JP4678593B2 - Moisture measurement method for sintered raw materials - Google Patents

Description

The present invention is capable of continuously measuring the moisture contained in the sintered raw material of the sintered ore, in particular, the moisture content of the water between the raw material particles existing between the raw material particles considered to have a large contribution to granulation with high accuracy. can be related to moisture measurement how of sintering material.

In the production process of sintered ore, the sintered raw material used as the raw material for sintered ore includes several types of iron ore, limestone as CaO source, serpentine as SiO ₂ and MgO source, powder coke as fuel and return ore, etc. It is composed of Usually, these raw materials are stored in a raw material tank for each brand, and are quantitatively cut out according to the blending ratio. The cut out raw materials are merged on a raw material transport belt conveyor and transported to a granulator. In the granulator, moisture is added to the raw material to perform mixed granulation. Further, the raw material after granulation is supplied to a sintering machine to form a raw material packed layer, and the uppermost portion thereof is ignited. Thereafter, the atmosphere is sucked downward into the raw material packed bed, whereby the sintering reaction proceeds from the upper part to the lower part of the packed bed. When the firing of the lower part is completed, it is crushed in the sinter machine ore and then cooled by a cooler.

  The role of the above-mentioned sintered raw material and moisture added thereto, and the necessity of moisture measurement, can be considered as follows. The granulation of the sintered raw material is performed by adhering the raw material particles with water as a binder. The granulated product generated by the adhesion between the particles is referred to as a pseudo particle, and the particle size of the pseudo particle is referred to as a pseudo particle size. Increasing the pseudo grain size improves the air permeability of the raw material packed layer when the sintering reaction proceeds. When the air permeability of the raw material packed layer is improved, the sintering speed is increased. Therefore, granulation of the sintered raw material is important in securing the production amount of the sintered ore. In this granulation, since moisture is an important factor for controlling the pseudo particle size, it is necessary to control the added moisture so that the target moisture can be obtained.

  Here, as a measurement device for controlling the amount of water added to the sintering raw material, continuous measurement with relatively good reproducibility is possible relatively repeatedly, as described in Patent Documents 1 to 3 and Non-Patent Document 1. An infrared absorption moisture meter (hereinafter also referred to as an infrared moisture meter) is widely used.

  More specifically, Patent Document 1 discloses a narrowband filter that selectively transmits light from a light source that emits infrared light having a continuous wavelength through a wavelength band near 1.94 μm absorbed by moisture, The sintered mixed raw material is irradiated through a filter rotating plate having a narrow band filter that selectively transmits a wavelength band near 2.10 μm that is not absorbed by water molecules and a wavelength band near 2.30 μm. The reflected light from the raw material is received by a photoelectric conversion element disposed in the light receiving section, and the moisture content of the sintered mixed raw material is obtained from the amount of infrared detected by the photoelectric conversion element. A method for measuring the water content of the mixed raw material has been proposed.

  Non-Patent Document 1 describes the following points regarding the infrared moisture meter. First, regarding the absorption wavelength, three wavelengths of 1.43 μm, 1.94 μm, and 2.95 μm are usually used as the absorption band of water, and 2.95 μm and 0 to 30% at low moisture of 0 to 2%. It is described that 1.94 μm is used for moisture, and 1.43 μm is used for more moisture. In Table 1, it is described that the moisture content of the sintered raw material in steel and metal is about 0 to 10%. Therefore, the moisture content of the sintered raw material in steel and metal is 1.94 μm. It can be said that it is suggested that the wavelength is used. Further, in Non-Patent Document 1, an infrared moisture meter captures a relative change in moisture and does not measure an absolute value. Therefore, a reference manual analysis value (such as an absolute dry moisture measurement method described later) is used. It is described that it can be measured as an on-line moisture meter for the first time by performing the matching.

  As is apparent from the description of Patent Document 1 and Non-Patent Document 1 described above, conventionally, in the moisture measurement of a sintered raw material using an infrared moisture meter, the absorption wavelength of water is around 1.9 μm, particularly 1. A wavelength band centered on 94 μm has been used.

