavelength of interest at the estimated temperature of the combustion flame;
a spectral emissivity calculation unit that calculates a spectral emissivity from a ratio of the spectral radiance acquired by the spectral radiance acquisition unit and the blackbody radiance calculated by the blackbody radiance calculation unit;
a time-varying recorder for recording the calculated time-varying spectral emissivity;
A dust generation rate evaluation device comprising: a dust generation rate estimation unit that estimates a generation rate of the dust based on the change over time of the spectral emissivity recorded by the time-varying change recording unit;
The dust generation rate evaluation device according to claim 1 , wherein the dust generation rate estimating unit estimates the dust generation rate based on a relational expression between a spectral emissivity and the dust generation rate that is obtained in advance. A refining furnace that controls the refining furnace based on the dust generation rate evaluated by the dust generation rate evaluation device described in claim 1 or 2. A method for evaluating the dust generation rate generated in the operation of a smelting furnace, comprising:
A spectral radiance acquisition step of acquiring a spectral radiance of a radiation spectrum at a wavelength of interest from a combustion flame generated at an opening of the refining furnace;
a combustion flame temperature estimating step of estimating a temperature of the combustion flame at the time when the spectral radiance was acquired in the spectral radiance acquiring step;
A blackbody radiation luminance calculation step of calculating a blackbody radiation luminance of the wavelength of interest at the estimated temperature of the combustion flame;
a spectral emissivity calculation step of calculating a spectral emissivity from a ratio of the spectral radiance acquired in the spectral radiance acquisition step and the blackbody radiance calculated in the blackbody radiance calculation step;
a time-varying recording step of recording the time-varying calculated spectral emissivity;
a dust generation rate estimating step of estimating a generation rate of the dust based on the change over time of the spectral emissivity recorded in the change over time recording step;
The dust generation rate evaluation method includes: The dust generation rate evaluation method according to claim 4, wherein the dust generation rate estimation step estimates the dust generation rate based on a relational expression between the spectral emissivity and the dust generation rate that has been determined in advance. A method for controlling a refining furnace, which controls the refining furnace based on the dust generation rate evaluated by the dust generation rate evaluation method described in claim 4 or 5.