JP7248106B2 - Steam treatment method for steelmaking slag - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for steaming steelmaking slag, which enables rational steam flow rate control in the operation of a steaming facility for steaming steelmaking slag.

Steelmaking slag is dense and hard and can support a large load when compacted, so it is used as a roadbed material. However, steelmaking slag such as converter slag, for example, has the property of exhibiting expandability after a long period of time. For this reason, it is common to carry out an aging treatment in which the reaction of the expansion source is accelerated in advance and the majority of the material is reacted before shipment as a roadbed material.

Steelmaking slag is crushed and processed as a steel slag roadbed material. Free lime (f-CaO) contained in the steelmaking slag reacts with moisture to become slaked lime (Ca(OH) ₂ ), and the steelmaking slag expands more than twice. If used without treatment, the roadbed may be destroyed within a few years, so "steam aging" treatment is performed in the manufacturing process to promote the reaction with moisture using steam. Non-Patent Document 1 can be used as a method for measuring the expansion rate.

In the steam aging treatment, treatment is often performed near the saturated steam temperature that is in equilibrium with the atmospheric pressure. For the treatment, several hundred to several thousand tons of steelmaking slag is placed on a bed in which it is almost flatly piled up. Steelmaking slag is often piled up in walled pits. After that, steam is blown from a steam supply pipe arranged under the steelmaking slag in the pit to raise the temperature of the steelmaking slag in the bed to about 100°C. Hold. Here, f--CaO reacts with moisture to greatly reduce the expansibility of the steelmaking slag.

As a method for such steam aging treatment, a method has been proposed in which a plurality of thermometers are inserted into the steelmaking slag in the bed and the steam flow rate of the steam supply pipe is controlled according to the temperature measurement results of the thermometers. (See Patent Document 1).

JP-A-4-175250 JIS A 5015:2013 Steel slag for roads Annex B

In the conventional steam aging treatment method, the larger the treatment facility, the better, from the viewpoint of rationalization of work man-hours and the amount of steam used. However, when processing equipment is enlarged, steelmaking slag with various histories enters a single pit, and it is difficult to maintain a constant loading pattern when working with heavy equipment to stack steelmaking slag on the bed. . Therefore, it becomes a steelmaking slag bed that includes the density difference for each location. For this reason, when steam is blown in from below to raise the temperature, uneven flow of steam occurs due to the coarseness and fineness of the steelmaking slag. become difficult.

At this time, if the steam injection time for the entire bed is extended by controlling the valve of the steam supply pipe according to the part of the steelmaking slag where the temperature rise is slow, a large amount of steam will flow into the part of the steelmaking slag already held at 100°C or higher. It is unreasonable to blow more. Even if the overall amount is increased or decreased, the portion where the flow is relatively difficult eventually changes with a smaller steam flow rate than the other portions. That is, a large amount of steam whose temperature has already been raised flows excessively even in areas where it is not required. This wasteful use of steam leaves some areas with insufficient steam and, most importantly, inconsistencies in expansion stabilization.

In addition, there is a numerical limit to inserting thermometers into the steelmaking slag as in the method disclosed in Patent Document 1, and the distance between the thermometers must be widened, resulting in unmeasured portions. Therefore, in the steelmaking slag in the bed, it is not possible to accurately grasp which part is uneven due to poor temperature rise. A portion where the temperature has not risen sufficiently may remain undetected, and the water immersion expansion ratio varies in size within one bed.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems of the prior art, and to provide a steam treatment method for steaming steelmaking slag, capable of rationally controlling the steam flow rate regardless of the state of the steelmaking slag in the bed. To provide a method for steaming steelmaking slag, which can steam-treat steelmaking slag while suppressing the amount of steam used.

In order to achieve the above-mentioned object, the present invention can measure the temperature of the entire surface of the steelmaking slag in the bed, and can grasp the distribution of the steam flow rate in the entire steelmaking slag in the bed. The inventors have found that the amount of slag can be controlled, and have developed a novel steelmaking slag steam treatment method described below.