  In addition, Patent Document 2 discloses a method (hereinafter referred to as an absolutely dry moisture measurement method) in which a sample is taken and moisture is measured from a weight change before and after drying immediately after a change in the composition of a sintered raw material that is intermittently performed. It is also proposed to create a new calibration curve for the infrared moisture meter based on the result, and to perform moisture measurement based on this calibration curve.

  Furthermore, in Patent Document 3, when controlling the amount of water sprayed to the mixer in combination with the feedforward control system and the feedback control system, the moisture value measured by an absolutely dry moisture measuring method and an infrared moisture meter as the actual moisture value. It has been proposed to use together.

On the other hand, Non-Patent Document 2 discloses that the moisture contained in the sintered raw material is roughly divided into water absorbed in the iron ore particles and water functioning as a binder between the raw material particles. Yes. More specifically, water penetrating into the true grains of the raw material or water that is chemically bonded to the raw material (so-called crystal water) has a small contribution to granulation, whereas It is disclosed that water existing as a binder (water between raw material particles) greatly contributes to granulation because the bonding between the particles proceeds by the surface tension. Based on such a theory, whether or not granulation is appropriate is evaluated by the amount of water between the raw material particles obtained by subtracting the amount of water absorbed in the raw material particles from the total amount of water contained in the sintered raw material. Therefore, it is considered that it is important to accurately measure the water content of the water between the raw material particles in order to control the water content in granulation with high accuracy.
JP 63-63948 A JP-A-6-34532 Japanese Patent Laid-Open No. 10-17946 Koichiro Takano, “Moisture Measurement in the Granule Process”, Measurement Technology, May 2000, p. 21-25 Satoshi Sato et al., “Study on granulation of sintering raw material and modeling of aeration phenomenon”, Iron and Steel, Vol. 68 (1982) p. 2174-2181

  Here, when measuring the amount of water contained in the sintered raw material using an infrared moisture meter, the measured value is affected by the type of iron ore, its blending ratio, the blending ratio of auxiliary materials, particle size, color, etc. There is a disadvantage that an error occurs. In other words, there is a drawback in that the variation in reflected light intensity (and thus the variation in absorbance) due to influencing factors other than moisture is greater than the moisture detection sensitivity.

  Therefore, the method described in Patent Document 1 tries to improve accuracy by adding a wavelength other than the absorption wavelength of water, but there is a problem in that sufficient accuracy cannot be obtained.

  In addition, the methods described in Patent Document 2 and Patent Document 3 are based on the infrared moisture meter and the absolute dry method in view of the fact that the measured value of the infrared moisture meter is easily affected by the blending ratio and particle size of the sintering raw material as described above. In combination with the moisture measurement method, every time the sintering raw material changes, the moisture content is measured by the absolute dry moisture measurement method, and the calibration curve of the infrared moisture meter is modified to improve the measurement accuracy. In order to increase the accuracy, there is a problem that complications such as increasing the measurement frequency in the absolutely dry moisture measurement method occur.

  And any of the methods described in Patent Documents 1 to 3 presents the means for solving the problem of evaluating the amount of water between the raw material particles that most affects the moisture control in the granulation of the sintered raw material. Not reached.

The present invention has been made to solve such problems of the prior art, and is present between raw material particles that are considered to have a large contribution to the water content, particularly granulation, contained in the sintered raw material of the sintered ore. the water content of between raw material particles water can be precisely measured continuously providing moisture measuring how the sintering material to an object.

In order to solve the above problems, the inventors of the present invention have made various studies on the infrared moisture meter, and as a result, have found the following new findings (1) and (2). That is,
(1) As a result of examining the infrared spectrum of the reflected light in detail when the sintered raw material is irradiated with infrared rays, when a wavelength near 2.78 μm is selected as the water absorption wavelength, it is compared with the wavelength used conventionally. The detection sensitivity to the change in the moisture content of the water between the raw material particles among the moisture content contained in the sintering material is high.
(2) When the water content is measured by selecting a wavelength in the vicinity of 2.78 μm as the water absorption wavelength, it is hardly affected by the mixing ratio and particle size of the sintered raw material, and there is a correlation with the water content between the raw material particles. It is the knowledge that it will become stronger.

