JPS6082624A - Detection of state of sintered raw material - Google Patents

Abstract

PURPOSE:To detect state of calcined material with good accuracy on line by irradiating a packed layer to be sintered during calcination with neutron and gamma-rays, and determining the water content in the packed layer by detecting the neutron and gamma-ray transmitted the packed layer. CONSTITUTION:Raw materials are charged from each bed hopper 33 and charging hopper 34 to a circulatorily moving pallet 3 moved by a sproket 31, 32, ignited in a igniting furnace 35, sucked by an air sucking box 37 to perform sintering of the packed layer 1. A neutron source 21a and a gamma-ray source 21b are provided between the air sucking boxes 37 to perform irradiation of the packed layer 1. Neutron and gamma-rays transmitted the packed layer 1 are detected by each detector 22a and 22b and the data are outputted to an operating section 38. The operating section 38 operates the value of the water content from the information basing on a predetermined formula and displays in a display device 28. By this method, progress of sintering is grasped continuously and accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting the firing status of a sintered material by measuring the moisture content of a sintered packed bed during firing.

More specifically, the present invention measures the moisture content of the sintered packed bed in a Dwight Lloyd sintering machine to determine the location of the combustion front in the sintered packed bed, that is, the thickness of the unburned area in the sintered packed bed. Concerning how to detect

] Widely used to produce sintered ore as charging material for blast furnaces.
The Dwight Lloyd sintering machine used drives a large number of pallets arranged in an endless manner, sequentially supplies sintering raw materials to them at the feed end, ignites the surface of the pallets, and releases the pallets. The wind is sucked in by the air collecting box placed under the moving area of the pallet, and the wind blows from the surface of the sintered raw material on the pallet to the lower side. By doing so, the firing progresses downward from the surface of the raw material, and the pallet is Sintering of the raw material is completed just before reaching the ore discharge end, and the sintered ore is sent out from the ore discharge end to successive cooling devices. If sintering is not completed before the pallet reaches the discharge end, the ore will be discharged from the pallet in an unsintered state, and the sintering process will be repeated again as return ore, reducing the yield.
Further, if the firing progresses too quickly, variations in firing tend to occur, and there are disadvantages such as increased amount of returned ore and increased calorific value, which tends to cause burnout of the pallet. Therefore, in the sintering process, it is necessary to appropriately control the moving speed of the pallet, the negative pressure of the air collection box, etc., which affect the firing completion position, but this requires an accurate understanding of the sintering progress status. Must.

One of the indicators for understanding the progress of sintering is the detection of the combustion front of the sintered packed bed.

The combustion front refers to the front end of the combustion zone in the sintered packed bed, and although combustion has not yet started, the sintered raw material whose moisture content has been adjusted in advance quickly dries, and the
A band-shaped part that is heated to ℃.

Conventional methods have been used to detect the combustion front of this sintered packed bed.

(a) A method of detecting the combustion front from the temperature distribution measured by inserting a thermocouple into the sintered packed bed.

In this method, thermocouples are inserted vertically into a sintered packed bed on a pallet of a Dwy-Lloyd sintering machine at multiple locations, and the combustion front is estimated from the vertical temperature distribution within the bed.