That is, the present invention relates to a steelmaking slag steam treatment method in which steelmaking slag is piled on a bed and steam is blown into the bed from below to steam-treat the steelmaking slag. , in each divided section, the temperature change over time on the steelmaking slag surface is measured, based on the measured temperature change over time, the steam flow rate distribution in each section of the steelmaking slag is estimated, and based on the estimated steam flow rate distribution, the steelmaking A steam treatment method for steelmaking slag, characterized by controlling the amount of steam blowing into each section of the slag.

In the steelmaking slag steam treatment method according to the present invention configured as described above,
(1) Measurement of the temperature-time transition in each section of the steelmaking slag surface is performed by thermal image observation of the upper surface of the steelmaking slag stacked on the bed from above the bed;
(2) The measurement of the temperature-time transition in each section of the steelmaking slag surface was performed by observing a plurality of thermometers inserted from the surface of the steelmaking slag and thermal image observation of the top surface of the steelmaking slag stacked on the bed from above the bed. and based on the results of measurements by both;
(3) performing the thermal image observation using thermography;
(4) Steam treatment is performed as a rectangle with the length of one side of the section of the steelmaking slag surface being 1/2 or more and 2 or less of the height of the stacked bed;
is considered to be a more preferable solution.

According to the steam treatment method for steelmaking slag according to the present invention, the surface of the steelmaking slag in the bed is divided into a plurality of sections, and the temperature-time transition of the entire surface of each section is measured over time in each divided section. By estimating the steam flow rate distribution in each section based on the time transition and reflecting the estimated steam flow rate distribution in the steam flow rate control of each section, more constant temperature rise and heat retention can be achieved. As a result, the temperature is kept uniform in one bed, the variation in the water immersion expansion ratio is reduced, there is no portion remaining with a large water immersion expansion ratio, and the average value is also lowered. Therefore, rational steam flow rate control becomes possible, and steam treatment can be performed while suppressing the amount of steam used.

1(a) and 1(b) are a perspective view and a cross-sectional view, respectively, for explaining a steam treatment method for steelmaking slag, which is the subject of the present invention. FIG. 2 is a diagram for explaining an example of a method of dividing the surface of steelmaking slag in a bed into a plurality of sections in the method for steaming steelmaking slag according to the present invention. (a) and (b) respectively show, in the steelmaking slag steam treatment method according to the present invention, when dividing the surface of the steelmaking slag into a plurality of sections, the range of the length of one side of the rectangle is divided into the steelmaking slag is a diagram for explaining an example of determination by a ratio to the stowage height. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram for explaining an example of a method for measuring temperature-time transition of a steelmaking slag surface in a steelmaking slag steam treatment method according to the present invention; FIG. 5 is a diagram for explaining another example of a method for measuring the temperature-time transition of the steelmaking slag surface in the steelmaking slag steam treatment method according to the present invention. FIG. 4 is a diagram for explaining an example of a method of controlling the amount of steam blown into each section of steelmaking slag based on the estimated steam flow rate distribution in the steelmaking slag steam treatment method according to the present invention.

<General steam treatment method for steelmaking slag>
1(a) and 1(b) are a perspective view and a cross-sectional view, respectively, for explaining the steam treatment method for steelmaking slag, which is the subject of the present invention. In the example shown in FIGS. 1(a) and 1(b), 1 is a slag treatment tank, 2 is a steam supply pipe, and 3 is steelmaking slag to be steamed. As shown in FIGS. 1(a) and 1(b), in the steelmaking slag steam treatment method according to the present invention, steelmaking slag 3 is piled on the bed of a slag treatment tank 1, and steam is supplied to the bed through a steam supply pipe 2. The steelmaking slag 3 is steam-treated by blowing from below. The steam supply pipe 2 is sometimes buried in a packed bed of relatively coarse-grained slag called bedding. In that case, the steelmaking slag 3 is piled on the bedding. The purpose of providing the bedding is to disperse and blow steam into the steelmaking slag 3 at locations other than directly above the steam supply pipe 2, and to prevent the steam from being blown into the steelmaking slag 3 when it is loaded and unloaded by heavy machinery or the like. The purpose is to prevent the supply pipe 2 from being damaged. For the former purpose, it is desirable to improve air permeability by using, for example, a sieve with an opening of 5 mm for the bedding. The surface of the steelmaking slag 3 piled on the bed of the slag treatment tank 1 has an upper surface facing upward and a slope whose thickness gradually becomes thinner at the end. included in the concept of the surface of

In the method for steaming steelmaking slag according to the present invention, in the example shown in FIGS. In each section, the temperature change over time on the surface of the steelmaking slag is measured. Based on the measured temperature change over time, the steam flow rate distribution in each section of steelmaking slag is estimated. Based on the estimated steam flow rate distribution, each section of steelmaking slag It is characterized by controlling the amount of steam blowing in.

