JPS5939751A - Detection of molten slag agitation granulation finishing point - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention The present invention collects molten slag discharged from a blast furnace or converter in a stirring pot, and detects the completion point of stirring and granulation in the process of stirring and granulating the molten slag. Regarding the method.

Conventionally, in order to recover the thermal energy of the molten slag, the molten slag received in a pot is stirred by a stirring granulation device, and the thermal energy obtained by radiation is recovered in this process, and the solid slag after granulation is completed. vi: The solid slag is placed in a shaft cooler, which is a vertical heat exchanger, and by circulating gas within the shaft cooler, heat is exchanged between the solid slag and the gas, and thermal energy is further recovered.

Here, the completion point of stirring and granulation of molten slag means that less heat energy is recovered by radiation from the slag being granulated by four-arm stirring, and it is better to recover heat energy by the subsequent shaft cooler, which results in a higher heat recovery rate. This is when the slag surface temperature reaches a temperature at which it becomes good. Furthermore, from the viewpoint of handling or product, the temperature is below the lag temperature at which the granulated solid slag granulated by stirring does not weld together again and form large lumps, and the temperature is below the lag temperature that prevents the granulated solid slag granulated by stirring from forming into large lumps. This is the time before the solid slag becomes fine enough to become unsuitable as a product, and before it reaches a particle size that increases the pressure loss of the circulating gas in the subsequent shaft cooler. From this point of view, it is important to detect the completion point of stirring and granulation of molten slag.

The purpose of the present invention is to efficiently recover thermal energy when molten slag received in a ladle is stirred and granulated using a 4-part stirring device, and the granulated slag is not re-welded and is finely granulated. It is an object of the present invention to provide a method for detecting the completion point of agitation granulation at which the granulation is in a state of failure.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of a part of the molten slag apparent recovery equipment that performs agitation granulation and heat recovery by radiant heat transfer. High-temperature molten slag 5 of, for example, 1400 to 1850° is poured down from a blast furnace or converter into a pot l in which a slag 4 of product slag has been formed in advance. The pot truck 8 moves to the stirring granulation position. Sensible heat of the molten slag is recovered by a radiant heat transfer tube 6 provided on the entire inner wall of the bar 7 rotated by the molten slag Vi electric motor 8 through which a fluid to be heated, such as water, passes. Molten slag is formed by stirring and granulation.
The slag is cooled to about 1100° C. by radiation heat transfer and becomes a granular slag. The granulated slag is fed into a vertical heat exchanger (shaft cooler) by a skip hoist, where the gas pushed in from below is heated by convection heat transfer, and the sensible heat is finally recovered in a heat generating boiler. be done.

A monochromatic radiation thermometer that detects infrared rays is attached to the center of the cover 7 of the stirring granulation section to measure the surface temperature of the slag inside the pot, and the detected temperature is recorded by a recording device.
Recorded by 4. In order to accurately detect the surface temperature of the thermometer 10KFi slag, a nozzle or the like is provided to purge the field of view of the thermometer 10 with clean gas. Further, the load current of the electric motor 8 is detected by a detector 16.

In this example, the temperature of the slag surface is measured at two points by the radiation thermometer 10. The temperature of the slag surface detected by the thermometer 10VC varies as shown in FIG. The width or synchronization of the fluctuations depends on the stirring s20 rotation interval and the progress of stirring granulation, but since the detected temperature signals fluctuate sharply, in order to soften the fluctuations, a calculation filter 11 is applied to each temperature signal θ. multiply.

In other words, a first-order delay calculator with a long time constant that takes into account the transient response to the image wave number input is provided as a filter, and the slowness of the output transient response to the input is used to detect large wave number fluctuations among severe signal fluctuations. The vibrations were eliminated, resulting in a smooth vibration signal as shown in FIG. In the embodiment, a delay calculator with a time constant of 80 seconds is used. A selector selector 12 selects and outputs the higher signal of the two temperature detection signals θf applied by the arithmetic filter 11.
Can be applied to.