The method according to the prior art will be explained with reference to the attached Fig. 1. Figure 1 (
It is a graph which shows the temperature change of the thermal lightning pair inserted in the sintered packed layer in the process of progressing of sintering as shown in (a). Figure 1 (
In both a) and (b), the horizontal axis shows the time elapsed from ignition on the surface of the sintered packed layer to the firing completion position, and the vertical axis shows the sintered filling in Figure 1 (a). Figure 1 (b) shows the layer height.
In Figure 1 (a), Δ is the sintered raw material zone, B is the combustion zone, C is the sintered ore zone, and the broken line is the sintered raw material heated to approximately 100°C. The line connecting the points (hereinafter referred to as the combustion front) and the white circle indicate the thermocouple insertion position. As is clear from Fig. 1 (a), when the surface of the sintered packed bed is ignited, the combustion front and combustion zone B (
The shaded area) is from the top to the bottom according to the movement of the moon.
Sintering progresses to the gray side of the pallet.
Along with this, the sintered raw material zone A gradually decreases, and the sintered ore zone C gradually increases. Then, at point Z2, which is located the required distance from the ore discharge end to the ore feed end, the combustion front reaches the point Z2, where the combustion zone B reaches the gray 1-bar of the throat, and the sintering raw material is finished. disappears, and then the combustion zone B disappears at the Z3 position immediately before the ore discharge end, and the sintered ore zone C alone reaches the ore discharge end. By the way, the temperature changes within the layer measured by thermal lightning pairs inserted from points 20 to 23 are as shown in FIG. 1 (b). Therefore, the combustion front within the sintered packed bed can be estimated from the temperature measured by this thermocouple.

However, with this method (a) of inserting thermocouples into the sintered packed bed, the accuracy of the thermocouple insertion position is low, or it is difficult to insert thermocouples continuously online. There is a problem in that it is not possible to keep track of the firing progress during the drying process.

(b) Method of detecting the combustion front from υ1 gas temperature.

In this method, the combustion status is estimated by detecting the temperature of the exhaust gas flowing into the air collection box placed under the pallet through the height of the sintered packed bed.

This prior art method (b) with reference to the attached FIG.
To explain this, Figure 2 (a) is a schematic diagram showing the progress of sintering for the sintered packed layer on the pallet, and Figure 2 (b) shows the progress of sintering as shown in Figure 2 (a). 3 is a graph showing changes in the temperature of exhaust gas sucked into a wind box through a sintered packed bed.

In both Figures 2 (a) and (b), the horizontal axis represents the position of the pallet in the moving direction from the ignition barrel to the point of completion of firing, and the vertical axis represents the firing height in Figure 2 (a). Figure 2 (b) shows the exhaust gas temperature;
, C, broken lines, and hatched areas are the same as those in FIG. 1(a). Figure 2 (a) shows that the firing progresses as described above.
During this period, the exhaust gas temperature rose to a predetermined temperature immediately after the sintered packed bed was ignited, and then rapidly rose to a maximum of 61
After reaching the maximum temperature, the exhaust gas temperature decreases as the combustion zone B decreases, and at the firing completion point Z3, the exhaust gas temperature becomes slightly lower than the maximum temperature. Therefore, by measuring the change in temperature of the exhaust gas sucked into the windbox through the sintered packed bed, the time point Z1 at which the combustion front reaches the great bar can be estimated.

In the method (b) of estimating the firing status from the 1/1 gas temperature, there are variations due to uneven ventilation in the sintered L3 FA, air leakage from the wind box seal part, uneven raw material distribution, etc. Accurate detection of Z when the combustion front reaches the great bar is difficult, and detection is only possible at Z. No information is available about the behavior of the combustion front in the region.

(C) A method of detecting the combustion front by measuring moisture in the sintered filling layer using a neutron detector.

JP-A-58-48609 discloses that a neutron source and a neutron detector are placed above and below a sintered packed layer during firing, and the neutrons emitted from the neutron source and transmitted through the sintered packed layer are detected by the neutron detector. A method for detecting the advancing position of a combustion front in a sintered packed bed based on the output of a neutron detector is disclosed.

Method (C) described in this Japanese Patent Application Publication No. 58-48609
Since it is closely related to the method of the present invention and is also the basis of the method of the present invention, its principle will be explained in detail.

Generally, sintering raw materials have a constant moisture content (approximately 5 to 7%)
However, when sintering is completed, the moisture content is approximately zero, and in the intermediate process, it changes as shown in FIGS. 3(a) and 3(b). Figure 3 (a) is a schematic diagram showing the ignition of the sintered packed bed, that is, the firing transition from the start of firing to the completion of firing, and Figure 3 (b) is the moisture content in the vertical cross section of each part of the sintered packed bed. This is a graph showing the content distribution, with the horizontal axis representing moisture (%) and the vertical axis representing the position in the layer thickness direction.

