JP2926449B2 - Kiln operation and refractory lining - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of operating a kiln for processing a high-temperature molten material and a method of lining a refractory of the kiln.

[0002]

2. Description of the Related Art In steel production, non-ferrous metal production, glass production, etc., containers or kilns (hereinafter collectively referred to as "kilns") for melting materials and adjusting the melting components thereof are used. ") Are used a lot. The refractory used as the lining of the kiln is worn and thinned by the reaction with the molten material, and eventually needs to be replaced. Refractory life has a direct impact on product manufacturing costs and is also relevant to the stable operation of kilns. If the refractory is short-lived, the use amount of the refractory increases, the production cost increases, and the operation becomes unstable.

[0003] On the other hand, the improvement and development of refractory materials are progressing steadily, and it is possible to obtain high-durability refractories suitable for specific use conditions (operating conditions of kilns). However, when the operating conditions change, the optimum use conditions are deviated, so that the wear of the refractory generally increases. In order to reduce the wear, it is necessary to change the operating conditions within a range that can be compromised or to change the refractory. Conventionally, the wear rate when these countermeasures are implemented is determined by adding experience to experiments in a laboratory. However, this method involves errors associated with experiments and requires time. In addition, since there is no theoretical support, if the conditions are further changed, there is a problem that it is not possible to respond immediately, and experiments and studies must be repeated each time, resulting in a large loss.

By the way, the operating conditions of a kiln include a long-term variation from a month to a year and a short-term variation from a processing charge to a processing charge or from a day to a week. Measures for long-term fluctuations, with some loss, can be determined to some extent by conventional methods. However, since measures against short-term fluctuations cannot be formulated by this method, it is a fact that refractories with sufficient margins for such short-term fluctuations are selected.

[0005]

As described above, if the operation or refractory is changed based on experimental and empirical predictions, the loss is large and short-term fluctuations cannot be dealt with, so there is a margin. That is, at present, it is necessary to select an expensive refractory which is not optimal but wasteful.

The present invention establishes a completely new method for predicting wear of refractories that can provide quantitative and accurate results in a short period of time, selects refractories having high suitability, secures the suitability of the refractories and secures the life of the refractories. It is intended to provide a method of operating a kiln and a method of lining a refractory capable of realizing the optimization of refractory.

[0007]

The present invention solves the above-mentioned problems.
The purpose is to make the summary.
Is as follows. (1) In the method of operating a kiln lined with refractories,
Based on equation (3), a total is calculated for each operating temperature or for each slag composition.
In slag where the calculated erosion rate index V 'is 0 or smaller than the current state
Determine the concentration C _L of the refractory components of, at the operating temperature
Or, the concentration of the slag should be adjusted to C _L with a change in the slag composition.
Of operating kiln characterized by controlling slag composition
Law. V ′ = D ^2/3 C (3) where V ′: calculated erosion rate index, D: diffusion coefficient, C:
Gradient _{(= C S -C L),} Cs: scan the refractory is saturated
The concentration of the refractory component of the lug, C _L: the refractory in the slag
Component concentration (2) Among kiln refractories that select any of a plurality of refractories
In the tensioning method, based on the expression (3) described in the above (1),
Refractory at a given operating temperature and slag composition
The calculated erosion rate index V 'of the product is determined, and the index V'
Furnace fire resistance characterized by lining small refractories
Material lining method.

In many cases, refractory wear is due to the chemical reaction between the melt and the refractory. The rate of erosion of the refractory by the reaction is expressed by a theoretical formula, and a necessary value is substituted into the equation to determine the rate of erosion of the refractory. By using this method, refractory wear due to changes in operating conditions can be quantitatively and quickly predicted, so that not only can time and labor losses associated with repeated experiments and the like which were inevitable in the past be avoided, but also in the past. It is possible to predict the short-term wear that was impossible, and by predicting the refractory wear online, it becomes possible to finely modify the operating conditions and minimize the wear of the refractory. by this,
It is easy to manage the life of the refractory, and it is not necessary to select a more expensive refractory for securing excessive safety as in the conventional case, and an optimal and less expensive refractory can be used.

[0009]

The erosion rate of the refractory is a function of the viscosity of the slag, the rate of diffusion of the refractory component into the slag and the solubility. Some theoretical formulas for refractory erosion rate have been proposed,
As an example, Asano et al. (Refractory, 1987, 39, 560-
561) can be presented. They propose the following formula,
It is reported that it is in good agreement with the actual erosion rate. _{^{V = kυ -1/6 {D O exp}} (-ΔE / RT)} 2/3 (C S ρ S - C L ρ L) SP ... (1) where V erosion rate k = 0.331 (u / X) ^1/2 u Slag flow velocity X Representative length 動 Kinematic viscosity coefficient of slag D _O exp (−ΔE / RT) Expression by Arrhenius equation of diffusion coefficient of refractory component in slag C _s Refractory is saturated erosion of the refractory component concentration [rho _S refractory liquid phase ratio refractory reciprocal P slag density density S refractory concentrations [rho _L slag refractory component density C _L slag slag saturated slag In order to obtain the absolute value of the speed, it is necessary to substitute all the variables in the equation (1). But actually,
Even if the relative ratio of the erosion rate can be calculated, sufficient information necessary for operation or change of refractory can be obtained.

