JPH04325616A - Method for operating bottom blowing converter - Google Patents

Abstract

PURPOSE:To enable the adjustment of the charging quantity of a slag coating material by recognizing the erosion condition of refractories around a tuyere and to perfectly eliminate operational trouble due to the refractory erosion around the tuyere with a technique enabling labor-saving. CONSTITUTION:In the operational method for restraining refractory erosion around the bottom blowing tuyere in a bottom blowing converter, a thermocouple is embedded in the vicinity of the bottom blowing tuyere, and besides the max. temp. in the bottom blowing converter operation from the thermocouple, steel tapping temp. and killing time are used as the furnace operational condition, and the furnace operational condition, membership function at a consequence part and theoretical matrix at condition and the consequence are stored in a calculator and corrected in the weight relation indicating the influenced degree of various operational condition of the furnace to the tuyere condition to obtain the tuyere condition from the composed result.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an operating method for suppressing erosion of refractories around a bottom-blowing tuyere in a bottom-blowing converter.

0002

[Prior Art] Conventionally, in the operating method of a bottom-blowing converter, hot metal is charged into the furnace, gas is blown into the furnace through the top-blowing lance and the bottom-blowing tuyere, and then the alloy is adjusted before being tapped. Yes, but
While pouring hot metal into the furnace after tapping, around the bottom blowing tuyere,
To protect the refractories around the tuyeres, it is common to deposit or spray a certain amount of slag coating material. However, the extent of the work is determined and executed based on the operator's knowledge base, and the reality is that it has not been managed based on conventionally unified parameters. Recently, knowledge engineering has been attracting attention as a system technology that effectively relies on human experiential knowledge. The ES (Expert System) that applies this technology has the following features that complement conventional system technology:
■Human experiential knowledge can be stored as a knowledge base,■
It is easy to add and modify knowledge because it is easy to treat knowledge in fragments. A well-known method for inferring results using such a knowledge base is deductive reasoning, which states that if X is A, then Y is B (knowledge), X is A (fact), then Y is B (conclusion), but this is difficult to apply to knowledge or facts that contain ambiguity (it is likely that the conditional parts cannot be matched, making it impossible to draw a conclusion). For this purpose, a method called fuzzy inference is being considered. In fuzzy reasoning, X is A
Then Y is B (knowledge), X is A' (fact),
Then, it is assumed that Y is B' (conclusion). Here A, A
', B, and B' are linguistic information (fuzzy set) with ambiguous boundaries. A fuzzy set is expressed by a membership function as shown in FIG.

0003

[Problem to be solved by the invention] The state of corrosion of refractories around the bottom blowing tuyeres is determined by the composition of the molten steel, the temperature of the molten steel during blowing, the processing time, the composition of the slag floating on the molten steel, and the amount of residual slag. etc., depending on various factors. In such a situation, simply depositing or spraying a certain amount of slag coating material will not improve the corrosion of the refractory around the bottom blowing tuyere, and excessive melting will cause molten steel to leak from the bottom of the bottom blowing converter. This is a situation where operational troubles cannot be avoided.

(Embodiment and operation) FIG. 1 is a schematic diagram of a top-bottom blowing converter showing an embodiment of the present invention. A top-bottom blowing converter has a refractory 1 inside a steel shell 3, and Ar, CO2, N2, and O2 gases are blown into it from a bottom-blowing tuyere refractory 2. At the same time, O2 is blown in from the top blow lance 10. By monitoring the condition of the supply gas from the pressure gauge 5 and flowmeter 6 installed in the bottom blowing supply gas piping 4, and by collecting data from the thermocouple 7 buried in the tuyere, the temperature distribution of the steel bath 11 and the sub-balance can be determined. At step 12, the temperature of the molten steel is determined, and at the calculator 8, the amount of slag coating material to be laid on the bottom-blown tuyere refractory is determined.