<Regarding the process of dividing the steelmaking slag surface into a plurality of sections>
FIG. 2 is a diagram for explaining an example of a method of dividing the surface of steelmaking slag in a bed into a plurality of sections in the steelmaking slag steam treatment method according to the present invention. In the example shown in FIG. 2, the surface of the steelmaking slag 3 in the bed of the slag treatment tank 1 is divided into 5 sections with the same width in the width direction and 3 sections with the same width in the depth direction, for a total of 15 sections. ing. In the present invention, the number of divisions described above is an example, and other numbers of divisions may be used.

3(a) and 3(b) respectively show, in the steelmaking slag steam treatment method according to the present invention, when dividing the surface of the steelmaking slag into a plurality of sections, the range of the length of one side of the rectangle is FIG. 4 is a diagram for explaining an example of determination by a ratio to the stowage height of steelmaking slag. Here, in the examples shown in FIGS. 3(a) and 3(b), the proper size of the surface section differs depending on the height (assumed to be H) of the slag stack. If each section is rectangular, if the length of one side is less than 1/2H, the width is too narrow and affected by vapor diffusion. It may be difficult to determine whether there is a problem. If the length of one side exceeds 2H, the compartment is too large, and steam variation may occur within the compartment, making it difficult to solve the problem by controlling the amount of steam in the entire compartment. Therefore, it is preferable to perform the steam treatment in a rectangular shape in which the length of one side (a or b) of the section of the surface of the steelmaking slag is 1/2 or more and 2 or less of the height of the stacked bed.

<Regarding the process of measuring the temperature change over time on the steelmaking slag surface>
FIG. 4 is a diagram for explaining an example of a method for measuring the temperature-time transition of the steelmaking slag surface in the steelmaking slag steam treatment method according to the present invention. In the example shown in FIG. 4 , a thermography 11 is provided on the bed of the slag treatment tank 1 in order to measure the surface temperature of the steelmaking slag 3 . Then, temperature transitions of the surface of the steelmaking slag 3 on the bed and each section of the slope are measured by the thermal imaging image of the thermography 11 .

In this example, instead of the thermography 11, the temperature of the surface of the steelmaking slag 3 can be measured by arranging closely spaced optical fibers capable of measuring the temperature at each position in the length direction. The optical fibers may be arranged like a net, but since the temperature can be measured by dividing them in the length direction, the optical fibers may be arranged in parallel in any direction. In order to measure the entire surface of the steelmaking slag 3 , it is necessary to line up the edge of the bed of the slag treatment tank 1 . The interval at which the optical fibers are arranged is 0.5 m or less, and it is desirable to narrow the interval to about 0.2 m.

As in the example shown in FIG. 4, when using the thermography 11, the digital image of the thermal image is observed multiple times during a certain period (several tens of seconds), and each pixel (bed ) is obtained as the temperature of each pixel. As a result, it is possible to avoid observation interference of steam rising from the bed, and the temperature distribution of each section on the surface of the steelmaking slag 3 can be accurately measured. Thus, the temperature distribution of each section is obtained from the maximum temperature of each pixel within a certain period. By measuring changes in the temperature distribution over time, the steam flow rate distribution of each section on the surface of the steelmaking slag 3 can be estimated. The estimated steam flow rate distribution of each section is reflected in the steam flow control for each section.