When estimating the actual erosion rate of a refractory,
When studying a specific kiln, that is, converter refractories, it is common to estimate the change in melting rate due to changes in operating conditions or refractory changes, assuming converter operation. is there. In this case, k in equation (1) is considered to be substantially constant. On the other hand, υ is raised to the power of ／,
It is considered that V has almost no effect. ρ _S and ρ _L can be considered to be almost constant within a normal slag composition range. S can be regarded as substantially constant assuming a normal refractory. P is considered to be 1.

From the above assumption, equation (1) can be easily rewritten as follows. ^{V = KD 2/3 C ... (2} ) where, K is a constant, D is the diffusion coefficient, C is the concentration gradient, i.e. C _S -C _L. To calculate the ratio of the erosion rate V, K disappears. Then, equation (2) is further simplified as follows.

V ′ = D ^2/3 C (3) where V ′ is a ratio of V. Therefore, if D and C are found,
V ′ can be calculated. This V 'is hereinafter referred to as a calculated erosion rate index. In order to predict the actual erosion rate, if K is calculated by the equation (2) based on the actual temperature, slag composition data, and erosion rate data, the temperature and the temperature are calculated using the equation (2). The erosion rate of the refractory can be calculated from the operating conditions related to the slag composition.

How to accurately calculate the values of D and C determines the accuracy of prediction. As for D, a theoretical or empirical calculation method has not been established, and thus the literature value is used. However, if a calculation method is established, it is desired to use this. C
Can be calculated with high precision by applying a phase balance calculation by a computer described below.

For the phase equilibrium calculation, a calculation model is required. An example of this is Gaye et al. (“Second International
l Symposium on Metallurgical Slags and Fluxes "p.3
57, ed.by HAFine and DRGaskell, The Metallurgi
cal Society of AIME, Warrendale Pennsylvania (198
4)) model can be given. This model includes the component system of slag and refractory and has relatively good accuracy, so that it can be used. Of course, other suitable models are available.

Calculation requires calculation software.
is there. One example is Eriksson's general-purpose phase equilibrium calculation software.
SOLGASMIX (Cemica Scripta, 1975, 8, 10
0 to 103). Other than this, Jansson & S
undman's THERMOCALC and other phase equilibrium calculation software
A can also be used for this calculation. By the way, refractory melting
To calculate the loss rate, a certain temperature under a certain temperature condition
It is necessary to determine the solubility of the refractory in the rug. the above
Models and calculation software allow for
Equilibrium phase of a composition, i.e., mineral combination, liquid
Phase composition, solid solution composition, etc. are determined, but solubility can be calculated.
Absent. Therefore, the mixing ratio of slag and refractory is changed to balance
Phase and refractory components appear in the equilibrium phase.
That is, the ratio of the least refractory component is determined. Fire resistance at this time
The refractory solubility is calculated by dividing the refractory component ratio by the slag component ratio.
(Hereinafter C₁). Also, in the liquid phase component at this time,
Between the concentration of refractory components in slag and that of slag
To C _TwoAnd The value to be substituted into equation (3) is C₁Is
But C_TwoCan be used in some cases.

[0016] In order to confirm the accuracy of predicting the refractory erosion rate by the method described above, the relationship between the actual erosion rate and the calculated erosion rate index was examined for magnesia carbon brick and alumina carbon brick. Brick both materials inside the induction furnace, where the pig iron is melted to 1430 ° C
Held in, CaO / SiO ₂ = 0.8~1 on it.
2. An experiment was conducted in which a synthetic slag mixed with a reagent of Al ₂ O ₃ = 8.5% and FeO = 2.0% was placed and dissolved, and this was used as an erosion material to dissolve the refractory by changing the slag composition. Was. After the experiment, the refractory was taken out and the amount of erosion was measured at the most eroded portion, and this was divided by the experimental time to calculate the erosion rate. FIG. 1 shows the relationship between the results and the calculated erosion rate index calculated based on the slag composition and temperature conditions at this time.

As can be seen from FIG. 1, there is a positive correlation between the calculated erosion rate index and the actual erosion rate, and the correlation coefficient is as high as 0.86. It can be seen that the loss speed can be predicted. The above formulas and calculation methods are merely examples, and if there are other good formulas and methods,
You can take advantage of it.

[0018]

【Example】

(Example 1) An example in which a measure for suppressing an increase in refractory wear due to a short-term change in operating conditions of a steel refining kiln is formulated and executed by the method according to the present invention will be described below. In a converter with magnesia carbonaceous refractory lining, the current tapping temperature is 1670 ° C on average, but it depends on the charge.
It varies from 1690 ° C higher by 1 ° C to 1640 ° C lower by 30 ° C. In addition, the average slag composition (SiO ₂ = 17%,
Al ₂ O ₃ = 2%, CaO = 52%, FeO = 15%,
MgO = 8%, MnO = 6%), and C in slag
aO / SiO ₂ also varies between 2.5 and 3.5.