The present invention has been completed based on the new findings found by the inventors. That is, the present invention is a method for measuring the amount of moisture contained in a sintering raw material by utilizing the absorption of irradiated infrared water by water, and is in the vicinity of 2.78 μm of the infrared ray irradiated on the sintering raw material before water inclusion. The step of measuring the reflected light intensity for the wavelength of the sample, the step of measuring the reflected light intensity for the wavelength in the vicinity of 2.78 μm of the infrared rays irradiated to the sintered raw material after the moisture treatment, Calculating the amount of water contained in the sintered raw material after the moisture content, based on the difference between the reflected light intensity of the binder material and the measured reflected light intensity of the sintered raw material after the moisture content. A method for measuring the moisture content of a sintered raw material is provided.

  According to such an invention, a wavelength in the vicinity of 2.78 μm is selected as the water absorption wavelength, and is less affected by the blending ratio, particle size, and the like of the sintering raw material compared to the conventionally used wavelength. Moreover, it is possible to continuously and accurately measure the water content of the water between the raw material particles existing between the raw material particles considered to have a large contribution to granulation.

In addition, according to the present invention , the sintering raw material before hydration (sintering raw material considered to be free of interparticle water) and the sinterd raw material after sintering (sintering raw material having interparticle water) Difference in reflected light intensity (difference in reflected light intensity in the present invention is not only literally a difference in reflected light intensity but also a broad concept including a difference in absorbance, etc., which is an index corresponding to the reflected light intensity) In order to calculate the moisture content (moisture content of raw material water) contained in the sintered raw material after hydration, once the calibration curve between the difference in reflected light intensity (difference in absorbance) and the moisture content is completely dry As long as it is created by a moisture measurement method or the like, there is an advantage that the calibration curve need not be corrected thereafter, or the calibration frequency can be remarkably reduced.

According to the moisture measuring how the sintering material according to the present invention, moisture contained in the sintering raw material sintered ore, between the raw material particles water especially existing between the raw material particles that are considered to be large contribution to granulation It is possible to measure the moisture content continuously with high accuracy.

  Hereinafter, an embodiment of a moisture measuring method for a sintering raw material according to the present invention will be described with reference to the accompanying drawings as appropriate.

<First Embodiment>
The moisture measurement method for a sintered raw material according to the first embodiment of the present invention is a method for measuring the amount of moisture contained in a sintered raw material by utilizing the absorption of irradiated infrared water by water. And measuring the reflected light intensity for a wavelength near 2.78 μm of the infrared ray irradiated and calculating the amount of water contained in the sintering raw material based on the measured reflected light intensity. It is said.

  If it demonstrates more concretely, the moisture measuring method concerning this embodiment will measure the reflected light intensity about the wavelength of 2.78 micrometer vicinity, and will calculate a light absorbency. A calibration curve is prepared in advance based on the relationship between the amount of moisture contained in the sintering raw material (the amount of water between the raw material particles) measured using an absolutely dry moisture measurement method and the like and the calculated absorbance. This is a method of calculating the amount of water contained in the sintered raw material based on this calibration curve and the calculated absorbance. Hereinafter, by the measurement method according to the present embodiment, moisture contained in the sintered raw material of the sintered ore, in particular, the moisture content of the water between the raw material particles existing between the raw material particles considered to have a large contribution to granulation is accurately determined. The reason why it can be measured will be described.

  FIG. 1 shows a pre-hydrated sample of a predetermined sintered raw material (sampled sintered raw material before granulation and sufficiently dried in an oven at 100 ° C.), and a post-hydrated sample (granulator for sintered raw material). An example of an infrared spectrum obtained by sampling after adding water and granulating in FIG. In FIG. 1, the horizontal axis indicates the wavelength, and the vertical axis indicates the spectral reflection intensity. As shown in FIG. 1, the spectral spectrum of the water-containing sample is very similar to the spectral absorption characteristic of water shown in FIG. 1 of Non-Patent Document 1, and is 1.43 μm, 1.94 μm and 2.95 μm. An absorption spectrum was observed.

  Judging from FIG. 1 alone, it can be considered appropriate to use a conventionally used wavelength as the absorption wavelength of water. However, in the spectrum of the pre-hydrated sample, strong absorption is observed in the vicinity of 2.9 μm, which is a so-called crystal water that remains in the pre-hydrated sample without being dried and is also present in the post-hydrated sample. It is considered that absorption due to OH groups and the like occurs.

