JPS5825413A - Monitoring method for slag formation in refining furnace - Google Patents

Abstract

PURPOSE:To monitor the slag forming conditions in a converter by detection of the level and density of molten slag in steel making and refining with the converter by blowing an inert gas through gas blowing ports provided in the positions upper than the level of molten steel and measuring the flow rate and back pressure of the gas. CONSTITUTION:Gas blowing ports 5, 6 consisting of porous bricks are installed above the level of the molten steel 2 in a converter 1. An inert gas such as Ar having no influence upon a refining effect is blown through the ports 5, 6 with air feed pipes 10, 20 provided with flowmeters 11, 21, flow regulating valves 12, 22 and pressure gags 14, 24. The back pressure values measured with the gauges 14, 24 when the flow rate of the gaseous Ar is kept constant are inputted to an arithmetic circuit 7, which detects the level and density of the molten slag 3 in the coverter. It is possible to control the slag formation precisely in the converter operation in accordance with the detected values.

Description

[Detailed description of the invention] The present invention relates to a slag monitoring method in a refining furnace such as a converter,
More specifically, the present invention proposes a monitoring method that improves the measurement accuracy of slag level and slag density and enables desired slag control.

The method of monitoring the slag formation inside the converter is to detect the jet sound of oxygen blown out from the lance nozzle above the furnace mouth, and analyze the acoustic data. There are known methods of detecting and analyzing the waves, and methods of projecting microwaves from above the furnace mouth and detecting and analyzing the reflected waves. The present invention is completely different in concept from these methods, and aims to provide a monitoring method that more directly detects the slag formation situation and enables precise slag control. The method for monitoring slag in a smelting furnace is to form a gas inlet by providing a porous brick or a nozzle, etc. in the side wall of a smelting furnace such as a converter, above the molten steel level, in the part where the slag slag is located. During melting, a gas that does not affect refining, such as argon, is blown from this gas inlet (gas containing oxygen, air, etc. may be used to assist refining), and the gas flow rate at this time is The slag level and density will be detected based on the relationship between this and the back pressure.

More specifically, ``Measure the back pressure while keeping the gas blowing flow rate constant, or blow gas while keeping the back pressure constant and measure the flow rate.''Then, the slag density is known from past experience, etc. If only the lag level is to be determined, one gas inlet may be sufficient, but generally it is better to provide two gas inlets at the top and bottom, separated by a suitable length.

A detailed explanation will be given below based on the drawings.

FIG. 1 shows the implementation of the method of the invention.

Slag 3 is present on top of the molten steel 2 in the converter 1, and refining is performed by blowing oxygen into the molten steel 2 from a lance. Porous bricks are fitted into the side wall of the converter 1 to form gas inlet ports 5 and 6. The gas inlet port 5 is formed on the lower side, and the gas inlet port 6 is formed on the upper side by a distance of ph. . Gas inlet 5.6
Argon gas is supplied to each of the pneumatic pipes 10 and 20 through pneumatic pipes No. 20, and a flow meter 11.
21 and flow rate adjustment valve 12. ．． 22, and a flow rate indicating controller 13.23 for controlling the opening degree of the latter based on the input signal from the former to maintain the set flow rate. The flow rate blown into the converter through the inlet ports 5 and 6 is kept constant. A pressure gauge 14,24 is provided between the flow regulating valves 12, 22 and the gas inlet 5.6 to measure the back pressure of the inlet. This measured pressure signal is input to the calculation circuit and performs the following calculation.

The vertical distance between the slag surface and the gas inlets 5 and 6 is LI
S L! Then, the back pressure P measured by the pressure gauge 14.24
A subordinate relationship is established between ,, P, and P.

L1=　　　　　　0P1　　...(1) p, -p.

L, = ・Umako h ... (2) P, P
.

The above (1) in the arithmetic circuit 7? The slug level is measured by executing processing such as calculating one of the equations (2) or calculating both of them and taking the average value. It goes without saying that h is given as a constant.