In this example, by measuring the temperature of each section on the surface of the steelmaking slag 3 over time, the steam flow rate distribution of each section is estimated. Then, by reflecting the obtained distribution of the steam flow rate in each section in the control of the steam flow rate in each section, it is possible to determine which section can reduce the amount of steam blowing and which section needs to increase the amount of steam blowing. Steam can be blown reasonably. As a result, the temperature of the steelmaking slag 3 can be raised and kept more constant, and steam treatment can be performed while reducing the amount of steam used.

FIG. 5 is a diagram for explaining another example of the method of measuring the temperature-time transition of the steelmaking slag surface in the steelmaking slag steam treatment method according to the present invention. In the example shown in FIG. 5, in addition to measuring the surface temperature of the steelmaking slag in each section with the thermography 11, the thermometer 12 measures the surface temperature of each section. According to this example, by also measuring the surface temperature of each section with the thermometer 12, the distribution of the steam flow rate can be obtained from an earlier stage when the temperature of the steelmaking slag is raised in the lower part of the temperature rise process. becomes possible. In addition, it is possible to estimate the distribution of the steam flow rate based on the measurement data of more depths, thereby increasing the accuracy of measurement and enabling more rational steam flow rate control, which is preferable.

<Regarding the process of controlling the amount of steam blowing>
FIG. 6 is a diagram for explaining an example of a method of controlling the amount of steam blown into each section of steelmaking slag based on the estimated steam flow rate distribution in the steelmaking slag steam treatment method according to the present invention. The example shown in FIG. 6 shows the structure of the rear surface of the bed of the slag treatment tank 1 . In the example shown in FIG. 6, the steam supply pipe 2 has a main flow control valve 21 on its upstream side and five first branch pipes 22 on its downstream side. Each first branch pipe 22 is provided with three second branch pipes 23 . Each second branch pipe 23 includes, from the upstream side, a flow rate control valve 24, a flow meter 25, a piping section 26 without steam ejection holes, and a piping section 27 with steam ejection holes. A total of 15 sections are exemplified on the surface of the steelmaking slag.

Control of the main flow control valve 21 and the flow control valve 24 is performed as follows. First, a thermal image of each section on the surface of steelmaking slag (not shown) stacked on the slag treatment tank 1 is captured by the thermography 11 . Next, the image processing unit 31 estimates the steam flow rate distribution of each section from the captured thermal image, and determines the steam blowing amount of each section based on the estimated steam flow rate distribution of each section. The valve control unit 32 controls the main flow control valve 21 and the flow control valve 24 according to the determined amount of steam to be blown into each section, and blows steam into each of the 15 sections individually. do.

With the above configuration, the degree of opening of each of the main flow control valve 21 and the flow control valve 24 is automatically adjusted at regular time intervals, allowing a large amount of steam to flow in sections where the steam flow rate is lower than others, and conversely, the steam flow rate is higher than that of other sections. The steam flow rate is suppressed in sections that are larger than or excessive. In order to balance the heating rate of steelmaking slag in the entire bed, the steam flow rate of the entire bed can be improved by not only increasing the steam flow rate in sections with poor temperature rise, but also by selecting sections that flow easily and suppressing the steam flow rate. can be reduced compared to the case without section-by-section control.

The steam pipes such as the steam supply pipe 2, the first branch pipe 22 and the second branch pipe 23 are separated from the temperature measurement point. Therefore, it should be noted that there is a time lag between when the steam flow rate is changed and when the measured temperature changes. When controlling the steam flow rate based on the level of the distribution of the steam flow rate estimated based on temperature measurement, it is necessary to perform control in consideration of the above-described time difference. For example, in PID control, it is desirable to determine each parameter by measuring the steam flow rate and temperature in advance. However, since the slag particle size distribution and filling conditions are not necessarily constant, the optimum values of the parameters change for each treatment. Therefore, it is desirable to prevent overshoot by setting the P time and the I time about 1.2 to 1.5 times longer than the parameters determined from previous measurements.

According to the steam treatment method shown in FIGS. 1(a) and 1(b), converter slag with a particle size range of 0 to 40 mm was steam treated, and a subbase course material of CS-40 was produced from the steam treated converter slag. For the steam treatment of the converter slag, the prepared converter slag was stacked at a height of 2.5 m above the bed of the slag treatment tank. The slope of the stacked converter slag on the inlet side of the slag treatment tank was about 40°. The surface of the converter slag was divided into 15 sections with the same area, and the amount of steam injected into each of the 15 sections was controlled according to the steam treatment method of the present invention, and the converter slag was subjected to steam treatment. The sizes of the partitions were a=1.8H and b=1.6H for a and b shown in FIGS. 3(a) and 3(b).