Under these operating conditions, a slag control operation in which lightly fired dolomite is introduced to suppress the wear of the refractory is performed, and the MgO concentration in the slag is maintained at 8% to suppress the wear of the refractory. . The method according to the present invention examines how the MgO concentration can be adjusted according to the temperature condition of each charge to reduce the unit consumption of lightly fired dolomite and suppress the wear of refractories. did. That is, the MgO concentration in the slag at which the calculated erosion rate index of magnesia was 0 was calculated under the temperature condition of each charge or the slag composition condition, and a necessary and sufficient amount of lightly fired dolomite was charged.

Tables 1 and 2 show examples of the calculation results. When the temperature becomes 1640 ° C., which is 30 ° C. lower than the current 1670 ° C., the same effect can be obtained even if the MgO concentration in the slag is reduced by 1%. On the other hand, the temperature is higher by 20 ° C.16
When the temperature reaches 90 ° C., it can be seen that if the amount of lightly burnt dolomite is increased to make the MgO concentration in the slag 9%, wear of the magnesia carbon brick can be suppressed. On the other hand, even if CaO / SiO ₂ increases or decreases, the necessary and sufficient M
It can be seen that the gO concentration changes. In this way, the necessary and sufficient MgO concentration accompanying the change in the temperature and slag composition was calculated for each charge, and the converter was operated with the lightly fired dolomite input amount changed accordingly.
The life of the refractory lining could be extended by 15%.

Conventionally, such quantitative indices could not be obtained in a short time, so that it was necessary to select refractories in consideration of waste of lightly burned dolomite, abnormal wear of refractories, or a margin. These problems have been solved by the method according to the invention.

[0022]

[Table 1]

[0023]

[Table 2]

Embodiment 2 An example in which the optimum operating conditions and the optimum refractory are selected according to the present invention with the aim of reducing the wear rate of the refractory due to a large change in the operating conditions will be described below. The operating conditions of the smelting furnace changed, and the wear rate of the magnesia carbon brick, which had been conventionally lined, increased. To suppress this, we calculated the calculated erosion rate index of magnesia,
It was found that increasing the MgO concentration in the slag can significantly reduce the erosion rate. Table 3 shows this situation.

[0025]

[Table 3]

From the above findings, the addition of lightly fired dolomite was able to significantly reduce the melting damage of magnesia carbon brick in this kiln. On the other hand, it is possible to extend the life of the refractory lining by changing the refractory material rather than by modifying the operating conditions such as changing the MgO concentration in the slag, so compare the calculated erosion rate index for magnesia and alumina. did. Table 4 shows the results.
It was found that by changing the aggregate from magnesia to alumina, the erosion rate could be almost halved.

According to the above results, when Al ₂ O ₃ —SiC—C brick using alumina aggregate was used for the lining of this kiln, the wear rate of the brick was 60% of that when magnesia carbon brick was used. And the result was almost as predicted by calculation.

[0028]

[Table 4]

[0029]

As described above, by using the method according to the present invention, it is possible to predict the wear rate of refractories due to short-term or long-term fluctuations in operating conditions, and to take quantitative measures based on this. Can be. As a result, the refractory can be used under the most suitable conditions, the refractory can be selected without waste, and the unit consumption of the refractory protective material can be reduced. As described above, the effect of the present invention is very large, and it can be said that the present invention is a useful invention.

[Brief description of the drawings]

FIG. 1 shows a relationship between a erosion test in an induction furnace and a calculated erosion rate index (conditions: slag C / S = 0.8 to 1.
2, Al ₂ O ₃ = 8.5%, FeO = 2.0%, temperature 1
430 ° C.).

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C21C 5/44 C03B 5/42 F27D 1/00

Claims (2)

(57) [Claims] 1. A method of operating a kiln furnace lined with refractories.
Then, based on the equation (3), for each operating temperature or slag group
Each time the calculated erosion rate index V 'is 0 or smaller than the current state
Determine the concentration C _L of the refractory components in the slag, the operating temperature
And the concentration C _L with a change in the, or slag composition
A method for operating a kiln, comprising controlling the slag composition so that the slag composition is controlled . ^{V '= D 2/3 C ... (} 3) where, V': calculated erosion rate index D: diffusion coefficient C: concentration gradient _{(= C S -C L) C} S: refractory slag refractory is saturated the concentration of the object component C _L: concentration of the refractory components in the slag 2. A furnace furnace for selecting one of a plurality of refractories.
In the method for lining a fire, the formula (3) according to claim 1 is used.
Based on the given operating temperature and slag composition respectively
Of the refractory calculated as described above, the index V 'is obtained.
A refractory lining method for a kiln characterized by lining a refractory with the smallest size .