The time when the calculated temperature θS of the slag surface reaches the temperature θ5ojc at the completion of stirring granulation, which was known in advance by experiment, and θS continues to be 0 or less than θsO for a certain period of time Ta2 [
Detects 0. In this embodiment, this fixed time Ts is determined by taking into account the fluctuation of the temperature signal θS.
The temperature was set at 50°C and Ts = 80 sec.

Since the VC whose agitation granulation is completed at time to measures the temperature of only a portion of the surface of the slag in the pan, there is a possibility that the temperature has locally decreased in that portion.

Therefore, the stirring time T based on the amount of slag received, the amount of slag, and the number of rotations of the stirring rod is determined in advance through experiments, and the stirring time T determined according to the operating conditions is set using a timer, and from the start of stirring. The time when the same conditions that time T has elapsed and time to has been detected are established as the stirring completion point TO. At this time TO, the electric motor 3 is stopped by the control circuit 13 shown in FIG. 1, and the stirring granulation is completed. As a result, the recovery efficiency of radiation in the stirring granulation section and the heat recovery efficiency of convective heat transfer in the shaft cooler are improved.

In the method of the present invention, by increasing the number of thermometers and arranging them at appropriate positions, the number of hot water temperature measurement points on the surface of the slag in the pot increases, and as a result, the accuracy of detecting the maximum temperature on the surface of the slag in the pot increases. The detection accuracy of the stirring completion point is improved.

In the above-mentioned method for detecting the completion point of agitation granulation, in order to reliably prevent the slag from re-welding after granulation, there is a tendency to set the set time T to be unnecessarily long on the safe side. There is a risk that the granulated slag will become finer.

Therefore, an embodiment that does not depend on time setting and solves the above-mentioned problems will be described next. The temperature of the slag surface detected by the thermometer IO and recorded in the recording device 14 changes as shown in FIG.

When stirring of the slag is started by the stirring body 2 at time tlVc, the detected temperature on the slag surface changes by 11 steps depending on the rotation period of the stirring rod 2, and the width of the change dθ becomes smaller as the stirring time passes. . The maximum width d at the stirring start time tllc is the temperature change width dθ on the slag surface.
θl. According to the method of the present invention, the time when the temperature change width dθ on the slag surface reaches a predetermined first ratio dθ/dθ1=α (constant) with respect to the maximum width dθIVC is detected. The time at this time is indicated by the reference mark [2 in FIG. 4, and the temperature change range on the slag surface at this time is
It is shown in According to the inventor's experiments, this first ratio dθ0/dθl−α is as shown in the first equation.

1 in dθ0/dθl...11)
dθ0 is approximately 30 to 50°C in terms of temperature.

In the experimental results shown in Fig. 4, the width of change dθ in the temperature of the slag surface reached the maximum width dθ1 at the stirring start time ti, but the maximum width may be obtained after the stirring start time [1]. Also, the time at which the temperature change width dθ of the slag surface reaches a predetermined first ratio with respect to the maximum width is detected.

The time course of the load current of the motor 3 detected by the detector 16YC is shown in FIG. When stirring is started at time tl, the variation width di of the load current gradually increases, finally reaches the maximum width dilK, and then decreases. According to the method of the present invention, the change width di of the load current is determined by a predetermined second ratio di/d with respect to the maximum width dil K.
Detect the time when il=β (constant). The time at this time is indicated by reference t2 in FIG. 5, and the width of change in the load current at this time is indicated by diO. This second
According to the inventor's experiments, the ratio diO/dll=β is a value determined by the second equation.

diO/dil 1 2 ° - [2) It is not enough to detect the time when the ratio dθ/d 01 of the temperature change range on the slag surface reaches the first ratio α. Since the ratio dθ/dθ1 of the width of temperature change on the slag surface varies depending on the variation in width, the stirring method, the rotation period and direction of rotation of the stirring body 2, etc., there is a risk of erroneously determining the completion point of stirring granulation. Furthermore, although the ratio di/dil of the width of change in the load current generally decreases over time, it fluctuates, so it is not enough to simply detect the time when the ratio di/dil of the width of change in the load current reaches the second ratio β. , the completion point of agitation granulation may be mistaken.