Therefore, from the measurement results in FIG. 1, the absorbance for each wavelength of the post-hydrated sample and the pre-hydrated sample was calculated, and the difference in absorbance (differential absorbance) of each sample was calculated. FIG. 2 (a) shows the absorbance for each wavelength of the hydrated sample and the sample before hydrated, and FIG. 2 (b) shows the differential absorbance (absorbance of the sample after hydrate-absorbance of the sample before hydrated). The absorbance is a value represented by the following formula (1), where I0 is the amount of infrared irradiation on each sample and I is the amount of reflected light on each sample. A value corresponding to a numerical value.
Absorbance = ln (I / I0) = ln (1 / r) (1)

  It is considered that the differential absorbance shown in FIG. 2 (b) reflects the amount of water between the raw material particles present in the post-water-containing sample, not the crystal water present in the sintered raw material. As shown in FIG. 2B, the strongest absorption peak at 2.78 μm exists in the differential absorbance. That is, when light having this wavelength is used as the absorption wavelength, the detection sensitivity with respect to the change in the amount of water between the raw material particles is higher than that of a conventionally used wavelength. From this point, the inventors of the present invention have come to think that it is effective to make the absorption wavelength of water around 2.78 μm in the infrared moisture meter.

  Furthermore, the inventors of the present invention use the conventionally used wavelengths of 1.94 μm and 2.95 μm as the water absorption wavelength in the infrared moisture meter, and the case of using 2.78 μm. Particles obtained by granulating various sintered raw materials (5 types of iron ores A to E and 4 types of those mixed by changing their mixing ratio and particle size as appropriate) The correlation between the moisture content of the interstitial water and the reflection intensity (specifically, absorbance) was investigated.

  FIG. 3 shows an example of the survey result. FIG. 3 (a) shows the correlation between the amount of moisture between particles and the absorbance (difference absorbance) when 2.78 μm is used as the water absorption wavelength, and FIG. 3 (b) shows 1.94 μm as the water absorption wavelength. The correlation between the water content of the interparticle water | moisture content and the light absorbency (differential light absorbency) at the time of using is shown. The horizontal axis in FIG. 3 means the moisture content of the moisture between the raw material particles, and was obtained as a weight increment accompanying the addition of moisture before and after granulation. In addition, the raw material before granulation used what was fully dried with 100 degreeC oven similarly to the case where the result shown in FIG.1 and FIG.2 was obtained.

Comparing the correlation coefficient (R ² ) between FIGS. 3 (a) and 3 (b), R ² = 0.819 in the wavelength 2.78 μm (FIG. 3 (a)), whereas the wavelength 1. At 96 μm (FIG. 3B), the correlation is weak with R ² = 0.49. Although not shown, the correlation is weak with R ² = 0.47 even at a wavelength of 2.95 μm. From the above points, if a wavelength near 2.78 μm is used as the absorption wavelength of water in the infrared moisture meter, it is less affected by the blending ratio and particle size of the sintered raw material than the conventionally used wavelength, and the raw material particles It can be seen that there is a strong correlation with the amount of interstitial water.

  From the above examination results, if a wavelength near 2.78 μm is used as the water absorption wavelength in the infrared moisture meter, the absorbance of the reflected light itself is an influencing factor (crystal water and sintered water) other than the raw material interparticle water as in the prior art. Although it varies depending on the mixing ratio and particle size of the raw materials, it can be said that the increase in absorbance accompanying the variation in the water content between the raw material particles does not depend on the influencing factors, and a relatively close value can be obtained. In other words, the constant amount (Y-intercept) of the calibration curve obtained by plotting the water content of raw material interparticle water measured using the absolute dry moisture measurement method on the horizontal axis and the absorbance on the vertical axis is the sintered raw material. However, since the gradient is substantially constant, the amount of water between the raw material particles can be accurately measured as long as the calibration curve is appropriately calibrated for at least a constant amount.