As is clear from this graph, assuming that the water content of the sintered raw material charged into the baren l- is 5%, and when firing starts, the combustion zone B and the completed firing zone, that is, the sintered ore zone C, contain moisture. On the other hand, some of the water vaporized in this region condenses as it passes through the unfueled teapot due to the sintered material blowing downward from the top surface of the sintered material, resulting in the moisture content in the unburned zone decreasing. Figure 3 (a) will increase from 5% to around 8%.
(See the graph in FIG. 3 (b) corresponding to position b). As the firing progresses, the areas of combustion zone B, firing completion zone C, and immediate moisture content area gradually expand, but the moisture content of unburned zone A reaches a saturated state of about 8%, and remains unchanged. The water content does not rise above that level, and the area continues to shrink while maintaining the water content at 8% (Fig. 3 (a), c,
(Refer to the graph in FIG. 3 (b) corresponding to position d), when viewed in a vertical section, the overall water content decreases as the baren 1- moves. When the combustion zone B reaches the bottom of the pallet and the unfueled zone A becomes zero, the water content also becomes approximately zero over almost the entire vertical section. Therefore, from the above results, if it is possible to detect the moisture content in the vertical cross section of each part of the sintered raw material on the bullet after the ignition position, then from this moisture content, the combustion zone B
The position of the combustion front can be estimated.

On the other hand, fast neutrons have the property of being decelerated by hydrogen atoms and becoming thermal neutrons, so materials containing hydrogen atoms,
For example, when fast neutrons are emitted toward a substance containing water, the amount returned to thermal neutrons in the material increases depending on the amount of hydrogen atoms, or in other words, the amount of water in the material. decrease,
As a result, the number of fast neutrons that pass through the material increases or decreases, and by measuring the transmittance of fast neutrons, the amount of water in the material can be detected.

The principle of this conventional method (C1) is illustrated in FIG. 4. In FIG. 4, 1 indicates a sintered packed bed as an object to be monitored, and 2 indicates a neutron moisture meter.

The neutron moisture meter 2 consists of a neutron source 21, a neutron detector 22, and a display section 28.
are placed oppositely above and below the sintered packed layer 1, and the neutron source 21
As for 8m-241/Be (Americium-241
/-・Lilium), “Cf (Carfornium 25
2) etc., and as the neutron detector 22, a proportional counter or the like submerged in paraffin is used. Neutron source 2
From 1, α emitted from Am-241 that constitutes this
Fast neutrons generated by the nuclear reaction when the wire collides with Be are launched toward the sintered packed bed 1, but part of the I
On the way, the neutrons are decelerated by collisions with hydrogen atoms and become thermal neutrons, and the other part passes through the sintered packed bed 1 and reaches the middle 1n detector 22. The neutron detector 22 is submerged in paraffin. Therefore, most of the fast neutrons that reach this point are converted into thermal neutrons by the hydrogen atoms in the paraffin, and the number of these thermal neutrons is counted. In other words, the water content in the sintered filling JMl can be detected by calculating the transparent high neutron number.

However, in this method (c) using a neutron moisture needle, the packing density of the sintered packed bed varies by about 20% at most during raw material supply or firing due to chemical composition, powder distribution due to moisture content, etc. is possible. Now, the vertical position of the combustion front is constant, and the packing density of the raw material layer is 1.6.
g/c+d 2. When the neutron count rate changes to Og/cot, the neutron count rate at a packing density of 1.8 g/cnt is set to 1103
cp, the neutron count rate fluctuates by about 40% to 50% as shown in FIG. Also, if the moisture value in the sintered packed bed changes by 1% by weight, the packing density will change by 1%.
．． When the rate is constant at 8 g/cffl, the neutral weight counting rate fluctuates by only about 10% as shown in FIG.

