JPS5844954B2 - Method for monitoring inside ferroalloy electric furnaces - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for monitoring the inside of ferroalloy electric furnaces, and in particular, a method for obtaining dynamic data on the shape of deposits in the furnace and the surface temperature pattern by continuously imaging the inside of the furnace using an infrared camera. It is intended to be used to judge the condition of the furnace.

Conventionally, in closed-type electric furnaces, the temperature inside the furnace was measured by hanging a thermocouple inserted from the furnace lid 1 to 2 meters above the surface of the charge pile. There is a temperature gradient between the gas temperature and the temperature of the particles in the furnace.
Since the high-temperature gas is mixed with the low-temperature gas near the furnace wall, in the end, we are only measuring the average gas atmosphere temperature, and it is not possible to measure or estimate the true surface temperature of the charge material. It was possible.

Furthermore, in order to understand the shape of the surface of the furnace contents deposited,
Conventionally, electricity was temporarily interrupted and the inside of the furnace was looked through the small lid of the furnace lid, and the angle of repose of the deposition surface was measured, including the observation of the fired state of the electrode surface and the extent to which the raw material covered the electrode. However, due to the problems of a drop in the furnace temperature and a drop in operation rate due to interruptions in operation, there are many restrictions on measurement opportunities, and as a result, only a small amount of information can be obtained during the operation cycle, making it difficult to monitor furnace conditions and charging. Estimates of how things were falling became rough, and the reactor had to be operated based on experience.

This invention was made in order to improve the situation similar to "blind operation" as described above. The purpose is to constantly monitor the temperature and shape of the surface.

That is, in the method for monitoring the interior of ferroalloy electric furnaces of the present invention, an infrared camera images the inside of the operating furnace through an observation window that is installed in the furnace lid with a heat-insulating structure, and the angle of repose of the charge deposition is determined from the image. The purpose is to measure and obtain the temperature patterns of the deposition surface and the electrode surface, and to obtain various information for determining the condition of the furnace by comparing it with actual data when the furnace is in good condition.

To describe this invention in detail with reference to the drawings, FIG. 1 is a sectional view showing an infrared camera system for photographing inside the furnace and its attachment mechanism to the furnace lid, in which 1 is the electric furnace main body, 2 is the furnace lid, 3 is the hearth lid 2
4 is an opening for an observation window provided in the inclined part 3,
A hood-shaped valve seat 6 reinforced by a reinforcing plate 5 is fixed to this opening 4 without any gaps, and an observation window with a shutter mechanism and a wiper mechanism and an infrared camera support are attached to the flange γ at the tip of the valve seat. ing.

That is, a shack plate 9 is attached to the flange portion 7 to block heat transfer from the furnace lid shell via a water cooling ring 8, and this shack plate 9 is connected to a motor 11 which is controlled by a command signal from a control panel 12. It is opened and closed via a speed reducer 10, and is kept open only when shooting images, and closed when shooting is not necessary to protect the camera section from high-temperature radiation inside the furnace and flying debris from charged raw materials.

On the outside of this shack board 9, observation windows 14 surrounded by heat-resistant graphite packing 13 are stacked and fixed via a similar water cooling ring 8, and the outside of the window 14 is fixed to the camera 1.
7 mounting parts.

The observation window 14 is, for example, in the near-infrared wavelength range (1.5 μm to 8 μm).
(m) is fitted with silicon glass having a high transmittance so that the radiant energy of the objects in the furnace (50°C to 1200°C) is sufficiently transmitted.

A wiper 16 operated by a shaft 15 passing through the graphite packing 13 is attached to occasionally wipe away dust adhering to the inner surface of the observation window 14, and a wiper 16 is also provided which is operated by a shaft 15 passing through the graphite gasket 13. A clean gas nozzle 22 is also provided to prevent dust from accumulating on the inner shutter plate, etc., and the graphite gasket 13 maintains the sealing properties of these wiper shafts, nozzles, and the fitting parts of the observation window glass, and prevents the gas in the furnace from accumulating. Prevents leakage.

The camera 17 is surrounded by a strong magnetic field due to the furnace energization, so it is more suitable for a photodiode array that scans using a semiconductor switching method than a camera that scans using an electromagnetic deflection method such as a vidicon. Using an infrared camera using a sensor is more advantageous in terms of electromagnetic shielding.

The camera 17 directs its optical axis into the furnace with an angle of depression α determined by the installation orientation, and sends an image of the inside of the furnace within its field of view as a video signal to an amplifier 19 via a cable 18, and then to a signal processing circuit 20. The brightness or hue corresponding to the temperature is determined and sent to the video monitor 21 along with the brightness or color temperature scale, digital temperature numerical scale, date and time, etc., and the instantly changing deposition surface shape and temperature pattern are displayed moment by moment. Display images in black and white or in color.

An example of this image is shown in FIG. 2, in which a color temperature scale 26 is displayed in multiple colors in multiple stages from low temperature to high temperature H at the top.

The electrode surface portion 23 is displayed as a high temperature pattern, and the conical deposit surface portion 25 in the foreground is displayed as a low temperature. It is tilted at a certain angle due to its presence.