  On the other hand, in an infrared moisture meter using a conventional absorption wavelength, not only the constant of the calibration curve but also the gradient varies depending on the blending ratio and particle size of the sintered raw material. And it is a sampled water content that can be measured at once using the absolutely dry moisture measurement method. Therefore, when the calibration curve is calibrated using the moisture content measured at once by the absolute dry moisture measurement method, only one of the constant or the gradient of the calibration curve is corrected, and sufficient calibration accuracy is naturally obtained. It will not be possible. In order to correct both the constant and the slope of the calibration curve, it is necessary to obtain the measurement results of two or more absolute dry moisture measuring methods with different moisture contents, which causes troubles such as increasing the measurement frequency. .

  For the reason described above, as described above, the moisture measuring method according to the present embodiment measures the reflected light intensity at a wavelength in the vicinity of 2.78 μm of the infrared ray irradiated to the sintering raw material, And a step of calculating the amount of water contained in the sintered raw material based on the measured reflected light intensity.

  The moisture measuring apparatus for carrying out the moisture measuring method according to the present embodiment described above includes a light source that irradiates the sintering material with infrared light, and the infrared sintering material that is irradiated from the light source. Between the light source and the sintering raw material and / or between the sintering raw material and the detecting element and detecting an infrared ray having a wavelength in the vicinity of 2.78 μm. It is possible to employ a configuration including an optical filter that selectively transmits light. In other words, the moisture measuring device according to the present embodiment is the same as a conventional infrared moisture meter (conventional device) as disclosed in, for example, Patent Document 1, and the main components are the same. The point is that it is replaced with an optical filter that selectively transmits infrared light having a wavelength in the vicinity of .78 μm, the point that a preferable element is used to detect the wavelength in the vicinity of 2.78 μm, and the wavelength in the vicinity of 2.78 μm. This is different from the conventional apparatus in that a light source, a lens and the like suitable for the above are used.

  More specifically, the moisture measuring device according to the present embodiment includes a light source for irradiating the sintering raw material with infrared light including a wavelength in the vicinity of 2.78 μm, a light projecting optical system such as a lens and a mirror, and irradiation. Detection element for detecting the light reflected by the sintering material, a detection optical system such as a lens and a mirror for condensing the reflected light on the detection element, and a projection optical system or detection optical Either or both of the systems include a filter mechanism including a filter that selectively transmits at least a light having a wavelength in the vicinity of 2.78 μm out of the projected light or reflected light. The center wavelength of the filter is preferably about 2.78 μm, and the passband width is preferably 300 nm or less, and is about 100 nm, which is about the half-value width of the spectrum near 2.78 μm shown in FIG. Is particularly preferred.

  The filter mechanism includes a filter that selectively transmits light having a wavelength near 2.78 μm, and a filter that selectively transmits light having a wavelength near 3.2 μm as a preferred configuration. It is set as the structure switched sequentially. In order to sequentially switch the two types of filters in time series, for example, the two types of filters are arranged on the circumference of a specific radius of a rotating disc, and the projection optical system or the detection optics is rotated by rotating the disc. A configuration in which both filters cross the optical axis of the system may be employed. A filter that selectively transmits light having a wavelength in the vicinity of 3.2 μm is attached to a lens, a mirror, or the like, a change in the amount of infrared light emitted from the light source with time, deterioration of an amplifier that amplifies an output signal from the detection element. It is preferably used to correct the influence of fluctuations in the amount of reflected light (and thus the absorbance) detected due to contamination. More specifically, the absorbance for light having a wavelength near 2.78 μm is calculated based on the absorbance for light having a wavelength near 3.2 μm (for example, the absorbance of light having a wavelength near 2.78 μm). If the difference from the absorbance of light having a wavelength in the vicinity of 3.2 μm is calculated as the absorbance of light having a wavelength in the vicinity of 2.78 μm), the variation factor as described above can be obtained by comparing the light having the wavelength in the vicinity of 2.78 μm with the light having a wavelength of 3 in the vicinity of 2.78 μm. Since it occurs in both light having a wavelength in the vicinity of 2 μm, the influence can be reduced.

  Moreover, as a light source which comprises the moisture measuring device which concerns on this embodiment, the halogen lamp sealed with the heater wire or quartz glass can be used. As the detection element, PbS or PbSe whose temperature is controlled stably at a low temperature can be used.