In other words, the change in the packing density of the sintered packed bed during firing is as large as about 20% at most, and the change in the detection value of the neutron moisture needle due to this change is 40 to 50%, and sometimes the actual moisture value changes even more. This may be greater than the fluctuation in the detected value of a neutron moisture meter. Therefore, with this conventional method (C), it is not possible to accurately grasp the sintering progress, and the desired precise control of the firing rate cannot be achieved.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a method for detecting the firing status of a sintering raw material with high accuracy and online.

More specifically, the object of the present invention is to provide a method for measuring moisture in a sintered packed bed using a neutron moisture meter and detecting a combustion front, further measuring the packing density of the sintered packed bed, thereby achieving the above-mentioned results. An object of the present invention is to provide a method for more accurately detecting a combustion front by correcting a moisture measurement value.

Therefore, the purpose of the present invention is to accurately detect the position of the sintering front of the sintered packed bed during firing, and thereby to control the moving speed of the bullet in Doi 1, Lloyd's sintering machine, etc., and the air collecting box. The object of the present invention is to provide sintered ore with excellent hot reduction pulverization index and cold strength by controlling the negative pressure, etc. of the sintered ore to properly maintain the progress of sintering.

According to the present invention, the sintered packed layer during firing is exposed to neutron beams and γ
A neutron source and a gamma ray source are placed opposite a neutron detector and a gamma ray detector so that the rays pass through the sintered filling layer, and the neutrons and 7 rays that have passed through the sintered filling layer are stimulated by the neutron detector and the gamma ray detector, respectively. Based on the outputs of these neutron detectors and gamma ray detectors, the moisture content of the sintered packed bed is measured without being affected by variations in the packing density of the sintered packed bed. A method for detecting the firing status of a sintered raw material is provided, which is characterized by detecting the advancing position of a combustion front in a compacted packed bed.

That is, according to the method of the present invention...
- In the method described in Publication No. 48609, a gamma ray source is added or a source that emits neutrons and gamma rays at the same time is installed, and a gamma ray detector is added or a detection method capable of separating neutrons and gamma rays is added. Set up the equipment. Then, the count rate of neutrons and gamma rays that have passed through the sintered packed bed is measured, and moisture in the sintered packed bed is estimated using the method described below in a manner that is not affected by fluctuations in the density of the sintered packed bed. , thereby detecting the advancing position of the sintering front.

The principle of detecting the combustion front of a sintered packed bed from the outputs of a neutron beam detector and a gamma ray detector in the present invention will be explained.

FIG. 6 is a schematic diagram showing the principle of the method of the present invention. 6th
In the figures, members that are the same as or common to those shown in FIG. 4 are designated by the same reference numerals.

In the figure, 1 is a sintered packed bed to be measured, 21a is a neutron source, 21b is a gamma ray source, and 22a and 22b are a neutron detector and a gamma ray detector, which are placed opposite to 21a and 21b, respectively. . i;I:Am as neutron source 21a
-241/Be or 2”% r, etc. can be used as a gamma ray source.
Co.

'J9r r, /37C3, etc. are used. Or neutron source 21. A source that simultaneously emits neutrons and γ-rays may be used instead of the γ-ray sources 21b and 21b.

Next, a calculation formula for calculating the moisture content of the sintered packed bed from the outputs of the detectors 22a and 22b will be explained.

The neutron detector 22a and the γ-ray detector 22b are manufactured by Japanese Patent Application Laid-open No. 1983.
The detector is a known quib detector such as a proportional counter submerged in paraffin as described in Japanese Patent No. 48609. Alternatively, a detector capable of separating and detecting neutrons and gamma rays may be used instead of the neutron detector 22a and the gamma ray detector 22b. 38
indicates a calculation means that calculates the moisture percentage of the sintered packed bed 1 from the outputs of the detectors 22a and 22b according to the calculation formula described later, and further calculates the advancing position of the sintering front from this calculated value,
28 is a display device for the calculation results.