In the distant view section 24, as the thickness of the gas in the furnace increases, the permeability of the gas decreases, and the radiation from the dust mist contained in the gas becomes stronger, so that the surface of the distant deposits is covered with haze. shape and temperature pattern are not clearly visible.

The image above includes display in hues that correspond to the radiant energy, so the shape and temperature of the surface of the electrode and the foreground deposit, the temperature pattern, and the slope of the surface of the foreground deposit, i.e., the rest as described below. Contains information such as angle calculation data.

Therefore, it is first possible to understand the firing state of the electrode from the melting state of the casing under the holder in the furnace and the temperature pattern of the exposed carbon part, and to quantify the heat dissipated from the exposed carbon surface, which allows the firing state of the electrode to be changed. be understood.

Next, by checking the temperature pattern of the electrode-contacting surface of the deposit and the presence or absence of an atrium, it is possible to estimate the gas generation situation near the electrode and detect the atrium.Of course, this can also be analyzed as dynamic data through continuous observation. It is available.

Furthermore, with this invention, the dynamic angle of repose of the deposition for each raw material input chute on the furnace cover can be measured as shown below, and by dynamically understanding the angular difference between the angle of repose between the electrode side and the furnace wall side, it is possible to measure the horizontal direction. In addition to estimating the unloading speed distribution of each chute, the relationship between the dissolution amount of sediment and the angle of repose for each chute can also be understood.

In other words, when the angle of repose of the conical charge deposition surface directly below the chute is observed through the observation window 14 with the camera 17, if this shape is similar to a right circular cone, then the angle of repose in Figure 3 is a y b y C.
A relationship as shown in z d occurs.

In this case, when the angle of depression α of the viewpoint increases, the apparent angle of repose θ′ of the isosceles triangle projected from the right circular cone (the angle of repose that appears on the screen)
decreases, and as α approaches the actual true angle of repose θ, θ′ approaches zero.

In this invention, the purpose of observation includes observation of the electrode surface temperature and observation of the dynamic angle of repose and temperature pattern of the charge deposition surface, so in order to simultaneously satisfy both, the depression angle is preferably set to around 19 degrees. There is a need.

Now, if we assume that the surface shape of the raw material deposited into the furnace from each chute is a right conical shape, the apparent angle of repose θ' and the true angle of repose of the right cone θ when looking down on this right cone are The relationship is explained below with reference to FIG. 3 a t b z C+ d.

Figure 3a shows the relationship between the contour of the deposited right cone in the vertical plane that includes the optical axis of the camera and the depression angle α of the line of sight. The projection view of the cone, FIG. 3d, is a perspective explanatory view showing the overall relationship.

When looking at the vertex of height A of a right circular cone with true angle of repose θ from a height of angle of depression α as shown in Figure 3a, the projected image taken by the camera and appearing on the screen is as shown in Figure 3C. , the apparent angle of repose θ' is expressed by the following equation (1).

Therefore, the above equation (1) can be rearranged as follows.

In the end, θ' and θ are as follows.

The relationship between θ' and θ is shown in the diagram of FIG. 4, and the true angle of repose θ can be easily determined from the depression angle α and the apparent angle of repose θ' on the screen.

The angle of repose of the charged raw material in the furnace is affected by the unloading speed gradient in the radial direction of the furnace, and therefore, changes in the angle of repose of each of the multiple deposits in the furnace can be observed simultaneously using several infrared observation devices. Dynamically grasping the situation of the contents inside the reactor can be grasped moment by moment, providing unlimited information for stable operation.

Generally, as the angle of repose increases, the degree of electrode immersion decreases, and the high temperature gas flow concentrates near the electrodes, resulting in an increase in heat loss outside the furnace.

According to this invention, such an abnormality can be immediately recognized as an increase in the gradient of the temperature distribution on the screen or an increase in the angle of repose, and can be compared with actual image information under normal favorable conditions. Various operations such as confirmation of raw material charging status and temperature distribution, electrode immersion status, gas flow status, electrode casing melting status and electrode firing status, detection of the furnace vent, and unloading status. The above information can be obtained dynamically and used to optimize and streamline electric furnace operation.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a block diagram of an example of the configuration of a device used to carry out the present invention, FIG. 2 is an explanatory diagram of a screen image showing an example of an image display, and FIGS. 3a and 3b. c and d are explanatory diagrams showing the relationship between the projection of a right circular cone, the angle of depression, and the angle of repose, and FIG. 4 is a diagram showing the relationship between the apparent angle of repose and the true angle of repose. 1: electric furnace body, 2: furnace cover, 6: valve seat, 8: water h') ring, 9: shutter plate, 14: observation window, 17: infrared camera, 20: signal processing circuit, 21: video monitor.

Claims (1)

[Claims] 1. Photographing the inside of the furnace using an infrared camera through an observation window provided in the furnace lid, and calculating the true angle of repose from the depression angle of the optical axis of the camera and the apparent angle of repose on the image. 1. A method for monitoring the inside of ferroalloy electric furnaces, characterized in that the angle of repose of deposits of the contents in the furnace directly under each chute is measured moment by moment. 2. The method for monitoring the inside of a ferroalloy electric furnace according to claim 1, wherein the temperature pattern of the deposition surface of the contents in the furnace and the electrode surface is obtained on a video screen.