Figure 2 shows the results of slag level measurement using the method of the present invention (horizontal axis) and the results obtained using the method of determining the slag level by measuring conductivity with an electrode attached to a sublance (vertical axis) from the furnace mouth. It is expressed in terms of distance. It can be seen from this figure that the two show good correspondence.

The slightly higher results obtained with Sublance are thought to be due to slag splash.

Now, if the slag density p is known, then L! =P+/1' (3) It is possible to calculate as follows, and it is possible to use one gas blowing system, but when this density is used as monitoring information for the progress of slag formation. In this case, two systems of gas blowing are essential, and the arithmetic circuit calculates the following equation (4).

P = (Pt Pg)/h...(4) Third
The figure shows the results of measuring the slag density using the method of the present invention. It is expressed as a ratio to Since the density pu decreases as the slag progresses, I)/P@ti 1 changes to become smaller, and it can be said that in the illustrated example, good slag formation progressed.

If there is almost no change from l as shown by the one-dot chain line, the slag formation is poor, and as shown by the two-dot chain line, < P
If /Pa decreases extremely, it can be determined that there is excessive slag formation, or that there is a risk of slopping.

Figures 1 and 4 show the slag level (Lt
This is a graph showing the relationship between (depending on the value) and 147 Pa, and black circles indicate the occurrence of slopping. As can be understood from this result, there is a slopping occurrence region determined by the relationship between slag level and slag density. Therefore, in the arithmetic circuit 〒, functions representing the slopping prevention line shown by the two-dot chain line in Fig. 4 and the slopping prevention line shown by the one-dot chain line corresponding to the 90th line are set, and the syslag level is determined by these functions. In the case of entering a high-rise area, a corresponding alarm is issued, and the amount of oxygen blown, the height of the lance, or the addition of sedatives such as limestone and fluorite are manually controlled.
Alternatively, slopping can be effectively prevented by automatic adjustment.

Note that in all cases above, normal back pressure was measured for the two gas inlets, but the upper gas inlet 6
Or, if the slag has not reached both gas inlets 6, 6, the measured back pressure P or PI.

Of course, if P is too small, poor slag formation can be detected.

According to the method of the present invention, the hot metal blending ratio is 0.03 to 0.10% in a fi 160) converter under conditions of 85 to 100%.
When we controlled slag formation during the melting of low carbon steel [C], the result was 1lP4! : Not only has the slagging rate improved, but the slopping rate has decreased from about 65% to 15%, and the slag situation has also been significantly improved, and in particular, the rate of excessive slag has decreased significantly. .

As described in detail above, according to the present invention, stable blowing is possible and black sloping can be prevented, the accuracy of the blowing needle is improved, and the tapping yield is improved. Furthermore, the present invention has excellent effects such as the reduction of auxiliary raw materials as it becomes possible to precisely control the slag formation state.It goes without saying that the present invention can also be applied to smelting furnaces other than converters.

[Brief explanation of the drawing]

Figure 91 is a schematic diagram showing the implementation state of the present invention, Figure 2 is a comparison diagram of slag level measurement results between the method of the present invention and the method using sublance, Figure N3 is a graph showing the change in slag density over time, and Figure 4 is a graph showing the change in slag density over time. It is a graph showing the relationship between Sushigreperu slag density. 1... Converter 5, 6... Gas inlet 10, 20.
... Pneumatic pipe 11.21 ... Flowmeter 12.22 Stream cover adjustment valve 14,24 ... Pressure gauge Patent applicant Sumitomo Metal Industries Co., Ltd. representative Noboru Kono Hana Figure 1 91 Kishigo Nao (η) Figure 2, Figure 3, Figure 4

Claims (1)

[Claims] 1. Gas is blown from the side wall to a position above the molten steel level in the refining furnace, and the slag level is detected based on the blown flow rate and back pressure;
Slag monitoring method 0 characterized by monitoring the slag formation status 2. Gas is blown from the side wall to a position above the molten steel level in the smelting furnace, the slag density is detected based on the blown flow rate and back pressure, and slag formation is performed. A slag monitoring method characterized by monitoring the situation.