In order to solve such problems, in the method of the present invention, the time t2 at which the first equation holds and the second equation holds is set as the completion point of stirring granulation. At this time t2, the Na machine 3 is stopped by the control circuit 15 shown in FIG.
As a result, the recovery efficiency of radiation in the agitation granulation section and the recovery efficiency of thermal energy through convection in the shaft cooler are improved, and the slag is reduced in the process after agitation granulation. It does not re-weld and is not refined to a particle size that would increase the pressure loss of the circulating gas in the Shikamo shaft cooler.

In addition, when a drive device other than an electric motor is used for the stirring device, the load torque is detected instead of the ratio of the variation width of the load current value, and the change in the variation width of the load torque is also the same as the load current value. Similarly, the second ratio β becomes β'. According to the inventor's experiments, β' is 0.65...1
3).

As another embodiment of the method of the present invention, the above-mentioned slag surface temperature is detected at multiple locations, and the stirring is performed at a time when the highest detected value among the detected values becomes below a set value and a predetermined time has passed. A method of detecting the granulation completion point, a detection method of detecting the slag surface temperature, a detection method in which the range of change in the detected value reaches a predetermined first ratio to the maximum width, and the range of change in the load current of the stirring motor is the maximum. It is also possible to compromise with a detection method in which the time when a predetermined second ratio is reached is the completion point of stirring granulation, and furthermore, by logically calculating the success or failure of the conditions of each method, stirring granulation can be performed. The accuracy of detection of the completion point may be increased.

As still another embodiment of the method of the present invention, the average value θ of the temperatures detected by the thermometer IO is determined with reference to FIG.
The completion point of stirring granulation may be determined by detecting that the CIC is reached and at the same time as the conditions shown in the first and second equations are satisfied. By detecting that the average value θ of the temperature reaches the predetermined value θ0 in this manner, the point at which stirring granulation is completed can be detected more accurately.

As described above, according to the method of the present invention, it is possible to accurately detect the completion point of agitation granulation, thereby efficiently recovering the thermal energy of molten slag, and preventing re-welding of slag after granulation. Furthermore, the granulation of the slag, which is not desirable as a product, is suppressed, and the pressure loss of the circulating gas due to the granulation of the solid slag in the shaft cooler is reduced.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of the stirring granulation part of one embodiment of the present invention, Fig. 2
The figure shows the relationship between the slag surface temperature θ detected by the monochromatic radiation thermometer IO and the stirring time, and Figure 8 shows the relationship between the calculated slag surface temperature θf (θS) and the stirring time. , FIG. 4 is a diagram showing the relationship between the slag surface temperature θ detected by the monochromatic radiation thermometer IO and the stirring time, and FIG. 5 is a diagram showing the relationship between the load current of the electric motor 3 and the stirring time. l... Pot, 8... Electric motor, 5... Molten slag, l
O... Monochromatic radiation thermometer, θ... Slag surface temperature measured by monochromatic radiation thermometer, dθ... Slag surface temperature change width, dθl... Slag surface temperature maximum change width, α...
・First ratio, di...Load current change width, dil
...Maximum change width of load current, β...Second ratio agent Patent attorney Kei NishiP#Weighing time r $i Time Figure 5 Circulation time

Claims (2)

[Claims] (1) The molten slag caught in the pot is driven by an electric motor.
11 When granulating by stirring 1 (with a stirring means,
The slag surface temperature in the pot is detected at multiple locations, and the 4-rush granulation is completed when the highest detected value among the detected values becomes below the set value and a predetermined time has passed from the start of stirring. A method for detecting the completion point of agitation granulation of molten slag, characterized in that the point is determined as a point. (2) When the molten slag received in the ladle is stirred and granulated by a stirring means driven by an electric FaI machine, the surface temperature of the slag in the ladle is detected, and the range of change of the detected value is the maximum width. reaches a predetermined first ratio to
A method for detecting the completion point of agitation granulation of molten slag, characterized in that the agitation granulation completion point is defined as the time when the variation range of the load current of the III machine reaches a predetermined second ratio with respect to the maximum width.