FIGS. 2(a), (b), (c), (d), (
e) is a diagram showing the state of the bottom-blown gas tuyere according to the invention. Regarding pattern 1, the mushroom 13 is in good condition, and the tuyere 15 and the area around the tuyere 16 are not melted and damaged, but the entire tuyere is covered with slag, and if slag coating is continued in this state, the tuyere The gas does not pass through the mushroom 13 at the tip of the tuyere and the surrounding brick 1
Gas escapes to the upper part of the steel bath 11 through the gap between the steel bath 11 and the slag 14, reducing the metallurgical effect and causing problems such as spalling and wear of the bricks. Regarding pattern 2, the mushroom 13 is in good health, the tuyere 15 and the area around the tuyere 16 are not melted, and the tuyere is appropriately coated with slag 14. This condition is the best. To do this, leave an appropriate amount of molten slag from the previous charge and shake the furnace several times to coat it. This work is hereinafter referred to as slag coating work. Regarding pattern 3, the mushroom 13 is in a healthy state, but the tuyere 15 and the tuyere periphery 16 are exposed, and there is no coating layer of slag 14 at all, just before being melted away. For this reason, during slag coating work, appropriate amounts of quicklime and light mud are added to improve the viscosity of the slag. Regarding pattern 4, the state of the tuyere is that the mushroom 13 is melted and damaged, the area around the tuyere 16 is melted and damaged 17, and the tuyere 15 is in a state just before melting, and if left as it is, the tuyere will be severely damaged and missing. invite. For this purpose, appropriate amounts of quicklime, light mud, and fresh mud are added during slag coating work. Sufficient and appropriate repairs are required. Regarding pattern 5, there are no mushrooms 13, and the tuyeres 15, the hearth bottom, and the melted parts 17 of the bricks around the tuyeres have progressed locally, and if left as is, it will lead to a serious accident of molten steel leaking from the hearth bottom. For this purpose, during the slag coating work, a large amount of quicklime, light sludge, and green sludge are added, and while inert gas is flowed from the tuyere 15 to prevent tuyere burying, the melting of the bricks at the hearth bottom and around the tuyeres in 17 is carried out. Repair the damaged part.

The means for estimating the above-mentioned tuyere condition will be explained below. The knowledge for determining the tuyere condition obtained from the operator is, for example, if the tuyere temperature is high, the tuyere condition is pattern 4. It is something like that. The logical matrix in Table 1 shows the knowledge for making decisions about various operating conditions that affect the tuyere condition. In this table, the leftmost column shows a group of furnace operation conditions that affect the tuyere condition, and the top row shows the degree of these furnace operation conditions. VS, S, M, L, and VL are defined by the membership functions shown in FIGS. 4(a), (b), and (c) under each furnace operation condition. The definition of each is as follows.

[0007]

[Table 1]

FIG. 4(a) shows the shape of the membership function of tuyere temperature. VS is "lower", S is "lower"
, M is "normal", L is "high", and VL is "higher". The horizontal axis is 0 to 1100℃ at the tuyere, and the vertical axis is the confidence level of 0.
~1.0. FIG. 4(b) shows the shape of the membership function of tapping temperature. VS is “lower” and S is “lower”.
M is "normal", L is "high", and VL is "higher". The horizontal axis is the tapping temperature of 1600 to 1750℃,
The vertical axis represents the confidence level from 0 to 1.0. FIG. 4(c) represents the shape of the sedation time membership function. VS is “shorter”, S is “shorter”, M is “normal”, L
is “longer” and VL is “longer”. The horizontal axis represents sedation time from 0 to 15 minutes, and the vertical axis represents confidence from 0 to 1.0. 1, 2, 3, 4, and 5 in the matrix in Table 1 represent the tuyere conditions, and pattern 1 in FIG.
Figure 2(a) of pattern 2 shows 1, Figure 2(b) of pattern 2 shows 2,
Figure 2(c) of pattern 3 shows 3, and Figure 2(d) of pattern 4 shows 3.
) corresponds to 4, and pattern 5 in FIG. 2(e) corresponds to 5. FIG. 4(d) is a consequent membership function representing the above-mentioned tuyere state. 1 is Fig. 2(a) pattern 1, 2 is also Fig. 2(b) pattern 2, 3 is Fig. 2(c) pattern 3,
4 is Fig. 2(d) pattern 4, 5 is Fig. 2(e) pattern 5
It is. The horizontal axis represents the parameterization of the tuyere state, and the vertical axis represents the confidence level from 0 to 1.0.

[0009] FIG. 4 and Table 1 can be created by compiling what the operator has obtained empirically. These membership functions and logical matrices are stored in the computer in advance. Figure 3 shows the actual calculation flow. During data acquisition, three data items are acquired: tuyere temperature, settling time, and tapping temperature for one charge. The tuyere temperature shall be the maximum value recorded every 30 seconds from the start of blowing to the end of tapping. The sedation time is the time from the end of blowing to the end of tapping. The tapping temperature shall be the final molten steel measurement temperature in the relevant charge.