In Invention Example 1, as shown in FIG. 3, the surface temperature of converter slag was measured only by thermography. In Invention Example 2, as shown in FIG. 4, in addition to the thermography, thermometers (thermocouples) were inserted at 1 m depth from the top of the converter slag at intervals of 1.5 m in all directions, and the thermograph and the thermometer were used to measure the converter slag. was measured. In the comparative example, as in the conventional example, the surface temperature of the converter slag was measured only with a thermometer arranged in the same manner as in the above invention example 2, and the steam injection amount was not adjusted individually for each of the 15 sections, but the total adjustment for all sections was performed. performed.

In Invention Examples 1, 2 and Comparative Examples, the temperature rising period was started at an initial 0.6 kg/t-slag and continued until all points (all coordinates in Invention Examples 1 and 2) reached 100°C. Here, in Inventive Example 1 and Inventive Example 2, the amount of steam blowing was reduced so as to maintain 100°C in the section where the temperature reached 100°C halfway through according to the temperature measurement results. In addition, the heat retention period was started with 0.6 kg/t-slag and held for 48 hours. Here, in Inventive Examples 1 and 2, the amount of steam blowing was reduced so as to maintain 100°C in the section where the temperature reached 100°C in the middle. After completion of the steam treatment, 10 samples were taken from the converter slag in each section, and the water immersion expansion ratio was determined according to the method described in Non-Patent Document 1. The results are shown in Table 1 below.

From the results in Table 1, when comparing the invention examples 1 and 2 with the comparative example, the temperature rise delays because the steam amount is changed according to the temperature rise condition on the surface of the converter slag during the temperature rise period. It was found that the 100° C. reaching time was shortened in Invention Examples 1 and 2 compared to Comparative Example, and the steam consumption rate was also reduced. In addition, when comparing Invention Example 1 and Invention Example 2, it is found that, compared to Invention Example 1, Invention Example 2 starts controlling the amount of steam at an earlier stage of temperature rise, so that the temperature rise time and the steam consumption rate can be further reduced. I found out. As a result, it was found that invention examples 1 and 2 enabled production of roadbed material products with higher reliability than the comparative example.

According to the steam treatment method for steelmaking slag of the present invention, rational steam flow rate control is possible not only for steelmaking slag but also for treatment of other lumps or powdery granules that require steam treatment. Steam treatment can be performed with reduced consumption.

Reference Signs List 1 slag treatment tank 2 steam supply pipe 3 steelmaking slag 11 thermography 12 thermometer 21 main flow control valve 22 first branch pipe 23 second branch pipe 24 flow control valve 25 flow meter 26 piping section without steam ejection hole 27 steam Piping section with ejection holes 31 Image processing section 32 Valve control section

Claims (3)

In a steam treatment method for steelmaking slag, the steelmaking slag is piled on a bed and steam is blown into the bed from below to steam-treat the steelmaking slag,
dividing the surface of the steelmaking slag in the bed into multiple compartments,
Temperature time measured by multiple thermometers inserted from the surface of the steelmaking slag in each divided section, and measurement by thermal image observation of the top surface of the steelmaking slag stacked on the bed from above the bed. Obtain the measurement results of the transition ,
Estimate the steam flow distribution in each section of the steelmaking slag based on both the results of the measurement results of the thermometer and the measurement results of the thermal image observation ,
Based on the estimated steam flow rate distribution, control the amount of steam injection in each section of the steelmaking slag,
A steam treatment method for steelmaking slag, characterized by: The steam treatment method for steelmaking slag according to claim 1 , wherein the thermal image observation is performed using thermography. 3. The steam treatment according to claim 1 or 2 , wherein the length of one side of the section of the steelmaking slag surface is a rectangle with a length of 1/2 or more and 2 or less of the height of the stacked bed. A method for steaming steelmaking slag.

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