The number of particles that transmit neutrons and γ-rays is expressed by the following formula.

N n -N noHK n -q, gl Hc
- treatment p %ρLχ.

・・・・・・(1) S ding Nr-Nr, °K r ° plane e-'f; pnLP person ・ ・ ・ ・ (2) However, Nn, NI: δ1 number of transmitted neutron, T-ray case N n
, , N T6 : Number of neutrons emitted from the radiation source, number of γ-rays Kn,
γ: detection efficiency S: detector incident area T: counting time R: distance between source and detector μ%, μγ, ,: mass absorption coefficient for neutrons and γ rays ρL: density of permeable substance (i) χ, : Apparent thickness of the transmitted substance (i) Under the conditions that the radiation source and detector are fixed, Barrett's absorption is constant, and the counting time is constant, equations (1) and (2) are Nn-Nn,
°exp (, Un, l), x, −Nn2 ρ2 x2
...(3) N)--Nny, ・eXp(II TH('+Xl
/' 72 +') X2...(4) It can be expressed as follows. However, NrrI and NI- are the transmission coefficients of neutrons and γ-rays, respectively, when Pareno 1- is empty, and the permeable substance is i=l: sintering raw material i=2: water.

Equations (3) and (4) become...(6), and using these, Equation (5) G can be fied as follows.

・ ・ ・ ・(8) From equation (8), if the mass absorption coefficients of water and sintering raw materials for neutrons and γ-rays are known, and the counts are made in advance when the baren 1- is empty, then the transmitted neutron beams and By measuring gamma rays, the moisture value of the sintered raw material during firing can be obtained without being affected by fluctuations in packing density.

Next, a concrete implementation state of the method of the present invention will be explained. FIG. 7 is a schematic side view of a Twight Lloyd sintering machine to which the present invention is applied, and FIG. 8 is a partially enlarged side view with a portion cut away. In the figure, 3 indicates a bullet. Baren 1
-3 is arranged in a state of being connected to an endless path formed by a drive sprocket 31, an idler sprocket 32, and a gail arranged between these two sprockets 1-31, 32. It is configured to rotate around both sprockets 31 and 32 in the direction of the white arrow. The bedding hopper 33, the charging hopper 34, the ignition furnace 35, and the heat retention furnace 36 are located on the side of the driving sprocket 32, that is, the ore discharge end, facing above the moving area of the bullet 3. A large number of air collection boxes 37 are arranged in the above-mentioned order below the movement area of the bullet 3 from directly below the ignition furnace 35 to near the ore discharge end.

As shown in FIG. 8, each bullet 3 has a rectangular shape formed by ribs 3a and 3b that are combined in a lattice pattern vertically and horizontally, and has a large number of great bars 3 on the upper surface of the pallet frame.
0, side plays 1 to 3d are erected at the required height on both sides, and wheels 3e, 3e are provided at the bottom of both sides, protruding to the left and right.
The 3C is placed on a guide rail that forms a freeway. On the barrel 1-3, bedding ore and sintering materials are charged to the gray 1-bar 3CJ2 at a uniform height from the bedding ponopa 33 and the charging hopper 34 on the ore feeding end side, and the ignition furnace 35 In the process of passing through, the surface is ignited, and the heat is retained in the heat retention furnace 36. On the other hand, an exhaust fan (not shown) connected to each collection box 37
The suction force is applied to the lower surface of the barrel 1-3, blowing air downward from the upper surface of the sintered raw material, and the firing of the sintered raw material progresses downward from the surface. The firing of the sintered raw material is completed just before reaching the fi end, and the raw material is sent out for the next cooling process as sintered ore.