Next, the tuyere state is estimated using the membership function. In the explanation, a logical equation showing the relationship between tuyere temperature and tuyere condition will be used as an example. Assuming that the tuyere temperature is 550°C as shown in Figure 5, "normal" in Figure 5(b)
The probability of the tuyere temperature is 0.75 from the conditional membership function for "high" in Figure 5(c), and the probability of the tuyere temperature is 0.25 from the conditional membership function for "high" in Figure 5(c). , and the certainty of the tuyere temperature from other conditional membership functions is all zero. The probability (confidence) of the conditional part obtained in this way is multiplied by the membership function of each consequent part, and the results shown in FIGS. In other words, from the logic equation matrix in Table 1, when the tuyere temperature is normal (M), the tuyere state is pattern 3, so multiplying the consequent membership function of pattern 3 by 0.75 yields (d). A solid line is obtained. The dotted line is the consequent membership function before multiplication, or when the ordinary certainty of the tuyere temperature is 1.0. Similarly, when the tuyere temperature is high (L),
Multiplying the 4-membership function of the tuyere state pattern by 0.25 yields the solid line in Figure 5(e). Figure 5(f) is a collection of (d) and (e) in the same figure (a composite of the consequent membership functions), and the horizontal axis parameter value of the center of gravity of this area is expressed as Use as status value. Similar processing was performed regarding the settling time and molten steel temperature shown in Table 1, and the respective tuyere conditions were determined. Then, the weights shown in Table 1 are added to each tuyere condition value, and the weighted average value is taken as the final tuyere condition value. The results are displayed on the screen shown in FIG. FIG. 6 is an explanatory diagram showing the relationship between the tuyere wear rate for the method of the present invention and the conventional method. According to this figure, it is clearly seen that the method of the present invention has an extremely slow tuyere wear rate compared to the conventional method.

[0011]

According to the present invention, it is possible to ascertain the state of melting and damage of the refractory material around the tuyere and adjust the amount of slag coating material to be added. In addition, the labor-saving technology makes it possible to completely eliminate operational troubles caused by erosion of the refractories around the tuyeres. Conventional methods require operator knowledge and
Sales are cut and executed based on experience, and the rate of wear and tear on the tuyeres varies widely due to variations in the quality of the operator.
And the absolute value is also large. The method of the present invention can ensure the operator's best condition and has a stable effect with little variation.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a top-bottom blowing converter showing an embodiment of the present invention;

FIG. 2 is a diagram showing the state of the bottom-blown gas tuyere according to the present invention,

FIG. 3 is a diagram showing an actual calculation flow according to the present invention;

FIG. 4 is an explanatory diagram for implementing the present invention under the operating conditions;

[Figure 5
] Estimated diagram of the tuyere state using the membership function of the present invention,

FIG. 6 is an explanatory diagram showing the relationship between the tuyere wear rate for the method of the present invention and the conventional method.

[Explanation of symbols]

1 Refractories 2 Bottom-blown tuyere refractories 3 Iron skin 4 Bottom-blown supply gas piping 5 Pressure gauge 6 Flow meter 7 Tuyere buried thermocouple 8 Arithmetic unit 9 Display device 10 Top blowing lance 11 Steel bath 12 Sublance 13 Mushroom 14 Slag 15 Tuyere 16 Hearth brick around tuyere

Claims (1)

[Claims] Claim 1: An operating method for suppressing the erosion of refractories around the bottom blowing tuyere in a bottom blowing converter, wherein a thermocouple is installed near the bottom blowing tuyere in order to determine the erosion state of the refractory around the tuyere. The maximum temperature during bottom-blowing converter operation, the temperature of molten steel measured at the end of blowing, and the time from the end of blowing until the completion of tapping are the furnace operation conditions, and the condition section membership Store the function and its consequent membership function in a computer, and calculate VS, S, M, L, VL of the various furnace operating conditions.
A logical formula matrix showing the relationship between Patterns 1 to 5 of the tuyere condition at the time of For the furnace operation condition value, use the condition part membership function to find values indicating the degrees of VS, S, M, L, and VL, and use these values to calculate the corresponding consequent membership function obtained from the matrix using the above logic. A method for operating a bottom-blowing converter, characterized in that the modified membership functions of each consequential part are synthesized, and the tuyere state under the operating conditions is determined from the result of the synthesis.