  As described above, according to the moisture measuring method according to the present embodiment, a wavelength in the vicinity of 2.78 μm is selected as the absorption wavelength of water, and compared with the conventionally used wavelength, the sintering raw material is selected. Therefore, it is possible to measure the moisture content of the water between the raw material particles existing between the raw material particles which are hardly affected by the blending ratio and particle size of the raw material and are considered to have a large contribution to granulation with high accuracy.

<Second Embodiment>
The method for measuring moisture content of a sintered raw material according to the second embodiment of the present invention includes a step of measuring reflected light intensity at a wavelength in the vicinity of 2.78 μm of infrared rays irradiated to the sintered raw material before water inclusion, The step of measuring the reflected light intensity at a wavelength in the vicinity of 2.78 μm of the infrared ray irradiated to the sintered raw material, the measured reflected light intensity of the sintered raw material before water content, and the measured sintering after water content And a step of calculating the amount of water contained in the sintered raw material after the water content based on the difference from the reflected light intensity of the raw material.

  More specifically, in the moisture measuring method according to the present embodiment, the sintering raw material before granulation (sintering raw material before water content) is sampled and dried at a predetermined temperature, and then the vicinity of 2.78 μm. The absorbance is calculated by measuring the intensity of reflected light for each wavelength. Next, with respect to the sintered raw material after granulation (sintered raw material after hydration), the reflected light intensity at a wavelength near 2.78 μm is measured, and the absorbance is calculated. Next, the difference in absorbance between the two (difference absorbance) is calculated. Then, a calibration curve is prepared in advance based on the relationship between the moisture content (moisture content of raw material water) contained in the sintered raw material measured using an absolutely dry moisture measurement method and the calculated differential absorbance. In other words, the moisture content contained in the sintered raw material after granulation is calculated based on the calibration curve and the calculated differential absorbance.

  Since the method according to the present embodiment is configured to calculate the amount of water using the difference in absorbance (difference absorbance) between the sintered raw materials before and after water inclusion, unlike the first embodiment, a calibration curve that depends on the sintered raw materials. The constant (Y intercept) is substantially omitted by calculating the difference in absorbance. Therefore, as long as a calibration curve between the differential absorbance and the moisture content is first prepared by an absolute dry moisture measurement method or the like, a constant component of the calibration curve can be obtained according to the change of the sintering raw material as in the first embodiment. There is an advantage that the correction frequency of the calibration curve can be significantly reduced.

  In addition, in order to implement the moisture measuring method according to the present embodiment, a moisture measuring device having the same configuration as that described in the first embodiment may be disposed in each of the steps before and after granulation. Since the configuration itself is the same as that of the first embodiment, a detailed description thereof is omitted. Moreover, in this embodiment, as a sintering raw material before water containing which measures the reflected light intensity about the wavelength of 2.78 μm, the sintered raw material before granulation is sampled and dried at a predetermined temperature. It is not limited, and a sintered raw material conveyed by a belt conveyor before granulation can be used, and a sample after measuring moisture content with an absolutely dry moisture meter after granulation can also be used.

FIG. 1 shows an example of infrared spectroscopic spectra of a pre-hydrated sample and a post-hydrated sample for a predetermined sintering raw material. FIG. 2A shows the absorbance for each wavelength of the water-containing sample and the water-containing sample shown in FIG. 1, and FIG. 2B shows the differential absorbance (absorbance of the sample after water-absorbance of the sample before water-containing). FIG. 3 (a) shows the correlation between the amount of moisture between particles and the absorbance (difference absorbance) when 2.78 μm is used as the water absorption wavelength, and FIG. 3 (b) shows 1.94 μm as the water absorption wavelength. The correlation between the water content of the interparticle water | moisture content and the light absorbency (differential light absorbency) at the time of using is shown.

Claims (1)

A method for measuring the amount of moisture contained in a sintering raw material by utilizing absorption of irradiated infrared water by water,
Measuring the reflected light intensity at a wavelength in the vicinity of 2.78 μm of infrared rays irradiated to the sintered raw material before water content;
Measuring the reflected light intensity at a wavelength near 2.78 μm of infrared rays irradiated to the sintered raw material after water inclusion;
A step of calculating the amount of water contained in the sintered raw material after moisture content based on the difference between the measured reflected light intensity of the sintered raw material before moisture content and the measured reflected light intensity of the sintered raw material after moisture content. The moisture measuring method of the sintering raw material characterized by including these.

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