In the apparatus for carrying out the method of the present invention, there are a plurality of locations (two locations in the embodiment) under the movement area of the bullet 3 from the ore supply side to the ore discharge side, and under the movement area of the barrens 1-3. A radiation source 2 that faces between the mouth edges of the interconnected wind collecting box 37 and 37 and emits neutrons and gamma rays simultaneously.
1, and a detector 22 capable of separating and detecting neutrons and gamma rays is mounted on an immovable member such as a machine frame of a sintering machine above the movement range of the bullet 3. Alternatively, instead of a radiation source that simultaneously emits neutrons and gamma rays, a neutron source 21a and a gamma ray source 21b are installed separately as shown in FIG. 6, and a detector 22 capable of separating and detecting neutrons and gamma rays is used. Instead, a neutron detector 22a and a gamma ray detector 22b are installed, and a calculation unit 38 is installed that calculates the advancing position of the sintering front without being affected by fluctuations in the density of the sintered packed bed.

As described above, in the present invention, the density of the sintered filler 1fjFi can be detected using a plurality of neutron and γ-ray detectors installed in the direction of sintering progress. Instantly measures moisture without being affected by fluctuations, correcting for fluctuations in packing density. Since the combustion front position of the sintered packed bed is detected based on this measured value, the sintering progress from the start of firing of the sintered packed bed to the completion of firing can be accurately determined using fiTC.
What's more, it can be monitored continuously online, making it possible to precisely control the firing speed by adjusting pallet movement speed, suction air volume, etc. This improves the quality of sintered ore and reduces return ore. The present invention has excellent effects such as a significant improvement in yield.

[Brief explanation of the drawing]

Figure 1 is an explanatory schematic diagram of the prior art, Figure 1 (a) is a schematic diagram showing the sintering progress of the sintered packed layer on the pallet, and Figure 1 (b) is a schematic diagram showing the sintering progress of the sintered packed layer on the pallet. It is a graph showing the temperature change of a thermocouple inserted in the inside. FIG. 2 is an explanatory schematic diagram of another conventional technique, and FIG. B) is a graph showing the temperature change of the exhaust gas sucked into the wind box. Figure 3 shows the relationship between the sintering progress of 1ffl F'J and the change in moisture content. Figure 3 (A) shows the former, Figure 3 (
B) is a graph showing the distribution of moisture in the vertical cross section of each part of the sintered packed bed. FIG. 4 is a schematic diagram of the principle of the third-mentioned prior art. FIG. 5 is a graph showing the effect of variation in raw material packing density in the neutron water needle on the neutron count rate. FIG. 6 is a schematic diagram of the principle of the method of the invention. FIG. 7 is a schematic side view of a Dwight Lloyd sintering machine which is an embodiment of the method of the present invention. FIG. 8 is a partially enlarged side view, partially cut away, of the Dwight Lloyd sintering machine shown in FIG. 7. (Main reference numbers) ■... Sintered packed bed, 3... Barrett, 21a... Neutron source, 21b... Gamma ray source, 22a... Neutron detector, 22b... Gamma ray detector, 28...・Display device, 31.. Drive sprocket, 32.. Idle sprocket, 3t.. Charging hopper, 35.. Ignition furnace, 36.. Heat retention furnace-137.. Air collecting hook, 38.. Calculating means' patent Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent Attorney Masahiko Arai Figure 1 Figure 2 Figure 3 *R<2() -h(y,>ph(Beno yht7.
i)! h (1) Figure 4 Figure 5 /, 6 /, 7 1. FI/,'? 2.0 eyebrow fJ-
Capturing back the northern region (≠53) Figure 6

Claims (1)

[Claims] A neutron source and T-ray source and a neutron detector and a gamma ray detector are placed opposite each other so that neutron beams and gamma rays pass through the sintered packed layer during firing. are facilitated by a neutron detector and a gamma ray detector, respectively.
Based on the outputs of these neutron detectors and gamma ray detectors, the moisture content of the sintered filling layer is measured without being affected by variations in the packing density of the sintered optical bottom layer. A method for detecting the firing status of a sintering raw material, characterized by detecting the advancing position of a combustion front in a layer.